JP2000027686A - Fuel injection control device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simultaneously inject fuel for all engine cylinders before completion of determination of an engine cylinder, by surely recognizing an injection reference signal serving as a reference for the fuel injection timing. SOLUTION: In a system incorporating a crank angle sensor which delivers reference signals at a BTDC α deg. serving as a reference for injection, at a BTDC β deg. serving as a reference for ignition and at a BTDC γ deg. corresponding to a cylinder determination timing (α<β<γ), respectively, and a cam sensor for delivering a cylinder determination signal between BTDC α and BTDC γ, if a cylinder determination signal is produced just after the reference signal is delivered from the crank angle sensor, this reference signal just before is recognized as a reference signal for the BTDC α deg which serves as a reference for injection. Thus, the timing with which simultaneous fuel injection for all cylinders is carried out is controlled.

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 device for an engine, and more particularly, to a technique for improving the startability by performing fuel injection early at the time of starting.

[0002]

2. Description of the Related Art Conventionally, as a fuel injection control of an engine having a fuel injection valve in an intake system of each cylinder, a crank angle sensor for generating a reference signal at a piston position serving as a reference of fuel injection timing of each cylinder has been used. A cam sensor for generating a number of cylinder discrimination signals corresponding to the cylinder number between the reference signals, and performing cylinder discrimination based on the number of cylinder discrimination signals generated between the reference signals, Sequential fuel injection control is known in which fuel injection timing adjusted to the intake stroke of each cylinder is detected based on each reference signal, and fuel injection is performed individually for each cylinder. ing.

[0003] Conventionally, prior to the completion of cylinder discrimination, simultaneous injection of all cylinders is performed so that the first fuel injection is performed as soon as possible, so that a first explosion is expedited to improve startability. For example, at the time of starting, simultaneous injection of all cylinders is performed simultaneously with generation of the first reference signal,
The timing of simultaneous injection of all cylinders has been controlled based on the reference signal.

[0004]

By the way, a system having a crank angle sensor for generating a reference signal based on a piston position serving as a reference for ignition timing in addition to a piston position serving as a reference for fuel injection timing has been developed. In such a system, since the reference signal is output for each of the plurality of piston positions, it is possible to perform the simultaneous injection of all cylinders by recognizing the generation of the reference signal as it is as the injection reference position, as in the conventional case described above. As a result, there is a problem that the start of fuel injection may be delayed.

The present invention has been made in view of the above problems, and has a crank angle sensor for generating a reference signal based on a piston position serving as a reference for ignition timing, in addition to a piston position serving as a reference for fuel injection timing. In the system, before the completion of the cylinder discrimination, the injection reference signal is distinguished,
An object is to enable simultaneous injection of all cylinders.

[0006]

SUMMARY OF THE INVENTION Therefore, the invention according to claim 1 is a fuel injection control device for an engine having a fuel injection valve in an intake system of each cylinder, which is configured as shown in FIG. . In FIG. 1, reference signal output means is provided on a crankshaft and outputs a reference signal for each of a plurality of piston positions including a piston position serving as a reference for fuel injection timing.

The cylinder discriminating signal output means is provided on the camshaft, and outputs a reference signal between the reference signal output from the reference signal output means at a piston position serving as a reference for the fuel injection timing and the next reference signal. A cylinder discrimination signal is output. Here, when the cylinder discrimination signal is output from the cylinder discrimination signal output means, the injection reference signal detection means uses the reference signal output immediately before from the reference signal output means as a reference which serves as a reference for the fuel injection timing. Detect as a signal.

[0008] The injection timing setting means sets the fuel injection timing based on a reference signal detected by the injection reference signal detection means and serving as a reference for the fuel injection timing. According to this configuration, when the reference signal is generated, it is determined retrospectively whether or not the reference signal is an injection reference signal serving as a reference of fuel injection timing, based on whether or not the cylinder determination signal is output immediately thereafter. I do. Then, the reference signal generated immediately before the output of the cylinder discrimination signal is regarded as the injection reference signal, and is used for setting the fuel injection timing. Therefore, it is possible to use the first injection reference signal for injection control when starting the engine.

According to the present invention, the unit signal output means for outputting a unit signal for each unit crank angle, the unit signal counting means for counting the number of unit signals generated from the unit signal output means, and the reference signal Resetting means for resetting the count of the unit signal by the counting means each time a reference signal is generated from the signal output means, wherein the injection timing setting means is configured to determine the count of the unit signal by the counting means. To set the fuel injection timing.

According to this configuration, the counting means counts the unit signal, and the count result is reset every time the reference signal is generated, so that the counting result by the counting means indicates an angle from each reference signal. become.
Therefore, when the counting is restarted from the time when the injection reference signal was output, the count value indicates the angle from the injection reference signal, and it was found that the immediately preceding reference signal was the injection reference signal later. However, since the angle from the injection reference signal up to that point is known, the fuel injection timing can be detected when the fuel injection timing is given as the angle from the injection reference signal.

According to a third aspect of the present invention, the injection timing setting means is configured to perform simultaneous injection of all cylinders based on a reference signal which is a reference of fuel injection timing first detected by the injection reference signal detecting means at the time of engine start. The fuel injection timing is set. According to such a configuration,
When the first injection reference signal is output when the engine is started, and immediately after that, the cylinder discrimination signal is output, and it is found that the immediately preceding reference signal was the injection reference signal retroactively.
Simultaneous injection of all cylinders is performed based on the injection reference signal without waiting for generation of the next reference signal, that is, completion of cylinder determination.

For example, when cylinder discrimination is performed by counting the number of cylinder discrimination signals generated between the injection reference signal and the next reference signal, when the cylinder discrimination is performed until the next reference signal is generated after the injection reference signal is generated. In the case where the cylinder discrimination is not completed and the sequential injection is performed, the cylinder discrimination is performed based on the counting result, and the fuel injection for each cylinder is performed based on the injection reference signal output after the completion of the cylinder discrimination. However, in the invention according to claim 3, the first injection reference signal is determined at the time of starting, and all-cylinder simultaneous injection that does not require cylinder determination is performed based on the first injection reference signal.

According to the present invention, the injection timing setting means detects the first closing timing of the intake valve based on a reference signal serving as a reference for the fuel injection timing, and determines the closing timing of the intake valve in all cylinders. It was configured to be set as simultaneous injection start timing. According to this configuration, in the cylinder in which the intake valve is closed at the start timing of the simultaneous injection of all cylinders, the entire amount of the injected fuel stays upstream of the intake valve until the next time the intake valve is opened. Similarly, in the cylinder in the middle of the previous opening period and the next opening period of the intake valve, the injected fuel stays upstream of the intake valve until the next intake stroke. Also,
Since the closing timing of the intake valve is generally after BDC, if simultaneous injection is performed for all cylinders at the same timing as the closing timing of the intake valve for a certain cylinder, the cylinder with the open intake valve will be in the middle of the piston descent. Therefore, the injected fuel can be sucked into the cylinder by a large negative pressure to form an air-fuel mixture that can be ignited and burned. Naturally, all cylinders can be simultaneously injected at a relatively early stage during the intake stroke. Is carried out so that mixing with air can be performed well.

[0014]

According to the first aspect of the present invention, the generation of the injection reference signal is determined retrospectively based on the output of the cylinder discrimination signal immediately after the reference signal, and based on the determined injection reference signal. Since the injection timing is set, the fuel can be injected and burned early using the first injection reference signal as the injection reference when starting the engine, so that the fuel remaining in the cylinder is burned during cranking. Therefore, there is an effect that the exhaust emission at the time of starting can be improved.

According to the second aspect of the present invention, the number of unit signals generated is counted from all the reference signals. Therefore, even if the generation of the injection reference signal is determined retroactively, the generation of the unit signal is performed based on the count number. The angle of the
Thus, there is an effect that the injection timing can be detected as a position at a predetermined angle from the injection reference signal. According to the third aspect of the present invention, by performing simultaneous injection of all cylinders that do not require cylinder discrimination based on the first injection reference signal at the time of engine start, fuel injection can be performed before completion of cylinder discrimination. This has the effect.

According to the fourth aspect of the present invention, it is possible to form an air-fuel mixture excellent in combustion stability in each cylinder by simultaneous injection of all cylinders. This has the effect of making it possible to obtain the first explosion.

[0017]

Embodiments of the present invention will be described below. FIG. 2 is a diagram showing a system configuration of the engine according to the embodiment. Air is drawn into the in-line four-cylinder engine 1 through an air cleaner 2, an intake duct 3, a throttle chamber 4, and an intake manifold 5.

The intake duct 3 is provided with an air flow meter 6 for detecting an intake air flow rate Qa of the engine 1. The throttle chamber 4 is provided with a throttle valve 7 that opens and closes in conjunction with an accelerator pedal (not shown).
The throttle valve 7 regulates the intake air flow rate Qa. An electromagnetic fuel injection valve 8 is provided for each cylinder at each branch portion (upstream of an intake valve not shown) of the intake manifold 5, and an air-fuel mixture is formed for each cylinder.

The BTDCα ° (for example, BTDC) of each cylinder
DC10 °) and the BT of each cylinder
The ignition reference signal output at DCβ ° (for example, BTDC60 °) and the BTDCγ ° (for example, BTDC100
°), and a crank angle sensor 9A (reference signal output means) for generating a cylinder discrimination timing signal which is output as a unit crank angle (for example, 3 degrees).
°) a ring gear sensor 9B (unit signal output means) for outputting a unit signal for each cylinder is provided on the crankshaft, and a cylinder indicating cylinder discrimination information based on the number of generated pulses between the injection reference signal and the cylinder discrimination timing signal. A cam sensor 10 (cylinder discrimination signal output means) for generating a discrimination signal is provided on the cam shaft (see FIGS. 3 and 4).

Here, the number of pulses generated between the injection reference signal and the cylinder discrimination timing signal from the cam sensor 10 is limited to three types of 1, 2, 3 as shown in FIG. Pulses are output in the order of individual → 3 → 1 → 2. The number of cylinder discrimination signals generated between the injection reference signal and the cylinder discrimination timing signal is 1
When the number of pulses is 3, it indicates that the next cylinder to be the compression TDC is either the # 1 cylinder or the # 2 cylinder, and the pulse number is 3
When the number of pulses is 2, the next compression TDC is # 3 cylinder, and when the number of pulses is 2, the next compression TDC is # 3.
Indicates that DC is # 4 cylinder. Here, if the count number of the first cylinder discrimination signal is one, the cylinder group discrimination for discriminating the cylinders in groups is completed, and the next count number is two or three. Thus, the cylinder discrimination for individually discriminating the cylinders is completed.

The order of ignition in the in-line four-cylinder engine of this embodiment is in the order of # 1 → # 3 → # 2 → # 4, and between the injection reference signal and the cylinder discrimination timing signal. Is generated at a predetermined piston position. In the above system configuration, usually, the crank angle sensor 9
The number of cylinder discrimination signals generated from the cam sensor 10 is counted at the generation interval of the detection signal from A, and the detection signal generated next from the crank angle sensor 9A based on the generation of the cylinder discrimination signal is converted to a cylinder discrimination timing signal. And performs cylinder discrimination based on the cylinder discrimination signal counted from the cylinder discrimination timing signal to the immediately preceding detection signal (injection reference signal). Then, a detection signal output from the crank angle sensor 9A next to the cylinder discrimination timing signal is recognized as an ignition reference signal, and ignition control for each cylinder is performed based on the cylinder discrimination result. Then, the detection signal output from the crank angle sensor 9A is recognized as an injection reference signal, and injection timing control (sequential fuel injection control) for each cylinder is performed based on the cylinder determination result.

On the other hand, at the stage of starting and before the cylinder discrimination is completed, as shown in the flowchart of FIG.
The simultaneous injection of all cylinders is performed only once, and thereafter, the process is shifted to the sequential injection. In the simultaneous injection of all cylinders, the same amount of fuel is injected simultaneously from each fuel injection valve 8 as the amount injected once every two rotations in sequential injection.

In the flowchart of FIG. 5, at S1,
When cranking is started, the process proceeds to S2, where a flag F initialized to 0 when the ignition switch is turned on is determined. If the flag F = 0, the process proceeds to S3. In S3,
It is determined whether or not a reference signal, which is one of an injection reference signal, an ignition reference signal, and a cylinder determination timing signal, is first generated from the crank angle sensor 9A.

When the first generation of the reference signal is detected, the process proceeds to S4, where the flag F is set to 1, and then the process proceeds to S7, where the unit signal generated from the ring gear sensor 9B is counted. C is counted (unit signal counting means). In S8, it is determined whether or not a cylinder determination signal has been generated from the cam sensor 10. If no cylinder determination signal has been generated, the process returns to S2.

By setting 1 to the flag F,
The process proceeds from S2 to S5. In S5, it is determined whether or not the second or subsequent reference signal is generated. When the reference signal is generated for the second time or later, the process proceeds to S6, where the count number C is reset to 0, and then returns to S2 (reset means). On the other hand, if it is determined in S5 that the second and subsequent reference signals have not been generated, the process proceeds to S7, and the counting of the unit signals based on the count number C is continued.

By the above processing, the count number C is reset to 0 each time the reference signal is generated, and indicates the number of unit signals generated since the generation of the reference signal, that is, the crank angle from the reference signal (see FIG. 4). 4), if the generation of the cylinder determination signal from the cam sensor 10 is determined in S8 while the unit signal is being counted, the process proceeds to S9. In S9,
Based on the generation of the cylinder discrimination signal, it is recognized that the reference signal generated from the crank angle sensor 9A immediately before was the injection reference signal (injection reference signal detection means). As described above, in the present embodiment, the cylinder discrimination signal is output between the injection reference signal and the cylinder discrimination timing signal, so that the occurrence of the cylinder discrimination signal is The reference signal will be an injection reference signal.

In S10, an angle Tti is set from the injection reference signal recognized retroactively as described above to a timing (injection start timing) at which simultaneous injection of all cylinders is performed. In this embodiment, since the simultaneous injection of all cylinders is set to the closing timing of the intake valve closest to the injection reference signal, the angle Tti
Is calculated as an angle from the injection reference signal to the closest intake valve closing timing (see FIG. 4). However, the angle Tti
Is constant unless the closing timing of the intake valve is changed by the variable valve timing mechanism. Therefore, when the closing timing is constant, a configuration may be adopted in which the closing timing is given as a fixed value. Further, the angle Tti may be obtained as an added value of the angle from the injection reference signal to the first cylinder discrimination signal and the angle from the first cylinder discrimination signal to the injection timing.

In step S11, the count C is equal to the angle T.
It is determined whether or not a value corresponding to ti has been reached, and the angle Tti is determined.
When the count has not reached, the unit signal is continued to be counted in S12 and the process returns to S11 again. If it is determined in S11 that the count number C has reached a value corresponding to the angle Tti, the process proceeds to S13 and the fuel An injection pulse signal is output to all the injection valves 8 at the same time so that fuel injection is performed simultaneously in all cylinders. The functions of S10 to S13 correspond to injection timing setting means.

In the present embodiment, the first one of the cylinder discrimination signals is output before the closing timing of the intake valve immediately after the injection reference signal. If the angle from the injection reference signal up to that point is known at the point in time when the occurrence of is detected, the first intake valve closing timing comes after that. The timing can be detected as the timing of simultaneous injection of all cylinders.

As described above, according to this embodiment, the immediately preceding reference signal is retroactively recognized as the injection reference signal based on the generation of the cylinder discrimination signal, and the simultaneous injection of all cylinders is performed based on the recognized injection reference signal. Is performed, it is possible to reliably use the first injection reference signal as the injection reference at the time of startup, and thus to perform early injection at the time of startup.

As the injection amount in the simultaneous injection of all cylinders, the same value as the injection amount for the sequential injection performed once for every two rotations (one cycle) for each cylinder is used. Therefore, the first cylinder that requires fuel injection after all-cylinder simultaneous injection is the cylinder in which fuel injection was performed with the intake valve opened by all-cylinder simultaneous injection, and two rotations (one cycle) Fuel injection is required in the subsequent next intake stroke. At this time, since cylinder discrimination has been definitely completed, fuel injection is performed by scene sequential injection. That is, in the present embodiment, the simultaneous injection of all cylinders is performed only once when the first injection reference signal is generated at the time of starting, and after the simultaneous injection of all cylinders, fuel is injected for each cylinder by sequential injection. Combustion air-fuel mixture is formed by sequential injection following the initial explosion by simultaneous injection of all cylinders.

In the above description, the timing of simultaneous injection of all cylinders is set to the closing timing of the intake valve closest to the injection reference signal. For example, the timing is synchronized with the first cylinder discrimination signal which is the recognition timing of the first injection reference signal. A configuration in which all cylinders are simultaneously injected may be adopted. However, as described above, if simultaneous injection is performed for all cylinders with the closing timing of the intake valve as the injection start timing, there is no cylinder in which fuel injection is performed immediately before the closing timing of the intake valve. It is possible to avoid the occurrence of lean misfire due to the injection of a part of the injected fuel into the cylinder immediately before the closing timing and the discharge of unburned components.

On the other hand, for cylinders in which simultaneous injection of all cylinders is performed during the opening period of the intake valve, the injected fuel is immediately sucked into the cylinder, but fuel injection is performed relatively early. Therefore, mixing of fuel and air can be performed sufficiently, and high combustion stability can be obtained.
The first explosion is surely obtained. That is, it is avoided that only a part of the fuel injected by the all-cylinder simultaneous injection (more precisely, a part of the fuel amount expected to be drawn into the cylinder) is drawn into the cylinder. , The simultaneous injection of all cylinders may be performed while avoiding the period from the vicinity of BDC (bottom dead center) to the closing timing of the intake valve. However, when simultaneous injection of all cylinders is performed immediately before BDC, the intake valve opens. Even if the entire amount of injected fuel can be sucked into the cylinder in the cylinder, it is difficult to obtain high combustion stability due to insufficient mixing with air, and the first explosion occurs stably. It is difficult.

On the other hand, if the closing timing of the intake valve is set as the injection start timing as described above, it is possible to avoid the occurrence of a cylinder in which fuel is sucked halfway, while at the same time sucking the entire amount. In such a cylinder, sufficient mixing with air can be performed, and a first explosion can be stably generated. In this embodiment, the engine 1 is connected in series 4
Although the engine is a cylinder engine, it is obvious that the number of cylinders and the cylinder arrangement of the engine are not limited.

Further, a configuration may be adopted in which a cam sensor 10 for generating a pattern corresponding to the number of cylinders is provided as the cylinder determination signal, and further, the crank angle sensor 9A outputs a reference signal including cylinder determination information. It may be.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a fuel injection control device according to claim 1.

FIG. 2 is a system configuration diagram of an engine according to the embodiment.

FIG. 3 is a time chart showing signal characteristics of a crank angle sensor and a cam sensor in the embodiment.

FIG. 4 is a time chart showing characteristics of simultaneous injection of all cylinders at the time of starting according to the embodiment.

FIG. 5 is a flowchart showing all-cylinder simultaneous injection control at the time of starting according to the embodiment;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 2 Air cleaner 3 Intake duct 4 Throttle chamber 5 Intake manifold 6 Air flow meter 7 Throttle valve 8 Fuel injection valve 9A Crank angle sensor 9B Ring gear sensor 10 Cam sensor 12 Control unit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3G084 AA03 BA15 CA01 DA09 DA28 EA11 EB02 EB24 EC02 EC03 FA00 FA36 FA38 FA39 3G301 HA01 HA06 JA03 JA23 KA01 LB02 MA04 MA11 MA18 MA19 NA06 NC08 NE23 PE03Z PE04Z PE05Z PE10Z PF16Z

Claims (4)

[Claims] 1. A fuel injection control device for an engine provided with a fuel injection valve in an intake system of each cylinder, wherein a plurality of piston positions including a piston position which is provided on a crankshaft and serves as a reference for fuel injection timing are provided. A reference signal output means for outputting a reference signal to the camshaft, and a reference signal output from the reference signal output means at a piston position serving as a reference for the fuel injection timing and a next reference signal, Cylinder discrimination signal output means for outputting a cylinder discrimination signal, and when the cylinder discrimination signal is output from the cylinder discrimination signal output means, the reference signal output immediately before from the reference signal output means is used as the fuel injection timing. Injection reference signal detection means for detecting a reference signal serving as a reference, and a reference signal serving as a reference for the fuel injection timing detected by the injection reference signal detection means And a fuel injection timing setting means for setting a fuel injection timing based on the fuel injection control device. A unit signal output unit for outputting a unit signal for each unit crank angle; a unit signal counting unit for counting the number of unit signals generated from the unit signal output unit; and a reference signal from the reference signal output unit. Resetting means for resetting the count number of the unit signal by the counting means each time the occurrence occurs, wherein the injection timing setting means sets the fuel injection timing based on the count number of the unit signal by the counting means. The fuel injection control device for an engine according to claim 1, wherein: 3. The injection timing setting means, based on a reference signal which is a reference of fuel injection timing first detected by the injection reference signal detection means at the time of starting the engine,
3. The fuel injection control device for an engine according to claim 1, wherein a fuel injection timing of all cylinders simultaneous injection is set. 4. The injection timing setting means detects an initial closing timing of an intake valve based on a reference signal serving as a reference of the fuel injection timing, and sets the intake valve closing timing as an injection start timing for all cylinders simultaneously. The fuel injection control device for an engine according to claim 3, wherein the setting is performed.