JPH10339196A - Cylinder direct injection internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove a sticking material such as carbon of an injection valve nozzle port part by comparing a pulse width to the demand air-fuel ratio with an initial preset value when detected that air-fuel ratio feedback control is performed, and increasing fuel injection pressure when the pulse width to the demand air-fuel ratio exceeds the initial preset value. SOLUTION: An operation condition of an engine is detected (1), and whether or not it is adapted to a self-diagnosable condition of an injection valve is judged (2), and when it is adapted, an actual injection pulse width at self- diagnosing time is detected (3), and its rate of change is calculated (4). This rate of change and an allowable rate of change are comparted (5) with each other, and when it is not less than the allowable rate of change, operation indication of a pump and a fuel supply system is issued to increase fuel injection pressure, and injection pulse width reducing correction 6 is performed on a fuel injection pulse width. A fuel injection correcting pulse is used simultaneously when a injection pressure change is confirmed, and fuel injection is continuously performed before injection pressure is changed. Therefore, a sticking material such as carbon sticking to an injection valve nozzle port part is removed by injection pressure of fuel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-cylinder direct injection type internal combustion engine which performs self-diagnosis and restoration control of injection valve operation of a direct injection type internal combustion engine which directly injects fuel into a cylinder.

[0002]

2. Description of the Related Art As a conventional in-cylinder direct injection type internal combustion engine, for example, the one shown in the drawings of Japanese Patent Application Laid-Open No. 8-35429 is known.

In this prior art, as shown in FIG. 7, fuel injected from a fuel injection valve 1 mounted so as to face the inside of a cylinder is diffused into surrounding air while maintaining a lump of air-fuel mixture. The air-fuel mixture is placed on the air flow 5 in the cylinder and swirls in the depression on the ball 4 provided on the piston crown surface, reaches the vicinity of the ignition plug 2 near the compression top dead center, where it is ignited and suitable for combustion. This is a stratified combustion system in which the combustion is performed in a portion of the concentration and the piston 3 is pushed down to move the engine.

[0004] The point of this stratified combustion system is to suppress the diffusion of the spray from the injection valve and maintain a lump of air-fuel mixture having a good concentration for combustion until ignition. For this reason, the spray state, the shape of the combustion chamber, the air flow, and the fuel injection pressure are set to be suitable in a wide operating range.

[0005]

However, in such a conventional direct injection type internal combustion engine, in order to stratify the air-fuel mixture, as shown in the lower part of FIG. It is unavoidable that an excessively rich portion of the air-fuel mixture occurs in the fuel, and the combustion of the rich air-fuel mixture generates smoke, fouls the spark plug due to carbon, and changes the spray shape due to the fouling of the fuel injection valve. There is a problem that the amount may decrease, the operation of the injection valve may malfunction, or the like.

[0006] As another combustion system, there is a uniform combustion system in which fuel is directly injected into the cylinder to form a uniform mixture in the cylinder and burn at an early stage before the latter half of the compression stroke. Also in this method, as the injection amount increases due to a high load or the like, a portion of the mixture in the cylinder becomes richer, causing smoke due to combustion of the rich mixture, fouling of the spark plug by carbon and fuel. There is a problem similar to that of the conventional direct injection type internal combustion engine, in which a change in the spray shape, a decrease in the injection amount, and a malfunction of the injection valve due to the contamination of the injection valve may occur.

The present invention has been made in view of the above situation, and has as its object the change in spray shape caused by the contamination of a fuel injection valve caused by carbon generated by combustion of a rich mixture. An object of the present invention is to provide a direct injection type internal combustion engine that can effectively prevent deterioration of engine performance by performing self-restoration control by detecting a decrease in injection amount, malfunction of an injection valve, etc. in advance. It is.

[0008]

According to the present invention, a direct injection type internal combustion engine for directly injecting fuel into a cylinder is provided with an air-fuel ratio feedback control under a specific operating condition. A control device having means for detecting that control is being performed and means for comparing a pulse width with respect to the required air-fuel ratio with an initial set value is provided, and the control device includes:
When the pulse width for the required air-fuel ratio exceeds a predetermined value with respect to the initial set value, the fuel injection pressure is increased.

In the present invention, the means for comparing the pulse width with respect to the required air-fuel ratio with an initial set value is provided when it is determined that the pulse width with respect to the required air-fuel ratio exceeds a predetermined value with respect to the initial set value. The fuel injection timing is advanced during the intake stroke to increase the fuel injection pressure.

In the present invention, in consideration of maintainability, the means for comparing the pulse width with respect to the required air-fuel ratio with an initial set value is provided in advance. If it is determined that the specified value has been exceeded,
The present invention is characterized in that it is configured to warn that the performance of the injection valve has deteriorated.

Further, in the present invention, in consideration of controllability, the control device returns the fuel injection pressure to its original state after the fuel injection pressure is increased, and sets the demand before the fuel injection pressure is increased. It is characterized in that a correction value of the injection pulse width for the required injection amount of the injection valve is learned as compared with the pulse width for the air-fuel ratio.

According to another aspect of the present invention, there is provided a direct injection type internal combustion engine for directly injecting fuel into a cylinder, wherein the operation of the engine is under air-fuel ratio feedback control under a specific operating condition. A control unit having means for detecting the air-fuel ratio for a constant pulse width and comparing the air-fuel ratio with the initial air-fuel ratio, wherein the control unit determines that the change in the air-fuel ratio for the constant pulse width is a predetermined value. , The fuel injection pressure is increased when the pressure exceeds.

[0013]

Therefore, according to the first or fifth aspect of the present invention, a change in combustion due to a change in the shape of the spray or an increase in the required fuel injection pulse width due to the narrowing of the injection hole of the injection valve. When a change in the performance of the injection valve is detected, the control device increases the fuel injection pressure and increases the fuel penetration force of the injection hole, and thus removes deposits such as carbon at the injection valve injection hole. it can.

According to the second aspect of the present invention, the fuel injection when the fuel injection pressure is increased is performed under the condition that the in-cylinder pressure is lower. Is applied, and the fuel penetration force of the injection hole portion is further increased, so that deposits such as carbon on the injection valve injection hole portion can be more reliably removed.

Further, according to the third aspect of the present invention,
By issuing a warning when a change in the performance of the fuel injection valve is detected, it is possible to warn the driver or others that a change in the performance of the fuel injection valve has occurred, making maintenance easier. And the performance of the engine can be easily maintained.

Further, according to the present invention, the amount of change from the initial value of the injection amount to the injection valve after the end of the operation in which the injection pressure has been increased is detected and learned. Therefore, even if the injection valve changes the injection characteristic, the air-fuel ratio feedback control is not performed by correcting the change in the injection amount of the fuel injection valve when calculating the fuel injection pulse width from the required injection amount. Good combustion can be maintained even below.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on an embodiment shown in the accompanying drawings.

FIG. 1 is a diagram showing the relationship between in-cylinder pressure and injection pressure in fuel injection according to a first embodiment of the present invention, and FIG. 2 is a flowchart relating to the system of the present embodiment.

As shown in FIG. 2, the operating state of the engine is detected (step 3-1), and it is determined whether the self-diagnosis condition of the injection valve is satisfied (step 3-2). If the self-diagnosis condition conforms to predetermined operating conditions, that is, the load representative value such as feedback control, engine speed, intake air amount or throttle opening, and the self-diagnosis condition is satisfied, the initial value for the load representative value under that condition The actual injection pulse width at the time of self-diagnosis with respect to the calculated pulse width is detected (step 3-3), and the rate of change is calculated as: change rate = (actual injection pulse width−initial pulse width relative to load representative value) / (load (The initial pulse width for the representative value) (step 3-4).

Next, the change value is compared with a predetermined allowable change width (step 3-5). If the change value is within the allowable change width, the diagnosis is terminated. On the other hand, if it is equal to or larger than the allowable change width, the process shifts to the injection amount restoration control of the injection valve.

First, in order to increase the fuel injection pressure, an operation instruction of a pump and a fuel supply system (not shown) is issued, and the fuel injection pulse width is subjected to the injection pulse width reduction correction accompanying the increase of the injection pressure (step 3-). 6).

When the change in the injection pressure is confirmed, the fuel injection correction pulse is used at the same time, and the fuel injection is performed continuously before the change in the injection pressure.

FIG. 1 shows the relationship between the fuel injection and the in-cylinder pressure. In the fuel injection initially performed at the injection pressure A and the pulse width a, the pressure is increased to B and the pulse width is reduced at the same time. The pulse width becomes b. The operation in which the fuel pressure is increased is continued for a fixed time, and the time is managed by an elapsed time count (step 3-7).

By the operation in which the fuel pressure is increased, the volume of carbon or the like that has adhered to the injection hole of the injection valve and has affected the fuel injection is removed by the injection pressure.

After a predetermined time has elapsed, the fuel injection pressure and the pulse width are returned to the same state as before the injection pressure was increased (step 3-8), and the self-diagnosis and the restoration control are completed.

FIGS. 3 and 4 show a second embodiment of the present invention. In this embodiment, the steps up to the fifth step are the same as those in the first embodiment. However, when the change rate of the pulse width is larger than a predetermined value, the injection pressure is increased to correct the pulse width, and at the same time, the fuel injection is performed. It is configured to advance the time.

FIG. 3 shows the relationship between the fuel injection and the in-cylinder pressure in this embodiment. In the fuel injection performed initially with the injection pressure A and the pulse width a, the pressure is raised to B and at the same time. The pulse width is shortened to the pulse width b, and at the same time, the injection timing is advanced from B ′ to C ′. As described above, by advancing the fuel injection timing, the differential pressure between the fuel injection pressure and the in-cylinder pressure, that is, the actual injection fuel pressure increases from BX before the advance of the injection timing to BC. For this reason, the volume of carbon or the like that has adhered to the injection valve nozzle hole and has affected the fuel injection is more easily removed than in the first embodiment.

As described above, the operation in which the fuel pressure is increased and the injection timing is advanced is continued for a fixed time, and this time is filled with the elapsed time count (step 5-7).

By the operation in which the fuel pressure is increased, the volume such as carbon which has adhered to the injection hole of the injection valve and has affected the fuel injection is removed by the injection pressure.

After a lapse of a predetermined time, the fuel injection pressure, the pulse width, and the injection timing are returned to the same state as before the increase in the injection pressure (step 5-8), and the self-diagnosis and the restoration control are completed.

FIG. 5 shows a third embodiment of the present invention. In this embodiment, unlike the second embodiment,
After the operation of increasing the fuel injection pressure is completed, the injection characteristics of the injection valve are examined again, the deviation of the injection characteristics is calculated, and the deviation is learned to improve the control accuracy of the fuel injection amount. ing.

In this embodiment, the procedure proceeds to step 8 in FIG. 5 in the same manner as in the second embodiment, but thereafter, it is again confirmed that the self-diagnosis condition of the injection valve is satisfied (step 6-9). Then, the actual injection pulse width at the time of self-diagnosis with respect to the initial pulse width calculation value of the load representative value under the condition is detected (step 6-10), and the change rate of the injection pulse width is calculated as a change rate α = (actual Injection pulse width−initial pulse width for load representative value / (initial pulse width for load representative value) is calculated (step 6-11).

In the next step, the injection pulse width change rate α obtained by the above calculation is learned (step (6-12)).
This value is used as a deviation of the injection characteristic of the injector as a correction amount when calculating the injection pulse width. Assuming that the pulse width calculation value for this load representative value is T, the injection pulse width T ′ after learning is calculated as T ′ = (l + α) × T.

By performing this correction, even when the injection amount restoring operation does not provide a sufficient effect and does not return to the initial injection characteristics, the correction is performed at the stage of calculating the injection pulse width and the injection amount is accurately determined. Can be controlled.

FIG. 6 shows a fourth embodiment of the present invention. In this embodiment, predetermined operating conditions (feedback control, engine speed, intake air amount, throttle opening degree, etc. (Step 7-5), and if the rate of change is equal to or larger than the allowable change width with respect to the predetermined allowable change width, the flow shifts to injection quantity restoration control of the injection valve (Step 7-5). This is different from the embodiment shown in FIG. 5 in that, at the same time as performing step 7-6), a warning is given (step 7-13) that the injection valve characteristic has changed.

This warning may be displayed on a diagnosis display, but may be stored in a memory as a self-diagnosis result. By this step, maintenance of the injection valve can be easily performed.

As described above, the warning timing may be performed at the same time as the shift to the injection amount restoration control of the injection valve (steps 7-6 and thereafter), or may be performed after a certain number of times, or may be restored. After learning of the injection characteristic deviation after the control is completed, the correction may be performed when the correction coefficient exceeds a predetermined value, or may be performed so that the driver can perceive the correction coefficient. It may be configured as follows.

[0038]

Next, the operation of the present embodiment will be described. According to the first aspect of the present invention, the required fuel injection based on the change in combustion due to the change in the shape of the spray or the narrowing of the injection valve injection hole. When a change in the performance of the injection valve due to an increase in the pulse width is detected, the fuel injection pressure is increased, the penetration force of the fuel in the injection hole portion is increased, and deposits such as carbon on the injection valve injection hole portion can be removed.

According to the second aspect of the present invention,
Since the fuel injection when the fuel injection pressure is increased is performed under the condition that the in-cylinder pressure is lower, the pressure difference between the fuel injection pressure and the in-cylinder pressure is added, and the fuel penetration force of the injection hole portion is reduced. Since the size is further increased, the ability to remove deposits such as carbon at the injection hole of the injection valve is increased.

According to the third aspect of the present invention, a warning is issued when a change in the performance of the fuel injection valve is detected. It can be warned that this has occurred, which facilitates maintenance and facilitates engine performance maintenance.

Further, according to the present invention, the amount of change from the initial value of the injection amount of the injection valve after the end of the operation with the increased injection pressure is detected and learned. Even when the injection valve changes the injection characteristics, the air-fuel ratio feedback control is not performed by correcting the change in the injection amount of the fuel injection valve when calculating the fuel injection pulse width from the required injection amount. However, good combustion can be maintained.

When the relationship between the air-fuel ratio and the pulse width is tested in common to each embodiment, the change rate of the air-fuel ratio with respect to the pulse width may be used instead of the change rate of the pulse width with respect to the air-fuel ratio. Similar effects can be obtained.

[0043]

As described above, according to the present invention, the spray shape changes due to the contamination of the fuel injection valve by the carbon generated by the combustion of the direct injection internal combustion engine, the injection amount decreases, and the injection valve It is possible to obtain an effect that an operation failure can be detected in advance and self-restoration can be performed.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing the relationship between in-cylinder pressure and injection pressure in an in-cylinder direct injection internal combustion engine according to a first embodiment of the present invention.

FIG. 2 is a flowchart of a system according to the embodiment.

FIG. 3 is an explanatory diagram showing a relationship between in-cylinder pressure and injection pressure in a direct injection internal combustion engine according to a second embodiment of the present invention;

FIG. 4 is a flowchart of a system according to the embodiment.

FIG. 5 is a flowchart of a system according to a third embodiment of the present invention.

FIG. 6 is a flowchart of a system according to a fourth embodiment of the present invention.

FIG. 7 is an explanatory diagram showing a form of an air-fuel mixture in a combustion chamber of a direct injection type internal combustion engine using a conventional injection method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fuel injection valve 2 Spark plug 3 Piston 4 Ball provided on piston crown 5 Air flow in cylinder

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 41/32 F02D 41/32 A 41/34 41/34 N

Claims (5)

[Claims] 1. A direct injection type internal combustion engine which directly injects fuel into a cylinder, a means for detecting that the operation of the engine is under air-fuel ratio feedback control under a specific operating condition, and a pulse width for a required air-fuel ratio. Means for comparing the fuel injection pressure with the initial setting value when the pulse width for the required air-fuel ratio exceeds a predetermined value for the initial setting value. An in-cylinder direct injection internal combustion engine characterized by being raised. And means for comparing the pulse width with respect to the required air-fuel ratio with an initial set value when determining that the pulse width with respect to the required air-fuel ratio exceeds a predetermined value with respect to the initial set value. The direct injection type internal combustion engine according to claim 1, wherein the fuel injection pressure is increased by advancing the fuel injection pressure during the intake stroke. Means for comparing the pulse width with respect to the required air-fuel ratio with an initial set value, when it is determined that the pulse width with respect to the required air-fuel ratio exceeds a predetermined value with respect to the initial set value, The direct injection internal combustion engine according to claim 1, wherein the internal combustion engine is configured to warn that performance has deteriorated. 4. The control device according to claim 1, wherein after the fuel injection pressure is increased, the fuel injection pressure is returned to its original value, and the required injection of the injection valve is compared with a pulse width for a required air-fuel ratio before the fuel injection pressure is increased. The direct injection internal combustion engine according to claim 1, characterized in that it is configured to learn a correction value of the injection pulse width with respect to the amount. 5. A direct injection type internal combustion engine in which fuel is directly injected into a cylinder, a means for detecting that the operation of the engine is under air-fuel ratio feedback control under a specific operating condition, and an air-fuel ratio for a fixed pulse width. Means for comparing with the initial air-fuel ratio;
A direct injection type in-cylinder system characterized by increasing the fuel injection pressure when the change in the air-fuel ratio for a certain pulse width exceeds a predetermined value. Internal combustion engine.