JP2002235582A - Fuel injection amount control method for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection amount control method for an internal combustion engine capable of reducing a variation in rotation of the engine by eliminating the updating of a fuel injection correction amount for a single rotation component varied by an external force such as the loads of an air conditioner compressor and a vacuum pump. SOLUTION: When the engine is run idle, a difference between rotation variable deviations for each cylinder is detected. When the difference between the rotation variable deviations in a previous time and this time for each cylinder exceeds a specified value SK (threshold), a correction to a fuel injection amount of a corresponding cylinder is stopped. Accordingly, the fuel correction amount for the single rotation variable component based on the specifications and variations of the air conditioner compressor and vacuum pump is not updated. Thus, discomfortable cyclic rotation variation caused during the idle run can be reduced, and stable and smooth idle run can be realized to provide comfortableness.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fuel injection type multi-cylinder engine (hereinafter referred to as an engine) such as a gasoline engine or a diesel engine. The present invention relates to a fuel injection amount control method for an internal combustion engine that adjusts and corrects the amount of fuel injection.

[0002]

2. Description of the Related Art In an engine such as a gasoline engine or a diesel engine, fuel is controlled so as to have a uniform injection amount common to all cylinders. To achieve this, the accuracy of the components between the cylinders was increased to the limit, but it was ineffective against disturbances caused by changes over time and variations in the opening and closing timing of intake and exhaust valves on the engine side. For this reason, the same stable combustion cannot be obtained in all the cylinders, and there is a possibility that unpleasant periodic rotation fluctuations may be induced particularly during idle rotation at no load.

[0003] By the way, in recent years, the demand for improvement in fuel efficiency has reduced the idling rotational speed to a relatively low level. In particular, passenger cars are required to have a smoother idling rotational state from the viewpoint of comfort. For this reason, there has been a major problem in how to reduce unpleasant periodic rotation fluctuations and the like that occur during idling and achieve stable idling.

To cope with this problem, a fluctuation control method has been proposed as a measure for reducing the rotation fluctuation of the engine. In this variation control method, a variation in the rotational speed of each cylinder is detected during idle rotation, an injection correction amount for each cylinder is determined according to the variation amount, and the correction amount is updated (learned) for each injection. .

[0005]

However, in an engine, a spontaneous rotation fluctuation that is not synchronized with the first order of the explosion is caused depending on the specifications of the cooling / heating compressor or the vacuum pump or the variation of the thing. In the above-described fluctuation control method, there is a disadvantage that the fuel injection correction amount is updated even for such a single rotation fluctuation component due to the external force, and the rotation fluctuation of the engine is rather increased.

[0006] The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to provide a multi-cylinder internal combustion engine in a predetermined operating state.
The difference in the rotational speed between the previous cycle and the current cycle for each cylinder is detected, and when this difference exceeds a predetermined value, the correction for the fuel injection amount of the corresponding cylinder is stopped, and a predetermined level is set from the viewpoint of comfort. An object of the present invention is to provide a method for controlling a fuel injection amount for an internal combustion engine which reduces unpleasant periodic rotation fluctuations generated during an operation state and realizes stable and smooth rotation.

[0007]

According to a first aspect of the present invention, there is provided a fuel injection amount control method for an internal combustion engine which corrects a fuel injection amount for each cylinder of a multi-cylinder internal combustion engine according to an operation state.
When the multi-cylinder internal combustion engine is in a predetermined operation state, a variation in rotation speed for each cylinder is detected. If the difference between the previous and current rotation speeds of each cylinder exceeds a predetermined value, updating of the correction for the fuel injection amount for each cylinder is stopped.

As described above, in a predetermined operating state, a variation in the rotational speed of each cylinder is detected, and when a difference between the previous and current rotational speeds of each cylinder exceeds a predetermined value, The correction for the fuel injection amount of the corresponding cylinder is stopped. Therefore, the injection correction amount is not updated for a single rotation fluctuation component based on an external force such as a load of a cooling / heating compressor or a vacuum pump. This reduces unpleasant periodic rotation fluctuations that occur during a predetermined driving state from the viewpoint of comfort, and achieves stable and smooth rotation.

(Regarding claim 2) The predetermined operating state is as follows.
The multi-cylinder internal combustion engine is in an idle rotation state, and a difference between the rotation speeds of the respective cylinders in the idle rotation state is detected. For this reason, during idling, variations in the rotational speed of each cylinder are detected, and if the difference between the previous and current rotational speeds of each cylinder exceeds a predetermined value, the fuel injection of the corresponding cylinder is performed. Stop the correction for the quantity.

[0010] (Claim 3) The variation in the rotational speed of each cylinder is the rotational fluctuation deviation at the time of fuel injection for each cylinder. When the difference exceeds a predetermined value, updating of the correction for the fuel injection amount is stopped.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment in which the present invention is applied to a diesel engine as a multi-cylinder internal combustion engine will be described with reference to the drawings. In FIG. 1, (a) shows the cylinder numbers (0 to 3) of the four cylinders of the diesel engine.
(B) shows the engine speed for each cylinder, and (c) shows the rotation fluctuation level (variation in rotation speed) for each cylinder.
(D) shows the level of the rotation fluctuation deviation for each cylinder, and (e) shows the difference of the rotation fluctuation deviation (difference in rotation speed) for each cylinder. (F) is a correction amount of the fuel injection amount for each cylinder, and (g) is a fuel injection amount command value. (H) is a pulse diagram showing an opening / closing timing for driving a spill valve for adjusting a fuel injection amount.

FIG. 2 is a flowchart showing a method for controlling the fuel injection amount for the internal combustion engine. In step S1 of FIG. 2, as shown in FIG. 3, the determination circuit 1 connected to the engine control unit ECU determines whether the operation state of the diesel engine is idling. Based on this identification, it is determined whether a predetermined learning (correction) condition is satisfied for each cylinder. If the determination is negative, the process proceeds to step S9, where the post-cylinder correction injection amount command value (QFIN + QCYk × MK) is canceled, and fuel injection is performed for each cylinder based on the pre-cylinder correction injection amount command value (QFINC). The amount is controlled.

If the learning (correction) condition is satisfied in step S1, the process proceeds to step S2. Here, the maximum rotation speed time (TNHk) for each cylinder by the rotation speed sensor 2
And a minimum rotation time (TNLk) is detected based on the pulse interval time. The difference between these rotation speeds becomes the rotation fluctuation time (DNEk), and the rotation fluctuation width for each cylinder is calculated.

In step S3, the fluctuation calculation circuit 3 calculates the average rotation fluctuation (DNLT) of the rotation fluctuation time (DNEk) with respect to the number of cylinders (DNLT ← ΣDNEk /
4).

In step S4, the average rotation fluctuation (DNLT) and the rotation fluctuation time (DNEk) are calculated by the deviation calculation circuit 4.
And the rotational fluctuation deviation (DDNE) for each cylinder
k) is calculated.

In step S5, the cylinder correction amount (QCY
k), that is, it is determined whether or not the correction of the fuel injection amount for each cylinder should be updated. This is performed by calculating the difference between the present rotational fluctuation deviation (DDNEk) and the previous rotational fluctuation deviation (DDNEOLDk) by the difference operator 5. Then, a spontaneous rotation fluctuation component is generated based on an external force such as a load of a cooling / heating compressor or a vacuum pump,
If the difference between the present and previous rotation fluctuation deviations exceeds a predetermined value SK (threshold value), the process proceeds to step S8 to cancel the current rotation fluctuation deviation (DDNEk). Therefore, the correction for the fuel injection amount is stopped, and the control of the fuel injection amount is determined based on the previous rotation fluctuation deviation (DDNEOLDk).

Then, the process proceeds to step S9, in which the post-cylinder correction injection amount command value (QFIN + QCYk × MK) is canceled, and the fuel from the injection nozzle I is supplied to each cylinder based on the pre-cylinder correction injection amount command value (QFINC). The injection amount is controlled. This situation is indicated by a symbol A in FIGS. 1 (d) to 1 (h). When the difference between the present and previous rotation fluctuation deviations exceeds SK (threshold), each cylinder correction amount (f) And the fuel injection amount command value (g) remains unchanged as shown by the solid line,
It turns out that it is not updated.

In step S5, the present rotational fluctuation deviation (DDNEk) and the previous rotational fluctuation deviation (DDNEOL)
If the difference from Dk) is equal to or less than SK (threshold), the process proceeds to step S6. In step S6, an integral correction amount (DQCMP) is calculated based on the current rotation fluctuation deviation (DDNEk), and the process proceeds to step S7.

In step S7, the correction amount update arithmetic circuit 6
The correction amount (QCY _ki ) for each cylinder is calculated by the equation (QCY
_ki-1 ± DQCMP), and the fuel injection amount from the injection nozzle I is correctly corrected for each cylinder.

As described above, when the diesel engine is idling, the difference in rotation fluctuation deviation for each cylinder is detected. Then, when the difference between the previous and current rotation fluctuation deviations for each cylinder exceeds a predetermined value SK (threshold), the correction for the fuel injection amount of the corresponding cylinder is stopped. Therefore, the injection correction amount is not updated for a single rotation fluctuation component based on an external force such as a load of a cooling / heating compressor or a vacuum pump. Thus, unpleasant periodic rotation fluctuations occurring during idling from the viewpoint of comfort are reduced, and stable and smooth idle rotation can be realized.

[Modifications] (1) In the embodiment of the present invention, as the variation of the rotation speed for each cylinder, the rotation variation deviation is calculated by the difference between the average rotation variation (DNLT) and the rotation variation time (DNEk). However, the rotation fluctuation deviation may be calculated from the difference between the rotation fluctuation median (or the rotation fluctuation intermediate value) and the rotation fluctuation time (DNEk). (2) The magnitude of SK (threshold), which is the difference between the previous and current rotation fluctuation deviations for each cylinder, can be set as desired in relation to the required degree of vibration reduction and quietness. it can.

(3) The injection amount adjustment method is not limited to the electromagnetic method, and can be applied to a structure in which a spill ring is moved via an eccentric ball by a shaft connected to a rotor. (4) Further, the present invention is not limited to the diesel engine, and can be variously modified in a concrete implementation such as being applicable to a general fuel injection type multi-cylinder internal combustion engine without departing from the gist of the present invention.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing variables of fuel injection control according to an embodiment of the present invention in a graph.

FIG. 2 is a flowchart showing a fuel injection amount control method according to one embodiment of the present invention.

FIG. 3 is a block diagram according to one embodiment of the present invention.

[Explanation of symbols]

 DNLT Average rotation fluctuation DDNEk Current rotation fluctuation deviation DDNEOLDk Previous rotation fluctuation deviation SK Difference in rotation fluctuation deviation (threshold) I Injection nozzle

Claims (3)

[Claims] 1. A fuel injection amount control method for an internal combustion engine that corrects a fuel injection amount for each cylinder of a multi-cylinder internal combustion engine according to an operation state. When the internal combustion engine is in a predetermined operating state, the variation of the rotation speed of each cylinder is detected.If the difference between the rotation speed of the previous cylinder and the variation of the current rotation of each cylinder exceeds a predetermined value, each cylinder is detected. A method for controlling a fuel injection amount for an internal combustion engine, wherein updating of correction for a fuel injection amount for each time is stopped. 2. The method according to claim 1, wherein the predetermined operating state is an idle rotation state of the multi-cylinder internal combustion engine, and detects a difference in rotation speed of each cylinder when the multi-cylinder internal combustion engine is in an idle rotation state. 2. The method according to claim 1, wherein the fuel injection amount is controlled for an internal combustion engine. 3. The variation in the rotational speed of each cylinder is as follows:
This is the rotational fluctuation deviation during fuel injection for each cylinder.The rotational fluctuation deviation during fuel injection is determined for each cylinder, and the difference between the rotational fluctuation deviation between the previous and current injections for each cylinder is calculated. 3. The fuel injection amount control method for an internal combustion engine according to claim 1, wherein the update of the correction for the fuel injection amount is stopped when it is detected that the fuel injection amount exceeds a predetermined value.