JP2627838B2 - Electronically controlled fuel injection device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multipoint engine which cuts fuel (stops injection) when the number of revolutions rises to a certain extent during high engine rotation such as when the engine is idling, thereby avoiding engine damage. The present invention relates to an electronically controlled fuel injection device for an internal combustion engine of an injection system.

[0002]

2. Description of the Related Art When the engine speed rises beyond a limit,
Engine is damaged. Therefore, conventionally, as shown in FIG. 6, a fuel cut speed A for all cylinders is set, and when the engine speed exceeds this speed A, fuel cut is performed for all cylinders.

[0003]

However, for example, during idling, the number of revolutions rises sharply.
Even if the fuel is cut after exceeding the all-cylinder fuel cut rotation speed A, the rotation may overshoot and exceed the engine destruction rotation speed C. In view of such a conventional problem, the present invention provides an electronic control system for an internal combustion engine that can stabilize a maximum engine speed near an all-cylinder fuel cut engine speed without causing the engine speed to reach an engine destruction speed. It is an object to provide a fuel injection device.

[0004]

In order to achieve the above object, the present invention, as shown in FIG. 1, comprises an internal combustion engine having a fuel injection valve for each cylinder and injecting fuel in a predetermined order. In the electronic control fuel injection device, the following means (a) to (h) are provided. (A) Engine speed detecting means for detecting the engine speed at the time of outputting a reference signal from the crank angle sensor at the same interval as the injection interval. (B) Subtracting the previous engine speed from the detected current engine speed. (C) an engine speed estimating means for estimating the engine speed at the time of outputting the next reference signal based on the detected current engine speed and the amount of change. (D) First comparing means for comparing the next predicted engine speed with a predetermined high-speed fuel cut speed. (E) As a result of the comparison by the first comparing means, when the predicted engine speed is a predetermined high speed. When the fuel cut speed is exceeded,
All-cylinder fuel cut means for stopping fuel injection by the fuel injection valve for all cylinders; (f) comparing a value obtained by subtracting the next predicted engine speed from a predetermined high-speed fuel cut speed with a predetermined value; (G) count value setting means for setting a count value corresponding to the subtracted value when the subtracted value is equal to or less than a predetermined value as a result of the comparison by the second comparing means; Counting, and fuel cut means for each count value for stopping injection for the next injection cylinder every time the count value reaches the count value.

[0005]

According to the above arrangement, the following operations are provided. The engine speed detecting means detects the engine speed at the time of outputting the reference signal from the crank angle sensor at the same interval as the injection interval, and the engine speed change amount calculating means detects the previous engine speed from the detected engine speed. The amount of change is calculated by subtracting the engine speed.

Then, the engine speed at the next output of the reference signal is predicted by the engine speed prediction means based on the detected current engine speed and the amount of change. Thereafter, the first comparison means compares the next predicted engine speed with a predetermined high-speed fuel cut speed, and as a result, when the predicted engine speed exceeds the predetermined high-speed fuel cut speed. The fuel injection by the fuel injection valve is stopped for all cylinders by the fuel cut means for all cylinders.

If the predicted engine speed is equal to or lower than a predetermined high-speed fuel cut speed, the second comparing means determines
A value obtained by subtracting the next predicted engine speed from the predetermined high-speed fuel cut engine speed is compared with a predetermined value, and as a result, when the subtracted value is equal to or less than the predetermined value, the value subtracted by the count value setting means. Set the count value according to
The number of generations of the reference signal is counted by the fuel cut means for each count value, and the injection is stopped for the next injection cylinder every time the count value reaches the count value.

Accordingly, although the engine speed increases due to air blowing or the like and does not reach the predetermined fuel cut speed at the time of high revolution, when approaching this, the number of cylinders for which injection is stopped (thinning out) becomes closer as the engine speed approaches. By increasing the ratio, the rotation increase is suppressed before a predetermined high-speed fuel cut rotation speed is reached, and if it still exceeds, the fuel cut is performed for all cylinders.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment according to the present invention will be described below.
As shown in FIG. 2, a reference signal REF is output from the crank angle sensor 1 to the control unit 2 at every predetermined crank angle (for example, every 120 ° in the case of six cylinders).

An electric signal corresponding to the intake air flow rate Q is output to the control unit 2 from an air flow meter 3 provided in an intake passage of the engine. The control unit 2 incorporates a microcomputer including a CPU, a ROM, a RAM, and an input / output interface. The control unit 2 calculates an engine speed N based on a generation cycle of the reference signal REF, and calculates a fuel injection amount Tp (= K · Q / N; K
In a normal operating state, a drive pulse signal having a width corresponding to this is output to each fuel injector 4 in a predetermined order at a predetermined timing synchronized with the engine (sequential control).

The fuel injection valve 4 receives the drive pulse signal, opens for a time corresponding to the pulse width, and injects and supplies fuel adjusted to a predetermined pressure to the cylinder. Further, the microcomputer in the control unit 2 executes the fuel cut control routine shown in the flowchart of FIG. 3 when the reference signal is generated. Hereinafter, the routine of FIG. 3 will be described with reference to FIGS. 4 and 5.

In step 1 (referred to as S1 in the figure, the same applies hereinafter), the engine speed N is detected, and in step 2, the previously detected engine speed Nold is subtracted from the engine speed N to obtain a change ΔN Is calculated (see FIG. 4). In step 3, a predicted change amount ΔTN of the engine speed is calculated by subtracting the previous engine speed Nold from the current engine speed TN calculated last time.

Then, based on these, in step 4, the next predicted engine speed TNnew (= N + (ΔN / ΔTN) ×
ΔN) is calculated. Here, for the next time, step 5
In step 6, the engine speed N is stored and held as Nold, and in step 6, the next predicted engine speed TNnew is stored and held as the predicted engine speed TN.

In step 7, the next predicted engine speed TN
Compare new with the all-cylinder fuel cut rotation speed A. As a result of the comparison, when TNnew <A, in step 8, A-TNne
w is compared with a predetermined value d (= AB). Here, B is a predetermined rotation speed smaller than the all-cylinder fuel cut rotation speed A,
This is the rotation speed at which the thinned fuel cut is started.

As a result of comparison, when A-TNnew> d,
The routine is terminated as it is in order to continue the normal sequential injection. However, when A-TNnew ≦ d, the current engine speed N is between the full cylinder fuel cut speed A and the thinned fuel cut speed B. Therefore, the process proceeds to steps 9 to 14. In step 9, a count value C, which is an index of the thinning rate, is obtained according to the following equation.

C ≒ (A-TNnew) × k / ΔTN; Here, k is a constant, and C is an integer closest to the value on the right side. That is, the difference between the all-cylinder fuel cut rotation speed A and the next predicted engine rotation speed TNnew is obtained by A-TNnew, and the difference is multiplied by k / ΔTN, which becomes smaller as the difference becomes smaller, to obtain the next predicted engine rotation speed. As the rotational speed TNnew approaches the all-cylinder fuel cut rotational speed A, the value of C decreases and the rate of thinning increases (steps 11 to 13).

In step 10, the count value R of the reference signal is counted up. In step 11, the count value R of the reference signal is compared with the count value C. If R <C, the next injection is permitted as usual, and the routine is terminated. And R ≧ C
(When the count value R of the reference signal reaches a value equal to the count value C), the next injection is prohibited in step 13,
In step 14, the count value R of the reference signal is reset for the next time.

Specifically, as shown in FIG. 5, when the rotation speed N is close to the thinned fuel cut rotation speed B, the count value C is, for example, fuel cut every six cylinders. Increases, the fuel is cut every five cylinders and the engine speed N
Approaches the all-cylinder fuel cut rotation speed A, the state gradually approaches the all-cylinder fuel cut state, such as a fuel cut every three cylinders and a fuel cut every two cylinders.

On the other hand, if it is determined in step 7 that the next predicted engine speed TNnew ≧ the fuel cut rotation speed A of all cylinders, fuel injection is prohibited (fuel cut) for all cylinders in step 15 and the routine ends. I do. Here, step 1 corresponds to the engine speed detecting means, step 2 corresponds to the engine speed change amount calculating means, steps 3 and 4 correspond to the engine speed predicting means, and step 7 corresponds to the first comparison. Step 8 corresponds to the second comparison means, Step 9 corresponds to the count value setting means, Steps 10 to 13 correspond to the count value-specific fuel cut means, and Step 15 corresponds to the all cylinder fuel cut. It corresponds to a means.

[0020]

As described above, according to the present invention,
When the engine is running at high engine speeds, such as during idling, the engine speed must rise excessively and stabilize the maximum engine speed to around the fuel cut speed of all cylinders without causing the engine speed to reach the engine destruction speed. Can be.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing a configuration of the present invention.

FIG. 2 is a system diagram showing an embodiment of the present invention.

FIG. 3 is a flowchart showing control contents.

FIG. 4 is a diagram showing a state of predicting an engine speed;

FIG. 5 is a diagram showing a state of fuel cut when the engine speed is increased.

FIG. 6 is a diagram showing a behavior of an engine speed at the time of idling or the like showing a conventional problem.

[Explanation of symbols]

 Reference Signs List 1 crank angle sensor 2 control unit 4 fuel injection valve

Claims (1)

(57) [Claims] 1. An electronically controlled fuel injection system for an internal combustion engine having a fuel injection valve for each cylinder and injecting fuel in a predetermined order, the engine being configured to output a reference signal from a crank angle sensor having an equal injection interval. Engine speed detecting means for detecting the engine speed; engine speed change amount calculating means for calculating the amount of change by subtracting the previous engine speed from the detected current engine speed; and the detected current engine An engine speed prediction means for predicting the engine speed at the time of outputting the next reference signal based on the speed and the amount of change; and a second comparing the next predicted engine speed with a predetermined high-speed fuel cut speed at high speed. As a result of the comparison by the first comparing means and the first comparing means, when the predicted engine speed exceeds a predetermined high-speed fuel cut speed, the fuel injection by the fuel injection valve is stopped for all cylinders. Fuel cut hand And second comparison means for comparing a value obtained by subtracting the next predicted engine rotation speed from the predetermined high-speed fuel cut rotation speed with a predetermined value, as a result of the comparison by the second comparison means, A count value setting means for setting a count value according to the subtracted value when the count value is equal to or less than the count value, and counting the number of occurrences of the reference signal, and injecting the next injection cylinder every time the count value reaches the count value. An electronically controlled fuel injection device for an internal combustion engine, comprising: a count value-based fuel cut means for stopping.