JPH04318252A - Fuel injection quantity control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To perform control accurately to target injection probability even when it is changed during transient operation, relating to a fuel injection amount control device for suppressing vibration in a vehicle longitudinal direction at transient operation time of a multicylinder internal combustion engine. CONSTITUTION:Target injection probability Pi of the next cylinder is obtained (step 101) from the present operational condition to calculate(step 102, 103) a threshold value from a number of times ki of actually executing fuel injection in injection timing by N times in the past, and the Pi is compared with the threshold value to determine(steps 104 to 106) whether execution is possible or not of fuel injection of the next cylinder for fuel to be injected.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection amount control device for an internal combustion engine, and more particularly to a device for controlling the fuel injection amount to suppress vibrations in the longitudinal direction of a vehicle during transient operation of a multi-cylinder internal combustion engine.

0002

[Prior Art] In a vehicle equipped with a multi-cylinder internal combustion engine, during transient operation of the multi-cylinder internal combustion engine (hereinafter simply referred to as the internal combustion engine), a sudden change in the generated torque causes the vehicle to move forward and backward, known as shakuri. It is known that directional vibration occurs and deteriorates drivability. Therefore, in order to suppress this vibration, conventional fuel A fuel injection amount control device is known that sets a cut pattern and executes fuel injection removal (fuel cut) using the fuel cut pattern at the start of acceleration (Japanese Patent Laid-Open No. 1-315637).

0003

However, in the conventional fuel injection amount control device described above, the fuel cut pattern is determined according to the operating state immediately before the start of acceleration of the internal combustion engine. If the target injection probability changes due to a change in the operating state during acceleration, the injection omission probability will differ from the intended one, and the target smooth torque change may not be obtained. This is because the past history of injection omission is not taken into consideration at all during acceleration operation.

[0004] The present invention has been made in view of the above points.
It is an object of the present invention to provide a fuel injection amount control device for an internal combustion engine that solves the above-mentioned problems by determining whether to perform the next fuel injection based on the history of past injection omissions during transient operation.

[0005]

[Means for Solving the Problems] FIG. 1 shows a diagram of the principle configuration of the present invention that achieves the above object. As shown in the figure, the present invention provides fuel injection amount control that performs injection withdrawal control that appropriately thins out fuel injection in each cylinder during transient operation when injecting fuel independently into each cylinder of a multi-cylinder internal combustion engine 10. The apparatus includes a first calculation means 11 that calculates a target injection probability of the cylinder to which fuel is to be injected next from the current operating state of the internal combustion engine 10, and a threshold value for determining injection based on the past injection probability. The second calculation means 12 compares the target injection probability calculated by the first and second calculation means 11 and 12 with the threshold value, and determines the execution of fuel injection for the next cylinder to be injected with fuel. Determination means 13 for determining availability
It is configured to have the following.

[0006]

[Operation] In the present invention, in addition to the target injection probability depending on the current operating state of the internal combustion engine 10, it is determined whether or not to perform fuel injection based on the injection probability indicating the ratio of fuel injections performed in the past. Therefore, the target engine torque can always be generated even during transient operation.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 shows a configuration diagram of an internal combustion engine and its peripheral mechanisms equipped with an embodiment of the apparatus of the present invention. In the same figure, 21 is 4
It shows a structural cross section of an arbitrary cylinder of an internal combustion engine (engine), and a piston 23 that reciprocates in the vertical direction is housed in an engine block 22, and a combustion chamber 2
4 is communicated with an intake manifold 25 via an intake valve 26, and communicated with an exhaust manifold 28 via an exhaust valve 27. Further, an ignition plug 29 is provided such that a plug gap projects into the combustion chamber 24.

On the upstream side of the intake manifold 25,
A throttle valve 31 and an air flow meter 30 are provided in common to each of the four cylinders. The opening degree of the throttle valve 31 is adjusted in conjunction with an accelerator pedal 32, and the opening degree is detected by a throttle position sensor 33. An intake temperature sensor 34 for measuring intake air temperature is provided downstream of the air flow meter 30.

A fuel injection valve 35 injects fuel into the airflow passing through the intake manifold 25 of each cylinder according to instructions from a microcomputer 40, which will be described later. Also,
A catalyst device 36 for purifying exhaust gas is provided downstream of the exhaust manifold 28. The oxygen concentration detection sensor 37 is provided so as to partially protrude through the exhaust manifold 28 and detects the oxygen concentration in the exhaust gas before entering the catalyst device 36. A water temperature sensor 38 is provided so as to penetrate through the engine block 22 and partially protrude into the water jacket, and detects the temperature of the engine cooling water. 39 is an igniter that opens and closes the primary current of an ignition coil (not shown).

40 is a microcomputer, which includes a central processing unit (CPU) 41 that executes arithmetic processing, a read-only memory (ROM) 42 that stores computer programs, various maps, etc. in advance, and stores various data. It also consists of a random access memory (RAM) 43 from which it is read, a timer 44 that generates an interrupt signal at the time set by the CPU 41, an input interface circuit 45 and an output interface circuit 46, which are They are connected to each other via bus lines 47 on both sides.

Further, 50 is a distributor, which includes a cylinder discrimination sensor 51 that generates a reference position detection signal of the engine crankshaft, and a cylinder discrimination sensor 51 that generates an engine rotation speed signal, for example.
It has a rotation angle sensor 52 that generates a rotation angle every ℃A. The microcomputer 40 described above is the air flow meter 3.
0, intake temperature sensor 34, throttle position sensor 3
3. Various detection signals from the water temperature sensor 48, oxygen concentration detection sensor 37, cylinder discrimination sensor 51, rotation angle sensor 52, etc. are input to the input interface circuit 45, and based on these, the CPU 41 executes predetermined arithmetic processing. The obtained data is output to the igniter 3 via the output interface circuit 46.
9 to perform ignition timing control, and also send a control signal to the fuel injection valve 35 to control the fuel injection time, that is, the fuel injection amount per unit time. In this embodiment, the fuel injection valves of the four cylinders of the four-cylinder internal combustion engine 21 are caused to perform fuel injection independently, and each process of the first and second calculation means 11 and 12 and the determination means 13 is performed. is executed by this microcomputer 40.

Next, one embodiment of fuel injection amount control by the microcomputer 40 will be described. FIG. 3 is a flowchart showing an injection withdrawal control routine according to an embodiment of the present invention, which is executed every time from the fuel injection timing of each cylinder of the four-cylinder internal combustion engine 21 to the fuel injection timing of the next cylinder. First, the current operating state of the four-cylinder internal combustion engine 21 (
For example, the amount of change ΔTA in the opening degree of the throttle valve 31 (throttle opening degree) per unit time,
A two-dimensional map as shown in FIG. 4(A) stored in the ROM 42 is indexed from ΔTA and ΔNE, and then the fuel The cylinder to be injected (hereinafter, for convenience, the "next cylinder")
Calculate the target injection probability P (step 101
).

The above target injection probability P (denoted as Pi because the fuel injection timing of the next cylinder is the i-th one from the time of engine startup) is the number of times fuel injection is performed out of a predetermined number of fuel injection timings. It shows the target percentage of
As can be seen from Fig. 4(A), the same amount of change in engine speed △
In the case of NE, the larger the throttle opening change amount ΔTA is, the smaller it is, and when the same throttle opening change amount ΔTA is, the larger the engine speed change amount ΔNE is, the smaller it is.

That is, during acceleration, △TA and △NE are larger than during steady operation, so during acceleration, the target injection probability P
i is made small, and the number of times of injection skipping at the fuel injection timing is increased.

Next, the CPU 41 reads from the RAM 43 the number of times ki in which fuel injection was actually performed during the past N times (N is a preset natural number) total fuel injection timing for all cylinders, and loads it into the CPU 41. rear(
Step 102), set the threshold value for injection decision to (ki +
0.5)/(N+1) (1) (Step 103). However, when i≦N immediately after the engine starts, the above threshold value is (ki +0.5)/i
Although it is calculated using equation (2), in the following explanation, for simplicity, the threshold value will be explained as being calculated using equation (1).

Next, the target injection probability Pi is compared in magnitude with the threshold value (step 104), and Pi ≧(ki
+0.5)/(N+1), that is, the injection probability (ki
+1)/(N+1) is closer to or equal to Pi than the injection probability ki/(N+1) when fuel injection is thinned out next time, the injection skip flag F is set to execute injection in the next cylinder. Set it to “0” and store it in RAM4.
3 (step 105), and ends this routine (step 107).

On the other hand, as a result of the size comparison in step 104, when it is determined that Pi < (ki +0.5)/(N+1), that is, when fuel injection is performed next time, the injection probability (ki +1) /(N+1) is the injection probability ki when the next fuel injection is thinned out /(N+1
), the injection removal flag F is set to "1" so as not to perform injection in the next cylinder.
The data is stored in the AM 43 (step 106), and this routine is ended (step 107).

As described above, in the injection removal control routine shown in FIG.
1, the second calculating means 12 is realized in steps 102 and 103, and the determining means 103 is realized in steps 104 to 106, so that the actual injection probability approaches the target injection probability Pi. , fuel injection control is performed.

Next, fuel injection control by the microcomputer 40 will be explained with reference to FIG. FIG. 5 is a flowchart showing a fuel injection control routine, which is executed as part of the main routine. First, the fuel injection time TAU is calculated based on the following well-known formula (step 201).

[0020] TAU=TP×α+TV
(3) However, in the above formula, TP is the basic fuel injection time,
It is a value according to the ratio of intake air amount and engine speed NE,
α is a correction coefficient, which is a coefficient for correcting the target air-fuel ratio according to the engine usage condition, such as the engine cooling water temperature. In addition, the TV is voltage corrected, and due to voltage fluctuations, the fuel injection valve 3
This is a correction term for the change in injection amount due to the temporal change in operation that occurs in step 5.

Next, it is determined whether or not the fuel injection withdrawal flag F described above is "1" (step 202), and if it is "1", the fuel injection time TAU is cleared to "0" and then (
Step 203), and fuel injection for the next cylinder is performed (Step 204). That is, when F=1, even if fuel injection is performed in step 204 (in other words, even when the fuel injection timing has arrived), fuel injection will not be performed because TAU is "0". .

On the other hand, if it is determined in step 202 that the fuel injection removal flag F is not "1", that is, it is "0", then step 203 is skipped and step 20 is performed.
4, fuel injection is performed for the fuel injection time calculated in step 201.

Torque of internal combustion engine 21 (engine torque)
is a short period of N fuel injection timings,
Since it is approximately proportional to the number of times ki of actual fuel injection, according to this embodiment, even during transient operation, the engine torque at each fuel injection timing is reduced to 1/1/1 of that during normal operation (no injection removal). This means that it can be adjusted in steps of N times. Further, the engine torque in this embodiment is approximately expressed as Pi times the normal engine torque.

Therefore, even when normal fuel injection amount control causes a sudden change in engine torque and vibrations in the longitudinal direction of the vehicle, such as during transient operation when the throttle opening changes suddenly, the present embodiment is effective. In other words, it is possible to continuously generate the optimum engine torque according to the engine condition.
Moreover, the engine torque can be changed smoothly. Therefore, with the conventional device that uses the fuel cut pattern described above to suppress vibrations in the longitudinal direction of the vehicle during acceleration, it is not possible to deal with changes in the target injection probability during acceleration driving. Accordingly, it is possible to follow and respond to changes in the target injection probability. Furthermore, since fuel injection is thinned out during transient operation, fuel efficiency can also be improved.

Note that the present invention is not limited to the above-mentioned embodiments, and for example, the target injection probability Pi may be calculated based on the throttle opening TA from the throttle position sensor 33 and the engine rotation from the rotation angle sensor 52. It may also be calculated by indexing the two-dimensional map shown in FIG. 4(B) from the number NE, and the amount of change in throttle opening ΔTA and the amount of change in intake air amount per unit time from the air flow meter 30 Δ
It may be calculated by indexing the two-dimensional map shown in FIG. 4(C) from QN.

In the two-dimensional map shown in FIG. 4(B), the target injection probability Pi increases as the throttle opening TA and engine speed NE increase. This is to obtain the required engine torque by reducing the number of fuel injection withdrawals during high load operation where TA and NE are large.

Furthermore, in the two-dimensional map of FIG. 4(C), considering that △TA and △QN become larger during transient operation than during steady operation, the target injection probability Pi increases as △TA and △QN become larger. is calculated to a smaller value.

Furthermore, the present invention can be applied not only during acceleration but also during deceleration during high-speed operation.

[0029]

As described above, according to the present invention, the target engine torque can be generated even during transient operation, so even if the target injection probability changes during transient operation, the target injection probability after the change can be accurately It is possible to perform injection removal control that satisfies the probability.
It has the advantage of being able to more fully and smoothly suppress vibrations in the longitudinal direction of the vehicle during transient operation than in the past.

[Brief explanation of drawings]

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

FIG. 2 is a configuration diagram of an internal combustion engine equipped with an embodiment of the device of the present invention and its peripheral mechanism.

FIG. 3 is a flowchart showing an injection removal control routine according to an embodiment of the present invention.

FIG. 4 is a diagram showing examples of two-dimensional maps used to calculate the target injection probability in the flowchart of FIG. 3;

FIG. 5 is a flowchart of an embodiment of a fuel injection execution routine according to the present invention.

[Explanation of symbols]

10 Internal combustion engine 11 First calculation means 12 Second calculation means 13.Decision means 35 Fuel injection valve 40 Microcomputer

Claims (1)

[Claims] 1. A fuel injection amount control device for an internal combustion engine that performs injection withdrawal control to appropriately thin out fuel injection in each cylinder during transient operation when independently performing fuel injection in each cylinder of a multi-cylinder internal combustion engine, comprising: a first calculation means for calculating a target injection probability of a cylinder to which fuel is to be injected next from the current operating state of the internal combustion engine; A second calculation means for calculating a threshold value for determining injection based on an injection probability indicating a ratio, and a comparison between the target injection probability and the threshold value calculated by the first and second calculation means, respectively. 1. A fuel injection amount control device for an internal combustion engine, comprising: determining means for determining whether or not to perform fuel injection in a cylinder to which fuel is to be injected next.