JPH04101044A - Fuel feeding controller for multicylinder internal combustion engine - Google Patents

Abstract

PURPOSE:To reduce processing burden by correcting a basic fuel supply amount according to cylinders so that cylinder inner pressure rise rates become even among the cylinders when dispersion of air/fuel ratio is generated among the cylinders due to dispersion in fuel supply characteristics. CONSTITUTION:A fuel basic fuel supply amount for each cylinder is set by a setting means A according to an engine driving state, and by a correction amount according- to-cylinders setting means B, a correction amount of the basic fuel supply amount is set for each of the cylinders so that a rise rate of a cylinder inner pressure after ignition detected by a cylinder inner pressure detecting means C becomes even for each of the cylinders. And the basic fuel supply amount is corrected by a fuel supply amount setting means D based on the corrected value of each of the cylinders so as to set a final fuel supply amount for each of the cylinders, and a fuel supply means F of the corresponding cylinder is driven and controlled by a fuel supply control means E based on the final fuel supply amount. At this time, only when a steady driving state of an engine is detected by a steady driving detecting means G, setting of the correction value according to the cylinders is permitted by a correction amount setting permitting means H.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a fuel supply control device for a multi-cylinder internal combustion engine, and more particularly to a control device that can equalize the air-fuel ratio of each cylinder of a multi-cylinder internal combustion engine.

<Prior Art> Conventional fuel supply control devices for internal combustion engines include the following.

That is, while a fuel injection valve is provided for each cylinder, the engine intake air flow rate Q or the engine intake negative pressure pb, and the engine rotation speed N
Based on this, a basic fuel injection amount Tp is determined, and based on this basic fuel injection amount Tp, the fuel injection valves provided for each cylinder are controlled to open.

<Problems to be Solved by the Invention> By the way, in the so-called multi-point injection type fuel supply control device having a fuel injection valve for each cylinder as described above, there may be variations in the injection characteristics of each fuel injection valve. If this happens, the amount of fuel injected and supplied to each cylinder will vary, making it impossible to control the air-fuel ratio of each cylinder to its own target, which may result in surge torque or worsened exhaust properties due to variations in output between cylinders. There was a problem with this.

As a device to solve this problem,
Japanese Patent No. 2252 discloses that the indicated mean effective pressure for each cylinder is calculated based on the in-cylinder pressure, and the fuel injection amount is corrected and set for each cylinder so that the indicated mean effective pressure approaches a target.

However, as mentioned above, when calculating the indicated mean effective pressure, the sampling process of cylinder pressure is complicated.
There was a problem that the calculation load on the microcomputer to perform fuel control was large.

The present invention was developed in view of the above problems, and it detects variations in fuel supply amount (air-fuel ratio) for each cylinder by a simple sampling process of cylinder pressure, and based on the detection results, it detects variations in fuel supply amount (air-fuel ratio) for each cylinder. An object of the present invention is to provide a fuel supply control device that can equalize the fuel ratio.

<Means for Solving the Problems> Therefore, a fuel supply control device for a multi-cylinder internal combustion engine according to the present invention is configured as shown in FIG.

In FIG. 1, the basic fuel supply amount setting means sets the basic fuel supply amount by the fuel supply means provided for each cylinder in accordance with engine operating conditions.

Further, the cylinder pressure detection means is provided for each cylinder of the internal combustion engine to detect the cylinder pressure of each cylinder, and the cylinder-specific correction value setting means is configured to detect the cylinder pressure after ignition detected by the cylinder pressure detection means. The correction value of the basic fuel supply amount is set for each cylinder so that the rate of increase in the amount of fuel is uniform for each cylinder.

The fuel supply amount setting means corrects the basic fuel supply amount set by the basic fuel supply amount setting means based on the correction value for each cylinder set by the cylinder correction value setting means to obtain the final fuel supply amount. The supply amount is set for each cylinder, and the fuel supply control means drives and controls the fuel supply means for the corresponding cylinder based on the final fuel supply amount for each cylinder.

Here, it is preferable to provide a correction value setting permission means for permitting the cylinder-specific correction value setting means to set a correction value for each cylinder only when the steady-state operation state of the engine is detected by the steady-state operation detection means. .

<Operation> According to this configuration, since the rate of increase in cylinder pressure after ignition is approximately proportional to the output or torque generated in each cylinder, it is basically necessary to make the rate of increase in cylinder pressure after ignition uniform for each cylinder. If the fuel supply amount is corrected for each cylinder, the output or torque generated by each cylinder can be equalized among the cylinders, and as a result, the air-fuel ratio for each cylinder can be equalized, and the preparation for each cylinder can be made uniform. It is possible to absorb variations in the supply characteristics of the fuel supply means.

However, as mentioned above, since it is only necessary to detect the rate of increase in cylinder pressure after ignition, it is sufficient to sample the cylinder pressure at two different points after ignition. The calculation processing load for detecting air-fuel ratio variations is reduced.

Furthermore, by allowing the setting of cylinder-specific correction values only during steady operation, it is possible to prevent incorrect correction values from being set based on differences in output due to differences in intake air amount between cylinders during transient operation.

<Example> 'The present invention will be explained in detail below.

In FIG. 2 showing one embodiment, a 4-stroke, 4-cylinder internal combustion engine 1 includes an air cleaner 2. Throttle chamber 3.
Air is taken in through the intake manifold 4. The combustion exhaust gas is then transferred to the exhaust manifold 5. Exhaust duct 6, three-way catalyst 7. It is discharged into the atmosphere via the muffler 8.

The throttle chamber 3 is provided with a throttle valve 9 that opens and closes in conjunction with an accelerator pedal (not shown), and the intake air amount of the engine 1 is controlled by the throttle valve 9.

Furthermore, electromagnetic fuel injection valves 10a to 10d are installed in each branch of the intake manifold 4 as fuel supply means for injecting and supplying fuel to each cylinder, respectively, and a control unit 11 having a built-in microcomputer is installed. They are each independently controlled to open in response to injection pulse signals from the valves. The electromagnetic fuel injection valves 10a to 10d are supplied with fuel that is pressure-fed from a fuel pump (not shown) and adjusted to a predetermined pressure by a pressure regulator, and the fuel injection amount is controlled as the valve opening time. It is possible to do so.

Furthermore, cylinder pressure sensors 12a to 12d are provided as cylinder pressure detection means for detecting the cylinder pressure for each cylinder (#1 to #4), respectively.

Incidentally, the cylinder pressure sensors 12a to 12d mentioned above are
Although it may be of the type that is installed as a washer for the spark plug as disclosed in Publication No. 17432, etc., it is also possible to use a type of sensor that directly faces the combustion chamber and detects the cylinder pressure as an absolute pressure. Use or more desirable.

Further, a crank angle sensor 13 that detects the crank angle through the rotation of the camshaft is provided on the camshaft (not shown) of the engine I, and the crank angle sensor 13 is 180°, which corresponds to the stroke phase difference between the cylinders in 4 cylinders. a reference angle signal REF for each
A unit angle signal PO8 for each unit crank angle is output.

Further, the throttle valve 9 is provided with a potentiometer type throttle sensor 14 that detects the opening degree TVO of the throttle valve 9, and an air flow meter 15 such as a hot wire type is provided on the upstream side of the throttle valve 9. The intake air flow rate Q of the engine 1 is detected.

Furthermore, the exhaust duct 6 is provided with an oxygen sensor 16 that detects the oxygen concentration in the exhaust gas, which detects the oxygen concentration in the exhaust gas that varies depending on the air-fuel ratio, and determines the air-fuel ratio ( The average air-fuel ratio of each cylinder can be detected indirectly.

Here, the details of the fuel injection control by the control unit 11 will be explained based on the programs shown in the flowcharts of FIGS. 3 to 5, respectively.

In this embodiment, basic fuel supply amount setting means, cylinder-specific correction value setting means, and fuel supply amount setting means.

The functions of the fuel supply control means and the correction value setting permission means are provided by the control unit 11 in the form of software. Further, in this embodiment, the steady operation detection means corresponds to the throttle sensor 14 and the crank angle sensor 13, as will be described later.

The program shown in the flowchart of FIG. 3 is executed at every predetermined minute time (for example, lom s ). First, in step 1 (indicated as Sl in the figure; the same applies hereinafter), the throttle sensor 14 detects The opening degree TVO of the throttle valve 9 is input.

Then, in the next step 2, the opening change rate ΔTVO of the throttle valve 9 is calculated as the difference between the opening TVO input in step 1 during the previous execution of this program and the opening TVO input this time. .

Step 3 is the opening degree change rate Δ calculated in step 2.
It is determined whether the TVO is approximately zero.

When the opening change rate ΔTVO is approximately zero, the process proceeds to step 4, and it is determined whether the change rate ΔN of the engine rotational speed N calculated based on the detection signal from the crank angle sensor 13 is approximately zero. Here, when it is determined that ΔN is approximately zero, that is, when both ΔTVO and ΔN are approximately zero, it is determined that the engine 1 is in steady operation and jumps to step E.

On the other hand, if at least one of △TVO and ∆N is not approximately zero, the transient operating state of engine l is determined, and the process proceeds to step 5, where 1 is set to the flag ftr for determining whether engine l is steady or transient. The flag ftr is set so that the transient operating state of the engine 1 is determined by determining the flag ftr.

When the flag ftr is set to 1, the next step 6 is to set a predetermined value (for example, 100) to the counter Ttr for counting the elapsed time since transition from transient to steady operation.
Set.

In step 7, it is determined whether or not the counter Ttr is zero, and if it is not zero, the process proceeds to step 8, where the counter Ttr is decreased by one. On the other hand, step 7
When it is determined that the counter Ttr is zero, the process proceeds to step 9, where the flag ftr is set to φ, so that it is determined whether the engine 1 is in steady operation based on the determination of the flag ftr.

Since the counter Ttr is set to a predetermined value during the transient operation of the engine 1, the flag ftr is not immediately switched from 1 to φ even when the transition from transient to steady state occurs.
The flag ftr is set to φ after a predetermined period of time has passed since the transition to steady operation is detected based on the throttle valve opening TVO and the engine rotational speed N, and after the steady operation has stabilized.

The flag ftr is used to determine whether the engine l is steady or transient in a program shown in the flowchart of FIG. 5, which will be described later.

In the next step 10, the fuel injection amount (
The final fuel supply amount) Ti is calculated.

Ti−TpxChos(n)XαXC0EF+TsHere, Tp is the basic fuel injection amount (basic fuel supply amount),
It is calculated based on the intake air flow rate Q detected by the air flow meter 15, the engine rotational speed N, and the characteristic coefficients of the fuel injection valves 10a to 10d (Tp-Q/NXK). Also, C
Hos(n) is a correction coefficient for each cylinder that is set for each cylinder so that the rate of increase in cylinder pressure after ignition is uniform in each cylinder in the flowchart of FIG. 5, which will be described later. n) (n; cylinder number φ
-3), four types of fuel injection amounts Ti are calculated for each cylinder. Furthermore, C0EF is various correction coefficients mainly set for the cooling water temperature of the engine l, and α is an air-fuel ratio feedback for feedback-controlling the air-fuel ratio of the engine intake mixture detected by the oxygen sensor 16 to the target air-fuel ratio. The correction coefficient Ts is a correction amount for correcting changes in the effective valve opening time of the fuel injection valves 10a to 10d due to battery voltage.

The control unit 11 reads out the fuel injection amount Ti, which is set for each cylinder at every minute time, for each cylinder at a predetermined injection timing, and sets the fuel injection amount Ti to the corresponding fuel injection valves 10a to 10d. A drive signal with a corresponding pulse width is sent to the fuel injector 10a for a predetermined period of time.
~10d is driven open to inject and supply fuel to each cylinder.

On the other hand, the program shown in the flowchart of Fig. 4 is executed every 20 degrees before the compression TDC of each cylinder, and here, the normal ignition timing is set to 30 degrees to 50 degrees BTDC.
It is assumed that the flowchart in FIG. 4 is always executed immediately after ignition.

Then, in step 21, the detected value P of the cylinder pressure by the cylinder pressure sensors 12a to 12d provided in the cylinder currently undergoing the compression stroke is input.

In the next step 22, the cylinder pressure P input in step 21 is set as an initial value in Pl and stored.

This initial value P1 of the cylinder pressure P is used in the calculation process in the program shown in the flowchart of FIG. The program shown in the flowchart of FIG. 5 is executed at the compression TDC of each cylinder. First, in step 31, the in-cylinder pressure sensors 12a to 12d installed in the cylinder whose compression TDC is currently Cylinder pressure detection value P
Enter.

Then, in step 32, the initial value P1 inputted and stored when BTDC was 20° is inputted to the step 31 described above.
By subtracting it from the latest cylinder pressure P input in , the rate of increase in cylinder pressure P for each cylinder between BTDC20° and TDC after ignition is determined by dp/dθ(n) = (P-P 1)x
HO3(n) (n; cylinder number φ~3) is calculated.

The rate of increase in cylinder pressure after ignition is approximately proportional to the output torque of each cylinder, and the rate of increase in cylinder pressure for each cylinder is dp/
By determining dθ(n), it is possible to detect variations in output torque between cylinders, and by extension, variations in air-fuel ratio between cylinders.

Note that when calculating the rate of increase in the cylinder pressure P of each cylinder as described above, it is necessary to compensate for variations in the detection characteristics of the cylinder pressure sensors 12a to 12d so that the rate of increase can be accurately compared between cylinders. The correction coefficient for each cylinder for this purpose is shown as HOS (n). The correction coefficient for each cylinder HOS (n) is, for example, the correction coefficient for each cylinder pressure sensor 1 at a predetermined piston position before ignition during steady operation.
It is possible to set the cylinder pressures detected at 2a to 12d to be uniform.

Furthermore, in this embodiment, the amount of change in cylinder pressure P between predetermined crank angles after ignition is determined, or the amount of change in cylinder pressure P within a predetermined time after ignition may be determined. In this case, the rate of increase d of the cylinder pressure P per predetermined time is
p/dt has a value approximately equivalent to the engine output.

In the next step 33, the flag ftr that is set and controlled in the flowchart of FIG. 3 is determined. Here, when it is determined that the flag ftr is 1, it means that the engine l is in a transient operating state, and in such a transient operating state, variations in the amount of intake air between the cylinders may occur, which causes the cylinders to Since variations occur in the output torque (or output) between the cylinders, it is impossible to accurately detect the air-fuel ratio variations between the cylinders based on the rate of increase dP/dθ (or dp/dt).

Therefore, when it is determined in step 33 that the flag ftr is 1, the process advances to step 34, and the data of the rate of increase dp/dθ calculated in step 32 is used as data common to each cylinder and the increase rate for each cylinder is determined. rate d p/dθ(n
) set for each.

On the other hand, when it is determined in step 33 that the flag is ftr or φ, the engine 1 is in a steady operating state, and it can be assumed that the intake air amount of each cylinder is approximately equal, and the increase rate d The variation in p/dθ(n) between cylinders is
Since this simply represents the variation in air-fuel ratio between cylinders, the process advances to step 35 and the increase rate d p /
The target average value AVdp/dθ for making dθ(n) uniform is calculated as follows.

In the next step 36, the increase rate dp/dθ(
n) to the average value AVdp/dθ,
Correction coefficient (correction value) for each cylinder Chos (n) =
Set (AV d p/dθ)/(dP/dθ(n)).

Here, in the calculation of the fuel injection amount Ti in the flowchart of FIG. 3, the correction coefficient Chos(n) set for each cylinder is multiplied by the basic fuel injection amount Tp to set the fuel injection amount Ti for each cylinder. Then, the cylinder pressure increase rate d for each cylinder when the intake air amount of each cylinder is the same is
p/dθ(n), that is, the air-fuel ratio of each cylinder is corrected uniformly, and it is possible to correct the air-fuel ratio variation between cylinders due to the injection characteristic variation of the fuel injection valves 10a to 10d.

In this way, if air-fuel ratio variations between cylinders can be corrected and the air-fuel ratios of each cylinder can be made uniform, exhaust characteristics can be improved and surge torque can be reduced. Further, even if there is a variation in the injection characteristics of the fuel injection valves 10a to 10d, it can be corrected to some extent as described above, so that the required level of accuracy of the injection characteristics during manufacturing can be lowered and the yield can be improved.

However, as mentioned above, when detecting variations in output and torque between cylinders based on the cylinder pressure P, instead of calculating the indicated average effective pressure, the rate of increase in the cylinder pressure P after ignition is calculated. All you have to do is find the number of samples of cylinder pressure P, or
There is also the advantage that the calculation load on the control unit 11 for setting the correction coefficient Chos (n) is reduced.

In this example, the basic fuel injection amount (basic fuel supply amount)
In the above description, Tp is set based on the intake air flow rate Q detected by the air flow meter 15, but it is not limited to this. The basic fuel injection amount Tp may be set by a combination of the above, or the intake air amount may be determined and calculated from the cylinder pressure data before ignition.

<Effects of the Invention> As explained above, according to the present invention, when variations in the air-fuel ratio occur between cylinders due to variations in the fuel supply characteristics in the fuel supply means provided for each cylinder, this can be corrected for each cylinder. This is detected as a variation in the rate of increase in cylinder pressure after ignition, and the basic fuel supply amount is corrected for each cylinder so that the rate of increase in cylinder pressure is uniform between cylinders, making the air-fuel ratio uniform for each cylinder. This has the effect of not only improving exhaust properties and reducing surge torque, but also simplifying the sampling process of cylinder pressure for detecting air-fuel ratio fluctuations between cylinders, and reducing the computational processing load.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the configuration of the present invention, Fig. 2 is a system schematic diagram showing an embodiment of the invention, and Figs. 3 to 5 are flow charts showing the contents of the fuel supply means in the above embodiment. It is. ■...Internal combustion engine 4...Intake manifold 9...
・Throttle valve 10a to 10d...Fuel injection valve 1
1... Control unit 12a-12d...
・Cylinder pressure sensor 13...Crank angle sensor 1
4...Throttle sensor 15...Air flow meter patent applicant Fujioto Sasashima, agent of Japan Electronics Co., Ltd., patent attorney

Claims (2)

[Claims] (1) A fuel supply control device for a multi-cylinder internal combustion engine, which includes a fuel supply means for each cylinder of the internal combustion engine, and sets a basic fuel supply amount by the fuel supply means according to engine operating conditions. a setting means; an in-cylinder pressure detection means provided for each cylinder of the internal combustion engine to detect the in-cylinder pressure of each cylinder; cylinder-by-cylinder correction value setting means for setting a correction value for the basic fuel supply amount for each cylinder so that the basic fuel supply amount is set by the cylinder-by-cylinder correction value setting means; a fuel supply amount setting means for correcting the final fuel supply amount for each cylinder based on the set correction value for each cylinder; and based on the fuel supply amount for each cylinder set by the fuel supply amount setting means. 1. A fuel supply control device for a multi-cylinder internal combustion engine, comprising: a fuel supply control means for driving and controlling a fuel supply means for a corresponding cylinder; (2) Steady-state operation detection means for detecting a steady-state operating state of the internal combustion engine; and correction values for each cylinder by the cylinder-specific correction value setting means only when the steady-state operating state of the engine is detected by the steady-state operation detection means. The fuel supply control device for a multi-cylinder internal combustion engine according to claim 1, further comprising: correction value setting permission means for permitting setting.