JPH0233445A - Intake air quantity detecting device for engine - Google Patents

Abstract

PURPOSE:To prevent the over-rich state due to the erroneous detection of the intake air quantity by correcting the detection value of an air quantity detecting means based on the correction coefficient read out from a correction coefficient memory means and outputting the corrected detection value to the fuel feed quantity setting means of an engine as the detection value of the intake air quantity. CONSTITUTION:The decrease correction coefficient corresponding to the expected variation between the detection value of an air quantity detecting means B and the actual intake air quantity of an engine is stored in a correction coefficient memory means A for every operation state of the engine. The correction coefficient which is increased as the operation state of the engine becomes a high load is read out, the detection air quantity is corrected by it. The corrected detection value is outputted to the fuel feed quantity setting means C of the engine as the intake air quantity. The erroneous detection of the intake air quantity due to the intake air blow-over or the like is corrected, the fuel feed quantity control invariably based on the correct air quantity is performed.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention provides an intake air amount detection method that detects the intake air amount of an engine by providing, for example, a hot wire type air flow sensor in the intake passage in order to control the fuel supply of the engine. Regarding equipment.

(Prior Art) In an electronically controlled fuel injection device for an engine, an air flow sensor for detecting an air flow rate is generally provided in an intake passage, and a fuel injection amount is calculated according to the detected air flow rate. The airflow sensor used for fuel control of this engine is usually an intake responsive type (vane type) or a hot wire type.

By the way, these air flow sensors provided in the intake passage may output a detected value that deviates considerably from the amount of air actually taken into the engine, depending on the operating state of the engine. For example, in a vane type air foot sensor, overshoot due to inertia occurs during transitions such as acceleration or deceleration, so that the sensor outputs a detected value that is far from the actual amount of air. Therefore, in a fuel control device using such an air flow sensor,
Conventionally, as described in, for example, Japanese Unexamined Patent Publication No. 55-98624, a predetermined guard has been applied to the fuel injection amount calculated based on the detected value of an air flow sensor. The above-mentioned publication attempts to satisfy the required performance for each operating state by changing the guard value of the fuel injection amount according to the engine speed and load.

However, with this conventional method of guarding the fuel injection amount, it is not possible to efficiently eliminate the effects of intake pulsation and intake air blowback, which become noticeable especially when the engine is under high load. Especially in the case of a hot wire type air flow sensor,
The amount of air is detected by using the fact that the airflow absorbs the heat from the hot rays, and the direction of the flow cannot be detected, so if there is pulsation or blowback, it would normally have to be subtracted. The blowback amount is detected on the positive side. In addition, in the case of the hot wire type, there is also a drift of intake air due to the hot wire, and erroneous detection due to this will increase as the amount of intake air increases. For this reason, in the case of a hot wire type air flow sensor, the amount detected by the air flow sensor gradually deviates from the actual amount of intake air at high load sides where the engine has a large amount of intake air, and this also causes over-detection. However, false detections due to such blowback cannot be dealt with appropriately by simply placing a guard on the fuel injection amount and preventing the injection amount from exceeding a predetermined range as in the past. I can't.

In other words, by simply applying a guard to the set value of the fuel injection amount or the calculated value of the air amount, although the maximum value of the injection amount can be regulated, it is not possible to deal with deviations in the detected value on the way to the maximum regulated value.

FIG. 6 shows an example of control characteristics when the calculated value of the air amount (detected filling amount) is guarded. In the figure, the solid line is the calculated filling amount based on the output of the air flow sensor, and the maximum value is regulated. The two-dot chain line hypothetically shows a case where there is no maximum value regulation. When the actual intake air amount (actual filling amount) and the calculated value match, it is indicated by the dotted line in the same figure, and as is clear from this, the detection error remains as it is in the region up to the maximum regulation value, and the overflow is indicated by the dotted line. Rich occurs.

(Object of the Invention) The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to prevent the air-fuel ratio from becoming overrich due to erroneous detection of the amount of intake air caused by intake air blowback.

(Structure of the Invention) According to the present invention, the incorrectly detected amount of intake air amount (difference from the actual intake air amount) due to intake air blowback can be predicted as a value depending on the operating state of the engine, and therefore, It was discovered that erroneous detection of intake air amount can be accurately corrected by setting a correction coefficient for correcting the deviation of the predicted detected value as a map, and its configuration is shown in Figure 1. That's right. That is, the engine intake air amount detection device according to the present invention includes an air amount detection means for detecting the flow rate of air flowing through the intake passage of the engine, and an air amount detected by the air amount detection means and the actual intake air amount of the engine. A correction coefficient storage means for storing a reduction correction coefficient according to a predicted deviation width between the air amount and the air amount as a map in such a manner that it becomes larger as the operating state of the engine becomes higher in load; The engine is characterized by comprising a detected amount correcting means for correcting the detected value of the air amount detecting means based on the correction coefficient and outputting the corrected detected value to the fuel supply amount setting means of the engine as the detected value of the intake air amount. There is.

(Function) The correction coefficient storage means stores a reduction correction coefficient corresponding to the predicted deviation between the detected value of the air amount detection means and the actual intake air amount of the engine for each operating state of the engine. . Then, a correction coefficient that becomes larger as the operating state of the engine becomes higher in load is read out for the detected value of the air amount detection means, and the detected air amount is corrected accordingly. The detected value corrected in this way is output as the intake air amount to the fuel supply amount setting means of the engine. Therefore, erroneous detection of intake air amount due to intake air blowback etc. is corrected, and fuel supply amount control is always performed based on accurate air amount.

(Example) Examples will be described below based on the drawings.

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

In this embodiment, an ignition plug 3 is provided in the combustion chamber 2 of the engine 1, and the ignition plug 3 is connected to an ignition coil 5 via a power distributor 4.

Further, an injector 8 for fuel injection is provided in the intake passage 6 of the engine 1 in the vicinity of an intake boat 7, a throttle valve IO is provided upstream of the surge tank 9, and a hot-wire type air flow is provided further upstream of the surge tank 9. A sensor 11 is provided. Injector 8 and ignition coil 5 are controlled by control unit 12 . The control unit I2 receives an intake air amount signal which is the output of the air flow sensor 11, a crank angle signal from a crank angle sensor attached to the power distributor 4, etc., and calculates the ignition timing and fuel injection amount based on them. will be held.

Combustion air enters the intake passage 6 from an air cleaner (not shown) and is sucked into the combustion chamber 2 through the intake valve 13 along with fuel. In addition, the exhaust gas after combustion passes through the exhaust valve 14 into the exhaust passage! 5 and is discharged via a catalyst device 16.

The filling amount calculated based on the detected value of the air flow sensor 11 is corrected by a correction coefficient set in advance as a map according to the engine load and rotation speed. Third
The figure shows a map of this correction coefficient. As shown in this figure, the value of the correction coefficient (filling amount correction coefficient) Ce is l at low load (detected filling amount CE O/J'), and decreases as the load becomes high (CEO is large). It is set like this.

Furthermore, the lower the engine speed N, the smaller the value of CC1l. That is, a reduction correction amount of the intake air amount detection value is set as a coefficient in accordance with the predicted amount of intake air blowback. The amount of fuel injected from the injector 8 is calculated based on the corrected intake air amount detection value. Therefore, even if erroneous detection of the intake air amount occurs due to intake air blowback or the like, the fuel injection amount can always be calculated based on the actual intake air amount from which the influence of intake air blowback has been removed.

FIGS. 4 and 5 are flowcharts for executing specific control in this embodiment.

FIG. 4 shows a routine for calculating parameters for calculating the average flow rate of intake air, and is started by an interrupt every Ims. In this routine, first, the intake air flow rate Q output by the air flow sensor is read, then this is added up to find the total flow rate QSUM, and the number of additions NSUM is found.

FIG. 5 shows a routine for calculating the corrected filling amount in fuel injection control.

This routine starts with an intake top signal every 180 degrees of crank angle.

First, from the interrupt period, the engine rotation speed N
, is calculated.

Next, the raw average inspiratory flow rate Q S UM/N S UM
Calculate the filling amount CEO per revolution by multiplying by /N (where K is a constant), then QSUM and NS
Clear UM.

Next, from the map in FIG. 3, calculate the correction coefficient cc according to the current N, CEO. Read out. And this C to the CEO
A corrected filling amount CE is calculated by multiplying by 0°, and fuel injection is controlled based on the corrected filling amount CE.

In this embodiment, the correction coefficient map is set based on the detected filling amount and engine speed as described above, but the operating state parameters for setting the map are not limited to this. do not have.

Further, in the above embodiment, a correction map is set for the calculated filling amount, but it is also possible to provide a map that directly corrects the detected value of the air flow meter.

Further, in addition to correcting the detected air amount value using such a map, a maximum regulation value based on the conventional concept can also be used.

The present invention is applicable not only to hot wire type air flow meters but also to vane type air flow meters.

(Effects of the Invention) Since the present invention is configured as described above, it is possible to accurately correct the deviation in the detected air amount value due to intake air blowback. Therefore, it is possible to prevent the air-fuel ratio of the engine from becoming overrich due to incorrect detection of the intake air amount.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram of the present invention, Fig. 2 is an overall system diagram of an embodiment of the present invention, Fig. 3 is a map of correction coefficients in the embodiment, and Figs. 4 and 5 are the same embodiment. FIG. 6 is a flowchart showing the control characteristics of a conventional device. l: engine, 8: injector, 11: air flow sensor, I2: control unit.

Claims (1)

[Claims] (1) An air amount detection means that detects the flow rate of air flowing through the intake passage of the engine, and a predicted deviation width between the air amount detected by the air amount detection means and the actual intake air amount of the engine. a correction coefficient storage means for storing a corresponding reduction correction coefficient as a map such that it becomes larger as the operating state of the engine becomes higher in load; and detection by the air amount detection means based on the correction coefficient read from the correction coefficient storage means. An intake air amount detection device for an engine, comprising a detection amount correction means for correcting the detected value and outputting the corrected detection value as a detection value of the intake air amount to a fuel supply amount setting means of the engine.