JPH07167697A - Intake air flow rate detector for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve a detecting accuracy of intake air flow rate by detecting generation of a backflow even if an intake air pulsation including a backflow component occurs. CONSTITUTION:Maximum and minimum points of intake air flow rate Q to be detected by a temperature sensitive flowmeter are detected at steps S1, S2. A lapse time from the detected maximum point to the detected minimum point is calculated at a step S6. When a difference between the lapse time and a reference time to be estimated based on an engine operating state is a predetermined value or more at a step S7 and the minimum value is a predetennined value or less at a step S8, a backflow component is regarded as being detected, and a backflow correction is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake air flow rate detecting device for an internal combustion engine, and more particularly to a device for detecting an engine intake air flow rate based on a temperature-sensitive resistance arranged in an intake passage of the internal combustion engine.

[0002]

2. Description of the Related Art An electronically controlled fuel injection system for an internal combustion engine is equipped with an air flow meter (air flow meter) for detecting an intake air flow rate Q of the engine, and the intake air flow rate Q detected by this air flow meter is It is known that the basic fuel injection amount Tp = K × Q / Ne (K is a constant) is calculated from the engine speed Ne and the air flow meter is disclosed in Japanese Utility Model Laid-Open No. 59-78926. A temperature sensitive flow meter as disclosed in U.S. Pat.

In the temperature-sensitive flow meter, a so-called hot wire type or hot film type temperature sensitive resistor is arranged in the intake passage, and a current is supplied to the temperature sensitive resistor to generate heat at a constant temperature (resistance value). The temperature decrease due to the intake air is compensated for by increasing the current, and the intake air flow rate is calculated from the current value. That is, the temperature-sensitive flowmeter 1 in FIG. 2 will be described as an example. In addition to the temperature-sensitive resistance R _H (hot wire or hot film), temperature compensation resistance R _K, reference resistance R _s, fixed resistance R _{1 ,} R ₂ and the bridge circuit B is constituted by them.

The temperature sensing resistor R of the bridge circuit B
_H and the reference resistance R _s are connected in series, the potential of the voltage dividing point (the terminal voltage of the reference resistance R _s ) and the temperature compensation resistance R
_K and the potential at the voltage dividing point on the side where the fixed resistors R _{1 and} R ₂ are connected in series (the terminal voltage of the fixed resistor R ₂ ) are input to the differential amplifier OP. The supply current to the bridge circuit B is corrected via the transistor Tr according to the output of the dynamic amplifier OP.

That is, when the intake air flow rate of the engine increases, for example, when the bridge circuit B is in equilibrium,
The temperature sensitive resistance R _H is further cooled by this air flow, its resistance value decreases, and the terminal voltage of the reference resistance R _s increases,
The bridge circuit B becomes unbalanced and the output of the differential amplifier OP increases. As a result, the supply current to the bridge circuit B controlled by the transistor Tr increases, the temperature-sensitive resistor R _H is heated, and its resistance value increases, whereby the balanced condition of the bridge circuit B is restored.

Here, when the temperature of the intake air decreases, for example, the temperature-sensitive resistor R _H is cooled and its resistance value decreases, but the temperature-compensating resistor R _{K in the} same atmosphere as the temperature-sensitive resistor R _H.
At the same time, the resistance value of the bridge circuit B is reduced and the resistance value of the bridge circuit B is reduced, so that the current value supplied to the bridge circuit B is prevented from changing due to the temperature change of the intake air. Therefore, the intake air flow rate Q of the engine and the current supplied to the bridge circuit B correspond independently of the intake air temperature, and the intake air flow rate Q is measured by detecting the terminal voltage of the reference resistance R _s. be able to.

[0007]

By the way, when the throttle valve opening is large and the engine speed is in the low speed region or the high speed region, the intake pulsation including the backflow component is applied to the temperature sensitive flowmeter from the cylinder side. It may reach the temperature-sensitive resistance R _H. At this time, since the flow direction cannot be discriminated by the temperature-sensitive flow meter, the reverse flow is also detected in the same manner as the forward direction (see FIG. 8), and as a result, the true intake air flow rate (see FIG. 9) is obtained as the average flow rate. However, there was a problem that a large value would be detected.

When the intake air flow rate of the engine is detected to be larger than the true value as described above, the extra fuel is injected and supplied by the electronic fuel injection control based on the detected value to make the air-fuel ratio overrich. I will end up. The present invention has been made in view of the above problems, and it is possible to maintain the accuracy of flow rate detection even when intake pulsation including a backflow component occurs, and thereby improve the accuracy of fuel injection control. To aim.

[0009]

Therefore, as shown in FIG. 1, an intake air flow rate detecting device for an internal combustion engine according to the present invention responds to the intake air flow rate of a temperature-sensitive resistor arranged in an intake passage of the internal combustion engine. Temperature sensitive flow rate detecting means A for detecting the intake air flow rate of the engine based on the resistance value change, and flow rate maximum point detecting means for detecting the maximum point of the intake air flow rate change detected by the temperature sensitive flow rate detecting means A. B, a flow rate minimum point detection unit C that detects a minimum point of the intake air flow rate change detected by the temperature-sensitive flow rate detection unit A, and a reference from a maximum point of the intake pulsation to a minimum point based on the engine operating state. For comparing the reference time estimating means D for estimating the time and the reference time with the elapsed time from the maximum point detected by the flow maximum point detecting means B to the minimum point detected by the minimum flow rate detecting means C. Based on the A backflow determining section E for the intake air flow rate detected by the temperature sensitive type flow rate detecting means A was configured to include a reverse flow correction means F for correcting when it is determined that there backflow.

[0010]

When the intake pulsation including the backflow component is generated, the temperature-sensitive flow rate detecting means also detects the backflow component as the positive direction as shown in FIG. 8, and the backflow component is folded back in the positive direction. Output value will be output. Therefore, the elapsed time from the maximum point to the minimum point is shorter than when the backflow component does not exist. Therefore, the maximum point and the minimum point of the intake air flow rate change detected by the temperature-sensitive flow rate detecting means are detected, and the reference time from the maximum point to the minimum point of the intake pulsation estimated based on the engine operating state, When the difference from the detected maximum point to the minimum point has a predetermined time or more, it is determined that the minimum point is the minimum point generated by detecting the backflow component, and the backflow is present.

When it is determined that there is a backflow, the detected intake air flow rate is corrected based on the detected value.

[0012]

EXAMPLES Examples of the present invention will be described below. FIG. 2 shows the hardware configuration of the embodiment. In FIG. 2, the power supply voltage (battery voltage) V _B is applied to the temperature-sensitive flow meter 1 as the temperature-sensitive flow rate detecting means via the ignition switch 2. The output voltage Us of the temperature-sensitive flow meter 1 is input to the microcomputer 4 via the A / D converter 3.

In addition to the above, a rotation speed sensor 5 for detecting the engine rotation speed Ne (rpm) is provided, and the detection signal of the rotation speed sensor 5 together with the output voltage Us of the temperature-sensitive flow meter 1 is supplied to the microcomputer 4. It is designed to be input to. The opening TVO of the throttle valve (not shown)
A throttle sensor 6 for detecting is detected, and a detection signal is also input to the microcomputer 4.

Here, the microcomputer 4 determines the basic fuel injection amount based on the engine intake air flow rate Q detected by the temperature-sensitive flow meter 1 and the engine speed Ne detected by the speed sensor 5. Tp = K × Q / Ne (K is a constant) is calculated, and the final fuel injection amount Ti is calculated by appropriately correcting the basic fuel injection amount Tp.
The fuel supply to the internal combustion engine is electronically controlled by outputting an injection pulse signal having a pulse width corresponding to i to an electromagnetic fuel injection valve (not shown) at a predetermined timing synchronized with the engine rotation.

Since the structure and operation of the temperature-sensitive flow meter 1 have been described above, a detailed description of the temperature-sensitive flow meter 1 will be omitted here. Next, the microcomputer 4
The state of detection of the average intake air flow rate Qav of the engine performed by means of will be described with reference to the flowchart of FIG. still,
In the present embodiment, the functions of the maximum flow rate detecting means B, the minimum flow rate detecting means C, the reference time estimating means D, the backflow determining means E and the backflow correcting means F are as shown in the flow chart of FIG. 4 is provided as software.

In the flow chart of FIG. 3, first, in step 1 (denoted as S1 in the figure. The same applies hereinafter),
The maximum point H in the change of the intake air flow rate Q is detected based on the intake air flow rate Q obtained by converting the output voltage Us read through the A / D converter 3 by the conversion table. In detecting the maximum point H, the difference between the latest read intake air flow rate Q and the previously read intake air flow rate Q ₋₁ is sequentially calculated, and the point at which the sign of the difference is inverted from positive to negative, The maximum point H of the intake pulsation is determined (see FIG. 4).

That is, this step functions as the maximum flow rate point detecting means B. Then, the intake air flow rate Q at the maximum point H is stored as the maximum value CONV. In step 2, the minimum point L in the change of the intake air flow rate Q is detected based on the intake air flow rate Q obtained by converting the output voltage Us read through the A / D converter 3 by the conversion table.

The minimum point L is detected by the intake air flow rate Q read most recently and the intake air flow rate Q _-1 read last time.
And the point at which the sign of the difference is inverted from negative to positive is determined as the minimum point L of the intake pulsation (see FIG. 4). That is, the step has the function of the minimum flow rate point detection means C. Then, the intake air flow rate Q at the minimum point L is stored as the minimum value CONC.

At step 3, the opening TVO of the throttle valve detected by the throttle sensor 6 is TVO =
It is determined whether it is 0 and whether the engine has become idle. When it is judged that TVO = 0, the routine proceeds to step 4, where the maximum value CONV of the intake air flow rate Q stored at step 1 is set to the maximum value MAX.
Is stored as (MAX = CONV).

On the other hand, when it is judged that TVO ≠ 0, step 4 is skipped and the maximum value MAX currently stored is held as it is. In step 5, the number of samplings NUM from when the maximum value MAX of the intake air flow rate Q is obtained to when the next minimum point L is obtained is counted (see FIG. 5). In step 6, the elapsed time DUR from when the maximum value MAX of the intake air flow rate Q is obtained to when the next minimum point L is obtained is calculated according to the following equation (see FIG. 5). However, T _SAMP [msec] is a sampling period when sampling is performed.

DUR = NUM × T _SAMP [msec] Assuming that the number of cylinders is Cyl in a four-cycle in-line internal combustion engine, the intake stroke phase difference time, that is, the intake pulsation period T _M that does not include the backflow component is T _M = (60 × 2 × 1000) / (Ne × Cyl) [msec] (see FIG. 7). Here, when the backflow occurs, it occurs near the time of half or less of the intake stroke phase difference time. Therefore, the minimum point L in the change of the intake air flow rate Q due to the occurrence of the backflow is always The half cycle of the inspiratory pulsation period T _M is T _MM T _MM = (60 × 1000) / (Ne × Cyl) [msec] or less (see FIG. 6).

That is, the step is the reference time estimating means D.
Playing the function of. Here, in step 7, it is determined whether or not the difference between the half cycle T _MM of the intake pulsation cycle T _M and the elapsed time DUR calculated in step 6 is a predetermined time N × T _SAMP [msec] or more. Here, it is desirable that the minimum value of N is 1. That is, T _MM −DUR ≧ N × T _SAMP
When it is determined to be [msec], it can be determined that the minimum point L occurs before the half cycle T _MM of the intake pulsation cycle T _M.

Further, in step 8, the minimum value CONC
Is smaller than the intermediate value between the maximum value MAX stored in step 4 and the minimum value CONC _-1 read last time. And, CONC <(MAX + CONC _-1 )
When it is determined that the minimum point L is / 2, it is determined that the minimum point L is the minimum point L due to the occurrence of backflow, and the process proceeds to step 9.

That is, steps 7 and 8 serve the function of the backflow determining means. In step 9, the minimum value CONC
The air flow rate Q _G from the stored minimum point L to the next minimum point L _{NEXT is} calculated according to the following equation. Q _G = 2 × Q ₀ −Q where Q ₀ is the zero-time intake air flow rate obtained by converting the output voltage Us when the flow rate is 0.

That is, the step has the function of the backflow correction means F. In step 10, the maximum value MAX corresponding to the maximum value MAX stored in step 4 is set to the maximum value CO at the next maximum point H _NEXT for the next backflow determination.
It is determined whether or not it should be NV. If the number of cylinders is Cyl in a 4-cycle in-line internal combustion engine, even if a backflow occurs,
Since the backflow occurs in the vicinity of the time of half the intake stroke phase difference time or less, the cycle T _NEXT from the next minimum point L _NEXT to the true maximum point which is not noise is T _NEXT = ( It is calculated as 60 × 1000) / (MNe _NEXT × Cyl × 2) [msec].

However, MNe _NEXT is an average value of the engine speed Ne (rpm) at the next minimum point L _NEXT and the engine speed Ne (rpm) at the next maximum point H _NEXT . Therefore,
In step 10, from the next minimum point L _NEXT to the next maximum point H
Period DUR _NEXT until _NEXT is, determines whether to a maximum value CONV _NEXT in the T _NEXT or whether (DUR _NEXT ≧ T _NEXT) by the following maxima H _NEXT. When it is determined that the cycle DUR _NEXT is equal to or more than the T _NEXT , the maximum value CONV _NEXT at the next maximum point H _NEXT is stored as the next maximum value MAX in step 11, and the following calculation is performed. Run.

That is, intake pulsation including a backflow component is generated.
And between the pulsation peaks of the positive flow as shown in FIG.
, The pulsation peak as a result of detecting the backflow component appears.
Therefore, the interval from the adjacent maximum point to the minimum point is the inspiratory pulse.
Motion cycle T_MHalf cycle T_MMIt becomes the following. So adjacent
The interval from the maximum point to the minimum point is the intake pulsation cycle T_MHalf a round
Period T _MMIn the following cases, the minimum point this time corresponds to the backflow component
Authorize to do. Then, the minimum point L is
When it is recognized that the minimum point L is
Do not directly use the data for flow rate calculation,
Flow rate Q_GWill be used.

As described above, when the result of detecting the backflow component is not adopted and the intake pulsation including the backflow component occurs, the occurrence of the backflow is detected and corrected.
It is possible to avoid that the average flow rate is calculated to be larger than the true intake air flow rate due to the influence of the backflow component, so that the fuel control accuracy can be improved.

[0029]

As described above, according to the present invention, the reference time from the maximum point to the minimum point of the intake pulsation is estimated based on the engine operating state, and even if the intake pulsation including the backflow component is generated, the maximum value is obtained. There is an effect that the backflow can be judged based on the time lapse from the point to the minimum point and the reference time, and the intake air flow rate based on the backflow can be obtained, thus contributing to the improvement of the accuracy of fuel injection control. .

[Brief description of drawings]

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

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

FIG. 3 is a flowchart showing the control contents in the above embodiment.

FIG. 4 is a time chart showing how the maximum and minimum points of the intake air flow rate are detected.

FIG. 5 is a time chart showing an elapsed time DUR.

FIG. 6 is a time chart showing a state of intake pulsation including a backflow component.

FIG. 7 is a time chart showing how intake pulsation does not include a backflow component.

FIG. 8 is a time chart showing the occurrence of an average flow rate error due to backflow component detection.

FIG. 9 is a time chart showing a true engine intake air flow rate when a backflow component is generated.

[Explanation of symbols]

1 Temperature-sensitive flow meter 2 Ignition switch 3 A / D converter 4 Microcomputer 5 Rotation speed sensor _RH Temperature-sensitive resistance _RH

Claims (1)

[Claims] 1. A temperature sensitive flow rate detecting means for detecting an intake air flow rate of an engine based on a resistance value change of a temperature sensitive resistance arranged in an intake passage of an internal combustion engine according to an intake air flow rate, and the temperature sensitive system. Flow rate maximum point detecting means for detecting a maximum point of the change in intake air flow rate detected by the flow rate detecting means, and flow rate minimum point detecting means for detecting a minimum point of the intake air flow rate change detected by the temperature-sensitive flow rate detecting means A reference time estimating means for estimating a reference time from a maximum point of intake pulsation to a minimum point based on the engine operating state; and a maximum point detected by the maximum flow rate detecting means detected by the minimum flow rate detecting means. Based on the comparison between the elapsed time to the minimum point and the reference time, backflow determination means for determining the presence or absence of backflow, and inhalation detected by the temperature-sensitive flow rate detection means when it is determined that there is backflow Correct the air flow rate Intake air flow rate detection device for an internal combustion engine, characterized in that it is configured to include a reverse flow correction means.