JPH04116248A - Intake air flow measuring device for internal combustion engine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an intake air flow rate measuring device for an internal combustion engine, and more specifically, it outputs a detection signal that continuously changes according to the intake air flow rate of the engine. The present invention relates to an intake air flow rate measuring device that measures an intake air flow rate based on an output.

<Conventional technology> Conventionally, internal combustion engines equipped with this type of intake air flow rate measuring device are electronically controlled fuel injection equipped with an intake air flow rate measuring device (air flow meter) using a temperature-sensitive resistor using a platinum thin film. There is a system car (Japanese Unexamined Patent Publication No. 61-10
(See Publication No. 2522, etc.).

This consists of a bridge circuit that includes a temperature-sensitive resistor installed in the intake passage of the engine, and uses changes in the resistance value of the temperature-sensitive resistor based on changes in the intake air flow rate to determine the intake air flow rate QAN.
A continuous detection signal S having a current value that continuously changes in accordance with the current value is output.

The continuous detection signal SAN is input to the control unit, but the ROM of the microcomputer built in the control unit stores data of the discontinuous intake air flow rate QDI using the continuous detection signal SAN as a parameter. (digital signal) is stored,
Based on the continuous detection signal S AN, a discontinuous intake air flow rate Q a + of a predetermined number corresponding to the data is determined based on the continuous detection signal S AN.
Search for data related to.

That is, the control unit obtains a digital signal QDI of the intake air flow rate QAH, which is used in calculations to be described later.

Further, in view of cost issues and limitations in using digital signals, values other than the digital data QDI are converted from the analog value QAN to the digital value QDI by linear interpolation.

The control unit then outputs the retrieved digital intake air flow rate signal Q. 1 and the engine rotation speed N detected by a rotation speed sensor such as a crank angle sensor, the basic fuel injection amount Tp (=KXQ, , /N; is a constant)
At the same time, various correction coefficients C0FF according to engine operating conditions such as engine cooling water temperature, air-fuel ratio feedback correction coefficient α, correction amount due to battery voltage (corrects change in effective valve opening time of the fuel injection valve) Ts and After calculating the basic fuel injection amount Tp, the basic fuel injection amount Tp is corrected and calculated to obtain lx
Final fuel injection amount Ti (=TpXCOEFXα+Ts
).

When the fuel injection amount Ti is set in this way, an injection pulse signal with a pulse width corresponding to the fuel injection amount Ti is output to the electromagnetic fuel injection valve at a predetermined timing, and a predetermined amount of fuel is injected into the engine. Supplied.

<Problem to be Solved by the Invention> By the way, the output characteristic of the continuous detection signal SAN with respect to the intake air flow rate QAN is nonlinear as shown in FIG. curve).

Therefore, when converting the analog value Q AN to the digital value Q DI using the linear interpolation method for values other than the digital data Q DI, conversion errors may occur due to the upward convexity of the curve. Become.

That is, regarding points A and B in FIG. 5, digital values QA9. and QBtl, with no error (is it possible to convert? For the 0 point, first perform linear interpolation based on the analog values QAAN and QBAN to calculate the C' point, and convert to the digital value QC' for the C° point. Therefore, as shown in FIG. 5, ΔD=QC'.

-QCD, an error will occur, and when calculating the fuel injection amount, etc., the calculation will be performed for an intake air flow rate that is larger than the actual intake air flow rate, and the air-fuel ratio will become richer. There was a problem that the exhaust emission characteristics deteriorated.

Here, it is possible to reduce the error by increasing the number of bases as much as possible, but due to limitations related to digital quantity,
There are cost restrictions and there are limits.

The present invention was made in view of the above-mentioned conventional situation, and is designed to minimize the error when converting a continuous intake air flow rate detection signal into discontinuous intake air flow rate data Q, 1 in a control unit. An object of the present invention is to provide an intake air flow rate measuring device for an internal combustion engine that allows the air-fuel ratio to converge to a target air-fuel ratio as quickly as possible and provides good exhaust emission characteristics.

<Means for Solving the Problems> For this reason, in the present invention, as shown in FIG. detection signal output means A,
data storage means B for storing intake air flow rate data discontinuously corresponding to the detection signal; data search means C for searching for a plurality of data in the vicinity of the detection signal; and data search means C for searching for a plurality of data near the detection signal; interpolation calculation means for calculating the intake air flow rate by interpolation using multiple data;
In the intake air flow measuring device for an internal combustion engine, the detection signal output means A outputs a linearized continuous detection signal.

<Operation> With such a configuration, since the detection signal output means A outputs a linearized continuous detection signal, the interpolation calculation means uses the plurality of discontinuous intake air flow rate data stored in the data storage means B. When calculating the intake air flow rate by interpolation, it is possible to suppress the occurrence of errors as much as possible.

<Example> Embodiments of the present invention will be described below based on the drawings.

The intake air flow rate measuring device shown in FIG. 2 is a hot wire flowmeter 10.
A hot wire Rh placed in the intake air passage of an internal combustion engine
In addition to incorporating the bridge circuit 1, which is arranged on one side,
A pair of detection terminals T3. of this bridge circuit 1. A negative feedback loop is formed to variably control the voltage applied between the pair of power supply terminals TI and T2 of the bridge circuit 1 so that the potential difference between the pair of detection terminals T3 and T4 is constant.
A detection voltage V corresponding to the air flow rate in the intake air passage is taken out from one side (T4) of T4. That is, the hot wire flow meter 10 corresponds to a detection signal output means A that outputs a detection signal that continuously changes depending on the intake air flow rate of the engine.

The bridge circuit 1 includes a fixed resistor R1 as well as the hot wire Rh.
, R3 and a variable resistor R2. Further, the negative feedback loop is formed by an operational amplifier 2°NPN transistor 4, and its operating power source Vs is taken from the vehicle battery.

Here, as a configuration according to the present invention, the output voltage SAN of the operational amplifier 2 is connected to the NPN) transistor 12. Diode 13. The output voltage v of the intake air flow rate measuring device is input to the logarithmic converter 11 composed of a capacitor 14 and the like.
Output as s. Here, the input voltage SAN is converted into a linearized output voltage 6 by the logarithmic converter 11. Further, the comparison power supply voltage of the logarithmic converter 11 is taken from the constant voltage circuit 15.

That is, as shown in FIG. 3, the output voltage SAN of the hot wire flowmeter 10 is converted by the logarithmic converter 11 into a linearized continuous signal v8. Then, the A/D converter 21 converts it into a digital signal SDI.

On the other hand, the ROM of a microcomputer (not shown) built into the control unit stores intake air flow rate data Q, 1 that corresponds discontinuously to the continuous signal VS.
(digital signal) is stored, and based on the digital signal SDI, the microcomputer
A plurality of pieces of intake air flow rate data Q corresponding to values near DI are retrieved and converted.

That is, it corresponds to the ROM or data storage means of a microcomputer, and corresponds to the microcomputer or data retrieval means.

Furthermore, values other than the discontinuous intake air flow rate data Q DI are converted by interpolation using a plurality of intake air flow rate data Q DI corresponding to values in the vicinity of S o +. also functions as an interpolation calculation means.

In addition, when using a microcomputer to calculate values other than the above-mentioned Q DI data by interpolation, the hot wire flowmeter 1
Since the output voltage SAN output by 0 is a continuous signal VS linearized by the logarithmic converter 11, the curve when performing interpolation based on the radix (QD, ) is upwardly convex. The occurrence of errors caused by this can be suppressed as much as possible.

Then, the basic fuel injection amount Tp is calculated based on the engine rotation speed N by the microcomputer.

Therefore, as explained above, according to this embodiment, the output voltage SAN of the hot wire flowmeter 10 is converted into a linearized continuous signal V by the logarithmic converter 11, and the continuous signal V is used to Since the air flow rate data QD is searched and calculated, the error during conversion is small, and the intake air flow rate is accurately detected when calculating the fuel injection amount, etc., and the exhaust emission characteristics are improved. There is an effect.

Note that this effect becomes greater when the hot wire flowmeter 10 detects pulsations in the intake air flow rate.

Furthermore, instead of using the logarithmic converter 11, an inverse function converter having a quadratic function or higher may be used.

<Effects of the Invention> As explained above, according to the present invention, since the detection signal output means outputs a linearized continuous detection signal, the interpolation calculation means or a plurality of discontinuous intake air flow rate data are used to calculate the intake air flow rate. When calculating the air flow rate by interpolation, it is possible to suppress the occurrence of errors as much as possible, which has the effect of suppressing cost increases and obtaining good exhaust emission characteristics.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram according to the present invention, Fig. 2 is a system schematic diagram showing an embodiment of the present invention, Fig. 3 is a system configuration diagram according to the same embodiment, and Fig. 4 is a conventional intake air flow measurement method. A diagram showing the output of the device, FIG. 5 is an enlarged view of section P in FIG. 4. l... Bridge circuit 2... Operational amplifier 10...
・Hot wire flowmeter 11... Logarithmic converter 21...
・A/D converter patent applicant Fujio Sasashima, agent and patent attorney for Japan Electronics Co., Ltd. Figure 1 Figure 2

Claims (1)

[Claims] Detection signal output means installed in an intake system of an internal combustion engine and outputting a detection signal that continuously changes according to the intake air flow rate of the engine, and storing intake air flow rate data discontinuously corresponding to the detection signal. data storage means for searching for a plurality of data in the vicinity of the detection signal; and interpolation calculation means for calculating an intake air flow rate by interpolation using the plurality of data retrieved by the data search means. An intake air flow rate measuring device for an internal combustion engine, characterized in that the detection signal output means outputs a linearized continuous detection signal.