JPS6325513A - Engine suction air meter - Google Patents

Abstract

PURPOSE:To obtain an apparatus for generating a Karman vortex pulse of actual value constantly regardless of engine operation condition, by setting variably an operation constant of a binary circuit in response to the engine operation condition. CONSTITUTION:A signal 'a' issued out from a Karman vortex amount sensor 2, after passing through the No.1 low-altitude range passing filter 31, afters its mean value by the No.2 low-altitude range passing filter 32. And, binarization is performed by comparing outputs of these filters 31, 32 on outputs 'b', 'c', by a comparator 33 and a Karman vortex pulse 'd' is obtained. A computer unit 8, upon receiving the pulse 'd', calculates suction air amount of the engine and fuel injection quantity is determined correspondingly to this result. And, the unit 8, depending on an aperture of a throttle valve 6, adjusts time constants of the filters 31, 32 and generates a setting signal to adjust a hysteresis width. Thus, noise effect is eliminated for proper binarization.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an engine intake air amount measuring device that measures an intake air amount using a Karman vortex flow sensor.

[Conventional technology]

Various methods have been proposed in the past for measuring the flow rate of fluid based on the generation frequency of the Karman vortex generated downstream of a vortex generator provided in a conduit.
-41665 publication and Utility Model Application Publication No. 57-160625.

Utility Model Application Publication No. 54-41665 utilizes the fact that an ultrasonic signal wave transmitted and received through a flow path is phase-modulated by a Karman vortex generated in a fluid. -160625 is arranged in a flow path,
This method takes advantage of the fact that the resistance value of a thermistor heated at a constant current changes in response to the Karman vortex.

In both of these conventional examples, the output electrical signal is an anawag signal that changes in response to the Karman vortex, but when this is used as an intake air amount sensor for engine fuel injection control, for example, it is usually It is binarized and converted into a Karman vortex pulse for use. A conventional example of a specific method for converting into a pulse is, for example, Japanese Patent Publication No. 58-70131.

[Problem that the invention seeks to solve]

By the way, when this Karman vortex flow rate sensor is used as an engine intake air amount sensor,
As partially stated in Publication No. 31, the following problems occur.

In other words, when the throttle valve is at a high opening, air pulsations due to the intake operation of the engine reach the intake passage.
In response to this pulsation, the output level of the flow rate sensor varies greatly.

In addition, when the throttle valve is located at a low opening, intake air passes through the valve at high speed, causing so-called "wind noise", which also affects the Karman vortex sensor in the intake passage.
The output appears as a superimposed form of high-frequency noise.

Such an output signal may be used, for example, in the above-mentioned
As shown in Publication No. 131, when a Karman vortex pulse is obtained by comparing it with a predetermined voltage using a voltage comparator and binarizing it, the so-called "teeth" of the pulse occurs when the throttle valve is opened at a high opening. Moreover, when the opening degree is low, the superimposed high-frequency noise is output as a pulse as it is.

The present invention has been made to solve this problem, and an object of the present invention is to provide an engine intake air amount measuring device that always outputs a true Karman vortex pulse regardless of the operating state of the engine.

[Means to resolve the issue]

The engine intake air amount measuring device according to the present invention measures two continuously changing signals output from the Karman vortex flow rate sensor.
The system is provided with a binarization circuit for converting into values, and a means for variably setting the operating constant of the binarization circuit in accordance with the operating state of the engine such as the throttle opening of the engine.

[For production]

In this invention, the operating constant of the binarization circuit is variably set according to the operating state of the engine, and based on this operating constant, the binarization circuit converts the continuously changing signal output from the Karman vortex flow sensor into two. A value ratio circuit performs a binary ratio.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the engine intake air amount measuring device of the present invention will be described with reference to the drawings. FIG. 1 shows one embodiment of the present invention, and is a block diagram showing an example of use in fuel injection control.

In FIG. 1, numeral 1 denotes an intake passage of an engine, and numeral 2 denotes a Karman vortex flow rate sensor disposed within this intake passage 1. In FIG. The output a of this Karman vortex flow rate sensor 2 is binarized by a binarization circuit 3 to obtain a Karman vortex pulse d.

This binarization circuit 3 includes a first low-pass filter 31 for removing high-frequency noise components from the output a of the Karman vortex flow sensor 2, and a first low-pass filter 31 for averaging the output of this low-pass filter 31. The second low-pass filter 32 and the first low-pass filter 31 and the second low-pass filter 3
2 output.

The comparator 33 has a hysteresis characteristic to compare the magnitude of C. The time constants of the first low-pass filter 31 and the second low-pass filter 32 and the hysteresis width of the comparator 33 are determined by the computer unit 8. It is configured so that it can be set variably from

Further, a throttle valve 6 is provided in the intake passage 1, and the opening degree of the throttle valve 6 is detected by an opening degree sensor 7. The output of the opening sensor 7 is sent to a fan unit 8.

The above-mentioned Karman vortex pulse d is also input to the computer unit 8. The fuel chamber is controlled via the injection valve 5 according to this Karman vortex pulse d, the output of the opening sensor 7, the engine speed, etc., and the injection valve 5 is located near the cylinder 4 of the engine. It is arranged.

In addition, the comparator unit) 8id variable resistor VRI of the first low-pass filter 31 and the second low-pass filter 3
The variable resistor VR2 of the converter 2 and the variable resistor VR3 between the input and output terminals of the comparator 33 can be varied, thereby making it possible to variably set the operating constant of the binarizing circuit 3 according to the state of the engine. ing.

Next, the operation will be explained. 2 and 3 are timing charts showing the states of signals in each part of the binarization circuit 3, and in FIG. 2, the throttle valve 6 is located at a low opening, and as described above, the Karman vortex is generated. Output a of flow rate sensor 2
Fig. 3 shows a case where high-frequency noise is superimposed on the throttle valve 6 and the Karman vortex flow sensor 2.
This shows a case where the output a of is affected by the pulsation and its level fluctuates greatly.

In FIG. 1, the signal a output from the Karman vortex flow sensor 2 passes through a first low-pass filter 31 whose purpose is to remove high-frequency noise components, and then passes through a second low-pass filter 32. The average value is taken.

Therefore, the outputs of the first low-pass filter 31, the second low-pass filter 32, and the c'i comparator 3
By comparing the magnitudes in step 3, binarization is performed, and the Karman vortex pulses d are obtained.

The computer unit 8 receives this Karman vortex pulse d, calculates the intake air amount of the engine from this, and determines the fuel injection amount in accordance with the result.

Now, when the throttle valve 6 is at a low opening, the computer unit 8 uses the opening sensor 7.

This is detected, and a setting signal is sent to the binarization circuit 3 so that the time constants of the first and second low-pass filters 31 and 32 become longer and the hysteresis width of the comparator 33 becomes larger. (e p t * g in Figure 1
) occurs.

With this setting, the high frequency noise (a in Figure 2) that occurs when the throttle opening is low is reduced in noise level by the first low-pass filter 31, as shown in b r c in Figure 2. After passing through the damper 33, which has a reduced hysteresis width and is set to a large hysteresis width, the influence of the noise is completely removed.

Next, when the throttle valve 6 is located at a high opening degree, the computer unit 8 instructs the binarization circuit 31 to shorten the time constants of the first and second low-pass filters 31 and 32; , the setting signal e so that the hysteresis width of the comparator 33 becomes small.

Generate f and g.

With this setting, the output C of the second low-pass filter 32 for taking the average value can sufficiently follow the level fluctuations caused by the pulsation of the human power source, as shown in FIG. and change.

At this time, if the time constant of the second low-pass filter 32 is shortened in order to improve this followability, the difference between the two signals b r c input to the comparator 33 becomes smaller;
Since the hysteresis width of this comparator 33 is also set small, proper binarization is performed.

Incidentally, in the example shown in FIG. 1, the configuration of the binarization circuit 3 is expressed as an analog circuit for ease of explanation, but the same function can be achieved even if it is configured as a digital circuit. can be realized. That is, this can be easily realized by configuring the first and second low-pass filters 31 and 32 as low-pass diisotal filters, and configuring the comparator 33 as a magnitude comparator. The computer unit 8 is often composed of a microprocessor, but if the entire binarization circuit 3 is composed of a deisotal circuit like this, the microprocessor sets the filter time constant. , and the hysteresis width of the comparator can be easily set.

〔Effect of the invention〕

As explained above, in this invention, when the output of the Karman vortex flow sensor is fully binarized to obtain the Karman vortex pulse, the operating constant of the binarization circuit is variably set in accordance with the operating state of the entire engine. , has the effect of always generating true-value Karman vortex pulses.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the intake air amount measuring device for an engine according to the present invention, and FIGS. 2 and 3 are timing charts showing signals of each part of the intake air amount measuring device for the same engine. 1... Intake passage, 2... Karman vortex flow rate sensor, 3
...Binarization circuit, 4...Cylinder, 5...Injection valve, 6...Throttle valve, 7...Opening sensor, 8...
- Computer unit, 31... first low pass filter, 32... second low pass filter.

Claims (1)

[Claims] A Karman vortex flow sensor disposed in the intake passage of the engine, a binarization circuit that binarizes the output of the Karman vortex flow sensor to obtain a Karman vortex pulse, and an operating state of the engine including at least the throttle opening. 2 above depending on
1. An engine intake air amount measuring device, comprising means for variably setting an operating constant of a value converting circuit.