JPS6053811A - Output-signal processing device of karman vortex sensor - Google Patents

Abstract

PURPOSE:To prevent the erroneous detection of a flow rate due to missing of pulses, by guiding the output of a Karman vortex sensor to a period detecting means through a waveform shaping means, comparing one period with the maximum value, making the period lower than the maximum value, and computing the flow rate by a flow-rate operating means. CONSTITUTION:When vortexes are yielded in a pipe 1 by a vortex yielding body 2, the vortex pressure rotates and vibrates a vibrating plate 5 through an intake port 3 and a pressure transmitting path 4. A photodiode 9 detects light, which is emitted by a light emitting diode 8 and reflected by the vibrating plate 5. The output of the photodiode 9 becomes a sine wave state. The output signal in a sine wave shape from a Karman vortex sensor 31 is converted into a rectangular signal by a waveform shaping circuit 32 and inputted to an interrupting input of a CPU33. A clock signal is sent to a counter 35 from a clock signal generating circuit 34 based on the rise up of the rectangular signal. The period of the rectangular signal is sent to the CPU33 and compared with the maximum value stored in an ROM37. The value is set in the value lower than the maximum value, and the flow rate is computed. Therefore, erroneous detection of the flow rate due the missing of pulses can be prevented.

Description

TECHNICAL FIELD The present invention relates to an output signal processing device for a Karman vortex sensor used, for example, as an air flow meter for measuring the intake air amount of an engine.

BACKGROUND OF THE INVENTION In general, vane type flowmeters have been the main type of airflow meter for measuring the intake air amount of an engine (1), but recently Karman vortex sensors, which have advantages such as small size, have been developed. In the Karman vortex sensor, for example, as shown in Japanese Patent Application Laid-Open No. 58-80524 and Japanese Patent Application Laid-open No. 58-80525, a pipe 1 through which a fluid flows is used.
A Karman vortex generator is inserted in the &, and the pressure fluctuations generated at the intersection H near both sides of the Karman vortex generator are transmitted to the diaphragm outside the pipe via a pair of pressure transmission channels. The rotational displacement of the diaphragm is photoelectrically detected, and the velocity of the fluid is detected every 3L. In this case, the velocity of the fluid is determined by obtaining a sinusoidal electric signal corresponding to the rotational displacement of the diaphragm, converting the dirt into a square wave signal, and multiplying each pulse period of this square wave signal by d1. .

However, in the above-mentioned conventional type, no measures have been taken to prevent pulse loss due to instantaneous interruption of the sensor signal line or a ring of sensor output reduction in low-speed regions, and as a result, pulse +
If Wi omission occurs, the measured flow rate will be lower than the actual flow rate. Therefore, when used as an air flow meter for an engine, the air-fuel ratio is controlled to be lean, resulting in a problem such as a decrease in engine output torque and deterioration of exhaust gas.

Purpose of the Invention The purpose of the present invention is to solve the problems of the conventional type described above.
By setting the maximum value as the field lightning level judgment value in the pulse period of the above-mentioned rectangular wave signal, when there is a missing pulse, the maximum value is adopted as the pulse period to calculate the flow rate. When used as an air flow meter for an engine, the purpose is to prevent lean side control of the air-fuel ratio to prevent a decrease in engine output torque, deterioration of exhaust gas, etc.

Structure of the Invention The structure of the present invention for achieving the above object is shown in FIG. In FIG. 1, the Karman vortex sensor generates an output signal with a frequency corresponding to the flow rate of fluid, and the waveform shaping means shapes the output signal of the Karman vortex sensor to generate a rectangular wave signal. The period detection means is one period TQF of the rectangular wave signal.
X is detected and sent to the maximum value setting means. The maximum value setting means compares the period (3) T-Ko X with the maximum value TG II R11, and sets the period T-Ko χ to the maximum value TGIII11 or less. and,
The flow rate controlling means is period TO1iX or 4:t:TGI
Calculate the fluid flow rate using IRrl.

EXAMPLES Hereinafter, the present invention will be described in detail with reference to the drawings from FIG.

FIG. 2 (Δ) is a sectional view showing an example of a 1-Carmen vortex sensor. In FIG. 2(A), a vortex generator 2 is provided at the center of the pipe line 1, and the vortex generator 2 has a pair of MIIS pressure intake holes 3 and a pair of MIIS pressure intake holes 3. A pressure transmission passage 4 for transmitting pressure fluctuations to the outside of the pipe 1181 is provided. As a result, "C1
A rotational moment is generated in the moving plate 5.

As shown in FIG. 2(B), the diaphragm 5 (1) is supported on a rotation axis including its center of gravity by a pair of span hands t6a and 6h, and further includes a span hand 6a.

61+ is held in the frame 7. Therefore, the diaphragm 5 is almost (
4) It does not vibrate, and therefore rotates and vibrates only in response to pressure fluctuations in the pressure transmission passage 4 caused by Karman vortices.

In FIG. 2(A), 8 is a light emitting diode as a light emitting means, and 9 is a photodiode as a light receiving means. That is, in this case, the diaphragm 5 acts as a light reflecting plate, and therefore, when the diaphragm 5 rotates and vibrates due to Karman vortex pressure, the output signal of the photodiode 9 becomes a sine wave with a vortex frequency f. The present invention relates to processing of the sinusoidal output signal of the photodiode 9.

FIG. 3 is a circuit diagram showing an embodiment of an output signal processing device for a Karman vortex sensor according to the present invention, which is configured by, for example, a microcomputer. In FIG. 3, the portion surrounded by the dashed line is configured as a microcomputer, but the waveform shaping circuit 32 may be provided within the Karman vortex sensor 31.

The sinusoidal output signal of the Karman vortex sensor 31 is supplied to a waveform shaping circuit 32, where the sinusoidal (5) signal is converted into a rectangular wave 1d. This square wave signal is C
is fed to the interrupt input of PI+ 33, resulting in CI
l+ 334: An interrupt routine shown in FIG. 4, which will be described later, is executed in response to the rise of the i rectangular wave signal. 34 is a clock generation circuit that generates various clock signals, 35 is a counter for detecting one cycle of the rectangular wave signal of the waveform shaping circuit 32, 36 is an input/output interface, and 37 is a program, constants, etc. 110M, 3B, which stores data in advance, is an IAM (which temporarily stores data).

FIG. 4 is a flowchart 1 to 1 for explaining the circuit operation of FIG. 3, and is an intake air amount calculation routine. The interrupt step 401 is performed by the waveform shaping circuit 3 as shown in FIG.
At step 402, the value TnllX of the counter 35 is taken in and the counter 35 is reset for the next calculation cycle. In this case, the value T of the counter 35 corresponds to one of the periods T, χD, T, XI, . . . of the rectangular wave signal shown in FIG.

Next, in step 403, the period TQFX is set to the low flow rate difference (
6) TGUl as a judgment value? Compare with Il. As a result, if TKo×≦TGIIRD, the process directly proceeds to step 405, and on the other hand, if T[]IFX>TGIIRD, TQFX←−TGLIRrl is set in step 404.

That is, each time the maximum value TG[II?D is set to T(IFX).Next, in step 405, the period T is used to set the intake air amount Q to Q-/TQFX. However, K is a constant The routine then ends at step 406.

In this way, by setting the long period due to missing pulses as the abnormality determination value to be equal to or less than TGURD, missing pulses are prevented.

Effects of the Invention According to the present invention, as explained above, the long period due to missing pulses, for example, TQFX2 in FIG.
Since it is IIRD, it is possible to prevent false detection of flow rate due to missing pulses, and therefore, when used as an engine air flow meter, it is possible to prevent lean air-fuel ratio and reduce engine output torque (7). 4Jl gas can be prevented from turning into HIT.

[Brief explanation of the drawing]

11th W, 1 A block diagram showing the configuration of the present invention, FIG. 2 (A) is a sectional view showing an example of a Karman vortex wrench, FIG. 3 shows an output signal processing device 6 of a Karman vortex sensor according to the present invention.
FIG. 4 is a flowchart for explaining the circuit operation of FIG. 3, and FIG. 5 is a timing chart showing a supplementary explanation of flowchart 1- in FIG. 4. 1: Pipe line, 2: Vortex generator, 3: Temperature and pressure intake hole, 4: Pressure transmission passage, 5: Vibration plate, 8: Light emitting means, 9: Light receiving means, 3
1: Karman vortex sensor, 32: waveform shaping circuit. (8)

Claims (1)

[Claims] 1. A Karman vortex sensor that generates an output signal with a frequency corresponding to the flow rate of fluid, a waveform shaping means that shapes the output signal of the Karman vortex sensor to generate a rectangular wave signal, and detects one cycle of the rectangular wave signal. An output signal processing device for a Karman vortex sensor, comprising: a period detection means for setting a maximum value to the period, a maximum value setting means for setting a maximum value to the period, and a flow rate calculation means for calculating the flow rate of the fluid using the period.