JPS6026963B2 - displacement meter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a displacement meter capable of continuous detection using optical means, suitable for use in home appliances, measuring devices, and various types of equipment that require low cost and high reliability.

Conventionally, continuous displacement was detected as an electrical signal by mechanically moving an arm, converting this arm movement into a change in electrical resistance, and detecting displacement based on the amount of change. A known device uses a sonic transmitter to measure the reflection delay time of ultrasonic waves, and detects displacement based on the measured value. However, these detectors are difficult to miniaturize, are sometimes impossible to measure at short distances, and have problems in terms of durability.

Therefore, it was unsuitable for use as a displacement meter in various devices that require low cost and high reliability. Furthermore, conventional displacement meters using optical elements also have the disadvantage of being greatly affected by dirt.

The present invention has been made in view of the above points, and an object of the present invention is to provide a compact and long-life continuous displacement meter using an optical element.

To summarize the present invention, a light emitting element and a plurality of light receiving elements having different directivities are provided, a light reflector is placed opposite to these elements, and the amount of reflected light is detected by the light receiving element, and the relative value of the output of each light receiving element is determined. Therefore, the position of the object to be detected is continuously detected, and the amount of light emitted by the light emitting element is increased or decreased so that the output level of one light receiving element is always constant even if the object to be detected is displaced, and the output level of the other light receiving element is increased or decreased. The device is characterized in that displacement is detected based on the amount of light received by the light-receiving element.

In explaining the present invention, a liquid level bell detector, which is a type of displacement meter previously filed by the present applicant, will be explained below.

FIG. 1 shows a structural diagram of the liquid level bell detector.

In the drawings, the long bridge 1 has a circular cross section, has liquid and air inlets and outlets 2a and 2b at the bottom and upper part, and has a uniform reflectance on its inner wall.

A hemispherical float 3 is placed in a free state inside the long tube 1, and is made to move up and down within the long tube 1 according to the displacement of the liquid level A to be detected. At the upper end of the long strip 1, an infrared light emitting diode 4 and a phototransistor 5 are connected in parallel with a float 3.
It is placed towards.

Due to this configuration, a part of the light emitted from the light emitting diode 4 is reflected on the upper surface of the float 3 either directly or through reflection on the inner wall of the long tube 1, and travels in the opposite direction to reach the phototransistor 5. become.

In this case, the light beam reaching the phototransistor 5 changes depending on the position of the float 3 due to the spread of the light beam and attenuation due to reflection on the inner wall of the outer tube 1. Therefore,
From the output of the phototransistor 5, the float position, that is, the level of the liquid to be measured can be detected.

Although not shown in FIG. 1, an infrared light emitting diode drive circuit, a phototransistor output amplification circuit,
Of course, a liquid level display circuit and the like are separately provided.

As is clear from the above configuration, in this liquid level bell detector, the light is reflected by the inner wall of the outermost tube 1, so that the light from the light emitting diode 4 can be effectively used. Since the light intensity distribution becomes uniform, the requirements for accuracy regarding the mounting positions and angles of the light emitting diode 4 and phototransistor 5 can be relaxed, and as a result, variations in performance between individual detectors can be reduced.

Furthermore, since the light is reflected by the float 3,
It has the advantage of being able to obtain stronger reflected light than direct reflection from the liquid surface, being less sensitive to fluctuations in the liquid surface, and not depending on whether the liquid is transparent or not.

However, the above configuration has the disadvantage that the float 3, phototransistor 5, etc. are greatly affected by dirt.

On the other hand, the liquid level bell detector shown in FIGS. 2 and below has the advantage of not having this drawback.

In FIG. 2, the same parts as in FIG. 1 are given the same reference numerals, so that most of the configuration of the level detector of the present invention is the same as that in FIG. 1. However, in the one shown in FIG. 2, a light emitting diode 4 and two phototransistors 6 and 7 are arranged at the upper end of the long bridge 1 in a positional relationship corresponding to the vertices of an equilateral triangle, as shown in FIG. There is. The transistors 6 and 7 have different directivities as shown in FIG. 0 With such a configuration, the light emitted from the light emitting diode and reflected by the float 3 will be incident on the phototransistors 6 and 7 at approximately equal rates; Since each phototransistor has a different directivity, the outputs 1, 12 of each phototransistor 6, 7 in response to the displacement of the float 3 are as shown in FIG.

In other words, the rate of change of the output 1 with respect to the distance L to the float 3 of the phototransistor 6 with narrow directivity is clearly different from the rate of change of the output 12 with respect to the distance to the float 3 of the phototransistor 7 with wide directivity. There is. In addition,
The absolute value of the output of the phototransistors 6 and 7 depends on the type of element and has nothing to do with directivity. The directivity of each transistor 6, 7 is clearly expressed as the rate of change of the output with respect to the displacement of the float 3. As described above, if the rates of change in the outputs of the two transistors 6 and 7 with respect to the displacement of the float 3 are different, it should be possible to know the distance to the float 3 by taking these relative values.

Therefore, when we looked at the relationship between the output ratio 1,/12 and the distance L to the float 3, we obtained a characteristic that changes almost linearly as shown in FIG. 6. Therefore, by obtaining the outputs d, /12 of the phototransistors 6 and 7, the position of the float 3, that is, the level of the liquid surface, can be determined from FIG. Furthermore, with the above configuration, the liquid level can be obtained as the ratio between the outputs of the two phototransistors 6 and 7, and does not depend on the absolute value of the phototransistor output like the detector shown in FIG. Even if there is dirt on the 3rd class, it will hardly be affected by it. This is clear from FIG. 8, which shows the relationship between the output ratio 1,/12 and L when the reflective surface of the float 3 is painted black and when it is not. Although the liquid level bell detector shown in Figure 2 has extremely high performance,
In this case, the outputs 1, 12 of phototransistors 6, 7
The problem is a circuit that obtains a ratio of 1,/12.

As a circuit for obtaining 1 and /12, for example, the circuit shown in FIG. 7 can be considered. In the figure, 8 and 9 are known logarithmic amplifiers;
10 is a differential amplifier for taking the ratio of outputs logl, log12 of amplifiers 8 and 9, and 11 is this amplifier 10.
The output logl,/12 is 1. It is a reciprocal amplifier that converts to /12. The reason why the logarithmic amplifier 8.9 is used in this circuit is that the output range of the phototransistors 6 and 7 is extremely wide, ranging from 1 to 3 digits, depending on the upper and lower levels of the liquid level. However, the circuit described above requires a large number of circuit components (operating amplifiers, resistors, etc.) and is expensive.Although it is good when the input range is narrow, when the input range is wide, the output may become saturated or nonlinear. There is a problem. The present invention solves these problems all at once, and provides a circuit as shown in FIG. 9 as a circuit for obtaining 1,/12. In FIG. 9, 4 is a light emitting element (in this example, an LED), and 6 and 7 are light receiving elements having different directivity angles (in this example, two photodarlington transistors). R. ~R7 are resistors, 12 are capacitors, and OP is an oven amplifier. A constant voltage Vr divided by resistors R3 and R4 is supplied to the inverting input of the OBE amplifier through a resistor R5.

On the other hand, a phototransistor 6 is connected to the non-inverting input of the obeamp.
A potential difference Vi caused by the output current flowing through the resistor R, is supplied through the resistor R2. Therefore, when the float 3 of the liquid level gauge moves away from the element 4 and the output current of 6 becomes smaller, that is, V3i becomes smaller, the oven amplifier O
Since the output of P becomes smaller, a correspondingly larger current flows through the LED 4. Vi also increases accordingly. If the gain of the oven amplifier OP is ideally infinite, this system is a feedback system that always settles at VFVr regardless of the liquid level. In such a system, if the distance L between the light-emitting/light-receiving element and the float shown in FIG. 2 changes (i.e., the liquid level), the output voltage Vi of the phototransistor 6 shown in FIG. Regardless of the output voltage V of the phototransistor 7.

changes with L. That is, it can be seen that the output of the phototransistor 7 is exactly the ratio (1, /12) described above. FIG. 10 shows the relationship. In the figure, the solid line indicates a combination in which phototransistor 6 is an element with a wide directivity angle and 7 is an element with a narrow directivity angle, and the dotted line indicates a combination in which phototransistor 6 is an element with a narrow directivity angle and phototransistor 7 is an element with a wide directivity angle. This is the case for the combination. Although the liquid level gauge has been described above as a specific example, the displacement gauge of the present invention has many advantages as described below.

'11 Almost unaffected by changes in the light emitting intensity of the light emitting diode, and the temperature characteristics of the light emitting diode can be ignored.

'21 The temperature characteristics of the outputs of the phototransistors 6 and 7 can be canceled out.

'31 Less susceptible to changes in reflectance due to dirt on the reflector, etc.

{41 When using the outer tube that guides light like the above-mentioned liquid level gauge, the light from the light emitting diode can be effectively used because the light is reflected by the inner wall, and the light in the cross-sectional direction of the outer tube can be used effectively. Since the intensity distribution of the light emitting diode and the phototransistor becomes uniform, the requirements for precision regarding the position and angle of the light emitting diode and phototransistor can be relaxed, and as a result, the variation in performance between individual detectors can be reduced.

'5} Since no mechanical elements or large parts are used in the overall configuration of the detector, it can contribute to miniaturization.

{6} Since the light-emitting element and the light-receiving element can be made of optical semiconductors that can be used semi-permanently, high reliability and long life of the entire detector can be sufficiently achieved.

0.7) The mechanism and circuitry do not require expensive materials or parts, making it possible to construct an extremely inexpensive detector.

Shelf It can be used as a variety of displacement gauges, including the liquid level gauge mentioned above, and has a wide range of uses.

As described above, the displacement meter of the present invention compares the output of one of the plurality of light receiving elements in response to the displacement of the object to be detected with the reference potential, and responds to this comparison output to Controls the amount of light emitted so that the output of the above-mentioned - light-receiving element corresponds to the above-mentioned reference potential, and derives the output from the other light-receiving elements as an output corresponding to the output ratio of ZO between the outputs of each light-receiving element. The position of the detected object is detected by
The number of circuit components is small and the circuit configuration is simple.
Low price.

Furthermore, the displacement of the object to be detected can be detected over a wide range.

[Brief explanation of drawings]

Fig. 1: Structural diagram of the secondary liquid level bell detector, Fig. 2: Structural diagram of the liquid level bell detector of the present invention, Fig. 3: Top view of Fig. 2, Fig. 4: Photo Diagram showing the directional characteristics of the transistor, Fig. 5: Characteristic diagram showing the relationship between the liquid level and the outputs of the phototransistors 6 and 7, Fig. 6: Liquid level and the output ratio L/Z of the phototransistors 6 and 7 Characteristic diagram showing the relationship between
A block diagram showing an example of a circuit for obtaining 1, /ra from 2, Fig. 8: Liquid level bell and phototransistors 6, 7 when the reflective surface of the float 3 is dirty and when it is painted black.
The output Hd. Characteristic diagram showing the relationship with /12, Figure 9:1
, /12. FIG. 10: Characteristic diagram showing the output of each part in FIG. 9. Symbol, OP: Obeamp, R, ~R7: Resistor, 4: Infrared light emitting diode, 6, 7: Phototransistor. Figure 'Figure 2 Figure 3 Figure A Figure 6 Figure 6 Figure B Figure 0 Figure 9 Figure /0

Claims (1)

[Claims] 1. A light reflector that is displaced in accordance with the displacement of the object to be detected, and a light emitting element and a plurality of light receiving elements placed opposite to the reflector, the light from the light emitting element being reflected by the light reflector,
In the displacement meter, the amount of light reflected from the light reflector is detected by the plurality of light-receiving elements, and the position of the object to be detected is detected from the output ratio between the outputs of each light-receiving element. comparing means for comparing the output of one of the light receiving elements in response to the displacement of the object to be detected with a reference potential; A control means for controlling the output of the light receiving element to a value corresponding to the reference potential is provided, and the output of the other light receiving element is derived as a signal corresponding to the output ratio between the outputs of the respective light receiving elements. A displacement meter characterized in that it detects the position of a detection object.