JP4147130B2 - Photoelectric switch for wide range detection - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wide-range detection photoelectric switch for detecting an object whose passing or dropping position is not fixed.
[0002]
[Prior art]
In general, when optically detecting an object having a fixed passage position, one light projecting element and one light receiving element may be placed across the fixed passage position. With the photoelectric switch on the axis, if the passing position of the object deviates from the optical axis, it cannot be detected.
[0003]
Therefore, as a photoelectric switch for wide-range detection that can cover a wide passage range of an object, a plurality of light projecting elements and a plurality of light receiving elements are arranged facing each other at a predetermined detection distance, and the light projecting elements and the light receiving elements facing each other are arranged. A method of sequentially operating the elements so as to be in a state of being optically coupled to the elements synchronously is used (for example, refer to Patent Document 1).
[0004]
[Patent Document 1]
JP 2001-124867 A (refer to Embodiments [0020]-[0022] stage, FIGS. 1, 2 and 5)
[0005]
By the way, in this sequential synchronization method, an object that is between one optical axis that is optically coupled and an adjacent optical axis that is also optically coupled and does not obstruct any optical axis passes undetected, which is inconvenient. For this reason, efforts are being made to increase the number of light projecting elements and light receiving elements so that the distance between adjacent optical axes is as narrow as possible. However, such an increase in the number of elements is unreasonable. In particular, the number of components such as a lens, a rectifier circuit, an amplifier circuit, and an output circuit constituting the light receiving portion increases, resulting in a great disadvantage that the cost is increased.
[0006]
In view of such circumstances, the applicant has proposed a photoelectric switch for wide-range detection in which each element on the light projecting unit side sequentially emits light, but the light receiving unit side is always in a standby state (see, for example, Patent Document 2). According to this method, each light receiving element is sensitive to light coming from a plurality of light projecting elements other than the opposing light projecting elements (shifted obliquely), and therefore the dead zone as a whole is reduced.
[0007]
[Patent Document 2]
Japanese Patent Laid-Open No. 3-2591 (see claims and FIGS. 1-3).
[0008]
FIG. 1 shows a schematic configuration of such a multi-element array type photoelectric switch. The array of a plurality of (in this case, five) light projecting elements 1a to 1e has a timing control with oscillation / frequency division and counter functions. Driven sequentially by drive circuits D1 to D5 that operate according to the circuit 2, all emit light with a spread over each angular range θ1 to θ5 reaching all of the light receiving elements 3a to 3e. In this case, from the arrangement of the light receiving elements 3 that are always in the standby state, the number of light receiving elements (total received light amount) received during the light emission timing of each light projecting element 1 is determined by, for example, the delay AGC. For example, the output is cut and used as an article detection signal. A method of connecting each light receiving element to a “dark on” switching circuit that outputs a true output in a light-shielded state and using the true output as an article detection signal is also used.
[0009]
Therefore, if the test object passes through positions O1, O2, O3, etc. that block any activated light receiving axis of each light receiving element, the light receiving elements 3a and 1b emit light at the light projecting element 1a. Since the light receiving element 3e at the time of light emission of 3a and 1d does not receive light and does not receive all the light, the output of the delayed AGC is cut (article detection). However, if the size of the article is small compared to the optical axis interval and the passing position is not fixed, for example, the closest position F1 between the light projecting elements 1d and 1e, and the inner side between the light projecting element 1e and the light receiving element 3e. Various positions between the optical axes such as the deviated position F2, the closest position F3 between the light receiving elements 3d and 3e, the position F4 on the side of the center of the detection range, and the inter-optical axis position F5 relatively close to the light receiving element 3d. If it passes, no light receiving element is shielded, so that an article non-existence signal is generated despite the presence of an object in the detection region, resulting in false detection.
[0010]
In order to eliminate the erroneous detection as described above, it is necessary to eliminate the insensitive area in the detection area, and simply increase the number of light projecting elements and light receiving elements in the same manner as attempted in the light projection / light reception synchronization method. However, it is conceivable to make these arrangements dense, but the number becomes enormous and it is expected that a heat dissipating means or the like is required. Even if only the number of elements is simply increased, it is technically impossible to completely eliminate the insensitive area as long as both the light projecting part and the light receiving part are composed of elements.
[0011]
[Problems to be solved by the invention]
An object of the present invention is to solve the above inconveniences and to use a minimum number of light receiving elements, and to provide continuity in the light receiving band, so as to correspond to an array of a plurality of light projecting elements that are sequentially driven. It is an object of the present invention to provide a photoelectric switch for wide-range detection that can detect a passing state of an object within a range substantially without leakage.
[0012]
[Means for Solving the Problems]
In order to solve the above problems, the present invention comprises a) a plurality of light projecting elements arranged in the same plane, and a light projecting signal generating and distributing circuit for sequentially emitting these light projecting elements. A light emitting side,
b) A light receiving member whose one side is mainly a cylindrical light guide rod installed so as to receive light emitted from the plurality of light projecting elements arranged in an aligned manner, A light reflecting surface corresponding to a chord extending over a predetermined arc range opposite to the one side surface, and a light receiving element attached to at least one end of the light guide rod; and light reception at the at least one end A photodetection switch for wide-range detection comprising a light-receiving side portion including a light-receiving element operation and a signal processing circuit for operating the element is configured.
[0013]
As a light guide rod in the above configuration, a structure comprising a cylindrical transparent core having the light reflecting surface on the string side surface, and a transparent clad that protects the outer periphery of the transparent core, like a general optical fiber. Can be adopted. The presence of this cladding makes it possible to reliably form internal reflection on the transparent core described later.
[0014]
In the light guiding rod having the above core / cladding structure, side incidence and reflection optical systems as shown in FIGS. 2A and 2B are formed according to the present invention. Since the light guide rod 4 generally has a refractive index of the clad 5 smaller than that of the core 6, the light incident from one side surface (the upper side in FIG. 2) is refracted step by step. Reaches the inner surface of the light reflecting layer 7 on the opposite side (lower side in FIG. 2). In FIG. 2A, this inner surface is nothing but “light reflecting surface 8” formed on the chord surface across the arc ends of the light reflecting layer 7.
[0015]
As apparent from FIG. 2B, light from any one of the light projecting elements 1 (a to e) incident from one side of the light guide rod 4 is reflected through the core 6 of the light guide rod 4. When the light reaches the layer 8 and is irregularly reflected, a reflection component that proceeds obliquely toward one of the rod ends is generated. Of the reflection component, an angle larger than the critical angle θ in the refractive index of the cladding 5 with respect to the one side surface. The incident light is re-reflected from the clad 5 into the core 6. The re-reflected light reaches the light reflecting surface 8 again, and the reflected component traveling obliquely from the surface is surely generated. Therefore, the oblique folding process in the core 6 is repeated and is incident on one of the rod ends. .
[0016]
Since the incident angle to the rod end is sufficiently small, even if the light introduction medium of the light receiving element to be applied to the rod end has a refractive index smaller than that of the cladding 5 and a critical angle smaller than the above θ, the core 6 The light is transmitted into the light introduction medium without being reflected into the body, and can enter the light receiving element.
[0017]
In the present invention, basically, two light receiving elements are individually arranged at both ends of the light guide rod, respectively, so that the light reaching the both ends of the rod is detected as described above, and the inspection field is obtained with the total output. However, only one light receiving element is arranged at one end of the light guide rod, and a light reflecting mirror surface is attached to the other end of the rod, so that the light reaching this end surface is the same. The light may be reflected in the rod and ultimately received by the single light receiving element.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments will be described with reference to FIGS. First, as shown in FIG. 3, the photoelectric switch for wide range detection of the present invention is manufactured as a frame structure corresponding to the measurement object and the size of its passing range. The photoelectric switch frame 9 is sequentially projected from a base side 10 housing a central processing circuit for control and calculation, a light projecting side 11 housing a light projecting element array such as an LED, and each element in the light projecting element array. A light receiving side 12 having a groove in which a light guide rod for receiving the light that has been received is inserted, and a connecting side 13 that bridges and connects the light projecting side 11 and the tip of the light receiving side 12 as opposed sides of the base side 10. Is done. The front cover 14 is formed of a three-sided frame-like plate that covers the three sides 10, 11, 12 excluding the connecting side 13.
[0019]
A transparent lid 15 for a groove into which a light guide rod is inserted is fixed on the inner surface of the light receiving side 12 facing the light projecting side 11. In the surface lid 14, the corners on the side of the coupling side 13 of the light receiving side 12 are notched, and the operating state in which the device is electrically activated, and object detection (corresponding light blocking detection) or non-detection (substantial rod) An operation display window 16 that covers an LED indicating light reception over the entire length or the like is fitted. The operation display window 16 is formed in a bag shape having not only the side surface on the same surface as the surface lid 14 but also the side surfaces on the same surface as the outer surface and the bottom surface of the light receiving side 12 and the connecting side 13.
[0020]
In the surface lid 14, a lid attachment hole 17 is formed in a corner other than the corner having the operation display window 16, and appropriate fastening means such as a screw is fitted. A connector terminal 18 of an electric circuit is installed on an outer surface portion of the light projecting side 11 on the base side 10 side, and a connector 20 of an electric cable 19 including a signal line and a power line is connected thereto.
[0021]
4 collectively shows a rear side view (A), a left side view (B), a plan view (C) and a right side view (D) with the front cover 14 attached, of the photoelectric switch frame 9 shown in FIG. It is displayed. As shown in the rear side view (A), the connecting side 13 is a single unit independent of the frame body, and after being fitted to the open end of the three-sided frame, the frame is formed by screws 21 in the paragraph on the right side of the figure. Fixed to the body.
[0022]
In FIG. 4B, a setting switch cover 22 is detachably installed at a position near the base side 10 on the light receiving side 12 of the frame so that the operator can access the setting switch plate 23 (FIG. 5) in the side 12. It has become. The parts shown in FIGS. 4C and 4D have already been described with reference to FIG. 3 and can be easily understood by referring to the reference numerals.
[0023]
FIG. 5 shows a left side view (A), a plan view (B), and a right side view (C) of the photoelectric switch frame 9 with the front cover 14 removed. In the left side view (A) and the plan view (B), the operation display window 16 is equipped with the necessary number of LEDs (in this case, three) for operation display and object detection / non-detection. Is shown. The base side 10 is equipped with printed circuit boards p1 to p7 including IC chips incorporating various electric circuits to be described later, and a plurality of, in this case, five light emitting LEDs 1a are provided in the light projecting side 11. ~ 1e are equipped.
[0024]
In this embodiment, the light guide rod 4 in the light receiving side 12 is provided with photodiodes PD1 and PD2 as light receiving elements at both ends thereof. As described above, the connecting side 13 is a single unit independent of the frame 9 body, and is fixed to the frame 9 body by the screws 21 and the nuts 24 in a state of being fitted to the opening end of the three-side frame. The state of the single unit removed from the frame 9 is as shown by attaching a frame-type arrow in the upper part of FIG. 5B.
[0025]
FIG. 6 shows various electric circuits provided in a simply constructed frame 9. The light projecting side 11 side circuit includes light projecting signal generation circuits 25a to 25e and a light projecting signal distribution circuit 26, which are individually provided for sequentially emitting light from the light projecting elements 1a to 1e made of LEDs. The circuit 25a to 25e, 26 and 27 operate in response to a command from the central processing unit 28 for controlling the entire apparatus.
[0026]
The circuit on the side of the light receiving side 12 operates the photodiodes PD1 and PD2 at both ends of the light guiding rod 4 whose light receiving side faces are opposed to the arrangement of the light projecting elements 1a to 1e and processes the signal current. The light receiving element operation and signal processing circuit includes a pulse amplifier 29, a filter 30 that passes the amplified output, a comparator 31 that receives the filter signal and compares it with a reference value, and an electronic volume controller 32 that sets the reference value. These operate under the command of the central processing unit 28.
[0027]
In the above configuration, when each of the light projecting elements 1a to 1e diffuses and emits light (three-dimensionally) with a spread of an angle θ0 as shown in the figure, this light is diffused without a gap within the range of θ0. Then, it goes to the light guide rod 4. However, as in this simple embodiment, the projection window 11a '(the inner edge of the three-sided frame in FIG. 6) 11a' of the projection side 11 in the frame 9 barely covers the front ends of these projection elements 1a to 1e. When there is only tension, a region that is not covered within the spread angle θ0 of any element, that is, a dead band A, is formed in the element adjacent interval at a position close to the light projecting element in the detection space inside the frame 9. Therefore, when the test object passes through the dead zone A, no light directed from the light projecting element LED toward the light guide rod 4 is blocked, so that a detection error (mistake that there is no object) occurs.
[0028]
Therefore, in the light emitting side 11 of the frame 9 in the preferred embodiment, the light projecting elements 1a to 1e are disposed deeper than the light projecting window 11a as shown in FIG. 7 and FIG. The dead band A does not exist in the object detection space. Therefore, as is apparent from FIG. 7, the light from each light projecting element travels from the light projecting window 11a on the light projecting side 11 toward the light receiving side 12 in a state where there is no break in the transverse direction of the window, as shown in FIG. A detection region B that completely covers one surface from the arrangement of the light projecting elements 1a to 1e toward the light guide rod 4 is formed.
[0029]
In the embodiment of FIGS. 7 and 8, when the test object does not pass through the inner space (detection region) B of the frame 9, a considerable amount of light reaching the light guide rod 4 from the light projecting element. Light is applied to photodiodes PD1 and PD2 at both ends of the rod (when a reflecting mirror is arranged at the other end, photodiodes arranged only at one end: hereinafter, one or two photodiodes are collectively referred to as “PD”) Is received and represents the object non-passing.
[0030]
On the other hand, at the light projection timing of any one of the light projecting LEDs, for example, the LED 1a, any of the light receiving side surfaces of the light guide rod 4 is blocked, and the light to the light guide rod 4 is blocked. When the arrival amount decreases, the light reception output from the photodiode PD does not reach a substantial level, indicating that the object corresponding to the light shielding portion has passed at that time. The threshold value for determining the substantial light receiving output of the photodiode PD is set by adjusting the electronic volume controller 32 via the central processing unit 28 by operating the setting switch described above.
[0031]
This object detection / non-detection operation is performed by integrating and averaging the light emission amounts of sequential light projections in one cycle of the light projecting elements 1a to 1e by the central processing unit 28 in the electric circuit of the embodiment, and 1 for the total light amount. This is done by setting a reference level that determines how much the amount of light received during the cycle is to generate an object detection output. Therefore, when light is blocked by an object that has entered (dropped), the amount of light received in one cycle is below this reference level, and an object detection output is generated. These object detection outputs are sent to an external circuit by the output circuit 33 as necessary, and the indicator lamps 24 emit light indicating at least object detection / non-detection in each cycle or in an appropriate time zone. The color blinks.
[0032]
【The invention's effect】
As described above, the present invention reduces the output line to one circuit as a light receiving optical system comprising a single light guide rod and a light receiving element provided only at both ends or one end of the rod. By providing a single element, a wide-range detection photoelectric switch capable of detecting the passage state of an object within a predetermined range corresponding to the arrangement of a plurality of light-projecting elements that are sequentially driven is provided.
[0033]
This photoelectric switch eliminates the dead zone and contributes to significant cost savings as well as component failure compared to the conventional structure where multiple light receiving elements are provided corresponding to the arrangement of multiple light projecting elements. Such a great effect that the reduction of the probability can be achieved.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a partial configuration of a conventional multi-optical axis photoelectric switch.
FIGS. 2A and 2B are a cross-sectional view (A) and a side cross-sectional view (B) for illustrating a side incidence and reflection optical system formed in a light guide rod according to the present invention. FIGS.
FIG. 3 is a perspective view showing an appearance of an embodiment of the present invention.
4 is a collective display of a rear side view (A), a left side view (B), a plan view (C) and a right side view (D) with a front cover 14 attached, as shown in FIG. It is a thing.
FIG. 5 shows a left side view (A), a plan view (B), and a right side view (C) of the photoelectric switch frame with the front cover removed.
FIG. 6 shows various electrical circuits installed in a frame in a simple embodiment of the present invention.
FIG. 7 shows a frame structure in a preferred embodiment of the present invention equipped with an electric circuit similar to FIG.
FIG. 8 shows a preferred detection area realized in a frame structure similar to FIG.
[Explanation of symbols]
1, 1a to 1e Light projecting element 9 Photoelectric switch frame 10 Base side 11 Light projecting side 12 Light receiving side 13 Connection side 14 Surface cover 15 Transparent cover 16 Operation display window 17 Cover mounting hole 18 Connector terminal 19 Cable 20 Connector 21 Screw 22 Setting switch cover 23 Setting switch plate 24 Nuts 25a to 25e Light projection signal generation circuit 26 Light projection signal distribution circuit 27 Oscillation circuit 28 Central processing unit 29 Pulse amplifier 30 Filter 31 Comparator 32 Electronic volume controller 33 Output circuit

Claims (4)

a) a light projecting side portion comprising a plurality of light projecting elements arranged in the same plane, and a light projecting signal generating and distributing circuit for sequentially emitting the light projecting elements at predetermined intervals ;
b) One side surface is a light-receiving member mainly composed of a cylindrical light guide rod installed so as to be able to directly receive light emitted from the plurality of light-projecting elements arranged in an aligned manner. A light reflecting surface corresponding to a chord extending over a predetermined arc range opposite to the one side surface on the surface, and a light receiving element having a light receiving element attached to at least one end of the light guiding rod; A light-receiving side portion comprising a light- receiving element operating circuit for operating the light-receiving element and a light-receiving signal processing circuit for processing a light-receiving signal generated by the light-receiving element ,
c) The received light signal processing circuit stores, as the received light amount reference value, the total received light amount that the light receiving element should receive in one cycle of the predetermined cycle when there is no entry in the detection region, and the predetermined cycle Each time, the light receiving element compares the total received light amount received in the cycle with the received light amount reference value, and outputs an object detection signal when the received total received light amount is lower than the received light amount reference value. It has become,
A photoelectric switch for wide-range detection characterized by this. 2. The photoelectric switch according to claim 1, wherein the light guide rod includes a cylindrical transparent core having the light reflecting surface on the string side surface, and a transparent clad that protects an outer periphery of the transparent core. . The photoelectric switch according to claim 1, wherein the light receiving elements are disposed at both ends of the light guide rod. The photoelectric switch according to claim 1, wherein the light receiving element is disposed only at one end of the light guide rod, and a light reflecting mirror surface is provided at the other end of the rod.

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