JPH0443209B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a photoelectric switch for projecting light such as infrared rays and detecting the reflected light to measure the presence or absence of an object or the distance to the object. .

(Prior art) This type of photoelectric switch is used as a sensor on a production line in a factory to check whether an object has passed in front of it, or if high accuracy is required, to detect whether an object has passed within a certain distance from the sensor. It is used to detect whether or not it has passed.

The light emitting part and the light receiving part of such a photoelectric switch are as shown in FIG. A light emitting element 721 is placed at the back of the part 71a, and a light receiving element 72 is placed at the other cylindrical part 71b.
2, a condenser lens 731 is attached to the front surface of one cylindrical portion 71a, a condenser lens 732 is also attached to the front surface of the other cylindrical portion 71b, and each condenser lens 731, 732 is held with a light-shielding holder. It is held and fixed by a frame 74. Reference numeral 75 denotes a main body case to which the light projecting section and the light receiving section configured as described above are attached.

Incidentally, dirt attached to both the condensing lenses 731 and 732 must be cleaned and removed since it affects the performance of the photoelectric switch.
1,732, there will always be a step difference. Therefore, if there is this level difference, it is difficult to completely clean it.

Therefore, as shown in FIG. 13, a lens 76 is constructed in which a condensing lens for light emission and light reception is integrated, and the lens part 76a on one side is used for light emission, and the lens part 76b on the other side is used for light reception. There is one with a flattened front. With this configuration, there is no step on the front surface, so it is easy to clean dirt on the front surface. However, in this case, the tip portions of the light emitting tube portion 71a and the light receiving tube portion 71b are optically coupled by the intermediate portion 76c of the lens 76, causing light to circulate between them. Ru.

In order to completely eliminate this light circulation,
It is necessary to eliminate the transparent intermediate portion 76c of the lens 76, but if this is done, the problem pointed out in FIG. 12 will occur again.

(Object of the Invention) The present invention has been made in view of the above points, and its purpose is to form the front surface flat so as to prevent light from going around and to make it easy to clean dirt on the front surface. The object of the present invention is to provide a photoelectric switch that is easy to operate.

(Structure of the Invention) For this purpose, the present invention provides a light projecting section constituted by a light projecting light-shielding tube section that accommodates a light projecting element and a light projecting condensing lens, and an object to be detected by the projection light from the light projecting section. In the photoelectric switch, the photoelectric switch is equipped with a light-receiving section composed of a light-receiving element that receives reflected light from the light-receiving element, a light-receiving condensing lens, and a light-receiving light-shielding tube section that accommodates the light-receiving element and the light-receiving condensing lens. A dust-proof light-emitting window that covers the front surface, a dust-proof light-receiving window that covers the front surface of the light-receiving section, the light-emitting window, and the light-receiving window are connected by bypassing their alignment directions. A transparent insert plate consisting of a connecting portion and a light shielding member that surrounds each of the light emitting window portion and the light receiving window portion and optically separating them are provided, and the light shielding member is used for the light emitting The back surface of the part that separates the window part from the light-receiving window part and the tip part of the partition wall which separates the light-emitting light-shielding cylinder part and the light-receiving light-shielding cylinder part are fitted in a concave-convex structure or a stepped structure. It is constructed by combining them.

(Example) Hereinafter, an example of the photoelectric switch of the present invention will be described with reference to the drawings. As shown in FIG. 1, the photoelectric switch of this embodiment has a structure in which an optical unit and other components are provided inside 1a of a main body 1, and a top cover 2 is closed to cover them (FIGS. 4 and 5). It is. On the front side 1b of the main body case 1, there is an infrared light emitter A in the center, and light receivers B on both sides of the light emitter A at the same distance.
B' is provided. The light projecting section A and the light receiving sections B and B' constitute an optical unit. In addition, on one side surface 1c adjacent to the front surface 1b described above, there is a distance setting section C for setting a detection distance area and a distance for indicating when an object to be detected enters the set distance area. A display section D is provided. Furthermore, a cord connecting portion H is provided at the corner portion of the back surface.

The front surfaces of the light projecting section A and the light receiving sections B, B' are covered with a dustproof plate 3 as shown in FIGS. 2 and 3. This dustproof plate 3 includes an insert plate 31 made of a transparent member such as a red transparent member,
For example, a black light shielding member 32 having a light shielding property is formed integrally with the insert plate 31 by two-color resin molding so as to cover the front and back surfaces of the insert plate 31.

That is, the insert plate 31 has a dust-proof window 31a of the light-receiving section B' and a dust-proof window 31 of the light-emitting section A.
b. The dustproof window 31c of the light receiving section B has a protruding shape and is separated in the alignment direction by slits 31d, 31d having a step, and the windows 31a to 31c are connected to each other. By bypassing the direction of arrangement of 31a to 31c, the upper and lower connecting parts 31e, 3
1e.

On the other hand, on the front surface of the insert plate 31, the light shielding member 32 is provided with a window frame portion 32a so as to surround each of the window portions 31a to 31c and optically isolate them.
It is formed as a flange portion 32b on the back surface for suspending the O-ring 4. Notch 32c formed in this flange 32b
is for positioning the lens, which will be described later. Further, in the window frame portion 32a, a recess 32e into which the tip of a light shielding tube 5 (to be described later) fits is formed on the back surface of a light shielding portion 32d embedded in the slit 31d and continuous between the front and back sides.

Therefore, this dustproof plate 3 has window portions 31a to 31c.
The boundary between the front surface of the window frame section 32a and the front surface of the window frame section 32a has no step or the like and is flush and flat, so even if dust adheres to the front surface, the window sections 31a to 31c
All front surfaces of each can be easily cleaned with a cloth or the like. Moreover, since adjacent portions of the window portions 31a to 31c are separated by the light shielding portion 32d of the light shielding member 32, a phenomenon of light going around between the window portions 31a to 31c does not occur. Furthermore, since the light shielding member 32 is integrated with the insert plate 31 by integral molding, the resin of the light shielding member 32 is rolled into both the front and back sides of the insert plate 31.
The union between the two will be complete, and there will be no fear of separation.

The light-shielding tube 5 described above includes a tube section (not shown) for the light receiving section B', a tube section 5b for the light projecting section A, and a tube section 5c for the light receiving section B, and a partition wall that separates each tube section. As mentioned above, the tip of 5d is the light shielding member 3 of the dustproof plate 3.
2 with a concave-convex structure, and the outer peripheral portion 5
The tip of e is fitted inside the flange portion 32b of the light shielding member 32 in a stepped structure. For this reason, for example, the cylindrical portion 5
b and the cylindrical portion 5c, the recess 32 of the light shielding member 32
The abutting surface between e and the tip of the partition wall 5d becomes an optical path, but since the path is curved, there is no risk of light passing through. Incidentally, even if the light blocking portion 32d and the tip portion of the partition wall 5d are fitted in a stepped structure, such as the combination of the flange portion 32b and the outer peripheral portion 5e, light passage can be similarly prevented.

A condensing lens for light reception is placed in the cylindrical portion for the light receiving section B', a condensing lens 62 for light emission is placed in the cylindrical section 5b for the light emitting section A, and a condensing lens 62 for light emission is placed in the cylindrical section 5c for the light receiving section B. A condensing lens 63 for receiving light is arranged respectively. To attach the condenser lens 62, as shown in FIG. This is done by pressing the tip of the plate portion 5i. The same applies to other condensing lenses.

A light projecting element (light emitting diode) 8 is attached to the inner part of the cylindrical portion 5b of the light projecting section B via an aperture 7 (FIG. 4).

Further, an upper piece 5 is located at the back of the cylindrical part 5c of the light receiving part B.
f ₁ , lower piece 5f ₂ , and projection 5f ₃ guide part 5
f is formed, and the holder 92 is guided by this guide portion 5f. 92a is a recess that fits into the projection _5f3 . A position detection photodetector (PSD) 102 is fixed and held within this holder 92 with adhesive or the like. 11 is a filter for cutting out unnecessary wavelength ranges (FIG. 5).

This position detection light receiving element 102 has a horizontally elongated light receiving section 102a, and is configured to change the output current depending on where in the longitudinal direction of the light receiving section 102a the reflected beam from the object to be detected is received. has been done. 102b is a bias terminal, 102c
and 102d are output terminals.

In the position detecting light receiving element 102, a holder 92 is provided so as to be movable in the direction of the arrow x, thereby making the position detecting light receiving element 102 itself movable in the longitudinal direction. Position adjustment is possible. That is, a hole 5g is formed in the upper piece _5f1 of the guide part 5f at the back of the cylindrical part 5c, and a long groove 92b is also formed in the holder 92. Then, the main body 122a is inserted into the hole 5g with the pin 1.
22b into the long groove 92b.
2 is installed. 122c is a groove for a driver. Note that the eccentricity of the pin 122b from the axis of the main body 122a is L (FIGS. 7 and 8).

Therefore, when a driver is applied to the groove 122c and the eccentric stud 122 is rotated, the pin 122b is moved into the long groove 92b.
In order to move inside, the entire holder 92 is guided by the upper piece 5f ₁ , the lower piece 5f ₂ , and the protrusion 5f ₃ of the guide portion 5f, and moves by a maximum distance of 2L in the direction of the arrow x. Therefore, since the position detection light receiving element 102 also moves in the same way, its position can be adjusted.

To explain this point in more detail with reference to FIG. 9, if the eccentric rivet 122 is rotated in the direction of arrow α, a force E is applied to the holder 92 and at the same time a force F is applied to press the eccentric rivet 122. In this case, if the lower surface 92c of the holder 92 is used as the abutment surface, a moment M is applied around the lower surface 92c, and the holder 92, which should normally move from side to side, moves around the lower surface 92c. At this time, a fairly large stick slip phenomenon occurs at the lower surface 92c, making left and right adjustment difficult. In order to prevent this, it is sufficient to provide a contact surface of the force F on the surface of the eccentric rivet 122 on which the force E acts.

In this embodiment, since it is difficult to solve the above problem in terms of space, a recess 92a is formed in the holder 92 in order to bring the abutment surface that receives the force F as close as possible to the surface on which the force E acts on the eccentric rivet 122. In addition, a protrusion _5f3 is provided on the guide portion 5f, and the mating surface G of both
I decided to accept it. This is much improved compared to the case where the abutting surface is the lower surface 92c.

Although one light receiving section B has been described here, the position detection light receiving element 10 of the other light receiving section B' has been described.
1. The holder 91 and the eccentric stud 121 have exactly the same structure except that the entire structure is symmetrical.

The light emitting section A and the light receiving sections B and B' configured as described above are provided integrally with the light shielding tube 5 as one optical unit, and are attached to the main body case 1. It is attached to an opening 1d formed on the surface 1b side of 1 with an O-ring 4 in a buffer/watertight structure. That is, the dustproof plate 3
An O-ring 4 is attached to the outer surface of the flange 32b of the light shielding member 32.
When the O-ring 4 is fitted into the stepped portion _1d1 formed in the front part of the opening 1d, as shown in FIGS. 1, 4, 5, etc. ,
The entire optical unit is buffered against the main body case 1.
Installed in a watertight structure. In particular, with this mounting structure, even when external force is applied to the main body case 1,
Since the external force is absorbed by the O-ring 4, the force applied to the optical unit itself is buffered, and an adverse effect on the optical unit can be avoided.

The O-ring 4 used is one that is shaped during molding into a substantially rectangular shape similar to the outer shape of the flange 32b of the dust-proof plate 3 into which the O-ring 4 is fitted. If a circular O-ring is used, not only will it be difficult to assemble, but the corners of the dustproof plate 3 will apply force to the O-ring, causing it to stretch locally, making waterproofing less reliable. By using the O-ring 4, which is made approximately rectangular as described above, such drawbacks are prevented.

A distance setting section C for setting the detection distance area and a distance display section D for indicating that the object to be detected has entered the set area are located on the side surface 1 of the main body case 1.
(FIG. 1, FIG. 6). 13 is a printed wiring board;
A variable resistor 14 for distance setting and a display light source (light emitting diode) 15 for displaying the distance are attached to this part, and the rotary operation part 14 of the variable resistor 14
A knob 16 is attached to a via a connecting plate 17.

The printed wiring board 13 is positioned relative to the two protrusions 18a and 18b of the display body 18 made of a transparent member, and is fixed by welding one of the protrusions 18b. This display main body 18 is engaged in the opening 1e of the main body case 1 by engaging protrusions 18c and 18d, and is prevented from being pulled out. 18e is a display window formed into a protruding shape so that it can be seen from a wide range as a lens part;
Its surface is polished.

The knob 16 is attached within a recess 18f formed in the display body 18 via a waterproof O-ring 19. Further, the front part of the display main body 18 also has a step 1 on the opening surface of the opening 1e of the main body case 1.
_e1 has an O-ring 20 interposed therebetween to form a watertight structure.

A name plate 21 is attached to the stepped portion _1e2 of the main body case 1 and the front surface of the display main body 18 with double-sided tape. A ring-shaped sheet 22 is interposed between the name plate 21 and the knob 16 to prevent the name plate 21 and the knob 16 from adhering to each other. Therefore, the rotation of the knob 16 is not hindered.

Therefore, since the distance setting section C and the distance display section D are incorporated into the display main body 18 and are integrated as one display block, it is possible to inspect the display block as a single unit. Not only that, but also simplified assembly and main body case 1
(Especially when installing printed wiring board 1)
3, position adjustment between the variable resistor on the printed wiring board 13 and the window 18e, etc.) are no longer necessary.

FIG. 10 shows the principle of an optical system for detecting the object to be detected Q. The distance between the condensing lenses 61 and 63 with respect to the condensing lens 62 is the same l ₀ , and the condensing lenses 61, The distance between each of the position detection light receiving elements 101 and 102 is f. Note that the position detection light receiving element 101 is a semiconductor position sensing device (Position Sensing Device).
PSD) is used, and the output terminals 101c and 101d are equipped with spot lights.
An output current is generated that is inversely proportional to the distance between r' and the electrodes 101e and 101f. The same applies to the other position detection light receiving element 102. Moreover, the light receiving elements 101 and 102 for position detection include a condensing lens 61,
It is necessary to make sure that the distance from 63 is equal to l ₁ , which is the same as the eccentric rivet 12 mentioned above.
This is done by adjusting the position of the holders 91 and 92 in the direction of the arrow x by rotating the holders 91 and 92 by 1 and 122 degrees.

Now, when infrared rays are emitted from the light emitting element 8, the light is turned into a light beam P with a certain width by the condenser lens 92 and projected onto the object to be detected Q, and reflected beams R, R' is the condenser lens 6
1 and 63 and enter the position detection light receiving elements 101 and 102, respectively.

Therefore, the position detection light receiving elements 101, 10
By detecting the position of either one of the light receiving spots r and r' generated at point 2, the distance l to the detected object Q can be determined by triangulation. That is, if the distance l is short, for example, one light receiving spot r will be located relatively biased toward the opposite side (outside) from the light projecting element 8, and if it is long, it will be located relatively biased toward the light projecting element 8 side (inside). . Therefore, the light receiving element 102
By comparing the output currents of the output terminals 102c and 102d, it is possible to know where the light receiving spot is located. Then, a comparison signal obtained by comparing both of the above output currents indicates the distance l.

Therefore, if a reference level corresponding to a predetermined distance is set by the variable resistor 14 of the distance setting section C, the detected object can be detected by detecting whether or not the comparison signal exceeds the reference level. It is possible to detect whether Q is within a set distance.
Then, when the distance is within the set distance, the distance display section D
The display light source 15 can be turned on. It goes without saying that the presence or absence of an object to be detected can also be detected depending on whether or not the light receiving spot r is received by the position detecting light receiving element 102.

The same is true for the other position detection light receiving element 101, so it is sufficient to use only one of them, and it seems that both position detection light receiving elements 101 and 102 are unnecessary, but this corrects the detection error. It was established for this purpose.

That is, the light emitted from the light projecting element 8 is turned into a parallel light beam P by the condenser lens 62, but since the light beam P has a certain width, the entire light beam P is If a portion of the beam is projected onto the object to be detected, a light spot of the reflected beam from the projected portion enters the position detection light receiving element, causing a detection error there. In other words,
As shown in FIG. 11, even though the detected object Q' is at the same distance l as in the case of FIG. 10,
Since only a part of the light beam P is projected onto the detected object Q', the positional distribution of the light receiving spots r on the light receiving surface of the position detection light receiving element 102 is different from that in FIG. 10, and the output terminals 102c, The comparison signal for comparing the output currents from 102d is different from that shown in FIG. 10, and an error occurs.

Therefore, two position detection light receiving elements 101 and 1
02 is provided symmetrically with respect to the light projecting element 8.
In this way, if the above error occurs,
Comparison signals of the output currents of both position detection light receiving elements 101 and 102 change in opposite directions. Therefore, by adding the outputs of the inner terminals 101c and 102c of both position detection light receiving elements 101 and 102, adding the outputs of the outer terminals 101d and 102d, and comparing the two added signals, the error can be canceled out. and a signal indicating the correct distance l can be obtained.

(Effects of the Invention) As described above, according to the present invention, the light emitting window portion and the light receiving window portion of the dustproof plate are separated by the light shielding member, and the light emitting tube portion and the light receiving window portion are separated from each other by the light shielding member. Since the cylindrical portions are connected, it is possible to prevent light from going around between the light projecting portion and the light receiving portion.
Further, since it is easy to form the front surface of the dustproof plate flat, it is possible to easily and completely clean the front surface. In particular, since the minimum light receiving power of the distance measuring optical system is very small at around 10nW, even a small amount of light leakage causes large noise and significantly reduces the S/N. It can be prevented.

[Brief explanation of the drawing]

Fig. 1 is a top view of a photoelectric switch according to an embodiment of the present invention with the lid removed, Fig. 2 is a perspective view of the dustproof plate, Fig. 3 is a longitudinal cross-sectional view of the dustproof plate, and Fig. 4 is a cross-sectional view of the dustproof plate in the longitudinal direction.
The figure is a sectional view taken along the a-a line in Fig. 1, Fig. 5 is a sectional view taken along the bb line, and Fig. 6 is a sectional view taken along the d-d line.
A sectional view along the line, FIG. 7 is e- in FIG. 6.
8 is a plan view of the guide part of the holder of the light receiving element for position detection, FIG. 9 is an explanatory diagram of position adjustment using eccentric studs, and FIGS. 10 and 11 are diagrams for distance measurement. Explanatory optical diagrams, Figures 12 and 1
FIG. 3 is a sectional view showing a conventional photoelectric switch. A... Light emitting section, B, B'... Light receiving section, C... Distance setting section, D... Distance display section, H... Cord connection section, 1... Main body case, 2... Lid, 3... ...Dustproof plate, 31...Insert plate, 32...Light shielding member,
4... O ring, 5... Light shielding tube, 61, 62, 6
3...Condenser lens, 7...Aperture, 8...Light emitter, 91, 92...Holder, 101, 102...
Position detection light receiving element, 11...Filter, 12
1,122...Eccentric stud, 13...Printed wiring board, 14...Variable resistor for distance setting, 15...Light source for display, 16...Knob for distance setting, 17...
Connection plate, 18...display body, 19, 20...O ring, 21...name plate, 22...sheet.

Claims (1)

[Scope of Claims] 1. A light projecting section constituted by a light projecting light-shielding cylinder section that houses a light projecting element and a light projecting condensing lens, and a light projecting section that prevents reflected light from a detected object from being projected from the light projecting section. In a photoelectric switch, the photoelectric switch is equipped with a light-receiving section composed of a light-receiving element that receives light, a condensing lens for receiving light, and a light-receiving light-shielding cylinder section that accommodates the light-receiving element and condensing lens for light reception, and a dust-proofing device that covers the front surface of the light projecting section. window for lighting,
a transparent insert plate comprising a dust-proof light-receiving window that covers the front surface of the light-receiving section, a connecting portion that connects the light-emitting window and the light-receiving window by bypassing their alignment direction; A light shielding member that surrounds each of the light window and the light receiving window and optically separates them is provided, and the light transmitting window and the light receiving window of the light shielding member are separated. A photoelectric switch characterized in that the rear surface of the part and the tip of a partition wall separating the light-emitting light-shielding cylinder part and the light-receiving light-shielding cylinder part are fitted and connected by an uneven structure or a stepped structure.