JPS6246284Y2 - - Google Patents

Description

[Detailed description of the invention] Field of the invention This invention relates to a photoelectric sensor, in particular, which has a light-emitting element and a light-receiving element that are optically coupled, and detects light in response to interruption of light from the light-emitting element to the light-receiving element. The present invention relates to a so-called light-shielding photoelectric sensor that operates.

Description of the Prior Art A conventional light-shielding photoelectric sensor has a case made of an opaque material, and the case surfaces face each other with a space between them, from which light emitted by a light emitting element is output. Only the pair of opposing surfaces to which input is made are made of a transparent member. In other words, the case of a conventional light-shielding photoelectric sensor is made by so-called two-color molding or by bonding an opaque member and a transparent member to make only the necessary parts, that is, the light emitting and light receiving windows, transparent, while preventing light from other parts. They were made of opaque material to prevent the intrusion of foreign substances.

By the way, the light emitting window and light receiving window provided in the case play a role in determining and adjusting the direction and size of the optical path from the light emitting element to the light receiving element, so it is best to make these windows as small as possible. This is essential for improving the detection accuracy of this type of detection sensor, and is useful for preventing malfunctions caused by external light.

However, when the light emitting window and the light receiving window of the case are made smaller, a misalignment occurs between the optical axis from the light emitting element to the light receiving element and the center axis of the light emitting window and the light receiving window.
There was a drawback that light could no longer be transmitted from the light emitting element to the light receiving element, making it impossible to function as a detection sensor. Therefore, conventional light-blocking photoelectric sensors have certain limitations in their performance, and have drawbacks such as being unable to detect small objects.

Purpose of the invention The object of this invention is to provide a photoelectric sensor that eliminates the above-mentioned drawbacks and has significantly improved detection performance.

Summary of the invention Simply put, this invention includes a holding member that holds a light emitting element and a light receiving element facing each other at a certain interval, and the holding member maintains a path of light from the light emitting element to the light receiving element. A small hole is formed to define the optical axis of the light emitting element and the light receiving element, and the holding member holding the light emitting element and the light receiving element is surrounded by the outer peripheral surface of the holding member. It is a photoelectric sensor that is housed in a case formed into a shape, and the case is made of a material that transmits light with a long wavelength greater than a predetermined wavelength, but does not transmit light with a shorter wavelength less than the predetermined wavelength.

The above objects and features of this device will become clearer from the following description of preferred embodiments with reference to the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows the relationship between the wavelength and light transmittance of the case material of the preferred embodiment of this invention, as well as the light emitting diode (LED) and display LED described later.
FIG. 2 is a diagram showing the wavelength and output of light.

In the figure, the horizontal axis is the wavelength expressed in angstroms, and the vertical and horizontal axis indicate the light transmittance of the case or the output of the light emitting diode.

As shown, in this case the wavelength is 6.5×10 ³
It easily transmits light with a wavelength of 7.0 x 10 ³ angstroms or more, but hardly any light with a wavelength shorter than that. From another perspective, this means that the wavelength is 7.5×
Since 10 ³ to 8.0×10 ³ angstroms or more is infrared rays, the case will hardly allow visible light to pass through, except for part of the long wavelength side of visible red light. In other words, the case appears visually almost opaque. For example, "Iupilon" is a case material with such properties (characteristics).
There are colored material resins such as (trade name of Mitsubishi Plastics Chemical Co., Ltd.).

Next, the wavelength of the light from the projecting LED is infrared light of approximately 9.5×10 ³ angstroms in this embodiment, and the case easily transmits this light.

In addition, the wavelength of the light from the display LED is approximately 6.8 x 10 ³ angstroms of visible red light, and the case transmits this light, so if the display LED lights up inside the case, it will be visible from the outside. Can be confirmed.

Note that the boundary value of the wavelength of light transmitted through the case material, the wavelength of light of each LED, etc. can be changed as appropriate depending on the required use of the photoelectric sensor.

FIG. 2 is an exploded view of the preferred embodiment. This photoelectric sensor includes a light emitting/light receiving element holder 4, a light emitting LED 2, a light receiving photodiode 3, a printed circuit board 1 on which a predetermined electronic circuit is formed, and a case 5. The light emitting/receiving element holder 4 includes holding parts 43 that protrude at a predetermined interval, and masks 42 having small holes 421 are formed at the tips of the holding parts 43, respectively. In each small hole 421 of this mask 42, the light emitting part 2 of the LED for light projection is inserted.
The light emitting LED 2 and the light receiving photodiode 3 are each held by the holding part 43 so that the light receiving part 31 of the light emitting LED 1 and the light receiving LED 3 fit together (see FIG. 5).

Further, a printed circuit board 1 is attached to the light emitting/receiving element holder 4. This printed circuit board is electrically connected to the external output terminal 41 of the light emitting/light receiving element holder 4, and is also electrically connected to the terminal 2 of the light emitting LED 2.
2 and the terminal 32 of the photodiode 3 for light reception.

A groove 52 is formed in the case 5. This groove 52 is a groove formed to detect an object to be detected, and as will be described later, when an object to be detected is located in a predetermined portion within this groove, this photoelectric sensor detects the object. Note that 51 formed on both side surfaces of the case 5 are mounting portions for mounting this photoelectric sensor.

FIG. 3 is a perspective view of this embodiment when FIG. 2 is assembled.

Moreover, FIG. 4 is a plan view and a side view of the case 5 and the light emitting/light receiving element holder 4 of this embodiment explained in FIG. 2.

Next, FIG. 5 shows an embodiment showing the arrangement relationship between the light emitting/light receiving element holder 4 and the case, and the relationship between the small hole 421 that determines the light emitting optical path and the light receiving optical path, the light emitting LED, and the light receiving photodiode. FIG.

In the figure, the light emitting/light receiving element holder 4 is integrally formed of an opaque material. Two small holes 421 are formed in the center of the mask portion 42 of the holder 4.
In other words, the line connecting the central axes of the small holes 421 is defined as a straight line. This small hole 42
1 and the light projecting portion 21 of the light projecting LED 2 and the light receiving portion 31 of the light receiving photodiode 3 are respectively fitted. Therefore, the light emitted from the light projecting LED 2 comes out from one small hole 421 and the other small hole 4.
21 and is received by the light receiving photodiode 3.

Moreover, since this small hole 421 is provided in the integrally molded light emitting/light receiving element holder 4 as described above, even a very small hole can be defined so that its central axes are aligned in a straight line.

The case 5 that covers the light emitting/light receiving element holder 4, the light emitting LED 2, and the light receiving photodiode 3 is
As mentioned above, it is visually almost opaque, but
The light emitted by the light projecting LED 2 is easily transmitted. Therefore, the case 5 does not interfere with the transmission of light between the light emitting LED 2 and the light receiving photodiode 3.

However, this case 5 blocks visible light, ultraviolet rays, etc. with a wavelength of approximately 6.5×10 ³ angstroms or less from entering the light receiving photodiode 3, especially its light receiving portion 31, from the outside. Malfunctions due to reception of such light from the outside are prevented.

FIG. 6 is a block diagram showing an example of an electronic circuit formed on the printed circuit board 1 (FIG. 2). In this embodiment, the electronic circuits formed on the printed circuit board 1 include a power supply circuit 19, an oscillation circuit 10, a capacitor 11 that determines the time constant of the oscillation circuit, a frequency divider circuit 12, a driver circuit 13 for a light emitting LED, It includes a light receiving circuit 14 that receives the output of the light receiving photodiode 3, a capacitor 15, a comparator 16, a pulse conversion circuit 17, and an output circuit 18. The feature of this circuit is that the light emitting LED 2 is connected to the oscillation circuit 10.
It is turned on based on a predetermined clock pulse oscillated by the light receiving photodiode 3, and outputs a detection output when the light received by the light receiving photodiode 3 is interrupted in synchronization with the timing of the clock pulse. . That is, since the light received by the light-receiving photodiode 3 is normally synchronized with the clock pulse oscillated by the oscillation circuit 10 and output from the frequency dividing circuit 12, other light,
That is, even if the light receiving photodiode 3 receives light from the outside and the output from the light receiving circuit 14 is given to the comparator 16, unless it is synchronized with the clock pulse,
An output based on this is not output from the output circuit 18.

Therefore, by driving the light emitting LED 2 and the light receiving photodiode 3 with the modulated pulse signal of the electronic circuit as shown in Fig. 6, the light receiving photodiode 3 of the photoelectric sensor (Fig. Malfunctions can be prevented even when receiving infrared rays, etc.

In this embodiment, the printed circuit board 1 on which a predetermined electronic circuit is formed is built into the photoelectric sensor, but this electronic circuit is provided externally, and the output terminal 41 of the photoelectric sensor is connected to the external electronic circuit. It is also possible to have a configuration in which the two are connected.

Effects of the invention As described above, according to this invention, the optical path between the light emitting element and the light receiving element is determined only by the small hole formed in the light emitting/light receiving element holding member, resulting in very good detection performance. It can be made into a photoelectric sensor.

In addition, since the outer case is made of a material that transmits only light of a predetermined wavelength or more, there is no need for a light emitting window or a light receiving window, which eliminates the manufacturing and assembly difficulties associated with forming such windows. Since it can be integrally molded, it is possible to provide a low-cost photoelectric sensor with excellent water resistance and dust resistance.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between wavelength and light transmittance of the case material of a preferred embodiment of this invention.
FIG. 2 is an exploded perspective view of the embodiment. FIG. 3 is a perspective view of FIG. 2 when assembled. FIG. 4 is a plan view and a side view of the case and light emitting/receiving element holder shown in FIG. 2. FIG. 5 is a partial plan cross-sectional view of the embodiment. FIG. 6 is a circuit diagram of an electronic circuit of one embodiment. In the figure, 1 is a printed circuit board on which a predetermined electronic circuit is formed, 2 is a light emitting LED, 3 is a light receiving photodiode, 4 is a light emitting/light receiving element holder, and 5 is a light emitting/receiving element holder.
indicates a case.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) A photoelectric sensor that includes a light emitting element and a light receiving element and detects an object by blocking the light given from the light emitting element to the light receiving element, which uses light of a specific wavelength. A mask that holds a light emitting element that emits light and a light receiving element facing each other at a certain interval, and that has small holes on the opposing surfaces of the light emitting element and the light receiving element for adjusting the light emitting optical path and the light receiving optical path, respectively. a light emitting/light receiving element holding member, which is electrically connected to the light emitting element and the light receiving element, generates an electric signal that causes the light emitting element to emit light, and responds to a change in the output signal of the light receiving element; an electronic circuit for detecting an object, and a shape selected to surround the outer peripheral surface of the holding member,
and a case formed of a material that transmits light with a long wavelength equal to or more than a predetermined wavelength and does not transmit light with a short wavelength less than the predetermined wavelength. (2) The photoelectric sensor according to claim 1, wherein the electric signal for light emitting element light generated by the electronic circuit is a modulated pulse signal. (3) The predetermined wavelength is about 6.5×10 ³ to 7.0×
¹⁰³ angstrom, the photoelectric sensor according to claim 1 of the utility model registration. (4) The photoelectronic circuit according to claim 1 or 3, wherein the electronic circuit includes a light emitting element for detection and display, and the light emitted by the light emitting element is visible light that passes through the case. sensor.