JPH0452921Y2 - - Google Patents

Description

[Detailed explanation of the idea] 〔Technical field〕 This invention relates to a photoelectric detector.

[Background technology]

There are various types of photoelectric detectors, but
As one of them, a light emitting part and a light receiving part are provided facing each other, and a groove is formed between them, through which the object to be detected passes, and the light emitted from the light emitting element provided in the light emitting part passes through the groove. A photoelectric detector (referred to as a "groove-type photoelectric detector") is a photoelectric detector that is configured to cross the groove and enter a light-receiving element provided in the light-receiving section, and the object to be detected passing through the groove is detected by blocking the light. )
There is.

This device is used, for example, to detect coins (objects to be detected) in vending machines. However,
Metal objects to be detected, such as coins, are often charged, and the voltage generated by this charge is quite high, so when detecting such metal objects, the above The light emitting element and the light receiving element are likely to be destroyed due to the charge. This is element destruction due to so-called static electricity. There are two types of destruction mechanisms: one is when charge is directly discharged to the element, causing element destruction, and the other is when electric charge is induced around the element due to electrostatic induction, and this secondary charge causes element destruction. .

In order to prevent such destruction, it is conceivable to use, for example, a light emitting diode or a light receiving diode with high breakdown voltage. However, in this case, since it is difficult to predict the magnitude of the voltage caused by static electricity, it is necessary to use a voltage with a rating that is far from the normally required withstand voltage, resulting in a significant increase in cost. However, even if a single discharge does not cause damage, abnormally high voltage is still applied to the diode repeatedly, so it gradually deteriorates and eventually malfunctions in detection. Measures such as increasing the withstand voltage do not provide a fundamental solution.

[Purpose of invention]

In view of the above circumstances, this invention essentially prevents the object to be detected from being destroyed by static electricity, and also stabilizes the optical axis between the projecting and receiving elements, allowing normal object detection operation to be maintained for a long period of time. The purpose is to provide a photoelectric detector.

[Disclosure of invention]

In order to achieve the above object, this invention has a light emitting part and a light receiving part facing each other, a groove is formed between them for the object to be detected to pass through, and a light emitting element provided in the light emitting part emits light. In a photoelectric detector, the light crosses the groove and enters a light-receiving element provided in a light-receiving part, and the detection is performed when an object to be detected passing through the groove blocks the light, Each front surface of the optical elements is covered with a metal spring plate so as not to impede passage of the light, and these metal spring plates use their respective spring forces to move the optical elements to form a case of the light emitting/receiving section. The gist of the invention is a photoelectric detector that is pressed against the inner surface of a wall.

Hereinafter, this invention will be explained in detail with reference to the drawings showing one embodiment thereof.

FIG. 1 shows the appearance of one embodiment of the photoelectric detector according to this invention. FIG. 2 shows the internal structure of this photoelectric detector.

In this photoelectric detector 1, a light projecting part 3 is placed on a base 2.
and a light receiving section 4 are provided facing each other, and a groove 5 through which an object to be detected (for example, a coin M) passes is formed between them. A window 6 is provided in the case wall 3c of the light projector 3 facing the groove 5, and a window 6' is provided in the case wall 4c of the light receiver 4. Light emitted from the light projecting element 10 provided in the light projecting section 3 exits the window 6, crosses the groove 5, enters through the window 6', and hits the light receiving element 11 provided in the light receiving section 4. ing.

When the detected object does not pass through the groove 5, light is detected by the light receiving element 11, but when the detected object passes through the groove 5, the light is blocked and the light receiving element 11 no longer detects the light. Therefore, in this photoelectric detector 1,
When the light receiving element 11 is detecting light, it is determined that there is no object to be detected, and when the light receiving element 11 is not detecting light, it is determined that the object to be detected is present.

The light projecting element 10 includes an aspherical lens 13 for projecting light at the front and a light emitting diode chip 15 inside. The light-receiving element 11 includes an aspherical lens 14 for light reception at the front, and a light-receiving diode (or light-receiving transistor) chip 16 inside. Both optical elements 10 and 11 are mounted on a printed circuit board 20 by soldering their respective metal terminals 17 and 18 to the printed circuit board 20. The printed circuit board 20 itself is fixed to the base 2 by an appropriate method such as screwing (not shown). Electrical connections inside and outside the photoelectric detector 1 are made using cables 21...2
1.

The front surfaces of both the light emitting element 10 and the light receiving element 11 are covered with metal spring plates 25, 25 for electrostatic shielding so as not to obstruct the passage of light. These metal spring plates 25, 25 not only have an electrostatic shielding effect, but also serve as a shield for each optical element 10, 11.
are pressed by spring force against the inner surfaces 3b and 4b of the wall that constitutes the case of the light emitting/receiving section.

The configuration around the metal spring plate 25 will be described in detail below.

The metal spring plate 25 has a substantially U-shape as shown in FIGS. 2 and 3. Light emitting/receiving element 10,
11 is sandwiched between the U-shaped metal spring plates 25. A U-shaped piece 25a covering the front surface of the element is provided with a window 25b into which the aspherical lenses 13 and 14 are fitted, so that the passage of light is not obstructed.

As shown in FIG.
1, and the other piece 25a
The hem is widened. The metal spring plate 25 is pushed into the light receiving part 11, and the metal spring plate 25 is in contact with the inner surface 4a of the wall on the rear side of the light receiving element 11.
Due to the spring force of the piece 25c, the light receiving element 11
It is strongly pressed against the inner surface 4b of the wall that constitutes the light receiving section 11. The metal spring plate 25 of the light emitting element 10 is completely different from the light receiving element 11 described above, except that the inner surface 4a of the wall is replaced with the inner surface 3a, and the inner surface 3b of the wall is replaced with the inner surface 4b. The same thing can be said.

Note that both metal spring plates 25 have legs 25e, 25e.
is soldered to the printed board 20 and mounted on the board 20, and an electrical ground (common line) is connected on the printed board 20.

As seen above, the light emitting/receiving elements 10 and 11 of the photoelectric detector 1 are made of metal plates 25 and 25 for electrostatic shielding.
is installed. Therefore, even if the object to be detected is charged with static electricity, the electric charge will not be absorbed by the optical element 1.
From the metal spring plate 25 without passing through 0 and 11,
Discharged directly to earth. Furthermore, the charge generated by electrostatic induction is also directly discharged to the ground via the metal plate 25, and the amount of induced charge itself is reduced to the extent that no damage occurs due to the shielding effect of the metal plate 25. It is also done. In other words, optical element 1
Since the action of static electricity that caused the destruction of the optical elements 10 and 11 is no longer applied to the optical elements 10 and 11, or is reduced, an essential measure to prevent destruction has been taken.

We conducted repeated experiments in which a detection object made of a metal material was charged to a voltage of about 10,000 to 15,000 volts and actually detected.
No destruction of the optical elements 10 and 11 occurred at all.

Since both of the light emitting/receiving elements 10 and 11 are pressed against the inner surfaces 3b and 4b of the wall by the metal spring plates 25, their fixed positions do not shift. Therefore, the optical axis between the light emitting and receiving elements 10 and 11 is stabilized, and normal object detection operation is maintained over a long period of time.

Incidentally, FIG. 4 shows a part of the internal structure of another embodiment of the photoelectric detector according to this invention. This photoelectric detector 1' includes a light receiving element 10' in a light projecting section 3'.
Positioning ribs 3'h...3'h are formed in advance. Therefore, accurate positioning can be achieved simply by fixing the light projecting element 10' so that it hits the rib 3'h and stops, so that the optical axis can be set with high precision. It goes without saying that such positioning ribs may also be provided within the light receiving section.

FIG. 5 represents the electrical circuit of the photoelectric detectors 1, 1'.

While the light L from the light emitting diode D1 is received by the light receiving diode D2, the amplifier A makes the transistor T conductive. When the light L is blocked by the object to be detected and the light receiving diode D2 no longer receives light,
Amplifier A blocks transistor T. In other words,
Object detection is output as conduction/cutoff of transistor T. Note that Vc is a driving power supply section.

The invention is not limited to the above embodiments. The shape of the metal spring plate and the shape of the groove may be other than those shown. The photoelectric detector does not need to include a power supply, a transistor, or an amplifier. The structure may be such that the aspheric lenses of the light emitting element and the light receiving element do not protrude from the metal spring plate but are provided inside the spring plate. The photoelectric detector may have an open structure in which, for example, the upper wall or side wall of the light emitting/receiving section is used and the light emitting element and the light receiving element are exposed.

[Effect of idea]

The photoelectric detector according to this invention has the configuration described above. Therefore, damage to the detected object due to static electricity is essentially prevented.
The optical axis between the light receiving elements is stabilized and normal object detection operation is maintained for a long period of time.

[Brief explanation of drawings]

FIG. 1 is an external perspective view of an embodiment of the photoelectric detector according to this invention, FIG. 2 is a sectional view showing the internal structure of this photoelectric detector, and FIG. 3 is a light receiving element of the photoelectric detector. 4 is a partial sectional view of another embodiment of the photoelectric detector according to this invention, and FIG. 5 is an electric circuit of one embodiment of the photoelectric detector according to this invention. It is a diagram. DESCRIPTION OF SYMBOLS 1... Photoelectric detector, 2... Base, 3... Light projecting part, 4... Light receiving part, 5... Groove, 10... Light projecting element, 11... Light receiving element.

Claims (1)

[Scope of utility model registration request] A light emitting part and a light receiving part are provided facing each other, and a groove is formed between them for the object to be detected to pass through, and the light emitted from the light emitting element provided in the light emitting part crosses the groove and enters the light receiving part. In a photoelectric detector, the light is detected by a detected object passing through the groove blocking the light. It is covered with metal spring plates so as not to obstruct passage, and these metal spring plates press both the optical elements against the inner surface of the wall forming the case of the light emitting/receiving part by their respective spring forces. photoelectric detector.