JPH09127257A - Optical sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical sensor in which the destruction of an electronic component and the like due to static electricity is prevented by a low-cost means without using a protective circuit, an electrostatic shielding plate and the like. SOLUTION: Grounding patterns 25 at a ground potential are formed on a wiring board 14 which is installed inside a case 12, and openings 28 are formed in the case 12 near the grounding patterns 25. When a steel ball or the like which is charged with static electricity is passed, the static electricity is discharged to the grounding patterns 25 through the openings 28, and a circuit component is protected form the static electricity.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an optical sensor. In particular, it relates to measures against static electricity in optical sensors.

[0002]

2. Description of the Related Art FIG. 1 is a front view showing a photo interrupter A used for detecting a steel ball. In this photo interrupter A, a wiring board 5 on which a light emitting element 3 and a light receiving element 4 are mounted is inserted into a substantially U-shaped case 2 having an object detection groove 1, and the light emitting element 3 and the light receiving element 4 are attached to the object. The detection grooves 1 are arranged on both sides of the groove 1. FIG. 2 shows a circuit configuration of the photo interrupter A, in which a current limiting resistor 9 and a light emitting element 3 such as a light emitting diode are connected in series between a power supply terminal (Vcc) 6 and a ground terminal (GND) 8 of a wiring board 5. The light receiving element 4 such as a phototransistor and the capacitor 10 are connected in parallel between the output terminal (OUT) 7 and the ground terminal 8.

[0003]

Since this photo interrupter is used for detecting steel balls, static electricity generated in steel balls or the like is easily discharged. However, since the photo interrupter is almost entirely housed in the case, when static electricity is generated in a steel ball or the like and discharged to the photo interrupter side, it flows from the closest point to the ground through the inside of the circuit. I was there. For example, as indicated by an arrow in FIGS. 1 and 2, static electricity generated in the steel ball 11 is discharged to the output terminal 7 and flows from the output terminal 7 through the light receiving element 4 to the ground terminal 8. When static electricity flows in the internal circuit of the photo interrupter A in this way, electronic components vulnerable to static electricity are destroyed.

For this reason, conventionally, a protection circuit is provided for a portion vulnerable to static electricity, or an electrostatic shield is provided so as not to discharge directly to a portion vulnerable to static electricity. However, these methods have a problem that a protection circuit, an electrostatic shield plate, etc. are required, the countermeasure against static electricity is costly, and the miniaturization of the photo interrupter is hindered.

The present invention has been made in view of the above-mentioned drawbacks of the conventional example, and an object thereof is to improve the electrostatic withstand capability of an optical sensor by an inexpensive means without using an electrostatic shield plate or the like. Is to let.

[0006]

An optical sensor according to a first aspect of the present invention is characterized in that an opening is formed in the housing in proximity to a ground side lead terminal of an electronic component housed inside the housing. There is.

The optical sensor according to a second aspect of the invention is characterized in that an opening is formed in the housing in the vicinity of the ground pattern of the wiring board housed in the housing.

[0008]

In the optical sensor of the present invention, since the opening is formed in the housing in close proximity to the ground side lead terminal of the electronic component or the ground pattern of the wiring board, steel balls, coins or other detected objects are detected. Even if static electricity is generated, the static electricity is prevented from discharging from the opening of the casing to the ground side lead terminal or the ground pattern, and preventing the static electricity from flowing to the internal circuit of the optical sensor. Therefore, it is possible to prevent the internal circuit of the optical sensor and the parts sensitive to static electricity from being destroyed by static electricity, and it is possible to improve the static electricity resistance.

[0009]

FIG. 3 is a perspective view showing a photo interrupter B according to an embodiment of the present invention, and FIGS. 4 (a) and 4 (b).
Are a plan view and a sectional view thereof. The photo interrupter B is for detecting a steel ball such as a pachinko ball rolling on a rail, and includes a light emitting element 3, a light receiving element 4, and a wiring board in a case 12 and a holder 13. 14 are stored. The light emitting element 3 is a light emitting diode (LED) or a semiconductor laser (L) that emits infrared light.
D) and the like, and the light receiving element 4 is a phototransistor or the like that is sensitive to infrared light.

5 (a) and 5 (b) are diagrams showing a pattern on the front surface side and a pattern on the back surface side of the wiring board 14, and in both of them, the hatched region indicates the copper foil portion and the satin finish is applied. The portion is covered with the resist. 5A and 5B, 7 is an output terminal, 8 is a ground terminal, 6 is a power supply terminal, 15 is a pad for connecting the lead terminal 17a on the signal input side of the light emitting element 3, and 16
Is a pad for connecting the lead terminal on the ground side of the light emitting element 3, 18 is a pad for connecting the lead terminal on the signal output side of the light receiving element 4, and 19 is the lead terminal 20b on the ground side of the light receiving element 4. Pad for doing 21,
Reference numeral 22 is a pad for mounting the resistor 9, and 23 and 24 are pads for mounting the capacitor 10. Also, 2
Reference numeral 5 is a ground pattern provided on the edge of the wiring board 14 and is electrically connected to the ground terminal 8. Reference numeral t is a through hole for electrically connecting the front and back electrodes of the wiring board 14.

In the light emitting element 3, the lead terminals 17a on the signal input side are soldered to the pads 15, the lead terminals on the ground side are soldered to the pads 16, and the wiring board 14 is sandwiched between the lead terminals. And is mounted on the wiring board 14. Similarly, in the light receiving element 4, the lead terminal on the signal output side is soldered to the pad 18, and the lead terminal 20b on the ground side is soldered to the pad 19.
The wiring board 14 is mounted on the wiring board 14 so as to be sandwiched between the lead terminals. In addition, the pad 21,
A resistor 9 is mounted between 22 and a capacitor 10 is mounted between the pads 23 and 24 to form a photo interrupter B having a circuit configuration as shown in FIG.

The light emitting element 3 and the light receiving element 4 thus mounted on the wiring board 14 are set in a holder 13 made of synthetic resin, and are inserted into the case 12 together with the holder 13. The case 12 has a substantially U shape, and an object detection groove 1 through which a steel ball passes is formed in the central portion of the case 12.
A light projecting window 26 and a light receiving window 27 are largely opened on both sides of the object detection groove 1. The light emitting element 3 and the light receiving element 4, which are inserted into the case 12 together with the holder 13, respectively have a light projecting window 26
And the light receiving window 27, but the light projecting window 26 and the light receiving window 27 are closed by the holder 13. Case 1
Reference numeral 2 is formed of an opaque resin that does not transmit infrared light to block ambient light, but the holder 13 is formed of a resin that is transparent to infrared light. It also serves as a transparent cover for 27.

Therefore, the infrared light emitted from the light emitting element 3 passes through the holder 13 and enters the light receiving element 4, but when the steel ball passes through the object detection groove 1, the infrared light is blocked. Therefore, a steel ball is detected.

Further, as shown in FIG. 4B, the case 1
On the front surface side of the wiring board 14 inserted into the wiring board 2, the ground pattern 25 is located at the edge close to the object detection groove 1. Moreover, as shown in FIGS. 3 and 4 (a),
Three discharge openings 28 are formed in a position near the front surface of the inner peripheral surface of the case 12 opposite to the open side of the object detection groove 1, that is, a position facing the ground pattern 25. Then, when the steel ball passing through the object detection groove 1 is charged with static electricity, the static electricity is discharged to the ground pattern 25 through the opening 28. Therefore, it is possible to prevent static electricity from flowing to the circuit portion and destroy electronic components and circuit components that are sensitive to static electricity, and it is possible to improve the electrostatic withstand capability of the photo interrupter B.

FIG. 6 is a perspective view showing a photo interrupter C according to another embodiment of the present invention. In this photo interrupter C, without using the holder 13,
As shown in FIG. 8, one in which the light emitting element 3 and the light receiving element 4 are mounted on the wiring board 14 such that the wiring board 14 is sandwiched between the lead terminals 17a, 17b, 20a, 20b of the light emitting element 3 and the light receiving element 4, respectively. It is inserted in the case 12 as it is. A light receiving window 27 is opened on one side surface of the object detection groove 1 so as to face the light receiving element 4, and a discharge opening 2 is provided so as to face the lead terminal 20b on the ground side of the light receiving element 4.
9 are provided. Similarly, as shown in FIG. 7, a light projecting window 26 is opened on the other side surface of the object detection groove 1 so as to face the light emitting element 3 and faces the ground-side lead terminal 17 b of the light emitting element 3. A discharge opening 29 is provided. Reference numeral 28 is an opening for discharge that faces the ground pattern 25 of the wiring board 14.

However, in this photo interrupter C, when the steel ball 11 charged with static electricity passes through the object detection groove 1, static electricity is discharged from the opening 29 to the lead terminal 17b on the ground side of the light emitting element 3 or the light receiving element 4. , 20b to prevent static electricity from flowing into the circuit.

Here, the ground side lead terminal 17b of the light emitting element 3 and the ground side lead terminal 2 of the light receiving element 4 are used.
As shown in FIG. 9A, since 0b is on the opposite sides of the wiring board 14, the opening 29 is also different in the left and right, but it is on the ground side of the light emitting element 3 and the light receiving element 4. The lead terminals 17b and 20b may be joined to the same surface of the wiring board 14 so that all the openings 29 are located closer to the front, as shown in FIG. 9B. When the steel ball 11 passes through the object detection groove 1 from both sides, the former configuration is preferable, but when the steel ball 11 passes through the object detection groove 1 from only one direction like a pachinko ball, the latter configuration is used. It is desirable to position the opening 29 on the entry side of 11.

FIG. 10 is a perspective view showing a photo interrupter D according to still another embodiment of the present invention. In the photo interrupter D, the discharge openings 28, 2
9 is extended to the front side of the case 12 so that the steel ball 11 is discharged just before it enters the object detection groove 1. In addition,
In this photo interrupter D, both the left and right openings 29 are provided on the front surface side, but the left and right openings 29 may be divided in the front and back.

FIG. 11 is a front view showing a photo interrupter E according to still another embodiment of the present invention. In the photo interrupter E, the opening 29 facing the lead terminal 17b on the ground side of the light emitting element 3 and the light receiving element 4 are provided.
And an opening 28 facing the ground pattern 25 of the wiring board 14
Are provided on the front surface of the case 12.

In each of the above-mentioned embodiments, a plurality of openings are provided, but only one opening may be provided. The number of openings and the locations to be provided can be properly selected according to the circuit configuration and the level of withstand static electricity. Further, in the above embodiment, the case of a photo interrupter for detecting a steel ball such as a pachinko ball was described, but the present invention may be used for other applications, for example, an optical sensor for detecting a coin or the like. it can.

[0021]

In the optical sensor of the present invention, the generated static electricity is discharged through the opening of the housing to the ground side lead terminal of the electronic component or the ground pattern of the wiring board. It is possible to prevent destruction by static electricity.

Further, since a protection circuit, an electrostatic shield plate, etc. are not required to prevent damage due to static electricity, the cost of the optical sensor can be reduced and the optical sensor can be miniaturized. .

[Brief description of the drawings]

FIG. 1 is a front view showing a conventional photo interrupter.

FIG. 2 is a diagram showing a circuit configuration of the above.

FIG. 3 is a perspective view showing a photo interrupter according to an exemplary embodiment of the present invention.

4A and 4B are a plan view and a sectional view of the photo interrupter of the same.

5 (a) and 5 (b) are a detailed plan view and a rear view of the above wiring board.

FIG. 6 is a perspective view showing a photo interrupter according to another embodiment of the present invention.

FIG. 7 is a partial view of the photo interrupter of the above for showing the opening on the light emitting element side of the above.

FIG. 8 is a diagram showing a light emitting element and a light receiving element mounted on a wiring board.

9 (a) and 9 (b) are schematic views showing different arrangements of discharge openings provided facing the lead terminal on the ground side.

FIG. 10 is a perspective view showing a photo interrupter according to another embodiment of the present invention.

FIG. 11 is a front view showing a photo interrupter according to still another embodiment of the present invention.

[Explanation of symbols]

 3 Light emitting element 4 Light receiving element 6 Power supply terminal 7 Output terminal 8 Ground terminal 12 Case 13 Holder 14 Wiring board 17b Lead terminal on ground side of light emitting element 20b Ground lead terminal of light receiving element 25 Ground pattern 28 Discharge opening 29 Discharge Opening for

Claims (2)

[Claims] 1. An optical sensor, characterized in that an opening is formed in the housing in the vicinity of a ground side lead terminal of an electronic component housed in the housing. 2. An optical sensor, characterized in that an opening is formed in the housing in the vicinity of a ground pattern of a wiring board housed in the housing.