JPH06295648A - Electronic switch - Google Patents

Abstract

PURPOSE:To prevent malfunction due to electrostatic discharge in an electronic switch for detecting an object electrified with static electricity. CONSTITUTION:A printed circuit board 3 is inserted between a lower case 1 and an upper case 2 to constitute an electronic switch. This electronic switch is provided with a through-hole 4 for detecting an object 7 and a protrusion 3c of the printed circuit board 3 is provided for constituting a wall surface of the through-hole 4. A current collection pattern 3d is formed in the protrusion 3c and connected to a stable potential point of a proximity switch via a discharge pattern 3e. When an object 7 electrified with static electricity passes, electric discharge to the stable potential is conducted via the current collection pattern 3d and the discharge pattern 3e. Accordingly, damage to an internal circuit of the proximity switch and malfunction can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic switch such as a penetration type proximity switch for detecting penetration of a metal sphere or the like, and more particularly to an electronic switch for preventing malfunction of a detection body due to static electricity. .

[0002]

2. Description of the Related Art Conventionally, for example, in Japanese Utility Model Publication No. 52-47093, there is known a switch which shields an internal circuit from an electric field or a magnetic field static electricity by plating a surface of a resin case which constitutes a contactless switch. Has been. In such a method, when shielding against electric fields and magnetic fields, the same effect can be obtained by plating the inner surface of the case.

[0003]

However, when plating is applied to the inside of the case against the discharge of static electricity, static electricity may be transmitted through the surface of the case and discharged into the case through the gap between the cases. Therefore, static electricity may be discharged to the internal circuit, which may cause malfunction or destruction of the electronic switch. Therefore, it is necessary to apply plating to the outer surface of the case. In this case, it is necessary to connect the plating to the stable potential of the internal circuit, but there is a drawback in that the connection to the stable potential is structurally difficult and the assembly work becomes complicated.

The present invention has been made in view of such conventional problems, and it is possible to prevent malfunction due to static electricity by discharging the static electricity of the detection body of the electronic switch to a stable potential. To aim.

[0005]

According to the invention of claim 1 of the present application, there is provided an electronic switch for detecting passage of a detection body, wherein the detection body outside the case of the electronic switch is formed at a position where the detection body first approaches. And a discharging path connecting the collecting means and the stable potential of the electronic switch, and configured to discharge the static electricity of the detection body through the collecting means and the discharging path. Is.

According to a second aspect of the present invention, there is provided an electronic switch for detecting passage of a detection body, the current collection means being provided at a position where the detection body first comes close to the inside of the case of the electronic switch, and the current collection means. It is characterized by comprising a discharge path for connecting the means and a stable potential of the electronic switch, and an opening provided near the current collecting means of the case.

According to a fifth aspect of the present invention, there is provided an electronic switch which has a printed circuit board provided in a case and detects passage of a detection body. The printed circuit board first comes close to the detection body of the case. A conductive pattern is formed on a part of the conductive pattern, and the current collecting means has an end face of the conductive pattern exposed from the case, and a discharge path connecting the current collecting means to a stable potential of the electronic switch. is there.

According to a sixth aspect of the present invention, the discharge path is characterized in that a minute gap is formed between the stable potential and the current collecting means.

[0009]

The functions of claims 1 and 2 of the present application having such characteristics
According to the invention, when the electrostatically charged detection body approaches the electronic switch, it is discharged to the stable potential side of the electronic switch via the current collecting means and the discharge path inside or outside the case. Therefore, the circuit section in the electronic switch is not adversely affected. Further, in the invention of claim 5, the conductive pattern and the discharge path are formed by the printed circuit board in the case, and when the electrostatically charged detection body approaches the electronic switch, the static electricity is generated through the conductive pattern and the discharge path. To discharge. In this case as well, the circuit portion of the electronic switch is not adversely affected. Further, in the invention of claim 6, since the minute gap is formed in the discharge path, the internal potential of the switch is not exposed outside the case of the electronic switch by the discharge path and the current collecting means. Also, during discharge, discharge is performed through this gap.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an assembly configuration diagram of a penetration type proximity switch according to a first embodiment of the present invention. As shown in the figure, this proximity switch has a casing formed of a lower case 1 and an upper case 2, and a printed circuit board 3 is provided inside. The lower case 1 is configured to include a bottom plate and three side plates as shown in the drawing, and an octagonal through hole 4 and an inner wall 5 forming the through hole 4 are provided in a part thereof. Inner wall 5
As shown in the drawing, a rectangular notch 6 is formed on the wall surface 5a on the internal circuit side. The printed circuit board 3 in the case 1 is formed by integrally forming a flat plate-shaped portion 3a and an octagonal frame-shaped portion 3b, and the frame-shaped portion 3b is provided with the cutout portion 6 of the lower case 1 described above. A protrusion 3c having an end face that is flush with the constituting inner wall 5a is formed.

FIG. 2A is a view showing the back surface of the printed board 3, showing an example of its outer shape and pattern. As shown in these figures, a current collecting pattern 3d is formed up to the end surface of the protrusion 3c of the printed circuit board 3 as a current collecting means for collecting static electricity as shown in the figure. Then, an electrostatic discharge pattern 3e forming a discharge path is formed following the current collecting pattern 3d. Further, as shown in the figure, a pattern 3f is formed on the frame-shaped portion 3b along the frame. The same pattern is formed on the upper surface of the frame-shaped portion 3b, and the frame-shaped portion is formed as a coil through the through hole, and together with this coil, an oscillation circuit is configured as described later. The oscillator circuit and other electronic circuit parts are mounted on the flat plate-shaped portion 3a.

On the other hand, as shown in FIG. 1, the upper case 2 is formed of a flat plate-like member, and is provided with leg portions 2a, 2b and side plates 2c having a length corresponding to the height of the lower case 1. Further, wide leg portions 2d and 2e are provided on the left and right sides. An octagonal through hole 2f is formed at a position corresponding to the through hole 4 of the upper case 2. A downward projecting portion 2g that forms the same wall surface as the inner wall 5a of the lower case 1 is formed on the inner wall of the through hole 2f. The size of the protrusion 2g is the length until the protrusion 3c of the printed circuit board 3 comes into contact with the protrusion 2c.

In FIG. 3, the printed circuit board 3 is inverted from the state of FIG. 1 and inserted into the lower case 1, the upper case 2 is covered from the upper part thereof, and the legs 2a to 2e are provided in the grooves and openings of the lower case. FIG. 4 is a perspective view showing a state of being fitted along, and FIG. 4 is a vertical sectional view taken along line AA of the through hole 4 portion. When assembled in this manner, the tip end surface of the protrusion 2g of the upper case 2 and the back surface of the protrusion 3c of the printed circuit board 3 are brought into contact with each other, and the current collecting pattern 3d of the protrusion 3c and the bottom surface of the notch 6 of the lower case 1 Will come into contact.

FIG. 5 is a block diagram showing the structure of the proximity switch according to this embodiment. As shown in the figure, a coil 11 is formed in the frame-shaped portion 3b on the printed circuit board 3, and an oscillation circuit 12 using this coil as an oscillation coil is provided. The output of the oscillator circuit 12 is the Schmitt trigger circuit 1
Given to 3. The Schmitt trigger circuit 13 rectifies this oscillation output to shape the waveform, and its output is given to the output circuit 14. The output circuit 14 outputs an object detection signal based on the decrease in the amplitude level. Each of these circuit blocks has a power supply Vc and a ground terminal GND.
Are connected. The discharge pattern 3e is supplied from the power source independently of the grounding pattern of the electronic circuit section.
It is directly connected to the ND terminal. The ground terminal GND may be directly connected to the power supply terminal Vc.

In the proximity switch constructed in this way, as shown by the arrow in the cross-sectional view of FIG. 4, the detection body, here the metal ball 7, passes upward from the lower case 1 side.
Therefore, first, when the metal ball 7 is charged with static electricity, the metal ball 7 is discharged through the discharge pattern 3e toward the nearest pattern connected to the ground end of the printed circuit board 3, that is, the static electricity collection pattern 3d. Become. If there is no discharge at this position, even if there is a slight gap 8 between the lower case 1 and the upper case 2 as shown in FIG. 4, the pattern on the printed circuit board 3 will not be discharged. Therefore, the stability of the internal circuit on the printed circuit board 3 can be maintained without adversely affecting the circuit operation. The ground terminal GND of the power source itself has a stable potential, and even if the current is discharged to the current collecting pattern 3d when passing through the metal body, it is not directly transmitted to the ground terminal of the electronic circuit section, so that no malfunction occurs.

In the first embodiment described above, the discharge pattern 3e is directly connected to the ground terminal GND of the power source or the power source terminal Vc, but in this case, the internal potential is directly supplied to the outside from the through hole 4 of the case of the proximity switch. Is out. Therefore, if the point of this potential comes into contact with another external device, it is considered that the external device is adversely affected or the proximity switch is adversely affected. FIG. 2B shows a second embodiment made to solve such a problem, in which the pattern of the printed circuit board 3 is improved.
That is, the printed circuit board 3A has a gap 3g formed in a part of the discharge pattern 3e. Then, the internal voltage is not exposed to the outside of the proximity switch through the through hole 4 due to the gap 3g, and the other device collects the current collecting pattern 3d.
Even if it touches the end of the, malfunction does not occur. Further, when the metal ball 7 charged with static electricity passes through, the static electricity is discharged from the current collecting pattern 3d through the gap 3g due to the high static electricity voltage, and the discharge pattern 3e is discharged only in the case of discharging. It can be a road.

Next, a third embodiment of the present invention will be described. FIG. 6 is an assembly configuration diagram of the proximity switch according to the third embodiment, and detailed description of the same parts as those in the first embodiment will be omitted. Also in this embodiment, the lower case 21 and the upper case 22 form a housing, and the printed circuit board 23 is inserted therein. The lower case 21 has substantially the same shape as that of the first embodiment, and has a through hole 24 and an inner wall 25 forming the through hole. On the other hand, the upper case 22 has leg portions 22a to 22e and an octagonal through hole 22f, as in the first embodiment. In the present embodiment, unlike the first embodiment, a part of the through hole does not have a downward projection, and a rectangular through hole 22g is provided at a position close to the through hole 22f. In this embodiment, an L-shaped metal piece 26 is used as the current collector as shown in the figure. Metal piece 26
Is the printed circuit board 2 through the through hole 22g of the upper case 22.
3 discharge pattern 23a. The discharge pattern 23a has a shape in which the connecting portion with the metal piece 26 is shaped as shown in FIG. 8A or 8B, and the stable potential of the proximity switch, that is, input to the proximity switch, as in the first embodiment. Is connected to the ground terminal GND or the power source terminal Vc of the power source. In the pattern of FIG. 8A, the internal power source of the proximity switch is directly exposed to the outside of the case of the proximity switch through the metal piece 26. Therefore, as in the second embodiment,
It is preferable to connect to a stable potential via a minute gap 23b as shown in FIG. 8 (b).

According to this structure, when the metal ball 7 passing through the through hole 24 is charged with static electricity, the static electricity is first discharged toward the metal piece 26. Therefore, the internal circuit of the proximity switch is not discharged, and malfunction or damage can be prevented.

Next, a fourth embodiment of the present invention will be described. FIG. 9 is an assembly configuration diagram of a proximity switch according to the fourth embodiment, and FIG. 10 is a perspective view showing the proximity switch after assembly. In these figures, the same parts as those in the third embodiment are designated by the same reference numerals and detailed description thereof will be omitted. The lower case 21A according to the present embodiment has substantially the same shape as the lower case 21 of the third embodiment, and the upper portion of the inner wall 25 on which electronic components are mounted is notched as shown. Notch 25
a. The upper case 22A also has substantially the same shape, but is formed at a position facing the cutout portion 25a, and a cutout portion 22h is provided at that position. Other configurations are similar to those of the third embodiment. In this embodiment, a thin L-shaped metal piece 27 as shown in the figure is used as a current collecting means without protruding the metal piece to the outside. This metal piece 2
7 is inserted into the notch 22h of the upper case 22A, sandwiched by the notch 25a of the lower case 21A, and fixed as shown in FIG. The other end of this metal piece 27 is the third
Similar to the embodiment, the discharge pattern 23a of the printed circuit board 23
Shall be connected to a stable potential via. By doing so, the end surface of the metal piece 27 is exposed toward the through hole 24. Therefore, when the metal ball 7 charged with static electricity passes, the static electricity is discharged through the metal piece 27. In this case, since the metal piece 27 is exposed only in the through hole 24 of the proximity switch, the metal piece may be directly connected to the stable potential as shown in FIG. 8A.

FIG. 11 is an assembly configuration diagram of a proximity switch according to a fifth embodiment of the present invention, and FIG. 12 is a perspective view after assembly. In this figure, the same parts as those in the third embodiment are designated by the same reference numerals, and the lower case 21, the printed board 23 and the metal piece 26 are the same as those in the third embodiment. In this embodiment, the upper case 28 has a wall thickness as shown in the drawing, and a groove 28a is provided in a portion to which the metal piece 26 is attached so that the metal piece 26 does not project to the outside of the proximity switch. The third to
In the fifth embodiment, a similar effect can be obtained by using a material obtained by vapor deposition of a resin material instead of the metal pieces 26 and 27.

FIG. 13 is a perspective view showing a state in which the proximity switch of the sixth embodiment of the present invention is turned upside down. The lower case 21 is the same as the third embodiment and the upper case 2 described above.
Since 2B is the same as the third embodiment except that the through hole 22g is not provided, the description thereof will be omitted. In this embodiment, pin holes 31a to 31d are provided around the through hole 24 on the back surface of the upper case 22B as shown in the drawing. FIG. 14 is a vertical sectional view of the proximity switch taken along the line BB, and FIG. 15A is a rear view of the pattern on the printed circuit board. In this embodiment, the pattern of the printed circuit board is shown in FIG.
As shown in FIG. 3, a C-shaped current collecting pattern 23c, which is partially cut away, is formed around the frame-shaped portion, and the discharge pattern 2 is formed.
It is connected to the power supply terminal Vc or the ground terminal GND which is supplied to the proximity switch via 3d. By doing this, if the metal ball 7 charged with static electricity approaches from the direction of the arrow in FIG. 14, this current collecting pattern 23c will pass through the pinholes 31a to 31d.
Since static electricity is discharged to the inside, it does not adversely affect the internal circuit of the proximity switch. In this case, since the current collecting pattern 23c is not exposed to the outside of the case of the proximity switch, it can be directly connected to the power source terminal Vc or the ground terminal GND without providing a gap.

Further, in this embodiment, since the internal circuit of the proximity switch is formed only on one side of the through hole (on the right side in FIG. 13) as shown in the figure, the pinhole for guiding static electricity is shown in FIG. Only the internal circuit side 31a, 31b may be used. In this case, as shown in FIG. 15B, the discharge pattern 23e is formed at a position corresponding to this pinhole.

FIG. 16 is a perspective view showing a state in which the proximity switch according to the seventh embodiment of the present invention is turned upside down. This embodiment also uses upper and lower cases similar to those in the sixth embodiment. In this embodiment, instead of the pinholes 31a to 31d, notch portions 32a to 32d are formed by cutting out a part of the periphery of the through hole 24 in a triangular prism shape as shown in the figure, and the frame-shaped portion of the printed circuit board 23 is exposed to the outside. I am trying to let you. The current collecting pattern 23c and the discharge pattern 23d are shown in FIG.
The same as (a) is used. In this way, when a metal ball charged with static electricity passes from the upper side of the drawing, the static electricity is discharged to the discharge pattern and the stable potential through the cutout portions 32a to 32d, and malfunction can be prevented.

Next, an eighth embodiment of the present invention will be described. In this embodiment, the same parts as those in the third embodiment are designated by the same reference numerals and detailed description thereof will be omitted. 17A is a top view of the proximity switch of this embodiment, and FIG. 17B is a C- of the upper case 22c.
It is a C line longitudinal cross-sectional view. In the present embodiment, the upper case 22C does not have the through hole 22g, but instead has the downward insertion portion 22i, and the through hole 22 along the insertion portion 22i.
j is provided. Then, a metal thin film 33 or the like is formed by vapor deposition or the like on the rectangular upper surface from the insertion portion 22i and the through hole 22j to the octagonal piece forming the through hole 24. Here, the tip of the insertion portion 22i is inserted into the discharge pattern 23a of the printed board 23 as in the third embodiment, and is connected by soldering or heat staking. In this way, instead of the metal pieces 26, 27, the metal thin film 33.
Can be used as a current collector and connected to the discharge pattern of the printed circuit board 23. Therefore, it is possible to configure the discharge path with an extremely simple configuration without using a metal piece or the like. The metal thin film 33 is inserted into the insertion portion 2 as shown in the figure.
Although it is formed on the right side surface of 2i and the upper surface of the upper case, vapor deposition may be performed on the left side surface and the inner side. In this way, the discharge path can be formed without providing the through hole 22j.

Although each of the above-described embodiments describes the pass type proximity switch for detecting the passage of the metal body, the present invention can be applied to various types of electronic switches such as proximity switches and photoelectric switches. Is possible.

[0026]

As described above in detail, according to the inventions of claims 1 to 6 of the present application, even when the detection body of the electronic switch is charged with static electricity, the static electricity collects electricity and discharges electricity. It will discharge through the path towards the stable potential of the electronic switch. Therefore, the electronic circuit in the switch is protected, and it is possible to easily prevent malfunction and damage. According to the second aspect of the present invention, the structure is such that a part of the discharge path is not exposed to the outside of the case. Therefore, the electrodes are not exposed to the outside, damage due to contact with an external device can be prevented, and static electricity can be reliably discharged. Further, in the invention of claim 4, since the current collecting means is constituted by vapor-depositing a part of the case, the discharge path can be formed with a relatively simple structure, and countermeasures against electrostatic discharge of the detection body can be taken.

Further, in the invention of claim 5, the current collecting means and the discharge path are formed by the pattern of the printed circuit board, and the discharge pattern is exposed from the case. Therefore, the discharge path can be constructed very easily. You can Further, according to the invention of claim 6, even if the current collecting means is exposed to the outside of the electronic switch, it floats from the internal potential, so that the internal circuit of the electronic switch is not damaged. Further, during discharge, it is possible to discharge through this gap.

[Brief description of drawings]

FIG. 1 is an assembly configuration diagram of a proximity switch according to a first embodiment of the present invention.

FIG. 2A is a back view showing a print pattern of a proximity switch according to the first embodiment and FIG. 2B.

FIG. 3 is a perspective view of the first embodiment after assembly.

FIG. 4 is a partial cross-sectional view taken along the line AA showing the discharge path periphery of the present embodiment.

FIG. 5 is a block diagram showing a circuit configuration of a proximity switch according to the present embodiment.

FIG. 6 is an assembly configuration diagram of a proximity switch according to a third embodiment of the present invention.

FIG. 7 is a perspective view showing a state after assembly of the present embodiment.

FIG. 8 is a diagram showing a discharge pattern of a printed circuit board used in this embodiment.

FIG. 9 is an assembly configuration diagram of a proximity switch according to a fourth embodiment of the present invention.

FIG. 10 is a perspective view showing a state after assembly of the present embodiment.

FIG. 11 is an assembly configuration diagram of a proximity switch according to a fifth embodiment of the present invention.

FIG. 12 is a perspective view showing a state after assembly of this embodiment.

FIG. 13 is a perspective view showing a configuration of a proximity switch according to a sixth embodiment of the present invention.

FIG. 14 is a B- showing the vicinity of the discharge path of the sixth embodiment of the present invention.
It is a B line partial sectional view.

15A and 15B are diagrams showing a discharge pattern of a printed circuit board according to a sixth embodiment of the present invention.

FIG. 16 is a perspective view showing an assembled state of a proximity switch according to a seventh embodiment of the present invention.

FIG. 17 (a) is a top view showing a proximity switch according to an eighth embodiment of the present invention, and FIG. 17 (b) is a sectional view taken along line CC of the upper case.

[Explanation of symbols]

 1,2,21A Lower case 2,22,22A, 22B, 22C, 28 Upper case 2g, 3c Projection part 3,3A, 23,23A Printed circuit board 3d, 23c, 23e Current collecting pattern 3e, 23d Discharge pattern 3g, 23b Gap 4,22f, 22g, 22j, 24 Through hole 5,25 Inner wall 6,22h, 25a, 32a to 32d Cutout portion 7 Metal ball 22i Insertion portion 26,27 Metal piece 31a to 31d Pinhole 33 Metal thin film

Claims (6)

[Claims] 1. An electronic switch for detecting passage of a detection body, the current collection means being formed at a position where the detection body first comes close to the outside of a case of the electronic switch; and the current collection means and the electronic switch. An electronic switch, comprising: a discharge path connecting a stable potential, and configured to discharge static electricity of the detection body through the current collecting means and the discharge path. 2. An electronic switch for detecting passage of a detection body, the current collection means being provided in a position inside the case of the electronic switch where the detection body first approaches, and the current collection means and the electronic switch. An electronic switch comprising: a discharge path connecting a stable potential and an opening provided near the current collecting means of the case. 3. The electronic switch according to claim 1, wherein the current collector is made of a metal piece. 4. The electronic switch according to claim 1, wherein the current collecting means is formed by vapor-depositing a metal thin film when the detection body of the case first approaches. 5. An electronic switch having a printed circuit board provided in a case for detecting passage of a detection body, wherein the printed circuit board has a conductive pattern at a portion of the case where the detection body first approaches. An electronic switch, comprising: a current collector that is formed and has an end face of its conductive pattern exposed from a case; and a discharge path that connects the current collector to a stable potential of the electronic switch. 6. The electronic switch according to claim 1, wherein the discharge path has a minute gap formed between a stable potential and the current collecting means.