JP2008159563A - Key switch - Google Patents

Abstract

To provide a key switch capable of preventing a foreign matter from being sandwiched between a movable contact and a fixed contact and causing problems such as poor contact between the contacts, and maintaining a stable switch function over a long period of time.
A contact support 17 that supports a movable contact 15 at a position facing a fixed contact 13 on a substrate 11 defines a closed space 23 between the substrate 11 and a contact support for the substrate 11. Corresponding to the volume reduction of the closed space 23 when the body 17 is moved, the air in the closed space 23 is changed to the substrate 1.
1 is provided with a through-hole 25 for entering and exiting on the back surface side, and at a position approaching the through-hole 25, a foreign matter catching means 31 for catching foreign matter in and out of the through-hole 25 is provided. Prevent pinching.
[Selection] Figure 2

Description

The present invention provides a fixed contact provided on the surface of the substrate, a movable contact disposed opposite to the fixed contact away from the substrate surface, and a contact support that elastically supports the movable contact at a position spaced from the fixed contact. And a key switch for obtaining a state in which the movable contact is in contact with the fixed contact by moving the contact support to the substrate side.

In electronic devices such as mobile phones, mobile personal computers, electronic dictionaries, fixed telephones, etc., as key switches (push-down switches) used for the input operation unit, fixed contacts provided on the substrate surface, A movable contact disposed opposite to the fixed contact and a contact support that elastically supports the movable contact at a position separated from the fixed contact. The movable contact is fixed by moving the contact support to the substrate side. Many switches that obtain a state of contact with a contact and output a predetermined signal are used.

In such a key switch, if a minute foreign object enters the space between the movable contact and the fixed contact during assembly work, the foreign object is caught between the movable contact and the fixed contact during switch operation. As a result, there is a possibility of causing a functional failure due to poor contact between the contacts, or causing a functional shortage due to a contact short-circuited by a foreign object without performing a switch operation.

Thus, normally, such key switch assembly work is carefully performed in a clean room that is maintained in a clean environment so that foreign matter does not enter.

Further, in the above-described mobile phones and mobile personal computers, a large number of relatively small key switches are placed in a predetermined alignment state on a substrate having a fixed contact, and the top of each key switch is placed thereon. An assembly method may be employed in which each key switch is positioned by covering a case cover having a large number of protruding openings.

When carrying out such an assembly method, if some of the key switches arranged on the substrate with fixed contacts are inadvertently displaced due to vibration or the like, the misaligned key switch It cannot be aligned with the opening and cannot be assembled.

Therefore, the substrate on which the key switch (push button switch) is placed is previously provided with a suction through hole at the position where each key switch is placed, and negative pressure is applied to each through hole from the back side of the substrate. A switch configuration has been proposed in which a switch placed on a substrate is temporarily fixed to the substrate by applying a suction force (see, for example, Patent Document 1).
JP 2001-307590 A

By the way, by assembling the key switch in the clean room as described above, it is possible to prevent the inconvenience that minute foreign matter is mixed in the space between the movable contact and the fixed contact during the assembly work, and the switch performance is improved. Reliability can be improved.

However, by assembling in a clean room, the conventional key switch does not wear particles that are generated during use even if it is initially managed so that no foreign matter exists in the space between the movable contact and the fixed contact. As the removal of foreign matter such as is not considered, wear powder, etc. in the switch sliding part, etc. is generated in the space between the movable contact and the fixed contact due to repeated switch operation. And the fixed contact may cause problems such as poor contact between the contacts.

Further, as described in Patent Document 1, in the case where a through-hole for negative pressure suction is formed in a substrate on which a key switch is placed, the back surface of the substrate is restored by a return operation of the movable contact after the switch is pressed. Air on the side is sucked into the space between the movable contact and the fixed contact through the through hole. Then, together with the air that is sucked in, dust or the like on the back side of the substrate may enter the space between the movable contact and the fixed contact, causing problems such as poor contact between the contacts.

Accordingly, an object of the present invention is to solve the above-mentioned problems, and foreign matter generated due to wear of the sliding portion during use is sandwiched between the movable contact and the fixed contact, and problems such as poor contact between the contacts. In addition, foreign matter on the back side of the board is sucked into the space between the movable contact and the fixed contact, causing no problems such as poor contact between the contacts. It is to provide a key switch that can be maintained.

In order to solve the above problems, a key switch according to the present invention includes a fixed contact provided on a substrate surface, a movable contact disposed away from the substrate surface and opposed to the fixed contact, and the movable contact fixed to the fixed contact. And a contact support that elastically supports at a position separated from the key switch, and in the key switch that obtains a state in which the movable contact is in contact with the fixed contact by moving the contact support toward the substrate side. A closed space is formed between the substrate and the substrate, and the substrate is penetrated to allow the air in the closed space to enter and exit from the back side of the substrate in accordance with a decrease in the volume of the closed space when the contact support is moved. A hole is provided, and at a position approaching the through hole, there is provided a foreign matter capturing means for capturing foreign matter in and out of the air that enters and exits the through hole.

According to the above configuration, when the contact support is moved (switched) to bring the movable contact into contact with the fixed contact, the volume of the closed space defined between the contact support and the substrate is reduced. The air in the closed space compressed by the decrease in the volume is discharged to the outside from the through hole formed in the substrate.

Therefore, when foreign matter (abrasion powder) is generated due to wear of the sliding part due to repeated switch operation, the foreign matter penetrates along with the air exhausted from the through hole to the outside of the closed space when the switch is operated. It is discharged from the hole to the outside of the closed space, and at that time, it is captured by the foreign substance capturing means arranged close to the through hole.

Also, during the return operation of the switch that moves the movable contact away from the fixed contact, the air on the back side of the substrate returns to the closed space through the through hole, but the foreign matter discharged from the closed space first is captured by the foreign matter capturing means. Therefore, the foreign matter once discharged does not return to the closed space again, and the space between the movable contact and the movable contact is restored to a clean space where no foreign matter is present.

In addition, when the foreign matter that exists in the space on the back side of the substrate moves to the through hole side due to the air flow during the return operation of the switch, the foreign matter capturing means captures the foreign matter that has occurred in the space on the back side of the substrate. It is also possible to prevent a space between the movable contact and the fixed contact from entering the space through the hole.

Therefore, it is possible to prevent foreign matter generated due to wear of the sliding part during use from being sandwiched between the movable contact and the fixed contact and causing problems such as poor contact between the contacts. Can be sucked into the space between the movable contact and the fixed contact, causing problems such as poor contact between the contacts, and a stable switch function can be maintained over a long period of time.

Further, the foreign matter capturing means is an adhesive sheet disposed in an air flow path passing through the through hole (Claim 2).

With such a configuration, since the pressure-sensitive adhesive sheet as the foreign matter capturing means is inexpensive, an increase in cost due to the provision of the foreign matter capturing means can be suppressed.

In addition, the foreign matter capturing means is an electrode plate installed at a position approaching the through hole, and adsorbs and captures foreign matter in and out of the air that enters and exits the through hole when a switch is operated. Item 3).

With such a configuration, by appropriately setting the potential on the electrode plate as the foreign matter capturing means,
Charged foreign matter can be captured efficiently. The electrode plate as a foreign matter trapping means can be formed with high precision by printing on the back side of the substrate equipped with a fixed contact on the front side, compared with the case where independent electrode parts are attached one by one. Productivity can be improved.

Moreover, the said foreign material capture means is a nonwoven fabric sheet arrange | positioned in the position approaching the said through-hole (Claim 4).

With such a configuration, if the roughness of the nonwoven fabric as the foreign matter capturing means is appropriately selected, the foreign matter capturing means functions as a filter having air permeability while having foreign matter capturing performance. It is also possible to equip the through hole so as to cover it, and the degree of freedom in selecting the position of the foreign matter catching means is increased, and the foreign matter catching means is easily equipped.

Further, the foreign matter capturing means is movably attached so as to change a contact area with the air entering and exiting the through hole (Claim 5).

With such a configuration, in a part of the foreign matter capturing means, when the trapping performance is deteriorated due to the accumulation of trapped foreign matter, the region that still has sufficient trapping performance is the contact region with air. Thus, by adjusting the movement position of the foreign substance capturing means, the foreign substance capturing performance can be easily restored.

Further, the foreign matter catching means is detachably attached so that it can be replaced when the foreign matter catching performance is deteriorated (Claim 6).

With such a configuration, the foreign matter capturing performance of the foreign matter catching means can be favorably maintained for a longer period by replacing the foreign matter catching means.

Further, the foreign matter catching means is provided in both the substrate back surface and a position facing the through hole at a predetermined distance from the substrate back surface, approaching the through hole. (Claim 7).

With such a configuration, the trapping of the foreign matter is performed twice by changing the position,
Foreign matter removal performance is further improved.

  Further, the foreign matter capturing means is a cylindrical nonwoven fabric sheet disposed between the back surface of the substrate around the through hole and the top surface of the lower case facing the back surface of the substrate (claim). Item 8). With such a configuration, the performance of capturing foreign matter is maintained regardless of whether the electronic device is used horizontally or vertically.

In the key switch according to the present invention, when the contact support is moved (switch operation) in order to bring the movable contact into contact with the fixed contact, the volume of the closed space defined between the contact support and the substrate is reduced. The air in the closed space that is reduced and compressed by the reduction in the volume is discharged to the outside from the through hole formed in the substrate.

Therefore, when foreign matter (abrasion powder) is generated due to wear of the sliding part due to repeated switch operation, the foreign matter penetrates along with the air exhausted from the through hole to the outside of the closed space when the switch is operated. It is discharged from the hole to the outside of the closed space, and at that time, it is captured by the foreign substance capturing means arranged close to the through hole.

Also, during the return operation of the switch that moves the movable contact away from the fixed contact, the air on the back side of the substrate returns to the closed space through the through hole, but the foreign matter discharged from the closed space first is captured by the foreign matter capturing means. Therefore, the foreign matter once discharged does not return to the closed space again, and the space between the movable contact and the movable contact is restored to a clean space where no foreign matter is present.

In addition, when the foreign matter that exists in the space on the back side of the substrate moves to the through hole side due to the air flow during the return operation of the switch, the foreign matter capturing means captures the foreign matter that has occurred in the space on the back side of the substrate. It is also possible to prevent a space between the movable contact and the fixed contact from entering the space through the hole.

Therefore, it is possible to prevent foreign matter generated due to wear of the sliding part during use from being sandwiched between the movable contact and the fixed contact and causing problems such as poor contact between the contacts. Can be sucked into the space between the movable contact and the fixed contact, causing problems such as poor contact between the contacts, and a stable switch function can be maintained over a long period of time.

DESCRIPTION OF EMBODIMENTS Hereinafter, a preferred embodiment of a key switch according to the present invention will be described in detail with reference to the drawings.

1 is a front view of an essential part of an electronic device to which a first embodiment of a key switch according to the present invention is applied, FIG. 2 is a cross-sectional view taken along line AA in FIG. 1, and FIG. It is an arrow view.

FIG. 1 shows key switches K1 to K # arranged in four rows and three columns for inputting a telephone number or characters or selecting a function in a cellular phone.

Since the key switches K1 to K # have the same switch structure, the configuration thereof will be described by taking K1 and K4 whose cross sections are shown in FIG. 2 as an example.

Each of the key switches K1 to K # shown here is a so-called push-type switch that brings the contacts into contact with each other by a push operation, and as shown in FIG. 2, a fixed contact 13 provided on the surface 11a of the printed circuit board 11, A movable contact 15 disposed away from the surface 11 a of the substrate 11 and opposed to the fixed contact 13, and a contact support 17 that elastically supports the movable contact 15 at a position separated from the fixed contact 13.
As shown by an arrow C in FIG. 2, the movable contact 15 is brought into contact with the fixed contact 13 by moving the contact support 17 down to the substrate 11 side.

The printed circuit board 11 is a printed circuit board having a thickness of about 0.6 to 1 mm.
As shown in FIG. 3, reference numeral 3 denotes a pair of conductor portions 13a and 13b printed and formed on the surface 11a of the substrate 11 at a predetermined spacing.

The movable contact 15 is a disk-shaped conductor straddling the pair of conductor portions 13a and 13b.
When the contact state overlapped on 3 is established, the pair of conductor portions 13a and 13b are made conductive to enable a predetermined signal output.

The contact support 17 includes a main body 17a to which the movable contact 15 is attached to a lower surface portion facing the surface 11a of the substrate 11, and an end extending from the outer periphery of the main body 17a to be placed on the surface 11a of the substrate 11. The skirt portion 17b and the operation portion 17c protruding from the upper surface of the main body 17a are integrally formed of a rubber material having predetermined elasticity and insulation.

The upper surface of the operation portion 17c is inserted through a key window portion 21a formed in the upper case 21 of the mobile phone so that a pressing operation can be performed. As shown in FIG. 1, the input character type in charge is printed on the upper surface of the operation unit 17c.

The skirt portion 17 b surrounds the space between the fixed contact 13 and the movable contact 15, and defines a closed space 23 with the substrate 11. The skirt portion 17b also functions as a support portion that allows displacement of the main body 17a toward the substrate 11 side by being elastically deformed in accordance with the pressing operation of the operation portion 17c.

In the substrate 11, the air in the closed space 23 corresponds to the volume reduction of the closed space 23 during the movement operation (pressing operation) of the contact support 17, as shown by the arrow D in FIG. A through-hole 25 is provided for entering and exiting.

The through hole 25 is a round hole provided at a substantially intermediate position between the pair of conductor portions 13a and 13b. The diameter of the through-hole 25 is set to such a size that wear powder generated by a switch operation or the like, fine dust entering from the outside during maintenance (disassembly maintenance), etc. can enter and exit without being caught. For example, since the wear powder of the contact is 100 μm or less, the inner diameter of the through hole 25 is preferably set to 100 μm or more.

In the case of the present embodiment, the back surface side of the substrate 11 is covered with a lower case 27 of the mobile phone so as to secure a component storage space between the back surface of the substrate 11.

The distance between the lower case 27 and the back surface of the substrate 11 is L. In the case of the present embodiment, a foreign substance 29 in and out of the through hole 25 is placed at a position facing the through hole 25 on the inner wall surface of the case that is separated from the back surface of the substrate 11 by a predetermined distance L. A foreign matter catching means 31 for catching is provided.

  In the case of the present embodiment, an adhesive sheet N is employed for the foreign matter capturing means 31.

Further, the adhesive sheet N as the foreign matter catching means 31 is detachably attached by the locking means 33 provided on the inner wall surface of the lower case 27 so that it can be replaced when the foreign matter catching performance is deteriorated. .

According to the configuration of the key switches K1 to K # described above, the movable contact 15 is fixed to the fixed contact 13.
When the contact support 17 is moved (pressed down) to come into contact with the contact support 17
The volume of the closed space 23 that is defined between the substrate 11 and the substrate 11 decreases, and the air in the closed space 23 that is compressed by the decrease in volume decreases from the through hole 25 formed in the substrate 11 to the outside (lower case). 27
To the side).

Accordingly, when a foreign matter (abrasion powder or the like due to contact between the contacts) 29 is generated due to wear of the sliding portion due to repeated switch operation, the foreign matter 29 is closed from the through hole 25 when the operation portion 17c is pressed. Together with the air discharged to the outside of the space 23, the closed space 23 is opened from the through hole 25.
In this case, the foreign matter is caught by the foreign matter catching means 31 arranged facing the through hole 25.

Further, during the return operation of the switch in which the movable contact 15 is separated from the fixed contact 13, the air on the back side of the substrate 11 is sucked back into the closed space 23 through the through hole 25, but the foreign matter previously discharged from the closed space 23. 29 is captured by the foreign matter capturing means 31, so that the foreign matter 29 once discharged does not return to the closed space 23 again, and the space between the movable contact 15 and the movable contact 15 is
It is restored to a clean space free of foreign objects.

Further, when other foreign matter existing in the space on the back side of the substrate 11 moves to the through hole 25 side due to the air flow during the return operation of the switch, the foreign matter catching means 31 catches it. It is also possible to prevent other foreign matters generated in the space from entering the space between the movable contact 15 and the fixed contact 13 through the through hole 25.

Therefore, it can be prevented that the foreign matter 29 generated due to wear of the sliding portion of the switch during use is sandwiched between the movable contact 15 and the fixed contact 13 to cause problems such as poor contact between the contacts.
Furthermore, foreign matter on the back side of the substrate 11 is sucked into the space between the movable contact 15 and the fixed contact 13, and problems such as poor contact between the contacts are not caused, and a stable switch function is maintained for a long time. Can do.

Furthermore, in the key switches K1 to K # of the above embodiment, the adhesive sheet N is employed as the foreign matter capturing means 31, and the adhesive sheet N as the foreign matter capturing means 31 is inexpensive. The cost increase due to can be suppressed.

Furthermore, in the key switches K1 to K # of the above embodiment, the foreign matter catching means 31 is detachably attached so that it can be replaced when the foreign matter catching performance deteriorates. The foreign matter catching performance by the foreign matter catching means 31 can be favorably maintained over a longer period.

The through hole 25 formed in the printed circuit board 11 for discharging the foreign matter 29 is not limited to a straight hole having a constant hole diameter.

  FIG. 4 is a longitudinal sectional view of a second embodiment of the key switch according to the present invention.

The key switch of the second embodiment is an improvement of part of the first embodiment.
The improved point is that the through hole 25 formed in the printed circuit board 11 is a tapered hole (funnel-shaped hole) whose diameter gradually decreases toward the back side of the substrate.

When the through-hole 25 is formed in such a tapered shape, the through-hole 2 is obtained when the operation portion 17c is pressed.
The air flow discharged from the air flow is accelerated by gradually reducing the hole diameter, and the collision force against the adhesive sheet N (foreign material capturing means 31) disposed opposite to the through hole 25 is increased. The foreign matter 29 included in the flow is easily attached to the adhesive sheet N, and the trapping efficiency of the foreign matter 29 can be increased.

Further, the through hole 25 formed in the printed circuit board 11 for discharging the foreign matter 29 is not limited to a single hole located in the middle of the conductor portions 13a and 13b, as described in the above embodiment.

For example, as shown in FIG. 5, a plurality of through holes 25 may be used. Even in this case, it is desirable that the minimum hole diameter of each through hole 25 is set to 100 μm or more so as to be larger than the maximum particle diameter of the foreign matter 29 generated in the closed space 23.

In the present invention, the position where the foreign matter capturing means 31 is provided is not limited to the position shown in the above embodiment (that is, the position facing the through hole 25 with a predetermined distance L from the back surface of the substrate 11). The position where the foreign matter catching means 31 is equipped may be a location where foreign matter can be caught, and for that purpose, it may be a location close to the through hole 25. More specifically, it is possible to select a position extending along the air flow path passing through the through hole 25 and a position where the air flow path passing through the through hole 25 abuts.

  Further, the foreign matter capturing means is not limited to the pressure-sensitive adhesive sheet shown in the above embodiment.

6 to 8 show an embodiment in which the equipment position of the foreign matter catching means 31 is changed and an embodiment in which the material of the foreign matter catching means 31 is changed.

  FIG. 6 shows a longitudinal sectional view of a third embodiment of the key switch according to the present invention.

The key switch of the third embodiment is an improvement of a part of the first embodiment.
The improved point is that the material of the foreign matter catching means 31 is changed and the attachment position of the foreign matter catching means 31 is changed. Other configurations are the same as those in the first embodiment, and the same configuration is used. Are given the same numbers, and the description thereof is omitted.

In the case of the third embodiment, a non-woven fabric sheet F is employed as the foreign matter capturing means 31. Moreover, since the nonwoven fabric sheet F has air permeability, it is attached to the back surface of the printed circuit board 11 so as to close the through hole 25. Moreover, attachment of the nonwoven fabric sheet F to the printed circuit board 11 is detachable by the locking means 33.

In the configuration of the third embodiment, if the roughness of the nonwoven fabric as the foreign material capturing means 31 is appropriately selected, the foreign material capturing means 31 has air permeability while having foreign material capturing performance. Since it functions as a filter, it can be equipped so as to cover the through-hole 25 as shown in the figure, the degree of freedom in selecting the position of the foreign matter catching means 31 is increased, and the foreign matter catching means 31 is easily equipped.

  FIG. 7 is a longitudinal sectional view of a fourth embodiment of a key switch according to the present invention.

The key switch of the fourth embodiment is an improvement of a part of the first embodiment.
Specifically, the foreign matter capturing means 31 using the nonwoven fabric sheet F shown in the third embodiment is additionally provided in the configuration of the first embodiment.

That is, in the key switch according to the fourth embodiment, the foreign matter catching means 31 is provided both at the back surface of the substrate 11 and at a position facing the through hole 25 at a predetermined interval from the back surface of the substrate 11. ing.

And the foreign material capture | acquisition means 31 with which the back surface of the board | substrate 11 was equipped is the nonwoven fabric sheet F shown in 3rd Embodiment of FIG. 6, and the through-hole 25 is spaced apart from the back surface of the board | substrate by the predetermined space | interval L.
The foreign matter catching means 31 installed at the position opposite to is due to the adhesive sheet N shown in the first embodiment of FIG.

Thus, the through hole 25 is spaced a predetermined distance L from the back surface of the substrate 11 and the back surface of the substrate 11.
If the foreign substance capturing means 31 is provided at both the position opposite to the position, the foreign substance is captured twice by changing the position, so that the foreign substance removal performance is further improved.

  FIG. 8 is a longitudinal sectional view of a fifth embodiment of a key switch according to the present invention.

The fifth embodiment is an improvement of a part of the third embodiment shown in FIG. 6, and the improvement is that the non-woven sheet F is used as the foreign matter capturing means 31 provided on the back surface of the substrate 11. Instead, an electrode plate E is employed.

The electrode plate E is printed on the back surface of the printed circuit board 11, and the printed circuit board 1
By controlling the potential of the electrode plate E to an appropriate value by the control circuit 1 or the like, foreign matter in and out of the air entering and exiting the through hole 25 during switch operation is adsorbed and captured by static electricity.

 FIG. 10 is a sectional view of a sixth embodiment according to the present invention. A cylindrical nonwoven fabric sheet 41 is disposed between the back surface side 11 a of the substrate and the inner surface 27 a of the lower case 27. With this arrangement, foreign matter can be captured regardless of whether the main body of the electronic device is placed horizontally or vertically (installed on a wall surface). This is because if the key switch is pressed in any case, the air flow that has passed through the through hole 25 once hits the inner surface of the lower case and then hits the cylindrical nonwoven fabric sheet 41, and the air passes, This is because 29 is captured by the nonwoven fabric sheet.

9 shows a front surface (a) of the printed circuit board 11, a conductor wiring pattern (b) of the electrode plate E printed on the back surface of the printed circuit board 11, and a GG cross section (c) of the printed circuit board 11.
It is.

As a conductor wiring pattern of the electrode plate E, a pattern as shown in FIG. The printed circuit board 11 has a structure in which the dielectric portions 11b and 11d are bonded by an adhesive 11c. As shown in FIG. 9C, the cross-sectional structure of the through-hole 25 is such that the lower part of the wall surface of the through-hole 25 (the wall surface of the dielectric portion 11d) is covered with a conductor and has a conductive position with the electrode plate E. Electrically connected. However, the upper part of the wall surface of the through hole 25 (dielectric part 1
Since the wall 1b does not have a conductor, it is not electrically connected to the conductor portion of the surface 11a of the printed circuit board 11 as shown in FIG. 9A.

With such a configuration, the charged foreign matter can be efficiently captured by appropriately setting a potential on the electrode plate E as the foreign matter capturing means 31. Further, the electrode plate E as the foreign matter capturing means 31
Can be formed with high precision by printing on the back surface of the substrate 11 equipped with the fixed contact 13 on the front surface, and productivity is improved compared with the case where independent electrode parts are attached one by one. Can be improved.

In the first to fifth embodiments, the foreign matter capturing means 31 has a detachable attachment structure so that it can be easily replaced. Instead, the contact area with the air entering and exiting the through hole 25 is changed. Therefore, it may be attached so as to be movable.

With such a configuration, in the case where the trapping performance is reduced due to the accumulation of trapped foreign matter in a part of the foreign matter trapping means 31, a region that still has sufficient trapping performance is a contact area with air. Thus, by moving and adjusting the attachment position of the foreign matter catching means 31, the foreign matter catching performance can be easily restored.

In addition, a device in which the key switch of the present invention is adopted is not limited to the mobile phone shown in the above embodiment. The present invention is not limited to portable electronic devices and the like, and can be employed in various devices equipped with key switches for input operations.

Furthermore, in the key switch of the present invention, the specific structure of the contact support is not limited to the structure shown in the above embodiments.

For example, the contact support may have a dome-like raised structure and a push-button type switch structure in which the dome-like portion is pressed.

It is a front view of the principal part of the electronic device to which 1st Embodiment of the key switch which concerns on this invention was applied. It is AA sectional drawing of FIG. It is a BB arrow line view of FIG. It is a longitudinal cross-sectional view of 2nd Embodiment of the key switch which concerns on this invention. It is explanatory drawing of other embodiment of the board | substrate used with the key switch which concerns on this invention. It is a longitudinal cross-sectional view of 3rd Embodiment of the key switch which concerns on this invention. It is a longitudinal cross-sectional view of 4th Embodiment of the key switch which concerns on this invention. It is a longitudinal cross-sectional view of 5th Embodiment of the key switch which concerns on this invention. 4A is a conductor wiring pattern (b) of an electrode plate E formed by printing on the front surface (a) of the printed circuit board 11, the back surface of the printed circuit board 11, and a GG cross section (c) of the printed circuit board 11. FIG. It is a longitudinal cross-sectional view of 6th Embodiment of the key switch which concerns on this invention.

Explanation of symbols

11 Printed circuit board (board)
11a Front side (back side of substrate)
DESCRIPTION OF SYMBOLS 13 Fixed contact 13a, 13b Conductor part 15 Movable contact 17 Contact support body 17a Main body 17b Skirt part 17c Operation part 21 Upper case 21a Key window part 23 Closed space (1st closed space)
25 Through-hole 27 Lower case 27a Inner surface of lower case 29 Foreign matter 31 Foreign matter catching means 33 Locking means E Electrode plate (foreign matter catching means)
F Nonwoven fabric sheet (foreign matter capturing means)
K1 to K # Key switch N Adhesive sheet (Foreign matter catching means)
41 Cylindrical non-woven sheet (foreign matter capturing means)
43 Locking means 44 Quasi-flat space (second closed space)

Claims (8)

A fixed contact provided on the substrate surface, a movable contact disposed away from the substrate surface and opposed to the fixed contact, and a contact support for elastically supporting the movable contact at a position spaced from the fixed contact, In the key switch that obtains the state where the movable contact is in contact with the fixed contact by moving the contact support to the substrate side.
The contact support defines a closed space with the substrate;
The substrate is provided with a through-hole that allows air in the closed space to enter and exit from the back side of the substrate in accordance with the volume reduction of the closed space when the contact support is moved.
A key switch comprising a foreign matter catching means for catching foreign matter in the air entering and leaving the through hole at a position approaching the through hole. 2. The key switch according to claim 1, wherein the foreign matter catching means is an adhesive sheet disposed in an air flow path passing through the through hole. 2. The foreign matter capturing means is an electrode plate installed at a position approaching the through hole, and adsorbs and captures foreign matter in and out of the air that enters and exits the through hole at the time of a switch operation. Key switch as described. The key switch according to claim 1, wherein the foreign matter capturing means is a non-woven fabric sheet disposed at a position approaching the through hole. The key switch according to any one of claims 1 to 4, wherein the foreign matter capturing means is movably attached so as to change a contact area with air entering and exiting the through hole. The key switch according to any one of claims 1 to 4, wherein the foreign matter catching means is detachably attached so that it can be replaced when the foreign matter catching performance is deteriorated. The foreign object capturing means is provided in both the substrate back surface and a position facing the through hole at a predetermined distance from the substrate back surface, approaching the through hole. The key switch according to any one of 1 to 6.   The said foreign material capture | acquisition means is a cylindrical nonwoven fabric sheet arrange | positioned between the said substrate back surface around the said through-hole, and the inner surface of the lower case facing this substrate back surface. Key switch as described.

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