JP3275923B2 - Key switch in electronic device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a key switch for inputting data and control commands to electronic equipment.

[0002]

2. Description of the Related Art In an electronic apparatus using a microcomputer as a control means, control data and commands are input by a key switch normally arranged on a panel surface. In such a key switch, as shown in the figure, the switch is fixed to a circuit board, and the function of the key is clearly specified through a frame provided with a window corresponding to the switch operation unit on the surface of the switch. It is configured by arranging a flexible sheet.

The human body is charged to about several thousand volts due to friction with clothes and the like, and sometimes a discharge occurs between the switch and other electronic components when the switch is operated, and this discharge current is generated by a microcomputer or the like. Have the problem of flowing into and destroying electronic components. In order to solve such a problem, a metal shield plate is mounted on the board so as to form a wall around the switch, but the assembly work is complicated because it takes time to mount another member. In addition to the problem that the shield plate becomes a discharge counter electrode, the discharge counter electrode exists at a position close to the keytop, which induces a discharge even at a considerably low electrostatic potential, and causes a discharge to electronic components. There is a problem that noise caused by the discharge current flows in and a malfunction is likely to occur.

In order to solve such a problem, Japanese Utility Model Laid-Open No.
A technique of forming a ground pattern surrounding the periphery of a switch on a substrate provided with the switch as disclosed in -88276 has also been proposed. According to this, the ground pattern for discharging can be formed in accordance with the formation of the circuit pattern, so that the work efficiency can be improved. On the other hand, it is arranged near the switch and closer to the key top than the ground pattern. There is a problem that electric discharge is caused between the electronic component and the electronic component, thereby causing damage to the electronic component.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and an object thereof is to maintain a discharge voltage as high as possible while maintaining a switch and a switch. An object of the present invention is to provide a novel key switch that can reliably prevent discharge from occurring with a nearby electronic component.

[0006]

According to the present invention, there is provided a switch for turning on and off a contact mechanism by an external operation, a circuit board on which the switch is mounted on a surface, and a surface of the switch. abuts on, and a key-top cup-shaped surrounding the upper surface and the side peripheral surface of said switch, said formed around the key top, and a sidewall end portion is made of an electrically insulating material to reach the circuit board, wherein
On the surface of the circuit board on which the switch is mounted , the projection area of the space between the side wall and the key top is outside the side wall.
And a ground pattern formed in the region of (1).

[0007]

Since the ground pattern serving as a discharge counter electrode is located as far as possible from the surface of the key top, the discharge starting voltage is kept high to prevent unnecessary discharge, and the key formed in a cup shape. Since the discharge space is regulated by the top and side wall portions, no discharge occurs between the electronic components even at an extremely high charging voltage.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the illustrated embodiments. FIG. 2 shows an embodiment of an input device using the key input structure of the present invention. In the drawing, reference numeral 1 denotes a switch board, and as shown in FIG.
The switches 3, 3, 3 た with the operating rod 3 a for turning on and off the contact mechanism protruding from the upper surface are fixed, and the ground pattern 4 surrounds the switch 3.
4, 4}, and the display panel 5 is fixed if necessary. These ground patterns 4,
4, 4 # are connected to ground patterns 6 formed on the back surface of the circuit board 2 through through holes 7, 7 #.

Returning to FIG. 2, these switches 3, 3,
3 and the display panel 5 are connected by a cable via a connector 8 to an electronic device that requires the incorporation of a key switch. Reference numeral 10 denotes a frame member made of an electrically insulating material such as a polymer material, and key tops 7, 7, 7 # corresponding to the positions of the switches on the switch board 1.
‥ is formed, and a window 18 is formed in accordance with the display panel 5. FIGS. 1A and 1B show the structure near the key top 11 along the line AA and the line BB in FIG.
The key tops 11, 11, 11 # are shown in an enlarged scale as a cross section taken along a line, and are formed in a cup shape so as to surround portions other than the lower surface of the switch 3, leaving one side of the surface. The main body 12 is separated from the main body 12 by a slit 13 and is rotatably connected to the main body 12 by a flexible portion 15 formed by a concave portion. The side wall portion 11a forming the key top 11 is selected to have a gap with the circuit board 2 so that the lower end 11b produces a stroke capable of operating the switch 3, and has a central portion. Is the operating rod 3 of the switch 3
A projection 11c that is always in contact with a is formed.

On the other hand, a gap is provided around the key top 11 of the body 12 of the frame member 10 so as not to hinder the movement of the key top 11.
Is formed, and a lower end 12b thereof is formed.
Abuts on the surface of the ground pattern 4 and also serves as a support member for the main body 12. The height of the wall portion 12a is selected to be a value that regulates the distance between the key top 11 and the ground pattern 4 to a dischargeable voltage, for example, about 10 millimeters when a discharge is generated at about 1000 volts. The key top 11 and the main body 12
Can be integrally formed by plastic injection molding, or a key top can be retrofitted.

The frame member 10 constructed as described above
Switches the key top 11 to the switch 3 on the switch board 1
The base frame 20 is applied to the back surface of the switch board 1, the three members are integrally fixed with screws, and the decorative sheet 21 is fixed to the upper surface of the frame member 10. Assembled as a key input device.
Also, if necessary, grounding spring 2
2 and 22 are fixed to the base plate 20 so as to have a conductive relationship.

In this embodiment, when a predetermined key top 11 is pressed by a finger F in order to operate the switch 3, the key top 11 pivots downward around the flexible portion 15, and the switch 3 is moved through the projection 11c. , The switch 3 is turned on and off, and a predetermined signal is output to the apparatus main body. On the other hand, if the operator performs an operation in a state charged to a relatively low voltage, for example, about 3000 volts, the distance between the key top 3 and the ground pattern 4 is sufficiently secured,
The periphery of the switch 3 is the side wall 11a of the key top 11.
Since it is surrounded by the insulating material such as the wall portion 12a of the main body 12 and the like, the electric charge is not discharged unnecessarily, and a necessary signal is reliably output to the main body of the apparatus.

On the other hand, if the operator is charged to a very high voltage of 1000 volts or more, the key top 1
The insulation caused by the gap between the surface 1 and the ground pattern 4 is broken, and discharge occurs. However, key top 11
Are formed in the shape of a cup, the discharge path is regulated by the side wall 12a extending from the main body, and the ground pattern is formed in an area larger than the projection of the space 23 formed by these members. Since the switch 3 and the electronic components disposed in the vicinity of the switch 3 do not become a counter electrode of the discharge, the discharge path 24 is reliably formed between the switch 3 and the ground pattern 4 (FIG. 4). Without the charge of the human body.

[0014]

As described above, according to the present invention ,
The discharge voltage of the electric charge charged to the human body is maintained as high as possible to prevent unnecessary discharge, thereby maintaining the reliability of the device main body, and at the same time, the electric charge high enough to break the insulation of the switch. Discharge is generated only in the ground pattern outside the side wall to prevent the entire device from being destroyed.

[Brief description of the drawings]

FIGS. 1 (a) and 1 (b) are cross-sectional views each showing an enlarged structure of a key switch according to the present invention.

FIG. 2 is an exploded perspective view showing an embodiment of the key switch of the present invention.

FIGS. 3A and 3B are perspective views showing one embodiment of a front surface structure and a back surface structure of the same switch board, respectively.

FIG. 4 is an explanatory diagram showing a discharge path of the key switch.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Switch board 2 Substrate 3 Switch 4 Ground pattern 6 Ground pattern 10 Frame member 11 Key top 12a Side wall part

──────────────────────────────────────────────────続 き Continuation of the front page (56) References Japanese Utility Model Sho-63-69324 (JP, U) Japanese Utility Model Sho 61-87419 (JP, U) Japanese Utility Model Utility Model 4-21034 (JP, U) Japanese Utility Model Sho-62 37139 (JP, U) Japanese Utility Model 5-79828 (JP, U) Japanese Utility Model 1-135622 (JP, U) Japanese Utility Model 4-54114 (JP, U) Japanese Utility Model Application 60-51841 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01H 21/00 H01H 13/02 H05F 3/02

Claims (1)

(57) [Claims] 1. A switch whose contact mechanism is turned on and off by an external operation, a circuit board on which the switch is mounted on a surface, and a cup which is in contact with the surface of the switch and surrounds an upper surface and a side peripheral surface of the switch. A key top, a side wall formed around the key top and having an end reaching the circuit board, made of an electrically insulating material, and a side of the circuit board on which the switch is mounted, the side wall and the key. From the projection area of the space with the top of the side wall
A key switch in an electronic device comprising: a ground pattern formed in an outer region ;