JP2007027397A - Shield structure for operation panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a malfunction of a liquid crystal display unit by application of static electricity in an operation panel mounting a liquid crystal. <P>SOLUTION: In the operation panel mounting a liquid crystal module 2, a shield structure of the operation panel contains a sheathing of the operation panel, a printed board 1 mounting various electronic parts of the operation panel, a shield member 11 coating the electronic parts disposed between the sheathing and the printed board, and a slit 19 in a part of the shield member 11 so that it is difficult for current to flow in accordance with application of static electricity surrounding the liquid crystal module 2 and a liquid crystal driver IC. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a shield structure for protecting an operation panel from static electricity applied from the outside.

Conventionally, an operation panel has an operation panel board on which display means such as liquid crystal and LED and operation means such as a tact switch are mounted, an exterior of the operation panel, and a metal casing disposed between the operation panel board and the exterior. It is composed of a body and an electrostatic shield is constructed by connecting a metal casing to GND. (For example, refer to Patent Document 1.)
JP 2001-68863 A

  However, in the above conventional example, when an electrostatic component is applied to the metal casing from the outside and the electronic component is placed near the metal casing, the electronic component malfunctions due to electromagnetic induction noise. It was difficult to get close to the parts.

  In recent years, a liquid crystal module in which a liquid crystal driver IC is mounted on the same surface as the liquid crystal glass has been used, and the space between the liquid crystal driver IC on the liquid crystal module and the metal casing is widened. Things were getting harder.

  An object of the invention according to the present application is to prevent electromagnetic induction noise induced by an applied current of static electricity from being generated around a liquid crystal display unit when static electricity is applied to a shield plate formed of a metal casing.

  In order to achieve the above object, an invention according to the present application includes a printed circuit board on which various electronic components including a liquid crystal module are mounted, and a metal housing connected to a frame ground of an apparatus body that covers the periphery of the electronic component and the printed circuit board. And a current regulating means for regulating a current by increasing the impedance of a part of the metal casing, and the current regulating means makes it difficult for a current to flow around a specific electronic component.

  As described above, according to the present invention, the impedance of a part of the shield plate is increased so that the current does not easily flow around the liquid crystal display unit, which is generated by electromagnetic induction due to the applied current of static electricity. This prevents malfunction of the liquid crystal display unit.

Example 1
FIG. 1 and FIG. 2 are drawings that best illustrate the features of the present invention, in which 1 is a printed circuit board of an operation panel, 2 is a liquid crystal display module, and 3 is a liquid crystal drive driver IC built in the liquid crystal display module 2. It is mounted on the glass of the liquid crystal module and connected to the liquid crystal of each pixel by a transparent electrode. 4 is a display area of the liquid crystal display module 2, 5 a and 5 b are LEDs that display a state by turning on / off, 6 a, 6 b, 6 c, and 6 d are push switches (hereinafter referred to as SW), and 7 and 8 are printed circuit boards 1. The operation panel interface signal bundle is connected to a control hole (not shown). The operation panel interface signal bundle line includes a control signal for the liquid crystal display module 2, a drive signal for the LED 5, a detection signal for the SW 6, and a power source. 10 is an exterior of the operation panel, 11 is a metal having the same potential as the frame ground of the apparatus main body (not shown), a shield metal plate surrounding each part on the operation panel, and 12 and 13 are a shield metal plate 11 and a leaf spring 14, When the operation panel is attached to a main body (not shown), the screws 15 and 15 for fixing the printed board 1 and the printed circuit board 1 come into contact with the frame ground of the main body and become a ground path for the shield metal plate 11. Reference numerals 16a and 16b denote light guides for condensing the light from the LED 5. Reference numerals 17a, 17b, 17c, and 17d denote switch guide buttons that press the SW 6, 18 denotes a transparent protective sheet that covers the display area 4 of the liquid crystal display module 2, and 19 denotes a shield metal plate 11 that covers the periphery of the liquid crystal drive driver IC 3 of the liquid crystal display module 2. It is a slit opened in.

  As shown in FIG. 2, the operation panel is provided with a shield sheet metal 11 having the same potential as the frame ground under the exterior 10, and the printed circuit board 1 is disposed so as to be covered with the shield sheet metal 11. In such a configuration, the display area 4 of the liquid crystal module 2 is covered with a protective sheet 18, and no static electricity is applied from the outside, but around the light guide 16 and the switch guide button 17 between the exterior 10. Since there is a gap, static electricity may be applied from the outside.

  When electrostatic noise N1 is applied to the light guide 16b, the instantaneous current I1 generated by the electrostatic noise N1 avoids the slit 19 having a high impedance and is mainly a leaf spring connected to the frame ground indicated by the arrow I1. Flows in 14 directions.

  Further, when electrostatic noise N2 is applied to the switch guide button 17b, the instantaneous current I2 generated by the electrostatic noise N2 is mainly connected to the frame ground indicated by the arrow I2, avoiding the slit 19 having a high impedance. It flows in the direction of the plate spring 15.

  As described above, by providing a slit in the shield metal plate 11 that covers the periphery of the liquid crystal drive driver IC 3, an instantaneous current generated by electrostatic noise hardly flows through the shield metal plate that covers the upper surface of the liquid crystal drive driver IC 3. This has the effect of preventing the liquid crystal drive driver IC 3 from malfunctioning due to electromagnetic induction noise.

(Example 2)
FIG. 3 is a diagram showing a second embodiment of the present invention. In FIG. 3, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In the figure, 20 is a metal having the same potential as the frame ground of the apparatus main body (not shown), a shield metal plate surrounding each part on the operation panel, and 21 is a periphery of the liquid crystal drive driver IC 3 of the shield metal plate 20 and the periphery of the LED 16. A notch 22 separates between the periphery of the liquid crystal driving driver IC 3 of the shield metal plate 20 and the periphery of the SW 6a, 6b.

  In such a configuration, the display area 4 of the liquid crystal module 2 is covered with a protective sheet 18, and no static electricity is applied from the outside, but around the light guide 16 and the switch guide button 17 between the exterior 10. Since there is a gap, static electricity may be applied from the outside.

  When the static noise N3 is applied to the light guide 16b, the instantaneous current I3 generated by the static noise N3 does not flow to the notch 21, and therefore the leaf spring 14 connected mainly to the frame ground indicated by the arrow I3. Flow in the direction.

  In addition, when the electrostatic noise N4 is applied to the switch guide button 17b, the instantaneous current I4 generated by the electrostatic noise N4 does not flow to the notch 22 and is therefore mainly connected to the frame ground indicated by the arrow I4. It flows in the direction of the leaf spring 15.

  As described above, the shield sheet metal 11 is generated by electrostatic noise in the shield sheet metal covering the upper surface of the liquid crystal drive driver IC 3 by providing a cut between the part covering the periphery of the liquid crystal drive driver IC 3 and the part where static electricity is easily applied. This makes it difficult to cause the instantaneous current to flow, thereby preventing the liquid crystal drive driver IC3 from malfunctioning due to electromagnetic induction noise induced by the current.

(Example 3)
FIG. 4 is a diagram showing a third embodiment of the present invention. In FIG. 4, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In the figure, reference numeral 23 is a metal having the same potential as the frame ground of the apparatus main body (not shown), a shield metal plate surrounding each part on the operation panel, and 24 is a periphery of the liquid crystal drive driver IC 3 of the shield metal plate 23 and SW 6a, 6b. The notch 25 that separates the periphery from the periphery is a portion that is overlapped and shields the periphery of the liquid crystal drive driver IC 3 in a double manner. Even if static electricity is applied to the upper side of the double overlap, the notch 24 is separated. No instantaneous current flows through the lower shield. Reference numeral 26 denotes a folding position for making an overlapped portion.

  In the first and second embodiments, the protective sheet 18 in the display area 4 is configured to have a creeping distance that does not cause discharge against static electricity applied from the outside.

  In the present embodiment, the protective sheet 18 cannot be enlarged to a size that does not cause discharge, and static electricity may be applied from the vicinity of the display area 4.

  In such a configuration, when the electrostatic noise N5 is applied to the display area 4 portion, the instantaneous current I5 generated by the electrostatic noise N5 does not flow to the notch 24 portion, and therefore mainly to the frame ground indicated by the arrow I5. It flows in the direction of the connected leaf spring 15.

  As described above, the portion of the shield sheet metal 11 that covers the periphery of the liquid crystal drive driver IC 3 is configured to be superposed, and the current flowing through the overlap portion is regulated, so that the static electricity is applied to the upper side of the shield metal plate that covers the liquid crystal drive driver IC 3. Even if an instantaneous current generated by noise flows, current does not flow on the lower surface side, so that the liquid crystal drive driver IC 3 is prevented from malfunctioning due to electromagnetic induction noise induced by the current.

  Further, by combining the overlapping portion and the current regulating portion, it is possible to reduce the portion requiring regulation that does not generate discharge due to the application of static electricity.

It is a block diagram explaining the structure of the operation panel which concerns on 1st Example of this invention. It is a block diagram explaining the shield structure concerning the 1st example of the present invention. It is a block diagram explaining the shield structure which concerns on the 2nd Example of this invention. It is a block diagram explaining the shield structure which concerns on the 3rd Example of this invention.

Explanation of symbols

1 Printed Circuit Board 2 Liquid Crystal Module 3 Liquid Crystal Driver 11 Shield Sheet Metal 19 Slit

Claims (1)

A printed circuit board on which various electronic components including a liquid crystal module are mounted;
A metal casing connected to the frame ground of the apparatus body covering the periphery of the electronic component and the printed circuit board;
Current regulation means for regulating the current by increasing the impedance of a part of the metal casing;
A shield structure for an operation panel, characterized in that the current regulating means makes it difficult for current to flow around a specific electronic component.

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