JPH0950344A - Electrostatic discharge intrusion prevention structure for coordinate input device - Google Patents

Abstract

(57) Abstract: The present invention relates to a coordinate input device in which circuit components inside the device and the outside are not separated from each other so much that electrostatic discharge can be prevented from entering from a fitting portion of covers. It is intended to realize a structure for preventing electrostatic discharge intrusion of an input device. In a coordinate input device in which a ball and a rotary encoder that is rotated by the ball via a shaft are housed inside the housing so that a part of the ball is exposed, the housing 20 is provided. It is configured to have a double structure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic discharge intrusion prevention structure for a coordinate input device.

[0002]

2. Description of the Related Art Generally, a mouse is used as a coordinate input device.
A trackball or the like is used. FIG. 4 shows a mouse as an example of the coordinate input device. FIG. 2A is a front view,
(B) is a side view. In this mouse, a printed circuit board 4 is provided inside a housing 3 composed of an upper cover 1 and a lower cover 2, and the printed circuit board 4 penetrates the printed circuit board 4.
Further, the ball 5 is housed so that a part of the ball 5 is exposed to the outside from the bottom of the housing.

The printed circuit board 4 is provided with two shafts (not shown) which are rotated in contact with the balls 5 and are orthogonal to each other.
A rotary encoder is attached to each of the shafts. Further, a processing circuit 6 for processing a signal from the rotary encoder and sending it to the outside and a cable 7 are attached to the printed circuit board 4. In addition, reference numerals 8 and 8 ′ are switch buttons for sending an instruction signal to an external device. Further, 9 is a cap that can be removed when cleaning the ball. The ball 5 is rotated by sliding the mouse on the desk, the rotary encoder reads the rotation and the rotation direction, and the coordinate movement signal is sent to the computer through the cable 7.

[0004]

In the above-mentioned conventional coordinate input device, a human being directly touches and operates it. Therefore, the static electricity accumulated on the human body or the upper cover 1 and the lower cover 2 as shown in FIG. Of the fitting part of or,
As shown in (c), static electricity may be discharged from the gap between the ball 5 and the cap 9 to the wiring of the printed circuit board 4 inside the housing or a conductor such as a connector. This electrostatic discharge adversely affects the hangup of the computer system, the latchup of the IC, and the like. Conventionally, even though there is a shield structure that does not leak the noise generated by the electronic device itself to the outside, the only method of preventing the intrusion of electrostatic discharge from the outside has been to enclose it with an insulator.

However, a coordinate input device such as a mouse contains a mechanical component (mechanical rotary encoder), and a cap on the back of the device can be removed for maintenance problems (ball cleaning etc.). For that reason, it is very difficult to cover with an insulator having no gap, and it cannot be said to be a practical method. It has been confirmed by experiments that static electricity does not discharge to ± 18 [kv] if the fitting part of the cover and the periphery of the cap are actually closed with an insulating material such as vinyl tape.

It is generally known that electrostatic discharge does not occur if the distance between the electronic components (printed circuit board, IC, etc.) inside the apparatus and the insulating material (upper cover, lower cover, etc.) is set to some extent. A coordinate input device such as a mouse is also difficult to realize due to the size limitation of the device itself.

[0007]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, the present invention provides a coordinate input device in which circuit components inside the device and the outside are not separated from each other, and electrostatic discharge from the fitting portion of the covers is prevented. An attempt is made to realize an electrostatic discharge intrusion prevention structure for a coordinate input device that can prevent intrusion.

[0008]

In the structure for preventing electrostatic discharge intrusion of the coordinate input device of the present invention, a ball and a rotary encoder which is rotated by the ball via a shaft are part of the ball. In the coordinate input device that is housed inside the casing so as to be exposed, the casing 20
Is a double structure. In addition to that, the upper cover 24 and the lower cover 2 of the housing 20 are also included.
It is characterized in that the fitting portion 26 with 5 has a double structure and the concave and convex fitting portion 29 is provided in the middle of the overlapping. Alternatively,
The ball attaching / detaching cap 24 provided on the bottom of the housing is provided with a cylindrical wall 30 surrounding the ball 22.

By adopting this configuration, in the coordinate input device in which the circuit components inside the device and the outside are not separated from each other, it is possible to prevent electrostatic discharge from entering from the fitting portion of the covers. An electrostatic discharge intrusion prevention structure can be obtained.

[0010]

1 is a view showing a first embodiment of the present invention, in which FIG. 1 (a) is a side view and FIG. 1 (b) is (a).
It is sectional drawing of the housing | casing in the bb line of a figure. In the figure, reference numeral 20 denotes a housing, and the printed board 2 is provided in the housing 20.
1, a ball 22, a rotary encoder (not shown), etc. are accommodated. Further, a cap 23 that allows the balls to be removed for cleaning is detachably provided on the bottom of the housing 20. The housing 20 is composed of an upper cover 24 and a lower cover 25.
The outer wall of the lower cover 25 and the outer wall of the lower cover 25 are fitted together by a fitting portion 26. Further, the upper cover 24 has an inner wall 27 that reaches the bottom of the lower cover 25 at a distance from the outer wall to form a double wall structure.

In the first embodiment constructed as described above, even if the electrostatic discharge 28 enters from the fitting portion 26 during use, it cannot reach the conductor portion of the printed circuit board by being blocked by the inner wall 27. Therefore, it has a function of preventing electrostatic discharge intrusion.

2A and 2B are views showing a second embodiment of the present invention, in which FIG. 2A is a side view and FIG. 2B is a side view of FIG.
It is sectional drawing of the housing | casing in a b line. In the figure, reference numeral 20 denotes a housing, and the housing 20 houses a printed circuit board 21, balls 22, a rotary encoder (not shown), and the like. As in the first embodiment, a cap 23 that allows the balls to be removed for cleaning is detachably provided on the bottom of the housing 20. The feature of this embodiment is that the overlapping length of the fitting portion 26 between the outer wall of the upper cover 24 and the outer wall of the lower cover 25 is made large, and the concave and convex fitting portion 29 is provided in the middle of the overlapping.

In the second embodiment having the above-described structure, even if the electrostatic discharge 28 tries to enter from the fitting portion 26 during use, the overlapping length of the fitting portion 26 is long, and the concave and convex fitting portion is provided on the way. Since there is 29, it cannot reach the conductor portion of the printed circuit board. Therefore, it has the electrostatic discharge intrusion prevention function as in the first embodiment.

3A and 3B are views showing a third embodiment of the present invention. FIG. 3A is a side view, FIG. 3B is a side view of FIG.
It is a principal part expanded sectional view in the b line. 20 in the figure
Is a housing, and the housing 20 houses a printed circuit board 21, balls 22, a rotary encoder (not shown), and the like. As in the first embodiment, a cap 23 that allows the balls to be removed for cleaning is detachably provided on the bottom of the housing 20. The feature of this embodiment is that the cap 23 is provided with a cylindrical wall 30 so as to surround the ball 22. The height of the wall 30 is preferably higher than the upper surface of the printed board 21.

In the third embodiment having the above-described structure, when the electrostatic discharge 28 tries to enter through the gap between the outer circumference of the hole of the cap 23 and the ball 22 during use, the electrostatic discharge 28 is reached by the cylindrical wall 30. Since the path becomes long, it does not reach the conductor portion of the printed circuit board. Therefore, it has a function of preventing electrostatic discharge intrusion.

[0016]

According to the present invention, the wall of the housing is made into a double wall, the overlapping length of the fitting portion is lengthened, and the discharge path is lengthened. It is possible to prevent the electrostatic discharge from reaching the conductor portion of, and it is possible to contribute to the prevention of adverse effects on the computer and the like.

[Brief description of drawings]

1A and 1B are views showing a first embodiment of the present invention, FIG. 1A is a side view, and FIG. 1B is a sectional view taken along line bb of FIG. 1A.

2A and 2B are views showing a second embodiment of the present invention, in which FIG. 2A is a side view and FIG. 2B is a sectional view taken along line bb in FIG. 2A.

3A and 3B are views showing a third embodiment of the present invention, in which FIG. 3A is a side view and FIG. 3B is an enlarged cross-sectional view of a main part taken along line bb of FIG.

FIG. 4 is a diagram showing a mouse as an example of a conventional coordinate input device.

5A and 5B are views for explaining a problem to be solved by the invention, in which FIG. 5A is a sectional view, FIG. 5B is an enlarged view of a portion B of FIG. 5A, and FIG. FIG.

[Explanation of symbols]

 20 ... Housing 21 ... Printed circuit board 22 ... Ball 23 ... Cap 24 ... Upper cover 25 ... Lower cover 26 ... Fitting part 27 ... Inner wall 28 ... Electrostatic discharge 39 ... Uneven fitting part 30 ... Cylindrical wall

Claims (3)

[Claims] 1. A coordinate input device comprising a ball and a rotary encoder that is rotated by the ball via a shaft inside a housing so that a part of the ball is exposed. 20) is a double structure, which is an electrostatic discharge intrusion prevention structure for a coordinate input device. 2. A coordinate input device comprising a ball and a rotary encoder which is rotated by the ball via a shaft inside a casing so that a part of the ball is exposed. A coordinate input device characterized in that the fitting portion (26) of the upper cover (24) and the lower cover (25) of 20) has a double structure, and an uneven fitting portion (29) is provided in the middle of the overlapping. Electrostatic discharge intrusion prevention structure. 3. A coordinate input device comprising a ball and a rotary encoder which is rotated by the ball via a shaft in a housing so that a part of the ball is exposed. Provided ball attaching / detaching cap (23)
1. A structure for preventing electrostatic discharge intrusion of a coordinate input device, characterized in that a cylindrical wall (30) surrounding a ball (22) is provided.