JP2781253B2 - Key switch - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a key switch, and more particularly to a key switch in which a key top is elastically urged by a sheet-like elastic member in a return direction opposite to a pressing operation direction. Further, the present invention relates to a key switch having a torsion bar for preventing a key top from being caught.

2. Description of the Related Art Conventionally, in electronic devices having a keyboard such as a calculator, a typewriter, and a personal computer, operability is facilitated by using an elongated keytop for a frequently used key switch. In that case, the key switch has a torsion bar to prevent the key switch from tilting so that the key top does not tilt and get caught when pressing the end of the key top. Have been.

In particular, a key switch of a keyboard of a small electronic device such as a calculator uses a sheet-like elastic member provided with a movable contact called a key sheet, and the key sheet elastically pushes a key top in a return direction opposite to a pressing operation direction. Many types of biasing are used.

A conventional structure of a key switch provided with a torsion bar in the key sheet system will be described with reference to FIGS. 3 and 4. FIG.

First, the basic configuration of the key switch excluding the torsion bar mechanism will be described. In FIG. 3, reference numeral 1 denotes a key top, which is formed to be elongated in the left-right direction in the figure, and a key stem 2 is fixed to a central portion of the lower surface thereof.

The key stem 2 is slidably fitted to a cylindrical guide portion 3c formed on a frame 3 of an electronic device in which a key switch is incorporated, and is integrated with the key top 1 in the vertical direction (the key top (The return direction and the pressing operation direction).

A key sheet 4 is provided below the key stem 2. The key sheet 4 is formed from an elastic body such as silicone rubber,
A hollow dome portion (convex portion) 4b is formed so as to protrude from the flat base portion 4a, and a movable contact 4c made of conductive rubber is fixed to an inner ceiling portion of the dome portion 4b. Further, a ring portion 4d is formed at the top of the dome portion 4b. The ring portion 4d contacts the lower surface of the key stem 2 and the dome portion
4b is pushing the key stem 2 upward.

The key sheet 4 has a base portion on a printed circuit board 5.
4a is provided in close contact. On the upper surface of the printed circuit board 5, fixed contacts 5a, 5a of the input circuit of the key switch are formed, and the key sheet 4 is provided with movable contacts 5a, 5a.
4c are arranged to face each other.

In such a configuration, when the operator presses the key top 1 with a finger, the key stem 2 moves down together with the key top 1 to elastically deform the dome portion 4b, the movable contact 4c descends, and the fixed contact 5a, 5a The two contacts make a short circuit, and key input is performed. Also, from this state, the key top 1
When the finger is released, the dome portion 4b returns to its original shape and pushes up the key stem 2, so that the key stem 2 and the key top 1 return to the initial position before the operation.

 Next, the mechanism of the torsion bar will be described.

As shown in FIG. 3, a pair of torsion bar holders (hereinafter abbreviated as "bar holders") 6, 6 are implanted on the lower surfaces at both ends in the longitudinal direction of the key top 1 with the upper ends fixed by press-fitting or bonding. The bar holder 6 is inserted through the hole 3d of the frame 3, and a U-shaped groove 6b is formed at the lower end of the bar holder 6 facing the base portion 4a of the key sheet 4 as shown in FIG. ing. This bar holder 6
The torsion bar 7 is movably connected to the key top 1 via the.

The torsion bar 7 is formed in a substantially U-shape from a metal round bar, and both ends 7c are bent at a right angle in the same direction with respect to the intermediate portion 7b.
Are bent at right angles from both ends 7c toward each other. An intermediate portion 7b of the torsion bar 7 is made parallel to the longitudinal direction of the key top 1, and has an inverted U-shaped groove 3b formed at the lower end of a rib 3a extending downward from the frame 3 as shown in FIG. , Rib 3a and key sheet 4
Is rotatably held by a holding member 8 provided on the base portion 4a. That is, the torsion bar 7 is in the middle
The bearing is rotatably supported around 7b. Each of the working ends 7a of the torsion bar 7 fits into the corresponding groove 6b of the bar holder 6, and is coupled to the bar holder 6 so as to be rotatable and movable in the lateral direction.

 Next, the operation of the torsion bar mechanism will be described.

The operator places an arrow B on the left end of the key top 1 in FIG.
When the key is pressed as shown in FIG. 2, a counterclockwise rotational moment is applied to the key stem 2 in the figure, and the key top 1 tends to tilt together with the key stem 2 within the range of the angle due to the clearance between the key stem 2 and the guide portion 3c of the frame 3. .

At this time, the left bar holder 6 is lowered integrally with the key top 1, and pushes down the left working end 7a of the torsion bar 7. As a result, the left end 7c rotates counterclockwise in FIG. 4 about the intermediate portion 7b as a fulcrum.

Here, since the torsion bar 7 is made of a rigid metal round bar, the torsion bar 7 is slightly torsion-deformed, but the right end 7c is formed.
Also rotates similarly to the left side. Then, the right working end 7a pushes down the right bar holder 6, and the right end side of the key top 1 where the key top 1 is not pushed down also goes down. This makes Key Top 1
Descends smoothly with a slight inclination.

[Problems to be Solved by the Invention] By the way, in the above conventional example, the operating end of the torsion bar 7 is
The upper and lower width dimensions of the groove 6b are set with an appropriate allowance in consideration of the variation in the diameter of the torsion bar 7 and the processing error of forming so that 7a can operate smoothly in the groove 6b of the bar holder 6. . Also, the middle part of the torsion bar 7
Similarly, the dimensions of the groove 3b of the rib 3a bearing the 7b and the size of the holding member 8 are appropriately set with allowance for play.

However, when there is such play, when the key top 1 is pressed, the operating end 7a and the intermediate portion 7b of the torsion bar 7 hit the inner surfaces of the grooves 6b and 3b, respectively, and an unpleasant noise is produced.

In addition, the play causes the torsion bar mechanism to follow the operation of the key top 1 with a delay, so that if the play is large, the key top 1 will be activated before the operation of the torsion bar mechanism becomes effective when the end of the key top 1 is pressed. The angle of inclination of the key stem 2 becomes large, and the key stem 2 becomes the guide portion 3c of the frame 3.
In some cases.

Accordingly, an object of the present invention is to eliminate the above-mentioned disadvantages in this type of key switch.

[Means for Solving the Problems] According to a key switch of the present invention for solving the above problems, a key top movably provided in a pressing operation direction and a return direction opposite to the pressing operation direction, and the key top is moved in a return direction. A sheet-like elastic member elastically biased to the torsion bar, and a torsion bar that is rotatably supported about an intermediate portion as a fulcrum and has both ends movably coupled to the key top. A plurality of elastic pressing members are formed integrally with the sheet-like elastic member to elastically press the portion to remove play at the bearing portion of the torsion bar and play of the torsion bar at the torsion bar coupling portion of the key top. The configuration was adopted.

[Operation] According to such a configuration, the play of the torsion bar at the bearing portion and the play of the torsion bar at the torsion bar coupling portion of the keytop are eliminated by the pressing of the elastic pressing member.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

1 and 2 illustrate the structure of a key switch according to an embodiment of the present invention. In both figures, parts common or equivalent to those in FIGS. 3 and 4 of the conventional example are denoted by common reference numerals, and description of the common parts is omitted.

As shown in FIGS. 1 and 2, in the key switch of the present embodiment, a key sheet 4 made of an elastic material such as rubber is different from the conventional example, and a projection 4f and a bulging portion are formed on the upper surface of the key sheet 4.
4g is formed integrally with the key sheet 4 so as to protrude from the flat base portion 4a.

The projection 4f is formed in a rectangular shape and is solid, and is formed at a position directly opposite to the rib 3a. And torsion bar 7
The intermediate portion 7b is inserted into the groove 3b at the lower end of the rib 3a as shown in FIG. 2, and is rotatably held between the rib 3a and the projection 4f. Here, the height dimension of the groove 3b is the torsion bar 7
The protrusion 4f elastically presses the protruding portion upward to press the middle portion 7b of the torsion bar 7 against the inner surface of the groove 3b. As a result, the play of the intermediate portion 7b bearing in the groove 3b is eliminated. Since the projection 4f is elastically deformed, the torsion bar 7
Above-mentioned play is eliminated by absorbing the variation in diameter and the processing error.

On the other hand, the bulging portion 4g is formed at a portion facing each of both ends 7c of the torsion bar 7, and the bulging portion 4g is formed hollow while the projection 4f is solid. As shown in FIG. 2, the cross section parallel to the end 7c of the bulging portion 4g is formed in a semicircular shape, and the bulging portion 4g is formed on the end 7c of the torsion bar 7 by crushing the semicircle. It is pressed and elastically pushes up the end 7c by the repulsive force of the deformation. This bulge
The pressing force of 4 g acts on the end 7c even when the key top 1 is located at the top dead center. Then, the end portion 7c is urged clockwise in FIG. 2 by the pressing force of the bulging portion 4g, and the working end 7a is pressed against the upper surface of the groove 6b of the bar holder 6. Thereby, the play of the working end 7a with respect to the bar holder 6 is eliminated.

The structure of the other components of this embodiment is common to the above-described conventional example, and the operation is the same.

In this embodiment as described above, the play at the bearing of the torsion bar 7 and the play at the joint with the bar holder 6, that is, at the joint with the key top 1 integral with the bar holder 6, are caused by the protrusion 4f.
And the bulging portion 4g is removed by elastic pressing. Accordingly, the mechanism of the torsion bar 7 that operates as described above in accordance with the operation of the key top 1 has good followability, and the inclination of the key top 1 when the end of the key top 1 is pressed can be kept very small. . The key top 1 does not get caught unlike the case where the play of the torsion bar is large in the above-described conventional example, the key input can be reliably performed, and the reliability of the key switch can be improved.

Further, according to this embodiment, since there is no play of the torsion bar as described above, an unpleasant operation sound at the time of operation can be suppressed. In particular, since the lower portion of the intermediate portion 7b of the torsion bar 7 is received by the elastic projection 4f, when the operator suddenly presses the keytop 1, the impact can be buffered and the impact sound can be absorbed.

In addition, in this embodiment, the projection 4f and the stick-out portion 4g correspond to the key sheet 4
Therefore, the number of parts does not increase because of the integral structure, but the number of parts can be reduced by the amount of the holding member 8 of the conventional example, the number of assembling steps can be reduced, and the cost can be reduced.

In the configuration of this embodiment, the end of the torsion bar 7 is used.
The pressing force of the bulging portion 4g that pushes up 7c is sufficient if a pressing force necessary to bring the working end 7a of the torsion bar 7 into contact with the upper surface of the groove 6b when the key top 1 is at the top dead center is obtained. The bulging portion 4g is hollow to reduce the ratio of the repulsive force to the amount of elastic deformation. The reason is that if the repulsive force of the bulging portion 4g increases rapidly according to the pressing operation of the key top 1, the operational feeling of the switch is impaired.

The shapes of the projection 4f and the bulging portion 4g are not limited to those described above. Further, the key top 1 and the key stem 2 may be integrated, and the bar holder 6 may be integrally formed with the key top 1.

[Effects of the Invention] As is clear from the above description, according to the key switch of the present invention, a keytop movably provided in a return direction opposite to the pressing operation direction, and the keytop is elastically moved in the return direction. And a torsion bar that is rotatably supported with the middle portion as a dead center and has both ends movably coupled to the keytop. The middle portion and both ends of the torsion bar are provided. A configuration in which a plurality of elastic pressing members are formed integrally with the sheet-like elastic member to elastically press to remove play at the bearing portion of the torsion bar and play of the torsion bar at the torsion bar coupling portion of the key top. The torsion bar for the operation of the key top is removed by eliminating the play at the bearing of the torsion bar and the play of the torsion bar at the torsion bar joint of the key top. The followability of the key mechanism can be improved, the key top can be prevented from being caught, and the reliability of the key switch can be improved. In addition, it is possible to obtain an excellent effect that noise can be reduced by suppressing an unpleasant operation sound at the time of operation, and the cost can be reduced by reducing the number of parts and the number of assembling steps.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional front view showing the structure of a key switch according to an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along the line CC of FIG. 1, and FIG. FIG. 4 is a longitudinal sectional front view showing the structure of the switch, and FIG. 4 is a sectional view taken along line AA of FIG. DESCRIPTION OF SYMBOLS 1 ... Key top, 2 ... Key stem 3 ... Frame, 4 ... Key sheet 4c ... Movable contact, 4f ... Protrusion 4g ... Extended part, 5 ... Printed circuit board 5a ... Fixed contact, 6 …… Bar holder 7 …… Torsion bar

Claims (2)

(57) [Claims] A key top movably provided in a return direction opposite to the pressing operation direction, a sheet-like elastic member for elastically urging the key top in a return direction, and a pivot about an intermediate portion. A torsion bar which is movably coupled to the key top and is capable of elastically pressing an intermediate portion and both ends of the torsion bar to play in a bearing portion of the torsion bar, and the key. A key switch, wherein a plurality of elastic pressing members for removing play of a torsion bar at a top torsion bar coupling portion are formed integrally with the sheet-like elastic member. 2. The elastic pressing member for elastically pressing both ends of the torsion bar to remove play of the torsion bar at the torsion bar connecting portion of the key top is hollow. The key switch according to item 1.