JPH0228563Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) The present invention is applicable to key switches used, for example, as data input keys for electronic computers or input keys for word processors, which can provide a particularly sharp operating feel. This relates to a key switch mechanism.

(Prior Art) Key switches have a simple structure and can be installed compactly, so they are widely used in many fields. Particularly as office automation progresses, they are becoming popular as data input keys for computers and input keys for word processors, and demand is likely to continue to grow. Here, the structure of a conventionally used key switch will be explained.

FIG. 1 shows an example of a capacitance switch. In the figure, 1 is a board, 2 is a housing disposed on the board 1, and 3 is a switch that slides into a hole 2a provided in the housing 2. The key stem is arranged so that a hole 3a is provided at its upper end, and a shoulder 3b that abuts the lower surface of the housing 2 is integrally formed at its lower end. A key cap 4 is attached to the upper end of the key stem 3. A connecting portion 4a extending downward is formed in the center of the key cap, and the connecting portion 4a is fitted into a hole 3a provided at the upper end of the key stem 3. , is constructed integrally with the key stem 3.
Reference numeral 5 denotes a rubber spring disposed between the base plate 1 and the key stem 3. Normally, the rubber spring 5 pushes up the key cap 4 and the key stem 3 by its elastic force, and the shoulder portion 3b formed below the key stem 3 is moved upwardly by the elastic force. It is kept in contact with the bottom surface. 6 is attached to the upper and lower surface of the rubber spring 5 with an electrostatic pad, and an aluminum vapor-deposited film is attached to the lower end of the rubber spring 5, and a polyester film, which becomes the dielectric of the capacitor, is adhered to the lower surface of the aluminum vapor-deposited film. . 7a and 7b are electrodes that constitute a capacitance switch together with the electrostatic pad 6;
The rubber springs 5 are mounted on the top surface at intervals, and the rubber springs 5 are attached to the key cap 4 and the key stem 3.
When the electrostatic pad 6 is pushed upward, the electrostatic pad 6
is located away from the electrodes 7a and 7b, so the capacitance switch is in the OFF state. Then the key cap 4 is pushed down and the electrostatic pad 6
is pressed onto the electrodes 7a, 7b, the electrode 7
The capacitance between a and 7b increases via the capacitive pad 6, and the capacitance switch is turned on.

(Problems with the Prior Art) The key switch constructed as described above has operating characteristics as shown in FIG. 2 when an external force is applied to the key cap 4 from above during switch operation. That is, when the key cap 4 is pressed from the state shown in Figure 1, the load increases until the peak load of the rubber spring is P ₂ and moves to the stroke S ₁ , and then when the key cap 4 is further pressed, the peak load of the rubber spring is reached.
When _P2 is exceeded, the rubber spring 5 deforms greatly and the load decreases, and when the load reaches _P1 , the stroke becomes _S2 and the switch is turned on. When key cap 4 is further pressed, the load increases again and reaches stroke end _S3 . In this operating process, the load is P ₂ between the strokes S ₁ and S ₂
The click that decreases from P to ₁ is effective for obtaining a feeling of operation. This click is obtained by the rubber spring 5, but since the rubber spring 5 has a self-returning force, its structure makes it difficult to
As shown in the figure, the load difference from P ₂ to P ₁ is limited, and the load transfer from stroke S ₁ to S ₂ is slow, so it is difficult to obtain a sharp click operation feeling.

FIGS. 3A and 3B are explanatory views of air intake and exhaust in the space between the rubber spring 5 and the base plate 1 when the key switch having the configuration shown in FIG. 1 is turned OFF and ON. In a capacitance switch, the switch is turned ON as a measure to prevent the influence of external noise.
In order to increase the difference in capacitance values between the OFF and OFF states, the contact area between the electrostatic pad and the electrode is increased, so in Figure 3A, the rubber spring 5 is large. Become. Switch in the diagram
During the operation from ON to OFF, that is, when the key stem 3 is raised, the volume of the space between the rubber spring 5 and the base plate 1 changes greatly, and the amount of air sucked into the space increases. This intake of air uses the gap between the substrate 1 and the lower part of the housing 2 as a passage, so when the outside air is sucked into the rubber spring, dust in the outside air and dust on the substrate 1 near the gap are also removed. Inhale as shown in Figure 3A along with external air. Furthermore, when the switch is turned from OFF to ON, that is, when the key stem 3 is lowered, the rubber spring 5 is pressurized and the space between the rubber spring 5 and the base plate 1 is compressed as shown in FIG. 3B, so that the air in the space is Although the air is discharged, some of the dust in the air remains in the space, and the amount of residual dust increases with the number of switch OFF-ON operations. Therefore, the electrodes 7a, 7
Dust also enters between b and the electrostatic pad 6, and in a switch that uses changes in capacitance as a signal, as the capacitance value decreases, the signal output becomes unstable and the key switch becomes unstable. It turns out.

Furthermore, in the key switch having the configuration shown in Fig. 1, adhesive is required to adhere the electrostatic pad 6 to the lower center surface of the rubber spring 5, which makes automatic assembly difficult in the manufacturing process, resulting in a lack of productivity improvement. becomes.

By the way, Japanese Utility Model Application Publication No. 57-67342 discloses a switch mechanism for opening and closing two fixed contacts using a movable contact for the purpose of delaying the click point. In the keyboard switch shown here, the movable contact is directly supported at the center of the inner surface of an inverted cup-shaped rubber elastic body for supporting the movable contact, and as a result, when the movable contact is pushed down with the operator, In addition, the movable contact does not always descend parallel to the fixed contact on the insulating substrate, and the movable contact does not always descend parallel to the fixed contact, and the electrodes are fixed by pressing an electrostatic pad to which a dielectric is adhered, as in the invention of the present invention. When applied to a capacitance switch that increases the capacitance of a switch, the stability of its operation cannot be ensured.

FIG. 4 is an example of a conventional capacitive switch that takes into account the above-mentioned problems of the key switch shown in FIG.
In the figure, 8 is a housing, 9 is the housing 8
The key stem 9 is slidably disposed in a hole 8a provided in the housing 8, and the key stem 9 has a hole 9a at its upper end, and a shoulder 9b that contacts the lower surface of the housing 8 and an electrostatic pad 10 at its lower part. A holding portion 9c for holding the is integrally molded. A key cap 11 is attached to the upper end of the key stem 9, and a connecting portion 11a extending downward is formed in the center thereof, and the connecting portion 11a is fitted into a hole 9a provided in the key stem 9. It is constructed integrally with the key stem 9. A rubber spring 12 is disposed between the key stem 9 and the housing 8, and is normally disposed on the upper surface of the board 13 in order to keep the key cap 11, key stem 9, and electrostatic pad 10 pushed upward by its elastic force. installed electrode 1
4 and the electrostatic pad 10 are spaced apart, and the switch is
Retains OFF state.

Compared to the key switch with the configuration shown in Figure 1, a key switch with this configuration has problems such as the influence of dust due to the intake and discharge of external air between the electrostatic pad and the electrode, and problems with the adhesive method for holding the electrostatic pad. However, the operating characteristics when the switch is turned OFF and ON are almost the same as those shown in Figure 2, and it provides the same sharp click operation feeling as the key switch with the configuration shown in Figure 1. is difficult. Furthermore, since the rubber spring 12 is located outside the switch mechanism, it is difficult to reduce the height of the entire switch.

(Purpose of the invention) This invention was made in order to solve the problems of the conventional key switch mentioned above, and it is possible to ensure a sharp click operation feeling and stability of operation, and to increase the overall height of the switch. The object of the present invention is to provide a key switch mechanism that can automate production by preventing dust from forming inside the switch mechanism.

(Summary of the invention) In order to achieve the above object, the present invention provides a key switch mechanism for a capacitive switch that increases the capacitance between fixed electrodes by pressing an electrostatic pad to which a dielectric is attached. , a substrate to which a plurality of the electrodes are fixed, a housing that covers the substrate, a key stem slidably provided on the housing, a key cap mounted on the key stem, and a central cap provided on the substrate. a rubber spring having a hole formed in the upper part; a pad holder that fits freely into the hole of the rubber spring to hold the electrostatic pad parallel to the board; and a pad holder fitted between the pad holder and the key cap. This is a key switch mechanism with a coil spring.

(Embodiment) FIG. 5 shows an embodiment of the key switch according to the present invention. In the figure, 20 is a board, 21 is a frame disposed on the board 20, and 22 is a housing 23 attached to the frame 21. The key stem is slidably disposed through the key stem, and has a hole 22a in the center and a shoulder 22b formed at the lower part of the outer periphery. The housing 23 has an engagement shoulder 23a at its lower end, which is attached to the frame 21 by engaging with a hole 21a provided in the frame 21, and a hole at its upper end. 23b is provided, and the key stem 22 is slidably fitted and supported in the hole 23b, and the shoulder 22b formed on the key stem 22 abuts the peripheral edge 23c of the hole 23b, so that the key stem 22 is moved upwardly. Movement is regulated. Reference numeral 24 designates a key cap attached to the upper end of the key stem 22. A connecting portion 24a extending to the lower end is formed in the center of the key cap, and the connecting portion 24a is press-fitted into a hole 22a provided in the key stem 22. It has an integrated structure with 22. Reference numeral 25 denotes a pad holder disposed below the key cap. A pad mounting portion 25a is formed at the lower end of the pad holder 25, and an electrostatic pad 26 is held at the lower center of the pad holder 25. In addition, pad holder 25
A tubular portion 25b is formed at the upper center of the key stem 22, and is guided by the inner surface of the key stem 22 so as to be slidable in the vertical direction. , upward movement is now restricted. Also, the pad attachment part 25a at the lower end of the pad holder 25
The lower surface of the electrostatic pad 26 is formed in consideration of its downward dimension, that is, the thickness of the electrostatic pad when compressed, so that the amount of compression of the electrostatic pad 26 is appropriate when the switch is turned on. The electrostatic pad 26 is made of a material such as urethane foam, and an aluminum vapor-deposited film is attached to the lower end of the electrostatic pad 26. A polyester film that serves as the dielectric of the capacitor is adhered to the lower surface of the aluminum vapor-deposited film. electrode 27
A, 27b, etc. constitute a capacitance switch. 28 is a rubber spring provided on the substrate 20 and having a hole 28a formed in the upper center thereof. The pad holder 25 is freely fitted into the hole 28a of the rubber spring 28 to hold the electrostatic pad 26 parallel to the substrate 20. The rubber spring 28 is made of a rubber material such as silicone rubber or olefin elastomer and has an inverted cup shape.
is made of the same hard synthetic resin material as the housing 23 and the like. Therefore, the pad holder 25, which is freely fitted into the hole 28a of the rubber spring 28, can hold the electrostatic pad 26 parallel to the substrate 20. The operating characteristics of the rubber spring are as shown in FIG. 6, and the pad holder 25 is held by the self-returning action of the rubber spring 28, and is always urged upward. Reference numeral 29 denotes a compression coil spring disposed between the pad holder 25 and the key cap 24, which presses the pad holder 25 and the key cap 24 in a direction away from each other, and cooperates with the rubber spring to move each member into the fifth position. It is maintained in the state shown in the figure.

Next, the operation of the key switch configured as described above will be explained. When the key cap 24 is pressed, the coil spring 29 is compressed, and the key cap 24 strokes downward while balancing up to the peak load _P2 of the rubber spring 28 shown in FIG. As the key cap 24 strokes downward in this manner, the rubber spring 28 is suddenly deformed at the moment the compressed coil spring load exceeds the peak load _P2 of the rubber spring 28, as shown in FIG. Stroke S ₁
to S ₂ , the load decreases rapidly from P ₂ to P ₁ , and the key cap 24 and pad holder 25
falls rapidly, as if being sucked in. When the key cap 24 and the pad holder 25 fall downward, the electrostatic pad 26 held at the bottom of the pad holder 25 is brought into pressure contact with the electrodes 27a and 27b on the board 20, and the electrostatic pad 26 is stuck to the lower surface of the pad holder 26. The electrodes 27a and 27b are turned on via the dielectric polyester film.
Coil spring 2 at stroke S ₂
The load of 9 is the rubber spring 2 at this point.
8, the rubber spring 28 continues to be pushed, and the load gradually increases until it reaches the stroke end _S3 . Note that when the external force applied to the key cap 24 is removed, the rubber spring 28 and the coil spring 29
Due to the self-returning force of the pad holder 25 and the key cap 24 are instantly moved upward, and the electrostatic pad 26 held in the pad holder 25 is also separated from the electrodes 27a and 27b.
The switch will be in the OFF state.

FIG. 8 is a block diagram of the main parts of the key switch in the embodiment shown in FIG. 5 that provide click operation, and the numbers and names of each part are the same as those in FIG. 5.

As described above, the operating characteristics of the switch _of this embodiment are as shown in _{FIG .}
It decreases rapidly to P ₁ , giving a sharp clicky operating feel. Furthermore, since the electrostatic pad moves quickly and the capacitance value changes significantly, a stable signal with a high signal-to-noise ratio can be obtained.

FIG. 9 is an explanatory diagram of air flowing in and out of the space surrounded by the pad holder 25, rubber spring 28 and base plate 20 when the key switch of the embodiment shown in FIG. 5 is turned OFF and ON.
In the figure, the volume of the space surrounded by the pad holder 25, rubber spring 28, and base plate 20 is
When the switch is turned on from OFF, that is, pad holder 2
When the pad holder 5 is lowered, the rubber spring 28 is pressed downward and the volume of the space is narrowed, so that the air inside the space flows upward through the air hole 25c provided below the pad holder 25. Also switch
The pad holder 25 rises when OFF than ON,
Since the volume of the space expands, air flows through the air hole 2.
It flows into the space through 5c. In this way, when the switch is repeatedly turned on and off, the internal air in the space repeatedly flows in and out through the air hole 25c, but the upper part of the air hole 25c is covered with the housing 23, so that it does not come into direct contact with the outside air. Since the amount of dust is small, the amount of dust mixed in the external air is inhaled to a small extent, and therefore the negative influence of dust on the switch circuit is reduced.

(Effects of the invention) As described above, according to the invention, in the key switch mechanism of a capacitance switch that increases the capacitance between fixed electrodes by pressing an electrostatic pad to which a dielectric is attached. , a substrate to which a plurality of the electrodes are fixed, and a housing that covers the substrate;
A key stem slidably provided on the housing, a key cap mounted on the key stem, a rubber spring provided on the substrate and having a hole formed in the upper center thereof, and a rubber spring fitted into the hole of the rubber spring. It has a pad holder that is freely fitted and holds the electrostatic pad parallel to the board, and a coil spring that is fitted between the pad holder and the key cap, so it provides a sharp operating feel and stability of operation. can be ensured and a key switch mechanism can be provided. Note that due to this operating characteristic, the compression time of the electrostatic pad is short, and therefore the capacitance value changes rapidly, so a signal with a large signal-to-noise ratio can be obtained.

Further, in the present invention, the rubber spring and the pad holder are separated and placed inside the housing, so that there is less direct flow of outside air into and out of the switch mechanism when the switch is operated, and therefore it is less susceptible to external dust. Furthermore, by fitting the pad holder into the center hole of the rubber spring, the electrostatic pad can be held in the pad holder without using adhesives, making automatic assembly possible during switch production. , it is desired to improve productivity. Furthermore, according to the present invention, as mentioned above, the combined elastic force of the rubber spring and coil spring is utilized, so the stroke of the rubber spring can be made smaller, and the rubber spring can be made smaller and the rubber spring can be placed inside the switch mechanism. Therefore, it is possible to reduce the height of the entire switch.

It should be noted that the present invention is not limited to the one shown in the above embodiment, but can be applied to other types of switch mechanisms by replacing the pad holder portion.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an example of a conventionally used key switch, Fig. 2 is a diagram showing the operating characteristics of the key switch shown in Fig. 1, and Figs.
Figure B is an explanatory diagram of air intake and air discharge when the key switch shown in Figure 1 is operated;
FIG. 4 is a sectional view showing another example of a conventional key switch, FIG. 5 is a sectional view showing an embodiment of the key switch according to the present invention, and FIG. 6 is a sectional view of a rubber spring used in the key switch of FIG. FIG. 7 is a diagram showing the operating characteristics of the key switch shown in FIG. 5. FIG. 8 is an explanatory diagram of the quick operation mechanism of the key switch shown in FIG.
FIG. 6 is an explanatory diagram of air flowing in and out when the key switch shown in the figure is operated. 20... Board, 21... Frame, 22... Key stem, 23... Housing, 24... Key cap, 25... Pad holder, 26... Electrostatic pad, 27... Electrode, 28... Rubber spring, 29... …coil spring.

Claims (1)

[Scope of utility model registration request] In a key switch mechanism of a capacitive switch that increases the capacitance between fixed electrodes by pressing an electrostatic pad to which a dielectric is attached, a substrate having a plurality of electrodes fixed thereto, and a substrate covering the substrate are provided. a housing, a key stem slidably provided with respect to the housing, a key cap mounted on the key stem, a rubber spring provided on the substrate and having a hole formed in the upper center thereof; A key switch mechanism comprising: a pad holder which is freely fitted into a hole to hold the electrostatic pad parallel to a substrate; and a coil spring fitted between the pad holder and a key cap.