JPH0317376Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is arranged on the keyboard of electronic equipment such as computers and cash registers, and operates switching by changing the capacitance between the movable electrode and the fixed electrode by pressing a push button. This invention relates to a capacitive key switch that performs the following operations.

This type of key switch has a dielectric interposed between a pair of fixed electrodes and a movable electrode that face each other to form a so-called capacitor, and the movable electrode is connected to the fixed electrode side by an operating member such as a push button. By bringing the fixed electrode and the movable electrode into contact with each other, the electrostatic capacitance stored between the fixed electrode and the movable electrode is changed to perform a switching operation.

By the way, this type of switch is constructed so that the operability of the operating member and the capacitance change characteristic have a predetermined relationship. In other words, the special request was made in 1983.
The capacitive key switch proposed by the applicant in No. 119819 uses a conical coil spring as a movable electrode. This conical coil spring is
The capacitance change characteristic with respect to the depression stroke of the operating member is linearly proportional, and there is an advantage that the set value of the capacitance, that is, the ON operating point can be set arbitrarily.

However, when a conical coil spring is used as a movable electrode, the wires of the coil spring are brought into close contact with the fixed electrode via a dielectric, increasing capacitance and turning on the switch. , the sound of the coil spring hitting the fixed electrode occurs. This banging sound is quite annoying and becomes a noise in a room where many computers are used.

On the other hand, since this type of switch has a stem as an operating member that slides into sliding contact with an insulating case so that it can move up and down, the stem and case may wear out over a long period of use. If this abrasion powder adheres to the coil spring or fixed electrode side, there is a risk that a predetermined capacitance value cannot be secured even if the coil spring is brought into close contact with the fixed electrode.

Furthermore, in terms of mechanical retention of the coil spring, the upper end of the coil spring is connected to the lower surface of the stem by means such as gluing or locking, but since both the coil spring and the stem are small, the connection work is extremely difficult. There are some troublesome drawbacks.

Furthermore, when the operating member is pressed, the conical coil spring is compressed, so that this return reaction force is transmitted to the operator's fingers. For this reason,
In order to overcome this resistance, the operator begins to push (hit) the operating member forcefully, and as a result, the operator cannot tell the position of the switch by feeling with his/her fingers, so he/she starts hitting the switch even harder, and if the operator continues to operate it for a long period of time, fatigue may result. There are also some problems such as.

The present invention was developed based on these circumstances, and its purpose is to block the banging sound of the coil spring, and to prevent abrasion powder from the stem from adhering to the coil spring and fixed electrode. In addition, we provide a capacitive key switch that allows easy mechanical support and positioning of the coil spring, reduces the pressing force required by the operator, and allows the operator to determine the switch-on position by touch. This is what I am trying to do.

That is, in the present invention, a movable electrode made of a conical coil spring or a bell-shaped coil spring is covered with an elastic covering such as rubber, and this covering reduces the leakage of tapping sound to the outside. By preventing abrasion particles from falling on the coil spring and fixed electrode, and by making the shape of the sheath match the outer shape of the coil spring, the sheath mechanically supports and positions the coil spring. Furthermore, a constriction deformation portion is formed in this elastic covering so that the elastic covering reverses its elastic force when pushed beyond a predetermined stroke, thereby reducing the pressing force applied by the operator. It is characterized by making it possible to determine the position of the switch by the touch of the fingers.

An embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

In the figure, 1 is an insulating base, for example, a printed wiring board made of synthetic resin, and a fixed electrode 2 is formed on the upper surface of this board 1. This fixed electrode 2 is constructed by forming semicircular transmitting-side fixed electrodes 2a and receiving-side fixed electrodes 2b facing each other and spaced apart from each other. A dielectric material 3 such as a polyester film is adhered to the upper surface of the pair of fixed electrodes 2a and 2b.

The fixed electrode 2 is covered by a case 4 made of an electrical insulator such as synthetic resin, and the case 4 is fixed to a keyboard (not shown). A stem 5 as an operating member is attached to the case 4 so as to be movable up and down, and a push button 6 is connected to the upper end of the stem 5. A coil spring 7 is interposed between the push button 6 and the case 4 to push up and return the operating member consisting of the stem 5 and the push button 6. The stem 5 is formed with guide protrusions 8, 8, and these guide protrusions 8, 8 are fitted into guide grooves 9, 9 formed in the case 4 so as to be slid in the vertical direction. There is. Therefore, the stem 5 can freely move up and down without rotating relative to the case 4.

A movable electrode 10 is provided between the fixed electrode 2 and the stem 5. This movable electrode 10 is a conductive conical coil spring or a bell-shaped (semicircular)
It is made of a coil spring, and in this embodiment, a bell-shaped coil spring is shown. The lower end of the bell-shaped coil spring 10 is connected to both fixed electrodes 2a and 2b via a dielectric 3.
The upper end is opposed to the lower surface of the stem 5. When this coil spring 10 is pushed by the stem 5, it is pressed against the fixed electrode 2 sequentially from the lower end side, increasing the contact area.

The bell-shaped coil spring serving as the movable electrode 10 is covered with an elastic covering 11. The covering body 11 is made of a rubber sheet, for example,
It has a bell shape with a flange 12 on the periphery. As shown in FIG. 2, the flange 12 is sandwiched between the case 4 and the insulating base 1, thereby fixing the covering 11 itself in a predetermined position. This cover 11 has a shape that matches the outer shape of the bell-shaped coil spring 10, and
The coil spring 10 is therefore positioned and supported by this covering 11. At this time, a downward protrusion 13 is formed on the top surface of the covering 11 opposite to the lower surface of the stem 5, and by fitting this protrusion 13 into the upper end opening of the coil spring 10, the positioning of the coil spring 10 can be further enhanced. Maintains accuracy.

Further, the bell-shaped covering 11 is formed with a constricted portion 14, for example, in the middle of the vertical direction, and this constricted portion 14 promotes the deflection of the covering 11, and
When the covering 11 is deflected by a predetermined amount or more, a downward elastic force, that is, a reversing force is generated in the covering 11.

The switch according to the embodiment having such a configuration stands by by applying a predetermined voltage between the transmitting side electrode 2a and the receiving side electrode 2b of the fixed electrode 2. This state is shown in FIG. 2, and since only the lower end of the bell-shaped coil spring 10 as a movable electrode is in contact with the fixed electrodes 2a and 2b via the dielectric 3, the coil spring 10 and these fixed electrodes 2a, 2
The capacitance between the fixed electrodes 2a and 2b is small, and therefore both fixed electrodes 2a and 2b are kept in an electrically off state.

When pushbutton 6 is pressed, stem 5 is activated as shown in Figure 3.
is connected to the bell-shaped coil spring 10 via the elastic covering 11
Compress. In the coil spring 10, each wire is brought into close contact with the fixed electrodes 2a, 2b in order from the lower end side via the dielectric 3, and as the contact area increases, the capacitance increases. When this capacitance reaches a predetermined value or more, both the fixed electrodes 2a and 2b are electrically connected via the bell-shaped coil spring, that is, the movable electrode 10, and the switch is turned on.

When the push button 6 is released, the push button 6 and stem 5 are raised and returned by the elastic force of the return coil spring 7, and the bell-shaped coil spring 10 is expanded by its own return force. Therefore, the contact area of the bell-shaped coil spring 10 with the fixed electrode 2 decreases, returning to the switch-off state.

In such a key switch, when the bell-shaped coil spring 10 is compressed as shown in FIG. 3, it comes into close contact with the fixed electrode 2, producing a contact sound, that is, a tapping sound. However, since the coil spring 10 is covered with an elastic covering 11, this covering 11 blocks the tapping sound and prevents it from leaking to the outside. Therefore, operation noise is reduced.

Further, since the stem 5 moves up and down while slidingly contacting the case 4, long-term use causes wear between them and generates abrasion powder. This abrasion powder tends to land on the top surface of the bell-shaped coil spring 10 and the fixed electrodes 2a, 2b, but since the elastic covering 11 exists, the abrasion powder is removed from the coil spring 10 and the fixed electrodes 2a, 2b.
Do not allow it to adhere to Therefore, abrasion powder does not enter the contact surfaces between the coil spring 10 and the fixed electrodes 2a, 2b, and the capacitance characteristics can be maintained with high accuracy over a long period of time.

Furthermore, the elastic covering 11 is connected to the base 1 and the case 4.
In addition, since the shape of the covering body 11 is made to match the outer shape of the coil spring 10, the coil spring 1 housed in the covering body 11
0 can be positioned and held by this covering 11. Therefore, troublesome work such as joining the coil spring 10 and the stem 5 is not required. In particular, since the protrusion 13 is formed on the cover 11 to lock the upper end of the coil spring 10, even if the coil spring 10 and the cover 11 are bent as shown in FIG. 3, the positional relationship between them can be maintained constant.

By the way, when the push button 6 is pressed down, it is subjected to elastic resistance of the return coil spring 7, elastic resistance of the bell-shaped coil spring 10, and elastic resistance of the elastic cover 11. However, since the constricted portion 14 is formed in the elastic covering 11, this constricted portion 14 not only allows the covering 11 to deflect smoothly, but also increases the upward elastic force of the covering 11 when the amount of deflection exceeds a predetermined amount. Invert the elastic force downward as shown in the figure.
Therefore, when the push button 6 is pushed to a predetermined stroke, the resistance of the elastic covering 11 disappears, and rather the elastic covering 11 generates a downward force, so that the returning force of the returning coil spring 7 and the bell-shaped coil spring 10 are This cancels out a part of the return force and reduces the pressing force on the push button 6. In other words, as the pushbutton 6 is pressed, a portion where the pressing force becomes lighter occurs at a predetermined stroke. If the switch is set to turn on at the point where the pressing force is light, the operator will be able to tell when the switch is on by feeling the touch. If the resistance is increased when the switch is turned on, the operation will feel tiring, but if the resistance is reduced when the switch is turned on, as described above, fatigue can be reduced even during long-time operation.

Note that the present invention is not limited to the embodiments shown in FIGS. 1 to 4 above.

For example, the modifications shown in FIGS. 5 to 7 are
One output-side fixed electrode 50 is provided on the top surface of the base 1, and an input-side fixed electrode 51 is provided on the back surface of the base 1. and a bell-shaped coil spring 10
A connecting leg 52 is extended from the lower end, and this leg 52 is passed through the base 1 and is always connected to the input side fixed electrode 51. Since the other configurations are the same as those of the above-described embodiment, the same reference numerals are given and the explanation will be omitted.

In such a modified example, when the bell-shaped coil spring 10 serving as the movable electrode is extended as shown in FIG. 6, the capacitance between the movable electrode 10 and the output-side fixed electrode 50 is small, so the off state is maintained. , and in the case of FIG. 7 in which the push button 6 and stem 5 are pressed down, the bell-shaped coil spring 10 is compressed and the strands of the coil spring 10 come into close contact with the output side fixed electrode 50 via the dielectric 3. It becomes a switch state.

Furthermore, in each of the above embodiments, an example was explained in which a bell-shaped coil spring 10 was used as the movable electrode.
A conical coil spring may be used instead of the bell-shaped coil spring 10. The difference in characteristics between a bell-shaped coil spring and a conical coil spring is illustrated in FIGS. 8 and 9. That is, in FIGS. 8 and 9, the solid line A represents the characteristics of the bell-shaped coil spring, and the broken line B represents the characteristics of the conical coil spring. From Fig. 8, in the case of the conical coil spring B, there is a point where the resistance suddenly increases during the stroke, and such an increase in resistance may give the operator an uncomfortable feeling when operating the spring.
In addition, long-term operation causes fatigue, but in the case of the bell-shaped coil spring A, the stroke and change in resistance are linearly proportional, so there are no problems like the conical coil spring B.

Also, from Figure 9, in the case of the conical coil spring B, the capacitance is linearly proportional to the stroke, so the difference between switch-on and switch-off is not clear, and it is easy to cause malfunctions such as double-strike due to chattering etc. However, the bell-shaped coil spring A has a range in which the capacitance increases rapidly beyond a predetermined stroke, and therefore has the advantage of not causing malfunction due to a large difference in capacitance between switch-off and switch-on.

However, since the present invention uses the elastic sheath 11 to provide soundproofing, dustproofing, and positioning of the coil spring, even if a conical coil spring is used instead of the bell-shaped coil spring, the function of the elastic sheath will be the same. be effective.

Further, the dielectric 3 is not limited to being coated on the fixed electrodes 2, 50, but may be coated on each strand of a bell-shaped or conical coil spring as a movable electrode.

Furthermore, if the elastic restoring force of the elastic covering 11 is appropriately selected, the restoring coil spring 7 can be omitted.

As mentioned above, in the present invention, the movable electrode made of a bell-shaped coil spring or a conical coil spring is covered with an elastic covering, so that the above-mentioned tapping noise generated when this coil spring comes into close contact with the fixed electrode side is suppressed. Noise is reduced by blocking it with a covering. In addition, this covering prevents dust and abrasion powder from the operating member from adhering to the coil spring and fixed electrode, so that stable characteristics can be obtained over a long period of use. Furthermore, since the elastic covering conforms to the external shape of the coil spring, the coil spring is mechanically supported and positioned by this covering, so the installation work of the coil spring can be carried out easily and with high precision. Ru. Furthermore, the elastic covering is formed with a constricted deformation part so that the elastic covering reverses its elastic force when pushed beyond a predetermined stroke, so the pressing force applied by the operator can be reduced. At the same time, it becomes possible to determine the position of the switch by the touch of the fingers, which has the advantage of reducing fatigue and improving the operational feel.

[Brief explanation of the drawing]

1 to 4 show an embodiment of the present invention, FIG. 1 is an exploded perspective view, FIGS. 2 and 3 are sectional views showing different operating states, and FIG. 4 is an elastic covering. 5 to 7 show other embodiments of the present invention, FIG. 5 is an exploded perspective view, and FIGS. 6 and 7 are sectional views showing different operating states. It is. Also, Figures 8 and 9
The figures are a stroke-load characteristic diagram and a stroke-capacitance characteristic diagram that compare and show a conical coil spring and a bell-shaped coil spring. 1...Insulating base, 2,50...Fixed electrode, 4
...Case, 5...Stem (operating member), 6...
Push button (operating member), 10... Bell-shaped coil spring as a movable electrode, 11... Elastic covering.

Claims (1)

[Scope of utility model registration request] When the fixed electrode provided on the insulating base and the fixed electrode are provided opposite to this fixed electrode and compressed, each strand is brought into close contact with the fixed electrode, and based on the change in this contact area, the contact area between the fixed electrode and the fixed electrode is A movable electrode consisting of a bell-shaped coil spring or a conical coil spring that performs switching action by changing the capacitance, a dielectric provided on the fixed electrode or the movable electrode, and the movable electrode is pressed against the fixed electrode side. An operating member to be pressed, and an operating member that is provided between the operating member and the coil spring constituting the movable electrode, covers the coil spring, has a shape that follows the outer shape of the coil spring, and is pressed against the operating member. 1. A capacitive key switch comprising: an elastic cover having a constricted deformation portion that reverses the direction of elastic bias when a predetermined stroke is exceeded.