JP2007213834A - Pushbutton switch and its fixed contact members - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pushbutton switch which ensures a stable switching function by maintaining a good contact condition between a fixed contact and a movable contact during ON operation, and to provide its fixed contact members. <P>SOLUTION: This pushbutton switch comprises a first fixed contact 3 and a second fixed contact 4 which are mutually separated and juxtaposed on a support 2, a dome-like movable contact 10 composed of conductive elastic plates opposed to the fixed contacts, and a pusher 22 for applying a switching operation stress to the movable contact 10. The movable contact 10 comprises a dome margin 10a to be placed on the surface of the first fixed contact 3, and an operation stress application 10b set oppositely in a space on the surface of the second fixed contact 4. The surface position of the contact 4 subject to effects of attachment/detachment to/from the inside of the operation stress application part 10b is formed higher than that of the first fixed contact. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pushbutton switch and its fixed contact component, and more particularly to an improved dome-shaped movable contact built-in type pushbutton switch used as an operation switch for various electronic devices and its fixed contact component.

  In recent years, the fields of various electronic devices have been required to be reduced in size, thickness, and weight, and the same applies to pushbutton switches used for operation switches such as function operation buttons, numeric keys, and keyboards of these electronic devices. There is an increasing demand. As an example of the prior art that meets this requirement, a dome-shaped movable contact built-in type pushbutton switch as shown in Patent Document 1 below has been developed.

  The pushbutton switch disclosed in Patent Document 1 will be described. This switch has a donut-shaped (annular) conductive pattern (first fixed contact), and another disk-shaped conductive pattern (secondly arranged) disposed inside the switch. It is formed by combining a fixed contact) and a diaphragm (movable contact) made of an elastic metal plate having a spherical surface (dome) shape and facing these. The peripheral edge of the dome of the movable contact is in contact with the upper surface of the ring of the first fixed contact, and the top of the dome of the movable contact is pressed and recessed in the direction of the second fixed contact so that one of its inner walls is in contact. When the portion comes into contact with the second fixed contact, the first fixed contact and the second fixed contact are brought into conduction (ON). Next, when the pressing is released, the movable contact is restored, and the first and second fixed contacts become non-conductive (off). In Patent Document 1, there is no special explanation about the thickness relationship between the conductive patterns of the first and second fixed contacts.

  FIG. 4 is a general load-displacement characteristic curve diagram of the movable contact. When the push button is turned on, the dome top of the movable contact is pressed toward the second fixed contact (vertical axis). The relationship between the unit N) and the displacement amount (horizontal axis unit mm) of the dome top of the movable contact is shown. In the area A of the characteristic curve, the top of the dome gradually undergoes dent deformation as the push button is pressed (operational stress applied), and the dent displacement amount increases as the pressing load increases until the inflection point B (maximum value). To increase. In the region C, the amount of depression displacement further increases until the inflection point D (minimum value), but the amount of pressing load decreases. The inflection point D indicates an initial contact point (switch-on) with respect to the second fixed contact surface of the inner wall of the dome top. In the region E, even if the amount of pressing load increases, the amount of displacement is extremely small, and the inner wall of the dome top portion is strongly pressed against the surface of the second fixed contact.

In this way, the movable contact has a so-called negative region in which the pressing load amount decreases even if the displacement amount increases from the inflection point B to the region C, and causes a reverse bending phenomenon of the top of the dome. The phenomenon acts to make the user feel the click feeling in the push button operation.
Japanese Patent Publication No. 4-74805

  The movable contact must be in reliable contact with the second fixed contact, such as the inflection point D and the region E, to ensure the on state between the first and second fixed contacts. . However, the movable contact is manufactured by forming an elastic metal plate so as to be a spherical diaphragm. Due to manufacturing variations, the displacement amount of the top of the dome in the inversion region C becomes the inflection point D. There is a possibility that the contact with the second fixed contact is insufficient or cannot be made. As a result, there is a possibility that the switching accuracy is lowered or the function is lost. In addition, in order to reduce such variation, there is a problem that, if high molding processing accuracy is pursued, the cost of parts is increased.

  The present invention has been made in order to solve the above-described problems of the prior art, and ensures a good contact state between the fixed contact and the movable contact at the time of an on operation, and has a stable switching function. And it aims at providing the fixed contact component.

  A pushbutton switch according to a first aspect of the present invention includes a first fixed contact and a second fixed contact arranged in parallel with each other on a support, and a conductive elastic plate disposed so as to face the fixed contacts. A dome-shaped movable contact and a pressing element for applying a switching operation stress to the movable contact, wherein the movable contact is a dome edge placed on the surface of the first fixed contact and the second An operation stress applying portion that is spaced apart and opposed on the surface of the fixed contact is provided, and the surface position of the second fixed contact that is contacted and separated from the inner surface of the operation stress applying portion is greater than the surface position of the first fixed contact. It is formed so that it may become high.

  According to a second aspect of the present invention, in the pushbutton switch according to the first aspect, the second fixed contact has a protruding portion that protrudes toward the operation stress applying portion of the movable contact.

  According to a third aspect of the present invention, in the pushbutton switch according to the second aspect, the protruding portion of the second fixed contact is formed in an annular shape coaxial with the center of the operation stress applying portion of the movable contact. It is characterized by.

  According to a fourth aspect of the present invention, in the pushbutton switch according to the first or second aspect, the tip of the projecting portion has a curved surface that is convex toward the operation stress applying portion. .

  According to a fifth aspect of the present invention, there is provided a fixed contact constituting member having a first fixed contact and a second fixed contact which are arranged side by side on a support, and the surface position of the second fixed contact is the first position. A dome edge of a dome-shaped movable contact for a pushbutton switch is placed on the surface of the first fixed contact, and the surface of the second fixed contact has a high surface position. Is characterized in that the operation stress applying part of the dome of the movable contact is arranged to be spaced apart from each other.

  According to the push button switch and the fixed contact component of the present invention, the movable contact is opposed to the dome edge portion placed on the surface of the first fixed contact and the surface of the second fixed contact. An operation stress application section is provided, and the surface position of the second fixed contact that receives contact and separation with the inner surface of the operation stress application section is higher than the surface position of the first fixed contact. Therefore, even when there is a manufacturing variation in the displacement characteristics in the reverse deformation region of the operation stress application portion during the push button operation, the inner wall of the operation stress application portion of the movable contact is the second fixed with the high surface position. It is reliably contacted and pressed against the surface of the contact, its switching function is stabilized, and reliable on / off signal transmission to peripheral devices can be performed.

  In addition, when the second fixed contact has a protruding portion that protrudes toward the operation stress applying portion of the movable contact, foreign matter accumulation such as dust at the center of the second fixed contact is prevented, and the switching function is further improved. There is an effect that it becomes stable and reliable.

  Examples 1 to 3 as embodiments of the pushbutton switch and the fixed contact component according to the present invention will be described below with reference to FIGS. 1 to 3.

(Example 1):
FIG. 1A is a longitudinal sectional view showing a pushbutton switch according to a first embodiment of the present invention, and FIG. 1B is a longitudinal sectional view showing a modified example of the fixed contact constituting member.

  As shown in FIG. 1A, a fixed contact component 1 is composed of a support 2 such as a flat insulating substrate used for a circuit wiring board, for example, an annular pattern disposed on the surface of the support 2. The first fixed contact 3 and the second fixed contact 4 in a disk-like pattern are arranged in parallel on the surface of the support 2 so as to be spaced apart from the inner wall of the ring of the first fixed contact 3. The first fixed contact 3 has an annular outer diameter (diameter) of 6 mm, an inner diameter of 3.5 mm, and a wall thickness of 25 μm. The second fixed contact 4 has an outer diameter (diameter) of 2.5 mm and a wall thickness. The surface position of the second fixed contact 4 is higher than the surface position of the first fixed contact 3, and the difference h between these surface positions is 5 μm.

  The support 2 is an insulating film made of, for example, polyethylene naphthalate (PEN), and the fixed contacts 3 and 4 are formed by printing a conductive paste such as silver paste on the surface of the PEN film 2 by a screen printing method. ing.

  When the printing method is applied, in order to obtain the pattern shape of each fixed contact and the surface position difference h, first, mask printing corresponding to each pattern shape of the first and second fixed contacts 3 and 4 is performed. Then, a first conductive paste printed layer having a predetermined uniform thickness is formed, and the layer is subjected to a drying step. Next, a mask printing step is performed so that a second conductive paste print layer is formed on the surface of the print layer corresponding to the second fixed contact 4 with a thickness corresponding to the surface position difference h. And a drying step. In this way, the surface position difference h is easily formed with high accuracy. In addition, you may provide the electroconductive cover layer by electroconductive carbon printing etc. on the silver paste layer surface of each said fixed contact.

  The movable contact 10 coaxially disposed on the fixed contact component 1 is formed of an elastic metal plate having a thickness of 50 μm formed by processing a metal plate such as stainless steel (SUS301) or phosphor bronze into a spherical dome shape. It has a function as a diaphragm made of a conductive elastic plate. The outer diameter (diameter) of the dome edge 10a of the movable contact 10 is 4 mm, which is an intermediate value between the inner and outer diameters of the annular first fixed contact 3, and the dome edge 10a is the first fixed contact 3. Is placed on the ring in a contacted state.

  The outer surface height H (the distance between the bottom surface of the edge portion 10a and the apex of the dome top portion 10b) of the dome top portion 10b of the movable contact 10 is 0.2 mm. Here, the maximum distance between the inner surface of the dome top 10b and the center surface of the second fixed contact 4 is the difference between the height H of the dome outer surface and the surface position difference h of the second fixed contact 4 (H−h). ) Minus the plate thickness of the movable contact 10.

  The push button operation member 20 disposed on the dome of the movable contact 10 includes an insulating rubber sheet 21, a presser 22 provided in a convex shape at the center of the lower surface of the rubber sheet 21, and the center of the upper surface of the rubber sheet 21. Has a push button portion 23. The central axes of the pressing element 22 and the push button portion 23 are coaxial with the dome central axes of the second fixed contact 4 and the movable contact 10.

  The pressing element 22 is formed in, for example, a cone shape having a tip diameter of, for example, 1 mm. The shape and dimensions are such that deformation is likely to occur. Further, the rubber sheet 21 is made of a material having flexibility and elasticity that maintains durability against repeated operations of the push button part 23 many times, and smoothly in the sheet thickness direction according to the push button operation. The thickness of the peripheral portion close to the push button portion 23 is adjusted to be thinner than the thickness of the outer peripheral portion so as to be elastically deformed and the operability is enhanced.

  As described above, when the pushbutton switch shown as a single unit is incorporated in an electronic device such as a numeric keypad or a keyboard, a plurality of such unit bodies are arranged in a matrix. In that case, a plurality of sets of the first and second fixed contacts 2, 3 are patterned together in the matrix arrangement on the support 2 for the circuit wiring board, and a plurality of sets of the fixed contacts are formed on the rubber sheet 21. A plurality of sets of the push button portion 23 and the presser 22 arranged corresponding to each other are provided. A plurality of the movable contacts 10 corresponding to the matrix arrangement are disposed between the rubber sheet 21 and the support 2, and the rubber sheet 21 and the support 2 are supported at a predetermined interval. (Not shown) are supported and fixed to each other, and the movable contact 10 is supported by a spacer (not shown) or the like so as to suppress lateral displacement.

  Next, the operation of the pushbutton switch will be described. The movable contact 10 performs a dent deformation operation approximately along the load-displacement characteristic curve of FIG. 4 during a switching operation. By the way, since the second fixed contact 4 has the surface position difference h in relation to the first fixed contact 3, the push button switch operation includes an inflection point D in the characteristic curve of FIG. The region E is shifted to the left in the figure by the surface position difference h.

  Therefore, even if there is a manufacturing variation in the movable contact 10, the displacement of the dome top portion 10b (operation stress applying portion) of the movable contact 10 reliably reaches the inflection point D and the region E via the inversion region C. In addition, sufficient contact with the second fixed contact 4 having a surface position that receives contact and separation with the inner surface of the operation stress applying unit 10b is obtained, and a reliable switching function is achieved.

  Further, in order to increase the accuracy of the forming process of the elastic metal plate when the movable contact 10 is manufactured, the tensile residual internal stress (strain) must be taken into account. The second fixed contact 4 having the positional difference h can be easily formed with high accuracy simply by controlling the thickness thereof by, for example, the screen printing method as described above, and an increase in the component cost can be avoided.

  In addition, the larger the surface position difference h is, the more reliably the movable contact 10 reaches the inflection point D and the region E, but the good contact feeling of the movable contact 10 (the extremely inflection point B and inversion in FIG. 4). The upper limit of the surface position difference h is adjusted so that the operation of the region C) is reliably obtained. The surface position difference h is further adjusted in accordance with various component sizes such as a movable contact and the manufacturing variation degree of the movable contact as described above.

  By the way, the fixed contact component 1 is a flat plate such as a copper foil used as a material for the first and second fixed contacts 3 and 4 on an insulating substrate made of, for example, polyimide resin or glass epoxy resin used as the support 2. You may form using the printed circuit board material which laminated | stacked.

  An example of a method of forming the first and second fixed contacts in this case will be described. First, a first resist having a pattern shape corresponding to the first and second fixed contacts 3 and 4 is formed on the surface of the copper foil. A mask is applied, and the exposed surface of the copper foil is half-etched by chemical etching, for example. Next, a second resist mask having a pattern shape corresponding only to the second fixed contact 4 is deposited, and the copper foil is etched while exposing other portions.

  As a result, the copper foil between the first and second fixed contacts 3 and 4 is removed so that the surface of the support 2 is exposed, and the second fixed contact 4 has the same thickness as the material thickness of the copper foil. The first fixed contact 3 is formed to have a thickness half that of the second fixed contact 4. In this case, the surface position difference h is set to ½ of the thickness of the second fixed contact 4. Even if the second resist mask is formed by leaving the mask corresponding to the second fixed contact 4 in the first resist mask and removing other masks, the first mask is completely removed. However, it may be newly formed only on the second fixed contact 4.

  By the way, in the push button switch of the kind described above, on / off operations are generally repeated frequently, and in order to repeat the outflow / inflow of outside air between the space inside the dome of the movable contact and the outside, There is a phenomenon in which foreign matter such as insulating dust gathers in the dome, and this foreign matter generally tends to accumulate at the center of the second fixed contact facing the top of the dome.

  FIG. 1B shows a modification of the fixed contact constituting member 1 suitable for preventing the accumulation of foreign substances. That is, the second fixed contact 4a has a shape in which the surface facing the dome top 10a of the movable contact 10 has an upwardly convex curved surface 4b by using, for example, an etching technique. According to this modification, dust or the like that tends to accumulate in the center portion of the second fixed contact slides down from the center portion of the convex curved surface 4b to the periphery due to, for example, vibration of a key operation. Accumulation in the central portion is easily reduced, and the pressing contact between the second fixed contact 4 and the inner surface of the dome top portion 10b of the movable contact 10 becomes more reliable.

(Example 2):
FIG. 2A is a longitudinal sectional view showing a pushbutton switch according to a second embodiment of the present invention, and FIG. 2B is a longitudinal sectional view showing a modification of the fixed contact constituting member. The same parts as those of the push button switch of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  The second fixed contact 5 provided on the support 1 is arranged coaxially with the dome top portion 10b (operation stress applying portion) of the movable contact 10 and has a main body portion 5a having the same thickness as the first fixed contact 3. And a projecting portion 5b located at the center of the main body portion 5a and projecting toward the dome top portion 10b. The main body portion 5a of the second fixed contact is formed in a disc shape having an outer diameter (diameter) of 2.5 mm, and the projecting portion 5b is formed in a disc or column shape having an outer diameter (diameter) of 1.5 mm. The height h is a dimension corresponding to the surface position difference h in the first embodiment.

  A method of forming each of the fixed contacts will be described. The body portions 5a of the first fixed contact 3 and the second fixed contact 5 are screen-printed with a conductive paste having the pattern shape described in the first embodiment to have the same thickness. Formed simultaneously. The protrusion 5b of the second fixed contact 5 is further formed by screen-printing a conductive paste on the surface of the central portion of the main body portion 5a with a thickness constituting the protrusion height h. The fixed contact component 1 can also be formed using a copper foil-clad printed circuit board material. In this case, the first and second fixed contacts 3 and 5 correspond only to the protrusions 5b of the second fixed contact 5 after the half etching of the copper foil using the first resist mask described in the first embodiment. If a second resist mask having a pattern shape is applied, the other portions are exposed and the copper foil is etched, the shape as described above shown in FIG. 2A can be easily and accurately formed.

  Since the protruding portion 5b located at the center of the second fixed contact 5 has a smaller outer diameter than the main body portion 5a, foreign matter accumulation on the upper surface of the protruding portion 5b hardly occurs, and the protruding portion 5b. As a result, the gathering of foreign matters to the center portion of the second fixed contact 5 is reduced, and the pressing contact between the tip surface of the protrusion 5b of the second fixed contact and the dome top portion 10b of the movable contact 10 becomes more reliable.

  FIG. 2B shows a modification of the fixed contact constituting member 1 in the second embodiment, and the protruding portion 5b of the second fixed contact 5 is formed by using, for example, etching technique, the dome top portion 10a of the movable contact 10. The surface opposite to the upper surface is a shape having a convex curved surface 5c upward. According to this modified example, since the foreign matter that is about to gather near the center easily falls from the upper surface of the convex curved surface 5c toward the periphery and is difficult to accumulate, the dome of the second fixed contact 5 and the movable contact The pressing contact with the top 10b is further ensured.

(Example 3):
FIG. 3A is a longitudinal sectional view showing a pushbutton switch according to a third embodiment of the present invention, FIG. 3B is a longitudinal sectional view showing a modified example of the fixed contact constituent member, and FIG. Furthermore, it is a top view which shows the other modification of the 2nd fixed contact. The same parts as those of the push button switch of each of the embodiments are given the same reference numerals, and the description thereof is omitted.

  The second fixed contact 6 provided on the support body 1 has a main body portion 6a disposed coaxially with the dome top portion 10b of the movable contact 10, and faces the dome top portion 10b of the movable contact 10 at the center of the main body portion 6a. It has the annular protrusion part 6b which protrudes. The main body portion 6a has the same thickness as the first fixed contact 3, is formed in a disk shape having an outer diameter (diameter) of 2.5 mm, and the protruding portion 6b has an annular outer diameter (diameter). The inner diameter is 1.5 mm, and a cavity is formed at a portion facing the apex of the dome (the center of the top portion 10b). The protruding portion 6b has a protruding height corresponding to the surface position difference h described in each of the embodiments.

  Also in the third embodiment, the screen printing method as described in each of the above embodiments, except that each of the fixed contacts applies a mask pattern corresponding to the annular protrusion 6b of the second fixed contact. Similarly, it can be easily and accurately formed by mask etching of a copper foil-clad printed circuit board material.

  The annular protrusion 6b of the second fixed contact blocks the phenomenon of foreign matters such as dust gathering to the center of the second fixed contact, and the annular peripheral wall of the protrusion 6b is Since it contacts the inner wall of the dome top portion 10b of the movable contact 10, the contact area can be made larger than that of the protruding portion 5b in the second embodiment, and the switching pressing contact by the wide area contact that avoids the influence of the foreign matter is the second embodiment. It is obtained more reliably than the case of

  FIG. 3B shows a modification of the fixed contact constituting member 1 according to the third embodiment, and the annular protrusion 6b of the second fixed contact 6 is formed by using, for example, an etching technique, the dome of the movable contact 10. The surface facing the top portion 10a has a shape having a convex curved surface 6c upward. According to this modification, since the convex curved surface 6c is formed along the ring-shaped surface of the protruding portion 6b, the inner surface of the curved portion when the dome top portion 10b of the movable contact is deformed is further widened. It becomes possible to contact the convex curved surface 6c with an area, and switching pressing contact can be obtained more reliably.

  FIG. 3C shows another modification of the second fixed contact 6 according to the third embodiment, and an annular protrusion 6d provided on the disk-shaped main body portion 6a of the second fixed contact includes: It has a plurality of slits 6e formed along the ring. That is, an inner / outer passage formed by the slit 6e is formed between the central portion of the second fixed contact 6 and the outside thereof regardless of the presence of the protruding portion 6d. FIG. 3C shows the circuit wiring layer 7 connected to the main body portion 6a of the second fixed contact.

  According to this modification, even if the foreign matter is accumulated in the central portion of the disk-shaped main body portion 6a, the foreign matter can move outward through the slit 6e in the lateral direction. The build-up of the foreign matter accumulation height in the (vertical direction) is suppressed, and the foreign matter accumulation is difficult to reach the upper surface of the protrusion 6d.

  In each of the above-described embodiments, the first and second fixed contacts and the movable contact have a circular planar shape. May be. Although the shape of the movable contact is expressed as a dome shape, it may be a plate shape, a bowl shape, a diaphragm shape, or a shape in which the planar shape is a cross-shaped plate or a strip-shaped plate, etc. In view of the objects and effects of the present invention, those having the same shape and function are generically expressed as a dome shape. Further, the term “contact” may be expressed as an electrode.

FIG. 1A is a longitudinal sectional view showing a pushbutton switch according to Embodiment 1 of the present invention, and FIG. 1B is a longitudinal sectional view showing a modified example of the fixed contact constituent member. FIG. 2A is a longitudinal sectional view showing a pushbutton switch according to Embodiment 2 of the present invention, and FIG. 2B is a longitudinal sectional view showing a modified example of the fixed contact constituting member. FIG. 3A is a longitudinal sectional view showing a pushbutton switch according to a third embodiment of the present invention, FIG. 3B is a longitudinal sectional view showing a modified example of the fixed contact constituent member, and FIG. It is a top view which shows the other modification of a stationary contact structural member. It is a characteristic curve figure for demonstrating the load-displacement characteristic of a pushbutton switch.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fixed contact component 2 Support body 3 1st fixed contact 4, 5, 6 2nd fixed contact 4b, 5c, 6c Convex curved surface 5b, 6b, Protrusion part 10 of 2nd fixed contact Movable contact 10a Dome of movable contact Edge 10b Dome top of movable contact (operation stress applying part)
20 Pushbutton operation member 21 Rubber sheet 22 Presser 23 Pushbutton

Claims (5)

  A first fixed contact and a second fixed contact arranged in parallel with each other on the support, a dome-shaped movable contact made of a conductive elastic plate disposed opposite to the fixed contact, and switching to the movable contact A pressing element for applying an operating stress, and the movable contact is a dome edge placed on the surface of the first fixed contact and an operating stress facing the surface of the second fixed contact with a space therebetween And an application portion, wherein the second fixed contact is formed such that a surface position where the second fixed contact is in contact with and separated from the inner surface of the operation stress application portion is higher than a surface position of the first fixed contact. Push button switch to do.   2. The pushbutton switch according to claim 1, wherein the second fixed contact has a protruding portion that protrudes toward an operation stress applying portion of the movable contact. 3.   3. The push button switch according to claim 2, wherein the protruding portion of the second fixed contact is formed in an annular shape coaxial with the center of the operation stress applying portion of the movable contact.   3. The push button switch according to claim 1, wherein a tip portion of the projecting portion has a curved surface that is convex toward the operation stress applying portion. 4.   A first fixed contact and a second fixed contact juxtaposed apart from each other on the support; a surface position of the second fixed contact is formed higher than a surface position of the first fixed contact; The dome edge of the dome-shaped movable contact for the pushbutton switch is placed on the surface of the fixed contact, and the operation stress applying part of the dome of the movable contact is separated on the surface of the second fixed contact having a high surface position. And a fixed contact constituent member arranged opposite to each other.

Images