Push switch

Abstract

This push switch 1 includes: a case 2 including a storage part 23; a central contact 3, a first outer contact 4a, and a second outer contact 4b provided separately from each other in the storage part 23; a pressure-sensitive member 5 that is provided so as to contact the first outer contact 4a and the second outer contact 4b and not to contact the central contact 3; a dome-shaped movable contact 7a; and a pressing member 8 disposed above the pressure-sensitive member 5 and the movable contact 7a. The pressure-sensitive member 5 is placed in a bottom plate 21 of the case 2 such that a pressing force is applied from above when a user executes a pressing operation. An electric signal flowing between the first outer contact 4a and the second outer contact 4b changes in accordance with the strength of the pressing force.

Description

Push switch CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to Japanese Patent Application No. 2023-223295 (titled "Push Switch"), filed on December 28, 2023, the contents of which are incorporated herein by reference in their entirety.

[0002] The present invention generally relates to a push switch, and more particularly to a push switch that operates with a clicking sensation when pressed.

[0003] Push switches with dome-shaped movable contacts are widely used as operation buttons in various electronic devices. These push switches can be made smaller and thinner, and provide users with a pleasant clicking sensation (a sense of operation when pressing the operation button) when the user presses it.

[0004] Patent Document 1 discloses a push switch 500 as shown in Fig. 1. Fig. 1 is a cross-sectional view of push switch 500. As shown in Fig. 1, push switch 500 includes a case 502 that houses a center contact 501a and an outer contact 501b in a state insulated from each other, a dome-shaped movable contact 503 that is disposed within case 502, a rubber sheet 504 that is placed on the upper surface of dome-shaped movable contact 503, a pressing member 505 that is placed on the upper surface of rubber sheet 504, and a cover 506 that is attached to case 502 from above and covers the interior space of case 502 from above.

[0005] 1, in its natural state where no external force is applied, the center contact 501a and the outer contact 501b are insulated from each other and held by the case 502. Also, in the natural state, the movable contact 503 is in contact with the outer contact 501b but not with the center contact 501a. Furthermore, in the natural state, the top of the movable contact 503 is in contact with the lower surface of the rubber sheet 504, and the upper surface of the rubber sheet 504 is in contact with a lower protrusion 505a that protrudes downward from the lower surface of the pressing member 505.

[0006] In the natural state, when a pressing operation is applied to the upper protrusion 505b of the pressing member 505, which protrudes upward from the cover 506, the lower protrusion 505a of the pressing member 505 presses the movable contact 503 downward via the rubber sheet 504. At this time, the central movable portion of the movable contact 503 is displaced downward and comes into contact with the central contact 501a. As a result, the central contact 501a and the outer contact 501b are brought into electrical continuity via the movable contact 503. A device using the push switch 500 can determine whether the pressing operation on the push switch 500 has been completed by detecting the electrical continuity between the central contact 501a and the outer contact 501b.

[0007] Furthermore, the movable contact 503 is a metal member that has a dome-shaped convex shape in its natural state. Therefore, when a pressing force equal to or greater than a predetermined operating force (the pressing force required to operate the push switch 500) is applied to the movable contact 503 from above, the central movable portion of the movable contact 503 undergoes sudden elastic deformation downward. This sudden elastic deformation provides a clicking sensation to the user who presses the push switch 500.

[0008] In this way, the push switch 500 can provide a click to the user and determine when the user's push operation is complete. However, the push switch 500 cannot determine the strength of the pressure applied by the user to the push switch 500. Meanwhile, there is a need to determine not only the completion of the user's push operation but also the strength of the pressure applied by the user to the push switch 500, and to provide a function corresponding to the strength of the pressure applied by the user. However, the push switch 500 cannot meet this need.

[0009] Japanese Patent Application Laid-Open No. 2007-200737

[0010] The present invention has been made in consideration of the above-mentioned problems of the conventional push switch, and its object is to provide a push switch that can determine not only whether a user has completed a pressing operation but also the strength of the pressing force applied by the user.

[0011] These objects can be achieved by the present invention as defined in (1) to (3) below. (1) A case including a storage section defined by a bottom plate and a wall extending upward from the bottom plate; a central contact, a first outer contact, and a second outer contact provided on the bottom plate within the storage section and spaced apart from one another; a pressure-sensitive member provided within the storage section so as to be in contact with the first outer contact and the second outer contact but not in contact with the central contact; a dome-shaped movable contact within the storage section that is displaceable between a first position that is convex upward and does not contact the central contact, and a second position that is convex downward and contacts the central contact; and a pressing member disposed above the pressure-sensitive member and the movable contact, and to which a user performs a pressing operation; the pressure-sensitive member is placed on the bottom plate of the case so that a pressing force is applied from above when the user performs the pressing operation on the pressing member; and the pressure-sensitive member is configured so that its electrical resistance changes depending on the strength of the pressing force applied from above to the pressure-sensitive member, A push switch characterized in that the electrical signal flowing between the first outer contact and the second outer contact changes according to the strength of the pressing force applied from above to the pressure-sensitive member while the movable contact is displacing from the first position to the second position.

[0012] (2) A push switch comprising: a central contact, a first outer contact, and a second outer contact arranged at a distance from one another; a pressure-sensitive member electrically connected to the first outer contact and the second outer contact; and a movable contact that is displaceable between a first position where it is not in contact with the central contact and a second position where it is in contact with the central contact in response to a pressing force applied by a user, wherein when the movable contact takes the second position, the central contact and the first outer contact or the second outer contact are electrically connected via the movable contact; the pressing force applied by the user to the movable contact is transmitted to the pressure-sensitive member via the movable contact; the pressure-sensitive member is configured so that its electrical resistance changes in response to the strength of the pressing force; and an electrical signal flowing between the first outer contact and the second outer contact changes in response to the strength of the pressing force while the movable contact is displaced from the first position to the second position.

[0013] (3) A push switch comprising: a central contact, a first outer contact, a second outer contact, and a third outer contact arranged at a distance from one another; a pressure-sensitive member electrically connected to the first outer contact and the second outer contact; and a movable contact that is displaceable between a first position where it is not in contact with the central contact and a second position where it is in contact with the central contact in response to a pressing force applied by a user; when the movable contact takes the second position, the central contact and the third outer contact are electrically connected via the movable contact; the pressing force applied by the user to the movable contact is transmitted to the pressure-sensitive member via the movable contact; the pressure-sensitive member is configured so that its electrical resistance changes in response to the strength of the pressing force; and the electrical signal flowing between the first outer contact and the second outer contact is configured so that it changes in response to the strength of the pressing force applied to the pressure-sensitive member from above.

[0014] In the push switch of the present invention, a pressure-sensitive member whose electrical resistance changes in response to pressure applied from above is placed in a housing of the case so as to contact the first outer contact and the second outer contact. Furthermore, the pressure-sensitive member is placed on the bottom plate of the case so that pressure is applied from above when a user presses the pressure member. Therefore, when a user presses the pressure member, the electrical resistance of the pressure-sensitive member changes in response to the strength of the pressure applied by the user to the pressure-sensitive member. As a result, the electrical signal flowing between the first outer contact and the second outer contact changes in response to the strength of the pressure applied by the user to the pressure-sensitive member. Therefore, by detecting the electrical signal flowing between the first outer contact and the second outer contact, the strength (magnitude) of the pressure applied by the user can be determined.

[0015] Furthermore, the change in the electrical signal flowing between the first and second outer contacts in response to the strength of the pressing force occurs even when the movable contact does not contact the center contact, so the push switch of the present invention can detect a user's pressing operation performed with less than the actuating force of the push switch.

[0016] Furthermore, in the push switch of the present invention, it is possible to determine whether the user's pressing operation is complete by detecting the electrical continuity between the center contact and the outer contact (the first outer contact, the second outer contact, or the third outer contact). In this way, the push switch of the present invention can determine not only the completion of the user's pressing operation but also the strength of the user's pressing force.

[0017] In addition, in the push switch of the present invention, the pressure-sensitive member is disposed within the housing of the case so as to contact the first outer contact and the second outer contact but not the central contact. Therefore, even when the movable contact is not in contact with the central contact, the strength of the pressing force applied by the user can be determined by detecting an electrical signal flowing between the first outer contact and the second outer contact. Furthermore, the completion of the user's pressing operation can be determined by detecting electrical continuity between the central contact and the outer contacts (the first outer contact, the second outer contact, or the third outer contact). Therefore, whether or not the user has performed a pressing operation can be determined regardless of changes in the electrical resistance of the pressure-sensitive member. This configuration clearly distinguishes (separates) the process for determining whether or not the user has performed a pressing operation from the process for determining the strength of the pressing force applied by the user, thereby simplifying the processing of devices that use push switches.

[0018] FIG. 1 is a cross-sectional view of a push switch according to a prior art. FIG. 2 is a perspective view of a push switch according to a first embodiment of the present invention. FIG. 3 is a perspective view of the push switch shown in FIG. 2 from another angle. FIG. 4 is an exploded perspective view of the push switch shown in FIG. 2. FIG. 5 is a top view of the case shown in FIG. 4. FIG. 6 is a perspective view of the center contact, the first outer contact, and the second outer contact. FIG. 7 is a schematic diagram for explaining the configuration and operating principle of the pressure-sensitive member shown in FIG. 4. FIG. 8 is a circuit diagram of the push switch shown in FIG. 2. FIG. 9 is a cross-sectional view of the push switch in its natural state taken along line A-A in FIG. 2. FIG. 10 is a cross-sectional view of the push switch in its pressed state taken along line A-A in FIG. 2. FIG. 11 is a graph showing the feeling curve and output waveform of the push switch shown in FIG. 2. FIG. 12 is a perspective view of a push switch according to a second embodiment of the present invention. FIG. 13 is a perspective view of the push switch shown in FIG. 12 from another angle. FIG. 14 is an exploded perspective view of the push switch shown in FIG. 12. FIG. 15 is a top view of the case shown in FIG. 14. FIG. 16 is a cross-sectional perspective view of the case shown in FIG. 14 . FIG. 17 is a cross-sectional view of the center contact, the first outer contact, the second outer contact, and the third outer contact. FIG. 18 is a circuit diagram of the push switch shown in FIG. 12 . FIG. 19 is a cross-sectional view of the push switch in its natural state taken along line B-B in FIG. 12 . FIG. 20 is a cross-sectional view of the push switch in its pressed state taken along line B-B in FIG. 12 . FIG. 21 is a graph showing a feeling curve and an output waveform of the push switch shown in FIG. 12 . FIG. 22 is a perspective view of a push switch according to a third embodiment of the present invention. FIG. 23 is an exploded perspective view of the push switch shown in FIG. 22 . FIG. 24 is a schematic diagram for explaining the configuration of the pressure-sensitive member shown in FIG. 23 . FIG. 25 is a graph showing a feeling curve and an output waveform of the push switch shown in FIG. 23 .

[0019] Push switches according to embodiments of the present invention will be described below based on preferred embodiments shown in the accompanying drawings. The drawings referred to below are schematic diagrams prepared for the purpose of explaining the present invention. The dimensions (length, width, thickness, etc.) of each component shown in the drawings do not necessarily reflect the actual dimensions. In addition, the same reference numerals are used for identical or corresponding components in each drawing. In the following description, the positive direction of the Z axis in each drawing may be referred to as "upward," and the negative direction of the Z axis may be referred to as "downward."

[0020] First Embodiment First, a push switch according to a first embodiment of the present invention will be described in detail with reference to FIGS. 2 to 11. FIG. 2 is a perspective view of the push switch according to the first embodiment of the present invention. FIG. 3 is a perspective view of the push switch shown in FIG. 2 from another angle. FIG. 4 is an exploded perspective view of the push switch shown in FIG. 2. FIG. 5 is a top view of the case shown in FIG. 4. FIG. 6 is a perspective view of the center contact, first outer contact, and second outer contact. FIG. 7 is a schematic diagram for explaining the configuration and operating principle of the pressure-sensitive member shown in FIG. 4. FIG. 8 is a circuit diagram of the push switch shown in FIG. 2. FIG. 9 is a cross-sectional view of the push switch in its natural state taken along line A-A in FIG. 2. FIG. 10 is a cross-sectional view of the push switch in its pressed state taken along line A-A in FIG. 2. FIG. 11 is a graph showing the feeling curve and output waveform of the push switch shown in FIG. 2.

[0021] The push switch 1 according to the first embodiment of the present invention, shown in FIGS. 2 and 3 , is mounted on a circuit board provided within a device. The push switch 1 is turned on when a user applies a pressing force that exceeds the actuation force of the push switch 1 and turned off when the pressing force is released. A device electrically connected to the terminals 33, 43a, and 43b (see FIG. 3 ) of the push switch 1 via the circuit board can determine the completion of the pressing operation on the push switch 1 by detecting the electrical continuity between the terminals 33 and 43a or between the terminals 33 and 43b. Furthermore, the electrical signal flowing between the terminals 43a and 43b of the push switch 1 changes depending on the magnitude of the pressing force applied to the push switch 1 by the user. Therefore, the device electrically connected to the terminals 33, 43a, and 43b via the circuit board can determine the magnitude of the pressing force applied to the push switch 1 by detecting the electrical signal flowing between the terminals 43a and 43b.

[0022] As shown in FIGS. 2 and 3 , the push switch 1 has a low-profile rectangular parallelepiped overall shape. The push switch 1 is very small, measuring, for example, approximately 3 mm (total length in the X direction) × approximately 2 mm (total length in the Y direction) × 1.45 mm (total length in the Z direction). Typically, the push switch 1 can be used as a switch for a smartphone. In this case, for example, multiple operations of the smartphone camera can be performed depending on the pressing operation of the push switch 1 and the strength of the pressing force applied to the push switch 1. In one example, the zoom operation and focus operation of the camera can be performed depending on the strength of the pressing force applied to the push switch 1, and the camera can take a picture when the pressing operation of the push switch 1 is completed.

[0023] As shown in FIG. 4, the push switch 1 according to the first embodiment of the present invention comprises a case 2 having a storage section 23 defined by a bottom plate 21 and the inner surface of a wall section 22 extending upward from the outer periphery of the bottom plate 21; a central contact 3, a first outer contact 4a, and a second outer contact 4b provided spaced apart on the bottom plate 21 within the storage section 23; a pressure-sensitive member 5 provided in the storage section 23 so as to come into contact with the first outer contact 4a and the second outer contact 4b; a conductive spacer 6 placed on the pressure-sensitive member 5 within the storage section 23; and a conductive spacer 6 disposed above the pressure-sensitive member 5 and the conductive spacer 6 within the storage section 23. the dome-shaped movable contact 7a that is displaceable between a first position where it is convex upward and does not contact the central contact 3, and a second position where it is convex downward and contacts the central contact 3; three auxiliary springs 7b that are stacked on top of the movable contact 7a; a pressing member 8 that is provided above the pressure-sensitive member 5, the movable contact 7a, and the auxiliary springs 7b and that presses the movable contact 7a and the auxiliary springs 7b downward, thereby displacing the movable contact 7a and the auxiliary springs 7b from the first position to the second position; and a cover film 9 that is placed above the movable contact 7a, the auxiliary springs 7b, and the pressing member 8 so as to cover the storage section 23.

[0024] The case 2 is a box-shaped member made of insulating resin and open upward. The case 2 includes a bottom plate 21, a wall 22, a storage section 23, a pair of lateral extensions 24 extending outward from the outer surfaces of the wall 22 on the +X and −X directions, respectively, and two positioning bosses 25 protruding downward from the bottom plate 21.

[0025] The bottom plate 21 is a plate-like member having a substantially rectangular planar shape and functions as the substrate of the push switch 1. As shown in FIG. 5 , the bottom plate 21 includes a protrusion 211 formed to protrude upward from the top surface of the bottom plate 21. The protrusion 211 is formed in the approximate center of the top surface of the bottom plate 21 and is a substantially cylindrical portion extending linearly with a constant diameter in the height direction. The top surface of the protrusion 211 is a flat surface perpendicular to the height direction. Furthermore, the height of the protrusion 211 (the height from the top surface of the bottom plate 21 to the top surface of the protrusion 211) is lower than the height from the top surface of the bottom plate 21 to the top surface of the wall portion 22. The protrusion 211 is provided to expose the contact surface 32 of the central contact 3 at a position higher than the top surface of the bottom plate 21.

[0026] The wall portion 22 is formed integrally with the bottom plate 21. The wall portion 22 also has a welding portion 221 formed on the upper surface of the wall portion 22 so as to surround the storage portion 23. The welding portion 221 is a rectangular flange portion that protrudes upward from the upper surface of the wall portion 22, and the cover film 9 is laser welded to the upper surface of the welding portion 221.

[0027] The storage section 23 is a recessed portion that is defined by the upper surface of the bottom plate 21 and the inner surface of the wall section 22 and has a generally rectangular planar shape that opens upward. Each component of the push switch 1 is stored in the storage section 23. In this way, the case 2 functions as a housing that stores each component of the push switch 1 in the storage section 23. The case 2 also holds the center contact 3, the first outer contact 4a, and the second outer contact 4b in a state insulated from one another.

[0028] The pair of lateral extensions 24 are block-shaped portions extending outward from the outer surfaces of the wall portion 22 on the +X and −X directions, respectively. The Y-direction outer surfaces of each of the pair of lateral extensions 24 are continuous with the Y-direction outer surface of the wall portion 22. Meanwhile, the upper surface of each of the pair of lateral extensions 24 is located below the upper surface of the wall portion 22, and the lower surface of each of the pair of lateral extensions 24 is located above the lower surface of the wall portion 22. Therefore, a step exists between the upper surface of each of the pair of lateral extensions 24 and the upper surface of the wall portion 22. This step is used in the laser cutting process for separating the cover film 9 from the carrier that connects the multiple cover films 9 together during the manufacturing process of the push switch 1. That is, the upper surface of each of the pair of lateral extensions 24 functions as a base for laser cutting the cover film 9 from the carrier during the manufacturing process of the push switch 1.

[0029] 3, the two positioning bosses 25 are cylindrical portions that protrude downward from the underside of the bottom plate 21 and are spaced apart from each other. When the push switch 1 is mounted on a circuit board, the two positioning bosses 25 are inserted into corresponding positioning holes formed on the circuit board. This positions the push switch 1 on the circuit board and prevents the push switch 1 from wobbling on the circuit board. The case 2 having the above-described configuration is obtained by arranging the center contact 3, the first outer contact 4a, and the second outer contact 4b in a mold having an interior shape corresponding to the shape of the case 2, injecting hot-molten insulating resin into the mold, and allowing it to cool and harden.

[0030] 6 shows a perspective view of the central contact 3, the first outer contact 4a, and the second outer contact 4b held by the case 2. The central contact 3, the first outer contact 4a, and the second outer contact 4b are each formed of a conductive material, more specifically, a metal material such as copper (e.g., phosphor bronze). The central contact 3, the first outer contact 4a, and the second outer contact 4b are held insulated from each other within the storage portion 23 of the case 2 and function as fixed electrodes.

[0031] The central contact 3, the first outer contact 4a, and the second outer contact 4b are each obtained by punching and bending a single metal plate that has been plated on both sides to improve conductivity. The central contact 3 includes a main body 31 embedded in the case 2, a contact surface 32 that contacts the movable contact 7a, and a terminal 33 that extends outside the case 2. The contact surface 32 is exposed upward within the storage section 23 of the case 2 and is the surface that contacts the movable contact 7a when the movable contact 7a is in the second position. The contact surface 32 is located above the top surface of the main body 31. The terminal 33 extends outward from the outer surface of the wall 22 of the case 2 on the +X direction side and functions as an external terminal that is connected to a circuit board or the like.

[0032] The first outer contact 4a includes a main body 41a embedded in the case 2, a contact surface 42a that contacts the pressure-sensitive member 5, a terminal 43a extending outside the case 2, and an edge 44a that protrudes upward from the contact surface 42a. Similarly, the second outer contact 4b includes a main body 41b embedded in the case 2, a contact surface 42b that contacts the pressure-sensitive member 5, a terminal 43b extending outside the case 2, and an edge 44b that protrudes upward from the contact surface 42b. The contact surfaces 42a and 42b are exposed upward within the storage section 23 of the case 2 at the same height as the upper surface of the bottom plate 21 of the case 2. Therefore, when the pressure-sensitive member 5 is placed on the bottom plate 21 within the storage section 23, the pressure-sensitive member 5 rests on the contact surfaces 42a and 42b. The terminal portions 43a, 43b extend outward from the outer surface of the wall portion 22 of the case 2 on the -X direction side and function as external terminals connected to a circuit board. The edge portions 44a, 44b are elongated protruding portions in the Y direction that protrude upward from the contact surfaces 42a, 42b, respectively. When the pressure-sensitive member 5 is placed on the contact surfaces 42a, 42b, the edge portions 44a, 44b bite into the pressure-sensitive member 5. This configuration further strengthens the contact between the pressure-sensitive member 5 and the first outer contact 4a and the second outer contact 4b.

[0033] As shown in FIG. 5 , a portion of the main body 31 and the contact surface 32 of the central contact 3 are exposed upward on the upper surface of the protrusion 211. The upper surface of the portion of the main body 31 that is exposed upward is located on the same plane as the upper surface of the protrusion 211. Therefore, the contact surface 32 is located higher than the upper surface of the protrusion 211. Furthermore, the contact surface 42a of the first outer contact 4a is exposed upward at the lower left corner of the storage section 23 in FIG. 5 , and the contact surface 42b of the second outer contact 4b is exposed upward at the upper left corner of the storage section 23 in FIG. 5 . The contact surfaces 42a and 42b are located on the same plane as the upper surface of the bottom plate 21. Therefore, within the storage section 23, the contact surface 32 is located higher than the contact surfaces 42a and 42b.

[0034] 3, the lower surface of the lateral extension 24 on the +X direction side is flush with the lower surface of the terminal 33 of the central contact 3. Furthermore, the lower surface of the lateral extension 24 on the −X direction side is flush with the lower surfaces of the terminal 43a of the first outer contact 4a and the terminal 43b of the second outer contact 4b. Therefore, when the push switch 1 is mounted on a circuit board and the bottom plate 21 of the case 2 contacts the upper surface of the circuit board, a gap is formed between the upper surface of the circuit board and the terminals 33, 43a, and 43b. By injecting solder into this gap, the corresponding terminals on the circuit board can be easily soldered to the terminals 33, 43a, and 43b of the push switch 1.

[0035] 4 , the pressure-sensitive member 5 is a sheet-like member including a sheet-like main body 51 and an opening 52 formed in the main body 51. The pressure-sensitive member 5 is provided in the storage section 23 so that the main body 51 contacts the contact surface 42 a of the first outer contact 4 a and the contact surface 42 b of the second outer contact 4 b, but does not contact the central contact 3 due to the opening 52.

[0036] The pressure-sensitive member 5 has a characteristic in which its electrical resistance changes in response to the pressure applied thereto. Typically, pressure-sensitive conductive rubber can be used as the pressure-sensitive member 5. FIG. 7 schematically illustrates the configuration and operating principle of pressure-sensitive conductive rubber. As shown in FIG. 7, pressure-sensitive conductive rubber is a sheet-like member obtained by mixing conductive particles 54 made of metal or carbon material into an insulating material 53 such as silicone rubber. In its natural state, when no pressure is applied to the pressure-sensitive conductive rubber, there is no conductive path within the pressure-sensitive conductive rubber. Therefore, the pressure-sensitive conductive rubber has extremely high electrical resistance (tens of thousands of ohms or more) and essentially functions as an insulating member. When pressure is applied to the pressure-sensitive conductive rubber, the pressure-sensitive conductive rubber is compressed, causing the conductive particles 54 within the insulating material 53 to come into contact with each other, forming conductive paths. The electrical resistance of the pressure-sensitive conductive rubber decreases in response to the magnitude of the applied pressure. As a result, the pressure-sensitive conductive rubber functions as a conductive member whose electrical resistance changes in response to the applied pressure. The pressure-sensitive member 5 is not limited to pressure-sensitive conductive rubber, and any member having the property of changing its own electrical resistance in response to the applied pressure may be used as the pressure-sensitive member 5. For example, a pressure-sensitive conductive sheet (such as the "I-SCAN series" sensor sheet manufactured by Nitta Corporation) may be used as the pressure-sensitive member 5. The pressure-sensitive conductive sheet has upper and lower electrodes covered with pressure-sensitive conductive ink arranged between a pair of flexible resin sheets, and is configured so that as the pair of flexible resin sheets are compressed by the application of pressure, the distance between the upper and lower electrodes decreases, thereby decreasing the electrical resistance between the upper and lower electrodes.

[0037] Returning to FIG. 4 , the main body 51 has a shape that fits within the storage section 23. In the illustrated embodiment, the main body 51 has a substantially rectangular planar shape, but the present invention is not limited to this as long as the shape fits within the storage section 23. For example, if the inner surface of the storage section 23 has a planar shape other than a substantially rectangular shape, such as a substantially elliptical or polygonal shape, the main body 51 may have a shape that corresponds to the planar shape formed by the inner surface of the storage section 23 so as to fit within the storage section 23. Furthermore, the upper and lower surfaces of the main body 51 are flat surfaces perpendicular to the height direction, and the thickness (length in the Z direction) of the main body 51 is constant. Furthermore, the thickness of the main body 51 is smaller than the height of the protrusion 211 of the case 2.

[0038] Because the main body 51 is placed on the upper surface of the bottom plate 21, when a pressing force is applied to the main body 51 from above, the portion of the main body 51 to which the pressing force is applied is compressed. Therefore, the electrical resistance of the pressure-sensitive member 5 changes in response to an increase in the strength of the pressing force applied to the main body 51. The opening 52 is an opening formed in approximately the center of the main body 51 and linearly penetrating in the height direction. The opening 52 has a planar shape that allows the protruding portion 211 of the case 2 to pass through. Furthermore, because the thickness of the main body 51 is smaller than the height of the protruding portion 211 of the case 2, when the pressure-sensitive member 5 is placed on the upper surface of the bottom plate 21, the protruding portion 211 passes through the opening 52 and protrudes upward, as shown in FIG. 9 .

[0039] Returning to FIG. 4 , a conductive spacer 6, a movable contact 7a, an auxiliary spring 7b, a pressing member 8, and a cover film 9 are disposed above the pressure-sensitive member 5. Therefore, when a user presses the pressing member 8 via the cover film 9, the pressing force applied by the user to the pressing member 8 is applied (transmitted) from above to the pressure-sensitive member 5 via the movable contact 7a, the auxiliary spring 7b, and the pressing member 8, changing the electrical resistance of the pressure-sensitive member 5. In this way, the pressure-sensitive member 5 is placed on the bottom plate 21 of the case 2 so that a pressing force is applied from above when the user presses the pressure-sensitive member 5. With this configuration, the electrical signal flowing between the first outer contact 4a and the second outer contact 4b changes depending on the pressing force applied by the user to the pressing member 8.

[0040] The conductive spacer 6 is a hard, conductive plate-like member placed on the upper surface of the pressure-sensitive member 5. The conductive spacer 6 is obtained by punching a conductive plate (such as a metal plate) that has been plated on both sides to improve conductivity. Typically, the conductive spacer 6 is made of a conductive material such as stainless steel or phosphor bronze. The conductive spacer 6 is placed on the main body 51 of the pressure-sensitive member 5 to apply a uniform pressing force to the main body 51, pressing the main body 51 and stabilizing the position of the movable contact 7 a, which is located above the conductive spacer 6, within the storage section 23.

[0041] The conductive spacer 6 includes a plate-shaped main body 61 having a planar shape corresponding to the main body 51 of the pressure-sensitive member 5, and an opening 62 formed in the main body 61 and having a planar shape corresponding to the opening 52 of the pressure-sensitive member 5. The top and bottom surfaces of the main body 61 are flat surfaces perpendicular to the height direction, and the main body 61 has a constant thickness (length in the Z direction). The thickness of the main body 61 is set so that the sum of the thicknesses of the main body 51 and the main body 61 is greater than the height of the protrusion 211 of the case 2. Therefore, as shown in FIG. 9 , when the pressure-sensitive member 5 and the conductive spacer 6 are installed in the storage compartment 23 of the case 2, the top surface of the main body 61 is located above the top surface of the protrusion 211. Furthermore, the top surface of the main body 61 is located above the top surface of the contact surface 32 of the central contact 3 exposed from the top surface of the protrusion 211.

[0042] With this configuration, when the movable contact 7a is placed on the upper surface of the main body 61 of the conductive spacer 6, the pair of outer edge portions 72 of the movable contact 7a can be positioned above the upper surface of the contact surface 32 exposed from the upper surface of the protrusion 211. As a result, the distance until the central movable portion 71 of the movable contact 7a contacts the contact surface 32, i.e., the amount of downward displacement of the central movable portion 71, can be increased, thereby increasing the stroke length of the push switch 1. Furthermore, by positioning the pair of outer edge portions 72 above the upper surface of the contact surface 32 with which the central movable portion 71 contacts, the return force of the push switch 1 can be reduced. By reducing the return force of the push switch 1, the click rate of the push switch 1 can be increased, providing the user with a good click feeling.

[0043] 4, the movable contact 7a and the three auxiliary springs 7b are each an elastic conductive member having an upwardly convex dome shape in their natural state when no pressing force is applied from above. The movable contact 7a and the three auxiliary springs 7b are arranged above the pressure-sensitive member 5 and the conductive spacer 6 in the storage section 23 of the case 2, with the three auxiliary springs 7b stacked above the movable contact 7a.

[0044] The movable contact 7a and the auxiliary spring 7b each have a shape that fits within the storage section 23 of the case 2. In the illustrated embodiment, the movable contact 7a and the auxiliary spring 7b each have a substantially quadrangular (more specifically, substantially rectangular) planar shape with arc-shaped ends on the X-direction side, but the present invention is not limited to this as long as the shape fits within the storage section 23. The movable contact 7a and the auxiliary spring 7b each are configured to be displaceable between a first position that is convex upward and a second position that is convex downward.

[0045] The movable contact 7a and the auxiliary springs 7b have the same configuration and are used in a stacked configuration. In the illustrated embodiment, three auxiliary springs 7b are used in a stacked configuration with the movable contact 7a, but the present invention is not limited to this. Depending on the required operating force and return force of the push switch 1, the auxiliary springs 7b may be omitted or the number of auxiliary springs 7b used in a stacked configuration may be changed as appropriate. The movable contact 7a and the auxiliary springs 7b are formed from the same conductive material. However, to improve corrosion resistance and conductivity, only the lower surface of the movable contact 7a, which comes into contact with the conductive spacer 6 and the contact surface 32 of the center contact 3, is plated with a highly corrosion-resistant and conductive metal such as silver.

[0046] Each of the movable contact 7a and the auxiliary spring 7b has a central movable portion 71 that is elastically deformable in the height direction and a pair of outer edge portions 72 formed at both ends of the central movable portion 71 in the X-axis direction. As shown in FIG. 9 , the central movable portion 71 has a substantially quadrangular (more specifically, substantially rectangular) planar shape, with both ends in the X-axis direction being arc-shaped. In its natural state, the central movable portion 71 has a dome-like shape that is convex upward. When a pressing force is applied to the central movable portion 71 from above, the central movable portion 71 is elastically deformable downward so that it becomes convex downward. The pair of outer edge portions 72 function as legs of the movable contact 7a or the auxiliary spring 7b. The outer edge portions 72 extend linearly downward and outward from the arc-shaped ends of the central movable portion 71 in the X-axis direction. The lower ends of the pair of outer edge portions 72 of the movable contact 7a contact the upper surface of the main body portion 61 of the conductive spacer 6, and the remaining portion of the movable contact 7a faces the main body portion 61 or the opening 62 of the conductive spacer 6 via a gap. In addition, the central movable portion 71 faces a part of the main body portion 31 and the contact surface 32 of the central contact 3 via the opening 62 of the conductive spacer 6.

[0047] As described above, the movable contact 7a is disposed above the pressure-sensitive member 5 via the conductive spacer 6. Because the conductive spacer 6 is a hard, plate-like member, placing the movable contact 7a on the pressure-sensitive member 5 stabilizes the orientation of the movable contact 7a and the auxiliary spring 7b within the housing 23. Furthermore, when a user presses the pressing member 8, the pressing force applied by the user is transmitted to the conductive spacer 6 via the pressing member 8, the movable contact 7a, and the auxiliary spring 7b, allowing the main body 61 of the conductive spacer 6 to press the main body 51 of the pressure-sensitive member 5 with a uniform pressing force. This stabilizes changes in the electrical resistance of the conductive spacer 6 due to the pressing force applied by the user. Furthermore, placing the movable contact 7a on the pressure-sensitive member 5 prevents the lower ends of the pair of outer edge portions 72 of the movable contact 7a from digging into the pressure-sensitive member 5. This configuration prevents wear on the pressure-sensitive member 5 and extends the product life of the push switch 1.

[0048] 4 , the pressing member 8 is provided within the storage section 23 of the case 2, between the lower surface of the cover film 9 and the upper surface of the uppermost one of the three auxiliary springs 7b. More specifically, the pressing member 8 is fixed to the lower surface of the central portion 91 of the cover film 9 by laser welding, and is held on the upper surface of the auxiliary spring 7b by the cover film 9. The pressing member 8 is used to efficiently transmit the pressing force applied to the push switch 1 by the user to the movable contact 7a via the auxiliary spring 7b, thereby pressing the movable contact 7a downward.

[0049] The pressing member 8 is a disk-shaped member made of a hard resin material (such as nylon). By using a resin material that is lighter than a metal material to form the pressing member 8, the pressing member 8 can be made lighter. Reducing the weight of the pressing member 8 reduces the downward bias force applied to the movable contact 7a and auxiliary spring 7b by the weight of the pressing member 8 when the push switch 1 is in its natural state, and increases the operating force of the push switch 1.

[0050] The cover film 9 is provided above the movable contact 7a, auxiliary spring 7b, and pressing member 8 so as to cover the storage section 23 of the case 2. The cover film 9 is made of a flexible resin material and is laser welded to a welding section 221 formed on the upper surface of the wall section 22 of the case 2 to seal the storage section 23. The cover film 9 has a circular central section 91 welded to the pressing member 8, a skirt section 92 extending diagonally downward from the central section 91, and a peripheral section 93 extending in the planar direction from the lower end of the skirt section 92.

[0051] The lower surface of the central portion 91 is welded to the upper surface of the pressing member 8 by surface welding using laser welding. In the natural state shown in Figure 9, the pressing member 8 is located in the space defined by the lower surface of the central portion 91 and the inner surface of the skirt portion 92. The peripheral portion 93 is welded to the weld portion 221 of the case 2 by laser welding, and the storage portion 23 of the case 2 is sealed by the cover film 9. The laser welding of the peripheral portion 93 to the weld portion 221 is not a point welding, but is performed all the way around the weld portion 221, which seals the inside of the storage portion 23 and achieves the dustproof function of the push switch 1.

[0052] The cover film 9 is made of a flexible resin material, and thus provides a spring load in the same manner as the movable contact 7 a and the auxiliary spring 7 b. As shown in Fig. 9, the diameter of the central portion 91 is larger than the diameter of the pressing member 8, and the skirt portion 92 extends obliquely downward from the side of the pressing member 8.

[0053] FIG. 8 shows a circuit diagram of the push switch 1 having the above-described configuration. As shown in FIG. 8, the terminal portion 33 of the central contact 3, the terminal portion 43a of the first outer contact 4a, and the terminal portion 43b of the second outer contact 4b function as external terminals electrically connected to other devices via a circuit board. The movable contact 7a functions as a normally open (NC) mechanical switch connected between the central contact 3 and the first outer contact 4a and between the central contact 3 and the second outer contact 4b. When the pressing force applied to the movable contact 7a exceeds the actuation force of the push switch 1, the mechanical switch in FIG. 8 closes, establishing electrical continuity between the central contact 3 and the first outer contact 4a or the second outer contact 4b. When the pressing force applied to the movable contact 7a is released, the mechanical switch in FIG. 8 opens, disconnecting electrical continuity between the central contact 3 and the first outer contact 4a or the second outer contact 4b.

[0054] The pressure-sensitive member 5 is connected between the first outer contact 4a and the second outer contact 4b. In its natural state, the pressure-sensitive member 5 has a very high electrical resistance. When a pressing force is applied to the movable contact 7a as an input, the pressure-sensitive member 5 functions as a variable resistor, decreasing its electrical resistance in accordance with the magnitude of the pressing force. Therefore, when a pressing force is applied to the pressure-sensitive member 5 and its electrical resistance decreases, the electrical signal between the first outer contact 4a and the second outer contact 4b and the electrical signal between the central contact 3 and the first outer contact 4a or the second outer contact 4b increases. In the push switch 1 of this embodiment, the electrical signal flowing between the first outer contact 4a and the second outer contact 4b is mixed with the electrical signal flowing between the central contact 3 and the first outer contact 4a or the second outer contact 4b. Other devices electrically connected to the terminal portions 33, 43a, 43b can determine the completion of the user's pressing operation by detecting conductivity between the central contact 3 and the first outer contact 4a or the second outer contact 4b, and can further determine the strength of the pressing force applied by the user by detecting the electrical signal flowing between the first outer contact 4a and the second outer contact 4b.

[0055] Next, the operation of the push switch 1 of this embodiment will be described in detail with reference to Figures 9 and 10. Figure 9 shows a vertical cross-sectional view (cross-sectional view taken along line A-A in Figure 2) of the push switch 1 in its natural state where no pressing force is applied to the push switch 1, and Figure 10 shows a vertical cross-sectional view (cross-sectional view taken along line A-A in Figure 2) of the push switch 1 in its pressed state where a pressing force exceeding the actuating force of the push switch 1 is applied to the push switch 1.

[0056] As shown in FIG. 9 , in the rest state of the push switch 1, the movable contact 7a and the auxiliary spring 7b are each in a first position, convex upward. In the first position, the outer edge 72 of the movable contact 7a contacts the upper surface of the main body 61 of the conductive spacer 6. In the rest state, the pressure-sensitive member 5 essentially functions as an insulating member. Therefore, in the rest state, the first outer contact 4a and the second outer contact 4b are substantially insulated by the pressure-sensitive member 5, and the electrical signal flowing between the terminals 43a and 43b is zero or very small. Furthermore, the movable contact 7a and the first outer contact 4a or the second outer contact 4b are substantially insulated by the pressure-sensitive member 5 and are not electrically connected. In the rest state, the central movable portion 71 of the movable contact 7a faces the contact surface 32 of the central contact 3 via a gap and is not in contact with it. Therefore, in the rest state, the movable contact 7a is not electrically connected to the central contact 3. Therefore, in a natural state, the central contact 3 and the first outer contact 4a, or the central contact 3 and the second outer contact 4b, are in a non-conductive state.

[0057] In the natural state, when a user presses the pressing member 8 via the cover film 9, the pressing force applied by the user to the pressing member 8 is applied (transmitted) from above to the main body 51 of the pressure-sensitive member 5 via the movable contact 7a, auxiliary spring 7b, and pressing member 8, compressing the main body 51. As a result, the electrical resistance of the pressure-sensitive member 5 decreases and the electrical signal flowing between the first outer contact 4a and the second outer contact 4b changes while the movable contact 7a and auxiliary spring 7b are displaced from the first position to the second position in accordance with the strength of the pressing force applied by the user to the pressing member 8. This change in the electrical signal flowing between the first outer contact 4a and the second outer contact 4b in accordance with the strength of the pressing force occurs even if the central movable portion 71 of the movable contact 7a does not contact the contact surface 32 of the central contact 3. Therefore, the push switch 1 of the present invention can detect a user's pressing operation performed with less than the actuation force of the push switch 1.

[0058] In the natural state, when a user presses the pressing member 8 through the cover film 9 with a pressing force greater than or equal to the actuation force of the push switch 1, the pressing member 8 presses the movable contact 7a and auxiliary spring 7b downward, displacing the movable contact 7a and auxiliary spring 7b to the second position, and the push switch 1 transitions to the pressed state shown in Figure 10.

[0059] 10 , the movable contact 7a and auxiliary spring 7b are in the second position. In the second position, the outer edge 72 of the movable contact 7a is in contact with the conductive spacer 6, and the electrical resistance of the pressure-sensitive member 5 is reduced by the pressing force applied by the user. Therefore, the movable contact 7a is electrically connected to the first outer contact 4a and the second outer contact 4b via the conductive spacer 6 and the pressure-sensitive member 5. Furthermore, the central movable portion 71 of the movable contact 7a is in contact with the contact surface 32 of the central contact 3. That is, when the movable contact 7a is in the second position, it is electrically connected to the central contact 3, the first outer contact 4a, and the second outer contact 4b. Therefore, when the movable contact 7 a is in the second position, the movable contact 7 a, the conductive spacer 6, and the pressure-sensitive member 5 function as a conductive path between the central contact 3 and the first outer contact 4 a or the second outer contact 4 b, and the central contact 3 and the first outer contact 4 a, or the central contact 3 and the second outer contact 4 b, are in a conductive state. Therefore, by detecting the conductive state between the central contact 3 and the first outer contact 4 a or the second outer contact 4 b, it can be determined that the user's pressing operation on the pressing member 8 has been completed.

[0060] When the pressing force on the pressing member 8 is released in the pressed state, the return force of the push switch 1 provided by the movable contact 7a, the auxiliary spring 7b, and the elastic restoring force of the cover film 9 causes the push switch 1 to return to its natural state shown in Figure 9.

[0061] FIG. 11 is a graph showing the feeling curve (load characteristics) and output waveform of the push switch 1 of this embodiment. The horizontal axis in FIG. 11 corresponds to the stroke (downward movement distance) of the pressing member 8, the left vertical axis in FIG. 11 corresponds to the load (pressing force) (N) applied to the pressing member 8, and the right vertical axis in FIG. 11 corresponds to the voltage (V) of the pressure-sensitive member 5 and the voltage (V) of the movable contact 7a. The voltage of the pressure-sensitive member 5 corresponds to the electrical signal flowing between the first outer contact 4a and the second outer contact 4b. When the electrical resistance of the pressure-sensitive member 5 decreases and the electrical signal flowing between the first outer contact 4a and the second outer contact 4b increases, the voltage of the pressure-sensitive member 5 changes. Similarly, the voltage of the movable contact 7a corresponds to the electrical signal flowing between the center contact 3 and the first outer contact 4a or the second outer contact 4b. When the central contact 3 and the first outer contact 4a or the second outer contact 4b are brought into conduction, the voltage of the movable contact 7a drops.

[0062] Regarding the feeling curve of the push switch 1, the load required to press down the pressing member 8 gradually increases until the load applied by the user to the pressing member 8 reaches the actuation force of the push switch 1, and once the load reaches the actuation force of the push switch 1, the load required to press down the pressing member 8 suddenly decreases. Therefore, when the load applied to the pressing member 8 reaches the actuation force of the push switch 1, the pressing member 8 is suddenly pressed down, providing the user with a clicking sensation. Thereafter, when the load applied to the pressing member 8 is released, the return force of the push switch 1 pushes the pressing member 8 upward, and the push switch 1 returns to its natural state.

[0063] The voltage of the movable contact 7a remains constant because the movable contact 7a does not come into contact with the central contact 3 until the load applied by the user to the pressing member 8 reaches the actuation force of the push switch 1. After that, when the load reaches the actuation force of the push switch 1 and the movable contact 7a comes into contact with the central contact 3, the central contact 3 becomes conductive with the first outer contact 4a and the second outer contact 4b via the movable contact 7a, the pressure-sensitive member 5, and the conductive spacer 6. As a result, the voltage of the movable contact 7a drops.

[0064] The voltage of the pressure-sensitive member 5 changes depending on the strength of the load applied by the user to the pressing member 8 until it reaches the actuation force of the push switch 1. That is, the electrical signal flowing between the first outer contact 4a and the second outer contact 4b changes depending on the strength of the load. After that, when the load reaches the actuation force of the push switch 1 and the movable contact 7a comes into contact with the central contact 3, the central contact 3 becomes conductive between the first outer contact 4a and the second outer contact 4b via the movable contact 7a and the pressure-sensitive member 5. As a result, the electrical signal flowing between the first outer contact 4a and the second outer contact 4b mixes with the electrical signal flowing between the central contact 3 and the first outer contact 4a or the second outer contact 4b.

[0065] As described above, in the push switch 1 of this embodiment, the pressure-sensitive member 5, whose electrical resistance changes in response to a pressing force applied from above, is placed in the storage portion 23 of the case 2 so as to be in contact with the first outer contact 4a and the second outer contact 4b. Furthermore, the pressure-sensitive member 5 is placed on the bottom plate 21 of the case 2 so that a pressing force is applied from above when the user presses the pressing member 8. Therefore, when the user presses the pressing member 8, the electrical resistance of the pressure-sensitive member 5 changes while the movable contact 7a and the auxiliary spring 7b are displacing from the first position to the second position, depending on the strength of the pressing force applied by the user to the pressure-sensitive member 5. As a result, the electrical signal flowing between the first outer contact 4a and the second outer contact 4b changes in response to the strength of the pressing force applied by the user to the pressure-sensitive member 5. Therefore, by detecting the electrical signal flowing between the first outer contact 4a and the second outer contact 4b, the strength (magnitude) of the pressing force from the user can be detected.

[0066] Furthermore, the change in the electrical signal flowing between the first outer contact 4a and the second outer contact 4b in accordance with the strength of the pressing force occurs even if the central movable portion 71 of the movable contact 7a does not contact the contact surface 32 of the central contact 3. Therefore, the push switch 1 of the present invention can detect a user's pressing operation that is performed with less than the actuating force of the push switch 1.

[0067] Furthermore, by detecting the electrical continuity between the central contact 3 and the first outer contact 4a or the second outer contact 4b, it is possible to determine whether the user has completed the pressing operation performed on the pressing member 8. In this way, the push switch 1 of this embodiment can determine not only whether the user has completed the pressing operation, but also the strength of the pressing force applied by the user.

[0068] Furthermore, in the push switch 1 of this embodiment, the pressure-sensitive member 5 is disposed within the storage compartment 23 of the case 2 so as to contact the first outer contact 4a and the second outer contact 4b but not the central contact 3. Therefore, even when the movable contact 7a is not in contact with the central contact 3, the strength of the pressing force applied by the user can be determined by detecting the electrical signal flowing between the first outer contact 4a and the second outer contact 4b. Furthermore, the completion of the user's pressing operation can be determined by detecting electrical continuity between the central contact 3 and the first outer contact 4a or the second outer contact 4b. Therefore, the completion of the user's pressing operation can be determined regardless of changes in the electrical resistance of the pressure-sensitive member 5. This configuration clearly distinguishes (separates) the process for determining whether the user has performed a pressing operation from the process for determining the strength of the pressing force applied by the user, thereby simplifying the processing of devices using the push switch 1.

[0069] Second Embodiment Next, a push switch according to a second embodiment of the present invention will be described in detail with reference to FIGS. 12 to 21 . FIG. 12 is a perspective view of the push switch according to the second embodiment of the present invention. FIG. 13 is a perspective view of the push switch shown in FIG. 12 from another angle. FIG. 14 is an exploded perspective view of the push switch shown in FIG. 12 . FIG. 15 is a top view of the case shown in FIG. 14 . FIG. 16 is a cross-sectional perspective view of the case shown in FIG. 14 . FIG. 17 is a perspective view of the center contact, the first outer contact, the second outer contact, and the third outer contact. FIG. 18 is a circuit diagram of the push switch shown in FIG. 12 . FIG. 19 is a cross-sectional view of the push switch in its natural state taken along line B-B shown in FIG. 12 . FIG. 20 is a cross-sectional view of the push switch in its pressed state taken along line B-B shown in FIG. 12 . FIG. 21 is a graph showing the feeling curve and output waveform of the push switch shown in FIG. 12 .

[0070] The following description of the push switch 1 of the second embodiment will focus on the differences from the push switch 1 of the first embodiment, and will omit a description of similar points. The push switch 1 of the second embodiment has a similar configuration to the push switch 1 of the first embodiment, except for the following: a base 212 and a thick portion 213 are formed on the bottom plate 21 of the case 2, the shape of the central contact 3 is changed, the push switch 1 further includes a third outer contact 4c held by the case 2, the shape of the pressure-sensitive member 5 is changed, the portion of the conductive spacer 6 that comes into contact with the pressure-sensitive member 5 is insulated, and the number of auxiliary springs 7b is changed to two.

[0071] Furthermore, while the first embodiment described above uses a pressure-sensitive conductive rubber or a pressure-sensitive conductive sheet as the pressure-sensitive member 5, this is not limited to this in the present embodiment. For example, a strain gauge may be used as the pressure-sensitive member 5. The strain gauge includes a plate-shaped strain element that deforms in response to an applied pressure, a grid resistor provided on the strain element, and a pair of terminals connected to both ends of the grid resistor. When the strain element deforms in response to the applied pressure, the grid resistor provided on the strain element expands or compresses, changing the electrical resistance of the grid resistor. As a result, the electrical signal flowing between the pair of terminals changes in response to the strength of the pressure applied to the strain element. When a strain gauge such as the one described above is used as the pressure-sensitive member 5, the main body 51 is a plate-shaped strain element, a grid resistor is provided on the main body 51, and a pair of terminals connected to both ends of the grid resistor are exposed downward and spaced apart from each other on the underside of the main body 51. The pressure-sensitive member 5 is provided in the storage section 23 so that a pair of terminals exposed on the underside of the main body section 51 contact the contact surface 42a of the first outer contact 4a and the contact surface 42b of the second outer contact 4b, respectively.

[0072] Furthermore, the pressure-sensitive member 5 is not limited to the above-mentioned pressure-sensitive conductive rubber, pressure-sensitive conductive sheet, and strain gauge, and any member or element having the property of changing its own electrical resistance in response to the pressure applied to the pressure-sensitive member 5 can be used as the pressure-sensitive member 5. For example, embodiments in which a piezo-type pressure sensor using a piezo-resistance element or a MEMS pressure sensor using a MEMS (microelectromechanical system) is used as the pressure-sensitive member 5 are also within the scope of the present invention.

[0073] A push switch 1 according to a second embodiment of this invention, shown in FIGS. 12 and 13 , is a switch that turns on when a user applies a pressing force that exceeds the actuation force of the push switch 1 and turns off when the pressing force applied by the user is released. A device electrically connected to terminals 33, 43a, 43b, and 43c (see FIG. 13 ) of the push switch 1 via a circuit board can determine the completion of a pressing operation on the push switch 1 by detecting the electrical continuity between the terminals 33 and 43c. Furthermore, an electrical signal flowing between the terminals 43a and 43b of the push switch 1 changes depending on the magnitude of the pressing force applied to the push switch 1 by the user. Therefore, a device electrically connected to the terminals 33, 43a, 43b, and 43c via the circuit board can determine the magnitude of the pressing force applied to the push switch 1 by detecting the electrical signal flowing between the terminals 43a and 43b.

[0074] 14, the push switch 1 of this embodiment further includes a third outer contact 4c that is spaced apart from the central contact 3, the first outer contact 4a, and the second outer contact 4b and that is provided on the bottom plate 21 of the case 2. Also, as shown in FIGS. 15 and 16, the bottom plate 21 of the case 2 of this embodiment further includes a base 212 that protrudes upward from the upper right corner of the storage section 23 in FIG. 15, and a thick portion 213 that protrudes upward from the right region of the storage section 23 in FIG.

[0075] The pedestal 212 is a columnar portion that protrudes upward from the upper right corner of the bottom plate 21 in FIG. 15 . The upper surface of the pedestal 212 is a flat surface perpendicular to the height direction. The height of the pedestal 212 (the length in the Z direction from the upper surface of the bottom plate 21 to the upper surface of the pedestal 212) is shorter than the height of the protruding portion 211. The main body 61 of the conductive spacer 6 is placed on the pedestal 212. The thick portion 213 is a portion provided to prevent the main body 31 of the central contact 3 from being exposed within the storage portion 23. The upper surface of the thick portion 213 is a flat surface perpendicular to the height direction. The height of the thick portion 213 (the length in the Z direction from the upper surface of the bottom plate 21 to the upper surface of the thick portion 213) is shorter than the height of the protruding portion 211.

[0076] Like the central contact 3, the first outer contact 4a, and the second outer contact 4b, the third outer contact 4c is formed of a conductive material, more specifically, a metal material such as copper (e.g., phosphor bronze). As shown in FIG. 17 , the third outer contact 4c includes a main body 41c embedded in the case 2, a contact surface 42c that contacts the conductive spacer 6, and a terminal 43c that extends outside the case 2. The contact surface 42c is exposed upward within the storage section 23 of the case 2 and contacts the main body 61 of the conductive spacer 6. The contact surface 42c is located above the upper surface of the main body 41c. The terminal 43c extends from the outer surface of the wall 22 of the case 2 on the +X direction side toward the outside and functions as an external terminal connected to a circuit board or the like.

[0077] 15 and 16 , at the lower right corner of the storage section 23 in FIG. 15 , a portion of the main body 41 c and the contact surface 42 c of the third outer contact 4 c are exposed upward from the upper surface of the thick portion 213. The upper surface of the portion of the main body 41 c that is exposed upward is located on the same plane as the upper surface of the thick portion 213. Therefore, the contact surface 42 c is located higher than the upper surface of the thick portion 213. The contact surface 42 c is also located on the same plane as the upper surface of the base 212.

[0078] Returning to FIG. 14 , the pressure-sensitive member 5 of this embodiment has a rectangular main body 51 elongated in the Y direction that fits between the inner surface of the wall 22 on the −X direction side and the protrusion 211 within the storage section 23 of the case 2, and does not have an opening 52. The pressure-sensitive member 5 is placed between the inner surface of the wall 22 on the −X direction side and the protrusion 211 so as to contact the contact surface 42a of the first outer contact 4a and the contact surface 42b of the second outer contact 4b. Therefore, the pressure-sensitive member 5 is electrically connected to the first outer contact 4a and the second outer contact 4b. Meanwhile, the pressure-sensitive member 5 is placed within the storage section 23 so as not to contact the central contact 3 and the third outer contact 4c. Therefore, the pressure-sensitive member 5 is not electrically connected to the central contact 3 and the third outer contact 4c. When the pressure-sensitive member 5 is placed between the inner surface of the wall portion 22 on the −X direction side and the protrusion 211, the upper surface of the pressure-sensitive member 5 is located on the same plane as the upper surface of the base 212 and the contact surface 42c of the third outer contact 4c. Therefore, within the storage portion 23, the conductive spacer 6 is in contact with the upper surface of the pressure-sensitive member 5, the upper surface of the base 212, and the contact surface 42c, which are located on the same plane, and is supported from below.

[0079] In the conductive spacer 6 of this embodiment, an insulating treatment is applied to the portion of the lower surface of the conductive spacer 6 that contacts the main body 51 of the pressure-sensitive member 5. Examples of the insulating treatment include applying insulating tape or applying an insulating film. In one example, insulating double-sided tape is applied to the portion of the lower surface of the conductive spacer 6 that contacts the main body 51 of the pressure-sensitive member 5, and the pressure-sensitive member 5 is attached to the lower surface of the conductive spacer 6 using the insulating double-sided tape. This insulating treatment insulates the conductive spacer 6 from the pressure-sensitive member 5. As described above, the conductive spacer 6 contacts the upper surface of the pressure-sensitive member 5, the upper surface of the base 212, and the contact surface 42c of the third outer contact 4c, and therefore the conductive spacer 6 is electrically connected to the third outer contact 4c. On the other hand, since the conductive spacer 6 is insulated from the pressure-sensitive member 5 by an insulating treatment, even if the electrical resistance of the pressure-sensitive member 5 changes due to the pressure applied by the user, the conductive spacer 6 will not be conductive to the first outer contact 4a and the second outer contact 4b.

[0080] FIG. 18 shows a circuit diagram of the push switch 1 having the above-described configuration. As shown in FIG. 18, the terminal portion 33 of the central contact 3, the terminal portion 43a of the first outer contact 4a, the terminal portion 43b of the second outer contact 4b, and the terminal portion 43c of the third outer contact 4c function as external terminals electrically connected to other devices via a circuit board. The movable contact 7a functions as a normally open (NC) mechanical switch connected between the central contact 3 and the third outer contact 4c. When the pressing force applied to the movable contact 7a exceeds the actuation force of the push switch 1, the mechanical switch in FIG. 18 closes, establishing electrical continuity between the central contact 3 and the third outer contact 4c. When the pressing force applied to the movable contact 7a is released, the mechanical switch in FIG. 18 opens, disconnecting the central contact 3 and the third outer contact 4c.

[0081] The pressure-sensitive member 5 is connected between the first outer contact 4a and the second outer contact 4b. In its natural state, it has a very high electrical resistance and functions as a variable resistor, receiving a pressing force applied to the movable contact 7a as an input and changing its electrical resistance depending on the magnitude of the pressing force. Therefore, when a pressing force is applied to the pressure-sensitive member 5 and its electrical resistance changes, the electrical signal between the first outer contact 4a and the second outer contact 4b increases. Also, as shown in FIG. 18 , in the push switch 1 of this embodiment, the center contact 3 and the third outer contact 4c are not electrically connected to the first outer contact 4a or the second outer contact 4b. Therefore, the electrical signal (ON / OFF signal) flowing between the center contact 3 and the third outer contact 4c and the electrical signal flowing between the first outer contact 4a and the second outer contact 4b are completely separated and do not mix. Other devices electrically connected to the terminal portions 33, 43a, 43b, 43c can determine the completion of the user's pressing operation by detecting conductivity between the central contact 3 and the third outer contact 4c, and can further determine the strength of the pressing force applied by the user by detecting the electrical signal flowing between the first outer contact 4a and the second outer contact 4b.

[0082] Next, the operation of the push switch 1 of this embodiment will be described in detail with reference to Figures 19 and 20. Figure 19 shows a vertical cross-sectional view of the push switch 1 in its natural state, where no pressing force is applied to the push switch 1 (cross-sectional view taken along line B-B in Figure 12), and Figure 20 shows a vertical cross-sectional view of the push switch 1 in its depressed state, where a pressing force exceeding the actuating force of the push switch 1 is applied to the push switch 1 (cross-sectional view taken along line B-B in Figure 12).

[0083] As shown in FIG. 19 , in the rest state of the push switch 1, the movable contact 7a and the auxiliary spring 7b are each in a first position, convex upward. In the first position, the outer edge 72 of the movable contact 7a is in contact with the upper surface of the conductive spacer 6. Because the conductive spacer 6 is in contact with the contact surface 42c of the third outer contact 4c, in the rest state, the movable contact 7a is electrically connected to the third outer contact 4c via the conductive spacer 6. Furthermore, in the rest state, the central movable portion 71 of the movable contact 7a faces the contact surface 32 of the central contact 3 across a gap and is not in contact with it. Therefore, in the rest state, the movable contact 7a is not electrically connected to the central contact 3, and the central contact 3 and the third outer contact 4c are not electrically connected to each other.

[0084] Furthermore, an insulating treatment is applied to the portion of the lower surface of the conductive spacer 6 that comes into contact with the main body 51 of the pressure-sensitive member 5. Therefore, the movable contact 7a and the pressure-sensitive member 5 are insulated from each other, and the movable contact 7a is not electrically connected to the first outer contact 4a and the second outer contact 4b located below the pressure-sensitive member 5.

[0085] In the natural state, when a user presses the pressing member 8 via the cover film 9, the pressing force applied by the user to the pressing member 8 is applied (transmitted) from above to the main body 51 of the pressure-sensitive member 5 via the movable contact 7a, auxiliary spring 7b, and pressing member 8, compressing the main body 51. As a result, the electrical resistance of the pressure-sensitive member 5 changes while the movable contact 7a and auxiliary spring 7b are displaced from the first position to the second position depending on the strength of the pressing force applied by the user to the pressing member 8, and the electrical signal flowing between the first outer contact 4a and the second outer contact 4b changes. However, unlike the first embodiment, even if the electrical resistance of the pressure-sensitive member 5 changes in response to the pressing force applied by the user, the pressure-sensitive member 5 and the conductive spacer 6 are insulated by an insulating treatment, so the movable contact 7a does not conduct electricity to the first outer contact 4a or the second outer contact 4b.

[0086] In the natural state, when a user presses the pressing member 8 through the cover film 9 with a pressing force greater than or equal to the actuation force of the push switch 1, the pressing member 8 presses the movable contact 7a and auxiliary spring 7b downward, displacing the movable contact 7a and auxiliary spring 7b to the second position, and the push switch 1 transitions to the pressed state shown in Figure 20.

[0087] In the pressed state shown in FIG. 20 , the movable contact 7a and auxiliary spring 7b are in the second position. Even in the second position, the pressure-sensitive member 5 and the conductive spacer 6 are insulated by an insulating treatment. Therefore, the movable contact 7a is not electrically connected to the first outer contact 4a or the second outer contact 4b. Meanwhile, the central movable portion 71 of the movable contact 7a is in contact with the contact surface 32 of the central contact 3. That is, when the movable contact 7a is in the second position, it is electrically connected to the central contact 3 and the third outer contact 4c. Therefore, when the movable contact 7a is in the second position, the movable contact 7a and the conductive spacer 6 function as a conductive path between the central contact 3 and the third outer contact 4c, and the central contact 3 and the third outer contact 4c are electrically connected. Therefore, by detecting the electrical connection between the central contact 3 and the third outer contact 4c, it is possible to determine whether the user's pressing operation on the pressing member 8 has been completed.

[0088] When the pressing force on the pressing member 8 is released in the pressed state, the return force of the push switch 1 provided by the movable contact 7a, the auxiliary spring 7b, and the elastic restoring force of the cover film 9 causes the push switch 1 to return to its natural state shown in Figure 19.

[0089] FIG. 21 is a graph showing the feeling curve (load characteristics) and output waveform of the push switch 1 of this embodiment. The graph in FIG. 21 shows the feeling curve (load characteristics) and output waveform of the push switch 1 when a pressure-sensitive conductive rubber or a pressure-sensitive conductive sheet is used as the pressure-sensitive member 5. The horizontal axis in the graph in FIG. 21 corresponds to the stroke amount (downward movement distance) of the pressing member 8, the vertical axis on the left side of the graph in FIG. 21 corresponds to the load (pressing force) (N) applied to the pressing member 8, and the vertical axis on the right side of the graph in FIG. 21 corresponds to the voltage (V) of the pressure-sensitive member 5 and the voltage (V) of the movable contact 7a. The voltage of the pressure-sensitive member 5 corresponds to the electrical signal flowing between the first outer contact 4a and the second outer contact 4b. When the electrical resistance of the pressure-sensitive member 5 decreases and the electrical signal flowing between the first outer contact 4a and the second outer contact 4b increases, the voltage of the pressure-sensitive member 5 changes. Similarly, the voltage of the movable contact 7a corresponds to the electrical signal flowing between the center contact 3 and the third outer contact 4c. When the center contact 3 and the third outer contact 4c are electrically connected, the voltage of the movable contact 7a becomes approximately zero.

[0090] Regarding the feeling curve of the push switch 1, the load required to press down the pressing member 8 gradually increases until the load applied by the user to the pressing member 8 reaches the actuation force of the push switch 1, and once the load reaches the actuation force of the push switch 1, the load required to press down the pressing member 8 suddenly decreases. Therefore, when the load applied to the pressing member 8 reaches the actuation force of the push switch 1, the pressing member 8 is suddenly pressed down, providing the user with a clicking sensation. Thereafter, when the load applied to the pressing member 8 is released, the return force of the push switch 1 pushes the pressing member 8 upward, and the push switch 1 returns to its natural state.

[0091] The voltage of the movable contact 7a remains constant because the movable contact 7a does not come into contact with the central contact 3 until the load applied by the user to the pressing member 8 reaches the actuation force of the push switch 1. After that, when the load reaches the actuation force of the push switch 1 and the movable contact 7a comes into contact with the central contact 3, the central contact 3 becomes conductive with the third outer contact 4c via the movable contact 7a and the conductive spacer 6. As a result, the voltage of the movable contact 7a becomes approximately zero.

[0092] The voltage of the pressure-sensitive member 5 changes depending on the strength of the load applied by the user to the pressing member 8. That is, the electrical signal flowing between the first outer contact 4a and the second outer contact 4b changes depending on the strength of the load. In the push switch 1 of this embodiment, the first outer contact 4a and the second outer contact 4b are not electrically connected to the central contact 3 and the third outer contact 4c. Therefore, even after the load reaches the actuation force of the push switch 1 and the movable contact 7a is electrically connected to the central contact 3, the electrical signal (ON / OFF signal) flowing between the central contact 3 and the third outer contact 4c and the electrical signal flowing between the first outer contact 4a and the second outer contact 4b do not mix and are completely separated.

[0093] In this way, the push switch 1 of this embodiment can detect the strength (magnitude) of the pressing force applied by the user by detecting the electrical signal flowing between the first outer contact 4a and the second outer contact 4b. Furthermore, by detecting the electrical continuity between the center contact 3 and the third outer contact 4c, it can be determined that the user's pressing operation on the pressing member 8 has been completed. In this way, the push switch 1 of this embodiment can determine not only whether the user's pressing operation has been completed, but also the strength of the pressing force applied by the user.

[0094] Furthermore, in the push switch 1 of this embodiment, the on / off signal that flows between the center contact 3 and the third outer contact 4c and is used to determine whether the user has completed the pressing operation is completely separate from, and not mixed with, the electrical signal that flows between the first outer contact 4a and the second outer contact 4b. This configuration completely separates the on / off signal used to determine whether the user has performed a pressing operation from the electrical signal used to determine the strength of the pressing force applied by the user, further simplifying the processing of devices that use the push switch 1.

[0095] <Third Embodiment> Next, a push switch according to a third embodiment of the present invention will be described in detail with reference to Figs. 22 to 25. Fig. 22 is a perspective view of the push switch according to the third embodiment of the present invention. Fig. 23 is an exploded perspective view of the push switch shown in Fig. 22. Fig. 24 is a schematic diagram for explaining the configuration of the pressure-sensitive member shown in Fig. 23. Fig. 25 is a graph showing the feeling curve and output waveform of the push switch shown in Fig. 23.

[0096] The following description of the push switch 1 of the third embodiment will focus on the differences from the push switch 1 of the first embodiment, and a description of similarities will be omitted. The push switch 1 of the third embodiment has a configuration similar to that of the push switch 1 of the first embodiment, except that the pressure-sensitive member 5 is a strain gauge having a full-bridge circuit formed by four grid resistors, the push switch 1 further includes a third outer contact 4c, a fourth outer contact 4d, a fifth outer contact 4e, an insulating film 11 provided between the conductive spacer 6 and the pressure-sensitive member 5, and a conductive support member 12 provided between the conductive spacer 6 and the movable contact 7a, and the number of auxiliary springs 7b has been changed to two.

[0097] 23, the push switch 1 of the present invention includes a third outer contact 4c, a fourth outer contact 4d, and a fifth outer contact 4e in addition to the central contact 3, the first outer contact 4a, and the second outer contact 4b. Like the first outer contact 4a and the second outer contact 4b, the third outer contact 4c, the fourth outer contact 4d, and the fifth outer contact 4e are each obtained by punching and bending a single metal plate that has been plated on both sides to improve conductivity.

[0098] As in the second embodiment, the third outer contact 4c includes a main body 41c embedded in the case 2, a contact surface 42c that contacts the conductive support member 12, and a terminal portion 43c extending outside the case 2. The fourth outer contact 4d includes a main body 41d embedded in the case 2, a contact surface 42d that connects to the terminal 57 (see FIG. 24 ) of the pressure-sensitive member 5, and a terminal portion 43d that extends outside the case 2. Similarly, the fifth outer contact 4e includes a main body 41e embedded in the case 2, a contact surface 42e that connects to the terminal 57 of the pressure-sensitive member 5, and a terminal portion 43e that extends outside the case 2. The contact surface 42d is exposed upward at the corners on the +X and +Y sides of the storage portion 23. The contact surface 42e is exposed upward at the corners on the +X and −Y sides of the storage portion 23 of the case 2. Contact surface 42c is exposed upward between contact surfaces 42d and 42e at the end of storage section 23 on the +X direction side, while being spaced apart from contact surfaces 42d and 42e. Terminal portion 33 of central contact 3, terminal portion 43a of first outer contact 4a, and terminal portion 43b of second outer contact 4b extend toward the −X direction from wall portion 22 on the −X direction side of case 2 and are exposed. Terminal portions 43c, 43d, and 43e extend toward the +X direction from the wall portion on the +X direction side of case 2 and are exposed.

[0099] 23 and 24 , the pressure-sensing member 5 is a strain gauge having a full bridge circuit formed by four grid resistors. As shown in FIG. 23 and FIG. 24 , the pressure-sensing member 5 includes a sheet-like main body 51 having a shape that fits within the storage section 23, a planar opening 52 through which the protrusion 211 of the case 2 can be inserted, a pair of rectangular terminals 55 spaced apart from each other and extending linearly outward (in the X direction) from both ends of the main body 51 in the X direction, four grid resistors 56 provided on the main body 51 and connected to each other to form a bridge circuit, and four terminals 57 provided on the four terminals 55, respectively, and connected to the bridge circuit formed by the four grid resistors 56.

[0100] Each of the four terminals 57 is exposed downward on the lower surface of the corresponding terminal portion 55. The pressure-sensitive member 5 is placed on the bottom plate 21 of the case 2 so that the two terminals 57 located on the +X direction side are in contact with the contact surface 42d of the fourth outer contact 4d and the contact surface 42e of the fifth outer contact 4e, respectively, and the two terminals 57 located on the −X direction side are in contact with the contact surface 42a of the first outer contact 4a and the contact surface 42b of the second outer contact 4b, respectively, and are electrically connected. The terminal portion 33 of the central contact 3, the terminal portion 43a of the first outer contact 4a, the terminal portion 43b of the second outer contact 4b, the terminal portion 43c of the third outer contact 4c, the terminal portion 43d of the fourth outer contact 4d, and the terminal portion 43e of the fifth outer contact 4e are electrically connected to the device. A voltage is applied to the full bridge circuit of the pressure-sensitive member 5 via the fourth outer contact 4d and the fifth outer contact 4e. Meanwhile, the strength of the electrical signal flowing between the first outer contact 4a and the second outer contact 4b varies depending on the electrical resistance of the four grid resistors 56 of the pressure-sensitive member 5. Furthermore, the pressure-sensitive member 5 does not contact the center contact 3 or the third outer contact 4c, and is not electrically connected to the center contact 3 or the third outer contact 4c.

[0101] When the user presses the pressing member 8 via the cover film 9, the main body 51 is distorted by the applied pressure, and the distortion of the main body 51 expands or compresses each of the four grid resistors 56. As a result, the electrical resistance of each of the four grid resistors 56 changes. Therefore, an electrical signal flowing between the first outer contact 4 a and the second outer contact 4 b, which are electrically connected via the pressure-sensitive member 5, changes in response to the pressure applied by the user to the pressing member 8 and transmitted to the pressure-sensitive member 5. Therefore, the device can determine the strength of the pressure applied by the user by detecting the electrical signal flowing between the first outer contact 4 a and the second outer contact 4 b.

[0102] Returning to Figure 23, insulating film 11 is a member that is provided between the upper surface of the main body of pressure-sensitive member 5 and the lower surface of conductive spacer 6, and provides insulation between pressure-sensitive member 5 and conductive spacer 6. Insulating film 11 is attached to the lower surface of conductive spacer 6. Insulating film 11 includes main body 111 having a planar shape corresponding to the planar shapes of main body 51 of pressure-sensitive member 5 and main body 61 of conductive spacer 6, and an opening 112 formed in main body 111. Opening 112 has a planar shape that corresponds to opening 52 of pressure-sensitive member 5 and opening 62 of conductive spacer 6.

[0103] The conductive support member 12 is made of a conductive material such as metal and functions as an electrical path between the movable contact 7a and the third outer contact 4c. Furthermore, the conductive support member 12 is positioned between the conductive spacer 6 and the movable contact 7a, supporting the movable contact 7a from below. The conductive support member 12 includes a plate-shaped main body 121 having a planar shape corresponding to the main body 61 of the conductive spacer 6, an opening 122 formed in the main body 121, and a pair of legs 123 extending diagonally downward and spaced apart from each other from both ends of the main body 121 in the X direction. The movable contact 7a is placed on the conductive support member 12 so that a pair of outer edge portions 72 of the movable contact 7a contact the main body 121. Furthermore, the central movable portion 71 of the movable contact 7a faces the contact surface 32 of the central contact 3 through the opening 122. Therefore, when the movable contact 7a assumes the second position, the central movable portion 71 can contact the contact surface 32.

[0104] Each of the pair of legs 123 located on the +X direction side is a plate-like portion extending diagonally downward from the end of the main body 121 on the +X direction side. Similarly, each of the pair of legs 123 located on the −X direction side is a plate-like portion extending diagonally downward from the end of the main body 121 on the −X direction side. When the conductive support member 12 is placed on the bottom plate 21 of the case 2, the lower ends of the pair of legs 123 located on the +X direction side contact the contact surface 42c of the third outer contact 4c, and the lower ends of the pair of legs 123 located on the −X direction side contact the bottom plate 21. As described above, the pair of outer edge portions 72 of the movable contact 7a contact the main body 121, thereby establishing electrical conduction between the movable contact 7a and the third outer contact 4c via the conductive support member 12.

[0105] In the natural state, the movable contact 7a and the auxiliary spring 7b are each in a first position that is convex upward. Also, in the natural state, the movable contact 7a is electrically connected to the third outer contact 4c via the conductive support member 12. Meanwhile, the central movable portion 71 of the movable contact 7a faces the contact surface 32 of the central contact 3 across a gap and is not in contact with it. Therefore, in the natural state, the movable contact 7a is not electrically connected to the central contact 3. Therefore, in the natural state, there is no electrical connection between the central contact 3 and the third outer contact 4c.

[0106] In the natural state, when a user presses the pressing member 8 via the cover film 9, the pressing force applied by the user to the pressing member 8 is applied (transmitted) from above to the main body 51 of the pressure-sensitive member 5 via the movable contact 7a, auxiliary spring 7b, and pressing member 8, compressing the main body 51. As a result, the electrical resistance of each of the four grid resistors 56 provided on the main body 51 changes depending on the strength of the pressing force applied by the user to the pressing member 8. Therefore, while the movable contact 7a and auxiliary spring 7b are displaced from the first position to the second position, the electrical resistance of the pressure-sensitive member 5 changes, and the electrical signal flowing between the first outer contact 4a and the second outer contact 4b changes. Unlike the first embodiment, the pressure-sensitive member 5 and the conductive spacer 6 are insulated by the insulating film 11, so the movable contact 7a is not electrically connected to the first outer contact 4a or the second outer contact 4b.

[0107] In the natural state, when a user presses the pressing member 8 through the cover film 9 with a pressure equal to or greater than the actuation force of the push switch 1, the movable contact 7a assumes the second position, and the central movable portion 71 of the movable contact 7a contacts the contact surface 32 of the central contact 3. As a result, the movable contact 7a and the conductive support member 12 function as a conductive path between the central contact 3 and the third outer contact 4c, and the central contact 3 and the third outer contact 4c are in a conductive state. Therefore, by detecting the conductivity between the central contact 3 and the third outer contact 4c, the device can determine that the user's pressing operation of the pressing member 8 has been completed. When the pressing force on the pressing member 8 is released in the depressed state, the push switch 1 returns to its natural state due to the return force of the push switch 1 provided by the movable contact 7a, the auxiliary spring 7b, and the elastic restoring force of the cover film 9.

[0108] Fig. 25 is a graph showing the feeling curve (load characteristics) and output waveform of the push switch 1 of this embodiment. The horizontal axis in the graph of Fig. 25 corresponds to the stroke amount (downward movement distance) of the pressing member 8, the vertical axis on the left side of the graph of Fig. 25 corresponds to the load (pressing force) (N) applied to the pressing member 8, and the vertical axis on the left side of the graph of Fig. 25 corresponds to the output voltage (V) of the electrical signal flowing between the first outer contact 4 a and the second outer contact 4 b.

[0109] 25 , as the stroke of the pressing member 8 increases, the load applied to the pressing member 8 and the output voltage of the electrical signal flowing between the first outer contact 4a and the second outer contact 4b increase. When the pressing force applied to the pressing member 8 by the user subsequently reaches the actuation force of the push switch 1, the movable contact 7a and the auxiliary spring 7b suddenly elastically deform downward and assume the second position. As a result, the load applied to the pressing member 8 suddenly decreases. Furthermore, as the load applied to the pressing member 8 suddenly decreases, the output voltage of the electrical signal flowing between the first outer contact 4a and the second outer contact 4b also suddenly decreases. 25 , during the period from when the movable contact 7 a and the auxiliary spring 7 b are displaced from the first position to the second position, i.e., during the period from when the stroke begins to when the load applied to the pressing member 8 suddenly decreases, high linearity is achieved between the load applied to the pressing member 8 and the output voltage of the electrical signal flowing between the first outer contact 4 a and the second outer contact 4 b. Therefore, by using the push switch 1 of this embodiment, the strength of the pressing force applied to the pressing member 8 can be more accurately calculated from the electrical signal flowing between the first outer contact 4 a and the second outer contact 4 b during the period from when the movable contact 7 a and the auxiliary spring 7 b are displaced from the first position to the second position.

[0110] Even with this configuration, the strength (magnitude) of the pressing force applied by the user can be detected by detecting the electrical signal flowing between the first outer contact 4a and the second outer contact 4b. Furthermore, by detecting the electrical continuity between the center contact 3 and the third outer contact 4c, it can be determined that the user's pressing operation on the pressing member 8 has been completed. Thus, the push switch 1 of this embodiment can determine not only whether the user's pressing operation has been completed, but also the strength of the pressing force applied by the user.

[0111] While the push switch of the present invention has been described above based on the illustrated embodiments, the present invention is not limited to these. Each component of the present invention can be replaced with any component that can perform the same function, or any component can be added to each component of the present invention.

[0112] Those skilled in the art and technology to which the present invention pertains will be able to modify the configuration of the push switch of the present invention as described without significantly departing from the principles, concepts, and scope of the present invention, and push switches having modified configurations are also within the scope of the present invention.

[0113] 2 to 25 are merely examples for the purpose of explanation, and the present invention is not necessarily limited thereto. The scope of the present invention also includes the addition or combination of any component, or the deletion of any component, as long as it does not deviate from the principles and intent of the present invention.

[0114] In the push switch of the present invention, a pressure-sensitive member whose electrical resistance changes in response to pressure applied from above is placed in a housing of the case so as to contact the first outer contact and the second outer contact. Furthermore, the pressure-sensitive member is placed on the bottom plate of the case so that pressure is applied from above when a user presses the pressure member. Therefore, when a user presses the pressure member, the electrical resistance of the pressure-sensitive member changes in response to the strength of the pressure applied by the user to the pressure-sensitive member. As a result, the electrical signal flowing between the first outer contact and the second outer contact changes in response to the strength of the pressure applied by the user to the pressure-sensitive member. Therefore, the strength (magnitude) of the pressure applied by the user can be determined by detecting the electrical signal flowing between the first outer contact and the second outer contact. Therefore, the present invention has industrial applicability.

Claims

1. A case including a storage portion defined by a bottom plate and a wall portion extending upward from the bottom plate, central contacts, a first outer contact, and a second outer contact provided on the bottom plate in the storage portion and spaced apart from each other, a pressure-sensitive member provided in the storage portion so as to contact the first outer contact and the second outer contact and not contact the central contact, a dome-shaped movable contact displaceable in the storage portion between a first position convex upward and not contacting the central contact and a second position convex downward and contacting the central contact, and a pressing member disposed above the pressure-sensitive member and the movable contact and on which a pressing operation by a user is performed, wherein the pressure-sensitive member is placed on the bottom plate of the case so that a pressing force is applied from above when the user performs the pressing operation on the pressing member, the pressure-sensitive member is configured such that its electrical resistance changes according to the strength of the pressing force applied from above to the pressure-sensitive member, and an electrical signal flowing between the first outer contact and the second outer contact changes according to the strength of the pressing force applied from above to the pressure-sensitive member while the movable contact is displaced from the first position to the second position. A push switch characterized by this.

2. Further including a conductive spacer located between the pressure-sensitive member and the movable contact in the storage portion of the case, the conductive spacer including a sheet-shaped main body portion and an opening formed in the main body portion, the main body portion of the conductive spacer contacting the pressure-sensitive member and the movable contact, and the movable contact facing the central contact through the opening of the conductive spacer. The push switch according to claim 1.

3. Further including a third outer contact provided on the bottom plate in the storage portion of the case and spaced apart from the central contact, the first outer contact, and the second outer contact, and when the movable contact is displaced from the first position to the second position by the pressing operation of the user performed on the pressing member, the central contact and the third outer contact are electrically connected through the movable contact, and further, the central contact is not electrically connected to the first outer contact or the second outer contact. The push switch according to claim 1.

4. When the movable contact takes the first position, the movable contact is in conduction with the third outer contact and is not in contact with the central contact. When the movable contact takes the second position, the movable contact is in conduction with the third outer contact and the central contact and functions as a conduction path between the third outer contact and the central contact. The push switch according to claim 3.

5. The push switch according to claim 1, wherein when the user performs the pressing operation on the pressing member, the pressing force is applied to the pressure-sensitive member via the movable contact.

6. The push switch according to claim 1, wherein the pressure-sensitive member is a pressure-sensitive conductive rubber whose electrical resistance decreases in response to the pressing force applied from above.

7. The pressure-sensitive member is a strain gauge including a strain body and a grid resistor provided on the strain body. When the user performs the pressing operation on the pressing member, the strain body is strained according to the pressing force, and the grid resistor is stretched or compressed, whereby the electrical resistance of the pressure-sensitive member changes. The push switch according to claim 1.

8. A central contact, a first outer contact, and a second outer contact provided apart from each other, a pressure-sensitive member electrically connected to the first outer contact and the second outer contact, a movable contact displaceable between a first position not in contact with the central contact and a second position in contact with the central contact in response to a pressing force applied by a user, when the movable contact takes the second position, the central contact is in conduction with the first outer contact or the second outer contact via the movable contact, the pressing force applied by the user to the movable contact is transmitted to the pressure-sensitive member via the movable contact, the pressure-sensitive member is configured such that its electrical resistance changes according to the strength of the pressing force, and an electrical signal flowing between the first outer contact and the second outer contact changes according to the strength of the pressing force while the movable contact is displaced from the first position to the second position. A push switch characterized by this.

9. A central contact, a first outer contact, a second outer contact, and a third outer contact provided separately from each other; a pressure-sensitive member electrically connected to the first outer contact and the second outer contact; and a movable contact displaceable between a first position where it does not contact the central contact and a second position where it contacts the central contact in response to a pressing force applied by a user, wherein when the movable contact takes the second position, the central contact and the third outer contact are electrically connected through the movable contact, the pressing force applied by the user to the movable contact is transmitted to the pressure-sensitive member through the movable contact, the pressure-sensitive member is configured such that its electrical resistance changes according to the strength of the pressing force, and an electrical signal flowing between the first outer contact and the second outer contact is configured to change according to the strength of the pressing force while the movable contact is displaced from the first position to the second position. A push switch characterized by the above.

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