WO2011007500A1

WO2011007500A1 - Pressure-sensitive input device

Info

Publication number: WO2011007500A1
Application number: PCT/JP2010/004086
Authority: WO
Inventors: 安藤均
Original assignee: 信越ポリマー株式会社
Priority date: 2009-07-13
Filing date: 2010-06-18
Publication date: 2011-01-20
Also published as: JP2011023114A

Abstract

Provided is a switch structure which can normally detect a pressure without depending on the dimensional accuracy of a switch and the assembly accuracy of a housing. A pressure-sensitive input device is comprised of a printed circuit board having an electrode for a first contact point, a contact rubber, and a detection device for detecting a pressure. In the pressure-sensitive input device, the contact rubber is comprised of a conductive elastic body, and a support member for supporting the conductive elastic body, which can change shape and which moves the conductive elastic body in a direction away from the printed circuit board after the conductive elastic body is brought into contact with the electrode for the first contact point, to alleviate the load applied to the conductive elastic body. The electrode for the first contact point has a function to reduce the electric resistance between the electrodes depending on the area which is in contact with the conductive elastic body. The detection device decides whether or not the variation of the electric resistance exceeds a predetermined threshold value. The detection device detects a pressure when deciding that the electric resistance exceeds the threshold value, and does not detect a pressure when the electric resistance does not exceed the threshold value.

Description

Pressure-sensitive input device

The present invention relates to a pressure-sensitive input device.

2. Description of the Related Art Conventionally, in-vehicle devices, multi-function fixed telephones, mobile phones, and the like are equipped with a pressure-sensitive input device capable of recognizing an input by pressing the button in the operation panel. Such a pressure-sensitive input device includes, for example, a button that can be pressed in the operation panel, and is provided with a rubber dome that can be bent and deformed below the button. A printed circuit is provided on the back of the top of the dome. The contact portion is fixed so as to face the contact electrode on the substrate (see, for example, Patent Document 1). In the pressure-sensitive input device having such a structure, when the button is pressed, the dome is deformed downward, the contact portion on the back side of the dome is electrically connected to the contact electrode on the printed circuit board, and the switch is turned on.

Also, the contact portion is a conductor made of hemispherical conductive rubber, and the conductor is disposed on the back side of the dome so that the curved bottom of the conductor faces the contact electrode on the printed circuit board. It is known (see, for example, Patent Document 2). When a contact portion using conductive rubber is used, unlike the pressure-sensitive input device disclosed in Patent Document 1, the contact area between the conductor and the contact electrode can be increased according to the force of pressing the button. it can. That is, the magnitude of the electrical resistance between the contact electrodes can be made to depend on the force with which the button is pressed. If such a variable resistance function is used, for example, the magnitude of the applied external force can be detected.

Japanese Utility Model Publication No. 5-38735 Japanese Patent Laid-Open No. 2003-083819

In realizing a pressure-sensitive mechanism using the function of the variable resistance, the pressure increases between the pressure applied to the contact portion made of conductive rubber and the electrical resistance between the contact electrodes on the printed circuit board. Ideally, the electrical resistance is linearly reduced. However, in reality, when the contact portion made of conductive rubber is crushed and the contact area with the contact electrode is increased, the electrical resistance between the contact electrodes is reduced and the contact portion is excessively deformed. Thus, the effect of increasing the electrical resistance of the conductive rubber itself begins to occur. As a result, when the contact portion made of conductive rubber is pushed toward the contact electrode, after a certain pushing amount, the electric resistance does not decrease but starts to be saturated or slightly increased. This is considered to be because when the conductive rubber itself is deformed to some extent, the distance between the carbon particles kneaded in the rubber is locally expanded along with the deformation, and the network of carbon particles is broken. For this reason, when conductive rubber is used for the contact portion, in order to realize a highly accurate pressure-sensitive input device, the electrical resistance is almost saturated after the contact portion contacts the contact electrode on the printed circuit board. Preferably, a limited pressure range is utilized.

FIG. 16 shows a structural example of a conventional pressure-sensitive input device using conductive rubber as a contact portion. (16A) is a sectional view of a conventional pressure-sensitive input device and its vicinity, and (16B) is a plan view of a contact electrode on a printed circuit board.

16 has a structure in which a contact rubber 320 made of an elastic member is fixed on a printed circuit board 310, and a key top 330 is fixed on the contact rubber 320. The pressure-sensitive input device 300 shown in FIG. On the surface of the printed circuit board 310, a contact electrode 313 including a pair of comb-

like electrodes

311 and 312 is provided by, for example, copper foil. The contact rubber 320 is made of, for example, silicone rubber, and can be bent in the vertical direction having a fixed portion 321 fixed to the printed circuit board 310 and a shape that narrows the opening area from the fixed portion 321 toward the key top 330. Dome 322 and a top surface portion 323 above the dome 322. The hemispherical contact portion 324 made of conductive rubber is fixed on the back surface of the top surface portion 323 and above the contact electrode 313 so that the spherical bottom faces the contact electrode 313. The key top 330 includes a pressing portion 331 that contacts an operator's finger when pushed from above, and a flange portion 332 that is connected to the lower side of the key top 330 and has a larger bottom area than the pressing portion 331, and the top surface portion of the contact rubber 320. It is fixed on H.323. Further, the housing 340 is formed with a hole 341, and only the pressing portion 331 of the key top 330 is exposed outward from the hole 341.

In the case of the pressure-sensitive input device 300 shown in FIG. 16, the gap t between the flange portion 332 and the housing 340 is caused by, for example, variation in dimensional accuracy of the key top 330 or variation in assembly accuracy between the housing 340 and the key top 330. May be larger. When the gap t is increased, dust and dirt easily enter the pressure-sensitive input device 300, and contact / non-contact between the housing 340 and the flange portion 332 is repeatedly caused by vibration of the device including the pressure-sensitive input device 300. The noise is likely to occur. In particular, when the pressure-sensitive input device 300 is used in a vibration-prone environment (for example, an in-car device), abnormal noise becomes intense, and the quality of the device (or the vehicle on which the device is mounted) is increased. It will decline. In order to avoid such a problem, the gap t between the flange portion 332 and the housing 340 can be designed to be extremely small or zero.

However, if the design is made so that the gap t is almost zero, as indicated by the one-dot chain line in FIG. 16 (16A), the rubber switch 320 has already been pushed downward in a state where the key top 330 is not pushed, and the contact portion 324 is There is a possibility of being pressed against the contact electrode 313. As described above, since the pressure range in which the conductive rubber can be used is limited, when pressure is applied to the contact portion 324 even when the key top 330 is not pressed, the key top 330 is pressed. The detectable range is narrowed. As a result, there arises a problem that a change in electrical resistance before and after pressing cannot be detected correctly.

The present invention has been made to solve such a problem, and an object thereof is to reduce the gap between the pressure-sensitive input device and the housing and realize accurate pressure detection.

As a result of diligent efforts to solve the above problems, the present inventor, even when the hemispherical contact portion made of conductive rubber is pressed against the contact electrode when the key top is not pressed, By relieving the load applied to the contact portion due to the pressing of the pressure so that excessive pressure is not applied to the contact portion, the inventors have obtained the knowledge that a range for detecting the press can be secured, and the present invention has been achieved.

Specifically, in one embodiment of the present invention, a printed circuit board having at least a first contact electrode composed of a plurality of first electrodes spaced apart from each other, and the printed circuit board disposed above the printed circuit board. A pressure-sensitive input device comprising: a contact rubber that can be elastically driven toward the surface of the substrate; and a detection device that detects a pressure from the contact rubber toward the printed circuit board. A conductive elastic body that protrudes toward the first contact electrode above the electrode for use and has a shape that reduces the horizontal cross section toward the tip, and a deformable member that supports the conductive elastic body. Then, after the conductive elastic body contacts the first contact electrode, the conductive elastic body is moved away from the printed circuit board to load the conductive elastic body. The first contact electrode has a function of reducing the electrical resistance between the first electrodes depending on the contact area with the conductive elastic body, and the detection device changes the electrical resistance. Is a pressure-sensitive input device that detects whether or not a predetermined threshold is exceeded, detects a pressure when it is determined that the threshold is exceeded, and does not detect a pressure when it is determined that the threshold is not exceeded.

In another embodiment of the present invention, the conductive elastic body has a space between the conductive rubber and the printed circuit board when the contact rubber is not pushed down toward the printed circuit board. It is in a non-contact state with the electrode.

In still another embodiment of the present invention, the printed circuit board further includes a second contact electrode composed of a plurality of second electrodes spaced apart from each other in addition to the first contact electrode. The detector is provided above the second contact electrode with a distance greater than the distance between the conductive elastic body and the first contact electrode, and the detection device is in contact with the conductive elastic body and the first contact electrode. When the conductor and the second contact electrode come into contact with each other by further pressing later, the next pressing is detected.

In still another embodiment of the present invention, in the contact rubber, the conductive elastic body is provided inside the conductor, and in the printed circuit board, the first contact electrode is more than the second contact electrode. Is also provided inside.

In still another embodiment of the present invention, in the case where an on / off switch of a digital circuit is configured between the conductor and the second contact electrode, the printed circuit board is a conductive elastic body. And an analog circuit including a variable resistor formed between the first contact electrode and the digital circuit, and the detection device is configured by a single output voltage obtained from the composite circuit. The first and second presses are detected.

According to the present invention, it is possible to reduce the gap between the pressure-sensitive input device and the housing, and to realize accurate pressure detection.

FIG. 1 is a plan view (1A) showing an example of a pressure-sensitive input device and a housing around it according to the first embodiment of the present invention, and a partially exploded perspective view (1B) of the pressure-sensitive input device. 2 is a cross-sectional view (2A) of the pressure-sensitive input device shown in FIG. 1 taken along the line AA in FIG. 1 (1A), and the first contact electrode and the second contact on the printed circuit board. It is a top view (2B) of the electrode for operation. FIG. 3 is a cross-sectional view showing a state when the key top of the pressure-sensitive input device shown in FIG. 2 is pressed, and (3A) shows a state when the conductive elastic body contacts the first contact electrode. , (3B) respectively show the state when the contact further contacts the second contact electrode. FIG. 4 is a graph showing a simulation of the load curve from when the pressure-sensitive input device shown in FIG. 2 is pressed to the key top until the second stage switch is turned on. (4B) shows a load curve combining both the conductive elastic body and the contact point, respectively. FIG. 5 is an electric circuit diagram exemplarily showing a portion of the two-stage switch detection circuit on the PCB shown in FIG. 2, and FIG. 5A shows that the first-stage switch detection circuit and the second-stage switch detection circuit are separately provided. (5B) shows a circuit configured by combining the first-stage switch detection circuit and the second-stage switch detection circuit. FIG. 6 is a diagram illustrating an example of a multiplex circuit including a plurality of composite circuits illustrated in FIG. FIG. 7 is a flowchart (7A) showing a flow of processing for detecting the input of the first-stage switch and a hardware configuration (7B) for performing the processing. FIG. 8 shows the pressure-sensitive input device shown in FIG. 1, in which the conductive elastic body is incorporated in the housing while being in contact with the first contact electrode, cut along line AA in FIG. Sectional view (8A) of the conductive elastic body from the start of pressing until the second-stage switch is turned on when the contact rubber is already pushed in by 0.30 mm at the time of assembly. A graph (8B) showing a simulation of the load curve, a graph (8C) showing a simulation of the total load curve of the conductive elastic body and the contact in the same state, and a state where the contact rubber is already pushed in by 0.57 mm at the time of assembly In some cases, the graph (8D) showing the simulation of the load curve of the conductive elastic body from the start of pressing until the second-stage switch is turned on, and the conductivity in the same state It is a graph showing a simulation of a sum of the load curve of the elastic body and the contact (8E). 9 is a cross-sectional view (9A) of the pressure-sensitive input device according to the second embodiment taken along the line AA in FIG. 1 and the first contact on the printed circuit board. It is a top view (9B) of an electrode and the electrode for 2nd contacts. FIG. 10 is a cross-sectional view showing a state when the key top of the pressure-sensitive input device according to the second embodiment is pressed, and (10A) shows that the conductive elastic body is in contact with the first contact electrode. (10B) shows the state when the contact is further advanced and the contact is in contact with the second contact electrode. 11 is a cross-sectional view (11A) when the pressure-sensitive input device according to the third embodiment is cut along a line similar to the AA line in FIG. 1, and for the first contact on the printed circuit board. It is a top view (11B) of an electrode. 12 is a diagram showing a state when the key top of the pressure-sensitive input device shown in FIG. 13 is pressed, and is a cross-sectional view showing a state when the conductive elastic body contacts the first contact electrode. . FIG. 13 is a diagram showing a plurality of types of conductive elastic bodies prepared in the examples. FIG. 14 is a graph showing changes in electrical resistance when the load applied to the plurality of types of conductive elastic bodies shown in FIG. 13 is changed. FIG. 15 is a graph showing changes in electrical resistance when the load applied to various conductive elastic bodies having three types of outer diameters prepared in the example is changed. FIG. 16 is a view showing an example of the structure of a conventional pressure-sensitive input device using conductive rubber as a contact portion. (16A) is a sectional view of the conventional pressure-sensitive input device and its vicinity, and (16B) is a print. Plan views of contact electrodes on the circuit board are respectively shown.

Next, embodiments of the pressure-sensitive input device of the present invention will be described with reference to the drawings. The pressure-sensitive input device described below is an input device provided in an in-vehicle device, but this is only an example, and the pressure-sensitive input device is an in-vehicle or home audio device, a power window of an automobile, a camera, etc. It can be widely applied to input devices provided in fixed telephones, remote controllers of various devices, and the like.

1. First Embodiment A first embodiment of a pressure-sensitive input device is a two-stage switch including a switch that is turned on first on the inside and a switch that is turned on second on the outside. is there.

FIG. 1 is a plan view (1A) showing an example of a pressure-sensitive input device 1 and a housing 4 around it, and a partially exploded perspective view (1B) of the pressure-sensitive input device 1. 2 is a cross-sectional view (2A) of the pressure-sensitive input device 1 shown in FIG. 1 taken along line AA of FIG. 1 (1A), and the first contact electrode 50 on the printed circuit board 5 and It is a top view (2B) of the electrode 51 for 2nd contacts.

As shown in FIG. 1 (1B) and FIG. 2 (2A), the pressure-sensitive input device 1 according to the first embodiment includes a key top 2, a contact rubber 3 and A printed circuit board (Printed Circuit Board: PCB, hereinafter referred to as “PCB”) 5 is provided. Here, the key top 2 is not essential for the pressure-sensitive input device 1, and the upper portion of the contact rubber 3 can be exposed outside the housing 4, and the upper portion can be replaced with the key top 2.

(1) Key Top The key top 2 includes a protruding portion 21 that protrudes upward from a hole provided in the housing 4, and a flange portion 22 that is directly below the protruding portion 21 and below the housing 4. The flange portion 22 has a size that cannot pass through the hole of the housing 4. The key top 2 can be made of a resin such as a thermoplastic resin, a thermosetting resin, or an ultraviolet curable resin, a metal such as aluminum or stainless steel, glass, or ceramics.

(2) Contact Rubber The contact rubber 3 is a member that is disposed above the PCB 5 and can be elastically driven toward the surface of the PCB 5. The contact rubber 3 is made of an elastic material such as urethane resin, thermoplastic elastomer, silicone rubber, or natural rubber so that it can move in the vertical direction according to the presence or absence of pressure from the key top 2 or the size. . Among these materials, silicone rubber or urethane thermoplastic elastomer is preferable. Further, the contact rubber 3 may be composed of one kind of material, or may be composed of two or more kinds of materials. For fixing the key top 2 and the contact rubber 3 or fixing the contact rubber 3 and the PCB 5, any fixing method such as adhesion, thermal fusion, chemical welding, and fitting can be employed.

The contact rubber 3 includes, in order from the PCB 5 toward the key top 2, a fixed portion 31 fixed to the PCB 5, a dome 32 connected to the upper portion of the fixed portion 31, and a key top placement portion 33 connected to the upper portion of the dome 32. Is provided. The fixed part 31 has a substantially flat plate shape, and a central part thereof is hollow. The dome 32 is a thin-walled member having a shape that decreases in diameter from the inside of the fixed portion 31 toward the key top placement portion 33 located on the inside upper side. The dome 32 is designed to be able to bend toward the cavity of the fixed portion 31 under pressure from the key top 2. The key top placement portion 33 is a portion that has a substantially annular shape as viewed from above and that fixes the key top 2 on the upper surface thereof. However, the shape of the key top mounting portion 33 may not be a complete ring, but may be an arc shape lacking a part of a circle. Furthermore, it may be a square shape instead of a ring. Inside the dome 32 and below the key top placement portion 33, a movable portion 34 is formed that protrudes toward the PCB 5 and can move downward upon receiving a pressure from the key top 2. The shape of the movable portion 34 may also be an annular shape, an arc shape lacking a part of a circle, or a square shape when viewed from the plane. A contact 41 made of a conductive material is fixed to the lower end of the movable portion 34. The contact 41 can be formed by a plate or a thin film made of, for example, metal or carbon.

A thin support member 36 extending downward from the key top placement portion 33 and a disk-like floating portion 37 connected to the lower end of the support member 36 are formed further inside the movable portion 34. . The support member 36 and the floating portion 37 are formed in a state of being suspended from the keytop placement portion 33. Above the support member 36 and the floating portion 37, a space 35 is formed that is surrounded by the keytop placement portion 33 so as to surround the entire outer periphery or a part of the outer periphery. The space 35 has a shape that opens on the key top 2 side, but may be a closed space in which the key top 2 side is closed. Immediately below the floating portion 37, a conductive elastic body 40 that protrudes toward the first contact electrode 50 and has a shape that reduces the horizontal cross section toward the tip is fixed. Specifically, the conductive elastic body 40 is substantially hemispherical, and is fixed with its spherical bottom facing downward. One end of the conductive elastic body 40 is not limited to a substantially hemispherical shape, and may be a substantially cone or pyramid shape, or a trapezoidal shape in which only the tip of the substantially cone or pyramid is flattened. The conductive elastic body 40 is made of a material rich in elasticity so that it can be deformed after receiving pressure from the key top 2 side and contacting the PCB 5. In addition, a conductive material is dispersed in the conductive elastic body 40 in order to impart conductivity. Examples of the conductive material include carbon, metal, and the like, but carbon having a small particle diameter (nano-level particles) can be easily produced, and carbon that can be easily handled is more preferable. Moreover, as a base material (matrix) of the electroconductive elastic body 40, silicone rubber, urethane resin, thermoplastic elastomer, and natural rubber can be used, and among these, silicone rubber is preferable. The mixing amount of the conductive material is preferably 15 to 40% by weight based on the total weight of the insulating matrix and the conductive material from the viewpoint of enhancing the conductivity and maintaining the elasticity of the silicone rubber. Is more preferably 15 to 35% by weight.

The inner diameter of the fixing portion 31 is L (mm), the height from the upper surface of the PCB 5 when the key top 2 is not pressed to the upper surface of the key top mounting portion 33 is H1 (mm), and from the upper surface of the PCB 5 in the same state. The distance to the upper end of the dome 32 is H2 (mm), the distance from the lower surface of the contact 41 to the second contact electrode 51 of the PCB 5 in the same state is D (mm), and the lower surface of the conductive elastic body 40 in the same state to the PCB 5 If the distance to the first contact electrode 50 is d (mm), the inner member from the lower end of the dome 32 is in the range of L (mm), and H1 (mm)> H2 (mm)> D (Mm)> d (mm). Depending on the dimensional tolerance of the contact rubber 3 or the key top 2, d (mm) may be zero when the key top 2 is not pressed, but in this embodiment, d (mm) is an example. explain. That is, the conductive elastic body 40 is not in contact with the first contact electrode 50 on the PCB 5 in a state where the key top 2 is not pressed. Here, when the suitable dimension of the contact rubber 3 is illustrated, they are L = 13.5 mm, H1 = 3.0 mm, H2 = 2.5 mm, D = 1.1 mm, and d = 0.25 mm.

The support member 36 is a deformable member that supports the conductive elastic body 40, and moves the conductive elastic body 40 away from the PCB 5 after the conductive elastic body 40 contacts the first contact electrode 50. This is a member having a function of relaxing the load on the conductive elastic body 40. In order to sufficiently exhibit such a function, in the case of the switch driving unit 3 having various exemplary dimensions described above, the thickness (W) of the support member 36 is 0.05 to 0.25 mm. It is preferably 0.12 to 0.18 mm. Note that the object of the present invention can be achieved even if the support member 36 is a non-curved dome similar to the dome 32 and the dome 32 is curved so as to protrude upward.

(3) PCB
The PCB 5 is a plate-like substrate having conductive wiring, contact electrodes and the like on its surface. As a material for the PCB 5, for example, a highly insulating resin such as glass or polyimide resin, a ceramic such as AlN, or a composite material such as glass epoxy can be preferably used, but is not limited thereto. A highly conductive substrate such as a metal can be used for the PCB 5, but in that case, it is necessary to perform a surface treatment to ensure insulation at least around the wiring and contact electrodes.

2 types of contact electrodes are provided on the surface of the PCB 5, as shown in FIG. 2 (2B). One is a first contact electrode 50 disposed below the conductive elastic body 40 fixed to the contact rubber 3, and the other is a second contact electrode 51 disposed below the contact 41. It is. The first contact electrode 50 is composed of two first electrodes (in this embodiment, comb-shaped comb-shaped electrodes) 50a and 50b, and one comb tooth is arranged in a gap between the other comb teeth. The

first electrodes

50a and 50b are arranged in a non-contact state. The first contact electrode 50 has a function of reducing the electrical resistance between the

first electrodes

50 a and 50 b depending on the contact area with the conductive elastic body 40. The second contact electrode 51 is composed of two second electrodes (concentric electrodes in this embodiment) 51a and 51b, respectively, and one is placed in the other and arranged in a non-contact state. It is configured as follows. However, as for the first contact electrode 50 and the second contact electrode 51, the

first electrodes

50a and 50b and the

second electrodes

51a and 51b constituting the first contact electrode 50 and the

second contact electrodes

51a and 51b are formed in different shapes or different arrangements, or three or more You may make it comprise from this electrode. The position where the first contact electrode 50 is disposed is preferably a position where the bottom of the conductive elastic body 40 is in contact with the center thereof. Further, the second contact electrode 51 is disposed at a position where the contact 41 connects the gap between the

second electrodes

51a and 51b. The material of the first contact electrode 50 and the second contact electrode 51 is not limited to a specific material as long as it is a highly conductive material. However, copper, tungsten, Gold, aluminum and the like are particularly preferable. The first contact electrode 50 and the second contact electrode 51 can be formed by attaching a foil, forming a thin film such as CVD or PVD, or any other known method.

FIG. 3 is a cross-sectional view illustrating a state when the key top 2 of the pressure-sensitive input device 1 is pressed. FIG. 3A illustrates a state when the conductive elastic body 40 contacts the first contact electrode 50. , (3B) respectively show the state when the contact 41 contacts the second contact electrode 51.

When the conductive elastic body 40 is in contact with the first contact electrode 50, the key top 2 and the contact rubber 3 are moved downward from the state where the key top 2 is not pressed (the state indicated by the one-dot chain line of 3A). It is sinking and the dome 32 is partially buckled inside. When the key top 2 is further pressed from this state, the conductive elastic body 40 is crushed and the contact area with the first contact electrode 50 is increased. Thereby, the resistance between the

first electrodes

50a and 50b becomes smaller. When the conductive elastic body 40 is deformed excessively, the distance between the conductive particles (preferably, carbon particles here) is locally increased with the deformation, and the electric resistance of the conductive elastic body 40 is increased. . For this reason, before the excessive pressure is applied, the thin support member 36 is deformed. Thereby, a part (F) of the force applied to the conductive elastic body 40 can be released upward.

When the key top 2 is further pressed after the conductive elastic body 40 comes into contact with the first contact electrode 50, as shown in (3B), the state (3A) (the state indicated by the two-dot chain line in 3B) Then, the contact 41 that sinks further downward and is disposed on the outer peripheral side of the conductive elastic body 40 contacts the second contact electrode 51. As a result, the second-stage switch is turned on from off. From this state, the force pressed from the key top 2 can be received by the contact point 41, so that the support member 36 is hardly or not deformed thereafter.

FIG. 4 is a graph showing a simulation of a load curve from the start of pressing on the key top 2 until the second-stage switch is turned on. (4A) is a load curve of only the conductive elastic body 40. (4B) shows load curves obtained by combining both the conductive elastic body 40 and the contact point 41, respectively. In FIG. 2 (2A), the pressure-sensitive input device 1 has dimensions of L = 13.5 mm, H1 = 3.0 mm, H2 = 2.5 mm, D = 1.1 mm, and d = 0.25 mm. Since d = 0.25 mm exists, the initial pressing amount when the key top 2 is not pressed is 0 mm.

As shown in FIG. 4 (4A), the load on the conductive elastic body 40 becomes gentle after the pushing amount of 0.5 mm and is suppressed to about 150 g even when the pushing amount exceeds 1.25 mm. This is because the support member 36 is deformed and the load applied to the conductive elastic body 40 is relaxed. On the other hand, as shown in FIG. 4 (4B), the combined load of both the conductive elastic body 40 and the contact point 41 increases from the start of the pressing on the key top 2 (point P0). Although the conductive elastic body 40 increases after contact with the contact electrode 50 at a position (amount: 0.25 mm), the dome 32 is greatly buckled and reduced at a displacement of 0.45 mm (point P1). Thereafter, the contact 41 contacts the second contact electrode 51 at a displacement of 1.10 mm (point P2), and the load increases rapidly.

FIG. 5 is an electric circuit diagram exemplarily showing a part of the two-stage switch detection circuit on the PCB 5, and FIG. 5A shows that the first-stage switch detection circuit and the second-stage switch detection circuit are configured separately. The circuit (5B) shows a circuit configured by combining the first-stage switch detection circuit and the second-stage switch detection circuit.

As shown in (5A), in the first-stage switch detection circuit, the resistance between the

first electrodes

50a and 50b gradually decreases as the contact area between the conductive elastic body 40 and the first contact electrode 50 increases. This is a so-called analog circuit 60. On the other hand, the switch detection circuit in the second stage is a so-called digital circuit 70 in which the resistance between the

second electrodes

51 a and 51 b is rapidly reduced by the contact between the contact 41 and the second contact electrode 51. The analog circuit 60 includes a portion in which a variable resistor 61 formed by a contact portion of the conductive elastic body 40 to the

first electrodes

50a and 50b and a reference resistor 62 are connected in series. By providing the analog circuit 60 with the reference resistor 62, the value of the variable resistor 61 can be easily obtained from the measurement of the output voltage (VOut). When detecting the input of the first-stage switch by touching the key top 2, when the ratio (or difference) of the output voltages before and after the touch exceeds a preset threshold, the input of the first-stage switch Can be detected. On the other hand, the digital circuit 70 includes a portion in which a resistor 71 and an on / off switch 72 configured between the contact 41 and the second contact electrode 51 are connected in series. Only when the contact 41 short-circuits the second contact electrode 51, the input of the switch can be detected.

As shown in (5B), the composite circuit 80 is a circuit combining a first-stage switch detection circuit and a second-stage switch detection circuit. The composite circuit 80 is an on / off type constituted by a variable resistor 81 formed by a contact portion of the conductive elastic body 40 to the

first electrodes

50a and 50b, and the contact 41 and the second contact electrode 51. The switch 82 is arranged in parallel, and the parallel circuit includes a portion in which a reference resistor 83 is connected in series. The composite circuit 80 is advantageous in that it can detect a two-stage switch with a simple configuration as compared with the separate circuit shown in (5A). By measuring a single output voltage (VOut), the input of each switch can be determined. Also in the composite circuit 80, by providing the reference resistor 83, the detection of the first-stage switch can be accurately obtained for the same reason as described above. Further, when the switch 82 is turned on, the output voltage (VOut) rapidly decreases, so that the input of the second-stage switch can be detected.

FIG. 6 is a diagram illustrating an example of the multiplexing circuit 90 including a plurality of composite circuits.

When there are a plurality of pressure-sensitive input devices 1, a multiplexing circuit 90 shown in FIG. 6 can be formed. The multiplex circuit 90 includes a switch switching unit 93 before supplying a voltage to the parallel circuits 91a to 91e, and includes a reference resistor 92 as a common resistor for the parallel circuits 91a to 91e. The multiplexing circuit 90 detects one output voltage (VOut) at the intersection of the reference resistor 92 and the parallel circuits 91a to 91e. The detection of the output voltage is synchronized with the switch switching unit 93, and it is possible to recognize which parallel circuit 91a to 91e is supplied with the voltage. When such a multiplex circuit 90 is configured, even when there are many two-stage switches, it is possible to detect inputs of the two-stage switches of the plurality of pressure-sensitive input devices 1 in a resource-saving and space-saving manner. .

FIG. 7 is a flowchart (7A) showing a flow of processing for detecting the input of the first-stage switch and a hardware configuration (7B) for performing the processing.

A microcomputer 95 and a memory (Random Access Memory: RAM, Read Only Memory: ROM, etc.) 96 electrically connected to the analog circuit 60 and the digital circuit 70 described in FIG. 5 are arranged on the PCB 5. . However, the composite circuit 80 and the multiplexing circuit 90 described with reference to FIGS. 5 and 6 may be connected to the microcomputer 95 and the memory 96, respectively. The microcomputer 95 has a function of performing various arithmetic processes. The memory 96 stores various computer programs, and also stores computer programs for executing the processes shown in FIG. 7 (7A). The microcomputer 95 is a detection device that detects a pressing in the direction from the contact rubber 3 to the PCB 5. The microcomputer 95 reads the computer program stored in the memory 96 and switches the switch based on the electrical signal from the analog circuit 60. Can be detected. The microcomputer 95 determines whether or not the change in the electrical resistance of the analog circuit 60 exceeds a predetermined threshold, detects a press when determining that the change exceeds the threshold, and determines that the change does not exceed the threshold. Does not detect pressing. Specifically, the following processing is performed.

First, the microcomputer 95 monitors the output voltage from the analog circuit 60 and determines whether or not a change has occurred in the output voltage (step ST1). When there is a change in the output voltage, the microcomputer 95 calculates the ratio of the output voltage before and after touching the key top 2 or the ratio of the variable resistance value calculated from the ratio (step ST2). Next, the microcomputer 95 determines whether or not the above ratio exceeds a threshold value stored in advance in the memory 96 (step ST3). If the ratio exceeds the threshold value as a result of the determination in step ST3, the microcomputer 95 determines that the first-stage switch has been pressed, and outputs a pressing signal (step ST4). On the other hand, if the above ratio does not exceed the threshold value as a result of the determination in step ST3, the microcomputer 95 determines that the first-stage switch has not been pressed, and proceeds to step ST1 without proceeding to step ST4. Return. The microcomputer 95 may be referred to as a central processing unit (CPU). Further, the ratio of the output voltages in step ST2 or the ratio of the variable resistance values calculated therefrom may be the difference of the output voltages or the difference of the variable resistance values calculated therefrom.

As described above, by performing the process of determining whether or not there is an input to the switch in the analog circuit 60 based on the relative value before and after touching the key top 2, it is possible to effectively prevent an input detection malfunction. Considering each dimensional tolerance of the key top 2 or the contact rubber 3 that makes the gap between the key top 2 and the housing 4 zero or extremely small, the contact is made with the pressure-sensitive input device 1 incorporated in the housing 4. The rubber 3 can be in a slightly pressed state. In this case, the conductive elastic body 40 is often in contact with the first contact electrode 50. In such a situation, for example, if the switch input is detected based on the output voltage or the absolute value of the variable resistance, the minimum resistance value in a state where the conductive elastic body 40 and the first contact electrode 50 are in contact with each other. Must be the threshold. Otherwise, it may be determined that the switch is input even though the key top 2 is not pressed. However, if the presence or absence of switch input is determined based on the relative values before and after the touch, the key top 2 can be used regardless of the resistance value when the pressure-sensitive input device 1 is incorporated in the housing 4. Since the resistance value when pressed is always lower, malfunctions can be reduced.

FIG. 8 shows the pressure-sensitive input device 1 shown in FIG. 1, in which the conductive elastic body 40 is incorporated in the housing 4 in a state where it is in contact with the first contact electrode 50, as shown in FIG. Sectional view when cut by line (8A) and when the contact rubber 3 is already pushed in at 0.30 mm at the time of assembly until the second switch is turned on The graph (8B) showing the simulation of the load curve of the conductive elastic body 40, the graph (8C) showing the simulation of the total load curve of the conductive elastic body 40 and the contact 41 in the same state, and the contact rubber 3 already in the assembly. Shows a simulation of the load curve of the conductive elastic body 40 from the start of pressing until the second switch is turned on. Off and (8D), a graph (8E) showing simulation of a sum of the load curve of the conductive elastic body 40 and the contact 41 in the same state.

As shown in FIG. 8 (8 A), when the pressure-sensitive input device 1 is assembled in the housing 4, the conductive elastic body 40 is already on the PCB 5 due to the dimensional tolerance or assembly state of the constituent members such as the key top 2. There is a case where the contact electrode 50 is in contact. In such a case, the conductive elastic body 40 is already crushed. However, since the support member 36 is deformed by pressing the key top 2 and an excessive load is not applied to the conductive elastic body 40, it is effective that the electric resistance between the

first electrodes

50a and 50b is saturated. Therefore, it is possible to accurately detect the input of the switch.

In the pressure-sensitive input device 1, in (8B), (8C), (8D), and (8E), L = 13.5 mm, H1 = 3.0 mm, H2 = 2.5 mm, D = 1.1 mm, d = Each dimension is 0 mm. That is, there is no gap (d) between the conductive elastic body 40 and the first contact electrode 50.

When the contact rubber 3 is already pushed in by 0.30 mm at the time of assembling, as shown in FIG. 8 (8B), the load on the conductive elastic body 40 gradually decreases after the pushing amount of 0.5 mm. Therefore, even if the push-in amount exceeds 1.25 mm, it is suppressed to about 150 g. This is because the support member 36 is deformed and the load applied to the conductive elastic body 40 is relaxed. On the other hand, the combined load of both the conductive elastic body 40 and the contact 41 shown in FIG. 8 (8C) increases rapidly from the start of pressing the key top 2 (point P0), and the displacement is 0.45 mm. At (point P1), the dome 32 is greatly buckled and becomes smaller. Thereafter, the contact 41 contacts the second contact electrode 51 at a displacement of 1.10 mm (point P2), and the load increases rapidly. Further, when the contact rubber 3 is already pushed in by 0.57 mm at the time of assembling, as shown in FIG. 8 (8D), the load on the conductive elastic body 40 is as follows. Even if the push-in amount exceeds 1.25 mm, the pressure is reduced to about 150 g. On the other hand, the combined load of both the conductive elastic body 40 and the contact 41 shown in FIG. 8 (8E) rises immediately after the start of pressing on the key top 2 (point P0 = 0.57 mm) (point P1). ) Since the dome 32 is already buckled, the load decreases thereafter. Thereafter, the contact 41 contacts the second contact electrode 51 at a displacement of 1.10 mm (point P2), and the load increases rapidly.

2. Second Embodiment A second embodiment of the pressure-sensitive input device is a two-stage switch similar to the first embodiment, except that the first input to the outside is the second switch inside. It is a form provided with the switch inputted into.

9 is a cross-sectional view (9A) of the pressure-sensitive input device 1 taken along the line AA in FIG. 1, and the first contact electrode 50 and the second contact on the printed circuit board 5. It is a top view (9B) of the electrode 52 for an object.

As shown in FIG. 9 (9A), the pressure-sensitive input device 1 according to the second embodiment has a configuration in which the key top 2, the contact rubber 100, and the PCB 5 are stacked in order from the top to the inside of the housing 4. Prepare. Since the key top 2 has a form common to the first embodiment, a duplicate description is omitted here.

(1) Contact Rubber Each fixing method of the contact rubber 100 and the key top 2 or the PCB 5 and the constituent material of the contact rubber 100 are the same as those in the first embodiment. The contact rubber 100 is connected to the fixed part 101 fixed to the PCB 5, the dome 102 connected to the upper inner side of the fixed part 101, the movable part 103 connected to the upper inner side of the dome 102, and the upper part from the movable part 103. A key top placement unit 105 is provided. The key top placement portion 105 is disposed substantially at the center on the plane of the contact rubber 100.

The fixing part 101 has a substantially flat plate shape, and its central part is hollow. The dome 102 is a thin-walled member having a shape that decreases in diameter toward the movable portion 103 from the inside of the cavity of the fixed portion 101 toward the movable portion 103, and can be bent inward when receiving a load from the key top 2. Designed. The movable portion 103 has a substantially cylindrical shape and has a shape that decreases in diameter toward the lower side, and is movable downward when the key top 2 is pushed in. The movable portion 103 has a substantially cylindrical shape, and is arranged in a suspended state while being connected to the dome 102 and the dome 104. A substantially hemispherical conductive elastic body 111 is fixed at a position above each first contact electrode 50 at the lower end of the movable portion 103 so that the spherical bottom portion faces downward. The constituent material of the conductive elastic body 111 and the conductive material kneaded therewith are the same as those of the conductive elastic body 40 described in the first embodiment, and therefore redundant description is omitted here.

The dome 104 is a thin-walled member having a shape that decreases in diameter from the inside of the movable portion 103 toward the keytop placement portion 105 toward the inside of the keytop, and presses the keytop 2 to form a conductive elastic body. It is designed such that 111 can be bent inward after contacting the first contact electrode 50 on the PCB 5. The dome 104 needs to be designed to bend without resisting the pressing on the key top 2 after the conductive elastic body 111 contacts the first contact electrode 50. On the other hand, the dome 102 needs to be designed to facilitate the lowering of the movable portion 103 after the key top 2 starts to be pressed. Accordingly, the dome 102 is designed to bend more easily than the dome 104. For this purpose, for example, the dome 104 is preferably designed to be thicker than the dome 102 or configured to have a larger angle from the horizontal plane. Further, the

domes

102 and 104 are deformed upward so that an excessive load is not applied to the conductive elastic body 111 after the conductive elastic body 111 contacts the first contact electrode 50 on the PCB 5. It is a member having a function of releasing That is, the

domes

102 and 104 are deformable members that support the conductive elastic body 111, and after the conductive elastic body 111 contacts the first contact electrode 50, the conductive elastic body 111 is separated from the PCB 5. It corresponds to a support member that moves in the direction to relieve the load on the conductive elastic body 111. In order to sufficiently exhibit the function as the support member, after the conductive elastic body 111 comes into contact with the first contact electrode 50, the thickness or the material is easily deformed in response to the pressing from the key top 2. It is preferable to comprise.

The key top mounting part 105 is substantially cylindrical and has a small diameter slightly downward. A contact 110 is fixed to the lower end of the key top placement portion 105. The contact 110 can be formed of, for example, a metal or carbon plate or a thin film. The distance from the lower surface of the contact 110 to the second contact electrode 52 of the PCB 5 when the key top 2 is not pressed is D (mm), and the first contact electrode of the PCB 5 from the lower surface of the conductive elastic body 110 in the same state. When the distance up to 50 is d (mm), the relationship is D (mm)> d (mm). d (mm) may not exist in a state where the key top 2 is not pressed, but exists in this embodiment. That is, the conductive elastic body 110 is not in contact with the first contact electrode 50 on the PCB 5 when the key top 2 is not pressed.

(2) PCB
The PCB 5 is a plate-like substrate having conductive wiring, contact electrodes and the like on its surface. Since the material of the PCB 5 is the same as that of the first embodiment, a duplicate description is omitted here. On the surface of the PCB 5, as shown in FIG. 9 (9B), two types of contact electrodes are provided. One is the first contact electrode 50 disposed below the conductive elastic body 111 in the contact rubber 100, and the other is the second contact electrode 52 disposed below the contact 110. The first contact electrode 50 includes comb-shaped

first electrodes

50a and 50b similar to those in the first embodiment. The second contact electrode 52 includes a circular second electrode 52a and a point-shaped second electrode 52b disposed therein. The

second electrodes

52a and 52b are disposed on the PCB 5 in a non-contact state. However, the first contact electrode 50 and the second contact electrode 52 may have shapes and arrangements other than those described above. For example, the second contact electrode 52 may be composed of two half-moon shaped electrodes arranged in a non-contact state. The position where the first contact electrode 50 is disposed is preferably a position where the bottom of the conductive elastic body 111 is in contact with the center thereof. The second contact electrode 52 is disposed at a position where the contact 110 connects the gap between the

second electrodes

52a and 52b. The material for the first contact electrode 50 and the second contact electrode 52 is not limited to a specific material as long as it is a highly conductive material. However, copper, tungsten, gold, aluminum, etc. may be used because of the ease of electrode formation. Particularly preferred. The first contact electrode 50 and the second contact electrode 52 can be formed by attaching a foil, forming a thin film such as CVD or PVD, or any other known method.

FIG. 10 is a cross-sectional view illustrating a state when the key top 2 of the pressure-sensitive input device 1 according to the second embodiment is pressed, and FIG. 10A illustrates the conductive elastic body 111 as the first contact electrode. (10B) shows the state when the contact 110 is in contact with the second contact electrode 52 by further proceeding.

When the conductive elastic body 111 is in contact with the first contact electrode 50, the key top 2 and the contact rubber 100 are entirely downward from a state where the key top 2 is not pressed (a state indicated by a one-dot chain line in 10A). It is sinking and the dome 102 is partially buckled inside. When the key top 2 is further pressed from this state, the conductive elastic body 111 is crushed and the contact area with the first contact electrode 50 is increased. Thereby, the resistance between the

first electrodes

50a and 50b becomes smaller. Thereafter, the dome 102 and the dome 104 are deformed so that an excessive load is not applied to the conductive elastic body 111, and thereby a part (F) of the force applied to the conductive elastic body 111 can be released upward. .

When the key top 2 is continuously pressed after the conductive elastic body 111 contacts the first contact electrode 50, as shown in (10B), the key top 2 and the contact rubber 100 are in the state (10B) (10B). It sinks further downward from the state indicated by the two-dot chain line. And the contact 110 arrange | positioned inside the electroconductive elastic body 111 contacts

2nd electrode

52a, 52b. As a result, the second-stage switch is turned on from off. From this state, the force pressed from the key top 2 can be received by the contact 110, so that the

domes

102 and 104 are hardly or not deformed thereafter.

3. Third Embodiment The third embodiment of the pressure-sensitive input device is a one-stage switch, unlike the first and second embodiments.

11 is a cross-sectional view (11A) of the pressure-sensitive input device 1 taken along the line AA in FIG. 1 and a plan view of the first contact electrode 50 on the printed circuit board 5 (FIG. 11). 11B).

As is clear from comparison between FIG. 11 and FIG. 2, the pressure-sensitive input device 1 according to this embodiment excludes the structure related to the second-stage switch from the pressure-sensitive input device 1 according to the first embodiment. It is what. Specifically, the pressure-sensitive input device 1 according to this embodiment includes a movable part 34, a contact 41 just below it, and a second on the PCB 5 provided in the pressure-sensitive input device 1 according to the first embodiment. The two-contact electrode 51 is not provided.

Since the key top 2 has a form common to the first embodiment, a duplicate description is omitted here. Each fixing method of the contact rubber 200 and the key top 2 or the PCB 5 and the constituent material of the contact rubber 200 are the same as in the first embodiment. The contact rubber 200 includes a fixing part 201 fixed to the PCB 5, a dome 202 connected to the upper inner side of the fixing part 201, a key top mounting part 203 connected to the upper inner side of the dome 202, and a key top mounting part 203. A thin-walled support member 206 extending downward from the inside of the disk and a disk-shaped floating portion 207 connected to the lower end of the support member 206. A space 205 is formed above the support member 206 and the floating portion 207 so as to be surrounded by the key top placement portion 203 around the entire outer periphery or a part of the outer periphery. Immediately below the floating portion 207, a substantially hemispherical conductive elastic body 40 is fixed with its spherical bottom facing downward. The conductive elastic body 40 is disposed above the first contact electrode 50. The fixed portion 201, the dome 202, the key top placement portion 203, the support member 206, the floating portion 207, and the conductive elastic body 40 are the fixed portion 31, the dome 32, and the key top placement portion described in the first embodiment. 33, the support member 36, the floating portion 37, and the conductive elastic body 40 are common to each other, and a duplicate description thereof will be omitted. The PCB 5 is provided with a first contact electrode 50 as shown in FIG. 11 (11B). Since this first contact electrode 50 is also common to the first contact electrode 50 described in the first embodiment, a duplicate description thereof is omitted.

FIG. 12 is a view showing a state when the key top 2 of the pressure-sensitive input device 1 is pressed, and is a cross-sectional view showing a state when the conductive elastic body 40 contacts the first contact electrode 50. .

When the conductive elastic body 40 is in contact with the first contact electrode 50, the key top 2 and the contact rubber 200 are generally lowered from the state where the key top 2 is not pressed (the state indicated by the one-dot chain line in FIG. 12). The dome 202 is partially buckled inside. When the key top 2 is further pressed from this state, the conductive elastic body 40 is crushed and the contact area with the first contact electrode 50 is increased. Thereby, the resistance between the

first electrodes

50a and 50b becomes smaller. When the conductive elastic body 40 is deformed excessively, the distance between the conductive particles (preferably, carbon particles here) is locally increased with the deformation, and the electric resistance of the conductive elastic body 40 is increased. . Therefore, the thin support member 206 is deformed before an excessive load is applied to the conductive elastic body 40. Thereby, a part (F) of the force applied to the conductive elastic body 40 can be released upward.

Hereinafter, examples of the present invention will be described. However, the present invention is not limited to the examples described below.

(Experiment 1: Examination of shape of conductive elastic body)
In the pressure-sensitive input device 1 according to the first embodiment (see FIGS. 1 and 2), the shape of the conductive elastic body 40 is preferably investigated. Specifically, the difference in displacement of the electric resistance can be sufficiently detected within a range where the load does not exceed 10 N (preferably up to 6 N), and the electric resistance rapidly decreases as the load increases. The shape of the conductive elastic body 40 that satisfies the condition of “not present” was examined. In FIG. 2 (2A), L = 13.5 mm, H1 = 3.0 mm, H2 = 2.5 mm, D = 1.1 mm, and d = 0.25 mm. Further, the initial pressing amount when the key top 2 was not pressed was 0 mm.

The conductive elastic body 40 was produced by the following method. Conductivity with a specific volume resistivity of about 5 ohms by blending 60 parts by weight of silicone rubber compound (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KE 951-U) with 40 parts by weight of acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd.) A rubber master batch (manufactured by Shin-Etsu Polymer Co., Ltd., product name: 87C40P-1) was prepared. 50 parts by weight of this conductive rubber masterbatch and 50 parts by weight of an insulating silicone rubber compound (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KE 961-U) are kneaded to produce a conductive rubber of 20% by weight of carbon black. did. Next, various molds were prepared so that one end had a spherical shape, a flat surface, a conical shape, and a trapezoidal shape, and the conductive rubber was molded to produce conductive elastic bodies 40 having various tip shapes.

FIG. 13 is a diagram showing a plurality of shapes of the conductive elastic body 40. FIG. 14 is a graph showing changes in electrical resistance when the load applied to the plurality of types of conductive elastic bodies 40 shown in FIG. 13 is changed. The horizontal axis of the graph is the load, and the vertical axis is the electrical resistance. The electrode with which the conductive elastic body 40 was brought into contact was the first contact electrode 50. The load and electric resistance were measured by a method of displacing the conductive elastic body 40 at a speed of 1.0 mm / sec using a load measuring machine.

Except for “A3”, various heights of the conductive elastic bodies 40 having the same overall height and one end having a spherical shape, a substantially planar shape, a conical shape, and a trapezoidal shape were prepared. There are three types of conductive elastic bodies 40 having a spherical shape at one end: “A1”, “A2”, and “A3”. “A1” is a conductive elastic body having an overall height of 0.50 mm, a diameter of 2.50 mm, a cylindrical portion height of 0.15 mm, and a spherical portion height of 0.35 mm. “A2” is a conductive elastic body having a total height of 0.50 mm, a diameter of 3.50 mm, a cylindrical portion height of 0.15 mm, and a spherical portion height of 0.35 mm. “A3” is a conductive elastic body having an overall height of 0.30 mm, a diameter of 2.50 mm, a cylindrical portion height of 0.15 mm, and a spherical portion height of 0.15 mm. There are two types of conductive elastic bodies 40 whose one ends are substantially planar, “B1” and “B2”. “B1” is a conductive elastic body having an overall height of 0.50 mm, a diameter of 2.50 mm, a cylindrical portion height of 0.40 mm, and a spherical portion height of 0.10 mm. “B2” is a conductive elastic body having an overall height of 0.50 mm, a diameter of 3.50 mm, a cylindrical portion height of 0.40 mm, and a spherical portion height of 0.10 mm. There are four types of conductive elastic bodies 40 having a conical shape at one end: “C1”, “C2”, “D1”, and “D2”. “C1” is a conductive elastic body having a total height of 0.50 mm, a diameter of 2.50 mm, a height of the cylindrical portion of 0.15 mm, and a height of the conical portion of 0.35 mm. “C2” is a conductive elastic body having a total height of 0.50 mm, a diameter of 3.50 mm, a cylindrical portion height of 0.15 mm, and a conical portion height of 0.35 mm. “D1” is a conductive elastic body having a total height of 0.50 mm, a diameter of 2.50 mm, a height of the cylindrical portion of 0.10 mm, and a height of the conical portion of 0.40 mm. “D2” is a conductive elastic body having an overall height of 0.50 mm, a diameter of 3.50 mm, a height of the cylindrical portion of 0.10 mm, and a height of the conical portion of 0.40 mm. The conductive elastic body 40 having a trapezoidal tip is only “E”. “E” is a conductive elastic body having a total height of 0.50 mm, a diameter of 2.50 mm, a height of the cylindrical portion of 0.10 mm, a height of the conical portion of 0.40 mm, and a diameter of the flat portion of the tip of 0.50 mm.

Comparing the load-resistance curves of the ten types of conductive elastic bodies 40, the ones close to the ideal curves in which the resistance gradually decreases with increasing load are shown as “A1” and “A1” shown in FIG. A2 "and" A3 ". Next, “C1”, “C2”, “D1”, and “D2” shown in FIG. 14 (14C) are ideal. Next was “B1” and “B2” shown in FIG. 14 (14B) and “E” shown in FIG. 14 (14D). As a result, the conductive elastic body 40 more preferable for realizing the variable resistance function has a tip portion having a spherical surface or a spire shape, and there is a position (displacement amount) where the resistance decrease greatly changes when the tip becomes a flat surface. It has been found that the parts tend to be relatively inferior to those of spherical or steeple shapes.

(Experiment 2: Examination of outer diameter of conductive elastic body)
Using the conductive rubber produced in Experiment 1, the outer diameter was changed to three types of 5.0 mm, 3.0 mm, and 2.5 mm in the same form as the conductive elastic body “A1” having one spherical surface. The conductive elastic body 40 was produced, and the change in electrical resistance when the load applied to the various conductive elastic bodies 40 was changed was examined. As the preferred outer shape of the conductive elastic body 40, as in Experiment 1, it is possible to sufficiently detect the difference in displacement of the electric resistance within the range where the load does not exceed 10N (preferably up to 6N), and the load The outer shape of the conductive elastic body 40 that satisfies the condition that there is no sudden decrease in electrical resistance with respect to the increase was adopted. The method for changing the load is the same as in Experiment 1.

FIG. 15 is a graph showing changes in electrical resistance when the load applied to various conductive elastic bodies 40 having three types of outer diameters of 5.0 mm, 3.0 mm, and 2.5 mm is changed. is there. The horizontal axis of the graph is the load, and the vertical axis is the electrical resistance.

As shown in FIG. 15, at any outer diameter, there was no sudden decrease in electrical resistance with respect to the increase in load. The conductive elastic body 40 having an outer diameter of 5.0 mm and an outer diameter of 3.0 mm has a larger electric resistance than the conductive elastic body 40 having an outer diameter of 2.5 mm even in a small load region (100 to 200 grams). It was found that the electric resistance difference with respect to the load increase can be clearly detected in this region. In particular, the conductive elastic body 40 having an outer diameter of 3.0 mm has a larger electric resistance in a region where the load is smaller than the conductive elastic body 40 having an outer diameter of 5.0 mm, and confirms a relatively good change in the electric resistance. I was able to.

(Experiment 3: Examination of thickness of support member)
A plurality of types of contact rubbers 3 with different thicknesses (W) of the support members 36 are prepared by molding, and conductive elastic bodies 40 having a spherical shape at one end and an outer diameter of 3 mm are provided on the floating portions 37 of the various contact rubbers 3. Attached. Next, when the contact rubber 3 is pressed from above at a speed of 1 mm / sec and is driven from 0 to 1.5 mm, the load applied to the conductive elastic body 40 is changed, and the driving is performed from 1.5 to 2.0 mm. The change in the load applied to the conductive elastic body 40 was examined. The results are shown in Table 1. The evaluation results in the table have three levels. The level that can be used but the electrical resistance may become unstable with respect to the load is “1”. The level that was stable or slightly difficult to transmit the load was set to “2”, and the level that could be used satisfactorily without any problem was set to “3”. And the level which cannot be used was set as no evaluation.

As shown in Table 1, it was found that the best thickness (W) for use of the support member 36 was 0.15 mm. The change in the electric resistance with respect to the load was slow, and even when it was movable 2 mm, the displacement of the electric resistance could be detected sufficiently. Next, the favorable thickness (W) was 0.10 mm and 0.20 mm. When the thickness (W) was 0.10 mm, the electric resistance was slightly unstable at the initial stage of movement, but the change in electric resistance with respect to the load was stably reduced in the subsequent movable range. Further, when the thickness (W) is 0.20 mm, the difference in displacement of the electric resistance can be sufficiently detected, but there is a load region in which the electric resistance slightly decreases. Finally, when the thickness (W) at level 1 is 0.05 mm and 0.25 mm, the load is not easily transmitted to the contacts to some extent, or a sudden change in electrical resistance is observed. Although it was a little inferior to the thing of 2, it turned out that it is the level which can be used.

The present invention can be used for switches of various devices including in-vehicle devices.

1 Pressure-sensitive input device 3 Contact rubber 5 PCB (printed circuit board)
36 support member 40 conductive elastic body 41 contact point (conductor)
50 First contact electrode 50a First electrode 50b First electrode 51 Second contact electrode

51a Second electrode

51b Second electrode 52 Second contact electrode

52a Second electrode

52b Second electrode 60 Analog circuit 70 Digital circuit 72 ON / Off-type switch 80 composite circuit 95 microcomputer (detection device)
100 Contact rubber 102 Dome (support member)
104 Dome (support member)
111 Conductive elastic body 110 Contact point (conductor)
200 Contact rubber 206 Support member

Claims

A printed circuit board having at least a first contact electrode composed of a plurality of first electrodes spaced apart from each other;
A contact rubber disposed above the printed circuit board and elastically driven toward the surface of the printed circuit board;
A detection device for detecting a pressure in the direction of the printed circuit board from the contact rubber;
A pressure-sensitive input device comprising:
The contact rubber is
A conductive elastic body provided above the first contact electrode and projecting toward the first contact electrode and having a shape that reduces the horizontal cross section toward the tip;
A deformable member that supports the conductive elastic body, and after the conductive elastic body contacts the first contact electrode, the conductive elastic body is moved away from the printed circuit board. A support member that relaxes the load on the conductive elastic body;
With
The first contact electrode has a function of reducing the electrical resistance between the first electrodes depending on the contact area with the conductive elastic body,
The detection device determines whether or not the change in the electrical resistance exceeds a predetermined threshold, detects a press when it is determined that the threshold is exceeded, and detects the press when it is determined that the threshold is not exceeded. A pressure-sensitive input device that is not detected.
The conductive elastic body has a space between the contact rubber and the first contact electrode in a non-contact state when the contact rubber is not pushed down toward the printed circuit board. The pressure-sensitive input device according to claim 1, wherein the pressure-sensitive input device is provided.
In addition to the first contact electrode, the printed circuit board further includes a second contact electrode composed of a plurality of second electrodes spaced apart from each other,
The contact rubber includes a conductor above the second contact electrode, the conductor being separated by a distance larger than the distance between the conductive elastic body and the first contact electrode,
The detection device detects the next press when the conductor and the second contact electrode come into contact with each other by further pressing after the contact between the conductive elastic body and the first contact electrode. The pressure-sensitive input device according to claim 1 or 2, wherein
In the contact rubber, the conductive elastic body is provided inside the conductor,
The pressure-sensitive input device according to claim 3, wherein the first contact electrode is provided inside the second contact electrode in the printed circuit board.
In the case of configuring an on / off switch of a digital circuit between the conductor and the second contact electrode,
The printed circuit board includes a composite circuit obtained by electrically combining an analog circuit having a variable resistor configured between the conductive elastic body and the first contact electrode and the digital circuit.
5. The pressure-sensitive input device according to claim 3, wherein the detection device detects each pressing of the first stage and the second stage based on a single output voltage obtained from the composite circuit. .