JPH0917276A - Pressure sensitive sensor - Google Patents

Abstract

PURPOSE: To widen a detectable load region, and provide almost straight, good load-electric resistance value characteristics by installing a movable sheet member, a buffer material, and a movable cover member. CONSTITUTION: When a load (pressing force) is applied to a movable cover member 7 which covers a spacer 4, a movable sheet member 5 and a buffer material 6, and whose peripheral is bonded to a surface of a substrate 2, the load is transmitted from the cover member 7 to a pressure sensitive conductive member 3 through the buffer material 6 and the sheet member 5. The member 3 is compressed and deformed, electric resistance change is produced, the electric resistance change is taken in with two electrodes 1a, 1b, and based on change in electric resistance value, the load applied to the member 7 is detected. Since the load applied to the member 7 is buffered and dispersed with the material 6, further dispersed uniformly with the member 5, and gently transmitted to the member 3, the electric resistance value of the member 3 is not decreased sharply even in a low load region. Detecting characteristics of a pressure sensitive sensor are extremely enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure-sensitive sensor which is soft to the touch with a finger and whose sensitivity changes in a substantially linear manner. The present invention relates to a pressure sensor for use as an input unit.

[0002]

2. Description of the Related Art Conventionally, a pressure-sensitive conductive material having a characteristic that an electric resistance value is lowered due to a compressive deformation caused by a pressing force has been known. This type of pressure-sensitive conductive material is one in which conductive particles such as metal or carbon are mixed and dispersed in an insulator such as rubber or elastomer, and when no pressure is applied, the individual conductive particles are separated from each other. Although they are separated and electrically insulated, in a state in which they are continuously applied with pressure to cause compressive deformation, individual conductive particles approach or contact each other, causing the electrical resistance value to gradually decrease. Is.

The pressure-sensitive conductive material having the above characteristics is used as sensors and switches in various fields. To give an example, a conductive electrode is attached to both sides in the thickness direction of a pressure-sensitive conductive rubber formed into a flat plate shape or a rectangular parallelepiped shape, and the electric resistance change due to compressive deformation is taken out from this electrode. There is a sensor.

As an improved sensor, for example, according to Japanese Patent Laid-Open No. 61-78101, a pair of electrodes are provided in a non-contact state on one surface of a pressure-sensitive conductive rubber having a uniform thickness. At the same time, an electrode is provided on the other surface so as to face both of the pair of electrodes, and a change in electrical resistance due to compressive deformation occurring in the thickness direction is taken out from the pair of electrodes on one side.

Further, in Japanese Utility Model Laid-Open No. 53-32366, a pressure-sensitive conductive rubber having a rectangular cross section is interposed between a support and a pressure member which are arranged in parallel with each other, and A pair of electrode plates insulated from each other is provided between the conductive rubber and the support, and a change in electrical resistance due to compressive deformation when pressure is applied to the pressure-sensitive conductive rubber from the pressure member. There is disclosed a pressure-sensitive switch configured to take out by the pair of electrode plates.

[0006]

However, in any of the above-mentioned conventional examples, since the pressure-sensitive conductive rubber is compressed and deformed by using a resin or a pressing body having a slight elasticity, the pressure-sensitive conductive rubber is obtained. The effect of compressive elastic deformation and compression set characteristic peculiar to the above was remarkably shown in the electric resistance change. That is, in FIG. 8 showing the relationship between the load applied to the pressure-sensitive conductive rubber and the electric resistance value, as shown by A in the load-electric resistance value characteristic of the conventional example, the electric resistance value rapidly increases in the low load region. Fall,
Since the electric resistance value becomes saturated in a relatively low load range (the electric resistance value hardly decreases even when the load increases),
The detectable load region is limited to a narrow range, and even in the detectable low load region, there is a problem that a correction circuit needs to be assembled because the change in the electrical resistance value is excessively rapid. On the other hand, when the sensitivity of the pressure-sensitive conductive rubber is reduced, the load region that can be detected is widened, but the problem of the decrease in detection accuracy cannot be avoided.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above problems and provides a pressure-sensitive sensor which has a wide detectable load region and which is substantially linear and has good load-electric resistance value characteristics. It is an object. Therefore, in the pressure-sensitive sensor according to claim 1, a substrate on the surface of which two electrodes are provided in a non-contact state with each other, a pressure-sensitive conductive member disposed on the two electrodes on one surface side, A spacer provided on the surface of the substrate so as to surround the periphery of the piezoelectric conductive member with a predetermined gap therebetween, facing the other surface side of the pressure-sensitive conductive member,
A flexible sheet member having a peripheral portion of one surface thereof supported by the spacer, a cushioning material disposed on the other surface of the flexible sheet member, the spacer, the flexible sheet member, and A flexible cover member is provided, which is covered with a cushioning material and whose peripheral portion is joined to the surface of the substrate.

According to another aspect of the pressure-sensitive sensor of the present invention, a substrate having two electrodes provided in a non-contact state on the surface of the substrate and a surface of the substrate so as to surround the two electrodes with a predetermined gap therebetween. A spacer provided, a pressure-sensitive conductive member whose one surface faces the two electrodes, and a peripheral edge portion of the one surface supported by the spacer, and the other surface of the pressure-sensitive conductive member. A flexible sheet member, a cushioning material disposed on the flexible sheet member, the spacer,
The pressure-sensitive conductive member, the flexible sheet member, and the cushioning material are covered, and a flexible cover member having a peripheral edge portion joined to the surface of the substrate is provided.

According to a third aspect of the present invention, in the pressure sensitive sensor according to the first or second aspect, the flexible sheet member is made of a thin resin material such as a polyester film having a thickness of about 0.1 mm and has a spring property. It is characterized by being made of an insulating plate.

According to a fourth aspect of the present invention, in the pressure sensitive sensor according to the first or second aspect, the flexible sheet member is made of a thin resin material such as a polypropylene film having a thickness of about 0.2 mm and has a spring property. It is characterized by being made of an insulating plate.

According to a fifth aspect of the present invention, in the pressure-sensitive sensor according to any one of the first to fourth aspects, the cushioning material is formed of various sponge rubber-based, urethane sponge-based, or fluorine sponge-based molding made of foamed material of various rubbers. It is characterized by being made of an elastic material such as a product or various sponge rubbers obtained by die punching, urethane sponge rubbers and the like.

According to a sixth aspect of the present invention, in the pressure-sensitive sensor according to any of the first to fourth aspects, the cushioning material is made of an elastic material such as rubber or thermoplastic elastomer.

[0013]

In the structure of claim 1, when a load (pressure) is applied to the cover member, this load is transmitted from the cover member to the pressure-sensitive conductive member via the cushioning member and the flexible sheet member, and the pressure-sensitive member is pressed. The electric resistance changes due to the conductive member being compressed and deformed. This change in electric resistance is taken out by the two electrodes, and the magnitude of the load applied to the cover member is detected based on the change in the electric resistance value.

In that case, the load applied to the cover member is dispersed by being buffered by the cushioning material, and the dispersed load is further uniformly dispersed by the flexible sheet member, so that the pressure-sensitive conductive member is dispersed. Since it is transmitted gently, unlike the prior art, the electric resistance value of the pressure-sensitive conductive member does not drop sharply even in the low load region, and the saturation point of the electric resistance value moves to the high load region side. The detectable load area is expanded, and the change in the electric resistance value becomes substantially linear in the entire detectable load area. As a result, the detection characteristic of the pressure sensitive sensor becomes extremely good.

When the pressure applied to the cover member is released, the repulsive force of the flexible sheet member causes the cushioning material to return to the unloaded position, so that compression permanent strain of the cushioning material is less likely to occur. Further, the flexible sheet member protects the pressure-sensitive conductive member from various chemicals, gas, etc. generated from a rubber cover member or penetrating through the cover member from the outside of the cover member, Prevents deterioration of the pressure-sensitive conductive member due to gas or the like.

In the unloaded state, the spacer supports the peripheral portion of the flexible sheet member, and the flexible sheet member supports the weight of the cushioning material, so that the weight of the flexible sheet member or the cushioning material is increased. It is prevented that a load due to is applied to the pressure-sensitive conductive member.

According to the second aspect of the present invention, the peripheral portion of the pressure-sensitive conductive member is supported by the spacer, and one surface side of the pressure-sensitive conductive member faces two electrodes on the substrate with a predetermined gap therebetween, or Alternatively, one surface side of the pressure-sensitive conductive member is in close contact with the two electrodes. When a load is applied to the cover member, this load is buffered and dispersed by the cushioning material, is evenly dispersed by the flexible sheet member, and is gently transmitted to the pressure-sensitive conductive member. The electrode is compressed and deformed, and the change in the electric resistance value accompanying this is taken out by the two electrodes. Also in this case, as in the first aspect, the load is dispersed by the cushioning material and the flexible sheet member, so that good detection characteristics can be obtained. In addition, when the load applied to the cover member is released, the flexible sheet member and the cushioning member are returned to the unloaded position by the repulsive force thereof, and the like.

According to the third aspect of the invention, since the flexible sheet member is made of a polyester film having a thickness of about 0.1 mm, the flexible sheet member has sufficient repulsive force and is applied to the cover member. When the pressing force is released, the cushioning material is immediately returned to the unloaded position to prevent the compression set of the cushioning material. Here, the thickness of about 0.1 mm does not have to be exactly 0.1 mm, but may be in the vicinity thereof, for example, 0.0 depending on the application and size of the pressure-sensitive sensor.
A thickness in the range of 5 to 0.5 mm can be arbitrarily selected.

In the structure of claim 4, since the flexible sheet member is made of a polypropylene film having a thickness of about 0.2 mm, it has sufficient repulsive force as in the case of claim 3. Here, the thickness of about 0.2 mm means, for example, a range of about 0.1 to 0.5 mm, and can be appropriately increased or decreased depending on the application and size of the pressure sensitive sensor.

In the structure of claim 5 or 6, since the cushioning material is made of a foamed material of rubber or an elastic material such as rubber or a thermoplastic elastomer, it has sufficient cushioning properties and a sufficient load from the cover member. The load can be dispersed and the load can be gently transmitted to the pressure-sensitive conductive member via the flexible sheet member.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. As shown in FIGS. 1 and 2, the pressure-sensitive sensor according to the first embodiment has a substrate 2 having two electrodes 1a and 1b formed on the surface thereof and a rectangular parallelepiped-shaped sensor provided on the two electrodes 1a and 1b. The pressure-sensitive conductive member 3 (pressure-sensitive conductive rubber or pressure-sensitive conductive elastomer) is fixed to the surface of the substrate 2 and has a planar shape that surrounds the four side surfaces of the pressure-sensitive conductive member 3 with a slight gap therebetween. -Shaped (frame-shaped) spacer 4, a peripheral portion of the lower surface is fixed to the upper surface of the spacer 4, and a small vertical gap is provided between the spacer 4 and the pressure-sensitive conductive member 3, and the planar shape is rectangular. Of the flexible sheet member 5, the cushioning member 6 in the shape of a rectangular parallelepiped fixed on the flexible sheet member 5, and the spacer 4, which is joined to the surface of the substrate 2 outside the spacer 4. 5 and each side surface of the cushioning material 6 and the upper surface of the cushioning material 6 may be covered with a slight gap. And a sex of the cover member 7.

The substrate 2 is made of various resin molding materials such as epoxy resin and ABS resin mixed with glass fiber or a rubber molded body into which a metal substrate is incorporated. The two electrodes 1a and 1b are formed on the substrate 2. For example, a parallel electrode shown in FIG. 2 is formed by plating a conductive material such as gold, silver, or tin with a chemical treatment similar to that. The electrodes 1a and 1b may be the rectangular or round spiral electrodes shown in FIG. 3 or 4, the comb-teeth electrodes shown in FIG. 5, scissors-like electrodes not shown, or the like.

The spacer 4 is made of various rubber materials such as silicone rubber or various resin molding materials. The spacer 4 may be a punch-molded product obtained by punching a sheet-shaped rubber or resin molding material into a desired shape with a mold. The spacer 4 has the same thickness as the pressure-sensitive conductive member 3 or is slightly thicker than the pressure-sensitive conductive member 3.
In the illustrated example, the pressure-sensitive conductive member 3 has a thickness of 0.5 m.
Although the thickness of the spacer 4 is 0.7 mm, the thickness of the spacer 4 can be appropriately changed within a range of about 0.5 to 2.0 mm. It can be changed according to the thickness of.

The flexible sheet member 5 is made of a resin having flexibility and high repulsive force, and has a thickness of 0.1 m, for example.
m polyester film or 0.2mm thick
An insulating plate having a spring property made of a thin resin material such as polypropylene film is used. Further, the flexible sheet member 5 may be formed of a rubber material having a high hardness of about 1 mm.

The cushioning material 6 is made of rubber or elastomer foam material such as foam material of various rubbers such as silicone rubber or urethane rubber or foam material of thermoplastic elastomer, and has sufficient cushioning property. Cushioning material 6
May be a punched product obtained by punching these rubber or elastomer foams into a desired shape with a mold. The cover member 7 is made of various flexible rubber such as silicone rubber, or foamed material (sponge rubber) of various rubbers,
It is made of various rubber or thermoplastic elastomer processed products.

In the above structure, in the unloaded state, there is a slight gap between the flexible sheet member 5 and the pressure-sensitive conductive member 3, and the spacer 4 supports the peripheral portion of the flexible sheet member 5. At the same time, since the flexible sheet member 5 supports the weight of the cushioning material 6 and a slight gap exists between the cover member 7 and the cushioning material 6, etc., the pressure-sensitive conductive member 3 is not loaded. Does not work.

As shown in FIG. 6, when pressure is applied to the cover member 7 in the direction indicated by the arrow P, the load associated with this pressure is buffered by the buffer material 6 and dispersed to provide flexibility. It is transmitted to the sheet member 5, is evenly dispersed by the flexible sheet member 5, and is applied to the pressure-sensitive conductive member 3.
On the other hand, when the pressure applied to the cover member 7 is released, the cushioning material 6 is pushed up by the repulsive force of the flexible sheet member 5, the load on the pressure-sensitive conductive member 3 is released, and the cushioning material is released. A compression set of 6 is prevented.

The load-electrical resistance value characteristic of the pressure-sensitive sensor of this embodiment is as shown by B in FIG. 8, and the electric resistance value does not sharply decrease even in the low load region. There is no need to assemble. Further, the saturation point of the electric resistance value moves to the high load area side, and the load area that can be detected is expanded, and in the semi-log graph of FIG. 8, the relationship between the load and the electric resistance value is substantially linear. Become. The characteristics shown in FIG. 8 are obtained by the pressure-sensitive sensor using the spiral electrode shown in FIG.

FIG. 7 shows a second embodiment. In this embodiment, the pressure-sensitive conductive elastomer 3 is formed larger than that of the first embodiment, the peripheral edge portion of the lower surface of the pressure-sensitive conductive elastomer 3 is fixed to the upper surface of the spacer 4, and the pressure-sensitive conductive elastomer 3 is formed. The flexible sheet 5 is fixed to the upper surface. Under no load, the lower surface of the pressure-sensitive conductive elastomer 3 and the electrode 1
And a vertical interval of about 0.3 to 0.5 mm is set between and.

When pressure is applied to the cover member 7, the first
Similar to the embodiment, the load due to the applied pressure is dispersed by the cushioning material 6, and the dispersed load is more evenly distributed by the flexible sheet member 5, and is gently transmitted to the pressure-sensitive conductive member 3, When the piezoelectric conductive member 3 is deformed downward while being compressed, the piezoelectric conductive member 3 comes into contact with the electrodes 1a and 1b, and the change in the electric resistance value of the pressure sensitive conductive member 3 is taken out by the electrodes 1a and 1b.
When the pressure applied to the cover member 7 is released, the cushioning material 6 is pushed up by the repulsive force of the flexible sheet member 5, and the pressure-sensitive conductive member 3 is separated from the electrodes 1a, 1b by its restoring force. Return to a substantially horizontal position.

[0031]

As described above, in the pressure-sensitive sensor of the present invention, the substrate having the two electrodes provided on the surface in a non-contact state with each other, and the sensor provided on one surface side on the two electrodes are provided. A pressure-conductive member, a spacer provided on the surface of the substrate so as to surround the pressure-sensitive conductive member with a predetermined gap therebetween, and the spacer is opposed to the other surface side of the pressure-sensitive conductive member. A flexible sheet member having a peripheral portion of one surface supported by the spacer, a cushioning material disposed on the other surface of the flexible sheet member, the spacer, the flexible sheet member, and the cushioning member. Since the cover member is covered with a flexible cover member whose peripheral portion is joined to the surface of the substrate, the load on the cover member is dispersed by being buffered by the buffer member. This distributed load is evenly distributed by the flexible sheet member. Is dispersed in the pressure-sensitive conductive member and is gently transmitted to the pressure-sensitive conductive member, so that the electric resistance value of the pressure-sensitive conductive member does not drop sharply even in a low load region, and the saturation point of the electric resistance value is high when the load is high. The load region that can be detected is expanded by moving to the region side, and the change in the electrical resistance value becomes substantially linear in the entire load region that can be detected. As a result, the detection characteristic of the pressure sensitive sensor becomes extremely good.

Further, when the pressure applied to the cover member is released, the repulsive force of the flexible sheet member returns the cushioning member to the no-load position, so that compression permanent strain of the cushioning member is less likely to occur. Since the flexible sheet member protects the pressure-sensitive conductive member from various chemicals, gas, etc. generated from the rubber cover member or penetrating the cover member from the outside of the cover member, the above-mentioned chemicals etc. The pressure-sensitive conductive member is less likely to deteriorate due to.

Further, since this pressure-sensitive sensor has a structure in which the periphery of the cushioning material having elasticity is covered with the flexible cover member, the feeling of being pressed by the finger is soft and good. On the other hand, when pressurizing with a machine or an automatic device, both the cover member and the cushioning material have elasticity, so the stroke size of the pressing force can be made sufficiently large, and when the pressure sensor is attached to the machine or the automatic device. The stroke size can be set easily.

Another pressure-sensitive sensor according to the present invention comprises a substrate having two electrodes provided on the surface in a non-contact state with each other,
A spacer provided on the surface of the substrate so as to surround the two electrodes with a predetermined gap therebetween,
A pressure-sensitive conductive member facing the two electrodes and having a peripheral edge on the one surface side supported by the spacer; and a flexible sheet member provided on the other surface of the pressure-sensitive conductive member. A flexible material in which a cushioning material arranged on a flexible sheet member, the spacer, the pressure-sensitive conductive member, a flexible sheet member and a cushioning material are covered, and a peripheral portion of the cushioning material is joined to the surface of the substrate. In the same manner as described above, the load applied to the cover member is buffered and dispersed by the cushioning material, and is evenly dispersed by the flexible sheet member, so that the pressure-sensitive conductive member is formed. And the load-electrical resistance characteristic becomes good. Further, when the load on the cover member is released, the flexible sheet member returns the cushioning material to the unloaded position, so that compression permanent strain of the cushioning material is unlikely to occur, which is also the same as above.

The flexible sheet member has a thickness of 0.1 m.
If the flexible sheet member has a sufficient repulsive force and is made of a thin resin material such as a polyester film having a spring property such as a polyester film, the pressure applied to the cover member is released. Then, the cushioning material is immediately returned to the unloaded position, and the compression set of the cushioning material can be prevented.

The flexible sheet member has a thickness of 0.2 m.
If it is made of a thin resin material such as a polypropylene film of about m and is made of an insulating plate having a spring property, the flexible sheet member has a sufficient repulsive force, as described above, When the pressing force is released, there is an advantage that the cushioning material is immediately returned to the unloaded position to prevent permanent compression strain of the cushioning material.

The cushioning material has elasticity such as various sponge rubber-based, urethane sponge-based, fluorine sponge-based molded products made of foamed materials of various rubbers, or various sponge rubbers and urethane sponge rubbers obtained by die punching. If the material is made of rubber or elastic material such as thermoplastic elastomer, the cushioning material has sufficient cushioning properties,
The load from the cover member can be sufficiently dispersed, and the load can be gently transmitted to the pressure-sensitive conductive member via the flexible sheet member.

[Brief description of the drawings]

FIG. 1 is a schematic vertical sectional view of a pressure-sensitive sensor according to a first embodiment of the present invention.

FIG. 2 is an enlarged schematic plan view showing a state in which a cover member, a cushioning material and a flexible sheet member of the pressure sensitive sensor are removed.

FIG. 3 is a schematic plan view showing a modified example of electrodes of the pressure-sensitive sensor.

FIG. 4 is a schematic plan view showing another modification of the electrodes of the pressure-sensitive sensor.

FIG. 5 is a schematic plan view showing still another modification of the electrodes of the pressure-sensitive sensor.

FIG. 6 is a schematic vertical sectional view showing a state in which a pressure is applied to the pressure sensitive sensor.

FIG. 7 is a schematic vertical sectional view of a pressure-sensitive sensor according to a second embodiment.

FIG. 8 is a semi-logarithmic graph showing the load-electrical resistance value characteristics of the pressure-sensitive sensor of the present invention and the conventional example.

[Explanation of symbols]

 1a, 1b Two electrodes 2 Substrate 3 Pressure-sensitive conductive member 4 Spacer 5 Flexible sheet member 6 Buffer material 7 Cover member

Claims (6)

[Claims] 1. A substrate on the surface of which two electrodes are provided in non-contact with each other, a pressure-sensitive conductive member disposed on the two electrodes on one surface side, and the periphery of the pressure-sensitive conductive member. And a spacer provided on the surface of the substrate so as to surround the substrate with a predetermined gap therebetween and the other surface side of the pressure-sensitive conductive member, and the peripheral portion of one surface thereof is supported by the spacer. A flexible sheet member, a cushioning material disposed on the other surface of the flexible sheet member, the spacer, the flexible sheet member and the cushioning material are covered, and the peripheral portion thereof is on the surface of the substrate. A pressure-sensitive sensor comprising: a joined flexible cover member. 2. A substrate having two electrodes provided on the surface in a non-contact state with each other, and a spacer provided on the surface of the substrate so as to surround the periphery of the two electrodes with a predetermined gap therebetween. A pressure-sensitive conductive member whose side faces the two electrodes and whose peripheral portion on the one surface side is supported by the spacer; and a flexible sheet member provided on the other surface of the pressure-sensitive conductive member. , The cushioning material disposed on the flexible sheet member, the spacer, the pressure-sensitive conductive member, the flexible sheet member and the cushioning material are covered, and the peripheral edge portion is bonded to the surface of the substrate. A pressure sensor comprising a flexible cover member. 3. The flexible sheet member has a thickness of 0.1.
The pressure-sensitive sensor according to claim 1 or 2, wherein the pressure-sensitive sensor is made of a thin resin material such as a polyester film having a thickness of about mm and made of an insulating plate having a spring property. 4. The flexible sheet member has a thickness of 0.2.
3. The pressure-sensitive sensor according to claim 1, wherein the pressure-sensitive sensor is made of a thin resin material such as a polypropylene film having a thickness of about mm and made of an insulating plate having a spring property. 5. The cushioning material has elasticity of various sponge rubber-based, urethane sponge-based, fluorine sponge-based molded products made of foamed materials of various rubbers, or various sponge rubbers and urethane sponge rubbers obtained by die punching. 5. The pressure-sensitive sensor according to claim 1, wherein the pressure-sensitive sensor is made of a material that has. 6. The pressure-sensitive sensor according to claim 1, wherein the cushioning material is made of an elastic material such as rubber or thermoplastic elastomer.