JPH0517861U - Pressure sensor - Google Patents

Abstract

(57) [Summary] [Purpose] In addition to improving the followability of the pressure detector to changes in the applied pressure, when pressure detection is performed using a pressure-sensitive conductive elastomer with high sensitivity characteristics, other than the pressure to be detected The various conditions described above prevent the non-insulated state between the electrodes and the malfunction caused by the non-pressurized state due to the action of the external force. [Structure] A through hole 7a is formed in a central portion of a cover member 7, a pressure detecting body 13 is attached to a diaphragm 2 stretched over the through hole 7a, and a pressing portion 3 at a tip of the pressure detecting body 13 is displaced. The pressure-sensitive conductive elastomer member 4 is arranged so as to be deformed as a result, and the electrodes 5, 5 are arranged with the pressure-sensitive conductive elastomer member 4 and a predetermined gap X interposed therebetween. Then, if necessary, a regulation means for regulating the movement of the pressure detection body 13 when the pressure value acting on the pressure detection body 13 becomes a predetermined value or more is provided.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a pressure-sensitive sensor that can be used as a variable input unit of, for example, a pressure detecting device, a motor rotation speed varying device, and a speaker volume varying device, and more particularly, to a pressure-sensitive conductive elastomer. It is related to the improvement technology of the pressure-sensitive sensor using the characteristics.

[0002]

[Prior Art]

 BACKGROUND ART Conventionally, a pressure-sensitive conductive rubber having a characteristic that an electric resistance value is lowered due to a compressive deformation caused by a pressing force has been known. This pressure-sensitive conductive rubber is made by mixing and dispersing conductive particles such as metal or carbon black in an insulator such as rubber or elastomer. In this pressure-sensitive conductive rubber, the individual conductive particles are separated from each other when no pressure is applied, and thus they are in an electrically insulated state. In such a case, the individual conductive particles come into contact with each other, so that the electric resistance value continuously decreases.

The pressure-sensitive conductive rubber having the above-mentioned properties is put to practical use or is in the process of being used as sensors and switches in various fields. To give an example, a conductive material that forms electrodes is attached to both sides in the thickness direction of pressure-sensitive conductive rubber molded in a flat plate shape or a rectangular parallelepiped shape, and the electric resistance change due to compressive deformation is extracted from this electrode. There is a sensor (variable resistor) that does so. Further, as an improvement to this, for example, according to Japanese Patent Laid-Open No. 61-78101, one side of a pressure-sensitive conductive rubber molded to have a uniform wall thickness (the one shown in the figure is rectangular in cross section) is formed. A sensor configured such that a pair of electrodes are provided in a non-contact state, an electrode that extends over the pair of electrodes is provided on the other surface, and electric resistance change due to compressive deformation occurring in the thickness direction is taken out from the pair of electrodes. (Variable resistor) is disclosed. Further, according to Japanese Utility Model Laid-Open No. 53-32366, a pressure-sensitive conductive rubber having a rectangular cross section (a pressure-sensitive resistor in the same publication) is interposed between a support and a pressure member arranged in parallel. At the same time, a pair of electrode plates insulated from each other is provided between the pressure-sensitive conductive rubber and the support to prevent compressive deformation when pressure is applied to the pressure-sensitive conductive rubber from the pressing member. A pressure-sensitive switch configured to take out the accompanying change in electrical resistance from the pair of electrodes is disclosed.

[0004]

[Problems to be solved by the device]

 However, in all of the conventional examples listed above, since the electrode is in contact with the pressure-sensitive conductive rubber even when no pressure is applied, the electrode is firmly attached to the pressure-sensitive conductive rubber. Therefore, if the sensitivity is low, that is, if the electric resistance value does not change unless the pressure is high, the problem does not occur as much as on the left, but even if the sensitivity is high, that is, the pressure is low. If the electric resistance value is sensitively changed, the pressure-sensitive conductive rubber is slightly deformed due to changes in atmospheric temperature, vibration, and atmospheric pressure. There was a problem that the insulation between the electrodes was lost. In addition, even when the pressure-sensitive conductive rubber and different materials are bonded together or after bonding, the pressure-sensitive conductive rubber is deformed due to the difference in shrinkage and expansion coefficient due to the influence of temperature change and humidity change. However, this also causes a problem that the pair of electrodes is not in an insulating state when no pressure is applied.

The present invention has been made in view of the above circumstances, and when performing pressure detection using a pressure-sensitive conductive elastomer having high sensitivity characteristics, external forces other than the pressure to be detected act. Therefore, it is a technical subject to prevent the non-insulation state between the electrodes and the malfunction caused by the non-insulation due to the above.

[0006]

[Means for Solving the Problems]

 The pressure-sensitive sensor according to the present invention, which has been made to achieve the above technical problems, has the following features. That is, a pressure detector attached to the diaphragm, a pressure-sensitive conductive elastomer member that deforms due to the displacement of the pressure detector, and an electrode that takes out an electric resistance change due to the deformation of the pressure-sensitive conductive elastomer member. In addition, a predetermined gap is provided between the pressure-sensitive conductive elastomer member and the electrode when no pressure is applied to the pressure detector. Then, if necessary, a regulation means is provided for regulating the movement of the pressure detection body when the pressure value acting on the pressure detection body exceeds a predetermined value.

[0007]

[Action]

 According to the above means, the pressure detecting element attached to the diaphragm acts on the pressure detecting element to deform and displace the diaphragm, and the pressure-sensitive conductive elastomer member is deformed accordingly. However, since there is a specified gap between this pressure-sensitive conductive elastomer member and the electrode, the pressure-sensitive conductive elastomer member may be slightly deformed due to temperature changes or vibrations. However, the electrodes do not come into contact with each other, so that the electrodes are maintained in the insulating state when the pressure sensor is not pressurized, that is, when the relatively large pressure to be detected is not applied. On the other hand, when the pressure to be detected acts on the pressure detector, the pressure-sensitive conductive elastomer member is largely deformed in the direction of the electrode and contacts the electrode across the gap. Then, when the pressure-sensitive conductive elastomer member comes into contact with the electrode lightly, it is in a state close to insulation, but the electrical resistance value of the pressure-sensitive conductive elastomer member gradually decreases by continuing to apply pressure. , This change in electrical resistance is taken out from the electrode. If a regulation means is provided to regulate the movement of the pressure detector when the pressure acting on the pressure detector exceeds a predetermined value, safety against excessive pressure is secured.

[0008]

【Example】

 An embodiment of the pressure-sensitive sensor according to the present invention will be described below with reference to the drawings. As shown in FIGS. 1 and 2, a circular through hole 7a is formed in the central portion of the rectangular parallelepiped cover member 7, and the diaphragm 2 is formed so as to partition the upper space and the lower space of the through hole 7a. A tension detecting member 13 composed of a detecting convex portion 1 and a pressing portion 3 is attached to the center of the diaphragm 2. Immediately below the pressing portion 3 of the pressure detecting body 13, the pressure-sensitive conductive elastomer sheet 4 is placed on the upper surface of the gap forming spacer 8 projecting inward from the through hole 7a from the cover member 7. In the illustrated state, that is, when the pressure is not applied, the pressure-sensitive conductive elastomer sheet 4 is not deformed, and the pressing portion 3 is in contact with the upper surface of the pressure-sensitive elastomer sheet 4 or is separated with a very small gap. Further, a substrate 6 having high rigidity is fixed to the cover member 7 just below the pressure-sensitive conductive elastomer sheet 4, and a pair of electrodes 5 and 5 are attached to the upper surface of the substrate 6. There is. A predetermined gap X is provided between the electrodes 5, 5 and the pressure-sensitive conductive elastomer sheet 4. In this case, the pressure-sensitive conductive elastomer sheet 4 is made by mixing and dispersing conductive particles such as metal or carbon black in an insulator such as rubber or elastomer. Further, the cover member 7, the diaphragm 2, the pressure detecting body 13 and the gap forming spacer 8 are made of, for example, various rubber materials or thermoplastic elastomers or their composites. It is not particularly limited. In the figure, reference numeral 9 is a board positioning pin, and reference numeral 10 is a bead for maintaining airtightness.

According to the above configuration, when the pressure to be detected does not act and no pressure is applied, the electrodes 5, 5 and the pressure-sensitive conductive elastomer sheet 4 are separated by a predetermined distance as shown in FIG. Therefore, even if the pressure-sensitive conductive elastomer sheet 4 is slightly deformed due to temperature change or vibration, it will not be deformed until the sheet 4 comes into contact with the electrodes 5 and 5. During pressurization, the insulation between the pair of electrodes is reliably maintained. On the other hand, as shown in FIG. 3, when the vertically downward pressing force 11 acts on the detection convex portion 1 of the pressure detection body 13, the pressure detection body 13 deforms the diaphragm 2 to move downward and its tip end. The pressing portion 3 deforms the central portion of the pressure-sensitive conductive elastomer sheet 4 downward, and as a result, the pressure-sensitive conductive elastomer sheet 4 contacts the pair of electrodes. After this contact, the electric resistance value of the compressed portion of the pressure-sensitive conductive elastomer sheet 4 changes as the applied pressure 11 increases and decreases, and this electric resistance change is taken out from the pair of electrodes 5, 5. ..

FIG. 4 shows a case in which the detection convex portion 1 of the pressure detection body 13 has a long rod shape and the pressing portion 3 has a cylindrical shape. With such a structure, as shown in FIG. Even when the lateral pressure 11 is applied to the detection convex portion 1, the peripheral edge of the bottom surface of the pressing portion 3 deforms the pressure-sensitive conductive elastomer sheet 4 according to the principle of leverage to cause the electrode 5 to move. , 5 are brought into contact with each other, and the electric resistance change due to the compressive deformation of the pressure-sensitive conductive elastomer sheet 4 is taken out from the electrodes 5, 5. Incidentally, a taper or a roundness may be formed on the peripheral portion of the bottom surface of the pressing portion 3.

6 and 7 show a modified example of the pressure-sensitive sensor according to the present invention. Of these, the one shown in FIG. 6 is one in which a rectangular through hole 7a is formed in the cover member 7 and A rectangular diaphragm 2 is stretched in the through hole 7a and the detection convex portion 1 of the pressure detection body 13 is rectangular, and the other constituent elements are the same as those in the above-mentioned embodiment, and also shown in FIG. The cover member 7 has an annular shape, and the other components are the same as in the above-described embodiment. The shape of the cover member 7, the shape of the through hole 7a, and the shape of the pressure detecting body 13 are not limited to those illustrated above, and various variations other than this are possible.

8 to 11 show a plurality of examples of the electrodes 5 and 5 arranged on the upper surface of the substrate 6, of which the ones shown in FIG. 8 and FIG. The electrodes 5 and 5 are arranged in parallel, and the electrodes shown in FIGS. 10 and 11 are a pair of comb-shaped electrodes 5 and 5 arranged in parallel. The shapes of the electrodes 5 and 5 are not limited to those illustrated above, and electrodes having other shapes may be used.

Further, as an additional means to the above embodiment, it is preferable to provide a regulating means for regulating the movement of the pressure detecting body 13 when the pressure acting on the pressure detecting body 13 becomes a predetermined value or more. .. As a specific configuration of this regulating means, for example, a protrusion or a collar portion that abuts the upper surface of the cover member 7 may be fixed to a predetermined position of the detection convex portion 1 of the pressure detection body 13. Then, the fixed position of the projection or the collar portion is determined in consideration of the maximum allowable limit value of the pressing force acting on the pressure detection body 13 and the corresponding displacement dimension of the detection convex portion 1. .. If such a regulation means is provided, the safety against over-pressurization can be secured.

[0014]

[Effect of the device]

 As described above, according to the pressure-sensitive sensor of the present invention, since the pressure detector is attached to the diaphragm, the pressure detector is displaced and the pressure is removed after the pressure-sensitive conductive elastomer member is deformed. In this case, the pressure detection body will be immediately and surely returned to the initial position by the urging force of the diaphragm, and the problem that residual pressure acts on the pressure-sensitive conductive elastomer member is avoided. The durability of the piezoelectric conductive elastomer member is improved. In addition, by mounting the pressure detector on the diaphragm in this way, it is possible to detect not only the pressure applied to the axial direction of the pressure detector, but also the pressure applied laterally to the shaft. It will be possible, and the usage will be expanded. Furthermore, since a predetermined gap is provided between the pressure-sensitive conductive elastomer member and the electrode when no pressure is applied to the pressure detecting body, it is possible to prevent temperature change, humidity change, vibration, etc. Even if the pressure-sensitive conductive elastomer member slightly deforms due to this, it does not deform until the pressure-sensitive conductive elastomer member contacts the electrodes through the gap. The situation of becoming non-insulated is avoided, and the malfunction caused by this is prevented. In addition, when a pressure to be detected is applied to the pressure detector, the pressure-sensitive conductive elastomer member is greatly deformed and contacts the electrode beyond the gap, and the electrical conductivity of the pressure-sensitive conductive elastomer member during this contact occurs. The resistance change is taken out from the electrode, and the original function as a pressure-sensitive sensor can be fully exerted.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional perspective view showing a pressure sensor according to a first embodiment of the present invention.

FIG. 2 is a vertical sectional front view of the pressure-sensitive sensor according to the first embodiment.

FIG. 3 is a vertical sectional front view showing the operation of the first embodiment.

FIG. 4 is a vertical sectional front view showing a pressure sensor according to a second embodiment of the present invention.

FIG. 5 is a vertical sectional front view showing the operation of the second embodiment.

FIG. 6 is a perspective view showing a pressure sensor according to a third embodiment of the present invention.

FIG. 7 is a perspective view showing a pressure sensor according to a fourth embodiment of the present invention.

FIG. 8 is a plan view showing a first example of electrodes arranged on a substrate.

FIG. 9 is a plan view showing a second example of electrodes arranged on a substrate.

FIG. 10 is a plan view showing a third example of electrodes arranged on a substrate.

FIG. 11 is a plan view showing a fourth example of electrodes arranged on a substrate.

[Explanation of sign]

 1 Convex Part for Detection 2 Diaphragm 3 Pressing Part 4 Pressure Sensitive Conductive Elastomer Member 5 Electrode 8 Spacer for Space Formation 11 Pressurization 13 Pressure Detector X Predetermined Gap

Claims (2)

[Scope of utility model registration request] 1. A pressure detection body attached to a diaphragm, a pressure-sensitive conductive elastomer member that deforms with displacement of the pressure detection body, and an electric resistance change due to deformation of the pressure-sensitive conductive elastomer member. An electrode having an electrode and a structure in which a predetermined gap is provided between the pressure-sensitive conductive elastomer member and the electrode when pressure is not applied to the pressure detection body. Pressure sensor. 2. The pressure-sensitive sensor according to claim 1, further comprising a regulation means for regulating the movement of the pressure detection body when the pressure value acting on the pressure detection body exceeds a predetermined value.