JP2006226858A - Fluctuation load sensor, and tactile sensor using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluctuation load sensor capable of detecting a shearing-directional fluctuation load or/and a compression-directional fluctuation load, by simple structure. <P>SOLUTION: This fluctuation load sensor used attached to a measured object has a pair of same-shaped surface electrodes arranged separately on a surface of a piezoelectric film, a surface strain amplifying member for covering the electrodes and the surface of the piezoelectric film, a load transmission member arranged on an upper face of the surface strain amplifying member, a pair of reverse face electrodes with a projection face overlapped on a reverse face of the piezoelectric film in the shape same to the surface electrodes, and a reverse face strain amplifying member of the quality same to that of the surface strain amplifying member for covering the reverse face electrodes and the reverse face of the piezoelectric film. The paired surface or reverse face electrodes are respectively arranged to be symmetric to a symmetry axis of the load transmission member, and not to be overlapped on the projection face of the load transmission member, and the pair of surface electrodes and the pair of reverse face electrodes are short-circuited in the fellow electrodes existing in diagonal positions. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fluctuating load sensor used by being attached to an object to be measured. In particular, the present invention relates to a variable load sensor that can detect a variable load in a shearing direction and / or a variable load in a compression direction applied to an object to be measured.

  Various sensors such as strain gauges are known as sensors capable of detecting a vertically varying load such as compression and tension. On the other hand, there are few examples of sensors that can detect a fluctuating load in the shear direction, but recently, a tactile sensor of a robot arm has attracted attention, and a shearing and / or compression direction that can be used for a tactile sensor or the like. Several fluctuating load sensors that can detect fluctuating loads are proposed.

  In Patent Document 1, a lower plate that is in contact with an object surface to be measured and an upper plate that receives a shearing force acting on the object surface while being substantially parallel to the lower plate are relatively aligned in the shear direction. A strain gauge integrated in a movable manner and provided between the upper and lower plates is a shear measurement sensor in which one end of a detection end for detecting a shear force is connected to the upper plate and the other end is connected to the lower plate. A shear measurement sensor has been proposed in which the upper plate and the lower plate are flexible.

  In Patent Document 2, at least two pressure-sensitive elements arranged in a horizontal direction on a substrate and a surface of each pressure-sensitive element on the side opposite to the substrate are in contact with each other, and a protruding portion is formed on the opposite side of the pressure-sensitive element. A compression direction received from an object using a force acting on two pressure-sensitive elements when the contactor is in contact with the object and receives a compressive force and a shearing force to bend and deform. A skin sensation sensor suitable for use in a manipulator such as an assembly robot capable of detecting the load in the shear direction and the load in the shear direction has been proposed.

  In Patent Document 3, a first plate-like strain-generating portion and a plate-like shape extending from a position at which the periphery of the first strain-generating portion is divided into four at substantially the same angle are provided. The second to fifth strain-generating portions configured to support the first strain-generating portion as legs of the portion, and the first strain-generating portion from each of the second to fifth strain-generating portions. First to fourth foot portions extending on different sides, a diaphragm-shaped first strain gauge attached on a disk surface of the first strain-generating portion, and the second to fifth portions There has been proposed a tactile pressure sensor comprising second to fifth strain gauges respectively attached on the plate surface of the strain generating portion.

  Patent Document 4 includes a substrate, a detection unit that detects a sense of contact with an object on the substrate, and a processing circuit that is connected to the detection unit and processes a signal output from the detection unit. In the tactile sensor, the detection unit includes a first pressure-sensitive element that detects a tensile force and a compressive force, and a first contact surface that is formed on the first pressure-sensitive element and contacts the object. And a contact surface with the object in the first contact is parallel to a surface in contact with the first pressure-sensitive element and is in contact with the object. A tactile sensor has been proposed in which the center position of the surface is deviated from the center position of the surface in contact with the first pressure sensitive element.

JP 2000-136970 A Japanese Patent Publication No. 04-48597 JP 2004-245717 A JP 2004-226380 A

  However, the conventional sensor capable of detecting the load in the shear direction and / or the compression direction has a complicated structure. In addition, it has a structure that requires a certain amount of thickness, and cannot easily measure a load in a shearing direction or a load in a compressing direction by adhering to an object having various shapes. Furthermore, since these sensors can only detect a very narrow range of loads acting on the sensors, such sensors are not suitable for constructing practical sensors, for example tactile sensors such as robot manipulators. A large number of tactile sensors must be constructed, and a special device must be provided for processing the signals from each sensor. As described above, the conventional sensor is not only complicated and large in size but also expensive. Although the sensor proposed in Patent Document 1 can constitute a relatively thin sensor, there is a problem that it is structurally difficult to construct a sensor for measuring a compressive load.

  In view of the conventional problems, the present invention has a simple structure and can detect a wide range of load fluctuations in the shear direction and / or variable load in the compression direction acting on the object to be measured in various shapes. It is an object of the present invention to provide a variable load sensor that can be used and a tactile sensor using the same.

  A fluctuating load sensor according to the present invention is a fluctuating load sensor that is used while being attached to an object to be measured, and a pair of front electrodes having the same shape and spaced apart on the surface of a piezoelectric film, A surface strain amplifying member covering the surface of the electrode and the piezoelectric film, a load transmitting member disposed on the upper surface of the surface strain amplifying member, and a projection surface having the same shape as the surface electrode on the back surface of the piezoelectric film A pair of overlapping back electrodes, and a back strain amplifying member of the same quality as the surface strain amplifying member covering the back electrode and the back surface of the piezoelectric film, and the pair of front or back electrodes are each loaded with the load The pair of front electrodes and the pair of back electrodes are arranged diagonally with respect to the symmetry axis of the transmission member so as not to overlap the projection surface of the load transmission member. Is short-circuited.

  Further, in the above configuration, a front center electrode provided on the surface of the piezoelectric film on the lower surface side of the front strain amplifying member and symmetric with respect to the symmetry axis of the load transmitting member and not overlapping with the pair of front electrodes, and back strain amplification A pair of central electrodes are provided on the lower surface side of the member on the back surface of the piezoelectric film and are formed of a back central electrode having the same shape as the front central electrode and overlapping the projection surface.

  Furthermore, it is a variable load sensor that is used by being attached to an object to be measured, and is a pair of first surface electrodes having the same shape and disposed on the surface of the first piezoelectric film, and the first piezoelectric film. A first sensor element having a pair of first back electrodes having the same shape as the first front electrode and overlapping the projection surface on the back surface of the first piezoelectric film, and bonded perpendicularly to the first sensor element. A pair of second front electrodes having the same shape spaced apart on the front surface, and a pair of second back electrodes having the same shape as the second front electrode on the back surface of the second piezoelectric film and overlapping the projection surface A surface strain amplification member that covers the surfaces of the first and second piezoelectric films and the first and second surface electrodes, and a load transmission member disposed on an upper surface of the surface strain amplification member. The front surface covering the back surface of the first and second piezoelectric films and the first and second back electrodes A back strain amplifying member of the same quality as the amplifying member, the first piezoelectric film and the second piezoelectric film have equivalent polarization characteristics, and the pair of first front and back electrodes are respectively Symmetrically with respect to the symmetry axis of the load transmission member, and disposed so as not to overlap the projection surface of the load transmission member, the pair of second front or back electrodes are respectively arranged on the symmetry axis of the load transmission member. The pair of first front electrodes and the pair of first back electrodes are short-circuited with each other, and are symmetrical with respect to the projection surface of the load transmitting member. The pair of second front electrodes and the pair of second back electrodes may be formed by short-circuiting the electrodes present at diagonal positions.

  Further, a first front center electrode provided on the surface of the first piezoelectric film on the lower surface side of the front strain amplifying member and symmetric with respect to the symmetry axis of the load transmitting member and not overlapping the pair of first front electrodes, A pair of first center electrodes formed on the lower surface side of the strain amplification member on the back surface of the first piezoelectric film and formed from a first back center electrode having the same shape as the front center electrode and overlapping the projection surface are provided. Can be.

  A second front center electrode which is provided on the lower surface side of the front strain amplifying member on the surface of the second piezoelectric film and which is symmetric with respect to the symmetry axis of the load transmitting member and does not overlap with the pair of second front electrodes; A pair of second central electrodes formed on the lower surface side of the amplifying member on the back surface of the second piezoelectric film and formed from a second back central electrode having the same shape as the second front central electrode and overlapping the projection surface; Can be.

  Furthermore, a first front center electrode which is provided on the surface of the first piezoelectric film on the lower surface side of the front strain amplifying member and is symmetric with respect to the symmetry axis of the load transmitting member and does not overlap with the pair of first front electrodes, and back strain amplification A pair of first central electrodes formed on the lower surface side of the member on the back surface of the first piezoelectric film and formed from a first back central electrode having the same shape as the front central electrode and overlapping the projection surface; A second electrode having the same shape as the center electrode, provided on the surface of the second piezoelectric film on the lower surface side of the surface strain amplifying member, symmetrical to the symmetry axis of the load transmitting member and not overlapping the pair of second surface electrodes. A pair of front center electrodes and a second back center electrode formed on the back surface of the second piezoelectric film on the lower surface side of the back strain amplifying member and having the same shape as the second front center electrode and overlapping the projection surface A second central electrode, and the first front central electrode has the first central electrode. Short-circuited with a second front or back center electrode having the same polarity as the front center electrode, and the first back center electrode is short-circuited with a second front or back center electrode having the same polarity as the first back center electrode. be able to.

  In the above invention, the strain amplifying member may have a lower elastic modulus than the piezoelectric film, and the load transmitting member may have a higher elastic modulus than the strain amplifying member.

  The fluctuating load sensor can be attached to a pedestal that can be bent and a load transmitting member can be disposed on the top, and can be used for a robot hand or the like to form a suitable tactile sensor.

  The variable load sensor according to the present invention has a simple structure and can form a thin sheet-like sensor. It is also possible to easily detect a wide range of fluctuating loads acting on the object to be measured having various shapes. Furthermore, a tactile sensor suitable for a robot hand can be configured using this variable load sensor.

  Embodiments of a variable load sensor according to the present invention will be described below with reference to the drawings. 1A and 1B are schematic views showing the configuration of the variable load sensor, in which FIG. 1A is a sectional view and FIG. 1B is a plan view. FIG. 2 is an electric circuit diagram of the variable load sensor. As shown in FIG. 1, the fluctuating load sensor 10 includes a piezoelectric film 11, electrodes 12 disposed on the front and back surfaces of the piezoelectric film 11, a strain amplification member 16 that covers the piezoelectric film 11 and the electrode 12, and a strain amplification. A load transmitting member 19 is provided on the upper surface of the member 16.

  As the piezoelectric film 11, a known film can be used. For example, PVDF (polyvinylidene fluoride) having a film thickness of 40 to 100 μm, a longitudinal elastic modulus of 2000 to 4000 MPa, and a Poisson's ratio of 0.3 to 0.35 can be used.

  The electrode 12 comprises a pair of electrodes 13A and 13B disposed on the surface of the piezoelectric film 11 and spaced apart from each other, and a pair of electrodes 14A and 14B disposed on the back surface of the piezoelectric film 11 spaced apart from each other. All have the same shape. Further, the electrode 14A on the back surface of the piezoelectric film 11 is disposed so as to overlap the projection surface of the front electrode 13A, and the electrode 14B is disposed so as to overlap the projection surface of the front electrode 13B.

  These electrodes 12 can be formed by vapor-depositing aluminum on the piezoelectric film 11, applying a conductive paint, or sputtering of copper or the like. The electrode 12 may be any electrode as long as it can follow the deformation without inhibiting the deformation of the piezoelectric film 11 and has excellent conductivity. As described below, since the size and arrangement position of the electrodes are related to the sensitivity of the sensor, the piezoelectric film 11 is subjected to predetermined masking by vapor deposition or sputtering, or vapor deposition or entire surface of the piezoelectric film. After forming the electrode by sputtering, it is preferable to form the electrode 12 by removing unnecessary portions with a corrosive solution or the like. It should be noted that the pair of electrodes 13A and 13B and 14A and 14B provided on the front and back surfaces of the piezoelectric film 11 are not connected to the edges of the electrodes 13A and 14A or the electrodes 13B and 14B so that they are not short-circuited. It is preferable that the edge of the film be slightly inward from the edge of the piezoelectric film 11.

  The strain amplification member 16 includes a surface strain amplification member 17 that covers the surface of the piezoelectric film 11 and the pair of electrodes 13A and 13B, and a back strain amplification member 18 that covers the back surface of the piezoelectric film 11 and the pair of electrodes 14A and 14B. The front strain amplifying member 17 and the back strain amplifying member 18 are made of the same elastic body having the same longitudinal and transverse elastic coefficients.

  As the strain amplifying member 16, an elastic body having an elastic coefficient smaller than that of the piezoelectric film 11 is used. As described below, the strain amplification member 16 increases the amount of charge generated by the polarization accompanying the strain by increasing the strain generated in the piezoelectric film 11 when a variable load or the like acts on the variable load sensor 10. It has a function of increasing the measurement sensitivity of the variable load sensor 10. For this reason, as the strain amplifying member 16, for example, an elastic body having a longitudinal elastic modulus of about 1/100 to 1/1000 of the elastic modulus of the piezoelectric film 11 is 1 to 10 Mpa (equivalent to a rubber hardness of 40 to 60 based on JISK6253). Should be used. As such an elastic body, silicon rubber, natural rubber or synthetic rubber is preferable. In particular, when a piezoelectric film made of PVDF is used, it is preferable to use silicon rubber as the elastic body.

  Since the strain amplifying member 16 increases the strain of the piezoelectric film 11 as described above, the joint portion between the strain amplifying member 16 and the piezoelectric film 11 must be joined so as to be integrally deformed. The joining means is not particularly limited, but the joining of the strain amplifying member 16 and the piezoelectric film 11 may be by adhesion. In the case of adhesion, it is preferable to use a silicone resin or rubber adhesive whose hardness after curing is substantially the same as that of the strain amplifying member 16 as an adhesive, and particularly when using PVDF for the piezoelectric film 11, a silicone resin adhesive. It is good to use. Silicon rubber or the like used as the strain amplifying member 16 is formed by applying liquid silicon rubber or the like to the piezoelectric film 11 to a certain thickness, or attaching a mold to the upper surface of the piezoelectric film and pouring the liquid silicon rubber or the like. It can also be configured integrally with the piezoelectric film 11 by curing.

  In order to obtain the strain amplification effect of the strain amplification member 16, the thickness of the front or back strain amplification members 17, 18 is preferably 1 mm to 5 mm. If the thickness of the strain amplifying member 16 is less than 1 mm, the strain amount of the strain amplifying member 16 itself becomes small and a desired strain amplifying effect cannot be obtained. On the other hand, when the thickness of the strain amplification member 16 exceeds 5 mm, the degree of the strain amplification effect is saturated. Further, it is preferable that the strain amplifying member 16 has a size that covers the entire surface of the piezoelectric film 11 and slightly protrudes. Thereby, a uniform and reliable strain amplification effect by the strain amplification member 16 can be obtained.

As shown in FIG. 1, the load transmitting member 19 is arranged on the upper surface of the front strain amplifying member 17 so that the pair of front or back electrodes 13 and 14 are symmetrical with respect to the symmetry axis of the load transmitting member 19, respectively. It is installed. That is, the load transmitting member 19 has a symmetry axis, and the pair of front or back electrodes 13, 14 has a shape and an arrangement that are symmetrical with respect to the symmetry axis. Further, the load transmitting member 19 is disposed so as not to overlap the projection surface of the front electrode 13 or the back electrode 14. As a result, the fluctuating load can be detected with high accuracy as described below. In order to prevent the load transmitting member 19 from overlapping the projection surface of the front electrode 13 or the back electrode 14, a gap dimension L (L ₁ , L) on the piezoelectric film 11 between the load transmitting member 19 and the electrode 12 shown in FIG. L ₂ ) should be 0.1 mm or more. This is because if the gap dimension L is 0.1 mm or more, manufacturing and management are facilitated. The upper limit of the gap dimension L is determined according to the shape of the object to be measured.

  The function of the load transmission member 19 is to directly transmit the variable load acting at any position where the action point of the variable load is on the surface of the load transmission member 19 to the strain amplifying member 16. For this reason, it is required that the load transmission member 19 has a high rigidity and that the load transmission member 19 and the strain amplifying member 16 are joined. It is not appropriate that the load transmitting member 19 itself is distorted to affect the strain amount of the strain amplifying member 16. As such a load transmission member 19, for example, a thin plate of about 0.1 mm thickness made of aluminum or copper can be used. Moreover, a resin sheet, a metal sheet, a high hardness rubber sheet, etc. can also be used. In the case of such a flexible thing, even if the shape of a to-be-measured object is a curved surface shape, the sensor which can detect the fluctuating load which acts on this can be formed easily. The above-mentioned rubber adhesive can be used for joining the load transmitting member 19 and the strain amplifying member 16. Further, the surface of the load transmitting member 19 on which the variable load acts can be covered with a sponge, rubber or the like to provide a slip stopper, so that the point of action of the variable load does not shift, and the detection accuracy can be improved.

When a shearing variable load acts on the load transmitting member 19 of the variable load sensor 10 as described above, the piezoelectric film 11 is distorted through the strain amplifying member 16, and the piezoelectric film 11 is charged by polarization. The variable load sensor 10 is provided with an output terminal for taking out the electric charge. That is, as shown in FIG. 2, the electrodes 13A and 14B are connected so that the electrodes existing at the diagonal positions of the pair of front electrodes 13 and the pair of back electrodes 14 are short-circuited, and the electrodes 13B And the electrode 14A are connected to each other, and the charges generated by the polarization by the wires reaching the output terminals V ₁ and V ₂ are taken out as the output voltage.

Note that the electric circuit diagram shown in FIG. 2 but the capacitance C ₁ and resistor R ₁ is provided, it may be provided as needed. For example, if the size of the piezoelectric film is small and the load speed of the fluctuating load is moderate, if the capacitance C _{l of} about 0.5 μF to 1 μF and the resistance R _l of about 1 MΩ to 10 MΩ are connected, the load speed will be An output voltage proportional to the fluctuating load can be obtained even if it is moderate.

  The wiring between the electrodes 12 can be formed, for example, by sticking the adhesive surface of a metal foil tape with a conductive adhesive to the electrode 12. The electrode 12 and a flexible conductive material such as conductive rubber or conductive fiber are bonded with a conductive adhesive, or the electrode 12 and the flexible conductive material are sandwiched between metal plates and connected by caulking to form a wiring. You can also.

Using such a fluctuating load sensor 10, the shear fluctuating load acting on the measurement object 50 can be measured as described below. FIG. 3 shows the variable load sensor 10 when the load sensor 10 is attached to the object to be measured 50 and the load transmission member 19 is loaded with a variable load F in the arrow (X-axis) direction (a variable load in the shear direction) F. It is explanatory drawing which represented typically the deformation | transformation state (FIG.3 (a)) and the distribution curve (FIG.3 (b)) of distortion | strain (epsilon) _x of the X-axis direction of the piezoelectric film 11 calculated | required elastically.

As described above, the load transmitting member 19 has high rigidity, and the load transmitting member 19 and the pair of front or back electrodes 13 and 14 have a symmetrical shape and arrangement with respect to the symmetry axis ZZ. Further, the strain amplifying member 16 has an elastic coefficient smaller than that of the piezoelectric film 11, and all the electrodes 12 have the same shape. Therefore, when the variable load F acts on the load transmitting member 19, the strain amplifying member 16 is distorted in the shear direction. This causes the piezoelectric film 11 to be axially distorted in the X-axis direction, and FIG. elongation distortion in the L _e part shown in a, the L _c unit produce L _e portion equal compressive strain magnitude. Then, since the elastic coefficient of the strain amplifying member 16 is smaller than the elastic coefficient of the piezoelectric film 11, and the distortion of the strain amplifying member 16 is larger than the distortion of the piezoelectric film 11, the distortion generated in the piezoelectric film 11 is amplified by the strain amplifying member 16. An output voltage corresponding to the distortion ε _x amplified from the output terminals V ₁ and V ₂ shown in FIG. 2 is detected. Thus, according to this variable load sensor, the variable load in the shear direction can be detected with high sensitivity.

Ε _x (strain in the X-axis direction at the x position of the piezoelectric film) generated in the piezoelectric film 11 is represented by a strain distribution curve shown in FIG. As shown in FIG. 3B, the strain distribution curve is a point-symmetrical curve with respect to the intersection O of the ZZ axis and the X axis. Then, in the portion of the piezoelectric film 11 where the electrodes 13A and 14A are disposed, a positive charge Q ₊ proportional to the hatched portion S ₊ shown in FIG. 3B is generated, and the electrodes 13B and 14B are disposed. proportional to - _- the charge Q ₊ and the absolute value is equal to the hatched portion S in part results in a _- charge Q of. That is, the shear fluctuation load F can be detected by detecting the difference between the charge Q ₊ and the charge Q ₋ as a voltage fluctuation by the electric circuit shown in FIG.

  As described above, the principle of detecting the shearing variable load by the variable load sensor 10 is that the distortion generated in the piezoelectric film 11 due to the variable load acting on the load transmitting member 19 is at the intersection O shown in FIG. It is assumed that the distribution is point-symmetric. That is, the accuracy regarding the shapes and arrangement positions of the electrodes 13A, 13B, 14A, 14B and the load transmission member 19 is important, and the accuracy affects the detection accuracy of the fluctuating load. Therefore, although the accuracy more than necessary is not required, it is necessary to determine the accuracy of the shape and arrangement position of the electrode 12 and the load transmission member 19 according to the required detection accuracy of the fluctuating load.

  When the load transmission member 19 is arranged so as to overlap the projection surface of the front electrode 13 or the back electrode 14 in the arrangement relationship between the load transmission member 19 and the electrode 12, the shape of the strain distribution curve is the load transmission member 19. It becomes different from the theoretical curve under the influence of. For this reason, the load transmitting member 19 should be disposed so as not to enter the projection surface of the front electrode 13 or the back electrode 14.

  As described above, the variable load sensor according to the present invention can form a thin sheet sensor having an overall thickness of 2 to 10 mm, and has an advantage of a simple structure. Further, it is possible to easily detect a wide range of fluctuating loads in the shearing direction acting on the object to be measured having various shapes. However, the variable load sensor according to the present invention is not limited to the above embodiment. A biaxial variable load sensor that can simultaneously detect not only the variable load in the shearing direction but also the variable load in the compression direction can be easily configured.

  FIG. 4 is a schematic diagram of a biaxial variable load sensor that can simultaneously detect a shear variable load and a compressive variable load. 4A is a cross-sectional view of the biaxial variable load sensor 110, and FIG. 4B is a plan view. FIG. 5 is an electric circuit diagram of the biaxial variable load sensor 110. As shown in FIG. 4 (a), the biaxial variable load sensor 110 has a pair of central electrodes 22 on the front and back surfaces of the piezoelectric film 11 in addition to the configuration of the variable load sensor 10 shown in FIG. ing. That is, the front center electrode 22A provided on the surface of the piezoelectric film 11 on the lower surface side of the front strain amplifying member 17 and symmetric with respect to the symmetry axis of the load transmission member 19, and not overlapping the pair of front electrodes 13, and the back strain amplifying member 18 has a pair of central electrodes 22 formed on the back surface of the piezoelectric film 11 on the lower surface side of 18 and formed from a back central electrode 22B having the same shape as the front central electrode 22A and overlapping the projection surface. The phrase “not overlapping the projection surface of the surface electrode 13” means that the gap between the central electrode 22 and the electrode 12 on the piezoelectric film 11 is 0.1 mm or more.

In the biaxial variable load sensor 110, as shown in FIG. 5, the electrical wiring of the electrode 12 portion has the same output terminals V ₁ and V ₂ as in FIG. 2, and is further connected to the center electrodes 22A and 22B, respectively. Output terminals V ₃ and V ₄ . In the case of FIG. 5, as in the case of FIG. 2, the capacitance C ₁ and the resistance R ₁ , the capacitance C ₂ and the resistance R ₂ are respectively added to the electric circuits on the electrode 12 side and the central electrode 22 side. Can be provided.

The biaxial fluctuating load sensor 110 can detect fluctuating load in the shearing direction from the output voltage from the output terminals V ₁ and V ₂ and detecting fluctuating load in the compressing direction from the output voltage from the output terminals V ₃ and V _4. . The distortion generated in the central electrodes 22A and 22B of the piezoelectric film 11 is amplified by the Poisson effect accompanying the compression of the distortion amplifying member 16 (17, 18), so that the output obtained from the output terminals V ₃ and V ₄ As the voltage, an output voltage associated with the amplified distortion is detected. Thereby, the variable load in the compression direction can be detected with high sensitivity in the same manner as the variable load in the shearing direction.

  Further, the variable load sensor according to the present invention can easily constitute a biaxial variable load sensor that can simultaneously detect a shear variable load in a direction perpendicular to each other. FIG. 6 shows a schematic diagram of the biaxial variable load sensor 120. 6A is a plan view of the biaxial variable load sensor 120, and FIG. 6B is a sectional view taken along line XX in FIG. 6A. FIG. 7 is an electric circuit diagram of the biaxial variable load sensor 120.

  As shown in FIG. 6, the biaxial variable load sensor 120 has a shape in which a first sensor element 100 and a second sensor element 101 are joined orthogonally to each other. The first sensor element 100 has the same configuration as the variable load sensor 10 shown in FIG. That is, a pair of first surface electrodes 13 (13A, 13B) having the same shape and spaced apart from each other on the surface of the first piezoelectric film 11, and the first surface electrode 13 on the back surface of the first piezoelectric film 11 It has a pair of first back electrodes 14 (14A, 14B) having the same shape as the first front electrode 13 provided so that the projection surfaces overlap. The second sensor element 101 includes a pair of second surface electrodes 131 (131A, 131B) having the same shape and spaced apart on the surface of the second piezoelectric film 111, and the second sensor element 101 on the back surface of the second piezoelectric film 111. The second front electrode 131 has a pair of second back electrodes 141 (141A, 141B) having the same shape as the second front electrode 131 provided so as to overlap the projection surface. For bonding the first sensor element 100 and the second sensor element 101, an adhesion or welding method can be used. When joining by the adhesion method, the above-mentioned silicon resin-based or rubber-based adhesive can be used. In this case, the thickness of the adhesive layer is preferably as thin as possible in order to reduce the load transmission loss to the piezoelectric film, and is preferably 0.1 mm or less.

  The biaxial variable load sensor 120 is disposed on the surface of the first and second piezoelectric films 11 and 111 and the surface strain amplification member 17 that covers the first and second surface electrodes 13 and 131, and on the upper surface of the surface strain amplification member 17. A load transmitting member 19 provided; a back strain amplifying member 17 covering the back surface of the first and second piezoelectric films 11 and 111 and the first and second back electrodes 14 and 141; Yes.

  In the biaxial variable load sensor 120, the pair of first front electrodes 13 or back electrodes 14 are symmetrical with respect to the symmetry axis of the load transmission member 19 and do not overlap the projection surface of the load transmission member 19. It is installed. Further, the pair of second front electrodes 131 or back electrodes 141 are arranged so as to be symmetrical with respect to the symmetry axis of the load transmission member 19 and not overlap the projection surface of the load transmission member 19. Further, as shown in FIG. 7, the pair of first front electrodes 13 and the pair of first back electrodes 14 are short-circuited with each other at the diagonal positions, and the pair of second front electrodes 131 and the pair of second electrodes. In the back electrode 141, the electrodes existing diagonally are short-circuited.

When the biaxial variable load sensor 120 is attached to the object to be measured and the shear variable load in the XX direction shown in FIG. 6A is applied to the load transmitting member 19, the output terminals V ₁ and V ₂ shown in FIG. The shear fluctuation load in the XX direction can be detected by the output voltage from. When the YY-direction shear fluctuation load shown in FIG. 6A is applied to the load transmission member 19, the YY-direction shear fluctuation load is detected by the output voltages from the output terminals V ₅ and V ₆ shown in FIG. be able to.

The reason why the shearing load in the XX and YY directions can be detected simultaneously is as follows. First, the first sensor element 100 will be described. In FIG. 6A, when the first piezoelectric film 11 receives a shearing variation load in the XX direction, the first piezoelectric film 11 is charged by polarization. Assuming that strains in the XX and YY directions generated in the first piezoelectric film 11 are ε _x and ε _y , respectively, the amount of charge Q _x generated is Q _x = b ₁ ε _x + b ₂ ε _y (where b ₁ , b ₂ Is a proportionality constant). Piezoelectric films generally have anisotropy, and the polarization in the stretching direction is larger than the polarization in the direction perpendicular to the stretching direction. For example, the piezoelectric film having a thickness of 40 [mu] m PVDF (Kureha Chemical), about b ₂ = 0.5b _l, also, because Poisson's ratio of the elastic body of silicone rubber or the like used in the distortion amplification member 16 is approximately 0.5 , Ε _y = −0.5ε _x , the charge amount Q _x is Q = 0.75b ₁ ε _x .

On the other hand, when the first piezoelectric film 11 is subjected to a shearing variable load in the YY direction, the charge amount Q _y generated in the first piezoelectric film 11 is expressed as Q _y = b ₁ ε _y + b ₂ ε _x . Substituting the above b ₂ = 0.5b _l and ε _y = −0.5ε _x into this equation gives Q _y = 0. That is, it can be seen that the first sensor element 100 can detect only the shear fluctuation load in the XX direction and cannot detect the shear fluctuation load in the YY direction.

  Similarly, the second sensor element 101 can detect only the shear fluctuation load in the YY direction and cannot detect the shear fluctuation load in the XX direction. That is, it can be seen that the shear variable load in any direction can be detected by the biaxial variable load sensor 120 in which the first sensor element 100 and the second sensor element 101 are integrally formed orthogonally.

  As described above, the piezoelectric film has anisotropy. For this reason, the sensitivity of the biaxial variable load sensor 120 is affected by the piezoelectric films constituting the first sensor element 100 and the second sensor element 101. Therefore, the piezoelectric films used for these sensors are preferably the same and have the same polarization characteristics with respect to strain in the XX direction or the YY direction.

As shown in FIG. 7, the wiring around the electrodes of the biaxial variable load sensor 120 is the same as the wiring shown in FIG. 2 for both the first sensor element 100 and the second sensor element 101. That is, for the first sensor element 100, the electrode 13A and the electrode 14B are connected so that the electrodes existing at the diagonal positions of the pair of front electrodes 13 and the pair of back electrodes 14 are short-circuited, and the electrode 13B And the electrode 14A are connected, and wirings reaching the output terminals V ₁ and V ₂ are formed. In addition, for the second sensor element 101, the electrode 131A and the electrode 141B are connected so that the electrodes existing at the diagonal positions of the pair of front electrodes 131 and the pair of back electrodes 141 are short-circuited, and the electrode 131B And the electrode 141A are connected, and wirings reaching the output terminals V ₅ and V ₆ are formed.

  Furthermore, the variable load sensor according to the present invention can easily constitute a three-axis variable load sensor capable of simultaneously detecting a shear variable load and a compression variable load in two orthogonal directions. That is, the triaxial variable load sensor 130 can be easily configured by adding a central electrode described below to the biaxial variable load sensor 120 shown in FIG.

  FIG. 8 schematically shows the configuration of the central electrode portion of the triaxial variable load sensor 130. FIG. 9 shows an electric circuit diagram. As shown in FIG. 8, the three-axis variable load sensor 130 includes a first front center electrode 22A provided on the surface of the first piezoelectric film 11 on the lower surface side of the front strain amplifying member 17, and a back strain amplifying member 18. And a pair of first center electrodes 22 formed from a first back center electrode 22B provided on the back surface of the first piezoelectric film. The first front center electrode 22A is disposed symmetrically with respect to the symmetry axis of the load transmitting member 19 and does not overlap the pair of first front electrodes 13. The first back center electrode 22B The same shape as the central electrode 22A is arranged so as to overlap the projection surface. The triaxial variable load sensor 130 has the same configuration as the biaxial variable load sensor 120 except for the first central electrode 22 portion.

  Instead of the first central electrode 22, a central electrode may be provided on the front and back surfaces of the second piezoelectric film 111. That is, the second front center electrode 221A provided on the surface of the second piezoelectric film 111 on the lower surface side of the front strain amplifying member 17 and the rear surface of the second piezoelectric film 111 on the lower surface side of the back strain amplifying member 18 are provided. The second back center electrode 221B is formed with a pair of second center electrodes 221. The second table center electrode 221A is symmetric with respect to the symmetry axis of the load transmitting member 19 and has a pair of second table electrodes 221B. The second back center electrode 221B may be disposed so as not to overlap the electrode 131, and may be disposed so as to overlap the projection surface in the same shape as the second front center electrode 221A.

  Further, both the first central electrode 22 and the second central electrode 221 may be included. In this case, the first center electrode 22 and the second center electrode 221 are disposed so that the projection surfaces overlap each other. An example of an electric circuit diagram in such a case is shown in FIG. In this example, the contact surfaces of the first back center electrode 22B and the second front center electrode 221A that are in contact with each other are insulated, and the surfaces of the first piezoelectric film 11 and the second piezoelectric film 111 that charge different charges from each other. The first front center electrode 22A and the second front center electrode 221A are short-circuited, and the first back center electrode 22B and the second back center electrode 221B are short-circuited.

  FIG. 10 is a graph showing the output voltage obtained when an equal compression fluctuating load is applied to each of the three-axis fluctuating load sensors 130 having the various center electrodes. In the illustrated parameters, the lower side indicates a triaxial variable load sensor 130 having only the second central electrode 221, and the upper side indicates a triaxial variable load sensor 130 having only the first central electrode 22. The parallel connection indicates the case of the triaxial variable load sensor 130 having the electric circuit of FIG. 9 provided with two of the first center electrode 22 and the second center electrode 221. For comparison, the results when the first back center electrode 22B and the second front center electrode 221A are short-circuited are shown as series connection. In the parallel connection, the area of the central electrode portion of the piezoelectric film where charges are accumulated is twice that of the other, so the output voltage is twice that of the other, and the sensitivity is improved twice.

  The variable load sensor according to the present invention has been described above. As described above, the fluctuating load sensor can constitute a thin sensor, and can easily form a curved or bent sensor such as a curved surface. In addition, it is possible to configure a sensor having an optimum size according to the size of the acting surface of the variable load to be detected. For example, a three-axis fluctuating load sensor 130 as shown in FIG. 11 can be configured, and a suitable small tactile sensor can be configured by being provided at the fingertip of the robot hand. This tactile sensor is configured by attaching a three-axis variable load sensor 130 to a trapezoidal fingertip member 51 which is provided integrally with a fingertip of a robot hand and has a leg portion curved downward from a flat top. A load transmission member 19 is disposed on the flat top of the fingertip member 51. By providing such a tactile sensor at each fingertip of the robot hand, the robot can be made to perform fine work.

  FIG. 12 shows an example in which a biaxial variable load sensor 140 is used for a grip member 52 of a robot hand that grips and moves an object (for example, a cup). In this example, a biaxial variable load sensor 140 is attached around the semi-cylindrical gripping member 52, the weight when the object is gripped is detected as a variable load in the shear direction, and the softness when the object is gripped is detected. A tactile sensor having a gripping function close to a skin sensation is configured by detecting the thickness as a compression fluctuation load.

  If such a tactile sensor is prepared in advance, a robot hand or the like that can quickly and highly sensitively detect a fluctuating load in the shearing direction and / or the compressing direction can be easily configured. That is, a tactile sensor in which several kinds of predetermined pedestals such as fingertip member 51 and gripping member 52 that can be curved and can be provided with a load transmitting member on the top are prepared, and a two- or three-axis variable load sensor is attached thereto. If the tactile sensor is prepared in advance, the tactile sensor is bonded or mechanically fixed to a required part, and a fluctuating load in the shearing direction and / or compression direction acting on the part is easily, rapidly and highly sensitively detected. be able to.

8 and 9 is fixed vertically on the load cell, and the shear load is applied when the shear load is applied in the arrow direction (45 ° direction) shown in FIG. And the output voltage of the triaxial variable load sensor 130 were obtained. As the piezoelectric films 11 and 111, PVDF having a thickness of 40 μm, 30 mm in length, and 60 mm in width with aluminum vapor deposition electrodes was used. Mask this to peel off the deposited metal other than the electrode part, and place the central electrode 22 and 221 with a side of 30mm on the front and back sides of the central part, and 5mm apart from the central electrode 22 and 221, respectively. A pair of rectangular electrodes 13, 14, 131, and 141 having a length of 30 mm and a width of 10 mm were attached to the front and back surfaces of the plate. To each electrode, one end of a metal foil tape with a conductive adhesive was adhered and fixed, and the other end was drawn out from these electrodes and wired to output terminals V _{1 to} V ₆ . Electrical wiring was connected to each terminal by soldering.

  Next, a silicon rubber plate (thickness 3 mm) having a rubber hardness of about 50 is adhered to the entire surface of the piezoelectric films 11 and 111 with a silicone resin adhesive on the strain elastic member 16, and the mounting portion of the output terminal is also an adhesive. Fixed with. Next, a load transmission member 19 of a square brass plate having a thickness of 0.1 mm and a side of 30 mm is adhered to the upper surface of the silicon rubber plate above the central electrodes 22 and 221 with the above-mentioned adhesive, and a slip of 0.5 mm thickness is formed thereon. The contact member of the stop rubber plate was adhered. The total thickness of the triaxial variable load sensor 130 was about 6.7 mm.

  Each electric wiring from the output terminal is connected in parallel with a capacitance of 0.47μF, and this is the same time as the load waveform of the load cell using a voltage recorder with an internal resistance of 1MΩ (NEC Sanei Co., Ltd. Omniace). Recorded at the timing. The test results are shown in FIG. The horizontal axis shows the load measured by the load cell, and the vertical axis shows the output voltage in the XX and YY directions. According to FIG. 13B, the output voltages in the XX and YY directions also agree well, and it can be seen that these output voltages are proportional to the shear load.

It is a schematic diagram of the variable load sensor which concerns on this invention. It is an electric circuit diagram of the variable load sensor. It is operation | movement principle explanatory drawing of the said fluctuating load sensor. It is a schematic diagram of a biaxial variable load sensor according to the present invention. It is an electric circuit of the said biaxial fluctuation load sensor. It is a schematic diagram of another biaxial variable load sensor according to the present invention. It is an electric circuit of the biaxial fluctuation load sensor shown in FIG. It is a schematic diagram of the center electrode part of the triaxial variable load sensor which concerns on this invention. 3 is an electric circuit of the three-axis variable load sensor. It is a graph which shows an output voltage at the time of having a various center electrode in a triaxial variable load sensor. It is explanatory drawing of the Example which utilized the triaxial fluctuation load sensor for the fingertip of the robot hand. It is explanatory drawing which shows the state which hold | gripped the cup with the robot hand using a biaxial fluctuation load sensor. It is the figure (a) which shows the direction of the fluctuating load of Example 1, and the graph (b) which shows a test result.

Explanation of symbols

10 Fluctuating load sensor
11 Piezoelectric film
12 electrodes
13 Front electrode
14 Back electrode
16 Strain amplification member
17 Surface strain amplification member
18 Back strain amplification member
19 Load transmitting member
22, 22A, 22B Center electrode, front center electrode, back center electrode
50 DUT
51 Fingertip material
52 Grip member
100 First sensor element
101 Second sensor element
110 Biaxial variable load sensor
120 Biaxial variable load sensor
130 3-axis variable load sensor
140 Biaxial variable load sensor

Claims (9)

A fluctuating load sensor used by being attached to an object to be measured,
A pair of identically shaped front electrodes disposed on the surface of the piezoelectric film, a surface strain amplification member that covers the surface electrode and the surface of the piezoelectric film, and an upper surface of the surface strain amplification member A load transmitting member, a pair of back electrodes that have the same shape as the front electrode on the back surface of the piezoelectric film and overlap the projection surface, and the same quality as the front strain amplification member that covers the back electrode and the back surface of the piezoelectric film. A back distortion amplifying member,
The pair of front or back electrodes are respectively arranged symmetrically with respect to the symmetry axis of the load transmission member and not overlapping the projection surface of the load transmission member,
The pair of front electrodes and the pair of back electrodes are fluctuating load sensors in which electrodes existing at diagonal positions are short-circuited.   A front center electrode that is provided on the surface of the piezoelectric film on the lower surface side of the front strain amplifying member and is symmetric with respect to the symmetry axis of the load transmitting member and does not overlap with a pair of front electrodes, and the piezoelectric film on the lower surface side of the back strain amplifying member The variable load sensor according to claim 1, further comprising a pair of center electrodes formed on the back surface of the back surface center electrode and having the same shape as the front center electrode and overlapping the projection surface. A fluctuating load sensor used by being attached to an object to be measured,
A pair of first surface electrodes having the same shape and spaced apart from each other on the surface of the first piezoelectric film, and a pair overlapping the projection surface in the same shape as the first surface electrode on the back surface of the first piezoelectric film. A first sensor element having a first back electrode of
A pair of second surface electrodes of the same shape joined orthogonally to the first sensor element and spaced apart on the surface of the second piezoelectric film, and the second surface electrode on the back surface of the second piezoelectric film A second sensor element having a pair of second back electrodes having the same shape as the front electrode and overlapping the projection surface;
A surface strain amplification member that covers the surfaces of the first and second piezoelectric films and the first and second surface electrodes;
A load transmission member disposed on the upper surface of the surface strain amplification member;
A back strain amplifying member of the same quality as the surface strain amplifying member covering the back surface of the first and second piezoelectric films and the first and second back electrodes;
The first piezoelectric film and the second piezoelectric film have equivalent polarization characteristics,
The pair of first front or back electrodes are respectively arranged symmetrically with respect to the symmetry axis of the load transmitting member and not overlapping the projection surface of the load transmitting member,
The pair of second front or back electrodes are respectively arranged symmetrically with respect to the symmetry axis of the load transmission member and not overlapping the projection surface of the load transmission member,
The pair of first front electrodes and the pair of first back electrodes are short-circuited between the electrodes present at diagonal positions,
A variable load sensor in which the pair of second front electrodes and the pair of second back electrodes are short-circuited to each other at the diagonal positions.   A first front center electrode which is provided on the surface of the first piezoelectric film on the lower surface side of the front strain amplifying member and which is symmetric with respect to the symmetry axis of the load transmitting member and does not overlap with the pair of first front electrodes; A pair of first central electrodes formed on the lower surface side of the first piezoelectric film is formed on the back surface of the first piezoelectric film and is formed of a first back central electrode having the same shape as the front central electrode and overlapping the projection surface. The variable load sensor according to claim 3.   A second front center electrode which is provided on the lower surface side of the front strain amplifying member on the surface of the second piezoelectric film and which is symmetric with respect to the symmetry axis of the load transmitting member and does not overlap with the pair of second front electrodes; A pair of second center electrodes formed on the back surface of the second piezoelectric film on the back surface of the second piezoelectric film and formed of a second back center electrode having the same shape as the second front center electrode and overlapping the projection surface. 3. The variable load sensor according to 3. A first front center electrode which is provided on the surface of the first piezoelectric film on the lower surface side of the front strain amplifying member and which is symmetric with respect to the symmetry axis of the load transmitting member and does not overlap with the pair of first front electrodes; A pair of first center electrodes formed on the lower surface side on the back surface of the first piezoelectric film and formed from a first back center electrode having the same shape as the front center electrode and overlapping the projection surface;
It has the same shape as the first central electrode, is provided on the surface of the second piezoelectric film on the lower surface side of the surface strain amplifying member, is symmetric with respect to the symmetry axis of the load transmitting member, and overlaps with the pair of second surface electrodes. A second front center electrode which is formed on the back surface of the second piezoelectric film on the lower surface side of the back strain amplifying member and has the same shape as the second front center electrode and which overlaps the projection surface. A pair of second central electrodes,
The first front center electrode is short-circuited with a second front or back center electrode having the same polarity as the first front center electrode;
The variable load sensor according to claim 3, wherein the first back center electrode is short-circuited with a second front or back center electrode having the same polarity as the first back center electrode.   The variable load sensor according to claim 1, wherein the strain amplifying member has a lower elastic modulus than that of the piezoelectric film.   The variable load sensor according to claim 1, wherein the load transmitting member has a higher elastic modulus than the strain amplifying member.   A tactile sensor comprising the fluctuating load sensor according to any one of claims 1 to 8 attached to a pedestal that is curved and on which a load transmitting member can be disposed.

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