JP5408687B2 - Shear stress sensor and distributed shear stress sensor - Google Patents

Description

  The present invention relates to a shear stress sensor for measuring shear stress (friction force) and a distributed shear stress sensor. In particular, the present invention relates to a uniaxial or biaxial misalignment stress sensor that is thin and can be installed on a curved surface portion, and a distributed misalignment stress sensor configured by arranging a plurality of misalignment stress sensors.

  There is a need for thin shear stress sensors for measuring shear stress, such as fingertip friction force, friction force between body part and bed, measurement of various mechanical quantities, and robots. As a detection, instead of a strain gauge that has been used conventionally, development of a sensor that uses a piezoelectric film that is much thinner than a sensor using a strain gauge is expected.

For example, Patent Document 1 discloses a sensor that uses a piezoelectric film and detects a fluctuating load in a shearing direction and a fluctuating load in a compression direction. A pair of front electrodes having the same shape spaced apart on the surface of the piezoelectric film and a pair of back electrodes having the same shape as the front electrode and overlapping the projection surface are disposed on the back surface of the piezoelectric film. The surface of the film is covered with a surface strain amplifying member, and the back electrode and the back surface of the piezoelectric film are covered with a surface strain amplifying member. And by arranging a load transmitting member on the upper surface of the front strain amplifying member, and deforming the front strain amplifying member and the back strain amplifying member with a deviation stress applied to the load transmitting member, the strain amount of the piezoelectric film is increased, The measurement sensitivity is increased by increasing the amount of charge generated by polarization accompanying the distortion.
JP 2006-226858 A

  In Patent Document 1, the piezoelectric film is covered with a front strain amplifying member and a back strain amplifying member, and the thickness of the strain amplifying member needs to be 1 mm to 5 mm, respectively. If it is thinner than 1 mm, the strain amount of the strain amplifying member itself becomes small, and the amplification effect cannot be obtained, so there is a limit to obtain a sensor thinner than this.

  And since it is necessary to install a load transmission member on the upper surface of the surface distortion amplifying member, and it is necessary to cover this load transmission member with rubber or the like in the case of implementation, the thickness further increases, and the total is about 5 mm. It will be thick.

  For this reason, there is a problem that the sensor cannot be used due to its thickness in a situation where the sensor must be installed in a narrow gap. When the thickness is about 5 mm, there is a problem that a sense of incongruity is generated due to a difference in level corresponding to the thickness of the sensor when used by being sandwiched between the body part of the bed and the object.

  In such a situation, the problem to be solved by the present invention is to provide a sheet-type shear stress sensor that can be installed on a thin curved surface with a thickness of about 1 mm and can accurately measure the shear stress. is there. Another object of the present invention is to provide a distributed shear stress sensor in which a plurality of sheet shear stress sensors are arranged linearly or two-dimensionally.

  The present invention includes a piezoelectric thin plate made of a piezoelectric material, and an upper transmission plate and a lower transmission plate provided so as to sandwich the piezoelectric thin plate, and the piezoelectric thin plate is bonded to the upper transmission plate at an upper adhesive portion, The lower transmission plate is bonded to the lower bonding portion, the upper and lower bonding portions are arranged so as not to substantially overlap, and the forces acting in the opposite directions on the upper transmission plate and the lower transmission plate due to the shift stress, It is transmitted to the piezoelectric thin plate through an upper and lower adhesive portion, and the piezoelectric thin plate is compressed or stretched to generate an electric charge to measure a shear stress.

  The present invention also provides a first piezoelectric thin plate and a second piezoelectric thin plate made of piezoelectric materials arranged adjacent to each other, an upper transmission plate and a lower transmission provided so as to sandwich the first piezoelectric thin plate and the second piezoelectric thin plate. The first piezoelectric thin plate is bonded to the upper transmission plate at the upper bonding portion, bonded to the lower transmission plate at the lower bonding portion, and the upper and lower bonding portions are not substantially overlapped with each other. The second piezoelectric thin plate is bonded to the upper transmission plate by an upper bonding portion, is bonded to the lower transmission plate and a lower bonding portion, and the upper and lower bonding portions are not substantially overlapped with each other. Furthermore, the upper adhesive portion of the first piezoelectric thin plate and the upper adhesive portion of the second piezoelectric thin plate are disposed in reverse, and forces acting in opposite directions on the upper transmission plate and the lower transmission plate, respectively, due to displacement stress, The first piezoelectric thin plate and the second piezoelectric thin plate via the adhesive portion The first piezoelectric thin plate is compressed or expanded to generate a charge, and the second piezoelectric thin plate is expanded or compressed to generate a charge in the opposite direction to the first piezoelectric thin plate. The shear stress is measured.

  Further, according to the present invention, the piezoelectric thin plate is formed by stretching a piezoelectric material, the upper and lower adhesive portions of the piezoelectric thin plate are linearly arranged in the stretching direction, and the piezoelectric thin plate is compressed or stretched in the stretching direction. It is characterized by that.

  Further, in the present invention, the piezoelectric thin plate, the upper transmission plate, and the lower transmission plate are bonded to each other via the upper and lower adhesive layers, and a sliding sheet having the same thickness as the upper and lower adhesive layers is adjacent to the upper and lower adhesive layers. The upper transmission plate, the lower transmission plate, and the piezoelectric thin plate are brought into flat contact with each other.

Further, the present invention provides a piezoelectric thin plate made of a piezoelectric material, an upper transmission plate and a lower transmission plate provided so as to sandwich the piezoelectric thin plate, an upper adhesive layer for bonding the piezoelectric thin plate and the upper transmission plate, It consists of a lower adhesive layer for bonding the piezoelectric thin plate and the lower transmission plate, and a sliding sheet having the same thickness as the upper adhesive layer and the lower adhesive layer, and linearly extends in the extending direction of the piezoelectric thin plate with the center of the piezoelectric thin plate The upper adhesive layer and the lower adhesive layer are disposed on each other, and the upper adhesive layer is bonded to the upper transmission plate at all of the upper adhesive layer on the upper surface side of the piezoelectric thin plate, and the lower adhesive layer is formed of the piezoelectric thin plate. All of the lower adhesive layers on the lower surface side are bonded to the lower transmission plate, and the upper adhesive layer and the lower adhesive layer are arranged so as not to substantially overlap, and the sliding sheet is connected to the upper adhesive layer. Adjacent to the lower adhesive layer and due to horizontal shear stress The force acting in the opposite direction on the upper transmission plate and the lower transmission plate is transmitted to the piezoelectric thin plate via the upper adhesive layer and the lower adhesive layer, and is generated by contracting or extending the piezoelectric thin plate. It has a shear stress detection element for measuring the magnitude of the shear stress with electric charge, and includes at least two sets of the shear stress detection elements facing each other, and the piezoelectric stress plate is stretched with one shear stress detection element facing each other. The direction is aligned with the X-axis direction, the magnitude of the shear stress in the X-axis direction is measured from the difference in output corresponding to the amount of strain of each piezoelectric thin plate, and the other shear stress detection elements facing each other are measured. The extending direction of the piezoelectric thin plate is arranged to coincide with the Y-axis direction, and the magnitude of the deviation stress in the Y-axis direction is measured from the difference in output corresponding to the amount of strain of each piezoelectric thin plate.

Further, according to the present invention, a plurality of displacement stress sensors according to any one of claims 1 to 3 are arranged one-dimensionally or two-dimensionally on the same plane, and each of the displacement stress sensors is arranged. It is characterized by taking out the electric charges individually and measuring the distribution of the magnitude of the shear stress .

  According to the present invention, the piezoelectric thin plate has a simple structure in which a part of the upper surface of the piezoelectric thin plate is bonded to the upper transmission plate, and the lower surface of the piezoelectric thin plate is bonded to the lower transmission plate. Also, it can be constructed from a thin one of several tens of micrometers to several hundreds of micrometers. For this reason, a thin uniaxial or biaxial displacement stress sensor having a thickness of 1 mm or less can be configured. Thus, the sensor can be used without any trouble even in a situation where the sensor must be installed in a narrow gap.

  Further, according to the present invention, the upper and lower adhesive portions are arranged so as not to substantially overlap, and when a shift stress is applied, the upper and lower transmission plates act in opposite directions. All of the shear stress is applied to the piezoelectric thin plate through the adhesive layer and is compressed or stretched. As a result, the piezoelectric thin plate generates electric charges according to the strain and the deviation stress, and the deviation stress can be measured by taking out this amount of electric charge.

  Furthermore, according to the present invention, two sets of displacement stress detection elements are arranged in parallel, and the upper adhesive portions are arranged in reverse so that the adhesive portions are staggered. When one shear stress detection element receives an excessive compressive load, the upper and lower transmission plates float and the piezoelectric thin plate deforms out of the plane, but the other shear stress detection element receives a tensile load. Works to hold down the piezoelectric thin plate from above and below. Accordingly, the upper and lower transmission plates do not float and the piezoelectric thin plate that receives the compressive load is prevented from being deformed out of the plane, so that the deviation stress can be detected accurately.

  Further, according to the present invention, the extending direction of the piezoelectric thin plate is configured to match the direction of the shear stress. When the piezoelectric thin plate is distorted in the stretching direction, the greatest polarization is generated and electric charges are generated. Therefore, it is possible to provide a stress sensor with higher detection accuracy.

  Furthermore, according to the present invention, since the sliding sheet having the same thickness as the adhesive layer is disposed adjacent to the adhesive layer, a step due to the bending of the piezoelectric thin plate does not occur, and the detection accuracy of the deviation stress is improved.

  Furthermore, according to the present invention, since the edge of the upper transmission plate and the edge of the lower transmission plate are connected by a connecting member such as rubber, the transmission plate does not turn up.

  Furthermore, according to the present invention, when a resin thin plate or a metal thin plate is used for the upper transmission plate and the lower transmission plate, a configuration with a small out-of-plane bending rigidity is possible. A stress sensor can be produced.

  Furthermore, according to the present invention, since two or more sets of shear stress detection elements are arranged orthogonally, the shear stress in the X-axis and Y-axis directions can be detected at a time.

  Furthermore, according to the present invention, since the plurality of displacement stress detection elements are arranged in a one-dimensional or two-dimensional manner, it is possible to detect the distributed stress acting in a wide range.

  A shear stress sensor 1 according to the first embodiment will be described with reference to FIGS. 1 to 3. FIG. 1 is a perspective view and a cross-sectional view showing a schematic configuration of a shear stress sensor 1, FIG. 2 is a perspective view showing a charge generation state of a piezoelectric thin plate, and FIG. 3 is a cross-sectional view showing a detection principle of the shear stress sensor. The shear stress sensor 1 of the present invention is a thin sheet-like shear stress sensor as shown in the perspective view of FIG.

  As shown in FIG. 1, the shear stress sensor 1 mainly includes a piezoelectric thin plate 11, an upper transmission plate 16 and a lower transmission plate 17 provided so as to sandwich the piezoelectric thin plate 11, and electrodes attached to both surfaces of the piezoelectric thin plate 11. Adjacent to the upper adhesive layer 13, the lower adhesive layer 14, and the upper and lower adhesive layers 13, 14 for bonding the piezoelectric thin plate 11 and the upper and lower transmission plates 16, 17 through the films 12a, 12b and the electrode films 12a, 12b. It comprises sliding sheets 15a and 15b.

  The piezoelectric thin plate 11 is made of a piezoelectric material that is polarized in accordance with strain and allows current to flow. For example, a material formed by stretching a polymer piezoelectric material such as polyvinylidene fluoride or vinylidene cyanide may be used. The piezoelectric thin plate 11 formed by stretching in this way generates the largest electric charge with respect to a strain that contracts or expands in the stretching direction. Therefore, the direction in which the shear stress is applied and the extending direction of the piezoelectric thin plate 11 are preferably matched. Since polarization efficiency is good even with a small shear stress, it can be measured with high accuracy.

  FIG. 2 shows the state of charge generation when the piezoelectric thin plate 11 is compressed or expanded when the positive electrode surface of the piezoelectric thin plate 11 is disposed on the upper side. In this way, when the piezoelectric thin plate 11 is arranged with the upper surface as the positive electrode surface (+) and the lower surface as the negative electrode surface (−), the piezoelectric thin plate 11 expands in the extending direction as indicated by the arrow in FIG. A positive charge (+ Q) is generated on the upper surface of the thin plate 11, and a negative charge (-Q) is generated on the lower surface. On the other hand, as shown by the arrow in FIG. 2B, when the piezoelectric thin plate 11 contracts in the extending direction, a negative charge (−Q) is generated on the upper surface of the piezoelectric thin plate and the positive charge is generated on the lower surface. (+ Q) will occur. The amount of charge generated in this way is proportional to the amount of strain due to contraction or expansion of the piezoelectric thin plate.

  The electrode films 12a and 12b are provided on the front and back surfaces of the piezoelectric thin plate 11 by vapor deposition, sputtering, etc., and electrical terminals are attached to the electrode films 12a and 12b with conductive paint, caulking, etc., and wirings 21a and 21b are connected thereto, respectively. Thereby, an output signal due to distortion of the piezoelectric thin plate 11 is taken out. Although a commercially available piezoelectric thin plate 11 provided with electrode films 12a and 12b may be used, for the purpose of the present invention, the piezoelectric thin plate 11 and the electrode films 12a and 12b are formed as thin as possible, for example, It is preferable to use one having a thickness of 20 μm to 200 μm.

  As the upper transmission plate 16 and the lower transmission plate 17, a plate having rigidity in the plane, such as a resin plate, a metal plate, or a fiber reinforced resin plate, is used. As long as the member has rigidity in the plane, a thin sheet member such as a resin thin plate, a metal thin plate, or a fiber reinforced resin thin plate that can be bent and deformed out of the surface may be used.

The adhesive layer 13 on the upper surface side of the piezoelectric thin plate 11 is bonded to the upper transmission plate 16, and the adhesive layer 14 on the lower surface side of the piezoelectric thin plate 11 is bonded to the lower transmission plate 17.

  In this case, the upper and lower adhesive layers 13 and 14 are arranged in the opposite direction along the extending direction of the piezoelectric thin plate 11. As described above, when the piezoelectric thin plate 11 is strained in the stretching direction, the piezoelectric thin plate 11 is polarized most greatly, and the accuracy of detecting the deviation stress with high accuracy is increased.

  The upper and lower adhesive layers 13 and 14 have a role of transmitting a displacement stress applied to the upper transmission plate 16 or the lower transmission plate 17 to the piezoelectric thin plate 11 and polarizing the piezoelectric thin plate 11 by compressing or expanding the piezoelectric thin plate 11. For this reason, the adhesive layers 13 and 14 are arranged so as not to substantially overlap when viewed from the thickness direction of the piezoelectric thin plate 11. The adhesive layers 13 and 14 are arranged on a straight line along the extending direction of the piezoelectric thin plate 11. By arranging the adhesive layers 13 and 14 in this way, when a shear stress acts on the upper transmission plate 16 or the lower transmission plate 17, the piezoelectric thin plate 11 is compressed or expanded via the respective adhesive layers 13 and 14. Acts as follows.

  The adhesive layers 13 and 14 are not particularly limited as long as the piezoelectric thin plate 11 provided with the electrode films 12a and 12b can be fixed to the upper transmission plate 16 and the lower transmission plate 17. For example, an adhesive or a strong adhesive sheet can be used.

  The sliding sheet 15 has a role to keep the piezoelectric thin plate 11 in a flat plane even when a distortion is applied due to a shift stress. For this reason, it is preferable that the sliding sheet 15 has substantially the same thickness as the adhesive layers 13 and 14 so that the flat surface can be maintained even when a tensile load or a contraction load is applied to the piezoelectric thin plate 11. The adhesive layers 13 and 14 and the sliding sheet 15 are preferably provided with the center of the piezoelectric thin plate 11 as a boundary so that a gap is not generated as much as possible. Moreover, by making it the same thickness as the adhesive layer 13, it can suppress that a level | step difference arises in the shift | offset | difference stress sensor 1, and the upper and lower transmission plates 16 and 17 and the piezoelectric thin plate 11 are the electrode film 12, the adhesive layer 13, 14 and the sliding sheet 15 can be contacted flat.

  The sliding sheet 15 uses a material that slides between the upper transmission plate 16 or the lower transmission plate 17 and the piezoelectric thin plate 11 with low frictional resistance. This is because when the resistance is large, the shear stress is relaxed by the frictional force, and the force for distorting the piezoelectric thin plate 11 is reduced. As such a material, fluororesin or waxed paper may be used.

  The sliding sheet 15 does not need to be fixed to either the piezoelectric thin plate 11 or the transmission plates 16 and 17, but is preferably fixed to either one with an adhesive or the like so that the sliding sheet 15 is not detached. .

  Next, with reference to FIG. 3, the principle of detecting the shear stress will be described. 3A is a cross-sectional view taken along the line AA ′ of FIG. 1 when a displacement stress is applied to the upper transmission plate 16 from the right to the left of the drawing, and FIG. 3B is a view when the displacement stress is applied from the left to the right of the drawing. 1 is a cross-sectional view taken along line AA ′ of FIG.

  First, the displacement stress sensor 1 is installed so that tension or compression due to displacement stress acts in the extending direction of the piezoelectric thin plate 11.

  As shown in FIG. 3A, when a shear stress is applied to the upper transmission plate 16 from right to left in the drawing, the sliding sheet 15a is not bonded to the upper transmission plate 16 or the piezoelectric thin plate 11, and the piezoelectric thin plate 11 is bonded to the upper transmission plate 16 by the upper adhesive layer 13, so that the right side of the piezoelectric thin plate 11 receives a compressive load toward the center of the piezoelectric thin plate 11 as indicated by the white arrow.

Further, since the lower transmission plate 17 is used with its lower surface fixed, a reaction force is applied from the left to the right as shown by the arrow. Since the sliding sheet 15b is not bonded to the lower transmission plate 17 or the piezoelectric thin plate 11, and the lower left surface of the piezoelectric thin plate 11 is bonded to the lower transmission plate 17 by the lower adhesive layer 14, the white arrow indicates As shown, the left side of the piezoelectric thin plate 11 receives a compressive load toward the center of the piezoelectric thin plate 11.

  As a result, the piezoelectric thin plate 11 is compressed from both sides and contracts by being contracted and polarized. As a result, charges corresponding to the amount of distortion are generated. For example, in the case where the upper surface of the piezoelectric thin plate 11 is disposed as a positive electrode and the lower surface is disposed as a negative electrode, when the piezoelectric thin plate 11 contracts, a negative charge (−Q) on the positive electrode side of the upper surface and a positive charge (− + Q) will occur.

  Since the amount of charge generated here is proportional to the magnitude of the shear stress, an output signal corresponding to the shear stress is obtained by taking out this charge through the electrode films 12a and 12b, and the magnitude of the shear stress is measured. be able to.

  On the other hand, as shown in FIG. 3B, when a shear stress is applied to the upper transmission plate 16 from the left side to the right side of the drawing, the right upper surface of the piezoelectric thin plate 11 is bonded to the upper transmission plate 16 by the upper adhesive layer 13. Thus, as indicated by the white arrow, the piezoelectric thin plate 11 receives a tensile load toward the right end.

  Further, since the lower transmission plate 17 has its lower surface fixed, a reaction force is applied from the right side to the left side as shown by the arrow. Since the left lower surface of the piezoelectric thin plate 11 is bonded to the lower transmission plate 17 by the lower adhesive layer 14, the piezoelectric thin plate 11 receives a tensile load toward the left end as shown by the white arrow.

  As a result, the piezoelectric thin plate 11 is pulled left and right toward both ends and stretched and distorted, so that an electric charge corresponding to the amount of distortion is generated. For example, in the case where the upper surface of the piezoelectric thin plate 11 is disposed as a positive electrode and the lower surface is disposed as a negative electrode, when the piezoelectric thin plate 11 expands, a positive charge (+ Q) is present on the positive electrode side of the upper surface, and Negative charge (-Q) is generated in the negative electrode.

  Since the amount of generated charge is proportional to the magnitude of the shear stress, an output signal corresponding to the shear stress can be obtained by taking out this charge through the electrode films 12a and 12b, and the magnitude of the shear stress can be measured. it can.

  Since the shear stress sensor 1 of the present invention has a portion where one surface of the shear stress detection element and the shear stress transmission plate are not joined, a compressive load in the vertical direction hardly acts on the shear stress transmission plate. When only the shear stress is applied, the edge portion of the shear stress transmission plate may be turned up.

  In order to suppress this, it is preferable to connect the peripheral portions of the upper and lower transmission plates 16 and 17 in a form that does not constrain the horizontal displacement deformation of the upper and lower transmission plates 16 and 17. For example, as shown in FIG. 4, when the edge portions of the upper and lower transmission plates 16, 17 are gently connected with thin rubber plates or connecting members 41 a, 41 b, 41 c, 41 d such as cloth, the upper and lower transmission plates 16 , 17 can be prevented from curling up without restraining the displacement deformation.

  Next, the shear stress sensor 2 of the second embodiment will be described with reference to FIGS. 5 is a perspective view showing a schematic configuration, FIG. 6 is a cross-sectional view taken along XX ′ and YY ′ in FIG. 5, and FIG. 7 is a cross-sectional view taken along XX ′ in FIG. YY ′ sectional view, and FIG. 8 is a ZZ ′ sectional view of FIG. 5 showing a wiring structure.

  As can be seen from FIG. 5, the shear stress sensor 2 of the second embodiment is roughly the above-described shear stress sensor 1 arranged in parallel on the same plane. The pair of piezoelectric thin plate 11, the electrode film 12, the upper and lower adhesive layers 13 and 14, and the upper and lower sliding sheets 15 will be described below as displacement stress detection elements 31a and 31b.

  As shown in the cross-sectional view of FIG. 6, the shear stress detection elements 31 a and 31 b have a form in which the upper adhesive layer 13 a and the upper adhesive layer 13 b are arranged in reverse. That is, the shear stress detection element 31b is a state in which the shear stress detection element 31b is horizontally rotated by 180 °.

As will be described later, the piezoelectric thin plate 11a (first piezoelectric thin plate) and the piezoelectric thin plate 11b (second piezoelectric thin plate) are preferably arranged in a state in which the positive electrode surface and the negative electrode surface are inverted. For example, the piezoelectric thin plate 11a is disposed with the negative electrode surface facing upward, and one piezoelectric thin plate 11b is disposed with the positive electrode surface facing upward.

  In the case of the above-described shear stress sensor 1, when the shear stress acts as shown in FIG. 3A, the piezoelectric thin plate 11 provided with the electrode film is compressed to generate an electric charge. However, since the piezoelectric thin plate 11 is thin, a compressive load is applied. When it becomes large to some extent, the upper and lower transmission plates 16 and 17 are lifted and deformed to be bent out of the plane.

In order to prevent this deformation, the deviation stress sensor 2 has two sets of deviation stress detection elements 31. The displacement stress detection elements 31a and 31b are connected to the upper adhesive layers 13a and 13b.
When b is reversed and arranged in parallel, even when a compressive load is applied to the piezoelectric thin plate 11 of one of the shear stress detection elements 31, the piezoelectric thin plate 11 of the other shear stress detection element 31 applies a tensile load. The upper and lower transmission plates 16 and 17 are not floated, and the piezoelectric thin plate 11 is not deformed to be bent out of plane.

  For example, as shown in FIG. 7, when the shear stress is applied from left to right, a compressive load is applied to the shear stress detection element 31b shown in FIG. 7B, so that the piezoelectric thin plate 11b is compressed and causes deformation. There is a fear. However, when the shear stress is applied in this way, a tensile load is applied to the other shear stress detection element 31a shown in FIG. 7A, and the upper and lower transmission plates 16 and 17 press the piezoelectric thin plates 11a and 11b from above and below. Thus, the upper and lower transmission plates 16 and 17 do not float. Since the upper and lower transmission plates 16 and 17 are bonded to both the shear stress detecting elements 31a and 31b via the upper and lower adhesive layers 13 and 14, as a result, the upper and lower transmission plates 16 and 17 are floated and the piezoelectric thin plate 11b. Keeps you from going out of the way.

  Further, by installing two sets of the deviation stress detection elements 31, the deviation stress can be detected with higher accuracy. FIG. 8 is a diagram for explaining a wiring method of the shear stress detecting element pair 31a and 31b. As an example, the positive electrode surface of the piezoelectric thin plate 11a of the first shear stress detection element 31a (the surface on which a positive signal is generated with respect to the tensile load) is on the upper side, and the piezoelectric thin plate 11b of the second shear stress detection element 31b is on the upper side. A case where the positive electrode surface is disposed on the lower side will be described.

  First, the electrode film 12c on the positive electrode surface of the piezoelectric thin plate 11b and the electrode film 12b on the negative electrode surface of the piezoelectric thin plate 11a are connected by the wiring 21c. Next, the electrode film 12d on the negative electrode surface of the piezoelectric thin plate 11b and the electrode film 12a on the positive electrode surface of the piezoelectric thin plate 11a are connected by a wiring 21d. Next, wiring is connected to the positive electrode surface and the negative electrode surface of either one of the piezoelectric thin plates 11 (here, the wiring 21a is connected to the negative electrode surface of the piezoelectric thin plate 11a and the wiring 21b is connected to the positive electrode surface), and is drawn out to the outside.

As shown in FIG. 8B, when the shear stress detecting element 31b is pulled, the piezoelectric thin plate 11b expands. As described above, the positive electrode + Q ₁ , resulting in negative charge -Q ₁ on the negative electrode surface of the lower surface.

On the other hand, since the compressive load acts on the shear stress detecting element 31a, the piezoelectric thin plate 11a contracts, and as described above, the negative charge on the upper surface of the piezoelectric thin plate 11a is positive + Q ₁ , and the negative electrode on the lower positive electrode surface is negative. results in a charge -Q _1.

Since the wiring is detected so as to detect the difference in output by reversing the polarities of the piezoelectric thin plate 11b and the piezoelectric thin plate 11a, a charge having a magnitude of 2Q ₁ (= + Q ₁ − (− Q ₁ )) is obtained. Can do.

Since the generated charge 2Q ₁ is proportional to the magnitude of the shear stress, the shear stress sensor 2 of the present invention extracts the time fluctuation d (2Q ₁ ) / dt of the charge 2Q ₁ by connecting the wirings 21a and 21b, measuring a signal proportional to 2Q ₁ by integrating the circuit.

  In this way, by arranging two sets of shear stress detection elements 31a and 31b, generating opposite charges from the two piezoelectric thin plates 11a and 11b, and detecting the output difference between the two charges, even with a small shear stress. It can be detected with high accuracy.

When the shear stress acts in the opposite direction, as shown in FIG. 8C, a compressive load is applied to the shear stress detection element 31b, the piezoelectric thin plate 11b contracts, and the upper surface of the piezoelectric thin plate 11b is contracted. negative charge -Q 1 to Seikyokumen _produces a positive charge + Q ₁ on the negative electrode surface of the lower surface. On the other hand, since a tensile load acts on the shear stress detection element 31a, the piezoelectric thin plate 11a expands, and a negative charge −Q ₁ is applied to the negative electrode surface on the upper surface of the piezoelectric thin plate 11a and a positive charge + Q _{1 is applied} to the positive electrode surface on the lower surface. And a charge of -2Q ₁ can be obtained.

  Thus, by arranging the polarities of the piezoelectric thin plate 11a and the piezoelectric thin plate 11b in opposite directions, the wiring connecting the displacement stress detection element 31a and the displacement stress detection element 31b can be easily performed without crossing.

  When the piezoelectric thin plate 11b and the piezoelectric thin plate 11a are disposed so that the upper sides thereof are both positive electrodes, the two wirings 21c and 21d are crossed and connected at the front and back surfaces. That is, the electrode film on the positive electrode surface of the piezoelectric thin plate 11b and the electrode film on the negative electrode surface of the piezoelectric thin plate 11a are connected by wiring, and the electrode film on the negative electrode surface of the piezoelectric thin plate 11b and the electrode film on the positive electrode surface of the piezoelectric thin plate 11a are connected by wiring. Then, the difference between the outputs of the two piezoelectric thin plates 11a and 11b can be detected.

  Since the other points are the same as those of the above-described shear stress sensor 1, description thereof will be omitted.

  Subsequently, the shear stress sensor 3 according to the third embodiment will be described with reference to FIGS. 9 and 10. The shear stress sensor 3 has a configuration in which four pairs of the shear stress detection elements described above are arranged.

  The deviation stress detection elements 31a, 31b, 31c, and 31d are all arranged in parallel on the same plane in accordance with the extending direction of the piezoelectric thin plate 11. This is a shear stress sensor 3 that measures an output signal proportional to the magnitude of the shear stress along the surfaces of the upper and lower transmission plates 16 and 17.

  FIG. 10 is a plan view of the four pairs of shear stress detection elements 31a, 31b, 31c, and 31d as viewed from above, and it can be seen that the adhesive layers 13 and the sliding sheets 15 are alternately arranged. By arranging in this way, even when a compressive load is applied to the piezoelectric thin plate 11 as described above, the upper and lower transmission plates 16 and 17 do not float and the piezoelectric thin plate 11 does not bend and deform out of plane.

The piezoelectric thin plates 11 of the shear stress detection element 31a and the shear stress detection element 31c are arranged so that the front side of the paper surface is a positive electrode, and the piezoelectric thin plates 11 of the shear stress detection element 31b and the shear stress detection element 31d are on the front side of the paper surface. It arrange | positions so that it may become a negative electrode. Accordingly, each electrode film 12 (not shown) on the front side of the paper surface is continuously connected by the wiring 21c and drawn out, and each electrode film (not shown) on the back side of the paper surface is continuously connected by the wiring 21d. Connected and drawn wiring 21a
Thus, as described in the shear stress sensor 2 of the second embodiment, an output signal proportional to the sum of the shear stresses can be measured.

  As described above, when a plurality of shear stress detection elements 31 are provided, the adhesive layer 13 is finely distributed. Therefore, the shear stress acting on the upper and lower transmission plates 16 and 17 is dispersed and transmitted to each shear stress detection element. can do. Further, by disposing a plurality of shear stress detection elements 31, it is possible to produce a shear stress sensor having a large area corresponding to a desired size.

  The other points are the same as described above, and the description is omitted.

  Next, a shear stress sensor 4 according to a fourth embodiment capable of detecting shear stress in two directions (X axis and Y axis) will be described with reference to FIG. FIG. 11A is a plan view showing the arrangement of the shear stress detection elements 31 of the shear stress sensor 4, and FIG. 11B is a plan view showing the displacement stress detection elements 31 that detect the shear stress in the X-axis direction. It is.

  The shear stress detection elements 31a and 31b are arranged in parallel with the X axis, and they are paired to detect shear stress in the X axis direction. And the deviation stress detection elements 31a and 31b are arranged in a form in which the upper adhesive layer 13 and the sliding sheet 15 are reversed left and right so as to face each other. Then, the deviation stress detection elements 31a and 31b are connected by the wirings 21e and 21f, and the difference in output due to the distortion is taken out from the wirings 21a and 21b to detect the deviation stress in the X-axis direction.

On the other hand, the deviation stress detection elements 31c and 31d are arranged in parallel with the Y axis, and they are paired to detect deviation stress in the Y axis direction. And the deviation stress detection elements 31c and 31d are arranged in the form that the upper adhesive layer 13 and the sliding sheet 15 are turned upside down so as to face each other. Then, the deviation stress detecting elements 31c and 31d are connected by the wirings 21g and 21h, and the difference in output due to the distortion is taken out from the wirings 21c and 21d to detect the deviation stress in the Y- axis direction.

  The upper and lower transmission plates 16 and 17 are attached so as to cover all four displacement stress detection elements 31a, 31b, 31c and 31d.

  By arranging in this way, a biaxial shear stress sensor in which the shear stress detection elements are formed from a single layer on the same plane can be constructed, so that the sensor can be made thin without increasing the thickness of the sensor.

  FIG. 11 (B) is a drawing obtained by taking out the portions (indicated by wavy lines) of the shear stress detecting elements 31a and 31b and the upper and lower transmission plates 16 and 17 for measuring the shear stress in the X-axis direction of FIG. 11 (A). However, both the shear stress detection elements 31a and 31b are arranged in parallel with the X axis, and are provided in a form in which the sliding sheet 15 and the upper adhesive layer 13 are horizontally reversed so as to face each other. The same applies to the shear stress detection elements 31c and 31d that measure the shear stress in the Y-axis direction.

  Of course, two uniaxial shear stress sensors that detect shear stress in only one direction as shown in the aforementioned shear stress sensors 1, 2, or 3 are overlapped in an orthogonal manner, and the overlapping surfaces are joined to form a biaxial A sheet type deviation stress sensor can also be configured.

  Since other points are the same as described above, the description thereof is omitted.

  FIG. 12 is a plan view for explaining the distributed shear stress sensor. A large number of the shear stress sensors of any of the first to fourth embodiments described above are arranged on the same plane in a one-dimensional or two-dimensional form (matrix), and the individual charges from the respective shear stress sensors. It is possible to measure the distribution of shear stress. For example, as shown in FIG. 12, 16 displacement stress sensors 2 are arranged on a predetermined sheet or substrate 51, and a wire bundle 52 in which the wires 21 from each sensor are bundled is sent from a part of the sheet or substrate 51 to the outside. It can be easily configured by pulling out.

  Accordingly, when it is desired to measure how much shear stress is applied to which part in a wide area, such as when used for a bed, it is effective to detect the shear stress of each part. In FIG. 12, wiring inside the sheet or substrate 51 is omitted.

  An experiment was performed with the uniaxial displacement stress sensor 3 according to the third embodiment described with reference to FIG. Piezoelectric thin plates were obtained by cutting four 80 μm-thick aluminum vapor-deposited electrode films with a size of 9 × 40 mm and arranging them in parallel at 1 mm intervals by alternately reversing the positive and negative electrode surfaces. The shear stress detection element was used.

  A masking tape for painting was used for the sliding sheet, and a double-sided pressure-sensitive adhesive sheet having a thickness of 0.15 mm was used for the adhesive layer. PET resin plates having a thickness of 0.2 mm were used for the upper and lower transmission plates, respectively. The size of the shear stress sensor is a square having a side of about 40 mm, and the overall thickness is 0.75 mm.

  Next, a vertical rigid plate was fixed upright on a commercially available load cell (capacity 500 N), and a shear stress sensor was attached to one surface of the rigid plate. Then, an experiment was conducted in which a non-slip silicon rubber sheet was placed on the transmission plate on the front side and repeatedly rubbed in the vertical direction with a finger from above.

  The wiring drawn from the shear stress sensor produces an output proportional to the time derivative of the shear stress, and this was integrated by connecting a capacitor with a capacitance of 4.4 μF in parallel to obtain an output proportional to the shear stress. Thereafter, the voltage was recorded with a voltage recorder (Omniace RA1300 (NEC Sanei)) having an input resistance of 1 M ohm.

The results are shown in FIGS. FIG. 13A shows the waveform of the shear stress measured by the load cell, and FIG. 13B shows the waveform of the output signal measured by the shear stress sensor. As shown in FIG. 13B, a slight drift due to the pyroelectric effect is seen in the waveform of the shear stress sensor due to the finger temperature being transmitted to the sensor. The waveform of the shear stress sensor is similar to that of the load cell of FIG. FIG. 14 is a plot of the relationship between the fluctuation width of the deviation stress measured by the load cell and the fluctuation width of the output signal measured by the deviation stress sensor. FIG. 14 shows that the force applied to the load cell and the output signal obtained from the shear stress sensor are in a proportional relationship.

  From this, it was proved that the shear stress sensor of the present invention can obtain an output signal corresponding to the magnitude of the shear stress applied to the transmission plate and can detect the shear stress with high accuracy.

  In this example, the shear stress sensor 3 according to the third embodiment has been described. However, the shear stress sensor 1 according to the first embodiment or the shear stress sensor 2 according to the second embodiment has almost the same result. . For example, assuming that the amount of strain of a piezoelectric thin plate when a shear stress of a certain force is applied to a shear force sensor 1 including a single piezoelectric thin plate is 1, four piezoelectric elements of the same size to which the same force shear stress is applied. In the shear force sensor 4 provided with a thin plate, since the force transmitted to each piezoelectric thin plate is dispersed, the amount of strain is 0.25. This is because the amount of charge generated by the piezoelectric thin plate is proportional to the amount of strain, and thus the amount of charge generated in any shear stress sensor is the same.

  However, since the strain amount of the piezoelectric thin plate is limited, the number of piezoelectric thin plates is small, and when excessive force is applied, it cannot be further distorted, the charge amount becomes constant, and a large displacement stress Since measurement becomes difficult, it is preferable to use a shear stress sensor using a plurality of piezoelectric thin plates.

  Next, the biaxial shear stress sensor 4 according to the fourth embodiment shown in FIG. Piezoelectric film with electrode film is cut out to the same size as in Example 1 to 15 mm x 30 mm dimension, and a pair of piezoelectric thin plates that are paired and placed in parallel so as to face each other in reverse is detected as shear stress Element pairs were used. These were arranged as shown in FIG. 11 and sandwiched between upper and lower transmission plates. The materials of the sliding sheet, the adhesive layer, and the shear stress transmission plate are the same as those in the first embodiment. The dimension of the biaxial sheet type stress sensor is a square with a side of about 47 mm, and the overall thickness is 0.75 mm.

  FIG. 15 shows an apparatus used in the experiment. A rigid plate 62 is vertically fixed on the load cell 61 and fixed, and the displacement stress sensor 4 is attached to one surface of the rigid plate 62. Then, an experiment was conducted in which a non-slip silicon rubber sheet was placed on the transmission plate on the front side and repeatedly rubbed in the vertical direction with a finger from above. In the experiment, as shown in FIG. 15, the attachment angle θ of the shift stress sensor 4 was varied and pasted. The measurement circuit and the recorder are the same as those in the first embodiment.

  FIG. 16 shows the result. FIG. 16A plots the relationship between the output voltage of the sensor in the X-axis direction and the Y-axis direction measured when the mounting angle θ of the shear stress sensor is about 30 degrees and the vertical load measured by the load cell. (B) is a plot of the relationship between the output voltage of the sensor in the X-axis direction and the Y-axis direction measured when the mounting angle θ of the shear stress sensor is about 45 degrees and the vertical load measured by the load cell. is there. In any case, it can be seen that the X-axis output voltage of the shear stress sensor and the load on the X-axis of the load cell, and the Y-axis output voltage of the shear stress sensor and the load on the Y-axis of the load cell are in a proportional relationship.

FIG. 17 shows the vertical direction measured by the load cell by calculating the vector output (VX ² + VY ² ) ^½ of the vertical output signal from the output signal VX of the sensor in the X-axis direction and the output voltage VY of the sensor in the Y-axis direction. It is compared with the fluctuation range of the load. From FIG. 17, the output of the biaxial shear force sensor is almost a straight line regardless of the installation angle of the sensor.

  From these, the biaxial shear stress sensor of the present invention can obtain an output signal corresponding to the magnitude of the shear stress applied to the transmission plate in the X-axis direction and the Y-axis direction, and can detect the shear stress with high accuracy. Proved.

It is a perspective view showing a schematic structure of a shear stress sensor concerning a 1st embodiment of the present invention. It is a perspective view which shows the electric charge generation state of the piezoelectric thin plate used for this invention. It is sectional drawing which shows the detection principle of the shear stress sensor of this invention. It is a perspective view of the shift | offset | difference stress sensor which connected the upper and lower transmission board with the connection member of this invention. It is a perspective view of the shear stress sensor concerning a 2nd embodiment of the present invention. It is sectional drawing of the shear stress sensor which concerns on 2nd Embodiment of this invention. It is sectional drawing which shows the detection principle of the shear stress sensor which concerns on 2nd Embodiment of this invention. It is sectional drawing which shows the wiring structure of the shear stress sensor which concerns on 2nd Embodiment of this invention, and the generation | occurrence | production state of an electric charge. It is a perspective view of a shear stress sensor concerning a 3rd embodiment of the present invention. It is a top view which shows the internal structure of the shear stress sensor which concerns on 3rd Embodiment of this invention. It is a top view which shows the internal structure of the shear stress sensor which concerns on 4th Embodiment of this invention. It is a top view which shows the structure of the distributed shear stress sensor of this invention. It is a measurement figure which shows the output waveform of the shear stress sensor which concerns on 2nd Embodiment of this invention. It is a measurement figure which shows the relationship between the output of the shear stress sensor which concerns on 2nd Embodiment of this invention, and a load. It is a front view which shows the outline of the apparatus used for the shear stress measurement of the shear stress sensor of this invention. It is a measurement figure which shows the relationship between the output of the shear stress sensor which concerns on 4th Embodiment of this invention, and a load. It is a measurement figure which shows the relationship between the output of the shear stress sensor which concerns on 4th Embodiment of this invention, and a load.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Shear stress sensor 2 Shear stress sensor 3 Shear stress sensor 4 Shear stress sensor 5 Distribution type shear stress sensor 11 Piezoelectric thin plate 12 Electrode film 13 Upper adhesive layer 14 Lower adhesive layer 15 Sliding sheet 16 Upper transmission plate 17 Lower transmission plate 21 Wiring 31 Displacement stress detection element 41 Transmission plate connecting member 51 Sheet or substrate 52 Wiring bundle 61 Load cell 62 Rigid plate

Claims (4)

A piezoelectric thin plate made of a piezoelectric material;
An upper transmission plate and a lower transmission plate provided so as to sandwich the piezoelectric thin plate;
An upper adhesive layer for bonding the piezoelectric thin plate and the upper transmission plate; a lower adhesive layer for bonding the piezoelectric thin plate and the lower transmission plate;
A slip sheet having the same thickness as the upper adhesive layer and the lower adhesive layer,
The upper adhesive layer and the lower adhesive layer are arranged in a straight line in the extending direction of the piezoelectric thin plate with the center of the piezoelectric thin plate as a boundary, and the upper adhesive layer is all of the upper adhesive layer provided on the upper surface side of the piezoelectric thin plate. And the lower adhesive layer is bonded to the lower transmission plate in all of the lower adhesive layer provided on the lower surface side of the piezoelectric thin plate,
The upper adhesive layer and the lower adhesive layer are arranged so as not to substantially overlap,
The sliding sheet is disposed adjacent to the upper adhesive layer and the lower adhesive layer,
A force acting in opposite directions on the upper transmission plate and the lower transmission plate due to a horizontal displacement stress is transmitted to the piezoelectric thin plate via the upper adhesive layer and the lower adhesive layer,
A shear stress sensor, wherein the piezoelectric thin plate is contracted or stretched to generate an electric charge, and the magnitude of the shear stress is measured. A first piezoelectric thin plate and a second piezoelectric thin plate made of piezoelectric materials disposed adjacent to each other;
An upper transmission plate and a lower transmission plate provided so as to sandwich the first piezoelectric thin plate and the second piezoelectric thin plate;
An upper adhesive layer of the first piezoelectric thin plate for bonding the first piezoelectric thin plate and the upper transmission plate, a lower adhesive layer of the first piezoelectric thin plate for bonding the first piezoelectric thin plate and the lower transmission plate, and the second An upper adhesive layer of a second piezoelectric thin plate that bonds the piezoelectric thin plate and the upper transmission plate; a lower adhesive layer of the second piezoelectric thin plate that bonds the second piezoelectric thin plate and the lower transmission plate;
The first piezoelectric thin plate sliding sheet having the same thickness as the first piezoelectric thin plate upper adhesive layer and the first piezoelectric thin plate lower adhesive layer, and the second piezoelectric thin plate upper adhesive layer and the second piezoelectric thin plate lower adhesive A second piezoelectric thin sheet sliding sheet having the same thickness as the layer,
Under the adhesive layer on the adhesive layer and the first piezoelectric thin plate of said first piezoelectric sheet in a straight line in the extending direction of the first piezoelectric thin plate is disposed in the boundary center of the first piezoelectric sheet, said first piezoelectric sheet The upper adhesive layer is bonded to the upper transmission plate by all the upper adhesive layers of the first piezoelectric thin plate provided on the upper surface side of the first piezoelectric thin plate, and the lower adhesive layer of the first piezoelectric thin plate is the first piezoelectric thin plate All the lower adhesive layers of the first piezoelectric thin plate provided on the lower surface side of the first piezoelectric thin plate are bonded to the lower transmission plate, and the upper adhesive layer of the first piezoelectric thin plate and the lower adhesive layer of the first piezoelectric thin plate are substantially Are arranged so as not to overlap,
The lower adhesive layer on the adhesive layer and the second piezoelectric sheet of the second piezoelectric sheet in a straight line in the extending direction of the second piezoelectric thin plate is disposed in the boundary center of the second piezoelectric thin plate, said second piezoelectric The upper adhesive layer of the thin plate is bonded to the upper transmission plate in all of the upper adhesive layer of the second piezoelectric thin plate provided on the upper surface side of the second piezoelectric thin plate, and the lower adhesive layer of the second piezoelectric thin plate is the second adhesive layer . All of the lower adhesive layer of the second piezoelectric thin plate provided on the lower surface side of the piezoelectric thin plate is bonded to the lower transmission plate, and the upper adhesive layer of the second piezoelectric thin plate and the lower adhesive layer of the second piezoelectric thin plate Are arranged so as not to substantially overlap,
The upper adhesive layer of the first piezoelectric thin plate and the upper adhesive layer of the second piezoelectric thin plate are alternately arranged so as to be reversed with respect to the extending direction of the first piezoelectric thin plate or the second piezoelectric thin plate,
The sliding sheet of the first piezoelectric thin plate is disposed adjacent to the upper adhesive layer of the first piezoelectric thin plate and the lower adhesive layer of the first piezoelectric thin plate, and the sliding sheet of the second piezoelectric thin plate is the second piezoelectric thin plate. Disposed adjacent to the upper adhesive layer and the lower adhesive layer of the second piezoelectric thin plate,
Forces acting in opposite directions on the upper transmission plate and the lower transmission plate due to a horizontal displacement stress are applied to the upper adhesive layer of the first piezoelectric thin plate and the lower adhesive layer of the first piezoelectric thin plate, respectively. Transmitted to the first piezoelectric thin plate, transmitted to the second piezoelectric thin plate through the upper adhesive layer of the other second piezoelectric thin plate and the lower adhesive layer of the second piezoelectric thin plate,
The first piezoelectric thin plate is contracted or expanded to generate electric charge, and the second piezoelectric thin plate is expanded or contracted to generate electric charge in the opposite direction to the first piezoelectric thin plate. A shear stress sensor characterized by measuring the magnitude of stress. A piezoelectric thin plate made of a piezoelectric material;
An upper transmission plate and a lower transmission plate provided so as to sandwich the piezoelectric thin plate;
An upper adhesive layer for bonding the piezoelectric thin plate and the upper transmission plate; a lower adhesive layer for bonding the piezoelectric thin plate and the lower transmission plate;
The upper adhesive layer and the lower adhesive layer are composed of a sliding sheet having the same thickness,
The upper adhesive layer and the lower adhesive layer are arranged in a straight line in the extending direction of the piezoelectric thin plate with the center of the piezoelectric thin plate as a boundary, and the upper adhesive layer is the entire upper adhesive layer on the upper surface side of the piezoelectric thin plate. Bonded to the upper transmission plate, the lower adhesive layer is bonded to the lower transmission plate in all of the lower adhesive layer on the lower surface side of the piezoelectric thin plate, and the upper adhesive layer and the lower adhesive layer are substantially It is arranged so as not to overlap,
The sliding sheet is disposed adjacent to the upper adhesive layer and the lower adhesive layer,
Forces acting in opposite directions on the upper transmission plate and the lower transmission plate due to a horizontal displacement stress are transmitted to the piezoelectric thin plate via the upper adhesive layer and the lower adhesive layer, and the piezoelectric thin plate contracts or A shear stress detecting element for measuring the magnitude of the shear stress with the electric charge generated by stretching;
Comprising at least two sets of the shear stress detection elements facing each other,
One shift stress detecting element facing each other is arranged so that the extending direction of the piezoelectric thin plate coincides with the X-axis direction, and the magnitude of the shift stress in the X-axis direction is determined from a difference in output according to the strain amount of each piezoelectric thin plate. Measuring
The other offset stress detecting elements facing each other are arranged such that the extending direction of the piezoelectric thin plate coincides with the Y-axis direction, and the magnitude of the offset stress in the Y-axis direction is determined from the difference in output according to the strain amount of each piezoelectric thin plate. A shear stress sensor characterized by measuring the thickness. A plurality of displacement stress sensors according to any one of claims 1 to 3 are arranged one-dimensionally or two-dimensionally on the same plane, and electric charges are individually taken out from each of the displacement stress sensors, A distributed shear stress sensor characterized by measuring the distribution of the magnitude of shear stress.