JP2008076122A - Angle and displacement sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that it has been difficult for a rotary encoder etc. applicable to the measurement of angular changes of sections which rotate on a center of rotation to measure angular changes of sections such as a joint part of a body of which the center of rotation is unknown or moves with rotation. <P>SOLUTION: A distortion detection element 200 in which both surfaces of a flexible elastic body 10 are sandwiched between piezoelectric films 1A and 1B is arranged at a neutral shaft in the vicinity of one end part of a tension transmitting member 30 made of a soft material. Parts of the tension transmitting member 30 and the distortion detection element 200 are superposed on and restrained to each other to form a part for restraining bending deformation of the distortion detection element 200. A means for providing tension for the member is pasted to and constituted at the other end part of the tension transmitting member 30. A bending angle generated due to the addition of an external force to the tension transmitting member 30 is detected as electrical output of the distortion detection sensor 200. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a displacement sensor that measures an angular change and a relative displacement of a line segment before movement and a line segment after movement when the line segment moves. In particular, the present invention relates to a technical field for measuring deformation of a structural member, angle change or deformation of a joint part of a robot or a body part, and a change of a relative position accompanying movement of two objects.

  Conventionally, there are a rotary encoder and a potentiometer as a sensor for measuring an angle change. Sensors that measure the change in length include a laser displacement meter, an operating transformer displacement meter, a capacitance displacement meter, a strain gauge displacement meter, and the like. In addition, the present inventors have proposed a sensor for measuring the elongation of a flexible elastic member such as rubber or the amount of contraction from the stretched state in Patent Document 1. However, rotary encoders and potentiometers measure the change in angle of the part that rotates around the center of rotation, and measuring the change in the angle of a line segment connecting two predetermined points of the object when the object is deformed It was difficult. Moreover, it is difficult to measure the angle change of a part where the center of rotation is unknown, such as a joint part of the body, or where the center of rotation moves with the rotation.

Patent Document 2 uses an angle sensor using a flexible resin piezoelectric element mixed with piezoelectric ceramic, and when the center of rotation is unknown or a part where the center of rotation moves with rotation, for example, bending and stretching movements. A method for measuring the angle of a part has been proposed. However, in order to measure the position of a specific point on a member that performs bending and stretching movements, it is necessary to know the distance between the fulcrum of bending and stretching movements and the point in addition to the measurement of the rotation angle. When changing, it is difficult to determine the position of the point only by measuring the rotation angle. Therefore, in the case where a length change occurs simultaneously with the rotation of a line connecting two predetermined points of an object, it is necessary to use two sensors for detecting an angle change and two for detecting a length change. .
Japanese Patent Application No. 2005-170378 JP-A-6-174407

  The present invention provides an angle sensor that can detect an angle change of a line segment connecting two predetermined points of the object when the target object is deformed, and a long line at the same time as the line segment connecting the two predetermined points of the object rotates. It is an object to provide a displacement sensor capable of measuring the relative displacement of a line segment connecting two points by detecting a change in angle and a change in length when a change in length occurs.

  As shown in FIG. 1, the angle and displacement sensor of the present invention for solving the above problems includes a strain detecting element 200 comprising a flexible elastic thin plate 10 and a pair of piezoelectric films 1A and 1B disposed on both sides thereof. The strain detecting element 200 is arranged by a deformation restraining member 40 disposed at a neutral axis position of one end of the flexible tension transmitting member 30 and provided over a predetermined length of the flexible tension transmitting member 30. The flexible tension transmitting member 30 is arranged to restrain bending deformation of a part of the length, and a tension load member 60 is attached to the other tip of the flexible tension transmitting member 30. Here, as the strain detection element 200, a structure in which a flexible elastic thin plate 10 is sandwiched between piezoelectric films 1A and 1B or a structure similar thereto can be applied. The arrangement of the strain detecting element 200 at the neutral axis position of the flexible tension transmitting member 30 is, for example, from the one end of the flexible tension transmitting member 30 along the neutral axis in the width direction of the tension transmitting member 30. A parallel method is provided, and a strain detection element is sandwiched between the grooves, or a similar method. The deformation restraining member 40 is typically a U-shaped part, such as a clip-shaped member having a U-shaped cross-section or two rigid plate members with a means for adjusting the distance between them. Alternatively, it is a member having a mechanism or a similar mechanism in which a flexible tension transmitting member having a strain detecting element 200 disposed between the two rigid plates is placed between the two rigid plates.

  Another configuration of the angle and displacement sensor of the present invention for solving the above-described problem is that, as shown in FIG. 2, a strain detection comprising a flexible elastic thin plate 11 and a pair of piezoelectric films 2A and 2B disposed on both sides thereof. The element 201 is disposed at a neutral axis position of the bending of one end of the flexible tension transmitting member 31, and the deformation restraining member 41 provided over a predetermined length of the flexible tension transmitting unit 30 is used. The strain detection element 202 is arranged so as to constrain bending deformation of a part of the length of the strain detection element 201, and includes a flexible elastic thin plate 12 and a pair of piezoelectric films 3A and 3B disposed on both sides thereof. A deformation restraining member disposed at the neutral axis position of the other end of the flexible tension transmitting member 31 and provided over a predetermined length of the material of the other end of the flexible tension transmitting portion 31 42, the length of a part of the strain detecting element 202 Characterized by being configured by arranging to restrain bending deformation. Here, the strain detection elements 201 and 202 have the same configuration as the strain detection element 200 described in the above 0005, and the flexible tension transmission member 31 has the same configuration as the tension transmission member 30 described in the above 0005. Similarly, the deformation restraining members 41 and 42 have the same configuration as the deformation restraining member 40 described in 0005 (Claim 2).

  The angle and displacement sensor of the present invention is characterized in that the deformation restraining member 40 or 41 and 42 is fixed to an object so as not to rotate, and is used in a state where tension is applied to the flexible tension transmitting member 30 or 31. (Claim 3).

  The angle and displacement sensor of the present invention has the same output that generates an output signal V1 and 1B corresponding to the electric charge generated between the back surfaces of the piezoelectric film 1A constituting the element due to the bending deformation of the strain detecting element 200. The signal is V2, and the value of the expression (V1-V2) is output as a signal corresponding to the angle change θ between the deformation restraining member 40 and the tension transmitting member 30. In the case of FIG. 2, the output signals corresponding to the charges generated on the front and back of the piezoelectric film constituting the strain detecting element 201 or 202 are V1 and V2, and the value of the expression (V1−V2) is set to the tension of the deformation restraining member 41 and the tension. A signal corresponding to an angle θ formed by the transmission member 31 or between the deformation restraining member 42 and the tension transmission member 31 is used.

  The angle detection principle of the angle and displacement sensor of the present invention will be described with reference to FIG. As shown in FIG. 3 (a), one end of a flexible elastic member having a small bending rigidity with respect to the tensile rigidity is fixed in a non-rotatable state and hung vertically. When pushed in the horizontal direction, the flexible elastic member is flexibly deformed out of the plane, so that it curves in a gentle curve. Since no tension acts on the flexible elastic member, bending vibration occurs in the curved part when the pressing speed is fast, and when the tip part is picked and pushed with a finger, the bending shape increases depending on how to pick it. Change. Further, in order to cause a large angle change at the tip, it is necessary to increase the length of the flexible elastic member.

  However, when the flexible elastic member is stretched by applying tension in the vertical direction and pushed in the horizontal direction, only the vicinity of the fixed portion is curved with a small radius of curvature as shown in FIG. Since the flexible elastic member below from the distant position is not easily bent by the tension, it is deformed into a linearly extending shape. The radius of curvature of the fixed portion decreases as the tension increases. Since the tension is applied to the flexible elastic member at this time, bending vibration hardly occurs even if the pressing speed is high, and the angle change in the vicinity of the fixed portion hardly changes depending on how the tip portion is picked. Further, even if the length of the flexible elastic member is short, if the angle change is the same, the bending deformation state in the vicinity of the fixed portion is hardly affected.

  In the angle and displacement sensor of the present invention, a local bending deformation is concentrated on the sensor by causing an angle change in a state where tension is applied to a flexible elastic member, and a local bending deformation is caused in the locally bent deformation portion. By detecting the bending strain by installing a piezoelectric film, it is possible to accurately measure the angle change with a small-sized sensor, and the angle and displacement that are less susceptible to vibration due to the angle change and less susceptible to the tension loading method. It constitutes a sensor.

  The strain detection elements 200, 201, and 202 of the angle and displacement sensor of the present invention will be described. The flexible elastic thin plates 10, 11 and 12 constituting the strain detection element have a thickness of 0.1 mm to 0.5 mm. Further, a flexible elastic material having an elastic modulus of 0.2 Mpa to 20 Mpa is used for the flexible elastic thin plates 10, 11 and 12. For example, as the flexible elastic thin plate, a natural rubber having a hardness of 30 to 80, a synthetic rubber, or a material obtained by combining various rubber materials is used (claims 5 and 6).

  For the piezoelectric films 1A, 1B, 2A, 2B, 3A and 3B of the strain detection element, those having a thickness of 0.02 mm to 0.1 mm in which electrodes are provided on both surfaces are used. Electrical wiring is connected to the electrodes on both sides of the piezoelectric film. The electrical wiring is connected to an integration circuit (or charge amplifier) or means for measuring charges generated on the front and back of the piezoelectric film, and an output signal obtained via the integration circuit is measured as an output signal of the piezoelectric film.

  The reason why the thickness of the flexible elastic members 10, 11 and 12 is 0.1 mm to 0.5 mm will be described. When the thickness of the flexible elastic member is greater than 0.5 mm, the distance between the pair of piezoelectric films becomes large, and a large bending strain occurs in the piezoelectric film due to bending deformation. For this reason, the strain detection element is difficult to bend, and if it is bent forcibly, the compression-side piezoelectric film is buckled. Further, when the thickness of the flexible elastic member is made thinner than 0.1 mm, it is easily bent and deformed, but the output signal of the piezoelectric film becomes small and the angle change cannot be measured with high accuracy.

  The reason for using a flexible elastic material having an elastic modulus of 0.2 Mpa to 20 Mpa for the flexible elastic thin plates 10, 11 and 12 will be described. When a metal thin plate or a hard resin thin plate is used as the flexible elastic thin plate, the bending rigidity of the strain detection element 200, 201 or 202 is increased, and local bending deformation is less likely to occur. In addition, another angle change occurs at the boundary portion that moves from the tension transmission member 30 or 31 to the tip of the strain detection element 200, 201, or 202, and the angle change occurs at a plurality of locations of the flexible tension transmission member. The angle change cannot be measured with high accuracy. In order to cause the bending deformation to be concentrated at one place on the boundary between the deformation restraining member 40, 41 or 42 and the tension transmitting member 30 or 31, and to bend the radius of curvature small, the flexibility within the above elastic modulus range is required. It is preferable to use a thin elastic plate.

  As the flexible tension transmitting members 30 and 31, a flexible elastic member having an elastic modulus of 0.2 Mpa to 20 Mpa is used. For example, as the flexible tension transmitting member 30 or 31, a flexible elastic member formed by combining natural rubber having a hardness of 30 to 80, synthetic rubber, or various rubber materials is used. The same material may be used for the flexible tension transmitting member 30 or 31 and the flexible elastic thin plate 10, 11 or 12 of the strain detecting element. Alternatively, a stretchable fabric having elastic characteristics can be used for the flexible tension transmitting member 30 or 31 (claim 7).

  The reason for not using a hard elastic member for the flexible tension transmitting members 30 and 31 is that the tension transmitting member has a two-layer structure in the portion where the strain detecting elements 200, 201 and 202 are disposed. This is because this portion is difficult to bend at a small radius of curvature, and if it is bent forcibly, buckling occurs in the tension transmitting member on the compression side. That is, it is preferable to use a flexible elastic member in order to reduce the bending rigidity of the sensor in the portion where the strain detection element is disposed and to cause local bending deformation in a concentrated manner.

  Next, the cross-sectional shape of the portion where the strain detection elements 200, 201 and 202 of the angle and displacement sensor of the present invention are disposed will be described. As described above, even when a flexible elastic member is used for the flexible tension transmitting member 30 or 31, if the cross sectional area of the flexible tension transmitting member 30 or 31 is large, the strain detecting element 200, 201 or 202 is used. This will inhibit local bending. If the flexible tension transmitting member 30 or 31 can play the role of transmitting the tension to the strain detecting element 200, 201 or 202 and holding the shape without hindering the bending deformation of the strain detecting element, the flexible tension transmitting member 30 or 31 can be bent as much as possible. Is preferably small.

  For this reason, the bending rigidity (E2 × I2) of the flexible tension transmitting member is equal to the bending rigidity (E0) of the flexible tension transmitting member in the angle of the portion where the strain detecting element 200, 201 or 202 is disposed and in the cross section of the displacement sensor. × I0 + E1 × I1), where E0, E1, and E2 are each a piezoelectric film, a flexible elastic thin plate, and an elastic modulus of a flexible tension transmitting member, and I0, I1, and I2 are a pair of piezoelectric films, a flexible elastic thin plate, It is preferable to make it smaller than the second moment of inertia of the flexible tension transmitting member.

  FIG. 4 is a diagram illustrating another reason for using the angle and displacement sensor of the present invention with tension applied thereto, taking the angle and displacement sensor according to claim 1 as an example. When the angle and displacement sensor is bent and deformed without applying tension as shown in FIG. 4A, the flexible tension transmitting member 30 and the piezoelectric film 1A in the vicinity of the deformation restraining member 40 are smoothly stretched and bent on the pulling side. However, on the compression side, buckling occurs in the flexible tension transmitting member 30 and the piezoelectric film 1B due to compressive strain, and the surface becomes uneven. Concavities and convexities on the compression side surface are generated when the bending angle is larger than a certain degree, and are more likely to occur as the thickness of the flexible tension transmitting member 30 increases. However, when bending deformation is performed with tension applied as shown in FIG. 4B, uniform tensile strain is applied to the entire cross-section of the flexible tension transmitting member 30 and the strain detecting element 200, so that the detecting element 200 is large. Even when it is bent, it is smoothly deformed without causing irregularities on the compression side surface.

  The deformation restraining members 40, 41 and 42 will be described. The deformation restraining member fixes the angle and displacement sensor to the object in a state in which a part of the strain detecting element is constrained so as not to bend and deform. Therefore, the deformation restraining member is made of a rigid material such as a metal. What can restrain both sides of 200, 201, or 202 is good.

  The angle and displacement sensor according to claim 1 will be described as an example of the dimensional relationship between the length of the strain detection elements 200, 201, and 202 and the deformation restraining member that restrains the bending deformation at a predetermined length portion at the end of the strain detection element. To do. In FIG. 1, the length of the strain detection element 200 in the portion where the deformation is not restrained by the deformation restraining member 40 is more than five times the total thickness including the thickness of the strain detection element 200 and the flexible tension transmitting member 30. Also make long. Further, the length of the portion of the strain detecting element where the deformation is restrained by the deformation restraining member is set to be substantially the same as the length of the portion not restrained (claim 9).

FIG. 5 shows the bending strain ε _B (x) (where x is the distance from the left end of the piezoelectric film in FIG. 5) acting on the piezoelectric film 1A on the pull side of the angle and displacement sensor of the present invention, and the tensile strain ε _T due to tension. It is the figure which showed (x) typically. As can be seen from the bending strain distribution of the piezoelectric film 1 </ b> A shown in FIG. 5A, the curvature radius of the strain detecting element 200 at the portion where the bending deformation is locally generated is not uniform at the bending portion, and the deformation restraining member 40. And decreases as the tip moves to the tip of the flexible tension transmitting member 30. Therefore, the entire length of the unconstrained portion of the strain detection element 200 needs to be longer than the length of the portion that is bent and deformed.

  However, it is difficult to determine the position at which the bending deformation in the strain detection element 200 completely changes to a linear deformation, and the length of the bending deformation portion changes depending on the magnitude of the tension. In order to accurately measure the bending angle, the strain detecting element 200 needs to extend to a portion where the flexible tension transmitting member 30 is linear. The length of the detection element 200 is preferably longer than five times the total thickness including the thickness of the strain detection element 200 and the flexible tension transmission member 30.

  Moreover, although the deformation | transformation of the flexible tension | tensile_strength transmission member 30 of the part restrained by the deformation | transformation restraint member 40 is restrained deformation | transformation on the surface, bending distortion arises in piezoelectric film 1A, 1B of the internal distortion detection element 200. Therefore, the length of the strain detection element 200 in the portion of which the deformation is restrained by the deformation restraining member 40 is also set to the same length as the length of the portion of the strain detection element 200 in which the deformation is not restrained by the deformation restraining member 40. Good.

Taking the angle and displacement sensor of claim 1 as an example, the relationship between the output signals of the pair of piezoelectric films 1A and 1B and the angle change θ and elongation change δ will be described. Since tension and bending act on the strain detecting element 200, bending strain ε _B (x) and tensile strain ε _T (x) are generated in the piezoelectric films 1A and 1B, and the upper surface is curved in a convex manner. The distortion of the piezoelectric film 1A on the side is ε (x) = ε _B (x) + ε _T (x), and the distortion of the piezoelectric film 1B on the lower surface side is ε (x) = − ε _B (x) + ε _T (x) Become.

  Since the output signal of the piezoelectric film is proportional to the total distortion, in the case of a piezoelectric film having a constant width and a length L, the potential difference V1 on the back surface of the piezoelectric film 1A (or the output voltage of the integration circuit may be V1). (V2 is also the same), and the potential difference V2 on the back surface of the piezoelectric film 1B is as shown in Equation (1).

However, k is a proportionality constant.

From the material mechanics, the relationship between the bending strain ε _B (x) and the angle change θ is given by Equation 2, and the relationship between the tensile strain ε _T (x) and the elongation δ is given by Equation 3.

Here, h is the distance from the neutral axis of bending of the tension transmitting member 40 to the center of the piezoelectric film.
Using these relationships, the difference (V1−V2) and the sum (V1 + V2) between V1 and V2 in Equation 1 are calculated to obtain Equation 4.

That is, the difference (V1−V2) between the output signals of the pair of piezoelectric films is proportional to the angle change θ between the deformation restraining member 40 and the tension transmitting member 30, and the sum (V1 + V2) of the output signals is the tension transmitting member 30. It is proportional to the elongation change δ.

  In Equation 4, (V1−V2) is irrelevant to the elongation δ of the tension transmitting member 30, and (V1 + V2) is irrelevant to the angle change θ. This means that (V1-V2) is not affected by the elongation δ even if the sensor is stretched and deformed during use as an angle sensor. On the other hand, when the displacement measurement is performed by a sensor having the same configuration as the angle and displacement sensor of the present invention described later, even if an angle change occurs in the tension transmission member (30 or 31), (V1 + V2) is an angle change θ. This means there is no need to consider the impact.

  A tension load member 60 for applying tension to the angle and displacement sensor according to claim 1 of the present invention will be described. The tension load member 60 may be any member that can be fixed to an object or the like with tension applied to the flexible tension transmission member 30. For example, it is possible to attach a metal tension load member by adhering to the tension transmission member, or to attach the tension transmission member by making a screw hole in the tension transmission member. Although it is desirable to fix the tension load member 60 to the object in a rotatable manner, the tension load member 60 may be a hooking means or a bolt fixing means.

  Moreover, as shown in FIG. 6, the spring of the tension load member 61 with a spring may be extended and fixed to an object. In this way, even when the length of the flexible tension transmitting member 30 is short and the tension transmitting member is little stretched (or contracted), the necessary tension can be supplemented with the tension of the spring.

Next, the case where the angle and displacement sensor of the present invention is used as a displacement sensor will be described with reference to FIG. In the description, first, the distribution of tensile strain of the piezoelectric films 1A and 1B of the strain detection element of FIG. When bending deformation occurs in the angle sensor, a tensile strain ε _T (x) as shown in FIG. 5B is distributed on the piezoelectric films 1A and 1B in accordance with the applied tension. The piezoelectric film 1A and the compression-side piezoelectric film 1B are the same. Therefore, as shown in Equation 4, a signal corresponding to the sensor elongation δ can be measured from the sum (V1 + V2) of the output signals of the pair of piezoelectric films 1A and 1B.

  That is, the angle and displacement sensor described above detects a signal corresponding to the sensor length change δ from the sum of the output signals of the pair of piezoelectric films (V1 + V2), and also detects the angle change θ from (V1−V2). By doing so, it can be used as a displacement sensor. This displacement is calculated by taking the tension axis direction when the angle sensor is stretched as the X axis and the direction perpendicular to the tension axis as the Y axis, as shown in FIG. 12, δy = (L1 + δ) × sin θ, δx. = (L1 + δ) × cos θ−L1 (where L1 is the length of the angle sensor when stretched) (claim 12).

  As described above, any of the angle and displacement sensors described above can be used as a displacement sensor.

  According to the angle and displacement sensor of the present invention, it is possible to provide a small angle sensor that can measure an angle change with high accuracy with a simple structure. In addition, by detecting the angle change and the length change with an integrated sensor unit, a small size that can accurately measure the relative displacement between two predetermined points of the object or two predetermined points of the object. A displacement sensor can be provided. As a result, deformation of the structural member, angle change or deformation of the joint portion of the robot or body part, and measurement of the angle change or displacement of the two objects can be easily realized. In addition, a sensor in which a plurality of angle sensors and displacement sensors are connected can easily realize angle change and displacement measurement of a plurality of points or a plurality of line segments connecting predetermined points of a plurality of objects.

(Example 1)
FIG. 7 is a diagram for explaining an embodiment of a method for measuring an angle change, taking the sensor according to claim 1 as an example. Now, the deformation restraining member 40 of the angle sensor having the effective length L0 indicated by the broken line is fixed to the first object so as not to rotate, and the flexible tension load member 30 is stretched by applying tension to the flexible tension load. The member 30 is fixed to the second object. The effective length of the sensor at this time is L1. The second object may be an extension direction of the deformation restraining member 40, or may be fixed with an initial angle.

  Next, for example, it is assumed that the second object moves and an angle change θ occurs in the angle sensor as illustrated. Then, the angle change θ can be obtained from Equation 4 by θ = (V1−V2) / 2 kh. At this time, the angle sensor has an elongation δ as shown in the figure (or contracted from the expanded state), but (V1-V2) is not affected by the elongation δ as described above.

(Example 2)
FIG. 8 is a view for explaining an embodiment of a method for measuring an angle change by the angle and displacement sensor according to claim 2. First, in a state where tension is applied to the flexible tension transmitting member 31, the deformation restraining members 41 and 42 at both ends are fixed to the surfaces of the first and second objects so as not to rotate. Next, it is assumed that at least one of the first and second objects moves and is displaced as shown in FIG. If the angle changes θ1 and θ2 are respectively measured from the output signals of the strain detection elements 201 and 202 at both ends at this time, the relative angle changes of the predetermined surfaces of the two objects can be measured.

(Example 3)
FIG. 9 is a view for explaining an embodiment of the angle and displacement sensor according to the tenth aspect. The neutral axis of bending of the strain detecting element 203 coincides with the rotary joint portion of the two rigid members 90 and 91 made of metal or the like and rotatably connected by the rotary joint 50, and the center of the rotary joint 50, and The deformation restraining member 44 is attached to the rigid member 90 so that the end of the deformation restraining member 44 at the portion where the strain detecting element is bent and deformed coincides with the center of the rotary joint 50. Next, the tension load member 62 is attached to the other rigid member 91 with a stop pin or the like while the tension is applied to the flexible tension transmission member 33. When (V1−V2) when the two rigid members 90 and 91 rotate at the rotary joint portion is measured by the method described above, the angle change θ between the two rigid members can be measured.

Example 4
FIG. 10 is a view for explaining another embodiment of the angle and displacement sensor according to the tenth aspect. Three rigid members 92, 93, 94 made of metal or the like are connected in series by two rotary joints 51, 52. Next, the deformation restraining members 45 and 46 are fixed to the rigid members 92 and 94 so as not to rotate in a state where tension is applied to the flexible tension transmitting member 34 of the angle sensor in which strain detecting elements are arranged at both ends. When the two rigid members 92 and 94 rotate at the rotary joint, the strain detection elements 204 and 205 bend and deform according to the change in the angle of the rotary joints 51 and 52, respectively. By measuring the change in angle at that time with the strain detection elements 204 and 205 at both ends, the state of change in the angle of the rigid members 92, 93, and 94 can be measured.

(Example 5)
FIG. 11 shows an embodiment applied to an application of measuring the deformation of a long structure and the relative displacement of a plurality of objects by connecting the angle and displacement sensor according to claim 11. As shown in FIG. 11, at least two angle and displacement sensors 500, 501, and 502 are connected via connecting members 70 and 71, and the flexible tension transmitting member of each sensor is deformed in a state where tension is applied. When the restraint member is fixed to a rotational load at a predetermined position by a fixing tool, deformation of a structural member having a long dimension or a change in relative positions of a plurality of objects can be measured.

(Example 6)
FIG. 18 shows an embodiment in which an end 48 of the opening that is a part of the deformation restraining member 40 and sandwiches a part of the flexible tension transmitting member 30 is formed into a smooth shape. In order to smooth the bending deformation generated in the transmission member 30 at the terminal portion 48, the 48 is formed in a rounded shape such as a semicircle (claim 13). It is within the scope of the present invention to apply the rounded shape to the same opening end of the deformation restraining member 41 or 42.

  If the shape of the corner portion of the end portion 48 of the deformation restraining member 40 is linear, it may be impossible to form a smooth bending deformation on the flexible tension transmitting member 30 at the end portion. For example, the above-described state can occur when the flexible tension transmitting member changes its angle by more than 90 degrees from a state in which the flexible tension transmitting member extends in a straight line. However, if the end portion 48 of the deformation restraining member 40 is made smooth as shown in FIG. 18, even if the flexible tension transmitting member 30 is deformed to an angle exceeding 90 degrees, the deformed shape is smooth, and it is useful for angle measurement. There is no effect.

  A semicircular rod having a radius of 1 mm is further bonded to the opening end of the deformation restraining member 40 made of acrylic to form a rounded end shape 48, and then the flexible tension transmitting member 30 is 90 degrees or more on one side. FIG. 19 shows experimental data obtained by measuring the angle after deformation. From FIG. 19, it was confirmed that accurate angle measurement was possible even in a state bent 90 degrees or more.

(Example 7)
An experiment conducted using the angle and displacement sensor of the present invention will be described. FIG. 13 shows a 0.5 mm-thick silicon rubber tension transmission member on both sides of a strain detection element in which a piezoelectric film having a length of 50 mm and a width of 13 mm is arranged on both sides of a 0.2 mm-thick silicon rubber elastic thin plate. The angle sensor 510, which is bonded and is provided with an acrylic resin deformation restraining member over an interval of 25 mm from the end of the strain detection element, is suspended vertically by fixing the deformation restraining member at the upper end to the jig (initially the angle sensor). Effective length L0 = 237 mm), weights of 5.7 N, 10.4 N, and 12.8 N were suspended from the tip of the sensor and swung like a pendulum. The angle change was measured by placing a board with a protractor on the back of the sensor. The output signals V1 and V2 of the sensor were measured while varying the deflection angle, and measured with a voltage recorder via an integrating circuit composed of a resistor and a capacitor.

  FIG. 14 shows the relationship between the output signal difference (V1−V2) and the deflection angle change θ. In the figure, it can be seen that there is a good proportional relationship between (V1−V2) and the angle change θ regardless of the weight of the weight, that is, the tension acting on the sensor. That is, it can be seen that the angle sensor of the present invention can accurately measure the angle change without being affected by the magnitude of the tension.

  Next, a displacement measurement experiment using an angle and displacement sensor will be described. As shown in FIG. 15, from the state in which the angle and displacement sensor 600 is suspended, the tension load member 62 at the tip of the sensor is grasped with a finger and pulled to a predetermined point P. An experiment was conducted in which the tension load member 62 was held and moved from the point P to another position (for example, the point Q). The experiment was performed by placing a board with a grid pattern on the back of the sensor and placing an insect pin at a predetermined position where the angle change, the length change, or both the angle change and the length change change. Experiments were performed by changing the coordinates of point P and point Q in various ways.

  As an example in FIG. 16, the tension load member 62 is attached to various points Q on the left half of the grid panel from the point P where the angle and displacement sensor are vertically suspended and stretched right below to give the initial elongation L1−L0 = 53 mm. The relationship between the difference (V1−V2) in the output signal of the piezoelectric film and the angle change θ when moved and when returning from the point Q to the point P is shown. From the figure, it can be seen that there is a good proportional relationship between (V1−V2) and the angle change θ until the angle change reaches 90 degrees.

  FIG. 17 shows the relationship between the sum (V1 + V2) of the output signals of the piezoelectric film and the elongation δ (or shrinkage from the stretched state) obtained in the above experiment. As can be seen from the figure, the output signal when the elongation δ changes with respect to the magnitude of the output signal when the angle changes, and there is some variation, but an output signal corresponding to the elongation δ is obtained. You can see that

  The solid line in the figure indicates that the relationship between (V1 + V2) and elongation δ when the angle and displacement sensor 600 is pulled straight is separately obtained by experiment, and the origin is moved by the initial elongation L1−L0 = 53 mm. However, when the angle and displacement sensor is moved from the point P to the point Q, or when the angle and displacement sensor is returned from the point Q to the point P, the plot points of (V1 + V2) and δ are in good agreement. ing.

It is a figure explaining one Example of a structure of an angle and a displacement sensor. It is a figure explaining another Example of a structure of an angle and a displacement sensor. It is a figure explaining the angle detection principle of an angle and a displacement sensor. It is a figure explaining the reason used in the state which applied tension to the angle and displacement sensor of the present invention. It is a figure explaining the distribution state of the bending distortion of the local bending deformation part of an angle and a displacement sensor. It is a figure explaining another Example of the tension load member of the angle and displacement sensor of this invention. It is a figure explaining the angle measuring method of the angle and displacement sensor of Claim 1. It is a figure explaining the angle measuring method of the angle and displacement sensor of Claim 2. It is a figure explaining one Example of the angle and displacement sensor of Claim 10. It is a figure explaining another Example of the angle and displacement sensor of Claim 10. It is a figure explaining one Example of the angle sensor formed by connecting an at least 2 angle and displacement sensor. It is a figure explaining the displacement measuring method using an angle and a displacement sensor. It is a figure explaining the experiment which suspends and shakes a weight to the tension load member of an angle and displacement sensor. It is a figure which shows the relationship between the difference (V1-V2) of the output signal of the piezoelectric film calculated | required by experiment, and swing angle change (theta). It is a figure explaining the experiment which measures the angle change and elongation change of an angle and a displacement sensor. It is a figure which shows the relationship between the difference (V1-V2) of the output signal of a piezoelectric film calculated | required by experiment using an angle and a displacement sensor, and angle change (theta). It is a figure which shows the relationship between the sum (V1 + V2) of the output signal of a piezoelectric film calculated | required by experiment using an angle and a displacement sensor, and elongation (delta). It is a figure which shows the angle and the displacement sensor which improved the shape of the opening edge part of a deformation | transformation restraint member. It is an experimental data which shows the effect of the deformation | transformation restraint member which has the improved opening edge part.

Explanation of symbols

1A, 1B Piezoelectric film 2A, 2B Piezoelectric film 3A, 3B Piezoelectric film 4A, 4B Piezoelectric film 10, 11, 12, 13 Flexible elastic thin plates 30, 31, 32 Flexible tension transmission member 33, 34 Flexible tension transmission member 40 , 41, 42 Deformation restraint members 43, 44 Deformation restraint members 45, 46 Deformation restraint member 48 Deformation restraint member opening end 50 Rotating joints 51, 52 Rotating joint 60 Tension load members 61, 62 Tension load member 70 Connecting members 90, 91 Rigid members 92, 93, 94 Rigid members 200, 201, 202 Strain detection element 203 Strain detection elements 204, 205 Strain detection elements 500, 501, 502 Angle sensor 510 Angle sensor 600 Displacement sensor

Claims (13)

  A strain detecting element 200 including a flexible elastic thin plate 10 and a pair of piezoelectric films 1A and 1B disposed on both sides thereof, and a flexible tension transmitting member, which is located at a neutral axis position of bending near one end. A flexible tension transmitting member 30 provided with the strain detecting element 200 and a predetermined length of an end of the flexible tension transmitting member 30 are provided, and bending deformation of a part of the length of the strain detecting element 200 is performed. An angle and displacement sensor (see FIG. 1), characterized by comprising a deformation restraining member 40 for restraining and a tension load member 60 attached to the tip of the flexible tension transmitting member 30.   It consists of a flexible elastic thin plate 11 and a strain detecting element 201 consisting of a pair of piezoelectric films 2A and 2B disposed on both sides thereof, and a flexible elastic thin plate 12 and a pair of piezoelectric films 3A and 3B arranged on both sides thereof. Another strain detecting element 202, a flexible tension transmitting member, and a flexible tension transmitting member 31 in which the strain detecting elements 201 and 202 are respectively disposed at the neutral axis positions of bending near both ends; It is composed of deformation restraining members 41 and 42 which are provided over a predetermined length at both ends of the flexible tension transmitting member 31 and restrain the bending deformation of a part of the length of the strain detecting elements 201 and 202, respectively. Angle and displacement sensor (see FIG. 2).   The deformation restraining member (40 or 41 and 42) according to claim 1 or 2 is fixed to an object for measuring an angle or displacement so as not to rotate, and tension is applied to the flexible tension transmitting member (30 or 31). The angle and displacement sensor according to claim 1 or 2, wherein the sensor is used in a state (see Figs. 7 and 8).   A signal V1 output from one piezoelectric film and a signal V2 output from the other piezoelectric film due to deformation of the pair of piezoelectric films constituting the strain detecting element (200 or 201 and 202) according to claims 1 to 3. According to the difference (V1−V2), a signal corresponding to an angle change θ between the deformation restraining member (40 or 41 and 42) and the flexible tension transmitting member (30 or 31) stretched is detected. The angle and displacement sensor according to any one of claims 1 to 3.   The flexible elastic thin plate (10 or 11 and 12) constituting the strain detecting element according to any one of claims 1 to 4 has a thickness of 0.1 mm to 0.5 mm. The angle and displacement sensor described in 1.   The elastic modulus E1 of the flexible elastic thin plate (10 or 11 and 12) according to any one of claims 1 to 5 is 0.2 Mpa <E1 <20 Mpa, according to any one of claims 1 to 5. Angle and displacement sensor.   The elastic modulus E2 of the flexible tension transmitting member (30 or 31) according to any one of claims 1 to 6 is 0.2 Mpa <E2 <20 Mpa, Displacement sensor.   The bending rigidity (E2 × I2) of the flexible tension transmitting member (30 or 31) in the cross section of the angle sensor where the strain detecting element (200 or 201 and 202) according to claim 1 is disposed. , Bending rigidity (E0 × I0 + E1 × I1) of the strain detection element (where E0, E1, E2 are piezoelectric film, flexible elastic thin plate, elastic modulus of flexible tension transmitting member, and I0, I1, I2 are respectively The angle and displacement sensor according to any one of claims 1 to 7, wherein the angle and displacement sensor are smaller than a pair of piezoelectric films, a flexible elastic thin plate, and a sectional moment of inertia of a flexible tension transmitting member.   A portion where the strain detecting element (200 or 201 and 202) according to claim 1 is disposed, wherein the deformation detecting element (200 or 201 and 202) is not restrained by the deformation restraining member (40 or 41 and 42). The length of 201 and 202) is longer than five times the total thickness of the strain sensing element plus the thickness of the flexible tension transmitting member (30 or 31). The angle and displacement sensor according to claim 8.   The angle and displacement sensor according to any one of claims 1 to 9 is applied to two or three rigid members connected via a rotary joint, and tension is applied to the tension transmission member according to any one of claims 1 to 9. 10. An angle and displacement sensor attached in a loaded state, wherein the neutral axis of bending of the strain detecting element according to claim 1 is coincident with the center of the rotary joint, and the rotary joint An angle and displacement sensor characterized in that the end of the deformation restraining member according to any one of claims 1 to 9 coincides with a portion where the strain detecting element bends and deforms at the center of the sensor.   An angle and displacement sensor comprising at least two of the angle and displacement sensors according to claim 1 connected through a connecting member.   The angle and displacement sensor according to any one of claims 1 to 9, wherein from the sum (V1 + V2) of the output signals V1 and V2 of the pair of piezoelectric films according to claim 4, the angle and displacement sensor length change δ. The corresponding signal is detected, and the displacement from the tension axis direction (X-axis direction) and the direction perpendicular to the tension axis (Y-axis direction) when the angle sensor is tensioned is expressed as δy = (L1 + δ) × sin θ, δx = (L1 + δ) × cos θ−L1 (where L1 is the angle at the time of stretching and the effective length of the displacement sensor).   An end portion of an opening portion that is a portion of the deformation restraint member (40 or 41 and 42) according to claim 1 to 9 and sandwiches a portion of a predetermined length from the end portion of the flexible tension transmitting member (30 or 31). 48) is formed into a smooth shape, and the angle and displacement sensor according to claim 1-9 (see FIG. 18)