Piezoelectric sensor and gripper

Abstract

A piezoelectric sensor capable of detecting a force application direction when a force is applied from a plurality of different directions, and a gripper provided with such a piezoelectric sensor are provided. A piezoelectric sensor characterized by comprising: an elastic body having a first face; a restriction portion disposed at a position facing the first face of the elastic body, which restricts deformation of the elastic body; and a piezoelectric element which deforms along with deformation of the elastic body and has a portion fixed to the restriction portion, the piezoelectric element outputting a voltage signal that increases or decreases from a reference voltage according to a deformation direction.

Description

TECHNICAL FIELD

[0001] The present application relates to a piezoelectric sensor and a gripper. BACKGROUND

[0002] In Patent Literature 1, as an industrial robot used in a production line or the like, a robot having a gripping device provided with a pressure-sensitive sensor is disclosed. The pressure-sensitive sensor is a sensor that outputs pressure as an electric signal.

[0003] The gripping device is provided with a pair of gripping portions capable of opening and closing and a pressure-sensitive sensor provided to the gripping portions. When an object to be gripped is gripped by the gripping portions, the pressure-sensitive sensor is deformed in contact with the object to be gripped, and an electric voltage signal is output from the pressure-sensitive sensor. In a control device of the robot, the gripping force of the gripping device is controlled on the basis of the electric voltage signal.

[0004] The pressure-sensitive sensor has a first electrode and a second electrode, and an intermediate layer as a piezoelectric body provided between the first electrode and the second electrode and generating electricity by deformation. Electricity is generated by a change in electrostatic capacitance between each electrode and the intermediate layer. The pressure-sensitive sensor functions by detecting the amount of electricity generated and the presence or absence of electricity generation.

[0005] Patent Literature 1: Japanese Patent Application Publication No. 2018-72024

[0006] In the pressure-sensitive sensor described in Patent Literature 1, electricity is generated if the intermediate layer is deformed, but even if the deformation occurs in different modes, it cannot be distinguished. For example, when the pressure-sensitive sensor is pressed by the object to be gripped, a compressive force is imparted to the intermediate layer. On the other hand, in a case where the object to be gripped is picked up by the robot in a state where the object to be gripped is gripped by the gripping device, a pushing force derived from the gravity of the object to be gripped is imparted to the intermediate layer of the pressure-sensitive sensor together with the compressive force.

[0007] However, in the pressure-sensitive sensor described in Patent Literature 1, these compressive forces and pushing forces cannot be distinguished. Therefore, in the control device of the robot, there is a technical problem that it cannot be distinguished whether the object to be gripped is merely gripped or picked up in a state where it is gripped. SUMMARY

[0008] The piezoelectric sensor according to an application example of the present application is characterized by including an elastic body having a first face, a restriction portion disposed at a position facing the one face of the elastic body to restrict deformation of the elastic body, and a piezoelectric element deformed along with deformation of the elastic body and having a part fixed to the restriction portion, the piezoelectric element outputting a voltage signal increased or decreased from a reference voltage according to a direction of deformation.

[0009] The hand of the application example is characterized by being provided with the piezoelectric sensor of the application example. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 is a diagram showing the hand of the embodiment.

[0011] Figure 2 is an enlarged view of the tip of the finger of Figure 1 is a perspective view showing the piezoelectric sensor of the first embodiment.

[0012] Figure 3 is a plan view when the piezoelectric sensor shown in Figure 2 is viewed from a position on the X axis.

[0013] Figure 4 is one example of an output circuit that amplifies the voltage generated by the piezoelectric element.

[0014] Figure 5 is a diagram for explaining the deformation mode of the elastic body when a force is applied to the piezoelectric sensor shown in Figure 3 from various directions.

[0015] Figure 6 is a diagram showing one example of the waveform (output waveform) of the voltage signal output from the piezoelectric element shown in Figure 5 when the elastic body is deformed in the deformation mode shown in Figure 3

[0016] Figure 7 is a diagram showing one example of the output waveform obtained from the piezoelectric sensor in the case where the degree of the relaxation phenomenon is different.

[0017] Figure 8 is a plan view when the piezoelectric sensor of the second embodiment is viewed from a position on the X axis.

[0018] Figure 9 is a diagram showing one example of the waveform (output waveform) of the voltage signal output from the piezoelectric element shown in Figure 5 when the elastic body is deformed in the deformation mode shown in Figure 8

[0019] Figure 10 is a plan view when the piezoelectric sensor of the third embodiment is viewed from a position on the X axis.

[0020] Figure 11 is a diagram for explaining the deformation mode of the elastic body when a force is applied to the piezoelectric sensor shown in Figure 10 from various directions.

[0021] ​​Figure 12 is a plan view of the piezoelectric sensor according to the fourth embodiment as viewed from a position on the X axis.

[0022] Figure 13 is a plan view of the piezoelectric sensor according to the fifth embodiment as viewed from a position on the X axis.

[0023] Figure 14 is a plan view of the piezoelectric sensor according to the sixth embodiment as viewed from a position on the X axis.

[0024] Figure 15 is a diagram for explaining a deformation mode of the elastic body when a force is applied to the piezoelectric sensor shown in Figure 14

[0025] Figure 16 is a diagram showing a waveform (output waveform) of a voltage signal output from the piezoelectric element shown in Figure 15 Figure 14

[0026] Figure 17 is a plan view of the piezoelectric sensor according to the seventh embodiment as viewed from a position on the X axis.

[0027] Figure 18 is a diagram showing a waveform (output waveform) of a voltage signal output from the piezoelectric element shown in Figure 15 Figure 17

[0028] Figure 19 is a plan view of the piezoelectric sensor according to the eighth embodiment as viewed from a position on the X axis.

[0029] Figure 20 is a plan view of the piezoelectric sensor according to the ninth embodiment as viewed from a position on the X axis.

[0030] BRIEF DESCRIPTION OF REFERENCE NUMERALS

[0031] ​​​​​1 piezoelectric sensor; 1A piezoelectric sensor; 1B piezoelectric sensor; 1C piezoelectric sensor; 1D piezoelectric sensor; 1E piezoelectric sensor; 1F piezoelectric sensor; 1G piezoelectric sensor; 1H piezoelectric sensor; 2 elastic body; 3 restriction portion; 10 gripper; 11 base; 12 slide; 13 slide; 14 finger; 15 finger; 16 motor; 17 motor; 31 first wall portion; 32 first wall portion; 33 second wall portion; 34 second wall portion; 41 piezoelectric element; 42 piezoelectric element; 43 piezoelectric element; 44 piezoelectric element; 49 output circuit; 141 gripping surface; 151 gripping surface; 201 first surface; 202 second surface; 203 third surface; 204 fourth surface; 205 fifth surface; 206 sixth surface; 207 convex curved surface; 351 columnar portion; 352 columnar portion; 353 columnar portion; 354 columnar portion; 491 amplifier; 492 power supply; 493 power supply; 494 detection portion; 495 measurement portion; 496 calculation portion; 497 determination portion; R internal resistance; W object; t1 thickness; t2 thickness. DETAILED DESCRIPTION

[0032] Hereinafter, preferred embodiments of the piezoelectric sensor and the gripper according to the present application will be described in detail based on the drawings.

[0033] 1. Gripper

[0034] First, the gripper according to the embodiments will be described.

[0035] Figure 1 is a view showing the gripper according to the embodiments. Note that, in Figure 1 , as three axes orthogonal to each other, an X axis, a Y axis, and a Z axis are provided. Each axis is indicated by an arrow, with the front end side being "positive" and the base end side being "negative". In the following description, for example, the "X axis direction" includes both the positive direction and the negative direction of the X axis. In addition, in the following description, the Z axis positive side will sometimes be described as "up" and the Z axis negative side will sometimes be described as "down".

[0036] Figure 1 The gripper 10 shown in FIG. 1 has a pair of fingers 14 and 15. By changing the distance between the finger 14 and the finger 15, it is possible to sandwich and grip an object W from both sides or to release the gripped object W.

[0037] The gripper 10 has a base 11, a pair of slides 12 and 13 that slide with respect to the base 11, fingers 14 and 15 that are fixed to the slides 12 and 13, motors 16 and 17 that cause the slides 12 and 13 to slide, and a piezoelectric sensor 1. Note that the structure of the gripper is not limited to this.

[0038] Slider members 12 and 13 are respectively capable of sliding relative to base 11 in the X-axis direction. Furthermore, a motor 16 is connected to slider 12, and slider 12 slides by being driven by motor 16. Similarly, a motor 17 is connected to slider 13, and slider 13 slides by being driven by motor 17.

[0039] By selecting the rotation direction of motors 16 and 17 to move sliders 12 and 13 in opposite directions, fingers 14 and 15 can be brought closer together or separated. This allows the fingers 14 and 15 to grasp or release the object W. It should be noted that the gripper 10 can also be a structure that moves one of the fingers 14 and 15 while fixing the other.

[0040] Piezoelectric sensors 1 are respectively provided on the finger portions 14 and 15. The piezoelectric sensors 1 are located on the opposing surfaces of the finger portions 14 and 15, namely the gripping surfaces 141 and 151. When an object W is held between the gripping surfaces 141 and 151, the piezoelectric sensors 1 are positioned between the gripping surfaces 141 and 151 and the object W. Therefore, each piezoelectric sensor 1 receives a reaction force from the object W and outputs a voltage corresponding to that reaction force. Thus, the gripper 10 has the function of detecting the gripping state of the object W based on the output voltage from the piezoelectric sensors 1. It should be noted that the piezoelectric sensors 1 may also be provided only on one of the finger portions 14 and 15.

[0041] The above describes the gripper 10, but the piezoelectric sensor 1 can also be used in various devices other than the gripper 10, such as tactile sensors, game controllers, remote control controllers, MR (mixed reality) controllers, flexible user interfaces, and various ON / OFF sensors.

[0042] 2. The piezoelectric sensor according to the first embodiment

[0043] Next, the piezoelectric sensor according to the first embodiment will be described.

[0044] Figure 2 It is an enlarged representation Figure 1 The perspective view of the front end of the finger portion 14 is an exploded perspective view of the piezoelectric sensor 1 according to the first embodiment. Figure 3 Observed from the position on the X-axis Figure 2 The top view of the piezoelectric sensor 1 shown.

[0045] Figure 2 as well as Figure 3 The piezoelectric sensor 1 shown is mounted on the gripping surface 141 of the finger portion 14. The piezoelectric sensor 1 includes an elastomer 2, a limiting portion 3, and a piezoelectric element 41.

[0046] The elastic body 2 has elasticity and is arranged in contact with the holding surface 141. Note that an arbitrary object can be interposed between the elastic body 2 and the holding surface 141. Elasticity refers to a property of deforming in accordance with an applied force and returning to the original shape once the force is removed. Therefore, if a force is applied to the elastic body 2, the elastic body 2 deforms and the force propagates to each portion of the elastic body 2.

[0047] Figure 2 and Figure 3 The elastic body 2 shown in FIG. 2 is a plate shape extending along the Y-Z plane and has six surfaces. Two surfaces of the six surfaces that intersect the Y axis are set as a first surface 201 and a second surface 202, two surfaces that intersect the X axis are set as a third surface 203 and a fourth surface 204, and two surfaces that intersect the Z axis are set as a fifth surface 205 and a sixth surface 206.

[0048] The third surface 203 and the fourth surface 204 are two main surfaces that have a front-back relationship with each other in the elastic body 2. The third surface 203 is a surface facing the object W, and the fourth surface 204 is fixed to the holding surface 141. Figure 3 The third surface 203 and the fourth surface 204 shown in FIG. 2 each have a rectangular shape. In addition, in the elastic body 2 shown in FIG. 2, the third surface 203 has a convex curved surface 207 in the central portion. Figure 2 In the elastic body 2 shown in FIG. 2, the central portion of the third surface 203 is a convex curved surface 207. Thus, when the third surface 203 comes into contact with the object W, the convex curved surface 207 can come into contact first. As a result, when a force is applied to the elastic body 2, the force can propagate from the central portion of the third surface 203 toward the peripheral portion.

[0049] As a material constituting the elastic body 2, for example, rubber, an elastomer, a foamed resin, or the like is exemplified. Among them, as the rubber, for example, polyisobutylene, polyisoprene, chloroprene rubber, butyl rubber, silicone rubber, fluororubber, acrylic rubber, urethane rubber, ethylene-propylene rubber, butadiene rubber, nitrile rubber, styrene-butadiene rubber, or the like is exemplified.

[0050] Figure 2 and Figure 3 The restriction portion 3 shown in FIG. 2 is provided to the holding surface 141 and has a frame shape surrounding the elastic body 2. The inner side surface of the restriction portion 3 is in contact with the outer side surface of the elastic body 2. That is, when the third surface 203 of the elastic body 2 is observed from above, the elastic body 2 is included in the inner side of the restriction portion 3. Note that a slight gap can exist between the restriction portion 3 and the elastic body 2. In addition, an arbitrary object can be interposed between the restriction portion 3 and the holding surface 141.

[0051] The restriction portion 3 has two first wall portions 31 and 32 extending along the Z axis and two second wall portions 33 and 34 extending along the Y axis.

[0052] The thickness t1 of each of the first wall portions 31, 32 is thicker than the thickness t2 of each of the second wall portions 33, 34. Thus, the first wall portions 31, 32 have higher bending stiffness than the second wall portions 33, 34. As a result, even if the first wall portions 31, 32 are pushed by the elastic body 2, it is difficult for them to deform. That is, the first wall portion 31 and the first wall portion 32 face the first face 201 and the second face 202 of the elastic body 2 in the natural state. Specifically, the first wall portion 31 and the first wall portion 32 are in contact with, or adjacent to, the first face 201 and the second face 202 of the elastic body 2 with a slight gap therebetween. Therefore, when the elastic body 2 is deformed in the Y-axis direction by an external force, the deformation is restricted. Note that the thickness of the first wall portions 31, 32 refers to the length in the Y-axis direction.

[0053] The thickness of each of the second wall portions 33, 34 is thinner than the thickness of each of the first wall portions 31, 32. Thus, the second wall portions 33, 34 have lower bending stiffness than the first wall portions 31, 32. As a result, the second wall portions 33, 34 are easily deformed when pushed by the elastic body 2. That is, the second wall portions 33, 34 are in contact with, or adjacent to, the elastic body 2 in the natural state with a slight gap therebetween. Therefore, when the elastic body 2 is deformed in the Z-axis direction by an external force, the second wall portions 33, 34 also displace in the Z-axis direction along with the deformation of the elastic body 2. That is, the second wall portions 33, 34 are bent and deformed in the Z-axis direction. At this time, the both ends of the second wall portions 33, 34 in the Y-axis direction are hardly displaced because they are connected to the first wall portions 31, 32. Note that the thickness of the second wall portions 33, 34 refers to the length in the Z-axis direction.

[0054] The material constituting the restriction portion 3 is not particularly limited, and examples include resin materials, ceramic materials, metal materials, and the like.

[0055] The thickness of the first wall portions 31, 32 is appropriately set according to the material constituting the first wall portions 31, 32, and as one example, is preferably 0.5 mm or more and 20 mm or less, and more preferably 1 mm or more and 10 mm or less. Thus, the first wall portions 31, 32 have sufficient bending stiffness, and it is particularly difficult for them to deform even if a force is applied to the elastic body 2.

[0056] The thickness of the second wall portions 33, 34 is also appropriately set according to the material constituting the second wall portions 33, 34, and as one example, is preferably 60% or less of the thickness of the first wall portions 31, 32, and more preferably 5% or more and 40% or less. Thus, the second wall portions 33, 34 have sufficient flexibility, and are easily deformed in conjunction with the elastic body 2 when a force is applied to the elastic body 2. Therefore, it is also easy for the second wall portions 33, 34 to transmit the deformation to the piezoelectric element 41, and it is possible to improve the sensitivity of the piezoelectric sensor 1.

[0057] Although not shown, the piezoelectric element 41 has a piezoelectric body and a pair of electrodes provided across the piezoelectric body. The piezoelectric body generates a voltage between the electrodes by a piezoelectric effect, for example, at the time of bending deformation. The direction and magnitude of the force received are determined by detecting the voltage output from the piezoelectric element 41.

[0058] Figure 2 The piezoelectric element 41 shown is provided between the fifth surface 205 of the elastic body 2 and the second wall portion 33. Thus, when bending deformation occurs in the second wall portion 33 as the elastic body 2 deforms, the piezoelectric element 41 also similarly deforms. In this way, by fixing a portion of the piezoelectric element 41 to the second wall portion 33, damage to the piezoelectric element 41 due to bending deformation can be suppressed. That is, by reinforcing the piezoelectric element 41 with the second wall portion 33, even if the piezoelectric element 41 repeatedly deforms due to bending deformation at a short cycle, the piezoelectricity of the piezoelectric element 41 is unlikely to decrease. In addition, at the time of unloading, the piezoelectric element 41 easily returns to its original shape. That is, the piezoelectric element 41 improves in followability to the deformation of the elastic body 2. Thus, the accuracy of force detection can be suppressed from decreasing.

[0059] As a piezoelectric material constituting the piezoelectric body, for example, piezoelectric ceramics such as lead zirconate titanate (PZT), barium titanate, lead titanate, piezoelectric plastics such as polyvinylidene fluoride, polylactic acid, and the like are exemplified.

[0060] Note that the piezoelectric body has anisotropy in piezoelectric effect depending on the piezoelectric constant of the piezoelectric material. In the present embodiment, the piezoelectric material is selected in a manner that a voltage is generated between the electrodes due to bending deformation occurring in the Z-axis direction. Thus, the direction and magnitude of the force received by the elastic body 2 can be determined from the output from the piezoelectric element 41. As a piezoelectric constant representing such piezoelectricity, for example, d 31 or the like is exemplified.

[0061] As a material constituting the electrodes, for example, Al, Cu, Ni, Ag, Au, or the like, either alone or as an alloy, or the like is exemplified.

[0062] Figure 4 is one example of an output circuit that amplifies the voltage generated in the piezoelectric element 41.

[0063] Figure 4 The output circuit 49 shown has an amplifier 491, a power supply 492, a power supply 493, and a detection portion 494. The piezoelectric element 41 is connected between the inverting input terminal and the non-inverting input terminal of the amplifier 491. The power supply 492 is connected to the non-inverting input terminal. The power supply 493 is connected to the power supply terminal of the amplifier 491. The detection portion 494 is connected to the output terminal of the amplifier 491.

[0064] In such an output circuit 49, the voltage generated by the piezoelectric element 41 is amplified and output as a voltage signal with a large amplitude. Note that, as shown in FIG. 4, in a case where a power supply 492 is connected to the input terminal of the amplifier 491, the input signal is offset by the power supply 492. Thus, the voltage after the offset, that is, the voltage signal increased or decreased from the reference voltage, is output to the detection section 494. Note that the power supply 492 can be omitted as needed. Figure 4

[0065] The detection section 494 has a function of detecting a temporal change in the voltage signal increased or decreased from the reference voltage, a function of judging the holding state of the object W based on the voltage value, and the like. As one example, the detection section 494 shown in FIG. 4 has a measurement section 495, a calculation section 496, and a judgment section 497. The measurement section 495 measures the amplitude of the voltage signal output from the amplifier 491. The calculation section 496 calculates the increase or decrease in the amplitude of the voltage signal with respect to the reference voltage. The judgment section 497 performs a comparison between the calculation result of the calculation section 496 and a predetermined allowable range, for example, and outputs the result if it is determined that there is an abnormality in the holding state or the like. Figure 2 Figure 4

[0066] At least a part of the detection section 494 is configured of hardware having a processor, a memory, an external interface, and the like. As the processor, a CPU (Central Processing Unit) is exemplified, for example. The function of the detection section 494 is realized by the processor reading and executing a program stored in the memory. Note that the hardware configuration is not limited thereto, and can be a configuration having an LSI (Large Scale Integration), an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or the like.

[0067] In addition, the circuit structure of the output circuit provided in the piezoelectric sensor 1 is not limited to the circuit structure shown in FIG. 4, and can be a circuit including a charge amplifier or the like, for example. Figure 4

[0068] Figure 5 is a diagram for explaining a deformation mode of the elastic body 2 when a force is applied to the piezoelectric sensor 1 shown in FIG. 1 from various directions. Figure 3 is a diagram for explaining a deformation mode of the elastic body 2 when a force is applied to the piezoelectric sensor 1 shown in FIG. 1 from various directions. Figure 6 is a diagram for explaining a deformation mode of the elastic body 2 when a force is applied to the piezoelectric sensor 1 shown in FIG. 1 from various directions. Figure 5 is a diagram for explaining a deformation mode of the elastic body 2 when a force is applied to the piezoelectric sensor 1 shown in FIG. 1 from various directions. Figure 3 ​​​​The diagram shows an example of the waveform (output waveform) of the voltage signal output by the piezoelectric element 41. It should be noted that... Figure 6 The example shown illustrates the waveform of the relative potential with respect to the reference voltage.

[0069] When no force is applied to the piezoelectric sensor 1, the elastic body 2 maintains its natural state, therefore... Figure 5 As shown in the upper left figure, the piezoelectric element 41 does not deform. Therefore, theoretically, no voltage is generated in the piezoelectric element 41.

[0070] When a downward force is applied to piezoelectric sensor 1, such as Figure 5 As shown by the arrow in the upper right figure, a downward pulling force is applied to the third surface 203 of the elastic body 2. Consequently, the elastic body 2 deforms by being pulled downwards, and a downward bending deformation occurs in the piezoelectric element 41. At this time, as... Figure 6 As shown, a voltage signal, for example, negative relative to a reference voltage, is output from the piezoelectric element 41. That is, the output voltage signal decreases from the reference voltage. This allows determination of the downward force applied to the piezoelectric sensor 1. It should be noted that since the output direction of the voltage signal relative to the reference voltage is determined by the polarization direction of the piezoelectric element and the circuit structure, the output direction of the voltage signal can also be opposite to the above. In this case, the subsequent output will also be the opposite result.

[0071] It should be noted that when the gripper 10 is used to hold the object W and the object W is held in the air, the weight of the object W exerts a downward force on the piezoelectric sensor 1. Therefore, it is possible to determine the state in which the gripper 10 is picking up the object W based on the output waveform from the piezoelectric element 41.

[0072] When an upward force is applied to piezoelectric sensor 1, such as Figure 5 As shown by the arrow in the lower left figure, an upward pulling force is applied to the third surface 203 of the elastic body 2. Consequently, the elastic body 2 deforms by being pulled upwards, and a corresponding upward bending deformation occurs in the piezoelectric element 41. At this time, as... Figure 6 As shown, a voltage signal that is positive relative to a reference voltage is output from the piezoelectric element 41. That is, a voltage signal that increases from the reference voltage is output. Thus, it is possible to determine the upward force applied to the piezoelectric sensor 1.

[0073] It should be noted that when the gripper 10 is used to hold the object W, and the gripper 10 is moved to press the lower surface of the object W against the object, an upward force is applied to the piezoelectric sensor 1. Therefore, based on the output waveform from the piezoelectric element 41, it is possible to determine the state in which the gripper 10 is pressing the object W against the object.

[0074] If a force in the pressing direction, that is, a force in the direction from the positive side of the X axis to the negative side of the X axis is applied to the piezoelectric sensor 1 Figure 5 as shown in the right lower drawing of FIG. 4, a deformation extending in the up-and-down direction is generated on the third face 203 of the elastic body 2. Then, since the elastic body 2 extends in the up-and-down direction, a bending deformation in the upward direction is generated in the piezoelectric element 41 in conjunction therewith. However, the amount of deformation of the bending deformation is smaller than that in the case where the force in the upward direction is applied as described above. Therefore, as shown in FIG. 5, a positive voltage signal whose voltage value is relatively small with respect to a reference voltage is output from the piezoelectric element 41. Thus, it is possible to determine that the force in the pressing direction is applied to the piezoelectric sensor 1. Figure 5 Figure 6

[0075] Note that if the handgrip 10 holds the object W, a reaction force from the object W presses the piezoelectric sensor 1 against the holding face 141. Therefore, it is possible to determine that the handgrip 10 is holding the object W based on the output waveform from the piezoelectric element 41.

[0076] The above describes an example of the deformation mode, but the deformation directions in the upward direction and the downward direction can be directions other than these.

[0077] In addition, as shown in FIG. 6, in the piezoelectric element 41, the voltage generated in the piezoelectric element 41 decreases over time due to the influence of the internal resistance R, a leakage current in the output circuit 49, a parasitic capacitance, and the like, and the like due to a relaxation phenomenon. Therefore, as shown in FIG. 7, the output waveform from the piezoelectric sensor 1 changes depending on the degree of the relaxation phenomenon. Figure 4 Figure 7 Figure 7 is a graph showing one example of the output waveform from the piezoelectric sensor 1 in the case where the degree of the relaxation phenomenon is different.

[0078] In the case where there is no relaxation, the voltage hardly decreases over time as in the waveform shown in FIG. 8. Figure 6 In the case where the relaxation is small, the voltage decreases over time, but the decrease is relatively small. In contrast, in the case where the relaxation is large, the decrease is relatively large. Thus, in the case where the direction and the magnitude of the force applied to the piezoelectric sensor 1 are determined based on the output waveform from the piezoelectric element 41, it is preferable to take into account the change in the waveform based on such a relaxation phenomenon.

[0079]

[0080] ​​​​​As described above, the piezoelectric sensor 1 according to the present embodiment includes the elastic body 2, the restriction portion 3, and the piezoelectric element 41. The elastic body 2 has the first surface 201. The restriction portion 3 is provided at least at a position facing the first surface 201 of the elastic body 2, and restricts deformation of the elastic body 2. A part of the piezoelectric element 41 is fixed to the restriction portion 3, and the piezoelectric element 41 deforms in accordance with the deformation of the elastic body 2. The deformation of the piezoelectric element 41 means that the shape of the piezoelectric element 41 changes from the shape of the piezoelectric element 41 when the elastic body 2 is not deformed. Then, the piezoelectric element 41 outputs a voltage signal that increases or decreases from a reference voltage, in accordance with the direction of the deformation.

[0081] According to the piezoelectric sensor 1 as described above, the direction of application of force can be detected when force is applied from a plurality of different directions, such as upward, downward, and pressing directions. That is, the piezoelectric sensor 1 can distinguish between detecting a compression force and a pushing force. Thus, in the gripper 10 including the piezoelectric sensor 1, in addition to being able to determine that an object W is being held, for example, it is also possible to determine a state in which the object W is being picked up, or a state in which the object W is being pressed against an object. Therefore, the gripper 10 can be appropriately operated in accordance with these different states, and convenience can be improved.

[0082] In addition, since force is transmitted to the piezoelectric element 41 via the elastic body 2, it is possible to suppress the impact from being directly applied to the piezoelectric element 41. Thus, the piezoelectric element 41 is less likely to be damaged.

[0083] Thus, the gripper 10 according to the above-described embodiment includes the piezoelectric sensor 1 as described above.

[0084] In the case where the piezoelectric sensor 1 is used for Figure 1 In the case of the gripper 10 as illustrated in FIG. 1, for example, it is possible to realize a gripper 10 that can not only determine that an object W is being held, but also determine a state in which the object W is being picked up, or a state in which the object W is being pressed against an object.

[0085] In addition, the piezoelectric sensor 1 is configured such that the elastic body 2 comes into contact with the object W. Thus, even if the piezoelectric sensor 1 comes into contact with the object W, a large impact is less likely to occur, and therefore, even in the case where the object W has low rigidity, it is possible to hold the object W with the gripper 10 without damaging the object W. In addition, it is possible to suppress damage to the piezoelectric element 41 accompanying the impact. Note that the gripper 10 can include the piezoelectric sensor according to each of the embodiments described below.

[0086] In addition, in the piezoelectric sensor 1 according to the present embodiment, the restriction portion 3 includes two first wall portions 31 and 32, and two second wall portions 33 and 34. The second wall portions 33 and 34 connect the first wall portion 31 and the first wall portion 32, and have a thickness that is thinner than the thickness of the first wall portions 31 and 32. Furthermore, the piezoelectric element 41 is fixed at a position that comes into contact with the second wall portion 33.

[0087] With this structure, since the piezoelectric element 41 is fixed in contact with the second wall portion 33, the durability of the piezoelectric element 41 is improved, and the piezoelectric element 41's ability to follow the deformation of the elastomer 2 is improved.

[0088] In addition, the elastomer 2 has a third surface 203 in a rectangular shape. Furthermore, the elastomer 2 is plate-shaped with the third surface 203 as the main surface.

[0089] With this structure, since the relatively wide third surface 203 faces the object W, a large contact area between the object W and the elastic body 2 can be ensured. Therefore, a large force can be applied to the elastic body 2, and the displacement of the fifth surface 205 facing the piezoelectric element 41 increases. As a result, the sensitivity of the piezoelectric sensor 1 can be further improved.

[0090] It should be noted that the shape of the third face 203 is not limited to a rectangle; it can also be other shapes, such as a square or a polygon. Additionally, it can be a shape with rounded or chamfered corners.

[0091] In addition, such as Figure 2 As shown, the elastomer 2 has a convex surface 207 as a contact surface that contacts the object W. The convex surface 207 is located at a position separate from the piezoelectric element 41.

[0092] With this structure, contact between the piezoelectric element 41 and the object W can be avoided when the convex surface 207 contacts the object W. This prevents damage to the piezoelectric element 41. Furthermore, since the elastic body 2 is elastic, even if the piezoelectric element 41 is positioned separately from the convex surface 207, the frictional force generated between the elastic body 2 and the object W is effectively converted into deformation of the piezoelectric element 41. Therefore, frictional force can be efficiently detected in the piezoelectric element 41. As a result, a piezoelectric sensor 1 with excellent sensitivity is achieved.

[0093] It should be noted that the elastomer 2 can also replace the convex surface 207 and have a convex surface of any shape, but if it is a convex surface 207, it is easy to realize a piezoelectric sensor 1 that can effectively detect forces applied from various directions.

[0094] 3. The piezoelectric sensor involved in the second embodiment

[0095] Next, the piezoelectric sensor involved in the second embodiment will be described.

[0096] Figure 8 This is a top view of the piezoelectric sensor according to the second embodiment, viewed from the position on the X-axis.

[0097] The second embodiment will now be described, but the description will focus on the differences from the first embodiment, while identical details will be omitted. It should be noted that in the figures, the same reference numerals are used to label the same components as in the first embodiment.

[0098] The piezoelectric sensor 1A according to the second embodiment includes a piezoelectric element 41 and a piezoelectric element 42. Otherwise, it is the same as the piezoelectric sensor 1 according to the first embodiment.

[0099] like Figure 8 As shown, the piezoelectric element 42 is disposed between the elastic body 2 and the second wall portion 34. Therefore, when the second wall portion 34 undergoes bending deformation due to the deformation of the elastic body 2, the piezoelectric element 42 also undergoes bending deformation in the same way. The structure of the piezoelectric element 42 is the same as that of the piezoelectric element 41.

[0100] It should be noted that the relationship between the bending deformation direction of piezoelectric element 42 and the output waveform from piezoelectric element 42 can be the same as the relationship between the bending deformation direction of piezoelectric element 41 and the output waveform from piezoelectric element 41, but is preferably opposite. That is, it is preferable that the signs of the output voltage signals are different when piezoelectric element 42 is bent in the same direction as piezoelectric element 41. As a result, the direction of the force applied to the elastic body 2 can be determined more accurately based on the output waveforms from the two piezoelectric elements 41 and 42.

[0101] Figure 9 It means in Figure 5 When the elastic body 2 deforms under the deformation mode shown, from Figure 8 The diagram shows an example of the waveform (output waveform) of the voltage signal output by the piezoelectric elements 41 and 42. It should be noted that... Figure 9 The output waveforms shown are those that output voltage signals of different signs when the piezoelectric elements 41 and 42 are bent in the same direction relative to each other. Additionally, in Figure 9 The example shown illustrates the waveform of the relative potential with respect to the reference voltage.

[0102] When a downward force is applied to the piezoelectric sensor 1A, downward bending deformation occurs in the piezoelectric elements 41 and 42. Therefore, voltage signals of different signs are output from the piezoelectric elements 41 and 42. For example, in... Figure 9 In the example shown, based on the fact that the voltage signal output from piezoelectric element 41 is negative and the voltage signal output from piezoelectric element 42 is positive, it is possible to determine that a downward force is applied to the piezoelectric sensor 1A. It should be noted that, similar to the first embodiment, the sign of the voltage signals described above and thereafter can also be reversed.

[0103] When a force in the upward direction is applied to the piezoelectric sensor 1A, the piezoelectric elements 41, 42 are each subjected to bending deformation in the upward direction. Therefore, voltage signals of mutually different signs are output from the piezoelectric elements 41, 42. For example, in the example shown in FIG. 6, the sign of the voltage signal output from the piezoelectric element 41 is positive, and the sign of the voltage signal output from the piezoelectric element 42 is negative, so it is possible to determine that a force in the upward direction has been applied to the piezoelectric sensor 1A. Figure 9 When a force in the upward direction is applied to the piezoelectric sensor 1A, the piezoelectric elements 41, 42 are each subjected to bending deformation in the upward direction. Therefore, voltage signals of mutually different signs are output from the piezoelectric elements 41, 42. For example, in the example shown in FIG. 6, the sign of the voltage signal output from the piezoelectric element 41 is positive, and the sign of the voltage signal output from the piezoelectric element 42 is negative, so it is possible to determine that a force in the upward direction has been applied to the piezoelectric sensor 1A.

[0104] When a force in the upward direction is applied to the piezoelectric sensor 1A, the piezoelectric elements 41, 42 are each subjected to bending deformation in the upward direction. Therefore, voltage signals of mutually different signs are output from the piezoelectric elements 41, 42. For example, in the example shown in FIG. 6, the sign of the voltage signal output from the piezoelectric element 41 is positive, and the sign of the voltage signal output from the piezoelectric element 42 is negative, so it is possible to determine that a force in the upward direction has been applied to the piezoelectric sensor 1A. Figure 8 When a force in the upward direction is applied to the piezoelectric sensor 1A, the piezoelectric elements 41, 42 are each subjected to bending deformation in the upward direction. Therefore, voltage signals of mutually different signs are output from the piezoelectric elements 41, 42. For example, in the example shown in FIG. 6, the sign of the voltage signal output from the piezoelectric element 41 is positive, and the sign of the voltage signal output from the piezoelectric element 42 is negative, so it is possible to determine that a force in the upward direction has been applied to the piezoelectric sensor 1A.

[0105] In this second embodiment as well, the same effects as in the first embodiment are obtained.

[0106] As described above, the elastic body 2 of the piezoelectric sensor 1A has a fifth face 205 and a sixth face 206 as two opposing faces corresponding to two edges that are mutually opposite when the third face 203 is viewed from above. Furthermore, the piezoelectric element 41 and the piezoelectric element 42 are disposed at positions facing the fifth face 205 and the sixth face 206.

[0107] According to this structure, for example, by making the signs of the voltage signals output when bent in the same direction different between the piezoelectric elements 41, 42, one of the voltage signals output from the piezoelectric elements 41, 42 can be made a signal that increases from a reference voltage, and the other can be made a signal that decreases from the reference voltage. As a result, the difference in the waveforms of the voltage signals output from the piezoelectric elements 41, 42 becomes more distinct. As a result, for example, even in the case where noise is mixed into the voltage signals, it is possible to easily determine the direction of the force applied to the elastic body 2.

[0108] 4. Piezoelectric sensor according to the third embodiment

[0109] Next, a piezoelectric sensor according to the third embodiment will be described.

[0110] Figure 10 is a plan view of the piezoelectric sensor according to the third embodiment as viewed from a position on the X axis.

[0111] The following describes the third embodiment, but in the following description, the description is centered on the points of difference from the first embodiment, and the description of the same matters is omitted. Note that in each drawing, the same reference signs are applied to the same structures as those of the first embodiment.

[0112] In the piezoelectric sensor 1B according to the present embodiment, the elastic body 2 has a second face 202 opposite to the first face 201. In addition, the restriction portion 3 has two first wall portions 31, 32. The first wall portion 31 is disposed at a position facing the first face 201 of the elastic body 2, and the first wall portion 32 is disposed at a position facing the second face 202 of the elastic body 2.

[0113] That is, in the aforementioned first embodiment, the restriction portion 3 has two first wall portions 31, 32 and two second wall portions 33, 34. In contrast to this, in the present embodiment, the second wall portions 33, 34 are omitted. As a result, in the present embodiment, as shown in FIG. 8, the restriction portion 3 is composed of only the two first wall portions 31, 32. Figure 10

[0114] In addition, in the aforementioned first embodiment, the piezoelectric element 41 is fixed to the second wall portion 33, in contrast to this, in the present embodiment, the piezoelectric element 41 is fixed so as to connect the first wall portions 31, 32. Specifically, the piezoelectric element 41 is disposed at a position facing the fifth face 205 of the elastic body 2, and the end portion of the piezoelectric element 41 on the positive side of the Y axis is fixed to the first wall portion 31, and the end portion of the piezoelectric element 41 on the negative side of the Y axis is fixed to the first wall portion 32.

[0115] According to such a structure, as in the first embodiment, the deformation of the elastic body 2 is restricted by the two first wall portions 31, 32 extending along the Z axis. In addition, in the present embodiment, the second wall portions 33, 34 provided in the first embodiment are omitted. Therefore, the fifth face 205 of the elastic body 2 is not restricted in deformation by the second wall portions 33, 34. As a result, the amount of deformation of the piezoelectric element 41 is liable to be larger than in the first embodiment.

[0116] Thus, by disposing the piezoelectric element 41 at a position facing the fifth face 205, it is possible to further improve the sensitivity of the piezoelectric sensor 1B.

[0117] Figure 11 is a diagram for illustrating the deformation mode of the elastic body 2 when a force is applied to the piezoelectric sensor 1B from various directions. Figure 10

[0118] When a downward force is applied to the piezoelectric sensor 1B, as shown in the upper right drawing of FIG. 10, the piezoelectric element 41 is bent and deformed in the downward direction. At this time, as shown in the lower right drawing of FIG. 10, the fifth face 205 of the elastic body 2 is deformed in the upward direction. Figure 11 Figure 6 ​​​As shown in the lower right view of FIG. 16B, the piezoelectric element 41 is bent and deformed in the upward direction. Therefore, as shown in the lower right view of FIG. 16B, a positive voltage signal is output from the piezoelectric element 41, for example. Thus, it is determined that the force in the upward direction is applied to the piezoelectric sensor 1B.

[0119] When the force in the upward direction is applied to the piezoelectric sensor 1B, as shown in the lower right view of FIG. 16B, the piezoelectric element 41 is bent and deformed in the upward direction. Therefore, as shown in the lower right view of FIG. 16B, a positive voltage signal is output from the piezoelectric element 41, for example. Thus, it is determined that the force in the upward direction is applied to the piezoelectric sensor 1B. Figure 11 Figure 6 As shown in the lower right view of FIG. 16B, the piezoelectric element 41 is bent and deformed in the upward direction. Therefore, as shown in the lower right view of FIG. 16B, a positive voltage signal is output from the piezoelectric element 41, for example. Thus, it is determined that the force in the upward direction is applied to the piezoelectric sensor 1B.

[0120] When the force in the upward direction is applied to the piezoelectric sensor 1B, as shown in the lower right view of FIG. 16B, the piezoelectric element 41 is bent and deformed in the upward direction. Therefore, as shown in the lower right view of FIG. 16B, a positive voltage signal is output from the piezoelectric element 41, for example. Thus, it is determined that the force in the upward direction is applied to the piezoelectric sensor 1B. Figure 11 Figure 11 As shown in the lower right view of FIG. 16B, the piezoelectric element 41 is bent and deformed in the upward direction. Therefore, as shown in the lower right view of FIG. 16B, a positive voltage signal is output from the piezoelectric element 41, for example. Thus, it is determined that the force in the upward direction is applied to the piezoelectric sensor 1B. Figure 6

[0121] In the third embodiment as well, the same effects as those of the first embodiment can be obtained.

[0122] 5. Piezoelectric sensor according to the fourth embodiment

[0123] Next, a piezoelectric sensor according to the fourth embodiment will be described.

[0124] Figure 12 is a plan view when the piezoelectric sensor according to the fourth embodiment is viewed from a position on the X axis.

[0125] Hereinafter, the fourth embodiment will be described, but in the following description, the different points from the second and third embodiments will be described, and the same matters will be omitted. Note that in each drawing, the same reference numerals are attached to the same structures as those of the second and third embodiments.

[0126] The piezoelectric sensor 1C according to the fourth embodiment has the piezoelectric element 42 in addition to the piezoelectric element 41, and is the same as the piezoelectric sensor 1B according to the third embodiment except for this.

[0127] As shown in the lower right view of FIG. 16B, the piezoelectric element 41 is bent and deformed in the upward direction. Therefore, as shown in the lower right view of FIG. 16B, a positive voltage signal is output from the piezoelectric element 41, for example. Thus, it is determined that the force in the upward direction is applied to the piezoelectric sensor 1B. Figure 12 ​​​As shown, the piezoelectric element 42 is fixed so as to connect the first wall portions 31, 32. Specifically, the piezoelectric element 42 is disposed at a position facing the sixth face 206 of the elastic body 2, and the end portion of the Y-axis positive side of the piezoelectric element 42 is fixed to the first wall portion 31, and the end portion of the Y-axis negative side of the piezoelectric element 42 is fixed to the first wall portion 32.

[0128] According to such a structure, as with the second embodiment, for example, by making the signs of the voltage signals output when bent in the same direction different between the piezoelectric elements 41, 42, for the voltage signals output from the piezoelectric elements 41, 42, one can be a signal in which the reference voltage is increased, and the other can be a signal in which the reference voltage is decreased. Thus, the difference between the two becomes clear, and even in the case where noise is mixed into the output signals, the direction of the force applied to the elastic body 2 can be easily determined.

[0129] In the fourth embodiment as well, the same effects as the first to third embodiments can be obtained.

[0130] 6. Piezoelectric sensor according to the fifth embodiment

[0131] Next, a piezoelectric sensor according to the fifth embodiment will be described.

[0132] Figure 13 is a plan view when the piezoelectric sensor according to the fifth embodiment is viewed from a position on the X-axis.

[0133] Hereinafter, the fifth embodiment will be described, but in the following description, the description will be centered on the points of difference from the third embodiment, and the description of the same matters will be omitted. Note that in each drawing, the same reference numerals are attached to the same structures as the third embodiment.

[0134] The piezoelectric sensor 1D according to the fifth embodiment is the same as the piezoelectric sensor 1B according to the third embodiment except for the shape of the restriction portion 3.

[0135] Figure 13 The restriction portion 3 shown has four columnar portions 351 to 354. The four columnar portions 351 to 354 are disposed at positions corresponding to the four corners of the elastic body 2.

[0136] According to such a structure, it is possible to suppress the restriction portion 3 to the minimum necessary volume. Thus, it is possible to achieve weight reduction of the piezoelectric sensor 1D.

[0137] The columnar portion 351 is disposed at the corner of the elastic body 2 on the Y-axis positive side and the Z-axis positive side, and the columnar portion 352 is disposed at the corner on the Y-axis positive side and the Z-axis negative side. The columnar portion 353 is disposed at the corner of the elastic body 2 on the Y-axis negative side and the Z-axis positive side, and the columnar portion 354 is disposed at the corner on the Y-axis negative side and the Z-axis negative side.

[0138] As shown in FIG. 4, the piezoelectric element 41 is fixed so as to connect the columnar portions 351, 353. Figure 13

[0139] In the above-described fifth embodiment, the same effects as those of the third embodiment can also be obtained.

[0140] 7. Piezoelectric sensor according to the sixth embodiment

[0141] Next, the piezoelectric sensor according to the sixth embodiment will be described.

[0142] Figure 14 is a plan view when the piezoelectric sensor according to the sixth embodiment is viewed from a position on the X-axis.

[0143] Hereinafter, the sixth embodiment will be described, but in the following description, the description will be centered on the points different from the fourth and fifth embodiments, and the description of the same matters will be omitted. Note that in each drawing, the same reference numerals are attached to the same structures as those of the fourth and fifth embodiments.

[0144] The piezoelectric sensor 1E according to the sixth embodiment has the piezoelectric element 43 in addition to the piezoelectric element 41, and is the same as the piezoelectric sensor 1D according to the fifth embodiment except for this.

[0145] As shown in FIG. 6, the piezoelectric element 43 is fixed so as to connect the columnar portions 353, 354. Figure 14

[0146] That is, the piezoelectric sensor 1E has a plurality of piezoelectric elements 41, 43. Further, the piezoelectric elements 41, 43 are deformed in different deformation directions from each other as the elastic body 2 is deformed.

[0147] Specifically, the above-described fourth embodiment also has a plurality of piezoelectric elements 41, 42, but these piezoelectric elements 41, 42 are deformed in the same deformation direction as the elastic body 2 is deformed. For example, the piezoelectric elements 41, 42 are deformed in the downward direction as the elastic body 2 is deformed because the piezoelectric elements 41, 42 have detection axes parallel to the Z-axis.

[0148] ​​On the other hand, in the piezoelectric sensor 1E according to the present embodiment, the piezoelectric element 41 is arranged at a position facing the fifth surface 205 of the elastic body 2, and the piezoelectric element 43 is arranged at a position facing the second surface 202 of the elastic body 2. That is, the piezoelectric element 41 has a detection axis parallel to the Z-axis, and the piezoelectric element 43 has a detection axis parallel to the Y-axis. Therefore, the piezoelectric sensor 1E can detect not only the deformation of the elastic body 2 in the Z-axis direction, but also the deformation in the Y-axis direction.

[0149] In the sixth embodiment described above, the same effects as those of the fourth and fifth embodiments can be obtained.

[0150] Figure 15 is a diagram for explaining the deformation mode of the elastic body 2 when a force is applied to the piezoelectric sensor 1E shown in Figure 14 from various directions. Figure 16 is a diagram showing a wave form (output wave form) of a voltage signal output from the piezoelectric elements 41, 43 when the elastic body 2 is deformed in the deformation mode shown in Figure 15 . Figure 14 is a diagram showing a wave form (output wave form) of a voltage signal output from the piezoelectric elements 41, 43 when the elastic body 2 is deformed in the deformation mode shown in Figure 16 .

[0151] When a force in the downward direction is applied to the piezoelectric sensor 1E, as shown by an arrow in the upper right of Figure 15 , a force in the downward direction is applied to the third surface 203 of the elastic body 2. Then, the piezoelectric element 41 is bent in the downward direction. At this time, as shown in Figure 16 , a voltage signal of, for example, negative with respect to a reference voltage is output from the piezoelectric element 41. Thus, it is determined that a force in the downward direction is applied to the piezoelectric sensor 1E. On the other hand, the piezoelectric element 43 is hardly deformed. Thus, a voltage signal of, for example, plus or minus from the reference voltage is hardly output from the piezoelectric element 43. Note that, as in the first embodiment, the positive and negative of the above and subsequent voltage signals can be reversed.

[0152] When a force in the upward direction is applied to the piezoelectric sensor 1E, as shown by an arrow in the left center of Figure 15 , a force in the upward direction is applied to the third surface 203 of the elastic body 2. Then, the piezoelectric element 41 is bent in the upward direction. At this time, as shown in Figure 16 , a voltage signal of, for example, positive with respect to a reference voltage is output from the piezoelectric element 41. Thus, it is determined that a force in the upward direction is applied to the piezoelectric sensor 1E. On the other hand, the piezoelectric element 43 is hardly deformed. Thus, a voltage signal of, for example, plus or minus from the reference voltage is hardly output from the piezoelectric element 43.

[0153] If a force in the pressing direction, that is, a force pressing from the positive side of the X axis toward the negative side of the X axis is applied to the piezoelectric sensor 1E Figure 15 as shown in the right middle drawing of FIG. 10, a deformation spreading to the four directions occurs in the third face 203 of the elastic body 2. As a result, the piezoelectric element 41 is deformed in the upward direction. At this time, as shown in the right middle drawing of FIG. 10, a positive voltage signal in which the voltage value is relatively small with respect to the reference voltage is output from the piezoelectric element 41. In addition, the piezoelectric element 43 is deformed in the left direction (the negative side of the Y axis). At this time, as shown in the right middle drawing of FIG. 10, a positive voltage signal in which the voltage value is relatively small with respect to the reference voltage is output from the piezoelectric element 43. According to these voltage waveforms, it is possible to determine that a force in the pressing direction is applied to the piezoelectric sensor 1E. Figure 15 Figure 16 Figure 16

[0154] When a force in the left direction (the negative side of the Y axis) is applied to the piezoelectric sensor 1E, as shown by the arrows in the lower left drawing of FIG. 11, a force pulling in the left direction is applied to the third face 203 of the elastic body 2. As a result, the piezoelectric element 43 is deformed in the left direction. At this time, as shown in the lower left drawing of FIG. 11, a voltage signal in which the voltage value is positive with respect to the reference voltage is output from the piezoelectric element 43. Thus, it is possible to determine that a force in the left direction is applied to the piezoelectric sensor 1E. On the other hand, the piezoelectric element 41 hardly deforms. Thus, a voltage signal in which the voltage value is added or subtracted from the reference voltage is hardly output from the piezoelectric element 41. Figure 15 Figure 16

[0155] When a force in the right direction (the positive side of the Y axis) is applied to the piezoelectric sensor 1E, as shown by the arrows in the lower right drawing of FIG. 12, a force pulling in the right direction is applied to the third face 203 of the elastic body 2. As a result, the piezoelectric element 43 is deformed in the right direction. At this time, as shown in the lower right drawing of FIG. 12, a voltage signal in which the voltage value is negative with respect to the reference voltage is output from the piezoelectric element 43. Thus, it is possible to determine that a force in the right direction is applied to the piezoelectric sensor 1E. On the other hand, the piezoelectric element 41 hardly deforms. Thus, a voltage signal in which the voltage value is added or subtracted from the reference voltage is hardly output from the piezoelectric element 41. Figure 15 Figure 16

[0156] The above describes an example of the deformation mode, but the deformation directions in the upward direction, the downward direction, the left direction, and the right direction can be directions other than these.

[0157] As described above, the elastic body 2 of the piezoelectric sensor 1E has the fifth face 205 and the second face 202 as two adjacent faces corresponding to two edges adjacent to each other when the third face 203 is viewed from above. In addition, the piezoelectric element 41 and the piezoelectric element 43 are disposed at positions facing the fifth face 205 and the second face 202. ​​​​​​​

[0158] According to such a structure, even when a force is applied from more directions than in the third embodiment, the piezoelectric sensor 1E that can detect the direction in which the force is applied can be realized. Specifically, for example, not only can the forces applied in the upward direction and the downward direction be distinguished, but also the forces applied in the leftward direction and the rightward direction can be distinguished. Thus, various motions of the gripper 10 can be captured more in detail based on the output results of the piezoelectric sensor 1E. As a result, the gripper 10 can be caused to operate more appropriately, and the convenience can be further improved.

[0159] 8. Piezoelectric sensor according to the seventh embodiment

[0160] Next, the piezoelectric sensor according to the seventh embodiment will be described.

[0161] Figure 17 is a plan view when the piezoelectric sensor according to the seventh embodiment is viewed from a position on the X axis.

[0162] Hereinafter, the seventh embodiment will be described, but in the following description, the different points from the fourth and sixth embodiments will be described, and the same matters will be omitted. Note that in each drawing, the same reference numerals are attached to the same structures as those of the fourth and sixth embodiments.

[0163] The piezoelectric sensor 1F according to the seventh embodiment has piezoelectric elements 42 and 44 in addition to the piezoelectric elements 41 and 43, and is the same as the piezoelectric sensor 1E according to the sixth embodiment except for this.

[0164] The piezoelectric element 42 is fixed so as to connect the columnar portions 352 and 354. The piezoelectric element 44 is fixed so as to connect the columnar portions 351 and 352.

[0165] That is, the piezoelectric sensor 1F has a plurality of piezoelectric elements 41 to 44. Specifically, as four outer sides corresponding to four edges constituting the outer periphery when the third surface 203 is viewed in plan, the elastic body 2 of the piezoelectric sensor 1F has a first surface 201, a second surface 202, a fifth surface 205, and a sixth surface 206. Further, as shown in FIG. 8, the piezoelectric element 41 is disposed at a position facing the fifth surface 205, the piezoelectric element 42 is disposed at a position facing the sixth surface 206, the piezoelectric element 43 is disposed at a position facing the second surface 202, and the piezoelectric element 44 is disposed at a position facing the first surface 201. Figure 17

[0166] ​According to such a structure, since the four piezoelectric elements 41 to 44 are arranged in a manner surrounding the periphery of the elastic body 2, a voltage signal is output from at least two piezoelectric elements regardless of the direction of the force applied to the elastic body 2. Thus, the piezoelectric sensor 1F according to the present embodiment has both the effects of the fourth embodiment and the sixth embodiment. Specifically, for example, it is possible to distinguish the forces applied in the upward direction, the downward direction, the left direction, and the right direction, and to make one of the voltage signals output from the two piezoelectric elements a signal that increases from the reference voltage and the other a signal that decreases from the reference voltage. Thus, it is possible to detect the forces applied in various directions with higher accuracy.

[0167] Figure 18 is a graph showing one example of a waveform (output waveform) of the voltage signals output from the piezoelectric elements 41 to 44 when the elastic body 2 is deformed in the deformation mode shown in Figure 15 Figure 17 In the example shown in Figure 18 , the waveform of the relative potential with respect to the reference voltage is shown.

[0168] When a force in the downward direction is applied to the piezoelectric sensor 1F, the piezoelectric element 41 is bent and deformed in the downward direction, and outputs, for example, a voltage signal that is negative with respect to the reference voltage, as shown in Figure 18 . In addition, the piezoelectric element 42 is also bent and deformed in the downward direction, and outputs, for example, a voltage signal that is positive with respect to the reference voltage, as shown in Figure 18 .

[0169] When a force in the upward direction is applied to the piezoelectric sensor 1F, the piezoelectric element 41 is bent and deformed in the upward direction, and outputs, for example, a voltage signal that is positive with respect to the reference voltage, as shown in Figure 18 . In addition, the piezoelectric element 42 is also bent and deformed in the upward direction, and outputs, for example, a voltage signal that is negative with respect to the reference voltage, as shown in Figure 18 .

[0170] When a force in the pressing direction, that is, a force pressing the elastic body 2 shown in Figure 17 from the positive side of the X axis to the negative side of the X axis, is applied to the piezoelectric sensor 1F, the piezoelectric element 41 is bent and deformed in the upward direction, the piezoelectric element 42 is bent and deformed in the downward direction, the piezoelectric element 43 is bent and deformed in the left direction, and the piezoelectric element 44 is bent and deformed in the right direction, and outputs, for example, positive voltage signals whose voltage values are relatively small with respect to the reference voltage, respectively, as shown in Figure 18 .

[0171] When a force in the left direction is applied to the piezoelectric sensor 1F, the piezoelectric element 43 is bent and deformed in the left direction, and outputs, for example, a voltage signal that is negative with respect to the reference voltage, as shown in Figure 18 ​is shown, for example, a positive voltage signal is output. In addition, the piezoelectric element 44 also generates a bending deformation in the left direction, as shown by an arrow Figure 18 is shown, for example, a negative voltage signal with respect to a reference voltage is output.

[0172] When a force in the right direction is applied to the piezoelectric sensor 1F, a bending deformation in the right direction is generated in the piezoelectric element 43, as shown by an arrow Figure 18 is shown, for example, a negative voltage signal with respect to a reference voltage is output. In addition, the piezoelectric element 44 also generates a bending deformation in the right direction, as shown by an arrow Figure 18 is shown, for example, a positive voltage signal with respect to a reference voltage is output.

[0173] In the seventh embodiment described above, the same effects as those of the fourth and sixth embodiments can be obtained.

[0174] 9. Piezoelectric sensor according to the eighth embodiment

[0175] Next, the piezoelectric sensor according to the eighth embodiment will be described.

[0176] Figure 19 is a plan view when the piezoelectric sensor according to the eighth embodiment is viewed from a position on the X axis.

[0177] The eighth embodiment will be described below, but in the following description, the different points from the second embodiment will be described, and the same matters will be omitted. Note that the same reference numerals are assigned to the same structures as those of the second embodiment in the drawings.

[0178] The piezoelectric sensor 1G according to the eighth embodiment is the same as the piezoelectric sensor 1A according to the second embodiment except that the restriction portion 3 is in a circular ring shape.

[0179] With the restriction portion 3 in a circular ring shape, when the third face 203 of the elastic body 2 is viewed in plan, as shown in Figure 19 is shown, the elastic body 2 is in a circular shape. That is, the third face 203 of the elastic body 2 is in a circular shape. The circular shape includes a perfect circle, an oblong, an ellipse, and the like.

[0180] Thus, since the plan-view shape of the elastic body 2 is in a circular shape, the shape anisotropy of the elastic body 2 is reduced as compared with the case where the plan-view shape of the elastic body 2 is in a rectangular shape. Thus, it is possible to detect the direction and magnitude of a force while suppressing the deviation of the sensitivity caused by the direction of the force applied to the piezoelectric sensor 1G.

[0181] The portion on the positive side of the Y axis in the restriction portion 3 in a circular ring shape is the first wall portion 31, and the portion on the negative side of the Y axis is the first wall portion 32. In addition, the portion on the positive side of the Z axis is the second wall portion 33, and the portion on the negative side of the Z axis is the second wall portion 34.

[0182] In addition, the portion of the side surface of the elastic body 2, that is, the third surface 203 and the fourth surface 204, on the positive side of the Y axis is the first surface 201, the portion on the negative side of the Y axis is the second surface 202, the portion on the positive side of the Z axis is the fifth surface 205, and the portion on the negative side of the Z axis is the sixth surface 206. The first wall portion 31 is disposed at a position facing the first surface 201, the first wall portion 32 is disposed at a position facing the second surface 202, the second wall portion 33 is disposed at a position facing the fifth surface 205, and the second wall portion 34 is disposed at a position facing the sixth surface 206.

[0183] Further, in the second embodiment described above, the piezoelectric element 41 is provided between the elastic body 2 and the second wall portion 33, and the piezoelectric element 42 is provided between the elastic body 2 and the second wall portion 34, and in contrast to this, in the present embodiment, the piezoelectric element 41 is fixed to the surface of the second wall portion 33 on the side opposite to the elastic body 2, and the piezoelectric element 42 is provided to the surface of the second wall portion 34 on the side opposite to the elastic body 2.

[0184] In the eighth embodiment described above as well, the same effects as those of the second embodiment can be obtained.

[0185] 10. Piezoelectric sensor according to the ninth embodiment

[0186] Next, the piezoelectric sensor according to the ninth embodiment will be described.

[0187] Figure 20 is a plan view when the piezoelectric sensor according to the ninth embodiment is viewed from a position on the X axis.

[0188] Hereinafter, the ninth embodiment will be described, but in the following description, the description will be centered on the differences from the sixth and eighth embodiments, and the description of the same matters will be omitted. Note that in each drawing, the same reference numerals are attached to the same structures as those of the sixth and eighth embodiments.

[0189] The piezoelectric sensor 1H according to the ninth embodiment is the same as the piezoelectric sensor 1E according to the sixth embodiment except that the restriction portion 3 is in the shape of a circular ring.

[0190] With the restriction portion 3 in the shape of a circular ring, as shown in Figure 20 , the elastic body 2 is in the shape of a circle when the third surface 203 of the elastic body 2 is viewed in plan.

[0191] Thus, since the shape of the elastic body 2 when viewed in plan is a circle, the shape anisotropy of the elastic body 2 is reduced as compared to the case where the shape of the elastic body 2 when viewed in plan is a rectangle. Due to this, it is possible to detect the direction and magnitude of the force while suppressing the deviation of the sensitivity caused by the direction of the force applied to the piezoelectric sensor 1H.

[0192] Figure 20 The restriction portion 3 shown has four columnar portions 351 to 354. The columnar portion 351 is located on the positive side of the Y axis and the positive side of the Z axis with the center of the elastic body 2 as a reference. The columnar portion 352 is located on the positive side of the Y axis and the negative side of the Z axis. The columnar portion 353 is located on the negative side of the Y axis and the positive side of the Z axis. The columnar portion 354 is located on the negative side of the Y axis and the negative side of the Z axis. Further, the columnar portions 351 and 352 are disposed at positions facing the first face 201, and the columnar portions 353 and 354 are disposed at positions facing the second face 202. Further, the piezoelectric element 41 is fixed so as to connect the columnar portions 351 and 353, and the piezoelectric element 43 is fixed so as to connect the columnar portions 353 and 354.

[0193] In the ninth embodiment described above, the same effects as those of the sixth and eighth embodiments can be obtained.

[0194] The piezoelectric sensor and the gripper of the present application have been described above based on the illustrated embodiments, but the piezoelectric sensor and the gripper of the present application are not limited to the above-described embodiments, and for example, each portion of the above-described embodiments can be replaced with any structure having the same function, any structure can be added to the above-described embodiments, and a plurality of the above-described embodiments can be combined.

Claims

1. A piezoelectric sensor, characterized by, Possessing: an elastic body having a contact surface that contacts an object and a first surface that intersects the contact surface; a restriction portion having four columnar portions that are arranged in positions corresponding to the four corners of the elastic body and that restrict deformation of the elastic body; and a piezoelectric element that is fixed so as to connect the columnar portions and that deforms along with deformation of the elastic body, the piezoelectric element outputting a voltage signal that increases or decreases from a reference voltage according to a direction of deformation and an amount of deformation, the piezoelectric element possessing a first piezoelectric element that is arranged in a position facing the first surface of the elastic body.

2. The piezoelectric sensor according to claim 1, wherein the elastic body has a second surface that intersects the contact surface and that opposes the first surface, the piezoelectric element possesses a second piezoelectric element that is arranged in a position facing the second surface.

3. The piezoelectric sensor according to claim 1, wherein the contact surface is a convex curved surface.

4. The piezoelectric sensor according to any one of claims 1 to 3, wherein the elastic body is in the shape of a plate having the contact surface as a main surface, the contact surface being in the shape of a rectangle.

5. The piezoelectric sensor according to claim 2, wherein the first piezoelectric element and the second piezoelectric element deform in mutually different directions of deformation along with deformation of the elastic body.

6. The piezoelectric sensor according to claim 5, wherein the elastic body has two opposing surfaces corresponding to two mutually opposing sides when the contact surface is viewed from above, the first piezoelectric element is arranged in a position facing one of the two opposing surfaces, the first surface.

7. The piezoelectric sensor according to claim 5, wherein the elastic body has two adjacent surfaces corresponding to two mutually adjacent sides when the contact surface is viewed from above, the first piezoelectric element is arranged in a position facing one of the two adjacent surfaces, the first surface.

8. The piezoelectric sensor according to claim 5, wherein the elastic body has four outer surfaces corresponding to four sides that constitute an outer edge when the contact surface is viewed from above, the first piezoelectric element is arranged in a position facing one of the four outer surfaces, the first surface.

9. The piezoelectric sensor according to any one of claims 1 to 3, wherein the elastic body has the contact surface in the shape of a circle. Possessing the piezoelectric sensor according to any one of claims 1 to 9.

10. A handgrip characterized in that ​

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