1. Technical Field
The present invention relates to a sensor device, a force detection device, and a robot.
2. Related Art
In the related art, a force sensor using a piezoelectric material as described in JP-A-4-231827 is known. That is, in FIG. 15 of JP-A-4-231827, a force sensor is described in which a signal electrode 15 is clamped by crystal discs 16 made of a piezoelectric material, and a plurality of measurement elements clamped by metal cover discs 17 are arranged.
However, in the measurement element described in JP-A-4-231827, there is no description that the two crystal discs which clamp the signal electrode in the force detection direction accurately arrange the crystal direction to form the measurement element. It is difficult to form the sensor element while arranging the crystal direction of the crystal disc with high precision so as to obtain an output signal with high precision as the force sensor. When a plurality of sensor elements are arranged and used as a force sensor, degradation in sensor sensitivity during operation can occur due to, for example, movement of the sensor elements when the sensor elements are arranged in the device or fixed to the device, or misalignment between the elements may occur due to minor impact.
An advantage of some aspects of the invention is that it provides a sensor device, a force detection device, and a robot capable of maintaining high sensor sensitivity without misalignment of sensor elements during integration in the force detection device.
This application example of the invention is directed to a sensor device including a sensor element which is formed by laminating a piezoelectric substance and an electrode, a first case and a second case which store the sensor element, and a pressing portion which presses the sensor element in the lamination direction of the piezoelectric substance and the electrode by the first case and the second case.
According to this application example, while the sensor element is stored in the internal space defined by the first case and the second case, the sensor element is pressed in the lamination direction of the piezoelectric substance and the electrode. Therefore, it is possible to suppress integration misalignment of the piezoelectric substance and the electrode due to vibration when carrying the sensor device or external force during integration in the device, and to stably maintain high detection precision of the sensor device.
This application example of the invention is directed to the above-described application example, wherein the pressing portion is an elastic member which is pressed by the first case and the second case.
According to the above-described application example, an elastic member having desired elastic force is selected and used, making it easy to adjust a pressing force against the sensor element. The elastic member functions as a buffer material which suppresses the application of an excessive pressing force to the sensor element, thereby preventing the sensor element, and in particular the piezoelectric substance, from being damaged.
This application example of the invention is directed to the above-described application example, wherein the elastic member is a gasket which is formed of rubber, an elastic elastomer, or a metal.
According to the above-described application example, the material, size, and sectional shape of the gasket are appropriately selected, thereby setting an appropriate pressing force, suppressing the application of an excessive pressing force to the sensor element, and preventing the sensor element, and in particular the piezoelectric substance, from being damaged.
This application example of the invention is directed to the above-described application example, wherein the pressing portion is a bellows portion which is formed in the first case or the second case.
According to the above-described application example, a bellows shape having excellent stretchability is provided, thereby easily adjusting a pressing force against the sensor element, suppressing the application of an excessive pressing force to the sensor element, and preventing the sensor element, and in particular the piezoelectric substance, from being damaged.
This application example of the invention is directed to the above-described application example, wherein the first case and the second case have a connection portion which connects the first case and the second case.
According to the above-described application example, the first case and the second case are connected together by the connection portion to form a storage case for the sensor element, thereby integrating the sensor element in the apparatus or device in a state where the pressing force applied to the sensor element by the pressing portion is maintained. Therefore, it is possible to suppress integration misalignment of the piezoelectric substance and the electrode due to vibration when carrying the sensor device or external force during integration in the device, and to stably maintain high detection precision of the sensor device.
This application example of the invention is directed to the above-described application example, wherein when the lamination direction of the sensor element is a Z direction, and directions which are orthogonal to the Z direction and orthogonal to each other are respectively an X direction and a Y direction, the sensor device includes at least a first sensor element which detects a force in the X direction, a second sensor element which detects a force in the Y direction, and a third sensor element which detects a force in the Z direction.
According to the above-described application example, relative misalignment of the sensor elements which detect force in the X, Y, and Z directions, a so-called 3-axis direction, is suppressed. Therefore, it is possible to stably maintain high detection precision with no loss in a sensor device which detects force in the three-axis direction.
This application example of the invention is directed to the above-described application example, wherein the piezoelectric substance is quartz crystal.
According to the above-described application example, quartz crystal is used as the piezoelectric substance, thereby obtaining a sensor device which includes a sensor element having high detection capability capable of generating a large quantity of electric charges with slight deformation. It is also possible to easily obtain a piezoelectric substance which detects deformation in various directions depending on the cut direction of the quartz crystal.
This application example of the invention is directed to a force detection device including the above-described sensor device.
The force detection device of this application example can easily calculate and measure an external force load depending on the quantity of electric charges and the polarity of the electric charges. Thus, it is possible to obtain a 3-axis force detection sensor with simple configuration. With the use of a plurality of sensor devices, it is possible to easily obtain a 6-axis force detection device or the like which includes torque measurement, for example.
This application example of the invention is directed to a robot including the above-described force detection device.
The robot of this application example reliably detects contact of an actuating robot arm or robot hand with an obstacle during a predetermined operation or a contact force of the robot arm or robot hand with an object by the force detection device, and feeds back the detection result to a robot control device, thereby enabling stable and fine operation.
The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements.
Hereinafter, embodiments of the invention will be described with reference to the drawings.
The sensor element 60 is a plate-shaped piezoelectric substrate which is formed of, for example, quartz crystal, lead zirconate titanate <PZT:Pb(Zr,Ti)O3>, lithium niobate (LiNbO3), or the like. In this embodiment, the piezoelectric substance 40 (hereinafter, referred to as a quartz crystal plate 40) in which a quartz crystal substrate is formed in a disc shape is used. As shown in
As shown in the schematic view of
Similarly, the quartz crystal plates 42a and 42b are laminated such that the Y axis of the quartz crystal plate is in the γ direction. In this example, the X axis of the quartz crystal plate 42a is in the β(+) direction, and the X axis of the quartz crystal plate 42b is in the β(−) direction. The quartz crystal plates 42a and 42b are arranged to be clamped by the electrodes 51b, 53, and 51c, thereby forming a sensor element 62 which can detect displacement according to a force applied in the β direction by the quartz crystal plates 42a and 42b.
The quartz crystal plates 43a and 43b are formed of so-called X-cut plates. The quartz crystal plate 43a is laminated such that the X axis of the quartz crystal plate is in the γ(−) direction, and the quartz crystal plate 43b is laminated such that the X axis of the quartz crystal plate is in the γ(+) direction. The Y and Z axes are arranged to be orthogonal to each other in the quartz crystal plates 43a and 43b. The quartz crystal plates 43a and 43b are arranged to be clamped by the electrodes 51c, 54, and 51d, thereby forming a sensor element 63 which can detect displacement according to a force in the γ direction by the quartz crystal plates 43a and 43b. Thus, the sensor element 60 which can detect the force in the so-called 3-axis direction by the sensor elements 61, 62, and 63 is formed.
The sensor element 60 has a structure in which the quartz crystal plates 41a, 41b, 42a, 42b, 43a, and 43b and the electrodes 51a, 51b, 51c, 51d, 52, 53, and 54 are just placed in the lamination direction, and a fixing mechanism, for example, adhesion is not used. However, as shown in
The connection of the first case 10 and the second case 20 of the sensor device 100 shown in
The first case 10 and the second case 20 are covered such that the sensor element 60 is stored inside the first case 10 and the second case 20, and the flange portion 10a of the first case 10 is inserted into the inner circumference 20c of the cylindrical portion 20b of the second case 20. Thereafter, the gasket 30 is placed on the flange portion 10a, a part of the cylindrical portion 20b on the opening side is bent in an arrow direction of the drawing to form a so-called caulking portion 20d, and the gasket 30 is compressed by the caulking portion 20d. In this way, the first case 10 and the second case 20 are connected together. At this time, the gasket 30 is compressed by the caulking portion 20d, and a repulsive force indicated by an arrow f is generated. With this repulsive force f, the first case 10 and the second case 20 are attracted in an arrow f′ direction, and the sensor element 60 is pressed in the lamination direction and fixed through a sensor pressing portion 10c of the first case 10 and a sensor pressing portion 20e of the second case 20 shown in
The gasket 30 serving as the pressing mechanism is compressed, and the sensor element 60 stored in the first case 10 and the second case 20 is pressed and fixed by the repulsive force, making it possible to obtain a stable pressing force. In a force detection device using the sensor device 100 described below, even if the force detection device is used in an environment in which the force detection device is exposed to, for example, a lubricant, a liquid such as water or medicine, or the like, the gasket 30 has a function as a seal member, thereby protecting the internal sensor element 60. Therefore, it is possible to obtain the reliable sensor device 100.
Although in the sensor device 100, the gasket 30 is a component serving as the pressing mechanism, the invention is not limited thereto, and, for example, a form shown in
As shown in
As shown in
In the sensor device 100, the sensor element 60 which is formed by simply stacking the quartz crystal plates 40 serving as a piezoelectric substance and the electrodes 50 is pressed in the staking (lamination) direction of the quartz crystal plates 40 and the electrodes 50 by the first case 10 and the second case 20. The first case 10, the second case 20, and a pressing portion arranged in the connection portion of the first case 10 and the second case 20 connect the first case 10 and the second case 20 while pressing the sensor element 60, thereby preventing misalignment of the quartz crystal plates 40 serving as a piezoelectric substance and the electrodes 50 of the sensor element 60. Accordingly, it is possible to suppress degradation in sensitivity due to misalignment of the quartz crystal plates 40 and the electrode caused by vibration or impact during an integration operation of the sensor device 100 in the device, thereby obtaining the sensor device 100 capable of maintaining high sensitivity.
Misalignment of the quartz crystal plates 40 and the electrodes 50 will be described with reference to
Although the quartz crystal plates and the electrodes are hardly affected by a shift in the rotation direction relative to the γ axis, the quartz crystal plates and the electrodes are relatively shifted in the α and β directions, and therefore, a functional region as a sensor decreases, making it difficult to obtain predetermined precision. Accordingly, a relative shift of the electrodes in the α and β directions from the quartz crystal plates is also referred to as misalignment.
The sensor element 60 is stored to be covered with the first case 10 and the second case 20, thereby preventing external contaminants such as, for example, water, medicine, oil, or the like from entering the case. In particular, as shown in
As a second embodiment, a force detection device in which the sensor device 100 is integrated will be described.
The force detection device 1000 is mounted in a detection device mounting portion 2000 of a device to be integrated by a mounting mechanism (not shown), and detects a force between a detection device mounting portion 2100 and a detection device mounting portion 2200. The force detection device 1000 of this embodiment is configured such that four sensor devices 100 are fixed, in addition to detection of the force in the x, y, and z directions shown in the drawing, rotation torque Tx, Ty, and Tz between the first base 310 and the second base 320 can be calculated on the basis of a schematic view of
Fx=Fx1+Fx2+Fx3+Fx4
Fy=Fy1+Fy2+Fy3+Fy4
Fz=Fz1+Fz2+Fz3+Fz4
Mx=b×(Fz1+Fz2−Fz3−Fz4)
My=a×(−Fz1+Fz2−Fz3−Fz4)
Mz=b×(−Fx1−Fx2+Fx3+Fx4)+a×(Fy1+Fy4−Fy2−Fy3)
ax=(Fx×az0−My)/Fz
ay=(Fy×az0+My)/Fz
Tx=b×(Fz1+Fz2−Fz3−Fz4)+Fy×az0
Ty=a×(−Fz1+Fz2+Fz3−Fz4)−Fx×a z0
Although the force detection device 1000 is a so-called 6-axis force detection device which includes four sensor devices 100, the invention is not limited thereto. The force detection device 1000 may be a force detection device which includes one sensor device 100 or two or more sensor devices 100 depending on the force to be detected.
As a third embodiment, a robot which includes the force detection device 1000 will be described.
The arm portion 3200 includes a first frame 3210, a second frame 3220, a third frame 3230, a fourth frame 3240, and a fifth frame 3250. The first frame 3210 is rotatably or bendably connected to the main body portion 3100 through a rotary bending shaft. The second frame 3220 is connected to the first frame 3210 and the third frame 3230 through a rotary bending shaft. The third frame 3230 is connected to the second frame 3220 and the fourth frame 3240 through a rotary bending shaft. The fourth frame 3240 is connected to the third frame 3230 and the fifth frame 3250 through a rotary bending shaft. The fifth frame 3250 is connected to the fourth frame 3240 through a rotary bending shaft. The arm portion 3200 moves with the composite rotation or bending of each of the frames 3210 to 3250 around the corresponding rotary bending shaft under the control of the control unit.
In the fifth frame 3250 of the arm portion 3200, the robot hand portion 3300 is attached to aside that is different from a connection portion to the fourth frame 3240. A robot hand 3310 which can grip an object is connected to the fifth frame 3250 by a robot hand connection portion 3320 which has an internal motor for rotation operation.
The force detection device 1000 of the second embodiment is embedded in the robot hand connection portion 3320 along with the motor, and when the robot hand portion 3300 has moved to a predetermined operation position under the control of the control unit, detects, as a force, contact with an obstacle, contact with an object by an operation command beyond a predetermined position, or the like by the force detection device 1000, and feeds back the detection result to a control unit of the robot 3000, thereby allowing the robot to carry out an avoidance operation.
With the use of the robot 3000, it is possible to obtain a robot which can do safe and intricate jobs including an obstacle avoidance operation, an object damage avoidance operation, or the like which is handled with difficulty by position control in the related art. The invention is not limited to this embodiment, and may be applied to a two or more armed robot.
The sensor device 100 of the first embodiment may be a sensor device 110 shown in
The cylindrical case 90 is formed of an elastic material, for example, rubber, an elastic elastomer, plastic, or the like, and inner circumferential stepped portions 90a and 90b are formed in the openings at both ends of the cylindrical case 90. A fitting portion 13a is formed on the outer circumference of the cap 13, and a fitting portion 23a is formed on the outer circumference of the cap 23. After the caps 13 and 23 are placed at both ends of the sensor element 60 in the lamination direction, a fitting region m is formed by the fitting portions 13a and 23a. The fitting region m is set to be greater than a gap n between the inner circumferential stepped portions 90a and 90b of the cylindrical case 90, and the cylindrical case 90 is fitted to the caps 13 and 23 placed on the sensor element 60, so that the cylindrical case 90 is stretched.
The cylindrical case 90 is stretched and fitted to the caps 13 and 23, so that the caps 13 and 23 are attracted by the cylindrical case 90, and a pressing force is applied to the sensor element 60. Accordingly, the pressing force is constantly applied to the sensor element 60. Therefore, the sensor device 110 can obtain high precision without causing misalignment of the quartz crystal plates 40 and the electrodes 50 of the sensor element 60 during a job, such as integration in the force detection device. With the configuration of the sensor device 110, the sensor element 60 is sealed, thereby obtaining the reliable sensor device 110 which is not affected by the external environmental conditions.
If a bellows portion described with reference to
The entire disclosure of Japanese Patent Application No. 2011-089841 filed Apr. 14, 2011 is expressly incorporated herein by reference.
Number | Date | Country | Kind |
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2011-089841 | Apr 2011 | JP | national |