Force sensor device

Abstract

This reduces variations in strain gauge output values ​​caused by variations in the placement of the strain gauges. [Solution] The force sensor device includes a first stage, a second stage positioned behind the first stage with a gap between them, a plurality of cantilever beams fixed to the second stage and the first stage, and strain gauges attached to each of the plurality of cantilever beams. The first stage moves relative to the second stage in response to a force applied from the front, the plurality of cantilever beams deform in response to the movement of the first stage, and each of the plurality of cantilever beams includes a decreasing region in which at least one of the width and thickness decreases monotonically from one of the fixed positions with respect to the first stage and the second stage toward the other, and the strain gauges are installed in the decreasing region.

Description

Technical Field

[0001] The present disclosure relates to a force sensor device.

Background Art

[0002] In recent years, electronic devices equipped with touch panels, such as smartphones and car navigation systems, have become widespread. When a user operates an object such as an icon included in a user interface displayed via a touch panel, the electronic device activates the function corresponding to the object.

[0003] Since the surface of the touch panel is uniformly hard, the user's finger gives the same tactile sensation regardless of which part of the touch panel it touches. Therefore, a technique for providing feedback to the user to perceive the presence of an object or to perceive that an operation corresponding to the activation of the function of the object has been received is known. The technique presents a tactile sensation to the touching finger by vibrating the touch panel in the in-plane direction of the touch panel.

[0004] An electronic device (haptic presentation device) using the haptic presentation technique may further include a force sensor device. The force sensor device includes a cantilever beam connecting two components of the electronic device and a strain gauge attached to the cantilever beam. The electronic device detects the movement of the component due to the user's pressing from the output of the strain gauge and presents a tactile sensation to the user's finger according to the detection.

[0005] In addition, a force sensor device including a strain gauge attached to a cantilever beam connecting components is also implemented in various electronic devices different from the haptic presentation device including the touch panel as described above.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

[0007] Strain gauges output values ​​corresponding to the strain at the attachment point on the cantilevered beam. Therefore, variations in the attachment position of strain gauges between products can result in variations in the output values ​​of the strain gauges. [Means for solving the problem]

[0008] A force sensor device according to one aspect of the present disclosure includes a first stage, a second stage positioned behind the first stage with a gap between them, a plurality of cantilever beams fixed to the second stage and the first stage, and strain gauges attached to each of the plurality of cantilever beams, wherein the first stage moves relative to the second stage in response to a force applied from the front, the plurality of cantilever beams deform in response to the movement of the first stage, and each of the plurality of cantilever beams includes a reduction region in which at least one of the width and thickness decreases monotonically from one of the fixed positions with respect to the first stage and the second stage toward the other, and the strain gauges are installed in the reduction region. [Effects of the Invention]

[0009] This reduces variations in strain gauge output values ​​caused by variations in the placement of the strain gauges. [Brief explanation of the drawing]

[0010] [Figure 1] A schematic example of the configuration of a haptic presentation display system according to one embodiment of this disclosure is shown. [Figure 2A] This is a schematic cross-sectional view showing the connection structure between the force sensor stage, the base stage, and the double-supported beam. [Figure 2B] This is a schematic cross-sectional view showing the deformation of the cantilevered beam due to the downward pressure of the force sensor stage. [Figure 2C] It is a cross-sectional view schematically showing the deformation of the simply supported beam accompanying the depression of the force sensor stage. [Figure 3A] It is a perspective view seen from the rear side of a configuration example of a force sensor device including a simply supported beam according to an embodiment of the present disclosure. [Figure 3B] It is a perspective view of the beam component and the surrounding part seen from the rear side. [Figure 3C] It is a plan view of the beam component and the surrounding part seen from the rear side. [Figure 4A] It is a plan view of the beam component. [Figure 4B] It is a perspective view showing the shape of the simply supported beam. [Figure 5] Examples of specific dimensional values of the simply supported beam are shown. [Figure 6] The simulation results when a force is applied in the Z-axis direction at the load point are shown. [Figure 7] Examples of the shape and specific dimensional values of the simply supported beam to be simulated are shown. [Figure 8] The simulation results when a force is applied in the Z-axis direction at the load point are shown. [Figure 9] The shapes of three simply supported beams to be simulated are shown. [Figure 10] The simulation results when a force is applied in the Z-axis direction at the load point of each simply supported beam are shown. [Figure 11A] It is a plan view of the simply supported beam. [Figure 11B] It is a perspective view showing the shape of the simply supported beam. [Figure 12] Examples of specific dimensional values of the simply supported beam are shown. [Figure 13] The simulation results when a force is applied in the Z-axis direction at the load point are shown. [Figure 14A] It is a plan view showing the shape of the simply supported beam according to an embodiment of the present disclosure. [Figure 14B] The simulation results of the strain amount of the simply supported beam are shown. [Figure 15A]It is a plan view showing the shape of a simply supported beam of an embodiment of the present disclosure. [Figure 15B] It shows the simulation result of the amount of strain of the simply supported beam. [Figure 16] It is a plan view showing the shape of a simply supported beam of an embodiment of the present disclosure. [Figure 17] It is a plan view showing the shape of a simply supported beam of an embodiment of the present disclosure. [Figure 18] It shows an example of specific dimensional values of each simply supported beam. [Figure 19] It shows the simulation result when a force is applied in the Z-axis direction at the load point of each simply supported beam. [Figure 20A] It shows a perspective view of the simply supported beam. [Figure 20B] It shows a cross-sectional view perpendicular to the X-axis of the simply supported beam. [Figure 21] It shows the dimensional values of the simply supported beam to be simulated. [Figure 22] It shows a graph of the simulation result. [Figure 23] It shows an example of a load measurement configuration using a strain gauge. [Figure 24] It shows a region where the display screen is divided into nine parts. [Figure 25] It shows the simulation result of a rectangular simply supported beam. [Figure 26] It shows the simulation result of the simply supported beam shown in FIG. 5. [Figure 27] It shows the simulation result of the simply supported beam shown in FIG.​​​​​​​​​​​​​​​ [Figure 30] An example configuration using two Wheatstone bridge circuits is shown. [Figure 31] An example configuration using four Wheatstone bridge circuits is shown. [Modes for carrying out the invention]

[0011] Embodiments of this disclosure will be described below with reference to the attached drawings. It should be noted that these embodiments are merely examples for realizing this disclosure and do not limit the technical scope.

[0012] One embodiment of the present disclosure discloses a force sensor device. Force sensors can be used in various electronic devices. As an example of such electronic devices, a haptic presentation display device is described below, which includes a display device having a touch sensing function and a haptic presentation device that provides tactile feedback to a finger touching the touch surface of the display device.

[0013] Figure 1 schematically shows an example of the configuration of a tactile presentation display system according to one embodiment of the present disclosure, as an example of an electronic device on which the force sensor device of the present disclosure is implemented. The tactile presentation display system includes a tactile presentation display device 10 and a control device 20 that controls the tactile presentation display device 10.

[0014] The haptic feedback display system presents the user with a UI (user interface) that includes at least one object and accepts operations via the UI. Furthermore, the haptic feedback display system provides feedback to allow the user to perceive the object included in the UI and feedback to allow the user to perceive that an operation on the object has been accepted.

[0015] Figure 1 schematically shows the cross-sectional structure of the haptic presentation display device 10. Note that the control device 20 is shown as a functional block and its physical structure is not shown. The haptic presentation display device 10 includes a display device 11, a force sensor stage 12 (first stage), and a base stage 13 (second stage), which are stacked together. In the following description, the side where the user viewing the display image is located will be referred to as the front side, and the opposite side as the back side. In Figure 1, the display device 11 is located in front of the force sensor stage 12, and the base stage 13 is located behind the force sensor stage 12.

[0016] In Figure 1, the front-to-back direction or stacking direction is the Z-axis direction, and the X-axis direction (second direction) and Y-axis direction (first direction) are in-plane directions of the display device 11, the display device 11, the force sensor stage 12, or the base stage 13. The X, Y, and Z axes are perpendicular to each other.

[0017] The display device 11 is, for example, a display device with a touch sensor. The display device 11 may include, for example, a touch panel including a touch surface 111 and a display behind it. The display may be, for example, an OLED (Organic Light Emitting Diode) display, a microLED display, or a liquid crystal display. The liquid crystal display may include a liquid crystal panel and a backlight unit behind it.

[0018] The touch surface 111 and its back surface are the main surfaces of the display device 11. The touch surface 111 is also the image display surface that displays images to the viewer. The external shape of the display device 11 is, for example, rectangular, but its shape is arbitrary. The touch sensor function of the display device 11 may be omitted.

[0019] A force sensor stage 12 is positioned behind the display device 11, with an air gap between them. The force sensor stage 12 is connected to the rear surface of the display device 11 via an actuator 14 and a leaf spring 15. In other words, the display device 11 is supported by the actuator 14 and the leaf spring 15, which are fixed to the force sensor stage 12.

[0020] Actuator 14 is a lateral actuator that generates movement in a direction parallel to the image display surface. The movement of actuator 14 causes the display device 11 to vibrate in the X-axis direction. The leaf spring 15 is oriented to elastically deform in the X-axis direction but not in the Z-axis direction. As a result, the leaf spring 15 elastically supports the display device 11 in the X-axis direction and vibrates in the X-axis direction in accordance with the vibration of the display device 11 caused by the movement of actuator 14. The leaf spring 15 is used as a mechanism to generate vibration in accordance with the movement of actuator 14. The number and layout of actuators 14 and leaf springs 15 are arbitrary and are appropriately determined by the design.

[0021] The base stage 13 is positioned on the mounting surface via a damper 18. In Figure 1, one damper is indicated by reference numeral 18 as an example. The base stage 13 may or may not be fixed to the mounting surface. When the tactile presentation display device 10 is in operation, the base stage 13 is stationary on the mounting surface.

[0022] The force sensor stage 12 is positioned between the base stage 13 and the display device 11. The force sensor stage 12 is positioned in front of the base stage 13, with a gap between them. The rear surface of the force sensor stage 12 is connected to the base stage 13 via two cantilever beams 16A and 16B. The cantilever beams 16A and 16B are fixed to the base stage 13 and the force sensor stage 12, respectively.

[0023] Strain gauges (not shown) are attached to the double-supported beams 16A and 16B. The user's pressing force on the display device 11 pushes the display device 11 down in the Z-axis direction. At this time, the leaf spring 15 does not deform in the Z-axis direction, so the display device 11 and the force sensor stage 112 are pushed down together without changing the distance between them. The force sensor stage 12 is pressed towards the base stage 13 by the pressing force from the display device 11.

[0024] In other words, the force sensor stage 12 moves to the rear and approaches the base stage 13. The cantilever beams 16A and 16B deform in accordance with the change in the relative position of the force sensor stage 12 with respect to the base stage 13. The strain gauges output values ​​to the control device 20 corresponding to the amount of deformation of the cantilever beams 16A and 16B. In this way, the force exerted by the user's finger perpendicular to the display screen (touch surface) can be measured by the output from the strain gauges attached to the cantilever beams 16A and 16B.

[0025] The force sensor stage 12, base stage 13, and double-supported beams 16A and 16B are included in the force sensor device. Note that Figure 1 shows two double-supported beams 16A and 16B, but the number and arrangement of the double-supported beams 16A and 16B are appropriately selected according to the design.

[0026] For example, the control device 20 detects contact of a user's finger with the touch surface (display screen) and identifies the position of the user's finger on the display screen based on the output from the display device 11, which includes a touch sensor. The control device 20 detects a user press event on a displayed object based on the output value of a strain gauge, the position of the user's finger on the display screen, and pre-set information. For example, the control device 20 determines that a press event has been detected when a specific area on the display device 11 is touched and the force measurement value obtained from the output value of the strain gauge exceeds a threshold.

[0027] When the control device 20 detects a press event on an object, it controls the operation of the actuator 14 to generate mechanical vibrations in the display device 11 in order to make the user perceive that the object has been manipulated. The control device 20 applies a drive pulse to the actuator 14, for example, to give the user's finger 205 a click sensation.

[0028] For example, it consists of a first pulse and a second pulse, and the first and second pulses have the same voltage amplitude. The actuator 14 shifts the touch surface from its initial state in one direction by applying the first pulse, and then starts shifting in the reverse direction and begins reciprocating motion when the application of the first pulse ends. After a predetermined period of no pulse application, the shift is stopped when the touch surface returns to its initial state by applying the second pulse.

[0029] Figure 1 shows one example configuration of the tactile presentation display device 10 of this disclosure, and the tactile presentation display device 10 may have other configurations. For example, the actuator 14 and leaf spring 15 may connect the base stage 13 and the force sensor stage 12, and the cantilever beams 16A and 16B to which strain gauges are attached may connect the force sensor stage 12 and the display device 11.

[0030] Figures 2A-2C are schematic cross-sectional views illustrating the deformation of the double-support beam 16A as the force sensor stage 12 is pushed down. The double-support beam 16B deforms in the same way as the double-support beam 16A. Figure 2A shows the shape of the double-support beam 16A in its initial state, and Figure 2B shows the shape of the double-support beam 16A when the force sensor stage 12 is pushed down.

[0031] Figure 2C shows the strain at different positions of the double-support beam 16A when the force sensor stage 12 is pressed down. In Figure 2C, the load point 210 is the connection point (fixed point) between the double-support beam 16A and the force sensor stage 12. The direction of the strain is in the Y-axis direction. The base stage side end of the double-support beam 16A is constrained in the X, Y, and Z axis directions, and the force sensor stage side end is constrained in the X and Y axis directions.

[0032] At position 211, close to the load point 210, the cantilevered beam 16A is contracting. At the central position 213, there is no strain. The amount of contraction (amount of strain) decreases from the load point 210 (end on the force sensor stage side) toward the central position 213. For example, the amount of contraction at position 211, close to the load point 210, is greater than the amount of contraction at position 212, close to the central position 213.

[0033] On the other hand, the double-supported beam 16A extends in the Y-axis direction at the base stage side end. The amount of extension increases from the central position 213 toward the base stage side end. For example, the amount of extension at position 215, which is close to the base stage side end, is greater than the amount of extension at position 214, which is close to the central position 213.

[0034] Thus, the magnitude and direction of strain along the Y-axis can change depending on the position of the double-supported beam 16A on the Y-axis. Therefore, variations in the placement of the strain gauges between products will result in variations in the output values ​​of the strain gauges between products. Variations in the output values ​​of the strain gauges hinder the accurate detection of the indentation by the force sensor stage 12.

[0035] One embodiment of the present disclosure reduces variations in the output value of strain gauges due to variations in the mounting position of strain gauges by employing a specific shape of a double-supported beam and a specific mounting position for strain gauges. The shape of the double-supported beam and the mounting position of strain gauges on the double-supported beam according to one embodiment of the present disclosure will be described below.

[0036] Figure 3A is a rear-view perspective view of an example configuration of a force sensor device 100 including a double-supported beam according to one embodiment of the present disclosure. The force sensor device 100 includes a force sensor stage 12 and a base stage 13. The force sensor device 100 further includes beam components 160A-160D that connect the force sensor stage 12 and the base stage 13. As will be described later, the central portion of the beam components 160A-160D constitutes a double-supported beam.

[0037] The force sensor stage 12 is a rectangular plate-shaped component and can be made of, for example, metal or resin. The shape of the force sensor stage 12 is arbitrary and not limited. The force sensor stage 12 includes prism-shaped support bases 122A and 122B on its rear side surface 121. The support bases 122A and 122B are spaced apart in the Y-axis direction and extend along the X-axis.

[0038] The base stage 13 is a rectangular plate-shaped component with an opening in the center, and can be made of, for example, metal or resin. The shape of the base stage 13 is arbitrary and not limited. As explained with reference to Figure 1, under normal conditions, there is a gap between the base stage 13 (front side) and the rear side 121 of the force sensor stage 12.

[0039] In the configuration example shown in Figure 3A, the base stage 13 is positioned within the area sandwiched between the support bases 122A and 122B. One end of each of the four beam components 160A-160D is fixed to the force sensor stage 12, and the other end is fixed to the base stage 13. One end of beam components 160A and 160C is fixed to the rear side of support base 122A, and the other end is fixed to the front side of the base stage 13. One end of beam components 160A and 160C is fixed to the rear side of support base 122B, and the other end is fixed to the front side of the base stage 13.

[0040] Beam components 160A and 160C are fixed to one side of the base stage 13, while beam components 160B and 160D are fixed to opposite sides of the base stage 13. Beam components 160A-160D are arranged symmetrically with respect to the X and Y axes (axis of symmetry). Note that the number and placement of beam components are not limited to this example, and appropriate values ​​and positions will be selected according to the design.

[0041] Figures 3B and 3C are perspective and plan views of beam component 160D and its surrounding area, viewed from the rear. Beam components 160A-160D have the same shape, and the description of beam component 160D can be applied to 160A-160C. Beam component 160D is fixed to the support base 122B by screws 124. A rectangular washer 125 is placed between the screws 124 and beam component 160D. Beam component 160D may also be fixed to the front side of the base stage 13 using washers and screws. Note that the fixing of beam component 160D to the force sensor stage 12 and the base stage 13 may be achieved by other structures, and the fixing structures on the force sensor stage 12 and the base stage 13 may be the same or different.

[0042] Referring to Figure 3C, the dashed rectangle indicates a portion of the beam component 160D that constitutes the double-supported beam 16D. The double-supported beam 16D is a region that is not in contact with or fixed to the force sensor stage 12 and the base stage 13, and is a free region that is not constrained in the X, Y, and Z axis directions. The force sensor stage side end and the base stage side end of the double-supported beam 16D are linear load areas. Although the base stage side end is fixed, it is a relative load area.

[0043] Figure 4A is a plan view of beam component 160. Beam components 160A-160D have the same shape as beam component 160. Beam component 160 is composed of multiple regions, and the arrows indicate each region of beam component 160. Beam component 160 is composed of fixed regions 162A, 162B and the cantilevered beam 16 region between them. Fixed regions 162A and 162B are dashed rectangular regions and have holes 166A and 166B through which screws pass, respectively. Beam component 160 has a shape that is symmetrical with respect to the X and Y axes.

[0044] For example, the fixed area 162A is fixed to the force sensor stage 12, and the fixed area 162B is fixed to the base stage 13. As illustrated with reference to Figures 3B and 3C, the fixed areas 162A and 162B are fixed in contact with and pressed against the surfaces of the force sensor stage 12 and the base stage 13 via screws and rectangular washers. The double-support beam 16 is spaced apart from other components, including the force sensor stage 12 and the base stage 13.

[0045] As explained with reference to Figure 2A-2C, when the force sensor stage 12 is pushed down relative to the base stage 13, the cantilever beam 16 deforms significantly in the Z-axis direction. Furthermore, the cantilever beam 16 strains in the Y-axis direction. In this embodiment, the downward pressure on the force sensor stage 12 is measured by measuring the strain in the Y-axis direction.

[0046] The strain of the cantilevered beam 16 is measured by strain gauges attached to the surface of the cantilevered beam 16. As explained with reference to Figure 2C, the amount of strain of the cantilevered beam 16 can vary depending on its position along the Y-axis. To reduce product-to-product variability in strain measurements, it is preferable to attach the strain gauges to a region where the change in strain amount due to Y-axis position is small.

[0047] The cantilevered beam 16 is composed of three regions 164A, 163, and 164B aligned along the Y-axis. Region 163 is sandwiched between the two regions 164A and 164B. Region 164A is a decreasing region whose width W1 decreases as it moves away from the load region. Width W1 is the dimension along the X-axis. The end edge 641A of region 164A is the load region. End edge 641A is the boundary between region 164A and the fixed region 162A.

[0048] Along the Y-axis, the width W1 of region 164A decreases monotonically as it moves from the end side 641A toward the center of the cantilevered beam 16. In the example shape shown in Figure 4A, the sides 642A and 643A that define the width of region 164A are straight lines. The shape of region 164A is symmetrical with respect to the X-axis.

[0049] Region 164B is a decreasing region whose width W3 decreases as it moves away from the load region. Width W3 is a dimension along the X-axis. The edge 641B of region 164B is the load region. Edge 641B is the boundary between region 164B and fixed region 162B.

[0050] Along the Y-axis, the width W3 of region 164B decreases monotonically from the end side 641B toward the center of the cantilevered beam 16. In the example shape shown in Figure 4A, sides 642B and 643B that define the width of region 164B are straight lines. The shape of region 164B is symmetric with respect to the X-axis. The shapes of region 164B and region 164A are symmetric with respect to the Y-axis.

[0051] The central region 163, sandwiched between two width-reducing regions 164A and 164B, has a constant width W2. The opposing sides 632 and 633 that define width W2 are parallel to the Y-axis. Width W2 coincides with the minimum values ​​of widths W1 and W3 of regions 164A and 164B. The central region 163 may be omitted.

[0052] One embodiment of this disclosure involves arranging strain gauges within a width reduction region. This reduces variations in the output values ​​of the strain gauges due to variations in the attachment position along the Y-axis. Furthermore, the reduction region shown in Figure 4A has a symmetrical shape with respect to the Y-axis. This reduces variations in the output values ​​of the strain gauges due to variations in the attachment position along the X-axis.

[0053] For example, at least the centroid of the strain gauge is located within the width reduction region. Furthermore, the entire area of ​​the strain gauge may be included within the width reduction region. In Figure 4A, the attachment position 601 shows an example of the centroid position of the strain gauge to be attached. The attachment position 601 may also be the center position on the X-axis. That is, the distance between the point where a virtual line along the Y-axis passing through the attachment position 601 intersects sides 642A and 643A and the attachment position 601 may be the same. The attachment position 601 may be a position different from the center position on the X-axis.

[0054] Figure 4B is a perspective view showing the shape of the cantilevered beam 16. The beam component 160 is thin plate-shaped. The thickness T of the beam component 160 is constant, and the thickness T of the cantilevered beam 16 is also constant. The shape of the cross-section perpendicular to the thickness direction (Z-axis direction) of the cantilevered beam 16 is constant. In other words, all sides of the cantilevered beam 16 are parallel to the Z-axis.

[0055] The following explains the effect of the width reduction region on reducing strain variation. Figure 5 shows an example of specific dimensions for the cantilevered beam 16. The unit of each number is mm. The cantilevered beam 16 is made of stainless steel and has a thickness of 2 mm. The load point 210 is a point on end 641A, and end 641A is constrained in the X-axis and Y-axis directions. The opposite end 641B is constrained in the X-axis, Y-axis and Z-axis directions.

[0056] The attachment position 601 is the reference attachment position for the strain gauge. The strain gauge is placed within the width reduction region 164. The positions on either side of the reference attachment position 601 indicate attachment positions moved 1 mm to the left or right from the reference attachment position 601.

[0057] Figure 6 shows the simulation results when a force of 175 N is applied in the Z-axis direction at the load point 210. In the graph in Figure 6, the horizontal axis represents the distance in the Y-axis direction from the reference attachment position 601 on the cantilevered beam 16. The vertical axis represents the amount of strain along the Y-axis. Referring to Figure 6, the strain at positions shifted 1 mm to the left and right of the reference attachment position 601 differs from the strain at the reference attachment position 601 by only 1% or -1.3%, respectively.

[0058] Figures 7 and 8 show the simulation results for a rectangular (cuboidal) cantilevered beam. Figure 7 shows the shape and specific dimensional examples of the cantilevered beam 3 being simulated. All numbers are in units of mm. The cantilevered beam 3 is made of stainless steel and has a thickness of 2 mm. The load point 33 is a single point on end 31A, and end 31A is constrained in the X-axis and Y-axis directions. The opposite end 31B is constrained in the X-axis, Y-axis, and Z-axis directions.

[0059] The attachment position 32 is the reference attachment position for the strain gauge. The positions on either side of the reference attachment position 32 represent attachment positions shifted 1 mm to the left and right from the reference attachment position 601. Figure 8 shows the simulation results when a force of 175 N is applied in the Z-axis direction at the load point 33. In the graph of Figure 8, the horizontal axis represents the distance in the Y-axis direction from the reference attachment position 32 on the cantilevered beam 3. The vertical axis represents the amount of strain along the Y-axis. Referring to Figure 8, the strain at positions shifted 1 mm to the left and right from the reference attachment position 32 differs from the strain at the reference attachment position 32 by -14.0% or 15.4%, respectively.

[0060] Comparing the simulation results in Figures 6 and 8, it can be seen that the width reduction region of the double-supported beam 16 can significantly reduce the difference in strain due to positional differences. In other words, it is shown that the variation in measured values ​​due to variations in the placement of strain gauges can be significantly reduced.

[0061] Figures 9 and 10 show the simulation results for multiple cantilevered beams. Figure 9 shows the shapes of the three cantilevered beams 3, 16, and 30 that were simulated. The shape of cantilevered beam 3 is the same as the shape of cantilevered beam 3 shown in Figure 7, and the shape of cantilevered beam 16 is the same as the shape of cantilevered beam 3 shown in Figure 5.

[0062] The shape of the double-supported beam 30 differs from that of the double-supported beam 16 in the length of the width reduction regions on both sides (dimensions along the Y-axis). Aside from the dimensional differences in other parts due to the different lengths of the width reduction regions on both sides, the shape of the double-supported beam 30 is the same as that of the double-supported beam 16. The units of some of the dimensions shown in Figure 9 are in mm. The thickness of the double-supported beams 3, 16, and 30 is 2 mm, and they are made of stainless steel.

[0063] Figure 10 shows the simulation results when a force of 175 N is applied in the Z-axis direction at load points 210, 33, and 310 for cantilevered beams 3, 16, and 30, respectively. In the graph in Figure 10, the horizontal axis represents the distance from the load point. The vertical axis represents the amount of strain in the Y-axis direction of the cantilevered beam. Line 341 shows the simulation result for cantilevered beam 3. Line 342 shows the simulation result for cantilevered beam 16. Line 343 shows the simulation result for cantilevered beam 30. Arrow 362 indicates the width reduction region of cantilevered beam 16, and arrow 363 indicates the width reduction region of cantilevered beam 30.

[0064] Simulation result 341 for the double-supported beam 3 shows that the amount of strain gradually decreases with distance from the load point 210. Simulation result 342 for the double-supported beam 16 shows that the change in the amount of strain in the width reduction region 362 is significantly reduced compared to the double-supported beam 3. Simulation result 343 for the double-supported beam 30 shows that the change in the amount of strain in the width reduction region 363 is significantly reduced compared to the double-supported beam 3. Thus, the width reduction region can effectively reduce the change in the amount of strain due to changes in position.

[0065] The following describes the shapes of several cantilever beams according to the embodiments of this disclosure. The cantilever beams described below can be applied to beam components including the fixed area described above. Figure 11A is a plan view of a cantilever beam 35. The cantilever beam 35 is composed of multiple areas, and the arrows indicate each area of ​​the cantilever beam 35. The cantilever beam 35 is composed of three areas 354A, 353, and 354B arranged along the Y axis. Area 353 is sandwiched between two areas 354A and 354B. Area 354A is a decreasing area whose width W1 decreases as it moves away from the load area. Width W1 is a dimension in the X axis. The end edge 261A of area 354A is the load area. The end edge 361A is the boundary between area 354A and a fixed area not shown.

[0066] Along the Y-axis, the width W1 of region 354A decreases monotonically from the end side 361A toward the center of the cantilevered beam 35. In the example shape shown in Figure 11A, the sides 362A and 363A that define the width of region 354A are curved. The shape of region 354A is symmetrical with respect to the X-axis.

[0067] Sides 362A and 363A are each composed of two curves. Specifically, they consist of curve 367, which is convex outward from the end side 361A toward the center, and curve 368, which is convex inward that follows. In Figure 11A, the labels 367 and 368 are shown only for side 362A as an example. For example, curve 367 is a circular arc (e.g., with an angle of 90°), and curve 368 is a circular arc with a larger radius of curvature than curve 367 (e.g., with an angle of 90°).

[0068] Region 354B is a decreasing region whose width W3 decreases as it moves away from the load region. Width W3 is a dimension along the X-axis. The edge 361B of region 354B is the load region. Edge 361B is the boundary between region 354B and a fixed region not shown.

[0069] Along the Y-axis, the width W3 of region 354B decreases monotonically from the end side 361B toward the center of the cantilevered beam 35. In the example shape shown in Figure 11A, the sides 362B and 363B that define the width of region 354B are curved. The shape of region 354B is symmetric with respect to the X-axis. The shapes of region 354B and region 354A are symmetric with respect to the Y-axis.

[0070] The central region 353, sandwiched between two width-reducing regions 354A and 354B, has a constant width W2. The opposing sides 365 and 366 that define width W2 are parallel to the Y-axis. Width W2 coincides with the minimum values ​​of widths W1 and W3 of regions 354A and 354B.

[0071] In Figure 11A, the attachment position 357 of the strain gauge shows an example of the centroid position of the strain gauge to be attached. The attachment position 357 is located within the width reduction region 354A. The attachment position 357 may also be the center position on the X-axis. The attachment position 357 may also be a position different from the center position on the X-axis.

[0072] Figure 11B is a perspective view showing the shape of the cantilevered beam 35. The thickness T of the cantilevered beam 35 is constant. The shape of the cross-section perpendicular to the thickness direction (Z-axis direction) of the cantilevered beam 35 is constant.

[0073] The following explains the effect of the width reduction region of the double-supported beam 35 in reducing strain variation. Figure 12 shows an example of specific dimensions of the double-supported beam 35. The unit of each number is mm. The double-supported beam 35 is made of stainless steel and has a thickness of 2 mm. The load point 370 is a point on end 361A, and end 361A is constrained in the X-axis and Y-axis directions. The opposite end 361B is constrained in the X-axis, Y-axis and Z-axis directions.

[0074] The attachment position 371 is the reference attachment position for the strain gauge. The strain gauge is placed within the width reduction region 354A. The positions on either side of the reference attachment position 371 indicate attachment positions moved 1 mm to the left or right from the reference attachment position 371.

[0075] Figure 13 shows the simulation results when a force of 175 N is applied in the Z-axis direction at load point 370. In the graph of Figure 13, the horizontal axis represents the distance in the Y-axis direction from the reference attachment position 371 on the cantilevered beam 35. The vertical axis represents the amount of strain along the Y-axis. The strain at positions shifted 1 mm to the left and right from the reference attachment position 371 differs from the strain at the reference attachment position 371 by -5.7% or 1.6%, respectively. This shift is a significant improvement compared to the rectangular cantilevered beam 3 described with reference to Figures 7 and 8.

[0076] Figure 14A is a plan view showing the shape of a cantilevered beam 40 of one embodiment of the present disclosure. The cantilevered beam 40 is composed of three regions 404A, 403, and 404B aligned along the Y-axis. Region 403 is sandwiched between two regions 404A and 404B. Region 404A is a decreasing region whose width W1 decreases as it moves away from the load-bearing end 441A.

[0077] Along the Y-axis, the width W1 of region 404A decreases monotonically as we move from the load-bearing end 441A toward the center of the cantilevered beam 40. The edges defining the width of region 404A are straight lines. The shape of region 404A is symmetrical with respect to the X-axis.

[0078] Region 404B is a decreasing region whose width W3 decreases as it moves away from the load-bearing end 441B. Along the Y-axis, the width W3 of region 404B decreases monotonically as it moves from the end 441B toward the center of the cantilever beam 40. The edges defining the width of region 404B are straight lines. The shape of region 404B is symmetric with respect to the X-axis. The shapes of region 404B and region 404A are symmetric with respect to the Y-axis.

[0079] The central region 403, sandwiched between the two width-reducing regions 404A and 404B, has a constant width W2. The opposing sides defining width W2 are parallel to the Y-axis. Width W2 coincides with the maximum values ​​of widths W1 and W3 of regions 404A and 404B.

[0080] In Figure 14A, the attachment position 421 of the strain gauge shows an example of the centroid position of the strain gauge to be attached. The attachment position 421 is located within the width reduction region 404A. The attachment position 421 may also be the center position on the X-axis. The attachment position 421 may also be a position different from the center position on the X-axis.

[0081] Figure 14B shows the simulation results for the strain of the cantilevered beam 40. In the cantilevered beam 40 being simulated, the maximum widths W1 and W3 and width W2 are 15 mm, the minimum widths W1 and W3 are 5 mm, the length (dimensions on the Y axis) of regions 404A and 404B is 5 mm, the length (dimensions on the Y axis) of region 403 is 10 mm, and the thickness is 2 mm. The material is stainless steel. The load point is the center of end side 441A. As shown in Figure 14B, the change in strain is greatly reduced in the width reduction region 404A up to 4 mm from the load point.

[0082] Figure 15A is a plan view showing the shape of a cantilevered beam 45 in one embodiment of the present disclosure. The cantilevered beam 45 is composed of three regions 454A, 453, and 454B aligned along the Y-axis. Region 453 is sandwiched between two regions 454A and 454B. Region 454A is a tapering region whose width W1 decreases as it moves away from the load-bearing end 441A.

[0083] Along the Y-axis, the width W1 of region 454A decreases monotonically as we move from the load-bearing end 491A toward the center of the cantilevered beam 45. The edges defining the width of region 454A are straight lines. The shape of region 454A is symmetrical with respect to the X-axis.

[0084] Region 454B is a decreasing region whose width W3 decreases as it moves away from the load-bearing end 441B. Along the Y-axis, the width W3 of region 454B decreases monotonically as it moves from the end 491B toward the center of the cantilever beam 45. The edges defining the width of region 454B are linear. The shape of region 454B is symmetric with respect to the X-axis. The shapes of region 454B and region 454A are symmetric with respect to the Y-axis.

[0085] The central region 453, sandwiched between two width-reducing regions 454A and 454B, has a width W2 that varies along the Y-axis. Specifically, as you move towards the center along the Y-axis from the boundary with width-reducing region 454A, the width W2 increases linearly. As you move towards the center along the Y-axis from the boundary with width-reducing region 454B, the width W2 increases linearly. The widths W1 and W2 at the boundary between the central region 453 and width-reducing region 454A are the same and are their minimum values. The widths W2 and W3 at the boundary between the central region 453 and width-reducing region 454B are the same and are their minimum values. The maximum value of width W2 in the central region 453 is the same as the maximum value of widths W1 and W3.

[0086] In Figure 15A, the attachment position 471 of the strain gauge shows an example of the centroid position of the strain gauge to be attached. The attachment position 471 is located within the width reduction region 454A. The attachment position 471 may also be the center position on the X-axis. The attachment position 471 may also be a position different from the center position on the X-axis.

[0087] Figure 15B shows the simulation results for the strain of the cantilevered beam 45. In the cantilevered beam 45 being simulated, the maximum widths W1, W2, and W3 are 15 mm, the minimum widths W1, W2, and W3 are 5 mm, the length (dimension on the Y-axis) of regions 454A and 454B is 5 mm, the length (dimension on the Y-axis) of region 453 is 10 mm, and the thickness is 2 mm. The material is stainless steel. The load point is the center of end side 491A. As shown in Figure 15B, the change in strain is greatly reduced in the width reduction region 454A up to 4 mm from the load point.

[0088] Figure 16 is a plan view showing the shape of a cantilevered beam 50 according to one embodiment of the present disclosure. The cantilevered beam 50 is composed of three regions 504, 503, and 505 aligned along the Y-axis. Region 503 is sandwiched between two regions 504 and 505. Region 504 is a decreasing region whose width W1 decreases as it moves away from the end side 541A, which is the load area.

[0089] Along the Y-axis, the width W1 of region 504 decreases monotonically as it moves from the load-bearing end 541 toward the center of the cantilevered beam 50. The edges defining the width of region 504 are straight lines. The shape of region 504 is symmetrical with respect to the X-axis.

[0090] Region 505 is a region with a constant width W4 and is a non-decreasing region. The width W4 coincides with the maximum value of the width W1 of region 504. The edge 542 is a load region. The edge defining the width W4 of region 505 is a straight line and is parallel to the Y-axis. The shape of region 505 is rectangular and is symmetrical with respect to the X-axis.

[0091] The central region 503 has a constant width W2. The opposite sides defining width W2 are parallel to the Y-axis. Width W2 coincides with the minimum value of width W1 of region 504, and width W2 is smaller than width W4 of region 505.

[0092] In Figure 16, the attachment position 421 of the strain gauge shows an example of the centroid position of the strain gauge to be attached. The attachment position 521 is located within the width reduction region 504. The attachment position 521 may also be the center position on the X-axis. The attachment position 521 may also be a position different from the center position on the X-axis.

[0093] Figure 17 is a plan view showing the shape of a cantilevered beam 55 according to one embodiment of the present disclosure. The cantilevered beam 55 is composed of two regions 554 and 555 aligned along the Y-axis. Region 554 is a decreasing region in which its width W1 decreases as it moves away from the end side 591A, which is the load area.

[0094] Along the Y-axis, the width W1 of region 554 decreases monotonically from the load-bearing end 591 toward the center of the cantilevered beam 55. The edges defining the width of region 554 are straight lines. The shape of region 554 is symmetrical with respect to the X-axis. The width W1 of region 554 is minimum at the boundary with region 555.

[0095] Region 555 is a region with a constant width W4 and is a non-decreasing region. The width W4 coincides with the maximum value of the width W1 of region 554. The edge 592 is a load region. The edge defining the width W4 of region 555 is a straight line and is parallel to the Y-axis. The shape of region 555 is rectangular and is symmetrical with respect to the X-axis.

[0096] In Figure 17, the attachment position 571 of the strain gauge shows an example of the centroid position of the strain gauge to be attached. The attachment position 571 is located within the width reduction region 554. The attachment position 571 may also be the center position on the X-axis. The attachment position 571 may also be a position different from the center position on the X-axis.

[0097] The following explains the effect of the width reduction region of the double-supported beams 50 and 55 in reducing strain variation. Figure 18 shows examples of specific dimensions for the double-supported beams 50 and 55. The unit of each number is mm. The double-supported beams 50 and 55 are made of stainless steel and have a thickness of 2 mm.

[0098] The load point 570 of the double-supported beam 55 is a single point on end 591, and end 591 is constrained in the X-axis and Y-axis directions. The opposite end 592 is constrained in the X-axis, Y-axis and Z-axis directions. The load point 520 of the double-supported beam 50 is a single point on end 541, and end 541 is constrained in the X-axis and Y-axis directions. The opposite end 542 is constrained in the X-axis, Y-axis and Z-axis directions.

[0099] Figure 19 shows the simulation results when a force of 175 N is applied in the Z-axis direction at load points 570 and 520, respectively, for cantilevered beams 55 and 50. In the graph of Figure 19, the horizontal axis represents the distance from the load point. The vertical axis represents the amount of strain in the Y-axis direction of the cantilevered beam. Line 501 shows the simulation result for cantilevered beam 55. Line 502 shows the simulation result for cantilevered beam 50. Arrow 503 indicates the width reduction region for cantilevered beams 55 and 50.

[0100] The simulation results 501 and 502 for the double-supported beams 50 and 55 show that the change in strain in the width reduction region 503 is significantly reduced compared to the double-supported beam 3 shown in Figure 7. Furthermore, the simulation result 501 for the double-supported beam 50 shows that the change in strain in the width reduction region 503 is reduced compared to the double-supported beam 55. Thus, the width reduction region can effectively reduce the change in strain due to changes in position. Moreover, a configuration in which the adjacent region to the width reduction region is a rectangular region having the minimum width of the width reduction region can achieve an even greater effect.

[0101] In addition, in the shapes shown in Figures 14A to 17, the width reduction region may have two opposing curved sides that define the width, as shown in Figure 11A. The shapes of the above-mentioned multiple cantilevered beams are symmetric with respect to the Y-axis. The shape of the cantilevered beam in one embodiment of this disclosure may be asymmetric with respect to the Y-axis.

[0102] The lengths of the force sensor stage side end (e.g., end 641A, 541, etc.) and the base stage side end (e.g., end 641B, 542, etc.) of the double-supported beam may be the same or different. From the viewpoint of the safety factor, the length of the end opposite to the reduction region where strain gauges are attached (where strain gauges are not attached) may be greater than or equal to the length of the end of the reduction region. For example, in the double-supported beam 50 shown in Figure 16, the length of end 542 may be greater than or equal to the length of end 541.

[0103] The double-supported beam according to the embodiment of this disclosure includes a width reduction region to which strain gauges are attached. Double-supported beams according to other embodiments of this disclosure may include a thickness reduction region to which strain gauges are attached. The thickness reduction region can reduce the change in strain amount with respect to changes in the attachment of strain gauges.

[0104] Figure 20A shows a perspective view of the cantilevered beam 70. The cantilevered beam 70 is composed of three regions (parts). The cantilevered beam 70 is composed of regions 704A, 703, and 704B, which are aligned along the Y-axis. Regions 704A and 704B are thickness reduction regions where the thickness T changes along the Y-axis, and the central region 703 is sandwiched between these regions 704A and 704B. Position 721 shows an example of the position where a strain gauge is attached. The strain gauge is placed in the thickness reduction region.

[0105] Figure 20B shows a cross-sectional view of the cantilevered beam 70 perpendicular to the X-axis. Figure 20B shows a cross-sectional view at the strain gauge attachment position 721. The cross-sectional shape of the cantilevered beam 70 is the same at all X-axis positions. Region 704A is a thickness reduction region in which its thickness T1 decreases as it moves away from the load region. Thickness T1 is the dimension in the Z-axis. The edge 741A of region 704A is the load region. Edge 741A is the boundary between region 704A and a fixed region (not shown). The fixed region may be, for example, a rectangular parallelepiped.

[0106] Along the Y-axis, the thickness T1 of region 704A decreases monotonically as it moves from the end edge 741A toward the center of the cantilevered beam 70. In the example shape shown in Figure 20B, the edges 742A and 743A that define the thickness of region 704A are straight lines. The shape of region 704A is symmetrical with respect to the Y-axis.

[0107] Region 704B is a thickness reduction region in which its thickness T3 decreases as it moves away from the load region. Thickness T3 is a dimension in the Z-axis. Edge 741B of region 704B is the load region. Edge 741B is the boundary between region 704B and a fixed region (not shown). The fixed region may be, for example, a rectangular parallelepiped.

[0108] Along the Y-axis, the thickness T3 of region 704B decreases monotonically from the end side 741B toward the center of the cantilevered beam 70. In the example shape shown in Figure 20B, sides 742B and 743B that define the width of region 704B are straight lines. The shape of region 704B is symmetric with respect to the Y-axis. The shapes of region 704B and region 704A are symmetric with respect to the Z-axis.

[0109] The central region 703, sandwiched between two width-reducing regions 704A and 704B, has a constant thickness T2. The opposing sides 732 and 733 that define the thickness T2 are parallel to the Y-axis. The thickness T2 coincides with the minimum values ​​of the thicknesses T1 and T3 of regions 704A and 704B.

[0110] One embodiment of this disclosure involves placing strain gauges within a thickness reduction region. This reduces variations in the output values ​​of the strain gauges due to variations in the attachment position along the Y-axis. Furthermore, the thickness reduction region shown in Figures 20A and 20B has a symmetrical shape with respect to the Y-axis. This reduces variations in the output values ​​of the strain gauges due to variations in the attachment position along the X-axis.

[0111] For example, at least the centroid of the strain gauge is located within the width reduction region. Furthermore, the entire area of ​​the strain gauge may be included within the width reduction region. In Figures 20A and 20B, the attachment position 721 shows an example of the centroid position of the strain gauge to be attached. The attachment position 721 may be the center position on the X-axis. The attachment position 721 may be a position different from the center position on the X-axis.

[0112] Figures 21 and 22 show the simulation results of strain in the thickness reduction region. Figure 21 shows the dimensions of the cantilevered beam 70 that was simulated. The unit of the dimensions is mm. The dimension in the X-axis direction is 15 mm, and the material is stainless steel. The load point 731 is located at the center of the X-axis on the end face of the thickness reduction region 704.

[0113] Figure 22 shows a graph of the simulation results. The horizontal axis represents the distance from the load point, and the vertical axis represents the amount of strain. Line 751 shows the simulation results for a cantilevered beam with constant thickness. Specifically, the dimensions on the X, Y, and Z axes represent the simulation results for a rectangular parallelepiped with dimensions of 15 mm, 20 mm, and 2 mm, respectively. Line 752 shows the simulation results for the cantilevered beam 70 shown in Figure 21. Referring to Figure 22, it can be seen that the change in strain in the thickness reduction region is significantly reduced compared to the cantilevered beam with constant thickness.

[0114] Furthermore, the thickness reduction region may have a width of reduction, as explained with reference to Figure 3A-17.

[0115] The following describes a measurement method using strain gauges attached to a double-supported beam. Figure 23 shows an example of a load measurement configuration using strain gauges. In one embodiment of this disclosure, the force sensor device 100 measures the load using a Wheatstone bridge (WB) circuit 801. The strain gauges are placed in the width reduction regions of each of the four beam components 160A-160D.

[0116] Only one strain gauge is attached to each cantilevered beam. Furthermore, the strain gauges for beam components 160A and 160D are located on their rear surfaces, while the strain gauges for beam components 160B and 160C are located on their front surfaces. The front surface is the surface facing the force sensor stage 12.

[0117] The four strain gauges are incorporated into the Wheatstone bridge circuit 801. The instrumentation amplifier 802 amplifies the output from the Wheatstone bridge circuit 801. The components of the Wheatstone bridge circuit 801 other than the strain gauges and the instrumentation amplifier 802 may be included in the control device 20 shown in Figure 1.

[0118] When attaching strain gauges to a double-supported beam, variations in position can alter the detected strain, potentially leading to variations in the output value of the strain gauges. Furthermore, when obtaining output values ​​using a Wheatstone bridge circuit 801 with strain gauges on a double-supported beam, calibration for in-plane variations is required for each product. As described above, the embodiments of this disclosure can reduce variations in output values ​​due to variations in the attachment position of the strain gauges.

[0119] The following explains the effect of a double-supported beam with a width reduction region. We will describe the results of a static load simulation performed on an example of a device configuration in which a double-supported beam of a different shape is applied to the configuration shown in Figure 23. In the simulation, as shown in Figure 24, the voltage output from the Wheatstone bridge circuit 801 was calculated when a load (5N in the Z-axis direction) was applied to the center of each of the nine regions p1 to p9, which were divided into nine sections on the display screen.

[0120] Figure 25 shows the simulation results for a rectangular cantilevered beam. In the graph in Figure 25, the horizontal axis represents the divided regions, and the vertical axis represents the output voltage from the Wheatstone bridge circuit 801. In each divided region, the bar on the left shows the output voltage from the strain gauge at the reference position, and the bar on the right shows the output voltage when the attachment position of one of the four strain gauges is shifted by 1 mm. The numbers above the bar pairs in the divided region indicate the change in output voltage.

[0121] Figure 26 shows the simulation results for the cantilevered beam 16 shown in Figure 5. In the graph in Figure 26, the horizontal axis represents the divided regions, and the vertical axis represents the output voltage from the Wheatstone bridge circuit 801. In each divided region, the bar on the left shows the output voltage from the strain gauge at the reference position, and the bar on the right shows the output voltage when the attachment position of one of the four strain gauges is shifted by 1 mm. The numbers above the bar pairs in the divided region indicate the change in output voltage.

[0122] Figure 27 shows the simulation results for the cantilevered beam 35 shown in Figure 12. In the graph in Figure 27, the horizontal axis represents the divided regions, and the vertical axis represents the output voltage from the Wheatstone bridge circuit 801. In each divided region, the bar on the left shows the output voltage from the strain gauge at the reference position, and the bar on the right shows the output voltage when the attachment position of one of the four strain gauges is shifted by 1 mm. The numbers above the bar pairs in the divided region indicate the change in output voltage.

[0123] Comparing the simulation results in Figure 25 with those in Figure 26 or 27, it can be seen that the change in output voltage of a double-supported beam with a width reduction region is significantly improved compared to the change in output voltage of a rectangular double-supported beam.

[0124] Several combinations of different strain gauge placements and different Wheatstone bridge circuit configurations are possible. Up to four strain gauges can be attached to each cantilever beam. The number of strain gauges attached to each cantilever beam is generally one, two, or four.

[0125] Figures 28A-28D show examples of strain gauge placement layouts for a double-supported beam. In the layout of Figure 28A, one strain gauge is placed in one width reduction region. In the layout of Figure 28B, two strain gauges are placed on both sides of the width reduction region. In the layout of Figure 28C, two strain gauges are placed on the same surface of two width reduction regions. In the layout of Figure 28D, four strain gauges are placed on both sides of two width reduction regions.

[0126] Three types of Wheatstone bridge circuits are known: the one-gauge method, the two-gauge method, and the four-gauge method. The one-gauge method uses one strain gauge in its circuit configuration, the two-gauge method uses two strain gauges in its circuit configuration, and the four-gauge method uses four strain gauges in its circuit configuration.

[0127] Figure 29 shows an example configuration of a two-gauge Wheatstone bridge circuit 801. The Wheatstone bridge circuit 801 includes two strain gauges 871A and 871B and two resistive elements 881A and 881B. These are connected in a ring shape. In the one-gauge method, one of the strain gauges 871A and 871B is replaced with a resistive element, and in the four-gauge method, both resistive elements 881A and 881B are replaced with strain gauges.

[0128] Figure 30 shows an example configuration using two Wheatstone bridge circuits. The force sensor device 100 includes two Wheatstone bridge circuits 811A and 811B, and instrumentation amplifiers 812A and 812B that amplify the outputs of the Wheatstone bridge circuits 811A and 811B, respectively.

[0129] The Wheatstone bridge circuit 811A includes strain gauges for two beam components 160A and 160C, while the Wheatstone bridge circuit 811B includes strain gauges for two beam components 160B and 160D. The combination of the number of strain gauges attached to each beam component (cantilever beam) and the type of Wheatstone bridge circuit is either a one-strain-gauge x two-gauge method or a two-strain-gauge x four-gauge method. By calibrating the combination of the output voltage balance of the two Wheatstone bridge circuits 811A and 811B and the actual touch position, the load and the touch position in the Y-axis direction can be detected.

[0130] Figure 31 shows an example configuration using four Wheatstone bridge circuits. The force sensor device 100 includes four Wheatstone bridge circuits 821A-821D and instrumentation amplifiers 822A-822D that amplify the outputs of the Wheatstone bridge circuits 821A-821D, respectively.

[0131] Wheatstone bridge circuit 821A includes strain gauges for beam component 160, Wheatstone bridge circuit 821B includes strain gauges for beam component 160B, Wheatstone bridge circuit 821C includes strain gauges for beam component 160C, and Wheatstone bridge circuit 821D includes strain gauges for beam component 160D.

[0132] The combination of the number of strain gauges attached to each beam component (cantilever beam) and the type of Wheatstone bridge circuit is one strain gauge × 1-gauge method, two strain gauges × 2-gauge method, or four strain gauges × 4-gauge method. By calibrating the combination of the output voltage balance of the four Wheatstone bridge circuits 821A-821D and the actual touch position, the load and touch position in the X and Y axes can be detected.

[0133] This section describes a measurement method using four Wheatstone bridge circuits 821A-821D. The coordinates of the load point ultimately determined by the control device 20 are denoted as (x5, y5), and the load applied to the load point is denoted as W. The positions of the four cantilevered beams (for example, their centroids) are denoted as (x1, y1), (x2, y2), (x3, y3), and (x4, y4) in the XY coordinate system, and the forces acting on them are denoted as F1, F2, F3, and F4. From the equilibrium of forces and moments, the following equations hold. W = F1 + F2 + F3 + F4 x5W = x1F1 + x2F2 + x3F3 + x4F4 y5W = y1F1 + y2F2 + y3F3 + y4F4

[0134] The load F in a cantilevered beam is expressed by the following equation, using the strain ε and elastic modulus (Young's modulus) E detected by the cantilevered beam and the Wheatstone bridge circuit, the cross-sectional area A of the cantilevered beam, and the stress σ. This equation allows us to determine the loads F1, F2, F3, and F4 acting on each cantilevered beam. F=Aσ=AEε

[0135] Since the coordinates (x1, y1), (x2, y2), (x3, y3), and (x4, y4) of each cantilevered beam are known, the coordinates of the load point (x5, y5) and the load W can be calculated from the calculated F1, F2, F3, and F4.

[0136] According to one embodiment of the present disclosure, the shape of the cantilever beam to which the strain gauges are attached is such that the width decreases monotonically from the end to the center, and the attachment positions of the strain gauges are within the range where the width decreases monotonically. This reduces the variation in the output values ​​of the strain gauges even if the attachment positions of the strain gauges vary, thereby eliminating the need for calibration.

[0137] Although embodiments of the present application have been described above, this disclosure is not limited to the embodiments described above. Those skilled in the art can easily modify, add to, and transform each element of the above embodiments within the scope of this disclosure. It is possible to replace parts of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. [Explanation of symbols]

[0138] 10. Tactile feedback display device 11 Display device 12 Force Sensor Stage 13-Base Stage 16, 35, 70 Double-supported beams 100 Force sensor device 160 Beam components 164A, 164B, 354A, 354B width reduction area 163, 353, 703 central area 704A, 704B Thickness reduction region 801, 811, 821 Wheatstone bridge circuit

Claims

1. A force sensor device, Stage 1 and A second stage is positioned behind the first stage with a gap between them, A plurality of double-supported beams are fixed to the second stage and the first stage, Strain gauges attached to each of the aforementioned multiple cantilever beams, Includes, The first stage moves relative to the second stage in response to a force applied from the front. The plurality of double-supported beams deform in accordance with the movement of the first stage, Each of the plurality of double-supported beams includes a decreasing region in which at least one of the width and thickness decreases monotonically from one fixed position to the first stage and the second stage toward the other. The strain gauge is installed in the reduction region. Force sensor device.

2. A force sensor device according to claim 1, The width of the reduction region decreases monotonically from one of the fixed positions toward the other. Force sensor device.

3. A force sensor device according to claim 2, The reduction region has a shape that is symmetrical with respect to a line axis along a first direction from one of the fixed positions toward the other. Force sensor device.

4. A force sensor device according to claim 3, The shape of the two support beams is symmetrical with respect to an axis of symmetry along the first direction and a second direction perpendicular to the direction of the load applied to the two support beams. Force sensor device.

5. A force sensor device according to claim 2, The edges defining the width of the aforementioned reduction region are straight lines. Force sensor device.

6. A force sensor device according to claim 2, The edges defining the width of the aforementioned reduction region are curved. Force sensor device.

7. A force sensor device according to claim 2, The aforementioned reduction region is the first width reduction region, The force sensor device further includes, A second width reduction region having a width that monotonically decreases from the other toward the one of the fixed positions between the first stage and the second stage, The central region between the first width reduction region and the second width reduction region, Includes, The width of the central region at the boundary with the first width reduction region is the same as the minimum width of the first width reduction region. The width of the central region at the boundary with the second width reduction region is the same as the minimum width of the second width reduction region. Force sensor device.

8. A force sensor device according to claim 2, The shape of the two support beams is symmetrical with respect to an axis of symmetry perpendicular to the direction from one of the fixed positions toward the other and the direction of the load on the two support beams. Force sensor device.

9. A force sensor device according to claim 1, The strain gauge is included in the Wheatstone bridge circuit. Force sensor device.

10. It is an electronic device, The force sensor device according to claim 1, A display device attached to the front of the first stage, Electronic devices, including those mentioned above.

11. The electronic device according to claim 10, The device further includes an actuator that vibrates the display device to provide a tactile sensation to the user. electronic equipment.

Images