Force sensor device

Abstract

The present invention relates to a force sensor apparatus. The force sensor apparatus includes a first stage, a second stage disposed behind the first stage with a gap between the first stage and the second stage, a plurality of beams fixed to the second stage and the first stage, and strain gauges attached on the plurality of beams. The first stage is configured to move relative to the second stage in response to a force applied from the front. The plurality of beams, which are fixed, are configured to deform with the movement of the first stage. Each of the plurality of beams includes a decreasing region in which at least one of a width and a thickness monotonically decreases from a first fixed point fixed to one of the first stage and the second stage toward a second fixed point fixed to the other of the first stage and the second stage. Each strain gauge is attached within the decreasing region.

Description

Technical Field

[0001] This invention relates to a force sensor device. Background Technology

[0002] In recent years, electronic devices including touch panels, such as smartphones and car navigation systems, have become commonplace. When a user interacts with objects, such as icons, in the user interface displayed via a touch panel, the electronic device activates the functions associated with those objects.

[0003] The surface of a touch panel is uniformly hard, so the touch panel will provide the same tactile sensation to the finger no matter which part of the touch panel it touches. For this reason, there is a known technique for providing feedback that allows the user to perceive the presence of an object or receive an operation on the object while activating the function associated with the object. This technique causes the touch panel to vibrate in the planar direction of the touch panel to provide tactile stimulation to the finger in contact with the touch panel.

[0004] Electronic devices utilizing this haptic feedback technology (haptic feedback devices) may also include a force sensor. The force sensor comprises a fixed beam connecting two components of the electronic device and a strain gauge attached to the beam. The electronic device detects movement of the component pressed by the user based on the output of the strain gauge and, in response to the detected movement, provides haptic stimulation to the user's finger.

[0005] In addition to haptic prompting devices with touch panels as described above, various electronic devices also include such force sensor devices, which include strain gauges attached to a fixed beam connecting two components. Summary of the Invention

[0006] Strain gauges output values ​​based on the strain at their bonding point on a beam. Therefore, changes in the bonding point of strain gauges between products can cause changes in the output value of the strain gauges.

[0007] A force sensor device according to one aspect of the invention includes a first unit, a second unit disposed rearward of the first unit and having a gap between the second and third units, a plurality of beams fixed to the second and first units, and strain gauges attached to the plurality of beams. The first unit is configured to move relative to the second unit in response to a force applied from the front. The fixed plurality of beams are configured to deform as the first unit moves. Each of the plurality of beams includes a decreasing region in which at least one of its width and thickness monotonically decreases from a first fixing point fixed to one of the first and second units toward a second fixing point fixed to the other of the first and second units. Each strain gauge is attached to the decreasing region.

[0008] One aspect of the present invention reduces the variation in strain gauge output values ​​caused by changes in the strain gauge's adhesion points.

[0009] It should be understood that the above general description and the following detailed description are exemplary and explanatory, and do not limit the invention. Attached Figure Description

[0010] Figure 1 The illustration shows a configuration example of a tactile prompting display device system according to an embodiment of the present invention.

[0011] Figure 2A It is a schematic cross-sectional view showing the connection structure of the force sensor platform, base, and beam.

[0012] Figure 2B This is a schematic cross-sectional view showing the deformation of a beam caused by the downward pressure of a force sensor platform.

[0013] Figure 2C This is a schematic cross-sectional view showing the deformation of a beam caused by the downward pressure of a force sensor platform.

[0014] Figure 3A This is a perspective view of an example configuration of a force sensor device including a beam in one embodiment of the present invention, when viewed from the rear.

[0015] Figure 3B It is a perspective view of the beam components and their surroundings when viewed from the rear.

[0016] Figure 3C It is a plan view of the beam components and their surroundings when viewed from the rear.

[0017] Figure 4A This is a plan view of the beam component.

[0018] Figure 4B It is a perspective view showing the shape of the beam.

[0019] Figure 5 Specific examples of some beam dimensions are provided.

[0020] Figure 6 Simulation results are provided when a force in the z-axis direction is applied to the load point.

[0021] Figure 7 The shape of another beam used in the simulation and some of its specific dimensions are shown.

[0022] Figure 8 Simulation results are provided when a force in the z-axis direction is applied to the load point.

[0023] Figure 9 The shapes of the three beams used in the simulation are shown.

[0024] Figure 10 Simulation results are provided when forces in the z-axis direction are applied to the load points of the three beams.

[0025] Figure 11A This is a plan view of another beam.

[0026] Figure 11B It is a perspective view showing the shape of the beam.

[0027] Figure 12 Specific examples of some beam dimensions are provided.

[0028] Figure 13 Simulation results are provided when a force in the z-axis direction is applied to the load point.

[0029] Figure 14A This is a plan view of the beam in another embodiment of the present invention.

[0030] Figure 14B Simulation results of the strain of the beam are provided.

[0031] Figure 15A This is a plan view of the beam in another embodiment of the present invention.

[0032] Figure 15B Simulation results of the strain of the beam are provided.

[0033] Figure 16 This is a plan view of the beam in another embodiment of the present invention.

[0034] Figure 17 This is a plan view of the beam in another embodiment of the present invention.

[0035] Figure 18 Provided Figure 16 and Figure 17 Specific examples of some dimensions of the beam shown.

[0036] Figure 19 Simulation results are provided when forces in the z-axis direction are applied to the load points of the two beams.

[0037] Figure 20A This is a perspective view of another beam.

[0038] Figure 20B It is a cross-sectional view of a beam cut perpendicular to the x-axis.

[0039] Figure 21 The dimensions of the beams used in the simulation are provided.

[0040] Figure 22 This is a graph showing the simulation results.

[0041] Figure 23An example configuration for measuring load using strain gauges is shown.

[0042] Figure 24 The nine sub-regions obtained by dividing the display screen are shown.

[0043] Figure 25 Simulation results for a cuboid beam are provided.

[0044] Figure 26 Provided Figure 5 The simulation results for the beam shown are as follows.

[0045] Figure 27 Provided Figure 12 The simulation results for the beam shown are as follows.

[0046] Figure 28A An example of a strain gauge bonding layout on a beam is shown.

[0047] Figure 28B Another example of a strain gauge bonding layout on a beam is shown.

[0048] Figure 28C Another example of a strain gauge bonding layout on a beam is shown.

[0049] Figure 28D Another example of a strain gauge bonded layout on a beam is shown.

[0050] Figure 29 An example configuration of a Wheatstone bridge circuit is shown.

[0051] Figure 30 An example configuration of a force sensor device including two Wheatstone bridge circuits is shown.

[0052] Figure 31 An example configuration of a force sensor device including four Wheatstone bridge circuits is shown. Detailed Implementation

[0053] In the following description, embodiments of the present invention are illustrated with reference to the accompanying drawings. It should be noted that these embodiments are merely examples of implementing the present invention and do not limit the scope of the invention.

[0054] One embodiment of the present invention discloses a force sensor device. This force sensor device can be used in various electronic devices. As an example of such an electronic device, a tactile cue display device is described below. This tactile cue display device includes a display device with touch sensing functionality and a tactile cue device that provides tactile stimulation to a finger touching the touch surface of the display device.

[0055] Figure 1The illustration schematically shows a configuration example of a tactile feedback display device system according to an embodiment of the present invention, which is an example of an electronic device including the force sensor device of the present invention. The tactile feedback display device system includes a tactile feedback display device 10 and a controller 20 for controlling the tactile feedback display device 10.

[0056] The haptic feedback display device system presents a user interface (UI) including at least one object to the user and accepts user actions through the UI. The system also provides feedback to allow the user to perceive the objects included in the UI and to notify the user that their actions on the objects have been accepted.

[0057] Figure 1 The cross-sectional structure of the haptic cue display device 10 is schematically shown. The controller 20 represents a functional block, but its physical structure is not shown. The haptic cue display device 10 includes a display device 11, a force sensor stage (first stage) 12, and a base (second stage) stacked one on top of the other. In the following description, the side from which the user observes the displayed image is defined as the front, and the opposite side as the rear. Figure 1 In the center, the display device 11 is located in front of the force sensor platform 12, and the base 13 is located behind the force sensor platform 12.

[0058] exist Figure 1 In the diagram, the front-back direction or the stacking direction is the z-axis direction, and the x-axis direction (second direction) and y-axis direction (first direction) are the in-plane directions of the display device 11, the force sensor stage 12, or the base 13. The x-axis, y-axis, and z-axis are perpendicular to each other.

[0059] Display device 11 may be a display device with a touch sensor. Display device 11 may include a touch panel with a touch surface 111 and a display module behind it. The display module may be, for example, an organic light-emitting diode (OLED) display module, a micro LED display module, or a liquid crystal display module. The liquid crystal display module may include a liquid crystal panel and a backlight unit behind it.

[0060] The touch surface 111 and the back surface are the main surfaces of the display device 11. The touch surface 111 is also an image display surface for displaying images to the user. An example of the display device 11 has a quadrilateral shape, but the display device 11 can have any shape. The touch sensor functionality of the display device 11 is optional.

[0061] A force sensor stage 12 is disposed behind the display device 11, with a gap between them. The force sensor stage 12 is connected to the back 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 fixed to the force sensor stage 12.

[0062] Actuator 14 is a lateral actuator; it is a device for generating movement in a direction parallel to the image display surface. Due to the movement of actuator 14, display device 11 vibrates in the x-axis direction. Leaf spring 15 is mounted in such an orientation that it elastically deforms in the x-axis direction but not elastically in the z-axis direction. Due to this arrangement, leaf spring 15 elastically supports display device 11 in the x-axis direction and vibrates in the x-axis direction with the vibration of display device 11 caused by the movement of actuator 14. Leaf spring 15 serves as a mechanism for generating vibration according to the movement of actuator 14. The number and arrangement of actuator 14 and leaf spring 15 are not specifically limited and can be appropriately determined according to the design.

[0063] The base 13 is placed on the mounting surface, and the damper 18 is positioned between the two. Figure 1 In the example shown, one of the dampers is provided with reference numeral 18. The base 13 may be fixed or not fixed to the mounting surface. When the haptic cue display device 10 is in operation, the base 13 is stationary on the mounting surface.

[0064] A force sensor stage 12 is disposed between a base 13 and a display device 11. The force sensor stage 12 is positioned in front of the base 13, with a gap between them. The back of the force sensor stage 12 is connected to the base 13 by two beams 16A and 16B. Each of beams 16A and 16B is fixed to the base 13 and the force sensor stage 12.

[0065] Strain gauges (not shown) are attached to each of beams 16A and 16B. The display device 11 is lowered in the z-axis direction by pressure applied by the user. Since the leaf spring 15 does not deform in the z-axis direction, the display device 11 and the force sensor stage 12 are lowered as a whole without reducing the gap between them. The force sensor stage 12 is pushed towards the base 13 by the pressure from the display device 11.

[0066] In other words, the force sensor stage 12 moves backward to be closer to the base 13. In response to the change in position of the force sensor stage 12 relative to the base 13, the fixed beams 16A and 16B deform. Strain gauges output values ​​corresponding to the amount of deformation of the fixed beams 16A and 16B to the controller 20. Thus, the force applied by the user's finger perpendicular to the display screen (touch surface) can be measured based on the output from the strain gauges attached to the fixed beams 16A and 16B.

[0067] The force sensor device includes a force sensor stage 12, a base 13, and beams 16A and 16B. Although Figure 1 Two beams, 16A and 16B, are shown, but the number and arrangement of beams can be appropriately determined according to the design.

[0068] In one example, controller 20 detects contact between a user's finger and a touch surface (display screen) based on output from display device 11, which includes a touch sensor, and locates the position of the user's finger on the display screen. Controller 20 detects whether the user has pressed a displayed object based on strain gauge output values, the position of the user's finger on the display screen, and predetermined information. For example, when a specific area of ​​display device 11 is touched and the force calculated based on the strain gauge output values ​​is greater than a threshold, controller 20 determines that an object pressing event has occurred.

[0069] When a pressing event is detected, the controller 20 controls the movement of the actuator 14 to generate mechanical vibration of the display device 11, so that the user will perceive that the operation on the object has been accepted. For example, the controller 20 applies a drive pulse to the actuator 14 to provide a tactile click sensation to the user's finger.

[0070] An example of a drive pulse includes a first pulse and a second pulse having the same voltage amplitude. Actuator 14, in response to the application of the first pulse, causes the touch surface to deflect from its initial position in one direction, and in response to stopping the application of the first pulse, deflects in the opposite direction to initiate reciprocating motion. After a predetermined period without application, controller 20 applies the second pulse to stop the touch surface from deflecting from its initial position.

[0071] Figure 1 An example configuration of the haptic cue display device 10 of the present invention is shown; the haptic cue display device 10 may have different configurations. For example, actuator 14 and leaf spring 15 may be connected to base 13 and force sensor stage 12, and beams 16A and 16B with strain gauges may be connected to force sensor stage 12 and display device 11.

[0072] Figures 2A to 2C This is a schematic cross-sectional view showing the deformation of the fixed beam 16A caused by the downward pressure of the force sensor platform 12. The fixed beam 16B also deforms in the same way as the fixed beam 16A. Figure 2A The shape of beam 16A in its initial state is shown. Figure 2B The shape of beam 16A is shown when force sensor stage 12 is pressed down.

[0073] Figure 2C The strain at different points on beam 16A is shown when force sensor stage 12 is pressed down. Figure 2C In the diagram, load point 210 is the connection point (fixed point) between beam 16A and force sensor platform 12. The strain direction is the y-axis direction. It is assumed that the base end of beam 16A is constrained in the x-axis, y-axis, and z-axis directions, while its opposite end (force sensor platform end) is constrained in the x-axis and y-axis directions.

[0074] At point 211, near load point 210, the fixed beam 16A contracts. At midpoint 213, no strain occurs. From load point 210 (the end of the force sensor platform) to midpoint 213, the amount of contraction (strain) decreases. For example, the amount of contraction at point 211, near load point 210, is greater than the amount of contraction at point 212, near midpoint 213.

[0075] The fixed beam 16A extends along the y-axis at the end of the base. The extension increases from the midpoint 213 to the end of the base. For example, the elongation at point 215 near the end of the base is greater than the elongation at point 214 near the midpoint 213.

[0076] As can be understood from the above, the amplitude and direction of the strain of the fixed beam 16A along the y-axis vary depending on its position on the y-axis. Therefore, if the bonding points of the strain gauges differ between products, the output values ​​of the strain gauges will vary between products. These variations in the strain gauge output values ​​hinder accurate detection of the downward pressure on the force sensor stage 12.

[0077] One embodiment of the present invention employs a beam of a specific shape and specific attachment points for strain gauges on the beam to reduce variations in the output values ​​of the strain gauges caused by changes in the attachment points. The shape of the beam and the attachment points for the strain gauges on the beam in one embodiment of the present invention are described below.

[0078] Figure 3A This is a perspective view of an example configuration of a force sensor device 100 including a beam, as viewed from the rear, according to an embodiment of the present invention. The force sensor device 100 includes a force sensor stage 12 and a base 13. The force sensor device 100 also includes beam members 160A to 160D connecting the force sensor stage 12 and the base 13. As will be described later, the intermediate portions of the beam members 160A to 160D correspond to a beam.

[0079] The force sensor stage 12 is a rectangular plate-shaped component and can be made of metal or resin. The force sensor stage 12 can have any shape, and there are no particular limitations on its shape. The force sensor stage 12 includes prismatic supports 122A and 122B on its back surface 121. The supports 122A and 122B are positioned away from each other in the y-axis direction, and each of them extends along the x-axis.

[0080] The base 13 is a rectangular plate-shaped component with a central opening, and can be made of metal or resin. The base 13 can have any shape, and there are no particular limitations on its shape. (See reference...) Figure 1 As described above, under normal conditions, there is a gap between the base 13 (its front side) and the back side 121 of the force sensor stage 12.

[0081] exist Figure 3AIn the configuration example, base 13 is positioned in the area sandwiched between supports 122A and 122B. Each of the four beam members 160A to 160D is fixed at one end to the force sensor stage 12 and at the other end to base 13. Beam members 160A and 160C are fixed at one end to the back of support 122A and at the other end to the front of base 13. Beam members 160B and 160D are fixed at one end to the back of support 122B and at the other end to the front of base 13.

[0082] Beam components 160A and 160C are fixed to one side of base 13, and beam components 160B and 160D are fixed to the other side of base 13. Beam components 160A to 160D are arranged symmetrically about the x-axis and y-axis (axis of symmetry). The number and installation position of beam components are not limited to this example; an appropriate number and position can be selected according to the design.

[0083] Figure 3B and Figure 3C These are perspective and plan views of beam component 160D and its surroundings, viewed from the rear. Beam components 160A to 160D have the same shape; the description of beam component 160D applies to beam components 160A to 160C. Beam component 160D is secured to support member 122B by screws 124. A rectangular washer 125 is disposed between screws 124 and beam component 160D. Beam component 160D can also be secured to the front of base 13 in the same manner using washer and screws. Beam component 160D can be secured to force sensor stage 12 and base 13 by other structures; the fixing structures of force sensor stage 12 and base 13 can be the same or different.

[0084] Reference Figure 3C The portion of beam component 160D within the area enclosed by the dashed line is beam 16D. Beam 16D is the area that is neither in contact with nor fixed to the force sensor stage 12 or the base 13; it is a free region unconstrained in any of the x-axis, y-axis, and z-axis directions. The force sensor stage-side and base-side ends of beam 16D are linear load regions. Although the base-side end is fixed, it is a relative load region.

[0085] Figure 4A This is a plan view of beam component 160. Beam components 160A to 160D have the same shape as beam component 160. Beam component 160 consists of multiple regions; each solid line with an arrow represents a region of beam component 160. Beam component 160 consists of fixed regions 162A and 162B and the region of beam 16 between them. Fixed regions 162A and 162B are rectangular regions surrounded by dashed lines, and they have holes 166A and 166B, respectively, for screws to extend through. Beam component 160 has a linearly symmetrical shape about the x-axis and y-axis.

[0086] In one example, fixed region 162A is fixed to force sensor stage 12, while fixed region 162B is fixed to base 13. See reference... Figure 3B and Figure 3C The fixed areas 162A and 162B are in contact with the surfaces of the force sensor stage 12 and the base 13 for clamping and securing by screws and rectangular washers. The beam 16 is located away from other components, including the force sensor stage 12 and the base 13.

[0087] For reference Figures 2A to 2C As described above, when the force sensor stage 12 is pressed down toward the base 13, the beam 16 deforms significantly in the z-axis direction. Furthermore, the beam 16 experiences strain in the y-axis direction. This embodiment measures the downward pressure of the force sensor stage 12 by measuring the strain in the y-axis direction.

[0088] The strain of beam 16 was measured using strain gauges attached to the surface of beam 16. (See reference...) Figure 2C The strain of beam 16 can vary with its position on the y-axis. To reduce the variation in strain measured between products, it is preferable to attach strain gauges to areas where the strain varies little with position on the y-axis.

[0089] Beam 16 consists of three regions 164A, 163, and 164B arranged side-by-side along the y-axis. Region 163 is sandwiched between regions 164A and 164B. Region 164A is a decreasing region whose width W1 decreases with increasing distance from the load region. Width W1 is the dimension along the x-axis. The edge (far end) 641A of region 164A is the load region. Edge 641A is the boundary between region 164A and the fixed region 162A.

[0090] The width W1 of region 164A monotonically decreases along the y-axis from edge 641A toward the center of beam 16. Figure 4A In the example shape shown, the sides 642A and 643A that define the width of region 164A are straight lines. The shape of region 164A is linearly symmetric about the y-axis.

[0091] Region 164B is another decreasing region whose width W3 decreases with increasing distance from the load region. Width W3 is the dimension along the x-axis. The edge (far end) 641B of region 164B is the load region. Edge 641B is the boundary between region 164B and fixed region 162B.

[0092] The width W3 of region 164B monotonically decreases along the y-axis from edge 641B toward the center of beam 16. Figure 4A In the example shape shown, the sides 642B and 643B that define the width of region 164B are straight lines. The shape of region 164B is linearly symmetric about the y-axis. The shapes of regions 164B and 164A are linearly symmetric about the x-axis.

[0093] The intermediate region 163, sandwiched between regions 164A and 164B with decreasing widths, has a uniform width W2. Opposite sides 632 and 633 defining the width W2 are parallel to the y-axis. The value of the width W2 is equal to the minimum of the width W1 of region 164A and the width W3 of region 164B. The intermediate region 163 may be optional.

[0094] In one embodiment of the present invention, the strain gauge is positioned in a region with decreasing width. Therefore, variations in the strain gauge's output value caused by changes in the strain gauge's attachment point on the y-axis can be reduced. Furthermore, Figure 4A The decreasing region shown has a symmetrical shape about the y-axis. Therefore, the variation in strain gauge output values ​​caused by changes in the strain gauge's attachment point on the x-axis can be reduced.

[0095] For example, at least the centroid of the strain gauge is located in the region of decreasing width. Furthermore, the entire strain gauge can be included within the region of decreasing width. Figure 4A The attachment point 601 represents the centroid of the strain gauge being attached. The attachment point 601 can be located at the midpoint of the x-axis. That is, the distance from the attachment point 601 to the intersection of the virtual line extending along the x-axis and passing through the attachment point 601 with edges 642A and 643A can be equidistant. The attachment point 601 can also be located at a point different from the midpoint of the x-axis.

[0096] Figure 4B This is a perspective view showing the shape of beam 16. Beam member 160 has a plate-like shape. The thickness T of beam member 160 is uniform, and the thickness T of beam 16 is also uniform. The cross-sections perpendicular to the thickness direction (z-axis direction) of beam 16 are identical. In other words, all sides of beam 16 are parallel to the z-axis.

[0097] The effect of the width-decreasing region on reducing strain variation is described. Figure 5 Specific examples of some dimensions for beam 16 are provided. The units of the values ​​are millimeters. Assume that beam 16 is made of stainless steel and has a thickness of 2 mm, load point 210 is a point on edge 641A, which is constrained in the x-axis and y-axis directions, and the opposite edge 641B is constrained in the x-axis, y-axis, and z-axis directions.

[0098] Adhesion point 601 is the reference adhesion point for the strain gauge. The strain gauge is positioned within the width-decreasing region 164A. The points on either side of reference adhesion point 601 are adhesion points located approximately 1 mm from reference point 601.

[0099] Figure 6 Simulation results are provided for applying a force of 175 N in the z-axis direction to load point 210. Figure 6In the chart, the horizontal axis represents the distance along the y-axis from the reference bonding point 601 on beam 16. The vertical axis represents the strain along the y-axis. (Refer to...) Figure 6 The strain at a point approximately 1 mm from the reference bonding point 601 differs from the strain at the reference bonding point 601 by 1% and -1.3%, respectively.

[0100] Figure 7 and Figure 8 Simulation results for rectangular (cube-shaped) beams are provided. Figure 7 The shape of beam 3, with some specific dimensional values, is shown in the simulation. The units of the values ​​are millimeters. Beam 3 is made of stainless steel and has a thickness of 2 mm. Load point 33 is a point on the edge (far end) 31A that is constrained in the x-axis and y-axis directions. The opposite edge (far end) 31B is constrained in the x-axis, y-axis, and z-axis directions.

[0101] Adhesion point 32 is the reference adhesion point for the strain gauge. The points on either side of reference adhesion point 32 are adhesion points located approximately 1 mm from reference adhesion point 32. Figure 8 Simulation results are provided when a force of 175 N in the z-axis direction is applied to load point 33. Figure 8 In the chart, the horizontal axis represents the distance along the y-axis from the reference bonding point 32 on beam 3. The vertical axis represents the strain along the y-axis. (Refer to...) Figure 8 The strain at a point approximately 1 mm from the reference bonding point 32 differs from the strain at the reference bonding point 32 by -14.0% and 15.4%, respectively.

[0102] Figure 6 and Figure 8 The comparison of simulation results shows that the width-decreasing region of beam 16 significantly reduces the strain variation caused by positional differences. In other words, the simulation results indicate that the width-decreasing region significantly reduces the measurement variation caused by changes in the strain gauge adhesion points.

[0103] Figure 9 and Figure 10 Simulation results for multiple beams are provided. Figure 9 The shapes of the three beams 3, 16, and 30 used in the simulation are shown. Beam 3 has the same shape as... Figure 7 Beam 3 shown has the same shape; beam 16 has the same shape as... Figure 5 The beam shown is the same shape as beam 16.

[0104] The difference between beam 30 and beam 16 lies in the lengths (dimensions along the y-axis) of the left and right width-decreasing regions. Aside from other dimensional differences caused by the difference in lengths of the left and right width-decreasing regions, beam 30 has the same shape as beam 16. Figure 9The units for the dimensions shown are millimeters. Beams 3, 16, and 30 are 2 mm thick and are made of stainless steel.

[0105] Figure 10 Simulation results are provided when a force of 175 N in the z-axis direction is applied to load point 33 of beam 3, load point 210 of beam 16, and load point 310 of beam 30. Figure 10 In the graphs, the horizontal axis represents the distance from the load point, and the vertical axis represents the strain of the beam along the y-axis. Curve 341 represents the simulation results for beam 3; curve 342 represents the simulation results for beam 16; and curve 343 represents the simulation results for beam 30. Line 362 with an arrow represents the width-decreasing region of beam 16, and line 363 with an arrow represents the width-decreasing region of beam 30.

[0106] Simulation results 341 for beam 3 show that the strain gradually decreases with increasing distance from load point 33. Simulation results 342 for beam 16 show that, compared to beam 3, the strain variation within its width-decreasing region 362 is significantly smaller. Simulation results 343 for beam 30 show that, compared to beam 3, the strain variation within its width-decreasing region 363 is significantly smaller. These results demonstrate that the width-decreasing region can effectively reduce the variation of strain with location.

[0107] In the following sections, some beams with different shapes are described in other embodiments of the invention. The beams described below are applicable to the beam components with fixed regions described above. Figure 11A This is a plan view of beam 35. Beam 35 consists of multiple regions; each line with an arrow represents a region of beam 35. Beam 35 consists of three regions 354A, 353, and 354B arranged side by side along the y-axis. Region 353 is sandwiched between regions 354A and 354B. Region 354A is a decreasing region whose width W1 decreases with increasing distance from the load region. Width W1 is the dimension along the x-axis. The edge (far end) 361A of region 354A is the load region. Edge 361A is the boundary between region 354A and a fixed region (not shown).

[0108] The width W1 of region 354A monotonically decreases along the y-axis from edge 361A toward the center of beam 35. Figure 11A In the example shape shown, the sides 362A and 363A that define the width of region 354A are curves. The shape of region 354A is linearly symmetric about the y-axis.

[0109] Each of edges 362A and 363A consists of two curves. Specifically, it consists of a convex (outwardly protruding) curve 367 extending from edge 361A toward the center and a concave curve 368 continuing from curve 367. Figure 11AReference numerals 367 and 368 for edge 362A are provided only as examples. For instance, curve 367 is a 90-degree arc, and curve 368 is a 90-degree arc with a radius of curvature larger than that of curve 367.

[0110] Region 354B is another decreasing region whose width W3 decreases with increasing distance from the load region. Width W3 is the dimension along the x-axis. The edge (far end) 361B of region 354B is the load region. Edge 361B is the boundary between region 354B and a fixed region (not shown).

[0111] The width W3 of region 354B monotonically decreases along the y-axis from edge 361B toward the center of beam 35. Figure 11A In the example shape shown, the edges 362B and 363B that define the width of region 354B are curves. The shape of region 354B is linearly symmetric about the y-axis. The shapes of regions 354B and 354A are linearly symmetric about the x-axis.

[0112] The intermediate region 353, sandwiched between regions 354A and 354B with decreasing widths, has a uniform width W2. Opposite edges 365 and 366 defining width W2 are parallel to the y-axis. The value of width W2 is equal to the minimum of the width W1 of region 354A and the width W3 of region 354B.

[0113] Figure 11A The bonding point 357 of the strain gauge indicates the centroid of the bonded strain gauge. Bonding point 357 is located within the width-decreasing region 354A. Bonding point 357 can be located at the midpoint on the x-axis, or at a point different from the midpoint on the x-axis.

[0114] Figure 11B This is a perspective view showing the shape of beam 35. The thickness T of beam 35 is uniform. The cross-sections perpendicular to the thickness direction (z-axis direction) of beam 35 are identical.

[0115] The effect of the width-decreasing region of beam 35 on reducing strain variation is described. Figure 12 Specific examples of some dimensions for beam 35 are provided. The units of the values ​​are millimeters. Assume that beam 35 is made of stainless steel and has a thickness of 2 mm, load point 370 is a point on edge 361A, which is constrained in the x-axis and y-axis directions, and the opposite edge 361B is constrained in the x-axis, y-axis, and z-axis directions.

[0116] Adhesion point 371 is the reference adhesion point for the strain gauge. The strain gauge is positioned within the width-decreasing region 354A. The points on either side of reference adhesion point 371 are adhesion points located approximately 1 mm from reference adhesion point 371.

[0117] Figure 13Simulation results are provided when a force of 175 N in the z-axis direction is applied to load point 370. Figure 13 In the chart, the horizontal axis represents the distance along the y-axis on beam 35 from the reference bonding point 371. The vertical axis represents the strain along the y-axis. The strain at points approximately 1 mm from the reference bonding point 371 differs from the strain at the reference bonding point 372 by -5.7% and 1.6%, respectively. (Compared to reference...) Figure 7 and Figure 8 Compared to the differences described for rectangular beam 3, these differences have been significantly improved.

[0118] Figure 14A This is a plan view of beam 40 in another embodiment of the present invention. Beam 40 consists of three regions 404A, 403, and 404B arranged side by side along the y-axis. Region 403 is sandwiched between regions 404A and 404B. Region 404A is a decreasing region whose width W1 decreases as the distance from the edge (far end) 441A of the load region increases.

[0119] The width W1 of region 404A decreases monotonically along the y-axis from the edge 441A of the load region toward the center of beam 40. The edge defining the width of region 404A is a straight line. The shape of region 404A is linearly symmetric about the y-axis.

[0120] Region 404B is another decreasing region whose width W3 decreases with increasing distance from the edge (far end) 441B of the load region. The width W3 of region 404B monotonically decreases along the y-axis from edge 441B toward the center of beam 40. The edge defining the width of region 404B is a straight line. The shape of region 404B is linearly symmetric about the y-axis. The shapes of regions 404B and 404A are linearly symmetric about the x-axis.

[0121] The intermediate region 403, sandwiched between regions 404A and 404B with decreasing widths, has a uniform width W2. The opposite sides defining width W2 are parallel to the y-axis. The value of width W2 is equal to the maximum of the width W1 of region 404A and the width W3 of region 404B.

[0122] Figure 14A The bonding point 421 of the strain gauge represents the centroid of the bonded strain gauge. Bonding point 421 is located within the width-decreasing region 404A. Bonding point 421 can be located at the midpoint on the x-axis, or at a point different from the midpoint on the x-axis.

[0123] Figure 14BSimulation results for the strain of beam 40 are provided. In the beam 40 used in the simulation, the maximum width W2 and widths W1 and W3 are 15 mm, the minimum widths W1 and W3 are 5 mm, the lengths (along the y-axis) of regions 404A and 404B are 5 mm, the length (along the y-axis) of region 403 is 10 mm, and the thickness is 2 mm. The material of beam 40 is stainless steel. The load point is located at the midpoint of edge 441A. Figure 14B As shown, in the region 404A where the width decreases, especially in the region 4 mm from the load point, the change in strain is significantly smaller.

[0124] Figure 15A This is a plan view of beam 45 in another embodiment of the present invention. Beam 45 consists of three regions 454A, 453, and 454B arranged side by side along the y-axis. Region 453 is sandwiched between regions 454A and 454B. Region 454A is a decreasing region whose width W1 decreases as the distance from the edge (far end) 491A of the load region increases.

[0125] The width W1 of region 454A decreases monotonically along the y-axis from the edge 491A of the load region toward the center of beam 45. The edge defining the width of region 454A is a straight line. The shape of region 454A is linearly symmetric about the y-axis.

[0126] Region 454B is another decreasing region whose width W3 decreases with increasing distance from the edge (far end) 491B of the load region. The width W3 of region 454B monotonically decreases along the y-axis from edge 491B toward the center of beam 45. The edge defining the width of region 454B is a straight line. The shape of region 454B is linearly symmetric about the y-axis. The shapes of regions 454B and 454A are linearly symmetric about the x-axis.

[0127] The width W2 of the intermediate region 453, sandwiched between the decreasing width regions 454A and 454B, varies with its position on the y-axis. Specifically, the width W2 monotonically increases along the y-axis from the boundary of the decreasing width region 454A towards the center of region 453. At the boundary between the intermediate region 453 and the decreasing width region 454A, the width W2 of the intermediate region 453 reaches the same minimum value as the width W1 of the decreasing width region 454A. At the boundary between the intermediate region 453 and the decreasing width region 454B, the width W2 of the intermediate region 453 also reaches the same minimum value as the width W3 of the decreasing width region 454B. The maximum value of the width W2 of the intermediate region 453 is equal to the maximum value of widths W1 and W3.

[0128] Figure 15AThe bonding point 471 of the strain gauge represents the centroid of the bonded strain gauge. Bonding point 471 is located within the width-decreasing region 454A. Bonding point 471 can be the midpoint on the x-axis, or it can be a point different from the midpoint on the x-axis.

[0129] Figure 15B Simulation results for the strain of beam 45 are provided. In the simulation of beam 45, the maximum widths W1, W2, and W3 are 15 mm, the minimum widths W1, W2, and W3 are 5 mm, the lengths (along the y-axis) of regions 454A and 454B are 5 mm, the length (along the y-axis) of region 453 is 10 mm, and the thickness is 2 mm. The material of beam 45 is stainless steel. The load point is located at the midpoint of edge 491A. Figure 15B As shown, in the region 454A where the width decreases, especially in the region 4 mm from the load point, the change in strain is significantly smaller.

[0130] Figure 16 This is a plan view of beam 50 according to another embodiment of the present invention. Beam 50 consists of three regions 504, 503 and 505 arranged side by side along the y-axis. Region 503 is sandwiched between regions 504 and 505. Region 504 is a decreasing region whose width W1 decreases as the distance from the edge (far end) 541 of the load region increases.

[0131] The width W1 of region 504 monotonically decreases along the y-axis from the edge 541 of the load region toward the center of beam 50. The edge defining the width of region 504 is a straight line. The shape of region 504 is linearly symmetric about the y-axis.

[0132] Region 505 is a non-decreasing region with a uniform width W4. The width W4 is the maximum value of the width W1 of region 504. Edge (far end) 542 is the load region. The edge defining the width W4 of region 505 is a straight line parallel to the y-axis. Region 505 is rectangular in shape and is linearly symmetric about the y-axis.

[0133] The intermediate region 503 has a uniform width W2. The opposite sides defining the width W2 are parallel to the y-axis. The value of the width W2 is the same as the minimum value of the width W1 of region 504, and is narrower than the width W4 of region 505.

[0134] Figure 16 The bonding point 521 of the strain gauge indicates the centroid of the bonded strain gauge. The bonding point 521 is located within the decreasing width region 504. The bonding point 521 can be located at the midpoint of the x-axis, or at a point different from the midpoint on the x-axis.

[0135] Figure 17This is a plan view of beam 55 in another embodiment of the present invention. Beam 55 consists of two regions 554 and 555 arranged side by side along the y-axis. Region 554 is a decreasing region whose width W1 decreases as the distance from the edge (far end) 591 of the load region increases.

[0136] The width W1 of region 554 monotonically decreases along the y-axis from the edge 591 of the load region toward the center of beam 55. The edge defining the width of region 554 is a straight line. The shape of region 554 is linearly symmetric about the y-axis. The width W1 of region 554 is minimized at the boundary with region 555.

[0137] Region 555 is a non-decreasing region with a uniform width W4. The width W4 is the same as the maximum value of the width W1 of region 554. Edge (far end) 592 is the load region. The edge defining the width W4 of region 555 is a straight line parallel to the y-axis. Region 555 is rectangular in shape and is linearly symmetric about the y-axis.

[0138] Figure 17 The bonding point 571 of the strain gauge indicates the centroid of the bonded strain gauge. Bonding point 571 is located within the width-decreasing region 554. Bonding point 571 can be located at the midpoint on the x-axis, or at a point different from the midpoint on the x-axis.

[0139] The following describes the effect of the width-decreasing regions of beams 50 and 55 on reducing strain variation. Figure 18 Specific examples of some dimensions for beams 50 and 55 are provided. The units for the values ​​are millimeters. It is assumed that beams 50 and 55 are made of stainless steel and have a thickness of 2 mm.

[0140] The load point 570 of beam 55 is a point on the edge (far end) 591, which is constrained in the x-axis and y-axis directions. The opposite edge 592 is constrained in the x-axis, y-axis, and z-axis directions. The load point 520 of beam 50 is a point on the edge 541, which is constrained in the x-axis and y-axis directions. The opposite edge (far end) 542 is constrained in the x-axis, y-axis, and z-axis directions.

[0141] Figure 19 Simulation results are provided when a force of 175 N in the z-axis direction is applied to load point 570 of beam 55 and load point 520 of beam 50. Figure 19 In the graph, the horizontal axis represents the distance from the load point. The vertical axis represents the strain of the beam along the y-axis. Curve 501 represents the simulation result for beam 50, and curve 502 represents the simulation result for beam 55. The line with arrow 503 represents the width-decreasing region of beams 50 and 55.

[0142] Simulation results 501 for beam 50 and 502 for beam 55 show that, with Figure 7 Compared to the simulation results for beam 3, the strain variation in its width-decreasing region 503 is significantly smaller. Furthermore, the simulation results 501 for beam 50 show that the strain variation in its width-decreasing region 503 is smaller compared to that of beam 55. These results demonstrate that width-decreasing regions can effectively reduce the variation of strain with location. Moreover, the configuration where the width-decreasing region is adjacent to a rectangular region with a width equal to the minimum width of the width-decreasing region exhibits even better results.

[0143] about Figures 14A to 17 The shape shown, with the width decreasing region, can have the following characteristics: Figure 11A The two opposite curved sides with defined widths are shown. The shapes of the aforementioned beams are linearly symmetrical about the y-axis. In another embodiment of the invention, the shapes of the beams may be asymmetrical about the y-axis.

[0144] The force sensor end face (e.g., edge 641A or 541) and the base end face (e.g., edge 641B or 542) of the beam can have equal or different lengths. From a safety factor perspective, the edge (far end) opposite the decreasing region where the strain gauge is attached, or the edge (far end) in the region where the strain gauge is not attached, can be equal to or longer than the edge (far end) in the decreasing region. Figure 16 Taking the beam shown as an example, side 542 can be equal to or longer than side 541.

[0145] In the above embodiments of the present invention, the beam includes a width-decreasing region for attaching strain gauges. In another embodiment of the present invention, the beam may include a thickness-decreasing region for attaching strain gauges. The thickness-decreasing region can reduce the variation of strain with the position of the strain gauge attachment point.

[0146] Figure 20A This is a perspective view of beam 70. Beam 70 consists of three regions (parts), namely regions 704A, 703, and 704B arranged side by side along the y-axis. Regions 704A and 704B are thickness-decreasing regions whose thickness T varies along the y-axis, and the intermediate region 703 is sandwiched between these regions 704A and 704B. Point 721 is an example of a strain gauge attachment point. The strain gauge is placed in the thickness-decreasing region.

[0147] Figure 20B This is a cross-sectional view of beam 70 taken perpendicular to the x-axis. Figure 20BThis is a cross-sectional view at the strain gauge attachment point 721. The cross-section of beam 70 is identical at any location along the x-axis. Region 704A is a thickness-decreasing region whose thickness T1 decreases with increasing distance from the load region. Thickness T1 is the dimension along the z-axis. The edge (far end) 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 have a cuboid shape.

[0148] The thickness T1 of region 704A decreases monotonically with increasing distance along the y-axis from edge 741A toward the center of beam 70. Figure 20B In the example of the shape, the edges 742A and 743A that define the thickness of region 704A are straight lines. The shape of region 704A is linearly symmetric about the y-axis.

[0149] Region 704B is another region with decreasing thickness T3, where the thickness decreases with increasing distance from the load region. Thickness T3 is the dimension along the z-axis. The edge (far end) 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 have a cuboid shape.

[0150] The thickness T3 of region 704B decreases monotonically with increasing distance along the y-axis from edge 741B toward the center of beam 70. Figure 20B In the example of the shape, the edges 742B and 743B that define the thickness of region 704B are straight lines. The shape of region 704B is linearly symmetric about the y-axis. The shapes of regions 704B and 704A are linearly symmetric about the z-axis.

[0151] The intermediate region 703, sandwiched between regions 704A and 704B with decreasing thickness, has a uniform thickness T2. Opposite edges 732 and 733 defining thickness T2 are parallel to the y-axis. The value of thickness T2 is the same as the minimum value of thickness T1 in region 704A and thickness T3 in region 704B.

[0152] One embodiment of the invention places the strain gauge within a thickness decreasing region. Therefore, variations in the strain gauge's output value caused by changes in the strain gauge's attachment point along the y-axis can be reduced. Furthermore, Figure 20A and Figure 20B The thickness-decreasing region shown has a symmetrical shape about the y-axis. Therefore, the variation in strain gauge output values ​​caused by changes in the strain gauge's attachment point on the x-axis can be reduced.

[0153] For example, at least the centroid of the strain gauge is located in the thickness-decreasing region. Furthermore, the entire strain gauge may be contained within the thickness-decreasing region. Figure 20A and Figure 20BThe attachment point 721 represents the centroid of the strain gauge being attached. The attachment point 721 can be located at the midpoint on the x-axis, or at a point different from the midpoint on the x-axis.

[0154] Figure 21 and Figure 22 Simulation results of the strain in the thickness decreasing region are provided. Figure 21 The dimensions of beam 70 used in the simulation are provided. Dimensions are in millimeters. The dimension along the x-axis is 15 mm, and the material is stainless steel. Load point 731 is located at the midpoint of the x-axis on the end face of the thickness-decreasing region 704A.

[0155] Figure 22 This is a graph showing the simulation results. The horizontal axis represents the distance from the load point, and the vertical axis represents the strain. Curve 751 shows the simulation results for a beam of uniform thickness. Specifically, the beam is a cuboid with dimensions of 15 mm, 20 mm, and 2 mm along the x-axis, y-axis, and z-axis, respectively. Curve 752 shows the simulation results for... Figure 21 The simulation results for beam 70 are shown. Figure 22 This indicates that the strain variation in the region with decreasing thickness is significantly smaller compared to that of a beam with uniform thickness.

[0156] For reference Figures 3A to 17 The thickness-decreasing region may also have a decreasing width.

[0157] The measurements taken using strain gauges attached to a fixed beam are described below. Figure 23 An example configuration for measuring loads using strain gauges is shown. In one embodiment of the invention, the force sensor device 100 measures the load using a Wheatstone bridge (WB) circuit 801. Strain gauges are positioned in the width-decreasing regions of the four beam members 160A to 160D.

[0158] Only one strain gauge is attached to each beam. The strain gauges for beam components 160A and 160D are attached to the back of the beam components, while the strain gauges for beam components 160B and 160C are attached to the front of the beam components. The front faces the force sensor stage 12.

[0159] Four strain gauges are integrated into a Wheatstone bridge circuit 801. An instrumentation amplifier 802 amplifies the output of the Wheatstone bridge circuit 801. Components of the instrumentation amplifier 802 and the Wheatstone bridge circuit 801, excluding the strain gauges, may include... Figure 1 In the controller 20 shown.

[0160] If the adhesion point between the strain gauge and the beam changes, the strain to be measured will differ, resulting in a change in the strain gauge's output value. When using strain gauges fixed to the beam to obtain output values ​​from the Wheatstone bridge circuit 801, each product requires calibration for in-plane variations. As described above, embodiments of the present invention reduce the output value variation caused by changes in the strain gauge's adhesion point.

[0161] The effects on beams with a decreasing width region are described. The results of static loading simulations performed on several different equipment configurations are also described. Figure 23 In the configurations shown, these devices utilize beams of varying shapes. The simulation calculated the voltage output of the Wheatstone bridge circuit 801 when a load (a force of 5 N in the z-axis direction) is applied to the center of each of the nine sub-regions p1 to p9. Figure 24 As shown, these sub-regions are obtained by dividing the display screen.

[0162] Figure 25 Simulation results for a rectangular beam are provided. Figure 25 In the chart, the horizontal axis represents the sub-regions of the display screen, and the vertical axis represents the output voltage of the Wheatstone bridge circuit 801. For each sub-region, the left bar represents the output voltage when the strain gauge is attached at the reference point, and the right bar represents the output voltage when one of the four strain gauges is displaced by 1 mm. The values ​​above the pair of bars for each sub-region represent the changes in output voltage.

[0163] Figure 26 Provided for Figure 5 The simulation results for beam 16 are shown. Figure 26 In the chart, the horizontal axis represents the sub-regions of the display screen, and the vertical axis represents the output voltage of the Wheatstone bridge circuit 801. For each sub-region, the left bar represents the output voltage when the strain gauge is attached at the reference point, and the right bar represents the output voltage when one of the four strain gauges is displaced by 1 mm. The values ​​above the pair of bars for each sub-region represent the changes in output voltage.

[0164] Figure 27 Provided Figure 12 The simulation results for beam 35 are shown. Figure 27 In the chart, the horizontal axis represents the sub-regions of the display screen, and the vertical axis represents the output voltage of the Wheatstone bridge circuit 801. For each sub-region, the left bar represents the output voltage when the strain gauge is attached at the reference point, and the right bar represents the output voltage when one of the four strain gauges is displaced by 1 mm. The values ​​above the pair of bars for each sub-region represent the changes in output voltage.

[0165] Will Figure 26 or Figure 27 The simulation results and Figure 25Comparing the simulation results, each change in output voltage obtained from a beam with a decreasing width region is significantly improved compared to the corresponding change obtained from a cuboid beam.

[0166] There are multiple combinations of different numbers of strain gauges to be bonded and different circuit configurations of the Wheatstone bridge circuit. Each beam can be provided with up to four strain gauges. Typically, one, two, or four strain gauges are bonded to one beam.

[0167] Figures 28A to 28D An example of the adhesive layout of strain gauges on a beam is shown. Figure 28A The layout allows only one strain gauge to be attached to a region with decreasing width. Figure 28B The layout allows two strain gauges to be attached to two surfaces of a region with decreasing width. Figure 28C The layout allows two strain gauges to be attached to the same surface in two regions with decreasing widths. Figure 28D The layout allows four strain gauges to be attached to two surfaces of two regions with decreasing widths.

[0168] There are three types of Wheatstone bridge circuits. They are used in single-strain gauge, double-strain gauge, and four-strain gauge methods. The circuit configuration for the single-strain gauge method includes one strain gauge; the circuit configuration for the double-strain gauge method includes two strain gauges; and the circuit configuration for the four-strain gauge method includes four strain gauges.

[0169] Figure 29 An example configuration of a Wheatstone bridge circuit 801 for the dual strain gauge method is shown. The Wheatstone bridge circuit 801 includes two strain gauges 871A and 871B and two resistive elements 881A and 881B. They are connected in a ring configuration. For the single strain gauge method, either strain gauge 871A or 871B is replaced with a resistive element. For the four strain gauge method, both resistive elements 881A and 881B are replaced with strain gauges.

[0170] Figure 30 An example configuration of a force sensor device 100 including two Wheatstone bridge circuits is shown. The force sensor device 100 includes two Wheatstone bridge circuits 811A and 811B, and two instrumentation amplifiers 812A and 812B, respectively, for amplifying the outputs of the Wheatstone bridge circuits 811A and 811B.

[0171] The Wheatstone bridge circuit 811A includes strain gauges on two beam members 160A and 160C, and the Wheatstone bridge circuit 811B includes strain gauges on two beam members 160B and 160D. The combination of the number of strain gauges attached to each beam member (its beam) and the type of Wheatstone bridge circuit can be a one-strain gauge × two-strain gauge method or a two-strain gauge × four-strain gauge method. By calibrating the balance between the output voltages of the two Wheatstone bridge circuits 811A and 811B in combination with the actual contact point, the detection of load and contact point in the y-axis direction can be achieved.

[0172] Figure 31 An example configuration of a force sensor device 100 including four Wheatstone bridge circuits is shown. The force sensor device 100 includes four Wheatstone bridge circuits 821A to 821D and four instrumentation amplifiers 822A to 822D for amplifying the outputs of the Wheatstone bridge circuits 821A to 821D, respectively.

[0173] Wheatstone bridge circuit 821A includes a strain gauge on beam member 160A; Wheatstone bridge circuit 821B includes a strain gauge on beam member 160B; Wheatstone bridge circuit 821C includes a strain gauge on beam member 160C; Wheatstone bridge circuit 821D includes a strain gauge on beam member 160D.

[0174] The combination of the number of strain gauges attached to each beam component (its beam) and the type of Wheatstone bridge circuit can be a one-strain gauge × single strain gauge method, a two-strain gauge × double strain gauge method, or a four-strain gauge × four-strain gauge method. By calibrating the balance between the output voltages of the four Wheatstone bridge circuits 821A to 821D and combining them with the actual touch points, the load and touch points on the x and y axes can be detected.

[0175] The measurement method using four Wheatstone bridge circuits 821A to 821D is described. The coordinates of the load point, ultimately determined by the controller 20, are represented as (x5, y5), the load applied at the load point is represented as W, and the positions of the four beams (e.g., the positions of their centers of mass) are represented as (x1, y1), (x2, y2), (x3, y3), and (x4, y4); the forces applied to them are F1, F2, F3, and F4. The following formula is established based on the ratio of the forces and the ratio of the moments:

[0176] W = F1 + F2 + F3 + F4,

[0177] x5W = x1F1 + x2F2 + x3F3 + x4F4, and

[0178] y5W = y1F1 + y2F2 + y3F3 + y4F4

[0179] The load F on the fixed beam is expressed by the following formula using strain ε, elastic modulus (Young's modulus) E, cross-sectional area A of the beam, and stress σ detected by strain gauges and Wheatstone bridge circuits on the beam:

[0180] F = Aσ = AΕε.

[0181] The loads F1, F2, F3 and F4 of each beam can be calculated using this formula.

[0182] Since the coordinates (x1, y1), (x2, y2), (x3, y3), and (x4, y4) of the beam are known, the coordinates (x5, y5) of the load point and the load W can be calculated based on the calculated F1, F2, F3, and F4.

[0183] According to one embodiment of the invention, the beam to which strain gauges are to be provided is shaped such that its width monotonically decreases from the distal end toward the center, and the strain gauges are adhered to the region where the width monotonically decreases. Therefore, even if the adhesion points of multiple strain gauges vary, the output value of the strain gauges varies only slightly, thus eliminating the need for calibration.

[0184] As described above, embodiments of the present invention have been presented; however, the present invention is not limited to the embodiments described above. Those skilled in the art can readily modify, add to, or transform each element in the above embodiments within the scope of the present invention. A portion of the configuration of one embodiment can be replaced by the configuration of another embodiment, or the configuration of one embodiment can be incorporated into the configuration of another embodiment.

Claims

1. A force sensor device, comprising: The first one; The second unit is located behind the first unit and has a gap between them; Multiple beams, the multiple beams being fixed to the second unit and the first unit; as well as Strain gauges, which are attached to the plurality of beams, The first unit is configured to move relative to the second unit in response to a force applied from the front. The fixed plurality of beams are configured to deform as the first unit moves. Each of the plurality of beams includes a decreasing region in which at least one of its width and thickness monotonically decreases from a first fixing point fixed to one of the first and second platforms toward a second fixing point fixed to the other of the first and second platforms. Each strain gauge is attached to the decreasing region.

2. The force sensor device according to claim 1, wherein, The width of the decreasing region decreases monotonically from the first fixed point toward the second fixed point.

3. The force sensor device according to claim 2, wherein, The decreasing region has a linearly symmetrical shape about an axis of symmetry that extends in a first direction from the first fixed point toward the second fixed point.

4. The force sensor device according to claim 3, wherein, Each beam has a line-symmetric shape about an axis of symmetry that extends in a second direction perpendicular to the first direction and the load direction of the beam.

5. The force sensor device according to claim 2, wherein, The edge defining the width of the decreasing region is a straight line.

6. The force sensor device according to claim 2, wherein, The edge defining the width of the decreasing region is a curve.

7. The force sensor device according to claim 2, in, The decreasing region is the first decreasing width region. The force sensor device further includes: The second width-decreasing region has a width that decreases monotonically from the second fixed point toward the first fixed point. The intermediate region is located between the first width-decreasing region and the second width-decreasing region. Wherein, the width at the boundary between the intermediate region and the first width-decreasing region is equal to the minimum width of the first width-decreasing region, and Wherein, the width at the boundary between the middle region and the second width-decreasing region is equal to the minimum width of the second width-decreasing region.

8. The force sensor device according to claim 2, wherein, Each beam has a line-symmetric shape about an axis of symmetry that extends perpendicularly to the direction from the first fixed point toward the second fixed point and the load direction of the beam.

9. The force sensor device according to claim 1, wherein, Each strain gauge is included in a Wheatstone bridge circuit.

10. An electronic device, comprising: The force sensor device according to claim 1; as well as The display device installed in front of the first unit.

11. The electronic device of claim 10, further comprising: An actuator configured to cause the display device to vibrate in order to provide tactile stimulation to a user.

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