Scales, strain gauges, and load cells

Abstract

To provide a weighing machine capable of suppressing the effect of instrument error in performance, a strain-generating body, and a load cell.SOLUTION: The weighing machine includes: a housing base; a housing cover that is placed on the housing base and to which a weight is applied. The weighing machine includes: multiple strain-generating bodies each having a strain-generating part that supports the housing cover on the housing base, and which undergoes elastic deformation under the load applied to the housing cover; and a strain sensor that is provided to the strain-generating part of the strain-generating body the resistance value of which changes according to the expansion and contraction caused by the deformation of the strain-generating part. The strain sensor includes, with the strain-generating part elastically deformed, a first strain gauge placed in an area that deforms into a concave shape and a second strain gauge that is placed in an area that deforms into a convex shape. One strain sensor of the strain-generating body is placed on the front side of the strain-generating part, and the other strain sensor of the strain-generating body is placed on the rear side of the strain-generating part.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a scale, a strain element, and a load cell. [Background technology]

[0002] Patent Document 1 shows a weighing device having a strain-generating body at each of its four corners. Strain sensors are attached to the strain-generating parts of the strain-generating body.

[0003] The strain sensor is composed of a pair of strain gauges spaced apart in the longitudinal direction of the strain generating portion, and the weighing device measures the applied load based on the resistance value of each strain gauge. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2014-109438 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the above-mentioned weighing device, if the rigidity of the upper plate to which the load is applied is low, the upper plate will bend due to the applied load, and the input direction of the load input from the upper plate to the strain body will be tilted. Then, compared to the case where the load is input vertically to the strain body, the deformation state of the strain-generating part where distortion occurs in the strain body will change.

[0006] In this case, the difference in strain occurring in each strain gauge of the strain sensor provided on the strain generating portion becomes large, and the influence of this becomes apparent in the instrument error performance.

[0007] The present invention has been made in consideration of the above problems, and has an object to provide a scale, a strain element, and a load cell that can suppress the effect on instrument error performance. [Means for solving the problem]

[0008] According to one aspect of the present invention, a balance includes a housing base and a housing cover disposed on the housing base and to which a load is applied. The balance includes a plurality of strain-generating bodies that support the housing cover on the housing base and have strain-generating parts that elastically deform in response to a load applied to the housing cover, and a strain sensor that is provided on the strain-generating parts of the strain-generating bodies and changes resistance value in response to expansion and contraction accompanying deformation of the strain-generating parts. The strain sensor includes a first strain gauge that is disposed in a portion that deforms concavely and a second strain gauge that is disposed in a portion that deforms convexly when the strain-generating parts are elastically deformed. For all pairs of two adjacent strain bodies, The strain sensor of one of the adjacent flexure bodies is disposed on the front surface of the flexure part, and the strain sensor of the other flexure body is disposed on the rear surface of the flexure part. Effect of the Invention

[0009] In this type of scale, when the housing cover is bent and the load input direction to the strain body is tilted, the amount of strain in one of the concave portion that deforms concavely and the convex portion that deforms convexly appears large, and the amount of strain in the other portion appears small. This changes the balance between the tensile force and the compressive force generated in each gauge in the single strain sensor.

[0010] As a countermeasure to this, in this embodiment, in order to eliminate the change in the balance between the tensile force and the compressive force generated in each gauge due to the inclination of the load input direction, the strain sensor of one of the pair of strain-generating bodies is arranged on the back surface of the strain-generating part, and the strain sensor of the other strain-generating body is arranged on the front surface of the strain-generating part.

[0011] In one of the flexure bodies, where the strain sensor is arranged on the back surface, for example, the tensile force generated in the first strain gauge arranged in the concave portion is large and the compressive force generated in the second strain gauge arranged in the convex portion is small, whereas in the other flexure body, where the strain sensor is arranged on the front surface, the compressive force generated in the first strain gauge arranged in the concave portion is large and the tensile force generated in the second strain gauge arranged in the convex portion is small.

[0012] Therefore, the influence appearing in the output on the tension side can be suppressed by combining the output of the first strain gauge in one strain body where the tensile force is large and the output of the second strain gauge in the other strain body where the tensile force is small. Also, the influence appearing in the output on the compression side can be suppressed by combining the output of the first strain gauge in the other strain body where the compressive force is large and the output of the second strain gauge in one strain body where the compressive force is small.

[0013] This makes it possible to suppress the effect on instrument error performance even when the input direction of the load input to the strain element is inclined and the difference in strain generated in each strain gauge of the strain sensor provided on each strain element becomes large. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a perspective view showing a scale according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a partially transparent view showing a plan view of the scale according to the first embodiment of the present invention. [Diagram 3] FIG. 3 is a cross-sectional view taken along the line AA in FIG. [Figure 4] FIG. 4 is an enlarged view showing a main part of FIG. [Diagram 5] FIG. 5 is a plan view showing the support according to the first embodiment. [Figure 6] FIG. 6 is an exploded perspective view showing a support according to the first embodiment. [Figure 7] FIG. 7 is a plan view showing the flexure body according to the first embodiment. [Figure 8] FIG. 8 is a plan view showing a strain-flexing part of a strain-flexing body according to the first embodiment and a strain sensor provided on the strain-flexing part. [Figure 9] FIG. 9 is a circuit diagram showing a connection state of the strain gauges of each strain sensor according to the first embodiment. [Figure 10] FIG. 10 is a wiring diagram showing a state in which the strain sensors provided on the respective flexure bodies according to the first embodiment are connected by wiring. [Figure 11]FIG. 11 is a cross-sectional view showing a state of the strain body of the third support when the housing cover according to the first embodiment is bent. [Figure 12] FIG. 12 is a cross-sectional view showing a state of the strain body of the fourth support when the housing cover according to the first embodiment is bent. [Figure 13] FIG. 13 is a circuit diagram showing a connection state of strain gauges of each strain sensor according to the second embodiment. [Figure 14] FIG. 14 is a plan view showing a strain-generating part of a strain-generating body according to the second embodiment and a strain sensor provided on the strain-generating part. [Figure 15] FIG. 15 is a cross-sectional view showing a main part of a scale according to the third embodiment. [Figure 16] FIG. 16 is a circuit diagram showing a connection state of strain gauges of each strain sensor according to the third embodiment. [Figure 17] FIG. 17 is a wiring diagram showing an example of a state in which each strain gauge provided on a flexure element according to the third embodiment is connected by wiring. [Figure 18] FIG. 18 is a circuit diagram showing a connection state of strain gauges of each strain sensor according to the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0016] First Embodiment Fig. 1 is a perspective view showing a scale 10 according to a first embodiment of the present invention, and Fig. 2 is a partially transparent view showing a plan view of the scale 10 according to the first embodiment of the present invention. Also, Fig. 3 is a cross-sectional view taken along line AA in Fig. 1, and Fig. 4 is an enlarged view showing a main part of Fig. 3.

[0017] This scale 10 constitutes a weighing scale for measuring the weight of a user. As shown in Fig. 1, the scale 10 includes a rectangular housing base 12 and a square housing cover 14 disposed on the housing base 12. The weight of a user standing on the housing cover 14 is applied to the housing cover 14.

[0018] In the present embodiment, the case where the housing cover 14 is square-shaped will be described, but the present invention is not limited to this. For example, the housing cover 14 may be rectangular-shaped.

[0019] 2 to 4, the scale 10 includes a first support 20, a second support 22, a third support 24, and a fourth support 26 that support the housing cover 14 on the housing base 12. The supports 20, 22, 24, and 26 are disposed at the four corners of the housing cover 14.

[0020] Fig. 5 is a plan view showing the support body (20, 22, 24, 26) according to the first embodiment, and Fig. 6 is an exploded perspective view showing the support body (20, 22, 24, 26) according to the first embodiment. Fig. 7 is a plan view showing the flexure body (30, 32, 34, 36) according to the first embodiment, showing a state in which the flexure body (30, 32, 34, 36) is provided with the strain sensors (90, 92, 94, 96) described later.

[0021] As shown in Figs. 5 and 6, each of the supports 20, 22, 24, and 26 includes a strain generating body (30, 32, 34, and 36) made of a metal plate.

[0022] Specifically, the first support 20 includes a first flexure body 30, and the second support 22 includes a second flexure body 32. In addition, the third support 24 includes a third flexure body 34, and the fourth support 26 includes a fourth flexure body 36.

[0023] As shown in FIG. 6, each of the flexure bodies 30, 32, 34, 36 has a sheet metal bridge 38 disposed at the top thereof and a mountain-shaped bridge rubber 40 disposed at the top of the sheet metal bridge 38 fixed thereto by a fastening screw 42.

[0024] 4 and 7, each of the flexure bodies 30, 32, 34, 36 has a C-shaped fixing portion 48 that is fixed to a protrusion 46 formed on the housing base 12. In addition, each of the flexure bodies 30, 32, 34, 36 has an E-shaped load receiving portion 50 that is fixed to the housing cover 14 via a sheet metal bridge 38 and a bridge rubber 40.

[0025] Here, the fixed part 48 fixed to the housing base 12 can be rephrased as a fixed part constituting the fixed side. Also, the load receiving part 50 fixed to the housing cover 14 can be rephrased as a movable part constituting the movable side, since it is movable with respect to the fixed part 48.

[0026] In each of the supports 20, 22, 24, 26, the fixing portions 48 of the respective flexure bodies 30, 32, 34, 36 are supported by the housing base 12, and the load receiving portions 50 of the respective flexure bodies 30, 32, 34, 36 support the housing cover 14. As a result, the housing cover 14 is supported by the housing base 12 via the respective flexure bodies 30, 32, 34, 36.

[0027] 7, a triangular lower triangular portion 52 extends inward from the center of the fixed portion 48, and a triangular upper triangular portion 54 extends from the center of the load-receiving portion 50 toward the lower triangular portion 52 of the fixed portion 48. The apex of the lower triangular portion 52 and the apex of the upper triangular portion 54 are connected via a rectangular strain-flexing portion 56, as shown in FIGS. 6 and 7, and the load-receiving portion 50 and the fixed portion 48 are connected via the strain-flexing portion 56.

[0028] Insertion holes 58 are formed at both ends of the fixing portion 48, and the fixing portion 48 is fixed to the protrusion 46 of the housing base 12 by screws inserted into the insertion holes 58. Screw holes 60 are formed at both ends of the load receiving portion 50, as shown in Fig. 6. The sheet metal bridge 38 and the bridge rubber 40 are fixed to the load receiving portion 50 by screwing the fastening screws 42, which have passed through the round holes 62 of the bridge rubber 40 and the round holes 64 of the sheet metal bridge 38, into the screw holes 60.

[0029] An insert nut 66 is provided on the top surface of the bridge rubber 40, and as shown in FIG. 4, by screwing a fixing screw 68 that has passed through the housing cover 14 into the insert nut 66, the housing cover 14 is supported by the load-receiving portions 50 of the strain bodies 30, 32, 34, and 36.

[0030] 6, the sheet metal bridge 38 has drawn portions 70 formed on the outer periphery of the round hole 64 so as to retreat toward the respective strain bodies 30, 32, 34, 36. The drawn portions 70 protrude toward the corresponding strain bodies 30, 32, 34, 36, and the sheet metal bridge 38 is fixed to the respective strain bodies 30, 32, 34, 36 with the drawn portions 70 in surface contact with the load receiving portions 50 of the corresponding strain bodies 30, 32, 34, 36. As a result, a space is secured between the sheet metal bridge 38 and the strain parts 56 to allow the housing cover 14, supported via the bridge rubber 40, to move downward.

[0031] The insertion hole 58 of the fixing part 48 which is fixed to the housing base 12 and the screw hole 60 of the load-receiving part 50 which supports the housing cover 14 via the bridge rubber 40 are arranged on an imaginary straight line 72, and the strain-generating part 56 is arranged on this imaginary straight line 72.

[0032] The strain-flexing portion 56 is formed with a narrower width than the fixed portion 48 and the load-receiving portion 50, and by concentrating the load applied to the load-receiving portion 50 on the strain-flexing portion 56, the strain-flexing portion 56 elastically deforms as the load-receiving portion 50 displaces downward.

[0033] The strain-flexing portion 56 is disposed on an imaginary straight line 72 along which the insertion hole 58 constituting the fixed point to the housing base 12 and the screw hole 60 constituting the fixed point to the housing cover 14 are aligned. As a result, when the load-receiving portion 50 receives a load from the housing cover 14 and is displaced downward, the strain-flexing portion 56 is elastically deformed into an S-shape.

[0034] Specifically, when the load receiving portion 50 is displaced downward and the strain-flexing portion 56 is elastically deformed, as shown in Fig. 4, a downwardly curved portion 80 that deforms into a curved shape protruding downward is formed in the strain-flexing portion 56 on the movable side on which the load receiving portion 50 that supports the housing cover 14 is provided. Also, an upwardly curved portion 82 that deforms into a curved shape protruding upward is formed in the fixed side on which the fixed portion 48 that is fixed to the housing base 12 is provided.

[0035] Here, the downward curved portion 80 that deforms into a curved shape that protrudes downward represents a concave portion that deforms into a concave shape, and the upward curved portion 82 that deforms into a curved shape that protrudes upward represents a concave portion that deforms into a convex shape.

[0036] As shown in FIG. 7, the strain-flexing portion 56 is provided with strain sensors (90, 92, 94, 96) whose resistance value changes in response to expansion and contraction accompanying the elastic deformation of the strain-flexing portion 56.

[0037] Specifically, a first strain sensor 90 is provided on the strain-generating portion 56 of the first flexure body 30, and a second strain sensor 92 is provided on the strain-generating portion 56 of the second flexure body 32. Further, a third strain sensor 94 is provided on the strain-generating portion 56 of the third flexure body 34, and a fourth strain sensor 96 is provided on the strain-generating portion 56 of the fourth flexure body 36.

[0038] FIG. 8 is a plan view showing the strain-generating parts 56 of the strain-generating bodies 30, 32, 34, 36 according to the first embodiment, and the strain sensors 90, 92, 94, 96 provided on the strain-generating parts 56. As shown in FIG.

[0039] Each of the strain sensors 90, 92, 94, 96 is formed in a rectangular shape. Each of the strain sensors 90, 92, 94, 96 has a first strain gauge 90a, 92a, 94a, 96a provided on one side in the longitudinal direction, and a second strain gauge 90b, 92b, 94b, 96b provided on the other side in the longitudinal direction.

[0040] Each of the strain sensors 90, 92, 94, 96 is provided with a pair of triangular longitudinal center marks 100 at the center in the longitudinal direction, and each longitudinal center mark 100 is arranged so that its apex faces outward in the width direction. Each of the strain sensors 90, 92, 94, 96 is provided with a pair of triangular lateral center marks 102 at both ends in the longitudinal direction, and each lateral center mark 102 is arranged so that its apex faces both ends.

[0041] When fixing each of the strain sensors 90, 92, 94, 96 to the strain-flexing part 56, a first mark extending in the length direction through the widthwise center is provided on the strain-flexing part 56, and a second mark extending in the width direction from the lengthwise center is provided. Then, each of the strain sensors 90, 92, 94, 96 is attached and fixed to the strain-flexing part 56 with the apex of the longitudinal width center mark 100 of the corresponding strain sensor 90, 92, 94, 96 aligned with the first mark and the apex of the lateral width center mark 102 aligned with the second mark. This places each of the strain gauges 90a, 92a, 94a, 96a, 90b, 92b, 94b, 96b of each of the strain sensors 90, 92, 94, 96 in a specified position.

[0042] Each of the strain gauges 90a, 92a, 94a, 96a, 90b, 92b, 94b, and 96b includes a resistor 104 that is folded back multiple times, and the electrical resistance of the resistor 104 changes in response to expansion and contraction.

[0043] As a result, the resistance value of each of the strain gauges 90a, 92a, 94a, 96a, 90b, 92b, 94b, and 96b decreases when compressed due to a compressive force, and the resistance value of each of the strain gauges 90a, 92a, 94a, 96a, 90b, 92b, 94b, and 96b increases when stretched due to a tensile force.

[0044] Each of the strain sensors 90, 92, 94, 96 includes a first connection terminal 106a connected to one end of a resistor 104 constituting a first strain gauge 90a, 92a, 94a, 96a. Also, each of the strain sensors 90, 92, 94, 96 includes a second connection terminal 106b connected to one end of a resistor 104 constituting a second strain gauge 90b, 92b, 94b, 96b.

[0045] Furthermore, each of the strain sensors 90, 92, 94, 96 has a third connection terminal 106c connected to the other end of the resistor 104 constituting the first strain gauge 90a, 92a, 94a, 96a and the other end of the resistor 104 constituting the second strain gauge 90b, 92b, 94b, 96b.

[0046] Each of the connection terminals 106a, 106b, and 106c can be referred to as a solder tab.

[0047] With each strain sensor 90 , 92 , 94 , 96 provided on the strain-flexing portion 56 , the first strain gauges 90 a , 92 a , 94 a , 96 a are disposed in the downward curved portion 80 , and the second strain gauges 90 b , 92 b , 94 b , 96 b are disposed in the upward curved portion 82 .

[0048] Of the flexure bodies 30, 32, 34, 36 of the paired supports 20, 22, 24, 26, the strain sensors 90, 94 of one of the flexure bodies 30, 34 are disposed on the lower surface 56d of the flexure part 56. The strain sensors 92, 96 of the other of the flexure bodies 32, 36 are disposed on the upper surface 56u of the flexure part 56.

[0049] Here, the upper surface 56u of the strain-flexing part 56 indicates the front surface of the strain-flexing part 56. The lower surface 56d of the strain-flexing part 56 indicates the back surface of the strain-flexing part 56.

[0050] 2, the supports 20, 22, 24, 26 arranged at four locations on the balance 10 are provided with the flexure bodies 30, 32, 34, 36, and the flexure bodies 30, 32, 34, 36 are arranged at four locations. Of the adjacent flexure bodies 30, 32, 34, 36, one flexure body 30, 34 has the strain sensors 90, 94 arranged on the lower surface 56d of the flexure part 56, and the other flexure body 32, 36 has the strain sensors 92, 96 arranged on the upper surface 56u of the flexure part 56.

[0051] More specifically, in the first support 20 and the fourth support 26 adjacent to each other in the width direction of the scale 10, the first flexure body 30 of the first support 20 has a first strain sensor 90 disposed on the lower surface 56d of the flexure part 56. Moreover, the fourth flexure body 36 of the fourth support 26 has a fourth strain sensor 96 disposed on the upper surface 56u of the flexure part 56.

[0052] In the second support 22 and the third support 24 adjacent to each other in the width direction of the scale 10, the third flexure body 34 of the third support 24 has a strain sensor 94 disposed on the lower surface 56d of the strain portion 56. In addition, the second flexure body 32 of the second support 22 has a second strain sensor 92 disposed on the upper surface 56u of the strain portion 56.

[0053] (Circuit configuration) FIG. 9 is a circuit diagram showing the connection state of the strain gauges 90a, 92a, 94a, 96a, 90b, 92b, 94b, and 96b of the strain sensors 90, 92, 94, and 96 according to the first embodiment, and shows a Wheatstone bridge circuit 110.

[0054] The Wheatstone bridge circuit 110 includes a first side 120, a second side 122, a third side 124, and a fourth side 126. The first side 120 and the third side 124 face each other, and the second side 122 and the fourth side 126 face each other.

[0055] The first side 120 is composed of a series-connected circuit of a second strain gauge 90b of a first strain sensor 90 arranged on the underside 56d of the upward curved portion 82 of the first flexure body 30 and a first strain gauge 96a of a fourth strain sensor 96 arranged on the upper surface 56u of the downward curved portion 80 of the fourth flexure body 36.

[0056] The second side 122 is composed of a series-connected circuit including a second strain gauge 96b of the fourth strain sensor 96 arranged on the upper surface 56u of the upward curved portion 82 of the fourth flexure body 36 and a first strain gauge 94a of the third strain sensor 94 arranged on the lower surface 56d of the downward curved portion 80 of the third flexure body 34.

[0057] The third side 124 is composed of a series-connected circuit including a second strain gauge 94b of the third strain sensor 94 arranged on the lower surface 56d of the upward curved portion 82 of the third flexure body 34 and a first strain gauge 92a of the second strain sensor 92 arranged on the upper surface 56u of the downward curved portion 80 of the second flexure body 32.

[0058] The fourth side 126 is composed of a series-connected circuit including a second strain gauge 92b of a second strain sensor 92 arranged on the upper surface 56u of the upward curved portion 82 of the second flexure body 32 and a first strain gauge 90a of a first strain sensor 90 arranged on the lower surface 56d of the downward curved portion 80 of the first flexure body 30.

[0059] The connection portion between the first side 120 and the fourth side 126 of this Wheatstone bridge circuit 110 constitutes a positive electrode input portion 130 to which a positive electrode is applied, and the connection portion between the second side 122 and the third side 124 constitutes a negative electrode input portion 132 to which a negative electrode is applied. In addition, the connection portion between the third side 124 and the fourth side 126 constitutes a positive electrode output portion 134 that outputs a positive electrode, and the connection portion between the first side 120 and the second side 122 constitutes a negative electrode output portion 136 that outputs a negative electrode.

[0060] The positive output unit 134 and the negative output unit 136 are connected to a control device (not shown). The control device calculates the load applied to the housing cover 14 from the potential between the positive output unit 134 and the negative output unit 136, and displays the calculation result as weight.

[0061] (Wiring diagram) FIG. 10 is a wiring diagram showing a state in which the strain sensors 90, 92, 94, and 96 provided on the respective strain bodies 30, 32, 34, and 36 according to the first embodiment are connected by wiring.

[0062] To specifically describe this wiring, the second connection terminal 106b of the first strain sensor 90 is connected to the first connection terminal 106a of the fourth strain sensor 96 via a first wiring 400. The second connection terminal 106b of the fourth strain sensor 96 is connected to the first connection terminal 106a of the third strain sensor 94 via a second wiring 402.

[0063] The second connection terminal 106b of the third strain sensor 94 is connected to the first connection terminal 106a of the second strain sensor 92 via a third wiring 404. The second connection terminal 106b of the second strain sensor 92 is connected to the first connection terminal 106a of the first strain sensor 90 via a fourth wiring 406.

[0064] The third connection terminal 106c of the first strain sensor 90 constitutes a positive electrode input section 130 and is applied with a positive electrode. The third connection terminal 106c of the third strain sensor 94 constitutes a negative electrode input section 132 and is applied with a negative electrode.

[0065] The third connection terminal 106c of the second strain sensor 92 constitutes the positive output section 134 and outputs a positive pole. The third connection terminal 106c of the fourth strain sensor 96 constitutes the negative output section 136 and outputs a negative pole.

[0066] In this embodiment, the first strain sensor 90 and the third strain sensor 94 are provided on the lower surfaces of the first flexure body 30 of the first support 20 and the third flexure body 34 of the third support 24. Also, a case will be described in which the second strain sensor and the fourth strain sensor 96 are provided on the upper surfaces of the second flexure body 32 of the second support 22 and the fourth flexure body 36 of the fourth support 26, but the present invention is not limited to this.

[0067] For example, a first strain sensor 90 and a third strain sensor 94 may be provided on the upper surfaces of the first flexure body 30 of the first support 20 and the third flexure body 34 of the third support 24. A second strain sensor 92 and a fourth strain sensor 96 may be provided on the lower surfaces of the second flexure body 32 of the second support 22 and the fourth flexure body 36 of the fourth support 26.

[0068] (Action and Effects) Next, the effects of this embodiment will be described.

[0069] The scale 10 of this embodiment includes a housing base 12 and a housing cover 14 that is disposed on the housing base 12 and to which a load is applied. The scale 10 includes a plurality of strain-generating bodies 30, 32, 34, 36 that support the housing cover 14 on the housing base 12 and have strain-generating parts 56 that elastically deform when subjected to a load applied to the housing cover 14. The scale 10 also includes strain sensors 90, 92, 94, 96 that are provided on the strain-generating parts 56 of the respective strain-generating bodies 30, 32, 34, 36 and whose resistance values ​​change in response to expansion and contraction accompanying the deformation of the strain-generating parts 56.

[0070] Each of the strain sensors 90, 92, 94, 96 includes a first strain gauge 90a, 92a, 94a, 96a arranged in a portion that deforms concavely when the strain-flexing portion 56 is elastically deformed. Also, each of the strain sensors 90, 92, 94, 96 includes a second strain gauge 90b, 92b, 94b, 96b arranged in a portion that deforms convexly when the strain-flexing portion 56 is elastically deformed.

[0071] The strain sensors 90, 92, 94, 96 of one of the adjacent flexure bodies 30, 32, 34, 36 are disposed on the front surface of the flexure part 56. The strain sensors 90, 92, 94, 96 of the other of the adjacent flexure bodies 30, 32, 34, 36 are disposed on the back surface of the flexure part 56.

[0072] In addition, in this embodiment, the flexure body includes, as an example, a first flexure body 30 having a first strain sensor 90 provided on its upper surface, and a second flexure body 32 arranged adjacent to the first flexure body 30 and having a second strain sensor 92 provided on its lower surface.

[0073] In this configuration, when the housing cover 14 is bent and the direction of the load applied to the strain bodies 30, 32, 34, and 36 is tilted, the amount of distortion of one of the downward curved portion 80 and the upward curved portion 82 is large. Also, the amount of distortion of the other of the downward curved portion 80 and the upward curved portion 82 is small.

[0074] As a result, the balance between the tensile force and the compressive force acting on each of the strain gauges 90a, 92a, 94a, 96a, 90b, 92b, 94b, 96b in each of the strain sensors 90, 92, 94, 96 changes.

[0075] In this embodiment, the strain sensors 90, 94 of one of the pair of flexure bodies 30, 34 are arranged on the lower surface 56d of the flexure part 56, and the strain sensors 92, 96 of the other flexure bodies 32, 36 are arranged on the upper surface 56u of the flexure part 56.

[0076] In one of the flexure bodies 30, 34 in which the strain sensors 90, 94 are arranged on the lower surface 56d, for example, a large tensile force is generated in the first strain gauges 90a, 94a arranged in the downward curved portion 80. In addition, a small compressive force is generated in the second strain gauges 90b, 94b arranged in the upward curved portion 82.

[0077] On the other hand, in the other flexure body 32, 36 in which the strain sensors 92, 96 are arranged on the upper surface 56u, a large compressive force is generated in the first strain gauges 92a, 96a arranged in the downward curved portion 80. Also, a small tensile force is generated in the second strain gauges 92b, 96b arranged in the upward curved portion 82.

[0078] Therefore, by combining the output of the first strain gauge 90a, 94a of one of the strain bodies 30, 34 where the tensile force is large, and the output of the second strain gauge 92b, 96b of the other strain body 32, 36 where the tensile force is small, the influence on the output on the tensile side can be suppressed.

[0079] In addition, by combining the output of the first strain gauge 92a, 96a of the other strain body 32, 36 where the compressive force is large and the output of the second strain gauge 90b, 94b of the other strain body 30, 34 where the compressive force is small, the effect of the compression side output can be suppressed.

[0080] Here, if the housing cover 14 is deflected and the load input direction to each of the strain bodies 30, 32, 34, 36 is tilted, the difference in strain generated in each of the strain gauges 90a, 92a, 94a, 96a, 90b, 92b, 94b, 96b of each of the strain sensors 90, 92, 94, 96 will become large. However, even in this case, it is possible to suppress the influence on the instrument error performance.

[0081] Even if the housing cover 14 is bent, the influence on the instrument error performance can be suppressed, so the housing cover 14 can be formed thin. This makes it possible to reduce the cost and weight of the scale 10.

[0082] In this embodiment, the flexure bodies 30, 32, 34, 36 are disposed at four locations, and one of the flexure bodies 30, 34 among the adjacent flexure bodies 30, 32, 34, 36 has the strain sensors 90, 94 disposed on the lower surface 56d of the flexure body 30, 34. The other of the adjacent flexure bodies 30, 32, 34, 36 has the strain sensors 92, 96 disposed on the upper surface 56u of the flexure portion 56.

[0083] According to this configuration, the support state of the housing cover 14 is stabilized, and the influence on the instrument error performance caused by the bending of the housing cover 14 can be further suppressed.

[0084] A specific description will be given with reference to Figures 11 and 12. Figure 11 is a cross-sectional view showing the state of the third flexure body 34 of the third support body 24 when the housing cover 14 according to the first embodiment is deflected, and Figure 12 is a cross-sectional view showing the state of the fourth flexure body 36 of the fourth support body 26 when the housing cover 14 according to the first embodiment is deflected. Figures 11 and 12 show a state in which the central part of the housing cover 14 is deflected so as to protrude downward due to an applied load.

[0085] 11, in this state, in the third strain sensor 94 disposed on the lower surface 56d of the third flexure body 34 of the third support 24, the tensile force generated in the first strain gauge 94a disposed in the downward curved portion 80 becomes large, and the compressive force generated in the second strain gauge 94b disposed in the upward curved portion 82 becomes small.

[0086] Moreover, the first support 20 arranged diagonally from the third support 24 has a first strain sensor 90 arranged on the lower surface 56d of the first flexure body 30. For this reason, similarly to the third support 24, in the first strain sensor 90 of the first support 20, the tensile force generated in the first strain gauge 90a arranged in the downward curved portion 80 becomes large, and the compressive force generated in the second strain gauge 90b arranged in the upward curved portion 82 becomes small.

[0087] 12, in the fourth strain sensor 96 disposed on the upper surface 56u of the fourth flexure body 36 of the fourth support 26, the compressive force generated in the first strain gauge 96a disposed in the downward curved portion 80 becomes large, and the tensile force generated in the second strain gauge 96b disposed in the upward curved portion 82 becomes small.

[0088] In addition, the second support 22 arranged diagonally from the fourth support 26 has a second strain sensor 92 arranged on the upper surface 56u of the second flexure body 32. Therefore, similar to the fourth support 26, in the second strain sensor 92 of the second support 22, the compressive force generated in the first strain gauge 92a arranged in the downward curved portion 80 becomes large, and the tensile force generated in the second strain gauge 92b arranged in the upward curved portion 82 becomes small.

[0089] As shown in FIG. 9, the first arm 120 of the Wheatstone bridge circuit 110 is composed of a series-connected circuit of the second strain gauge 90b of the first strain sensor 90, which indicates a small compressive force, and the first strain gauge 96a of the fourth strain sensor 96, which indicates a large compressive force.

[0090] The second arm 122 of the Wheatstone bridge circuit 110 is composed of a series circuit of the second strain gauge 96b of the fourth strain sensor 96, in which a small tensile force is detected, and the first strain gauge 94a of the third strain sensor 94, in which a large tensile force is detected.

[0091] The third side 124 opposite the first side 120 is configured with a series connection circuit of the second strain gauge 94b of the third strain sensor 94, which indicates a small compressive force, and the first strain gauge 92a of the second strain sensor 92, which indicates a large compressive force.

[0092] In addition, the fourth side 126 opposite the second side 122 is configured as a series connection circuit of the second strain gauge 92b of the second strain sensor 92, in which a small tensile force is detected, and the first strain gauge 90a of the first strain sensor 90, in which a large tensile force is detected.

[0093] Here, when the load input direction to each of the flexure bodies 30, 32, 34, 36 is tilted, the difference in strain generated in each of the strain gauges 90a, 92a, 94a, 96a, 90b, 92b, 94b, 96b of each of the strain sensors 90, 92, 94, 96 increases. Even in such a case, the influence on the resistance value of each of the sides 120, 122, 124, 126 can be suppressed. Therefore, the potential difference balance in the Wheatstone bridge circuit 110 can be maintained.

[0094] In this way, by combining the strain gauges 90a, 94a, which show a large tensile force, with the strain gauges 92b, 96b, which show a small tensile force, the influence on the tensile side can be suppressed. Also, by combining the strain gauges 92a, 96a, which show a large compressive force, with the strain gauges 90b, 94b, which show a small compressive force, the influence on the compressive side can be suppressed.

[0095] Therefore, even if the difference in strain generated in each of the strain gauges 90a, 92a, 94a, 96a, 90b, 92b, 94b, and 96b of the strain sensors 90, 92, 94, and 96 due to bending of the housing cover 14 increases, it is possible to suppress the effect on the instrumental error performance.

[0096] In this embodiment, the strain sensor (90, 92, 94, 96) includes a first connection terminal 106a connected to one end of the first strain gauge 90a, 92a, 94a, 96a and a second connection terminal 106b connected to one end of the second strain gauge 90b, 92b, 94b, 96b. The strain sensor (90, 92, 94, 96) also includes a third connection terminal 106c connected to the other end of the first strain gauge 90a, 92a, 94a, 96a and the other end of the second strain gauge 90b, 92b, 94b, 96b.

[0097] According to this configuration, it is not necessary to connect the other ends of the first strain gauges 90a, 92a, 94a, 96a to the other ends of the second strain gauges 90b, 92b, 94b, 96b by wiring, which facilitates wiring work.

[0098] In this embodiment, the scale 10 is described as having the strain bodies 30, 32, 34, and 36 that respectively support the four corners of the housing cover 14, but this is not limited to this, and it is sufficient that there are at least two strain bodies that support the housing cover 14 and detect the load.

[0099] Second Embodiment 13 is a circuit diagram showing the connection state of the strain sensors 90, 92 according to the second embodiment, and shows a Wheatstone bridge circuit 140. The scale 10 according to the second embodiment differs from the first embodiment in that the strain body that supports the housing cover 14 and detects the load is composed of a first strain body 30 and a second strain body 32. Parts that are the same as or equivalent to those in the first embodiment are given the same reference numerals and will not be described.

[0100] 13, a first side 150 of the Wheatstone bridge circuit 140 is composed of the second strain gauge 90b of the first strain sensor 90 in which a compressive force is small, and a second side 152 of the Wheatstone bridge circuit 140 is composed of the first strain gauge 92a of the first strain sensor 90 in which a tensile force is large.

[0101] The third side 154 opposite the first side 150 is composed of the first strain gauge 92a of the second strain sensor 92 in which a compressive force is large, and the fourth side 156 opposite the second side 152 is composed of the second strain gauge 92b of the second strain sensor 92 in which a tensile force is small.

[0102] The connection portion between the first side 150 and the fourth side 156 of this Wheatstone bridge circuit 140 constitutes a positive electrode input portion 130 to which a positive electrode is applied, and the connection portion between the second side 152 and the third side 154 constitutes a negative electrode input portion 132 to which a negative electrode is applied. In addition, the connection portion between the third side 154 and the fourth side 156 constitutes a positive electrode output portion 134 that outputs a positive electrode, and the connection portion between the first side 150 and the second side 152 constitutes a negative electrode output portion 136 that outputs a negative electrode.

[0103] The positive electrode output unit 134 and the negative electrode output unit 136 are connected to a control device (not shown), and the control device calculates the load applied to the housing cover 14 from the potential between the positive electrode output unit 134 and the negative electrode output unit 136, and displays the calculation result as body weight.

[0104] 14 is a plan view showing the strain-flexing portion 56 of each of the strain-flexing bodies 30, 32 (34, 36) according to the second embodiment, and the strain sensors 90, 92 (94, 96) provided on the strain-flexing portion 56. The strain sensors 90, 92 (94, 96) have a different number of connection terminals compared to the strain sensors 90, 92, 94, 96 used in the first embodiment.

[0105] The strain sensors 90, 92 (94, 96) are used in the second and subsequent embodiments. Therefore, reference numerals that are not used in the second embodiment are written in parentheses.

[0106] The strain sensors 90, 92 (94, 96) each include a first connection terminal 106-1 connected to one end of the resistor 104 constituting the first strain gauge 90a, 92a (94a, 96a). The strain sensors 90, 92 (94, 96) each include a second connection terminal 106-2 connected to the other end of the resistor 104 constituting the first strain gauge 90a, 92a (94a, 96a).

[0107] Furthermore, the strain sensors 90, 92 (94, 96) include a third connection terminal 106-3 connected to one end of the resistor 104 constituting the second strain gauge 90b, 92b (94b, 96b). The strain sensors 90, 92 (94, 96) also include a fourth connection terminal 106-4 connected to the other end of the resistor 104 constituting the second strain gauge 90b, 92b (94b, 96b).

[0108] In this embodiment, a case will be described in which the first strain sensor 90 is provided on the upper surface 56u of the first flexure body 30 and the second strain sensor 92 is provided on the lower surface 56d of the second flexure body 32, but the present invention is not limited to this. For example, the first strain sensor 90 may be provided on the lower surface 56d of the first flexure body 30 and the second strain sensor 92 may be provided on the upper surface 56u of the second flexure body 32.

[0109] (Action and Effects) In this embodiment, a combination of a first side 150 and a third side 154, and a combination of a second side 152 and a fourth side 156 that affect the outputs of the positive output section 134 and the negative output section 136 in the Wheatstone bridge circuit 140 will be described.

[0110] The first side 150 and the third side 154 are configured by a combination of the second strain gauge 90b of the first strain sensor 90 which indicates a small compressive force and the first strain gauge 92a of the second strain sensor 92 which indicates a large compressive force. The second side 152 and the fourth side 156 are configured by a combination of the first strain gauge 90a of the first strain sensor 90 which indicates a large tensile force and the second strain gauge 92b of the second strain sensor 92 which indicates a small tensile force.

[0111] Here, when the input direction of the load to each of the flexure bodies 30, 32 is tilted, the difference in strain generated in each of the strain gauges 90a, 90b, 92a, 92b of each of the strain sensors 90, 92 provided on each of the flexure bodies 30, 32 becomes large. Even in such a case, the influence on the output from the positive electrode output unit 134 and the negative electrode output unit 136 can be suppressed.

[0112] Therefore, even if the deflection of the housing cover 14 tilts the input direction of the load to each of the strain gauges 30, 32 and the difference in strain generated in each of the strain gauges 90a, 90b, 92a, 92b of each of the strain sensors 90, 92 increases, it is possible to suppress the effect on the instrument error performance.

[0113] In this embodiment, the strain sensor (90, 92) includes a first connection terminal 106-1 connected to one end of the first strain gauge 90a, 92a (94a, 96a) and a second connection terminal 106-2 connected to the other end of the first strain gauge 90a, 92a (94a, 96a). The strain sensor (90, 92) also includes a third connection terminal 106-3 connected to one end of the second strain gauge 90b, 92b (94b, 96b) and a fourth connection terminal 106-4 connected to the other end of the second strain gauge 90b, 92b (94b, 96b).

[0114] According to this configuration, wiring can be connected to each of the connection terminals 106-1, 106-2, 106-3, and 106-4 of each of the strain gauges 90a, 92a, 94a (96a, 90b), and 92b (94b, 96b), thereby increasing the degree of freedom in circuit configuration.

[0115] <Third embodiment> 15 is a cross-sectional view showing a main part of a scale 160 according to a third embodiment, and shows a strain generating body according to the third embodiment. In this third embodiment, the same or equivalent parts as those in the first embodiment are denoted by the same reference numerals and the description thereof will be omitted, and only the different parts will be described.

[0116] Each of the flexure bodies 30, 32, 34, 36 according to the third embodiment includes a load receiving portion 50 and a fixed portion 48, similar to the first embodiment (only the third flexure body 34 is shown in FIG. 15). Each of the flexure bodies 30, 32, 34, 36 includes a strain generating portion 56 that connects the load receiving portion 50 to the fixed portion 48 and elastically deforms in association with downward displacement of the load receiving portion 50. Each of the flexure bodies 30, 32, 34, 36 also includes strain sensors (170, 172, 174, 176, 180, 182, 184, 186) that are provided in the strain generating portion 56 and whose resistance value changes in response to expansion and contraction associated with elastic deformation of the strain generating portion 56.

[0117] The strain sensors (170, 180) include a first lower strain sensor 170 arranged on the lower surface 56d of the strain-generating portion 56 of the first flexure body 30, and a first upper strain sensor 180 arranged on the upper surface 56u of the first flexure body 30. The strain sensors (172, 182) include a second lower strain sensor 172 arranged on the lower surface 56d of the strain-generating portion 56 of the second flexure body 32, and a second upper strain sensor 182 arranged on the upper surface 56u of the second flexure body 32.

[0118] Here, the first lower strain sensor 170 arranged on the lower surface 56d of the strain-generating part 56 of the first flexure body 30 indicates a first back surface strain sensor arranged on the back surface of the strain-generating part 56 of the first flexure body 30. The first upper strain sensor 180 arranged on the upper surface 56u of the first flexure body 30 indicates a first surface strain sensor arranged on the surface of the first flexure body 30.

[0119] Further, the second lower strain sensor 172 arranged on the lower surface 56d of the strain generating portion 56 of the second flexure body 32 indicates a second back surface strain sensor arranged on the back surface of the strain generating portion 56 of the second flexure body 32. The second upper strain sensor 182 arranged on the upper surface 56u of the second flexure body 32 indicates a second surface strain sensor arranged on the surface of the second flexure body 32.

[0120] The strain sensors (174, 184) include a third lower strain sensor 174 arranged on the lower surface 56d of the strain-generating portion 56 of the third flexure body 34, and a third upper strain sensor 184 arranged on the upper surface 56u of the third flexure body 34. The strain sensors (176, 186) include a fourth lower strain sensor 176 arranged on the lower surface 56d of the strain-generating portion 56 of the fourth flexure body 36, and a fourth upper strain sensor 186 arranged on the upper surface 56u of the fourth flexure body 36.

[0121] Here, the third lower strain sensor 174 arranged on the lower surface 56d of the strain-generating part 56 of the third flexure body 34 indicates a third back surface strain sensor arranged on the back surface of the strain-generating part 56 of the third flexure body 34. The third upper strain sensor 184 arranged on the upper surface 56u of the third flexure body 34 indicates a third surface strain sensor arranged on the surface of the third flexure body 34.

[0122] Further, the fourth lower strain sensor 176 arranged on the lower surface 56d of the strain-generating portion 56 of the fourth flexure body 36 represents a fourth back surface strain sensor arranged on the back surface of the strain-generating portion 56 of the fourth flexure body 36. The fourth upper strain sensor 186 arranged on the upper surface 56u of the fourth flexure body 36 represents a fourth surface strain sensor arranged on the surface of the fourth flexure body 36.

[0123] Each of the strain sensors 170, 172, 174, 176, 180, 182, 184, 186 has a first strain gauge 170a, 172a, 174a, 176a, 180a, 182a, 184a, 186a arranged in the downward curved portion 80 of the strain-flexing portion 56. Also, each of the strain sensors 170, 172, 174, 176, 180, 182, 184, 186 has a second strain gauge 170b, 172b, 174b, 176b, 180b, 182b, 184b, 186b arranged in the upward curved portion 82 (see FIG. 8).

[0124] When fixing each of the strain sensors 170, 172, 174, 176, 180, 182, 184, 186 to the strain-flexing portion 56, the apex of the longitudinal center mark 100 of each of the strain sensors 170, 172, 174, 176, 180, 182, 184, 186 is aligned with the first scribed line of the strain-flexing portion 56. Also, the apex of the transverse center mark 102 is aligned with the second scribed line of the strain-flexing portion 56. In this state, each of the strain sensors 170, 172, 174, 176, 180, 182, 184, 186 is fixed to the strain-flexing portion 56.

[0125] As a result, the strain gauges 170a, 172a, 174a, 176a of the lower strain sensors 170, 172, 174, 176 and the strain gauges 180a, 182a, 184a, 186a of the upper strain sensors 180, 182, 184, 186 are disposed at positions corresponding to each other.

[0126] The scale 160 according to the third embodiment includes the above-mentioned flexure bodies 30, 32, 34, 36, and a housing cover 14 supported by the load receiving portions 50 of the flexure bodies 30, 32, 34, 36. The scale 160 according to the third embodiment also includes a housing base 12 supporting the fixing portions 48 of the flexure bodies 30, 32, 34, 36.

[0127] The housing cover 14 is rectangular in shape, as in the first embodiment. The four corners of the housing cover 14 are supported by the supports 20, 22, 24, and 26, and the above-mentioned flexure bodies 30, 32, 34, and 36 are provided on the supports 20, 22, 24, and 26. As a result, the flexure bodies 30, 32, 34, and 36 are disposed at the four corners of the housing cover 14.

[0128] (Circuit configuration) FIG. 16 is a circuit diagram showing the connection state of each of the strain gauges of the strain sensors 170, 172, 174, 176, 180, 182, 184, and 186 according to the third embodiment.

[0129] In this circuit diagram, a first Wheatstone bridge circuit 190, a second Wheatstone bridge circuit 192, a third Wheatstone bridge circuit 194, and a fourth Wheatstone bridge circuit 196 are connected in parallel.

[0130] The first Wheatstone bridge circuit 190 is composed of a first lower strain sensor 170 arranged on the lower surface 56d of the first flexure body 30 and a first upper strain sensor 180 arranged on the upper surface 56u of the first flexure body 30.

[0131] A first arm 200 of the first Wheatstone bridge circuit 190 is composed of the first strain gauge 180a of the first upper strain sensor 180, which exhibits a large compressive force. A second arm 202 of the first Wheatstone bridge circuit 190 is composed of the second strain gauge 180b of the first upper strain sensor 180, which exhibits a small tensile force.

[0132] The third side 204 opposite the first side 200 is composed of the second strain gauge 170b of the first lower strain sensor 170, in which a compressive force is small, and the fourth side 206 opposite the second side 202 is composed of the first strain gauge 170a of the first lower strain sensor 170, in which a tensile force is large.

[0133] A connection portion between the first side 200 and the fourth side 206 of the first Wheatstone bridge circuit 190 is connected to a positive electrode input portion 130 to which a positive electrode is applied, and a connection portion between the second side 202 and the third side 204 is connected to a negative electrode input portion 132 to which a negative electrode is applied. In addition, a connection portion between the third side 204 and the fourth side 206 is connected to a positive electrode output portion 134 that outputs a positive electrode, and a connection portion between the first side 200 and the second side 202 is connected to a negative electrode output portion 136 that outputs a negative electrode.

[0134] The second Wheatstone bridge circuit 192 is composed of a second lower strain sensor 172 arranged on the lower surface 56d of the second flexure body 32 and a second upper strain sensor 182 arranged on the upper surface 56u of the second flexure body 32.

[0135] A first side 210 of the second Wheatstone bridge circuit 192 is composed of the first strain gauge 182a of the second upper strain sensor 182 which exhibits a large compressive force. A second side 212 of the second Wheatstone bridge circuit 192 is composed of the second strain gauge 182b of the second upper strain sensor 182 which exhibits a small tensile force. A third side 214 facing the first side 210 is composed of the second strain gauge 172b of the second lower strain sensor 172 which exhibits a small compressive force, and a fourth side 216 facing the second side 212 is composed of the first strain gauge 172a of the second lower strain sensor 172 which exhibits a large tensile force.

[0136] A connection portion between the first side 210 and the fourth side 216 of the second Wheatstone bridge circuit 192 is connected to the positive electrode input section 130, and a connection portion between the second side 212 and the third side 214 is connected to the negative electrode input section 132. In addition, a connection portion between the third side 214 and the fourth side 216 is connected to the positive electrode output section 134, and a connection portion between the first side 210 and the second side 212 is connected to the negative electrode output section 136.

[0137] The third Wheatstone bridge circuit 194 is composed of a third lower strain sensor 174 arranged on the lower surface 56d of the third flexure body 34 and a third upper strain sensor 184 arranged on the upper surface 56u of the third flexure body 34.

[0138] A first arm 220 of the third Wheatstone bridge circuit 194 is formed of the first strain gauge 184a of the third upper strain sensor 184, which exhibits a large compressive force. A second arm 222 of the third Wheatstone bridge circuit 194 is formed of the second strain gauge 184b of the third upper strain sensor 184, which exhibits a small tensile force.

[0139] The third side 224 opposite the first side 220 is composed of the second strain gauge 174b of the third lower strain sensor 174, in which a small compressive force is detected, and the fourth side 226 opposite the second side 222 is composed of the first strain gauge 174a of the third lower strain sensor 174, in which a large tensile force is detected.

[0140] A connection portion between the first side 220 and the fourth side 226 of the third Wheatstone bridge circuit 194 is connected to the positive electrode input section 130, and a connection portion between the second side 222 and the third side 224 is connected to the negative electrode input section 132. In addition, a connection portion between the third side 224 and the fourth side 226 is connected to the positive electrode output section 134, and a connection portion between the first side 220 and the second side 222 is connected to the negative electrode output section 136.

[0141] The fourth Wheatstone bridge circuit 196 is composed of a fourth lower strain sensor 176 arranged on the lower surface 56d of the fourth flexure body 36 and a fourth upper strain sensor 186 arranged on the upper surface 56u of the fourth flexure body 36.

[0142] A first arm 230 of the fourth Wheatstone bridge circuit 196 is made up of the first strain gauge 186a of the fourth upper strain sensor 186 which exhibits a large compressive force. A second arm 232 of the fourth Wheatstone bridge circuit 196 is made up of the second strain gauge 186b of the fourth upper strain sensor 186 which exhibits a small tensile force.

[0143] The third side 234 opposite the first side 230 is composed of the second strain gauge 176b of the fourth lower strain sensor 176, which indicates a small compressive force, and the fourth side 236 opposite the second side 232 is composed of the first strain gauge 176a of the fourth lower strain sensor 176, which indicates a large tensile force.

[0144] A connection portion between the first side 230 and the fourth side 236 of the fourth Wheatstone bridge circuit 196 is connected to the positive electrode input section 130, and a connection portion between the second side 232 and the third side 234 is connected to the negative electrode input section 132. In addition, a connection portion between the third side 234 and the fourth side 236 is connected to the positive electrode output section 134, and a connection portion between the first side 230 and the second side 232 is connected to the negative electrode output section 136.

[0145] The positive electrode output unit 134 and the negative electrode output unit 136 are connected to a control device (not shown), and the control device calculates the load applied to the housing cover 14 from the potential between the positive electrode output unit 134 and the negative electrode output unit 136, and displays the calculation result as body weight.

[0146] FIG. 17 is a wiring diagram showing an example of a state in which the strain gauges 170a, 172a, 170b, 172b, 180a, 182a, 180b, and 182b provided on the flexure bodies 30, 32, 34, and 36 according to the third embodiment are connected by wiring.

[0147] 17, a wiring board 410 is provided on the upper surface of each of the flexure bodies 30, 32, 34, 36. A first wiring pattern 412 having a positive electrode input portion 130 at one end, and a second wiring pattern 414 having a negative electrode input portion 132 at one end are formed on the wiring board 410. In addition, a third wiring pattern 416 having a positive electrode output portion 134 at one end, and a fourth wiring pattern 418 having a negative electrode output portion 136 at one end are formed on the wiring board 410.

[0148] At the other end of the first wiring pattern 412, lands c and e are formed, and at the other end of the second wiring pattern 414, lands b and f are formed.

[0149] The other end of the third wiring pattern 416 is bifurcated, with a land a formed at one end of the bifurcation and a land g formed at the other end. The other end of the fourth wiring pattern 418 is bifurcated, with a land d formed at one end of the bifurcation and a land h formed at the other end.

[0150] The lands c of the first wiring pattern 412 are connected to the first connection terminals 106-1 of the corresponding lower strain sensors 170, 172, 174, 176 provided on the lower surfaces of the flexure bodies 30, 32, 34, 36. The lands e of the first wiring pattern 412 are connected to the second connection terminals 106-2 of the corresponding upper strain sensors 180, 182, 184, 186 provided on the upper surfaces of the flexure bodies 30, 32, 34, 36.

[0151] The land b of the second wiring pattern 414 is connected to the third connection terminal 106-3 of the corresponding lower strain sensor 170, 172, 174, 176 provided on the lower surface of each of the flexure bodies 30, 32, 34, 36. In addition, the land f of the second wiring pattern 414 is connected to the fourth connection terminal 106-4 of the corresponding upper strain sensor 180, 182, 184, 186 provided on the upper surface of each of the flexure bodies 30, 32, 34, 36.

[0152] The land a of the third wiring pattern 416 is connected to the fourth connection terminal 106-4 of the corresponding lower strain sensor 170, 172, 174, 176 provided on the lower surface of each of the flexure bodies 30, 32, 34, 36. In addition, the land g of the third wiring pattern 416 is connected to the second connection terminal 106-2 of the corresponding lower strain sensor 170, 172, 174, 176 provided on the lower surface of each of the flexure bodies 30, 32, 34, 36.

[0153] The lands d of the fourth wiring pattern 418 are connected to the third connection terminals 106-3 of the corresponding upper strain sensors 180, 182, 184, 186 provided on the upper surfaces of the flexure bodies 30, 32, 34, 36. The lands h of the fourth wiring pattern 418 are connected to the first connection terminals 106-1 of the corresponding upper strain sensors 180, 182, 184, 186 provided on the upper surfaces of the flexure bodies 30, 32, 34, 36.

[0154] In this manner, the wiring board 410 is connected by wires to the connection terminals 106-1, 106-2, 106-3, and 106-4 of the strain sensors 170, 172, 174, 176, 180, 182, 184, and 186. In this manner, the Wheatstone bridge circuits 190, 192, 194, and 196 are formed.

[0155] The flexure bodies 30, 32, 34, 36 are provided with the strain gauges 170a-176a, 170b-176b, 180a-186a, 180b-186b, and wiring that forms the Wheatstone bridge circuits 190, 192, 194, 196. A load cell 420 is formed by the flexure bodies 30, 32, 34, 36, the strain gauges 170a-176a, 170b-176b, 180a-186a, 180b-186b, and the wiring.

[0156] Although the structure in which the Wheatstone bridge circuits 190, 192, 194, and 196 are formed using the wiring board 410 has been described as being applied to this embodiment, the present invention is not limited to this. The structure in which the Wheatstone bridge circuits 190 and 192 are formed using the wiring board 410 may be applied to, for example, the fourth embodiment.

[0157] In this embodiment, the Wheatstone bridge circuits 190, 192, 194, and 196 are configured as follows.

[0158] That is, the first sides 200, 210, 220, 230 and the second sides 202, 212, 222, 232 are configured with the respective strain gauges 180a, 182a, 184a, 186a, 180b, 182b, 184b, 186b of the respective upper strain sensors 180, 182, 184, 186. The third sides 204, 214, 224, 234 and the fourth sides 206, 216, 226, 236 are configured with the respective strain gauges 170a, 172a, 174a, 176a, 170b, 172b, 174b, 176b of the respective lower strain sensors 170, 172, 174, 176. However, the present invention is not limited to this configuration.

[0159] For example, the first sides 200, 210, 220, 230 and the second sides 202, 212, 222, 232 may be formed of the respective strain gauges 170a, 172a, 174a, 176a, 170b, 172b, 174b, 176b of the lower strain sensors 170, 172, 174, 176. Also, the third sides 204, 214, 224, 234 and the fourth sides 206, 216, 226, 236 may be formed of the respective strain gauges 180a, 182a, 184a, 186a, 180b, 182b, 184b, 186b of the respective upper strain sensors 180, 182, 184, 186.

[0160] In addition, in the present embodiment, the Wheatstone bridge circuits 190, 192, 194, and 196 are connected in parallel to form an average value circuit that calculates an average value, but the present invention is not limited to this. For example, the outputs of the Wheatstone bridge circuits 190, 192, 194, and 196 may be added together.

[0161] (Action and Effects) Each of the flexure bodies 30, 32, 34, 36 in this embodiment includes a load receiving portion 50 that receives a load, and a fixed portion 48 that is fixed to an object to be attached. Each of the flexure bodies 30, 32, 34, 36 also includes a strain generating portion 56 that connects the load receiving portion 50 and the fixed portion 48 and elastically deforms in association with downward displacement of the load receiving portion 50. Each of the flexure bodies 30, 32, 34, 36 also includes a strain sensor (170, 172, 174, 176, 180, 182, 184, 186) that is provided in the strain generating portion 56 and whose resistance value changes in response to expansion and contraction associated with elastic deformation of the strain generating portion 56.

[0162] Each of the strain sensors 170, 172, 174, 176, 180, 182, 184, 186 has a first strain gauge 170a, 172a, 174a, 176a, 180a, 182a, 184a, 186a arranged in the downward curved portion 80. Also, each of the strain sensors 170, 172, 174, 176, 180, 182, 184, 186 has a second strain gauge 170b, 172b, 174b, 176b, 180b, 182b, 184b, 186b arranged in the upward curved portion 82.

[0163] Further, each of the strain sensors 170, 172, 174, 176, 180, 182, 184, 186 has a lower strain sensor 170, 172, 174, 176 arranged on the lower surface 56d of the strain-flexing part 56. Further, each of the strain sensors 170, 172, 174, 176, 180, 182, 184, 186 has an upper strain sensor 180, 182, 184, 186 arranged on the upper surface 56u of the strain-flexing part 56.

[0164] In each of the flexure bodies 30, 32, 34, 36 in this configuration, lower strain sensors 170, 172, 174, 176 are arranged on the lower surface 56d of the flexure part 56, and upper strain sensors 180, 182, 184, 186 are arranged on the upper surface 56u of the flexure bodies 30, 32, 34, 36.

[0165] Additionally, each of the strain sensors 170, 172, 174, 176, 180, 182, 184, 186 has a first strain gauge 170a, 172a, 174a, 176a, 180a, 182a, 184a, 186a arranged in the downward curved portion 80. Additionally, each of the strain sensors 170, 172, 174, 176, 180, 182, 184, 186 has a second strain gauge 170b, 172b, 174b, 176b, 180b, 182b, 184b, 186b arranged in the upward curved portion 82.

[0166] Here, when the input direction of the load to each of the strain generating bodies 30, 32, 34, 36 is tilted, the amount of strain in one of the downward curved portion 80 that deforms into a curved shape protruding downward and the upward curved portion 82 that deforms into a curved shape protruding upward appears large, and the amount of strain in the other portion appears small. This changes the balance between the tensile force and the compressive force generated in each of the strain gauges 170a, 172a, 174a, 176a, 180a, 182a, 184a, 186a, 170b, 172b, 174b, 176b, 180b, 182b, 184b, 186b of each strain sensor.

[0167] Therefore, by combining the output of the strain gauge of one strain sensor in which the strain amount is large with the output of the strain gauge of the other strain sensor in which the strain amount is small, the influence appearing in the output can be suppressed.

[0168] Therefore, even if the deflection of the housing cover 14 tilts the direction of the load input to each of the strain elements 30, 32, 34, 36 and the difference in strain generated in each strain gauge of each strain sensor increases, it is possible to suppress the effect on the instrument error performance.

[0169] The scale 160 of this embodiment also includes the aforementioned flexure bodies 30, 32, 34, 36, a housing cover 14 supported by the load receiving portions 50 of the flexure bodies 30, 32, 34, 36, and a housing base 12 supporting the fixing portions 48 of the flexure bodies 30, 32, 34, 36.

[0170] This scale 160 can also achieve the same effects as those of the first embodiment.

[0171] Furthermore, in the scale 160 of this embodiment, the housing cover is rectangular, and the strain bodies 30, 32, , and are disposed at the four corners of the housing cover .

[0172] In this configuration as well, the same or equivalent parts as those in the first embodiment can achieve the same effects.

[0173] An example will be described in which the housing cover 14 is deflected and the direction of the load input to each of the flexure bodies 30, 32, 34, 36 is tilted. In this case, in the lower strain sensors 170, 172, 174, 176, the tensile force generated in the first strain gauges 170a, 172a, 174a, 176a arranged in the downward curved portion 80, for example, increases. Also, in the lower strain sensors 170, 172, 174, 176, the compressive force generated in the second strain gauges 170b, 172b, 174b, 176b arranged in the upward curved portion 82 decreases.

[0174] On the other hand, in the upper strain sensors 180, 182, 184, 186, the compressive force generated in the first strain gauges 180a, 182a, 184a, 186a arranged in the downward curved portion is large, and in the upper strain sensors 180, 182, 184, 186, the tensile force generated in the second strain gauges 180b, 182b, 184b, 186b arranged in the upward curved portion is small.

[0175] Here, the output of each Wheatstone bridge circuit 190, 192, 194, 196 is affected by a combination of the resistance values ​​of the first legs 200, 210, 220, 230 and the third legs 204, 214, 224, 234. In addition, the output of each Wheatstone bridge circuit 190, 192, 194, 196 is affected by a combination of the resistance values ​​of the second legs 202, 212, 222, 232 and the fourth legs 206, 216, 226, 236. For this reason, these combinations will be described.

[0176] The first and third sides are configured by a combination of first strain gauges 180a, 182a, 184a, 186a of upper strain sensors 180, 182, 184, 186 and second strain gauges 170b, 172b, 174b, 176b of lower strain sensors 170, 172, 174, 176. A large compressive force appears in the first strain gauges 180a, 182a, 184a, 186a of upper strain sensors 180, 182, 184, 186, and a small compressive force appears in the second strain gauges 170b, 172b, 174b, 176b of lower strain sensors 170, 172, 174, 176.

[0177] The second and fourth sides are configured by a combination of second strain gauges 180b, 182b, 184b, 186b of upper strain sensors 180, 182, 184, 186 and first strain gauges 170a, 172a, 174a, 176a of lower strain sensors 170, 172, 174, 176. The second strain gauges 180b, 182b, 184b, 186b of upper strain sensors 180, 182, 184, 186 exhibit small tensile forces, and the first strain gauges 170a, 172a, 174a, 176a of lower strain sensors 170, 172, 174, 176 exhibit large tensile forces.

[0178] Therefore, even if the direction of the load input to each of the strain bodies 30, 32, 34, and 36 is tilted and the difference in strain generated in each strain gauge of each strain sensor becomes large, the effect on the output from the positive output portion 134 and the negative output portion 136 can be suppressed.

[0179] Therefore, even if the difference in strain generated in each strain gauge of each strain sensor becomes large due to the bending of the housing cover 14, it is possible to suppress the influence on the instrumental error performance.

[0180] In this embodiment, a plurality of flexure bodies (30, 32, 34, 36) are provided, and the Wheatstone bridge circuits 190, 192, 194, 196 formed by the respective flexure bodies (30, 32, 34, 36) are connected in parallel. More specifically, the Wheatstone bridge circuits 190, 192, 194, 196 formed by the respective strain gauges 170a, 172a, 174a, 176a, 180b, 182b, 184b, 186b of the respective flexure bodies (30, 32, 34, 36) are connected in parallel.

[0181] According to this configuration, since a measurement result can be obtained using the outputs of each of the Wheatstone bridge circuits 190, 192, 194, and 196 connected in parallel, it is possible to improve the measurement accuracy.

[0182] In this embodiment, the scale 160 is described as having the strain bodies 30, 32, 34, and 36 that respectively support the four corners of the housing cover 14. However, the scale is not limited to this, and it is sufficient that there are at least two strain bodies that support the housing cover 14 and detect the load.

[0183] <Fourth embodiment> FIG. 18 is a circuit diagram showing a connection state of strain gauges 170a, 172a, 180a, 182a, 170b, 172b, 180b, and 182b of the strain sensors 170, 172, 180, and 182 according to the fourth embodiment.

[0184] A scale 300 according to the fourth embodiment differs from the third embodiment in that the strain body that supports the housing cover 14 and detects the load is composed of a first strain body 30 and a second strain body 32. In the fourth embodiment, parts that are the same as or equivalent to those in the third embodiment are given the same reference numerals and descriptions thereof will be omitted.

[0185] As shown in FIG. 18, the first Wheatstone bridge circuit 190 is composed of a first lower strain sensor 170 arranged on the lower surface 56d of the strain-generating portion 56 of the first flexure body 30, and a first upper strain sensor 180 arranged on the upper surface 56u of the strain-generating portion 56 of the first flexure body 30.

[0186] In addition, the second Wheatstone bridge circuit 192 is composed of a second upper strain sensor 182 arranged on the upper surface 56u of the strain-generating portion 56 of the second flexure body 32, and a second lower strain sensor 172 arranged on the lower surface 56d of the strain-generating portion 56 of the second flexure body 32.

[0187] A first side 200 of the first Wheatstone bridge circuit 190 is composed of the second strain gauge 170b of the first lower strain sensor 170, which exhibits a small compressive force. A second side 202 of the first Wheatstone bridge circuit 190 is composed of the first strain gauge 170a of the first lower strain sensor 170, which exhibits a large tensile force.

[0188] The third side 204 opposite the first side 200 is composed of the first strain gauge 180a of the first upper strain sensor 180, in which a large compressive force is observed, and the fourth side 206 opposite the second side 202 is composed of the second strain gauge 180b of the first upper strain sensor 180, in which a small tensile force is observed.

[0189] A connection portion between the first arm 200 and the fourth arm 206 of the first Wheatstone bridge circuit 190 is connected to the positive electrode input section 130, and a connection portion between the second arm 202 and the third arm 204 is connected to the negative electrode input section 132. In addition, a connection portion between the third arm 204 and the fourth arm 206 is connected to the positive electrode output section 134, and a connection portion between the first arm 200 and the second arm 202 is connected to the negative electrode output section 136.

[0190] A first arm 210 of the second Wheatstone bridge circuit 192 is formed of the second strain gauge 172b of the second lower strain sensor 172 where a compressive force is small. A second arm 212 of the second Wheatstone bridge circuit 192 is formed of the first strain gauge 172a of the second lower strain sensor 172 where a tensile force is large.

[0191] The third side 214 opposite the first side 210 is composed of the first strain gauge 182a of the second upper strain sensor 182 in which a compressive force is large, and the fourth side 216 opposite the second side 212 is composed of the second strain gauge 182b of the second upper strain sensor 182 in which a tensile force is small.

[0192] A connection portion between the first side 210 and the fourth side 216 of the second Wheatstone bridge circuit 192 is connected to the positive electrode input section 130, and a connection portion between the second side 212 and the third side 214 is connected to the negative electrode input section 132. In addition, a connection portion between the third side 214 and the fourth side 216 is connected to the positive electrode output section 134, and a connection portion between the first side 210 and the second side 212 is connected to the negative electrode output section 136.

[0193] The positive electrode output unit 134 and the negative electrode output unit 136 are connected to a control device (not shown), and the control device calculates the load applied to the housing cover 14 from the potential between the positive electrode output unit 134 and the negative electrode output unit 136, and displays the calculation result as body weight.

[0194] In this embodiment, the first sides 200, 210 and the second sides 202, 212 of each Wheatstone bridge circuit 190, 192 are formed by the strain gauges 170a, 172a, 170b, 172b of the lower strain sensors 170, 172. The third sides 204, 214 and the fourth sides 206, 216 are formed by the strain gauges 180a, 182a, 180b, 182b of the upper strain sensors 180, 182. However, the present invention is not limited to this.

[0195] For example, the first sides 200, 210 and the second sides 202, 212 of each Wheatstone bridge circuit 190, 192 may be formed from the strain gauges 180a, 182a, 180b, 182b of the upper strain sensors 180, 182. The third sides 204, 214 and the fourth sides 206, 216 may be formed from the strain gauges 170a, 172a, 170b, 172b of the lower strain sensors 170, 172.

[0196] (Action and Effects) In this embodiment as well, the same effects as those of the third embodiment can be achieved.

[0197] The load cell 420 of this embodiment also includes a strain body (30, 32) and wiring that configures each of the Wheatstone bridge circuits 190, 192. The wiring connects the first strain gauges 180a, 182a of the upper strain sensors 180, 182 in the strain bodies (30, 32) to the second strain gauges 180b, 182b of the upper strain sensors 180, 182. The wiring also connects the first strain gauges 170a, 172a of the lower strain sensors 170, 172 to the second strain gauges 170b, 172b of the lower strain sensors 170, 172.

[0198] According to this configuration, a measurement result can be obtained using the outputs of the Wheatstone bridge circuits 190 and 192 formed by the strain gauges 170a, 172a, 170b, 172b, 180a, 182a, 180b, and 182b.

[0199] Moreover, the load cell 420 of this embodiment includes a plurality of strain bodies (30, 32), and the Wheatstone bridge circuits 190, 192 formed by the respective strain bodies (30, 32) are connected in parallel.

[0200] According to this configuration, since a measurement result can be obtained using the outputs of each of the Wheatstone bridge circuits 190, 192 connected in parallel, it is possible to improve the measurement accuracy. [Explanation of symbols]

[0201] 10 scales 12 Chassis base 14 Case cover 30 First strain body 32 Second strain body 34 Third strain body 36 Fourth strain body 48 Fixed part 50 Load receiving part 56 Strain part 56d Bottom surface (back surface) 56u top (front) 80 Downward curved area (concave area) 82 Upper curved area (convex area) 90 First strain sensor 90a, 92a, 94a, 96a First strain gauge 90b, 92b, 94b, 96b Second strain gauge 92 Second strain sensor 94 Third strain sensor 96 Fourth Strain Sensor 160 Scales 170 First lower strain sensor (first rear surface strain sensor) 170a, 172a, 174a, 176a First strain gauge 170b, 172b, 174b, 176b Second strain gauge 172 Second lower strain sensor (second rear surface strain sensor) 174 Third lower strain sensor (third rear surface strain sensor) 176 Fourth lower strain sensor (fourth rear surface strain sensor) 180 First upper strain sensor (first surface strain sensor) 180a, 182a, 184a, 186a First strain gauge 180b, 182b, 184b, 186b Second strain gauge 182 Second upper strain sensor (second surface strain sensor) 184 Third upper strain sensor (third surface strain sensor) 186 Fourth upper strain sensor (fourth surface strain sensor) 300 scales 420 Load Cell

Claims

1. The housing base, a housing cover that is disposed on the housing base and to which a load is applied; a plurality of strain bodies each having a strain portion that supports the housing cover on the housing base and elastically deforms when a load is applied to the housing cover; a strain sensor provided on the strain-flexing portion of the strain-flexing body, the resistance value of which changes in response to expansion and contraction caused by deformation of the strain-flexing portion; Equipped with The strain sensor includes a first strain gauge arranged at a portion that deforms concavely when the strain-flexing portion is elastically deformed, and a second strain gauge arranged at a portion that deforms convexly, The strain bodies are arranged at at least four locations, For every pair of two adjacent flexure bodies, the strain sensor of one of the adjacent flexure bodies is disposed on a front surface of the flexure part, and the strain sensor of the other flexure body is disposed on a rear surface of the flexure part. Scales.

2. The housing base, a housing cover that is disposed on the housing base and to which a load is applied; a plurality of strain bodies each having a strain portion that supports the housing cover on the housing base and elastically deforms when a load is applied to the housing cover; a strain sensor provided on the strain-flexing portion of the strain-flexing body, the resistance value of which changes in response to expansion and contraction caused by deformation of the strain-flexing portion; Equipped with The strain sensor includes a first strain gauge arranged at a portion that deforms concavely when the strain-flexing portion is elastically deformed, and a second strain gauge arranged at a portion that deforms convexly, The strain sensor of one of the adjacent strain bodies is disposed on a front surface of the strain-generating portion, and the strain sensor of the other of the adjacent strain bodies is disposed on a rear surface of the strain-generating portion, For two adjacent strain bodies, the first strain gauge arranged on the back surface of one of the strain bodies and the second strain gauge arranged on the front surface of the other of the strain bodies are connected to be aligned on the same side of a bridge circuit. Scales.

3. A weighing machine according to claim 1 or 2, The strain sensor includes: A first connection terminal connected to one end of the first strain gauge; A second connection terminal connected to one end of the second strain gauge; a third connection terminal connected to the other end of the first strain gauge and the other end of the second strain gauge; Equipped with Scales.

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