Load cell and load cell output adjustment method

Abstract

According to the present invention, it is possible to adjust an initial balance of a resistance value while compensating for temperature characteristics of a load cell using a strain gauge having a relatively large element resistance value and having temperature dependency. The load cell comprising a bridge circuit that converts a change in resistance of a strain gauge that changes in accordance with load to an electrical signal and outputs the same comprises: in a first path on one side of the bridge circuit, a first chip resistor for adjusting an initial balance of the bridge circuit; and a thermistor for compensating for temperature characteristics of the bridge circuit, and a first adjustment resistor for adjusting a shift in the initial balance in a state in which the thermistor is provided, the thermistor and the first adjustment resistor each being connected in series with the first chip resistor and being connected in parallel with each other. The load cell further comprises: in a second path on the other side of the bridge circuit, a second chip resistor for adjusting the initial balance of the bridge circuit; and a second adjustment resistor for adjusting a shift in the initial balance caused by providing the first adjustment resistor in the first path, the second adjustment resistor being connected in series with the second chip resistor.

Description

[Technical field]

[0001] The present disclosure relates to a load cell including a bridge circuit and a method for adjusting the output of the load cell. [Background technology]

[0002] Load cells using strain gauges, whose resistance changes with strain caused by a load, are widely used. For example, a load cell is known in which a strain gauge is incorporated in a bridge circuit, which is a conversion circuit that converts the change in resistance of the strain gauge caused by a load into an electrical signal, and the load cell is configured to output the change in resistance as an electrical signal.

[0003] In a load cell configured as described above, both the strain gauge and the strain body to which the strain gauge is attached have temperature characteristics that cause distortion due to temperature changes, and may output as if a load is applied even when there is no load. When a strain gauge is used in a bridge circuit, the bridge circuit is configured to cancel the linear expansion of the strain gauge, so the difference in the temperature characteristics of each strain gauge or strain body is output as the temperature characteristic of the load cell. For this reason, appropriate temperature compensation is required to detect the amount of strain caused by a load applied to the strain gauge.

[0004] For example, Patent Document 1 discloses a load cell equipped with a zero balance (initial balance) adjustment circuit in which chip resistors are provided so that the potential difference extracted from the bridge circuit when the load is zero at a predetermined temperature is set to zero. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2008-151596 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, in load cells with large output, such as force detection sensors that are attached to the axles of automobiles to detect the load applied to the wheels, or load cells that detect multiple component forces and have significantly different sensitivities to each component force, the range of change in the resistance value of the strain gauge that depends on temperature is wide, and it is not easy to adjust the initial balance while compensating for the temperature characteristics.

[0007] The present disclosure has been made in consideration of the above problems, and an object of the present disclosure is to provide a load cell and a method for adjusting the output of a load cell that makes it possible to adjust the initial balance of resistance values ​​while compensating for the temperature characteristics of a load cell that uses a strain gauge having a relatively large element resistance value and temperature dependency. [Means for solving the problem]

[0008] In order to solve the above problem, according to one aspect of the present disclosure, A load cell equipped with a bridge circuit that converts the change in resistance of a strain gauge, which changes according to the load, into an electrical signal and outputs it. A first path on one side of the bridge circuit, a first chip resistor for adjusting an initial balance of the bridge circuit; a thermistor for compensating for temperature characteristics of the bridge circuit, the thermistors being respectively connected in series with the first chip resistors and connected in parallel with each other, and a first adjustment resistor for adjusting a deviation of the initial balance in a state where the thermistors are provided; A second path on the other side of the bridge circuit, a second chip resistor for adjusting the initial balance of the bridge circuit; a second adjustment resistor connected in series with the second chip resistor for adjusting a deviation in the initial balance caused by providing the first adjustment resistor in the first path; A load cell is provided.

[0009] In order to solve the above problems, according to another aspect of the present disclosure, A method for adjusting the output of a load cell equipped with a bridge circuit that converts the change in resistance of a strain gauge that changes according to the load into an electrical signal and outputs the signal, comprising the steps of: a first chip resistor for adjusting an initial balance of the bridge circuit is connected to a first path on one side of the bridge circuit; a second chip resistor for adjusting an initial balance of the bridge circuit is connected to a second path on the other side of the bridge circuit; a thermistor for compensating for temperature characteristics of the bridge circuit, the thermistor being connected in series with the first chip resistor, and a first adjustment resistor for adjusting a deviation of the initial balance when the thermistor is provided, are connected in parallel to each other in the first path; a second adjustment resistor is connected to the second path in series with the second chip resistor, the second adjustment resistor being for adjusting a deviation in the initial balance caused by providing the first adjustment resistor in the first path; A method for adjusting the output of a load cell is provided. Effect of the Invention

[0010] As described above, according to the present disclosure, it is possible to easily adjust the initial balance of resistance values ​​while compensating for the temperature characteristics of a load cell that uses a strain gauge having a relatively large element resistance value and temperature dependency. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional view showing a load cell (six-component force detector) according to the present embodiment. [Diagram 2] FIG. 2 is a schematic diagram showing the arrangement of strain gauges in the load cell according to the embodiment. [Diagram 3] FIG. 2 is an explanatory diagram showing a configuration of a bridge circuit of the load cell according to the embodiment; [Figure 4] 4 is a flowchart showing the steps of a method for adjusting the output of a load cell according to the present embodiment. [Diagram 5] FIG. 4 is an explanatory diagram showing a first adjustment of the output adjustment method of the load cell according to the present embodiment. [Figure 6] FIG. 4 is an explanatory diagram showing an output state after a first adjustment in the output adjusting method for the load cell according to the present embodiment. [Figure 7] FIG. 10 is an explanatory diagram showing a configuration of a bridge circuit of a load cell according to an application example of the present embodiment. [Figure 8] 10 is a flowchart showing the steps of a method for adjusting the output of a load cell according to an application example. [Figure 9] FIG. 11 is an explanatory diagram showing an output state after a second adjustment in the output adjusting method for a load cell according to an application example. [Figure 10] FIG. 11 is an explanatory diagram showing an output state after a third adjustment in the output adjusting method for a load cell according to an application example. [Figure 11] FIG. 13 is a schematic diagram showing the arrangement of strain gauges in a six-component force detector of a modified example. [Figure 12] FIG. 2 is an explanatory diagram showing a gauge pattern of a biaxial shear strain gauge. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In this specification and the drawings, components having substantially the same functional configurations are denoted by the same reference numerals, and redundant description will be omitted.

[0013] <<1. Overview of the embodiments of the present disclosure>> <1-1. Detailed Description of the Background of the Present Disclosure> First, the background to the creation of the technology of the present disclosure will be described. Note that the background described below merely shows one aspect of the configuration of a load cell to which the technology of the present disclosure can be applied, and the load cell to which the present disclosure can be applied is not limited to the load cell having the configuration exemplified below.

[0014] There is known a six-component force detector that detects loads (Fx, Fy, Fz) applied in the longitudinal direction (hereinafter also referred to as the "x-axis direction"), width direction (hereinafter also referred to as the "y-axis direction"), and height direction (hereinafter also referred to as the "z-axis direction") of the vehicle as loads applied to the wheels of a vehicle such as an automobile, and moments (Mx, My, Mz) about the x-axis, y-axis, and z-axis, respectively. Such a six-component force detector has a cylindrical strain element attached to the axle, but when considering the resistance to the applied load, it is difficult for a general foil strain gauge with a gauge factor of about 2 to obtain an output equivalent to that of a load cell that detects loads in only one axis direction.

[0015] In response to this, it is believed that the desired output can be obtained by using a thin-film strain gauge with a large element resistance such as Cr-N and a large gauge factor (for example, the gauge factor for a Cr-N gauge is 10 to 12). However, the temperature dependency of the element resistance of the Cr-N gauge is large, which poses a problem in its application to a six-component force detector. In other words, when using a strain gauge with a large element resistance and a large gauge factor, the change in resistance due to temperature change in the operating temperature range becomes large, and therefore there is a problem that it is not easy to compensate for the temperature characteristics of the output of the six-component force detector.

[0016] Another characteristic of the six-component force detector is that the sensitivity of the strain gauges varies greatly depending on the direction of the force components. For this reason, even if a bridge circuit is configured using general foil strain gauges and the initial balance is adjusted to match the force components with low sensitivity, there is a risk that the compensation for the temperature characteristics will be insufficient for the force components with high sensitivity.

[0017] In response to this, it is possible to prepare temperature characteristic map data that determines the characteristics of temperature-dependent output changes in advance, for example by directly measuring the temperature of the strain gauge, and then using a processor to correct the output from the six-component force detector based on the temperature characteristic map data. However, this is not a desirable solution, as it requires the addition of a temperature sensor and software calculation functions that are not actually necessary.

[0018] Under such circumstances, the technology disclosed herein provides a load cell and a method for adjusting the output of a load cell that are capable of adjusting the initial balance while compensating for the temperature characteristics in the operating temperature range, without adding a temperature sensor or software function, even when using a strain gauge with a large element resistance value and a large gauge factor.

[0019] <1-2. Features of the embodiment of the present disclosure> (1-2-1) An embodiment of the present disclosure relates to a load cell having a bridge circuit that converts a change in resistance of a strain gauge that changes in response to a load into an electrical signal and outputs the electrical signal, A first path on one side of the bridge circuit, a first chip resistor for adjusting an initial balance of the bridge circuit; a thermistor for compensating for temperature characteristics of the bridge circuit, the thermistors being respectively connected in series with the first chip resistors and connected in parallel with each other, and a first adjustment resistor for adjusting a deviation of the initial balance with the thermistors provided; A second path on the other side of the bridge circuit, a second chip resistor for adjusting the initial balance of the bridge circuit; The configuration includes a second adjustment resistor connected in series with the second chip resistor for adjusting the deviation in the initial balance caused by providing the first adjustment resistor in the first path.

[0020] In addition, the embodiment of the present disclosure can also be realized as an output adjustment method for adjusting the output of a load cell having a bridge circuit that converts the change in resistance of a strain gauge that changes depending on the load into an electrical signal and outputs it.

[0021] This configuration makes it possible to easily adjust the initial balance while compensating for the temperature characteristics of a load cell that uses a strain gauge with a relatively large element resistance of, for example, 1 kΩ or more and has a large temperature characteristic, or a load cell that is configured to detect multiple force components, thereby improving the reliability of the load cell output.

[0022] Note that "a first path on one side of the bridge circuit" and "a second path on the other side of the bridge circuit" refer to two current paths in the bridge circuit. Each of the first path and the second path is configured with two strain gauges.

[0023] Moreover, "initial balance" refers to the difference (potential difference) between the potential between the two strain gauges provided in the first path and the potential between the two strain gauges provided in the second path when no load is applied to the load cell. "Adjusting the deviation of the initial balance" means adjusting the potential difference when no load is applied so that it approaches zero.

[0024] Furthermore, "temperature characteristics of the bridge circuit" refers to the characteristics of the load cell output that change with temperature. "Large temperature characteristics" refers to the large fluctuation range of the load cell output that changes with temperature. "Compensating for the temperature characteristics of the bridge circuit" means adjusting the fluctuation range of the load cell output that changes with temperature to be within a specified range.

[0025] (1-2-2) In addition, in the embodiment of the present disclosure, The first adjustment resistor and the second adjustment resistor may be the same resistor element.

[0026] This configuration eliminates the need to individually select the first and second adjustable resistors that can compensate for the temperature characteristics when the first and second chip resistors are connected to the bridge circuit. Even if the first and second adjustable resistors are the same resistor element, the initial balance of the bridge circuit can be kept within a predetermined range.

[0027] (1-2-3) In addition, in the embodiment of the present disclosure, At least one of the first path and the second path, A third adjustment resistor may be provided for adjusting the deviation of the initial balance caused by providing the second adjustment resistor.

[0028] With this configuration, even if a slight deviation in the initial balance occurs when the first adjustment resistor and the second adjustment resistor, which are the same resistance elements, are placed in the first path and the second path, respectively, the deviation in the initial balance can be easily adjusted.

[0029] (1-2-4) In addition, in the embodiment of the present disclosure, The strain gauge may have an element resistance of 1 KΩ or more.

[0030] With this configuration, a relatively large desired load can be detected by the load cell whose temperature characteristics are compensated even though a strain gauge having a relatively large element resistance value is used.

[0031] (1-2-5) In addition, in the embodiment of the present disclosure, The load cell is The detector may be a multi-force detector having a plurality of the bridge circuits and detecting a plurality of force components.

[0032] With this configuration, even in a case where a plurality of bridge circuits whose sensitivity to distortion differs depending on the direction of the force components is provided, the initial balance can be easily adjusted while compensating for the temperature characteristics of the output from each bridge circuit.

[0033] <<2. Details of the embodiment of the present disclosure>> <2-1. Example of load cell (6-component force detector) configuration> Next, a configuration example of a load cell according to an embodiment of the present disclosure will be described. In this embodiment, an example will be described in which the technology of the present disclosure is applied to a six-component force detector capable of detecting six-component forces (Fx, Fy, Fz, Mx, My, Mz) applied to a wheel of a vehicle, as one aspect of a load cell. The load cell according to this embodiment is a six-component force detector that detects six-component forces applied to a wheel, and is incorporated in a hub bearing unit that is attached to a suspension device and rotatably supports the wheel of a vehicle such as an automobile.

[0034] Fig. 1 shows a cross-sectional view of a hub bearing unit including a six-component force detector, cut along a plane including the axle. In Fig. 1, the right side shows the outer side in the vehicle width direction, and the left side shows the inner side in the vehicle width direction. Note that the configuration of the hub bearing unit shown in Fig. 1 is merely an example, and is not limited to the configuration shown in Fig. 1.

[0035] The hub bearing unit 100 is configured to include a hub 110, an outer cylinder 120, an inner cylinder 130, rolling elements 140, a base 150, and a six-component force detector 1. The hub 110 is a member to which a rim disc portion of a wheel (not shown) consisting of a rim and a tire is fastened. The hub 110 is configured by integrally forming a cylindrical portion 111, a flange portion 112, a collar portion 113, etc.

[0036] The cylindrical portion 111 is formed in a cylindrical shape concentric with the rotation axis (axle) of the wheel. The cylindrical portion 111 is inserted into the inner diameter side of the inner tube 130, the sensor 10, and the base portion 150. A spline hole 111a that fits with a spline shaft portion of a drive shaft (not shown) is formed in the vehicle width direction outer region of the inner peripheral surface portion of the cylindrical portion 111. The flange portion 112 is a disk-shaped portion formed by protruding from the end portion of the cylindrical portion 111 on the vehicle width direction outer side in a brim-like shape to the outer diameter side. The surface portion of the flange portion 112 on the vehicle width direction outer side functions as a base portion to which the rim disc is fastened. The flange portion 112 has openings 112a into which hub bolts are inserted, for example, about five openings 112a are formed on a predetermined pitch circle diameter at equal intervals in the circumferential direction. The collar portion 113 is a cylindrical portion concentric with the axle protruding from the surface portion of the flange portion 112 on the vehicle width direction outer side. The collar portion 113 fits into a center bore, which is a circular opening formed in the center of the rim disc, and improves the mounting accuracy of the wheel.

[0037] The outer cylinder 120, the inner cylinder 130, and the rolling elements 140 cooperate to form a rolling bearing (hub bearing) that rotatably supports the wheel. The outer cylinder 120 is formed by integrally forming a tubular portion 121, a flange portion 122, etc. The tubular portion 121 is a cylindrical portion that is concentric with the axle. A raceway surface that guides the rolling elements 140 is formed on the inner peripheral surface of the tubular portion 121. The inner end of the tubular portion 121 on the vehicle width direction is formed to protrude inward in the vehicle width direction with respect to the inner end of the tubular portion 131 of the inner cylinder 130 on the vehicle width direction.

[0038] The flange portion 122 is formed so as to protrude radially outward from the end portion of the cylindrical portion 121 on the outer side in the vehicle width direction in a brim-like shape. The flange portion 122 is a portion to which the flange portion 112 of the hub 110 is fastened. An outer surface portion of the flange portion 122 in the vehicle width direction abuts against an inner surface portion of the flange portion 112 of the hub 110 in the vehicle width direction. The flange portion 122 has a screw hole 122a formed concentrically with the opening 112a of the hub 110. A hub bolt (not shown) used to secure the wheel is fastened to the screw hole 122a.

[0039] The inner cylinder 130 is configured by integrally forming a cylindrical portion 131, a flange portion 132, and the like. The cylindrical portion 131 is a cylindrical member concentric with the axle, and is inserted into the inner diameter side of the cylindrical portion 121 of the outer cylinder 120. A predetermined gap is provided between the outer peripheral surface of the cylindrical portion 131 and the inner peripheral surface of the cylindrical portion 121 of the outer cylinder 120. A raceway surface that guides the rolling element 140 is formed on the outer peripheral surface of the cylindrical portion 131. The flange portion 132 is formed by protruding from the outer end of the cylindrical portion 131 in the vehicle width direction to the inner diameter side. The flange portion 132 holds the outer end of the first flange 12 of the sensor 10 in the vehicle width direction. The rolling element 140 is a bearing incorporated between the raceway surfaces of the outer cylinder 120 and the inner cylinder 130. The rolling element 140 is incorporated between the outer cylinder 120 and the inner cylinder 130 together with a retainer 141 and a retainer 142 that position the rolling element 140 between the outer cylinder 120 and the inner cylinder 130 .

[0040] The base 150 is a portion that fastens and fixes the hub bearing unit 100 to an upright (hub knuckle) (not shown) of a suspension device. The base 150 is configured by integrally forming a tubular portion 151, a flange portion 152, a recess 153, a protrusion 154, etc. The tubular portion 151 is a cylindrical member that is concentric with the axle, and an end portion on the inside in the vehicle width direction of the tubular portion 111 of the hub 110 is inserted into the tubular portion 151. The outer peripheral surface of the tubular portion 111 of the hub 110 is disposed opposite the inner peripheral surface of the tubular portion 151 at a predetermined radial distance.

[0041] The flange portion 152 is formed so as to protrude from the end portion of the cylindrical portion 151 on the outer side in the vehicle width direction toward the outer diameter side in a brim-like shape. The flange portion 152 is a fastening surface portion for fastening the base portion 150 to an upright (not shown). The flange portion 152 is formed with a plurality of openings 152a distributed in the circumferential direction into which a plurality of bolts used for fastening to the upright are inserted. Inside the flange portion 152, a through hole 152b is formed from inside the space portion in which the outer peripheral surface of the cylindrical portion 11 of the sensor 10 is disposed to the outer peripheral edge portion of the flange portion 152, in which wiring connected to a strain gauge and the like are disposed.

[0042] The recess 153 is a portion formed by stepwise expanding the inner diameter of a region of the inner circumferential surface of the base 150 that corresponds to the flange portion 152 in the axial direction. The recess 153 is a portion that holds the second flange 13 of the sensor 10. The protruding portion 154 is a cylindrical portion formed protruding outward in the vehicle width direction from a radially intermediate portion of the flange portion 152. The outer circumferential surface of the protruding portion 154 is disposed opposite to, and spaced apart from, the inner circumferential surface of the tubular portion 121 of the outer cylinder 120 at the end portion on the inner side in the vehicle width direction.

[0043] The six-component force detector 1 is a load cell capable of detecting loads acting on a wheel in three orthogonal axial directions and moments around the three orthogonal axes. The six-component force detector 1 is configured with a sensing body 10 formed substantially in a cylindrical shape, a plurality of strain gauges provided on the sensing body 10, and a bridge circuit including the strain gauges.

[0044] The sensing body (sensor core) 10 is formed to have a cylindrical portion 11, a first flange 12, a second flange 13, etc. The cylindrical portion 11 is a cylindrical portion having substantially constant inner and outer diameters over a predetermined axial length, and is a portion to which a plurality of strain gauges, described below, are attached (bonded). The first flange 12 is provided at the outer end of the cylindrical portion 11 in the vehicle width direction, and is a portion formed to protrude both on the outer diameter side and the inner diameter side with respect to the cylindrical portion 11. The first flange 12 has an outer peripheral surface that is in contact with the inner cylinder. 130 The inner circumferential surface of the inner circumferential surface of the tubular portion 131 is in contact with the outer end of the tubular portion 131 in the vehicle width direction, and the end surface of the inner circumferential surface of the flange portion 132 is in contact with the inner circumferential surface of the inner circumferential surface of the flange portion 132 in the vehicle width direction. 130 is fixed at.

[0045] The second flange 13 is provided at the end of the cylindrical portion 11 on the inner side in the vehicle width direction, and is formed to protrude radially outward and radially inward from the cylindrical portion 11. The second flange 13 is fixed to the base portion 150 with its outer peripheral surface and end surface fitted into the recess 153 of the base portion 150. With this configuration, substantially all of the force acting on the wheel is transmitted between the base portion 150 and the sensing body 10 via the sensing body 10.

[0046] The six-component force detector 1 has an Fx detection system, an Fy detection system, an Fz detection system, an Mx detection system, a My detection system, and an Mz detection system, each having a bridge circuit including a strain gauge provided on the cylindrical portion 11 of the sensing body 10 described above. The Fx detection system detects a radial force Fx (x-axis direction) acting on the cylindrical portion 11 of the sensing body 10. The Fy detection system detects an axial force Fy (y-axis direction) acting on the cylindrical portion 11 of the sensing body 10. The Fz detection system detects a radial force Fz (z-axis direction) acting on the cylindrical portion 11 of the sensing body 10 in a direction perpendicular to the x-axis direction. The Mx detection system detects a moment Mx about the x-axis acting on the cylindrical portion 11 of the sensing body 10. The My detection system detects a moment My about the y-axis acting on the cylindrical portion 11 of the sensing body 10. The Mz detection system detects a moment Mz acting on the cylindrical portion 11 of the sensor 10 about the z-axis.

[0047] The above-mentioned Fx detection system, Fy detection system, Fz detection system, Mx detection system, My detection system, and Mz detection system are each configured with a bridge circuit including four strain gauges. Fig. 2 is a schematic diagram showing the arrangement of strain gauges in the six-component force detector 1. Fig. 3 is a diagram showing the arrangement of strain gauges in the Fx detection system and the configuration of the bridge circuit in the six-component force detector 1, and shows a representative example of the arrangement of strain gauges and the configuration of the bridge circuit in each force detection system (Fx detection system, Fy detection system, Fz detection system) and each moment detection system (Mx detection system, My detection system, Mz detection system).

[0048] As shown in Figs. 2 and 3, the Fx detection system is configured to include strain gauges 21 to 24. The strain gauges 21 to 24 are single-axis strain gauges, and are attached to the outer circumferential surface of the cylindrical portion 11 so that their detection direction is parallel to the central axis direction of the cylindrical portion 11. The strain gauge 21 is attached to the area of ​​the outer circumferential surface of the cylindrical portion 11 on the first flange 12 side. In the region The strain gauge 22 is disposed on a straight line that passes through the strain gauge 21 and is parallel to the axial direction of the cylindrical portion 11, and is disposed on the outer peripheral surface of the cylindrical portion 11 on the second flange 13 side. In the regionThe strain gauge 23 is disposed at a position shifted by 180 degrees around the central axis of the cylindrical portion 11 when viewed from the strain gauge 22 (a position symmetrical about the central axis of the cylindrical portion 11 with respect to the strain gauge 22). The strain gauge 24 is disposed at a position shifted by 180 degrees around the central axis of the cylindrical portion 11 when viewed from the strain gauge 21 (a position symmetrical about the central axis of the cylindrical portion 11 with respect to the strain gauge 21).

[0049] 3, the bridge circuit of the Fx detection system is configured as a Wheatstone bridge circuit, in which strain gauges 21 to 24 are sequentially connected in a loop shape, and the positive and negative poles of a power supply are connected between strain gauge 22 and strain gauge 23, and between strain gauge 21 and strain gauge 24, respectively. The bridge circuit extracts potential differences between strain gauge 21 and strain gauge 22, and between strain gauge 23 and strain gauge 24, as outputs. The configuration of the bridge circuit will be described in detail later.

[0050] The Fy detection system is configured with strain gauges 41 to 44. The strain gauges 41 to 44 are single-axis strain gauges, and are attached to the outer circumferential surface of the cylindrical portion 11 so that their detection direction is parallel to the central axis direction of the cylindrical portion 11. The strain gauge 41 is disposed midway between the strain gauges 21 and 22 of the Fx detection system. The strain gauges 42, 43, and 44 are disposed at positions that are shifted in phase by 90 degrees, 180 degrees, and 270 degrees, respectively, around the central axis of the cylindrical portion 11 with respect to the strain gauge 41. The bridge circuit of the Fy detection system is the same as that of the Fx detection shown in FIG. system The configuration is the same as that of the first embodiment except that the strain gauges 21 to 24 are replaced with strain gauges 41 to 44.

[0051] The Fz detection system is configured with strain gauges 31 to 34. The strain gauges 31 to 34 are single-axis strain gauges, and are attached to the outer circumferential surface of the cylindrical portion 11 so that their detection direction is parallel to the central axis direction of the cylindrical portion 11. The strain gauge 31 is disposed at a 90° offset around the central axis of the cylindrical portion 11 with respect to the strain gauge 21 of the Fx detection system. The strain gauge 32 is disposed at a 90° offset around the central axis of the cylindrical portion 11 with respect to the strain gauge 22 of the Fx detection system. The strain gauges 31 and 32 are disposed on the same straight line parallel to the axial direction of the cylindrical portion 11. The strain gauge 33 is disposed at a position offset 180° around the central axis of the cylindrical portion 11 from the strain gauge 32 (a position symmetrical to the strain gauge 32 with respect to the central axis of the cylindrical portion 11). The strain gauge 34 is disposed at a position shifted by 180 degrees around the central axis of the cylindrical portion 11 from the strain gauge 31 (at a position symmetrical about the central axis of the cylindrical portion 11 with respect to the strain gauge 31). The bridge circuit of the Fz detection system is the same as that of the Fx detection system shown in FIG. system The configuration is the same as that of the first embodiment except that the strain gauges 21 to 24 are replaced with strain gauges 31 to 34.

[0052] The Mx detection system is configured with strain gauges 51 to 54. The strain gauges 51 to 54 are single-axis strain gauges and are attached to the outer circumferential surface of the cylindrical portion 11 so that their detection direction is parallel to the central axis direction of the cylindrical portion 11. The strain gauge 51 is disposed adjacent to the strain gauge 31 of the Fz detection system in the central axis direction of the cylindrical portion 11. The strain gauge 52 is disposed adjacent to the strain gauge 32 of the Fz detection system in the central axis direction of the cylindrical portion 11. The strain gauges 51 and 52 are disposed on the same straight line parallel to the axial direction of the cylindrical portion 11. The strain gauge 53 is disposed at a position shifted by 180 degrees around the central axis of the cylindrical portion 11 from the strain gauge 52 (a position symmetrical to the strain gauge 52 with respect to the central axis of the cylindrical portion 11). The strain gauge 54 is disposed at a position shifted by 180 degrees around the central axis of the cylindrical portion 11 as viewed from the strain gauge 51 (a position symmetrical about the central axis of the cylindrical portion 11 with respect to the strain gauge 51). The bridge circuit of the Mx detection system is the same as that of the Fx detection system shown in FIG. systemThe configuration is the same as that of the first embodiment except that the strain gauges 21 to 24 are replaced with strain gauges 51 to 54.

[0053] The My detection system is configured with strain gauges 71-74. The strain gauges 71-74 are shear type strain gauges, and are attached to the outer circumferential surface of the cylindrical portion 11 so that their detection direction is the circumferential direction of the cylindrical portion 11. The strain gauge 71 is disposed midway between the strain gauges 41 and 42 of the Fy detection system. The strain gauge 72 is disposed midway between the strain gauges 42 and 44 of the Fy detection system. The strain gauges 73 and 74 are disposed at positions symmetrical with respect to the central axis of the cylindrical portion 11 with respect to the strain gauges 72 and 71, respectively. The bridge circuit of the My detection system is the same as the Fx detection circuit shown in FIG. 3. system Strain gauges 21 to 24 71~74 It has the same configuration except for replacing

[0054] The Mz detection system is configured with strain gauges 61 to 64. The strain gauges 61 to 64 are single-axis strain gauges, and are attached to the outer circumferential surface of the cylindrical portion 11 so that their detection direction is parallel to the central axis direction of the cylindrical portion 11. The strain gauge 61 is disposed adjacent to the strain gauge 21 of the Fx detection system in the central axis direction of the cylindrical portion 11. The strain gauge 62 is disposed adjacent to the strain gauge 22 of the Fx detection system in the central axis direction of the cylindrical portion 11. The strain gauge 61 and the strain gauge 62 are disposed on the same straight line parallel to the axial direction of the cylindrical portion 11. The strain gauge 63 is disposed at a position shifted by 180 degrees around the central axis of the cylindrical portion 11 from the strain gauge 62 (a position symmetrical to the strain gauge 62 with respect to the central axis of the cylindrical portion 11). The strain gauge 64 is disposed at a position shifted by 180 degrees around the central axis of the cylindrical portion 11 from the strain gauge 61 (at a position symmetrical about the central axis of the cylindrical portion 11 with respect to the strain gauge 61). The bridge circuit of the Mz detection system is the same as that of the Fx detection system shown in FIG. system The configuration is the same as that of the first embodiment except that the strain gauges 21 to 24 are replaced with strain gauges 61 to 64.

[0055] <2-2. Bridge circuit> Next, taking the bridge circuit of the Fx detection system shown in FIG. 3 as an example, configuration examples of the bridge circuits of each force detection system and each moment detection system will be specifically described.

[0056] The bridge circuit 80 of the Fx detection system shown in FIG. 3 has four terminals, a first terminal 81, a second terminal 82, a third terminal 83, and a fourth terminal 84, and four strain gauges 21, 22, 23, and 24. The strain gauge 21 is provided between the first terminal 81 and the second terminal 82, and the strain gauge 22 is provided between the second terminal 82 and the fourth terminal 84. The strain gauge 24 is provided between the first terminal 81 and the third terminal 83, and the strain gauge 23 is provided between the third terminal 83 and the fourth terminal 84. A current path passing through the first terminal 81, the strain gauge 21, the second terminal 82, the strain gauge 22, and the fourth terminal 84 constitutes a first path 86. A current path passing through the first terminal 81, the strain gauge 24, the third terminal 83, the strain gauge 23, and the fourth terminal 84 constitutes a second path 87.

[0057] The strain gauges 21, 22, 23, and 24 are resistive elements whose resistance value changes according to the amount of strain. In this embodiment, the strain gauges are made of a material with a gauge factor of 4 or more. For example, the strain gauges may be made of a Cr-N thin film. If the gauge factor of the strain gauge is 4 or more, it is possible to obtain an output that is desired for a six-component force detector 1 that detects a load applied to a wheel. However, the strain gauge is not limited to a Cr-N thin film.

[0058] In the bridge circuit 80, when a load is applied to the strain body, a strain is generated in each of the strain gauges 21, 22, 23, and 24, and the resistance value of each of the strain gauges 21, 22, 23, and 24 changes according to the amount of strain. The bridge circuit 80 outputs an electric signal according to the potential difference between the second terminal 82 of the first path 86 and the third terminal 83 of the second path 87.

[0059] In this embodiment, the bridge circuit 80 includes a first chip resistor 91 (91a, 91b), a thermistor 95, and a first adjustment resistor 96 between the strain gauge 22 of the first path 86 and the fourth terminal 84. The thermistor 95 and the first adjustment resistor 96 are connected in series to the first chip resistor 91 and are connected in parallel to each other. The bridge circuit 80 also includes a second chip resistor 93 (93a, 93b) and a second adjustment resistor 97 between the strain gauge 23 of the second path 87 and the fourth terminal 84. The second adjustment resistor 97 is connected in series to the second chip resistor 93.

[0060] These elements provided in the first path 86 and the second path 87 are provided in the following order with respect to the bridge circuit 80: a first chip resistor 91, a second chip resistor 93, a thermistor 95, a first adjusting resistor 96, and a second adjusting resistor 97.

[0061] The first chip resistor 91 is a resistive element for adjusting the deviation of the initial balance measured in a state where the strain gauges 21, 22, 23, and 24 are provided in the bridge circuit 80. Since the target resistance value is relatively large, a chip resistor is used as the resistive element. In the example of the bridge circuit 80 shown in FIG. 2, the first chip resistor 91 has two resistive elements 91a and 91b connected in parallel to each other. Similarly, the second chip resistor 93 is a resistive element for adjusting the deviation of the initial balance measured in a state where the strain gauges 21, 22, 23, and 24 are provided in the bridge circuit 80. In the example of the bridge circuit 80 shown in FIG. 2, the second chip resistor 93 has two resistive elements 93a and 93b connected in parallel to each other.

[0062] Generally, a plurality of chip resistors designed to have a predetermined resistance value are prepared at an arbitrary interval. As the first chip resistor 91 and the second chip resistor 93 provided in a state where the strain gauges 21, 22, 23, and 24 are connected to the bridge circuit 80, chip resistors having appropriate resistance values ​​that make the resistance values ​​of the first path 86 and the second path 87 the resistance values ​​according to the purpose are used. In this embodiment, first, chip resistors (hereinafter also referred to as "temporary resistors") 91a and 93a having arbitrary resistance values ​​that can make the resistance values ​​of the first path 86 and the second path 87 the resistance values ​​according to the purpose are selected and connected to the first path 86 and the second path 87, respectively.

[0063] Furthermore, with the temporary resistors 91a and 93a connected to the bridge circuit 80, the initial balance of the bridge circuit 80 at a predetermined reference temperature is measured, and chip resistors (hereinafter also referred to as "shunt resistors") 91b and 93b having resistance values ​​that can eliminate the deviation in the initial balance are selected and connected in parallel with the temporary resistors 91a and 93a, respectively. This makes it possible to bring the deviation in the initial balance of the bridge circuit 80 at the predetermined reference temperature within a desired range. However, if the deviation in the initial balance of the bridge circuit 80 at the predetermined reference temperature comes within the desired range only with the temporary resistors 91a and 93a, the shunt resistors 91b and 93b do not need to be provided.

[0064] Assuming that the initial balance of the bridge circuit 80 is adjusted with the first chip resistor 91 and the second chip resistor 93 connected to the bridge circuit 80, if the sides on which the strain gauges 21, 22, 23, and 24 are provided have the same temperature characteristics, the temperature characteristics are cancelled by the configuration of the bridge circuit 80, and no output is generated when no load is applied. On the other hand, if an output is generated even when no load is applied, it can be determined that the initial balance of the bridge circuit 80 is misaligned. For this reason, in this embodiment, the temperature characteristics are compensated for by incorporating a thermistor 95, which is a temperature compensation element with an inverse characteristic to the temperature characteristic reflected in the output from the bridge circuit 80, into the bridge circuit 80.

[0065] The thermistor 95 is a resistive element for compensating for the temperature characteristics of the bridge circuit 80 in a state in which the first chip resistor 91 and the second chip resistor 93 are connected to the bridge circuit 80. As the thermistor 95, an NTC (Negative Temperature Coefficient) thermistor having a characteristic that the resistance value decreases with an increase in temperature is used. The thermistor 95 is generally an element having a high resistance value (for example, 1 kΩ or more) and suitable for compensating for temperature characteristics. It is preferable that the thermistor 95 has a large resistance temperature coefficient, which indicates the rate of decrease in the resistance value associated with an increase in temperature. The first adjustment resistor 96 is a resistive element for adjusting the deviation of the initial balance in a state in which the first chip resistor 91 and thermistor 95 are provided in the bridge circuit 80. The second adjustment resistor 97 is a resistive element for adjusting the deviation of the initial balance caused by providing the first adjustment resistor 96 in the first path 86.

[0066] Although the initial balance of the bridge circuit 80 to which the first chip resistor 91 and the second chip resistor 93 are connected is adjusted at a predetermined reference temperature, the first chip resistor 91 and the second chip resistor 93 each have a temperature characteristic, and therefore the output of the bridge circuit 80 also has a temperature characteristic. Therefore, a thermistor 95 capable of measuring the temperature characteristic of the bridge circuit 80 to which the first chip resistor 91 and the second chip resistor 93 are connected and compensating for the temperature characteristic, and a first adjustment resistor 96 for restoring the deviation in the initial balance caused by connecting the thermistor 95 to the first path 86 are connected in parallel with each other and in series with the first chip resistor 91.

[0067] In addition, a second adjustment resistor 97 for balancing the resistance values ​​of the first path 86 and the second path 87 is connected in series with the second chip resistor 93. The resistance value of the second adjustment resistor 97 may be made different from that of the first adjustment resistor 96 to eliminate the initial imbalance in the resistance values ​​of the first path 86 and the second path 87. However, since it is difficult to grasp the temperature characteristics of the thermistor 95 and the first adjustment resistor 96 in advance, the second adjustment resistor 97 may be provisionally made the same resistance element as the first adjustment resistor 96.

[0068] The first and second adjustment resistors 96 and 97 for adjusting the initial balance deviation are preferably resistor elements having a low resistance temperature coefficient, which indicates the rate of change in resistance value relative to temperature change, for example, 1 Ω or less. Examples of such resistor elements include elements made of one or a mixture of two or more of zinc, tungsten, aluminum, pure iron, iridium, steel, copper, gold, nickel, silver, platinum, palladium, and tin.

[0069] <2-3. How to adjust the load cell output> Next, a method for adjusting the output of a load cell according to this embodiment will be described using the six-component force detector 1 as an example. In the method for adjusting the output of a load cell described below, an example will be described in which the output is adjusted with a target compensation value of 0.2 mV / V for the temperature characteristics of each force detection system and each moment detection system.

[0070] FIG. 4 is a flowchart showing the steps of a method for adjusting the output of a load cell. First, electrical wiring is performed by connecting gauge leads to strain gauges arranged on a cylindrical portion as a strain generating body via an insulating layer, and a bridge circuit is formed in which four strain gauges are electrically connected (step S11). For example, in the bridge circuit of the Fx detection system, a strain gauge 21 is connected between a first terminal 81 and a second terminal 82, and a strain gauge 22 is connected between the second terminal 82 and a fourth terminal 84. A strain gauge 24 is connected between the first terminal 81 and a third terminal 83, and a strain gauge 23 is connected between the third terminal 83 and a fourth terminal 84.

[0071] At the completion of step S11, the points to which the resistive elements are to be connected for adjusting the initial balance and compensating for the temperature characteristics are shorted. The step of electrically connecting the four strain gauges is performed for six sets of four strain gauges that constitute each force detection system and each moment detection system.

[0072] Next, a first chip resistor and a second chip resistor are connected to the first path on one side of the bridge circuit and the second path on the other side of the bridge circuit, respectively, and a first adjustment is performed to adjust the initial balance of the bridge circuit (step S13). For example, in the bridge circuit of the Fx detection system, as shown in Fig. 5, a first chip resistor 91 (temporary resistor 91a and shunt resistor 91b) is connected between the strain gauge 22 and the fourth terminal 84 of a first path 86 passing through the first terminal 81, the strain gauge 21, the second terminal 82, the strain gauge 22, and the fourth terminal 84. In addition, a second chip resistor 93 (temporary resistor 93a and shunt resistor 93b) is arranged between the strain gauge 23 and the fourth terminal 84 of a second path 87 passing through the first terminal 81, the strain gauge 24, the third terminal 83, the strain gauge 23, and the fourth terminal 84.

[0073] More specifically, the temporary resistors 91a and 93a having arbitrary resistance values ​​that can make the resistance values ​​of the first path 86 and the second path 87 a resistance value suitable for the purpose are selected and connected to the first path 86 and the second path 87, respectively. The resistance values ​​of the temporary resistors 91a and 93a may be calculated based on the resistance values ​​of the strain gauges 21, 22, 23, and 24 and the electric wiring such as the gauge leads. Furthermore, in a state where the temporary resistors 91a and 93a are connected to the bridge circuit 80, the initial balance of the bridge circuit 80 at a predetermined reference temperature is measured, and the shunt resistors 91b and 93b having resistance values ​​that can eliminate the deviation of the initial balance are selected and connected in parallel to the temporary resistors 91a and 93a, respectively. This makes it possible to make the deviation of the initial balance of the bridge circuit 80 at the predetermined reference temperature within a desired range. However, if the deviation of the initial balance of the bridge circuit 80 at the predetermined reference temperature is within the desired range only with the temporary resistors 91a and 93a, the shunt resistors 91b and 93b do not need to be connected.

[0074] In step S13, a first chip resistor and a second chip resistor are connected to the first paths and the second paths of the bridge circuits of the six detection systems, respectively.

[0075] Next, the temperature characteristics of the output of the bridge circuit are measured with the first chip resistor and the second chip resistor connected to the bridge circuit (step S15). Here, the temperature characteristics of the output of each force detection system and each moment detection system are measured in the operating temperature range of the six-component force detector 1. The method for measuring the temperature characteristics may be a conventionally known method.

[0076] Fig. 6 shows an example of the temperature characteristics of the outputs of six detection systems in the expected operating temperature range (0 to 100°C) measured in a state in which a first chip resistor is connected to the first path of the bridge circuit and a second chip resistor is connected to the second path (after the first adjustment). In the example shown in Fig. 6, the temperature characteristics of the outputs of three of the six detection systems are 0.5 mV / V or more, exceeding the target for temperature characteristic compensation.

[0077] In response to the measurement result of the temperature characteristics, in the next step S17, a thermistor for compensating for the temperature characteristics and a first adjustment resistor for adjusting the deviation of the initial balance caused by providing the thermistor are connected in parallel to each other and in series with the first chip resistor to the first path (step S17). Next, in order to reduce the deviation of the balance of the resistance values ​​caused by connecting the thermistor and the first adjustment resistor to the first path, the second adjustment resistor is connected in parallel to the second chip resistor to the second path (step S19). For example, in the bridge circuit of the Fx detection system, the thermistor 95 and the first adjustment resistor 96 are connected in parallel to each other and in series with the first chip resistor 91 to the first path 86, and the second adjustment resistor 97 is connected in series with the second chip resistor 93 to the second path 87 (see FIG. 3).

[0078] In steps S17 to S19, a thermistor, a first adjustment resistor, and a second adjustment resistor are connected to the first path and the second path of the bridge circuit of the six detection systems, respectively. This adjusts the outputs of all six detection systems to be less than 0.2 mV / V, which is the target for compensating for the temperature characteristics.

[0079] In this way, according to the load cell and the load cell output adjustment method according to the embodiment of the present disclosure, even if the change in resistance value due to temperature change in the operating temperature range is large, the temperature characteristics of the output of the bridge circuit can be easily compensated. Also, even in the case of a six-component force detector that detects multiple force components, the temperature characteristics of the output of all detection systems can be made less than the target. Therefore, the initial balance of the resistance value can be easily adjusted while compensating for the temperature characteristics of the load cell.

[0080] In the above embodiment, a thermistor and a first adjusting resistor are connected to the first path of the bridge circuit, and a second adjusting resistor is connected to the second path, but in this case, the first path may be either the positive or negative side of the input.

[0081] <2-4. Application Examples> The load cell and the method for adjusting the output of the load cell according to the present embodiment have been described above. Next, application examples of the technology of the present disclosure will be described.

[0082] In the above embodiment, if a second adjustment resistor 97 identical to the first adjustment resistor 96 is provided in the second path 87, the combined resistance of the thermistor 95 and the first adjustment resistor 96 in the first path 86 becomes small, and the resistance value of the first path 86 may be returned too much. For this reason, in the application example, the initial balance of the bridge circuit 80 is measured again with the first chip resistor 91, the second chip resistor 93, thermistor 95, the first adjustment resistor 96, and the second adjustment resistor 97 connected to the bridge circuit 80, and a third adjustment resistor is connected to further adjust the deviation of the initial balance.

[0083] FIG. 7 is an explanatory diagram showing the configuration of a bridge circuit 80A according to an application example, and illustrates a bridge circuit of an Fx detection system, similar to FIG.

[0084] In the application example, the bridge circuit 80A includes a second chip resistor 93 (93a, 93b), a second adjustable resistor 97, and a third adjustable resistor 98 between the strain gauge 23 of the second path 87 and the fourth terminal 84. The second adjustable resistor 97 and the third adjustable resistor 98 are connected in series to the second chip resistor 93 and in parallel with each other.

[0085] These elements provided in the first path 86 and the second path 87 are provided in the following order with respect to the bridge circuit 80A: the first chip resistor 91 and the second chip resistor 93, the thermistor 95, the first adjusting resistor 96 and the second adjusting resistor 97, and the third adjusting resistor 98. The third adjusting resistor 98 is a resistive element for adjusting a deviation in the initial balance caused by providing the second adjusting resistor 97 in the second path 87. It is desirable that the third adjusting resistor 98, like the first adjusting resistor 96 and the second adjusting resistor 97, be a resistive element having a low resistance temperature coefficient indicating the rate of change in resistance value with respect to temperature change, for example, 1Ω or less.

[0086] 7, the third adjusting resistor 98 is connected to the second path 87 in parallel with the second adjusting resistor 97, but depending on the deviation of the initial balance, it may be connected to the first path 86 in parallel with the thermistor 95 and the first adjusting resistor 96. Furthermore, if the deviation of the initial balance is not eliminated even after the third adjusting resistor 98 is connected, a fourth adjusting resistor may be further connected to the first path 86 or the second path 87 so that the deviation of the initial balance falls within a predetermined range.

[0087] 8 is a flow chart showing the procedure of the load cell output adjustment method according to the application example. Steps S11 to S19 are performed in accordance with the procedure described in the above embodiment. In the application example, after the second adjustment is performed, the temperature characteristics of the outputs of six detection systems are further measured (step S21). Fig. 9 shows an example of the temperature characteristics of the outputs of six detection systems measured in a state in which a first chip resistor, a thermistor, and a first adjustment resistor are connected to a first path of a bridge circuit, and a second chip resistor and a second adjustment resistor are connected to a second path (after the second adjustment). As shown in Fig. 9, although all but one of the six detection systems are below the temperature characteristic compensation target of 0.2 mV / V, the temperature characteristic of one detection system may be 0.3 mV / V, exceeding the temperature characteristic compensation target.

[0088] Therefore, in the next step S23, a third adjustment is performed by connecting a third adjustment resistor to the first path or the second path to adjust the deviation of the initial balance caused by providing the second adjustment resistor in the second path (step S23). In other words, the temperature characteristic is measured again after the compensation of the temperature characteristic by the thermistor is made slightly overcompensated, and if the temperature characteristic still exceeds the target, double compensation is performed, thereby enabling compensation with higher accuracy. For example, in the bridge circuit of the Fx detection system, as shown in FIG. 7, a third adjustment resistor 98 is connected in parallel with the second adjustment resistor 97 to the second path 87. Depending on whether the output due to the temperature characteristic is deviated to the positive side or the negative side, it is determined whether the third adjustment resistor is connected to the first path or the second path.

[0089] Fig. 10 shows an example of the temperature characteristics of the outputs of six detection systems measured in a state where the first chip resistor, thermistor, and first adjustment resistor are connected to the first path of the bridge circuit, and the second chip resistor, second adjustment resistor, and third adjustment resistor are connected to the second path (after the third adjustment). In the example shown in Fig. 10, by connecting the third adjustment resistor, the outputs of all six detection systems are below 0.2mV / V, which is the target for compensation of the temperature characteristics.

[0090] Even if the third adjustment resistor is connected to the first path or the second path, if the temperature characteristic of at least one output of the six detection systems significantly exceeds the target, a step of connecting a fourth adjustment resistor to the first path or the second path is further performed. The final resistance value of the adjustment resistor, such as the above-mentioned third adjustment resistor or fourth adjustment resistor, for bringing the temperature characteristic within the compensation target may be calculated based on the measurement result of the temperature characteristic.

[0091] In this way, according to the load cell and the load cell output adjustment method of the application example, it is possible to increase the reliability of compensating for the temperature characteristics of the output of the bridge circuit even when the change in resistance value due to temperature change in the operating temperature range is large.

[0092] Although the preferred embodiment of the present disclosure has been described in detail above with reference to the accompanying drawings, the present disclosure is not limited to such examples. It is clear that a person having ordinary knowledge in the technical field to which the present disclosure belongs can conceive of various modified or amended examples within the scope of the technical ideas described in the claims, and it is understood that these also naturally belong to the technical scope of the present disclosure.

[0093] For example, in the above embodiment, an example of a load cell using a single-axis strain gauge has been described, but the load cell to which the technology of the present disclosure can be applied is not limited to such an example. For example, the technology of the present disclosure can be applied to a load cell using a biaxial shear strain gauge as shown in Figs. 11 and 12.

[0094] Specifically, Fig. 11 is a schematic diagram showing the arrangement of strain gauges in a six-component force detector of a modified example, and Fig. 12 is an explanatory diagram showing the gauge pattern of a biaxial shear strain gauge. The six-component force detector shown in Fig. 11 is provided with shear strain gauges 271, 272 of the Fx detection system and shear strain gauges 275, 277 of the Fz detection system, which will be described below, instead of the above-mentioned strain gauges 21-24 of the Fx detection system and the strain gauges 31-34 of the Fz detection system. Fig. 12 shows the shear strain gauge 271 as an example, but the shear strain gauges 272, 275, 277 also have substantially the same gauge pattern.

[0095] The shear strain gauge 271 is configured as a so-called arrow-shaped two-axis (two-pole). The shear strain gauge 271 has a first detection part 271a and a second detection part 271b made of a Cr-N thin film or the like formed on a common insulating layer 271c, which is a thin film of an insulating material. 271b Each of the first and second detection sections 271a and 271b is configured by sequentially connecting in series a plurality of straight sections arranged in parallel along the detection direction. The first detection section 271a and the second detection section 271b are set so that the electrical resistance is likely to change according to the strain in the direction in which the straight sections expand and contract (detection direction). The detection directions of the first detection section 271a and the second detection section 271b are arranged so as to be substantially perpendicular to each other. The shear strain gauge 271 is attached to the outer circumferential surface of the cylindrical section 250 so that the detection directions of the first detection section 271a and the second detection section 271b are inclined at 45° in opposite directions with respect to the central axis direction of the cylindrical section 250. The shear strain gauges 272, 275, and 277 are also attached to the outer circumferential surface of the cylindrical section 250 in a similar manner.

[0096] As shown in Fig. 11, shear strain gauges 271, 272, 275, and 277 are attached to the outer circumferential surface of the central portion in the central axis direction of cylindrical portion 250. Fx detection system shear strain gauge 271 is disposed midway between Mx detection system strain gauges 251 and 252. Fx detection system shear strain gauge 272 is disposed midway between Mx detection system strain gauges 253 and 254 (at a position symmetrical about the central axis with shear strain gauge 271). Fz detection system shear strain gauge 275 is disposed midway between Mz detection system strain gauges 261 and 262. Fz detection system shear strain gauge 277 is disposed midway between Mz detection system strain gauges 263 and 264 (at a position symmetrical about the central axis with shear strain gauge 275).

[0097] Further, the Fy detection system strain gauges 281-284 and the My detection system strain gauges 291-294 are arranged at positions shifted around the central axis to avoid interference with the Fx detection system strain gauges 271, 272 and the Fz detection system strain gauges 275, 277. For example, as shown in Fig. 11, the shear strain gauge 271, the strain gauge 282, the strain gauge 292, the shear strain gauge 277, the strain gauge 284, the strain gauge 294, the shear strain gauge 272, the strain gauge 283, the strain gauge 293, the shear strain gauge 275, the strain gauge 281 and the strain gauge 291 may be arranged sequentially at positions shifted at intervals of 30° around the central axis along the circumferential direction of the cylindrical portion 250.

[0098] The first and second detection parts of the shear strain gauges 271 and 272 of the Fx detection system constitute a bridge circuit similar to the bridge circuit shown in FIG. Cylindrical Part 250 generates an output according to the Fx direction component force input to the shear strain gauge 275. Similarly, the first and second detection parts of the shear strain gauges 275 and 277 of the Fz detection system form a bridge circuit similar to the bridge circuit shown in FIG. Cylindrical Part It generates an output according to the Fz direction force component input to 250.

[0099] The technology of the present disclosure can be applied to a load cell using a biaxial shear strain gauge configured in this manner, and the effects obtained by the above embodiment can be achieved. [Explanation of symbols]

[0100] 21, 22, 23, 24: strain gauge, 80, 80A: bridge circuit, 81: first terminal, 82: second terminal, 83: third terminal, 84: fourth terminal, 86: first path, 87: second path, 91: first chip resistor, 91a: resistive element (temporary resistor), 91b: resistive element (shunt resistor), 93: second chip resistor, 93a: resistive element (temporary resistor), 93b: resistive element (shunt resistor), 95: thermistor, 96: first adjustable resistor, 97: second adjustable resistor, 98: third adjustable resistor

Claims

1. A load cell equipped with a bridge circuit that converts the change in resistance of a strain gauge, which changes according to the load, into an electrical signal and outputs it. A first path on one side of the bridge circuit, a first chip resistor for adjusting an initial balance of the bridge circuit; a thermistor for compensating for temperature characteristics of the bridge circuit, the thermistors being respectively connected in series with the first chip resistors and connected in parallel with each other, and a first adjustment resistor for adjusting a deviation of the initial balance in a state where the thermistors are provided; A second path on the other side of the bridge circuit, a second chip resistor for adjusting the initial balance of the bridge circuit; a second adjustment resistor connected in series with the second chip resistor for adjusting a deviation in the initial balance caused by providing the first adjustment resistor in the first path; Load cell.

2. the first adjustment resistor and the second adjustment resistor are the same resistor element; 2. The load cell of claim 1.

3. At least one of the first path and the second path, a third adjustment resistor for adjusting a deviation in the initial balance caused by providing the second adjustment resistor; 3. The load cell according to claim 2.

4. The element resistance value of the strain gauge is 1 KΩ or more.

2. The load cell of claim 1.

5. The load cell is 2. The load cell according to claim 1, which is a multi-force detector for detecting a plurality of force components.

6. A method for adjusting the output of a load cell equipped with a bridge circuit that converts the change in resistance of a strain gauge that changes according to the load into an electrical signal and outputs the signal, comprising the steps of: a first chip resistor for adjusting an initial balance of the bridge circuit is connected to a first path on one side of the bridge circuit; a second chip resistor for adjusting an initial balance of the bridge circuit is connected to a second path on the other side of the bridge circuit; a thermistor for compensating for temperature characteristics of the bridge circuit, the thermistor being connected in series with the first chip resistor, and a first adjustment resistor for adjusting a deviation of the initial balance in a state where the thermistor is provided, are connected in parallel to each other in the first path; a second adjustment resistor is connected to the second path in series with the second chip resistor, the second adjustment resistor being for adjusting a deviation in the initial balance caused by providing the first adjustment resistor in the first path; How to adjust the load cell output.

7. a third adjustment resistor is connected to at least one of the first path and the second path for adjusting a deviation in the initial balance caused by providing the second adjustment resistor; The method for adjusting an output of a load cell according to claim 6.

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