LOAD CELL AND OUTPUT ADJUSTMENT METHOD FOR A LOAD CELL

Abstract

It becomes possible to adjust an initial resistance value and at the same time compensate for the temperature characteristics of a load cell that uses a strain gauge with a relatively large element resistance value and a relatively large temperature dependence. A load cell comprises a bridge circuit designed to convert a change in the resistance of a strain gauge, which varies according to a load, into an electrical signal and to output that electrical signal. The load cell includes, in a first path on one side of the bridge circuit, a first chip resistor designed to adjust for an initial balance of the bridge circuit, a thermistor designed to compensate for a temperature characteristic of the bridge circuit, and a first matching resistor designed to adjust for a deviation of the initial balance in a state where the thermistor is present. These two resistors are arranged in series with the first chip resistor and in parallel with each other.The load cell has, in a second path on the other side of the bridge circuit, a second chip resistor designed to adjust the initial calibration of the bridge circuit, and a second matching resistor designed to adjust the deviation of the initial calibration caused by the arrangement of the first matching resistor in the first path, and which is arranged in series with the second chip resistor.

Description

Technical field

[0001] The present invention relates to a load cell with a bridge circuit and an output adaptation method for a load cell. State of the art

[0002] In commonly used load cells, a change in the resistance value of a strain gauge is caused by deformation induced by a load. Well-known load cells are designed, for example, as described below. A strain gauge is arranged in a bridge circuit, which is a transducer circuit that converts the change in the strain gauge's resistance value due to a load into an electrical signal, and the change in resistance value is thus output as an electrical signal.

[0003] In load cells with this configuration, both the strain gauge and the deformation generator to which the strain gauge is attached have temperature characteristics where a temperature change produces a deformation. Thus, even when no load is actually present, an output can be generated as if a load were being applied. When the strain gauge is used in a bridge circuit, the bridge circuit is designed to cancel out the linear expansion of the strain gauge. Therefore, any difference between the temperature characteristics of the strain gauge or the deformation generator is output as the temperature characteristics of the load cell. This is expected to provide suitable temperature compensation to detect the extent of deformation due to the load applied to the strain gauge.

[0004] PTL 1 discloses, for example, a load cell with an adjustment circuit for zero adjustment (initial adjustment) in which a chip resistor is arranged such that a potential difference extracted from a bridge circuit becomes zero when a load is zero at a predetermined temperature. State of the artPatent literature

[0005] PTL 1: Unexamined Japanese patent application publication no. 2008-151596 Brief description of the invention: Technical problem

[0006] However, some load cells exhibit a large range of change in the strain gauge resistance value depending on the temperature, making it difficult to adjust the initial calibration while simultaneously compensating for temperature characteristics. Such load cells also include those with a high output, such as force detection sensors mounted on a vehicle axle to detect a load applied to a wheel, as well as load cells that detect component forces and exhibit large differences in sensitivity to each component force.

[0007] The present invention has been designed with regard to the aforementioned problems. The object of the present invention is to provide a load cell and an output adjustment method for a load cell that can adjust the initial resistance value and thereby compensate for the temperature characteristics of the load cell, wherein a strain gauge with a relatively large element resistance value and a relatively large temperature dependence is used. Solution to the problem

[0008] To solve the aforementioned problems, according to one aspect of the present invention, the following is stated: A load cell with a bridge circuit designed to convert a change in the resistance of a strain gauge, which changes according to a load, into an electrical signal and output the electrical signal. The load cell has the following features: in a first path on one side of the bridge circuit: a first chip resistor designed to adjust an initial bridge circuit calibration; and a thermistor designed to compensate for a temperature characteristic of the bridge circuit, and a first matching resistor designed to adjust for a deviation of the initial adjustment in a state in which the thermistor is present, wherein the thermistor and the first matching resistor are arranged in series with the first chip resistor and in parallel to each other, and in a second path on the other side of the bridge circuit: a second chip resistor designed to adjust the initial calibration of the bridge circuit; and a second matching resistor designed to adjust for the deviation of the initial adjustment caused by the placement of the first matching resistor in the first path, wherein the second matching resistor is placed in series with the second chip resistor.

[0009] To solve the aforementioned problems, according to a further aspect of the present invention, the following is provided: An output adaptation method for a load cell with a bridge circuit, designed to convert a change in the resistance of a strain gauge, which changes according to a load, into an electrical signal and to output the electrical signal. The output adaptation method comprises the following measures: Arranging a first chip resistor designed to match an initial adjustment of the bridge circuit in a first path on one side of the bridge circuit; Arranging a second chip resistor, designed to adjust the initial alignment of the bridge circuit, in a second path on the other side of the bridge circuit; Arranging a thermistor designed to compensate for a temperature characteristic of the bridge circuit, and a first matching resistor designed to adjust for a deviation of the initial adjustment in a state where the thermistor is present, in the first path, wherein the thermistor and the first matching resistor are arranged in series with the first chip resistor and in parallel with each other; and Arranging a second matching resistor in the second path, designed to adjust for the deviation of the initial adjustment caused by the arrangement of the first matching resistor in the first path, wherein the second matching resistor is arranged in series with the second chip resistor. Advantageous effects of the invention

[0010] As described above, according to the present invention it is possible to easily adjust the initial resistance value and at the same time compensate for the temperature characteristics of the load cell by using a strain gauge with a relatively large element resistance value and a relatively large temperature dependence. Short description of the drawings

[0011] The drawings show in: Fig. 1 A cross-sectional view of a load cell (six-component force detector) according to one embodiment. Fig. 2 a schematic representation of an arrangement of strain gauges in the load cell according to the embodiment. Fig. 3 an explanatory representation of a configuration of a bridge circuit in the load cell according to the embodiment. Fig. 4 a flowchart illustrating the sequence of an output adjustment procedure for a load cell according to the embodiment. Fig. 5 an explanatory representation of a first adjustment in the output adjustment procedure for a load cell according to the embodiment. Fig. 6 an explanatory representation of an output state after the first adjustment in the output adjustment procedure for a load cell according to the embodiment. Fig. 7 An explanatory representation of a configuration of a bridge circuit in a load cell according to an application example of the embodiment. Fig. 8 a flowchart that illustrates the sequence of an output adjustment procedure for a load cell according to the application example. Fig. 9 an explanatory representation of an output state after a second adjustment in the output adjustment procedure for a load cell according to the application example. Fig. 10 an explanatory representation of an output state after a third adjustment in the output adjustment procedure for a load cell according to the application example. Fig. 11 a schematic representation of an arrangement of strain gauges in a six-component force detector according to a modification. Fig. 12 an explanatory illustration of a strain measurement pattern of a biaxial shear strain gauge. Description of the embodiments

[0012] A preferred embodiment of the invention is described in detail below with reference to the accompanying drawings. Components with essentially the same function and configuration are designated by the same reference numerals in the description and in the drawings, and redundant descriptions thereof are omitted. 1. Summary of the embodiment according to the present invention 1-1. Detailed description of the background of the present invention

[0013] First, the background for the creation of the technology of the present invention is described. It should be noted that the background described below represents only one aspect of the configuration of a load cell for which the technology according to the present invention can be used. The load cell for which the present invention can be used is not limited to a load cell with the configuration shown below as an example.

[0014] Known six-component force detectors detect loads (Fx, Fy and Fz) applied to a wheel of a vehicle, such as a car, in the front-to-back direction (hereinafter also referred to as the "x-axis direction") of the vehicle, in the vehicle width direction (hereinafter also referred to as the "y-axis direction") and in the vertical direction (hereinafter also referred to as the "z-axis direction").

[0015] The six-component force detector also detects moments (Mx, My, and Mz) about the x-axis, y-axis, and z-axis, respectively. Such a six-component force detector has a cylindrical deformation generator mounted on a wheel axle. However, considering the tolerance to an applied load, it is difficult to obtain a result equivalent to that of a load cell detecting a load in only one axial direction when using a general-purpose film strain gauge with a strain factor of approximately 2.

[0016] In contrast, it is assumed that a desired output can be obtained by using a thin-film strain gauge, such as a Cr-N strain gauge, with a large element resistivity and a large strain factor (e.g., the strain factor of the Cr-N strain gauge is between 10 and 12). However, the Cr-N strain gauge has a large temperature dependence of the element resistivity, which poses a problem when used for a six-component force detector.

[0017] This means that if a strain gauge with a large element resistance value and a large strain factor is used, the change in resistance value due to a temperature change within a service temperature range will be large. Therefore, the problem is that it is not easy to compensate for the temperature characteristics of the output from a six-component force detector.

[0018] Furthermore, the six-component force detector has the characteristic that the sensitivity of the strain gauge varies considerably depending on the direction of the component force. For this reason, even if the bridge circuit is designed with a general-purpose foil strain gauge and the initial calibration is adjusted according to the component force with low sensitivity, the compensation for the temperature characteristics may be insufficient for the component force with high sensitivity.

[0019] Accordingly, the situation described below is also conceivable. The characteristics of a change in output depending on temperature are recorded, and the temperature parameters are generated in advance. For example, the temperature of the strain gauge is measured directly, and a processor uses the temperature parameters to correct the output from the six-component force detector. However, since it requires adding a temperature sensor and an arithmetic processing function in the software, which were not originally necessary, this is not a desirable solution.

[0020] Against this background, the technology of the present invention provides a load cell and an output adjustment method for a load cell that can adjust an initial calibration and simultaneously compensate for temperature characteristics within a service temperature range. The load cell and the output adjustment method for a load cell are designed to function without the addition of a temperature sensor or software function, even when a strain gauge with a high element resistance value and a large strain factor is used. 1-2. Features of the embodiment according to the present invention

[0021] (1-2-1) One embodiment according to the present invention is a load cell with a bridge circuit that converts a change in the resistance of a strain gauge, which changes according to a load, into an electrical signal and outputs the electrical signal. The load cell has a configuration comprising the following: in a first path on one side of the bridge circuit: a first chip resistor for adjusting an initial calibration of the bridge circuit; and a thermistor for compensating a temperature characteristic of the bridge circuit and a first matching resistor for adjusting a deviation of the initial adjustment in a state in which the thermistor is present, wherein the thermistor and the first matching resistor are arranged in series with the first chip resistor and in parallel to each other, and in a second path on the other side of the bridge circuit: a second chip resistor for adjusting the initial calibration of the bridge circuit; and a second matching resistor for adjusting the deviation of the initial adjustment caused by the arrangement of the first matching resistor in the first path, wherein the second matching resistor is arranged in series with the second chip resistor.

[0022] It should be noted that the embodiment according to the present invention can also be implemented as an output adaptation method for adapting an output of a load cell with a bridge circuit that converts a change in the resistance of a strain gauge, which changes depending on a load, into an electrical signal and outputs the electrical signal.

[0023] This configuration allows for easy adjustment of the initial calibration while simultaneously compensating for the temperature characteristics of subsequent load cells. These load cells include, for example, a load cell with a strain gauge exhibiting a relatively high element resistance of 1 kΩ or more and significant temperature characteristics, as well as a load cell designed to detect component forces. This improves the reliability of the load cell's output.

[0024] It should be noted that the expression "first path on one side of the bridge circuit" and the expression "second path on the other side of the bridge circuit" refer to two current paths in the bridge circuit. The first path and the second path are each designed to have two strain gauges.

[0025] Furthermore, the term "initial adjustment" refers to a difference (potential difference) between the potential between the two strain gauges in the first path and the potential between the two strain gauges in the second path in a state where no load is applied to the load cell. The expression "adjusting the initial adjustment deviation" means that the potential difference is adjusted so that it approaches zero in a state where no load is applied.

[0026] The term "bridge circuit temperature characteristics" further specifies characteristics where the load cell output changes with temperature. The term "large temperature characteristics" indicates that the range of variation in the load cell output that changes with temperature is large. The term "bridge circuit temperature characteristics compensation" indicates that the range of variation in the load cell output that changes with temperature is adjusted so that it falls within a predetermined range.

[0027] (1-2-2) Furthermore, in the embodiment according to the present invention, the first matching resistor and the second matching resistor can be identical resistance elements.

[0028] This configuration eliminates the need to individually select the first and second matching resistors to compensate for temperature characteristics when the first and second chip resistors are connected to the bridge circuit. Furthermore, even if the first and second matching resistors are identical resistors, the initial bridge circuit calibration deviation can fall within the predetermined range.

[0029] (1-2-3) Furthermore, in the embodiment according to the present invention, a third adjustment resistor can be arranged in at least one of the first path and the second path to adjust the deviation of the initial adjustment caused by the arrangement of the second adjustment resistor.

[0030] With this configuration, the initial adjustment deviation can be easily adjusted. The initial adjustment deviation can also be easily adjusted even if a slight deviation is generated when the first and second adjustment resistors, which are identical resistor elements, are located in the first and second paths, respectively.

[0031] (1-2-4) Furthermore, in the embodiment according to the present invention, the strain gauge can have an element resistance value greater than or equal to 1 kΩ.

[0032] With this configuration, a relatively large desired load can be detected by the load cell, where the temperature characteristics are compensated when a strain gauge with a relatively large element resistance value is used.

[0033] (1-2-5) Furthermore, in the embodiment according to the present invention, the load cell can include the bridge circuits. and the load cell can be a multi-component force detector designed to detect component forces.

[0034] With this configuration, even if the bridge circuits have different sensitivities to deformation depending on the directions of the component forces, it is possible to easily adjust the initial balance and at the same time compensate for the temperature characteristics of the outputs of the corresponding bridge circuits. 2. Details of the embodiment according to the present invention 2-1. Configuration example for a load cell Six-component force detector

[0035] Next, a configuration example for a load cell according to the embodiment of the present invention will be described.

[0036] An example is described in this embodiment. In this example, the technology of the present invention is used as one aspect of a load cell for the six-component force detector, which can detect six force components (Fx, Fy, Fz, Mx, My, and Mz) applied to a wheel of a vehicle. The load cell according to this embodiment is a six-component force detector that detects six force components applied to the wheel. The load cell is arranged in a hub bearing unit that is attached to a suspension device on which the wheel of a vehicle, such as a car, is rotatably mounted.

[0037] Fig. Figure 1 is a cross-sectional view of the hub bearing unit, which includes the six-component force detector, along a plane containing a wheel axle. Fig. 1 indicates the right side as the outside in the direction of the vehicle's width, and the left side as the inside in the direction of the vehicle's width. It should be noted that the in Fig. The configuration of the hub bearing unit shown in point 1 is merely an example and does not reflect the configuration shown in the diagram. Fig. The configuration shown is limited to 1.

[0038] A hub bearing unit 100 comprises a hub 110, an outer cylinder 120, an inner cylinder 130, a rolling element 140, a base 150, and a six-component force detector 1. The hub 110 is an element to which a rim disc of a wheel (not shown) is attached, the wheel having a rim and a tire. The hub 110 is formed by the permanent attachment of a cylinder 111, a flange 112, a collar 113, and the like.

[0039] The cylinder 111 is cylindrical and concentric to the axis of rotation (wheel axis) of the wheel. The cylinder 111 is inserted into the inner diameter of the inner cylinder 130, a detection unit 10, and the base 150. A wedge bore 111a, into which a splined shaft of a drive shaft (not shown) is to be inserted, is formed in a region on the outside of an inner circumferential surface of the cylinder 111 in the vehicle width direction.

[0040] The flange 112 is disc-shaped and designed to protrude from one end on the outside of the cylinder 111 in the vehicle width direction towards the outer diameter side, acting as a hand guard. A surface on the outside of the flange 112 in the vehicle width direction serves as a base to which the rim disc is attached.

[0041] The flange 112 has, for example, approximately five openings 112a formed at equal intervals around a predetermined pitch circle diameter in the circumferential direction, into which hub bolts are to be inserted. The collar 113 has a cylindrical shape that projects from the surface on the outside of the flange 112 in the vehicle width direction and is concentric with the wheel axle. The collar 113 is fitted into a central bore, which is a circular opening formed in the center of the rim disc, and improves the assembly accuracy of the wheel.

[0042] The outer cylinder 120, the inner cylinder 130, and the rolling element 140 together form a rolling bearing (hub bearing) on ​​which the wheel is rotatably mounted. The outer cylinder 120 is formed by the permanent attachment of a cylinder 121, a flange 122, and the like. The cylinder 121 has a cylindrical shape concentric with the wheel axis.

[0043] A raceway surface for guiding the rolling element 140 is formed on the inner circumferential surface of the cylinder 121. One end on the inside of the cylinder 121, in the vehicle width direction, is formed such that it projects inwards in the vehicle width direction relative to an end on the inside of a cylinder 131 of the inner cylinder 130.

[0044] The flange 122 is designed such that it protrudes from one end on the outside of the cylinder 121 in the vehicle width direction towards the outer diameter side, forming a hand guard. The flange 112 of the hub 110 is attached to and fixed to the flange 122. A surface on the outside of the flange 122 in the vehicle width direction rests against a surface on the inside of the flange 112 of the hub 110 in the vehicle width direction. The flange 122 has screw holes 122a, which are formed concentrically with the openings 112a of the hub 110. A hub bolt (not shown), used to fasten the wheel, is to be inserted into the respective screw holes 122a.

[0045] The inner cylinder 130 is formed by a permanent attachment of the cylinder 131, a flange 132, and the like. The cylinder 131 is a cylindrical element concentric with the wheel axis and is inserted into the inner diameter face of the cylinder 121 of the outer cylinder 120. A predetermined distance is formed between the outer circumferential surface of the cylinder 131 and the inner circumferential surface of the cylinder 121 of the outer cylinder 120.

[0046] A raceway surface for guiding the rolling element 140 is formed on the outer circumferential surface of the cylinder 131. The flange 132 is designed such that it projects from one end on the outside of the cylinder 131 in the vehicle width direction towards the inner diameter side. The flange 132 holds one end on the outside of a first flange 12 of the detection unit 10 in the vehicle width direction.

[0047] The rolling element 140 is a bearing located between the raceway surfaces of the outer cylinder 120 and the inner cylinder 130. The rolling element 140 is positioned between the outer cylinder 120 and the inner cylinder 130 together with a cage 141 and a cage 142 for positioning the rolling element 140 between the outer cylinder 120 and the inner cylinder 130.

[0048] The base 150 attaches and secures the hub bearing unit 100 to a support (a hub stub) (not shown) of the suspension device. The base 150 is formed by the permanent attachment of a cylinder 151, a flange 152, a recess 153, a projection 154, and the like. The cylinder 151 is a cylindrical element that is concentric to the wheel axle and has one end inserted into it on the inside of the cylinder 111 of the hub 110 in the vehicle width direction. The outer circumferential surface of the cylinder 111 of the hub 110 is arranged such that it faces the inner circumferential surface of the cylinder 151 with a predetermined distance between them in the radial direction.

[0049] The flange 152 is designed such that it projects from one end of the cylinder 151 in the direction of the vehicle width towards the outer diameter, forming a hand guard. The flange 152 is a mounting surface that secures the base 150 to the support (not shown). Circumferentially distributed openings 152a are formed in the flange 152, into which bolts for fastening to the support are inserted.

[0050] A through-hole 152b is formed in the flange 152, leading from the inside of a space in which the outer circumferential surface of a cylinder 11 of the detection unit 10 is arranged, to the outer circumferential edge of the flange 152. For example, wiring connected to a strain gauge is arranged in the through-hole 152b.

[0051] A recess 153 is formed in the axial direction of the inner circumferential surface of the base 150 by progressively widening the inner diameter of a region corresponding to the flange 152. The recess 153 holds a second flange 13 of the detection unit 10. The projection 154 has a cylindrical shape and is formed to protrude radially from a central region of the flange 152 towards the outside of the vehicle width.

[0052] The outer circumferential surface of the projection 154 is arranged such that it faces the inner circumferential surface at one end on the inside of the cylinder 121 of the outer cylinder 120 in the vehicle width direction, with a gap in the radial direction formed between them.

[0053] The six-component force detector 1 is a load cell capable of detecting loads and moments about these three axes acting on the wheel. The six-component force detector 1 comprises a substantially cylindrical sensing unit 10, strain gauges mounted on the sensing unit 10, and a bridge circuit incorporating the strain gauges.

[0054] The sensing unit (sensor core) 10 comprises the cylinder 11, the first flange 12, the second flange 13, and the like. The cylinder 11 is cylindrical, with its inner and outer diameters being substantially constant over a predetermined length in the axial direction, and the strain gauges described later are attached (bonded) to the cylinder 11. The first flange 12 is mounted at one end on the outside of the cylinder 11 in the vehicle width direction and is shaped to project from the cylinder 11 towards both the outer and inner diameter sides.

[0055] The first flange 12 is attached to the inner cylinder 30 in a state in which the outer circumferential surface rests against the inner circumferential surface near an end on the outside of the cylinder 131 of the inner cylinder 30 in the vehicle width direction, and an end surface rests against a surface on the inside of the flange 132 in the vehicle width direction.

[0056] The second flange 13 is attached at one end to the inside of the cylinder 11 in the vehicle width direction and is designed to project towards the cylinder 11 on both the outer and inner diameter sides. The second flange 13 is attached to the base 150 in such a way that its outer circumferential surface and end face are inserted into the recess 153 of the base 150. In this configuration, essentially all forces acting on the wheel are transmitted to and from the base 150 via the sensing unit 10.

[0057] The six-component force detector 1 comprises 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 with a bridge circuit containing strain gauges formed on the cylinder 11 of the detection unit 10 described above. The Fx detection system detects a force Fx acting on the cylinder 11 of the detection unit 10 in the radial direction (x-axis direction).

[0058] The Fy detection system detects a force Fy acting on cylinder 11 of the detection unit 10 in the axial direction (y-axis direction). The Fz detection system detects a force Fz acting on cylinder 11 of the detection unit 10 in the radial direction (z-axis direction) orthogonal to the x-axis direction.

[0059] The Mx detection system detects a moment Mx acting on cylinder 11 of the detection unit 10 about the x-axis. The My detection system detects a moment My acting on cylinder 11 of the detection unit 10 about the y-axis. The Mz detection system detects a moment Mz acting on cylinder 11 of the detection unit 10 about the z-axis.

[0060] Each of the Fx detection system, Fy detection system, Fz detection system, Mx detection system, My detection system and Mz detection system described above has a bridge circuit that includes four strain gauges. Fig. Figure 2 is a schematic representation of an arrangement of the strain gauges in the six-component force detector 1. Fig. Figure 3 shows the arrangement of the strain gauges of the Fx detection system and the configuration of the bridge circuit in the six-component force detector 1.

[0061] Fig. Figure 3 provides an illustrative example of the arrangement of the strain gauges of each force detection system (the Fx detection system, the Fy detection system and the Fz detection system) and each moment detection system (the Mx detection system, the My detection system and the Mz detection system) as well as the configuration of the bridge circuit.

[0062] As in Fig. 2 and Fig. Figure 3 shows that the Fx detection system comprises strain gauges 21 to 24. The strain gauges 21 to 24 are uniaxial. They are mounted on the outer circumferential surface of the cylinder 11 such that their detection directions are parallel to the central axis of the cylinder 11. Strain gauge 21 is located in a region on the side of the first flange 12 (in the vicinity of an intermediate region 14) on the outer circumferential surface of the cylinder 11.

[0063] The strain gauge 22 is arranged on a straight line passing through the strain gauge 21 and parallel to the axial direction of the cylinder 11, and is located in a region on the side of the second flange 13 (region near an intermediate region 15) on the outer circumferential surface of the cylinder 11. The strain gauge 23 is arranged at a position offset by 180° around the central axis of the cylinder 11 from the strain gauge 22 (position that is symmetrical to the strain gauge 22 with respect to the central axis of the cylinder 11).

[0064] The strain gauge 24 is arranged in a position offset by 180° around the central axis of the cylinder 11 from the strain gauge 21 (position which is symmetrical to the strain gauge 21 with respect to the central axis of the cylinder 11).

[0065] As in Fig. Figure 3 shows the bridge circuit of the Fx detection system, which is configured as a Wheatstone bridge circuit. In this circuit, the strain gauges 21 to 24 are arranged in a circular sequence. A positive electrode and a negative electrode of a power source are connected between strain gauge 22 and strain gauge 23, and between strain gauge 21 and strain gauge 24, respectively. The bridge circuit extracts a potential difference between a terminal between strain gauge 21 and strain gauge 22 and a terminal between strain gauge 23 and strain gauge 24 as its output. The configuration of the bridge circuit will be described in detail later.

[0066] The Fy detection system comprises strain gauges 41 to 44. These strain gauges are uniaxial. They are mounted on the outer circumferential surface of the cylinder 11 such that their detection directions are parallel to the central axis of the cylinder 11. Strain gauge 41 is positioned midway between strain gauges 21 and 22 of the Fx detection system.

[0067] The strain gauges 42, 43, and 44 are arranged at positions offset by 90°, 180°, and 270° respectively around the central axis of the cylinder 11 with respect to the strain gauge 41. The bridge circuit of the Fy detection system has the same configuration, except that the strain gauges 21 to 24 of the Fig. The Fx detection system shown in section 3 is replaced by the strain gauges 41 to 44.

[0068] The Fz detection system comprises strain gauges 31 to 34. The strain gauges 31 to 34 are uniaxial. The strain gauges 31 to 34 are mounted on the outer circumferential surface of the cylinder 11 such that their detection directions are parallel to the central axis of the cylinder 11. The strain gauge 31 is offset by 90° around the central axis of the cylinder 11 with respect to the strain gauge 21 of the Fx detection system.

[0069] The strain gauge 32 is arranged offset by 90° around the central axis of the cylinder 11 with respect to the strain gauge 22 of the Fx detection system. The strain gauges 31 and 32 are arranged on the same line parallel to the axis of the cylinder 11. The strain gauge 33 is arranged at a position offset by 180° around the central axis of the cylinder 11 from the perspective of the strain gauge 32 (a position that is symmetrical to the strain gauge 32 with respect to the central axis of the cylinder 11).

[0070] The strain gauge 34 is arranged in a position offset by 180° around the central axis of the cylinder 11 from the perspective of the strain gauge 31 (a position symmetrical to the strain gauge 31 with respect to the central axis of the cylinder 11). The bridge circuit of the Fz detection system has the same configuration, except that the strain gauges 21 to 24 of the Fig. The Fx detection system shown in section 3 is replaced by the strain gauges 31 to 34.

[0071] The Mx detection system comprises strain gauges 51 to 54. Strain gauges 51 to 54 are uniaxial. They are mounted on the outer circumferential surface of the cylinder 11 such that their detection directions are parallel to the central axis of the cylinder 11. Strain gauge 51 is positioned adjacent to strain gauge 31 of the Fz detection system on the central axis of the cylinder 11.

[0072] The strain gauge 52 is arranged such that it is located adjacent to the strain gauge 32 of the Fz detection system on the central axis of the cylinder 11. The strain gauges 51 and 52 are arranged on the same line parallel to the axis of the cylinder 11. The strain gauge 53 is located at a position offset by 180° around the central axis of the cylinder 11 from the strain gauge 52 (a position that is symmetrical to the strain gauge 52 with respect to the central axis of the cylinder 11).

[0073] The strain gauge 54 is arranged in a position offset by 180° around the central axis of the cylinder 11 from the perspective of the strain gauge 51 (a position symmetrical to the strain gauge 51 with respect to the central axis of the cylinder 11). The bridge circuit of the Mx detection system has the same configuration, except that the strain gauges 21 to 24 of the Fig. The Fx detection system shown in section 3 is replaced by the strain gauges 51 to 54.

[0074] The My detection system comprises strain gauges 71 to 74. Strain gauges 71 to 74 are shear strain gauges. Strain gauges 71 to 74 are mounted on the outer circumferential surface of the cylinder 11 such that their detection directions are the circumferential direction of the cylinder 11. Strain gauge 71 is positioned midway between strain gauges 41 and 42 of the Fy detection system. Strain gauge 72 is positioned midway between strain gauges 42 and 44 of the Fy detection system.

[0075] The strain gauges 73 and 74 are arranged in positions symmetrical to the strain gauges 72 and 71 respectively, with respect to the central axis of the cylinder 11. The bridge circuit of the My detection system has the same configuration, except that the strain gauges 21 to 24 of the Fig. The Fx detection system shown in section 3 is replaced by the strain gauges 61 to 64.

[0076] The Mz detection system comprises strain gauges 61 to 64. The strain gauges 61 to 64 are uniaxial. The strain gauges 61 to 64 are mounted on the outer circumferential surface of the cylinder 11 such that their detection directions are parallel to the central axis of the cylinder 11. The strain gauge 61 is positioned adjacent to the strain gauge 21 of the Fx detection system on the central axis of the cylinder 11.

[0077] The strain gauge 62 is arranged such that it is located adjacent to the strain gauge 22 of the Fx detection system on the central axis of the cylinder 11. The strain gauges 61 and 62 are arranged on the same line parallel to the axis of the cylinder 11. The strain gauge 63 is located at a position offset by 180° around the central axis of the cylinder 11 from the strain gauge 62 (a position that is symmetrical to the strain gauge 62 with respect to the central axis of the cylinder 11).

[0078] The strain gauge 64 is arranged in a position offset by 180° around the central axis of the cylinder 11 from the strain gauge 61 (a position symmetrical to the strain gauge 61 with respect to the central axis of the cylinder 11). The bridge circuit of the Mz detection system has the same configuration, except that the strain gauges 21 to 24 of the Fig. The Fx detection system shown in section 3 is replaced by the strain gauges 61 to 64. 2-2. Bridge circuit

[0079] Next, the bridge circuit of the [unclear text] will be used as an example. Fig. Figure 3 describes a configuration example for the bridge circuit of each force detection system and each moment detection system.

[0080] A bridge circuit 80 of the in Fig. The Fx detection system shown in Figure 3 has four ports: the first, second, third, and fourth ports 81, 82, 83, and 84, respectively, as well as four strain gauges 21, 22, 23, and 24. Strain gauge 21 is located between the first port 81 and the second port 82, and strain gauge 22 is located between the second port 82 and the fourth port 84. Strain gauge 24 is located between the first port 81 and the third port 83, and strain gauge 23 is located between the third port 83 and the fourth port 84.

[0081] 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 forms 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 forms a second path 87.

[0082] The strain gauges 21, 22, 23, and 24 are resistive elements whose respective resistance values ​​change according to the degree of deformation. In this embodiment, the strain gauge has a material with a strain factor of 4 or more. The strain gauge can, for example, be a Cr-N thin film. If the strain gauge has a strain factor of 4 or more, an output can be obtained that is desirable for the six-component force detector 1 for detecting the load applied to the wheel. However, the strain gauge is not limited to the Cr-N thin film.

[0083] When a load is applied to the deformation-generating body in the bridge circuit 80, a deformation 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 extent of the deformation. The bridge circuit 80 outputs an electrical signal corresponding to a potential difference between the second terminal 82 of the first path 86 and the third terminal 83 of the second path 87.

[0084] In this embodiment, the bridge circuit 80 comprises a first chip resistor 91 (91a and 91b), a thermistor 95, and a first matching resistor 96 between the strain gauge 22 and the fourth terminal 84 in the first path 86. The thermistor 95 and the first matching resistor 96 are arranged in series with the first chip resistor 91 and in parallel with each other. The bridge circuit 80 further comprises a second chip resistor 93 (93a and 93b) and a second matching resistor 97 between the strain gauge 23 and the fourth terminal 84 in the second path 87. The second matching resistor 97 is arranged in series with the second chip resistor 93.

[0085] These elements arranged in the first path 86 and in the second path 87 are arranged for the bridge circuit 80 in the following order: the first chip resistor 91, the second chip resistor 93, the thermistor 95, the first matching resistor 96 and the second matching resistor 97.

[0086] The first chip resistor 91 is a resistive element for adjusting a deviation in the initial calibration, measured in a state where the strain gauges 21, 22, 23, and 24 are arranged in the bridge circuit 80. Since the target resistance value is relatively large, a chip resistor is used as the resistive element. In the Fig. In the example shown for the bridge circuit 80, the first chip resistor 91 has two resistor elements 91a and 91b arranged in parallel to each other.

[0087] Similarly, the second chip resistor 93 is a resistive element for adjusting the deviation of the initial calibration, measured in a state where the strain gauges 21, 22, 23 and 24 are arranged in the bridge circuit 80. In the Fig. In the example shown for the bridge circuit 80, the second chip resistor 93 has two resistor elements 93a and 93b arranged in parallel to each other.

[0088] Generally, chip resistors with predetermined resistance values ​​are arranged at given intervals. Since the first chip resistor 91 and the second chip resistor 93 are arranged in a state where the strain gauges 21, 22, 23, and 24 are arranged in the bridge circuit 80, the following chip resistors are used. The chip resistors have suitable resistance values ​​that make the resistance values ​​of the first path 86 and the second path 87 appropriate.

[0089] In this embodiment, chip resistors (hereinafter also referred to as "temporary resistors") 91a and 93a with given resistance values ​​are first selected, which can be used to define the resistance values ​​of the first path 86 and the second path 87 as suitable resistance values. Then the chip resistors 91a and 93a are arranged in the first path 86 and the second path 87, respectively.

[0090] Furthermore, the initial calibration of the bridge circuit 80 is measured at a predetermined reference temperature in a state in which the temporary resistors 91a and 93a are arranged in the bridge circuit 80. The chip resistors (hereinafter also referred to as "shunt resistors") 91b and 93b are selected with resistance values ​​that can eliminate the deviation of the initial calibration and are arranged in parallel with the temporary resistors 91a and 93a, respectively.

[0091] Consequently, the deviation of the initial adjustment of the bridge circuit 80 at the predetermined reference temperature can fall within a desired range. It should be noted that the shunt resistors 91b and 93b may be unnecessary if the deviation of the initial adjustment of the bridge circuit 80 falls within the desired range at the predetermined reference temperature using only the temporary resistors 91a and 93a.

[0092] It is assumed that the initial adjustment of the bridge circuit 80 is performed in a state where the first chip resistor 91 and the second chip resistor 93 are located in the bridge circuit 80. If, in this case, the sides equipped with the strain gauges 21, 22, 23, and 24 exhibit equivalent temperature characteristics, the corresponding temperature characteristics are canceled out by the configuration of the bridge circuit 80, and no output is generated in a state where no load is applied.

[0093] If, on the other hand, an output is generated even when no load is applied, it can be determined that the initial calibration of the bridge circuit 80 deviates. Therefore, in this embodiment, the thermistor 95, which is a temperature compensation element with characteristics inverse to those reflected in the output from the bridge circuit 80, is integrated into the bridge circuit 80 to compensate for the temperature characteristics.

[0094] The thermistor 95 is a resistive element used to compensate for the temperature characteristics of the bridge circuit 80 in a state where the first chip resistor 91 and the second chip resistor 93 are arranged in the bridge circuit 80. The thermistor 95 is an NTC (negative temperature coefficient) thermistor with characteristics where its resistance decreases with increasing temperature. The thermistor 95 generally has a high resistance value (e.g., 1 kΩ or more) and is suitable for compensating for temperature characteristics.

[0095] The temperature coefficient of the resistor, which indicates the rate at which the resistance value of thermistor 95 decreases with increasing temperature, is desirablely larger. The first matching resistor 96 is a resistive element for adjusting the deviation of the initial adjustment in a state where the first chip resistor 91 and thermistor 95 are arranged in the bridge circuit 80. The second matching resistor 97 is a resistive element for adjusting the deviation of the initial adjustment caused by the arrangement of the first matching resistor 96 in the first path 86.

[0096] In the bridge circuit 80, in which the first chip resistor 91 and the second chip resistor 93 are arranged, the initial adjustment of the bridge circuit 80 is set at the predetermined reference temperature. However, since both the first chip resistor 91 and the second chip resistor 93 exhibit temperature characteristics, the output of the bridge circuit 80 also exhibits these temperature characteristics.

[0097] Therefore, the thermistor 95 and the first matching resistor 96 are arranged in parallel to each other and in series with the first chip resistor 91. The thermistor 95 can measure the temperature characteristics of the bridge circuit 80, in which the first chip resistor 91 and the second chip resistor 93 are arranged, and compensate for these temperature characteristics. The first matching resistor 96 serves to restore the initial calibration, which deviated when the thermistor 95 was placed in the first path 86.

[0098] Furthermore, the second matching resistor 97 is arranged in series with the second chip resistor 93 to balance the resistance values ​​of the first path 86 and the second path 87. The resistance value of the second matching resistor 97 can differ from the resistance value of the first matching resistor 96 in order to eliminate the initial mismatch between the resistance values ​​of the first path 86 and the second path 87. However, it is difficult to predict the temperature characteristics of the thermistor 95 and the first matching resistor 96 in advance, so the second matching resistor 97 may temporarily have the same resistance as the first matching resistor 96.

[0099] The first matching resistor 96 and the second matching resistor 97 for adjusting the deviation of the initial adjustment are preferably resistive elements with a low resistance-temperature coefficient, which indicates the rate of change of a resistance value with respect to a temperature change, e.g., 1 Ω or less. Examples of such a resistive element include elements made of one, or a mixture of, two or more of the elements zinc, tungsten, aluminum, pure iron, iridium, steel, copper, gold, nickel, silver, platinum, palladium, and tin. 2-3. Output adjustment procedure for a load cell

[0100] Next, the output adjustment procedure for a load cell according to this embodiment is described using a six-component force detector 1 as an example. The output adjustment procedure for a load cell described below provides an example where the output is adjusted with a target value for compensating the temperature characteristics of each force detection system and each torque detection system, which is specified as 0.2 mV / V.

[0101] Fig. Figure 4 is a flowchart that illustrates the output adjustment procedure for a load cell.

[0102] First, for example, measuring leads are connected to strain gauges, which are arranged with an intermediate insulating layer on a cylinder as a deformation generating body to form electrical wiring, and a bridge circuit is formed in which four strain gauges are electrically connected (step S11).

[0103] In the bridge circuit of the Fx detection system, for example, the strain gauge 21 is arranged between the first terminal 81 and the second terminal 82, and the strain gauge 22 is arranged between the second terminal 82 and the fourth terminal 84. Furthermore, the strain gauge 24 is arranged between the first terminal 81 and the third terminal 83, and the strain gauge 23 is arranged between the third terminal 83 and the fourth terminal 84.

[0104] After completion of step S11, the positions where the resistance elements are to be connected for initial calibration and temperature compensation are short-circuited. The step of electrically connecting the four strain gauges is performed for the six sets of four strain gauges that form the force detection systems and the torque detection systems.

[0105] Subsequently, a first chip resistor and a second chip resistor are arranged in a first path on one side and a second path on the other side of the bridge circuit, respectively, and an initial adjustment is performed to adapt the initial calibration of the bridge circuit (step S13). For example, in the bridge circuit of the Fx detection system, as in Fig. Figure 5 shows the first chip resistor 91 (the temporary resistor 91a and the shunt resistor 91b) arranged between the strain gauge 22 and the fourth terminal 84 in the first path 86.

[0106] The first path 86 leads through the first terminal 81, the strain gauge 21, the second terminal 82, the strain gauge 22, and the fourth terminal 84. Furthermore, the second chip resistor 93 (the temporary resistor 93a and the shunt resistor 93b) is arranged between the strain gauge 23 and the fourth terminal 84 in the second path 87. The second path 87 leads through the first terminal 81, the strain gauge 24, the third terminal 83, the strain gauge 23, and the fourth terminal 84.

[0107] For example, temporary resistors 91a and 93a are selected with given resistance values, which can be used to specify the resistance values ​​of the first path 86 and the second path 87 as suitable resistance values, and are placed in the first path 86 and the second path 87, respectively. The resistance values ​​of the temporary resistors 91a and 93a can be calculated based on the resistance values ​​of the strain gauges 21, 22, 23, and 24 and the electrical wiring, such as the measuring leads.

[0108] Furthermore, the initial adjustment of the bridge circuit 80 is measured at the predetermined reference temperature in a state in which the temporary resistors 91a and 93a are arranged in the bridge circuit 80. Then, the shunt resistors 91b and 93b are selected with resistance values ​​that can eliminate the deviation of the initial adjustment and are arranged in parallel with the temporary resistors 91a and 93a, respectively.

[0109] Consequently, the deviation of the initial adjustment of the bridge circuit 80 at the predetermined reference temperature can fall within the desired range. It should be noted that the shunt resistors 91b and 93b do not necessarily need to be present if the deviation of the initial adjustment of the bridge circuit 80 falls within the desired range at the predetermined reference temperature using only the temporary resistors 91a and 93a.

[0110] In step S13, the first chip resistor and the second chip resistor are arranged in the first path and the second path, respectively, in the bridge circuit of the six detection systems.

[0111] The temperature characteristics of the bridge circuit output are then measured in a state where the first and second chip resistors are located in the bridge circuit (step S15). The temperature characteristics of the outputs of force detection systems and torque detection systems are measured within a service temperature range of the six-component force detector 1. A method for measuring the temperature characteristics can be a known prior art method.

[0112] Fig. Figure 6 presents an example of the temperature characteristics of the outputs of six detection systems within an assumed operating temperature range (0 °C to 100 °C). The temperature characteristics are measured in a state where the first chip resistor is located in the first path of the bridge circuit and the second chip resistor is located in the second path (after the first matching). In the Fig. In the 6 examples shown, the temperature characteristics of the outputs from three detection systems differ from the outputs of the six detection systems by 0.5 mV / V or more and exceed the target value for temperature characteristic compensation.

[0113] In response to the temperature characteristic measurements, a second adjustment is performed in the subsequent step S17. During this second adjustment, a thermistor for compensating the temperature characteristics and a first matching resistor for adjusting the deviation from the initial adjustment caused by the thermistor's placement are arranged in parallel to each other and in series with the first chip resistor in the first path. Subsequently, a second matching resistor is arranged in parallel with the second chip resistor in the second path to reduce the resistance value deviation caused by the placement of the thermistor and the first matching resistor in the first path (step S19).

[0114] In the bridge circuit of the Fx detection system, for example, the thermistor 95 and the first matching resistor 96 are arranged in parallel to each other and in series with the first chip resistor 91 in the first path 86. Furthermore, the second matching resistor 97 is arranged in series with the second chip resistor 93 in the second path 87 (see Fig. 3).

[0115] In steps S17 to S19, the thermistor and the first matching resistor are placed in the first path, and the second matching resistor in the second path, in the bridge circuit of the six detection systems. Consequently, the outputs of all six detection systems are adjusted so that they are less than 0.2 mV / V, which is the target value for temperature characteristic compensation.

[0116] In this way, according to the load cell and the output adjustment method for a load cell according to the present invention, the following can be achieved. Even if the change in resistance value due to temperature changes is large within the operating temperature range, it is possible to easily compensate for the temperature characteristics of the bridge circuit output. Even with the six-component force detector, which detects the component forces, the temperature characteristics of the outputs of all detection systems can be reduced below the target value. Therefore, the initial resistance value adjustment can be easily adjusted while compensating for the temperature characteristics of the load cell.

[0117] In the embodiment described above, the thermistor and the first matching resistor are arranged in the first path of the bridge circuit, and the second matching resistor is arranged in the second path. In this case, the first path can be either the positive or the negative side of the input. 2-4. Application example

[0118] The load cell and the output adjustment method for a load cell according to this embodiment have been described above. Next, an application example of the technology of the present invention will be described.

[0119] If, in the embodiment described above, the second matching resistor 97, identical to the first matching resistor 96, is arranged in the second path 87, the following can occur: The combined resistance of the thermistor 95 and the first matching resistor 96 becomes small in the first path 86, and the resistance value of the first path 86 may be reported as excessively high.

[0120] Therefore, in the application example, the initial adjustment of the bridge circuit 80 is measured again in a state in which the first chip resistor 91, the second chip resistor 93, the thermistor 95, the first matching resistor 96, and the second matching resistor 97 are arranged in the bridge circuit 80. To further adjust the deviation of the initial adjustment, a third matching resistor is also added.

[0121] Fig. Figure 7 is an explanatory representation of the configuration of an 80A bridge circuit according to the application example and represents the bridge circuit of the Fx detection system as shown in Fig. 3.

[0122] In the application example, the bridge circuit 80A has the second chip resistor 93 (93a and 93b), the second matching resistor 97, and a third matching resistor 98 between the strain gauge 23 and the fourth terminal 84 in the second path 87. The second matching resistor 97 and the third matching resistor 98 are arranged in series with the second chip resistor 93 and in parallel with each other.

[0123] These elements in the first path 86 and in the second path 87 are arranged in the following order for the bridge circuit 80A: the first chip resistor 91 and the second chip resistor 93, the thermistor 95, the first matching resistor 96 and the second matching resistor 97, and the third matching resistor 98. The third matching resistor 98 is a resistor element for adjusting the deviation of the initial adjustment caused by the arrangement of the second matching resistor 97 in the second path 87.

[0124] Similar to the first matching resistor 96 and the second matching resistor 97, the third matching resistor 98 is desirablely a resistive element with a low resistance temperature coefficient, which indicates a rate of change of a resistance value with respect to a temperature change, e.g. 1 Ω or less.

[0125] The third matching resistor 98 is located in the one in Fig. In the example shown in Figure 7, the second path 87 is arranged in parallel with the second matching resistor 97. However, depending on the deviation of the initial adjustment, the third matching resistor 98 can also be arranged in the first path 86 in parallel with the thermistor 95 and the first matching resistor 96.

[0126] Furthermore, the deviation of the initial adjustment is not necessarily eliminated even after the third matching resistor 98 is installed. In this case, a fourth matching resistor can also be installed in the first path 86 or the second path 87, so that the deviation of the initial adjustment can fall within a predetermined range.

[0127] Fig. Figure 8 is a flowchart illustrating the sequence of an output adjustment procedure for a load cell according to the application example. Steps S11 to S19 are performed according to the sequence described in the preceding embodiment.

[0128] In the application example, after the second adjustment has been carried out, the temperature characteristics of the outputs of the six detection systems are also measured (step S21). Fig. Figure 9 shows an example of the temperature characteristics of the outputs of the six detection systems measured in the following state (after the second matching process). The first chip resistor, the thermistor, and the first matching resistor are arranged in the first path of the bridge circuit, and the second chip resistor and the second matching resistor are arranged in the second path.

[0129] As in Fig. As shown in Figure 9, the temperature characteristics of the six detection systems, with the exception of one, are lower than 0.2 mV / V, which is the target value for temperature characteristic compensation. However, it is possible that the temperature characteristics of the one detection system could reach 0.3 mV / V and exceed the target value for temperature characteristic compensation.

[0130] Accordingly, in response to the temperature characteristic measurements, a third adjustment is performed in the subsequent step S23, as described below. The third adjustment resistor, used to compensate for the deviation of the initial adjustment caused by the placement of the second adjustment resistor in the second path, is placed in either the first or the second path. That is, after the temperature characteristics are slightly overcompensated by the thermistor, the temperature characteristics are measured again. If the temperature characteristics still exceed the target value, a double compensation is performed, allowing for higher accuracy.

[0131] In the bridge circuit of the Fx detection system, as in Fig. As shown in Figure 7, the third matching resistor 98 is arranged in the second path 87 in parallel with the second matching resistor 97. Whether the third matching resistor is arranged in the first path or in the second path is determined depending on whether the output deviates towards the positive or negative side due to the temperature characteristics.

[0132] Fig. Figure 10 presents an example of the temperature characteristics of the outputs of the six detection systems measured in the following state (after the third matching process). The first chip resistor, the thermistor, and the first matching resistor are arranged in the first path of the bridge circuit, and the second chip resistor, the second matching resistor, and the third matching resistor are arranged in the second path. In the Fig. In the 10 examples shown, the outputs of all six detection systems fall below 0.2 mV / V by placing the third matching resistor, which is the target value for compensating the temperature characteristics.

[0133] Even if the third matching resistor is placed in the first or second path, the following step continues as long as the temperature characteristics of the output from at least one of the six detection systems significantly exceed the target value. In this step, a fourth matching resistor is placed in the first or second path.

[0134] The final resistance value of the matching resistor, such as the third matching resistor or the fourth matching resistor, where the temperature characteristics are within the compensation target value, can be calculated based on the measurement results of the temperature characteristics.

[0135] In this way, the following can be achieved with the load cell and the output adjustment method for a load cell according to the application example. Even if the change in resistance value due to temperature changes is large within the operating temperature range, it is possible to compensate more reliably for the temperature characteristics of the bridge circuit output.

[0136] The preferred embodiment of the invention has been described in detail above with reference to the accompanying drawings, but the invention is not limited to such examples. It is clearly evident that a person skilled in the art can make various modifications or corrections within the scope of the technical idea described in the claims. It seems obvious that these naturally fall within the technical scope of the invention.

[0137] In the embodiment described above, for example, an example of a load cell using a uniaxial strain gauge was described, but the load cell for which the technique of the present invention can be used is not limited to such an example. For example, the technique of the present invention can also be used for a load cell that uses a uniaxial strain gauge. Fig. 11 and Fig. The 12 illustrated biaxial shear extensometers are used.

[0138] Fig. Figure 11 is, for example, a schematic diagram showing an arrangement of strain gauges in a six-component force detector according to a modification, and Fig. Figure 12 is an explanatory illustration of a strain measurement pattern of the biaxial shear strain gauge. The in Fig. The six-component force detector shown in Figure 11 is equipped with the shear strain gauges 271 and 272 of the Fx detection system and the shear strain gauges 275 and 277 of the Fz detection system, which are described below.

[0139] Shear strain gauges 271 and 272, as well as shear strain gauges 275 and 277, are arranged in place of strain gauges 21 to 24 of the Fx detection system and strain gauges 31 to 34 of the Fz detection system. Fig. Figure 12 shows the shear strain gauge 271 as an example, but the shear strain gauges 272, 275 and 277 also have essentially the same strain measurement pattern.

[0140] The shear strain gauge 271 is designed as a so-called arrow-shaped biaxial (bipolar) strain gauge. In the shear strain gauge 271, a first detector 271a and a second detector 271b, formed from a Cr-N thin film or the like, are arranged on a common insulating layer 271c, which is also an insulating thin film. The first detector 271a and the second detector 271b are each configured by arranging linear regions in series that are parallel along the detection directions.

[0141] The first detector 271a and the second detector 271b are configured such that their electrical resistance changes simply according to the deformation in the direction (detection direction) in which the linear region expands and contracts. The detection directions of the first detector 271a and the second detector 271b are arranged so that they are substantially orthogonal to each other. The shear strain gauge 271 is mounted on the outer circumferential surface of a cylinder 250 as described below.

[0142] The detection directions of the first detector 271a and the second detector 271b are inclined in opposite directions by 45° with respect to the central axis of the cylinder 250. It should be noted that the shear strain gauges 272, 275 and 277 are mounted on the outer circumferential surface of the cylinder 250 in essentially the same manner.

[0143] As in Fig. As shown in Figure 11, the shear strain gauges 271, 272, 275, and 277 are mounted on the outer circumferential surface of the center of the cylinder 250 in the direction of the central axis. The shear strain gauge 271 of the Fx detection system is located midway between the strain gauges 251 and 252 of the Mx detection system. The shear strain gauge 272 of the Fx detection system is located midway between the strain gauges 253 and 254 of the Mx detection system (at a position that is symmetrical about the central axis with respect to the shear strain gauge 271).

[0144] The shear strain gauge 275 of the Fz detection system is located midway between the strain gauges 261 and 262 of the Mz detection system. The shear strain gauge 277 of the Fz detection system is located midway between the strain gauges 263 and 264 of the Mz detection system (at a position symmetrical to the shear strain gauge 275 with respect to the central axis).

[0145] Furthermore, the strain gauges 281 to 284 of the Fy detection system and the strain gauges 291 to 294 of the My detection system are arranged at positions offset around the central axis. This serves to avoid interference with the strain gauges 271 and 272 of the Fx detection system and the strain gauges 275 and 277 of the Fz detection system.

[0146] For example, as in Fig. Figure 11 shows that the shear extensometer 271, the extensometer 282, the extensometer 292, the shear extensometer 277, the extensometer 284 and the extensometer 294 are arranged successively along the circumferential direction of the cylinder 250 at positions that are offset at intervals of 30° around the central axis.

[0147] Furthermore, the shear extensometer 272, the extensometer 283, the extensometer 293, the shear extensometer 275, the extensometer 281 and the extensometer 291 can also be arranged successively along the circumferential direction of the cylinder 250 at positions that are offset at intervals of 30° around the central axis.

[0148] The first and second detectors contained in each of the shear strain gauges 271 and 272 of the Fx detection system form a bridge circuit that is essentially the same as the one described in Fig. The bridge circuit shown in Figure 3 is similar. This bridge circuit generates an output that corresponds to a force component applied to cylinder 250 in the Fx direction.

[0149] Similarly, the first and second detectors contained in each of the shear strain gauges 275 and 277 of the Fz detection system form a bridge circuit that is essentially the same as that in Fig.The bridge circuit shown in section 3 is identical. This bridge circuit generates an output that corresponds to a force component applied to cylinder 250 in the Fz direction.

[0150] The technology of the present invention can also be used for a load cell that uses biaxial shear strain gauges, as described above, and the effects obtained by the embodiment described above can be achieved. List of reference symbols 21, 22 strain gauges 23, 24 extensometer 80, 80A bridge circuit 81 first connection 82 second connection 83 third connection 84 fourth connection 86 first path 87 second path 91 first chip resistor 91a Resistor element (temporary resistance) 91b Resistor element (shunt resistor) 93 second chip resistor 93a Resistor element (temporary resistance) 93b Resistor element (shunt resistor) 95 Thermistor 96 first matching resistor 97 second matching resistor 98 third matching resistor QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2008-151596

[0005]

Claims

[1] A load cell having a bridge circuit adapted to convert a change in the resistance of a strain gauge, which changes according to a load, into an electrical signal and to output the electrical signal, the load cell comprising: in a first path on one side of the bridge circuit: - a first chip resistor configured to adjust an initial balance of the bridge circuit; and - a thermistor configured to compensate for a temperature characteristic of the bridge circuit, and a first adjustment resistor configured to adjust a deviation of the initial adjustment in a state in which the thermistor is present, wherein the thermistor and the first adjustment resistor are arranged in series with the first chip resistor and in parallel with each other, and in a second path on the other side of the bridge circuit: - a second chip resistor designed to adjust the initial balance of the bridge circuit; and - a second matching resistor configured to adjust the deviation of the initial adjustment caused by the arrangement of the first matching resistor in the first path, wherein the second matching resistor is arranged in series with the second chip resistor. [2] Load cell according to claim 1, wherein the first matching resistor and the second matching resistor are identical resistance elements. [3] Load cell according to claim 2, further comprising: in one or both of the first path and the second path: - a third matching resistor designed to adjust the deviation of the initial adjustment caused by the arrangement of the second matching resistor. [4] A load cell according to claim 1, wherein the strain gauge has an element resistance value greater than or equal to 1 kΩ. [5] The load cell of claim 1, wherein the load cell comprises a multi-component force detector configured to detect component forces. [6] An output adjustment method for a load cell having a bridge circuit configured to convert a change in the resistance of a strain gauge, which changes according to a load, into an electrical signal and output the electrical signal, the output adjustment method comprising the following measures: - arranging a first chip resistor configured to adjust an initial balance of the bridge circuit in a first path on one side of the bridge circuit; - arranging a second chip resistor, which is designed to adjust the initial balance of the bridge circuit, in a second path on the other side of the bridge circuit; - arranging a thermistor configured to compensate for a temperature characteristic of the bridge circuit and a first matching resistor configured to adjust a deviation of the initial adjustment in a state in which the thermistor is present in the first path, wherein the thermistor and the first matching resistor are arranged in series with the first chip resistor and in parallel with each other; and - arranging a second matching resistor, which is designed to adjust the deviation of the initial adjustment caused by the arrangement of the first matching resistor in the first path, in the second path, wherein the second matching resistor is arranged in series with the second chip resistor. [7] An output adjustment method for a load cell according to claim 6, further comprising: Disposing, in one or both of the first path and the second path, a third matching resistor configured to adjust the initial balance deviation caused by the disposition of the second matching resistor.

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