Calibration mechanism and method for constructing the force sensor thereof - Patents.com

Abstract

The present invention discloses a force sensor (100) and a method for configuring a calibration mechanism within such a force sensor (100), the method comprising the steps of: connecting an end of a calibration lever (1071) to the loading end (103) of the force sensor (100); adjusting the center of gravity (G0) of the unloaded calibration lever (1071) in an unloaded state so that the center of gravity (G0) is located on a substantially horizontal line (H) passing through the center of the calibration lever fulcrum (1031) at the fixed end (103) of the force sensor (100); and adjusting the center of gravity (G1) of the calibration lever (1071) under the load of a calibration weight (106) in a fully loaded state so that the center of gravity (G1) is located on a substantially horizontal line (H) passing through the center of the calibration lever fulcrum (1031). By controlling the position of the lever and the position of the fulcrum within the force sensor to be approximately on the same horizontal line, calibration errors caused by tilt within the force sensor are reduced.

Description

[Technical Field]

[0001] The present invention relates to a method for constructing a calibration mechanism and to a force sensor constructed by the method. [Background technology]

[0002]

[0002] In the field of weighing, the accuracy of a scale or weighing device equipped with a force sensor will decrease with prolonged or frequent use, and in order to maintain the accuracy of the device, it is necessary to periodically calibrate the scale or weighing device.

[0003]

[0003] Currently, there are two calibration methods in the weighing field: internal calibration and external calibration. External calibration is achieved by loading an external weight, ranging from a few kilograms to a few hundred kilograms, onto the balance or weighing device. The external calibration method is very inconvenient and expensive to implement because it requires continuous loading and unloading of the external weight.

[0004]

[0004] At present, internal calibration is mainly used in electromagnetic force balance sensors. Due to the principle of electromagnetic force balancing with gravity, an internal calibration structure can be integrated into the sensor, thereby realizing high accuracy of the electronic balance.

[0005]

[0005] With regard to the internal calibration of load cells, a distinction must be made between electromagnetic force compensation load cells (MFR-LC) and strain gauge load cells (SG-LC). This is because electromagnetic force compensation load cells and strain gauge load cells have different measurement principles. In MFR load cells, the weight force of the weighing object is measured by electrical displacement. In such weighing cells, also known as magnetic force restoration load cells (MFR-LC), which function according to the principle of electromagnetic force compensation, the weight force of the weighing object is transmitted directly or via one or more force transmission levers to an electromechanical measuring transducer, which generates a compensation force corresponding to the weight force of the weighing object and simultaneously supplies an electrical signal (coil current), which is further processed by an electronic weighing module in the processing unit and displayed on a display panel. Since the magnitude of the coil current and the resultant force are proportional to each other according to the laws of electromagnetism, the weight of an object to be weighed placed on the load cell can be determined through measuring the coil current.

[0006]

[0006] A strain gauge load cell (SG-LC) is structurally comprised of an elastic body to which a strain gauge is affixed. The elastic body is typically made of aluminum, alloy steel, or stainless steel, making it very robust but minimally elastic. When referring to the body of the load cell, this elasticity can be referred to as a "spring element." When a force is applied to one end of the load cell, the spring element is slightly deformed and always returns to its original shape unless overloaded. As the spring element deforms, the strain gauge also changes shape. The resulting change in the resistance of the strain gauge can be measured as a voltage. The change in voltage is proportional to the magnitude of the force applied to the cell, and therefore the magnitude of the force can be calculated from the output of the strain gauge.

[0007]

[0007] In summary, the difference between these two measurement principles is the state when the load cell is loaded with a weight: the MFR load cell returns the deflection to a balanced state for load measurement, whereas the SG load cell maintains the deflection for load measurement.

[0008]

[0008] In the prior art, attempts have also been made to integrate an internal calibration mechanism into an SG force sensor. For example, a calibration system for a scale is disclosed in U.S. Patent No. 6,414,252 (B1), in which an internal calibration mechanism comprising an internal calibration weight and a lever is added to a strain gauge sensor, so that the internal calibration mechanism is loaded when calibration is required and unloaded when calibration is not required, thereby conveniently achieving calibration of the strain gauge sensor and preventing degradation of the accuracy of the sensor.

[0009] However, the internal calibration mechanism disclosed in U.S. Patent No. 6,414,252 (B1) has a large calibration error in practice, which can reach 1%, far exceeding the required standard certified by the standard. Therefore, this internal calibration mechanism cannot be effectively applied to the SG force sensor.

[0010]

[0010] In the prior art, there are also internal calibration mechanisms that are directly manufactured into force sensors, such as the sensor disclosed in DE20022494U1, in which a structure specially used for loading an internal calibration weight is designed into the elastic body. The processing and installation of such internal calibration mechanisms is very complicated, and the internal calibration mechanisms are not applicable to force sensors with other structures, so their application range is also narrow. Summary of the Invention [Problem to be solved by the invention]

[0011]

[0011] The technical problem solved by the present invention is that the internal calibration mechanisms of the prior art have large errors and are therefore not effective or reliable in maintaining the accuracy of the force sensor. [Means for solving the problem]

[0012]

[0012] The present invention solves the above technical problems through the following technical solutions: A method for configuring a calibration mechanism in a force sensor, The method comprises: connecting an end of the calibration lever to a loading end of the force sensor; In an unloaded state, adjusting the center of gravity of the unloaded calibration lever so that the center of gravity is located substantially on a horizontal line passing through the center of the calibration lever fulcrum at the fixed end of the force sensor; adjusting the center of gravity of the calibration lever under the load of the calibration weight in a fully loaded state so that the center of gravity is substantially located on a horizontal line passing through the center of the calibration lever fulcrum; Includes:

[0013] Therefore, by configuring the position of the lever and the position of the fulcrum within the force sensor to be on approximately the same horizontal line, calibration errors caused by tilt of the force sensor or the internal calibration mechanism are reduced.

[0014]

[0014] In the unloaded and fully loaded states, the lines connecting the centers of the calibration lever fulcrums and the individual centers of gravity have acute interior angles between -2° and +2° with respect to the horizontal, thus making the calibration error relatively small and reducing its effect on weighing accuracy.

[0015]

[0015] Furthermore, the method comprises: Configuring the center of gravity of the calibration lever with or without the calibration weight so as to position the respective center of gravity away from the connecting end of the calibration lever for application of the calibration weight load and near the center of the calibration lever fulcrum. Further includes:

[0016] Preferably, the end of the calibration lever is connected to a fulcrum at the load end of the force sensor so that rotation of the calibration lever impels movement of the load end.

[0017]

[0017] According to this solution, the center of gravity position of the lever is close to the fulcrum position while the internal angle between the line connecting the center of gravity position of the calibration mechanism or lever and the fulcrum position and the horizontal line is within a certain angle range, thereby reducing the calibration error caused by the tilt of the internal calibration mechanism.

[0018]

[0018] A force sensor, comprising: an elastic body, the elastic body comprising: fixed end, a loading end for applying a load of the weight of the object to be weighed; and an intermediate portion provided between the fixed end and the loading end, the intermediate portion being equipped with a transducer mechanism for converting a weight applied to the loading end of the elastic body into a weighing signal; an elastic body having Equipped with This force sensor A calibration mechanism capable of applying a calibration force to the load end, the calibration mechanism comprising: calibration weight, a calibration lever connected to a fixed end via a calibration lever fulcrum; a calibration mechanism comprising: Furthermore, A calibration mechanism is constructed according to the method mentioned above.

[0019]

[0019] According to the calibration mechanism of this solution, when the calibration weight is loaded, i.e., in the internal calibration state, and after the calibration weight is lowered, i.e., during normal weighing operation, the center of gravity position of the entire calibration mechanism including the lever and internal calibration weight and the fulcrum position at the fixed end are controlled to be approximately on the same horizontal line, and as a result, when the calibration weight is lowered, the error caused by the tilt of the sensor is reduced, and the calibration error caused by the tilt of the sensor or the tilt of the internal calibration mechanism is reduced, further maintaining the accuracy of the force sensor.

[0020]

[0020] In this solution, a fulcrum mechanism can support the lever and enable it to pivot relative to a fixed end.

[0021]

[0021] Furthermore, the force sensor further comprises a weight loading mechanism for loading a calibration weight onto or unloading the calibration weight from the loading end of the lever.

[0022]

[0022] Furthermore, the lever further comprises a center of gravity adjustment device for adjusting the position of the center of gravity of the lever or the calibration structure.

[0023]

[0023] Furthermore, the center of gravity adjustment device has at least one counterweight carrying portion provided on the lever.

[0024]

[0024] In this solution, a counterweight is added onto the lever provided within the internal calibration mechanism to fine-tune the position of the center of gravity of the lever, so that the position of the center of gravity of the calibration mechanism and the center position of the fulcrum of the fulcrum mechanism can be adjusted to be on the same horizontal line.

[0025]

[0025] Furthermore, the force sensor further includes a tilt sensor for sensing a tilt of the force sensor relative to a horizontal plane, and the force sensor compensates the calibrated weighing value output by the force sensor based on the tilt sensed by the tilt sensor.

[0026] In this solution, the tilt of the force sensor is used to further correct the calibration value of the internal calibration by compensation.

[0027]

[0027] Furthermore, the transducer mechanism comprises a strain gauge sensor or a capacitive pressure sensor, or an optical sensor.

[0028]

[0028] The transducer mechanisms of this solution all measure force by sensing the deformation of an elastic body, and therefore any transducer mechanism based on a deformation measurement principle is applicable to the present invention.

[0029]

[0029] A weighing device, comprising: At least one force sensor as described above Equipped with a calibration weight value and a tilt value are obtained when an internal calibration mechanism of the force sensor is subjected to the load of the calibration weight; A calibration compensation value is calculated from the calibration weight value and the tilt value; A calibrated weighing value is output by the device corrected according to the calibrated compensation value.

[0030]

[0030] The effective and progressive effects of the above solution are as follows: by configuring the position of the lever and the position of the fulcrum in the force sensor to be on approximately the same horizontal line, the calibration error caused by the tilt of the force sensor or the internal calibration mechanism is reduced, thus maintaining the accuracy of the force sensor. Furthermore, an angle sensor is used to sense the tilt of the force sensor, and the tilt is used to calculate and compensate the calibration value to further maintain the accuracy of the force sensor.

[0031]

[0031] The above-mentioned and other features, characteristics and advantages of the present invention will become more apparent from the following description of the embodiments, which refers to the accompanying drawings, in which like reference numerals refer to like features throughout the several views. [Brief explanation of the drawings]

[0032] [Figure 1] FIG. 1 is a schematic isometric view illustrating a force sensor according to an embodiment of the present invention. [Figure 2] 2 is a schematic vertical cross-sectional view of the lever of the force sensor of FIG. 1 in an unloaded calibration mechanism state; FIG. [Figure 3] 3 is a schematic vertical cross-sectional view of the force sensor of FIG. 2 with the lever in a state where the calibration mechanism is under load; FIG. [Figure 4]FIG. 2 is a schematic isometric view of a weighing apparatus with a cutaway cross-sectional view including the force sensor shown in FIG. 1. [Figure 5] FIG. 10 is a schematic isometric view illustrating a force sensor according to another embodiment of the present invention. [Figure 6] 6 is a schematic vertical cross-sectional view of the lever of the force sensor of FIG. 5 in an unloaded assembly state. DETAILED DESCRIPTION OF THE INVENTION

[0033]

[0032] The present invention will be further described below by way of examples, but the present invention is not limited to the scope of the described embodiments only.

[0033] In the process of loading / lowering the calibration weight by the loading mechanism of the force sensor, the alignment of the center of gravity of the lever relative to the position of the lever fulcrum is configured and controlled to be approximately on the same horizontal line, thereby reducing calibration errors caused by the tilt of the force sensor or the tilt of the internal calibration mechanism; further, the tilt of the force sensor sensed by an angle sensor such as an inclination sensor is used to further compensate for the calibration, thereby maintaining the accuracy of the force sensor.

[0034]

[0034] Hereinafter, implementations of the present invention will be illustrated by way of example through the following embodiments.

[0035] 1 to 4, according to the weighing device, a fixed end 103 fixed to a base panel A and a loading end 102 equipped with a tray B are present between both ends of an elastic body 101 of a force sensor 100. The both ends of the elastic body 101 are connected by two parallel beams 104 that are parallel to each other. A set of strain gauges is provided on the parallel beams 104.

[0036] A calibration lever 1071 of the internal calibration mechanism is formed between the parallel beams 104 and is connected to the fixed end 103 at a lever fulcrum 1031 about which the calibration lever 1071 rotates. Furthermore, when calibrating the force sensor, the calibration lever 1071 is connected to the loading end 102 by a loading lever fulcrum 1021.

[0037] An end portion of the calibration lever 1071 extends beyond the loading end 102 and is equipped with a V-shaped weight bracket. The calibration weight 106 can be placed within the weight bracket, and the V-shaped weight bracket can prevent the calibration weight 106 from sliding and vibrating within the weight bracket.

[0038]

[0038] In this embodiment, a loading mechanism 105 is fixed to the base panel A and provided on the side of the loading end 102, and the loading mechanism 105 loads the calibration weight 106 onto the weight bracket or removes the calibration weight 106 from the weight bracket by a lifting motion shown in Figures 2 and 3.

[0039]

[0039] When configuring the calibration mechanism of this embodiment, first, the calibration lever 1071 is connected to the loading fulcrum 1021 located at the loading end 102 of the force sensor. After connection, when the calibration lever 1071 is unloaded, the center of gravity G0 of the calibration lever 1071 is adjusted in an unloaded state so that it is located substantially on a horizontal line H passing through the center of the calibration lever fulcrum 1031. When the calibration weight 106 is loaded on the calibration lever 1071 by the loading mechanism 105, the center of gravity G1 of the calibration lever 1071 integrated with the calibration weight 106 is adjusted in a fully loaded state so that it is located substantially on a horizontal line H passing through the center of the calibration lever fulcrum 1031.

[0040] 3, after the loading mechanism 105 loads the calibration weight 106 onto the calibration lever 1071, the center of gravity of the calibration lever under the load of the calibration weight 106 is G1. A horizontal line H is defined by leveling the calibration lever fulcrum 1031 as shown. The line connecting the lever center of gravity G1 and the calibration lever fulcrum 1031 is below the horizontal line H and forms an acute angle of −2° with the horizontal line H.

[0041] In another configuration, the line connecting the calibration lever center of gravity G1 and the calibration lever fulcrum 1031 is above the horizontal line H and forms an acute angle of +2° with the horizontal line H. In another variation, the calibration lever center of gravity G1 and the calibration lever fulcrum 1031 are on the horizontal line H, i.e., the line connecting the center of gravity G1 and the calibration lever fulcrum 1031 coincides with the horizontal line H of the environment in which the force sensor 100 is placed.

[0042]

[0042] In these settings, the acute angle formed between the horizontal line H and the straight line connecting the calibration lever gravity center G1 and the calibration lever fulcrum 1031 is controlled between -2° below the horizontal line and +2° above the horizontal line H. In this case, the calibration error caused by the inclination of the calibration lever can be controlled, thereby reducing the effect on weighing accuracy.

[0043]

[0043] When the calibration mechanism is configured before the loading mechanism 105 loads the calibration weight 106 onto the calibration lever 1071 or after the calibration weight 106 has been lowered from the calibration lever 1071, the calibration lever center of gravity G0 and the calibration lever fulcrum 1031 of the calibration lever 1071 are on the same horizontal line H, that is, the straight line connecting the calibration lever center of gravity G0 and the calibration lever fulcrum 1031 coincides with the horizontal line H of the environment in which the force sensor 100 is placed.

[0044] In another configuration, the line connecting the calibration lever center of gravity G0 and the calibration lever fulcrum 1031 is above the horizontal line H and forms an acute angle of +2° with the horizontal line H. In another variation, the line connecting the calibration lever center of gravity G0 and the calibration lever fulcrum 1031 is below the horizontal line H and forms an acute angle of −2° with the horizontal line H.

[0045]

[0045] As set forth above, when the calibration lever 1071 is unloaded, the interior angle formed between the horizontal line H and the line connecting the center of gravity position G0 of the calibration lever 1071 and the lever fulcrum 1031 is controlled between -2° below the horizontal line and +2° above the horizontal line H. This further improves the controllability of the calibration error caused by the inclination of the calibration lever, thereby reducing the effect on weighing accuracy.

[0046]

[0046] In another embodiment, as shown in Figures 5 and 6, the calibration lever 1071 is further equipped with a counterweight loading hole 10711. As shown in Figure 5, the counterweight 108 is inserted into one of the counterweight loading holes 10711, so that the counterweight 108 is loaded on the calibration lever 1071, thereby enabling the lever center of gravity of the calibration lever 1071 to be adjusted more precisely and for the calibration lever center of gravity and the calibration lever fulcrum 1031 to be positioned on the same horizontal line H as much as possible. Furthermore, two counterweight loading holes 10711 are provided on the calibration lever 1071, and counterweights of other weights can be hooked and loaded on these two counterweight holes 10711.

[0047]

[0047] In another embodiment, counterweight loading portions are provided at various positions on the calibration lever, and each counterweight loading portion has at least one counterweight hole or counterweight loading position. In this embodiment, the structure of the counterweight loading portion formed by two counterweight loading holes can be more simplified, for example, the calibration lever has only one counterweight loading position or loading through hole.

[0048]

[0048] The force sensor 100 of this embodiment is further equipped with a tilt sensor (not shown), which may be provided on the fixed end 103 of the force sensor 100 to sense the tilt of the force sensor 100 relative to a horizontal plane.

[0049]

[0049] In this embodiment, when the force sensor 100 performs calibration, the calibration weight 106 is loaded on the V-shaped weight bracket. Using the leverage transmission rate of the calibration mechanism, a load force that is a multiple of the calibration weight is applied to the loading end 102, and the strain gauge converts the load force into an electrical signal of a calibration weighing value. Then, in this embodiment, a calibration compensation value is calculated using the calibration weighing value and the tilt value sensed by the tilt sensor, and the calibration weighing value is further corrected by the calibration compensation value. Then, to maintain the accuracy of the force sensor 100, the calibration weighing value is used to calibrate the weighing output of the force sensor 100.

[0050]

[0050] A platform scale in another embodiment includes the four force sensors 100 of the above embodiment. After the platform scale transmits a calibration command to each force sensor 100, each force sensor 100 performs an internal calibration operation, such as loading an internal calibration weight, outputting a calibration weighing value, and then lowering the internal calibration weight. During the internal calibration operation, the tilt value is sensed simultaneously.

[0051]

[0051] The platform balance receives the calibrated weighing value and tilt value from each force sensor 100, and the processing unit of the platform balance completes the calculation and correction of the calibrated weighing value, and further calibrates the weighing output of the platform balance. [Explanation of symbols]

[0052]

[0052] 100 Force Sensor 101 Elastic Body 102 Loading end 1021 Loading lever fulcrum 103 Fixed end 1031 Calibration lever fulcrum 104 parallel beam 105 Loading mechanism 106 Calibration weight 1071 Calibration Lever 10711 Counterweight loading hole 108 Counterweight A Base Panel B Tray G0 Center of gravity of unloaded calibration lever G1 Lever center of gravity including loaded calibration weight H horizontal line

Claims

1. A method for configuring a calibration mechanism in a force sensor (100), comprising: connecting an end of a calibration lever (1071) to the loading end (102) of said force sensor (100); In the no-load state, the center of the calibration lever fulcrum (1031) at the fixed end (103) of the force sensor (100) and the center of gravity (G ０ The center of gravity (G) of the unloaded calibration lever (1071) is adjusted so that a line connecting the center of gravity (G) of the unloaded calibration lever (1071) has an acute interior angle between -2° and +2° with respect to a horizontal line (H) passing through the center of the calibration lever fulcrum (1031). ０ ) adjusting the In a fully loaded state, the center of the calibration lever fulcrum (1031) and the center of gravity (G １ The center of gravity (G) of the calibration lever (1071) under the load of the calibration weight (106) is set so that the line connecting the center of gravity (G) has an acute interior angle between -2° and +2° with respect to the horizontal line (H). １ ) adjusting the A method comprising:

2. The center of gravity (G) is located away from the connecting end of the calibration lever (1071) for applying the load of the calibration weight (106) and close to the center of the calibration lever fulcrum (1031). ０ , G １ ) of the calibration lever (1031) with or without the calibration weight (106) so as to position the center of gravity (G ０ , G １ ) Steps to configure The method of claim 1 further comprising:

3. connecting said end of said calibration lever (1071) to a fulcrum (1021) located at said loading end (102) of said force sensor (100); The method of claim 1 further comprising:

4. A force sensor (100), An elastic body (101), comprising: fixed end (103), a loading end (102) for applying the weight of the object to be weighed; and an intermediate portion (104) provided between the fixed end (102) and the loading end (103), the intermediate portion (104) being equipped with a transducer mechanism for converting a weight applied to the loading end (102) of the elastic body (100) into a weighing signal; An elastic body (101) having Equipped with The force sensor (100) a calibration mechanism capable of applying a calibration force to the loading end (102), the calibration mechanism comprising: Calibration weight (106), a calibration lever (1071) connected to said fixed end (103) via a calibration lever fulcrum (1031); a calibration mechanism comprising: Furthermore, The calibration mechanism is configured according to the method of any one of claims 1 to 3. A force sensor (100).

5. The calibration lever (1071) is located at the calibration lever center of gravity (G ０ , G １ a center of gravity adjusting device for adjusting the position of the The force sensor according to claim 4 .

6. the center of gravity adjustment device comprises at least one counterweight carrying portion (108) provided on the calibration lever (1071); The force sensor according to claim 5 .

7. a weight loading mechanism (105) for loading the calibration weight (106) onto the loading end (103) of the calibration lever (1071) or for unloading the calibration weight (106) from the loading end (103) of the calibration lever (1071); The force sensor of claim 4 further comprising:

8. the force sensor further comprises a tilt sensor for sensing tilt of the force sensor (100) relative to a horizontal plane; The force sensor (100) compensates the calibrated weighing value output by the force sensor (100) based on the tilt sensed by the tilt sensor. The force sensor according to claim 4 .

9. the transducer mechanism comprises a strain gauge sensor, a capacitive pressure sensor, or an optical sensor; The force sensor according to claim 4 .

10. Weighing device comprising at least one force sensor (100) according to any one of claims 4 to 9, Calibration weight and tilt values ​​are obtained when an internal calibration mechanism of the force sensor (100) is subjected to the load of a calibration weight (106); a calibration compensation value is calculated from the calibration weight value and the tilt value; a calibrated weighing value is output by the device corrected according to the calibration compensation value; Weighing device.

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