Weight measuring device

Abstract

To provide a weight measuring device in which the measurement result of a measurement target does not change no matter where the measurement target is placed.SOLUTION: A weight measuring device 10 comprises: a measurement table 1 that places a measurement target 20 thereon; a force sensor 2 for detecting a force of a load F of the measurement target 20, the force being received from the measurement table 1; multiple support parts 3, which support the support points of the measurement table 1, and have one or more groups, each of which has the same spring constant with elastic deformation in the vertical direction and has at least two support points; and weight calculation means for calculating the weight F of the measurement target 20 based on the detected force by the force sensor 2 and the spring constants of the multiple support parts 3. When the support parts 3 belonging to a group are three or more, the force sensor 2 receives a force from the center of gravity to the support points corresponding to all the support parts 3 belonging to the group. When the support parts 3 belonging to the group are two, the force sensor receives the force from the midpoint of the line segment connecting two support points corresponding to the two support parts 3 belonging to the group.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] An embodiment of the present invention relates to a weight measuring device for measuring weight. [Background technology]

[0002] Generally, devices for measuring forces such as weight are known. For example, a device for measuring various forces including torque using a sensor that detects the distortion of a strain generating body has been disclosed (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2023-56768 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in a weight measuring device, the measurement results may vary depending on the position where the measurement object is placed.

[0005] The present embodiment aims to provide a weight measuring device in which the measurement result does not change even if the measurement object is placed in any position. Effect of the Invention

[0006] According to this embodiment, it is possible to provide a weight measuring device in which the measurement result does not change even if the measurement object is placed in an arbitrary position. [Means for solving the problem]

[0007] A weight measuring device according to an embodiment of the present invention comprises a measurement stage for placing an object to be measured, a force sensor for detecting a force received from the measurement stage due to the load of the object to be measured, a plurality of support parts which support the support points of the measurement stage, elastically deform in the vertical direction with the same spring constant for each of one or more groups, at least two of which belong to each of the groups, and a weight calculation means for calculating the weight of the object to be measured based on the force detected by the force sensor and the spring constants of the plurality of support parts, and when there are three or more support parts belonging to the group, the force sensor receives a force from the position of the center of gravity with respect to the support points corresponding to all of the support parts belonging to the group, and when there are two support parts belonging to the group, the force sensor receives a force from the position of the midpoint of a line segment connecting two support points corresponding to two of the support parts belonging to the group. [Brief description of the drawings]

[0008] [Figure 1] 1 is a configuration diagram showing the configuration of a weight measuring device according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a side view showing the configuration of the force sensor according to the first embodiment. [Diagram 3] FIG. 2 is a top view showing the configuration of the force sensor according to the first embodiment. [Figure 4] FIG. 4 is a conceptual diagram showing a calculation method for measuring the weight of a measurement object in a calculation processing unit according to the first embodiment. [Diagram 5] FIG. 4 is a conceptual diagram showing a calculation method for measuring the weight of a measurement object placed on a square measurement table in the calculation processing unit according to the first embodiment. [Figure 6] FIG. 4 is a conceptual diagram showing a calculation method for measuring the weight of a measurement object placed on a triangular measurement table in the calculation processing unit according to the first embodiment. [Figure 7] FIG. 4 is a simplified diagram showing distortion of a measurement table according to the first embodiment. [Figure 8] FIG. 6 is a configuration diagram showing the configuration of a weight measuring device according to a second embodiment of the present invention. [Figure 9] FIG. 11 is a diagram showing the configuration of a weight measuring device according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] (First embodiment) 1 is a diagram showing the configuration of a weight measuring device 10 according to a first embodiment of the present invention. In the drawings, the same parts are given the same reference numerals.

[0010] The weight measuring device 10 includes a measurement stage 1, a force sensor 2, a plurality of supports 3, and a calculation processing unit 4. The weight measuring device 10 is a sensor that measures the weight F of a measurement object 20 placed on the measurement stage 1.

[0011] The measurement stage 1 is a stage on which the measurement object 20 is placed. The measurement stage 1 is plate-shaped. The shape of the top surface of the measurement stage 1 may be a circle, an ellipse, a triangle, a rectangle, a polygon, etc., or may be an asymmetrical shape, an irregular shape, or any other shape. It is desirable that the measurement stage 1 has a shape and material that is highly rigid and does not easily deform even when the measurement object 20 is placed on it. Here, the amount of deformation of the measurement stage 1 is described as being small enough to be negligible in measuring the weight of the measurement object 20.

[0012] The force sensor 2 is a sensor that detects a force applied downward from the measurement table 1 due to the weight of the measurement object 20. The force sensor 2 outputs the detected force as a detection signal to the calculation processing unit 4. For example, the detection signal is an electric signal, and the detected force is represented by the magnitude of resistance, voltage, or current.

[0013] The multiple support parts 3 are members that support the measurement table 1. Each support part 3 is configured to elastically deform in the vertical direction like a spring. For example, the support part 3 may be formed of an elastic material (e.g., rubber), may be formed in an elastic shape (e.g., a spring), or may be configured as a combination of these.

[0014] The support parts 3 are divided into groups. There may be any number of groups as long as there is at least one. Each group includes at least two support parts 3. A spring constant is determined in advance for each group, and all of the support parts 3 belonging to each group have the same spring constant. The spring constant may be different for each group, may be the same for all groups, or may be the same for some groups.

[0015] In each group, the support parts 3 are arranged so that the force sensor 2 is located at a point that produces the average displacement due to the forces received at the support points supported by all the support parts 3 belonging to the group (for example, the points where the support parts 3 are connected to the measurement table 1).

[0016] Specifically, in each group, the support parts 3 are arranged as follows: When a group includes three or more support parts 3, the support parts 3 are arranged so that the position of the center of gravity determined by the support points supported by all of the support parts 3 belonging to the group coincides with the position BC where the force sensor 2 receives a force from the measurement table 1. When a group includes two support parts 3, the support parts 3 are arranged so that the midpoint of the line segment connecting the support points supported by the two support parts 3 coincides with the position BC where the force sensor 2 receives a force from the measurement table 1.

[0017] Next, we will explain how to determine the position BC at which the force sensor 2 is placed from the support points supported by the support part 3. Here, the number of support points (i.e., the number of support parts 3) is n, and the support points are placed on an xy coordinate system where the x axis and y axis are perpendicular to each other on a plane.

[0018] First, a case where there are three or more support points (n is 3 or more) will be described. In this case, the center of gravity for all the support points is the position BC.

[0019] The coordinates of the first support point P1 to the n-th support point Pn can be expressed as (x1, y1), (x2, y2), ..., (xn, yn). In this case, the x and y coordinates of the center of gravity (xg, yg) for the first to n-th support points P1 to Pn can be calculated as follows. xg=(x1+x2+…+xn) / n, yg=(y1+y2+…+yn) / n The position of the center of gravity thus determined is the position BC.

[0020] When there are two support points, the midpoint of the line segment connecting the two support points (the point that bisects the two line segments) is position BC. Therefore, the x coordinate of position BC is (x1+x2) / 2 and the y coordinate is (y1+y2) / 2.

[0021] From these, the x coordinate of position BC is the average of the x coordinates of all the support points, and the y coordinate of position BC is the average of the y coordinates of all the support points. Based on the arrangement of the supports 3 provided on the measurement table 1, the force sensor 2 is provided below the position BC of the measurement table 1 thus obtained.

[0022] The calculation processing unit 4 calculates the weight of the measurement object 20 based on the detection signal detected by the force sensor 2. The calculation processing unit 4 outputs the calculated weight as a calculation result. The calculation processing unit 4 is mainly composed of a computer. The calculation processing unit 4 executes a program to perform calculation processing according to the procedure described in the program. The calculation result may be output in any manner, such as by displaying it on a display, printing it, or transmitting it as data.

[0023] The configuration of the force sensor 2 will be described with reference to Fig. 2 and Fig. 3. Fig. 2 is a side cross-sectional view showing the configuration of the force sensor 2 according to this embodiment. Fig. 3 is a top view showing the configuration of the force sensor 2 according to this embodiment. Note that the configuration of the force sensor 2 described here is just one example, and any configuration may be used as long as it can detect a force applied from directly below the center of gravity BC of the measurement table 1.

[0024] The force sensor 2 includes a strain detection element 21, a diaphragm 22, a load portion 23, and a base portion 24. For example, the diaphragm 22, the load portion 23, and the base portion 24 are integrally formed.

[0025] The strain detection element 21 is provided on the surface of the diaphragm 22. The strain detection element 21 is an element for detecting the magnitude of the strain of the diaphragm 22 caused by the load of the measurement object 20. The strain detection element 21 outputs an electrical signal indicating the magnitude of the strain of the diaphragm 22 in response to the force applied to the diaphragm 22. For example, the strain detection element 21 is a strain gauge, and indicates the magnitude of the strain of the diaphragm 22 by the magnitude of the resistance value.

[0026] The strain detection element 21 may be any element capable of detecting the magnitude of the strain of the diaphragm 22, and may be a piezoelectric body that generates a piezoelectric effect due to strain. The strain detection element 21 is an element that constitutes an electric circuit, and the electric circuit may be configured in any manner. Two or more strain detection elements 21 may be provided. Furthermore, the electric circuit may be provided with a power source for supplying electricity.

[0027] The diaphragm 22 is a thin plate-like member made of an elastically deformable material. The shape of the upper surface of the diaphragm 22 is, for example, circular, but may be any shape. The diaphragm 22 bends in a sinking manner due to the load F of the measurement object 20, causing distortion.

[0028] The load section 23 is located directly below position BC of the measurement stage 1, and is provided in the central portion of the surface of the diaphragm 22 (for example, the center portion of a circle). The load section 23 is a portion to which the load of the measurement object 20 is applied via the measurement stage 1. The load section 23 is formed in a convex shape so that it receives a force from position BC of the measurement stage 1 at one point (the apex portion). For example, the upper side of the load section 23 is spherical, and the lower surface is flat. The load section 23 receives the force from position BC of the measurement stage 1 at the apex portion of the spherical shape.

[0029] Loading section 23 may have any shape as long as it receives a force at one point from position BC of measurement stage 1 when a load is applied to measurement stage 1. By providing loading section 23, a force is transmitted from position BC of measurement stage 1 to diaphragm 22 so as to cause distortion in diaphragm 22 in a fixed direction.

[0030] The base portion 24 is a portion that serves as a base for supporting the entire force sensor 2. The base portion 24 has a cylindrical shape with a flat bottom surface, and the diaphragm 22 is stretched on the upper surface of the base portion 24. Note that the base portion 24 may have any configuration as long as it is configured to support the diaphragm 22 so that the force sensor 2 functions.

[0031] A calculation method for measuring weight F of measurement object 20 in calculation processing section 4 will be described with reference to FIG.

[0032] Here, the weight of the measurement table 1 will be described as being negligibly light compared to the weight F of the measurement target 20, but in reality, the weight F is measured taking into account the weight of the measurement table 1. Also, for ease of explanation, the number of support parts 3 in each group will be described as n (n is 2 or more), but the number of support parts 3 in each group may be different, and even in this case, calculations can be performed based on the following explanation.

[0033] Let i represent the group number, and j represent the number of the support part 3 in the group. The group number i is a consecutive number assigned to all groups in order starting from 1, and the maximum value of i is the total number of groups. The support part 3 number j is a consecutive number assigned to the support parts 3 in each group in order starting from 1, and the maximum value of j is the total number of support parts 3 in that group.

[0034] If the weight of the measurement object 20 placed at an arbitrary position on the measurement table 1 is F, the reaction force of the force sensor 2 is Fs, and the reaction force of the j-th support part 3 in the i-th group is Fij, the following equation holds due to the balance of forces.

[0035]

number

[0036] Since the force sensor 2 is located at the position of the center of gravity of the support points supported by the support parts 3 of each group or at the midpoint of the line segment connecting the two support points, the average displacement amount of the support parts 3 of each group becomes the displacement amount of the force sensor 2 (the displacement amount of the diaphragm 22). Therefore, if the displacement amount of the force sensor 2 is xs and the displacement amount of the jth support part 3 of the i-th group is xij, the following equation is established.

[0037]

number

[0038] If the reaction force of the j-th support portion 3 in the i-th group is Fij and the spring constant of the i-th group is ki, the following equation holds.

[0039]

number

[0040] If the spring constant of the force sensor 2 (the spring constant of the diaphragm 22) is ks, the following equation can be derived from equations (2) and (3).

[0041]

number

[0042] The following equation is derived from equations (1) and (4).

[0043]

number

[0044] Therefore, from equation (5), the weight F of the measurement object 20 can be obtained from the force Fs received by the force sensor 2 regardless of the position at which the measurement object 20 is placed on the measurement table 1.

[0045] With reference to FIG. 5, a calculation method for determining weight F of measurement object 20 in weight measuring device 10 in which measurement table 1 is shaped like a rectangle (e.g., a square) and support parts 3 are provided at each vertex of the rectangle will be described.

[0046] The four supports 3 are divided into two groups. The two supports 3 located diagonally belong to the same group. In the first group, the spring constant is k1, the forces received by the two supports 3 are F11 and F12, respectively, and the displacements of the two supports 3 are x11 and x12, respectively. In the second group, the spring constant is k2, the forces received by the two supports 3 are F21 and F22, respectively, and the displacements of the two supports 3 are x21 and x22, respectively.

[0047] The force sensor 2 is disposed so as to measure a force Fs applied from a position BC of the center of gravity (the intersection of two diagonals of a rectangle) for each support point of the support part 3 belonging to the same group. The weight F of the measurement object 20 is calculated from the force Fs measured by the force sensor 2 using the following formula.

[0048]

number

[0049] With reference to FIG. 6, a calculation method for determining weight F of measurement object 20 in weight measuring device 10 in which measurement table 1 has a triangular shape and supports 3 are provided at each vertex of the triangle will be described.

[0050] All three supports 3 belong to one group. The spring constant is k1, the forces acting on the three supports 3 are F11, F12, and F13, respectively, and the displacements of the three supports 3 are x11, x12, and x13, respectively.

[0051] The force sensor 2 is disposed so as to measure a force Fs received from a position BC of the center of gravity (center of gravity of a triangle) for each support point of the support part 3. The weight F of the measurement object 20 is calculated from the force Fs measured by the force sensor 2 using the following formula.

[0052]

number

[0053] Next, the error caused by the distortion of the measurement table 1 will be described. 7, when the measurement object 20 is placed on the measurement stage 1, distortion occurs in the measurement stage 1. A distortion width d caused by this distortion becomes a measurement error by the weight measuring device 10. Therefore, by making the measurement stage 1 highly rigid so that it is difficult to deform, the measurement error can be reduced.

[0054] The degree of distortion of the measurement stage 1 relative to the weight F of the measurement object 20 may be measured in advance, and the calculation processing unit 4 may perform calculations based on the measurement results of the degree of distortion to correct the measurement error due to the distortion of the measurement stage 1. Alternatively, the distortion width d of the measurement stage 1 may be detected in the same manner as the diaphragm 22 to obtain the reaction force of the measurement stage 1, and the force detected by the force sensor 2 may be obtained using the obtained reaction force of the measurement stage 1.

[0055] According to this embodiment, the position BC of the measurement table 1 where the force sensor 2 is provided is determined based on the arrangement of the support part 3 that supports the measurement table 1, and the weight F of the measurement object 20 placed at any position on the measurement table 1 can be obtained by measuring the load applied to the determined position BC of the measurement table 1.

[0056] Second embodiment FIG. 8 is a diagram showing the configuration of a weight measuring device 10A according to the second embodiment of the present invention.

[0057] The weight measuring device 10A is configured by providing a height adjustment unit 5 to the weight measuring device 10 according to the first embodiment shown in Fig. 1. In other respects, it is similar to the weight measuring device 10 according to the first embodiment.

[0058] The height adjustment unit 5 includes a mechanism for adjusting the height of the force sensor 2. The height adjustment unit 5 is connected in series below the force sensor 2. The height adjustment unit 5 adjusts the height of the force sensor 2 so that the load unit 23 of the force sensor 2 properly contacts the lower surface of the measurement table 1. By adjusting the height of the force sensor 2 with the height adjustment unit 5, the force that the force sensor 2 receives from the measurement table 1 can be properly detected. Note that the height adjustment unit 5 may be configured as a part of the base unit 24 of the force sensor 2.

[0059] The height adjustment unit 5 may be configured to have elasticity due to its material or shape, similar to the support unit 3. The height of the height adjustment unit 5 is adjusted by elastic deformation. In this case, the calculation processing unit 4 calculates the weight F of the measurement object 20 based on the force detected by the force sensor 2 and the force absorbed by the elastic deformation of the height adjustment unit 5.

[0060] The height adjustment unit 5 may also include a mechanism that allows the height to be freely changed. For example, the height adjustment unit 5 may include a screw and a screw hole, and the height can be adjusted by adjusting the amount of insertion of the screw into the screw hole. The height adjustment unit 5 may include either an elastic structure or a mechanism that allows the height to be freely changed, or may include both.

[0061] According to this embodiment, in addition to the effects of the first embodiment, the following effects can be obtained. By providing a height adjustment unit 5 to the force sensor 2, the weight measuring device 10A can place the force sensor 2 at an appropriate position relative to the measurement table 1 even if the installation surface Ds of the weight measuring device 10A is uneven. This allows the weight measuring device 10A to be installed on the installation surface Ds so that the weight F of the measurement target 20 can be appropriately measured.

[0062] Third embodiment FIG. 9 is a diagram showing the configuration of a weight measuring device 10B according to a third embodiment of the present invention.

[0063] The weight measuring device 10B is configured such that all of the support parts 3 of the weight measuring device 10 according to the first embodiment shown in Fig. 1 are provided with height adjustment parts 6. Other points are similar to those of the weight measuring device 10 according to the first embodiment.

[0064] The height adjustment unit 6 is provided in each of all the support units 3. The height adjustment unit 6 is connected in series with the support units 3 in the vertical direction. The height adjustment unit 6 may be provided above or below the support unit 3, or may be configured as a part of the support unit 3. The force sensor 2 may be provided with the height adjustment unit 6 like the support unit 3, or may be provided with the height adjustment unit 5 according to the second embodiment.

[0065] The height adjustment unit 6 includes a mechanism for adjusting the height of the support unit 3. For example, the height adjustment unit 6 includes a screw and a screw hole, and the height can be adjusted by adjusting the insertion amount of the screw into the screw hole.

[0066] The height adjustment unit 6 adjusts the height of the support unit 3 so that the elastic parts of the support unit 3 are in an appropriate contracted state. The height of each support unit 3 is adjusted by each height adjustment unit 6 so that the elastic parts of all the support units 3 are in a predetermined initial state, and the measurement table 1 is made horizontal. This allows the weight measuring device 10B to be appropriately installed on the installation surface Ds, and the weight F of the measurement target 20 to be appropriately measured.

[0067] According to this embodiment, in addition to the effects of the first embodiment, the following effects can be obtained. By providing a height adjustment unit 6 to each support part 3, the weight measuring device 10B can appropriately expand and contract each support part 3 even if the installation surface Ds of the weight measuring device 10B is uneven. This allows the weight measuring device 10B to be installed on the installation surface Ds so that the weight F of the measurement target 20 can be appropriately measured.

[0068] However, additional advantages and modifications may readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific detailed representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents. [Explanation of symbols]

[0069] 1... measuring table, 2... force sensor, 3... support part, 4... calculation processing part, 10... weight measuring device, 20... measurement object, 21... strain detection element, 22... diaphragm, 23... load part, 24... base part, BC... position, F... load.

Claims

1. a measurement table for placing an object to be measured; a force sensor for detecting a force received from the measurement table due to a load of the measurement object; a plurality of support parts each supporting a support point of the measurement table, and elastically deforming in a vertical direction with the same spring constant for each of one or more groups, at least two of which belong to each of the groups; a weight calculation means for calculating a weight of the object to be measured based on the force detected by the force sensor and the spring constants of the plurality of supports, When the number of the support parts belonging to the group is three or more, the force sensor receives a force from a position of a center of gravity with respect to the support points corresponding to all of the support parts belonging to the group, and when the number of the support parts belonging to the group is two, the force sensor receives a force from a position of a midpoint of a line segment connecting two of the support points corresponding to two of the support parts belonging to the group. A weight measuring device comprising:

2. The force sensor is a diaphragm that is distorted by a force applied from the measurement table; a strain detection element for detecting the magnitude of the strain occurring in the diaphragm.

2. The weight measuring device according to claim 1 .

3. A force sensor height adjustment unit for adjusting the height of the force sensor The weight measuring device according to claim 1 , further comprising:

4. The force sensor height adjustment portion has elasticity that allows deformation in the vertical direction.

4. The weight measuring device according to claim 3,

5. A height adjustment unit for a plurality of support parts that adjusts the height of each of the plurality of support parts The weight measuring device according to claim 1 , further comprising:

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