Load measuring instrument

Abstract

To provide a load measuring instrument capable of automatically obtaining rigidity suitable for a measuring load by reducing the rigidity when a loading load is low and increasing the rigidity when the loading load is high.SOLUTION: A load measuring instrument 50 includes a plurality of elastic deformation structures 1, 2 each including a stationary part, a displacement part, and an elastic spring part that elastically deforms when a load is applied to the displacement part. In the elastic deformation structures, the stationary parts are connected. The first elastic deformation structure 1 is provided with a displacement sensor for measuring a displacement amount of the displacement part, and a load loading plate 5 coupled to the displacement part. When no load is applied, a first gap d1 is formed between the displacement part of the second elastic deformation structure and the load loading plate. When the displacement amount is the first gap or more in a loaded state, the load loading plate is joined with the displacement part of the second elastic deformation structure so that the load is received in a manner that the load loading plate and the displacement parts of the first elastic deformation structure and the second elastic deformation structure are integrated.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a load measuring device such as a load sensor, a force sensor, a scale, or a load cell. [Background technology]

[0002] An example of a conventional load measuring device will be described. FIG. 8(a) is a side view of the conventional load measuring device, and FIG. 8(b) is a view of the load measuring device elastically deformed by a load. A conventional load measuring device 15 has a fixed portion 16, which is fixed to a floor or the like, and a displacement portion 17, which displaces when a load is applied, connected by parallel elastic spring portions 18a and 18b. A displacement sensor 19 for measuring the displacement of the displacement portion 17 is provided on the fixed portion 16. When a weight 20 is placed on the displacement portion 17, as shown in FIG. 8(b), the elastic spring portions 18a and 18b deform, and a constant displacement d corresponding to the rigidity of the elastic spring portions 18a and 18b occurs in the displacement portion 17. This displacement d is proportional to the load within the range of elastic deformation of the elastic spring portions 18a and 18b. Therefore, the load of the weight 20 can be measured by measuring this displacement d with the displacement sensor 19.

[0003] As a specific example of conventional load measuring device 15, if the stiffness of elastic spring parts 18a and 18b is 6×10^4 N / m and a capacitance type displacement sensor is used as displacement sensor 19, and the characteristics are a measurement range of 50 μm, an output voltage range of 0 to 10 V, and an electrical noise of 1 mV, then load measuring device 15 has a load measurement range of 0 to 3 N and a load measurement resolution of 0.3 mN. In other words, the resolution of the load measuring device is limited by the electrical noise of the displacement sensor.

[0004] Since the electrical noise of the displacement sensor 19 is almost constant regardless of the displacement measurement range, for example, if the load measurement range is 0 to 1 N, reducing the rigidity to one-third, 2 x 10^4 N / m, will triple the displacement at 1 N, improving the load measurement resolution to 0.1 mN.

[0005] However, a load measuring device capable of measuring large loads requires high rigidity. Therefore, there is a problem that measuring small loads using such a highly rigid load measuring device results in reduced resolution. Patent Document 1 discloses a spindle or load cell equipped with both a low-resolution load sensor and a high-resolution load sensor for the purpose of measuring a certain range of loads with high resolution. The high-resolution load sensor is used for relatively small loads and the low-resolution load sensor is used for relatively large loads. Such a spindle or load cell can measure a wider range of loads than a typical spindle, and by incorporating a non-contact measurement system for the high-resolution load sensor, the high-resolution load sensor can be prevented from being damaged even under high loads. However, such a load measuring device requires the installation of two types of load sensors, resulting in complex and costly equipment. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special Publication No. 2018-53437 Summary of the Invention [Problem to be solved by the invention]

[0007] In view of the above circumstances, the object of the present invention is to provide a load measuring instrument that can automatically adjust the rigidity to suit the load being measured by lowering the rigidity when the applied load is low and increasing the rigidity when the applied load is high. [Means for solving the problem]

[0008] According to the load measuring instrument of the present invention, the load measuring instrument is provided with a plurality of elastically deformable structures, each of which has a fixed portion, a displacement portion that displaces when a load is applied, and an elastic spring portion that connects the fixed portion and the displacement portion and elastically deforms when a load is applied to the displacement portion, and the elastically deformable structures are arranged in parallel with their respective fixed portions connected to each other, and a first of the elastically deformable structures is provided with a displacement sensor that measures the displacement amount of the displacement portion and a load-bearing plate that is connected to the displacement portion, and when no load is applied, the elastically deformable structure to which the load-bearing plate is not connected is designated as the second elastically deformable structure, and a first gap is provided between the displacement portion of the second elastically deformable structure and the load-bearing plate, and when a load is applied and the displacement amount measured by the displacement sensor is equal to or greater than the first gap, the load-bearing plate and the displacement portion of the second elastically deformable structure are joined together, so that the load-bearing plate, the displacement portion of the first elastically deformable structure, and the displacement portion of the second elastically deformable structure are integrated to receive the load.

[0009] Furthermore, when no load is applied, the device has a third elastic deformation structure to which the load-bearing plate is not connected, and a second gap larger than the first gap is formed between the displacement portion of the third elastic deformation structure and the load-bearing plate; when a load is applied and the displacement amount measured by the displacement sensor is equal to or larger than the second gap, the load-bearing plate and the displacement portion of the third elastic deformation structure are joined together, so that the load-bearing plate, the displacement portion of the first elastic deformation structure, the displacement portion of the second elastic deformation structure, and the displacement portion of the third elastic deformation structure can bear the load as a single unit.

[0010] Also, a load measuring instrument may include first and second elastically deformable structures each having a fixed portion, a displacement portion that displaces when a load is applied, and an elastic spring portion that connects the fixed portion and the displacement portion and elastically deforms when a load is applied to the displacement portion. The load measuring instrument may include a displacement sensor that measures the displacement of the displacement portion of the first elastically deformable structure, the displacement portion of the first elastically deformable structure and the displacement portion of the second elastically deformable structure being arranged opposite each other in the direction of load application with a gap therebetween, and when the displacement of the displacement portion caused by the load applied to the first elastically deformable structure becomes larger than the gap, the adjacent displacement portion of the first elastically deformable structure and the displacement portion of the second elastically deformable structure are joined together to form a single unit, and the rigidity of the elastic spring portion of the first elastically deformable structure and the elastic spring portion of the second elastically deformable structure are added together to function. Furthermore, the fixed portion of the first elastically deformable structure and the fixed portion of the second elastically deformable structure may be made of the same member. Furthermore, the displacement sensor may include a strain gauge provided in the elastic spring portion. [Effects of the Invention]

[0011] In the load measuring device according to the present invention, when the applied load increases, several displacement sections are joined to the load-applying plate, thereby lowering the rigidity when the applied load is low and increasing the rigidity when the applied load is high, thereby achieving a rigidity suitable for the measured load, thereby always obtaining optimal resolution from low to high loads. Furthermore, since the optimal rigidity is automatically set, the device is highly convenient. Furthermore, since one displacement sensor can accommodate multiple load measurement ranges, low cost can be achieved. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a diagram illustrating a load measuring instrument according to the present invention. [Figure 2] 1A and 1B are diagrams showing a first elastically deformable structure according to the present invention, in which (a) is a diagram showing the state when no load is applied, and (b) is a diagram showing the state when elastically deformed by applying a load. [Figure 3] 10A and 10B are diagrams showing second and third elastic deformation structures according to the present invention; [Figure 4]10A and 10B are diagrams illustrating how the load measuring instrument of the present invention automatically changes its stiffness in accordance with the load. [Figure 5] 10 is a graph showing the relationship between load and sensor voltage in the load measuring device of the present invention. [Figure 6] 10 is a diagram illustrating an example of the shape of the tip of a displacement portion. [Figure 7] FIG. 10 illustrates another embodiment of the present invention. [Figure 8] (a) is a side view of a conventional load measuring device, and (b) is a view of the load measuring device in a state where it has been elastically deformed by a load. [Figure 9] 10(a) and 10(b) are cross-sectional views of another embodiment of the load measuring device of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0014] FIG. 1 is a diagram illustrating a load measuring device of the present invention. As shown in FIG. 1, a load measuring device 50 of the present invention has a plurality of elastically deformable structures 1, 2, and 3 arranged in parallel and coupled to a base plate 4, with the first elastically deformable structure 1 disposed at the center, two second elastically deformable structures 2, 2 disposed symmetrically on either side of the first elastically deformable structure 1, and two third elastically deformable structures 3, 3 disposed outside the second elastically deformable structure 2, 2. Note that the arrangement is not limited to the above, and there may also be a configuration in which only the first and second elastically deformable structures 1, 2 are included without the third elastically deformable structure 3. Here, an example having the first to third elastically deformable structures as shown in FIG. 1 will be described.

[0015] 2A and 2B are diagrams showing a first elastically deformable structure according to the present invention, with (a) showing the structure without load and (b) showing the structure elastically deformed by the application of a load. As shown in FIG. 2A, the first elastically deformable structure 1 comprises a substantially L-shaped fixed portion 61 fixed to a floor or the like and a displaceable portion 71 that displaces when a load is applied, connected via two parallel elastic spring portions 81a and 81b. The fixed portion 61 and the displaceable portion 71 are each sufficiently rigid members that do not deform themselves. When a weight 10 is placed on the displaceable portion 71 and a load is applied, as shown in FIG. 2B, the elastic spring portions 81a and 81b elastically deform, causing the displaceable portion 71 to sink in the direction of arrow A, and the resulting displacement d can be measured by a displacement sensor 9.

[0016] Fig. 3 is a diagram showing second and third elastic deformation structures according to the present invention. As shown in Fig. 3, the structure of the second elastic deformation structure 2 is similar to that of the first elastic deformation structure 1 except that the displacement sensor 9 is not attached, and the fixed portion 62 and the displacement portion 72 are connected via two parallel elastic spring portions 82a and 82b. Similarly, the third elastic deformation structure 3 has a structure in which the fixed portion 63 and the displacement portion 73 are connected via two parallel elastic spring portions 83a and 83b.

[0017] When these elastically deformable structures 1, 2, and 3 are arranged as shown in Figure 1, the base plate 4 has a stepped shape, with the position where it is connected to the first elastically deformable structure 1 being the highest, the position where it is connected to the third elastically deformable structure 3 being the lowest, and the position where it is connected to the second elastically deformable structure 2 being at a height in between.

[0018] A weight loading plate 5 for loading a weight or applying a load is coupled to the displacement portion 71 of the first elastic deformation structure 1. Here, a first gap d1 is provided between the upper end surface of the displacement portion 72 and the weight loading plate 5 in the second elastic deformation structure 2. Although this first gap d1 is basically set by providing a step on the base plate 4, it is also possible to set the first gap d1 by making the sizes of the respective elastic deformation structures different or by providing a step on the weight loading plate 5. Similarly, for the elastic deformation structure 3, a second gap d2 larger than the first gap d1 is provided between the upper end surface of the displacement portion 73 and the weight loading plate 5 by providing a step on the base plate 4 or the like.

[0019] FIG. 4 is a diagram for explaining that the rigidity of the load measuring device of the present invention automatically changes according to the load. When no load is applied to the weight loading plate 5, the weight loading plate 5 is coupled only to the displacement portion 71, and a first gap d1 is formed between the displacement portion 72 and the weight loading plate 5, and a second gap d2 is formed between the displacement portion 73 and the weight loading plate 5. When a load 11 is applied to the weight loading plate 5, as shown in FIG. 4(a), a displacement d due to the elastic deformation of the displacement portion 71 occurs, the size of the first gap becomes d1 - d, and the size of the second gap becomes d2 - d. Here, when 0 ≦ d < d1 for the displacement d, the weight loading plate 5 is supported only by the displacement portion 71. That is, when the displacement d is smaller than the first gap d1, the load is received only by the weight loading plate 5 and the displacement portion 71 of the first elastic deformation structure 1.

[0020] Next, when a heavier load 12 is applied to the weight loading plate 5 and d1 ≦ d < d2 for the displacement d, the first gap disappears, and the size of the second gap becomes d2 - d. Then, as shown in FIG. 4(b), the weight loading plate 5 is supported by the displacement portion 71 and the displacement portions 72, 72. That is, when the displacement d is larger than the first gap d1, the load is received by the weight loading plate 5, the displacement portion 71 of the first elastic deformation structure 1, and the displacement portion 72 of the second elastic deformation structure 2 integrally.

[0021] Furthermore, when a heavier load 13 is applied to the load-bearing plate 5 and the displacement d is d2≦d, both the first and second gaps disappear, and the load-bearing plate 5 is supported by the displacement portions 71, 72, 72, and 73, 73, as shown in Fig. 4(c). In other words, when the displacement d is larger than the second gap d2, the load-bearing plate 5, the displacement portion 71 of the first elastic deformation structure 1, the displacement portion 72 of the second elastic deformation structure 2, and the displacement portion 73 of the third elastic deformation structure 3 all bear the load together.

[0022] Therefore, if the rigidity of the first elastically deformable structure 1, the combined rigidity of the two second elastically deformable structures 2,2, and the combined rigidity of the two third elastically deformable structures 3,3 are all equal to k, then the load measuring device 50 will function with a rigidity of k when the load is 11, a rigidity of 2k when the load is 12, and a rigidity of 3k when the load is 13.

[0023] As a specific example, the stiffness of the first elastic deformation structure 1 is 2×10^4 N / m, and a capacitive displacement sensor 9 with a measurement range of 150 μm is attached. In this case, the second elastic deformation structure 2 has a stiffness of 1×10^4 N / m and is arranged in parallel to the left and right of the first elastic deformation structure 1. The third elastic deformation structure 3 also has a stiffness of 1×10^4 N / m and is arranged in parallel to the outside of the second elastic deformation structure 2. The first gap d1 between the load-bearing plate 5 and the second elastic deformation structure 2 is 50 μm, and the second gap d2 between the load-bearing plate 5 and the third elastic deformation structure 3 is 100 μm.

[0024] In the load measuring device 50 configured as described above, when a load of 1 N is applied to the load-bearing plate 5, the first elastic deformation structure 1 sinks 50 μm, and the load-bearing plate 5 is joined to the two second elastic deformation structures 2, 2. At this time, the rigidity of the load measuring device 50 is 4×10^4 N / m, which is the sum of the rigidities of the first elastic deformation structure 1 and the two second elastic deformation structures 2, 2.

[0025] Next, when a load of 3N is applied to the load-bearing plate 5, the first elastic deformation structure 1 and the two second elastic deformation structures 2,2 sink an additional 50μm, and the load-bearing plate 5 joins with the two third elastic deformation structures 3,3. At this time, the rigidity of the load measuring device 50 is 6×10^4 N / m, which is the sum of the rigidities of the first elastic deformation structure 1, the two second elastic deformation structures 2,2, and the two third elastic deformation structures 3,3. Taking all of these changes in rigidity into consideration, when a load of 6N is applied, the plate will sink 150μm.

[0026] In other words, when the applied load is 0 to 1 N, it functions as a load measuring instrument 50 with a rigidity of 2×10^4 N / m, which is the rigidity of the first elastic deformation structure 1. When the applied load is 1 to 3 N, it functions as a load measuring instrument 50 with a rigidity of 4×10^4 N / m, which is the combined rigidity of the first elastic deformation structure 1 and the two second elastic deformation structures 2,2. When the applied load is 3 to 6 N, it functions as a load measuring instrument 50 with a rigidity of 6×10^4 N / m, which is the combined rigidity of the first elastic deformation structure 1, the two second elastic deformation structures 2,2, and the two third elastic deformation structures 3,3.

[0027] Here, if the measurement range of the displacement sensor 9 is 150 μm, the sensor output voltage is 10 V, and the sensor noise is 1 mV, the displacement resolution is 15 nm.

[0028] Therefore, when calculating the resolution, the stiffness is 2×10^4N / m when the load is 0 to 1N, so the resolution is 0.3mN. When the load is 1 to 3N, the stiffness is 4×10^4N / m, so the resolution is 0.6mN. When the load is 3 to 6N, the stiffness is 6×10^4N / m, so the resolution is 0.9mN.

[0029] This is because when the stiffness of a load measuring device with a measurement range of 6N is 6×10^4 N / m, the resolution when measuring loads of 3N or less is also 0.9 mN. Therefore, the load measuring device 50 of the present invention can measure with the optimal stiffness for the load being measured, so that even at low loads, the displacement due to elastic deformation becomes large, making it possible to improve the measurement resolution. Furthermore, the stiffness of the load measuring device 50 automatically switches depending on the applied load, making it highly convenient. Figure 5 is a graph showing the relationship between load and sensor voltage in the load measuring device of the present invention. There is a one-to-one correspondence between load and sensor voltage, and the angle changes as the stiffness switches between loads of 1N and 3N.

[0030] 6 is an example of the shape of the tip of the displacement portion, showing the state in which the load-bearing plate 5 and the displacement portions 72, 73 are joined together. In order to improve the joining between the displacement portions 72, 73 and the load-bearing plate 5 and to ensure the accuracy of the contact, it is preferable that the tip of the displacement portions 72, 73 contact the load-bearing plate 5 with point contact or line contact rather than surface contact. This is because surface contact can make it difficult to determine whether or not contact has occurred, and can easily result in slight misalignment of the contact.

[0031] The specific tip shape of the displacement portions 72, 73 may be, for example, a triangular shape as shown in Figure 6(a) so as to make line contact with the load-bearing plate 5, or a triangular pyramid shape as shown in Figure 6(b) or a spherical shape as shown in Figure 6(c) so as to make point contact with the load-bearing plate 5.

[0032] Fig. 7 is a diagram showing another embodiment of the present invention. As shown in Fig. 7, as displacement sensors attached to the first elastically deformable structure 1, strain gauges 14a and 14b may be attached to elastic spring portions 81a and 81b of the first elastically deformable structure 1, and a configuration may be adopted in which displacement is measured from strain.

[0033] 9(a) and 9(b) are cross-sectional views of another embodiment of the load measuring device of the present invention. The load measuring devices 51 shown in FIGS. 9(a) and 9(b) are configured such that the displacement portion 33 of the first elastic deformation structure 1 is connected to the fixed portion 35 by four elastic spring portions 31a, 31b, 31c, and 31d, and the displacement portion 34 of the second elastic deformation structure 2 is connected to the fixed portion 35 by four elastic spring portions 32a, 32b, 32c, and 32d. The fixed portion 35 may be a fixed portion that is connected separately to each elastic deformation structure, or may be a fixed portion 35 that is common to each elastic deformation structure, as in this embodiment. Here, the fixed portion 35 consists of a bottom portion 35a and a wall portion 35b, and most of the first and second elastic deformation structures 1, 2 are housed inside the fixed portion 35, and all of the elastic spring portions 31a, 31b, 31c, 31d, 32a, 32b, 32c, 32d are each connected to the wall portion 35b.

[0034] Here, the rigidity of the elastic spring portions 31a, 31b, 31c, and 31d is k1, and the rigidity of the elastic spring portions 32a, 32b, 32c, and 32d is k2. The displacement portions 33 and 34 are arranged to face each other in the direction in which the load 21 acts, with a first gap d1 between the lower surface of the displacement portion 33 and the upper surface of the displacement portion 34.

[0035] A second gap d2 is provided between the lower surface of the displacement portion 34 and the bottom portion 35a of the fixed portion 35. A displacement measuring unit 40 is provided on the lower surface of the displacement portion 33, and a displacement sensor 41 is provided on the bottom portion 35a of the fixed portion 35 so as to face it. The displacement measuring unit 40 and the displacement sensor 41 may be provided on the outside of the displacement portion 33, or, as shown in the figure, they may be provided on the inside of the displacement portion 34 by making the interior of the displacement portion 34 hollow. A load-bearing plate 5 is attached to the upper surface of the displacement portion 33. When a load 21 is applied to the load-bearing plate 5, the displacement portion 33 is displaced due to the rigidity k1 of the elastic spring portions 31a, 31b, 31c, and 31d. The amount of displacement at this time is measured by the displacement sensor 41. Because the elastic spring portions 31a, 31b, 31c, and 31d elastically deform, the amount of displacement is proportional to the load, and the load can be measured from the measured displacement and rigidity.

[0036] Furthermore, when a larger load is applied to the load-bearing plate 5 and the amount of displacement becomes larger than the first gap d1, the lower surface of the displacement portion 33 and the upper surface of the displacement portion 34 join together, and the displacement portions 33 and 34 are displaced as a unit. At this time, the overall rigidity seen from the load-bearing plate 5 is k1+k2, which is the stiffness k1 of the first elastic deformation structure 1 plus the stiffness k2 of the second elastic deformation structure 2. In other words, when the amount of displacement due to the load 21 is smaller than the gap d1, the instrument operates as a load measuring instrument with stiffness k1, and when the amount of displacement becomes larger than the first gap d1, the instrument operates as a load measuring instrument with stiffness k1+k2.

[0037] The second gap d2 may be made sufficiently larger than the displacement due to the maximum measured load, but by making it approximately the same, it acts as a stopper when an overload is applied, preventing plastic deformation of the elastic spring portions 31a, 31b, 31c, 31d and 32a, 32b, 32c, 32d.

[0038] As a specific example of load measuring device 51, the stiffness of elastic spring portions 31a, 31b, 31c, and 31d of first elastic deformation structure 1 is k1 = 1 x 10^4 N / m, and the stiffness of elastic spring portions 32a, 32b, 32c, and 32d of second elastic deformation structure 2 is k2 = 5 x 10^4 N / m. Displacement sensor 41 is a capacitance-type displacement sensor with a measurement range of 100 μm, a sensor voltage output range of 0 to 10 V, and electrical noise of 1 mV. Furthermore, the first gap d1 between the lower surface of displacement portion 33 and the upper surface of displacement portion 34 is 20 μm.

[0039] Here, when a load 21 of 0.2 N is applied to the load-bearing plate 5, the stiffness k1 = 1 × 10^4 N / m results in a displacement of 20 μm, and the first gap d1 disappears. That is, when the load is in the range of 0 to 0.2 N, the load-bearing plate 5 operates as a load measuring instrument with stiffness k1 = 1 × 10^4 N / m. When an even larger load is applied to the load-bearing plate 5, the first gap d1 disappears, the lower surface of the displacement portion 33 and the upper surface of the displacement portion 34 join together, and the load measuring instrument operates as a load measuring instrument with stiffness k1 + k2 = 1 × 10^4 N / m + 5 × 10^4 N / m = 6 × 10^4 N / m. Here, since the measurement range of the displacement sensor 41 is 100 μm, it can measure up to 6 N. Therefore, by setting the gap d2 to about 100 μm, even if an overload is applied to the load-bearing plate 5, the displacement portion 34 will collide with the fixed portion 35, thereby preventing plastic deformation of the elastic spring portions 31a, 31b, 31c, 31d and 32a, 32b, 32c, 32d.

[0040] Furthermore, the electrical noise of the displacement sensor 41 is 1 mV, and the electrical noise width is taken as the measurement resolution, which is 10 nm. When the load is 0 to 0.2 N, the stiffness is k1 = 1 x 10^4 N / m, so the measurement resolution of the load is 0.1 mN. Similarly, when the load is 0.2 N to 6 N, the stiffness is k1 + k2 = 6 x 10^4 N / m, so the measurement resolution of the load is 0.6 mN. If there is a load measuring device with a stiffness of 6 x 10^4 N / m and a measurement range of 6 N, its measurement resolution is 0.6 mN regardless of the magnitude of the load, so it can be said that the load measuring device of the present invention is capable of measuring with a higher resolution when the measurement load is small.

[0041] Although the present embodiment has been described with reference to a case where there are two elastically deformable structures, it goes without saying that there may be three or more. Furthermore, the amount of displacement caused by applying the load 21 to the load-carrying plate 5 can be measured by measuring the amount of displacement of the displacement portion 33, but it is also possible to monitor the displacement sensor voltage when the displacement portion 33 comes into contact with the displacement portion 34 by measuring the amounts of displacement of the displacement portion 33 and the displacement portion 34 separately.

[0042] 9(b), the displacement sensor 41 may include strain gauges 44a, 44b, 44c, and 44d attached to the elastic spring portions 31a, 31b, 31c, and 31d in addition to the capacitance-type displacement sensor. As already mentioned, strain gauges may also be attached to the elastic spring portions 32a, 32b, 32c, and 32d to monitor the displacement sensor voltage when the first elastic deformation structure 1 comes into contact with the second elastic deformation structure 2.

[0043] Although the embodiment shown in Fig. 1 and the embodiment shown in Fig. 9 differ in the arrangement of the elastically deformable structures, they have the same configuration in which stiffness is added when a desired displacement occurs. Therefore, they can be used in different ways depending on the location where the load measuring device is used, etc. [Explanation of symbols]

[0044] 1 (first) elastically deformable structure 2 (Second) Elastically Deformable Structure 3 (Third) Elastically Deformable Structure 4 base plates 5 Load-bearing plate 9 Displacement Sensor 10, 11, 12, 13 Weight (load) 14a, 14b Strain gauge 15 Conventional load measuring device 16 Fixed part 17 Displacement section 18a, 18b Elastic spring part 19 Displacement Sensor 20,21 Weight (load) 31a, 31b, 31c, 31d, 32a, 32b, 32c, 32d Elastic spring part 33,34 Displacement section 35 Fixed part 35a bottom part 35b wall part 40 Displacement measurement section 41 Displacement Sensor 44a, 44b, 44c, 44d Strain gauges 50,51 Load measuring device 61,62,63 Fixed part 71, 72, 73 Displacement section 81a, 81b, 82a, 82b, 83a, 83b Elastic spring part d1 First gap d2 Second gap

Claims

1. A load measuring instrument including a plurality of elastically deformable structures, each of which has a fixed portion, a displacement portion that displaces when subjected to a load, and an elastic spring portion that connects the fixed portion and the displacement portion and elastically deforms when a load is applied to the displacement portion, the elastically deformable structures are arranged in parallel with the fixed portions connected to each other, a first elastic deformation structure of the elastic deformation structures is provided with a displacement sensor that measures a displacement amount of the displacement portion and a load-bearing plate that is coupled to the displacement portion; When no load is applied, the elastically deformable structure to which the load-bearing plate is not coupled is a second elastically deformable structure, and a first gap is provided between the displacement portion of the second elastically deformable structure and the load-bearing plate; A load measuring instrument characterized in that when a load is applied and the displacement amount measured by the displacement sensor is equal to or greater than the first gap, the load-bearing plate and the displacement portion of the second elastic deformation structure are joined together, so that the load-bearing plate, the displacement portion of the first elastic deformation structure, and the displacement portion of the second elastic deformation structure are integrally supported by the load.

2. a third elastic deformation structure to which the load-bearing plate is not coupled when no load is applied, and a second gap larger than the first gap is formed between the displacement portion of the third elastic deformation structure and the load-bearing plate; The load measuring instrument of claim 1, characterized in that when a load is applied and the displacement amount measured by the displacement sensor is equal to or greater than the second gap, the load-bearing plate and the displacement portion of the third elastic deformation structure are joined together, so that the load-bearing plate, the displacement portion of the first elastic deformation structure, the displacement portion of the second elastic deformation structure, and the displacement portion of the third elastic deformation structure are integrally supported by the load.

3. A load measuring instrument including first and second elastic deformation structures each having a fixed portion, a displacement portion that displaces when subjected to a load, and an elastic spring portion that connects the fixed portion and the displacement portion and elastically deforms when a load is applied to the displacement portion, a displacement sensor is provided that measures the amount of displacement of the displacement portion of the first elastic deformation structure; A load measuring instrument characterized in that the displacement portion of the first elastic deformation structure and the displacement portion of the second elastic deformation structure are arranged opposite each other in the direction of load application with a gap between them, and when the displacement amount of the displacement portion caused by the load applied to the first elastic deformation structure becomes larger than the gap, the adjacent displacement portion of the first elastic deformation structure and the displacement portion of the second elastic deformation structure join together to become one, the rigidity of the elastic spring portion of the first elastic deformation structure and the elastic spring portion of the second elastic deformation structure are added together to function, and the displacement amount of the integrated displacement portions of the first and second elastic deformation structures is measured by the displacement sensor.

4. 4. The load measuring device according to claim 3, wherein the fixing portion of the first elastically deformable structure and the fixing portion of the second elastically deformable structure are made of the same material.

5. 5. The load measuring instrument according to claim 1, wherein the displacement sensor has a strain gauge provided in the elastic spring portion.

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