Method for manufacturing a weighing structure, and weighing structure

Abstract

The present invention provides a method for manufacturing a weighing structure and a weighing structure that can improve processing accuracy and ease of assembly. [Solution] The method for manufacturing a weighing structure is a method for manufacturing a weighing structure in which a second strain-generating body 4 including a movable part that moves when subjected to a load is manufactured by cutting a metal block 100, and comprises the steps S102 and S103 of forming screw holes 71 to 76 in the metal block 100 and screwing screw members 107 into the screw holes 71 to 76, and the step S104 of forming a movable part by cutting the metal block 100 while the screw members 107 are screwed into the screw holes 71 to 76. In steps S102 and S103, screw holes 71 to 76 are formed at positions that restrict the movement of the movable part, and screw members 107 are screwed into the screw holes 71 to 76.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a metering structure and a metering structure.

Background Art

[0002] Patent Document 1 describes a load measurement mechanism including a roboval part, a first force conversion part connected to the roboval part, a second force conversion part connected to the first force conversion part, and a force sensor attached to the second force conversion part. In this load measurement mechanism, the load applied to the force receiving part of the first force conversion part is reduced according to the lever ratio of the lever provided in the first force conversion part and transmitted to the force sensor. Further, in this load measurement mechanism, by applying the load of a calibration weight to the force receiving part of the second force conversion part, the force receiving part is displaced downward, and the displacement is transmitted to the force sensor. Patent Document 2 describes a weighing mechanism having the same configuration as the load measurement mechanism.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In Patent Document 2 above, the first force conversion part is said to be manufactured by hollowing out one metal block. A number of cut portions are provided in the first force conversion part, and a plurality of levers are incorporated. The plurality of levers transmit the load from the roboval part while reducing it according to the lever ratio. Therefore, the first force change part is also an example of a metering structure including a lever which is a movable part that moves by receiving a load. [[ID=**]] [[ID=**]]

[0005] [[ID=**]] When manufacturing such weighing structures or attaching them to other components such as the Roberval, it is conceivable to press-fit pins into the block component that forms the basis of the weighing structure, and into the weighing structure manufactured from the block component, to prevent the movable parts, such as levers, from moving unintentionally. However, in this case, after attaching the weighing structure to the other component, it is necessary to remove the pins from the weighing structure to release the movable parts. However, the work of removing the pins from the weighing structure is not easy, and there is room for improvement in assembly efficiency. In addition, there is a need to improve the machining accuracy during the cutting of the block component.

[0006] Therefore, the purpose of this disclosure is to provide a method for manufacturing a weighing structure and a weighing structure that can improve processing accuracy and ease of assembly. [Means for solving the problem]

[0007] The method for manufacturing a weighing structure according to the present disclosure is [1] "a method for manufacturing a weighing structure including a movable part that moves when subjected to a load, by cutting a block member, comprising: a first step of forming a screw hole in the block member and screwing a screw member into the screw hole; and a second step of forming the movable part by cutting the block member after the first step, while the screw member is screwed into the screw hole, wherein in the first step, the screw hole is formed at a position that restricts the movement of the movable part and the screw member is screwed into the screw hole."

[0008] In this manufacturing method, first, a screw hole is formed in the block member, and a screw member is screwed into the screw hole. Then, in this state, the block member is machined to form a movable part that moves when subjected to load. In particular, the screw member is screwed into a screw hole formed at a position that restricts the movement of the movable part. Therefore, when the movable part is formed during the machining process, unintended movement of the movable part is suppressed, resulting in improved machining accuracy. Furthermore, after the manufactured weighing structure is attached to another member, it can be easily removed by turning the screw member, compared to removing a press-fitted pin, thus improving ease of assembly.

[0009] The method for manufacturing a weighing structure according to the present disclosure may also be [2] "the method for manufacturing a weighing structure according to [1] above, wherein the block member includes a first surface and a second surface opposite to the first surface, and in the first step, the screw hole is formed such that there is a bottom between the first surface and the second surface." In this case, the screw hole and the screw member act as a blind screw, enabling secure fixing of the movable part. Specifically, the effect of the blind screw is that by tightening the screw member all the way into the screw hole and bringing it into contact with the bottom of the screw hole, backlash is eliminated (no rattle in the gap between the screw hole and the screw member is eliminated), enabling secure fixing of the movable part. As a result, high-precision machining becomes possible. In addition, in this case, since the screw hole and screw member are not exposed on the second surface, machining of the second surface is easy and highly accurate.

[0010] The method for manufacturing a weighing structure according to this disclosure may also be [3] "the method for manufacturing a weighing structure according to [2] above, wherein the first step includes a first cutting step of cutting the block member from the first surface side and a screwing step of forming the screw hole by screwing from the first surface side, and the second step includes a second cutting step of cutting the block member from the second surface side." In this case, as described above, the cutting in the second cutting step is performed on the second surface where the screw hole and screw member are not exposed, making the processing easier and more accurate.

[0011] The method for manufacturing a weighing structure according to this disclosure may also be [4] "the method for manufacturing a weighing structure according to [3] above, wherein in the first cutting step, the block member is cut from the first surface side to define the outer edge of the movable part and form a groove that does not reach the second surface, and in the second cutting step, the block member is cut from the second surface side to connect the groove to the second surface side and form the movable part." Thus, the movable part may be formed by cutting from both the first surface and the second surface of the block member.

[0012] The method for manufacturing a weighing structure according to this disclosure may also be the method for manufacturing a weighing structure according to any one of [1] to [4] above, wherein the screw member is a bolt including a shaft and a head provided at the tip of the shaft. In this case, the screw member can be removed more easily, and assembly can be further improved.

[0013] The weighing structure relating to this disclosure is [6] "a weighing structure comprising a block-shaped base, a movable part integrally provided with the base and movable when subjected to a load, and a screw hole provided in the base at a position in which a screw member is screwed in to restrict the movement of the movable part."

[0014] In this weighing structure, the unintended movement of the movable part can be suppressed by screwing a screw member, for example, into a screw hole formed at a position that restricts the movement of the movable part. As a result, the processing accuracy during the manufacturing of the weighing structure can be improved. Furthermore, after attaching the weighing structure with the screw member screwed in to another component, it can be easily removed by rotating the screw member, compared to removing a press-fitted pin, thus improving ease of assembly.

[0015] The metering structure according to the present invention may be "[7] The base body includes a first surface and a second surface opposite to the first surface, and the screw hole is formed so as not to reach from the first surface to the second surface, the metering structure according to [7] above". In this case, the screw hole and the screw member that can be screwed into the screw hole form a tapping screw, and for example, due to the reasons described above, the movable part can be securely fixed.

Effects of the Invention

[0016] According to the present disclosure, it is possible to provide a method for manufacturing a metering structure capable of improving processing accuracy and assembly properties, and a metering structure.

Brief Description of the Drawings

[0017] [Figure 1] FIG. 1 is a perspective view of a metering mechanism according to an embodiment. [Figure 2] FIG. 2 is an exploded perspective view of the metering mechanism shown in FIG. 1. [Figure 3] FIG. 3 is a plan view of the first strain generating body shown in FIG. 1. [Figure 4] FIG. 4 is a plan view of the second strain generating body shown in FIG. 1. [Figure 5] FIG. 5 is a diagram showing a step of the method for manufacturing a metering structure according to the present embodiment. [Figure 6] FIG. 6 is a diagram showing a step of the method for manufacturing a metering structure according to the present embodiment. [Figure 7] FIG. 7 is a diagram showing a step of the method for manufacturing a metering structure according to the present embodiment.

Embodiments for Carrying Out the Invention

[0018] Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings. In the following description, the same or corresponding elements are denoted by the same reference numerals, and redundant descriptions are omitted. In the drawings, some parts are exaggerated for easy explanation of the characteristic parts according to the embodiment. Therefore, the dimensional ratios of the respective parts in the drawings may be different from the actual dimensional ratios.

[0019] FIG. 1 is a perspective view of a weighing mechanism according to an embodiment. FIG. 2 is an exploded perspective view of the weighing mechanism shown in FIG. 1. As shown in FIGS. 1 and 2, the weighing mechanism 1 includes a first strain body 2, a second strain body 4, a weight placement portion 6, a weight moving mechanism 7, a load sensor 8, and a calculation unit 9. The second strain body 4 is fixed to the first strain body 2 by two bolts 11 and 12. Further, the load sensor 8 is fixed to the first strain body 2 by bolts 13 and 14. The weight moving mechanism 7 is configured to be able to grip and move a calibration weight W of the weighing mechanism 1. The weight moving mechanism 7 places the weight W on the weight placement portion 6 during calibration of the weighing mechanism 1. The weight W is a built-in weight of the weighing mechanism 1. The weighing mechanism 1 is built in, for example, a weighing device having a weighing pan, and weighs the mass of the object to be weighed placed on the weighing pan.

[0020] Each of the first strain body 2 and the second strain body 4 has an outer shape of a substantially rectangular parallelepiped (rectangular block shape) that is long in a predetermined direction. Each of the first strain body 2 and the second strain body 4 has a so-called Roberval mechanism. Each of the first strain body 2 and the second strain body 4 is an elastic body formed of a metal such as an aluminum alloy or stainless steel, and is manufactured by hollowing out a metal block (block member). In the following description, the above-mentioned predetermined direction is referred to as the Y-axis direction, a direction perpendicular to the Y-axis direction is referred to as the X-axis direction, and a direction perpendicular to both the Y-axis direction and the X-axis direction is referred to as the Z-axis direction (vertical direction). Each of the X-axis direction and the Y-axis direction is a direction parallel to the horizontal direction.

[0021] [[ID=--]] The details of the first strain body 2 will be further explained with reference to Figure 3. Figure 3 is a plan view of the first strain body shown in Figure 1. The first strain body 2 is a member that receives the first load, which is the load of the object being weighed. The first strain body 2 has a load receiving portion 21, a base portion 22, an upper link member 23, a lower link member 24, flexure portions 25, 26, 27, 28, and a fixing portion 29.

[0022] The load-receiving portion 21 is the part that receives the first load from the weighing pan of the weighing device. The load-receiving portion 21 corresponds to one end of the first strain-generating body 2 in the Y-axis direction (left side in Figure 3). The weighing pan of the weighing device is connected to the upper surface 21a of the load-receiving portion 21. The base portion 22 is the part that is fixed to, for example, the housing of the weighing device. The base portion 22 corresponds to the other end of the first strain-generating body 2 in the Y-axis direction (right side in Figure 3). For example, the load-receiving portion 21 is a free end that is not fixed to the housing of the weighing device, while the base portion 22 is a fixed end that is fixed to the housing of the weighing device.

[0023] The upper link member 23 is the part that connects the load-receiving portion 21 and the base portion 22 on one side in the Z-axis direction (upper side in Figure 3). The lower link member 24 is the part that connects the load-receiving portion 21 and the base portion 22 on the other side in the Z-axis direction (lower side in Figure 3). The upper link member 23 and the lower link member 24 extend parallel to each other along the Y-axis direction. The first strain-generating body 2 has a Roberval mechanism composed of the load-receiving portion 21, the base portion 22, the upper link member 23, and the lower link member 24.

[0024] Each of the flexure sections 25-28 is thinner than the other parts. Each of the flexure sections 25-28 is thinner than the other parts because curved recesses are provided on both the upper and lower sides.

[0025] The flexure portion 25 connects the load-receiving portion 21 to one end of the upper link member 23 in the Y-axis direction (the load-receiving portion 21 side). The flexure portion 25 has a through hole 25a that penetrates the flexure portion 25 along the Z-axis direction. The flexure portion 26 connects the base portion 22 to the other end of the upper link member 23 in the Y-axis direction (the base portion 22 side). The flexure portion 26 has a through hole 26a that penetrates the flexure portion 26 along the Z-axis direction.

[0026] The flexure portion 27 connects the load-receiving portion 21 to one end of the lower link member 24 in the Y-axis direction (the side with the load-receiving portion 21). The flexure portion 28 connects the base portion 22 to the other end of the lower link member 24 in the Y-axis direction (the side with the base portion 22). Each of the flexure portions 27 and 28 has a through hole (not shown) that passes through them along the Z-axis direction, similar to the flexure portions 25 and 26.

[0027] The fixing portion 29 is the part to which the second strain body 4 and the load sensor 8 are fixed. The fixing portion 29 is connected to the base portion 22 and extends along the Y-axis toward the load receiving portion 21. The fixing portion 29 is positioned between the upper link member 23 and the lower link member 24 in the Z-axis direction. The fixing portion 29 has two screw holes 29a that extend along the X-axis direction and open on one side in the X-axis direction (the front side of the page in Figure 3). Two bolts 11 are screwed into the two screw holes 29a from one side in the X-axis direction to fix the second strain body 4 to the first strain body 2. The fixing portion 29 also has a screw hole (not shown) that extends along the X-axis direction and opens on the other side in the X-axis direction (the back side of the page in Figure 3). A bolt 13 is screwed into this screw hole from the other side in the X-axis direction to fix the load sensor 8 to the first strain body 2.

[0028] The first strain-generating body 2 further includes a weighing lever mechanism 30. The weighing lever mechanism 30 is a mechanism for reducing the first load. The weighing lever mechanism 30 has a main body portion 31 and thin-walled portions 32 and 33. When viewed from the X-axis direction, the weighing lever mechanism 30 is located inside the Roberval mechanism of the first strain-generating body 2, which is composed of a load-receiving portion 21, a base portion 22, an upper link member 23, and a lower link member 24.

[0029] The main body portion 31 is a rod-shaped part extending along the Y-axis direction. The main body portion 31 is positioned between the upper link member 23 and the fixing portion 29 in the Z-axis direction, and between the load receiving portion 21 and the base portion 22 in the Y-axis direction. The main body portion 31 has an end portion 31a positioned on one side (the load receiving portion 21 side) in the Y-axis direction, and an end portion 31b (transmission portion) positioned on the other side (the base portion 22 side) in the Y-axis direction. The end portion 31b has a screw hole 31c that extends along the X-axis direction and opens on one side in the X-axis direction (the front side of the paper in Figure 3). A bolt 12 for fixing the second strain body 4 to the first strain body 2 is screwed into the screw hole 31c from one side in the X-axis direction. The end portion 31b has a screw hole (not shown) that extends along the X-axis direction and opens on the other side in the X-axis direction (the back side of the paper in Figure 3). A bolt 14 is screwed into the screw hole to fix the load sensor 8 to the first strain body 2 from the other side in the X-axis direction.

[0030] Each of the thin-walled sections 32 and 33 is a part that is thinner than the rest of the structure. The thin-walled section 32 connects the load-receiving section 21 to the end 31a of the main body section 31. The thin-walled section 32 extends along the Z-axis direction from the end 31a toward the lower link member 24. The thin-walled section 33 connects the fixing section 29 to a portion 31d of the main body section 31 located between the end 31a and the end 31b. The portion 31d is located on the end 31a side. The thin-walled section 33 extends along the Z-axis direction from the portion 31d toward the fixing section 29.

[0031] In the weighing lever mechanism 30, the thin-walled section 32 constitutes the point of force application P1, the thin-walled section 33 constitutes the fulcrum P2, and the end section 31b constitutes the point of application P3. Figure 3 schematically shows the positions of the point of force application P1, the fulcrum P2, and the point of application P3. In the first strain-generating body 2, when the load-receiving section 21 receives the first load, the load-receiving section 21, together with the base section 22, the upper link member 23, and the lower link member 24, displaces downward while maintaining a parallelogram shape. Consequently, the end section 31a and the thin-walled section 32 are pulled downward, and the first load is transmitted to the point of force application P1. Then, the end section 31b (point of application P3) displaces upward with the thin-walled section 33 (fulcrum P2) as the fulcrum. In other words, the main body section 31 is a movable part that moves when it receives a load, and the first strain-generating body 2 is a weighing structure that includes this movable part and is used for mass measurement (weighing). Let L1 be the distance between the point of force application P1 and the fulcrum P2 in the Y-axis direction, L2 be the distance between the fulcrum P2 and the point of application P3 in the Y-axis direction, W1 be the first load transmitted to the point of force application P1, and W11 be the first load transmitted to the point of application P3. Then the relationship "W1 × L1 = W11 × L2" is satisfied. Here, since part 31d is located on the end 31a side, the relationship "L2 > L1" is satisfied. As a result, the first load transmitted to the point of force application P1 is reduced according to the lever ratio L1 / L2 and transmitted to the point of application P3.

[0032] The details of the second strain-generating body 4 will be further explained with reference to Figure 4. Figure 4 is a plan view of the second strain-generating body shown in Figure 1. The second strain-generating body 4 is a member that receives the second load, which is the load of the calibration weight. The second strain-generating body 4 has a load-receiving portion 41, a base portion 42, an upper link member 43, a lower link member 44, flexure portions 45, 46, 47, 48, and a fixing portion 49.

[0033] The load-receiving portion 41 is the part that receives the second load from the weight-holding portion 6. The weight-holding portion 6 is fixed to the load-receiving portion 41. The load-receiving portion 41 corresponds to one end of the second strain-generating body 4 in the Y-axis direction (left side in Figure 4). The load-receiving portion 41 has two screw holes 41a that extend along the X-axis direction and open to one side in the X-axis direction (the foreground side in Figure 4). Two bolts 15 are screwed into the two screw holes 41a from one side in the X-axis direction to fix the weight-holding portion 6 to the second strain-generating body 4 (load-receiving portion 41). The base portion 42 corresponds to the other end of the second strain-generating body 4 in the Y-axis direction (right side in Figure 4).

[0034] The upper link member 43 is the part that connects the load-receiving portion 41 and the base portion 42 on one side in the Z-axis direction (upper side in Figure 4). The lower link member 44 is the part that connects the load-receiving portion 41 and the base portion 42 on the other side in the Z-axis direction (lower side in Figure 4). The upper link member 43 and the lower link member 44 extend parallel to each other along the Y-axis direction. The second strain-generating body 4 has a Roberval mechanism composed of the load-receiving portion 41, the base portion 42, the upper link member 43, and the lower link member 44.

[0035] Each of the flexure sections 45-48 is thinner than the other parts. Each of the flexure sections 45-48 is thinner than the other parts because curved recesses are provided on both the upper and lower sides.

[0036] The flexure portion 45 connects the load-receiving portion 41 to one end of the upper link member 43 in the Y-axis direction (the side with the load-receiving portion 41). The flexure portion 46 connects the base portion 42 to the other end of the upper link member 43 in the Y-axis direction (the side with the base portion 42). The flexure portion 47 connects the load-receiving portion 41 to one end of the lower link member 44 in the Y-axis direction (the side with the load-receiving portion 41). The flexure portion 48 connects the base portion 42 to the other end of the lower link member 44 in the Y-axis direction (the side with the base portion 42).

[0037] The fixing portion 49 is the part of the first strain body 2 that is fixed to the fixing portion 29. The fixing portion 49 is connected to the base portion 42 and extends along the Y-axis toward the load receiving portion 41. The fixing portion 49 is positioned between the upper link member 43 and the lower link member 44 in the Z-axis direction. The fixing portion 49 has two through holes 49a that extend along the X-axis direction. Bolts 11 are inserted through the through holes 49a.

[0038] The second strain-generating body 4 further includes a calibration lever mechanism 50, a connecting portion 61, a thin-walled portion 62, and a fixing portion 63. The calibration lever mechanism 50 is a mechanism for increasing the second load. The calibration lever mechanism 50 has a main body portion 51, thin-walled portions 52, 53, and a flexure portion 54. When viewed from the X-axis direction, the calibration lever mechanism 50 is positioned inside the Roberval mechanism of the second strain-generating body 4, which is composed of a load-receiving portion 41, a base portion 42, an upper link member 43, and a lower link member 44.

[0039] The main body portion 51 is a rod-shaped part that extends along the Y-axis direction. The main body portion 51 is positioned between the upper link member 43 and the fixing portion 49 in the Z-axis direction, and between the load-receiving portion 41 and the base portion 42 in the Y-axis direction. The main body portion 51 has an end portion 51a positioned on one side (the load-receiving portion 41 side) in the Y-axis direction, and an end portion 51b positioned on the other side (the base portion 42 side) in the Y-axis direction.

[0040] Each of the thin-walled sections 52, 53 and the flexure section 54 is a part that is thinner than the rest of the structure. The thin-walled section 52 connects the load-receiving section 41 to the end 51a of the main body section 51. Specifically, the thin-walled section 52 is connected to the load-receiving section 41 via the connecting section 61 and the thin-walled section 62. The thin-walled section 52 extends along the Z-axis direction from the end 51a toward the lower link member 44. The thin-walled section 53 connects the fixing section 49 to a portion 51c of the main body section 51 located between the end 51a and the end 51b. The portion 51c is located on the end 51b side. The thin-walled section 53 extends along the Z-axis direction from the portion 51c toward the fixing section 59.

[0041] The flexure portion 54 connects the end portion 51b of the main body portion 51 to the fixing portion 63. The flexure portion 54 extends along the Z-axis direction from the end portion 51b toward the lower link member 44. The lower end of the flexure portion 54 is connected to the fixing portion 63. The fixing portion 63 has a through hole 63a that extends along the X-axis direction. The fixing portion 63 is fixed to the end portion 31b by inserting the bolt 12 through the through hole 63a and screwing it into the threaded hole 31c of the end portion 31b of the weighing lever mechanism 30. In other words, the flexure portion 54 is connected to the end portion 31b via the fixing portion 63.

[0042] In the calibration lever mechanism 50, the thin-walled section 52 constitutes the point of force application P4, the thin-walled section 53 constitutes the fulcrum P5, and the flexure section 54 constitutes the point of application P6. Figure 3 schematically shows the positions of the point of force application P4, the fulcrum P5, and the point of application P6. In the second strain body 4, when the load receiving section 41 receives the second load, the load receiving section 41, together with the base section 42, the upper link member 43, and the lower link member 44, displaces downward while maintaining a parallelogram shape. Consequently, the end section 51a and the thin-walled section 52 are pulled downward, and the second load is transmitted to the point of force application P4. Then, the end section 51b and the flexure section 54 (point of application P6) are displaced upward with the thin-walled section 53 (fulcrum P5) as the fulcrum.

[0043] If L3 is the distance between the point of force application P4 and the fulcrum P5 in the Y-axis direction, L4 is the distance between the fulcrum P5 and the point of application P6 in the Y-axis direction, W2 is the second load transmitted to the point of force application P4, and W21 is the second load transmitted to the point of application P6, then the relationship "W2 × L3 = W21 × L4" is satisfied. Here, since part 51c is located on the end 51b side, the relationship "L3 > L4" is satisfied. As a result, the second load transmitted to the point of force application P4 is increased according to the lever ratio L3 / L4 and transmitted to the point of application P6. The second load transmitted to the point of application P6 is transmitted to the fixed part 63 via the flexure part 54.

[0044] In the weighing mechanism 1, the calibration lever mechanism 50 is fixed to the end 31b of the weighing lever mechanism 30 via a fixing part 63. In other words, the other part of the weighing lever mechanism 30 and the calibration lever mechanism 50 is displaced in conjunction with the rotational movement of one of them. On the other hand, the rotational radius of the weighing lever mechanism 30 (main body 31) and the rotational radius of the calibration lever mechanism 50 (main body 51) may be different from each other. Even in this case, in the weighing mechanism 1, the flexure part 54 positioned in front of the fixing part 63 flexes, allowing the weighing lever mechanism 30 and the calibration lever mechanism 50 to rotate without the fixing part 63 becoming rigid.

[0045] The load sensor 8 is a sensor that detects load and is manufactured by hollowing out a relatively thin metal block. As shown in Figure 2, the load sensor 8 has a load receiving part 81, a fixing part 82, and a tuning fork 83.

[0046] A through hole 81a is formed in the load-receiving portion 81. The load-receiving portion 81 is fixed to the end 31b by inserting a bolt 14 through the through hole 81a and screwing it into a threaded hole formed in the end 31b of the weighing lever mechanism 30 of the first strain-generating body 2. In other words, the end 31b is connected to the load-receiving portion 81. As a result, the first strain-generating body 2 transmits the first load (the first load reduced by the weighing lever mechanism 30) to the load-receiving portion 81 via the end 31b. The second strain-generating body 4 also transmits the second load (the second load increased by the calibration lever mechanism 50) to the load-receiving portion 81 via the end 31b.

[0047] A through hole 82a is formed in the fixing portion 82. The bolt 13 is inserted through the through hole 82a and screwed into a threaded hole formed in the fixing portion 29 of the first strain body 2, thereby fixing the fixing portion 82 to the fixing portion 29.

[0048] The tuning fork 83 receives the first and second loads that the load receiving section 81 receives. The vibration frequency of the tuning fork vibrator in the tuning fork 83 changes according to the magnitude of the load (tension acting on the tuning fork vibrator). In the load sensor 8, a piezoelectric element (not shown) provided on the tuning fork 83 converts the vibration of the tuning fork vibrator into a voltage, and a substrate (not shown) connected to the piezoelectric element counts the period of the voltage and converts it into a frequency. Then, in the load sensor 8, a computer (e.g., a calculation unit 9), such as a microcontroller, processes the data based on the frequency to obtain the first and second loads. As a result, the load sensor 8 detects the first load transmitted from the first strain body 2 (the first load reduced by the weighing lever mechanism 30) and the second load transmitted from the second strain body 4 (the second load amplified by the calibration lever mechanism 50).

[0049] The calculation unit 9 is electrically connected to the load sensor 8 and processes the load detected by the load sensor 8. The calculation unit 9 is composed of a computer including, for example, a processor (CPU), and recording media such as RAM and ROM. The calculation unit 9 calculates a third load by magnifying the second load detected by the load sensor 8 by a predetermined magnification. The calculation unit 9 then sets the third load as the calibration load value and calibrates the load sensor 8. The predetermined magnification is, for example, smaller than the lever ratio L3 / L4 of the calibration lever mechanism 50. The reciprocal L2 / L1 of the lever ratio of the weighing lever mechanism 30 is, for example, smaller than the value obtained by multiplying the lever ratio L3 / L4 of the calibration lever mechanism 50 by the predetermined magnification.

[0050] As an example, the weighing lever mechanism 30 described above reduces the first load of the object to be weighed so that it is 90% or more of the weighing capacity of the load sensor 8. The calibration lever mechanism 50 increases the second load of the weight W so that it is 10% or more of the weighing capacity of the load sensor 8. As an example, the calibration lever mechanism 50 increases the second load of the weight W so that it is 10% or more but less than 90% of the weighing capacity of the load sensor 8. The calculation unit 9 magnifies the second load, which has been increased by the calibration lever mechanism 50, by a predetermined magnification so that it is 90% or more of the weighing capacity of the load sensor 8. In this case, the predetermined magnification is 10 times or less. The weighing capacity of the load sensor 8 refers to the maximum weight that the load sensor 8 can weigh. 90% or more of the weighing capacity refers to the range from 90% of the weighing capacity to the weighing capacity.

[0051] In the weighing mechanism 1 configured as described above, the weighing of the object to be weighed is performed as follows: When the load receiving part 21 receives the first load of the object to be weighed, the load receiving part 21 is displaced downward. Accordingly, the end part 31a and the thin-walled part 32 are pulled downward, and the first load is transmitted to the point of force application P1. The first load transmitted to the point of force application P1 is reduced according to the lever ratio L1 / L2 of the weighing lever mechanism 30 and transmitted to the point of application P3. The first load reduced by the weighing lever mechanism 30 is transmitted to the load receiving part 81 via the end part 31b. The load sensor 8 then detects the first load.

[0052] Furthermore, calibration is performed in the weighing mechanism 1 using a calibration weight W as follows: When the load receiving part 41 receives the second load of the weight W, the load receiving part 41 is displaced downward. Consequently, the end part 51a and the thin-walled part 52 are pulled downward, and the second load is transmitted to the point of force application P4. The second load transmitted to the point of force application P4 is amplified according to the lever ratio L3 / L4 of the calibration lever mechanism 50 and transmitted to the point of application P6. The second load amplified by the calibration lever mechanism 50 is transmitted to the load receiving part 81 via the flexure part 54, the fixed part 63, and the end part 31b. The load sensor 8 then detects the second load. The calculation unit 9 calculates the third load by amplifying the second load by a predetermined magnification. The calculation unit 9 sets the third load as the calibration load value and performs calibration of the load sensor 8.

[0053] As described above, the main body 51 constituting the calibration lever mechanism 50 is a movable part that moves when subjected to a load. In the second strain body 4, the connecting part 61 connected to the main body 51 via a thin-walled part 52 (point of force application P4), the beam-like part 64 connected to the connecting part 61 via a thin-walled part 62, and the fixed part 63 connected to the main body 51 via a flexible part 54 (point of application P6) are also movable parts, connected to the base body 70 via flexible parts. Thus, the second strain body 4 has a block-shaped base body 70 and a plurality of movable parts integrally provided on the base body 70, and is a weighing structure used for mass measurement (weighing).

[0054] Furthermore, the second strain-generating body 4 has a configuration for fixing the movable part to prevent it from moving unintentionally during its manufacture or when it is attached to the first strain-generating body 2. Specifically, the second strain-generating body 4 has a plurality of screw holes 71 to 76 provided in the base body 70 at a plurality of positions that restrict the movement of the movable part. Screw hole 71 is provided at a position between the end 51b of the main body portion 51 and the fixing portion 63. Screw holes 72 and 73 are provided at positions that sandwich the connecting portion 61 from both sides in the Y-axis direction. Screw hole 74 is provided at a position that contacts the tip 64b on the opposite side of the base end 64a connected to the base body 70 in the beam-shaped portion 64. Screw hole 75 is provided at a position that contacts the end 63b in the Z-axis direction of the fixing portion 63. Screw hole 76 is provided at a position that sandwiches the fixing portion 63 between screw hole 71 and the fixing portion 63 along the Y-axis direction.

[0055] In the second strain-generating body 4, screw members such as cap bolts are screwed into each of the screw holes 71 to 76, thereby restricting the movement of the movable parts: the main body 51, the connecting part 61, the beam-like part 64, and the fixed part 63. In the illustrated example, the screw members have been removed from each of the screw holes 71 to 76, and the movable parts are in a released state. The screw holes 71 to 76 open into the first surface 70s of the base body 70 and have a bottom B between the first surface 70s and the second surface 70r on the opposite side of the first surface 70s (see Figure 5(b)). The screw holes 71 to 76 communicate with the second surface 70r via a hole H provided in the bottom B. In other words, the screw holes 71 to 76 penetrate the base body 70 together with the hole H. To put it another way, the relatively large diameter screw holes 71-76 and the relatively small diameter hole H are connected at a position (in the Z-axis direction) between the first surface 70s and the second surface 70r, creating a bottom B at the connection point. The bottom B is the part that receives contact with the tip of the screw member 107, which will be described later. Note that the fact that the screw holes 71-76 are relatively large in diameter relative to the hole H means that, at least, the diameter at the top of the screw threads of the screw holes 71-76 is larger than the diameter of the hole H.

[0056] Next, the method for manufacturing the second strain-generating body 4 will be described. As mentioned above, the second strain-generating body 4 is a weighing structure that includes a movable part. Therefore, the method for manufacturing the second strain-generating body 4 is an example of a method for manufacturing weighing structures.

[0057] Here, first, as shown in Figure 5(a), a metal block 100 (block member) is prepared and set in the processing machine (step S101). The metal block 100 is, for example, a 6-sided milled material and, as described above, is made of a metal such as aluminum alloy or stainless steel. The metal block 100 is rectangular in shape and has a plate-like form in which the length in the X-axis and Y-axis directions is greater than the thickness in the Z-axis direction. Also, the metal block 100 is longer in the Y-axis direction than in the X-axis direction. The metal block 100 includes a first surface 101 and a second surface 102 opposite to the first surface 101. The first surface 101 and the second surface 102 are substantially parallel to each other and are the largest surfaces of the metal block 100. The first surface 101 is the surface that becomes the first surface 70s of the base body 70, and the second surface 102 is the surface that becomes the second surface 70r of the base body 70.

[0058] Next, as shown in Figure 5(b), through holes 49a, 63a, screw holes 71-76, and grooves 103 are formed in the metal block 100 (process S102, first process). More specifically, in process S102, screw holes 71-76 are formed by threading from the first surface 101 side (threading process). As described above, screw holes 71-76 are formed in positions that restrict the movement of the movable part. Here, first, for example, a through hole is formed from the first surface 101 to the second surface 102 using a drill, and then, for example, a tap is used to form screw threads in the through hole from the first surface 101 side. At this time, the screw threads are formed up to an intermediate position between the first surface 101 and the second surface 102 in the through hole. As a result, a portion of the through-hole on the first surface 101 side becomes a relatively large-diameter screw hole 71-76, and the remaining portion of the through-hole on the second surface 102 side becomes a relatively small-diameter hole H that connects the screw holes 71-76 to the second surface 102. The screw holes 71-76 have a bottom B at the connection point with the hole H. That is, the screw holes 71-76 have a bottom B between the first surface 101 and the second surface 102. Note that the hole H is not required (i.e., the screw holes 71-76 do not need to communicate with the second surface 102). Simultaneously, in step S102, a groove 103 that defines the outer edge of the movable part (for example, the main body part 51) is formed by cutting from the first surface 101 side (first cutting step). Furthermore, in step S102, through holes 49a and 63a are formed from the first surface 101 to the second surface 102 by drilling from the first surface 101 side.

[0059] Figure 6(a) is a plan view of the metal block 100 after process S102 has been performed, shown from the second surface 102 side. As shown in Figure 6(a), even after process S102, the through holes 49a and 63a open to the second surface 102, but the grooves 103 do not open to the second surface 102. Also, the screw holes 71 to 76 communicate with the second surface 102 via the holes H, but the screw holes 71 to 76 themselves do not open to the second surface 102. In other words, in process S102, the grooves 103 are formed so as not to reach the second surface 102, and the screw holes 71 to 76 are formed so as to have a bottom B between the first surface 101 and the second surface 102.

[0060] In the next step, as shown in Figure 6(b), the metal block 100 is removed from the processing machine, and the screw members 107 are screwed into each of the screw holes 71 to 76 (step S103, first step). At this time, the tip of the screw member 107 can be brought into contact with the bottom B of the screw holes 71 to 76. The screw member 107 may be a grub screw without a head, but in this embodiment, it is a cap bolt having a shaft and a head provided at the tip of the shaft and having a larger diameter than the shaft.

[0061] Next, with the screw members 107 screwed into each of the screw holes 71 to 76, the metal block 100 is set back on the processing machine, and the movable part is formed by cutting the metal block 100 from the second surface 102 side as shown in Figure 7 (process S104, second process, second cutting process). More specifically, in process S104, the groove portion 103 is made to communicate with the second surface 102 side (opening to the second surface 102 side) by cutting the metal block 100 from the second surface 102 side. This forms a movable part, such as the main body portion 51. As a result, the second strain-generating body 4 is obtained from the metal block 100.

[0062] Subsequently, the obtained second strain body 4 is fixed to the first strain body 2 using the through holes 49a and 63a, while maintaining the state in which the screw members 107 are screwed into each of the screw holes 71 to 76. After the second strain body 4 is fixed to the first strain body, the screw members 107 are removed from each of the screw holes 71 to 76, and the movable part of the second strain body 4 is released, thereby obtaining the weighing mechanism 1.

[0063] As described above, in the weighing structure manufacturing method according to this embodiment, first, screw holes 71 to 76 are formed in the metal block 100 (step S102), and screw members 107 are screwed into the screw holes 71 to 76 (step S103). Then, in that state, the metal block 100 is machined to form a movable part (for example, the main body 51) that moves when subjected to a load (step S104). In particular, the screw members 107 are screwed into the screw holes 71 to 76 which are formed at positions that restrict the movement of the movable part. Therefore, when the movable part is formed during the machining process, unintended movement of the movable part is suppressed, resulting in improved machining accuracy. Furthermore, after the manufactured weighing structure (second strain body 4 in this embodiment) is attached to another member (first strain body 2 in this embodiment), it can be easily removed by rotating the screw members 107 compared to removing the press-fitted pin, thus improving ease of assembly.

[0064] Furthermore, in the weighing structure manufacturing method according to this embodiment, the metal block 100 includes a first surface 101 and a second surface 102 opposite to the first surface 101, and in step S102, screw holes 71 to 76 are formed such that there is a bottom B between the first surface 101 and the second surface 102. As a result, the screw holes 71 to 76 and the screw member 107 become blind screws, enabling secure fixing of the movable part. That is, by making the screw holes 71 to 76 and the screw member 107 blind screws, the screw member 107 is tightened all the way into the screw holes 71 to 76 and brought into contact with the bottom B of the screw holes 71 to 76, eliminating backlash (i.e., eliminating rattle in the gap between the screw holes 71 to 76 and the screw member 107), enabling secure fixing of the movable part. As a result, high-precision machining becomes possible. Furthermore, since the screw holes 71-76 and the screw members 107 are not exposed on the second surface 102, the machining of the second surface 102 is easy and highly accurate.

[0065] Furthermore, in the weighing structure manufacturing method according to this embodiment, step S102 includes a first cutting step of cutting the metal block 100 from the first surface 101 side, and a threading step of forming screw holes 71-76 by threading from the first surface 101 side. Step S104 also includes a second cutting step of cutting the metal block 100 from the second surface 102 side. Here, the second cutting step for forming (releasing) the movable part is performed on the second surface 102 where the screw holes 71-76 and the screw member 107 are not exposed, making the processing easy and highly accurate.

[0066] Furthermore, in the method for manufacturing a weighing structure according to this embodiment, in the first cutting step, the metal block 100 is cut from the first surface 101 side to define the outer edge of the movable part and form a groove 103 that does not reach the second surface 102, and in the second cutting step, the metal block 100 is cut from the second surface 102 side to connect the groove 103 to the second surface 102 side and form the movable part. Thus, the movable part may be formed by cutting from both the first surface 101 and the second surface 102 of the metal block 100.

[0067] Furthermore, in the manufacturing method for weighing structures according to this embodiment, the screw member 107 is a bolt including a shaft and a head provided at the tip of the shaft. Therefore, the removal of the screw member 107 becomes easier, and assembly efficiency is further improved.

[0068] Furthermore, the second strain-generating body 4 according to this embodiment is a weighing structure comprising a block-shaped base 70, a movable part (main body 51, etc.) integrally provided on the base 70 and movable when subjected to a load, and screw holes 71 to 76 provided on the base 70 at positions in which the movement of the movable part is restricted by screwing in a screw member 107.

[0069] In the second strain-generating body 4, the unintended movement of the movable part can be suppressed by screwing, for example, a screw member 107 into screw holes 71-76 formed at positions that restrict the movement of the movable part. As a result, the processing accuracy of the second strain-generating body 4 can be improved during manufacturing. Furthermore, after attaching the second strain-generating body 4 with the screw member 107 screwed in to another member (the first strain-generating body 2 in this embodiment), it can be easily removed by rotating the screw member 107, compared to removing a press-fitted pin, thus improving ease of assembly.

[0070] Furthermore, in the second strain-generating body 4 according to this embodiment, the base body 70 includes a first surface 70s and a second surface 70r opposite to the first surface 70s, and the screw holes 71 to 76 are formed to have a bottom B between the first surface 70s and the second surface 70r. As a result, the screw holes 71 to 76 and the screw members 107 that can be screwed into the screw holes 71 to 76 become set screws, enabling secure fixing of the movable part.

[0071] The above embodiments illustrate one aspect of the present invention. Therefore, the present invention can be derived by arbitrarily modifying the above embodiments.

[0072] For example, in the above embodiment, a method for manufacturing the second strain body 4 was described as an example of a method for manufacturing a weighing structure. However, as another example of a method for manufacturing a weighing structure, the first strain body 2 or the load sensor 8 may also be manufactured. In other words, the workpiece of the weighing structure manufacturing method can be any structure used for weighing, including a movable part that moves when subjected to a load.

[0073] Furthermore, in the above embodiment, in step S102, screw holes 71 to 76 were formed such that they have a bottom B between the first surface 101 and the second surface 102 of the metal block 100. However, in step S102, screw holes 71 to 76 may also be formed as through holes extending from the first surface 101 to the second surface 102. In other words, screw holes 71 to 76 do not necessarily have a bottom B.

[0074] Furthermore, in the above embodiment, in step S102, a groove 103 is formed by cutting from the first surface 101 side of the metal block 100 so as not to reach the second surface 102, and in step S104, a movable part is formed by connecting the groove 103 to the second surface 102 by cutting from the second surface 102 side. However, in step S104, the groove 103 may be formed by cutting from the first surface 101 side of the metal block 100 so as to reach the second surface 102, thereby forming the movable part. In other words, cutting from the second surface 102 side is not essential.

[0075] Furthermore, although the load sensor 8 in the above embodiment was a so-called tuning fork type load sensor, the load sensor 8 may also be a so-called electromagnetic type load sensor. The load sensor 8 may also have a lever mechanism, similar to the first strain body 2 and the second strain body 4. [Explanation of symbols]

[0076] 4...Second strain-generating body (measuring structure), 51...Main body (movable part), 61...Connecting part (movable part), 63...Fixed part (movable part), 64...Beam-like part (movable part), 70...Base, 70s...First surface, 70r...Second surface, 71~76...Screw holes, 100...Metal block (block member), 101...First surface, 102...Second surface, 103...Groove, 107...Screw member.

Claims

1. A method for manufacturing a weighing structure, which includes a movable part that moves when subjected to a load, by cutting a block member, The first step involves forming a screw hole in the block member and screwing a screw member into the screw hole, Following the first step, a second step is to form the movable part by cutting the block member while the screw member is screwed into the screw hole, Equipped with, In the first step, the screw hole is formed at a position that restricts the movement of the movable part, and the screw member is screwed into the screw hole. A method for manufacturing a weighing structure.

2. The block member includes a first surface and a second surface opposite to the first surface, In the first step, the screw hole is formed such that it has a bottom between the first surface and the second surface. A method for manufacturing a weighing structure according to claim 1.

3. The first step is, A first cutting step in which the block member is cut from the first surface side, The process includes a screw machining step of forming the screw hole by performing screw cutting from the first surface side, The second step includes a second cutting step of cutting the block member from the second surface side, A method for manufacturing a weighing structure according to claim 2.

4. In the first cutting step, the block member is cut from the first surface side to define the outer edge of the movable part and form a groove that does not reach the second surface. In the second cutting step, the movable part is formed by cutting the block member from the second surface side, thereby connecting the groove to the second surface side. A method for manufacturing a weighing structure according to claim 3.

5. The screw member is a bolt including a shaft and a head provided at the tip of the shaft. A method for manufacturing a weighing structure according to any one of claims 1 to 4.

6. A block-shaped base, A movable part is integrally provided with the base and moves when subjected to a load, A screw hole is provided in the base body at a position where the movement of the movable part is restricted by the screw member being screwed in, A weighing structure equipped with [a specific feature].

7. The substrate includes a first surface and a second surface opposite to the first surface. The screw hole has a bottom between the first surface and the second surface. The weighing structure according to claim 6.

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