Precision balance

Abstract

The disclosed precision balance 10 comprises a plate 11 placed on a placement surface, a weight measurement unit 12 provided above the plate 11, a support 17 provided between the plate 11 and the weight measurement unit 12 and supporting the weight measurement unit 12, and a sample stage 22 provided on the weight measurement unit 12 and on which a sample is placed. The support 17 has a conical shape, the apex 18 of the support 17 is brought into contact with the plate 11, and the bottom surface 19 of the support 17 is brought into contact with the weight measurement unit 12.

Description

precision balance CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This disclosure claims the benefit of priority to Japanese Patent Application No. 2024-143268, filed on August 23, 2024, in the Japan Patent Office, the entire contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a precision balance.

[0003] Conventionally, precision balances for measuring the weight of a sample with high accuracy have been known (for example, Patent Document 1). Patent Document 1 discloses a precision balance characterized by incorporating a "vibration isolation unit" in which a "resin laminated spring plate" is formed by laminating a viscoelastic resin having vibration damping capacity between skin spring steel plates, and is integrally processed to have flange-shaped ends and a convex central portion, and which is alternately stacked in a honeycomb shape so as to be able to deflect under load.

[0004] JP 2014-35344 A

[0005] However, in the precision balance of Patent Document 1, vibrations transmitted from the mounting surface can be amplified on the top plate (or sample stage). This is because free-end reflection occurs on the top plate, and the incident wave and the reflected wave are superimposed so as to reinforce each other. If the top plate vibrates significantly, the measurement accuracy of the precision balance decreases. In such a situation, one of the objects of the present disclosure is to improve measurement accuracy.

[0006] One aspect of the present disclosure relates to a precision balance including a plate placed on a mounting surface, a weight measuring unit provided above the plate, a support provided between the plate and the weight measuring unit and supporting the weight measuring unit, and a sample stage provided on the weight measuring unit and on which a sample is placed, the support having a conical shape with its apex in contact with the plate and its bottom in contact with the weight measuring unit.

[0007] According to the present disclosure, measurement accuracy can be improved. The novel features of the present invention are set forth in the appended claims, but the present invention, both in terms of structure and content, together with other objects and features of the present invention, will be better understood from the following detailed description taken in conjunction with the drawings.

[0008] FIG. 1 is a partial cross-sectional view schematically showing a precision balance according to embodiment 1. FIG. 2 is a conceptual diagram for explaining a mechanism for suppressing vibration of a sample stage. FIG. 3 is a front view schematically showing the apex of a support according to embodiment 2. FIG. 4 is a front view schematically showing the apex of a support according to embodiment 3. FIG. 5 is a front view schematically showing the apex of a support according to embodiment 4.

[0009] An embodiment of a precision balance according to the present disclosure will be described below using examples. However, the present disclosure is not limited to the examples described below. While specific numerical values ​​and materials may be used in the following description, other numerical values ​​and materials may be used as long as the effects of the present disclosure are obtained.

[0010] The precision balance according to the present disclosure is a device for measuring the weight of a sample with high precision. The sample may be, for example, a battery in the manufacturing process (e.g., a secondary battery in the process of injecting an electrolyte). The weight of one sample may also be measured using one precision balance. The precision balance according to the present disclosure includes a plate, a weight measurement unit, a support, and a sample stage.

[0011] The plate is placed on a support surface (e.g., the top surface of a vibration isolation table or a rubber mat). The plate may have a function of attenuating vibrations transmitted from the support surface. Examples of materials for the plate include SUS, aluminum, brass, and engineering plastics (e.g., polyethylene, polypropylene, polycarbonate, polyimide, and nylon). When the sample is a battery in the manufacturing process, it is preferable to use a polyolefin-based engineering plastic that is resistant to the electrolyte.

[0012] The weight measuring unit is provided above the plate. The weight measuring unit may include a housing provided at the bottom thereof, a columnar body supported on the housing, a cylindrical body that is vertically movable relative to the columnar body and to which a sample stage is attached, and a spring provided between the housing and the sample stage that urges the sample stage upward. In this case, when a sample is placed on the sample stage, the sample stage and the cylindrical body descend against the spring's urging force in accordance with the sample's weight. This descent stops when the sample weight and the spring's urging force balance each other. The weight measuring unit is configured to output an electrical signal whose magnitude corresponds to the descending distance of the sample stage and the cylindrical body. The user can use the electrical signal in an appropriate manner to determine the weight of the sample. Note that the central axis of the weight measuring unit may or may not pass through the center of the sample stage.

[0013] The support is provided between the plate and the weight measurement unit. In other words, the support is provided above the plate and below the weight measurement unit. The support supports the weight measurement unit. Examples of materials that can be used to construct the support include SUS, aluminum, brass, and engineering plastics (e.g., polyethylene, polypropylene, polycarbonate, polyimide, and nylon). When the sample is a battery in the manufacturing process, it is preferable to use a polyolefin-based engineering plastic that is resistant to the electrolyte. Only one support may be provided per precision balance.

[0014] The sample stage is provided on the weight measurement unit. The sample stage may be attached to the cylindrical body of the weight measurement unit. A sample is placed on the sample stage. When the sample is placed on the sample stage, the weight of the sample can be measured according to the mechanism described above.

[0015] The support has a conical shape. The apex of the conical support is in contact with the plate (more specifically, the upper surface of the plate). The bottom surface of the conical support is in contact with the weight measuring unit (more specifically, the lower surface of the housing of the weight measuring unit). In other words, the conical support is arranged with its apex facing downward.

[0016] A precision balance having the above-described configuration can measure the weight of a sample with high accuracy even when vibrations are transmitted from the mounting surface. That is, vibrations from the mounting surface propagate upward in the following order: plate, support, weight measurement unit, and sample stage. Because the support has a downward-facing conical shape, vibrations incident on the apex of the support from the plate radiate from the apex and propagate upward, i.e., to the weight measurement unit and sample stage. When such vibrations are reflected from the free end of the sample stage, the sample stage experiences a mixture of positively constructive and negatively constructive interactions between the incident and reflected waves. Therefore, the two waves cancel each other out, resulting in reduced vibrations in the sample stage and enabling highly accurate weight measurement of the sample. This cancellation effect, which improves weight measurement, can be achieved regardless of the frequency of the vibrations transmitted from the mounting surface.

[0017] In a cross section passing through the central axis of the precision balance, the apex angle of the support (hereinafter also referred to as the first angle) may be equal to or greater than the angle (hereinafter also referred to as the second angle) formed by a line connecting the apex of the support to one end of the sample stage and a line connecting the apex of the support to the other end of the sample stage. In this case, the above-mentioned cancellation effect can be generated throughout the entire sample stage, further improving the measurement accuracy of the precision balance. The first angle may be, for example, three to six times the second angle, and preferably four to five times the second angle. The larger the first angle, the more improved the damping characteristics can be in the range where the frequency of vibrations transmitted from the mounting surface is low. On the other hand, the smaller the first angle, the more suppressed the deterioration of the damping characteristics when the precision balance resonates due to the vibrations.

[0018] The apex of the support may have a pointed shape. Here, a pointed shape includes a shape in which the apex is slightly rounded. For example, if the radius of curvature of the apex of the support is less than 0.15 mm, even if it is slightly rounded, it is considered to be a pointed shape. This configuration can particularly suppress deterioration of the damping characteristics when the precision balance resonates due to vibrations transmitted from the mounting surface.

[0019] The apex of the support may have a spherical shape. The diameter of the spherical shape may be, for example, 0.3 mm or more and 0.8 mm or less. This configuration can achieve a good balance between suppressing deterioration of the damping characteristics when the precision balance resonates due to vibrations transmitted from the mounting surface and improving the damping characteristics in a range where the frequency of the vibrations is low.

[0020] The apex of the support may have a dome shape (or a hemispherical shape). The radius of curvature of the dome shape may be, for example, 0.15 mm or more and 0.4 mm or less. This configuration can achieve a good balance between suppressing deterioration of the damping characteristics when the precision balance resonates due to vibrations transmitted from the mounting surface and improving the damping characteristics in a range where the frequency of the vibrations is low.

[0021] The apex of the support may have a flat surface parallel to the plate. The flat surface may be in surface contact with the plate. The diameter of the flat surface may be, for example, 0.3 mm or more and 0.8 mm or less. This configuration can particularly improve the damping characteristics in a region where the frequency of vibration transmitted from the mounting surface is low.

[0022] As described above, according to the present disclosure, by providing a downward-facing cone-shaped support, the measurement accuracy of the precision balance can be improved.

[0023] An example of a precision balance according to the present disclosure will be specifically described below with reference to the drawings. The components described above can be applied to the components of the example precision balance described below. The components of the example precision balance described below can be modified based on the above description. Furthermore, the matters described below may be applied to the above embodiment. Of the components of the example precision balance described below, components that are not essential to the precision balance according to the present disclosure may be omitted. Note that the diagrams shown below are schematic and do not accurately reflect the shapes and number of actual components.

[0024] Embodiment 1 Embodiment 1 of the present disclosure will be described. The precision balance 10 of this embodiment is a device for measuring the weight of a battery (not shown) during its manufacturing process. In this sense, the precision balance 10 of this embodiment can also be referred to as a precision balance for batteries. As shown in FIG. 1 , the precision balance 10 includes a plate 11, a weight measurement unit 12, a support 17, an auxiliary support 21, and a sample stage 22. Note that FIG. 1 shows the support 17, the auxiliary support 21, and a housing 13 (described below) of the weight measurement unit 12 in cross section.

[0025] The plate 11 is placed on the mounting surface S. The plate 11 has a function of attenuating vibrations transmitted from the mounting surface S. In this sense, the plate 11 of this embodiment can also be called a vibration absorbing plate.

[0026] The weight measuring unit 12 is provided above the plate 11. The weight measuring unit 12 has, from bottom to top, a housing 13, a columnar body 14, a cylindrical body 15, and a spring 16.

[0027] The housing 13 includes a generally disk-shaped base portion 13a and a rising portion 13b extending upward from the outer periphery of the base portion 13a. The housing 13 has a U-shape that is flat and angular in the vertical direction in a cross section passing through the central axis O of the precision balance 10.

[0028] The pillar 14 is fixed to the upper surface of the base portion 13a of the housing 13 in a position extending vertically. The pillar 14 is roughly cylindrical. A gap is formed between the pillar 14 and the rising portion 13b of the housing 13, into which the lower end of the cylindrical body 15 fits.

[0029] The cylindrical body 15 has a generally cylindrical shape that extends vertically, and the columnar body 14 is inserted into the internal space thereof. The cylindrical body 15 is movable vertically relative to the columnar body 14. A sample stage 22 is attached to the upper end of the cylindrical body 15.

[0030] The spring 16 is provided between the base portion 13a of the housing 13 and the sample stage 22. The spring 16 is made of a coil spring, and biases the sample stage 22 (and the columnar body 14 to which the sample stage 22 is attached) upward.

[0031] The support 17 is provided between the plate 11 and the housing 13 of the weight measuring unit 12. The support 17 supports the weight measuring unit 12. The support 17 has a conical shape. An apex 18 of the support 17 contacts the plate 11. A bottom surface 19 of the support 17 contacts the housing 13 of the weight measuring unit 12. In this embodiment, the conical axis of the support 17 coincides with the central axis O of the precision balance 10, but this is not limited to this. For example, the conical axis of the support 17 may pass through the central region of the sample stage 22 (i.e., the region of the sample stage 22 that is at a distance of 0 to 0.2R from the center, where R is the radius of the sample stage 22). The apex 18 of the support 17 in this embodiment has a pointed shape.

[0032] In a cross section passing through the central axis O of the precision balance 10 (cross section shown in FIG. 1 ), the magnitude of the apex angle θ1 of the support 17 is equal to or greater than the angle θ2 (θ1≧θ2) between a line connecting the vertex 18 of the support 17 to one end of the sample stage 22 and a line connecting the vertex 18 of the support 17 to the other end of the sample stage 22. In this embodiment, θ1 is approximately twice θ2, but is not limited to this.

[0033] The auxiliary support 21 is provided around the support 17 between the plate 11 and the housing 13 of the weight measuring unit 12. The auxiliary support 21 provides auxiliary support for the weight measuring unit 12. In this embodiment, the auxiliary support 21 has a ring shape, but is not limited to this. For example, a plurality of (e.g., three or four) columnar auxiliary supports (not shown) may be provided to surround the support 17.

[0034] The sample stage 22 is provided on the weight measurement unit 12. The sample stage 22 is attached to the upper end of the cylindrical body 15 of the weight measurement unit 12. A sample to be weighed (in this example, a battery in the manufacturing process; not shown) is placed on the sample stage 22.

[0035] Next, the mechanism by which vibration of the sample stage 22 is suppressed when vibration is transmitted from the mounting surface S in the precision balance 10 having the above-described configuration will be described with reference to Fig. 2. In Fig. 2, the positive wavefront is indicated by a solid line, and the negative wavefront is indicated by a dashed line.

[0036] As conceptually shown in FIG. 2 , vibrations incident on the plate 11 from the mounting surface S are transmitted to the sample stage 22 primarily via the apex 18 of the conical support 17. At this time, the vibrations transmitted from the apex 18 of the support 17 radiate from the apex 18 and are incident on the sample stage 22 (as an upwardly convex wavefront, or incident wave W1, in FIG. 2 ). The reflected wave W2 generated by free-end reflection at the sample stage 22 is transmitted downward as a downwardly convex wavefront in FIG. 2 . In the sample stage 22, the incident wave W1 and the reflected wave W2 constructively interact positively in a certain region (the region indicated by the black circle in FIG. 2 ), while constructively interact negatively in another region (the region indicated by the white circle in FIG. 2 ). Therefore, the two waves cancel each other out, suppressing vibrations across the sample stage 22 as a whole. This enables the weight of the sample to be measured with high precision.

[0037] Second Embodiment A second embodiment of the present disclosure will be described. The precision balance 10 of this embodiment differs from the first embodiment in the shape of the apex 18 of the support 17. Specifically, the apex of the support 17 of this embodiment has a spherical shape, as shown in Figure 3. The rest of the configuration is the same as the first embodiment.

[0038] Third Embodiment A third embodiment of the present disclosure will be described. The precision balance 10 of this embodiment differs from the first embodiment in the shape of the apex 18 of the support 17. Specifically, the apex of the support 17 of this embodiment has a dome shape, as shown in FIG. 4. The other configurations are the same as those of the first embodiment.

[0039] Fourth Embodiment A fourth embodiment of the present disclosure will be described. The precision balance 10 of this embodiment differs from the first embodiment in the shape of the apex 18 of the support 17. Specifically, the apex of the support 17 of this embodiment has a flat surface 18a that is parallel to the plate 11 (i.e., extends horizontally), as shown in FIG. 5 . The rest of the configuration is the same as the first embodiment.

[0040] <<Supplementary Notes>> The above embodiments disclose the following technologies. (Technology 1) A precision balance comprising: a plate placed on a placement surface; a weight measuring unit provided above the plate; a support provided between the plate and the weight measuring unit and supporting the weight measuring unit; and a sample stage provided on the weight measuring unit and on which a sample is placed, wherein the support has a conical shape, with its apex in contact with the plate and its bottom in contact with the weight measuring unit. (Technology 2) A precision balance according to Technology 1, wherein, in a cross section passing through the central axis of the precision balance, the apex angle of the support is equal to or greater than the angle formed by a line connecting the apex of the support to one end of the sample stage and a line connecting the apex of the support to the other end of the sample stage. (Technology 3) A precision balance according to Technology 1 or 2, wherein the apex of the support has a pointed shape. (Technology 4) A precision balance according to Technology 1 or 2, wherein the apex of the support has a spherical shape. (Technology 5) The precision balance according to Technology 1 or 2, wherein the apex of the support has a dome shape. (Technology 6) The precision balance according to Technology 1 or 2, wherein the apex of the support has a flat surface parallel to the plate.

[0041] The present disclosure can be used for precision balances.

[0042] While the present invention has been described in terms of presently preferred embodiments, such disclosure is not to be interpreted as limiting. Various changes and modifications will no doubt become apparent to those skilled in the art to which the present invention pertains upon reading the above disclosure. It is therefore intended that the appended claims be interpreted to cover all changes and modifications that do not depart from the true spirit and scope of the invention.

[0043] 10: Precision balance 11: Plate 12: Weight measurement unit 13: Housing 13a: Base portion 13b: Rising portion 14: Pillar body 15: Cylinder body 16: Spring 17: Support 18: Apex 18a: Flat surface 19: Bottom surface 21: Auxiliary support 22: Sample stage O: Central axis S: Placement surface W1: Incident wave W2: Reflected wave θ1: Size of apex angle of support θ2: Angle formed by two straight lines

Claims

1. A precision balance comprising: a plate placed on a mounting surface; a weight measuring unit provided above the plate; a support provided between the plate and the weight measuring unit and supporting the weight measuring unit; and a sample stage provided on the weight measuring unit and on which a sample is placed, wherein the support has a conical shape, with its apex in contact with the plate and its base in contact with the weight measuring unit.

2. A precision balance as described in claim 1, wherein in a cross section passing through the central axis of the precision balance, the apex angle of the support is equal to or greater than the angle between a line connecting the apex of the support to one end of the sample stage and a line connecting the apex of the support to the other end of the sample stage.

3. The precision balance according to claim 1 or 2, wherein the apex of the support has a pointed shape.

4. The precision balance according to claim 1 or 2, wherein the apex of the support has a spherical shape.

5. The precision balance according to claim 1 or 2, wherein the apex of the support has a dome shape.

6. The precision balance according to claim 1 or 2, wherein the apex of the support has a flat surface parallel to the plate.

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