JP6551543B2 - electronic balance - Google Patents

Description

  The present invention relates to an electronic balance in which a weighing pan is attached to a block-like mechanism formed by hollowing out one base material.

  A so-called electromagnetic force balance type electronic balance is provided with an electromagnetic force generator having a moving coil and a magnetic circuit, for example. The magnetic circuit has a configuration including a permanent magnet and a yoke, and can form a static magnetic field therein. The movable coil is disposed in a static magnetic field formed by a magnetic circuit, and can be displaced along its axial direction.

  The weighing pan on which the measurement object is placed is connected to the movable coil via the lever, and as the lever is displaced by the load of the measurement object, the movable coil connected to the lever is displaced. At this time, the mass of the object to be measured can be measured from the current value by detecting the displacement of the lever with a detector and performing feedback control of the current flowing through the movable coil so that the lever is not displaced.

  This type of electronic balance is provided with a Robert mechanism that regulates the displacement of the weighing pan in the vertical direction, for example. The Roberval mechanism is a mechanism for connecting the movable column to which the weighing pan is attached and the fixed column fixed to the base member of the electronic balance body, and the load of the object to be measured displaces the movable column. The Roverval mechanism is configured to bend. The lever is connected to a movable column, and the lever is displaced as the movable column is displaced.

  Heretofore, it has been known that a block-like mechanism formed by hollowing out one base material integrally forms the above-mentioned Roberval mechanism, movable column, fixed column and lever (for example, the following patent) Reference 1). Thus, the response and the temperature characteristic can be improved by adopting the integral uniform configuration.

  FIG. 6 is a schematic cross-sectional view showing a configuration example of a conventional electronic balance. This electronic balance is of an electromagnetic force balance type and includes a weighing pan 101, a block-like mechanism 102, a first frame 103, a second frame 104, a base member 105, an electromagnetic force generator 106, and the like.

  The block-like mechanism body 102 has a configuration in which the movable column 102a, the fixed column 102b, the Roberval mechanism 102c, etc. are integrally formed by hollowing out one base material. The upper end and the lower end of the movable column 102a and the fixed column 102b are connected to each other by a pair of horizontally extending Roberval mechanisms 102c. As a result, as the movable column 102a moves up and down, the pair of Roverval mechanisms 102c bend, and the displacement of the movable column 102a can be restricted in the vertical direction.

  A weighing pan 101 is attached to the upper surface of the movable column 102a. The fixed post 102b is formed with an elongated extension 102d extending along the Roberval mechanism 102c to the movable post 102a side, and one end of the first frame 103 by a plurality of bolts 107 with respect to the extension 102d. The side is fixed.

  The other end of the first frame 103 extends in the horizontal direction to the rear of the fixed post 102b (opposite to the movable post 102a), and the electromagnetic force generator 106 is attached to the other end. . Thereby, the electromagnetic force generator 106 is held by the first frame 103 together with the block-like mechanism 102 at a position adjacent to the fixed column 102b.

  The second frame 104 is fixed to the first frame 103 and supports the first frame 103 below the electromagnetic force generator 106. By supporting the second frame 104 with the base member 105, the block-like mechanism 102 can be held in a state where the movable column 102a can be displaced in the vertical direction. As described above, by mounting the relatively heavy electromagnetic force generator 106 on the base member 105 while being supported from below by the second frame 104, the electromagnetic force generator 106 and the electromagnetic force generator 106 are generated due to vibration during transportation and the like. It is possible to prevent the positional relationship with the block mechanism 102 from deviating.

Patent No. 4035724

  However, in the conventional electromagnetic force balance type electronic balance as described above, the first frame 103 may be deformed by a load on the weighing pan 101, and the deviation error characteristic may be deteriorated. In addition, when the block-like mechanism body 102 has a large own weight, the first frame 103 may be deformed before the measurement object is placed on the weighing dish 101, and the deviation error characteristic may be deteriorated.

  That is, as shown by the arrow in FIG. 6, the load on the weighing pan 101 and the weight of the block-like mechanism 102 act to push the first frame 103 downward via the respective bolts 107. Therefore, there is a problem that the first frame 4 is easily deformed with the boundary position 108 between the portion supported by the second frame 104 in the first frame 103 and the portion not supported.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide an electronic balance capable of improving the displacement error characteristic.

  The electronic balance according to the present invention comprises a weighing pan, a block-like mechanism, a first frame, a second frame, an electromagnetic force generator, and a base member. An object to be measured is placed on the weighing pan. The block-shaped mechanism is formed by hollowing out one base material, and the weighing pan is attached thereto. The first frame is fixed to the block mechanism by a plurality of fixing tools. The second frame is fixed to the first frame. The electromagnetic force generator is attached to the first frame or the second frame. The base member supports the second frame near the lower side of the electromagnetic force generator.

  The block-like mechanism body is integrally formed with a movable column, a fixed column, and a Roberval mechanism. The weighing pan is attached to the movable column. The first frame is fixed to the fixed column. The Roverval mechanism connects the movable column and the fixed column to regulate the displacement of the weighing pan in the vertical direction. The fixed post is formed with an elongated portion extending along the Roberbar mechanism to the movable post side, and at least an end of the extended portion on the movable post side is fixed by the fixture. It is fixed to one frame. The electromagnetic force generator is disposed adjacent to the fixed column. The second frame supports the first frame from the lower side, from the lower vicinity of the electromagnetic force generator to the lower vicinity of the fixing tool fixed to the end of the extending portion on the movable column side.

  According to such a configuration, the first frame is supported from below by the second frame over a wide range from the lower vicinity of the electromagnetic force generating device to the lower vicinity of the fixing tool fixed to the end of the extension section on the movable column side. can do. Thereby, even when the load on the weighing pan and the weight of the block-like mechanism act in a direction to push the first frame downward via the fixture, from the first frame near the lower side of the fixture A load can be transmitted to the second frame, and the load can be transmitted to the base member in the vicinity of the lower part of the electromagnetic force generator via the second frame. Therefore, it is possible to prevent the first frame from being deformed and to improve the offset error characteristic.

  The first frame includes a pair of separation frames which are held by the block-like mechanism in a width direction orthogonal to the longitudinal direction of the extension, and fixed to the extension by the fixing tool. May be In this case, the pair of separated frames may be fixed to the second frame.

  According to such a configuration, the first frame is separated into a pair of separation frames, and the block-like mechanism is held by the pair of separation frames, so that the first frame is deformed by internal stress. It can be prevented. However, in this case, by separating the first frame into a pair of separation frames, each separation frame may be easily deformed due to the load on the weighing pan and the weight of the block-like mechanism. . In the present invention, each separation frame of the first frame is supported from below by the second frame over a wide range from the lower vicinity of the electromagnetic force generating device to the lower vicinity of the fixture fixed to the end of the extension section on the movable column side. Therefore, it is possible to prevent the first frame from being deformed and to improve the offset error characteristic.

  The electromagnetic force generator is preferably attached to the second frame.

  According to such a configuration, the load of the electromagnetic force generator can be directly received by the second frame. Thus, the load acting on the first frame can be reduced, so that deformation of the first frame can be effectively prevented, and the offset error characteristic can be further improved.

  According to the present invention, the first frame is supported from below by the second frame over a wide range from the lower vicinity of the electromagnetic force generating device to the lower vicinity of the fixing tool fixed to the end of the extension portion on the movable column side. Therefore, it is possible to prevent the first frame from being deformed and to improve the offset error characteristic.

FIG. 1 is a perspective view showing an exemplary configuration of an electronic balance according to an embodiment of the present invention. It is a top view of the electronic balance of FIG. It is a side view of the electronic balance of FIG. It is a front view of the electronic balance of FIG. It is AA sectional drawing of the electronic balance in FIG. It is the schematic sectional drawing which showed the structural example of the conventional electronic balance.

  FIG. 1 is a perspective view showing a configuration example of an electronic balance according to an embodiment of the present invention. FIG. 2 is a plan view of the electronic balance of FIG. FIG. 3 is a side view of the electronic balance of FIG. FIG. 4 is a front view of the electronic balance of FIG. 5 is a cross-sectional view taken along the line AA of the electronic balance in FIG.

  In this electronic balance, each member is provided on the base member 1, and the measurement object can be placed on the weighing pan 2 to perform measurement. 1 and 2, the base member 1 and the weighing pan 2 of the electronic balance are omitted. Moreover, in FIGS. 3-5, a part of base member 1 is abbreviate | omitted and shown. In the electronic balance according to the present embodiment, in addition to the base member 1 and the weighing pan 2, the block-like mechanism 3, the first frame 4, the second frame 5, the electromagnetic force generator 6, the lever extension member 7, the detector 8 and a shutter 9 are provided.

  The weighing pan 2 is attached to the block-like mechanism 3. The block-like mechanism body 3 is formed by, for example, hollowing out one base material in the form of a square pole made of aluminum alloy, whereby the movable post 31, the fixed post 32, the robberval mechanism 33, the lever 34, the connecting portion 35, etc. The structure is formed integrally. However, the block-shaped mechanism 3 is not limited to a quadrangular prism-shaped member made of an aluminum alloy, and may be formed of other materials or shapes.

  The movable column 31 is, for example, a rectangular column-shaped portion extending in the vertical direction, and the weighing pan 2 is attached to the upper surface thereof. The movable column 31 constitutes one end of the block-like mechanism 3 in the horizontal direction. On the other hand, the fixed column 32 constitutes the other end portion in the horizontal direction of the block-like mechanism 3, and the fixed column 32 is fixed to the first frame 4. The mechanism 3 is supported.

  The Roberval mechanism 33 extends from one end to the other end of the block-like mechanism 3 along the horizontal direction, and connects the movable post 31 and the fixed post 32. In the present embodiment, the upper end and the lower end of the movable column 31 and the fixed column 32 are connected to each other by a pair of Roberval mechanisms 33. Thus, a pair of Roberval mechanisms 33 constitute the upper and lower surfaces of the block-like mechanism 3.

  Each Roberval mechanism 33 has a flat beam 331 extending in the horizontal direction, and a flexible portion 332 connecting both ends of the beam 331 to the movable column 31 and the fixed column 32, respectively. The flexible portion 332 has a shape that is easily elastically deformed by being formed with a thickness smaller than that of the beam 331. When the load of the measurement object is applied to the weighing pan 2, the flexible portion 332 of each Roverval mechanism 33 bends and the movable column 31 is displaced vertically downward. At this time, the displacement of the weighing pan 2 can be restricted in the vertical direction by the action of each of the rovalval mechanisms 33.

  In the fixed column 32 in the present embodiment, an elongated extension 321 is formed that extends to the movable column 31 side in the horizontal direction along the Roverval mechanism 33. The extension portion 321 is disposed between the pair of robberval mechanisms 33, and when the respective robberval mechanisms 33 bend, the extension portions 321 come into contact with each other by forming a predetermined distance from the respective robberval mechanisms 33. Can be prevented.

  The lever 34 is connected to the movable column 31 via the connecting portion 35. As shown in FIG. 5, the connecting portion 35 extends in the vertical direction between the extension portion 321 of the fixed column 32 and the movable column 31, and the lower end portion thereof is connected to the movable column 31 via a force point spring 351. In addition, the upper end portion is connected to one end portion of the lever 34 via a force point spring 352. The force point spring 352 is a very thin plate spring having a thickness of, for example, 0.1 mm or less, and moves up and down together with the connecting portion 35 in accordance with the displacement of the movable column 31.

  The lever 34 extends in the horizontal direction along the Roverval mechanism 33, and the central part thereof is connected to the extension part 321 of the fixed column 32 via a fulcrum spring 353. The fulcrum spring 353 is made of a very thin leaf spring having a thickness of 0.1 mm or less, for example, like the force spring 352. Thus, when the connecting portion 35 moves up and down with the displacement of the movable column 31, a force in the vertical direction is applied to one end of the lever 34 via the force point spring 352, and the lever 34 is centered on the fulcrum spring 353. It is supposed to swing.

  At the other end of the lever 34, that is, on the opposite side of the fulcrum spring 353 from the force point spring 352 side, the lever extension member 7 is attached by a fixing tool 341 consisting of, for example, a bolt and a nut. In this example, the block-like mechanism 3 is arranged in the width direction D2 (horizontal direction perpendicular to the longitudinal direction D1) so that the pair of lever extension members 7 extend along the longitudinal direction D1 of the block-like mechanism 3 respectively. It is provided on both sides. Each lever extension member 7 is fixed to the lever 34 at one end in the longitudinal direction D1.

  The first frame 4 is composed of a pair of separation frames 41 provided on both sides of the block-like mechanism 3 in the width direction D2. Each separation frame 41 is a member having an elongated shape along a longitudinal direction D1 formed of, for example, aluminum, and a cross section perpendicular to the longitudinal direction D1 is formed in an L shape.

  Each separation frame 41 is fixed to the block-shaped mechanism 3 by a plurality of fixtures 42 made of, for example, bolts and nuts. More specifically, as shown in FIG. 5, each fixing tool 42 is fixed so as to penetrate the extension portion 321 of the block-like mechanism 3 in the width direction D2. At least one fixing tool 42 among the plurality of fixing tools 42 is fixed to each separation frame 41 at an end of the extension section 321 on the movable column 31 side.

  The second frame 5 is made of, for example, aluminum, and a bottom plate 51 for supporting the first frame 4 from below, a side plate 52 extending upward from both ends in the width direction D2 of the bottom plate 51, and a bottom plate A back plate 53 extending upward from one end portion of the longitudinal direction D1 in 51 is integrally formed. Each separation frame 41 constituting the first frame 4 is fixed to the bottom plate 51 of the second frame 5 by a plurality of fixtures 43 made of bolts and nuts, for example.

  As shown in FIGS. 4 and 5, the bottom plate 51 of the second frame 5 is formed with a notch 511 at a position corresponding to the lower side of the block-like mechanism 3. As a result, the block-like mechanism 3 is disposed so as not to contact the bottom plate 51, and the block-like mechanism is produced even when each robber mechanism 33 of the block-like mechanism 3 is bent by the load on the weighing pan 2. 3 does not contact the bottom plate 51.

  The block-like mechanism 3 is attached in a state where the fixed column 32 is spaced from the back plate 53 of the second frame 5. Thereby, a space is formed between the fixed column 32 and the back plate 53 of the block-like mechanism 3, and the electromagnetic force generator 6 is arranged in the space. The electromagnetic force generator 6 is disposed on the bottom plate 51 of the second frame 5 in a state of being disposed adjacent to the rear side (the side opposite to the movable column 31 side) with respect to the fixed column 32 of the block-like mechanism 3. It is attached.

  As shown in FIG. 5, the electromagnetic force generator 6 includes a movable coil 61 and a magnetic circuit 62. The magnetic circuit 62 includes a permanent magnet and a yoke, and can form a static magnetic field therein. The movable coil 61 is disposed in the static magnetic field formed by the magnetic circuit 62, and is held displaceably along the vertical direction which is the axial direction.

  One end of each lever extension member 7 in the longitudinal direction D1 is fixed to the lever 34 of the block-like mechanism 3 as described above, while the other end is fixed to the movable coil 61 of the electromagnetic force generator 6 . Therefore, when the movable column 31 is displaced in the vertical direction by the load on the weighing pan 2 and the lever 34 swings about the fulcrum spring 353, the movable member 31 is fixed to the lever 34 via the lever extension members 7. The coil 61 is displaced in the vertical direction.

  The detector 8 is for detecting the displacement of the lever 34 and includes, for example, a light emitting element and a light receiving element mounted on the circuit board 81. In the present embodiment, the shutter 9 is connected to the lever extension member 7 attached to the lever 34, and the shutter 9 can block part of light incident on the light receiving element from the light emitting element . Accordingly, the amount of light blocked by the shutter 9 changes with the displacement of the lever 34, and the change of the amount of light is detected by the light receiving element, whereby the displacement of the lever 34 can be detected.

  When measuring the mass of the object to be measured, the displacement of the lever 34 is detected by the detector 8, and the current supplied to the movable coil 61 is feedback-controlled so that the lever 34 is not displaced. In this case, the larger the mass of the measurement object, the greater the value of the current flowing through the movable coil 61. Therefore, the mass of the measurement object can be measured based on the current value flowing through the movable coil 61.

  In the present embodiment, the second frame 5 is supported by the base member 1 in the vicinity below the electromagnetic force generator 6. In addition, the second frame 5 extends from the lower vicinity of the electromagnetic force generator 6 to the lower vicinity of the fixture 42 fixed to the end of the extension portion 321 of the block-like mechanism 3 on the movable column 31 side. 4 (each separation frame 41) is supported from below.

  That is, the bottom plate 51 of the second frame 5 of the fixtures 42 for fixing the first frame 4 to the extension part 321 of the block-like mechanism 3 is the lowermost part of the fixtures 42 fixed to the movable column 31 side. And side plates 52 extend. The bottom plate 51 and the side plate 52 are movable columns from the end of the block-like mechanism 3 on the fixed column 32 side over two thirds of the length along the longitudinal direction D1 of the block-like mechanism 3. It is preferable to extend toward the 31 side.

  As a result, the load on the weighing pan 2 and the weight of the block-like mechanism 3 act in a direction to push the first frame 4 downward via the fixture 42 as shown by the arrows in FIG. Also, the load is transmitted from the first frame 4 to the second frame 5 in the vicinity of the lower part of the fixing tool 42, and the load is transmitted to the base member 1 in the vicinity of the lower part of the electromagnetic force generator 6 via the second frame 5. can do. Thereby, it is possible to prevent the first frame 4 from being deformed and to improve the offset error characteristic.

  Further, in the present embodiment, since the first frame 4 is separated into a pair of separation frames 41 and the block-like mechanism 3 is held by the pair of separation frames 41, the first frame 4 is subjected to internal stress. It is possible to prevent deformation. However, in this case, by separating the first frame 4 into a pair of separation frames 41, each separation frame 41 is easily deformed due to the load on the weighing pan 2 and the weight of the block-like mechanism 3 Could be In the present embodiment, the separation frames 41 of the first frame 4 extend over a wide range from the lower vicinity of the electromagnetic force generator 6 to the lower vicinity of the fixing tool 42 fixed to the end of the extension portion 321 on the movable column 31 side. Since it is supported from below by the second frame 5, it is possible to prevent the first frame 4 from being deformed and to improve the deviation error characteristic.

  Furthermore, in the present embodiment, since the electromagnetic force generator 6 is attached to the second frame 5, the load of the electromagnetic force generator 6 can be directly received by the second frame 5. Thereby, since the load which acts on the 1st flame | frame 4 can be reduced, it can prevent effectively that the 1st flame | frame 4 deform | transforms and can further improve a deviation error characteristic.

  In the lower vicinity of the electromagnetic force generator 6, other than the direct direction of the electromagnetic force generator 6, for example, a range adjacent to the longitudinal direction D1 within 1 cm or within several cm from the direct direction is also included. Similarly, in the vicinity of the lower portion of the fixing device 42, in addition to the portion immediately below the fixing device 42, for example, a range adjacent to the longitudinal direction D <b> 1 within 1 cm or several centimeters from directly below.

  In the above embodiment, the configuration in which the first frame 4 is separated into the pair of separation frames 41 has been described. However, the present invention can also be applied to a configuration in which the first frame 4 is not separated into the separation frame 41. The electromagnetic force generator 6 is not limited to the configuration attached to the second frame 5, and may be attached to the first frame 4.

  The first frame 4 and the second frame 5 may be made of other materials without being limited to aluminum, but in order to suppress the influence of thermal expansion and thermal contraction on the displacement error characteristic, the block shape is used. It is preferable to be formed of the same or the same kind of material as the mechanism body 3.

DESCRIPTION OF SYMBOLS 1 Base member 2 Weighing pan 3 Block-shaped mechanism 4 1st frame 5 2nd frame 6 Electromagnetic force generator 7 Lever extension member 8 Detector 9 Shutter 31 Movable column 32 Fixed column 33 Robert valve mechanism 34 Lever 35 Connecting part 41 Separation frame 42 Fixing tool 43 Fixing tool 51 Bottom plate 52 Side plate 53 Back plate 61 Moving coil 62 Magnetic circuit 81 Circuit board 321 Extension part 331 Beam 332 Flexible part 341 Fixing tool

Claims (3)

A weighing pan on which a measurement object is placed;
A block-like mechanism formed by hollowing out one base material and having the weighing pan attached thereto;
A first frame fixed to the block-like mechanism by a plurality of fixtures;
A second frame fixed to the first frame;
And an electromagnetic force generator attached to the first frame or the second frame, and a base member supporting the second frame in the vicinity near the lower side of the electromagnetic force generator.
In the block-like mechanism, a movable column to which the weighing plate is attached, a fixed column to which the first frame is fixed, and a connection between the movable column and the fixed column to vertically displace the weighing plate Is integrally formed with the Roberval mechanism that regulates
The fixed post is formed with an elongated portion extending along the Roberbar mechanism to the movable post side, and at least an end of the extended portion on the movable post side is fixed by the fixture. Fixed to one frame,
The electromagnetic force generator is disposed adjacent to the fixed column;
The second frame supports the first frame from below from the lower vicinity of the electromagnetic force generation device to the lower vicinity of the fixing tool fixed to the end of the extending portion on the movable column side. A characteristic electronic balance. The first frame includes a pair of separation frames that sandwich the block-like mechanism in a width direction orthogonal to the longitudinal direction of the extension, and are fixed to the extension by the fixture. Yes,
The electronic balance according to claim 1, wherein the pair of separation frames are fixed to the second frame, respectively.   The electronic balance according to claim 2, wherein the electromagnetic force generator is attached to the second frame.

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