JP6794047B2 - Electromagnetic balanced weight sensor - Google Patents

Description

The present invention relates to an electromagnetically balanced weight sensor.

Conventionally, there is a weighing device such as an electronic balance that uses an electromagnetic equilibrium type weight sensor (see, for example, Patent Document 1).

In this electromagnetic equilibrium type weight sensor, a reverbal mechanism composed of an elastic body, a lever that displaces in conjunction with the displacement of a movable part of the reverbal mechanism, a means for detecting the displacement of the lever, and a lever in an equilibrium state (displacement). Some have an electromagnetic force generator (coil, magnet, etc.) that returns to 0). The reverbal mechanism is composed of a fixed portion that is statically fixed, a movable portion to which a load is applied, and a pair of upper and lower beam portions that connect the fixed portion and the upper portions and lower portions of the movable portions, respectively.

Japanese Unexamined Patent Publication No. 2002-296101

In the electromagnetic balance type weight sensor as described above, the lever is configured to have a lever mechanism having a constricted portion serving as a fulcrum for amplifying the displacement of the movable portion, but an excessive load is applied to the movable portion. An overload protection mechanism is provided in order to prevent damage such as deformation of the portion serving as a fulcrum of the lever mechanism due to such things (overload).

As such an overload protection mechanism, for example, as in Patent Document 1, a beam-shaped portion connecting a fixed portion and a movable portion is formed between a pair of upper and lower beam portions, and the beam-shaped portion is cut and fixed. It is separated into a portion side portion and a movable portion side portion, and in the separated portion, a convex portion is formed on the fixed portion side portion, and a concave portion into which the convex portion is inserted is formed on the movable portion side portion. In some cases, the convex portion and the concave portion are configured to have a minute gap. When an excessive load exceeding the permissible value is applied to the movable portion of the reverbal mechanism, the convex portion and the concave portion come into contact with each other, and the displacement of the movable portion beyond that can be regulated.

However, in this overload protection mechanism, the displacement of the movable portion is directly reflected in the positional relationship between the convex portion and the concave portion, and since the displacement of the movable portion is minute, the displacement between the convex portion and the concave portion is small. Difficult to process gaps. That is, there is a problem that it is difficult to manufacture an overload protection mechanism.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an electromagnetically balanced weight sensor from which an overload protection mechanism can be easily manufactured.

In order to achieve the above object, the electromagnetic balance type weight sensor according to an embodiment of the present invention has a displacement member in which the displacement of the reverbal mechanism appears at the tip portion and a displacement detection unit that detects the displacement of the tip portion of the displacement member. Then, a coil that is displaced in conjunction with the displacement of the reverbal mechanism is provided in the magnetic circuit that generates a static magnetic field, and a current is passed through the coil so that the displacement detected by the displacement detection unit approaches zero. There is a gap between the electromagnetic force generator, a through hole provided in the tip portion of the displacement member in a direction intersecting the direction in which the tip portion is displaced, and the inner surface of the through hole. It is provided with an overload protection mechanism composed of a rod-shaped stopper member that is inserted through a through hole and statically fixed.

According to this configuration, by providing the overload protection mechanism at the tip of the displacement member, the distance between the inner surface of the through hole constituting the overload protection mechanism and the stopper member can be increased, and the overload protection mechanism can be provided. Easy to manufacture.

A lever mechanism that amplifies the vertical displacement of the reverbal mechanism is further provided, the displacement member is connected to the lever mechanism and is provided so as to extend in the vertical direction, and the coil of the electromagnetic force generator is the coil. It may be configured to be displaced in conjunction with the displacement member.

According to this configuration, the overload protection mechanism regulates the displacement amount of the tip portion of the displacement member to be less than or equal to the gap between the inner surface of the through hole and the stopper member, so that an excessive load is applied to the movable portion. It is possible to prevent damage such as deformation of the narrowed portion that serves as a fulcrum of the lever mechanism due to such things (overload). Further, since the displacement member is connected to the lever mechanism and is provided so as to extend in the vertical direction, and the coil of the electromagnetic force generator is configured to be displaced in conjunction with the displacement member, the displacement member is displaced downward or upward of the lever mechanism. It can be configured to be long in the vertical direction in which the members and the electromagnetic force generator are arranged, the occupied area (installation area) can be reduced, and it can also be used for a weighing device having a small installation space.

The reverbal mechanism includes a fixed portion that is statically fixed, a movable portion that is arranged apart from the fixed portion and is loaded with a load, and a pair of upper and lower parts that connect the fixed portion and the upper and lower portions of the movable portion, respectively. It has a beam portion, and the lever mechanism is swingably connected to the fixed portion, one end is connected to the movable portion via a first connecting portion, and the other end is movable. The first lever portion, which appears when the displacement of the portion in the vertical direction is amplified, and the first lever portion, which is arranged below the first lever portion and is swingably connected to the fixed portion, and one end of the second connecting portion. The second lever is connected to the other end of the first lever via a second lever, and has a second lever that appears at the other end by amplifying the displacement of the other end of the first lever in the vertical direction. The displacement member extending downward may be connected to the portion.

According to this configuration, since the lever mechanism has a configuration having two lever portions, a first and a second lever portion, the displacement detection accuracy by the displacement detection unit is higher than that in the case where the lever mechanism has only one lever portion. And the current flowing through the coil to bring the displacement close to 0 can be reduced.

The present invention has an effect that it is possible to provide an electromagnetically balanced weight sensor having the configuration described above and capable of easily manufacturing an overload protection mechanism.

FIG. 1 is a front view of an electromagnetically balanced weight sensor according to an embodiment of the present invention. FIG. 2A is a perspective view of the electromagnetically balanced weight sensor of FIG. 1, and FIG. 2B is an enlarged perspective view of a displacement detection portion of the electromagnetically balanced weight sensor and a portion in the vicinity thereof. 2 (C) is a schematic plan view of the displacement detection unit of the electromagnetic equilibrium type weight sensor and its vicinity as viewed from above. FIG. 3A is a schematic cross-sectional view of the electromagnetic force generator, FIG. 3B is an external perspective view of the electromagnetic force generator, and FIG. 3C is a yoke of the electromagnetic force generator. It is a figure which shows the state which the lid is removed. FIG. 4A is a perspective view of the electromagnetic force generator of another example, and FIG. 4B is a side view of the electromagnetic force generator of another example.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the following, the same or corresponding elements will be designated by the same reference numerals throughout the drawings, and duplicate description thereof will be omitted. Moreover, the present invention is not limited to the following embodiments.

(Embodiment)
FIG. 1 is a front view of an electromagnetically balanced weight sensor according to an embodiment of the present invention. FIG. 2A is a perspective view of the electromagnetically balanced weight sensor of FIG. 1, and FIG. 2B is an enlarged perspective view of a displacement detection portion of the electromagnetically balanced weight sensor and a portion in the vicinity thereof. 2 (C) is a schematic plan view of the displacement detection unit of the electromagnetic equilibrium type weight sensor and its vicinity as viewed from above.

This electromagnetic equilibrium type weight sensor A is used in a weighing device B such as an electronic balance, and a fixing portion 11 constituting a reverbal mechanism described later is fixed to a stationary member (for example, a base portion B1 of the weighing device B). ) Is fixed by a bolt or the like, and the movable portion 12 is fixed to the mounting portion B3 that supports the object to be placed portion B4 such as a plate by the bolt or the like. For example, when the object to be measured is placed on the object to be placed B4, a load is applied to the movable portion 12.

The electromagnetic balance type weight sensor A includes a mechanism body 1, a displacement detection unit 2, an electromagnetic force generator 3, a stopper mechanism 4 which is an overload protection mechanism, and a controller 5.

The controller 5 is installed inside the weighing device B (for example, the base portion B1) away from the mechanism 1, and is configured to include, for example, a microcontroller or the like, and controls the entire weighing device B. The controller 5 is connected to the light emitting element 21a and the light receiving elements 22a and 22b of the displacement detection unit 2, and controls the driving (light emission) of the light emitting element 21a and corresponds to the amount of light received from each of the light receiving elements 22a and 22b. Enter the current to be Further, the controller 5 is connected to the coil 37 of the electromagnetic force generator 3, and a current is passed through the coil 37. Further, the controller 5 is connected to a display unit (not shown) of the weighing device B that displays the mass value of the weighted object mounted on the weighted object mounting unit B4, and the display unit is connected to the display unit (not shown). Control.

The mechanism body 1 includes a reverbal mechanism 1R and a displacement amplification mechanism 1A (lever mechanism 1L and arm portion 1B).

The reverbal mechanism 1R connects the fixed portion 11 that is statically fixed, the movable portion 12 that is horizontally separated from the fixed portion 11 and is arranged in parallel and is loaded with a load, and the fixed portion 11 and the movable portion 12, and connects each other. It includes upper and lower beam portions 13 and 14 arranged in parallel. The upper portions of the fixed portion 11 and the movable portion 12 are connected to each other by the upper beam portion 13 via the thin-walled portions 13a and 13b, and the lower portions thereof are connected to each other by the lower beam portion 14 via the thin-walled portions 14a and 14b. ing. In such a reverbal mechanism 1R, as is well known, when a load is applied to the movable portion 12, the movable portion 12 is lowered with respect to the fixed portion 11 while maintaining its posture (a state parallel to the fixed portion 11). It is designed to be displaced (vertically). The vertical length of the reverbal mechanism 1R is longer than the length in the direction in which the fixed portion 11 and the movable portion 12 are separated (longitudinal direction of the beam portions 13 and 14), and as shown in FIG. It has a vertically long shape that is approximately rectangular and long in the vertical direction.

The mechanism body 1 is provided with a displacement amplification mechanism 1A having a lever mechanism 1L and an arm portion (displacement member) 1B inside the reverbal mechanism 1R in order to amplify the vertical displacement of the movable portion 12. ..

In order to form the displacement amplification mechanism 1A, particularly the lever mechanism 1L, the mechanism body 1 has protrusions 11a and 11b protruding inward from the fixed portion 11 and protrusions 12a protruding inward from the movable portion 12. It is provided. Then, in order to form the lever mechanism 1L, first and second lever portions 16 and 18 extending in the horizontal direction and connecting portions 15 and 17 extending in the vertical direction are provided to form the arm portion 1B. The arm portion constituent member 19 of the above is provided.

The lever mechanism 1L has a first lever portion 16 and a second lever portion 18. One end of the first lever portion 16 is connected to the protruding portion 12a on the movable portion 12 side by a connecting portion 15 having narrowed portions 15a and 15b formed at both ends, and a portion slightly closer to the fixed portion 11 side than the one end is formed. It is connected to the protruding portion 11a on the fixing portion 11 side via the narrowed portion f1 that serves as the fulcrum. As a result, the first lever portion 16 is swingably connected to the fixed portion 11 via the narrowed portion f1, one end is connected to the movable portion 12 via the connecting portion 15, and the other end is movable. The vertical displacement of the portion 12 is amplified and appears.

The second lever portion 18 is arranged below the first lever portion 16. The portion of the second lever 18 near the fixing portion 11 is connected to the lower portion of the other end of the first lever 16 by a connecting portion 17 having narrowed portions 17a and 17b formed at both ends, and further near the fixing portion 11. Is connected to the protruding portion 11b on the fixed portion 11 side via the narrowed portion f2 that serves as the fulcrum of the lever. As a result, the second lever portion 18 is swingably connected to the fixed portion 11 via the narrowed portion f2, and one end is connected to the other end of the first lever portion 16 via the connecting portion 17. , The vertical displacement of the other end of the first lever 16 is amplified and appears at the other end.

An arm portion component 19 extending downward is connected to a portion of the second lever portion 18 near the movable portion 12 with a bolt. The arm portion component 19 is attached to the second lever portion 18 and extends parallel to the second lever portion 18 toward the movable portion 12 side, and the lever attachment portion 19x is below the end portion of the lever attachment portion 19x on the movable portion 12 side. It has an arm body portion 19v extending in the direction and an arm tip portion 19h extending in the horizontal direction from the lower end portion of the arm body portion 19v toward the fixing portion 11.

The arm portion component 19 constitutes an arm portion 1B that converts the vertical displacement of the movable portion 12 amplified by the lever mechanism 1L into a substantially horizontal displacement and amplifies it. The portion of the mechanism 1 other than the arm component 19 is composed of a single component, and the width (thickness) in the direction of arrow e in FIG. 2A is the same.

It may be considered that the lever mounting portion 19x of the arm portion constituent member 19 is included in the second lever portion 18, and the arm portion 1B is formed by the arm main body portion 19v and the arm tip portion 19h. Therefore, the base end portion of the arm portion 1B is connected to the lever mechanism 1L, and the tip portion (arm tip portion 19h) is provided with a light passing hole 19a and a through hole 19b described later.

Further, in this example, only the arm portion constituent member 19 is configured as a separate component in the mechanism body 1, but the entire mechanism body 1 including the arm portion constituent member 19 may be configured as a single component. Good. The mechanism 1 is made of, for example, an aluminum alloy.

As described above, when a load is applied to the movable portion 12, the movable portion 12 is displaced downward. As a result, one end of the connecting portion 15 and the first lever portion 16 is displaced downward (strictly speaking, displaced in an arc shape) as shown by the arrow a, and the other end of the first lever portion 16 and the connecting portion 17 are displaced. However, as shown by the arrow b, it is largely displaced upward (strictly speaking, it is displaced in an arc shape). Then, the portion of the second lever 18 near the movable portion 12 is displaced more upward (strictly speaking, it is displaced in an arc shape) as shown by the arrow c, and the arm portion component 19 is indicated by the arrow d. As shown, it rotates around the narrowed portion f2, which is the fulcrum of the second lever portion 18, and swings toward the movable portion 12. At this time, the displacement that appears in the portion of the second lever 18 near the movable portion 12 by the arm portion 1B is changed by 90 degrees in the displacement direction and is amplified and appears in the arm tip portion 19h, and the arm tip portion 19h is substantially abbreviated. Displace in the horizontal direction. Although the arrows a to d indicating the displacement directions are shown in large size, the actual displacement is very small.

Then, when the displacement of the arm tip portion 19h is detected by the displacement detecting unit 2, a current flows through the coil 37 of the electromagnetic force generator 3 so that the displacement approaches zero.

As shown in FIGS. 2B and 2C, the displacement detection unit 2 includes a light emitting unit 21 serving as a light emitting unit, a light receiving unit 22 serving as a light incident portion, and a light passing portion 19h provided at the arm tip portion 19h. It has a hole 19a and a displacement calculation unit (function of the controller 5). The light emitting unit 21 and the light receiving unit 22 are attached and fixed at appropriate positions on the attachment member 6. Further, the mounting member 6 is fixed to the fixing portion 11 with bolts. The light emitting unit 21 is configured to include, for example, one light emitting element 21a made of an LED or the like, and the light receiving unit 22 is configured to have, for example, two light receiving elements 22a, 22b made of a photodiode or the like. ..

The light passing hole 19a of the arm tip 19h is a small through hole provided so as to penetrate in a direction intersecting (for example, orthogonal to) the direction in which the arm tip 19h is displaced. The light emitting unit 21 and the light receiving unit 22 are arranged so as to face each other with the light passing hole 19a of the arm tip portion 19h interposed therebetween. Further, the two light receiving elements 22a and 22b of the light receiving unit 22 are arranged side by side in the direction in which the arm tip portion 19h is displaced and adjacent to each other.

The light emitted from the light emitting element 21a of the light emitting unit 21 passes through the light passing hole 19a, and the passed light is received by the two light receiving elements 22a and 22b of the light receiving unit 22, and the amount of light received by the light receiving elements 22a and 22b. A signal corresponding to (hereinafter, referred to as “light receiving signal”) is input to the controller 5.

Further, a rod-shaped (cylindrical) stopper member 4a for forming the stopper mechanism 4 is fixed to the mounting member 6. The arm tip 19h is provided with a through hole 19b having a diameter slightly larger than the diameter of the stopper member 4a, which penetrates in a direction intersecting (for example, orthogonal to) the direction in which the arm tip 19h is displaced. The stopper member 4a is inserted into the through hole 19b with a gap from the inner surface (wall surface) of the through hole 19b. The stopper mechanism 4 is composed of the through hole 19b of the arm tip 19h and the stopper member 4a. By this stopper mechanism 4, the displacement amount of the arm tip portion 19h is restricted to be equal to or less than the gap between the inner surface of the through hole 19b and the stopper member 4a, so that an excessive load is applied to the movable portion 12 (excessive load). It is possible to prevent damage such as deformation of the mechanism 1 caused by load) or the like. In particular, it is possible to prevent damage such as deformation due to overloading of a portion where a large force is applied, such as a narrow portion f1 and f2 which is a fulcrum of the lever mechanism 1L. The distance (the size of the gap) between the inner surface of the through hole 19b and the stopper member 4a can appropriately suppress the force applied to the narrowed portions f1, f2, etc., which are the fulcrums of the lever mechanism 1L, by using CAE or the like. It can be set to be an interval.

Next, the electromagnetic force generator 3 will be described with reference to FIG. 3 (A) is a schematic cross-sectional view of the electromagnetic force generator 3, FIG. 3 (B) is an external perspective view of the electromagnetic force generator 3, and FIG. 3 (C) is an electromagnetic force generator 3. It is a figure which shows the state which removed the lid 36 of the yoke of.

The electromagnetic force generator 3 includes a magnetic circuit 31 that forms a static magnetic field, and a coil (force coil) 37 that is arranged in the magnetic circuit 31.

The coil 37 is attached to a predetermined position of a portion closer to the tip (lower end) from the central portion of the arm main body portion 19v via a coil mounting bracket 38. The coil mounting bracket 38 is fixed to the arm body 19v with screws 39.

The magnetic circuit 31 is composed of, for example, two magnets (permanent magnets) 32 and 33, a pole piece 34, a yoke 35, and a yoke lid 36. The yoke 35 has a bottom portion having a bottomed cylindrical shape having an open end fixed to the fixing portion 11. The lid 36 of the yoke is made of the same metal as the yoke 35, such as iron, and is fixed to the opening side of the yoke 35.

A magnet 32, a pole piece 34, and a magnet 33 are stacked and fixed to the inner bottom of the yoke 35 in this order. The lid 36 of the yoke is each provided with two through holes 36h for inserting the coil mounting bracket 38. Further, the lid 36 of the yoke is divided into two semi-disc portions 36a and 36b, and the lid 36 (36a, 36b) can be closed after the coil 37 is arranged inside the yoke 35. ..

In this measuring device B, when a load is applied to the movable portion 12 by placing the object to be measured on the object placing portion B4, the movable portion 12 is displaced downward, and the arm tip portion 19h at this time. The displacement of is detected by the displacement detection unit 2. At this time, the controller 5 drives the light emitting element 21a in advance, and always displaces the arm tip 19h based on the difference in the amount of light received by the two light receiving elements 22a and 22b (difference in the light receiving signal). Displacement direction and displacement amount) are obtained (function as a displacement calculation unit of the controller 5).

Then, in order to generate an electromagnetic force that is balanced with the load of the movable portion 12 by the movement of the coil 37 in the opposite direction, the amount of light received by the two light receiving elements 22a and 22b is made equal (of the arm tip portion 19h). A current is passed through the coil 37 by feedback control (PID control) so that the displacement approaches 0). Then, the controller 5 uses a current mass conversion formula to determine the current value flowing through the coil 37 when the amount of light becomes substantially equal (when the displacement approaches 0 or becomes 0), and the object to be measured. Converted to the mass value (magnitude of load) of (function as load calculation unit of controller 5). Then, the mass value is output to a display unit (not shown) of the measuring device B and displayed. The controller 5 stores in advance the above-mentioned current-mass conversion formula, which is a conversion formula for converting the current value flowing through the coil 37 into a mass value, but the current flowing through the coil 37 is converted by a resistor. It may be taken out in the form of a voltage and the taken out voltage may be converted into a mass.

In the electromagnetic balance type weight sensor A of the present embodiment, the stopper mechanism 4 which is an overload protection mechanism is displaced more than the displacement of the movable portion 12 of the reverbal mechanism 1R, and the arm tip of the tip portion of the displacement amplification mechanism 1A. By providing the portion 19h, the distance between the inner surface of the through hole 19b constituting the stopper mechanism 4 and the stopper member 4a can be increased, and the stopper mechanism 4 can be easily manufactured. Further, in the stopper mechanism 4, since the stopper member 4a is inserted into the through hole 19b, the stopper function works with respect to the displacement in the forward and reverse directions.

Further, in the present embodiment, the displacement amplification mechanism 1A is composed of a lever mechanism 1L and an arm portion 1B, the arm portion 1B is provided so as to extend downward from the lever mechanism 1L, and the coil 37 of the electromagnetic force generator 3 is an arm. Since it is configured to be displaced in conjunction with the portion 1B, the arm portion 1B and the electromagnetic force generator 3 are arranged below the lever mechanism 1L to form a long structure in the vertical direction, and the occupied area (installation area) can be reduced. It can also be used for weighing devices with a small installation space.

Further, in the present embodiment, the lever mechanism 1L is configured to have two lever portions 16 and 18, but it may have one or more lever portions. For example, the lever mechanism 1L may have only one lever portion 16 and the arm portion 1B may be connected to the lever portion 16. When the lever mechanism 1L has two lever portions 16 and 18, the displacement detection accuracy can be improved and the displacement can be brought closer to 0 as compared with the case where only one lever portion 16 is provided. The current flowing through the coil 37 can be reduced.

Further, since the reverbal mechanism 1R has a vertically long shape that is long in the vertical direction, an eccentric load is applied to the movable portion 12, for example, because the object to be measured is unevenly placed on one end of the object to be placed B4. It is possible to improve the twist resistance at the time.

Further, the electromagnetically balanced weight sensor A may be configured upside down. In this case, for example, as can be seen by turning FIG. 1 upside down, the lever mechanism 1L is provided in the lower region inside the reverbal mechanism 1R, and the arm portion 1B whose base end portion is connected to the lever mechanism 1L is formed. It is provided so as to extend upward from the lever mechanism 1L, the electromagnetic force generator 3 is arranged above the lever mechanism 1L, and the stopper mechanism 4 and the like are further arranged above the lever mechanism 3.

In the present embodiment, the reverbal mechanism 1R has a vertically long shape, and a displacement amplification mechanism 1A (lever mechanism 1L and arm portion 1B) or the like is provided inside the reverbal mechanism 1R, but the displacement amplification mechanism is not limited to this configuration. All or part of 1A may be outside the displacement mechanism 1R. For example, the reverbal mechanism 1R may have a horizontally long shape, and a displacement amplification mechanism 1A, a displacement detection unit 2, an electromagnetic force generator 3, a stopper mechanism 4, and the like may be provided below the lower beam portion 14 of the reverbal mechanism 1R. ..

Further, the displacement amplification mechanism 1A may be configured to be provided with an extended portion in which the tip portion of the lever mechanism 1L is extended in the horizontal direction instead of the arm portion 1B extending in the vertical direction. In this case, an electromagnetic force generator 3 is provided for the stretched portion, a displacement detecting portion 2 is provided for detecting the displacement of the tip portion of the stretched portion, and a stopper mechanism 4 is provided for the tip portion of the stretched portion. do it.

Further, the characteristics of the mechanical body 1 including the reverbal mechanism 1R change depending on the temperature of its constituent member (elastic body). Therefore, a temperature sensor (for example, a thermistor) for measuring the ambient temperature of the reverbal mechanism 1R or the temperature of the reverbal mechanism 1R itself is provided, and the controller 5 calculates based on the current value of the coil 37 based on the measured temperature. The mass value of the object to be measured may be corrected. For example, the corrected mass value may be calculated using a predetermined calculation formula for temperature correction. By making such a correction, it is possible to suppress a measurement error due to a temperature change.

Further, although the light emitting unit 21 and the light receiving unit 22 of the displacement detection unit 2 are attached to the attachment member 6, the following may be applied. A light emitting side optical fiber in which the light emitting unit 21 and the light receiving unit 22 are attached farther from the electromagnetic force generator 3, for example, on or near the substrate of the controller 5, and the incident end is connected to the light emitting element 21a of the light emitting unit 21. And two light receiving side optical fibers whose emission ends are connected to each of the light receiving elements 22a and 22b of the light receiving unit 22 are provided. Then, the end face of the emission end of the light emitting side optical fiber and the end face of the incident end of the two light receiving side optical fibers are arranged so as to face each other with the light passing hole 19a of the arm tip 19h interposed therebetween. , The emitting end (light emitting portion) of the light emitting side optical fiber and the incident end (light incident portion) of the two light receiving side optical fibers may be attached to the mounting member 6. In this case, it is possible to eliminate the influence of the heat generated by the light emitting element 21a and the light receiving elements 22a and 22b on the magnetic field of the electromagnetic force generator 3 and suppress the measurement error caused by the heat generation. Here, an example in which an optical fiber is used for both the light emitting unit 21 and the light receiving unit 22 has been described, but an optical fiber may be used for only one of them.

Further, the electromagnetic force generator 3 may have another configuration, for example, a magnetic circuit may be configured by using one magnet. FIG. 4A is a perspective view of the electromagnetic force generator 3A of another example, and FIG. 4B is a side view of the electromagnetic force generator 3A of another example. In FIG. 4, the parts corresponding to those in FIG. 3 are designated by the same reference numerals, and the description thereof will be omitted. The electromagnetic force generator 3A has a configuration in which the magnet 33 and the lid 36 of the yoke are removed from the electromagnetic force generator 3 described above. In this case, the magnetic circuit is composed of a magnet 32, a pole piece 34, and a yoke 35.

The electromagnetic equilibrium type weight sensor A in the present embodiment can be used for a weighing device such as a digital precision balance such as the above-mentioned weighing device B, and for example, each of a combination scale having a plurality of weighing hoppers. It can also be used for weighing hoppers and the like. For example, in the case of a weighing hopper, the hopper that temporarily holds and discharges the object to be measured is connected and supported by the movable portion 12 of the reverbal mechanism 1R.

From the above description, many improvements and other embodiments of the present invention will be apparent to those skilled in the art. Therefore, the above description should be construed only as an example and is provided for the purpose of teaching those skilled in the art the best aspects of carrying out the present invention. The details of its structure and / or function can be substantially changed without departing from the spirit of the present invention.

The present invention is useful as an electromagnetically balanced weight sensor or the like from which an overload protection mechanism can be easily manufactured.

1R Reverbal mechanism 1A Displacement amplification mechanism 1L Lever mechanism 1B Arm part 2 Displacement detection part 3, 3A Electromagnetic force generator 4 Stopper mechanism 4a Stopper member 5 Controller 11 Fixed part 12 Movable part 13, 14 Beam part 15, 17 Connecting part 16 1st lever 18 2nd lever 19 Arm component 19v Arm body 19h Arm tip 19a Light passage hole 19b Through hole 21a Light emitting element 22a, 22b Light receiving element 31 Magnetic circuit 37 Coil

Claims (3)

The displacement member where the displacement of the reverbal mechanism appears at the tip,
A displacement detection unit that detects the displacement of the tip portion of the displacement member, and
A coil that is displaced in conjunction with the displacement of the reverbal mechanism is provided in a magnetic circuit that generates a static magnetic field, and an electromagnetic force is applied through the coil so that the displacement detected by the displacement detection unit approaches zero. With the generator
The through hole has a gap between a round hole-shaped through hole provided in the tip portion of the displacement member in a direction intersecting the direction in which the tip portion is displaced and the inner surface of the through hole. An overload protection mechanism consisting of a round bar-shaped stopper member that is inserted into and fixed statically.
Electromagnetic balance type weight sensor equipped with. A lever mechanism that amplifies the vertical displacement of the reverbal mechanism is further provided.
The displacement member is connected to the lever mechanism and is provided so as to extend in the vertical direction.
The coil of the electromagnetic force generator is configured to be displaced in conjunction with the displacement member.
The electromagnetically balanced weight sensor according to claim 1. The reverbal mechanism includes a fixed portion that is statically fixed, a movable portion that is arranged apart from the fixed portion and is loaded with a load, and a pair of upper and lower parts that connect the fixed portion and the upper portions and lower portions of the movable portion, respectively. It has a beam part and
The lever mechanism
A first lever that is swingably connected to the fixed portion, one end is connected to the movable portion via the first connecting portion, and the other end is amplified in the vertical displacement of the movable portion. Department and
It is arranged below the first lever and is swingably connected to the fixed portion, and one end is connected to the other end of the first lever via a second connecting portion, and the other end. It has a second lever that appears when the vertical displacement of the other end of the first lever is amplified.
The displacement member extending downward is connected to the second lever.
The electromagnetically balanced weight sensor according to claim 2.

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