JP2018205010A - Load sensor - Google Patents

Abstract

To provide a load sensor capable of performing dehumidification under circumstances where humidity is increased.SOLUTION: A displacement member 12 penetrates into a yoke 2 through cavities 14 formed in the yoke 2, so as to be displaced according to application of a load. A coil 10 is arranged in the yoke 2 in a manner to move relatively to a magnetic field generation part made of magnets 4, 8 and a pole piece 6 which are arranged in the yoke 2 in a magnetic field from the magnetic field generation part. The coil 10 is displaced according to displacement of the displacement member 12.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a load sensor such as an electromagnetic balance sensor, and more particularly to removal of moisture inside the load sensor.

  For example, there is one disclosed in Patent Document 1 as moisture-proofing in an electromagnetic balance type sensor. In the technique of Patent Document 1, the support that descends in response to the application of a load is a bobbin, a groove is formed in the outer periphery of the bobbin, a coil is wound in the groove, and the groove is covered with a moisture-proof ring. The bobbin is inserted into the yoke from its upper part, and the bobbin is lowered in the yoke in response to the application of a load. Since the coil is sandwiched between the bobbin and the moisture-proof ring, a moisture-proof effect is obtained.

Utility model registration No. 2518171

  The technique of Patent Document 1 is to prevent moisture by blocking moisture from the coil so that the coil does not absorb moisture, but it cannot be said that the moisture prevention measures are perfect. For example, if the environment in which the coil is wound around the bobbin is under humidity, it is meaningless to provide a moisture-proof ring. Further, when the moisture-proof ring is damaged due to some cause (for example, corrosion of the moisture-proof ring), the moisture outside the bobbin reaches the coil, so the moisture-proof effect is not perfect.

  An object of this invention is to provide the load sensor which can dehumidify in the condition where humidity increased.

  The load sensor of one embodiment of the present invention includes a sensor portion in a container, and the sensor portion includes at least a coil, and detects an applied load. A dehumidifying agent for dehumidifying the coil in the container is provided in the container. For this reason, it is possible to dehumidify even in a situation where the humidity inside the container has increased.

  The load sensor according to another aspect of the present invention includes a magnetic field generation unit and a coil that relatively moves in the magnetic field generated by the magnetic field generation unit. The coil is provided, for example, so that the magnetic field generated by the magnetic field generation unit passes through the inside. The magnetic field generation unit can be configured by a magnet, for example. The coil can be wound around a bobbin or can be an air core that is not wound around the bobbin. Further, in the load sensor of this aspect, the magnetic field generation unit and the coil inside the container are relatively displaced according to the displacement of the displacement member that is displaced according to the application of the load. For this reason, the present invention can be applied to an electromagnetic balance type load sensor, and a moisture-proof effect in the yoke of the electromagnetic balance type load sensor can be achieved.

  Furthermore, the load sensor according to another aspect of the present invention includes a container that is closed while leaving a gap. The container can be composed of, for example, a cylindrical body having one end opened and a lid that closes the opening. A displacement member enters the container through the gap, and the displacement member is displaced, for example, substantially linearly in response to the application of a load. The gap can be formed at any position of the container, but can also be provided, for example, in the lid.

  In the load sensor configured as described above, moisture enters the container through the gap, but even if the humidity changes due to changes in the surrounding environment, the dehumidifying agent is disposed in the container, so that the humidity increases. Therefore, there is almost no influence of the error due to the change of humidity on the measured value of displacement.

  In the load sensor according to another aspect of the present invention, the magnetic field generation unit and the coil are arranged close to each other. This improves the passage of the magnetic field to the coil.

  Furthermore, in the load sensor according to another aspect of the present invention, one of the magnetic field generation unit and the coil is a fixed unit and the other is a movable unit, and the movable unit is displaced according to the displacement of the load responsive member. The dehumidifying agent is disposed on the inner surface of the container. Or the dehumidifier is arrange | positioned at the fixing | fixed part. When the dehumidifying agent is disposed on the inner surface of the container or the fixed portion, it is preferably disposed in a non-contact manner with the movable portion.

  In the load sensor configured as described above, moisture enters the container through the gap, but even if the humidity changes due to changes in the surrounding environment, the dehumidifying agent is disposed in the container, so that the humidity increases. Therefore, the mass of the movable part does not increase, and the measurement value of the displacement has almost no influence of the error due to the change of moisture. In addition, since the dehumidifying agent is disposed in a non-contact manner on the movable part, the measured value is not further affected.

  The dehumidifying agent can be disposed on the inner surface of the container. If it arrange | positions to the inner surface of a case, the attachment will become easy and manufacture of a load sensor will become easy.

  The dehumidifying agent may be disposed on the fixed part. In particular, when a fixed part (for example, a magnetic field generating part) and a movable part (for example, a coil) are close to each other, a dehumidifying agent is disposed on the fixed part, so that the movable part can be efficiently dehumidified. . The dehumidifying agent can be disposed in non-contact with the movable part. In this case, since the weight of the dehumidifying agent is not added to the movable part, the measurement system can be enhanced.

  The movable part can be an air-core coil. For example, when a coil formed on a bobbin is used, a band can be provided to cover the coil wound around the bobbin to prevent moisture, but the bobbin and band are necessary and the configuration is complicated, but it is movable If a moisture-proof material is provided in contact with the coil, which is a part, the coil can be dehumidified even if it is an air core, the configuration can be simplified, and measurement that is not affected by humidity can be performed.

  The movable part can be a coil. In this case, the displacement of the movable part due to the displacement of the displacement member is compensated by passing a current through the coil. With this configuration, an electromagnetic balance type sensor can be configured and moisture in the electromagnetic balance type sensor can be removed, so that the electromagnetic balance type can be measured with high accuracy without being affected by moisture. A sensor is obtained.

  As described above, the displacement sensor according to the present invention can perform dehumidification in the presence of moisture, and can prevent a decrease in measurement accuracy due to moisture.

It is a vertical front view of the electromagnetic balance type sensor which implemented the load sensor of this invention. It is a top view of the electromagnetic balance type sensor of FIG. It is sectional drawing of the state seen from the AA line of FIG. 1 in the paper surface front direction (downward direction of the yoke 2). It is sectional drawing of the state seen from the BB figure of FIG. 1 in the reverse direction (upward direction of the yoke 2) with respect to the paper front side direction.

  A load sensor according to an embodiment of the present invention is an electromagnetic balance type sensor implemented by the present invention, and has a container, for example, a yoke 2 as shown in FIG. The yoke 2 has, for example, a cylindrical main body 2a whose upper part is opened and whose bottom is closed, and a disc-shaped lid 2b which closes the upper opening. The main body 2a and the lid 2b are made of metal through which a magnetic field passes. The main body 2a includes a disk-shaped bottom 2c and a peripheral wall 2d that stands up from the periphery of the bottom 2c.

  In the center of the inner surface of the bottom 2c of the main body 2a, a magnet 4 is disposed in contact with the center. A pole piece 6 is disposed in contact with the magnet 4. Further, another magnet 8 is disposed on the pole piece 6 in contact with the pole piece 6. The yoke 2, the magnets 4, 8 and the pole piece 6 form a magnetic field generator that generates a magnetic field in the yoke 2, and a magnetic field is generated between the yoke 2, the magnets 4, 8 and the pole piece 6. Yes.

  A coil 10 is arranged so as to cover the periphery of the pole piece 6 in the main body 2a. The coil 10 is present in the magnetic field generated by the magnetic field generator between the yoke 2 and the magnets 4 and 8 and the pole piece 6. The coil 10 has an air core that is not wound around a bobbin.

  The coil 10 is coupled to the displacement member 12. The displacement member 12 is formed, for example, in a generally inverted U shape, and its two leg portions 12a, 12a are lid portions via two rectangular gaps 14, 14 formed in the lid 2b as shown in FIG. 2b protrudes to the outside, and the projecting ends of these leg portions 12a and 12a are connected by the top portion 12b of the displacement member 12. The leg portions 12 a and 12 a of the displacement member 12 are not in contact with the edges of the gaps 14 and 14.

  When a load is applied to the electromagnetic balance sensor, the top 12b of the displacement member 12 is applied with a load via a load transmission mechanism (not shown), and moves downward in FIG. 1 according to the applied load. To do. Accordingly, when no load is applied as shown in FIG. 1, the coil 10 moves downward in FIG. 1 from the reference position where the coil 10 is located, and the coil 10 moves in the magnetic field generated by the magnetic field generation unit. . A current is supplied to the coil 10 from a control unit (not shown) so that the moved coil 10 returns to the reference position, and the magnitude of the load is measured from the supplied current.

  Thus, the sensor unit is formed by the coil 10 and the magnetic field generation unit, and the coil 10 functions as a movable unit and the magnetic field generation unit functions as a fixed unit.

  In this electromagnetic balance type sensor, gaps 14 and 14 are formed in the lid 2b in order to allow the legs 12a and 12b of the displacement member 12 to enter the main body 2a. Therefore, moisture penetrates into the main body 2a through the gaps 14 and 14. When the coil 10 adsorbs this moisture, the mass of the coil 10 changes, which may cause a measurement error. In particular, in an electromagnetic balance sensor for precision measurement, the adsorption of moisture to the coil 10 greatly affects the accuracy. As long as the air gap 14 is present, it is not possible to avoid the penetration of moisture into the main body 2a.

  If the bobbin is provided with a groove as disclosed in Patent Document 1, the coil is wound around the groove, and a moisture-proof ring is attached to the bobbin so as to cover the coil, it may be possible to temporarily prevent moisture. However, its manufacture requires a bobbin and a moisture-proof ring, which is troublesome, and there is a possibility that moisture may reach the coil due to corrosion of the moisture-proof ring or release from the coil of the moisture-proof ring described later. Measures are not perfect. In addition, the moisture-proof method of covering the coil wound around the bobbin with the moisture-proof ring cannot be performed if the air-core coil 10 is used as in this embodiment. In addition, when the moisture-proof ring is released from the coil due to aging or the like, the coil adsorbs moisture from the gap 14, and measurement errors may occur as described above.

  Therefore, in the electromagnetic balance type sensor of this embodiment, a dehumidifying agent is disposed at a location that is not in contact with the coil 10 in the yoke 2. In addition, as a dehumidifier, what has a dehumidification effect | action, such as a silica gel, can be used. Specifically, as shown in FIG. 3, the dehumidifying agent 16 is applied to the entire inner peripheral surface of the peripheral wall portion 2d of the main body 2a of the yoke 2 and the entire region other than the portion where the magnet 4 is in contact with the inner surface of the bottom portion 2c. Is attached. Similarly, as shown in FIG. 4, on the back side of the lid 2b of the yoke 2, the dehumidifying agent 18 adheres to the entire area excluding the gaps 14 and 14 and the annular overlapping portion 2e with the peripheral wall 2d of the main body 2a. Is attached by. As the dehumidifying agents 16 and 18, a sheet-like thing or a granular thing can be used. The dehumidifying agents 16 and 18 can also be attached by providing a groove on the inner surface of the yoke 2 and fitting into the groove.

  In the electromagnetic balance type sensor configured in this way, moisture inevitably enters the yoke 2 from the air gaps 14 and 14, resulting in a certain level of humidity. Even if the humidity in the yoke 2 rises due to changes in the surrounding environment, since the dehumidifying agents 16 and 18 are provided inside the yoke 2, moisture is adsorbed by the dehumidifying agents 16 and 18, and the coil 10 is newly added. It hardly adsorbs moisture. Therefore, it is possible to prevent the measurement accuracy from being lowered due to the change in humidity. Moreover, since the dehumidifying agents 16 and 18 are provided on the inner peripheral surface of the peripheral wall portion 2d of the main body 2a of the yoke 2, the inner peripheral surface of the bottom portion 2c, and the back surface of the lid portion 2b, the attachment work can be easily performed. Is called. Furthermore, since the dehumidifying agents 16 and 18 are not provided in the coil 10 that moves when a load is applied, even if the dehumidifying agents 16 and 18 absorb moisture and the weight increases, the measurement accuracy does not decrease. . Further, the dehumidifying agents 16 and 18 are simply configured to be disposed in the yoke 2 and can be implemented even when the coil 10 has an air core.

  In the above embodiment, the coil 10 has been shown to move downward when a load is applied. However, the coil 10 may be moved upward. In the above embodiment, as shown in FIG. 1, the cover 2b of the yoke 2 is arranged so as to be positioned on the upper part of the main body 2a. However, the cover 2b is rotated 90 degrees so that the cover 2b is on the right side or left side in FIG. It can also be arranged and used so that it may be located in. In that case, the coil 10 moves in the horizontal direction. In the above embodiment, the displacement member 12 moves substantially linearly, but may be moved in any manner within a range that does not affect the measurement accuracy. For example, movement in an arc shape or the like can be considered.

  In the above embodiment, the magnets 4 and 8 and the pole piece 6 are used, but it is sufficient that at least one magnet is provided. In the above embodiment, the dehumidifying agent 16 is provided on the main body 2a of the yoke 2 and the dehumidifying agent 18 is provided on each of the lids 2b of the yoke 2. However, the dehumidifying agent 18 may be provided on only one of them. Further, the dehumidifying agent 16 is provided on each of the peripheral wall 2d and the bottom 2c of the main body 2a of the yoke 2, but may be provided on only one of them. In addition, the dehumidifying agent can be provided in a magnetic field generating unit including the magnets 4 and 8 and the pole piece 6. In this case, since the dehumidifying agent can be brought close to the coil 10, the dehumidifying effect can be enhanced. In the above embodiment, the coil 10 is an air core, but the coil 10 is not limited to this, and a coil wound around a bobbin can also be used. Moreover, in said embodiment, although the coil 10 was made into the movable part and the magnetic field generation part which consists of the magnets 4 and 8 and the pole piece 6 was made into the fixed part, conversely, the coil 10 was made into the fixed part, and the magnetic field generation part was made into the movable part. It can also be. In this case, the dehumidifying agent is attached in the yoke 2 without contact with the movable part. In the above embodiment, the present invention is applied to an electromagnetic balance type sensor. However, the present invention is not limited to this. For example, the present invention can be applied to a differential transformer. In this case, a magnetic field does not pass in place of the yoke 2. Containers can also be used.

2 York (container)
4 8 Magnet (Magnetic field generator)
6 Pole piece (magnetic field generator)
10 Coil 12 Displacement member 16, 18 Dehumidifier

Claims (10)

A container,
A sensor unit provided in the container, having at least a coil, and detecting an applied load;
A load sensor having a dehumidifying agent disposed in the container. A displacement member that is displaced in response to application of the load;
The sensor unit includes a magnetic field generation unit disposed in the container, and the coil that moves relative to the magnetic field generation unit in the magnetic field generated by the magnetic field generation unit in the container. ,
The load sensor according to claim 1, wherein the magnetic field generation unit and the coil are relatively displaced according to the displacement of the displacement member. The container is closed leaving a gap;
The load sensor according to claim 2, wherein the displacement member enters the container through the gap.   The load sensor according to claim 2, wherein the magnetic field generation unit and the coil are arranged close to each other.   5. The sensor unit according to claim 2, wherein one of the magnetic field generation unit and the coil is a fixed unit and the other is a movable unit, and the movable unit is displaced according to displacement of the displacement member. The load sensor as described in the item.   The load sensor according to claim 1, wherein the dehumidifying agent is disposed on an inner surface of the container.   The load sensor according to claim 5 or 6, wherein the dehumidifying agent is disposed in the fixed portion.   The load sensor according to claim 6 or 7, wherein the dehumidifying agent is disposed in non-contact with the movable part.   The load sensor according to claim 1, wherein the coil is an air-core coil. The load sensor according to claim 5, wherein the movable part is a coil, and the displacement of the movable part due to the displacement of the displacement member is compensated by passing a current through the coil.

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