JP3691607B2 - Electromagnetic force generator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for generating electromagnetic force, and more particularly to an electromagnetic force generator that can be suitably used as an electromagnetic part of an electromagnetic balance type weighing apparatus commonly called an electronic balance.
[0002]
In the electromagnetic balance type weighing device (hereinafter referred to as “electronic balance”), the load of the weighing object is digitally displayed by generating an electromagnetic force that balances with the load of the weighing object transmitted via the beam. It is supposed to be.
[0003]
The electromagnetic force generator has a configuration in which a movable coil that is displaced in accordance with the load of a weighing object is disposed in a magnetic field formed by a permanent magnet (hereinafter referred to as “magnet”). The electronic balance has a feedback circuit that balances the displacement of the movable coil to zero by the Lorentz force due to the Lorentz force caused by the current flowing in the movable coil so as to be orthogonal to the magnetic flux of the static magnetic field of the magnet in the electromagnetic force generator. It is an apparatus that is configured to perform an arithmetic processing on the amount of electricity to be balanced at this time as the load of the weighing object.
[0004]
The magnet has a constant temperature coefficient, and the amount of magnetic flux generated from the magnet changes due to the influence of Joule heat generated by the current flowing through the movable coil, resulting in an error in the measured value of the weighing object. For this reason, a method is adopted in which a temperature change in the vicinity of the magnet is detected, and the measured value is corrected by calculating the temperature change as a correction value. However, with this method, it is difficult to accurately correct for a short-term temperature change.
[0005]
Here, if the amount of magnetic flux of the magnet is set large in advance, the current flowing through the movable coil can be reduced by that amount, and therefore the Joule heat generation can be suppressed low. In response to such technical demands, as shown in FIG. 5, an electromagnetic force generator (for example, Japanese Utility Model Publication No. 6-18248) using two magnets has been proposed. In this apparatus, a lower yoke 50, an intermediate yoke 51, and an upper yoke 52 are stacked, and a lower magnet 53 and a pole piece 54 are arranged in order from the bottom in the interior formed by these yokes. Has a configuration in which the upper magnet 55 is stacked so that the same pole as the pole of the lower magnet 53 faces.
[0006]
Reference numeral 56 denotes a movable coil disposed in an annular space between the pole piece 54 and the intermediate yoke 51, a connecting member 57 that passes through an opening 51 a formed in the intermediate yoke 51, and other members connected to the connecting member 57. The connecting member 58 is connected to the beam 59, and the displacement due to the load of the weighing object is transmitted to the movable coil 56 via the beam 59.
[0007]
[Problems to be solved by the invention]
The configuration shown in FIG. 5 is basically a very rational configuration for increasing the amount of magnetic flux, but on the other hand, at the stage of actually assembling and forming this configuration as an electromagnetic force generator, there are various types of configurations as follows. There's a problem.
[0008]
First, in order to realize the configuration shown in FIG. 5, the upper and lower magnets 55 and 53 and the yokes 50, 51 and 52 are fixed, that is, actually fixed using an adhesive. For this reason, when the magnetization of a member to be a magnet is to be performed after assembly, it is necessary to apply a magnetic field in the opposite direction to the close upper magnet 55 and lower magnet 53, which makes it difficult to set up manufacturing equipment. Specifically, it is difficult to set a magnetic coil insertion space due to a spatial restriction of the magnetic circuit. Also, when using magnets that have been pre-magnetized, if the pole piece 54 is sufficiently thick so that it does not become magnetically saturated, the upper and lower magnets 55 and 53 have the same polarity but are opposed to each other. Tries to attract the pole piece 54 violently.
[0009]
The upper and lower magnets 55 and 53 are small and thin in the magnetization direction, and are made of a relatively brittle material such as a rare earth magnet having a large coercive force. The possibility of breakage is extremely high. As a result, in order to construct the apparatus shown in the same figure, a special jig is required to prevent the pole piece 54 from being attracted violently and to the surrounding yoke. Requires skill in assembly work.
[0010]
Furthermore, in order to make the magnetic flux density uniform, the constituent members such as the upper and lower magnets and the respective yokes need to be accurately arranged at predetermined positions. However, the respective members are mainly attracted and repelled by the magnetic force of the magnets. It is quite difficult to place and fix (adhere) each of these members precisely because of their behavior. Furthermore, since the movable coil 56 is disposed in a very narrow space, if this movable coil is in contact with the intermediate yoke 51 or the pole piece 54 even if it is slightly in contact with the load of the weighing object, 56 will not be displaced accurately. For this reason, it is necessary to make fine adjustments regarding the arrangement of the movable coil 56 even after the entire apparatus is assembled. However, in the illustrated configuration, the upper yoke 52 is effectively bonded and fixed to the intermediate yoke 51. Adjustment of the movable coil 56 after mounting is very difficult.
[0011]
[Means for Solving the Problems]
The present invention is an electromagnetic force generator configured in view of the above-described problems of the prior art, and is based on the premise that a lower magnet, a pole piece, and an upper magnet are arranged in order from the bottom in the yoke. A shaft body is formed upright and arranged so as to share the axis with the central axis of the lower yoke, and the shaft body is made of a non-magnetic material, and the lower side of the shaft body is lower than the shaft body. The lower magnet, the pole piece, the upper magnet, and the upper yoke are inserted and arranged in this order, so that the shaft center of each member is the same as the shaft center of this shaft body, that is, each member is connected to the yoke via this shaft body. An electromagnetic force generator characterized by being placed in the yoke so as to have a common axis .
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The lower yoke constitutes the main body of the electromagnetic force generator, and the upper yoke also has a function as a lid for closing the inside of the lower yoke. An opening is formed at the center of the lower yoke, and a bolt, for example, is erected and arranged as a shaft so as to share the central axis with the lower yoke. The bolt is made of a nonmagnetic material such as brass, aluminum, stainless steel or the like.
[0013]
Each of the upper and lower magnets and the pole piece arranged in the middle has a shaft body insertion hole formed at the center, and the shaft body passes through this insertion hole, so that each member positions the pole piece outer diameter and the yoke inner diameter. By doing so, it is possible to automatically and very easily perform the placement in an accurate positional relationship, that is, centering. First, a lower magnet is inserted into the shaft body. The lower magnet may be magnetized in advance, or may be magnetized after being temporarily fixed to the lower yoke with a slight adhesive or the like.
[0014]
A pole piece, an upper magnet, and an upper yoke are stacked in this order on the lower magnet. Of course, the shaft is inserted through the center of each of these members, so that each member is properly centered without using a special jig, and the assembly of the electromagnetic force generator is accurate. And it becomes possible to carry out easily. The assembly order does not need to correspond to the final vertical positional relationship of each member. For example, the upper magnet (not yet magnetized) is preliminarily bonded and integrated with the upper yoke, and then integrated. It is also possible to employ a method such as magnetizing the upper magnet and inserting it into the shaft body. As with the lower magnet, the upper magnet can be magnetized during assembly to avoid adverse effects due to magnet attraction and repulsion during assembly.
[0015]
Further, if the outer diameter of the pole piece is made larger than the outer diameter of the magnet, not only the positioning of each magnet is facilitated, but also the horizontal component of the magnetic flux concentrated on the pole piece is increased. This prevents leakage of the vertical direction of the magnetic flux, leading to a reduction in the order moving coil current can be increased as a result effective flux.
[0016]
【Example】
Embodiments of the present invention will be specifically described below with reference to the drawings.
[0017]
1 and 2 show the configuration of an electromagnetic force generator according to a first embodiment of the present invention.
Reference numeral 1 denotes a lower yoke that constitutes a main body of the electromagnetic force generator, and is formed in a cylindrical shape having an open upper end. A recess 1a is formed at the center of the back surface of the floor portion 1c of the lower yoke 1, and an insertion hole 1b is formed so as to share the axis with the recess 1a. Reference numeral 2 denotes a bolt that is a shaft body that is erected in the lower yoke 1 through the insertion hole 1b. The bolt 2 is made of a nonmagnetic material such as brass, aluminum, or stainless steel.
[0018]
Reference numeral 3 denotes a lower magnet inserted through the upright bolt 2, and a bolt insertion hole 3 a is formed at the center of the lower magnet 3. Thus it is the lower magnet 3 by Rukoto a lower magnet 3 is inserted into the bolt 2 is automatically set in the center of a lower yoke 1, centering is adapted to exit. If necessary, the accuracy of centering can be further increased by using a jig for obtaining the assembly position accuracy.
A pole piece 4 having a bolt insertion hole 4a formed at the center is disposed at the upper part of the lower magnet 3, and a bolt is provided at the center of the pole piece 4 in the same manner as the lower magnet 3 and the pole piece 4. An upper magnet 5 having an insertion hole 5a is arranged. When the bolt 2 is inserted through the insertion holes 4a and 5a of the pole piece 4 and the upper magnet 5, the respective members are automatically centered and arranged at predetermined positions. Will be.
[0019]
When the upper magnet 5 is arranged, the nut 6 is screwed into the screw portion 2a of the bolt 2 protruding from the center of the upper magnet 5 to fix each member, and finally the upper yoke 7 is opened and the lower yoke 1 is opened. By fitting and fixing to the end, the electromagnetic force generator is configured so that all members have a common axis . Reference numeral H denotes an opening through which a member (see reference numeral 57 in FIG. 5) that connects a movable coil and a beam (both not shown) arranged inside is inserted. In the above configuration, when the upper yoke 7 is fitted into the upper end portion of the lower yoke 1, the centering is practically completed.
[0020]
In the above description, the case where the electromagnetic part is configured using the upper magnet 5 and the lower magnet 3 magnetized in advance is described. Next, the case where the magnet material is magnetized during the assembly of the electromagnetic part will be described.
[0021]
First, the lower magnet 3 that is not magnetized with respect to the lower yoke 1 is temporarily fixed in advance with, for example, a slight adhesive . Incidentally, when the fixing with the bolts 2 is completed, the fixing effect of the temporary fixing portion is completely unnecessary, and therefore, a small amount of adhesive is sufficient for temporary fixing. Similarly, the pole piece 4 and the upper magnet 5 are temporarily fixed . These temporary fixings are not affected by the magnetic force because the respective magnets are not yet magnetized, and can be easily centered simply by aligning the respective insertion holes 1b, 3a, 4a and 5a. There is no difficulty. If the pole piece and the magnet contact surface of the lower yoke are formed as recesses as in the configurations of FIGS. 3 and 4 of the embodiment described later, centering becomes easier. Next, after magnetizing each magnet, each part is assembled so that it may become a structure shown in FIG. 1, and each member is fixed with a common shaft center by finally screwing the nut 6 to the bolt 2 . Alternatively, the upper yoke 7 may be directly screwed into the screw portion 2a of the bolt 2 by eliminating the nut 6 itself and leaving the opening 7a of the upper yoke as a female screw portion as in the embodiments described later.
[0022]
In the configuration of the electromagnetic unit according to the present invention, the upper and lower magnets are separately magnetized, so that a conventional magnetization (magnetization) device can be used as it is. Incidentally, in the conventional configuration shown in FIG. 5, if the magnet part is to be magnetized after assembly, it is necessary to design and manufacture a dedicated special magnetizing device, and this magnetizing device cannot be used in other fields. Therefore, the production of the electromagnetic part has to be extremely uneconomical.
[0023]
FIG. 3 shows a second embodiment. First, a screw portion 2b is formed at the base of the bolt 2, and the insertion hole 1b of the lower yoke 1 is a female screw portion that is screwed with the screw portion 2b. As a result, the bolt 2 can be reliably set up with respect to the lower yoke 1. The pole piece 4 has an outer diameter larger than the outer diameters of the upper and lower magnets. The contact surfaces of the upper and lower magnets in the pole piece 4 are formed as recesses 4b and 4c, and the lower magnet 3 is formed in the recess 4b. In addition, the upper magnet 5 is configured such that a part thereof is fitted and disposed in the recess 4c. Thereby, the arrangement (centering) of the upper and lower magnets becomes more reliable and easy. In the illustrated configuration, the nut 6 is screwed into the screw portion 2a of the bolt 2 as in the configuration of FIG. 1, but the nut 6 is fixed to the upper yoke 7 side, or a third embodiment described later. As described above, the nut 6 may be eliminated, and the opening of the upper yoke 7 may be used as a female screw portion so that the upper yoke 7 is screwed onto the bolt 2.
[0024]
FIG. 4 shows a third embodiment of the present invention. An opening 7a formed at the center of the upper yoke 7 is formed as a female screw portion, and the screw portion 2a of the bolt 2 is configured to be directly screwed into the opening 7a. Further, the wall thickness W of the peripheral flange portion is slightly thinner than that of the above-described embodiment, and the gap S between the flange portion of the upper yoke 7 and the upper end edge of the lower yoke 1 after assembly of the electromagnetic force generator. This gap S is configured to be used for absorbing an assembly error of the apparatus. In this configuration, since the upper magnet 5 and the upper yoke 7 are always in contact with each other, the upper magnet 5 and the upper yoke 7, which are the second assembly method of the assembly methods described in the first embodiment, are fixed in advance. It is also a very convenient configuration for implementing the method.
[0025]
Reference numeral 1d denotes a magnet housing recess recessed in the floor surface 1c of the lower yoke 1, which is formed to be equal to the outer diameter of the lower magnet 3, and a part of the lower magnet 3 is inserted and arranged. ing. By simply placing the lower magnet 3 in the recess 1d, the lower magnet 3 is automatically centered without any special work for centering , and this configuration also implements the second assembling method. It is extremely effective.
[0026]
【The invention's effect】
As specifically described above, the present invention is configured so that the shaft body is inserted through all of the yoke, the upper and lower magnets, and the pole piece, and the shaft center of each member and the shaft body is common. These members are automatically arranged with an accurate positional relationship without using a special jig simply by inserting a shaft through each member, and the assembly thereof is very easy.
[0027]
Further, the upper and lower magnet enables assembly of the device regardless of whether the magnetization after the magnetization or assembled prior to assembly, it is possible to freely set the assembly procedure in accordance with the overall device process, moreover special wear It is not necessary to design and manufacture a magnetic device, and a conventionally used magnetizing device can be used as appropriate at the stage of assembling the device . Therefore, the reliability of the entire device can be improved while maintaining high economic efficiency.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of an electromagnetic force generator showing a first embodiment of the present invention.
2 shows a horizontal cross section of the electromagnetic force generator shown in FIG. 1, in which (A) is a cross-sectional view taken along the line AA, and (B) is a cross-sectional view taken along the line BB.
FIG. 3 is a longitudinal sectional view of an electromagnetic force generator showing a second embodiment of the present invention.
FIG. 4 is a longitudinal sectional view of an electromagnetic force generator showing a third embodiment of the present invention.
FIG. 5 is a longitudinal sectional view of a conventional electromagnetic force generator.
[Explanation of symbols]
1 Lower yoke 1b Bolt insertion hole 1c Lower yoke floor 2 Bolt (shaft)
3 Lower magnet 3a Bolt insertion hole 4 Pole piece 4a Bolt insertion hole 4b, 4c Recess for magnet insertion 5 Upper magnet 5a Bolt insertion hole 6 Nut 7 Upper yoke 7a Opening

Claims (7)

A device in which a lower magnet, a pole piece, and an upper magnet are arranged in order from the bottom in the yoke, and a movable coil is arranged in an annular space between the lower magnet, the pole piece, and the upper magnet and the yoke. in, the shaft as the center of the yoke which is shaft body upright made of a nonmagnetic material so as to share the yoke and the axis, and the lower magnet, pole piece, the upper magnet share axis relative to the yoke An electromagnetic force generator, wherein the electromagnetic force generator is inserted into a body . A device in which a lower magnet, a pole piece, and an upper magnet are arranged in order from the bottom in the yoke, and a movable coil is arranged in an annular space between the lower magnet, the pole piece, and the upper magnet and the yoke. The yoke includes a lower yoke and an upper yoke that functions as a lid for the lower yoke, and a shaft body made of a non-magnetic material is erected at the center of the lower yoke so as to share the axis with the lower yoke. And the lower magnet, the pole piece, and the upper magnet are inserted into the shaft body so as to share the axis with the lower yoke and the upper yoke , and the lower magnet, the pole piece, and the upper magnet are disposed. An electromagnetic force generating device characterized in that an upper yoke is fitted and arranged at the upper end of the magnet.   A screw portion is formed at the end of the shaft body standing upright on the shaft center, and the lower yoke, the lower magnet, the pole piece, and the upper magnet are connected via the shaft body by screwing a nut into the screw portion. 3. The electromagnetic force generator according to claim 1, wherein the electromagnetic force generator is fixed.   The opening at the center of the upper yoke is formed as a female screw portion, and the lower yoke, the lower magnet, the pole piece, the upper magnet and the upper yoke are fixed via the shaft body by screwing with the screw portion at the end of the shaft body. The electromagnetic force generator according to claim 3, wherein the electromagnetic force generator is configured as described above.   The pole piece is formed to have a diameter larger than the upper and lower magnets, and at least one of the upper and lower magnet contact surfaces of the pole piece has a recess having the same diameter as the magnet so that a part of the magnet is inserted and positioned. The electromagnetic force generator according to claim 1, wherein the electromagnetic force generator is formed.   6. The recess of the same diameter as that of the lower magnet is formed on the contact surface of the lower magnet of the floor surface of the lower yoke so that a part of the lower magnet is fitted and positioned. The electromagnetic force generator in any one.   5. The upper yoke lower surface is configured to come into contact with the upper magnet upper surface, and an error adjusting gap is formed between the periphery of the upper yoke lower surface and the lower yoke upper end surface. The electromagnetic force generator in any one of thru | or 6.

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