JPH034898Y2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Field of Industrial Application The present invention relates to an electromagnetic force generating device, and particularly to an electromagnetic force generating device suitable for use in an electromagnetic force balance type balance.

(b) Prior art An electromagnetic force generator used in an electromagnetic force balance type balance has a moving coil installed in a static magnetic field, a beam that is linked to the weighing pan of the balance is connected to this moving coil, and the moving coil is Detects the displacement and controls the current flowing through the moving coil so that the displacement becomes 0,
The load on the weighing pan of the balance is detected from the current. A typical structure of a conventional example of such an electromagnetic force generating device is shown in FIG. A current flows perpendicularly to the magnetic field within the magnetic field generated between the magnetic pole piece 2 and the magnetic pole part 3a of a static magnetic circuit consisting of the permanent magnet 1, the magnetic pole piece 2, and the yoke 3 having the magnetic pole part 3a on the upper inner circumference. An electromagnetic coil 4 wound in the same manner as shown in FIG. The structure is such that a current is passed through the electromagnetic coil 4 so as to generate an electromagnetic force that causes zero displacement of the movable winding frame 5 in opposition to the load on the plate. As is well known, heat is generated when current flows through the electromagnetic coil 4, but in this conventional device, the movable winding frame 5 for connecting the beams is shaped like a cup. , its heat dissipation effect is extremely poor. This heat changes the temperature of the permanent magnet 1, and is the main cause of errors caused by the temperature characteristics of the permanent magnet 1.

Conventionally, measures have been taken to provide several heat radiation holes on the upper surface of the movable winding frame 5 in order to improve the heat radiation effect. However, there is a limit to their number,
A large heat dissipation effect has not yet been achieved. In addition to the heat dissipation holes mentioned above, an air inlet was arranged at the bottom of the yoke 3 to increase the amount of heat dissipation due to the chimney effect. is used, and processing it into a complicated shape not only increases costs, but also
A problem arises in that the magnetic properties deteriorate.

(c) Purpose The present invention was made to solve the above-mentioned technical problems without increasing costs.
The object of the present invention is to provide an electromagnetic force generating device that has a greater heat dissipation effect than conventional devices without degrading magnetic properties.

(d) Configuration The electromagnetic force generating device of the present invention has magnetic pole pieces arranged at both ends of a permanent magnet in the magnetization direction, and a cylindrical space is formed around the outer periphery of the permanent magnet and both magnetic pole pieces.
A cylindrical yoke is joined to one of the magnetic pole pieces by a base plate made of a non-magnetic material to form a magnetic circuit, and a coil supported by a cylindrical movable frame is disposed in the cylindrical space. , between the inner circumferential surfaces of the coil and movable frame and the outer circumferential surfaces of the permanent magnet and both magnetic pole pieces, and between the outer circumferential surfaces of the coil and movable frame and the inner circumferential surface of the yoke, respectively. An open cylindrical void is formed on the other side of the piece, and
The base plate is characterized in that a through hole communicating with each of these voids is bored.

(e) Examples Examples of the present invention will be described below based on the drawings.

FIG. 1 is a central vertical sectional view of an embodiment of the present invention.

Magnetic pole pieces 12a and 12b are attached to both ends of the permanent magnet 11 in the magnetization direction, respectively. A cylindrical yoke 1 is formed so that a cylindrical gap is formed around the outer periphery of this permanent magnet 11 and each magnetic pole piece 12a, 12b.
3 are arranged. This yoke 13 is joined to the lower magnetic pole piece 12b via a base 14 made of a non-magnetic material. A magnetic circuit is formed by these permanent magnets 11, the upper magnetic pole piece 12a, the yoke 13, and the lower magnetic pole piece 12b. The base 14 is provided with an air inlet 14a that extends vertically through the base 14, as shown in FIG. 2, which is an external view of the base seen from below.

In the cylindrical gap formed between the permanent magnet 11 etc. and the yoke 13, upper and lower coils 15a and 1 are wound on the same axis as the cylindrical gap.
5b is arranged. These upper and lower coils 15a and 15b are supported by a movable coil frame 16 along the above-mentioned cylindrical gap. That is,
Figure 3 shows the coil frame 16 and the upper and lower coils 1.
5a, 15b, etc., the upper end surface of the upper coil 15a is joined to the lower end surface of the cylindrical coil frame 16, and the upper end surface of the spacer ring 17 is joined to the lower end surface of the upper coil 15a. Furthermore, the lower coil 1 is attached to the lower end surface of the spacer ring 17.
5b is joined. The upper and lower coils 15a and 15b integrated in this way are attached to the coil frame 1.
6 is connected to a beam interlocked with a weighing pan of an electronic balance by a mounting seat 16a formed at the upper end of the balance.

In the assembled state shown in FIG.
1. Between the outer peripheral surfaces of the upper and lower magnetic pole pieces 12a and 12b and the inner peripheral surfaces of the upper and lower coils 15a and 15b, the coil frame 16, and the spacer ring 17, and between the inner peripheral surface of the yoke 13 and the upper part, Lower coil 1
5a, 15b, coil frame 16, spacer ring 1
A cylindrical gap that is open upward is formed between the outer circumferential surface of each member 7 and the outer circumferential surface of each member 7 . The cylindrical voids formed inside and outside the coil are configured to communicate with the air inlet 14a of the base 14 described above, respectively.

According to the above embodiment of the present invention, the heat generated by the current flowing through the upper and lower coils 15a and 15b enters from the air inlet 14a as shown by the arrow in FIG. Heat is dissipated by the air flowing upward along the

In the above embodiments, the air inlet 14a is shown as a long hole, but it goes without saying that a large number of round holes may be made.
It is also effective to form a groove on the joint surface of the tube to allow air to flow into the cylindrical gap.

(f) Effects As explained above, according to the present invention, a cylindrical gap that is open upwards is formed inside and outside the coil, so the heat caused by the energization of the coil does not get trapped inside, and furthermore, the lower magnetic pole The base that connects the piece and the yoke is made of non-magnetic material and configured to allow an air inlet of any shape to be bored, and the chimney effect created by the air inlet and the above-mentioned cylindrical gap further improves the heat dissipation effect. be done. Therefore, compared to conventional electromagnetic force generators of this type, the temperature change of the permanent magnet is extremely small, and the occurrence of errors due to changes in the balance current is improved. In addition, in conventional devices, when the beam moves when it is hot, the air inside the device is replaced and the temperature changes in the permanent magnet, but with this device, air is constantly flowing due to the chimney effect. Therefore, such temperature changes hardly occur, and temperature correction becomes easy. Furthermore, compared to the conventional device shown in FIG. 4, the coil frame and yoke can be easily processed and costs can be reduced.

[Brief explanation of drawings]

FIG. 1 is a central vertical sectional view of an embodiment of the present invention, FIG. 2 is an external view of the base 14 seen from below, and FIG. 3 is an external perspective view of the coil portion. FIG. 4 is a sectional view of a conventional electromagnetic force generating device. 11...Permanent magnet, 12a, 12b...Magnetic pole piece, 13...Yoke, 14...Base, 14a...
...Air inlet, 15a... Upper coil, 15b...
...Lower coil, 16...Coil frame, 16a...Mounting seat, 17...Spacer ring.

Claims (1)

[Scope of utility model registration request] Magnetic pole pieces are arranged at both ends of the permanent magnet in the magnetization direction, and a cylindrical space is provided at one of the magnetic pole pieces by a base plate made of a non-magnetic material so that a cylindrical space is formed around the outer periphery of the permanent magnet and both magnetic pole pieces. A magnetic circuit is constructed by joining two shaped yokes, and a coil supported by a cylindrical movable frame is disposed in the cylindrical space, and the coil and the inner peripheral surface of the movable frame are connected to the permanent magnet and both. A cylindrical air gap opened to the other side of the magnetic pole piece is formed between the outer peripheral surface of the magnetic pole piece and between the outer peripheral surface of the coil and movable frame and the inner peripheral surface of the yoke, respectively, In the electromagnetic force generating device, the base plate is provided with a through hole that communicates with each of the upper cylindrical voids.