JPS61222208A - Electromagnet apparatus - Google Patents

Abstract

PURPOSE:To define a gap with parallel sides precisely, by bumping each other two electromagnets each consisting of a main cylindrical yoke with a cross sectional convex shape and a coil, with a spacer made of magnetic alloy having a low thermal expansion coefficient put between two return ring yokes to define the gap. CONSTITUTION:Coils 4,4' are inserted and fixed in spaces defined between return yokes 5, 5' and the projection side walls of main yokes 2, 2' respectively. The upper and lower electromagnets A, B so constructed having the same configuration are bumped with a gap 1 put between the projections of the main yokes. Within the gap defined between the bumpering sections of the return yokes, a spacer, for example made of 35% Ni-Fe alloy, is put, and the upper and lower electromagnets are fastened to finish an electromagnet apparatus. Since this electromagnet apparatus has the upper electromagnet A and lower electromagnet B arrayed symmetrically, paralleling the magnetic poles can be easily attained. Moreover, when the ring spacer 6 having the same height as that of the gap 1 to be defined between the main yokes is put between the upper and lower return yokes with being contacted to them, the magnet gap between the upper and lower yokes can be defined precisely.

Description

[Detailed description of the invention] [Industrial application field] Various magnetic measurements such as high-resolution nuclear magnetic resonance (NMR)
Used in electromagnetic equipment used for measurements.

[Conventional technology]

As an electromagnet device used for NMR measurement, there is a Pitter type electromagnet device as shown in FIG. This device inserts the gap part 1 and inserts the 0 type iron core 1. A commutating pole 3 of the yoke 2 faces the yoke 2, and a coil 4. .

4' is wound. When this coil is energized, magnetic flux is generated in the Iazzo section 1.

[Problem that the invention seeks to solve]

In order to perform high-resolution measurements, extremely high homogeneity and stability of the magnetic field are required. However, the electromagnetic device shown in FIG. 3 has a Q-shaped yoke, which makes it impossible to accurately align the gap in parallel during assembly, and the mechanical stability of the gap is poor. That is, when a coil is energized to generate a magnetic field, the left and right yokes abut each other with a spacer interposed therebetween due to the magnetic field, thereby forming a gap between the two electromagnets.

[For production]

The above-mentioned Ni--Fe alloy and the like have an extremely small coefficient of thermal expansion compared to pure iron. Therefore, by inserting a Ni--Fe alloy as a spacer between the gaps and mechanically tightening the gaps, the gaps can be maintained at substantially constant intervals without being thermally fluctuated.

〔Example〕

FIG. 1 shows a cross-sectional view (,) and a top perspective view showing one embodiment of an electromagnetic device according to the present invention. Reference numerals 2 and 2' indicate cylindrical main yokes each having a convex cross section. 4,41 is husband husband yoke 2
, 2' is a coil wound around the protrusion. 5, 5' is a ring-shaped return yoke, which is attached to yoke 2 by Deldoor.
2', and a coil 4, is installed in a space formed between the return yokes 5, 5' and the side wall of the protrusion of the main yoke.
4' is inserted and fixed. In the figure, the upper and lower electromagnets A and B constructed in this manner have the same shape.

Butt B with the protrusion of the main yoke through gap 1,
35 between the gap between the return yoke butt parts
The electromagnet device according to the present invention is completed by firmly tightening the upper and lower electromagnets by interposing a spacer 6 made of %Ni--Fe alloy. The electromagnet device according to the present invention has the above-described structure, and since the upper electromagnet A and the lower electromagnet B are arranged symmetrically, the parallelism of the magnetic poles can be easily obtained and the design height of the gap 1 of the main yoke can be adjusted. If ring-shaped spacers 6 of the same height are inserted in contact with the upper and lower return yokes, the magnetic gap between the upper and lower yokes can be formed extremely accurately. Furthermore, this spacer is made of a 35 at% Ni--Fe alloy and has a thermal expansion coefficient of I.times.10.sup.-6, which is significantly smaller than the 15.times.10-6 of a yoke or return yoke made of an iron core. FIG. 2 shows another embodiment of the present invention in which a ring-shaped centering yoke 8 made of carbon steel is inserted and tightened around the outer periphery of the spacer 6.

With this structure, the height is 15, the secondary outer diameter is 16.5cIn, the gap distance is 111R1E at the center, and the electromagnet generates a maximum of 2,200 Gauss.
A uniformity of X 10-5 was obtained. In addition, when this was incorporated into a magnetometer, the stability over time was as shown in Figure 4.
ppm or less was obtained.

〔Effect of the invention〕

The present invention has been described above.1 According to the present invention, not only can the gap between the yokes have good parallelism, but also the spacer for obtaining the gap distance has a coefficient of thermal expansion that is significantly smaller than that of pure iron35. ~36% By using a Ni-Fe alloy, the so-called Invar alloy, it was possible to significantly improve spatial uniformity and stability over time.

[Brief explanation of drawings]

Figure 1 shows one embodiment of the present invention (,) is a sectional view (b).
) is a top perspective view, and FIG. 2 shows another embodiment of the present invention. The left hand part has the same shape as the right hand part, so the cross section is omitted. Figure 3 is a schematic diagram of a conventional electromagnetic device; (a) sectional view;
(b) shows a side view. FIG. 4 shows the stability over time when the present invention was incorporated into a Lan magnetometer and measured. In the figure, l: gap, 2.2: main yoke, 4.4': coil,
5, 5': return coil, 6: spacer. 72 gilt, 8: Centering yoke. Figure 1 Figure 2 Z'

Claims (1)

[Claims] 1. A cylindrical main yoke with a convex cross section, a ring-shaped return yoke fitted around the outer periphery of the main yoke, and a ring-shaped return yoke inserted between the protrusion of the main yoke and the return yoke. A gap is formed between the two electromagnets by interposing a spacer made of a magnetic alloy having a low coefficient of thermal expansion between the two ring-shaped return yokes and interposing two electromagnets each consisting of a coil. An electromagnetic device featuring: 2. The electromagnet device according to claim 1, wherein the spacer has a coefficient of thermal expansion of 1×10^-^6 or less. 3. The electromagnet device according to claim 1, wherein the spacer is a 36% Ni-Fe alloy.