JPH0260035A - Permanent magnet for electron lens - Google Patents

Abstract

PURPOSE:To prevent the occurrence of a harmful temperature rise due to an eddy current loss and the like without any disturbance of the intensity of a magnetic field by applying the constitution wherein a sintered body comprising a sintered material is used to form the annular yoke of a specific material containing the predetermined elements and having a specific electric resistance, and having a groove for taking out a lead wire. CONSTITUTION:A sintered body comprising a sintered material is used to form an annular yoke 30 containing, for example, a silicon and having a specific electric resistance exceeding 20 micro-ohm centimeters and further having a groove 10 for taking out a lead wire 7 at one or two positions. Furthermore, the annular yoke 30 is clamped with both ends of annular permanent magnet, thereby forming a permanent magnet for an electron lens. According to the aforesaid construction, the distribution of a magnetic field is not disturbed, because it is unnecessary to provide a lead wire takeout hole at a magnetic piece for taking out the lead wire of a coil. In addition, the yoke 30 is made of sintered alloy and it is easy, therefor to form a groove at the end thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in a permanent magnet for an electron lens used, for example, for controlling an electron beam of a plan tube for a projector.

[Conventional technology]

Conventionally, as an example of this type of device, Japanese Patent Application Laid-Open No. 61-211940
No. [hereinafter referred to as ``example citation''].

In this conventional example, at least two magnets are separately magnetized in the Z-axis direction, which is the central axis direction of the ring, and are connected in the same magnetic pole direction.
These ring-shaped permanent magnets have a half-value width of magnetic flux distribution on two axes that is 80 to 200% of the inner diameter of the ring-shaped permanent magnet, and each of these ring-shaped permanent magnets has a This is a permanent magnet for an electronic lens that has magnetic pole pieces on both end faces.

However, in the conventional example, if the ring-shaped permanent magnet is to have a certain half-value width of the magnetic flux distribution on the Z-axis, the length (thickness) of the ring-shaped permanent magnet in the Z-axis direction must be made considerably long. Therefore, it is difficult and expensive to manufacture ring-shaped permanent magnets.

Therefore, the present applicant first filed a patent application filed in 1986-1 to solve this problem.
No. 02928 [hereinafter referred to as "precedent example"]. ] was proposed.

FIG. 3 is an explanatory diagram of this prior example, with FIG. 3(a) showing its side sectional view and FIG. 3(b) showing its plan view.

The ring-shaped permanent magnets 1a and lb are aligned in the Z-axis direction, that is, in the electron gun [
A yoke made of a ferromagnetic material and magnetized as shown in the figure is inserted in the traveling direction of the electron beam 8 emitted from the ring-shaped permanent magnets 1a and lb by sandwiching them between the end faces of the ring-shaped permanent magnets 1a and lb. A ring-shaped magnetic pole piece 2 made of magnetic material is attached to the end faces of both magnetic poles.
a and 2b are glued together, and a coil 5 for controlling the strength of the magnetic field based on the magnetic flux 9 centered on the Z-axis is attached to the bobbin 4.
The magnets are wound around and mounted inside the ring-shaped permanent magnets 1a and lb.

Naturally, the coil 5 is connected to the outside via a lead wire 7.

Therefore, it is usually necessary to provide an extraction hole 6 in one of the magnetic pole pieces 2a or 2b.

Also, ordinary magnetic pole pieces or yoke have a carbon content of 0. Soft iron of about 3% or less is used.

[Problem to be solved by the invention]

However, providing the extraction hole 6 for taking out the lead wire 7 to the outside in the magnetic pole piece 2a means that the magnetic pole piece 2a
This results in non-uniform physical conditions of the magnetic flux 9, which in turn disturbs the strength of the magnetic field based on the magnetic flux 9.

In addition, since soft iron with a carbon content of about 0.3% or less is used for the magnetic pole piece or yoke, if a high-frequency magnetic field is generated nearby, harmful heat rise will occur due to eddy current loss, etc. .

SUMMARY OF THE INVENTION An object of the present invention is to provide a permanent magnet for an electronic lens that overcomes these difficulties seen in the conventional and precedent examples.

[Means to solve the problem]

In order to achieve the above object, the present invention is made of a component containing, for example, St element and having an increased electric resistivity of 20 micro ohm cm or more, and is provided with one or two grooves for taking out the lead wire to the outside. The ring-shaped yoke is made of a sintered body made of a sintered material, and the ring-shaped yoke is sandwiched between the ends of both ring-shaped permanent magnets to form a permanent magnet for an electron lens.

[For production]

Because of the structure described above, when leading the lead wire of the built-in coil to the outside, there is no need to provide a lead wire extraction hole in the magnetic pole piece and disturb the magnetic field distribution, and the sintered alloy is used. Therefore, it is easy to create a groove at the end of a ring-shaped yoke.

Further, since it is a sintered alloy, it is easy to increase the specific resistance by adding components such as St base wire.

〔Example〕

The shape of one embodiment of the present invention is shown in FIG.

FIG. 1(a) is a side view, and FIG. 1(b) is a partially cutaway plan view.

In all drawings, the same reference numerals indicate the same parts.

The ring-shaped permanent magnets 1a and lb have an outer diameter of 58φmm.

Alnico (Alnico) with inner diameter 48φmm and thickness 8mm
A magnet made of i cO・8 (trade name), with an outer diameter of 56φam, an inner diameter of 33φmm, and a thickness of 3III on both outer end surfaces.
Eleven ring-shaped magnetic pole pieces 2a and 2b are bonded and fixed.

For example, attach about 5 insulated copper wires of 0.18φ to the heat-resistant bobbin 4.
It has a built-in coil 5 wound 30 times.

Then, a sintered body made of a ring-shaped sintered material with approximately the same outer diameter and inner diameter as the ring-shaped permanent magnets 1a and lb and a thickness of 9.
A groove [removal groove 10] having a width of 2 to 3 m+s and a depth of 2 III m is opened in the end face of the yoke 30 using a mold for forming a sintered body.

The composition of the sintered body/yoke 30 is, for example, 3.08% S.
It is a Fe-based component containing the element T and has an electrical resistivity of 35 microohm sennamometers.

The permanent magnet for an electronic lens according to the present invention produced in this way [hereinafter referred to as "the method of the present invention"] is a permanent magnet for an electronic lens that has the same outer diameter, inner diameter, and thickness as the permanent magnet for an electronic lens according to the present invention.
The yoke 3 is made of low carbon steel containing 25% C element [however, it does not have the take-out groove 10], and the lead wire 7 of the coil 5 is made.
When a 2.5φ extraction hole 6 is bored in one of the ring-shaped magnetic pole pieces 2a or 2b in order to take out the electron beam (this is referred to as the "conventional method"), The following table shows the variation in the strength of the magnetic field due to the magnetic flux 9 at distant locations.

Here, polarization is [(maximum value - minimum value) / (maximum value)
]X100.

As described above, the present invention has clearly smaller variations in the magnetic field than the conventional and preceding examples.

Next, an electron beam projector manufactured by a certain company [this will be referred to as the "conventional method"] and that of the present invention were energized under the same conditions, and the surface temperature of the socket-side magnetic pole piece was measured with a thermocouple.

The results are represented in FIG. 2 as characteristic curves for 21 the method of the present invention and 22 the conventional method.

Clearly, the temperature rise is lower with the method of the invention.

〔Effect of the invention〕

Thus, the present invention enables the lead wires of the ring-shaped permanent magnet and the coil built in the ring-shaped yoke and wound around the cylindrical bobbin to be taken out to the outside without disturbing the magnetic field distribution, and without disturbing the extraction groove in the yoke. It is easy to install, and since the yoke is made of a sintered alloy, the added components can increase the electrical resistivity and significantly suppress heat rise due to eddy current loss.

[Brief explanation of the drawing]

Figure 1 is a side view and partially cutaway plan view of an embodiment of the present invention, Figure 2 is a comparison diagram of heat rise based on eddy flow loss between the method of the present invention and the conventional method, and Figure 3 is a prior example. FIG. la, lb...Ring-shaped permanent magnets 2a, 2b...Ring-shaped magnetic pole pieces 3...Yoke [preceding example] 30...Yoke made of ferromagnetic material [present invention] 4...Bobbin 5... Coil 6... Take-out hole [preceding example] 7... Lead wire 8... Electron beam 9... Magnetic flux 10... Take-out groove [present invention]. Applicant's agent - Yu Sato (α) (b) Figure 1 8 duration (minutes) - Figure 2

Claims (1)

[Claims] 1. For an electron lens in which an electron beam passes through the inner holes of at least two ring-shaped permanent magnets that are magnetized in the Z-axis direction, which is the central axis direction of the ring, and connected in the same magnetic pole direction. In the case of permanent magnets, the inner and outer diameters of adjacent ring-shaped permanent magnets are approximately equal to those of the ring-shaped permanent magnets.
A yoke made of a ferromagnetic material with an arbitrary length in the axial direction is sandwiched between the end faces of both ring-shaped permanent magnets and inserted under pressure to increase the half width of the magnetic flux density distribution on the Z axis. A permanent magnet for an electronic lens, characterized in that the yoke and the ring-shaped permanent magnet are made of a sintered alloy having one or more grooves for taking out the lead wires of the coils built into the ring-shaped permanent magnet. 2. The electronic lens according to claim 1, wherein the magnetically conductive ferromagnetic yoke or magnetic pole piece used in the electronic lens permanent magnet is made of a sintered alloy having an electric resistivity of 20 microohm-cm or more. permanent magnet. 3. The permanent magnet for an electronic lens according to claim 1, wherein the groove is provided in a direction that does not affect the magnetic flux passing through the yoke. 4. Claim 1, wherein one groove is provided in the radial direction of the yoke.
Permanent magnet for electronic lenses described.