JPH08148331A - Electromagnet - Google Patents

Abstract

PURPOSE: To enhance heat removing effect by resin molding the lead wire of the coil in an electromagnet being used in the vacuum or a pressure reduced atmosphere. CONSTITUTION: The bobbin of an electromagnet is made of an aluminum material and subjected to Alumite processing thus forming an insulation layer on the surface thereof. A coated copper wire is then wound around the bobbin. Winding is carried out while wetting the copper wire with a molding resin, i.e., a thermosetting epoxy resin, so that the resin is spread sufficiently between the copper wires. Subsequently, the winding is heated to cure the resin. Since a heat removing mechanism is provided for Joule's heat of the lead wire of coil through molding method, temperature rise of the lead wire of coil causing breakage of short circuit thereof can be suppressed and reliable operation of electromagnet can be realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnet used in a vacuum or reduced pressure atmosphere.

[0002]

2. Description of the Related Art There are numerous applications in which the properties of attraction and repulsion due to the magnetic force of a permanent magnet are used for driving, conveying, rotating, fixing, etc. of an object, and an electromagnet is used instead of a permanent magnet to energize it. There are innumerable applications that utilize the generated magnetic force. Furthermore, in recent years, there are many examples of use under a vacuum or reduced pressure atmosphere.

[0003]

The electromagnet energizes and excites a coil conductor wire constituting the electromagnet to generate a magnetic force, but the electromagnet coil generates heat due to Joule loss due to the energization. When it is used in the atmosphere, the electromagnet is removed through the air molecules around the coil conductor even if it generates heat except when an extremely large current is applied.

However, in a vacuum or under reduced pressure, that is, in an atmosphere where the degree of vacuum is 1 to 10 Torr or less, there is no air as a heat transfer medium around the coil conductor, so that heat is removed or weakened, and the temperature of the coil conductor rises during energization. Then, a short circuit between the coil conductors or a disconnection of the coil conductors may occur. Since the direct current electric resistance value of the coil conductor is proportional to the wire length and inversely proportional to the cross-sectional area, this problem of heat generation is serious in an electromagnet with a thin conductor and a large number of turns.

[0005]

DISCLOSURE OF THE INVENTION The present invention has solved the above-mentioned problems. In an electromagnet used in a vacuum or reduced pressure atmosphere, the coil wire of the electromagnet is filled with resin and molded. The gist is a characteristic electromagnet.

That is, the above-mentioned problem of heat generation is due to the lack of a mechanism for releasing the heat of the conductor in a vacuum or under a reduced pressure atmosphere. In the present invention, a method of covering the coil conductor with a resin and solidifying it, that is, a molding method is applied to transfer heat generated by the conductor to the resin and further transfer the heat to the bobbin of the coil through the resin to remove the heat. is there. The thermal conductivity of the resin is generally not as high as that of the metal, but it is higher than that of the air, so that the heat removal effect is larger than that in the atmosphere. The heat removal effect can be further improved by using a resin having high thermal conductivity. The high heat conductive resin is obtained by filling a high heat conductive filler.

[0007]

[Function] The bobbin is usually made of a non-metal insulator such as plastic, but it is more effective to use a metal having high thermal conductivity in order to release the heat received from the coil through the resin to the bobbin support. . If the bobbin is made of metal, it is possible to break the conductor coating and electrically short the conductor to the bobbin in the process of winding the coil conductor, so the surface of the bobbin, especially the surface in contact with the winding, should be an insulator. The possibility of short circuit can be eliminated. For this purpose, a method of applying an insulating material to the surface of the bobbin and then winding it, or a method of applying a surface treatment to a metal bobbin to form an insulating layer may be applied.
For example, when using aluminum for the bobbin material,
An insulating layer can be easily formed by applying an alumite treatment.

As the molding resin, thermoplastic resins such as polyester resin, polyamide resin,
Acrylic resin etc. are illustrated. Examples of the thermosetting resin include Epokin resin, urethane resin, silicone resin and fluororesin. However, the epoxy resin is preferable for the purpose of the present invention in terms of workability and effect.

As the filler, those having excellent thermal conductivity are preferable, but those reducing electric insulation are not preferable. There is no particular limitation as long as it can meet such a purpose. Examples thereof include BN powder, silica, titanium oxide, talc, calcium carbonate and red iron oxide.

The resin can be treated by a known method such as dipping from the solution, brush coating, spray coating or powder coating.

[0011]

EXAMPLES Next, the electromagnet of the present invention will be described with reference to examples. Example An aluminum material was processed to prepare the bobbin of the electromagnet shown in FIG. The inner surface of the winding is 12 mm, the outer diameter is 36 mm, and the height is
18 mm. Next, this bobbin was anodized to form an insulating layer on its surface. This bobbin has a diameter of 0.1
An 18 mm coated copper wire was wound 3,900 times for a total length of 294 m (electromagnet A). Here, a thermosetting epoxy resin was used as the molding resin, and the winding was performed while the copper wire was wet with this resin so that the copper wire was sufficiently spread. After winding, it was heated to 150 ° C for 6 hours to cure the resin and mold it.

Measuring the coil copper wire temperature directly by energizing the coil with a thermocouple or the like raises doubts about the measurement accuracy, so the temperature was measured indirectly from the change in the coil resistance value.
The following experiment was conducted to confirm the effectiveness of this method.
Wrap a coated copper wire with a total length of 25m and a diameter of 0.2mm around a plastic rod and put it in the water of a beaker to change the water temperature from 0 ℃ to 100 ℃
The electric resistance of the coil copper wire was measured. The results are shown in FIG. 2 (dots ■). As theoretically expected, the resistance value of the coil was confirmed to be directly proportional to the absolute temperature. In this figure, the accuracy of the offset value of the resistance value at absolute zero is insufficient, but this value is originally a minute amount and can be ignored in this experiment. The resistivity ρ of copper is room temperature 23
Since it is 1.8 × 10 ^-6 Ω · cm at ℃, the formula R is ρ · L / πa ² (1). When the total length L = 25m and the diameter 2a = 0.2mm, the resistance R is calculated to be 14.3Ω. It agrees well with the value (point in Figure 2). From this experimental result, the temperature T _C of the coil copper wire can be obtained from the following equation by the ratio of the coil resistance value R and the resistance value R _RT at room temperature. T _C = [(T _RT + 273) × R / R _RT ] −273 (2) Here, T _RT is room temperature (° C.).

Next, the electromagnet (A) having the above-mentioned molding is attached to the inside of the vacuum chamber 4 as shown in FIG. 3, and a change in the resistance value R of the coil is measured by energizing it under a vacuum of about 10 ^-6 Torr. The temperature of the copper wire was calculated using the formula (2).
For comparison, an electromagnet (B) wound without molding was prepared, and the temperature of the coil copper wire was measured by the same method to examine the effect of resin molding. In the experiment, paying attention to the temperature difference between the bobbin and the coil copper wire, the heat of the bobbin was screwed as shown in FIG. 3 so as to be efficiently released to the vacuum chamber. A constant voltage power supply was used to energize the coil, and 30.0 v was applied to the electromagnet (A), and a terminal voltage of 21.4 v was applied to the electromagnet (B). Applied voltage between electromagnet terminals and measured current (Fig. 4)
The electromagnet resistance value calculated from a) is shown in FIG. 4b. Figure 4c
Shows the time variation from the initial value of the temperature of the electromagnet coil, that is, from room temperature (25 ° C). In FIG. 4, A and B
Data correspond to the electromagnet (A) and the electromagnet (B).

In the electromagnet coil (B) which is not molded, the coil copper wire is heated by Joule loss due to energization, its resistance value R is increased, and the energization current is greatly decreased with time under a constant voltage. In this case, the coil copper wire temperature rose to 136 ° C after 50 minutes of energization. On the other hand, in the electromagnet (A) with the molding, the decrease of the energizing current was small, and the coil temperature rise was suppressed to a low temperature of about 40 ° C., and it was confirmed that the heat removal effect by the molding is remarkably remarkable.

[0015]

EFFECTS OF THE INVENTION By using the electromagnet of the present invention having a heat removal mechanism by a molding method for Joule heat generation of the coil conductor, the temperature rise of the coil conductor which causes disconnection or short circuit of the coil conductor is suppressed and the electromagnet is suppressed. It is possible to secure the sound operation as.

[Brief description of drawings]

FIG. 1 is a top view (a) and a side view (b) showing a bobbin of an electromagnet coil.

FIG. 2 is a diagram showing a result of actual measurement of temperature dependency of a copper wire electric resistance value R.

FIG. 3 is a diagram of an experimental apparatus in which a temperature rise due to energization in vacuum of an electromagnet (A) with a molding and an electromagnet (B) without a molding was measured.

FIG. 4 is a graph showing changes in (a) current, (b) electric resistance, and (c) coil copper wire temperature with time when a magnetized electromagnet (A) and a magnetized electromagnet (B) are energized in a vacuum. It is the figure which showed.

[Explanation of symbols]

 1 ... Bobbin 2 ... Coil copper wire winding part 3 ... Screw hole 4 ... Vacuum chamber 5 ... Vacuum exhaust system

Front page continued (72) Inventor Akiyoshi Yokota 28-1 Nishikofukushima, Kubiki-mura, Nakakubiki-gun, Niigata Prefecture Shin-Etsu Engineering Co., Ltd., Niigata Plant (72) Kenichi Yoshihara 28 Nishifukushima, Kubiki-mura, Nakabuki-gun, Niigata Prefecture -1 Shinetsu Engineering Co., Ltd. Niigata Office

Claims (6)

[Claims] 1. An electromagnet used in a vacuum or reduced pressure atmosphere, wherein the coil wire of the electromagnet is filled with resin and molded. 2. The electromagnet according to claim 1, wherein the resin is a thermosetting epoxy resin. 3. The high thermal conductive resin containing a filler as the epoxy resin, as claimed in claim 1 or 2.
The electromagnet described in. 4. The electromagnet according to claim 1, wherein the winding bobbin of the electromagnet is made of metal. 5. The electromagnet according to claim 4, wherein in the metal bobbin, an electric insulator is applied to at least a surface of the bobbin which is in contact with the winding. 6. The electromagnet according to claim 4, wherein in the metal bobbin, an electric insulating layer is formed by surface treatment on at least a surface in contact with the winding.