JPS59145104A - Manufacture of cylindrical ceramics and core for injection molding - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a cylindrical fly material 1 having a complicated inner circumferential surface, such as a cylindrical fly material for rotarynidron cores, or injection molding of ceramics, and a conventional method during molding. Concerning a core used in place of an inner mold.

Conventionally, cylindrical ceramic products such as cylindrical ferrite 1 for rotary transformer cores having complex irregularities on the inner circumferential surface have been produced by manufacturing a cylindrical ceramic material and then forming the complex shape of the inner circumferential surface by machining. Because of this, many steps were required and it was difficult to obtain a product of good quality.

Therefore, injection molding methods, which can form complex shapes, have been adopted instead of machining. In general, the injection molding method for ceramics involves heating and kneading ceramic powder and organic material at the desired mixing ratio, and then molding them into pellets using an extrusion molding machine.
The pellet 1 is then heated and melted in an injection molding machine to form an outer mold and an inner mold having a desired shape and dimensions taking into account the shrinkage rate during sintering.

In this method, the molten material is injected under pressure into the injection space formed by the mold and the injection molding is completed. Therefore, the pressure applied to the molded body becomes a three-dimensional pressure, which is more suitable for molding complex shapes than press molding using the -axial compression molding method.

However, when injection molding something with a complex shape such as the rotary transformer core mentioned above, which has a groove on the inner circumferential surface, the mold structure becomes very complicated, - the cost of the mold increases, and the precision of the molded product and the mass production There were various problems with sexuality.

This invention enables easy molding, simple mold structure, low cost production, good appearance and high dimensional accuracy when manufacturing cylindrical ceramics such as cylinders and rectangular cylinders with complicated inner circumferential shapes. The purpose of the present invention is to provide a method for manufacturing cylindrical Reramix by injection molding, which is extremely effective for mass production.

That is, this invention melts a ceramic raw material for injection molding, and melts the outer mold to a decomposition temperature of 150 to 350 °C with a coefficient of thermal expansion of less than 6 × 10-5 / °C, and a decomposition temperature of 150 °C to 350 °C. The above molten material is injected into an injection molding space formed by a core having an inner circumferential shape and a similar outer circumferential shape to a cylindrical Reramix sintered body made of two or more different organic materials, and injection molding is performed. This method of manufacturing a cylindrical ceramic is characterized in that the molded body is subjected to a binder removal treatment, and at the same time, the core is decomposed and disappeared by heating, and then the molded body is sintered.

The manufacturing method according to the present invention will be specifically explained for manufacturing a rotary transformer core made of ferrite. FIG. 1 is a longitudinal sectional view of a rotary transformer core, and FIG. 2 is a side view of an injection molding core according to the present invention.

The rotary transformer core (1) is made of a cylinder, and has a shape in which two holes (2) are provided around the entire circumference on the inner peripheral surface of the rotary transformer core (1).

First, calcined and crushed powder of ferrite raw material with the composition necessary to obtain the characteristics of a rotary transformer core is heated and kneaded with an organic material as a binder at the required mixing ratio, and then formed into pellets of several millimeters in size using an extruder. None, this pellet molding material is heated and melted in an injection molding machine. Next, an outer mold having the required shape to form the outer shape of the core (1) and considering the shrinkage rate during sintering is installed in the injection molding machine.

On the other hand, the thermal expansion coefficient prepared in advance is 6x10-5/
It has a decomposition temperature of 150°C to 350°C below °C and is made of two or more organic materials each having a different decomposition temperature, and a second
As shown in the figure, a core (3) having an outer circumferential shape similar to the inner circumferential shape of the core (1) and having dimensions that take into account the shrinkage rate during sintering is first installed in the injection molding machine. Insert it into the outer mold. Then, the above molten material is injection molded into the injection molding space formed by the outer mold and the core (3), the obtained molded body is subjected to binder removal treatment, and at the same time, the above-mentioned core (3) is treated to remove the binder.
3) is decomposed and disappeared by heating, and then the molded body is sintered to obtain a predetermined rotary transformer core.

Next, a description will be given of the core material according to the present invention when soft ferrite is used as the injection molding material.

In general, the magnetic properties of soft ferrite, especially its magnetic permeability, are significantly reduced by the inclusion of carbon, so the organic material used as the core must completely volatilize and decompose when heated, and must have no residual carbon. , the coefficient of thermal expansion is 6X
Cracks or cracks in ceramic sintered bodies are caused by organic materials that are less than 10-5 /°C and whose volume changes linearly when heated.

Important for preventing deformation.

If the core is molded using only one type of AH material, the organic material will rapidly decompose at a certain temperature during the binder removal process, and the organic material will expand or soften due to the effects of pressure, etc. , cracks, cracks, and deformation occur in the grooves, etc. on the inner peripheral surface of the molded body. Furthermore, polyethylene, polypropylene, etc. are not preferred as such core materials because they expand rapidly when heated.

However, the core according to this invention has a coefficient of thermal expansion of 6x1.
0-5/°C, causes a linear volume change when heated, has a decomposition temperature of 150°C to 350°C, and is made by mixing and molding two or more organic materials each having a different decomposition temperature. During the sharp binder treatment, the core gradually decomposes and disappears, improving the dimensional accuracy and stabilizing the molded product, and preventing cracks, cracks, deformation, etc., which greatly improves productivity. effective.

In J5 of this invention, the organic material constituting the core is stearic acid, atactic, polypropylene (API-'
), polystyrene, etc. have a coefficient of thermal expansion of 6X10-5 as shown in Table 1.
Two or more types of organic materials having a temperature of 50°C and different decomposition temperatures can be used, and these are mixed and molded. In addition, this invention has 6 (Buru core is A P P
30wt% - 65wt%, polystyrene 35wt%
Preferably, the composition contains up to 70 wt% of stearin f9, or further contains 35 wt% or less of stearin f9.

The amount of residual carbon in the soft ferrite sintered body produced by the regular molding method using the core according to the present invention is almost the same as the amount of residual carbon in the molded body produced by the normal molding method.

The reason why the thermal expansion coefficient of the organic material constituting the core according to the present invention is limited is that the thermal expansion coefficient is 6X10-5/'C.
This is because cracks and fractures occur in the sintered body, reducing the product yield by 1", which is not preferable.

The reason for limiting the decomposition temperature of the organic material in the core is that if the decomposition temperature is less than 150'C, the melting point of the organic material will be as low as 100'C. This makes it difficult to manufacture cores, and the melting point of organic materials with decomposition temperatures exceeding 350°C is too high, exceeding 230"C, and the injection molding temperature of ordinary injection molding machines for manufacturing cores is too high. This is because it is unfavorable in terms of mass production.

Examples according to the present invention are shown in Table 1 and below, and the effects thereof are clearly explained.

First, 13 wt% of an organic material such as polyethylene as a binder is added to calcined and crushed powder of N-Si ZTI ferrite, heated and kneaded, formed into pellets of several millimeters in size using an extruder, and this pellet molding material is injection molded. It was heated and melted inside the machine. Next, an outer mold having the required shape to form the outer shape of the rotary transformer core shown in FIG. 1 and having a cutting method in consideration of the shrinkage rate during sintering was installed in an injection molding machine.

Stearic acid (decomposition temperature 180°C), APP (decomposition temperature 240°C), polystyrene (decomposition temperature 280°C)
) containing two or three types of organic materials 1;
It consists of various compositions shown in the table, and is shown in Fig. 2 mentioned above.
A core having an outer circumferential shape similar to the inner circumferential shape of the rotary 1-lance core shown in Fig. 1 and having dimensions that take into account the shrinkage rate during sintering is first installed in an injection molding machine. TRP was deposited inside the mold. Then, the above molten material was injection molded into the injection molding space formed by the outer mold and the core.

The temperature of the obtained molded body was raised to 400° C. at a rate of 5° C./hour in a bottle binder furnace, and the binder was removed and the core was decomposed and disappeared by heating.

Thereafter, this molded body was sintered in air at 1250°C for 2 hours to obtain the rotary 1-run core shown in Figure 1.

The magnetic properties of the sintered body according to the present invention were equivalent to those of the sintered body produced by the conventional molding method.

In addition, cracks, crack conditions, and dimensional accuracy of the obtained rotary transformer core were measured. The results are shown in Table 2.

It should be noted that the cracks and breakage conditions are the results of the visual inspection of the grooves on the inner circumferential surface of the core, and the number of samples measured was 100. The dimensional accuracy is expressed as the standard deviation of the width of the groove where no cracks or cracks have occurred, and the judicial error standard is 0.05.
mm or less.

As is clear from Table 2, samples 1 to 5 of the present invention were
It can be seen that a rotary transformer core with high dimensional accuracy was obtained without cracks, cracks, or deformation. a3. In the examples, the molding of rough 1 to ferrite was explained, but it is clear that the present invention can be similarly applied to molding of other ceramics.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a rotary transformer core, and FIG. 2 is a side view of an injection molding core according to the present invention. In the figure, 1... rotary transformer core, 2... groove, 3... core. 1st child 2nd child

Claims (1)

[Claims] 1. Melting ceramic raw material for injection molding, forming an outer mold,
Thermal expansion coefficient is less than 6x10-5/°C and 150°C to 35
An injection molding space formed by a core having an outer peripheral shape similar to the inner peripheral surface shape of a cylindrical ceramic sintered body made of two or more types of organic materials each having a decomposition temperature of 0°C and different decomposition temperatures. Production of cylindrical ceramics characterized by injecting the above-mentioned molten material, debinding the injection-molded compact, simultaneously decomposing and disappearing the core by heating, and then sintering and covering the above-mentioned compact. Method. 2 150℃ when the coefficient of thermal expansion is less than 6X10-5/'C
A cylindrical material having a decomposition temperature of ~350°C, made of two or more organic materials each having a different decomposition temperature, and having an outer circumferential shape similar to the inner circumferential shape of the cylindrical ceramic sintered body. Core for ceramic injection molding