JPH06246724A - Mold and powder molding method - Google Patents

Abstract

PURPOSE:To adjust the molding density of a leg part by making the chamfering dimension of the edge part in the outside direction of the cylinder of the upper end surface of the core rod of a mold constituted of a cylinder, upper and lower punches and the core rod smaller than that of the edge part in the center direction of the cylinder. CONSTITUTION:A core rod 1 is constituted so that the chamfer 3 of the outside edge part of the upper end surface thereof is different from the chamfer 2 of the inside edge part thereof and the chamfer 3 is set to a usual chamfering dimension and the chamfer 2 is set to a large chamfering dimension. When a squared {2169/64} shape ferrite magnetic core is used using the core rod 1, a lower punch 13 and the core rod 1 are held within a cylinder 11 to pack the cylinder 11 with a ferrite raw material powder 15 and, when an upper punch 16 is inserted in the cylinder 11 to perform compression molding, the powder 15 of a middle leg part is escaped into the upper punch 16 by the large chamfer 2 and the packing amt. of the middle leg part is reduced to adjust molding density. Therefore, the molding densities of the middle leg part and an outer leg part can be uniformized and the quality of the magnetic core is enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding die for powder compression molding of a ferrite core and a powder molding method.

[0002]

2. Description of the Related Art FIG. 5 shows a conventional method for forming a letter-shaped ferrite magnetic core. A lower punch 13 having two through-holes 12 as shown in FIG. 6 is inserted into a cylinder 11 having through-holes formed along the outer shape of a H-shaped ferrite magnetic core, and the mandrel is further inserted into the through-holes 12. 14 has been inserted. A perspective view of the mandrel 14 is shown in FIG. The lower punch 13 and the mandrel 14 are held at predetermined positions, the ferrite raw material powder 15 is filled, and the upper punch 16 is inserted to insert the ferrite raw material powder 15 into the ferrite raw material powder 15.
Was compression-molded between the upper punch 16 and the lower punch 13.
At this time, the mandrel 14 is inserted into the through hole 17 formed in the upper punch 16. FIG. 8 shows a perspective view of the formed H-shaped ferrite magnetic core. This letter-shaped ferrite magnetic core is fired and then cut to be used as an EI-type or EE-type ferrite magnetic core.

[0003]

In the conventional method for forming a day-shaped ferrite magnetic core, the molding density of the middle leg portion 18 is higher than that of the outer leg portion 19, and after firing, as shown in FIG.
The contraction of the middle leg was small, the contraction of the outer leg was large, and the back surface 20 had a convexly curved shape. The E-shaped ferrite core 21 is cut by cutting the letter-shaped ferrite core 21
When obtained, the shape becomes as shown in FIG. In the case of this E-type ferrite magnetic core 21, when the abutting surface 22 was polished, the E-type ferrite magnetic core 21 was unstable on the processing table 23, and uneven quality such as oblique polishing or bending occurred. An object of the present invention is to provide a molding die and a molding method that solve the above problems.

[0004]

SUMMARY OF THE INVENTION The present invention is a molding die comprising a cylinder, a lower punch, an upper punch, and a mandrel, and the chamfering dimension of the outer end of the cylinder on the upper end surface of the mandrel and the chamfered dimension. The molding die is characterized in that the chamfer dimension of the traverse portion in the center direction of the cylinder is different from the chamfer dimension of the traverse portion in the center direction of the cylinder. Further, the present invention is a molding die composed of a cylinder, a lower punch, an upper punch, and a mandrel, wherein the chamfer formed on the twill portion of the upper end surface of the mandrel has at least a part of another chamfered dimension. It is a molding die characterized by being larger than the size. The present invention also provides a cylinder having a rectangular through hole, which is inserted into the through hole of the cylinder and is inserted into two holes of a date-shaped upper punch and lower punch having two holes, the upper punch and the lower punch. Which has two mandrel, which is filled with ferrite raw material powder between the upper punch and the lower punch,
A molding die for compression-molding a H-shaped ferrite magnetic core, the chamfering dimension of the outer twill portion and the inner twill portion of the upper end surface of the mandrel is different, and the chamfering dimension of the inner twill portion is larger than that of the outer twill portion. It is a molding die characterized by being large. Further, in the present invention, in a powder molding method in which a lower punch and a mandrel are arranged in a cylinder, a powder raw material is filled, and compression molding is performed between the upper punch and the lower punch, the lower punch and the mandrel are formed on a twill portion of an upper end surface of the mandrel. Partially changing the chamfer size, adjusting the inflow amount of the powder raw material into the upper punch when the mandrel is inserted into the upper punch, and finely adjusting the molding density distribution of the powder compact. Is a powder molding method.

[0005]

In the conventional molding die and molding method, the molding density of the middle leg portion is higher than that of the outer leg portion, which causes a problem. In other words, the cause is that the ferrite raw material powder is easily clogged in the middle leg. Therefore, in the present invention, the chamfered dimension formed on the upper end surface of the mandrel is increased so that the chamfered portion allows the ferrite raw material powder to escape into the upper punch to adjust the compacting density.

[0006]

FIG. 1 is a perspective view of a mandrel according to an embodiment of the present invention.
Shown in. The mandrel 1 differs from the chamfer 3 on the outer twill portion on the upper end surface and the chamfer 2 on the inner twill portion, and the chamfer 3 on the outer twill portion has a normal chamfer dimension, and the chamfer 2 on the inner twill portion has a large chamfer dimension. The chamfering dimension of the inner twill portion was 1.5 mm and 3.0 mm. At this time, the chamfering dimension of the outer side twill was 0.2 mm. The chamfering dimension of this inner twill portion is 1.5 mm, which is taken as Example 1 and 3.0 m.
Let m be Example 2. A H-shaped ferrite magnetic core was formed using the mandrel of Examples 1 and 2 and fired. At this time, the upper punch, the lower punch, and the cylinder used were the same as in the conventional case. The state of molding using the mandrel of this example is shown in FIG. After holding the lower punch 13 and the mandrel 1 in a predetermined position in the cylinder 11 and filling the ferrite raw material powder 15, the upper punch 1
6 is inserted and compression molded. By forming a large chamfer on this mandrel 1, the upper punch 16
When is inserted, the ferrite raw material powder 15 in the middle leg portion escapes into the upper punch 16, the filling amount in the middle leg portion decreases, and the molding density is adjusted. Dimension B1 and outer leg 1 of the middle leg 18 of the H-shaped ferrite core after firing
Table 1 shows the results of measuring the dimension B2 of 9 (shown in FIG. 8). In the conventional example of Table 1, all chamfer dimensions are 0.2 mm.
The B1 and B2 dimensions are average values of 200 samples.

[0007]

[Table 1]

The H-shaped ferrite cores according to Examples 1 and 2 have B1 <B2, which is shown in FIG.
That is, the middle leg 18 portion contracts more than the outer leg 19 portion, and the back surface portion 20 has a concavely curved shape. In the case of the conventional example, almost B1 = B2, but this is an average value and individual variations occur. Therefore, the magnetic core as shown in FIG. 9 is also generated, which causes the above-mentioned conventional problems. The product size of the letter-shaped ferrite magnetic core shown in FIG. 8 on this day is 16 mm for the A size and 4.2 mm for the C size. According to this example, when the E-type ferrite magnetic core obtained by cutting the letter H-shaped ferrite magnetic core was polished, the back surface portion 20 was concavely curved, so that stable processing could be performed. As a result, the inductance of the winding product obtained by using this E-type ferrite magnetic core has a σ showing the variation of 2/3 or less of that of the conventional one, and the characteristics are stable. FIG. 2 is a perspective view of a mandrel according to another embodiment of the present invention.
Shown in. In this mandrel 4, in chamfering the top end surface of the twill portion, a part of the inner chamfer 6 is a large chamfer 5, and the outer chamfer 7 is a chamfer similar to the conventional one.
According to this embodiment, it is possible to partially adjust the filling amount. That is, it is understood that the chamfered dimension of the necessary portion may be changed in order to adjust the filling amount. As a result, the filling amount can be adjusted and the compacting density of the powder compact can be finely adjusted by changing the chamfered dimension of the desired portion without being limited to the shape of the above-described embodiment.

[0009]

According to the present invention, the density of the compact can be finely adjusted by increasing the chamfered dimension of the mandrel at a predetermined position in powder compacting. Further, according to the present invention, when an E-shaped ferrite magnetic core is obtained by forming a letter-shaped ferrite magnetic core, firing it, and then cutting it, it is possible to improve the quality and yield of the E-type ferrite magnetic core.

[Brief description of drawings]

FIG. 1 is a perspective view of a mandrel according to an embodiment of the present invention.

FIG. 2 is a perspective view of a mandrel according to another embodiment of the present invention.

FIG. 3 is an explanatory diagram of a molding process of an example according to the present invention.

FIG. 4 is a schematic diagram of a day-shaped ferrite core according to an embodiment of the present invention.

FIG. 5 is an explanatory diagram of a molding process of a conventional example.

FIG. 6 is a perspective view of a lower punch of a conventional example.

FIG. 7 is a perspective view of a conventional mandrel.

FIG. 8 is a perspective view of a H-shaped ferrite core.

FIG. 9 is a schematic diagram of a conventional letter-shaped ferrite magnetic core.

FIG. 10 is a schematic diagram of an E-type ferrite magnetic core of a conventional example.

[Explanation of symbols]

 1, 4, 14 Mandrel 2, 3, 5, 6, 7 Chamfer 11 Cylinder 12, 17 Through hole 13 Lower punch 15 Ferrite raw material powder 16 Upper punch 18 Middle leg 19 Outer leg 20 Rear part

Claims (4)

[Claims] 1. A molding die comprising a cylinder, a lower punch, an upper punch, and a mandrel, the chamfering dimension of the outer end of the mandrel on the upper end surface of the mandrel, and the chamfering of the center end of the mandrel. Different from the dimensions, the molding die is characterized in that the chamfer dimension of the twill portion in the center direction of the cylinder is larger. 2. A molding die comprising a cylinder, a lower punch, an upper punch, and a mandrel, wherein the chamfer formed on the twill portion of the upper end surface of the mandrel has at least a part of the chamfered dimension of another chamfer. Molding die characterized by being larger than dimensions. 3. A cylinder having a rectangular through hole, inserted into the through hole of the cylinder and inserted into two holes of a day-shaped upper punch and lower punch having two holes, the upper punch and the lower punch. Is a molding die having two mandrel, which is filled with ferrite raw material powder between the upper punch and the lower punch, and compression-molded to form a day-shaped ferrite magnetic core, the upper end surface of the mandrel. The chamfer dimensions are different between the outer and inner twill
A molding die characterized in that the chamfer dimension of the inner twill is larger than that of the outer twill. 4. In a powder molding method in which a lower punch and a mandrel are arranged in a cylinder, a powder raw material is filled, and compression molding is performed between the upper punch and the lower punch, the lower punch and the mandrel are formed on a twill portion of an upper end surface of the mandrel. Partially changing the chamfer size, adjusting the inflow amount of the powder raw material into the upper punch when the mandrel is inserted into the upper punch, and finely adjusting the molding density distribution of the powder compact. A powder molding method comprising: