JPH01307207A - Green body for flat plate type rotary transformer core - Google Patents

Abstract

PURPOSE:To omit the gate cutting process of a green body, and simplify the inspection process of trench depth after sintering and grinding by providing the surface on which coil trenches are not formed with a plurality of pin-gates, and arranging the pin gates so as to have symmetry with respect to the center of a circular ring, at recessed positions with respect to the flat surface. CONSTITUTION:On the upper surface of a green body 11 for core main body, two coil-trenches 12 of concentric circle type are arranged. Leading-out trenches 13 are formed in radial direction, in order to connect each of the trenches 12 with the external peripheral part. On the surface 14, of the green body 11 for core main body, on which the trenches are not formed, pin-gates 16 are arranged so as to be symmetric with respect to the center of a circular ring, at recessed positions 15 with respect to the surface. The green body 11 for core main body is molded as follows; mixture of sintering ferrite and binder is injection molded, melted material is filled in a metal mold to form a first spool 20, a runner 21, and a second spool 22, and injected into a forming part of the green body 11 for core main body, from the pin-gates 16 forming the tip part of the second spool. Thereby, the gate cut process at the time of degreasing and sintering of the green body 11 for core main body is omitted, and the inspection process of the trench depth of a grounded body can be simplified.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is made by injection molding a mixture of sinterable ferlast powder and a binder, and then undergoes degreasing and sintering processes to produce a flat rotary transformer core. In order to achieve mass production, it is possible to estimate the amount of deformation that occurred during sintering by observing the pin gate marks on the surface where the coil grooves are not provided on the core, which is made by grinding and polishing both sides after sintering. The present invention relates to a green body for a flat plate type rotary transformer core, which allows determination of defective groove depth.

[Conventional technology]

A rotary transformer is used in the rotating drum device of the rotating head fiVTH as a means of transmitting electrical signals between the rotating part and the stationary part.
It has a rotary core, which is an annular plate-shaped rotating part made of sintered ferrite, and a status core, which is a stationary part.

As shown in FIGS. 9 to 11, these cores have an annular plate shape; one surface of the core is provided with a plurality of concentric coil grooves 2, and these coil grooves 2 are arranged around the outer circumference of the core. A diametrical pull-out groove 5 is provided that connects with.

The rotor core and stator core configured in this way have a rotor core 4 provided with coil grooves 2 and a stator core 50 with a 20 to 70
They are arranged facing each other with a gap 6 of μm between them, and each coil groove 2 is wound with a predetermined number of turns of a rotor coil 7 and a stator coil 8, the end of which is pulled out through the pull-out groove 3 and V' ◎ In the rotary transformer with the above configuration, it is necessary to strictly control and maintain the relative positional relationship between the rotor core 4 and the stator 5. Therefore, the six grooves in the core depth and base,
High precision is required for the flatness and parallelism of the upper and lower wheels. Conventionally, rotary transformer cores (hereinafter referred to as cores) are made of a mixture of sinterable ferrite powder and a binder such as polyvinyl alcohol or methyl cellulose. It is made by pressing to form a green body, degreasing it, and sintering it, but since it deforms greatly during sintering,
The product is manufactured by creating a sintered body three times the size and grinding the groove surface and the opposite surface.In order to reduce the amount of grinding, the inventors have already developed a green body for the rotary transformer core body. We proposed molding using a film-like ring gate. (Patent Application No. 62-527101) [Problem to be Solved by the Invention] However, in order to produce a sintered body from a green body for a rotary transformer core body using the above-mentioned film-shaped ring gate, first the film-shaped ring gate is used. The process that needs to be removed consists of a punching process using a punching blade, and a process of processing the part that remains as paris after punching.

When a film-like ring gate is used in this way, an extra step is required to remove the gate.

Furthermore, even when degreasing and sintering a gate-treated green body, if there are variations in the temperature inside the furnace or variations in the moving speed of the feeding cart in a continuous furnace, harmful cracking or deformation may occur in the sintered body. However, if the groove depths of the sintered body are different between the center and the outer periphery after grinding, there is a problem that ridges are generated in each groove, and a process is required to remove these defective products. Due to defective groove depth (removal of defective products requires a complicated process of measuring all the groove depths of the grinding body and determining the dispersion, especially for multi-channels with many grooves) In terms of type, the accuracy of the groove depth is an important factor because it has a large effect on the transmission characteristics of the rotary transformer.

The inventors of the present invention have conducted extensive research to solve the above problems by injection molding a mixture of sinterable ferrite and a binder, and have found that a flat plate rotary transformer core body which is sintered to form a core. A process of omitting the gate cutting process when degreasing and sintering the green body for the core body by devising the gate of the green body (hereinafter referred to as the green body for the core body), and inspecting the groove depth of the ground body. The present invention has been made based on the above knowledge, and it is possible to omit the gate cutting process of the green body and simplify the groove depth inspection process after sintering and grinding. The purpose is to provide a green body for the core that can be used as a core material.

[Means to solve the problem]

The present invention achieves the above object, and the reason for this is that a green body for a flat rotary transformer core, which is made by injection molding a mixture of sinterable ferrite powder and a binder, has a concentric circular shape on one surface. A green body for a rotary transformer core body in the form of an annular plate with a plurality of coil grooves has a plurality of pin gates on the surface where the coil grooves are not provided, and the pin gates are symmetrical with respect to the center of the ring. It is located on the green body for the rotary transformer core provided in a recessed position.

[Effect]

Since the core green body according to the present invention has the above-mentioned configuration, the mixture injected into the mold through the pin gate at the tip of the spool will not flow between the spool part and the core body green body when the mold is closed. Although it is integrated into one piece, the spool part and the green body are cut at the gate opening when the mold is opened, and the gate processing step after injection molding is omitted.

The above-mentioned multiple pin gates are installed symmetrically about the center of the ring on a surface where no coil grooves are provided, and the tips are recessed from the plane, so that after sintering, the grooves do not form. When grinding the front and back surfaces, even if harmful deformations such as distortion or cracking occur in the sintered body, the depth of the groove can be determined by visually determining the remaining state of the dents and pin gates on the back surface. 9, it is possible to control the uniformity of the grinding body, and the complicated inspection process of the grinding body can be simplified.

[LOL example]

1 to 3 are perspective views showing one embodiment of a green body for a core made by injection molding a mixture of sinterable elastomer powder and bi-cedar according to the present invention.

In the back plan view and longitudinal sectional view, reference numeral 11 denotes a green body for the core body in the form of an annular plate. Two concentric coil grooves 12 are provided on the upper surface of this core body green body, and each coil groove 12 is provided with a diametrical pull-out groove 15 that connects each groove with the outer periphery. The surface 14 of the green body 11 for the core body on which the groove surface is not provided is a flat surface)
A pin gate 16 is provided at a recessed position 1115 symmetrically about the center of the ring. The sinterable ferrite powder used for injection molding of the green body for the core body configured as above is calcined powder of 7 elites of nickel-zinc type, magnesium-zinc type, and manganese-zinc type. Particles with a diameter of 1 to 200 μm can be used, but
(Ll~15111#m is preferable, especially α1~
A thickness of 100 μm is preferable. If the average particle size is less than 11 μm, uniform dispersion during kneading becomes difficult.
If it exceeds m, shape retention during sintering is poor, density after sintering is reduced, and magnetic properties 1 mechanical strength are reduced.

Examples of the binder used include styrene polymers, ethylene polymers, propylene polymers, ethylene-vinyl acetate copolymers, and alkyl (carbon atoms of 6 or less).
Copolymers containing methacrylate as a main component (more than sowts) (e.g. polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate),
The main component is alkyl (carbon number 6 or less) acrylate (50
(wt. The number average molecular weight of these synthetic resins was measured by Ingu's vapor osmotic pressure method, which was 2000.
500,000 to 500,000, particularly preferably 4000 to 300,000. In order to form a green body for the core body using the above-mentioned sinterable ferrite powder and binder, first, the ferrite powder and the binder are mixed in a predetermined ratio (usually 5 to 40 parts by weight of the binder to 100 parts by weight of the ferrite powder). Melt and knead the parts by weight and form them into a pellet. Fill the pellets with 0 into an injection molding machine, melt them, and inject them into a metal mold. The mold used has a recessed part with the green body 11 part for the core body as the boundary. An intermediate mold 17 having a groove surface, a movable mold 18 for forming the groove surface, and a fixed mold 19 for injecting the molten material into the mold. The mold forming the second stool 22 is filled, and the pin gate 22 forming the tip of the second spool is press-fitted into the molding part of the green body for the core body.After the injection is completed, it is cooled and solidified, and then the intermediate mold 17 and the movable mold are filled. When 18 is moved, the main body green body 11 is also released from the intermediate mold 17 and remains on the moving mold 1!18.
When the core body green body 11 is released from the intermediate mold 17, it is released by the second spool 22 and subjected to gate processing. The first spool 20, the runner 21, and the second spool 22 are discharged into the stationary mold 19. Moving mold 1
The green body 11 for the core body separated together with 8 is released from the mold by protruding the protruding bottle provided in the mold.

A core is obtained by sintering and further grinding, and then those lacking uniformity in groove depth are selected based on the balance of the remaining state of the concave portion on the back surface. The above degreasing and sintering steps may be performed continuously or separately.The thickness of the green body 11 for the core body according to the present invention varies depending on the performance of the target rotary transformer, but is usually 15 to 5 m/
m, diameter is 10-150m/m, inner diameter is 5-50m
/m. In addition, the recessed part on the surface without grooves should be circular or square with a diameter of 3 to ion/m or a side of 3 to ion/m, and a depth of α5 to 5 m/m, and be tapered or semicircular. Shapes and stair-like shapes are also included in the invention.

The diameter of the pin gate at the center of the recess is 115 to 5 Vm, and the number of pin gates is 3 to 8.

〔effect〕

As described above, since the green body for a core body according to the present invention has the above configuration, gate processing is not required.
When degreasing and sintering causes cracks or bends, and there is a problem with the uniformity of the groove depth after grinding, it is easy to sort out, and there is no need for a complicated sorting process. It has many advantages over multi-groove types, which tend to be affected by depth, such as being a stable product at a low cost.

[Brief explanation of the drawing]

1 to 3 show an embodiment of a green body for a rotary transformer core according to the present invention, in which FIG. 1 is a perspective view, FIG. 2 is a back plan view of FIG. 1, and FIG. is a longitudinal sectional view of FIG. 1; 4 to 6 show the shape of the gate recess according to the present invention, FIGS. 4(b) and 4(c) are plan views of the stepped recess, and FIG. 4(a) is a plan view of the stepped recess. 5(1)) and (e) are plan views of the tapered recess, FIG. 5(a) is a longitudinal sectional view of the tapered recess, and FIG. 6(b) is a semicircular recess. Plan view of Figure 6 (a
) is a vertical cross-sectional view of a semicircular recess ◎ Figures 7 and 8 are vertical cross-sections showing the positional relationship of the core body green body, spool, and runner when the mold is closed and open. It is a diagram. Figures 9 to 11 are plan views of the core grinding body], Figure 9 shows 2 grooves, Figure 10 shows 4 grooves, and Figure 11 shows 9 grooves.
◎Figure 12 is a vertical sectional view showing an example of a rotary transformer. Figures 13 to 18 are plan views showing the back side of the core grinder. Good product with uniform groove depth, Figures 14 to 1
FIG. 8 is a plan view showing an example of a defective product with uneven groove depth. DESCRIPTION OF SYMBOLS 1... Core grinding body, 2... Coil groove, T... Pull-out groove, 4... Rotor core, 5... Stator core, 6...
...Gap, 7...Rotor coil, 8...Starter coil, 11°...Green body for rotary transformer core body (green body for IA body), 12...Green body coil groove % 1511**Gree Integral drawer groove, 1
4 Kawagurin body lining, 15... pin gate recess, 16
... Pin gate, 17 ... Intermediate mold, 18 ... Moving mold, 19 ... Fixed metal Ml, 20 ... First stool, 21 ... Runner, 22 ... Second spool. 30th figure 7th figure 40th figure 140th

Claims (4)

[Claims] 1. In a green body for a flat rotary transformer core made by injection molding a mixture of sinterable ferlast powder and a binder, the rotary transformer core body is shaped like an annular plate and has a plurality of concentric coil grooves on one surface. For a flat rotary transformer core, the green body has a plurality of pin gates symmetrical about the center of the ring on the surface where the coil groove is not provided, and the pin gates are provided at positions recessed from the plane. Green body. 2. The vertical cross-sectional shape of the recess where the pin gate is provided is step-like,
2. The green body for a flat rotary transformer core according to claim 1, wherein the green body has a tapered shape or a semicircular shape. 3. 3. The flat rotary transformer according to claim 1, wherein a concave portion provided with a pin gate remains in the ground body obtained by grinding both surfaces of the green body after degreasing and sintering. 4. When injection molding a green body for a flat plate type rotary transformer core, at least three or more pieces are symmetrical about the center of the ring with the surface of the core green body where the plurality of concentric coil grooves are not provided as the border. It is molded using a mold that has a structure of a fixed mold that has an intermediate mold that forms the pin gate and the recess in the vicinity thereof, a movable mold that forms the coil groove, and a spool part that injects the melt into the mold. The green body for a flat rotary transformer core according to claim 1 or 2, characterized in that: