JPH0397113A - Rotary head assembly for magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To prevent a warp and a crack from being generated by the concentration of stress by smoothly forming a thickness change in the thin part of a rotary cylinder. CONSTITUTION:By forming a thin part 507, the temperature reduction of a forming material is supported, density in each part of a rotary cylinder 5 is equalized and shrinkage caused by cooling can be equalized. Further, recessed parts are prevented from being generated by the 'sink' of an outer peripheral surface 501. Namely, in the rotary cylinder 5, by smoothly changing the thickness in the thin part 507, the concentration of the stress generating in the edge of the thin part is prevented or relieved. Thus, the warp and the crack can be prevented from being generated by the concentration of the stress.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rotary head assembly of a magnetic recording/reproducing apparatus such as a video tape recorder or a digital audio table recorder, and particularly to an improvement of the rotary cylinder thereof.

[Conventional technology]

FIG. 4 is a vertical cross-sectional view of a rotary head assembly of a conventional magnetic recording/reproducing apparatus of the type described in, for example, Japanese Patent Application Laid-Open No. 63-164014, and FIG. 5 is an enlarged cross-sectional view of a main part of a conventional rotary cylinder. In a certain diagram, (υ is a magnetic tape, (2) is a magnetic tape (
1) The lead groove (201) that guides the outer peripheral surface (202)
a fixed cylinder (■ is a fixed cylinder (2), (4 is a bearing (hydraulic bearing in the case shown)), (S is a fixed cylinder (rotatable from a) via a bearing (4), (501) is the rotating cylinder (outer surface of the powder, (6) is attached to the rotating cylinder (0) and records information on the magnetic tape (1), or records information on the magnetic tape (υ). A magnetic head that reproduces the information being played, a rotary transformer that transfers information without contact between the magnetic head (■) and a stationary signal processing circuit (not shown), (8l is a rotating cylinder This is a motor that rotationally drives the rotary cylinder (9 is a bearing housing (502) for the bearing (4) and a magnetic tape (1).
a cylindrical part (503) that runs along its outer peripheral surface;
It consists of a disc part (504) which is coupled to this cylindrical part (503) and supports the magnetic head (0).

Next, the operation of the rotary head assembly will be explained. When the rotary cylinder (erect) is rotated by the motor (8), the magnetic head (6) also rotates around the central axis (rake), and is guided along the lead groove (201) to connect the fixed cylinder (a) and the rotating cylinder ( 51 outer peripheral surface (202), (
501) Information is recorded and reproduced on the magnetic tape (1) running thereon. At this time, information to be recorded or reproduced is exchanged between the magnetic head (0) and the signal processing circuit via the rotary transformer ('r).

By the way, the rotary cylinder (5) is generally formed by cutting a metal material because it is easy to achieve a certain level of accuracy, but since this cutting process requires a lot of time and effort, in recent years, efforts have been made to reduce costs. It is made of molded material such as plastic.

In a conventional rotary cylinder (5) molded with a molding material, a gate (9) provided in a mold (not shown) facing the center part (505) (through which the molding material flows into the mold) is used. A thin wall portion (507) is provided at the joint (506) between the cylindrical portion (503) and the disk portion (504) in order to compensate for the temperature drop due to heat radiation of the hollow material flowing into the mold from the inlet). In other words, the thin wall part (507) increases the flow resistance of the molding material, the heat generated by friction compensates for the temperature drop during the flow of the molding material, and the gate (odor) increases the flow resistance of the molding material. The temperature of the large material in the vicinity (50B) and the outer peripheral part (509), which is the end of the flow, is kept almost uniform.

By doing this, until the gate is cooled and closed, the rotating cylinder is supplemented with molding material to compensate for the shrinkage due to cooling in the mold.
As a result, the density of the molding material in each part of the rotating cylinder becomes equal, so the shrinkage of the molding material due to cooling (cooling inside the mold and cooling after taking it out from the mold) occurs evenly.
It has become easier to obtain the desired accuracy. In addition, the joint part (506)
is surrounded by the disk part (504) and the cylindrical part (503) and is cooled. Therefore, the surface of the cylindrical part (503) solidifies first, and then the inside solidifies and contracts. The solidified surface was pulled inward, creating a dent called a "sink mark" on the surface of the molded product, but by providing the above-mentioned thin wall part (507), the cooling of the joint part (506) was diverted from other parts. This makes it possible to prevent or reduce the occurrence of sink marks, making it easier to achieve the desired accuracy.

[Problem to be solved by the invention]

The rotary head assembly of a conventional magnetic recording/reproducing device is constructed as described above, and consists of a rotary cylinder (0 cylindrical part (
A thin wall portion (507) is formed at the joint (506) between the disk portion (503) and the disc portion (504);
Since the edge (510) of 07) is angularly shaped at an angle of approximately 90 degrees as clearly shown in FIG. Stress concentration occurs due to the filling pressure of the molding material, and as a result of this stress concentration, warpage and cracks occur at the edge portion (710) after the molding material is removed from the mold.
) There was a problem in that it was still difficult to ensure sufficient roundness, etc.

This invention was made in order to solve the above-mentioned problems, and is caused by stress concentration at the edge of the thin-walled part formed in the disc part at the joint between the cylindrical part and the disc part of the rotating cylinder. It is an object of the present invention to provide a rotary head assembly for a magnetic recording/reproducing device equipped with a rotary sill that can prevent or alleviate the occurrence of warpage and cracks and easily ensure a predetermined accuracy, especially the roundness of the outer peripheral surface. .

[Means to solve the problem]

A rotary head assembly for a magnetic recording and reproducing apparatus according to the present invention smoothes thickness changes in a thin portion of a disc portion of a rotary cylinder.

[Effect]

In the rotary cylinder according to the present invention, by smoothly changing the thickness of the thin wall portion, stress concentration occurring at the edge of the thin wall portion is prevented or alleviated.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. FIG. 1 is a longitudinal cross-sectional view of a rotary head assembly of a magnetic recording/reproducing apparatus according to an embodiment of the present invention, and FIG. 2 is an enlarged cross-sectional view of a main part of a rotary cylinder in the embodiment of FIG. Incidentally, the same or equivalent parts as those of the conventional one are given the same reference numerals, and the explanation thereof will be omitted.

In the figure, (9 is a rotating cylinder, and like the conventional cylinder, a thin wall part (507) is formed. Also, by forming a thin wall part (507), the temperature drop of the molding material is compensated for, It is possible to equalize the density of each part of the rotating cylinder (5) and equalize the shrinkage due to cooling, and furthermore, the outer peripheral surface (50
1) Preventing or mitigating the occurrence of dents due to "sink",
Similar to the conventional method, it is easy to obtain a predetermined accuracy (particularly the roundness of the outer peripheral surface (501), etc.).

In addition to these, the present invention is intended to smoothly change the thickness of the thin portion (507).

This prevents or alleviates the stress concentration that conventionally occurs at the edge (510), and prevents or suppresses the deterioration of accuracy due to warping or cracking caused by such stress concentration. As a method of smoothly changing the thickness of the thin wall portion (507), as shown in FIG. 2, the corner portion corresponding to the edge (510) has a radius of curvature R;
A typical method is to provide an inclined surface (511) as shown in FIG. 3, but any other shape may be used as long as the same effect can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, the thickness of the thin-walled portion of the rotating cylinder is shaped so as to change smoothly, thereby preventing or suppressing the occurrence of warping and cracking due to stress concentration at the corners of the thin-walled portion. , it becomes easier to obtain a predetermined accuracy (particularly the roundness of the outer circumferential surface, etc.) in the rotating cylinder, and there is an effect that high-precision rotating cylinders can be obtained in large quantities at low cost in a short time.

[Brief explanation of drawings]

1IN is a vertical cross-sectional view of a rotary head assembly of a magnetic recording/reproducing apparatus according to an embodiment of the present invention, FIG. 2 is an enlarged cross-sectional view of a main part of a rotary cylinder in the embodiment of FIG. 1, and FIG. FIG. 4 is an enlarged sectional view of a main part of a rotary cylinder in another embodiment, FIG. 4 is a longitudinal sectional view of a rotary head assembly of a conventional magnetic recording/reproducing apparatus, and FIG. 5 is an enlarged sectional view of a main part of a conventional rotary cylinder. In the figure, (1) is the magnetic tape, (force is the fixed cylinder, (201) is the beam groove, (202) is the outer circumferential surface, (3
is the central axis, (4 is the bearing, (S is the rotating cylinder, (501
) is the outer peripheral surface, (503) is the cylindrical part, (504) is the disc part, (506) is the joint part, (507) is the thin part, (511
) is an inclined surface, and (6) is a magnetic head. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] (1) A rotary head assembly for a magnetic recording and reproducing device that records and reproduces information on a magnetic tape, which includes a fixed cylinder having a lead groove on its outer circumferential surface for guiding the magnetic tape, and a fixed cylinder molded with a molding material. A rotary cylinder is rotatably supported through a bearing and a central axis, and supports a magnetic head for recording and reproducing information on the magnetic tape, and the rotary cylinder causes the magnetic tape to run along its outer peripheral surface. A rotary head assembly for a magnetic recording/reproducing device comprising a cylindrical part and a disc part coupled to the cylindrical part and supporting the magnetic head, wherein the disc part is connected to the cylindrical part at a joint between the disc part and the cylindrical part. 1. A rotary head assembly for a magnetic recording/reproducing device, characterized in that a thin wall portion is formed on a plate portion, and thickness changes in the thin wall portion are made smooth.