JPH03144910A - Rotary head assembly for magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To assemble a metallic die efficiently without causing a flaw on a center shaft of a fixed cylinder by decreasing the outer diameter of the center axis of the fixed cylinder to smaller than the positioning hole diameter of the metallic die and fitting a positioning pin of the metallic die to the hole provided on the center shaft. CONSTITUTION:A diameter D1 of a center shaft 3 of a fixed cylinder 2 is made relatively smaller than an inner diameter D2 so that the shaft is freely fit into a positioning hole 903 of a metallic die 9. A hole 304 is formed on the shaft end of the center shaft 3 in the axis direction and a positioning pin 905 is provided at the bottom of the positioning hole 903 of the metallic die 9. In the case of assembling a metallic die, the positioning hole 304 of the center shafter 3 is fitted to the positioning hole 903 of the metallic die 9 and a forming material is injected in the cavity 904. Thus, a flaw on the outer circumferential face 301 of the center shaft 3 resulting from scribing with the positioning hole 903 is avoided and the metallic die is assembled in a very short time and th productivity is improve.

Description

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

[Conventional technology]

Fig. 5 is a longitudinal sectional view of a rotary head assembly of a conventional magnetic recording/reproducing device, Fig. 6 is a longitudinal sectional view of a fixed cylinder of the 5FA, and Fig. 7 is a longitudinal sectional view of the fixed cylinder of Fig. 6 in a mold. FIG. 3 is a longitudinal cross-sectional view showing the state of molding.

In the figure, (1) shows the magnetic tape, and (2) shows the lead groove (201) that guides the magnetic tape (1) on the outer peripheral surface (202).
), (sum is the fixed cylinder (■), the central axis fixed to (301) is the central axis (outer circumferential surface of 3, (
302) is the center shaft (fixed cylinder (2) with a cutout formed on the outer circumferential surface (301) to prevent it from falling off, @) is the bearing, (5) is the bearing (fixed via the brown) A rotating cylinder rotatably supported from the cylinder (2), (501) is the outer peripheral surface of the rotating cylinder (0, (7) is a magnetic hekudo that reproduces information already recorded on a magnetic tape (υ). Rotary transformer for sending and receiving (0 is the rotating cylinder (
5).

Next, the operation of the rotary head assembly will be explained. When the rotary cylinder (5) is rotated by the motor <8), the magnetic head (Q) also rotates around the central axis (3) and is guided along the lead groove (201) to connect the fixed cylinder (force and rotary cylinder). (5) 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 (6) and the signal processing circuit via the rotary transformer (7).

By the way, the fixed 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.

To mold the fixed cylinder (21), use a mold (gl) as shown in Figure 7.
01) and a lower mold (902), the lower mold W (902
) is formed with a positioning hole (903) for holding the center shaft (3) in a predetermined position during molding. That is, during molding, one end (303) of the central axis (31) is located in the positioning hole (903).
It is inserted and held tightly. (10) is the upper mold (90
1) a nozzle of the molding machine disposed on the mold (101) for injecting the molding material into the cavity (904) in the mold (9);
) is a needle that controls opening and closing of the nozzle (10).

Therefore, in order to mold the fixed cylinder (2) using such a mold (GL), an upper mold (901) and a lower mold (901) are required.
02) and firmly fit the center shaft (marked one end (303)) into the positioning hole (903), then insert the upper mold (
901) and the lower mold (902), then close the nozzle (10
) is injected into the cavity 4 (904), and the central shaft ( ) and then remove the fixed cylinder (■) from the mold (9).

[Object to be solved by the invention 78] As mentioned above, when machining a fixed cylinder (□),
The center shaft (3) must be fitted into the positioning hole (903), but since the coaxiality of the fixed cylinder (desired outer peripheral surface (202) and center shaft (3) is required to be less than 5 μm, The fitting distance between the positioning hole (903) of the mold (91) and the center axis (east) must be less than that, for example, 2 μm or less, so the positioning hole (903) of the mold (91) must be adjusted in a short time, such as within a few seconds, to shorten the molding cycle. When trying to fit the center shaft (3) into the center shaft (○ is the positioning hole (903)
3) rub against the inner stirring surface of the central axis (the outer peripheral surface of the mark (301
) is scratched, and on the other hand, the outer peripheral surface (301
) If you try to avoid scratching the positioning hole (
903), it takes a lot of time to fit the center shaft (3) into the center shaft (3), which lengthens the molding cycle and reduces productivity.

However, if the central shaft (marked outer peripheral surface (301) is scratched, the bearing (when using a spiral group fluid bearing as shown in Figure 5 as a candle), the flow of lubricating oil will become uneven and the rotation will occur. If a ball bearing is used as the bearing (ψ), there will be problems such as run-out in the direction of the arrow (11) (Fig. 5) in the cylinder (Ω) or seizure between the center shaft (mark) and the rotating cylinder (6). In extreme cases, the outer peripheral surface (301) of the center shaft (■) may become uneven due to scratches, and in extreme cases, it may become impossible to fit the ball bearing onto the center shaft (3). Even if it is not possible, it will be difficult to fit them together, and even if they are fitted, there will be problems such as poor concentricity between the center shaft (cutout) and the ball bearing.

This invention is based on a magnetic field that allows the center shaft to be fitted into the positioning hole of a mold without damaging its outer peripheral surface, reducing the possibility of damage, and without requiring a long time. An object of the present invention is to provide a rotary head assembly for a recording/reproducing device.

[Means to solve the problem]

In order to achieve the above object, in the rotating head assembly of the present invention, the diameter of at least the portion of the central shaft to be inserted into the positioning hole of the mold is set relative to the inner diameter of the positioning hole so that it can be loosely fitted into the positioning hole. At the same time, an axial hole is formed at the center of the end of the central shaft to be inserted into the positioning hole, and this hole is fitted with a positioning pin formed at the center of the bottom of the positioning hole of the mold. The fixed cylinder is molded using the same method.

[Effect]

In the rotary held assembly configured as described above, the central axis is positioned in a predetermined position relative to the mold by fitting the axial hole formed in the central shaft into the positioning pin provided in the positioning hole of the mold. In addition, when fitting in this way, the diameter of the part of the central shaft inserted into the positioning hole is made smaller than the inner diameter of the positioning hole so that it can be loosely fitted into the positioning hole, so that the central shaft is Scratches caused by rubbing against the inner wall surface of the positioning hole are avoided, or at least the possibility of scratches is reduced. (Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 to 4. 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, FIG. 2 is a longitudinal cross-sectional view of a fixed cylinder shown in FIG. 1, and FIG. 3 is a vertical cross-sectional view of a fixed cylinder shown in FIG. 2. FIG. 4 is an enlarged partial sectional view showing a different configuration of the upper end of the central axis in the embodiment.

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, (3) is the central axis, and its diameter (Dl)
is the positioning hole (903) of the mold (9) as shown in Figure 3.
) of the positioning hole (903) so that the inner diameter (D
It is relatively smaller than the other. Also, the central axis (
fi (303) inserted into the positioning hole (903) of ■
An axial hole (304) is formed in the center of -
On the other hand, there is a central axis (3) at the center of the bottom of the positioning hole (903).
The positioning pin (90) corresponds to the axial hole (304) of
5) is provided. When molding the fixed cylinder, the center shaft (3) is positioned in a predetermined position by fitting the center shaft (3) into the positioning pin (905), and then the molding material is poured into the mold (gl). Cavite 4 (90
4) Inject inside.

Therefore, as mentioned above, the diameter (DI) of the center axis (3) is set relative to the inner diameter (D*) of the positioning large (903) so that the center axis (a) is loosely fitted into the positioning hole (908). By making the distance between the outer circumferential surface (301) of the central axis (3) and the inner wall surface of the positioning hole (903) smaller (G
) is larger than the conventional positioning hole (903) that holds and positions the center axis (3), and when inserting the center axis (mark) into the positioning hole (903), the center axis (the outer circumferential surface of the mark) The risk of the bearing (301) being scratched by rubbing against the positioning hole (903) is easily avoided without impairing productivity, and is at least less prone to scratches than the conventional bearing. Even if a hydrodynamic bearing is used as 4), it is possible to avoid or reduce problems such as the center shaft (3) wobbling as shown by the arrow (11) in FIG. Also,
When a ball bearing is used as the bearing (4), it may become impossible or difficult to fit the ball bearing to the center shaft (31), or there may be problems such as poor concentricity between the center shaft (a) and the ball bearing. This can be avoided or reduced.Furthermore, the central axis (3
) can be positioned without sacrificing predetermined accuracy by fitting the hole (304) formed in the center shaft (3) with the positioning pin (905) provided at the bottom of the positioning hole (903), as described above. be exposed.

By the way, the distance Elf (G) between the outer peripheral surface (301) of the central shaft (3) and the inner wall surface of the positioning hole (903) is approximately 2.
If it is 0 μ9 or more, it will actually be the outer peripheral surface of the central axis (3
1) can be prevented from being scratched. However, in order to prevent the molding material from flowing into the gap of 1 m (G) when injecting the molding material, the gap (()) should be set to approximately 30 μ vortex or less, although it depends on the viscosity of the molding material. is suitable. Of course, even if the molding material flows into the gap 1ffl (G) and sticks to the outer peripheral surface (301) of the central shaft (3), there is no problem as this can be removed with an appropriate solvent. As mentioned above, it is preferable to select the interval II (G) between approximately 20 and 30 μ vortices.
) is approximately 2 μm or less as in the conventional case, the outer peripheral surface (202) of the fixed cylinder (2) and the central axis ('5
The degree of coaxiality can be maintained within a predetermined range. In addition, the positioning pin (905) is shown in the lower mold (902).
), but it may be provided by attaching the S11 member by other suitable means such as press-fitting or interfacing.

Further, the description of the above embodiment will be continued. In the figure, (12
) is a fixed cylinder (after the force is removed from the mold (9),
A cap that covers the hole (304) of the central shaft (3),
The top surface (121) is used as a thrust fluid bearing that supports the load in the axial direction of the center shaft (3).
The shape of 121) may be flat as shown in Figure 4 (A), convex as shown in Figure 4 (A), or convex as shown in Figure 4 (A), depending on the performance required for the thrust fluid bearing. Figure←
As shown in →, it can be made into the shape of an equi-end chamber with a concave surface.

In addition, the cap (12) can be attached to the hole (304) of the center shaft (3), but if the center shaft (marked) satisfies the specified accuracy, press fitting, gluing, film fitting, cold fitting, etc. If a ball bearing is used as the bearing (4), the cap (12) may be omitted.

In the above embodiment, the diameter (Dl) of the center axis (■) is uniform over the entire length except for the undercut (302), but when forming the fixed cylinder (○), the diameter (Dl) of the mold (9) is uniform. It is sufficient that the diameter CDI) of the part inserted into the positioning hole (903) is relatively smaller than the inner diameter (D*) of the positioning hole (903), and the diameter of the part inserted into the other part, for example, the fixed cylinder (a) 903) may be equal to or larger than the inner diameter (D), or may be smaller than (D≧).

In addition, although the hole (304) of the center shaft (3) is shown as having a bottom, it can also be made into a through hole by changing the structure of the mold. can be used for example for wiring.

In addition, the outer peripheral surface (301) of the central axis (3) is undercut (3
In place of 02), other equivalent anti-dropping processing such as knurl processing may be used. Furthermore, the material for the center shaft (3) may be any material as long as it satisfies a predetermined rigidity and has a shrinkage rate comparable to that of the molding material for the fixed cylinder (7: J).

〔Effect of the invention〕

As described above, according to the present invention, the diameter of the center shaft and the inner diameter of the positioning hole of the mold are appropriately selected, and the hole in the axial direction for positioning is provided at one end of the center shaft. The effect of this method is that the center shaft can be fitted into the positioning hole of the mold without damaging the outer circumferential surface or reducing the possibility of damage, and without impairing productivity. It will be done.

[Brief explanation of the drawing]

IF! Figure 1 shows magnetic recording/reproduction I according to an embodiment of the present invention.
A longitudinal sectional view of the rotating head assembly of O@, ff12 is a longitudinal sectional view of the fixed cylinder of ff11, and Fig. 3 is a longitudinal sectional view showing the fixed cylinder of Fig. 2 being molded in a mold. , FIG. 4 is an enlarged partial sectional view showing a different configuration of the upper end of the central axis in the above embodiment, FIG. 5 is a longitudinal sectional view of a rotary head assembly of a conventional magnetic recording/reproducing device, and FIG. FIG. 7 is a vertical cross-sectional view of the fixed cylinder of the object, and is a vertical cross-sectional view showing the identification cylinder of FIG. 6 being molded in a mold. In the figure, (1) is the magnetic tape, (■ is the fixed cylinder, (3) is the central axis, (303) is the - princess, (304)
is an axial hole, (4) is a bearing, (5) is a rotating cylinder,
(0 is the magnetic head, (gl is the gold slip, (903) is the plaque hole, (904) is the cavity, (905) is the positioning pin, (10) is the nozzle. Note that the same symbols in each figure are the same. part or equivalent part.

Claims (1)

[Claims] (1) Molded by a mold into which molding material is injected into the cavity from the nozzle of the molding machine, a fixed cylinder that guides the running of the magnetic tape, and one end inserted into the positioning hole formed in the mold during the molding process. is inserted and retained, and has a central axis that is integrally identified by insert molding in the center of the identification cylinder, and is rotatably supported by the central axis via a bearing, and records and reproduces information on the magnetic tape. In a rotary head assembly for a magnetic recording and reproducing device, the diameter of at least a portion of the central shaft to be inserted into the positioning hole is set such that the diameter of at least the portion of the central shaft to be inserted into the positioning hole is loosely fitted into the positioning hole. a hole smaller than the inner diameter and an axial hole formed at the center of the one end;
A rotary head assembly for a magnetic recording/reproducing device, characterized in that the fixed cylinder is molded with this hole fitted into a positioning pin provided at the center of the bottom of the positioning hole.