JPH07129935A - Head drum - Google Patents

Abstract

PURPOSE:To sufficiently exhibit a fluid lubricating effect and to smoothly rotate a rotary drum at a high speed by forming a fluid bearing for rotatably supporting the rotary drum on a stationary drum by forming the grooves necessary for its journal part of plural molded materials, subjecting these materials to plating or forming the same by a combination of the molded materials different in the coefft. of thermal expansion. CONSTITUTION:Molding of spiral groove patterns 2 is conducted by using halved metal molds 3a, 3b for primary molding and molding the spiral groove patterns 2 in a relief shape by a resin 3 with which a plating treatment is infeasible, as shown in the section of the primary molding. Next, a resin 4 with which the plating treatment is feasible is insert molded between the patterns 2 formed in relief by using halves metal molds 4a, 4b for secondary molding to form a circular columnar shape which is exposed with the patterns 2 formed in relief by the secondary molding, has a smooth surface and has the prescribed accuracy of out-of-roundness and outside diameter. The molded goods obtd. by molding and finishing to the prescribed accuracy in such a manner are subjected to a plating treatment, by which a plating layer 5 is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a tape-shaped recording medium in a recording or reproducing apparatus such as a video tape recorder (hereinafter referred to as VTR) for recording a signal or reproducing a recorded signal, and a helical recording medium. The present invention relates to a head drum in which signals are recorded or reproduced by a rotating head that is in contact with each other.

[0002]

2. Description of the Related Art FIG. 7 is a sectional view showing an example of a head drum provided in a conventional VTR.

The head drum comprises a rotary drum 7, a fixed drum 8 and a head 10 which slides on a magnetic recording tape to record or reproduce a signal. And the drive coil 1 of the brushless motor that drives the rotating drum 7.
1 and recording in the rotating head 10 and VTR device
Rotation transformer 12 which is a signal transmission means to and from the reproduction circuit
Is built in.

In the illustrated example, the shaft 13 is fixed to the rotary drum 7, and the shaft 13 is rotatably supported by the fixed drum 8 by the ball bearing 14. However, the shaft 13 is fixed to the fixed drum side and is fixed to the rotary drum 7 side. There is also an example of a configuration in which the ball bearing is fixed to the rotary drum 7 so as to be rotatable.

In recent years, due to the problems of high-speed rotation of a rotating drum accompanying high-density recording and noise, the shaft can be rotated smoothly and at high speed with the shaft completely floating from the bearing surface. Tend to be used.

[0006]

SUMMARY OF THE INVENTION In the above fluid bearing,
In order to exert a fluid lubrication effect, it is necessary to precisely form a shallow groove (hereinafter, referred to as a groove) in a spiral pattern on a surface of a shaft surrounded by the bearing portion (hereinafter, referred to as a journal).

However, it is very difficult to form the above spiral groove pattern by machining. Generally, a method of forming a spiral groove pattern by etching is adopted, but the productivity is low. In recent years, the VTR has a smaller shaft diameter for downsizing. Therefore, it is difficult to form the groove by etching in order to satisfy the required performance by controlling the groove depth to several μm. ing.

The present invention has been made to solve the above-mentioned conventional problems, and provides a head drum capable of easily forming a precise spiral groove pattern of a fluid bearing to reduce the cost. The purpose is.

[0009]

For this reason, a head drum according to the present invention comprises a fixed drum and a rotary drum rotatably supported by a fluid bearing on the fixed drum so that a tape-shaped recording medium is helically formed. A head drum for contacting and recording a signal on a recording medium or reproducing a recorded signal by a head mounted on a rotary drum, wherein a groove of a journal portion of the fluid bearing is formed by a plurality of molding materials. The above-mentioned object is to be achieved by the constitution characterized by the above.

[0010]

With the above-described structure, the head drum has a plurality of molding materials, for example, a plating material capable of plating and a groove necessary for the journal portion of the fluid bearing for rotatably supporting the rotating drum on the fixed drum. Grooves in the journal can be easily and precisely formed by forming with a molding material, plating, or by combining molding materials with different thermal expansion coefficients, and sufficient fluid lubrication effect is achieved. The rotary drum can be rotated smoothly and at high speed.

[0011]

EXAMPLES A head drum according to the present invention will be described below with reference to examples.

FIG. 1 is a cross-sectional view of one embodiment, in which the same or corresponding portions as those of the conventional example are designated by the same reference numerals, and a duplicated description will be omitted.

In this embodiment, the shaft 1 is fixed to the fixed drum 8, and the rotating member 6 fixed to the rotating drum 7 is rotatably fitted and attached to the shaft 1 with a predetermined gap. ing.

A spiral groove pattern 2 is formed in the journal portion of the shaft 1 inserted in the rotating member 6, and a fluid bearing is formed with the corresponding portion of the rotating member 6.

The shaft 1 may be fixed to the rotary drum 7 side, a fluid bearing may be formed between the shaft 1 and the fixed drum 8 side, and the shaft 1 may be rotatably inserted.

Next, the forming process of the spiral groove pattern 2 which is a feature of this embodiment will be described with reference to the sectional view of FIG. 2 and FIG.
Will be described with reference to the external view of FIG.

First, as shown in the cross section of the primary molding of FIG. 2 (a), a resin 3 which cannot be plated is used by using two primary molding dies 3a and 3b. The spiral groove pattern 2 is formed into a relief shape and formed as shown in FIG.

Next, the resin 4 which can be plated between the embossed patterns 2 is formed by using the two-part secondary molding dies 4a and 4b shown in FIG. 2 (b). As shown in FIG. 3 (b), the pattern 2 that is embossed in the primary molding is exposed and the surface is smooth, and is formed into a columnar shape having a predetermined roundness and accuracy of the outer diameter. To do. If necessary, precision is achieved by grinding or the like.

As shown in FIGS. 2 (c) and 3 (c), the spiral formed at the beginning is subjected to a plating process as a third process on the molded product which has been molded as described above and whose accuracy has been improved. The plating layer 5 is formed on the portion other than the groove pattern 2.

As the resin 3 for primary molding and the resin 4 for secondary molding, for example, liquid crystal polymer, ordinary grade such as polyphenylene sulfide (PPS), and grade capable of plating are used. As the plating layer, for example, a plating layer having a thickness of 3 to 10 μm can be formed by nickel plating.

(Other Embodiments) FIG. 4 is an external view showing a state of primary molding for forming a spiral groove pattern of another embodiment, and FIG. 5 is a partially enlarged sectional view of the primary molding. is there.

In the above-described embodiment, the resin 3 which cannot be plated is used for the primary molding, but in this embodiment, the primary molding is performed by forming the pattern of the convex portion of the spiral groove pattern as shown in FIG. Is molded with a resin 4 that can be plated, and the resin 3 that cannot be plated is used for the secondary molding to fill the concave portion, and the molded product with precision is plated as the third processing. By performing the process 5, the plating layer 5 is formed on the spiral groove pattern portion as shown in FIG. 5, whereby the spiral groove pattern 2 similar to that in the above-described embodiment can be formed. 9
Is a resin hole formed for resin penetration in the secondary processing.

Further, in the primary molding, as in the above-described embodiment, the pattern of the convex portion of the spiral groove pattern is molded as shown in FIG. 4, and the secondary molding is performed by using the material 4a of the primary molding. It is also possible to form the groove by molding shrinkage as shown in the enlarged cross-sectional view of FIG. 6 by molding the material 3a having a large thermal expansion coefficient. In this example, the primary molding material 4a uses polyphenylene sulfide (PPS) and the secondary molding material 3a uses polyacetal (POM).

[0024]

As described above, according to the present invention, the fluid bearing for rotatably supporting the rotary drum on the fixed drum has a plurality of mold materials, for example, a moldable material for forming grooves required for the journal portion. The groove of the journal part can be easily and precisely formed by forming it with a non-platable mold material, plating it, or forming a combination of mold materials with different thermal expansion coefficients. The lubricating effect can be sufficiently exerted, the rotating drum can be smoothly rotated at high speed, and the cost can be reduced.

Furthermore, the plating treatment improves wear resistance and slidability, and can reduce the load at the time of starting.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment.

FIG. 2 is an explanatory cross-sectional view of processing a spiral groove pattern according to an embodiment.

FIG. 3 is an explanatory external view of processing of a spiral groove pattern according to an example.

FIG. 4 is an explanatory external view of processing a spiral groove pattern according to another embodiment.

FIG. 5 is an enlarged partial external view of processing of a spiral groove pattern according to another embodiment.

FIG. 6 is an enlarged partial external view of processing of a spiral groove pattern according to another embodiment.

FIG. 7 is a sectional view of a conventional head drum.

[Explanation of symbols]

 1 Shaft 2 Spiral groove pattern 3 Resin that cannot be plated 3a, 3b Primary molding die 4 Resin that can be plated 4a, 4b Secondary molding die 5 Plating layer 6 Rotating member 7 Rotation Drum 8 Fixed drum 10 Head

Claims (3)

[Claims] 1. A tape-shaped recording medium, which comprises a fixed drum and a rotating drum rotatably supported by a fluid bearing on the fixed drum, is brought into helical contact with the recording medium by a head attached to the rotating drum. Signal recording,
A head drum for reproducing a recorded signal, wherein the groove of the journal portion of the fluid bearing is formed by a plurality of molding materials. 2. A head drum according to claim 1, wherein the head drum is formed of a moldable mold material and a non-platable mold material, and is plated to form the groove of the journal portion. 3. The head drum according to claim 1, wherein the groove of the journal portion is formed by a combination of molding materials having different thermal expansion coefficients.