JPH05101347A - Rotary head drum device - Google Patents

Abstract

PURPOSE:To provide a rotary head drum device keeping linearity in the locus of a normal magnetic head by eliminating that external force applying on a shaft in an assembling process of the rotary head drum device recording and reproducing to a magnetic tape damages the perpendicularity of the shaft. CONSTITUTION:The clearance of an outer peripheral part is constituted between the upper end surface 8a of a fixed drum 8 and the lower end surface 9a of the rotary drum 9 so that the deformation of a fixed shaft holding part 8b is limited to elastic deformation even when the force is applied on the fixed shaft support 8b of the fixed drum 8 in the assembling process of the device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary head drum device which can be used in a video tape recorder.

[0002]

2. Description of the Related Art FIG. 3 is a sectional view of a conventional rotary head drum device. Explaining this, 1 is a fixed drum for guiding a magnetic tape, 2 is a fixed drum having a herringbone type groove 2a processed by etching or the like at two upper and lower outer peripheral surfaces in the axial direction and an upper end surface 2b. A fixed shaft 3 which is coaxially press-fitted and fixed to the fixed shaft holding portion 1a of 1 is rotatable coaxially with the fixed shaft 2 and has a bearing surface 3 facing the herringbone groove 2a on its inner peripheral surface.
sleeve 4 having a, 4 is the upper end surface 2b of the fixed shaft 2
A thrust plate 5 having a spiral groove (not shown) on the lower end surface 4a facing the sleeve 3 and screwed to the sleeve 3, 5 is a rotary drum coaxially fitted to the sleeve 3 and screwed, and 6 is a rotary drum 5 A pair of magnetic heads screwed together, 7 is a minute gap between the herringbone type groove 2a and the bearing surface 3a, and the upper end surface 2b of the fixed shaft 2.
The lubricant is present in a minute gap between the lower end surface 4a of the thrust plate 4 and the thrust plate 4.

The operation of the conventional rotary head drum device configured as described above will be described below.

When the rotating part including the sleeve 3 of this rotary head drum device rotates, the herringbone type groove 2
By the pumping action of the radial bearing constituted by a, the bearing surface 3a and the lubricant 7, the centripetal property of the rotating portion is maintained, and further the spiral groove (not shown), the upper end surface 2b of the fixed shaft 2 and the lubricant 7 are provided. By the pumping action of the thrust bearing configured by, the stable floating position of the rotating portion can be obtained, and normal rotation can be maintained.

[0005]

However, in the above construction, as shown in the relationship between the force acting on the fixed shaft holding portion 1a and the linearity of the locus of the magnetic head 6 in FIG. In, for example, when the rotary drum 5 is screwed to the sleeve 3, a force P2 exceeding the maximum value P1 of the force that the fixed shaft holding portion 1a of the fixed drum 1 stays in the elastic deformation region acts on the fixed shaft holding portion 1a, There is a problem in that the holding portion 1a undergoes plastic deformation, the perpendicularity of the fixed shaft 2 is impaired, and the linearity of the locus of the magnetic head 6 is adversely affected.

[0006]

According to the present invention, a fixed drum for guiding a magnetic tape, a fixed shaft coaxially fixed to the fixed drum, a sleeve rotating coaxially with the fixed shaft, and an upper end surface of the fixed shaft are provided. The thrust plate fixed to the upper end surface of the sleeve, the rotary drum mounted on the sleeve and having a pair of magnetic heads, and the lubrication interposed in the minute gap between the outer peripheral surface of the fixed shaft and the inner peripheral surface of the sleeve. Agent, a lubricant interposed in a minute gap between the upper end surface of the fixed shaft and the lower end surface of the thrust plate, and a dynamic pressure generating groove provided on at least one of the outer peripheral surface of the fixed shaft and the inner peripheral surface of the sleeve, It consists of a dynamic pressure generating groove provided on at least one of the upper end surface of the fixed shaft and the lower end surface of the thrust plate. Where A is the force acting on the fixed shaft holding portion and B is the maximum force that the fixed shaft holding portion of the fixed drum stays in the elastic deformation region, the lower end surface of the rotating drum is received by the upper end surface of the fixed drum. , A ≦ B, the gap between the outer peripheral portion formed by the upper end surface of the fixed drum and the lower end surface of the rotating drum is set.

[0007]

The present invention has the above-described structure, and in the assembly process of this apparatus, even if a force is applied to the fixed shaft holding portion of the fixed drum, the straightness of the trajectory of the normal magnetic head is not impaired without impairing the verticality of the fixed shaft. Provided is a rotary head drum device capable of maintaining the property.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A rotary head drum device according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a rotary head drum device according to an embodiment of the present invention. To explain this, 2 is a fixed shaft having a herringbone type groove 2a and an upper end surface 2b, 3 is a sleeve having a bearing surface 3a, 4 is a thrust plate having a spiral groove (not shown) at the lower end surface 4a, and 6 is A pair of magnetic heads, 7 is a lubricant, and these have the same structure as the conventional example. 8 is a fixed drum for guiding the magnetic tape, 9
Is a rotary drum that is coaxially fitted to the sleeve 3 and screwed.

The operation of the rotary head drum device constructed as described above will be described below.

When the rotating part including the sleeve 3 rotates, the herringbone type groove 2a, the bearing surface 3a and the lubricant 7 are provided.
Due to the pumping action of the radial bearing constituted by, the centripetality of the rotating portion is maintained, and further the pumping action of the thrust bearing constituted by the spiral groove (not shown), the upper end surface 2b of the fixed shaft 2 and the lubricant 7. As described above, a stable floating position of the rotating portion can be obtained and normal rotation can be maintained, as in the conventional example. FIG. 2 shows a rotary drum 5 of a conventional rotary head drum device.
A vertical load is applied to the sleeve 3 at a position where the sleeve 3 is screwed, and the force acting on the fixed shaft holding portion 1a and the amount of displacement in the height direction near the outer periphery of the lower end surface of the rotating drum 5 at that time are obtained, and the relationship is shown. It is a thing. From this, at the maximum value P1 where the fixed shaft holding portion 1a of the fixed drum 1 stays within the elastic deformation amount region, the vicinity of the outer periphery of the lower end surface of the rotating drum 5 is displaced by t. The clearance between the outer peripheral portion formed by the upper end surface 8a and the lower end surface 9a of the rotary drum 9 is set to be t or less including the dimensional tolerance. Therefore,
When the rotating drum 9 is screwed to the sleeve 3 and the force acting on the fixed shaft holding portion 8b exceeds P1, the lower end surface 9a of the rotating drum 9 is received by the upper end surface 8a of the fixed drum 8, so that the fixed drum 8 is fixed. The force acting on the shaft holding portion 8b is P1 or less. Therefore, the fixed shaft holding portion 8
The deformation of b stays within the elastic deformation region, and the normality of the magnetic head 6 shown in FIG.
The linearity of the locus of can be maintained.

As described above, according to this embodiment, the deformation of the fixed shaft holding portion 8b is elastically deformed within the gap between the outer peripheral portion formed by the upper end surface 8a of the fixed drum 8 and the lower end surface 9a of the rotary drum 9. The linearity of the locus of the normal magnetic head 6 can be maintained by setting so that

[0012]

As described above, according to the present invention, the linearity of the trajectory of the normal magnetic head can be maintained.

[Brief description of drawings]

FIG. 1 is a sectional view of a rotary head drum device according to an embodiment of the present invention.

FIG. 2 is a relationship diagram of a force acting on a fixed shaft holding portion of a conventional rotary head drum device and a displacement amount in a height direction near an outer periphery of a lower end surface of the rotary drum.

FIG. 3 is a sectional view of a conventional rotary head drum device.

FIG. 4 is a diagram showing the relationship between the force acting on the fixed shaft holding portion and the linearity of the locus of the magnetic head.

[Explanation of symbols]

 2 fixed shaft 2a herringbone type groove 2b upper end surface 3 sleeve 3a bearing surface 4 thrust plate 4a lower end surface 6 magnetic head 7 lubricant 8 fixed drum 8a upper end surface 8b fixed shaft holding portion 9 rotating drum 9a lower end surface

Claims (1)

[Claims] 1. A fixed drum that guides a magnetic tape, a fixed shaft coaxially fixed to the fixed drum, a sleeve that rotates coaxially with the fixed shaft, and an upper end surface of the fixed shaft that faces the fixed drum. A thrust plate fixed to the upper end surface of the sleeve, a rotary drum mounted on the sleeve and having a pair of magnetic heads, and a lubricant interposed in a minute gap between the outer peripheral surface of the fixed shaft and the inner peripheral surface of the sleeve. A lubricant intervening in a minute gap between the upper end surface of the fixed shaft and the lower end surface of the thrust plate, and for generating a dynamic pressure provided on at least one of the outer peripheral surface of the fixed shaft and the inner peripheral surface of the sleeve. A groove and a groove for dynamic pressure generation provided on at least one of the upper end surface of the fixed shaft and the lower end surface of the thrust plate. In the assembling process, when the force acting on the fixed shaft holding portion of the fixed drum is A and the maximum value of the force that the fixed shaft holding portion of the fixed drum stays in the elastic deformation region is B, the lower part of the rotating drum is A rotary head drum, characterized in that an end surface is received by the upper end surface of the fixed drum, and a gap between an outer peripheral portion formed by the upper end surface of the fixed drum and the lower end surface of the rotary drum is set so as to satisfy A ≦ B. apparatus.