JPH07334825A - Rotary head drum device - Google Patents

Abstract

PURPOSE:To enable a high density recording/high data rate recording/editing by improving the accuracy of the revolving part of a drum part revolving at a high speed. CONSTITUTION:A rotary shaft 19 is force-fitted into a middle drum 3 to which a magnetic head 1 is fitted and is held freely rotatably by upper and lower rolling bearings 20 21. The outer rings of rolling bearings 20, 21 are held by a second fixed drum 17. The wedge part 43a of a ring member 43 is inserted into the gap between the inner ring of the rolling bearing 21 and the rotary shaft 19 to eliminate the gap. Moreover, the deflection of the rotary shaft 19 at the time of the high-speed revolution is suppressed by forming respectively a first correcting groove 47 (attached to a lower shielding member 46), a second correcting groove 48 (attached to a disk 42) and a third correcting groove 50 (attached to a motor rotor 49) at positions including respective centroides of constituting parts revolving together with the rotary drum, thereby correcting dynamic balances.

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 used in a VTR or DAT for recording at high recording density and high data rate.

[0002]

2. Description of the Related Art Conventionally, a magnetic recording / reproducing apparatus such as a VTR (VHS system video tape recorder) and a DAT (digital audio tape recorder) has a rotating drum equipped with a magnetic head and a magnetic tape (hereinafter referred to as a tape). It has a structure with a fixed drum provided with a lead that guides the running of the call), but recently, in the trend of digitization of video signals and high density recording (HD), high data rate recording In order to increase the recording bandwidth, a large-diameter drum is used and a method of increasing the number of rotations of the drum is adopted.

When a drum having a relatively large diameter is used as described above, a rolling bearing is often used as a supporting component of the rotary drum, and the structure of the drum device inevitably results in a space between the rolling bearing and the rotary shaft. A gap occurs. This gap causes tilting of the rotating shaft and tilting of the rotating drum, which in turn causes the deviation of the scanning locus and vibration of the magnetic head itself, which requires highly accurate scanning. As a countermeasure against this problem, Japanese Patent Application Laid-Open No. 3-19121 discloses an example in which a collar having a tapered tip is pressed against an edge portion of an inner ring of a rolling bearing to eliminate a gap.

Now, let us consider a problem relating to the clearance between the rotary shaft and the inner ring of the rolling bearing. With respect to this problem, it is difficult to take practical measures because the gap is too small, and at present, the problem is avoided by selectively fitting the rotary shaft and the rolling bearing. However, this method is not sufficient in view of future high precision in addition to taking time and effort. Further, in the conventional dynamic balance correction method for a rotary body, the magnetic head height is adjusted to near the allowable limit for a VTR for commercial use or the like, which has a high speed rotation and a large diameter drum at present. Considering performance improvement such as high density recording in the next period, there is a great possibility that the drum will rotate at a higher speed as the performance becomes higher. In that case, the centrifugal force increases and the change in the height of the head due to the bending of the rotating shaft cannot be ignored, and a reliable recording / reproducing operation is hindered. Conventional countermeasures against such problems are shown in FIGS. 7 and 8.
Will be explained.

FIG. 7 is a sectional view showing the structure of the main part of a conventional VTR drum unit. In FIG. 7, the drum unit is configured to include, from the top, a fixed upper drum 16, a middle drum 3 to which the magnetic head 1 is attached and which rotates, a fixed lower drum 17 having a rotation drive motor built therein, and the like. The magnetic head 1 is attached to the outer periphery of the middle drum 3, and the disk 18 positioned inside is press-fitted onto the rotating shaft 19 to be rotatably held with respect to the lower drum 17. A rolling bearing 2 for rotatably holding the rotating shaft 19 of the middle drum 3 is provided at the center of the lower drum 17.
0 and 21 are provided. The upper drum 16 and the lower drum 17 are fixed from the outside by a U-shaped connecting jig (not shown).

The rolling bearings 20 and 21 are fixed by lightly press-fitting or shrink-fitting the outer ring portion thereof into the housing portion of the lower drum 17. The ring member 22 is a ring-shaped member that is in contact with the inner ring of the rolling bearing 21. The ring member 22 is in a state of being bent by applying a predetermined load to the leaf spring 23, and the fixing member 24 is fixed to the rotating shaft 19 with a screw (not shown), so that the inner ring of the rolling bearing 21 is preloaded. There is. Due to this preload, the rolling bearings 20 and 21 have no gaps between the outer and inner rings and the central ball,
At the same time, the bearing rigidity is increased and a stable rotation support function is obtained.

The circuit board 25, together with the upper shield member 26 and the lower shield member 27, is fixed to the disk 18 by screws 28. A corner portion 29 is provided on the upper surface of the upper shield member 26 so that a correction weight (not shown) can be installed as a dynamic balance correction surface of the middle drum 3. On the other hand, rotary rotary transformer 3
No. 0 is bonded to the lower part of the disc 18, and the lower drum 1
Signals are transmitted and received facing the fixed rotary transformer 31 fixed to 7.

The motor stator 33 is fixed to the lower drum 17, and the motor rotor 34 is fixed to the rotary shaft 19 to form a rotary drive motor for the middle drum 3. The rotating shaft 19, the disk 18, and the intermediate drum 3 are integrally rotated by this drive motor. In order to correct the dynamic balance of such rotating components, a correction weight is added to one surface axially distant from the center of gravity of each rotating body for convenience of workability and efficiency, and a necessary mass is added by a drill or the like. I used to delete it with a tool. With such a configuration, the magnetic head 1 attached to the middle drum 3 rotates to exchange signals with a tape (not shown) wound obliquely around the lower drum 17 for recording or reproduction.

[0009]

FIG. 8 is a partial cross-sectional view of FIG. 7, showing in detail the positional relationship among the rolling bearings 20 and 21, the rotary shaft 19, and the intermediate drum 3. Further, FIG. 9 schematically shows a recording or reproducing locus on the magnetic tape 36. Here, the magnetic tape 36 is the lower drum 1.
7 shows an example in which it is wound about 180 °. In the rolling bearing configuration as described above, due to variations in dimensional accuracy,
A minute gap is inevitably generated between the inner ring of the rolling bearing and the rotary shaft. When rotating, the rotating shaft 1 as shown in FIG.
9. Further, since the middle drum 3 supported by the rotating shaft 19 rotates while tilting, the magnetic head 1 located on the outer periphery of the middle drum 3
The scanning locus of is displaced from the ideal plane P shown in FIG.

That is, if the scanning locus of the magnetic head 1 is in the ideal plane P during recording, the track recorded on the magnetic tape 36 will be linear as shown by the solid track 37 in FIG. On the other hand, when tilted as shown in the drawing and deviated from the ideal plane P, for example, an arc shape is formed as shown by a broken line track 38 in FIG. 9, and a track deviation from the ideal track 37 occurs. 8 and 9 are exaggerated for convenience of explanation, the magnetic head 1 is in an inclined state as shown in FIG. 8, and various arc-shaped scanning loci including the example shown in FIG. When the VTR is formed, a deviation occurs between the recording track and the reproduction track when the VTR is compatible, and a so-called track deviation occurs. Due to this track deviation, a sufficient signal output cannot be obtained, the image quality is deteriorated, and if the narrow track which is one of the high-density recording methods is used, image noise is more likely to occur.

Next, due to the gap between the rolling bearings 20 and 21 and the rotary shaft 19, vibration occurs when the intermediate drum 3 rotates,
Various obstacles occur on the noise side and others. FIG. 10 is a schematic and exaggerated view of the state of dynamic balance correction of the disk 18 and the rotary rotary transformer 30. In FIG. 10, the middle drum 3 and the disk 18 have relatively good processing accuracy, and there are few unbalance factors. On the other hand, the rotary rotary transformer 30 is not well balanced due to the non-uniformity of the material surface and the winding and winding groove (both not shown). Therefore, there is an unbalanced mass point 39 that needs correction near the center of gravity of the rotary rotary transformer 30.

To correct the dynamic balance of the drum unit having such a structure, the corner portion 32 of the disk 18 is corrected.
In addition, a correction weight M that balances the unbalanced mass point 39 near the center of gravity of the rotary rotary transformer 30 is added to the opposite position. When the balance is corrected in this way, the unbalanced surface, which actually exists near the center of gravity, and the correction surface for balancing often largely separate in the axial direction. If you make such a balance adjustment,
When the middle drum 3 rotates, centrifugal force acts on each of the unbalanced mass point on the unbalanced surface and the modified mass point on the modified surface to generate a couple, and a moment for bending the rotating shaft 19 acts. However, in this state, even if the dynamic balance is corrected, the correction weight M and the unbalanced mass point of the rotary rotary transformer 30 are separated by the distance d in the axial direction. Therefore, a couple of forces are generated by the centrifugal force f indicated by the arrow generated when the middle drum 3 rotates, and the rotating shaft 1
Bending moment m = d × f is applied to 9. As a result, the middle drum 3 supported by the rotating shaft 19 is also tilted, and the height of the magnetic head 11 on the middle drum 3 changes on the tape.

Therefore, the rotary shaft 19 has a broken line R shown in FIG.
As described above, the rolling bearings 20 and 21 are curved as fulcrums, and at the same time, the middle drum 3 supported by the rotating shaft 19 rotates in an inclined state. Therefore, the magnetic head 1 on the middle drum 3 moves to the position of the broken line Q and its height changes. When recording is performed in such a state, the recording track width becomes non-uniform, and there is a high possibility that the output of the reproduction signal of the narrow track becomes insufficient. Especially, in the narrow track state at the time of high-density recording, it becomes large. It becomes a problem.

The present invention has been made in view of the above conventional problems, and in the rotary head drum device, it eliminates the gap between the rotary shaft and the inner ring of the rolling bearing, and is relatively simple and inexpensive. It is an object of the present invention to provide a rotary head drum device having a simple structure and capable of high-speed rotation and high density.

[0015]

According to the invention of claim 1 of the present application, a first fixed drum and a lead for guiding the running of the tape are formed, and a second fixed drum is mounted coaxially with the first fixed drum. A fixed drum, an intermediate drum that is rotatably mounted between the first fixed drum and the second fixed drum, and has a magnetic head, and a first rolling bearing and a second rolling bearing with respect to the second fixed drum. A rotary head drum device comprising a rotary shaft rotatably supported via a bearing and holding an intermediate drum, wherein a wedge-shaped tip is formed in a gap formed between an inner ring of the first rolling bearing and the rotary shaft. The first part is designed to enter
No. 2 ring member and a wedge portion that enters a gap formed between the inner ring of the second rolling bearing and the rotating shaft, and a plurality of slits notched in the rotating shaft direction are provided symmetrically with respect to the central axis. It is characterized in that a ring member and a biasing member for biasing the second ring member in the direction of press-fitting into the rotary shaft are provided.

According to a second aspect of the present invention, there is provided a first fixed drum, a second fixed drum formed with a lead for guiding the running of the tape, and mounted coaxially with the first fixed drum.
A rotary head drum device comprising: a first fixed drum and a second fixed drum rotatably attached, and a middle drum having a magnetic head, wherein the middle drum is a component forming the middle drum. The present invention is characterized in that a dynamic balance correction portion for a component is provided on a surface including the center of gravity of the component and perpendicular to the rotation axis of the middle drum.

[0017]

According to the invention of claim 1, the wedge-shaped tip of the first ring member enters the gap between the inner ring of the first rolling bearing and the rotary shaft. Further, the wedge portion of the second ring member enters the gap between the inner ring of the second rolling bearing and the rotating shaft. Then, the second ring member is elastically deformed by receiving the preload, and the gap (play) between the inner ring of the second rolling bearing and the rotating shaft is eliminated to suppress the inclination of the rotating shaft. Further, when the second ring member is rotated, a centrifugal force causes a force to spread from the slit portion, and further presses the inner ring of the second rolling bearing and the rotating shaft, so that no gap is generated. Therefore, the middle drum and the magnetic head rotate accurately and stably.

According to the invention of claim 2 of the present application, the dynamic balance is corrected by providing the dynamic balance correcting portion for the component rotating with the intermediate drum. This makes it possible to balance the rotor with the axial distance between the unbalanced mass point and the corrected mass point near the center of gravity of the component parts reduced. Therefore, the bending moment of both mass points with respect to the rotation axis due to the centrifugal force can be suppressed.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A rotary head drum device according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a sectional view showing the structure of the main part of the drum unit 40A of the first embodiment. The same parts as those in FIG. 7 showing the conventional example are designated by the same reference numerals, and the description thereof will be omitted.

In FIG. 1, the disk 42 is slightly different from the disk 18 shown in FIG. 7 in the shape of the central shaft portion. The disk 42 has a wedge-shaped tip portion 42 at a portion fitted with the rotating shaft 19.
It is assumed to include a first ring member having a formed therein. The tip portion 42a is formed by forming a wedge-shaped portion in contact with the inner ring of the rolling bearing 20, and is integrally formed with a boss in the central portion of the disk 42. Here, a ring member having a wedge portion at its tip may be separately prepared, and this ring member may be press-fitted onto the rotary shaft 19 together with the disc 42. Thus, there is no gap between the rotary shaft 19 and the inner ring of the rolling bearing 20.

The second ring member 43 shown in the lower part of FIG.
Is inserted in the gap between the inner ring of the rolling bearing 21 and the rotary shaft 19 with the upper portion thereof as a wedge portion 43a. FIG. 2 is a perspective view showing the outer appearance of the ring member 43. As shown in FIG. 2, a wedge portion 43a that enters the inner ring of the rolling bearing 21 of FIG.
In the radial direction, two slits 43b are provided axially symmetrically,
Further, the slits 43d are provided at two axially symmetrical positions on the flange portion 43c formed under the wedge portion 43a so as to facilitate the outward deformation. Then, when a preload is applied to the rolling bearing 21 via the ring member 43 by the leaf spring 23 and the fixing member 24 shown in FIG. 1, the ring member 43 elastically deforms and spreads outward, and the rolling bearing 20 and the rotary shaft 1
It is possible to eliminate rattling.

Next, the ring member 4 will be described with reference to FIGS. 3 and 4.
The operation of No. 3 will be described in detail. 3 and 4 are cross-sectional views of a necessary portion of FIG. 1, and FIG. 3 shows a state before the ring member 43 is assembled. From this state, the wedge portion 43a of the ring member 43 is moved to the inner ring of the rolling bearing 21 and the rotary shaft 19 as shown in FIG.
Then, it is fixed by applying a predetermined preload using the leaf spring 23 and the fixing member 24. With this, the force of the leaf spring 23 and the deformation effect of the slit 43b cause the ring member 43 to move.
The wedge portion 43a is elastically deformed inward. Then, the flange portion 43d of the ring member 43 fills the gap while elastically deforming outward.

In this way, the gap between the inner ring of the rolling bearing 21 and the rotary shaft 19 can be eliminated under the preload condition. Further, by making the structure of the ring member 43 as shown in FIG. 2, when the rotating shaft 19 rotates, the ring member 4
3 is subjected to centrifugal force, and the flange portion 43 of the ring member 43 is
c tends to spread further outward. For this reason, the restriction force of the ring member 43 on the rolling bearing 21 and the rotary shaft 19 increases, so that the above-mentioned effect of eliminating the gap is surely ensured.

FIG. 5 is a perspective view showing a modification of the ring member 44. In this ring member 44, slits are provided in the wedge portion and the flange portion at three locations, respectively. This makes elastic deformation of the ring member 44 easier. The slits of the ring member are not limited to those in this embodiment, and any number of slits may be provided. Also, the material is not particularly limited. Further, the means for applying the preload is not limited to the leaf spring described in this embodiment, but a coil spring or the like may be used.

Next, a rotary head drum device according to a second embodiment of the present invention will be described with reference to FIGS. 1 and 6. In the drum unit 40B shown in FIG. 1, the circuit board 25 is fixed to the disc 42 by screws 28 together with the upper shield member 45 and the lower shield member 46 as in FIG. A first correction groove 47 is provided on the outer circumference of the lower shield member 46. The correction groove 47 is a dynamic balance correction portion provided on the surface on which the center of gravity of the combined unit of the upper shield member 45, the circuit board 25, and the lower shield member 46 is present. Further, the disk 42 is provided with a second correction groove 48 at a position close to the center of gravity of the rotary rotary transformer 30. The correcting groove 48 is a correcting portion for adjusting the dynamic balance of the rotary rotary transformer 30. Further, a third correction groove 50 is also provided on the outer peripheral portion of the motor rotor 49. The correction groove 50 is a motor rotor 49.
Is a correction portion that is provided in the vicinity of the center of gravity of the motor and adjusts the dynamic balance of the motor rotor 49.

The drum unit 40 constructed in this way
The operation of the composite unit of the disk 42 and the rotary rotary transformer 30 in B will be described with reference to FIG.
FIG. 6 is a cross-sectional view showing the configuration of the main part of FIG. In FIG. 6, before fixing the middle drum 3, the dynamic balance of the disc 42 to which the rotary rotary transformer 30 is adhered is corrected. The dynamic balance correction is performed by attaching a rotating body including the middle drum 3 to a balancing machine and adding a correction weight to the correction groove 48, or by deleting a specific portion of each groove with a drill or the like. However, the rotary transformer 30 on the rotating side
Of the unbalanced mass 51 near the center of gravity of the
As described above, the correction weight 52, which is attached to the opposite side with the pinch sandwiched therebetween, is separated by a very small distance e in the axial direction. Therefore, even if the centrifugal force f generated when the middle drum 3 rotates is generated in the direction of the arrow, the bending moment m with respect to the rotating shaft 19 is m.
= E × f, and the value becomes small. Therefore, the bending of the rotary shaft 19 can be almost ignored.
As a result, the middle drum 3 and the magnetic head 1 fixed on the disk 42 can also rotate in a stable state without inclination.

In FIG. 6, the composite unit of the disk 42 and the rotary rotary transformer 30 is explained, but the correction groove 47 of the circuit board 25 and the motor rotor 49,
Similarly for 50, the dynamic balance is corrected. Further, the present embodiment can be applied to a rotating drum such as the middle drum 3 or the like.

[0028]

According to the first aspect of the present invention, it is possible to suppress the tilt of the rotary shaft by eliminating the gap between the rotary shaft and the rolling bearings that support the rotary shaft. Also, claim 2 of the present application
According to the invention, the dynamic balance correction surface can be set so that the unbalanced mass point of the rotating body and the mass point for correction thereof do not largely shift in the axial direction. By doing so, an excessive bending moment is not applied to the rotary shaft, and the rotary shaft can be rotated without being deformed. As a result, the rotary drum and the magnetic head supported by the rotary shaft rotate with high accuracy and low noise, and a VTR with high image quality without noise can be provided. In particular, the present invention is effective for high-density recording and high-speed rotation type VTRs such as those for business use or high definition.

[Brief description of drawings]

FIG. 1 is a front view of a drum unit in a rotary head drum device according to first and second embodiments of the present invention.

FIG. 2 is a perspective view of a ring member (No. 1) attached to the drum unit of the first embodiment.

FIG. 3 is a sectional view (No. 1) showing the action of the ring member of the first embodiment.

FIG. 4 is a sectional view (No. 2) showing the action of the ring member of the first embodiment.

FIG. 5 is a perspective view of a ring member (No. 2) attached to the drum unit of the first embodiment.

FIG. 6 is a sectional view showing the operation of the drum unit of the second embodiment.

FIG. 7 is a cross-sectional view showing a configuration example of a conventional drum unit.

FIG. 8 is a sectional view of a main portion of a conventional drum unit.

FIG. 9 is an explanatory diagram of recording tracks on the tape.

FIG. 10 is a cross-sectional view showing an operation example of a conventional drum unit.

[Explanation of symbols]

 1 Magnetic Head 3 Middle Drum 16 First Fixed Drum 17 Second Fixed Drum 19 Rotating Shaft 20, 21 Rolling Bearing 23 Leaf Spring 24 Fixing Member 25 Circuit Board 28 Screw 30 Rotating Side Rotary Transformer 31 Fixed Side Rotary Transformer 33 Motor Stator 40A, 40B Drum unit 42 Disc 42a Tip part 43, 44 Ring member 43a Wedge part 43b, 43d Slit 43c Flange part 45 Upper shield member 46 Lower shield member 47, 48, 50 Correction groove 49 Motor rotor 51 Unbalanced mass point 52 Correction weight

Claims (2)

[Claims] 1. A first fixed drum, a second fixed drum formed with a lead for guiding the running of a tape, and coaxially attached to the first fixed drum; the first fixed drum; A middle drum having a magnetic head, which is rotatably mounted between the second fixed drum, and a first rolling bearing and a second rolling bearing with respect to the second fixed drum.
A rotary head drum device, which is rotatably supported via a rolling bearing and holds the middle drum, and which occurs between an inner ring of the first rolling bearing and the rotary shaft. The first ring member has a wedge-shaped tip portion that fits into the gap, and the wedge portion that fits into the gap formed between the inner ring of the second rolling bearing and the rotary shaft. A second ring member having a plurality of slits provided symmetrically with respect to the central axis, and a biasing member for biasing the second ring member in a direction of press-fitting the second ring member into the rotary shaft. Rotating head drum device. 2. A first fixed drum, a second fixed drum formed with a lead for guiding the running of the tape, and coaxially attached to the first fixed drum; the first fixed drum; A middle drum having a magnetic head, which is rotatably mounted between the second fixed drums;
A rotary head drum device comprising: the middle drum, which includes a center of gravity of components constituting the middle drum, and a dynamic balance correction unit for each component is provided on a surface perpendicular to a rotation axis of the middle drum. A rotary head drum device characterized in that