JPH02230506A - Head drum - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Industrial field of application Overview of the invention Background art [Figure 9] Problem to be solved by the invention [Figure 9] Embodiments of means for solving the problem [Figures 1 to 8 Figure] F-1 First embodiment [Figures 1 to 5 a. Lower drum, upper drum [Figs. 1 to 3] b Mouth-tally transformer [Figs. 1 and 3 to 5 b-1 Stator [Figs. 1 and 3] b-2 Rotor [ 1, 3 to 5] Support shaft, upper tram support, etc. [Fig. 1 to 4] d Dynamic pressure bearing [Fig. 1, 4] e Motor [Fig. 1 to 4] Figure 3] f Effect F-2 Second embodiment [Figures 6 to 8 a. Lower tram, upper i-ram [Figure 6] b Rotary transformer [Figures 6 to 8 b-1 Stator [Figures 6 to 8] b-2. Rotor [Figures 6 and 7] C. Support of the rotating shaft, upper drum, etc. [Figures 6 to 8] d Dynamic pressure bearing [Figures 6 and 8] G Effect of the invention, i.e., rotation supporting the rotating magnetic head] - Ram and This is related to a head tram equipped with a rotary transformer, etc. for transmitting and receiving electrical signals between a fixed drum located coaxially with the rotating tram and the above-mentioned rotating magnetic head, and supports the ram rotatably from rotation 1 to rotation. By devising a bearing structure for this purpose, it is possible to accurately express the concentricity of the rotary transformer with respect to the rotation center of the drum and the parallelism between the rotor and stator of the rotary transformer without being affected by assembly precision. The present invention is intended to provide a new head drum that can be used to reduce the number of parts.

(A. Industrial Application Field) The present invention relates to a novel head drum. In detail, for example, a video table recorder (hereinafter referred to as rVTRJ).

) and rotating head audio table recorders (hereinafter referred to as r
It's called R-DATJ. ) and other recording and reproducing devices (B. Summary of the Invention) The wooden invention Hettram has a cylindrical bearing part integrally formed with the rotor or stator of a rotary transformer, and the bearing part is fixed relative to the support shaft. In addition to rotatably supporting the rotary transformer, the bearing portion is configured to form a dynamic pressure bearing between the support shaft and the concentricity of the rotary transformer with respect to the center of rotation of the tram and the parallelism between the rotor and the stator of the rotary transformer are controlled. It is possible to accurately display the product without being affected by assembly precision, and also to reduce the number of parts.

(C. Background Art) [Figure 9] For example, the recording and reproducing head of a VTR, R-DAT, etc. is equipped with a head tram for winding a magnetic tape at a predetermined angle. A drum usually includes a fixed tram fixed to a fixed member such as a chassis, a rotating tram coaxial with the fixed drum, bearing means for rotatably supporting the rotating drum, and a coil on the rotor side and a coil on the stator side. The coil is composed of a rotary transformer and the like supported separately by the two drums.

FIG. 9 shows an example a of such a head drum.

In the figure, b is a fixed tram fixed to the chassis C, d is a substantially cylindrical bearing housing part formed in the center of the fixed tram b, and both upper and lower ends of the bearing housing part d are shown. hair ring e. e is fixed with pressure,
These hair rings e. A rotary shaft g rotated by a motor f is rotatably supported on e. h is a rotating drum whose center part is fixed to the upper end of the rotating shaft g, and i is a stator J and a rotor k respectively attached to the mutually opposing surfaces of the fixed tram b and the rotating tram 11. A plane-opposed rotary transformer consisting of, β, k is a rotating tram h
There is a rotating magnetic head attached to the outer periphery of the lower surface of the rotor h, and the rotating magnetic head ρ,k is connected to the coil m.k of the rotor h. It is electrically connected to m.

When recording or reproducing is performed, the magnetic tape n is wound around the outer peripheral surface of the head tram a at a predetermined angle and is run, and the rotating shaft g, the rotating drum h, the rotor k, and the rotating magnetic head are ℃ and ρ are rotated together,
As a result, recording is performed on the tape n while forming a recording track using the rotating magnetic head k1, or reproduction is performed while tracing the recording track l with the rotating magnetic head. Rotating magnetic head k. Signals are sent and received between stator j and coil 0.
, o and the coil m of the rotor k. It is carried out between m.

(D Invention or problem to be solved) [Figure 9] By the way, in order for the rotary transformer 1 to function accurately, the axes of the stator J and rotor k must be precisely aligned with the axis of the head tram a, that is, the center of rotation. Moreover, it is necessary that the parallelism of the facing surfaces of the stator j and the rotor k be achieved with high accuracy.

For this reason, the machining of each part of the stator J and rotor k is usually carried out with an accuracy of microns or close to that, or even if the machining of the stator J and rotor k is performed with such high precision, When assembled as a part of the Kahet tram a, the concentricity and parallelism of the stator J and rotor k with respect to the axes may not always be accurately determined.

That is, the stator J and the rotor k are separately attached to a fixed drum b fixed to a chassis C and a rotating tram h fixed to a rotating shaft g, and the rotating shaft g is attached to a hair ring held by the fixed tram b. Since it is rotatably supported on the fixed drum b, the bearing e and the stator j are assembled to the fixed drum b, the bearing e and the rotor k are assembled to the rotating drum h, and the fixed tram b and the rotating shaft are rotated through the rotating shaft. Stator J must be assembled with tram h accurately.
The axes of the rotor k and the rotor k will be misaligned, and the parallelism of these opposing surfaces will become inconsistent.

Therefore, in the conventional het tram a of this type,
No matter how precisely the stator g and rotor k that make up the rotary lance i are machined, they ultimately fail]
・The concentricity of the stator j and the stator k with respect to the tram rotation center and the parallelism between opposing surfaces, which are assembled as elements of tram a, are largely influenced by the assembly accuracy of other parts. In addition, the conventional het tram a required a separate hair ring from the rotary tram and the fixed tram, resulting in a large number of parts.

(E Means for Solving the Problems) Therefore, in order to solve the above problems, the het tram of the present invention supports the bearing portion of the rotor or stator of the rotary transformer rotatably relative to the support shaft, and A dynamic pressure bearing is configured between the bearing portion and the support shaft.

Therefore, according to the het tram of the present invention, when the bearing part or the support shaft is rotated, dynamic pressure is generated to press the outer peripheral surface of the support shaft due to the action of the dynamic pressure bearing, and this dynamic pressure causes the rotor to move. Alternatively, the concentricity between the bearing part and the support shaft of the stator can be expressed with high accuracy, and thereby the concentricity between the rotor and the stator can be accurately expressed, and each part of the rotor and stator can be accurately expressed. If they are machined with high precision, the parallelism of the opposing surfaces can be accurately expressed, and furthermore,
Since bearing parts such as hair rings are not required, the number of parts can be reduced.

(Embodiment F) [Figures 1 to 8] Details of the tram according to the present invention will be described below according to the illustrated embodiments.

(F-1 First Embodiment) [Figures 1 to 5 Figures 1 to 5 show the tram of the present invention, which is equipped with a plane-facing rotary transformer, and the rotary tram is rotatably supported on a support shaft. This figure shows a first embodiment applied to a rotary sleeve type head drum.

(a Lower tram, upper tram) [Figures 1 to 3] In the figures, 1 is a head tram, 2 is a lower tram, and 3 is an upper drum.

The lower drum 2 has a relatively thick disc shape, and has an insertion hole 4 formed in its center that penetrates in the axial direction, and an outer peripheral surface 5 of the lower drum 2.
Lead 7 is formed on the top.

Such a lower drum 2 is fixed to the upper surface of the chassis 8 together with a support wall to be described later.

Further, the upper drum 3 has a disc shape having approximately the same size and diameter as the thickness and diameter of the lower tram 2, and its lower surface 9
A downwardly opening recess 10 having a relatively large diameter is formed in the recess 10 , and a hole 1 penetrating the center in the thickness direction.
2 is formed.

Reference numerals 13 and 13 designate a head substrate fixed to a portion near the outer peripheral edge of the lower surface 9 of the upper drum 3;
Rotating magnetic heads 14, 14 are supported respectively on the tape contacting surface 14 of the rotating magnetic heads 14, 14.
a, 14a are positioned so that they are substantially flush with the outer circumferential surface 15 of the upper tram 3.

A rotor of a rotary transformer, which will be described later, is fixed to the upper drum 3, and a support shaft, which will be described later, is inserted through a bearing housing portion of the rotor so that it is rotatably supported by the support shaft.

(b rotary transformer) [Figures 1, 3 to 5
Figure ] 16 is a rotary transformer, which consists of a stator fixed to the lower tram 2 and a rotor fixed to the upper tram 3.

(b-t. Stator) [Figures 1 and 3] 17 is a stator.

Reference numeral 18 denotes a coil base of the stator 17, which is made of ferrite and has a disk shape with a diameter approximately half the diameter of the lower tram 2, and has an insertion hole 18a formed in its center. Two stator coils 19a and 19b extending annularly on the upper surface are arranged concentrically with each other.

And, such a stator 17 has its coil base 1
Mounting pieces 18b, 18b protruding laterally from the outer peripheral surface of 8.
1 are fixed coaxially with the lower tram 2 by screws 20, 20, . . . in shallow recesses formed in the upper surface 6 of the lower tram 2.

(b-2 Rotor) [Figures 1, 3 to 5] 21 is a rotor.

The rotor 21 has a disk-shaped coil heir 2 having a diameter slightly larger than the diameter of the coil sheath 18 of the stator 17.
2 and a substantially cylindrical bearing portion 23 protruding downward from the center of the coil base 22 are integrally formed of ferrite, and two rotor coils 24a. 24b are arranged concentrically with each other.

Further, the bearing portion 23 has a length approximately twice as long as the thickness of the lower tram 2, and the upper end of the center hole 25 is connected to the coil base 2.
It opens on the top surface of 2.

A large number of fluid retaining grooves 26, 26, . . . are formed at a plurality of positions spaced apart in the axial direction on the inner circumferential surface 25a of the center hole 25, respectively, with constant bits in the circumferential direction. These fluid retaining grooves 26, 26, ... are formed on the inner circumferential surface 2.
When viewed from the direction perpendicular to the direction perpendicular to the groove 5a, the V-shape is approximately horizontally upside down, and the V-shape narrows toward the clockwise side when the fluid holding grooves 26 are viewed from above.

Thus, the coil base 22 of the rotor 21 is fixed concentrically to the upper drum 3 within the recess 10 of the upper tram 3 by screws 27, 27, . . . .

(c. Support shaft, upper tram support, etc.) [Figs. 1 to 4] Reference numeral 28 denotes a substantially annular support member, and its upper end has mounting portions 28a, 28a, ...
The mounting portions 28a. 28
Insert screws 29, 29, into the mounting holes formed in a, ...
... are inserted, and the screws 29, 29, ... pass through the chassis 8 and are screwed into the screw holes 30a, 30a, ... formed in the lower surface 30 of the lower drum 2, respectively,
Thereby, the lower tram 2 and the support member 28 are fixed to the chassis 8.

Reference numeral 31 denotes a disk-shaped support heir fixed so as to cover the lower opening of the support member 28, and a cylindrical post 32 is formed at a position coaxial with the axis of the lower tram 2.

Reference numeral 33 denotes a support shaft, which has a thickness approximately equal to the inner diameter of the center hole 25 of the bearing portion 23, its lower end portion is fixed to the boss 32 of the support head 31, and its middle portion is fixed to the boss 32 of the lower tram 2. It is inserted through the insertion hole 4 and the insertion hole 18a of the coil base 18 of the stator 17.

A support shaft 33 is rotatably inserted into the center hole 25 of the bearing portion 23 of the rotor 21, whereby the upper tram 3 is rotatably supported by the support shaft 33 via the rotor 21, and the rotor 21 rotor coils 24a and 2
41] or stator coils 19a and 19b of stator 17
They are each opposed to each other with a slight gap between them.

(d Dynamic Pressure Bearing) [Figures 1 and 4] When the support shaft 33 is inserted into the center hole 25 of the bearing part 23, the outer peripheral surface of the support shaft 33 and the inner peripheral surface of the center hole 25 are connected. In between is a viscous fluid, for example a fluid 34 having a certain degree of viscosity, such as grease or oil (only shown in FIG. 1).

) is injected, and the viscous fluid 34 is held within the fluid holding grooves 26, 26, .

Therefore, the bearing portion 23, the support shaft 33, the fluid retaining groove 26,
26,... and the viscous fluid 34, the dynamic pressure bearing 35
is configured.

(e. Motor) [Figures 1 to 3] Reference numeral 36 is a motor for rotating the upper tram 3, and the motor 36 is connected to a rotor unit 37 fixed to the lower end of the bearing part 23 and a support heath 31. The stator unit 38 is fixed to the stator unit 38.

The rotor unit 37 includes a rotor hub 39 which is fitted onto the lower end of the bearing 23 in a compressed manner, a rotor case 40 which is attached to the rotor boss 39, and a ring-shaped ring which is fixed to the lower surface of the rotor case 40. It consists of a magnet 41.

The stator unit 38 also includes a coil board 42 fixed to the upper surface of the support base 31, and coils 43, 43, which are arranged in a substantially annular shape on the upper surface of the coil board 42, facing the magnets 1 and 41.・Consists of.

As a result, a driving current is supplied to the coils 43, 43, .
1 and the upper drum 3 are rotated integrally.

44 is the upper end surface of the post 32 of the support heir 31 and the bearing portion 23
This is a thrust bearing inserted between the lower end surface of the

Note that the upper drum 3 is rotated in a counterclockwise direction when viewed from above.

(f. Effect) Then, when the motor 36 rotates and the rotor 21 also rotates, the support shaft 33
a and the outer circumferential surface of the support shaft 33 through the viscous fluid material 34, and the viscous fluid material 34 is in contact with the fluid holding groove 26,
26, . . are moved relative to this, and dynamic pressure is generated.

That is, the viscous fluid 34 enters into the fluid holding groove 26 from the V-shaped open ends 26b, 26b and reaches the bent part 26a, and at this time, the viscous fluid enters from the two open ends 26b, 26b. The objects 34 are collected at the bent portion 26a, and are discharged from the fluid holding groove 26, that is, toward the support shaft 33, and the discharge force is used as a pressing force that presses the support shaft 33 from the surroundings, that is, as dynamic pressure. It will work.

Therefore, the support shaft 33 is rotatably inserted into the center hole 25 of the bearing part 23, that is, with a predetermined clearance, or the support shaft 33 is inserted into the center hole 25 of the bearing part 23, or the support shaft 330 axis, that is, 1. The ram rotation center and the bearing part 230 axis match with high accuracy, and the stator 17
The parallelism of the opposing surfaces of the stator 17 and rotor 21 is determined depending on the machining accuracy of each component such as the rotor 21, the support shaft 33, and the trams 2 and 3.

(F-2. Second embodiment) [Figures 6 to 8 Figures 6 to 8 show the head drum of the present invention, which is equipped with a cylindrical rotary transformer and is rotated by a rotary ram or motor. This shows a second embodiment 46 applied to a type of het tram fixed to a rotating shaft.

Incidentally, in the head tram 46 shown in this second embodiment, parts having the same structure or function as each part in the head 1 to ram 1 shown in the first embodiment are designated by the same reference numerals as used for the head drum 1. is used.

(a Lower tram, upper drum) [Figure 6] The lower tram 47 has a relatively thick disc shape, and a stator pressure hole 48 is formed in the center of the lower tram and passes through the chassis in the axial direction. 8 by screws 29, 29, . . .

Reference numeral 49 denotes an upper tram, which is shaped like a disk and has a thickness and diameter that are approximately the same as the thickness and diameter of the lower tram 47, and has a relatively large circular recess 51 formed in the center of its lower surface 50. Further, a rotary shaft press-fit hole 52 is provided through the center of the upper tram 49.

(b. Rotary transformer) [FIGS. 6 to 8] A rotary transformer 53 is composed of a stator 54 fixed to the lower tram 47 and a rotor 55 fixed to the upper tram 49.

(b-1 Stator) [Figures 6 to 8] Stator 5
Reference numeral 4 indicates upper 1 - a thick disk-shaped coil base 56 having a smaller diameter than the inner diameter of the four parts 51 of the ram 49; and a cylindrical bearing portion 57 that protrudes downward from the center of the lower surface of the coil base 56. The coil head 56 has an annular groove 56a on its outer circumferential surface. 56a is formed,
These grooves 56a. Stator coils 58, 58 are wound around 56a.

A shaft insertion hole 59 penetrating in the axial direction is formed in the shaft center of the stator 54, and an inner circumferential surface 59a of the shaft insertion hole 59 is formed.
A large number of fluid retaining grooves 60 arranged at a constant pitch in the circumferential direction at a plurality of positions spaced apart in the axial direction, respectively;
60,... are formed, and these fluid retaining grooves 60
, 60, . . . form a sideways V-shape similar to the fluid retaining grooves 26, 26, . ... is formed with the direction facing in the counterclockwise rotation direction when viewed from above.

The bearing portion 57 of the stator 54 is press-fitted into a stator press-fit hole 48 formed in the lower drum 47 . Thereby, the stator 54 is coaxially coupled to the lower tram 47, and its coil base 56 is positioned so as to protrude from the upper surface of the lower drum 47.

(b-2 rotor) [Figures 6 and 7] Also, rotor 5
Reference numeral 5 denotes a coil hesse 61 having a substantially annular shape and the coil hesse 6
The coil base 6 is integrally formed with a mounting flange 62 formed to protrude outward from the upper edge of the coil base 6.
1 has an inner diameter slightly larger than the outer diameter of the coil head 56 of the stator 54, and its height is approximately the same as the depth of the recess 51 formed in the upper tram 49.

Further, the inner circumferential surface 61a of the coil heir 61 has grooves 6lb. extending in the circumferential direction at two positions spaced apart in the axial direction. 6l
The rotor coils 63, 63 are provided in these grooves 61b, 61b.

And, such a rotor 55 has its mounting flange 62.
There are screws 64, 64 in the recess 51 of the upper tram 49 at several places.
, . . , and the rotor 55 and the upper tram 49 are coaxially coupled by the rotor 58 and the rotor coils 63, 63 facing each other.

(c. Rotating shaft, upper tram support, etc.) [Figs. 6 to 8] Reference numeral 65 denotes a rotating shaft, and its intermediate portion is rotatably inserted into the shaft insertion hole 59 of the stator 54, and the shaft is inserted upward from the stator 54. The portion protruding from the stator 54 is press-fitted into the rotary shaft press-fitting hole 52 of the upper drum 49, and the rotor housing 39 of the rotor unit 37 of the motor 36 is fixed to the portion protruding downward from the stator 54.

A bearing support plate 66 is attached to the center of the lower surface of the support member 31, and the thrust bearing 6 is mounted on the upper surface of the bearing support plate 66.
7 is arranged to support the lower end of the rotating shaft 65.

Therefore, the coil base 61 of the rotor 55 is connected to the stator 5.
The stator coil 58 is positioned externally with a slight gap between the four coil heirs 56.

(d. Dynamic Pressure Bearing) [Figures 6 and 8] When the rotating shaft 65 is inserted into the shaft insertion hole 59 of the stator 54, the outer peripheral surface of the rotating shaft 65 and the inner peripheral surface of the shaft insertion hole 59 The viscous fluid 34 is injected between the grooves 59a and the viscous fluid 34 is held in the fluid holding grooves 60, 60, .

Therefore, the bearing part 57, the rotating shaft 65, the fluid retaining element 60,
60, . . . and the viscous fluid 34 create a dynamic pressure bearing 68.
is configured.

Therefore, the rotating shaft 65 is rotated (the direction of this rotation is
The direction is counterclockwise when viewed from above. ), the viscous fluid material 34 in contact with its outer peripheral surface is also moved counterclockwise, and the moved viscous fluid material 34 enters the fluid holding groove 60 from its V-shaped open ends 60b, 60b. and bent part 6
Since it is discharged from 0a, the viscous fluid 34 acts as a dynamic pressure that presses the rotating shaft 65 from around it when it is discharged from the bent portion 60a.

This dynamic pressure causes the axial center of the stator 54 and the axial center of the rotating shaft 65 to match with high precision, and to meet the machining accuracy of each component such as the stator 54, rotor 55, rotating shaft 65, tram 47, 49, etc. Parallelism of the opposing surfaces of the stator 54 and rotor 55 occurs.

(G Effect of the Invention) As is clear from the above description, the vehicle tram of the present invention includes a fixed tram and a rotating tram located coaxially with each other, a rotor fixed to the rotating tram and having a rotor coil, and a fixed drum. A head drum comprising a fixed stator having a stator coil, wherein a cylindrical bearing part is integrally formed in the axial center of the rotor or stator, and the bearing part of the rotor or stator is fixed relative to the support shaft. The support shaft is rotatably supported, and a dynamic pressure bearing is configured between the bearing portion and the support shaft.

Therefore, according to the head drum of the present invention, when the bearing part or the support shaft is rotated, dynamic pressure is generated to press the outer peripheral surface of the support shaft due to the action of the dynamic pressure bearing, and this dynamic pressure causes the rotor or the support shaft to be rotated. The concentricity between the bearing part and the support shaft of the stator can be expressed with high accuracy.Thereby, the concentricity between the rotor and the stator can be accurately expressed, and each part of the rotor and stator can be accurately expressed. If processed with high precision, the parallelism of the opposing surfaces can be accurately expressed, and furthermore,
Since bearing parts such as bearings are not required, the number of parts can be reduced.

Further, in each of the above embodiments, the bearing portion 23 of the rotor 21
Alternatively, since the bearing portion 57 of the stator 55 is made of ferrite, the viscous fluid 3 injected between the center hole 25 or shaft insertion hole 59 and the support shaft 33 or rotation shaft 65
4 can penetrate into and hold the inner peripheral surface of the center hole 25 or the shaft insertion hole 59, and so-called oil shortage due to aging can be reduced.

Furthermore, in the first embodiment, since the lower end surface of the bearing portion 23 of the rotor 21 is supported by the thrust bearing 44,
The viscous fluid 34 poured between the bearing part 23 and the support shaft 33 can be prevented from flowing out from the lower part of the bearing part 23.

In the first embodiment, the head tram of the present invention is applied to a head drum of a type that is equipped with a rotary transformer that faces the plane and the rotary drum is rotatably supported on a support shaft. In , the head tram of the present invention was applied to a head drum of a type that is equipped with a cylindrical rotary transformer and the rotating drum is fixed to a rotating shaft rotated by a motor. For example, a head drum with a flat-faced rotary transformer and a four-turn tram fixed to a rotating shaft rotated by a motor, or a head drum with a cylindrical rotary transformer supported by a rotating drum. It can also be applied to a type of head drum rotatably supported on a shaft.

Further, the grooves of the hydrodynamic bearing are not limited to those formed on the inner circumferential surface of the bearing part, but may be formed on the outer circumferential surface of the support shaft.

[Brief explanation of the drawing]

Figures 1 to 5 show a first example in which the head tram of the present invention is applied to a head tram equipped with a plane-facing rotary transformer.
Fig. 1 is an enlarged central vertical cross-sectional view, Fig. 2 is a perspective view, Fig. 3 is an exploded perspective view, and Fig. 4 is an enlarged view showing the rotor of a rotary transformer with a portion cut away. FIG. 5 is an enlarged perspective view showing grooves formed on the inner circumferential surface of the bearing portion of the rotor, and FIGS. 6 to 8 show a second head tram in which the head tram of the present invention is applied to a head drum equipped with a cylindrical rotary transformer. Fig. 6 is a central longitudinal sectional view, Fig. 7 is an enlarged exploded perspective view of the main parts, Fig. 8 is an enlarged perspective view showing a stator of a rotary transformer with a part cut away, FIG. 9 is a central vertical sectional view showing an example of a conventional head tram. Explanation of symbols: Head drum, Fixed drum, Stator, 19b Stator coil, Rotor, 23 Bearing section, 24b Rotor coil, Support shaft, 35 Dynamic pressure bearing,・Head drum, ・Fixed drum, ・Rotating drum, ・Stator, ・Bearing section, ・Stator coil, ・Rotor coil, ・Support shaft, 68...Dynamic pressure bearing 55... ・Rotor, 3...Rotating drum , 1 ・ ・ 2 ・ ・ 1 7 ・ 1 9 a1 2 1 ・ 2 4 a1 3 3 ・ ・ 4 6 ・ ・ 4 7 ・ ・ 4 9 ・ ・ 5 4 ・ ・ 5 7 ・ ・ 5 8 ・ ・ 6 3・ ・ 6 5 ・ ・ Central longitudinal cross-sectional view (conventional example) Fig.

Claims (1)

[Claims] A head drum comprising a fixed drum and a rotating drum located coaxially with each other, a rotor fixed to the rotating drum and having a rotor coil, and a stator fixed to the fixed drum and having a stator coil, the head drum having an axial center of the rotor or the stator. A cylindrical bearing part is integrally formed in the part, and the bearing part of the rotor or stator is rotatably supported relative to the support shaft, and a dynamic pressure bearing is configured between the bearing part and the support shaft. A head drum characterized by