JPH07226014A - Disk driver - Google Patents

Abstract

PURPOSE:To remarkably simplify the assembling process by making a core assembly to a printed circuit board integrally attachable/detachable in a disk driver. CONSTITUTION:The core assembly 70 is mounted on the printed circuit board 100 in the state having a spacer 60 on the bottom side. That is, two upper projections 64 of the spacer 60 are press-fitted into two holes 104 on the printed circuit board 100 respectively, and the assembly 70 is fixed temporarily to the board 100. Further, by screwing a screw 71 into the hole 105 of the board 100 through a long hole 43-1 of an attaching piece 43 and the hole 63 of the spacer 60, the assembly 70 is fixed to the board 100 in the state where the assembly 70 is separated from the board surface of the board 100. When a three-phase type D motor is constituted using 18 poles of coils, winding wire is performed so that the coil of a certain phase is connected in series at every third pole while holding two poles therebetween. Three lead wires are led from the winding wire of three phase parts, and the three outgoing wires are connected to a wiring pattern formed on the board 100 in respective positions 72-74 by using spaces of an inner peripheral side of a stator core.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk driver, and more particularly to an improvement around a direct drive motor (hereinafter abbreviated as D motor) for driving a disk table.

[0002]

2. Description of the Related Art FIG. 13 shows only the main part of the internal structure of a disk driver. One end side of the metal main frame 10 in the longitudinal direction is opened for loading and unloading the flexible disk 11 shown by the alternate long and short dash line, and a motor 13 for driving the carriage assembly 12 is installed on the other end side, It has a back wall 14 for installing a signal line connector (not shown). A disk table 15 for holding and rotating the flexible disk 11 is disposed in the center of the main frame 10.

On the lower surface side of the main frame 10, a printed wiring board (not shown) on which a predetermined circuit necessary for a disk driver is mounted and a board on which a D motor for rotating the disk table 15 is mounted (whichever is used) (Not shown) is also implemented.

FIG. 14 shows an iron circuit board for a D motor. A hole 21 is provided in the center of the circuit board 20 for mounting a metal support cylinder that supports the rotating shaft of the disk table 15 described above. Six coils 22-1 to 22-6 are mounted on the circuit board 20 around the hole 21. The reason why the circuit board 20 is made of iron is to form a magnetic circuit between each of the coils and a rotor assembly described below, and an insulating film for forming a printed wiring (not shown) is formed on the surface. Has been done.

FIG. 15 shows the six coils 22 shown in FIG.
It is the figure which looked at rotor assembly 30 provided so that -1 to 22-6 may be covered from the inner surface side, and in the inner surface area corresponding to coils 22-1 to 22-6 in metal disk-shaped cap member 31. Is provided with an annular first permanent magnet 32. The first permanent magnet 32 is formed in the hole 21 of the circuit board 20.
The coil 22-1 has a slightly larger inner diameter.
22-6 has an outer diameter that is located slightly outside the outer peripheral side. Although not shown, the first permanent magnet 32
Is magnetized in a mandarin splitting manner so that the N poles and the S poles alternate with each other. The coils 22-1 and 2-2
A sawtooth conductor pattern (not shown) for generating an FG (frequency generator) signal for rotation detection is formed around 2-6. Therefore, a ring-shaped second permanent magnet 33 is provided around the first permanent magnet 32 in the cap member 31 in a region corresponding to the conductor pattern. The second permanent magnet 33 corresponds to the first permanent magnet 3
It has a thickness slightly larger than 2. Although not shown, the second permanent magnet 33 also has a plurality of equally divided regions formed in the circumferential direction and is divided and magnetized so that the polarities are alternately opposite.

A hole 3 provided at the center of the cap member 31
4, the tip of the rotary shaft of the disk table 15 shown in FIG. 13 is opposed to this, and a female screw is provided in the axial direction at the tip of the rotary shaft. Then, as will be described later, by screwing a female screw of the rotary shaft from the outer surface side of the cap member 31, the rotor assembly 30
Is directly connected to the rotary shaft of the disk table 15.

FIG. 16 is a partial sectional view showing the rotation support structure of the disk table 15. A circuit board 20 on which a D motor is mounted is attached to the lower surface side of the main frame 10 by screws 23. A hole is provided in the main frame 10 at a position corresponding to the disk table 15, and the support cylinder 16 for supporting the rotating shaft is fixed to the hole. The support cylinder 16 has a length that extends over substantially the entire length of the rotary shaft 15-1 of the disk table 15,
There is a space around the rotary shaft 15-1 in the lower part, and a ball bearing 17 is arranged in this space.

The tip of the rotary shaft 15-1 is a cap member 31.
The rotor assembly 30 is directly connected to the rotary shaft 15-1 by abutting the inner surface of the rotary shaft 15-1 and contacting the inner surface of the rotary shaft 15-1 from the outside of the cap member 31 and being internally provided at the tip of the rotary shaft 15-1 through the hole 34. To be done. Such a D motor is called a surface facing type.

[0009]

By the way, the above-mentioned conventional D motor requires the following steps in assembling. That is, first, the circuit board 20 is attached to the main frame 10. Next, the plurality of coils 22-1 to 22-6 are individually fixed on the circuit board 20, and the lead wire of each coil is soldered to the wiring pattern formed on the circuit board 20. In FIG. 14, soldering points of the coil 22-1 are indicated by numbers 25 and 26. Furthermore, assembling the disc table 15 and the rotor assembly 30,
Directly connect with screws 35.

As is apparent from the above description, the conventional D motor has a problem in that the number of man-hours is increased because it is necessary to mount the coils one by one and then connect the lead wires by soldering. Further, since the circuit board 20 is made of iron, the weight becomes large.

Apart from the above-mentioned problems, the conventional D motor uses an expensive ball bearing for the bearing of the disk table 15, and also has several washers between the support cylinder 16 and the disk table 15. 18 (FIG. 16) is used, the rotation support structure of the disk table 15 becomes expensive.

In view of the above problems, a main object of the present invention is to provide a disk driver using a D motor which can greatly simplify the assembly process.

Another object of the present invention is to realize the rotation support of the disk table with an inexpensive structure without using a bearing.

[0014]

According to the present invention, in a disk driver in which a motor is assembled on a printed circuit board and mounted on a main frame, and a disk table is driven to rotate by the motor, the motor is a stator core having a plurality of magnetic poles. A core assembly integrally formed on the printed board, a cap member covering the core assembly, and a ring-shaped magnet attached to the cap member. It is characterized by comprising two assemblies, a rotor assembly directly connected to the rotary shaft of the table.

The core assembly includes a stator core having a plurality of magnetic poles radially protruding on the outer periphery of a ring-shaped core, a core cover made of an insulating material that covers at least the magnetic pole portion of the stator core, and the core cover. A plurality of coils wound around the respective magnetic poles, and a mounting piece for screwing to the printed board is provided on the inner peripheral side of the ring-shaped core.

Further, the core assembly is mounted on the printed circuit board in a state of being separated from the printed circuit board via a spacer which is detachable from the mounting piece.

On the other hand, the core cover comprises an upper cover that covers the upper side of the stator core and a lower cover that covers the lower side of the stator core. The upper cover and the lower cover are respectively
A ring-shaped portion corresponding to the ring-shaped core and a plurality of protruding portions radially protruding from the outer periphery of the ring-shaped portion so as to correspond to the plurality of magnetic pole portions, and the upper cover and the lower cover At least one location on the inner peripheral side of the ring-shaped portion is provided with a latching portion that engages with each other.

Further, the printed circuit board is mounted on the lower surface side of the main frame with the mounting surface side of the motor facing downward, and the disk table is mounted on the upper surface side of the main frame and the rotation shaft is The main frame and the printed circuit board are penetrated to be directly connected to the rotor assembly, and a cylindrical member having the rotary shaft inserted therein is interposed between the main frame and the disk table instead of the bearing. At the same time, a compression coil spring is interposed between the cylindrical member and the disc table.

[0019]

In the D motor according to the present invention, the core assembly has an integral structure, so that it can be easily mounted on the printed circuit board, and the windings applied to the plurality of magnetic poles are continuously wound in advance by an automatic winding machine. Since the number of lead wires is small, the soldering connection to the wiring pattern on the printed circuit board can be done at the minimum required number of points.

Further, the compression coil spring provided between the disk driver and the main frame acts so as to regulate the thrust play of the disk table in a fixed direction (thrust direction), and smoothly supports the rotation of the disk table together with the cylindrical member. To do.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 shows a state in which a core assembly 70 of a D motor applied to the present invention is mounted on a printed circuit board 100, and FIG. 2 shows a rotor assembly 80 for forming an outer rotor type D motor together with the core assembly 70. It is the figure seen from the side. Core assembly 7
0 will be described in detail later, but the printed circuit board 100
Around the core assembly 70, the sawtooth-shaped conductor pattern 101 for generating the FG signal is formed.

On the other hand, the rotor assembly 80 has a ring-shaped permanent magnet 8 on the outer periphery on the inner surface side of an iron cap member 81.
2 is fixed. The permanent magnet 82 is located on the conductor pattern 101 when directly connected to a disc table described later, and the end surface on the inner peripheral side has the core assembly 70.
Of the plurality of magnetic poles are opposed to each other. The permanent magnet 82 has a plurality of equally divided regions formed in the circumferential direction, and the N poles and S poles appear in the circumferential direction in each region of the inner wall, and the polarities are alternately reversed. It is magnetized. Such a rotor assembly 80
The D-motor according to is called a side facing type. As in the conventional case, the cap member 81 is provided at the center thereof with a hole 83 through which a screw is inserted in a line directly connected to the disc table.

FIG. 3 shows a stator core 41 for constructing the core assembly 70 shown in FIG. The stator core 40 has a plurality of (in this case, 18) T-shaped magnetic poles 42 that radially project on the outer circumference of a ring-shaped core 41, while the inner circumference of the printed circuit board 100 is provided at two mutually opposing locations. A mounting piece 43 for screwing is provided so as to extend in the radial direction. In this mounting piece 43, a long hole 43-1 for inserting a screw for screwing the printed circuit board 100 and a hole 4 for mounting a spacer described later are provided.
3-2 and are provided. Such a stator core 4
0 is made by stacking a plurality of punched and formed materials suitable for the core.

FIG. 4 shows a core cover for covering the surface of the stator core 40 shown in FIG. 3 for insulation. The core cover is made of an insulating material, for example, a resin material, and is provided to insulate the windings around the magnetic poles 42 of the stator core 40. The core cover includes an upper cover that covers the upper side of the stator core 40,
The lower cover covers the lower side of the stator core 40, and the upper cover and the lower cover have the same shape.
Then, only one upper cover 50 is shown from the inner surface side.

The upper cover 50 has the same shape as that of the stator core 40 excluding the mounting piece 43. That is, the upper cover 50 includes the ring-shaped portion 51 corresponding to the ring-shaped core 41 of the stator core 40 and the plurality of magnetic poles 42.
To have a plurality of T-shaped protruding portions 52 radially protruding from the outer periphery of the ring-shaped portion 51.

FIG. 5 is an enlarged view of a part of the upper cover 50.
Referring also to, the inner peripheral side of the ring-shaped portion 51 is provided with a plurality of (here, six) engaging portions 53 that engage with the lower cover at equal intervals in the circumferential direction. Engagement part 53
Are alternately formed with holes 53-1 and protrusions 53-2 that can be fitted into the holes 53-1. Flanges 51-1 and 52-1 are provided on the outer circumference of the ring-shaped portion 51 of the upper cover 50 and on the side edges of the protruding portion 52, respectively, so as to contact the outer circumferential surface of the ring-shaped core 41 of the stator core 40 and the side surface of the magnetic pole 42. Is provided. The height of these flanges 51-1 and 52-1 is the stator core 4
It is about half the thickness of 0, and as a result, the outer peripheral surface of the ring-shaped core 41 and the magnetic pole 4 when the upper cover and the lower cover are combined.
Two sides can be covered. In addition, the engaging part 5
The height of 3 is approximately the same as the thickness of the stator core 40.

The upper cover 50 can be easily formed by integrally molding a resin material, and the lower cover has the same shape. However, when covering the stator core 40,
For example, it goes without saying that the lower cover side engaging portion 53 having the protrusion 53-2 is used so as to face the upper cover side engaging portion 53 having the hole 53-1.

FIG. 6 shows a state in which the stator core 40 is covered with the core cover described above. The stator core 40 is covered by the core cover over the entire area other than the mounting pieces 43, the inner peripheral surfaces of the ring-shaped core 41 and the magnetic pole end surfaces of the magnetic poles 42. Although the tip of the magnetic pole 42 projects slightly from the core cover in FIG. 6, it does not have to project. Insulation for this type of stator core is usually provided by coating an insulating material. On the other hand, by using the core cover as in this example, it is possible to eliminate the coating step, and there is an effect that the price is low.

FIG. 7 shows that each magnetic pole 42 of the stator core 40 shown in FIG.
Figure 5 shows a core assembly 70 having a 5 formed. Since the winding of the coil 45 is performed by an automatic winding machine by a well-known method, the description of the winding method and form will be omitted.
The core assembly 70 needs to be slightly separated from the board surface when it is mounted on the printed board 100.
The spacer 60 is used for this purpose. This spacer 6
0 is made by molding an insulating material, for example, a resin material, and is attached to the attachment piece 43. FIG. 7 is a view of the core assembly 70 as viewed from the side mounted on the printed circuit board 100.

FIG. 8 is a view showing the spacer 60, and mounting members 62 are integrally formed on both sides of the ring 61 in the diametrical direction. A hole 63 is provided in a portion of the mounting member 62 near the ring 61, and an upper protrusion 64 protruding upward and a lower protrusion 65 protruding downward are integrally formed near the end. The upper protrusion 64 is for temporarily fixing the core assembly 70 to the printed circuit board 100. The lower protrusion 65 is for attaching the spacer 60 main body to the attachment piece 43 of the stator yoke 40, and is press-fitted into the hole 43-2 shown in FIG. The hole 63 is a hole through which a screw is inserted when the core assembly 70 is screwed to the printed circuit board 100, and the mounting piece 4 of the stator core 10 is inserted.
It is provided at a position corresponding to the long hole 43-1 provided in No. 3.

The distance between the two holes 63 has a length corresponding to the elongated hole 43-1 of the mounting piece 43, so that some dimensional error is allowed. However, the distance between the two upper protrusions 64 and the distance between the two lower protrusions 65 require precision. This is because, for example, when the dimension between the two lower protrusions 65 does not match the dimension between the two holes 43-2 provided in the two mounting pieces 43 of the stator core 40, the spacer 60 is attached to the stator core 40. This is because the spacer 60 is deformed when it is attached, which causes a hindrance when the core assembly 70 is mounted on the printed circuit board 100. This also applies to the dimension between the two upper protrusions 64.

9 and 10 show an improved example of the spacer 60 described above. In FIG. 9, a notch 66 is made from one side end of the two attachment members 62 at locations near the upper protrusion 64. By providing such a notch 66, 2
A degree of freedom can be given to the dimension between the two upper protrusions 64 and between the two lower protrusions 65. That is, 2
Even if the dimension between the two lower projections 65 is slightly deviated from the dimension between the two holes 43-2 in the mounting piece 43 of the stator core 40, this deviation can be absorbed in the notch 66, and Spacer 6 when mounting
The entire 0'is not deformed. This notch 66
May be provided only on one mounting member 62.

FIG. 10 shows another modification of FIG. This spacer 60 ″ has notches 67 and 68 from both side ends at positions near the upper protrusion 64 of the two mounting members 62. In this modification, the same effect as in FIG. 9 can be obtained. Of course, the two notches 67 and 68 may be provided only in the one mounting member 62. 2
A notch 66 as shown in FIG. 9 may be provided on one of the two attachment members 62, and two notches 67 and 68 as shown in FIG. 10 may be provided on the other.

FIG. 11 schematically shows the printed circuit board 100. In the area where the core assembly 70 is mounted, there are elongated insulating patterns 102 for aligning and insulating each magnetic pole of the core assembly 70 and the number of the magnetic poles 42. The same number is formed radially. The insulating pattern 102 is formed in a color different from the color of the substrate surface of the printed circuit board 100, for example, by silk printing. At the center of the mounting area of the core assembly 70, the rotary shaft 15 of the disk table 15 is provided.
A hole 103 for forming a -1 support portion is provided. Two holes 104 for press-fitting the two upper protrusions 64 of the spacer 60 described above are provided around the hole 103.
And two holes 105 into which male screws for screwing the core assembly 70 are screwed are formed in line in the diameter direction of the holes 103. In addition, this printed circuit board 1
00 is different from the conventional iron circuit board 20 described in FIG. 14 because it does not need to form a part of the magnetic circuit of the D motor. That is, an ordinary resin (for example, phenol resin) substrate may be used, and it is cheaper and lighter in weight than the circuit substrate 20.

Referring again to FIG. 1, core assembly 70
Is mounted on the printed circuit board 100 with the spacer 60 facing downward. That is, the two upper protrusions 64 of the spacer 60 are respectively connected to the two holes 1 of the printed circuit board 100.
The core assembly 70 is pressed into the printed circuit board 10
Temporarily stop at 0. Further, the screw 71 is screwed into the hole 105 (FIG. 11) of the printed circuit board 100 through the elongated hole 43-1 (FIG. 3) of the mounting piece 43 and the hole 63 (FIG. 8) of the spacer 60, whereby the core assembly 70 is formed. The spacer 60 fixes the printed circuit board 100 to the printed circuit board 100 in a state of being slightly separated from the surface of the printed circuit board 100. When a three-phase type D motor is constructed by using 18-pole coils as shown in the figure, a coil of a certain phase is wound so that every third pole is connected in series with two poles in between. . In this case, three lead wires are derived from the windings for three phases, and these three lead wires utilize the space formed on the inner peripheral side of the stator core at the positions 72, 73, 74 at the printed circuit board. It can be connected to the wiring pattern formed on 100.

FIG. 12 shows a disk table 1 according to the present invention.
5 is a partial sectional view of the rotation support structure of FIG. A hole is provided in the main frame 10, and a metal support cylinder 19 is fixed to the hole. The support cylinder 19 has a through hole through which the rotary shaft 15-1 of the disk table 15 can be inserted. The support cylinder 19 projects to the front surface side (the lower surface side in FIG. 12) of the printed board 100 through the hole 103 provided in the printed board 100. The rotating shaft 15-1 penetrates through the support cylinder 19 and projects below the support cylinder 19. As described with reference to FIG. 16, a female screw is axially cut at the tip of the rotary shaft 15-1. The female screw is passed through the hole 83 (FIG. 2) from the outside of the cap member 81, and the screw 35
The rotor assembly 80 is directly connected to the rotary shaft 15-1 by screwing. Note that, as shown in FIG. 3, the tip of the mounting piece 43 is formed in an arc shape so as to match the outer circumference of the support cylinder 19.

In the present invention, between the main frame 10 and the disc table 15, strictly speaking, the support cylinder 19 fixed to the main frame 10 and the boss 15-2 on the lower surface side of the disc table 15 are provided. A metallic cylindrical member 91 and a compression coil spring 92 are interposed therebetween. The length of the cylindrical member 91 is set to L1, and the disc table 1 is supported from the supporting surface of the cylindrical member 91, that is, the lower end surface.
L2> L1 where L2 is the distance to the 5th boss 15-2
As a result, (L2-L1) thrust play is generated. Further, a compression coil spring 92 is provided between the upper end of the cylindrical member 91 and the boss 15-2 of the disk table 15 so as to regulate the thrust play in a certain direction.
Is intervening. Of course, the biasing force of the compression coil spring 92 is set to a value that does not significantly affect the rotational torque applied to the disk table 15 by the D motor.

In the conventional rotary support structure of the disk table, it is usual that the disk table is completely free of play, but in order to carry out smooth rotary support, play is slight but slight. It is desirable to have an acceptable support structure. From such a viewpoint, the present invention realizes smooth rotational support by rotationally supporting the thrust rattling of (L2-L1) by the compression coil spring 92 in a fixed direction. With such a rotation support structure, an expensive bearing as in the conventional case is not required, and a washer can be omitted.

[0039]

As described above, in the disk driver according to the present invention, the man-hours for assembling can be greatly reduced by making the core assembly integrally attachable to and detachable from the printed circuit board. In particular, the number of soldered connection points for the coil lead wires in the core assembly is significantly reduced,
The step of insulating coating on the stator core can be eliminated. Further, in the central portion of the core assembly, an empty space is formed around the hole for rotation support provided on the printed circuit board, so that the lead wire of the coil can be soldered and connected using this space. . In addition, since the printed circuit board is made of resin unlike the conventional one, the printed circuit board is light in weight, and the weight of the entire disk driver can be reduced. Further, since an expensive bearing is not required for rotationally supporting the disk table, it is possible to significantly reduce the cost in addition to reducing the number of assembling steps and the insulating coating process.

[Brief description of drawings]

FIG. 1 is a plan view showing a state in which a core assembly of a D motor applied to the present invention is mounted on a printed board.

FIG. 2 is a view of a rotor assembly, which is combined with the core assembly shown in FIG. 1 and constitutes a D motor, as viewed from an inner surface side.

3 is a diagram showing a stator core for forming the core assembly shown in FIG. 1. FIG.

FIG. 4 is a view showing a core cover for covering the stator core shown in FIG.

FIG. 5 is an enlarged view of a part of the core cover shown in FIG.

6 is a view showing a state in which the stator core shown in FIG. 3 is covered with the core cover shown in FIG.

7 is a diagram showing the core assembly shown in FIG. 1. FIG.

FIG. 8 is a view showing a spacer used to mount the core assembly shown in FIG. 7 on a printed circuit board.

9 is a view showing another example of the spacer shown in FIG.

FIG. 10 is a view showing still another example of the spacer shown in FIG.

11 is a view showing the printed circuit board shown in FIG.

FIG. 12 is a partially cutaway side view of the rotation support structure of the disk table in the D motor applied to the present invention.

FIG. 13 is a diagram schematically showing the inside of a disk driver.

FIG. 14 is a plan view showing a coil portion of a conventional D motor.

FIG. 15 is a view of the rotor assembly assembled with the coil unit shown in FIG. 14 as viewed from the inner surface side.

FIG. 16 is a partially cutaway side view of a conventional disk table rotation supporting structure in a D motor.

[Explanation of symbols]

 10 Main Frame 15 Disc Table 40 Stator Core 43 Mounting Piece 45 Coil 50 Upper Cover 53 Engagement Part 60, 60 ', 60 "Spacer 70 Core Assembly 80 Rotor Assembly 81 Cap Member 82 Permanent Magnet 91 Cylindrical Member 92 Compression Coil Spring 100 Printed Circuit Board 101 Conductor pattern

Claims (5)

[Claims] 1. A disk driver in which a motor is assembled on a printed circuit board and mounted on a main frame, and a disk table is driven to rotate by the motor, wherein the motor has windings for each magnetic pole of a stator core having a plurality of magnetic poles. A core assembly integrally mounted on the printed circuit board, a metallic cap member covering the core assembly, and a ring-shaped magnet attached to the cap member. A disk driver comprising two assemblies of a rotor assembly directly connected. 2. The disk driver according to claim 1, wherein the core assembly has a stator core having a plurality of magnetic poles radially protruding on an outer periphery of a ring-shaped core, and an insulating material covering at least the magnetic pole portion of the stator core. And a plurality of coils wound around the magnetic poles via the core cover, and a mounting piece for screwing to the printed board is provided on the inner peripheral side of the ring-shaped core. A disk driver characterized by being made. 3. The disk driver according to claim 2, wherein the core assembly is mounted on the printed board in a state of being separated from the printed board via a spacer that is detachable from the mounting piece. Disk driver. 4. The disk driver according to claim 2, wherein the core cover includes an upper cover that covers an upper side of the stator core and a lower cover that covers a lower side of the stator core, and the upper cover and the lower cover respectively include the upper cover and the lower cover. A ring-shaped portion corresponding to the ring-shaped core and a plurality of protruding portions radially protruding from the outer periphery of the ring-shaped portion so as to correspond to the plurality of magnetic pole portions, and the rings of the upper cover and the lower cover. A disk driver, characterized in that at least one portion on the inner peripheral side of the shaped portion is provided with a latching portion which is engaged with each other. 5. The disk driver according to claim 2, wherein the printed circuit board is mounted on a lower surface side of the main frame with the mounting surface side of the motor facing downward, and the disk table is an upper surface of the main frame. Side, the rotary shaft penetrates the main frame and the printed circuit board and is directly connected to the rotor assembly, and the rotary shaft is provided between the main frame and the disk table instead of a bearing. A disk driver, characterized in that a cylindrical member having been inserted is interposed, and a compression coil spring is interposed between the cylindrical member and the disk table.