JPH09196058A - Cylinder rotating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact cylinder rotating device, which can stably rotate a head of a magnetic recording and reproducing device and in which the loss-torque is reduced. SOLUTION: A rotary shaft 2 to be fitted in a sleeve 1, which is integrally formed with a lower cylinder 4, is formed integrally with an upper cylinder 5 for holding a head H1 , and the rotary shaft 2 is rotated by the drive of a motor M1 . The rotary shaft 2 has an upper bearing part 11a and a lower bearing part 11b respectively having a herringbone groove, and shaft diameter of the upper bearing part 11a is larger than that of the lower bearing part 11b, and with this structure, the sufficient bearing rigidity, which can withstand a bearing load to be concentrated to an upper part of the rotary shaft 2, can be secured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder rotating device for rotating a head of a magnetic recording / reproducing apparatus used in audio equipment and video equipment.

[0002]

2. Description of the Related Art Generally, a fluid dynamic bearing device has advantages such as small runout and low noise, and is a magnetic recording / reproducing device for audio equipment and video equipment which are required to be small in size and have less rotational unevenness. It is suitable for the cylinder rotating device.

FIG. 3 shows a main part of a helical scan type magnetic recording / reproducing apparatus such as a VTR. This is head H ₀
And performs recording and reproducing by the magnetic tape (not shown) in a direction oblique to the cylindrical surface C ₀ of the cylinder D ₀ for holding.

In order to realize a magnetic recording apparatus having a high degree of reproducibility, it is necessary to strictly control the relative position and relative speed of the head H ₀ and the magnetic tape, and first, the rotation of the cylinder D ₀ is required. It is indispensable that the unevenness is small and the vibration and noise are small. Therefore, the cylinder D ₀
As the bearing portion of the above, a hydrodynamic bearing E _{0 including} a sleeve 101 and a rotary shaft 102 fitted and inserted therein is used.

A pair of bearings 111a and 111b having a herringbone groove are provided on the surface of the rotating shaft 102, and the lubricant between the sleeve 101 and the rotating shaft 102 is herringbone groove as the rotating shaft 102 rotates. It is configured so as to suck from both ends of each of the bearing portions 111a and 111b toward the center portion of each of the bearing portions 111a and 111b.
01 is rotated without contact.

The lower end 102a of the rotary shaft 102 is formed into a spherical shape and is integrally formed with the sleeve 101.
3, the thrust member 103 constitutes a thrust bearing that axially supports the rotating shaft 102.

The lower end of the sleeve 101 is press-fitted and fixed to the lower cylinder 104, and the upper end of the rotary shaft 102 is integrally connected to the upper cylinder 105 by a known method such as press-fitting. And the cylindrical surface of the upper cylinder 105 form a cylindrical surface C ₀ facing the traveling path of the magnetic tape.

The upper cylinder 105 holds a magnetic recording / reproducing head H ₀ in an internal space between the upper cylinder 105 and the lower cylinder 104, and the tip thereof projects radially outward from the cylindrical surface C ₀ .

A motor M _{0 for} rotating the upper cylinder 105 together with the head H ₀ is composed of a rotor 106 suspended from the upper cylinder 105 and a stator 107 fixed to the bottom of the lower cylinder 104. Stator 107
Is the stator coil 107a and the yoke 10 that supports it.
7b, the rotor 106 has a stator coil 107a.
And a yoke 106b that supports the rotor magnet 106a.

A circuit board 108 is fixed to the bottom of the lower cylinder 104 together with the stator 107, and the stator coil 107a is excited by a drive current supplied from a drive circuit (not shown) on the circuit board 108 to drive the rotor magnet 106a. Rotate.

Since the bearing portion of the upper cylinder 105 is the hydrodynamic bearing E ₀ as described above, the deflection of the rotating cylindrical surface C ₀ is extremely small as compared with the case of using a known ball bearing,
Also, there is little vibration or noise.

[0012]

However, according to the above-mentioned conventional technique, the bearing load applied to the hydrodynamic bearing E ₀ by the rotation of the cylinder D ₀ is mainly due to the weight of the head H ₀ , and therefore The position where the maximum load is applied to the hydrodynamic bearing E ₀ (maximum load point) is at the upper bearing portion 1.
If the overall length of the hydrodynamic bearing E ₀ is shortened in order to reduce the size of the entire magnetic recording / reproducing apparatus in the vicinity of 11a, the maximum load point will be located above the upper bearing portion 111a. The bearing load is concentrated on 111a.

That is, as shown in FIG. 4, the length from the upper end of the upper bearing portion 111a to the lower end of the lower bearing portion 111b, that is, the bearing length L ₁ is the lower end of the lower bearing portion 111b from the maximum load point. If the length L ₂ is shorter than the length L ₂ , the spring constants K ₁ of the bearings 111a and 111b,
If K ₂ is the same, the rotating shaft 1
Since the center of the rotational moment generated in 02 shifts from the center of the bearing length L ₁ to a position closer to the lower bearing portion 111b, the bearing load is concentrated on the upper bearing portion 111a, and locally large bearing rigidity is required. To do. Therefore, in order to increase the bearing rigidity of the hydrodynamic bearing E ₀ , the shaft diameter of the entire rotary shaft 102 is increased, or the sleeve 101 and the rotary shaft 102 are elongated so that the maximum load is applied between the bearing portions 111a and 111b. The device was designed so that the points would be located, the pattern width of the herringbone groove was enlarged, and the bearing gap was narrowed.

However, if the shaft diameter of the rotary shaft is made thicker overall, the loss torque increases and the power consumption increases, which increases the running cost, and if the rotary shaft and the like are elongated, the entire cylinder becomes bulky. Become. Further, in order to increase the pattern width of the herringbone groove, it is necessary to lengthen the rotating shaft, and reducing the bearing gap causes an increase in the processing cost of the rotating shaft and the sleeve and a decrease in mass productivity. There is inconvenience.

The present invention has been made in view of the above-mentioned unsolved problems of the prior art, and it is possible to stably rotate the head or the like of the magnetic recording / reproducing apparatus even if the bearing length is short. An object of the present invention is to provide a cylinder rotating device equipped with a hydrodynamic bearing that is small in size, high in performance, and low in running cost.

[0016]

In order to achieve the above object, the cylinder rotating device of the present invention comprises a shaft member and a sleeve fitted to each other, and a dynamic pressure generating means for generating a dynamic pressure in a fluid between the shaft member and the sleeve. A dynamic pressure fluid bearing having the same, a cylinder member rotatably supported by the dynamic pressure fluid bearing, and a drive means for rotating the same are provided, and a bearing load larger than a remaining portion is applied to a part of the dynamic pressure fluid bearing. In the cylinder rotation device configured as described above, the shaft diameter of the shaft member locally increases in the part of the hydrodynamic bearing.

The shaft member may be provided with a step for locally increasing the shaft diameter.

The shaft diameter of the shaft member may be tapered.

[0019]

The bearing load applied to the hydrodynamic bearing by the rotation of the cylinder member tends to be biased to a part of the hydrodynamic bearing. Therefore, the bearing rigidity is locally increased by increasing the shaft diameter of the shaft member only in a portion where a large bearing load is generated. Compared to the case where the shaft diameter of the entire shaft member is increased or the shaft member is lengthened, loss torque is less and there is no possibility that the entire cylinder rotating device becomes bulky.

As a result, the head of the magnetic recording / reproducing apparatus can be stably rotated, the power consumption is small, and the cylinder rotating apparatus suitable for downsizing the apparatus can be realized.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a cylinder D ₁ which is a cylinder rotating device according to the first embodiment.
And a hydrodynamic bearing E ₁ composed of a rotary shaft 2 which is a shaft member fitted to this.

A pair of bearings 11a and 11b having herringbone grooves, which are dynamic pressure generating means, are provided on the surface of the rotary shaft 2, and the fluid between the sleeve 1 and the rotary shaft 2 is rotated as the rotary shaft 2 rotates. Is sucked from the end of the herringbone groove toward the center of each bearing 11a, 11b, and the rotary shaft 2 has a dynamic pressure of the lubricant generated by such a pump action. The sleeve 1 is rotated without contact with the sleeve 1.

The lower end 2a of the rotary shaft 2 is processed into a spherical shape,
The thrust member 3 is in contact with the thrust member 3 which is integral with the sleeve 1, and the thrust member 3 is made of a material having high wear resistance such as ruby or zirconium. The rotating shaft 3 is supported in the thrust direction by the thrust member 3 during its rotation.

The lower end of the sleeve 1 is press-fitted and fixed to the lower cylinder 4, and the upper end of the rotary shaft 2 is integrally connected to the upper cylinder 5 which is a cylinder member by a method such as press-fitting. Of the upper surface of the upper cylinder 5 and the cylindrical surface of the upper cylinder 5, the cylindrical surface C facing the running path of the magnetic tape (not shown)
₁ is formed.

The upper cylinder 5 holds a magnetic recording / reproducing head H ₁ in an internal space between the upper cylinder 5 and the lower cylinder 4, and the tip thereof projects radially outward from the cylindrical surface C ₁ .

A motor M ₁ which is a driving means for rotating the upper cylinder 5 together with the head H ₁ is composed of a rotor 6 suspended from the upper cylinder 5 and a stator 7 fixed to the bottom of the lower cylinder 4. The stator 7 includes a stator coil 7a and a yoke 7b that supports the stator coil 7a, and the rotor 6 includes a rotor magnet 6a that faces the stator coil 7a and a yoke 6b that supports the rotor magnet 6a.

A stator 7 is attached to the bottom of the lower cylinder 4.
The circuit board 8 is fixed together with the stator coil 7a.
Is excited by a drive current supplied from a drive circuit (not shown) on the circuit board 8 to rotate the rotor magnet 6a.

The head H ₁ is attached to the upper cylinder 5 by a fixing screw 5a, and the height of the head H ₁ is adjusted by an adjusting screw 5b. Further, a screw 4a for fixing the stator coil 7a and the like to the lower cylinder 4
Alternatively, the screw 5c for fixing the rotor magnet 6a and the like to the upper cylinder 5 is made of a non-magnetic material in order to prevent generation of cogging torque of the motor.

An electric signal is exchanged between the head H ₁ rotated by the motor M ₁ and the fixed side of the lower cylinder 4, etc., by means of a transformer rotor 9a, a transformer stator 9b and a wire 9c.
Is performed via

The rotary shaft 2 according to this embodiment has a step 2b between the upper bearing portion 11a and the lower bearing portion 11b, and the shaft diameter of the upper bearing portion 11a is smaller than that of the lower bearing portion 11b. Is large. Further, as shown in FIG. 1B, the sleeve 1 also has a step 1a on its inner surface, and the dimension of the bearing gap between the sleeve 1 and the rotating shaft 2 is the same in both bearing portions 11a and 11b. Has been done.

Since the bearing load generated during the rotation of the rotary shaft 2 is mainly due to the weight of the head H ₁ located above the cylinder D ₁ , as described above, the upper bearing portion 1
Bearing load concentrates on 1a. Therefore, in this way, the shaft diameter of only the upper bearing portion 11a on which the bearing load is concentrated is increased to enhance the bearing rigidity, thereby ensuring the required bearing rigidity. As a result, the head H ₁ can be stably rotated even if the bearing length of the hydrodynamic bearing E ₁ is short.

Since the shaft diameter of the lower bearing portion 11b is smaller than that of the upper bearing portion 11a, loss torque is greatly reduced and power consumption is increased as compared with the case where the shaft diameter of the rotary shaft 2 is increased overall. Can be avoided. Further, by making the upper half portion of the rotary shaft 2 large in diameter, there is an added advantage that the precision of press fitting the rotary shaft 2 into the upper cylinder 5 is improved.

If it is not necessary to take into consideration troubles such as unstable bearing rigidity, a sleeve 21 having a uniform inner diameter without a step can be used on the inner surface as shown in FIG. 1 (c). Good.

Although the herringbone groove is provided on the surface of the rotary shaft 2 in this embodiment, a similar herringbone groove may be provided on the inner surface of the sleeve 1, or the sleeve 1 may be provided.
It is also possible to provide both on the rotating shaft 2.

FIG. 2 shows a cylinder D _{2 according} to the second embodiment. This uses a tapered rotating shaft 32 whose shaft diameter gradually decreases from the upper end to the lower end, instead of the rotating shaft 2 having the step 1a of the first embodiment.
The sleeve 31 into which is fitted is a tapered sleeve whose inner diameter decreases along the rotating shaft 32, as shown in FIG. Bearing portions 11a, 11 of the lower cylinder 4, the upper cylinder 5, the rotor 6, the stator 7, and the rotating shaft 32.
Since b and the like are the same as those in the first embodiment, they are represented by the same symbols,
Description is omitted.

If it is not necessary to consider a trouble such as unstable bearing rigidity, a cylindrical sleeve 41 having a uniform inner diameter may be used as shown in FIG. 2 (c).

[0038]

Since the present invention is configured as described above, it has the following effects.

It is possible to realize a small-sized, high-performance cylinder rotating device which is capable of stably rotating the head of the magnetic recording / reproducing device even if the bearing length is short and has a low running cost. By using such a cylinder rotating device, it is possible to greatly contribute to downsizing, high performance, and running cost reduction of the magnetic recording / reproducing device.

[Brief description of the drawings]

1A and 1B show a first embodiment, in which FIG. 1A is a schematic sectional view thereof, FIG. 1B is a partial sectional view showing only a hydrodynamic bearing of FIG. 1A, and FIG. It is a fragmentary sectional view showing only a hydrodynamic bearing.

2A and 2B show a second embodiment, in which FIG. 2A is a schematic sectional view thereof, FIG. 2B is a partial sectional view showing only the hydrodynamic bearing of FIG. 2A, and FIG. It is a fragmentary sectional view showing only a hydrodynamic bearing.

FIG. 3 is a schematic sectional view showing a conventional example.

FIG. 4 is a diagram illustrating a rotation moment generated during rotation of a cylinder.

[Explanation of symbols]

 1, 21, 31, 41 Sleeves 1a, 2b Steps 2, 32 Rotating shaft 4 Lower cylinder 5 Upper cylinder 6 Rotor 7 Stator 11a, 11b Bearing part

Claims (4)

[Claims] 1. A hydrodynamic bearing having a shaft member and a sleeve fitted to each other and a hydrodynamic pressure generating means for generating hydrodynamic pressure in a fluid between the shaft member and the sleeve, and rotatably supported by the hydrodynamic bearing. A cylinder rotating device having a cylinder member and a drive means for rotating the cylinder member, wherein a bearing load is applied to a part of the dynamic pressure fluid bearing larger than that of the remaining part. A cylinder rotating device in which a shaft diameter of the shaft member is locally increased at a part thereof. 2. The shaft member is provided with a step for locally increasing the shaft diameter.
The cylinder rotating device described. 3. The cylinder rotating device according to claim 1, wherein the shaft diameter of the shaft member changes in a tapered shape. 4. The cylinder rotating device according to claim 1, wherein the inner diameter of the sleeve changes along the shaft member.