JPS58134218A - Fluid bearing device - Google Patents

Abstract

PURPOSE:To prevent a rotation side unit from running off even if a product is put upside down and given a falling impact and a strong vibration by fixing a ring to prevent from running off in the upper part of a fixed shaft. CONSTITUTION:A disk 23 is provided with a spot facing part 23A, while a throttled part 21c is provided in the upper part of a fixed shaft 21 and its top face 28 is precisely processed for constructing a thrust bearing. Besides, a male screw 21d is cut on the throttled part 21c, while a ring 39 with a female screw cut in the inner diameter is screwed therein and a gap between the lower end face of the ring 39 and the disk 23 is restrained about in 0.05mm.. This construction permits to prevent a rotation side unit 31 from running off by the ring 39 provided therein even if it is put upside down and given an impact.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydrodynamic bearing device, and an object of the present invention is to obtain a hydrodynamic bearing device that is strong against drop impact loads.

The structure of a conventional hydrodynamic bearing will be explained based on FIGS. 1 and 2. FIG. 1 shows a VTR cylinder to which a conventional hydrodynamic bearing device is applied. A fixed shaft 1 is installed in the center of the lower cylinder 2.
is press-fitted and fixed, a disk 3 is rotatably inserted into the fixed shaft 1, and a thrust receiver 4, an upper cylinder 6, a magnetic head 9, and a head P plate 10 are attached to the upper part of the disk 3, forming a rotating side unit 11. do. A rotary-side rotary transformer 12 is attached to the lower part of the disk 3 for transmitting video signals extracted from a magnetic tape (not shown) to a fixed side via a rotating magnetic head 9. A fixed-side rotary transformer 13 is attached to receive the video signal.

Further, an armature magnet 16 of a planar opposed type motor and a planar magnet case 14 are attached to the disc 3, and the lower cylinder 2 opposite thereto has a
The stator coil unit 16 is attached, 14. ．．
15 and 16 constitute a plane facing motor 17.

The armature magnet 16 always has the power to attract the stator coil unit 16 with a force of 30 to 400 grams.

In addition, radial groups 6A are formed at two locations on the upper and center portions of the fixed shaft 1 by etching or the like.

6B is machined, and the tip surface 8 of the fixed shaft 1 is machined flat and at right angles with high precision, and a single row as shown in FIG. The spiral group 7 is processed by etching or the like. Since each of the three group parts is lubricated with lubricating oil, when the rotary part unit 11 is rotated by the planar motor 17, pressure is generated by the pumping action of the three group parts. However, the uniformity of the oil film increases and the rotation side
G4. has a fixed axis, and is completely floating and rotating while stationary. At this time, a force is applied to the rotating unit 11 in the downward direction in FIG. 1 due to the attraction force of the armature magnet 16 and the weight of the rotating unit. The force was generated upward in the diagram and balanced.

However, in this type of hydrodynamic bearing, when the product is placed upside down and subjected to a drop impact or strong vibration, the rotation side unit 11 consisting of the upper cylinder 6, disk 3, etc.
However, the suction force of the armature magnet 15 is no longer able to hold it and it tries to pull out from the fixed shaft 1, and the rotary transformer 12 on the rotating side strongly hits the rotary transformer 13 on the fixed side, causing the rotary transformer made of relatively fragile material such as ferrite to be pulled out. There have been accidents where the rotary transformer 12 on the rotary side is damaged and video signals cannot be taken out, or in severe cases, the rotary side unit 11 is thrown out. The present invention solves the above-mentioned drawbacks of the prior art by providing a ring for preventing extraction, and an embodiment thereof will be described below with reference to FIG. 3.

FIG. 3 shows an embodiment in which the hydrodynamic bearing device of the present invention is used in a VrR cylinder. A fixed shaft 21 is press-fitted into the center of the lower cylinder 22 and constitutes a fixed side unit 2o, and a disk 23 is rotatably inserted into the fixed shaft 21.
A thrust receiver 24, an upper cylinder 26, a magnetic head 29, and a head P plate 3o are attached to the upper part of the disk 23, and constitute a rotation side unit 31. Also disk 2
A rotating side rotary transformer 32 is attached to the lower part of the cylinder 3, and a stationary side rotary transformer 33 is attached to the lower cylinder 22 opposite thereto. Also disk 23
Furthermore, an armature magnet 36 of a circumferentially opposed direct drive motor and a cup-shaped magnet case 34 are included.
is attached, and a fixed side motor core 36 is attached inside the fixed side motor core 36 at an angle of 34 degrees and 35.36 degrees, forming a circumferentially opposed direct drive motor 37.

Two locations on the fixed shaft 21 are etched to a depth of 5.
The radial groups 26A and 26B of ~20 micrometers (hereinafter referred to as microns) are machined, and the radial clearance with the inner diameter of the disk 23 is controlled to 6 to 10 microns, and an appropriate amount of lubricating oil of about 20 centipoise is applied here. By applying oil, a radial fluid bearing is constructed. Also fixed shaft 2
The tip surface of 1 is precisely machined to be flat and at right angles.
On the opposing thrust receiver 24, a single-row spiral group 27 as shown in FIG. 2 is etched.
By applying an appropriate amount of oil, a thrust direction fluid bearing 4.0 is constructed and the rotating unit 31 is floated. The shape of this spiral group may be a double-row shape as shown in FIG.

On the surface of the motor core 36 on the fixed side facing the rotating 111111 unit 31, a permanent magnet 38 is fixed together with a magnet cover 70, with one plane magnetized to the north pole and the back side magnetized to the south pole. Of course magnet 38
may be directly bonded to the motor core 36. Since the permanent magnet 38 can use the motor core 36 made of silicon steel plate as a back core, the permanent magnet 38 can strongly
1 cup-shaped magnetic case 34 is attracted.

In FIG. 3, the disk 23 is provided with a counterbore portion 23A, and the upper portion of the fixed shaft 21 is provided with a diameter detail 216, the tip surface 28 of which is machined with high precision, and the thrust bearing It consists of In addition, a male thread 21d is cut in the diameter detail 2IC, and a ring 39 with an acid thread cut in the inner diameter is screwed here, so that the gap between the lower end surface of the ring 39 and the disc 23 is about 0.05 mm IJ. It's being held back. By providing the ring 39 in this way, the rotating side unit 31 is prevented from coming off by the ring 39 even if the rotating unit 31 is placed upside down and subjected to an impact, so that the rotating side rotary transformer 33 is prevented from coming into contact with the rotating side rotary transformer 32. There will be no more accidents such as falling over and getting damaged.

Although the fixed-shaft type hydrodynamic bearing device was described in FIG. 3, the motor core 36 on the fixed side of the motor is attached to the lower surface of the rotary transformer 32, and the cup-shaped magnet case 34 and the armature magnet 36 are attached to the lower cylinder 22. Needless to say, a shaft-rotating hydrodynamic bearing can be obtained.

As described above, according to the present invention, a fluid bearing structure that is strong against drop shock and vibration can be obtained, and its industrial value is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional example, FIG. 2 is a diagram showing the shape of the spiral group, FIG. 3 is a sectional view of a bearing device according to an embodiment of the present invention, and FIG. 4 is a double row of the same embodiment. FIG. 3 is a diagram showing the shape of a spiral group. 21...Shaft, 21C...Diameter detail, 21
d...0...male screw, 231I...-11@disk,
23A...φ...Spot facing part, 24...Thrust receiver, 28...Tip surface, 39...Ring. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] It has a shaft and a disk rotatably provided around the outer periphery of the shaft, a thrust receiver is fixed on the disk at a position facing three surfaces of one end of the shaft, and the thrust receiver of the shaft is fixed on the side. A diameter detail is provided in the disc, and 8 threads are cut in this diameter detail, and a spot facing part is provided on the inner diameter of the disc near the diameter detail of the shaft, and the inner diameter A ring having a diameter larger than the inner diameter of the disk is screwed onto the shaft, and lubricating oil is injected between the end face of the shaft and the thrust bearing to form a thrust direction fluid bearing. The hydrodynamic bearing device is configured such that the ring and the counterbore portion of the disk prevent the rotating portion from coming off.