JPS63149415A - Rotating device - Google Patents

Abstract

PURPOSE:To certainly keep and supply magnetic fluid by forming a magnetic circuit of a permanent magnet and a ferromagnetic body near a magnetic fluid dynamic pressure bearing formed between a rotating member and a fixed one to perform the sealing of the magnetic fluid. CONSTITUTION:An auxiliary rotating member 22 having a ferromagnetic sleeve 24 at its upper end is partly arranged in the recess part 20a of a housing 20. and a permanent magnet 25, a ferromagnetic yoke 26 and a nonmagnetic spacer 27 are fixed to the inner wall of a housing 20 opposite to the side of the sleeve 24. In this constitution, the line of magnetic force issued from the permanent magnet 25 is introduced to the ferromagnetic sleeve 24 on the side of a rotating member and then the ferromagnetic yoke 26 for the formation of a magnetic circuit, which can prevent the leakage of the magnetic fluid.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a rotating device using a magnetic fluid dynamic bearing.

[Prior art] There have been many types of bearings that support rotating members, and they are selected and used depending on the purpose, required accuracy, usage conditions, etc., but bearings that require particularly high accuracy are used. In precision i-machines such as ball bearings, rotation accuracy, torque loss, and support position of rotating parts change due to changes in preload due to temperature changes, and instead of bearings that are prone to deterioration, there is no wear, etc. Hydrodynamic bearings, which provide high accuracy, are increasingly being used.

Various hydrodynamic bearings have been proposed, including those that use air as the fluid, those that use oil, grease, etc., and those that use magnetic fluid.

FIG. 4 shows a case in which a hydrodynamic bearing having a magnetic fluid as a lubricant is applied to a rotary head assembly used in, for example, a household magnetic recording and reproducing device (hereinafter referred to as VTR).

In the figure, 1 is a fixed lower cylinder, 2 is a rotating shaft, 3 is a rotation auxiliary member, 4 is a rotating upper cylinder fitted and fixed to the rotation auxiliary member, 5a and 5b are magnetic heads, 6 is a pedestal,
7.8 is a rotating side core and a stationary side core which respectively constitute the rotary transformer 9; 10 is a motor section; 11 is a stator yoke; 12 is a stator coil; 13 is a rotor yoke;
14 is a rotor magnet.

Further, 15 and 16 are dynamic pressure radial bearings using magnetic fluid as a lubricant, and 17 are dynamic pressure thrust bearings also using magnetic fluid as a lubricant.

The radial bearings 15 and 16 have herringbone-shaped shallow grooves 15a and 16a carved in the inner wall of the hole in the fixed lower cylinder 1 into which the rotation @ 2 or rotation shaft 2 is inserted, and the lubricating grooves filled in the gaps between them. It is composed of agents. As the rotary shaft 2 rotates, the lubricant is forced through the shallow grooves, generating high dynamic pressure, and the rotary shaft 2 can be supported by the fixed lower cylinder 1 in a non-contact manner.

The thrust bearing 17 includes, for example, a shallow spiral groove (not shown) carved in at least one of the mutually opposing surfaces of the rotating flange 18 attached to the fixed lower cylinder 1 and the rotating shaft 2; It is made up of magnetic fluid filled between both sides. As the rotating shaft 2 rotates, dynamic pressure is generated by the shallow groove, and the flange 18, that is, the rotating upper cylinder 4 can be rotated without contacting the fixed lower cylinder 1.

19a and 19b are permanent magnets for sealing to prevent the magnetic fluid from scattering, overflowing, or leaking out when rotation is stopped from each bearing portion.

With the above configuration, the rotating member, that is, the rotating upper cylinder 4 can be rotationally supported with high precision and with little bearing loss.

(Problems to be Solved by the Invention) However, with the above configuration, there is a problem in the sealing means for the magnetic fluid used as the lubricant of the hydrodynamic bearing.

In other words, a permanent magnet that seals the magnetic fluid from flowing out of each bearing is simply placed near the bearing.
Since the magnetic fluid is only held by the attractive force of this permanent magnet, it is not possible to obtain sufficient holding force to the magnetic fluid, so it starts.

The lubricant may leak out due to photography of the rotating shaft 2 when stopped or external impact, or it may not be sufficiently retained near the magnetic fluid, resulting in poor lubricant flow and deterioration of rotation accuracy. Etc. [Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems, and has a method of reliably retaining the magnetic fluid lubricant in the bearing portion and improving the circulation of the magnetic fluid. The purpose of the present invention is to provide a hydrodynamic bearing that can reliably prevent scattering, leakage, etc. from the bearing part. In this rotating device, a magnetic circuit formed by a permanent magnet and a ferromagnetic member disposed close to each other near the bearing is configured to prevent the magnetic fluid from flowing out from the bearing portion. At the same time, consideration is given so that the Eft air circuit does not affect the rotation accuracy of the rotating member.

〔Example〕

FIGS. 1 and 2 show a case in which the rotating device of the present invention is similarly applied to a rotating head assembly of a VTR.

In the same figure, the same structure as the conventional example shown in FIG.
tn=bp day omitted.

2' has its lower end fixed to the lower cylinder 1, and its upper end fixed to the housing 2.
0 is a fixed shaft, around which is rotatably supported a rotation assisting member 22 to which an upper rotating cylinder 21 is attached by radial bearings 15, 16 and a thrust bearing 23.

The radial bearings 15 and 16 are formed between the shaft 2' and the inner wall of the insertion hole of the rotation auxiliary member 22, and have shallow grooves for obtaining dynamic pressure as described above, but the bearing itself Since it is the same as that of the conventional example shown in FIG. 4, the explanation will be omitted.

Further, the thrust bearing 23 is formed between the housing 2o and a sleeve 24 attached to the upper end of the rotation auxiliary member 22, and this also has shallow grooves (not shown) for obtaining dynamic pressure on at least one surface facing each other. ) is formed.

Further, a stator yoke 13 to which a stator coil 14 is attached is attached to the housing 20, and a rotor yoke 11° and a rotor magnet 12 are arranged inside the rotating upper cylinder 21, and the motor section 10 is constituted by these.

Therefore, the rotational upper cylinder 21 and the stator yoke 13 are urged toward each other by the attractive force of the motor magnet, and the rotational auxiliary member 22 is therefore urged toward the thrust bearing 23, that is, upward in the drawing.

On the other hand, the housing 20 is arranged such that a part of the rotation assisting member 22 is located in the recess 20a.
A ferromagnetic sleeve 24 is fitted to the upper end of the rotation auxiliary member 22 inside, and a permanent magnet 251 and a ferromagnetic yoke 26 are mounted on the inner wall of the housing 20 facing the side surface of the sleeve 24.
゜Non-magnetic spacers 27 are attached in a vertically stacked manner from the bearing 23 side.

The magnetic circuit formed by these members constitutes a sealing means for preventing the magnetic fluid from flowing out from the bearing portion.

FIG. 2 is an enlarged view for explaining the operation of the magnetic circuit.

Strong bB is placed on the side of the rotation auxiliary member 22 that faces the permanent magnet 25.
Since the magnetic sleeve 24 is arranged, the permanent magnet 25
The lines of magnetic force coming out from the ferromagnetic sleeve 24 on the rotating member side
and then into the ferromagnetic yoke 26, forming a magnetic circuit as shown by the broken line in the figure.

As a result, the magnetic fluid is mainly concentrated and held at the X and Y positions in the figure, and even if some of the magnetic fluid begins to flow toward the spacer 27 due to vibrations, etc., it is drawn back toward the yoke 26 by the magnetic circuit. , scattering, leakage, etc. can be prevented.

Further, the ferromagnetic yoke 26 has the effect of preventing the magnetic lines of force of the magnetic circuit from spreading downward as seen in the figure and strengthening the holding force of the magnetic fluid. Furthermore, if an anti-wetting agent 28 is applied to the surface of the non-magnetic spacer 27 placed below the yoke 26 facing the ferromagnetic sleeve 24, the magnetic fluid will be repelled by this area, thereby further ensuring the sealing effect. can do.

In addition, at the Y position in the figure, the magnetic fluid becomes a pool, and it is possible to secure a sufficient amount of magnetic fluid to be supplied to the thrust bearing 23, so that the convection of the magnetic fluid to the bearing can be performed smoothly ( During rotation, the magnetic fluid is forced in the axial direction by the bearing, so if the 6ii magnetic fluid is not sufficiently held at the Y position in the figure, the fluid will not flow smoothly).

As shown in the figure, a hole 2 is formed in the sleeve 24 made of a strong 6N material at the bearing portion, passing through from the shaft side to the permanent magnet 25 side.
4a, the magnetic fluid can be moved as indicated by arrow A in the figure.
The fluid can be circulated as shown in FIG. 2, thereby making it possible to smoothly and stably supply fluid to the bearing 23-2.

On the other hand, when installing the permanent magnet 25, if it is positioned above the bearing surface of the thrust bearing 23, that is, the upper surface of the ferromagnetic sleeve 24 on the upper part of the rotation auxiliary member 22, the 6i1 line of the permanent magnet 25 will act from above the sleeve 24. death,
A force acts to urge this upward, that is, toward the thrust bearing surface of the housing 2o. When this biasing force is combined with the force that biases the rotation auxiliary member 22 toward the thrust bearing 23 by the motor magnet described above, the biasing force against the bearing 23 becomes too strong, and the loss torque of the bearing becomes large. There is a risk of unstable rotation or damage to the thrust bearing when starting or stopping.

In the present invention, the mounting position of the permanent magnet 25 is determined in consideration of this point.

That is, when installing the permanent magnet 25, the permanent magnet is installed at a position that is closer to the thrust bearing surface than the thrust bearing surface of the housing 20, so that its attractive force does not urge the rotation auxiliary member 22 toward the thrust bearing surface of the housing 20. It is set to be on the lower rotation auxiliary member 22 side.

As a result, the attractive force of the permanent magnet 25 is applied to the rotation auxiliary member 22.
The torque loss of the thrust bearing 23 can be reduced, and damage to the thrust bearing can be prevented even when starting or stopping.

FIG. 3 shows another embodiment of the present invention, in which a thrust bearing 23 is formed between a fixed lower cylinder 1 and a rotating member consisting of a rotating upper cylinder 211, rotation auxiliary member 30, etc. . Components that are the same as those in each figure will be described using the same reference numerals.

A sleeve 24 made of a strong 6N material is fitted to the lower end of the rotation auxiliary member 30, and a hydrodynamic thrust bearing 23 is formed on the surface facing the fixed lower cylinder 1.

A permanent magnet 251, a ferromagnetic yoke 26, and a non-magnetic spacer 27 are arranged on the fixed lower cylinder 1 side facing the side surface of the sleeve 24, forming a magnetic circuit as shown in FIG. The magnetic fluid can be prevented from flowing out from the bearing 23, and the magnetic fluid can be smoothly supplied to the bearing.

Also in this embodiment, a hole 24a is formed in the sleeve 24, and the mounting position of the permanent magnet 25 is set to be located on the rotating member side with respect to the thrust bearing surface, so that the rotating member is placed on the thrust bearing 23 side. Consideration has been given to reducing the applied force.

〔Effect of the invention〕

As described above, according to the rotating device of the present invention, a magnetic circuit is formed by a permanent magnet and a ferromagnetic material in the vicinity of a magnetic fluid dynamic pressure bearing formed between a rotating member and a fixed member, and the magnetic circuit is formed by a permanent magnet and a ferromagnetic material. Since it is configured to seal the magnetic fluid, it can reliably and stably hold and supply the magnetic fluid to the bearing part, and there is no scattering or leakage of the magnetic fluid, resulting in high reliability and improved rotational accuracy and support. A rotating device with high positional accuracy can be realized.

The above-mentioned embodiments all show the case where the present invention is applied to a rotary head assembly of a VTR.
The present invention is not limited to this, and can be applied to any device that supports a rotating member.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view showing the case where the present invention is applied to a rotary head assembly of a VTR, Fig. 2 is an enlarged view of the main part to explain the magnetic fluid sealing means, and Fig. 3 is a diagram showing other parts of the present invention. FIG. 4 is a side sectional view of a conventional rotary head assembly. Explanation of symbols

Claims (4)

[Claims] (1) In a rotating device using a hydrodynamic bearing in which a magnetic fluid is arranged in a bearing that supports a rotating member, a permanent magnet and a ferromagnetic member are arranged close to each other near the bearing. A rotating device characterized in that a magnetic circuit is configured to prevent the magnetic fluid from flowing out from the bearing portion. (2) The rotating device according to claim 1, wherein one of the permanent magnet and the ferromagnetic body is arranged in a fixed part and the other in a rotating part. (3) The rotating device according to claim 1 or 2, characterized in that a ferromagnetic layer is provided at an end of the permanent magnet for regulating the direction of magnetic lines of force of the permanent magnet. (4) A patent characterized in that a non-magnetic layer coated with an anti-wetting agent on the surface facing the ferromagnetic member is provided on the side of the ferromagnetic layer opposite to the permanent magnet. A rotating device according to claim 3. (4) The rotating device according to claim 1, wherein the permanent magnet is mounted on the side where the rotating member is located with respect to the bearing.