JPH01320320A - Dynamic pressure bearing device - Google Patents

Abstract

PURPOSE:To improve wear resistance and to intend to improve durability by giving nitriding to at least either one member of a rotary body or a bearing member. CONSTITUTION:A ball body 2 is press fitted to a cylindrical body 1 as a bearing member at bottom end part on inner side, and together with support on the bottom end of a shaft 3, are formed radial bearing faces 4 in upper and lower two steps on bore surface of the cylindrical body 1 and dynamic pressure generating channels 5 at the positions facing to the bearing faces 4 on outer cylindrical surface of the shaft 3. The ball body 2 is given nitriding after heat treatment. It is possible to improve wear resistance and to improve durability accordingly.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a hydrodynamic bearing device, and is particularly used for supporting high-precision rotating parts such as video recorders, video disks, and magnetic disks. The present invention relates to a hydrodynamic bearing device.

[Conventional technology]

In general, in a hydrodynamic bearing device in which a dynamic pressure generating groove such as a herringbone groove or a spiral groove is formed on one side of the opposing surfaces of a rotating body that rotates at high speed and a bearing member that supports this, when the rotating body rotates at high speed, Due to the pumping action of the dynamic pressure generating groove, fluid is sent into the bearing gap between the rotating body and the bearing member, and the rotating body is supported by the fluid, so the rotational accuracy of the rotating body is high and noise and vibration are not generated. Very few.

For this reason, the hydrodynamic bearing device is widely used as a support device for rotating parts of OA equipment (office automation equipment) and AV equipment (audio-visual equipment).

[Problem to be solved by the invention]

By the way, in the above hydrodynamic bearing device, when the rotating body is stopped, the rotating body is in contact with the bearing surface of the bearing member, so at the beginning of rotation and just before stopping, the rotating body is in contact with the bearing member. The contact rotates, causing wear on the contact area.

In particular, in hydrodynamic bearing devices in which dynamic pressure generating grooves are formed on the radial bearing surface and the thrust bearing surface is in contact, the thrust bearing is constantly in contact, so the thrust bearing surface is subject to large wear. This caused the rotating body to be displaced in the axial direction, which caused problems with durability.

Therefore, the technical object of the present invention is to solve the problem described in -1- and to reduce wear on the bearing surface.

(Means for Solving the Problems) In order to solve the problem i!!! in item 1, in this invention, at least one of the opposing surfaces of a rotating body that rotates at high speed and a bearing member that supports it is moved. A configuration was adopted in which pressure generating grooves were formed and at least one of the rotating body and the bearing member was subjected to nitriding treatment.

Here, nitriding treatment refers to approximately 10% N1 added to the RX gas (endothermic atmospheric gas used for photovolatile hardening in carburizing treatment) in the atmosphere during quenching heating above point A+ (720°C).
(This refers to a process in which chinomine (N) is infiltrated into the surface of steel by adding gas.

[Effect]

As mentioned above, when at least one of the rotating body and the bearing member is subjected to nitriding treatment, nitrogen diffuses in the austenite state, and by quenching and rapidly cooling it, transformation from austenite to martensite occurs. The hardness can be set to 11RC60 or higher up to the inside.

Since the nitriding treatment can increase the amount of carbide, combined with the high hardness of martensite, it is possible to improve wear resistance, which is effective in suppressing wear at the contact area between the rotating body and the bearing member. can be mentioned.

〔Example〕

FIG. 1 shows an example of a hydrodynamic bearing device. In this hydrodynamic bearing device, a sphere 2 is compressed at the inner lower end of a cylindrical body 1 as a bearing member, and the lower end surface of a shaft 3 as a rotating body inserted inside the cylindrical body 1 is supported by the sphere 2. ing.

Further, radial bearing surfaces 4 are formed in two stages, upper and lower, on the inner diameter surface of the cylinder 1, while dynamic pressure generating grooves 5 are formed on the outer diameter surface of the shaft 3 at positions facing the radial bearing surfaces 4. It is formed.

FIG. 2 shows another example of a hydrodynamic bearing device, in which a thrust plate 6 is fixed to the inner lower end of the cylindrical body 1 instead of the sphere 2 in FIG. It supports a spherical part 7 formed at the lower end.

In the hydrodynamic bearing device shown in FIGS. 1 and 2, when the shaft 3 is rotated at high speed, the pumping action of the dynamic pressure generating groove 5 causes a radial radial ring formed between the radial bearing surface 4 and the outer diameter surface of the shaft 3. Pressure fluid is fed into the bearing clearance 8. Therefore, the shaft 3 is supported by the pressure fluid and rotates without contacting the radial bearing surface 4.

Further, the shaft 3 rotates while in contact with the sphere 2 or the thrust plate 6.

In the hydrodynamic bearing device shown in FIGS. 1 and 2M, the cylindrical body 1
is used as a bearing member and the shaft 3 is used as a rotating body, but contrary to the above, the cylindrical body 1 may be used as a rotating body and the shaft 3 may be used as a bearing member.

FIG. 3 shows an example in which a rotating drum 9 having a video head of a video tape recorder is supported by a dynamic pressure bearing H in which the shaft 3 is a bearing member and the cylinder 1 is a rotating body.

That is, the lower end of the shaft 3 is fixed to the base 10,
A rotating drum 9 is fixed to the outside of the cylindrical body 1 fitted to the outside of the shaft 3. Further, a motor rotor 11 is attached to the lower part of the rotating drum 9, and a motor stator 12 is attached to the upper surface side of the heath 10, so that the rotating drum 9 is rotated a long distance by energizing the motor stator 12.

By the way, since the thrust bearing of the hydrodynamic bearing device that supports the rotating drum 9 is of a contact type, when the rotating drum 9 rotates, wear occurs at the contact portion between the upper end of the shaft 3 and the sphere 2, and as the wear progresses, wear occurs. This causes a disadvantage that the position of the rotating drum 9 is displaced in the axial direction.

In order to eliminate this inconvenience, in this invention, the sphere 2 made of bearing steel type 2 C3UJ 2) is heat treated to provide H*
It is finished to a hardness of C60 to C67 and then subjected to nitriding treatment.

As mentioned above, when the sphere 2 made of bearing steel is subjected to nitriding treatment, chino(N) is formed in the austenitic state as described above.
Due to the diffusion of nitrogen, nitrogen penetrates not only into the surface layer but also into the inside, and by quenching and rapidly cooling it as it is, it transforms from austenite to martensite, so that the hardness can be increased to Il, C60 or higher even to the inside.

Further, since the nitriding treatment can increase the amount of carbide, together with the high hardness of martensite, the wear resistance of the sphere 2 can be improved and wear can be reduced. Therefore, the displacement of the rotating drum 9 in the axial direction can be reduced.

Note that instead of the sphere 2, the end of the shaft 3 may be nitrided, or the shaft 3 and the sphere 2 may each be nitrided. Further, as shown in FIG. 2, when the thrust load is supported by the thrust plate 6, at least one of the thrust plate 6 and the shaft 3 is nitrided.

By the way, in addition to the above-mentioned nitriding treatment, there is a nitriding treatment as a method of increasing hardness by infiltrating nitrogen.

However, since the nitriding process is performed below the A1 point (720°C), nitrogen diffuses in the ferrite state, and even after rapid cooling, only the surface layer is hard, and it is not possible to achieve high hardness inside. Nitrided compounds are hard and have excellent wear resistance, but they are brittle and can cause galling if there is a small chip in the surface nitrogen diffusion layer.

As described above, the nitriding treatment can increase the hardness even to the inside of the component, so that galling between the sphere 2 and the shaft 3 can be prevented.

FIG. 4 shows still another example of the hydrodynamic bearing device.

This dynamic pressure bearing H has a dynamic pressure generating groove 13 formed on the upper surface of the thrust plate 6 that supports the lower end of the shaft 3, as shown in FIG. 5, and the other structure is as shown in FIG. It has the same configuration as the device.

In the hydrodynamic bearing described above, when the shaft 3 rotates at high speed, pressure fluid is sent between the facing surfaces of the thrust plate 6 and the shaft 3 by the pumping action of the dynamic pressure generation groove 13 formed in the thrust plate 6. , the shaft 3 rotates without contacting the thrust plate 6, but at the beginning of the rotation of the shaft 3 and immediately before stopping, the shaft 3 rotates in contact with the thrust plate 6, so that the shaft 3 and the thrust plate 6
Wear occurs at the contact area.

Therefore, also in the case of the hydrodynamic bearing device as described above, at least one of the shaft 3 and the thrust plate 6 is subjected to nitriding treatment.

In the hydrodynamic bearing devices shown in FIGS. 1, 2, and 4, the outer diameter surface of the shaft 3 rotates in contact with the radial bearing surface 4 at the beginning of the rotation of the shaft 3 and just before it stops, and due to this contact, A problem arises in the rotation accuracy of the shaft 3 due to wear. Therefore, it is preferable to perform nitriding treatment on at least one of the shaft 3 and the cylinder 1 to suppress wear.

FIG. 6 shows the results of a wear comparison experiment between a standard heat-treated product in which bearing steel was quenched at a temperature of 830° C. to 840° C. and then tempered at 180° C., and a nitrided product made of the same material. This has an outer diameter of 30mm and an inner diameter of IQms.

This is a wear experiment in which a ring-shaped specimen with a thickness of 3 mm and a plate-shaped specimen with a thickness of 5 mm were brought into contact at a sliding speed of 120 m/l 1 inch under a load of 3 kgf. The roughness and the surface roughness of the plate-shaped test piece were each 0.88. Furthermore, a 60# spindle is used for the lubrication.

As is clear from FIG. 6, the wear of the nitrided product is reduced by about 18 times compared to the standard treated product.

Moreover, even if only one of the ring-shaped test pieces and the plate-shaped test pieces was nitrided, the wear was reduced to about 18.

In addition, in FIG. 7, the hydrodynamic bearing device shown in FIG. 1 is used,
When the sphere 2 and the shaft 3 are made of standard heat-treated products,
The results of a wear test are shown in which the sphere 2 is a nitrided product and the shaft 3 is a standard heat treated product. Here, the outer diameter of the shaft 3 is 2s, the bearing clearance is 12fm, and the outer diameter of the sphere 2 is 2fi.

In addition, fluorine-based oil is used as a lubricating oil, and the shaft 3 is
This is an abrasion experiment when continuously rotating at 000 rpm for 500 hours.

As is clear from these results, the effect of the nitrided product on wear is clear, and this effect can be confirmed in actual equipment.

Fig. 8 shows the hydrodynamic bearing device of Fig. 1 in which the sphere 2 is a nitrided product and the shaft 3 is a standard heat-treated product, and silicon oil, α-olefin oil, ester oil, and fluorine oil are used as lubricating oils. The test results are shown in which the wear depth was measured when The test conditions are the same as in FIG.

From Figure 8, the wear depth of ester oil and fluorine oil is about the same, but considering that litz oil has better temperature characteristics than ester oil, it is better to use fluorine oil for hydrodynamic bearings. is preferred.

〔Effect of the invention〕

As described above, according to the present invention, since at least one of the rotating body and the bearing member is subjected to nitriding treatment, the wear resistance of the bearing portion is significantly improved and the durability is improved. It is possible to achieve the second goal.

[Brief explanation of the drawing]

1 and 2 are longitudinal sectional front views showing each embodiment of the hydrodynamic bearing device according to the present invention, and FIG. 3 shows an example in which the hydrodynamic bearing device shown in FIG. 1 is used in a video tape recorder. 4 is a vertical sectional front view showing still another example of the same hydrodynamic bearing device as above, FIG. 5 is a plan view of the same thrust plate as above, and FIGS. 6 to 8 show the results of wear tests. It is a graph. 1... cylinder, 2... sphere,
3...Noyaft, 5.13...Dynamic pressure generation groove. Patent applicant: NCH NTOYO HAIRING CO., LTD.

Claims (1)

[Claims] (1) In a hydrodynamic bearing device in which a dynamic pressure generating groove is formed on one side of the opposing surfaces of a rotating body that rotates at high speed and a bearing member that rotatably supports the rotating body, of the rotating body and the bearing member, A hydrodynamic bearing device characterized in that at least one member is subjected to nitriding treatment.