JPH0832936B2 - Sintered metal material for oil-impregnated bearings with excellent compatibility - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION “Object of the Invention” The present invention relates to a sintered metal material for oil-impregnated shafts having excellent conformability, and provides a sintered metal material for oil-impregnated bearings having a low friction coefficient and remarkably excellent conformability. Is what you are trying to do.

(Industrial field of application) Sintered metal material for obtaining oil-impregnated bearings suitable for motor shafts and other bearings for portable audio equipment.

(Prior art) Recently, portable audio equipment has become widespread, and in various other equipment, small sintered motors and their bearings, as well as flywheel gears and other rotary shaft bearings that are linked to them, have copper-based sintered oil-impregnated bearings. Has been adopted. That is,
According to JIS, for example, JIS SBK1218 specifies that copper is the main component and that tin is 8 to 11 wt% and graphite is 2 wt% or less. JIS SBK2118 also specifies that copper is the main component and copper is 6 to 1 wt%.
It is specified to contain 0 wt%, lead 5 wt% or less, graphite 2 wt% or less, zinc 1 wt% or less.

In addition, in Japanese Examined Patent Publication No. 52-5002, lead is added to copper with tin to 2
It has been announced that low temperature sintering is performed at 350-500 ° C by adding ~ 34wt%.

Further, in Japanese Examined Patent Publication No. 59-34223, tin 3-9%, iron 3-10%, manganese 4-10%, molybdenum disulfide 10-30.
%, And a self-lubricating sintered member composed of the balance of copper has been proposed.

(Problems to be Solved by the Invention) However, in the portable audio device as described above, there is a limit to the power supply capacity, and it is required that stable operation can be obtained with less power consumption and less current. To be done. Therefore, a motor used in such a device, a bearing used for a rotating shaft or a sliding portion of the motor, and the like are required to have high conformability and a low friction coefficient. However, since the conventional ones as described above cannot immediately meet such a demand recently, some solid lubricants such as lead, graphite, molybdenum disulfide are added to compensate for such a problem. The solid lubricant increases the viscosity of the impregnated oils to enlarge the torcross and it is difficult to obtain a preferable reduction in friction coefficient.

The above-mentioned Japanese Examined Patent Publication No. 52-5002 has the advantage that it can be sintered at a low temperature such as 350 to 500 ° C. However, when it is used in combination with lead, it has a bad effect on the human body and is difficult to sinter. This is as described in the publication, and there is a disadvantage that the oils to be further contained are subject to considerable restrictions.

Further, in Japanese Patent Publication No. 59-34223 mentioned above, even if the content of Sn is 3 to 9%, it also contains 10 to 30% of molybdenum disulfide as a solid lubricant. Does not combine with the mixed and molded metal powder even after normal sintering, so it easily peels off during sliding, and in the case of a self-lubricating member, this peeled molybdenum disulfide shows an excellent lubricating action, As described above, it is not preferable to add a large amount of solid lubricant in the case of fluid lubrication using lubricating oil.

"Structure of the Invention" (Means for Solving the Problems) The present invention was devised to solve the problems in the conventional art as described above, and was created as follows.

A sintered metal material for oil-impregnated bearings, which is excellent in conformity and is characterized by containing 2 to 5.5 wt% of tin, and the balance consisting of copper and inevitable impurities, and having a powder compacted and sintered structure.

The amount of unavoidable impurities as the balance in the present invention is 0.5% or less, for example, as specified in SBK of JIS B1581.

Action By adding 2 wt% or more of tin to a copper-based sintered metal material, appropriate strength is imparted and the friction coefficient is stabilized. If the tin content is less than 2 wt%, the strength of the bearing material will be too low and the friction coefficient will be unstable.

By setting the amount of tin added to 5.5 wt% or less, the strength imparted by the addition of tin is moderately suppressed, that is, Cu as a sintered metal material is increased to 94 wt% or more, and the strength and hardness of the metal structure are appropriately adjusted. With this control, the pores on the load side (the side in contact with the shaft) of the bearing body are closed at the initial stage of rotation or sliding action. That is, in this type of oil-impregnated bearing, the lubricating oil contained when the shaft rotates or slides oozes out from the pores to the sliding surface due to its viscosity and thermal expansion, and this lubricating oil forms a lubricating film between the shaft and the bearing. It is well known that they are lubricated. However, this lubricating oil also returns to the bearing structure from the pores on the load side, and the lubricating film becomes scarce, so a good lubricating state cannot be expected. In this case, the pores on the load side of the bearing body (the side in contact with the lower surface of the shaft) are closed to prevent the lubricating film on the load side from re-penetrating into the bearing body. That is, the lubricating oil flowing out from the anti-load side maintains a preferable lubricating film on the load side, and forms an effective liquid lubrication condition.

(Example) A specific example of the present invention as described above will be described together with its comparative example.
Commercially available copper powder for powder metallurgy of 0.5% or less was used, and various sintered alloys containing tin in the range of 1.5 to 9 wt% were manufactured and studied. The porosity can be appropriately carried out at about 15 to 28% by volume, and the sintering temperature can be carried out at about 700 to 850 ° C. However, when the porosity is 19% by volume and the sintering temperature is 780 ° C, Is like.

Sinter each copper-tin bearing material with an inner diameter of 6 mm, an outer diameter of 12 mm, and a length of 6 mm, containing tin in amounts of 3 wt%, 5 wt%, 7 wt%, and 9 wt%, respectively.
Each sample was impregnated with 32 cst of turbine oil after sizing.

With respect to the four types of oil-impregnated bearings thus obtained, the peripheral speed was 38 m / min, and the PV values were 190, 360, 530, 690 and 103.
The results of the rotation test, which was changed to 0, were as shown in the attached drawings.

That is, Fig. 1 shows the change of the friction coefficient with respect to the PV value. The Sn content of 3 wt% and 5 wt% is lower than the other 7 wt% and 9 wt% of the PV value to the high PV value. The coefficient of friction is low over the entire area.

In addition, FIG. 2 shows the change with time of the friction coefficient when the PV value is 530 for each of the above-mentioned samples, but the Sn contents of 7 wt% and 9 wt% are unstable even after 60 minutes have passed. On the other hand, Sn content of 3 wt% and 5 wt% is 5-10 mi
It stabilizes at about n and shows a low value of 0.02 to 0.03μ.

The Sn content of 2 wt% showed a friction coefficient similar to that of the Sn: 5 wt% described above, but in the case where the Sn content was 1.5 wt%, the friction coefficient sharply increased, and The results based on Sn: 7 wt% in Figs. 1 and 2 are shown. Also Sn
Of 3.8 to 5.3 wt% has a PV value of around 900 and a friction coefficient of 0.01
It shows a minimum state of about μ and becomes stable in 7 to 8 minutes, but when this Sn becomes 5.8 wt%, the PV value is 500 and the friction coefficient is 0.
It became as high as 04-0.05μ and showed some instability even after 40-50 min.

[Advantages of the Invention] As described above, according to the present invention, the conformability to the shaft material is excellent, the friction coefficient is rapidly reduced in the initial stage of rotation, and thereafter a stable low friction coefficient can be maintained. Therefore, it is possible to exhibit preferable and stable characteristics by adopting such a device as a device having limited power supply and electric power such as a portable audio device which has been widely spread in recent years. It is a great invention.

BRIEF DESCRIPTION OF THE DRAWINGS The drawings show the technical contents of the present invention, and FIG. 1 is a diagram showing the relationship between the PV value and the friction coefficient of the present invention and its comparative material, FIG. The figure is a table showing changes in the friction coefficient with time for a PV value of 530, which is the same as in FIG.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-50-38610 (JP, A) JP-B 48-17965 (JP, B1) JP-B 59-34223 (JP, B2) JP-B 54- 35859 (JP, B2) JP 52-5002 (JP, B2) JP 54-35565 (JP, B2)

Claims (1)

[Claims] 1. Sintering for oil-impregnated bearings, which is excellent in conformability, characterized by containing 2 to 5.5 wt% of tin, and the balance being copper and inevitable impurities, and having a powder compacted and sintered structure. Metal material.