JPH10184688A - Sintered oil-retaining bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve wear resistance, load resistance, heat resistance and lubricating ability. SOLUTION: An iron sintered body containing an iron component at 80wt.% or more is impregnated with an oil composition formed by mixing 0.1-10wt.% of one or more kinds of extreme-pressure additives selected from a group formed of dithiophosphate or dithiocarbamate into a base oil containing one or more kinds of oil selected from a group formed of high refined mineral oil, ester group synthetic oil or ether-based synthetic oil.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sintered oil-impregnated bearing having improved abrasion resistance, load resistance, heat resistance and lubricity.

[0002]

2. Description of the Related Art Sintered oil-impregnated bearings are widely used in places where sufficient lubrication cannot be expected from an environmental or mechanical point of view because of their functionally non-lubricating nature.

[0003] The lubrication of this sintered oil-impregnated bearing is performed by the self-lubricating action of the lubricating oil from the oil-impregnated hole. The lubricating performance depends on the structure of the oil-impregnated hole, the oil content, the type of the lubricating oil, and the like. It is also affected by the strength and friction characteristics of

[0004]

[Problems to be Solved by the Invention] With the spread of small motors in recent years, these sintered oil-impregnated bearings are used in office equipment, home appliances, audio equipment, and even automobiles. Tend to be. In addition, with the high functionality, lightweight, and miniaturization of various devices, the performance required for sintered oil-impregnated bearings has become more sophisticated and diversified, and accordingly, there has been a demand for the development of more advanced lubrication technology.

Conventionally, in order to improve bearing performance, improvement of lubricating oil to be impregnated, improvement of shaft and bearing materials, improvement of bearing shape, and the like have been individually performed. Sufficient results have not been obtained in any of heat resistance and lubricity.

In particular, lubricating oil impregnating a sintered oil-impregnated bearing is
Since the amount used is small, there are few lubricating oils exclusively for sintered oil-impregnated bearings, and currently, they are selected from commercially available hydraulic oils and engine oils. Additives to be added to this type of lubricating oil have problems such as sludge formation, and the amount of the additive is as small as possible as compared with lubricating oil used for rolling bearings.

Therefore, the present invention is not limited to sole improvements such as improvement of lubricating oil, improvement of shaft and bearing materials, etc., which have been attempted in the past, but also improvement of total lubrication technology as a sintered oil-impregnated bearing. Accordingly, an object of the present invention is to provide a sintered oil-impregnated bearing having characteristics excellent in wear resistance, load resistance, heat resistance and lubricity.

[0008]

Means for Solving the Problems The sintered oil-impregnated bearing according to the present invention is an iron-based sintered body which is excellent in heat resistance, wear resistance and load resistance and contains an iron component of 80% by weight or more. Base oils containing one or more oils selected from the group consisting of highly refined mineral oils with excellent lubricity, ester-based synthetic oils or ether-based synthetic oils with excellent heat resistance, and dithiophosphates or dithiocarbamates One or more selected extreme pressure additives are impregnated with an oil composition obtained by mixing 0.1 to 10% by weight.

[0009] Among the base oils of the oil composition used in the present invention,
Highly refined mineral oil is a mineral oil obtained by removing impurities such as sulfur compounds, nitrogen compounds, and aromatic components contained in mineral oil by a special refining method, and improving shear stability, heat and oxidation stability. At this time, the viscosity (40 ° C.) is 10 to 1
It is preferable to use one having a size of 50 mm ² / s.

Among the base oils used in the present invention, the ester-based synthetic oils include polyol ester oils, diester oils, polyester oils, phosphate ester oils, silicate ester oils, and complex ester oils thereof. The viscosity (40 ° C.) is 10 to 150 mm ² / s,
It is preferable to employ one having a flash point of 220 ° C. or higher.

The polyol ester oil has three or four ester groups in the molecule, and as shown in the following chemical formula,
The β-carbon on the alcohol side is quaternary. A typical example is trimethylolpropane ester.

[0012]

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Examples of the phosphoric acid ester include a triaryl phosphate, a trialkyl phosphate and the like.

Among the base oils of the oil composition used in the present invention,
As the ether-based synthetic oil, phenyl ether oil or the like having a viscosity (40 ° C.) of 10 to 150 mm ² / s and a flash point of 220 ° C. or higher is preferably used. A typical example is an alkyl diphenyl ether oil. This alkyl diphenyl ether oil is composed of 1 mol of diphenyl ether and α having 10 to 22 carbon atoms.
-Obtained by addition reaction of 1 to 3 mol of olefin. An example of the alkyl diphenyl ether oil is shown in the following chemical formula.

[0015]

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As the base oil of the oil composition used in the present invention, there are the above-mentioned base oils. In order to improve both lubricity and heat resistance, highly refined mineral oil, ester-based synthetic oil or ether-based oil is used. It is desirable to use a mixture of two or more of the synthetic oils.

It is desirable to use highly refined mineral oil, ester-based synthetic oil and ether-based synthetic oil that contain as little impurities as possible in consideration of sludge and the like.

The extreme pressure additives to be added to the oil composition include:
Dithiophosphates or dithiocarbamates include, but dithiophosphates include zinc dithiophosphate, molybdenum dithiophosphate and lead dithiophosphate, and dithiocarbamates include zinc dithiocarbamate, molybdenum dithiocarbamate or lead dithiocarbamate. Is mentioned.

The extreme pressure additive reacts with the metal surface to form a surface film that is almost insoluble in oil, so that the convex portions between the metals break through the adsorbed oil film and come into contact with each other, and as the surface temperature increases, Even under severe lubricating conditions in which the adsorbed oil film is destroyed, wear is reduced as much as possible to avoid lubrication failure. Since the extreme pressure additives specified in the present invention are easily adsorbed or chemically bonded to iron,
In an iron-based sintered oil-impregnated bearing containing 80% by weight or more of an iron component, when added to the oil composition impregnated with the iron-based oil-impregnated bearing, the extreme pressure property of the oil composition and lubricity can be improved.

As the additives to be added to the oil composition, there are the above-mentioned ones. However, in order to improve abrasion resistance, load resistance and lubricity, a dithiophosphate and a dithiocarbamate are used in combination. It is desirable to do.

The oil composition may further contain, as other additives, an antioxidant, a rust inhibitor, and the like which are usually added to the oil composition.
A cleaning dispersant, an antifoaming agent, an oil agent, another extreme pressure agent, and the like can be added.

As the sintered body constituting the sintered oil-impregnated bearing,
80 iron components with excellent heat resistance, abrasion resistance and load resistance
Use an iron-based alloy containing at least% by weight. In this case, in particular, the surface porosity of the sliding surface is adjusted to that of a normal sintered oil-impregnated bearing (30%).
-45%) and preferably 5-30%. The reason why the surface porosity of the sliding surface is lower than that of the normal product is as follows.
This is for facilitating the adsorption or chemical bonding of the oil composition and for improving the lubricity of the oil composition.
In this case, it is more desirable that the surface porosity of the sliding surface be 5 to 15% in area ratio using a finishing method such as rotational sizing.

Further, as a component other than iron of the sintered body,
It is preferable to use at least one selected from the group consisting of phosphorus, sulfur, zinc, molybdenum, lead, nickel, chromium, copper or graphite, which easily adsorbs or chemically bonds to the oil composition.

The constituents other than iron (phosphorus, sulfur, zinc, molybdenum, and lead) are constituents of the extreme pressure additive, and nickel is the same Group 8 transition metal as iron, and chromium. Is a group 6A transition metal like molybdenum, and thus has an effect of facilitating adsorption or chemical bonding of the oil composition, respectively.

Further, the oil-impregnated sintered bearing of the present invention may contain, as other components, a solid lubricant (eg, graphite) or a sintering aid (eg, copper) which is generally used. .

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below.

FIG. 6 shows an example of a bearing device using the sintered oil-impregnated bearing according to the present invention. This bearing device comprises a housing (1) having one end open and the other end closed.
A sintered oil-impregnated bearing (2) having a bearing surface (2a) is press-fitted and fixed, and a rotor (3) is mounted on an inner peripheral portion of the sintered oil-impregnated bearing (2).
A rotating shaft (5) that rotates by an exciting force between the motor and the stator (4) is inserted, and is used for a scanner motor of a laser beam printer, for example. The thrust load of the rotating shaft (5) is supported by the thrust receiver (6).

In the sintered oil-impregnated bearing (2), a bearing surface (2a) that slides on a rotating shaft (5) is formed on a porous sintered body, and an oil to be described later is further lubricated thereon. It is impregnated with the composition, and is manufactured by a well-known method as an iron-based sintered alloy containing 80% by weight or more of an iron component having excellent heat resistance, wear resistance, and load resistance. On the sliding surface (bearing surface 2a) of the sintered oil-impregnated bearing (2), the surface porosity is preferably 5 to 30%, more preferably 5 to 15%, in order to facilitate adsorption or chemical bonding of the oil composition. And the normal surface porosity (30 to 45)
%).

The oil composition may be a highly refined mineral oil such as poly-α-olefin, an ester synthetic oil such as a polyol ester,
Or a base oil containing one or more oils selected from the group consisting of ether synthetic oils such as alkyl diphenyl ethers,
One or more extreme pressure additives selected from the group consisting of dithiophosphates or dithiocarbamates are produced by mixing at 0.1 to 10% by weight. As the dithiophosphate, at least one selected from the group consisting of zinc dithiophosphate, molybdenum dithiophosphate or lead dithiophosphate, and as the dithiocarbamate, zinc dithiocarbamate, molybdenum dithiocarbamate or lead dithiocarbamate is used. One or more selected from the group consisting of can be used.

The bearing device described above can be applied to various motors such as a polygon mirror motor of a laser beam printer, a spindle motor for a magnetic disk drive, electric products such as an axial fan, a ventilation fan and a fan, and electric components for automobiles. Can be used extensively.

[0031]

EXAMPLES In order to demonstrate the effects of the present invention, evaluation tests were performed on the following examples and comparative examples. The present invention is, of course, not limited to the configuration disclosed in each embodiment.

The following two tests were performed as evaluation tests.

[High-temperature endurance test] Inner diameter 6 mm, outer diameter 12 m
m, using a 6 mm wide sintered oil-impregnated bearing, with a rotation speed of 3000
rpm (constant), an ambient temperature of 150 ° C., and a radial load of 9.8 N / Brg. The test was conducted under the conditions of
mN · m) or more. (N =
3). In the evaluation of this test, when the time required to reach a certain torque or more is 1000 hours or more,
○ for 00 hr, Δ for 500 to 750 hr,
In the case of 500 hours or less, it was evaluated as x.

[High load wear test] Inner diameter 6 mm, outer diameter 12
mm, 6 mm wide sintered oil-impregnated bearing, rotation speed 0-2
000 rpm (ON-OFF), ambient temperature 80 ° C., radial load 118 N / Brg. , And the amount of wear after a certain time (500 hr) was measured (n = 3). In the evaluation of this test, the wear amount after the above-mentioned fixed time was 2 μm
In the following cases, ◎, 2 to 4 μm, ○, 4 to 6 μm, Δ, 6 μm or more, ×.

The compositions of the sintered oil-impregnated bearings in Examples and Comparative Examples are shown in FIGS. 1 to 4 (Example) and FIG. 5 (Comparative Example).

As the base oils of the oil compositions used in the examples and comparative examples, a high-purity mineral oil, a polyol ester was used as a typical example of an ester-based synthetic oil, and an alkyl diphenyl ether was used as a typical example of an ether-based synthetic oil.

As extreme pressure additives for the oil composition, zinc dithiophosphate and molybdenum dithiophosphate were used as representatives of dithiophosphate, and zinc dithiocarbamate and molybdenum dithiocarbamate were used as representative examples of dithiocarbamates.

To the oil composition, 0.5% by weight of dioctyldiphenylamine was uniformly added as an antioxidant.

The sintered body contains 93 to 97% by weight of an iron component and 3 to 7% by weight of graphite and copper as other components (solid lubricant, sintering aid, etc.). The thing whose surface porosity was 30-45% in area ratio was used. Further, in order to examine the influence of the difference in bearing material, a material containing 0.5% by weight of phosphorus, 1% by weight of sulfur, and 1.5% by weight of molybdenum was used. To examine the effect of the difference, 5-15% by area ratio
Was also used. In addition, a copper-iron-based sintered body having an iron component of 80% by weight or less was used.

[Examples 1 to 4] In Examples 1 to 4, the mixing ratio of the base oil in the oil composition was adjusted as shown in FIG. 1, and zinc dithiophosphate was added as an extreme pressure additive to 2.0%. % By weight.

[Examples 5 to 7] In Examples 5 to 7, 48.75% by weight of a highly refined mineral oil and a polyol ester were used as the base oils of the oil composition, respectively. Additives were compounded.

Examples 8 to 10 In Examples 8 to 10,
Highly refined mineral oil and polyol ester were each used as a base oil of the oil composition in an amount of 48.75% by weight, and zinc dithiophosphate and molybdenum dithiocarbamate were added in amounts of 1.0% by weight as extreme pressure additives. Also, the sintered body
Iron as the main component, phosphorus, sulfur and molybdenum
Was blended at the ratio shown in Table 1.

[Examples 11 and 12] In Examples 11 and 12, a highly refined mineral oil and a polyol ester were used as base oils of the oil composition in an amount of 48.75% by weight, respectively, and zinc dithiophosphate was used as an extreme pressure additive. And 1.0% by weight of molybdenum dithiocarbamate. The sintered body was composed of the composition shown in FIG. 4 containing iron as a main component, and the surface porosity of the sliding surface was 5 to 15% in area ratio.

Comparative Examples 1 and 2 In Comparative Examples 1 and 2, the composition of the oil composition was adjusted as shown in FIG.

Comparative Examples 3 and 4 In Comparative Examples 3 and 4, a highly refined mineral oil and a polyol ester were each used as the base oil of the oil composition at 48.75% by weight, and zinc dithiophosphate and dithiocarbamine were used as extreme pressure additives. A mixture of molybdenum acid at the ratio shown in FIG. 5 was used. As the sintered body, a copper-iron based sintered body having an iron component of 80% by weight or less was used.

As is apparent from the test results shown in FIGS. 1, 2 and 5, these sintered oil-impregnated bearings using an oil composition to which a dithiophosphate or a dithiocarbamate is added as an extreme pressure additive are more likely to be used. It can be understood that heat resistance, lubricity, load resistance and abrasion resistance are superior to sintered oil-impregnated bearings using an oil composition to which no is added.

As is clear from the test results shown in FIGS. 1, 2 and 5, among the sintered oil-impregnated bearings, those containing 80% by weight or more of iron component are excellent in load resistance and wear resistance. I can understand that

As is clear from the test results shown in FIGS. 2 and 3, the oil composition is adsorbed or chemically bonded as a component other than iron of the iron-based sintered oil-impregnated bearing containing 80% by weight or more of the iron component. Sintered oil-impregnated bearings containing one or more components selected from the group consisting of phosphorus, sulfur, zinc, molybdenum, lead, nickel, or chromium, are more heat-resistant, lubricious, load-bearing and wear-resistant. It can be understood that is improved.

As is clear from the test results shown in FIGS. 2 and 4, as the iron-based sintered oil-impregnated bearing containing 80% by weight or more of the iron component, the surface porosity of the sliding surface was 5 to 15 in area ratio. %
It can be understood that the sintered oil-impregnated bearing having improved heat resistance, no lubricity, load resistance and wear resistance.

[0050]

As described above, the sintered oil-impregnated bearing according to the present invention can improve the wear resistance, load resistance, heat resistance and lubricity of the sintered oil-impregnated bearing.

Further, the improvement of the total lubrication mechanism of the sintered oil-impregnated bearing is achieved, instead of the conventional improvement such as the improvement of the lubricating oil and the improvement of the sintered oil-impregnated material.

[Brief description of the drawings]

FIG. 1 is a diagram showing the results of an evaluation test for an example.

FIG. 2 is a diagram showing the results of an evaluation test for an example.

FIG. 3 is a diagram showing the results of an evaluation test for an example.

FIG. 4 is a diagram showing the results of an evaluation test for an example.

FIG. 5 is a diagram showing the results of an evaluation test for a comparative example.

FIG. 6 is a sectional view showing an example of a bearing device using a sintered oil-impregnated bearing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Housing 2 Sintered oil-impregnated bearing 3 Rotor 4 Stator 5 Rotation shaft 6 Thrust receiver

Claims (5)

[Claims] 1. A base oil comprising an iron-based sintered body containing at least 80% by weight of an iron component and one or more oils selected from the group consisting of highly refined mineral oil, ester-based synthetic oil and ether-based synthetic oil. One or more extreme pressure additives selected from the group consisting of dithiophosphates or dithiocarbamates,
A sintered oil-impregnated bearing impregnated with an oil composition obtained by mixing 0% by weight. 2. The sintered oil-impregnated bearing according to claim 1, wherein the dithiophosphate is at least one selected from the group consisting of zinc dithiophosphate, molybdenum dithiophosphate and lead dithiophosphate. 3. The sintered oil-impregnated bearing according to claim 1, wherein the dithiocarbamate is at least one selected from the group consisting of zinc dithiocarbamate, molybdenum dithiocarbamate and lead dithiocarbamate. 4. The sintered oil-impregnated bearing according to claim 1, wherein the surface porosity of the sliding surface of the iron-based sintered body is 5 to 30% in area ratio. 5. The non-iron component of the iron-based sintered body,
5. The sintered oil-impregnated bearing according to claim 1, wherein the bearing is at least one selected from the group consisting of phosphorus, sulfur, zinc, molybdenum, lead, nickel, chromium, copper and graphite.