FR2669386A1 - SLIDING BEARING FRITTE. - Google Patents

Abstract

Disclosed is a sintered sliding bearing comprising a porous sintered alloy in which the pores are filled at least in the surface layer of the sliding face with a thermoplastic resin having a melt viscosity of 10 to 2000 mPa.s at 250degree C. Applications: use at high temperatures.

Description

The present invention relates to a sintered sliding bearing and in particular

  a sintered slide bearing for use in a high temperature environment, such as a cylinder bearing

  heating in a copying machine.

  Hitherto, sintered alloy slip bearings have been widely used for small motors and electrical appliances of oil-impregnated sintered bearings, that is, sintered bearings in which the pores are

  impregnated with a lubricating oil.

  Sintered bearings impregnated with oil have the disadvantage

  when used in a high temperature environment.

  For example, at around 2500 ° C., the impregnation oil oozes through the pores and then degrades or burns, rendering the bearings unusable. A common measure to avoid the above disadvantage was either the use of a sintered alloy not impregnated with oil but containing in the alloy matrix a solid lubricant such as graphite or molybdenum disulfide, or the use of 'a

  ball bearing into which a special lubricant is

at high temperatures.

  However, in the case of a sintered bearing based on the lubrication with a solid, it is necessary to add a large amount of the solid lubricant to obtain sufficient lubricating effects, which causes a decrease in the resistance of the solid.

  In addition, the solid lubricant bearing is naturally

  These disadvantages reduce bearing applications. The solid lubricant bearing also has the disadvantage that the cost of production is higher than that of the lubricant bearing.

of the bearing impregnated with oil.

  The use of the ball bearing, on the other hand, has the disadvantage that it is extremely expensive in comparison with

  the current sintered sliding bearings.

  An object of the present invention is to provide a sintered sliding bearing which has excellent sliding characteristics in a high temperature environment and which has a

low cost.

  Another object of the invention is to provide a sintered sliding bearing suitable for use at high temperatures.

  and having a long service life.

  Another object of the invention is to propose a bearing

  sintered slider with low wear in the time range

  temperatures from normal temperatures to high temperatures.

  These objects and others that emerge from the description

  The following detailed description can be achieved according to the invention by a sintered sliding bearing comprising a porous sintered alloy in which the pores are filled at least in the surface layer of the sliding face with a thermoplastic resin having a

  melt viscosity of 10 to 2,000 m Pa S at 250 C.

  As porous sintered metal, Fe-Cu-C alloys, Fe-containing Fe alloys and / or a carbide-forming element, Cu-Sn alloys, Al alloys and so on can be used. Incorporating a solid lubricant into these alloys

  sintered material can give even better slip characteristics

  Particularly preferred is a sintered metal comprising at least one component selected from graphite, molybdenum disulfide, tungsten disulfide, lead, boron nitride and magnesium silicate dispersed in the matrix of an alloy.

Cu or an alloy of Fe.

  Preferably, the content of solid lubricant in the sintered alloy is not more than 20% by volume. A solid lubricant content exceeding 20% by volume can give a product.

resistance too weak.

  Most of the pores of the sintered metal are preferably

  impregnated with thermoplastic resin However, the

  if the pore is impregnated only in the superficial layer.

  or even the inner surface layer of the bearing, that is,

  ie the surface layer of the sliding face.

  The thermoplastic impregnating resin, in addition to a screw

  Melt cosity of 10 to 2000 m Pa S at 250 C, has properties such that it deteriorates with difficulty when subjected to repeated cycles of heating / cooling and it is not corosive So , this thermoplastic resin can be

called "synthetic wax".

  The reasons why the above range of visco-

  In the melt state, the following are preferred.

  melt cosity at 250 C is less than 10 m Pa s, the resin

  is likely to seep outside the landing during use.

  However, if the melt viscosity at 250 C is greater than 2000 m Pa s, it is difficult to impregnate the bearing with the resin because of the high temperature. its viscosity too high, even when the resin is heated to as high a temperature as possible

  in a range that does not cause deterioration of the resin.

  Examples of thermoplastic resins that possess

  the following properties are the low molecular weight polyolefins

  Such polyethylene and polypropylene are particularly preferred. Polyethylene having a molecular weight (MW) of 2,000 to 9,000 is preferred. Polyethylene having a MW of less than 2,000 has low heat stability as seen, for example by the depletion it undergoes by heating In addition, its viscosity during use at high temperature is too low A polyethylene having a MW of more than 9000, on the other hand, has a viscosity in the state

melted too high.

  The sintered slide bearing according to the invention can be produced, for example, by melting the thermoplastic resin having the melt viscosity mentioned above and impregnating the

  pores of the alloy sintered by the molten resin.

  The sintered slide bearing according to the invention in which the pores are filled with the specific thermoplastic resin, instead of the oil used in the oil-impregnated sintered bearings, has a low coefficient of friction when used in an environment. at high temperature, for example at 300 C, by the action of liquid lubricant of the resin

  softened or liquefied with a viscosity appropriate to the temperature

high level.

  When the sintered alloy of the bearing according to the invention

  also holds a solid lubricant such as graphite or disulfide

  molybdenum, the solid lubricant reduces wear during operation.

  at normal temperatures, compensating for insufficient liquid lubrication by the resin at normal temperatures.

  Moreover, at high temperatures, the solid lubricant serves to lower the

  the coefficient of friction and wear together with the

  liquid lubrication by the resin.

  As explained above, the sintered sliding bearing according to the invention has excellent qualities and furthermore it has

  a low cost in comparison with ball bearings As a result

  Accordingly, the sintered slide bearing according to the invention is suitable as a bearing for copying machines, high temperature apparatus, conveyor apparatuses and so forth in which the bearing is used at high temperatures and can therefore increase the

  field of application of the sintered bearing.

  The following examples illustrate the invention without any

  In these examples, the thermoplastic resin

  impregnation tick is referred to as "wax".

EXAMPLE 1

  In each experiment, a sintered body having a

  weight position of 9% of Sn, 3% of Co and the remainder of Cu was dimensioned to form a bearing having an internal diameter of 10 mm, an outside diameter of 16 mm and a length of 10 mm and a porosity of 20% by volume The bearing was then impregnated with one of the following waxes or oils: 1 Polyethylene Wax PM 4,000 2 Polyethylene Wax PM 2,000 3 Polyethylene Wax PM 1,000 4 Perfluoropolyalkyl Oligomer, PM 7,500 (PFPE, fluorinated oil) Perfluoropolyalkyl Oligomerous ether, MW 6,300 (fluorinated oil)

  6 Synthetic Poly-c-o Lefine Oil.

  The levels obtained in the experiments have now been

  naked in the air for 3 h at 250 C and then cooled, after which

  evaluated the oozing of the wax or oil from the bearings.

  The results are shown in Table 1 with the viscosities of the impregnating agents. In the table, the number

  experience corresponds to the number of the impregnating agent

above.

TABLE 1

  Viscosity (m Pa s) of Experience Impregnating Agent Results

at 40 C to 250 C

  1 57 no oozing observed 2 10 no oozing observed 3 2 oozing observed 4 741 6 oozing observed | 5 124 6 oozing observed i 6 100 the oil becomes a mud o

  The levels in experiments N 4 and 5 which use

  were conventional synthetic oils (fluorinated oils), pre-

  felt a very important ooze of the impregnating oils.

  This results from the fact that the oils have low viscosities,

  despite relatively high molecular weights.

  o The level of experiment N 6 that used a common lubricating oil is completely unacceptable because the oil is

turns into a mud.

  For the stages of the experiments N 1 to 3, the results of Table 1 show that when the polyethylene wax used has a viscosity of 10 m Pa S at 250 ° C. or more, it does not occur.

  seepage of the impregnating wax.

EXAMPLE 2

  In each experiment, a powder mixture having a weight composition of 9% Sn, 3% Co and the remainder of Cu was mixed with 5% powdered graphite and the resulting mixture was packed, sintered and calibrated to form a bearing similar to that of Example 1 The bearing obtained was impregnated with one

  waxes or oils mentioned above.

  The coefficient of friction of each of the bearings obtained was measured by putting it in contact with a steel shaft at

  carbon (545 C) and rotating in an environment at 200 C.

  The test conditions were as follows: slip speed: 9 m / min; pressure on the landing: 20 bar; operating time: 500 h.

  The test results are shown in Table 2.

  In the table, the experience number is the number

of impregnating agent above.

TABLE 2

  Experience Coefficient of friction

1 0.03

0.05

3 0.20

4 0.15

0.17

6 0.35

  The stages in the experiments N 1 and 2 according to the invention

  each had a low coefficient of friction, tan-

  At oo say that the stage of the experiment N 3 which used the low viscosity wax not falling within the scope of the invention and the

  levels of experiments 4 to 5 which used synthetic oils

  Classical ticks each had a high coefficient of friction. It is considered that the cause of high values in Experiments Nos. 3 to 5 is the loss of impregnating oil due to

  seepage outside the landing.

  The bearing in experiment No. 6 which used a common lubricating oil had a very high coefficient of friction

  It is considered that the cause is that the action of lubrifica-

  oil was almost lost and therefore slippage was only achieved by solid lubrication.

graphite.

  When experiments were performed using

  a sintered Fe alloy containing 1.5% by weight Cu as material

  the results presented a trend similar to that of

that observed above.

  Furthermore, when the experiments were carried out by varying the solid lubricant added to the bearing material, the graphite gave the highest coefficient of friction.

  low, although there is not much difference between the coefficients

  friction ficients of the various solid lubricants used

  value of the coefficient of friction increased in the following order

  graphite (low) <molybdenum disulfide <tungsten disulfide <boron nitride <magnesium silicate <lead (high).

Claims (6)

  1 sintered slide bearing characterized in that it com-   takes a porous sintered alloy in which the pores are filled at least in the surface layer of the sliding face with a thermoplastic resin having a melt viscosity of 10. at 2000 m Pa S at 250 C.   Sintered sliding bearing according to Claim 1, characterized in that the thermoplastic resin is a resin of   polyolefin of low molecular weight.   Sintered sliding bearing according to Claim 2,   characterized in that the low molecular weight polyolefin resin   is a polyethylene having a molecular weight of 2,000 to 9,000.   Sintered sliding bearing according to any one of   Claims 1 to 3, characterized in that the sintered alloy   takes at least one component selected from graphite, molybdenum disulfide, tungsten disulfide, lead, boron nitride and magnesium silicate dispersed in the matrix of a   alloy selected from Cu alloys and Fe alloys.   Sintered sliding bearing according to claim 1, characterized in that it is intended for use at elevated temperatures. Sintered sliding bearing according to claim 5, characterized in that it is intended for use as a bearing in an apparatus where the bearing is used in an environment in which high temperature.   Sintered slide bearing according to Claim 6, characterized in that the apparatus is selected from   copying, high-temperature devices and trans-   carriers. Sintered sliding bearing according to Claim 6, characterized in that it is intended for use as a bearing   for the heating cylinder of a copying machine.