MXPA99008587A - Sliding guide members lubricated with grease that have a low coefficient of friction and a better lifetime - Google Patents

Abstract

The present invention relates to a guide device for mechanical members, consisting of two parts designed to interact by friction sliding, one of the two parts, called the smooth part (11), which has a smooth functional surface, ie of friction, and the other part, called the perforated part (8), which has at least one surface, i.e. of friction (7) including pop-up cavities (9) designed to accommodate a grease of the lubricant paste type which it contains a soap-type constituent, an oil-type constituent and an extreme pressure additive characterized in that the contact angle 0 between the functional surface of the smooth part and the grease, measured at a temperature called the measurement temperature, which is 15 ° + 5ºC below the temperature at which the start of separation between said soap-type constituent and the constituent of the oil type occurs, is between 20 and 40 degrees and because the mat The perforated part is chosen in such a way that the contact angle, measured at the measurement temperature, between the functional surface of the perforated part and the grease is between 45 and 75 degrees.

Description

SLIDING GUIDE MEMBERS LUBRICATED WITH GREASE THAT HAVE A LOW COEFFICIENT OF FRICTION AND A LIFETIME IMPROVED DESCRIPTIVE MEMORY The present invention relates to greased mechanical components. More specifically, the invention relates to greased mechanical components that provide, by sliding friction, a translation or rotation guide function, in continuous or tiltable motion, and are designed to effectively satisfy the concerns of many industrial sectors with respect to the simplification of lubrication and reduction of maintenance frequency. Devices lubricated with grease are known in which, due to suitable sealing means, it is possible to cause two mechanical parts to rub against each other, even when subjected to very high load stresses, with a very low coefficient of friction: examples of them are given in the article "Theory and industrial practice of friction" of JJ Caubet, editor Dunod Technip, 1964, chapter 13. Document FR 910,999 of October 2, 1962, completed by its Certificate of Addition FR 921, 708 of January 17, 1963, describes a modality of said device in the case of bearings of autoalineación for high loads. However, such devices, whose technical effectiveness is recognized, have an important drawback associated with the complexity of their practical construction, which leads to high implementation costs incompatible with the current requirements of most of the industrial sectors in question. Therefore, an object of the present invention is to provide a guide device for mechanical members that makes possible the supply with the use of a sealing system. Another object of the invention is to propose a device of this type that is effective and inexpensive in the field in question. Additional objects and advantages of the invention will become apparent upon reading the following description. The invention proposes a guide device for mechanical members consisting of two parts designed to interact by sliding friction; one of the two parts, called the smooth part, has a smooth functional surface, ie, friction surface, and the other part, called the perforated part, has at least one functional surface, i.e. friction, which includes cavities pop-ups designed to accommodate a grease of the lubrication paste type and especially an EP grease (extreme pressure grease) containing a soap-type constituent, an oil-type constituent and an extreme pressure additive, characterized in that the contact angle between said functional surface of the smooth part and the gtrase, measured at a temperature called the measurement temperature, which is 15 ° ± 5 ° C below the temperature at which the start of the separation between said constituent of type of soap and the oil type constituent occurs and / or the start of the evaporation of the constituent of the oil type occurs, it is between 20 and 40 degrees and because the material of said perforated part is ge in such a way that the contact angle, measured at the measurement temperature, between the functional surface of the perforated part and the fat is between 45 and 75 degrees. The term "EP fat", which denotes an extreme pressure grease, is well known to those skilled in the art. The term "extreme pressure grease" should be understood as a grease capable of withstanding a high load without damage. Examples of such greases are lithium greases of the class SNR-LUB EP of type NLGI 2, or those of the type KLÜBER CENTOPLEX GLP 402 NLGI 2, or lithium greases and solid lubricants of the type KLÜBER COSTRAC GL 1501 MG NLGI 2. you should note that both the smooth part and the perforated part, each one, may have a non-functional surface, but this is not mandatory. The two parts (the smooth part and the perforated part) are designed to interact by friction by sliding, in translation or rotation, in a continuous or tiltable movement.

The shape of each of the two parts can be flat, cylindrical or spherical. Although commonly used by those skilled in the art, the concept of the contact angle of a drop of a liquid or viscous product placed on a solid surface is not the issue of standardization, nor even of a completely standardized measurement method, particularly when said product is a fat. The experimental conditions under which the contact angle is measured are therefore given below.

MEASUREMENT OF THE CONTACT ANGLE ACCORDING TO THE INVENTION First, the surface of the solid body on which the measurement is desired is cleaned and then a straight edge of grease is deposited thereon. The part is then heated until the temperature of its face in contact with the grease edge reaches a value of 20 ± 5 ° C higher than the limit use temperature of the grease. It is kept at this temperature for the time necessary for the fat to become sufficiently liquid to start smearing on the surface (approximately 90 seconds). The heating of the part is then stopped and allowed to cool. This has the effect of freezing the shape of the drop and allowing the measurement of its contact angle at room temperature.

Suitable materials for forming the smooth part according to the invention are chosen especially from steels, for example steels hardened in a housing, hardened with cooling and ground, steels hardened with ground HF cooling, steels that are hardened and then coated with chrome hard, nitrided steels and carbonitrided steels, chromium and nickel, as well as between steels coated with ceramics. It is necessary each time to measure the contact angle between the grease and the material that will form the smooth part, said angle must be between 20 and 40 degrees, in order to determine if this material is easily appropriate according to the invention. The material from which the perforated part is made can be a volume-forming material. This will usually be chosen from polymeric materials and copolymer materials. However, it can not be excluded that other bodies are suitable as long as their angle of contact with the grease satisfies the specified conditions. Suitable materials for making the perforated part according to the invention are especially chosen from among polyimides, filled polyimides, for example polyimides filled with graphite, epoxy resins, epoxy resins filled, such as epoxy resins filled with molybdenum disulfide M0S2, resins of polyacetal, polyethylene, substituted or unsubstituted fluorocarbons, and especially poly (PH) (perfluoroalkoxy) terephthalate, polyethersulfone, polyamides and polyetheretherketone. It is also necessary each time to measure the contact angle between the grease and the material with which the perforated part is to be formed, whose angle must be between 45 and 75 degrees, in order to determine if this material is really appropriate in accordance with the invention. The material from which the perforated part is made can also be a substrate covered with a coating. The coating is generally deposited as a thin film, typically having a thickness of about 5 to about 50 μm. In this case, the substrate is any material, in volume form or in the form of a thin sheet, for example a flat carbon steel, an alloy steel, a stainless steel, an aluminum alloy, a copper alloy, a titanium alloy, etc. The elongated laminated steel is advantageously produced in accordance with Applicant's Patent FR-B-2,693,520. When the material from which the perforated part is made is a substrate covered with a coating, it is advantageously a steel that is pre-nitrided and then covered with a polymer. The material from which the coating is made is then chosen from among polymeric materials and copolymeric materials, especially of polyimides, filled polyimides, for example polyimides filled with graphite, epoxy resins, epoxy resins filled, such as epoxy resins filled with M0S2 molybdenum disulfide, polyacetal resins, polyethylene, substituted or unsubstituted fluorocarbons, and especially PFA ( perfluoroalkoxy) polyethylene terephthalate, polyethersulfone, polyamides and polyetheretherketone. When the material from which the perforated part is made is a substrate covered with a coating, it is advantageously a steel that has been previously subjected to a surface hardening treatment. This surface hardening treatment can be a thermochemical treatment which causes a heterogeneous element, for example nitrogen, to diffuse into the steel. Said thermochemical treatment is preferably a nitriding treatment in a molten bath of alkali metal cyanates and carbonates and further advantageously contains an amount of at least one species of sulfur, for example in accordance with FR-B-2,708,623 of the Applicant. In a particularly advantageous embodiment of the invention, the perforated part is made in the form of a thin sheet, according to FR-B-2,693,520 mentioned above, made of nitrided steel according to the aforementioned FR-B-2,708,623 and coated with a polymer. In this case, it will also be necessary to verify that the contact angle of the coating material of the perforated part with the grease is between 45 and 75 degrees to determine if this coating is really appropriate according to the invention.

According to a preferred embodiment of the invention, the cavities, which form "support pads", are distributed practically over the entire surface of the perforated part. It is then advantageous that at least three cavities contribute to support a load applied to the two parts. Then it is also advantageous that the area occupied by the cavities on the development of the functional surface of the perforated part represents between approximately 20 and approximately 40% of the total area of said development. The cavities may or may not be more or less the same ones that others The cavities may or may not be distributed more or less regularly, especially to the surface of the perforated part. If the cavities are not more or less the same as one another and / or are more or less unevenly distributed above all to the surface of the perforated part, the shortest distance between the edges of two juxtaposed cavities will advantageously be greater than approximately 2 mm The emerging surface of each cavity usually has an area of between about 3 mm2 and about 40 mm2, advantageously between about 10 mm2 and about 30 mm2. According to an advantageous arrangement of the invention, the cavities emerging on the functional surface of the perforated part do not communicate with one another on the side containing said functional surface of the perforated part. The cavities may or may not communicate on the side containing a non-functional surface of the perforated part. If the cavities communicate on the side containing a non-functional surface of the perforated part, for example, through a system of channels, a cover will advantageously cover the cavities. In the context of the present invention, when the cavities are preferred as cavities communicating with each other, it should be understood that these cavities are "connected through channels (conduits) ntentionally created on the surface when removing material". The cavities, for example, can be cylindrical. The smooth part and the perforated part can be flat, cylindrical or spherical. The present invention makes it possible to obtain an arrow / bearing device in which the smooth part is the arrow and the perforated part is the bearing, a sliding track device / bearing surface in which the smooth part is the sliding track and the perforated part is the bearing surface, or a ball / receptacle device in which the smooth part is the ball and the perforated part is the receptacle. In addition to the two-part rubbing guide devices, the present invention makes it possible to design an arrangement in which there are three rubbing parts, and not two. For example, in the case of a perforated part in the form of a bushing, the two surfaces (the inner bore and the outer cylinder) of the drilled bushing are then functional. In this configuration, the perforated bushing becomes "floating", its rotation speed is then only a fraction of that of the arrow, depending on the coefficients of friction. The advantage of said arrangement is relatively limited in the case of an articulation-type oscillation system since the sliding speeds involved are then recessively low, of the order of 0.2 m / sec. On the other hand, it becomes more important for guide systems in continuous rotation, especially those in which the speeds of sliding reach high speeds of approximately 8 to 10 m / sec, or even higher. A bushing in accordance with the invention can then advantageously replace, at a lower cost, a more complex design guide member, for example a needle bearing. The description will be understood more clearly with reference to the appended figures in which: Figure 1 illustrates schematically the basic principle of the prior art in accordance with FR 910,999 and its Certificate of Addition FR 921, 708; Figures 2 to 5 illustrate schematically the measurement of the contact angle according to the invention; Fig. 6 is a schematic sectional view of a guide member of the sliding track / bearing surface type according to the invention; Figure 7 is a bottom view of the bearing surface in Figure 6; Fig. 8 schematically shows a variant of guide member of the sliding track / bearing surface type in Fig. 6; Figure 9 schematically shows a guide member according to the invention in the arrow / bearing configuration; Fig. 10 shows schematically the bearing bushing in Fig. 9; Figure 11 schematically shows a device of the ball-joint type according to the invention; Figure 12 schematically shows a device of the bearing / rail surface type where there is a slope of the bearing surface; Figure 13 schematically shows the support of the bearing surface by three pads; Figure 14 shows schematically an arrow / bearing configuration in which there are three rubbing parts, with two functional surfaces; Fig. 15 schematically shows an arrow / bearing configuration in continuous rotation with two rubbing portions, in which one face is adjusted in a contracted manner on the level of the arrow with the functional surface of the perforated bearing (ring); Figure 16 schematically shows an arrangement with three rubbing parts and with two functional surfaces, which is a variant of figure 15, with two bearing sleeves, one fitted in a contracted manner on the arrow and the other fitted within the hole of a accommodation. Figure 1 shows a bearing surface 1, in this case made of steel, designed to be rubbed on a rail 2, also made of steel, against which it is supported with a resultant force F. A circular groove has been formed in the face lower surface of bearing 1, within whose space a ring seal has been set to O, 3, space E thus leaves the inside of the O-ring seal being filled with grease 4. Thus designed, the surface of bearing 1 becomes "floating", being supported by a real "pad" of grease, thus making it possible to obtain very low coefficients of friction, typically less than 0.01, even under a high load and when moving slowly. In this regard, it will be noted that a simplified arrangement of the bearing surface 1 in Figure 1 in which the O-ring seal 3 is omitted would be adequate. This is because under the effect of the pressure of the load 1 against 2, the fat would in fact be expelled very quickly from the contact region; the rub of 1 over 2 would then take place by metal on metal and inevitably clogging would occur in a very short space of time. On the other hand, this does not occur when the seal 3 is put in place, so that then the grease 4 can not escape since the bushing is waterproof. To measure the contact angle? According to the invention, the first method consists in correctly cleaning the surface 5 of the solid body on which the measurement is desired. Next, a straight edge of grease 6 of approximately 2 mm in diameter is deposited using a syringe, on the surface of the solid body on which the measurement is desired (FIG. 2). The part is then placed on a hot plate (not shown) until the temperature of its face in contact with the grease edge reaches a value of 20 ± 5 ° C higher than the limit usage temperature of the grease. It is kept at this temperature for approximately 90 seconds. The part is then removed from the hot plate and allowed to cool, which has the effect of freezing the shape of the drop and thus allowing its contact angle to be measured at room temperature by means of a conventional device of the binocular amplifier type Equipped with a protractor. The direction of observation is indicated by "DO". The results obtained are shown schematically in Figures 3 (side cross-sectional view of the initial fat edge 6 before heating), 4 and 5 each showing a side cross-sectional view of the fat edge after heating and after cooling, respectively in the case of a smooth part 5 'and a perforated part 5. "In accordance with the invention, it is necessary to have? = 20-40 ° (6 ') in case of a smooth part and? = 45-75 ° (6") in the case of a perforated part. In Figure 6, which shows a bearing surface device 8 / slideway 11, cavities 9 are made in the lower face 7 of the bearing surface 8, ie the face which is functional and which interacts with the track Slip 11 in sliding friction. Figure 7 shows the bottom view of the bearing surface, ie its functional surface 7. The cavities in the bearing surface are cylindrical and are arranged in a regular manner. They do not communicate with each other on the side that contains this face 7. The development of the rubbing surface here is the bottom face 7 of the bearing surface 8, whose area is equal to the product L x l. L and l, respectively, the length and width of the bearing surface. The area occupied by the cavities is equal to npf2 / 4 (where n is the number of cavities) and d is the shortest distance separating the face edges of two juxtaposed cavities. In accordance with the preferred arrangements of the invention, it is necessary to have: npf2 / 4 = 20 to 40% (L x l) d >; approximately 2 mm approximately 3 mm2 < npf2 / 4 < approximately 40 mm2.

In the arrangement shown in Figures 6 and 7, the cavities do not emerge on the non-functional side 10 of the bearing surface. However, it is conceivable that this is otherwise, that is, so that the holes are no longer blind. Then it is important to avoid, by suitable means such as a cover 12 covering the cavities (Figure 8), that the fat that fills the cavities will escape through the non-functional rear surface 10 of the bearing surface. In the arrangement shown in Figure 7, the cavities do not communicate with each other on the side containing the face 10. However, it is conceivable that they can do so, for example, through a system of suitable channels. In the attached figures, the cavities have been shown in the form of cylindrical holes, these being the same ones as others and arranged in a regular manner. However, this is not a necessary condition and can be arranged differently without these other provisions thus departing from the scope of the invention. Figure 9 shows a guide member according to the invention in the configuration of arrow 13 / bearing or bearing bushing 14. The cavities are made in the bearing bushing 14 (Figure 10). In this case, the developed surface of the bearing bushing 14 is discussed, this being obtained by grooving the bushing in a direction parallel to its axis and then unrolling it until a rectangular sheet is obtained. All the considerations developed above with respect to the rolling surface type device / sliding track can then be transposed to the arrow / bearing system. Figure 11 shows a ball-type device 15 / receptacle 16, produced according to the invention, the cavities 9 being formed in the receptacles, that is to say the concave sliding parts. Figure 12 repeats the bearing and rail surface of Figure 1, but in a configuration in which the load F of the bearing surface does not give a resultant passage through the center of the O-ring seal 3. In this case , the bearing surface 1 tilts, leading to an undesirable phenomenon of bearing surfaces on sharp edges, which generate over tension - resulting in premature deterioration of the surfaces in sliding contact. To avoid this, the bearing surface 1 can be supported by at least 3 (pads) 17, the resultant of the load that presses the bearing surface onto the rail, then falling into the support polygon thus defined (Figure 3). Figure 14 shows a guide member according to the invention in an arrow / bearing configuration which is distinguished from that of Figure 9 by the fact that there are three parts of rubbing: the arrow 13, the bearing (hub 14) perforated with holes 9 and the housing 18. According to this arrangement, there are two functional surfaces on the perforated bushing 14, one of its internal holes and the other its outer cylinder.

In this configuration, the perforated bushing is "floating". Figure 15 shows an arrangement with two rubbing parts, which are the arrow 13 and the bearing (bushing 14) drilled with holes 9. A bearing sleeve 19 made of bearing steel of the type 100C6 has been fitted in a contracted manner on the same. The bushing 14 itself is tightly fitted through its outside diameter into a hole in the housing 18. Figure 16 is a variant of Figure 15 with a "floating" drilled bearing (bushing) rubbing on two bearing sleeves 19 and 20 made of bearing steel type 100C6, respectively lying on the shaft and fitted inside the hole in the housing. The present invention will be described in greater detail with reference to the following examples.

EXAMPLE 1 (COMPARATIVE) This example illustrates tests on oscillating bearings. The configuration is arrow / bearing (bearing bushing). Nature of the arrow: hardened 16NC6 steel with cooled case. Nature of the bearing (bearing bushing): polyimide filled with 40% graphite type Pl 5508. Diameter of the arrow: 30 mm.

Bearing bushing width: I = 20 mm. Developed length of the bearing bushing: D x 30 = 94.25 mm. Movement: alternating rotation over 90 ° of arc at a frequency of 1 Hz. Pressure calculated on the calculated surface: 10 MPa. Sliding speed: 0.2 m / s. Extreme pressure grease: lithium soap, type SNR-LUB EP, NLGI grade 2, operating temperature -30 to + 110 ° C. Greased during assembly, after operation without additional grease supply. In order to determine the contact angles? for arrow / grease and bearing / grease, an average of 5 measurements were made as indicated above, with fat edges deposited on parallelepiped shaped specimens, heated at 130 ° C for 90 seconds and then cooled. The results are the following: in the case of the arrow (steel 16NC6 hardened in cooled box):? = 30 ° C; in the case of bearing (polyimide filled with 40% graphite):? = 60 ° C. This example was made with a smooth bearing bushing, ie outside the field of the invention.

Test results Average coefficient of friction: 0.11; number of oscillations before a rapid increase in the coefficient of friction: 35,000.

EXAMPLE 2 (IN ACCORDANCE WITH THE INVENTION) Example 1 is repeated, except that the bearing bushing was drilled with 40 holes (cavities), each 4 mm in diameter, arranged in a regular manner with d (shorter distance separating the edges of the face from two cavities juxtaposed) = 4 mm.

Test results: Average friction coefficients: 0.009; number of oscillations before a rapid increase in the coefficient of friction: > 250,000 (proof stopped before its conclusion).

EXAMPLE 3 (COMPARATIVE) Example 1 was reproduced, except that, in the case of the material from which the bearing bushing is made, the polyimide was replaced by bronze of type UE 12 P which is an alloy commonly used for bearings.

The bearing bushing is smooth, ie outside the invention. The contact angle? for bearing / grease bushing, measured under the conditions of Example 1, is 35 °.

Test results: Average friction coefficients: 0.12; number of oscillations before a rapid increase in the coefficient of friction: 25,000.

EXAMPLE 4 (COMPARATIVE) Example 2 was repeated, except that in the case of the material of which the perforated bearing bushing is made, instead of the polyimide a bronze of type UE 12 P is used, which is an alloy commonly used for bearings. The contact angle? for the bearing / grease bushing, measured under the conditions of Example 1, is 35 °, ie outside the scale of the invention for the perforated part.

Test results: Average friction coefficient: 0.09; number of oscillations before a rapid increase in the coefficient of friction: 80,000.

Comments about examples 1 to 4 1) When the bearing bushings are smooth, ie outside the invention, their life time is of the same order of magnitude, whether they are made of polyimide or bronze. The coefficients of friction are themselves comparable and correspond to a hybrid mode, this continuing as long as the lubricant remains in the contact region. When the grease, which can escape from the edges of the bearing, is completely eliminated, the coefficient of friction rapidly increases; the bearing is then heated and then deteriorated by the thermal effect, with the polyimide or the bronze of the bearing bushing that is on the steel shaft. 2) The life times of the perforated bushings made of polyimide (in accordance with the present invention) and made of bronze (outside the invention) are significantly longer than those of the plain bearing bushings. When dismantling, at the end of the tests, it was observed that all the available grease in the cavities had been consumed, this reveals the beneficial aspect of the "lubricant reserves" that constitute the cavities. 3) The coefficient of friction of the perforated bronze bearing bushing is less than that of the smooth bronze bearing bushing. This may be at least partially due to a more regular supply of fat to the contact region and a more even distribution of this fat in this contact region., thus reducing the risk of metal / metal contact between the bearing bronze and the arrow shaft. 4) On the other hand, the explanation in 3) does not consider the very low coefficient of friction registered with the perforated polyimide bearing bushing (in accordance with the invention). In fact, a value of 0.009 typically corresponds to a hydrodynamic lubrication mode, something that is unexpected to find in a relatively high load bearing oscillation bearing in which the sliding speed is not very high. The lifetime of the perforated plumid bearing (more than 250,000 oscillations) is also surprising when compared to that of the bronze bearing bushing (80,000 oscillations). Esquatically, everything happens as if the double fact of the bearing bushing that is made of polyimide being drilled would, as a result, on the one hand , an improvement in the effect of bearing capacity and, on the other hand, an increase in the duration necessary to exhaust the reserve of lubricant. The theoretical model of these phenomena has not been carried out and only an explanatory hypothesis can be foreseen. This will be illustrated more conveniently with reference to Figure 1. The grease 4 contained in the available space E between the bearing surface 1, the rail 2 and the ring seal in O, 3, laterally transmits only a fraction of I normal pressure that it experiences, this fraction being lower while more viscous is the fat (this arises from the fact that the fat obeys to the laws of the rheology, unlike oils that obey the law of Pascal and the hydrostatic law). A relatively high load can therefore be tolerated, ie an improvement in the bearing capacity effect, and a relatively large amount of play, ie an increase in the lubricant reserve, before the start of seal 3 extrusion and the appearance of leakage of lubricant. In the configuration of the invention, seal 3 does not exist. This has an advantageous consequence, associated with the fact that the sliding of the bearing surface on the rail takes place without it being necessary that the friction of the seal on the same rail is overcome, thus contributing to the creation of a coefficient of friction low. There is also another consequence, this disadvantage being that the fat that is no longer contained naturally tends to escape through the edges of the bearing surface. This can occur more easily and quickly as the lubricant is better moistened on the surface, that is, the smaller the contact angle between the grease and the materials from which said surface is made. The above can be extrapolated directly from a rolling surface device / sliding track to another arrow / bearing type device, as explained in the previous examples with a polyimide bearing bushing (grease contact angle = 60 °) ), the lubricant is contained better than with a bronze bearing bushing (contact angle with grease = 35 °). 5) It is conceivable that another phenomenon will occur to explain the markedly superior behavior of the oscillating bearing with a steel shaft and a polyimide bearing bushing compared to that of the oscillation bearing with a steel shaft and a bronze bearing bushing. Although, as we saw earlier, the grease is better contained in the contact region with a polyimide bearing bushing than with a bronze bearing bushing, however the fact remains that there is a consumption of lubricant in both cases. Now, in the presence of two metal surfaces that have to be moistened, it is energetically more favorable that the lubricant comes in contact with one that has the smallest wetting angle with the grease, in this case the steel arrow instead of the bushing. polyimide bearing. Therefore, it can be hypothesized that each time the surface of the steel arrow passes through a cavity of the polyimide bearing bushing, said surface will attract some of the grease contained in said cavity. The rotation of the arrow therefore constantly fills the lubricant on its surface, which in turn helps to stabilize the lubrication regime and therefore improves the effect of bearing capacity and the life of the bearing. In the case of the bronze bearing bushing (contact angle of the same order as steel), this phenomenon does not occur.

EXAMPLE 5 (COMPARATIVE) Example 1 was repeated, except that in the case of the material from which the bearing bushing is made, the polyimide is replaced by tempered carbon steel of type XC 38 on its functional surface with 10 μm of an organic varnish based on a resin. epoxy filled with M0S2. The bearing bushing is smooth, ie outside the invention. The XC 38 steel plus varnish / grease contact angle?, Measured within the conditions of example 1, is 70 °.

Test results: Average friction coefficient: 0.09; number of oscillations before a rapid increase in the coefficient of friction: 45,000 (intense wear at the end of the test).

EXAMPLE 6 (IN ACCORDANCE WITH THE INVENTION) Example 5 was repeated, except that the bearing bushing is punctured by 40 holes (cavities), each 4 mm in diameter, arranged in a regular manner with d (shorter distance separating the face edges of two juxtaposed cavities) = 4 mm.

Test results: Average friction coefficient: 0.0075; number of oscillations before a rapid increase in the coefficient of friction: > 250,000 (the test was stopped before its conclusion).

EXAMPLE 7 (COMPARATIVE) Example 5 was repeated, except that the bearing bushing is made of an uncoated tempered carbon steel of type XC 38. The bearing bushing remains smooth, ie outside the invention. The contact angle? of XC 38 steel / grease, measured under the conditions of Example 1, is 25 °.

Test scores: Average coefficient of friction: unstable; number of oscillations before a rapid increase in the coefficient of friction: a few tens before clogging.

EXAMPLE 8 (COMPARATIVE) Example 6 was repeated, except that the perforated bearing bushing is made of an uncoated tempered carbon steel of type XC 38. The contact angle? of the XC 38 / grease steel, measured under the conditions of Example 1, is 25 °, ie outside the scale of the invention for the perforated part.

Test results: Average friction coefficient: 0.15; number of oscillations before a rapid increase in the coefficient of friction: a few hundred before clogging.

Comments about examples 5 to 8 The same comments can be made as in Examples 1 to 4, except that the tests result in a more marked degradation, type of heavy wear, or even clogging, as a result of steel contact / steel when the fat reserve has been consumed and / or when the varnish coating has been worn.

EXAMPLES 9 TO 14 Example 6 was repeated, with perforated bearing bushings made of steel coated with varnish, varying the number of holes (with a constant diameter) in order to vary the area occupied by the cavities. This area is measured on the development of the rubbing surface and is expressed as a percentage of the total area of that development. The area occupied by the cavities as a percentage of the total area is denoted by "S". The number of oscillations is denoted by "N". The results are given in Table I.

TABLE I Comment When the area occupied by the cavity is less than 20% of the total area of bearing development, the life of the latter decreases rapidly, reaching that of the bearing equipped with a plain bearing bushing. Above 40%, the decrease is even faster and, when removing the bearing at the end of the tests, it is observed that the surface on the bearing bushing is highly degraded, with scratches and peeling of the varnish.

EXAMPLES 15 TO 17 (IN ACCORDANCE WITH THE INVENTION) Example 2 was repeated, ie with a perforated polyimide bearing bushing, but varying the nature of the material from which the arrow is made. The grease / arrow contact angle is denoted by?. The coefficient of friction is denoted by C. The number of oscillations is denoted by "N". The results are given in Table II.

TABLE II The coefficients of friction are comparable but the lifetimes, represented by the number of oscillations, vary significantly, while still being good.

EXAMPLE 18 (COMPARATIVE) Example 6 was repeated, but the nature of the polymer coating varied. The steel of the bearing bushing is placed on the lining on its functional surface with 10 μm of PTFE (polytetrafluoroethylene). The contact angle? of the grease / bearing bushing is 85 °, ie outside the invention. The coefficient of friction is of the order of 0.008. The number of oscillations is 90,000.

EXAMPLES 19 AND 20 These Examples refer to a continuously rotating bearing configuration (guide of an arrow rotating in the hole of a housing). Examples 19 and 20 illustrate, with reference to Figures 15 and 16, the housings of the two rubbing portions (a single functional surface) and three rubbing portions (two functional surfaces), respectively. The experimental conditions are as follows : smooth part material: bearing steel type 100C6; Perforated part material: carbon steel type XC 38 nitrided with 12 μm of an organic varnish made of perfluoroalkoxy; nature of the fat: the same as in Example 1; diameter of the arrow: 30 mm; bearing bushing width: 25 mm; pressure calculated on the projected area: 5 bar. The tests were conducted at various values of the rotation speed of the arrow. In all cases, the movement can continue for hundreds of hours without any anomaly of operation and with a torque of very low resistance, corresponding to an extremely low coefficient of the order of 0.005 to 0.0005, typically friction in a lubrication regime very good hydrodynamics. The distinction between the fixation with two rubbing parts and that with three rubbing parts appears at the two extremes of the scale of the rotation speed variation. Below 2,000 to 3,000 rpm, the system with two parts of rubbing (Example 19) gives better ability to reproduce the results (100% success), unlike that with three parts of rubbing (Example 20: a success 90%). Above 10,000 to 12,000 rpm, the reverse is the case. Those skilled in the art will understand that while the invention has been described and illustrated in the case of particular embodiments, numerous variants may be made while within the scope of the invention as defined in the following claims.

Claims (33)

NOVELTY OF THE INVENTION CLAIMS

1. - A guide device for mechanical members, consisting of two parts designed to interact by friction sliding, one of the two parts, called the smooth part (11), which has a smooth functional surface, ie friction, and the another part, called the perforated part (8), having at least one functional surface, i.e. of friction (7) including pop-up cavities (9) designed to accommodate a grease of the lubricant paste type containing a constituent of soap type, an oil type constituent and an extreme pressure additive characterized in that the contact angle? between the functional surface of the smooth part and the fat, measured at a temperature called the measurement temperature, which is 15 ° ± 5 ° C below the temperature at which the separation start between said soap-like constituent and of the constituent of the oil type occurs, it is between 20 and 40 degrees and because the material of the perforated part is chosen in such a way that the contact angle, measured at the measurement temperature, between the functional surface of the perforated part and the fat It is between 45 and 75 degrees.

2. A device according to claim 1, further characterized in that the material from which the smooth part is made is chosen from steels, chromium and nickel.

3. - The device according to claim 2, further characterized in that the steel is chosen from hardened steels in housing, hardened with cooling and grinding, chilled-hardened steels of frosted HF, steels that are hardened and then coated with hard chrome, steels nitrided, steels coated with ceramics and carbonitrided steels.

4. The device according to any of claims 1 to 3, further characterized in that the material from which the perforated part is made is a volumetric material.

5. The device according to any of claims 1 to 3, further characterized in that the material from which the perforated part is made is chosen from among polymer materials and copolymer materials.

6. The device according to claim 5, further characterized in that the material from which the perforated part is made is chosen from among polyimides, filled polyimides, epoxy resins, epoxy resins filled, polyacetal resins, polyethylene, fluorocarbons substituted or not substituted, polyethylene terephthalate, polyethersulfone, polyamides and polyetheretherketone.

7. The device according to any of claims 1 to 5, further characterized in that the material from which the perforated part is made is chosen from among volumetric substrates, thin rolled steels and substrates covered with a coating.

8. - The device according to claim 7, further characterized in that the material from which the coating is made is a material chosen from among polymer materials and copolymer materials.

9. The device according to claim 8, further characterized in that the material from which the coating is made is chosen from polyimides, filled polyimides, epoxy resins, epoxy resins filled, polyacetal resins, polyethylene, substituted or unsubstituted fluorocarbons. , polyethylene terephthalate, polyethersulfone, polyamides and polyetheretherketone.

10. The device according to any of claims 6 and 9, further characterized in that the fluorocarbon is PFA (perfluoroalkoxy).

11. The device according to claim 8, further characterized in that the material from which the perforated part is made is chosen from among pre- nitrated steels.

12. The device according to claim 11, further characterized in that the steel has been subjected beforehand to a surface hardening treatment by causing the nitrogen to diffuse to the steel.

13. The device according to claim 12, further characterized in that said hardening treatment is a thermochemical nitriding treatment in a molten bath of alkali metal cyanates and carbonates.

14. The device according to claim 13, further characterized in that the molten bath further contains an amount of at least one species of sulfur.

15. The device according to any of claims 1 to 14, further characterized in that the cavities are distributed substantially over the entire surface of the perforated part.

16. The device according to claim 15, further characterized in that at least three cavities contribute to supporting a load applied to the two parts.

17. The device according to claim 15, further characterized in that the area occupied by the cavities on the development of the functional surface of the perforated part represents between approximately 20 and approximately 40% of the total area of said development.

18. The device according to any of claims 1 to 17, further characterized in that the cavities are more or less the same as others.

19. The device according to any of claims 1 to 17, further characterized in that the cavities are distributed more or less evenly over the entire surface of the perforated part.

20. - The device according to any of claims 1 to 17, further characterized in that the cavities are no more or less the same as others.

21. The device according to any of claims 1 to 17 and 20, further characterized in that the cavities are distributed more or less irregularly over the entire surface of the perforated part.

22. The device according to any of claims 20 and 21, further characterized in that the shortest distance between the edges of two juxtaposed cavities is greater than about 2 mm.

23. The device according to any of claims 1 to 22, further characterized in that the emerging surface of each cavity has an area between about 3 mm2 and about 40 mm2.

24. The device according to any of claims 20 and 21, further characterized in that the shortest distance between the edges of the juxtaposed cavities is greater than about 2 mm and the emerging surface of each cavity has an area of between about 10 mm2 and approximately 30 mm2.

25. The device according to any of claims 1 to 24, further characterized in that the cavities emerging on the functional surface of the perforated part do not communicate with each other on the side containing the functional surface of the perforated part.

26. The device according to any of claims 1 to 25, further characterized in that the cavities that merge on the functional surface of the perforated part do not communicate with each other on the side containing a non-functional surface of the perforated part.

27. The device according to any of claims 1 to 25, further characterized in that the cavities emerging on the functional surface of the perforated part communicate with each other on the side containing a non-functional surface of the perforated part through of a channel system.

28. The device according to claim 27, further characterized in that a cover (12) covers the cavities.

29. The device according to any of claims 1 to 28, further characterized in that the cavities are cylindrical.

30. The arrow / bearing device according to any of claims 1 to 29, further characterized in that the arrow is the smooth part and the bearing is the perforated part. 31.- The rolling surface device / sliding track according to any of claims 1 to 29, further characterized in that the sliding path is the smooth part and the rolling surface is the perforated part. 32. The ball / receptacle device according to any of claims 1 to 29, further characterized in that the ball is the smooth part and the receptacle is the perforated part. 33. The device according to claim 30, further characterized in that the bearing has two functional surfaces.