WO2012161259A1

WO2012161259A1 - Seal member

Info

Publication number: WO2012161259A1
Application number: PCT/JP2012/063343
Authority: WO
Inventors: 山本　智久; 片山　竜雄; 横田　理津子; 千尋浅沼
Original assignee: 内山工業株式会社
Priority date: 2011-05-26
Filing date: 2012-05-24
Publication date: 2012-11-29
Also published as: JP2012246974A

Abstract

A seal member (7) comprises a rubber base (70) that includes a sliding contact surface (4a) that is in elastic sliding contact with a partner member (2), and is characterized in that a large number of small holes (8) with a depth of 3 to 20 μm and an opening size of not more than 70 μm are formed by laser processing on a surface that includes at least the sliding contact surface (4a) of the rubber base, and the percentage of the area occupied by the openings of the small holes in an area in which the small holes are formed is set at 5 to 50%.

Description

Seal member

The present invention relates to a rubber seal member, for example, a rubber seal member incorporated in a seal ring of a bearing.

The seal ring of the bearing as described above includes a rubber seal member that is integrally fixed to the metal core, and is interposed between two members (for example, an outer ring and an inner ring) that rotate relative to each other. The seal member is fitted to one member of the two members via the cored bar, and the seal lip portion is incorporated so as to be in sliding contact with the other member of the two members directly or via a slinger. When the two members rotate relative to each other, the seal lip portion elastically slides on the mating member (the other member or slinger or the like) and functions to seal the bearing space of the bearing.

In the seal ring incorporating the seal member as described above, in order to reduce the resistance when sliding against the mating member while maintaining the sealing performance, grease or the like is applied to the sliding portion of the mating member of the seal lip portion. Lubricant is applied. In order to improve the retention of the lubricant and to reduce wear and friction, fine concavo-convex processing (roughening treatment) is also performed on the sliding contact portion of the seal lip portion. Patent Documents 1 to 3 describe seal members that have been subjected to such roughening treatment. Patent Document 4 describes a surface treatment method for a vulcanized rubber in which a surface of the vulcanized rubber is irradiated with an ultraviolet laser to form a fine uneven structure on the surface of the rubber.

JP 2001-355740 A Japanese Patent Application Laid-Open No. 2004-267338 JP 2008-8455 A Japanese Patent No. 3380124

Conventionally, as a method of roughening the surface of rubber, a method is used in which a molding surface of a mold for molding a rubber base material is subjected to embossing, and the embossed surface is transferred to the rubber base material during molding. A method of subjecting the surface of the rubber base material to blast shot processing or polishing processing has been implemented. In Patent Document 1, it is described that the roughening of the sliding surface of the seal lip made of a rubber elastic body of an oil seal is performed by a satin finish, a screw protrusion or a parallel protrusion, or a knurling process. No specific surface roughening treatment method is described. Further, Patent Document 2 describes that a roughened surface is formed on a contact surface of a seal lip made of a rubber elastic body of a seal ring with a mating member. There is no description about the method. In Patent Document 3, fine irregularities are formed on a molding surface of a molding die by irradiation of a short pulse laser, and when the sealing member is molded by loading resin into the die, the above-described mold formed on the die is formed. It is described that fine irregularities are formed on the contact surface of the sealing member with the inner ring (counter member) by transferring the irregularities to the sealing member.

When the method described in Patent Document 3 is applied to the surface processing of a rubber substrate, the releasability at the time of molding is poor, thereby reducing the yield of the rubber substrate as a molded product, and stable mass production. It was difficult to convert. In this case, it is also possible to form fine irregularities on the inner surface of the mold by cutting, etching or shot processing instead of laser irradiation, but the irregularity formation mode cannot be arbitrarily controlled. Therefore, it is difficult to secure a flat portion serving as a seal point. For this reason, when it is applied to a seal member, there is a case where reliability is lacking in sealing performance. Furthermore, it was impossible to regularly form a large number of small holes having a small hole diameter and a depth.

As described above, Patent Document 4 describes a surface treatment method for vulcanized rubber by irradiating the surface of the vulcanized rubber with an ultraviolet laser to form a fine uneven structure on the surface of the rubber. There is a description that the concavo-convex structure can be controlled by changing the fluence and the number of irradiations per unit time. However, the purpose of forming the fine concavo-convex structure here is to improve the tribological characteristics of the rubber product such as prevention of adhesion between vulcanized rubber products or control of the friction coefficient. It is not intended to improve the retention of the lubricant, the wettability of the lubricant, or the like at the contact portion. In addition, since there are convex portions, when applying to a seal member that seals the portions that are in sliding contact with each other, wear powder is generated at the time of sliding contact, or the presence of the convex portions may be a factor that hinders sealing performance. is expected.

The inventors of the present invention have reduced wear by forming a large number of dimple-shaped small holes on the surface of the rubber base material for sealing by laser processing and improving the retention of the lubricant interposed in the sliding contact portion with the mating member. In addition, intensive trial and error were repeated in order to find the optimum formation mode of the small holes capable of reducing the friction. As a result, according to the laser processing, the optimum formation mode can be realized with good reproducibility with respect to the depth of the small hole, the opening diameter, and the ratio of the occupied area of the small hole opening in the small hole forming region. It was. Based on such knowledge, the present invention is excellent in retention of lubricant, low wear and low friction, and is made of rubber that can capture rubber wear powder and foreign matter from the outside to reduce wear on the seal surface. The object is to provide a sealing member.

The seal member according to the present invention is a seal member made of a rubber base material including a sliding contact surface that is elastically slidably contacted with a counterpart member, and on the surface including at least the sliding contact surface of the rubber base material, A large number of dimple-shaped small holes having a depth of 3 to 20 μm and an opening diameter of 70 μm or less are formed by laser processing, and the ratio of the area occupied by the small hole openings in the region where the small holes are formed is 5 to 50%. It is characterized by being.

In the present invention, the rubber base material includes a base portion to which the rubber base is fixed and a seal lip portion extending from the base portion, and the sliding contact surface is provided on the front side of the seal lip portion. It is good as well. The small hole may be formed after peeling the surface layer portion of the rubber base material by continuous laser irradiation.

According to the present invention, since the surface including the sliding contact surface of the rubber base material elastically sliding relative to the counterpart member is provided with a large number of dimple-like small holes, the contact area with the counterpart member is reduced, A low friction seal member is obtained. Therefore, if this seal member is applied to a seal ring or the like in a wheel bearing device of an automobile, the rotational torque is reduced and the fuel consumption is reduced. In particular, when used in a state where a lubricant is interposed between the region where the small hole is formed and the mating member, the lubricant is held in the small hole, and the lubricant is gradually supplied from the small hole so that the sliding is performed. Lubricant depletion on the contact surface can be prevented. As a result, smooth sliding contact is maintained, low friction and low wear of the seal member are realized, and a long life is achieved. In addition, rubber wear powder generated during sliding contact and foreign matter entering from the outside can be captured in small holes, reducing wear such as scratches on the sliding contact surface due to biting of wear powder or foreign matter on the sliding contact surface. be able to. The characteristics of the sealing member of the present invention are as follows. The depth of the small hole is 3 to 20 μm, the opening diameter of the small hole is 70 μm or less, and the ratio of the area occupied by the small hole opening in the region where the small hole is formed (hereinafter, It is expressed very suitably by setting the occupied area ratio) to 5 to 50%. In addition, the small holes whose shape and the like are specified in this way are formed with good reproducibility by laser processing, and can provide a consumer with a stable quality sealing member.

Incidentally, when the depth of the small hole is less than 3 μm, the effect of reducing the frictional resistance of the sliding contact surface with the mating member in the state where the lubricant is interposed tends to be reduced. Moreover, when the depth of the small hole is less than 3 μm, the variation in the frictional resistance tends to increase. When the depth of the small hole exceeds 20 μm, the variation in the frictional resistance becomes small, but the amount of lubricant supplied from the small hole to the sliding contact surface decreases, and this tends to increase the frictional resistance. On the other hand, when the opening diameter of the small holes exceeds 70 μm, the substantial sealing points are reduced and the sealing performance tends to be lowered. Further, when the occupied area ratio is less than 5%, the effect of reducing the frictional resistance tends to be small and the variation of the frictional resistance tends to increase, and when it exceeds 50%, the substantial sealing point decreases and the sealing performance is reduced. It tends to decrease.

In the present invention, the rubber base material includes a base portion to which the rubber base is fixed and a seal lip portion extending from the base portion, and the sliding contact surface is provided on the front side of the seal lip portion. If it is, it is preferably applied to a seal ring or the like in the wheel bearing device. In addition, when the small hole is formed after peeling the surface layer portion of the rubber base material by continuous laser irradiation, the surface layer portion of the rubber base material is peeled off by laser processing, so that the compatibility with the lubricant is achieved. , Lipophilicity is obtained. Therefore, combined with the characteristics due to the formation of the small holes, the suitability as a seal member used with the lubricant interposed therebetween is further improved.

It is sectional drawing which shows the example which applied the seal member which concerns on one Embodiment of this invention to the pack seal type seal ring integrated in a bearing apparatus. It is a conceptual diagram which shows the point which forms a small hole in the sample for rubber base materials with a laser processing machine. It is the figure which summarized the preparation conditions of the sample for rubber base materials. It is the figure which put together the detail of the laser processing machine to be used. It is the figure which put together the relationship between the shape of the small hole obtained by performing laser processing using f100 lens, changing a laser frequency, shutter opening time, and a laser output. It is the figure which put together the relationship between the shape of the small hole obtained by performing laser processing using the f160 lens and changing the laser frequency, shutter opening time, and laser output. It is the figure which put together the relationship between these processing factors and the shape of the obtained small hole, performing laser processing using f300 lens, changing a laser frequency, shutter opening time, and a laser output. FIG. 8 is a diagram summarizing the results shown in FIGS. 5 to 7 as a small hole shape controllable range by beam and lens type. It is a figure which shows notionally the state which performs the measurement test of the friction coefficient of the sample for rubber base materials using a friction abrasion tester. It is the figure which put together the conditions of the measurement test of a friction coefficient. It is the figure which put together the measurement result of the friction coefficient at the time of changing the occupation area rate of a small hole. It is a graph which shows roughly the same measurement result as a relationship between the occupation area rate of a small hole, and a friction coefficient. It is a graph which shows the difference by the time change of the friction coefficient by the solvent (ethanol) wiping presence or absence about the same sample. It is the figure which put together the measurement result of the friction coefficient at the time of changing the opening diameter of a small hole. It is a graph which shows roughly the same measurement result as a relationship between the opening diameter of a small hole, and a friction coefficient. It is the figure which put together the measurement result of the friction coefficient at the time of changing the depth of a small hole. It is a graph which shows roughly the same measurement result as a relationship between the depth of a small hole, and a friction coefficient. It is a graph which shows the difference by the time change of the friction coefficient of an optimal laser processing sample and an unprocessed sample. It is the figure which put together the observation result of the sample after a measurement test. It is a conceptual diagram which shows the point which forms a small hole in a rubber base material with a laser processing machine, after peeling off the surface layer part of the sample for rubber base materials by laser continuous irradiation in advance. It is a graph which shows the relationship between the hydrophilicity of the sample surface for rubber base materials which peel-processed the surface layer part by continuous irradiation of a laser, and a new oil property, and the frequency of an irradiation laser, (a) is a rubber base material when water is dripped. (B) shows the relationship between the contact angle of the hexadecane droplet on the rubber substrate sample surface and the frequency of the irradiation laser when hexadecane is dropped. Show.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an example in which the seal member according to the present invention is applied to a seal lip portion of a pack seal type seal ring. The illustrated seal ring 1 is, for example, a seal ring that is mounted on a bearing device (not shown) that rotatably supports a vehicle wheel. The seal ring 1 includes a metal slinger (a mating member) 2 that is integrally fitted to an inner ring or shaft (not shown) on the rotating side, and an inner fitting that is integrally fitted to an outer ring (not shown) on the fixed side. And a rubber seal member 7 including three seal lip portions 4 to 6 which are integrally fixed to the core metal 3 and elastically slidably contact the slinger 2. Is done. The seal member 7 in the illustrated example has two side (axial)

lip portions

4 and 5 that elastically slidably contact the axial surface of the slinger 2 as a seal lip portion, and 1 that elastically slidably contact the radial surface of the slinger 2. A sheet of grease (radial) lip 6 is provided. Grease G is applied to the elastic sliding contact portion between the seal lip portions 4 to 6 and the slinger 2. In the figure, a two-dot chain line indicates an original shape in which the seal lip portions 4 to 6 are not elastically deformed. The seal member 7 is formed of a molded body of a rubber base material 70. The rubber base material 70 includes a base portion 700 fixed to the core metal 3, and the three annular seal lips extending from the base portion 700. Parts 4-6. Sliding contact surfaces 4a to 6a that elastically slide on the slinger 2 are provided on the front sides of the seal lip portions 4 to 6.

At least one elastic sliding contact portion including the sliding contact surfaces 4a to 6a of the

side lip portions

4 and 5 and the grease lip portion 6 with the slinger (mating member) 2 is subjected to a number of processes by laser processing described later. Dimple-shaped small holes 8 are formed. The enlarged portion in FIG. 1 shows an elastic sliding contact portion including the sliding contact surface 4 a of the side lip portion 4. In the elastic sliding contact portion including the sliding contact surface 4a of the seal lip portion 4, a large number of small holes 8 are formed in a regular or random spot shape, and the elastic sliding contact portion and small holes including the sliding contact surface 4a are formed. 8... Is provided with the applied grease G. Due to the rotation of the inner ring or the shaft, the slinger 2 and the sliding contact surfaces 4a to 6a of the seal lip portions 4 to 6 are in sliding contact with each other elastically. At this time, since a large number of small holes 8 are formed in at least the sliding contact surface 4a, the contact area with the slinger 2 is small, and therefore the rotational torque of the slinger 2 is small. In addition, since the grease G is interposed between the elastic sliding contact portions, an increase in rotational torque is suppressed by this lubricating action. Further, the low rotational torque is maintained for a long time due to the grease retention, low wear and low friction properties due to the large number of small holes 8. In particular, by holding the grease G in the small holes 8..., The grease G is gradually supplied from the small holes 8, thereby preventing the grease G from being depleted in the elastic sliding contact portion, and the low wear and low friction properties. Is long lasting. Further, rubber abrasion powder generated at the time of sliding contact and foreign matter entering from the outside can be captured in the small holes 8... And wear such as scratches on the elastic sliding contact portion due to biting of these foreign matters and the like is reduced. Therefore, the life of the seal member 7 can be extended. Such a characteristic is realized by an optimum form of the small holes 8 to be described later.

Next, a method for forming the small holes 8... As described above by laser processing and details of an optimal formation mode will be described. FIG. 2 is a conceptual diagram showing a procedure for forming small holes in a sample for a rubber base material 70 (hereinafter referred to as a rubber base material sample 70) by a laser processing machine. A laser beam machine 9 shown in FIG. 2 is a fine laser beam machine (ML-7112AH, ML-7111A) manufactured by Miyachi Technos Co., Ltd., which includes an oscillator 9a, a Q switch 9b, a shutter 9c, and a galvanometer mirror 9d. Laser oscillation with a wave and a Q-switch pulse wave is possible. FIG. 2 shows a small hole 8 formed by irradiating the surface of the rubber substrate sample 70 with the laser R while scanning the rubber substrate sample 70 or the laser processing machine 9 (see arrow a). It shows the state of small holes in the formation process). In this laser beam machine 9, the laser type is LD excitation YVO ₄ , the oscillation wavelength is 1064 nm, and the Q switch pulse frequency is 0.01 to 199.9 kHz.

FIG. 3 shows conditions for producing a sheet-like rubber base material sample 70 as a target sample for processing and forming the small holes 8 by the laser processing machine 9. Although unvulcanized NBR is used as the rubber material, the present invention is not limited to this, and other rubber materials frequently used for the seal member 7 as shown in FIG. 1, for example, HNBR, ACM, FKM, EPDM, AEM, VMQ , FVMQ, BR, CR, etc. can also be adopted. FIG. 4 shows detailed specifications of the laser processing machine 9.

In order to optimize the laser specifications, irradiation was performed by changing the laser beam type and lens type, and the shape of the small hole was observed. A normalski differential interferometer (DM400M-4 manufactured by Leica Microsystems) is used for observing the surface of the rubber substrate sample 70 after laser processing, and an ultra-deep shape measuring microscope (VK manufactured by Keyence Corporation) for observing the cross section. -8500) were used respectively. An fθ lens was used as the lens. The fθ lens is a lens designed so that the relationship between the image height h and the incident angle is h = fθ. FIGS. 5 to 7 show the measurement results of the opening diameter and depth of the small holes 8 when processed using the lenses in the single mode. FIG. 8 summarizes these results as a small hole shape controllable range depending on the beam and lens type. In FIG. 8, WD is the distance between the lens and the sample.

From FIG. 5 to FIG. 8, it is understood that when compared with the f160 lens, the single mode has a smaller opening diameter than the multi mode, and deep small holes can be processed. This is considered to be due to the feature of the single mode in which the power peak is concentrated at one central point of the beam. Further, when the shape of the small hole is compared in the single mode depending on the lens, it is understood that the processing of the lens having a small θ allows the processing of a deeper small hole with a smaller opening diameter. Since it is necessary to ensure sealing performance as a function of the seal product, it is necessary to control the seal surface (the surface of the rubber substrate sample 70) more finely. Therefore, it is desirable that a small hole having a smaller opening diameter can be processed. From this point of view, the single mode was selected as the beam quality for small hole processing, and the f100 lens was adopted as the lens type. However, when a small hole having a depth smaller than 15 μm is required, processing may be performed using an f160 lens in a single mode.
In FIGS. 5 to 7,

reference numerals

15A, 23A, and 31A denote irradiation outputs in the laser oscillator 9a in terms of current values (amperes).

FIG. 9 is a diagram conceptually showing a state in which a friction coefficient test test of the rubber base material sample 70 is performed using a friction and wear tester in order to identify the optimum shape of the small hole 8. As a friction and wear tester 10 shown in FIG. 9, FPR-2100 manufactured by Reska Co., Ltd. was used. The friction and wear tester 10 applies grease to the surface of the sample 70 for rubber base material, and rolls the ball 10a applied with a predetermined load on the application surface into a circular shape, whereby the ball 10a and grease are applied. The coefficient of friction with the surface of the sample 70 for rubber substrate is measured. FIG. 10 shows the friction test conditions. The amount of grease applied in FIG. 10 is the amount applied along the circular track 10b (see FIG. 9) on which the balls 10a roll. The viscosity of the grease used is 600 [dPa · s] (25 ° C.) (measured with a high viscosity for the Viscotester).

In order to investigate the optimum occupied area ratio of the small holes 8, a friction test was performed on a sample in which the occupied area ratio was changed by the laser irradiation pitch. Here, the occupied area ratio of the small holes 8 is the ratio of the total area of the openings of the small holes 8 in the region where the small holes 8 are formed as described above (the region surrounded by the outermost peripheral portion of the small hole forming zone). It is. In this laser processing, an f100 lens was used, the shutter opening time was 0.01 ms, the irradiation output was 31 A, the laser frequency was 1 kHz, the small hole opening diameter was 52 μm, and the depth was 14 μm. Further, a friction test was similarly performed on a sample (sample with an irradiation pitch of 100 μm) whose surface was wiped off with ethanol. FIG. 11 and FIG. 12 show this result together with the result for a raw sample (without small holes). According to this result, when the occupation area ratio exceeds 5% (see the white arrow in FIG. 12), the friction coefficient of the rubber base material sample 70 is ¼ to ５ compared to the unprocessed sample, It can also be seen that there is less variation. FIG. 13 shows the friction coefficient test results for the sample (b) that was wiped with ethanol and the sample (a) that was not. From FIG. 11 to FIG. 13, in the case of the sample subjected to the wiping treatment with ethanol, the friction coefficient was confirmed to be slightly smaller than that of the sample not subjected to the wiping treatment, and the frictional pin splash phenomenon disappeared. It is understood that Thus, it is understood that, after the laser processing, the ablated decomposition product remains slightly on the surface, and it is possible to suppress the frictional pin splash phenomenon by removing it.

In order to investigate the optimum aperture diameter of the small hole 8, the aperture diameter was controlled by changing the lens type, shutter opening time, laser output, and frequency, and the influence of the friction coefficient on the aperture diameter was confirmed. The occupation area ratio was fixed to about 10%. 14 and 15 show the results of this study. From this result, it is understood that when the opening diameter of the small hole is 50 to 90 μm, the friction coefficient is significantly smaller than that of the unprocessed one, and when the opening diameter is 50 to 90 μm, there is no difference due to the difference in opening diameter. .
In addition, since the small hole whose opening diameter is 40 micrometers or less cannot be processed with an example laser processing machine (especially lens kind), the laser processing was performed using the femtosecond laser, and this was evaluated separately. This evaluation result will be described later.

In order to investigate the optimum depth of the small hole 8, the depth was controlled by changing the lens type, shutter opening time, laser output, and frequency, and the influence of the friction coefficient on the depth was confirmed. The occupation area ratio was fixed to about 10%. FIG. 16 and FIG. 17 show the examination results. From FIG. 17, it is understood that the coefficient of friction is smaller than that of the unprocessed sample when the depth of the small hole 8 is around 16 μm, and the variation is the smallest. It is also found that when the depth is smaller than 5 μm, the friction coefficient is reduced as compared with the unprocessed sample, but the variation is large. On the other hand, as the depth becomes larger than 30 μm, the coefficient of friction increases, so that the depth of the small hole 8 is desirably 3 to 20 μm, and most desirably about 15 μm.

As described above, the optimum formation mode of the small holes 8 can be set to a depth of 3 to 20 μm, an opening diameter of 70 μm or less, and an area occupation ratio of the opening of 5 to 50%. And when the optimal formation mode of the said small hole 8 is applied to the sealing member 7, the following can be said. The depth of the small hole is 3 to 20 μm, the opening diameter of the small hole is 70 μm or less, and the ratio of the area occupied by the opening of the small hole in the region where the small hole is formed (hereinafter referred to as the occupied area ratio) is 5 to 50%. By doing so, it can be said that the characteristics of the seal member 7 are expressed very suitably. In addition, the small holes whose shape and the like are specified in this way are formed with good reproducibility by laser processing, and can provide the customer with the seal member 7 with stable quality. When the depth of the small hole is less than 3 μm, the effect of reducing the frictional resistance of the sliding contact surfaces 4a to 6a with the slinger 2 in the state where the lubricant is interposed tends to be reduced. Moreover, when the depth of the small hole is less than 3 μm, the variation in the frictional resistance tends to increase. When the depth of the small hole exceeds 20 μm, the variation in the frictional resistance becomes small, but the amount of lubricant supplied from the small hole to the sliding contact surface decreases, and this tends to increase the frictional resistance. On the other hand, when the opening diameter of the small holes exceeds 70 μm, the substantial sealing points are reduced and the sealing performance tends to be lowered. Further, when the occupied area ratio is less than 5%, the effect of reducing the frictional resistance tends to be small and the variation of the frictional resistance tends to increase, and when it exceeds 50%, the substantial sealing point decreases and the sealing performance is reduced. It tends to decrease.
FIG. 18 is a graph showing the difference of the friction coefficient between the optimum laser processed sample (rubber base material sample 70) and the unprocessed sample due to the change over time. Here, the optimum laser processed sample is a sample that has been laser processed so that the opening diameter of the small hole is 50 μm, the depth is 15 μm, and the occupation area ratio is 10% (laser irradiation pitch 140 μm). Based on these results, it can be understood that the sample having the most remarkable effect of reducing the friction coefficient has a friction coefficient reduced by about 70% compared to the unprocessed sample, as shown in FIG. In FIG. 18, the upper side of the arrow indicates the unprocessed sample (c), and the lower side indicates the optimum laser processed sample (d) (both are n = 2).

Next, we will consider the factors that reduced the friction coefficient. FIG. 19 shows the result of observing the small hole 8 and its vicinity by the above-described observation method for the sample after the friction test, in comparison with the state before the friction test. In the case of the sample having a small hole depth of 16 μm, after the friction test, a trace of the grease moving from the small hole 8 to the small hole 8 was observed (see the portion indicated by arrow A in FIG. 19). Thus, when the depth of the small hole 8 is optimum, the grease accumulated in the small hole 8 moves from the small hole 8 to the small hole 8, so that the grease is supplied from the small hole 8 to the sliding contact surface (see FIG. 1) with the mating member. Therefore, it can be estimated that the friction coefficient was reduced. On the other hand, when the depth of the small hole is small (refer to the case of 2 μm depth in FIG. 19), grease accumulation does not occur, and there is no movement of grease between the small holes, so the amount of grease intervening on the sliding contact surface becomes unstable, It is presumed that the variation in the coefficient of friction has increased. Further, when the depth is large (see the case of 53 μm depth in FIG. 19), the depth after the friction test is smaller than the original depth (see “Cross-sectional shape” column in FIG. 19). Although it can be confirmed that the grease has accumulated, the trace of movement of the grease is not seen so much, so that the amount of grease intervening on the sliding contact surface is small, and it is presumed that the coefficient of friction has increased.

As described above, the exemplary laser processing machine cannot process a small hole with an opening diameter of 40 μm or less, so there is no thermal diffusion and it is possible to suppress the influence of thermal alteration by ablation processing, which is much more extreme than the YVO ₄ laser. Laser processing was performed with a femtosecond laser with a small pulse width. The smallest hole opening diameter that could be processed by the femtosecond laser used was 15 μm, and the depth was 3 μm. Further, when trying to form a small hole of about 15 μm, which is the optimum depth in terms of frictional characteristics, the opening diameter was 26 μm. About a sample (opening diameter 26 μm, depth 15 μm, occupied area ratio 8%) processed with this femtosecond laser and a sample processed with a small hole with YVO ₄ laser (opening diameter 52 μm, depth 14 μm, occupied area ratio 10%) When the friction characteristics were tested in the same manner as described above, the sample with the femtosecond laser did not achieve the friction reduction effect as much as the sample with the YVO ₄ laser. However, it is possible to make the aperture diameter smaller than 26 μm by changing the conditions of the femtosecond laser, and by reducing the viscosity of the grease, the mobility of the grease between the small holes is improved and the friction reducing effect is obtained. It can also be increased. Therefore, by appropriately using the YVO ₄ laser and the femtosecond laser, the aperture diameter can be controlled to 5 to 70 μm, and in this sense, the desired range of the aperture diameter can be set to 5 to 70 μm. However, when only the YVO ₄ laser is used, the preferable range of the aperture diameter is 40 to 70 μm. Here, the femtosecond laser is used for processing a small hole of 40 μm or less, but the present invention is not limited to this, and the processing may be performed using a picosecond laser.

FIG. 20 is a conceptual diagram showing a procedure for forming small holes in the rubber base material sample 70 by a laser processing machine after the surface layer portion of the rubber base material sample 70 is peeled off in advance by continuous laser irradiation. The two-dot chain line in FIG. 20 indicates that the surface layer portion of the rubber base material sample 70 has been removed in advance. Such removal of the surface layer portion is performed by irradiating while scanning at a predetermined speed in the continuous (CW) mode. 21 (a) and 21 (b) show the hydrophilicity and lipophilicity of the surface of the rubber substrate sample 70 from which the surface layer portion has been removed by continuous laser irradiation as described above and the frequency of laser irradiation during processing. The result of investigating the relationship is shown. FIG. 21 (a) shows a case where water droplets are dropped on the surface of the rubber substrate sample 70 from which the surface layer portion has been removed by continuous laser irradiation at each frequency, and the water droplets contact the surface of the rubber substrate sample 70. The result of measuring the corner is shown. From this result, it is understood that as the frequency of laser irradiation is increased, the hydrophilicity of the processed surface is deteriorated and the water repellency is increased. FIG. 21B shows a case where a small drop of hexadecane is dropped on the surface of the rubber substrate sample 70 from which the surface layer portion has been removed by continuous laser irradiation at each frequency, and the hexadecane droplet on the surface of the rubber substrate sample 70. The result of measuring the contact angle at is shown. From this result, as the laser irradiation frequency is increased, the lipophilicity of the processed surface is improved, and when the frequency exceeds 20 kHz, hexadecane becomes familiar with the surface of the rubber substrate sample 70, the droplet shape collapses, and the rubber substrate sample 70 To spread on the surface.

Thus, by appropriately setting the frequency of laser irradiation, the water repellency and oleophilicity of the rubber base material can be appropriately controlled according to the purpose of use. In particular, when used for a seal lip portion such as a seal ring of a bearing, it is effective for preventing intrusion of muddy water from the outside into the bearing by increasing water repellency, and by increasing the lipophilicity, a lubricant As a result, the compatibility with the grease used as an additive improves, and the lubricating effect becomes more prominent. This and the above-mentioned characteristics due to the formation of the small holes are synergistic, and the suitability as a bearing seal member is further enhanced.

1 shows an example in which the rubber base material subjected to the processing of the present invention is a seal member 7 including seal lip portions 4 to 6 constituting a pack seal type seal ring 1. However, the present invention is not limited to this, and the present invention can be applied to seal members having other configurations, thereby obtaining the same effect. Further, in FIG. 1, the pack seal type seal ring applied to the inner ring side rotation and outer ring side fixed bearing is taken as an example. Needless to say, the present invention can also be applied to a seal ring. Furthermore, although grease G was illustrated as a lubricant, the seal member of the present invention can also be applied when other lubricating oil is used.

2 Slinger (mating member)
3 Core 7 Seal member 70 Rubber base 700 Base 4-6 Seal lip 4a-6a Sliding surface 8 Small hole G Grease (lubricant)

Claims

A seal member made of a rubber base material including a sliding contact surface that is elastically slidable relative to the mating member,
A large number of dimple-shaped small holes having a depth of 3 to 20 μm and an opening diameter of 70 μm or less are formed by laser processing on the surface including at least the sliding contact surface of the rubber substrate, and small holes in the region where the small holes are formed are formed. A sealing member characterized in that the ratio of the area occupied by the opening is 5 to 50%.
The seal member according to claim 1,
The rubber base material includes a base portion fixed to a metal core and a seal lip portion extending from the base portion, and the sliding contact surface is provided on the front side of the seal lip portion. A sealing member.
The seal member according to claim 1 or 2,
The small hole is formed after the surface layer portion of the rubber base material is peeled off by continuous laser irradiation.