JP5550029B2 - Manufacturing method of rolling member - Google Patents

Description

  The present invention relates to a rolling member, a rolling bearing, and a method of manufacturing the rolling member, and more specifically, manufacturing of a rolling member, a rolling bearing, and a rolling member that employ a sintered body mainly composed of β sialon. It is about the method.

  Ceramics such as silicon nitride and sialon are characterized by having a specific gravity smaller than steel and high corrosion resistance, as well as insulating properties. For this reason, when ceramics is used as a component of a rolling bearing (including a hub unit) including a race member and a rolling element, for example, a material for the race member and the rolling element is used, the weight of the bearing can be reduced, and It is possible to suppress damage due to corrosion, shortening of the life of rolling bearings due to electrolytic corrosion, and the like.

  In addition, a hub unit, which is a kind of rolling bearing, is often used in an environment where moisture may enter inside, and lubrication may be insufficient. Rolling parts such as rolling elements and race members made of ceramics have a feature that they are not easily damaged even in the above-mentioned insufficient lubrication environment. Therefore, the durability of the hub unit used in an insufficient lubrication environment can be improved, for example, by adopting ceramics as the material for the rolling parts.

  However, ceramics such as silicon nitride and sialon are expensive to manufacture compared to steel, so there is a problem that the manufacturing cost of rolling bearings increases significantly when ceramics are used as the material for the components of rolling bearings. .

On the other hand, in recent years, a method for producing β sialon, which is a ceramic, at a low cost by employing a production process including a combustion synthesis method has been developed (see, for example, Patent Documents 1 to 3). Therefore, it is possible to consider the production of a low-cost rolling bearing that employs this β sialon as the material of the component parts.
JP 2004-91272 A JP 2005-75652 A JP 2005-194154 A

  However, in order to employ the β sialon as a material for the component of the rolling bearing, the component of the rolling bearing made of β sialon needs to have a sufficient rolling fatigue life. The rolling fatigue life does not necessarily match the fracture strength of the member, and it cannot be said that the components of the rolling bearing made of β sialon have a sufficient rolling fatigue life. For this reason, there is a problem in that it is not easy to stably ensure sufficient durability even in a rolling bearing provided with components made of β sialon.

  Accordingly, an object of the present invention is to provide a rolling bearing composed of a β sialon sintered body (sintered body containing β sialon as a main component) that is inexpensive and can ensure sufficient durability stably. It is to provide a rolling member as a part and a manufacturing method thereof, and a rolling bearing (including a hub unit) including the rolling member.

The rolling member according to one aspect of the present invention is a rolling member that is a rolling member disposed on an annular raceway in contact with the raceway member in the rolling bearing. This rolling member is composed of a sintered body containing β sialon as a main component and the remaining impurities. And, in the region including the rolling surface that is a surface in contact with the other rolling member, a dense layer that is a layer having a higher density than the inside is formed, and in the region including the surface of the dense layer, A highly dense layer, which is a denser layer than other regions in the dense layer, is formed .

The rolling member according to another aspect of the present invention is a rolling member that is a rolling member disposed on an annular raceway in contact with the race member in the rolling bearing. This rolling member is composed of a sintered body containing β sialon as a main component and the remaining sintering aid and impurities. And, in the region including the rolling surface that is a surface in contact with the other rolling member, a dense layer that is a layer having a higher density than the inside is formed, and in the region including the surface of the dense layer, A highly dense layer, which is a denser layer than other regions in the dense layer, is formed .

  The inventor has investigated in detail the relationship between the rolling fatigue life of a rolling member mainly composed of β sialon and the configuration of the rolling member. As a result, the following knowledge was obtained and the present invention was conceived.

  That is, in the rolling member made of the above-mentioned sintered body containing β sialon as a main component, the denseness greatly affects the rolling fatigue life which is one of the most important durability in the rolling member. In contrast, the rolling member of the present invention is made of a sintered body containing β sialon as a main component, and a dense layer that is a denser layer than the inside is formed in a region including the rolling surface. . As a result, according to the rolling member of the present invention, it is inexpensive and sintered with β sialon as a main component that can stably ensure sufficient durability by improving the rolling fatigue life. A rolling member made of a body can be provided.

  Here, the high-density layer is a layer having a low porosity (high density) in the sintered body, and can be investigated as follows, for example. First, the rolling member is cut in a cross section perpendicular to the surface of the rolling member, and the cross section is mirror-wrapped. Thereafter, the mirror-wrapped cross section is photographed with oblique light (dark field) of an optical microscope at, for example, about 50 to 100 times and recorded as an image of 300 DPI (Dot Per Inch) or more. At this time, the white region observed as a white region corresponds to a region with high porosity (low density). Therefore, a region where the area ratio of the white region is low is denser than a region where the area ratio is high. Then, after binarizing the image recorded using the image processing device with the luminance threshold, the area ratio of the white area is measured, and the denseness of the photographed area can be known from the area ratio. That is, in the rolling member of the present invention, a dense layer that is a layer having a lower area ratio of the white region than the inside is formed in the region including the rolling surface. In addition, it is preferable to perform the said imaging | photography at 5 or more places at random, and to evaluate the said area ratio by the average value. Moreover, the area ratio of the said white area | region inside a rolling member is 15% or more, for example.

  In order to further improve the rolling fatigue life of the rolling member, the dense layer preferably has a thickness of 100 μm or more. Furthermore, as the sintering aid employed in the rolling member in the above other aspects, magnesium (Mg), aluminum (Al), silicon (Si), titanium (Ti), rare earth element oxide, nitride, At least one of oxynitrides can be selected. In order to achieve the same effect as that of the rolling member according to one aspect of the present invention, the sintering aid is desirably 20% by mass or less in the sintered body.

  In the rolling member, preferably, when the cross section of the dense layer is observed with oblique light of an optical microscope, the area ratio of the white region observed as a white region is 7% or less.

  By improving the denseness of the dense layer to such an extent that the area ratio of the white region is 7% or less, the rolling fatigue life of the rolling member is further improved. Therefore, with the above configuration, the rolling fatigue life of the rolling member of the present invention can be further improved.

Te the rolling member odor, the region including the surface of the dense layer, a high dense layer is a layer higher in density than other areas of the dense layer is formed.

  By forming the high dense layer with higher denseness in the region including the surface of the dense layer, the durability of the rolling member against rolling fatigue is further improved, and the rolling fatigue life is further improved.

  In the rolling member, preferably, when the cross section of the highly dense layer is observed with oblique light from an optical microscope, the area ratio of the white region observed as a white region is 3.5% or less.

  By improving the denseness of the highly dense layer to such an extent that the area ratio of the white region is 3.5% or less, the rolling fatigue life of the rolling member is further improved. Therefore, with the above configuration, the rolling fatigue life of the rolling member of the present invention can be further improved.

  The rolling bearing according to the present invention includes a race member and a plurality of rolling elements that are in contact with the race member and disposed on an annular raceway. And at least any one of a track member and a rolling element is the rolling member of the said invention.

  The rolling bearing of the present invention is inexpensive but has sufficient durability by including the rolling member of the present invention capable of stably ensuring sufficient durability while being inexpensive. It is possible to provide a rolling bearing provided with a rolling member made of a β sialon sintered body capable of stably ensuring the above.

A rolling member manufacturing method according to one aspect of the present invention is a rolling member manufacturing method for a rolling bearing, which is a rolling member disposed on an annular track in contact with the race member or the race member. . In this method of manufacturing a rolling member, a molded body is produced by preparing a raw material powder containing β sialon as a main component and remaining impurities, and forming the raw material powder into a rough shape of the rolling member. A step, a step in which the formed body is sintered under a pressure of 1 MPa or less, and a step in which a surface of the sintered formed body is processed and a region including the surface is removed . And the thickness of the molded object removed in the process in which the surface of the sintered molded object is processed is 150 micrometers or less.

A rolling member manufacturing method according to another aspect of the present invention is a rolling member manufacturing method for a rolling bearing that is a rolling member disposed on an annular raceway in contact with the raceway member or the raceway member. . This rolling member manufacturing method includes forming a raw material powder comprising β sialon as a main component and the remaining sintering aid and impurities, and forming the raw material powder into a rough shape of the rolling member. A step of producing a body, a step of sintering the molded body under a pressure of 1 MPa or less, and a step of processing a surface of the sintered molded body and removing a region including the surface. I have. And the thickness of the molded object removed in the process in which the surface of the sintered molded object is processed is 150 micrometers or less.

  In a method for manufacturing a rolling member made of a ceramic sintered body, a hot isostatic pressing (HIP) method is used to suppress the occurrence of defects that reduce the rolling fatigue life of the rolling member. In general, sintering by a pressure sintering method (a method in which sintering is performed under a pressure of 10 MPa or more) such as gas pressure sintering (GPS) is generally employed. According to this conventional manufacturing method, the porosity of a rolling member falls and a rolling member with high density can be manufactured. However, the conventional manufacturing method employing the pressure sintering method increases the manufacturing cost. Furthermore, in the manufacturing method employing the pressure sintering method, an abnormal layer whose material has been altered is formed on the surface layer portion of the rolling member. Therefore, in the finishing process of the rolling member, it is necessary to remove the abnormal layer, and the manufacturing cost of the rolling member further increases. On the other hand, when the pressure sintering method is not adopted, there is a problem that the porosity of the rolling member is increased and defects are generated, and the rolling fatigue life of the rolling member is reduced.

  On the other hand, the inventor manufactured a rolling member by sintering a molded body made of β sialon under a pressure of 1 MPa or less, thereby including a rolling surface formed on the surface of the rolling member. Furthermore, it has been found that a dense layer having a higher density than the inside can be formed. In the manufacturing method of the rolling member of the present invention, the manufacturing cost associated with the use of pressure sintering is included by including a step in which the compact mainly composed of β sialon is sintered under a pressure of 1 MPa or less. A dense layer can be formed in a region including the rolling contact surface (surface) while suppressing the rise. As a result, according to the rolling member manufacturing method of the present invention, a rolling member made of a β sialon sintered body capable of stably ensuring sufficient durability can be manufactured at low cost.

  The step of sintering the molded body is preferably performed under a pressure of 0.01 MPa or more in order to suppress the decomposition of β sialon, and it is performed under a pressure of atmospheric pressure or more in consideration of cost reduction. More preferred. Moreover, in order to form a dense layer while suppressing the manufacturing cost, it is preferable to perform the step of sintering the molded body under a pressure of 1 MPa or less.

  Preferably, in the method for producing the rolling member, in the step of sintering the molded body, the molded body is sintered in a temperature range of 1550 ° C. or higher and 1800 ° C. or lower.

  If the temperature at which the green body is sintered is less than 1550 ° C, densification by sintering is difficult to proceed. Therefore, the temperature at which the green body is sintered is preferably 1550 ° C or higher, more preferably 1600 ° C or higher. preferable. On the other hand, if the temperature at which the green body is sintered exceeds 1800 ° C., there is a concern that the mechanical properties of the sintered body will deteriorate due to the coarsening of β sialon crystal grains. It is preferable that it is 0 degreeC or less, and it is more preferable that it is 1750 degrees C or less.

  Preferably, in the method of manufacturing the rolling member, in the step of sintering the molded body, the molded body is sintered in an inert gas atmosphere or a mixed gas atmosphere of nitrogen and oxygen.

  By sintering the compact in an inert gas atmosphere, it is possible to suppress the decomposition and structural change of β sialon. Further, the sintered body is sintered in a mixed gas atmosphere of nitrogen and oxygen, whereby the nitrogen and oxygen contents of the β sialon sintered body can be controlled.

  Preferably, the rolling member manufacturing method further includes a step of processing the surface of the molded body before the molded body is sintered.

  When the molded body is sintered, the hardness of the molded body becomes extremely high and processing becomes difficult. For this reason, adopting a finishing process in which, after sintering, for example, the formed body is processed significantly to finish it as a rolling member is accompanied by an increase in the manufacturing cost of the rolling member. On the other hand, the manufacturing cost of the rolling member can be reduced by processing the green body before sintering the green body and suppressing the amount of processing of the green body after sintering in the finishing step or the like. . In particular, the manufacturing method employing the pressure sintering method requires a relatively large amount of processing after sintering in order to remove the abnormal layer. In the method for producing a member, since a step of sintering a molded body made of β sialon under a pressure of 1 MPa or less is employed, the processing amount for removing the abnormal layer is suppressed, and the merit of the above steps is Very big.

Production how of the rolling member is machined surface of the sintered molded body, further comprising the step of region including the surface is removed. And the thickness of the said molded object removed in the process in which the surface of the sintered molded object is processed is 150 micrometers or less.

  In the rolling member manufacturing method of the present invention, the above-mentioned highly dense layer having a thickness of about 150 μm is formed in the region including the surface. Therefore, when the surface of the sintered compact is processed and a region including the surface is removed, for example, a finishing process is performed, the thickness of the compact removed in the process is 150 μm or less. Thus, a highly dense layer can remain on the rolling surface of the rolling member. Therefore, by adopting the above process, it is possible to manufacture a rolling member having a further improved rolling fatigue life. In order to leave the highly dense layer more reliably, the thickness of the sintered compact removed in the above step is more preferably 100 μm or less.

  As is apparent from the above description, according to the rolling member, the rolling bearing, and the rolling member manufacturing method of the present invention, β sialon that is inexpensive and can stably ensure sufficient durability. It is possible to provide a rolling member made of a sintered body, a manufacturing method thereof, and a rolling bearing provided with the rolling member.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

(Embodiment 1)
FIG. 1 is a schematic cross-sectional view showing a configuration of a deep groove ball bearing as a rolling bearing in the first embodiment which is an embodiment of the present invention. FIG. 2 is a schematic partial cross-sectional view showing an enlarged main part of FIG. With reference to FIG. 1 and FIG. 2, the deep groove ball bearing as a rolling bearing in Embodiment 1 is demonstrated.

  Referring to FIG. 1, a deep groove ball bearing 1 includes an annular outer ring 11 as a race member, an annular inner ring 12 as a race member disposed inside the outer ring 11, and an outer ring 11 and an inner ring 12. And a plurality of balls 13 as rolling elements that are arranged and held by an annular cage 14. An outer ring rolling surface 11 </ b> A is formed on the inner circumferential surface of the outer ring 11, and an inner ring rolling surface 12 </ b> A is formed on the outer circumferential surface of the inner ring 12. And the outer ring | wheel 11 and the inner ring | wheel 12 are arrange | positioned so that 12A of inner ring | wheel rolling surfaces and 11A of outer ring | wheels may mutually oppose. Further, the plurality of balls 13 are in contact with the inner ring rolling surface 12A and the outer ring rolling surface 11A at the ball rolling surface 13A, and are arranged at a predetermined pitch in the circumferential direction by the cage 14, thereby causing an annular track. It is held so that it can roll freely. With the above configuration, the outer ring 11 and the inner ring 12 of the deep groove ball bearing 1 are rotatable relative to each other.

  Here, referring to FIG. 2, outer ring 11, inner ring 12, and ball 13 as rolling members in the present embodiment are formed of a sintered body mainly composed of β sialon and made of remaining impurities. And in the area | region containing the outer ring | wheel rolling surface 11A which is a rolling surface of the outer ring | wheel 11, the inner ring | wheel 12, and the ball | bowl 13, inner ring | wheel rolling surface 12A and the ball rolling surface 13A, it is denser than the inside 11C, 12C, 13C. The outer ring dense layer 11B, the inner ring dense layer 12B, and the ball dense layer 13B, which are higher layers, are formed. When cross sections of the outer ring dense layer 11B, the inner ring dense layer 12B, and the ball dense layer 13B are observed with oblique light from an optical microscope, the area ratio of the white region observed as a white region is 7% or less. Therefore, the deep groove ball bearing 1 in the present embodiment is a rolling member (outer ring 11, inner ring 12, and ball made of a β sialon sintered body that is inexpensive and can stably ensure sufficient durability. It is a rolling bearing provided with 13). The impurities include inevitable impurities including those derived from raw materials or those mixed in the manufacturing process.

  In the present embodiment, the outer ring 11, the inner ring 12 and the balls 13 as rolling members may be composed of a sintered body mainly composed of β sialon and the balance of sintering aid and impurities. Good. By including a sintering aid, it is possible to easily reduce the porosity of the sintered body, and to provide a rolling member made of a β sialon sintered body that can stably ensure sufficient durability. The provided rolling bearing can be easily provided. The impurities include inevitable impurities including those derived from raw materials or those mixed in the manufacturing process.

  Further, referring to FIG. 2, the outer ring is formed in a region including outer ring rolling surface 11A, inner ring rolling surface 12A and ball rolling surface 13A which are the surfaces of outer ring dense layer 11B, inner ring dense layer 12B and ball dense layer 13B. An outer ring high dense layer 11D, an inner ring high dense layer 12D, and a ball high dense layer 13D, which are denser layers than the other regions in the dense layer 11B, inner ring dense layer 12B, and ball dense layer 13B, are formed. . When cross sections of the outer ring high-density layer 11D, the inner ring high-density layer 12D, and the ball high-density layer 13D are observed with oblique light from an optical microscope, the area ratio of the white region observed as a white region is 3.5% or less. It has become. Thereby, the durability with respect to rolling fatigue of the outer ring 11, the inner ring 12 and the ball 13 is further improved, and the rolling fatigue life is further improved.

  FIG. 3 is a schematic cross-sectional view showing a configuration of a thrust needle roller bearing as a rolling bearing in a modification of the first embodiment. FIG. 4 is a schematic partial cross-sectional view showing, in an enlarged manner, a main part of the bearing ring provided in the thrust needle roller bearing of FIG. FIG. 5 is a schematic partial cross-sectional view showing an enlarged main part of the needle roller provided in the thrust needle roller bearing of FIG. With reference to FIGS. 3-5, the thrust needle roller bearing as a rolling bearing in the modification of Embodiment 1 is demonstrated.

  3-5, the thrust needle roller bearing 2 has basically the same configuration as the deep groove ball bearing 1 described with reference to FIG. 1 and exhibits the same effects. However, the thrust needle roller bearing 2 is different from the deep groove ball bearing 1 in the configuration of the raceway member and the rolling element. That is, the thrust needle roller bearing 2 has a disk-like shape, and a pair of race rings 21 as race members disposed so that one main surfaces thereof face each other, and a plurality of needle rollers 23 as rolling elements. And an annular retainer 24. The plurality of needle rollers 23 are in contact with the raceway rolling surface 21A formed on the main surfaces of the pair of raceways 21 facing each other on the roller raceway 23A, which is the outer circumferential surface thereof, and in the circumferential direction by the cage 24. By being arranged at a predetermined pitch, it is held so as to roll on an annular track. With the above configuration, the pair of race rings 21 of the thrust needle roller bearing 2 can rotate relative to each other.

  Here, the bearing ring 21 and the needle roller 23 as rolling members in the present modification correspond to the outer ring 11 or the inner ring 12 and the ball 13 described above, respectively, and the same inner 21C, 23C, dense layer (tracking ring). It has a dense layer 21B, a roller dense layer 23B) and a highly dense layer (track ring high dense layer 21D, roller highly dense layer 23D). Therefore, the thrust needle roller bearing 2 in this modification is a rolling member (the race ring 21, the needle roller 23) made of a β sialon sintered body that is inexpensive and can stably ensure sufficient durability. ).

  Next, the manufacturing method of the rolling bearing in Embodiment 1 which is one embodiment of this invention is demonstrated. FIG. 6 is a diagram showing an outline of a method for manufacturing a rolling bearing in the first embodiment which is an embodiment of the present invention. Moreover, FIG. 7 is a figure which shows the outline of the manufacturing method of the rolling member contained in the manufacturing method of the rolling bearing in Embodiment 1 of this invention.

  Referring to FIG. 6, in the method for manufacturing a rolling bearing in the present embodiment, first, a race member manufacturing process for manufacturing a race member and a rolling element manufacturing process for manufacturing a rolling element are performed. Specifically, in the track member manufacturing process, the outer ring 11, the inner ring 12, the track ring 21, and the like are manufactured. On the other hand, in the rolling element manufacturing process, balls 13 and needle rollers 23 are manufactured.

  And the assembly process which assembles a rolling bearing is implemented by combining the track member manufactured in the track member manufacturing process, and the rolling element manufactured in the rolling element manufacturing process. Specifically, for example, the deep groove ball bearing 1 is assembled by combining the outer ring 11 and the inner ring 12 and the ball 13. And a race member manufacturing process and a rolling element manufacturing process are implemented using the manufacturing method of the following rolling members, for example.

  Referring to FIG. 7, in the method of manufacturing a rolling member in the present embodiment, first, a β sialon powder preparation step of preparing β sialon powder is performed. In the β sialon powder preparation step, β sialon powder can be produced at low cost by, for example, a production step employing a combustion synthesis method.

  Next, a mixing step is performed in which a sintering aid is added to and mixed with the β sialon powder prepared in the β sialon powder preparation step. This mixing step can be omitted if no sintering aid is added.

  Next, referring to FIG. 7, a forming step of forming the β sialon powder or the mixture of the β sialon powder and the sintering aid into a schematic shape of the rolling member is performed. Specifically, by applying a molding technique such as press molding, cast molding, extrusion molding, rolling granulation, etc. to the above β sialon powder or a mixture of β sialon powder and a sintering aid, rolling A molded body formed into a schematic shape such as the outer ring 11, inner ring 12, ball 13, race ring 21, needle roller 23, and the like, which are members, is produced.

  Next, a pre-sintering processing step is performed in which the surface of the formed body is processed so that the formed body is shaped to be closer to the shape of the desired rolling member after sintering. Specifically, by applying a processing method such as green body processing, the molded body becomes a shape closer to the shape of the outer ring 11, the inner ring 12, the ball 13, the race ring 21, the needle roller 23, etc. after sintering. To be molded. This pre-sintering processing step can be omitted when a shape close to the shape of the desired rolling member is obtained after sintering at the stage where the molded body is formed in the forming step.

  Next, referring to FIG. 7, a sintering step is performed in which the molded body is sintered under a pressure of 1 MPa or less. Specifically, the molded body is heated and sintered by a heating method such as heater heating, electromagnetic wave heating using microwaves or millimeter waves, etc., so that the outer ring 11, the inner ring 12, the ball 13, the race ring 21, and the needle A sintered body having a schematic shape such as the roller 23 is produced. Sintering is performed by heating the molded body to a temperature range of 1550 ° C. or higher and 1800 ° C. or lower in an inert gas atmosphere or a mixed gas atmosphere of nitrogen and oxygen. As the inert gas, helium, neon, argon, nitrogen, or the like can be employed, but nitrogen is preferably employed from the viewpoint of reducing manufacturing costs.

  Next, a finishing process for completing the rolling member is performed by performing a finishing process in which the surface of the sintered body produced in the sintering process is processed and a region including the surface is removed. Specifically, by polishing the surface of the sintered body produced in the sintering step, the outer ring 11, the inner ring 12, the ball 13, the race ring 21, the needle roller 23, etc. as rolling members are completed. The rolling member in the present embodiment is completed through the above steps.

  Here, as a result of sintering in the above-described sintering step, a region having a thickness of about 500 μm from the surface of the sintered body is denser than the inside, and when the cross section is observed with oblique light of an optical microscope, a white region is obtained. A dense layer in which the area ratio of the observed white region is 7% or less is formed. Furthermore, the region having a thickness of about 150 μm from the surface of the sintered body has a higher density than the other regions in the dense layer, and is observed as a white region when the cross section is observed with an oblique light of an optical microscope. A highly dense layer in which the area ratio of the white region is 3.5% or less is formed. Therefore, in the finishing step, it is preferable that the thickness of the sintered body to be removed is 150 μm or less particularly in a region to be a rolling surface. As a result, the high-density layer remains in the region including the outer ring rolling surface 11A, the inner ring rolling surface 12A, the ball rolling surface 13A, the raceway rolling surface 21A, and the roller rolling surface 23A, thereby rolling the rolling member. The fatigue life can be improved.

(Embodiment 2)
FIG. 8 is a schematic cross-sectional view showing a configuration of a hub unit which is a rolling bearing in the second embodiment which is an embodiment of the present invention. FIG. 9 is a schematic partial cross-sectional view showing an enlarged main part of FIG. With reference to FIG. 8 and FIG. 9, the hub unit in Embodiment 2 is demonstrated.

  Referring to FIGS. 8 and 9, the hub unit 3 has basically the same configuration as the deep groove ball bearing 1 described with reference to FIG. However, the hub unit 3 is different from the deep groove ball bearing 1 in the configuration of the raceway member and the rolling element. That is, the hub unit 3 is a device that is interposed between the wheel and the vehicle body and supports the wheel rotatably with respect to the vehicle body. The hub unit 3 includes an outer ring 31, which is a race member, a hub ring 32 and an inner ring 33, and a plurality of balls 34 as rolling elements.

  The outer ring 31 as an outer member is an annular track member having rolling surfaces 31A1 and 31A2 formed in two rows on the inner peripheral surface. The hub wheel 32 as an inner member is a track member that has a rolling surface 32A that faces one rolling surface 31A1 of the outer ring 31, and is disposed so that a part thereof is surrounded by the outer ring 31. The inner ring 33 as an inner member has a rolling surface 33A opposite to the other rolling surface 31A2 of the outer ring 31, and is fitted and fixed so as to contact a part of the outer peripheral surface of the hub wheel 32. The ring member is an orbital member having an annular shape fixed to the hub wheel 32 by fitting the ring 38 so as to contact a part of the outer peripheral surface of the hub wheel 32.

  The plurality of balls 34 are in contact with one rolling surface 31A1 of the outer ring 31 and the rolling surface 32A of the hub wheel 32, and are arranged at a predetermined pitch in the circumferential direction by an annular retainer 39A. A double row (two rows) of rows arranged in contact with the other rolling surface 31A2 of the outer ring 31 and the rolling surface 33A of the inner ring 33 and arranged at a predetermined pitch in the circumferential direction by an annular retainer 39B. ) Is arranged on a ring-shaped orbit. With the above configuration, the outer ring 31 as the outer member and the hub ring 32 and the inner ring 33 as the inner members can rotate relative to each other.

  Further, the hub wheel 32 has a hub wheel flange 35, and a hub wheel through hole 35 </ b> A is formed in the hub wheel flange 35. The hub wheel flange 35 and a wheel (not shown) constituting the wheel are fixed to each other by a bolt 36 inserted into the hub wheel through hole 35A. On the other hand, the outer ring 31 has an outer ring flange 37, and an outer ring through hole 37 </ b> A is formed in the outer ring flange 37. The outer ring flange 37 and a suspension device (not shown) fixed to the vehicle body are fixed to each other by a bolt (not shown) inserted into the outer ring through hole 37A. With the above configuration, the hub unit 3 is interposed between the wheel and the vehicle body, and rotatably supports the wheel with respect to the vehicle body.

  That is, the hub unit 3 in the present embodiment is a hub unit that is interposed between the wheel and the vehicle body and rotatably supports the wheel with respect to the vehicle body. The hub unit 3 is formed with an outer ring 31 as an outer member having an inner peripheral surface on which annular rolling surfaces 31A1 and 31A2 are formed, and an annular rolling surface 32A facing the rolling surface 31A1 of the outer ring 31. Then, a hub wheel 32 as an inner member disposed so that at least a part thereof is surrounded by the inner peripheral surface of the outer ring 31, and an annular rolling surface 33A facing the rolling surface 31A2 of the outer ring 31 are formed. And an inner ring 33 as an inner member disposed so that at least a part of the inner ring is surrounded by the inner circumferential surface of the outer ring 31. Further, the hub unit 3 is in contact with the rolling surfaces 31A1 and 31A2 of the outer ring 31 and the rolling surfaces 32A and 33A of the hub wheel 32 and the inner ring 33 at the ball rolling surface 34A, and is arranged on an annular track. The ball 34 is provided.

  Here, referring to FIGS. 8 and 9, outer ring 31, hub ring 32, inner ring 33 and ball 34 as rolling members in the present embodiment are the same as outer ring 11 and inner ring 12 in the first embodiment, respectively. Corresponding to the ball 13, the same inner 31C, 32C, 33C, 34C, dense layer (outer ring dense layer 31B, hub ring dense layer 32B, inner ring dense layer 33B, ball dense layer 34B) and high dense layer (outer ring high dense layer) Layer 31D, hub ring high-density layer 32D, inner ring high-density layer 33D, and ball high-density layer 34D). Therefore, the hub unit 3 in the present embodiment is a rolling member (outer ring 31, hub ring 32, inner ring made of a β sialon sintered body that is inexpensive and can stably ensure sufficient durability. 33, a ball bearing 34). The hub unit 3 as a rolling bearing in the second embodiment and the outer ring 31, the hub wheel 32, the inner ring 33, and the ball 34 as rolling members provided in the hub unit 3 are manufactured in the same manner as in the first embodiment. can do.

  In the above embodiment, the deep groove ball bearing, the thrust needle roller bearing and the hub unit, and the rolling member included in these are described as an example of the rolling bearing and rolling member of the present invention. However, the rolling bearing of the present invention includes them. Not limited. For example, the race member may be a shaft or a plate used so that the rolling elements roll on the surface. That is, the track member that is the rolling member of the present invention may be a member on which a rolling surface for rolling of the rolling element is formed. Further, the rolling bearing of the present invention may be a thrust ball bearing or a radial roller bearing.

  In the above embodiment, the case where both the race member and the rolling element of the rolling bearing of the present invention are the rolling members of the present invention made of β sialon has been described. However, the rolling bearing of the present invention is not limited to this. I can't. In the rolling bearing of the present invention, at least one of the race member and the rolling element may be the rolling member of the present invention. And when any one of a track member and a rolling element is the rolling member of this invention, when the manufacturing cost of a rolling bearing is considered, it is preferable that a rolling element is a rolling member of this invention.

  At this time, the material of the race member in the rolling bearing of the present invention is not particularly limited. For example, steel, specifically bearing steel such as JIS standard SUJ2, or carburized steel such as SCR420 and SCM420 can be employed. Moreover, you may employ | adopt ceramics, such as a silicon nitride, as the raw material of the track member in the rolling bearing of this invention.

  Embodiment 1 of the present invention will be described below. The test which investigates the formation state of the dense layer in the cross section of the rolling member of this invention and a highly dense layer was done. The test procedure is as follows.

First, a β sialon powder (product name: Melamix, manufactured by Isman Jay Co., Ltd.) having a composition of Si ₅ AlON ₇ prepared by a combustion synthesis method is prepared, and the rolling described in Embodiment 1 with reference to FIG. A cubic test piece having a side of about 10 mm was produced in the same manner as the method for producing the member. A specific manufacturing method is as follows. First, β sialon powder refined to submicron, aluminum oxide (manufactured by Sumitomo Chemical Co., Ltd., AKP30) and yttrium oxide (manufactured by HC Starck Co., Ltd., Yttrium oxide grade C) as a ball mill Were mixed by wet mixing. Then, granulation was performed with a spray dryer to produce granulated powder. The granulated powder was molded into a predetermined shape with a mold and further pressed by cold isostatic pressing (CIP) to obtain a molded body. Subsequently, the cube test piece was manufactured by heating and sintering the molded body at 1650 ° C. in a nitrogen atmosphere at a pressure of 0.4 MPa.

  Thereafter, the test piece was cut, and the cut surface was lapped with a diamond lapping machine, and then mirror lapping with a chromium oxide lapping machine was performed to form a cross section for observation including the center of the cube. And the said cross section was observed with the oblique light of the optical microscope (the Nikon Corporation make, Microphoto-FXA), and the 50-times-magnification instant photograph (Fujifilm Corporation FP-100B) was image | photographed. Thereafter, the obtained photographic image was taken into a personal computer using a scanner (resolution: 300 DPI). And the binarization process by a brightness | luminance threshold value was performed using the image processing software (Mitani Corporation WinROOF) (binarization separation threshold value in a present Example: 140), and the area ratio of the white area | region was measured.

  Next, test results will be described. FIG. 10 is a photograph of a cross section for observation of the test piece taken with oblique light from an optical microscope. FIG. 11 is an example showing a state in which the image of the photograph of FIG. 10 is binarized using a luminance threshold using image processing software. FIG. 12 is a diagram showing a region (evaluation region) where image processing is performed when the image of the photograph of FIG. 10 is binarized using a luminance threshold value using image processing software. In FIG. 10, the upper side of the photograph is the surface side of the test piece, and the upper end is the surface.

  With reference to FIG. 10 and FIG. 11, the test piece in the present Example produced by the same manufacturing method as the rolling member of the present invention has a layer having a white area smaller than the inside in the area including the surface. I understand that. Then, as shown in FIG. 12, the photographed photograph image is divided into three regions according to the distance from the outermost surface of the test piece (the region having a distance from the outermost surface of 150 μm or less, the region exceeding 150 μm and within 500 μm, When the area ratio of the white area was calculated by performing image analysis for each area and obtaining the area ratio of the white area, the results shown in Table 1 were obtained. In Table 1, the average value and the maximum value of the area ratio of the white area in five fields of view obtained from five photographs taken at random are shown with each field shown in FIG. 12 as one field of view. Yes.

  Referring to Table 1, the area ratio of the white region in this example was 18.5% in the inside, whereas it was 3.7% in the region having a depth of 500 μm or less from the surface. It was 1.2% in the region where the depth from the region was 150 μm or less. From this, in the test piece in this example manufactured by the same manufacturing method as the rolling member of the present invention, a dense layer and a highly dense layer with less white area than the inside are formed in the area including the surface. It was confirmed.

  Embodiment 2 of the present invention will be described below. The test which confirms the rolling fatigue life of the rolling member of this invention was done. The test procedure is as follows.

First, a method for producing a test bearing to be tested will be described. First, a β sialon powder (product name: Melamix, manufactured by Isman Jay Co., Ltd.) having a composition of Si ₅ AlON ₇ prepared by a combustion synthesis method is prepared, and the rolling described in Embodiment 1 with reference to FIG. A 3/8 inch ceramic sphere having a diameter of 9.525 mm was produced in the same manner as the method for producing the member. A specific manufacturing method is as follows. First, β sialon powder refined to submicron, aluminum oxide (manufactured by Sumitomo Chemical Co., Ltd., AKP30) and yttrium oxide (manufactured by HC Starck Co., Ltd., Yttrium oxide grade C) as a ball mill Were mixed by wet mixing. Then, granulation was performed with a spray dryer to produce granulated powder. The granulated powder was molded into a sphere with a mold, and further pressurized by cold isostatic pressing (CIP) to obtain a spherical molded body.

  Next, the green body is green processed so that the processing allowance after sintering becomes a predetermined dimension, and the green body is subsequently heated to 1650 ° C. in a nitrogen atmosphere at a pressure of 0.4 MPa to be sintered. Thus, sintered spheres were manufactured. Next, lapping was performed on the sintered spheres to obtain 3/8 inch ceramic spheres (rolling elements; JIS grade G5). And the bearing of the JIS standard 6206 model number was produced in combination with the bearing ring made from bearing steel (JIS standard SUJ2) prepared separately. Here, the thickness (processing allowance) of the sintered sphere removed by the lapping process on the sintered sphere was changed in eight stages, and eight types of bearings were produced (Examples A to H). On the other hand, for comparison, lapping is performed on sintered spheres (EC 141 manufactured by Nippon Special Ceramics Co., Ltd.) sintered by pressure sintering using raw material powders composed of silicon nitride and a sintering aid in the same manner as described above. Processing was performed, and a bearing of JIS standard 6206 model number was manufactured in combination with a bearing ring (JIS standard SUJ2) prepared separately (Comparative Example A). The machining allowance for lapping was 0.25 mm.

Next, test conditions will be described. For the bearing of JIS standard 6206 model number produced as described above, maximum contact surface pressure Pmax: 3.2 GPa, bearing rotation speed: 2000 rpm, lubrication: circulating oil supply of turbine oil VG68 (clean oil), test temperature: room temperature, A fatigue test was performed under the conditions of The vibration of the bearing during operation is monitored by the vibration detection device, and the test is stopped when the rolling element is damaged and the vibration of the bearing exceeds a predetermined value. Recorded as bearing life. The number of tests was 15 in each of the examples and the comparative examples, and after calculating the L ₁₀ life, the durability was evaluated by the life ratio with respect to Comparative Example A.

  Table 2 shows the test results of this example. Referring to Table 2, it can be said that the life of the bearings of the examples is good in consideration of the manufacturing cost and the like. The life of the bearings of Examples D to G in which the dense layer remains on the surface of the rolling element by setting the machining allowance to 0.5 mm or less is about 1.5 to 2 times the life of Comparative Example A. It was. Furthermore, the life of the bearings of Examples A to C in which the high-density layer remained on the surface of the rolling element by setting the machining allowance to 0.15 mm or less was about three times the life of Comparative Example A. From this, it was confirmed that the rolling bearing provided with the rolling member of the present invention is excellent in durability. And the rolling bearing provided with the rolling member of the present invention has a working cost of the rolling member of 0.5 mm or less, the life is improved by leaving a dense layer on the surface, and the machining cost of the rolling member is reduced to 0. It was found that the lifetime was further improved by leaving the highly dense layer on the surface at a thickness of .15 mm or less.

  The embodiments and examples disclosed herein are illustrative in all respects and should not be construed as being restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The rolling member, rolling bearing, and rolling member manufacturing method of the present invention are particularly advantageously applied to a rolling member, a rolling bearing, and a rolling member manufacturing method that employ a sintered body containing β sialon as a main component. obtain.

FIG. 3 is a schematic cross-sectional view showing the configuration of the deep groove ball bearing in the first embodiment. It is a schematic fragmentary sectional view which expands and shows the principal part of FIG. FIG. 6 is a schematic cross-sectional view showing a configuration of a thrust needle roller bearing in a modified example of the first embodiment. FIG. 4 is a schematic partial cross-sectional view showing an enlarged main part of a bearing ring provided in the thrust needle roller bearing of FIG. 3. FIG. 4 is a schematic partial cross-sectional view showing an enlarged view of a needle roller provided in the thrust needle roller bearing of FIG. 3. It is a figure which shows the outline of the manufacturing method of the rolling bearing in Embodiment 1. FIG. It is a figure which shows the outline of the manufacturing method of the rolling member contained in the manufacturing method of the rolling bearing in Embodiment 1. FIG. FIG. 5 is a schematic cross-sectional view showing a configuration of a hub unit in a second embodiment. It is a general | schematic fragmentary sectional view which expands and shows the principal part of FIG. It is the photograph which image | photographed the cross section for observation of a test piece with the oblique light of the optical microscope. It is an example which shows the state which binarized the image of the photograph of FIG. 10 by the brightness | luminance threshold value using image processing software. It is a figure which shows the area | region (evaluation area | region) which performs an image process, when the image of the photograph of FIG. 10 is binarized by a luminance threshold value using image processing software.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Deep groove ball bearing, 2 Thrust needle roller bearing, 3 Hub unit, 11 Outer ring, 11A Outer ring rolling surface, 11B Outer ring dense layer, 11C, 12C, 13C Inside, 11D Outer ring high dense layer, 12 Inner ring, 12A Inner ring rolling surface , 12B inner ring dense layer, 12D inner ring dense layer, 13 balls, 13A ball rolling surface, 13B ball dense layer, 13D ball high dense layer, 14, 24, 39A, 39B cage, 21 race ring, 21A race ring rolling Surface, 21B raceway ring dense layer, 21C, 23C inside, 21D raceway ring dense layer, 23 needle roller, 23A roller rolling surface, 23B roller dense layer, 23D roller dense layer, 31 outer ring, 31A1, 31A2, 32A, 33A Rolling surface, 31B Outer ring dense layer, 31C, 32C, 33C, 34C Inside, 31D Outer ring dense layer, 32 Hub wheel, 32B Ring dense layer, 32D Hub ring high dense layer, 33 Inner ring, 33B Inner ring dense layer, 33D Inner ring high dense layer, 34 balls, 34A Ball rolling surface, 34B Ball dense layer, 34D Ball high density layer, 35 Hub ring flange , 35A Hub ring through hole, 36 bolt, 37 outer ring flange, 37A outer ring through hole, 38 fixed ring.

Claims (5)

In a rolling bearing, a method of manufacturing a rolling member which is a rolling member disposed on an annular raceway in contact with the raceway member or the raceway member,
a step of preparing a raw material powder comprising β sialon as a main component and the remaining impurities;
A step of producing a molded body by molding the raw material powder into a schematic shape of the rolling member;
A step in which the molded body is sintered under a pressure of 1 MPa or less;
The surface of the sintered compact is processed, and the region including the surface is removed.
The method for manufacturing a rolling member, wherein the thickness of the molded body removed in the step of processing the surface of the sintered molded body is 150 μm or less. In a rolling bearing, a method of manufacturing a rolling member which is a rolling member disposed on an annular raceway in contact with the raceway member or the raceway member,
a step in which a raw material powder comprising β sialon as a main component and the remaining sintering aid and impurities is prepared;
A step of producing a molded body by molding the raw material powder into a schematic shape of the rolling member;
A step in which the molded body is sintered under a pressure of 1 MPa or less;
The surface of the sintered compact is processed, and the region including the surface is removed.
The method for manufacturing a rolling member, wherein the thickness of the molded body removed in the step of processing the surface of the sintered molded body is 150 μm or less. The method for manufacturing a rolling member according to claim 1 or 2 , wherein in the step of sintering the molded body, the molded body is sintered in a temperature range of 1550 ° C or higher and 1800 ° C or lower. The process according to any one of claims 1 to 3 , wherein, in the step of sintering the molded body, the molded body is sintered in an inert gas atmosphere or a mixed gas atmosphere of nitrogen and oxygen. Manufacturing method of moving member. The method for manufacturing a rolling member according to any one of claims 1 to 4 , further comprising a step of processing a surface of the molded body before the molded body is sintered.