JP2010001994A - Rolling bearing for prime mover - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rolling bearing for a prime mover capable of reducing weight in a rolling element, and capable of improving seizure resistance, while restraining damage of a track member caused by vibration and impact. <P>SOLUTION: A ball 13 for constituting a deep groove ball bearing 1 for rotatably supporting a main shaft of the prime mover to a member oppositely arranged to the main shaft, is constituted of a sintered body expressed by a composition formula of Si<SB>6-Z</SB>Al<SB>Z</SB>O<SB>Z</SB>N<SB>8-Z</SB>, mainly composed of βsialon for satisfying 0.1≤z≤3.5 and composed of a residual part of an impurity, and a Young's modulus is set to 180 GPa-270 GPa. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a rolling bearing for a prime mover, and more particularly to a rolling bearing for a prime mover including a component made of a sintered body containing β sialon as a main component.

  Generally, a prime mover fulfills the function of supplying rotational energy to various mechanical devices connected to the prime mover by taking out expansion energy obtained by burning fuel as rotation of the main shaft. Here, the said main axis | shaft is rotatably hold | maintained with a rolling bearing with respect to members, such as a housing arrange | positioned so as to oppose the outer peripheral surface of a main axis | shaft. A deep groove ball bearing or the like is employed as a prime mover rolling bearing that is a rolling bearing that supports the main shaft (see, for example, Patent Document 1).

  Here, since the rolling bearing for motor | power_engine is arrange | positioned in the vicinity of the combustion chamber which burns a fuel in a motor | power_engine, it will be used in a high temperature environment. Therefore, there is a possibility that lubrication is insufficient in the rolling bearing for the prime mover, and improvement in seizure resistance is required. Further, the rotational speed of the main shaft of the prime mover may exceed several thousand revolutions, and the rolling bearing for the prime mover is used in an environment where it rotates at high speed. Therefore, from the viewpoint of reducing the centrifugal force acting on the rolling elements, it is also required to reduce the weight of the rolling elements.

On the other hand, a rolling element made of silicon nitride may be employed as a rolling element of a rolling bearing for a prime mover. Since silicon nitride has a smaller specific gravity than steel generally used as a material for the rolling elements, it can contribute to weight reduction of the rolling elements. Also, by adopting silicon nitride as the rolling element material, the raceway member made of steel and the rolling element such as balls and rollers are made of different materials, and the rolling element has wear resistance and heat resistance. Because it improves, seizure resistance also improves. Therefore, by adopting silicon nitride as the material of the rolling elements of the rolling bearing for the prime mover, it is possible to achieve the above-described weight reduction and improvement in seizure resistance.
JP 2007-71343 A

  On the other hand, in the prime mover, vibrations and impacts accompanying fuel combustion and the like occur, and the vibrations and impacts also act on the rolling bearings for the prime mover. Here, silicon nitride has a characteristic that it has a Young's modulus larger than that of steel and is less likely to be elastically deformed. For this reason, the contact area between the rolling element made of silicon nitride and the raceway member is smaller than the rolling element made of steel, and the contact surface pressure tends to increase. Therefore, when a rolling element made of silicon nitride is employed as the rolling element of the rolling bearing for the prime mover, damage such as indentation is likely to occur on the race member when vibration or impact is applied. When damage such as indentation occurs in the raceway member, the life of the rolling bearing may be reduced. In other words, when a silicon nitride rolling element is used as the rolling element for the prime mover rolling bearing, there is a problem in that the race member is likely to be damaged by vibrations and impacts acting on the prime mover rolling bearing.

  Accordingly, an object of the present invention is to provide a rolling bearing for a prime mover that can achieve reduction in the weight of the rolling element and improvement in seizure resistance while suppressing damage to the raceway member due to vibration and impact. is there.

  The rolling bearing for a prime mover according to the present invention is a rolling bearing for a prime mover that rotatably supports the main shaft of the prime mover with respect to a member disposed so as to face the main shaft. The motor rolling bearing includes a race member and a rolling element that contacts the race member and is disposed on an annular raceway. And the rolling element consists of ceramics which can suppress the impact with respect to a track member compared with the case where it consists of silicon nitride. More specifically, for example, the rolling element is made of ceramics having a Young's modulus smaller than that of silicon nitride.

  According to the rolling bearing for a prime mover of the present invention, since damage to the raceway member is suppressed even when an impact is applied, the rolling element is reduced in weight and seizure resistance while suppressing damage to the raceway member due to vibration and impact. It is possible to provide a rolling bearing for a prime mover capable of achieving improvement in performance.

  The rolling bearing for a prime mover according to one aspect of the present invention is a rolling bearing for a prime mover that rotatably supports a main shaft of the prime mover with respect to a member disposed so as to face the main shaft. The motor rolling bearing includes a race member and a rolling element that contacts the race member and is disposed on an annular raceway. And a rolling element is comprised from the sintered compact which has (beta) sialon as a main component and consists of remainder impurities.

  The prime mover rolling bearing according to another aspect of the present invention is a prime mover rolling bearing that rotatably supports a main shaft of a prime mover with respect to a member disposed so as to face the main shaft. The motor rolling bearing includes a race member and a rolling element that contacts the race member and is disposed on an annular raceway. And a rolling element is comprised from the sintered compact which has (beta) sialon as a main component and consists of a remainder sintering auxiliary agent and an impurity.

In the rolling bearing for a prime mover according to one aspect of the present invention, a β sialon sintered body (sintered body containing β sialon as a main component), which is ceramic, is employed as the rolling element. Therefore, weight reduction of the rolling element and improvement of seizure resistance are achieved. Further, the β sialon sintered body has a Young's modulus smaller than a sintered body made of a general ceramic such as silicon nitride (Si ₃ N ₄ ) or alumina (Al ₂ O ₃ ). Therefore, it is possible to suppress damage to the track member due to vibration and impact caused by the high Young's modulus. As described above, according to the rolling bearing for a prime mover in one aspect of the present invention, it is possible to reduce the weight of the rolling element and improve seizure resistance while suppressing damage to the raceway member due to vibration or impact. It is possible to provide a rolling bearing for a prime mover that is capable of achieving the above.

  A prime mover rolling bearing according to another aspect of the present invention basically has the same configuration as that of the prime mover rolling bearing according to one aspect of the present invention, and exhibits the same effects. However, the prime mover rolling bearing according to another aspect of the present invention differs from the prime mover rolling bearing according to one aspect of the present invention in that the sintered body contains a sintering aid. According to the rolling bearing for the prime mover in another aspect of the present invention, the adoption of the sintering aid makes it easy to lower the porosity of the sintered body and can stably ensure sufficient durability. A rolling bearing can be easily provided.

  As the sintering aid, at least one of magnesium (Mg), aluminum (Al), silicon (Si), titanium (Ti), rare earth element oxide, nitride, and oxynitride is employed. be able to. In addition, in order to achieve the same effect as the motor rolling bearing according to the one aspect of the present invention, the sintering aid is preferably 20% by mass or less in the sintered body.

In the motor rolling bearing, preferably, the β sialon is represented by a composition formula of Si _6-Z Al _Z O _Z N _8-Z and satisfies 0.1 ≦ z ≦ 3.5.

  The inventor has investigated in detail the relationship between the rolling fatigue life of a rolling element made of a β sialon sintered body and the composition of β sialon. As a result, the following knowledge was obtained. By adopting a production process including combustion synthesis, β sialon can be produced inexpensively with various compositions having a value of z (hereinafter referred to as z value) of 0.1 or more. In general, the hardness that greatly affects the rolling fatigue life hardly changes in the range of the z value of 4.0 or less that is easy to manufacture. However, when the relationship between the rolling fatigue life of the rolling element made of β sialon sintered body and the z value is investigated in detail, when the z value exceeds 3.5, the rolling fatigue life of the rolling element may decrease. I understood.

  More specifically, when the z value is in the range of 0.1 or more and 3.5 or less, the rolling fatigue life is substantially the same, and if the operation time of the rolling bearing exceeds a predetermined time, the surface of the rolling element is peeled off. Occurs and breaks. On the other hand, if the z value exceeds 3.5, the rolling elements are likely to be worn, resulting in a decrease in the rolling fatigue life. That is, it becomes clear that the failure mode of the rolling element made of β sialon changes with the composition having the z value of 3.5 as a boundary, and the rolling fatigue life decreases when the z value exceeds 3.5. It was. Therefore, in the rolling element made of β sialon sintered body, the z value is preferably set to 3.5 or less in order to ensure a stable and sufficient life. As described above, when the β sialon satisfies 0.1 ≦ z ≦ 3.5, a rolling bearing for a prime mover that is inexpensive and excellent in durability can be provided.

In the motor rolling bearing, preferably, the β sialon is represented by a composition formula of Si _6-Z Al _Z O _Z N _8-Z and satisfies 0.5 ≦ z ≦ 3.0.

  Thereby, durability of the rolling bearing for motor | power_engine when a vibration and an impact act can be improved further.

  In the motor rolling bearing, the Young's modulus of the rolling element is preferably 180 GPa or more and 270 GPa or less.

  When the Young's modulus of the rolling element increases, the strength of the material (β sialon sintered body) constituting the rolling element tends to increase. However, when the Young's modulus of the rolling element is increased, the rolling element is less likely to be elastically deformed, so that the contact area with the raceway member is reduced and the contact surface pressure is increased. As a result, the track member is likely to be damaged. On the other hand, when the Young's modulus of the rolling element becomes low, the rolling element is easily elastically deformed, so that the contact area with the raceway member increases and the contact surface pressure decreases. However, on the other hand, when the Young's modulus of the rolling element becomes low, the strength of the material constituting the rolling element tends to decrease. For this reason, the Young's modulus of the rolling element needs to be within a range in which a balance between the strength of the material constituting the rolling element and the reduction of the contact surface pressure between the race members can be secured.

  More specifically, when the Young's modulus of the rolling element made of β sialon sintered body is less than 180 GPa, the influence of the strength reduction of the material constituting the rolling element exceeds the effect of reducing the contact surface pressure, and the rolling element rolling Dynamic fatigue life is reduced. Further, as the contact area with the raceway member increases, the frictional force acting between the raceway member and the bearing torque increases, and the efficiency of the prime mover decreases. Therefore, the Young's modulus of the rolling element made of the β sialon sintered body is preferably 180 GPa or more, and more preferably 220 GPa or more.

  On the other hand, if the Young's modulus of the rolling element made of β sialon sintered body exceeds 270 GPa, the effect of increasing the contact surface pressure exceeds the effect of increasing the strength of the material constituting the rolling element, and the indentation is formed on the rolling surface of the race member. Damage is likely to occur. Therefore, the Young's modulus of the rolling element made of the β sialon sintered body is preferably 270 GPa or less, and preferably 260 GPa or less.

  In the motor rolling bearing, the race member may be made of steel. In this case, the surface hardness of the track member is preferably HV680 or more. Thereby, damage to the track member when vibration or impact is applied can be suppressed.

  Preferably, in the rolling bearing for a prime mover, the rolling element has a dense layer that is a layer having higher density than the inside in a region including a rolling surface that is a surface in contact with the race member.

  In the rolling element made of the above-described β sialon sintered body, the denseness greatly affects the rolling fatigue life. On the other hand, according to the said structure, a rolling fatigue life improves because the dense layer which is a layer denser than the inside is formed in the area | region containing a rolling surface. As a result, it is possible to provide a prime mover rolling bearing capable of stably ensuring sufficient durability.

  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 element is cut in a cross section perpendicular to the surface of the rolling element made of β sialon sintered body, 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. The recorded image is binarized using a luminance threshold using an image processing apparatus, and then the area ratio of the white area is measured, and the density of the photographed area can be known from the area ratio. .

  That is, in the motor rolling bearing, preferably, in the sintered body, a dense layer that is a layer having a lower area ratio in the white region than in 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 the said sintered compact is 15% or more, for example. In order to further improve the rolling fatigue life of the rolling element made of β sialon sintered body, the dense layer preferably has a thickness of 100 μm or more.

  In the prime mover rolling bearing, 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 element made of the β sialon sintered body is further improved. Therefore, the durability of the rolling bearing for prime mover of the present invention can be further improved by the above configuration.

  In the motor rolling bearing described above, a high-density layer, which is a layer having a higher density than other areas in the dense layer, is preferably formed in the region including the surface of the dense layer.

  By forming a high-density layer with higher density in the region including the surface of the dense layer, the durability of the rolling element made of β-sialon sintered body against rolling fatigue is further improved, and the life of the rolling bearing for prime mover is improved. Can be further improved.

  In the motor rolling bearing, preferably, when the cross section of the high-density layer is observed with oblique light of 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 element made of the β sialon sintered body is further improved. Therefore, the durability of the rolling bearing for prime mover of the present invention can be further improved by the above configuration.

  As is apparent from the above description, according to the rolling bearing for a prime mover of the present invention, it is possible to reduce the rolling element weight and improve seizure resistance while suppressing damage to the raceway member due to vibration and impact. It is possible to provide a rolling bearing for a prime mover that is capable of achieving the above.

  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.

  FIG. 1 is a schematic cross-sectional view showing a configuration of a general-purpose engine that is a prime mover provided with a deep groove ball bearing as a prime mover rolling bearing according to an embodiment of the present invention. With reference to FIG. 1, the general purpose engine provided with the deep groove ball bearing in one embodiment of this invention is demonstrated.

  Referring to FIG. 1, a general-purpose engine 90 in the present embodiment includes a piston 95 that reciprocates by combustion of fuel, a crankshaft 91 as a main shaft, and a connecting rod (connecting rod) that connects the piston 95 and the crankshaft 91. ) 93 and a plurality of deep groove ball bearings 1 serving as prime mover rolling bearings that rotatably support the crankshaft 91 with respect to the housing 99. The crankshaft 91 is bent so as to have a crankpin 92 extending parallel to the rotation axis of the crankshaft 91 and extending away from the rotation axis. The connecting rod 93 is connected to the piston pin 94 of the piston 95 and is connected to the crankpin 92 of the crankshaft 91, thereby connecting the piston 95 and the crankshaft 91. At least a pair of deep groove ball bearings 1 are arranged so as to sandwich the crank pin 92 of the crankshaft 91. In the deep groove ball bearing 1, the inner ring 12 is fitted into the outer peripheral surface 91 </ b> A of the crankshaft 91, and the outer ring 11 is fitted into a housing 99 that is disposed facing the crankshaft 91. Thereby, the crankshaft 91 is supported rotatably with respect to the housing 99. That is, the deep groove ball bearing 1 is for a prime mover that rotatably supports a crankshaft 91 that is a main shaft of a general-purpose engine 90 as a prime mover with respect to a housing 99 that is a member disposed so as to face the crankshaft 91. It is a rolling bearing.

  Next, the operation of the general-purpose engine 90 will be described. When the piston 95 reciprocates due to the combustion of fuel, one end of the connecting rod 93 connected to the piston pin 94 reciprocates. Here, since the crank pin 92 of the crankshaft 91 to which the other end of the connecting rod 93 is connected extends to a position away from the rotation axis of the crankshaft 91, the other end of the connecting rod 93 is connected to the crankshaft 91. It rotates around the rotation axis. As a result, the crankshaft 91 rotates around the axis with respect to the housing 99 while being supported by the deep groove ball bearing 1. The rotation of the crankshaft 91 is transmitted as power to the outside of the general-purpose engine 90.

  Next, the deep groove ball bearing 1 will be described. FIG. 2 is a schematic sectional view showing a configuration of a deep groove ball bearing as a rolling bearing in the present embodiment. FIG. 3 is a schematic partial cross-sectional view showing an enlarged main part of FIG.

  2 and 3, the deep groove ball bearing 1 includes an outer ring 11 as a first race member, an inner ring 12 as a second race member, balls 13 as a plurality of rolling elements, and a cage 14. It has. An outer ring rolling surface 11 </ b> A as an annular first rolling surface is formed on the inner peripheral surface of the outer ring 11. On the outer peripheral surface of the inner ring 12, an inner ring rolling surface 12A as an annular second rolling surface facing the outer ring rolling surface 11A is formed. In addition, a plurality of balls 13 is formed with a ball rolling surface 13A (the surface of the ball 13) as a rolling element rolling surface. The balls 13 are in contact with each of the outer ring rolling surface 11A and the inner ring rolling surface 12A at the ball rolling surface 13A, and are arranged at a predetermined pitch in the circumferential direction by an annular retainer 14. It is rotatably held on an annular track. Thereby, the outer ring | wheel 11 and the inner ring | wheel 12 can rotate relatively mutually.

Then, balls 13 serving as rolling elements in this embodiment _is represented by a composition formula of _{Si 6-Z Al Z O Z} N 8-Z, composed mainly of β-sialon satisfying 0.1 ≦ z ≦ 3.5 And the Young's modulus is 180 GPa or more and 270 GPa or less.

  Furthermore, with reference to FIG. 3, a ball dense layer 13 </ b> B that is a layer having a higher density than the inside 13 </ b> C is formed in a region including the ball rolling surface 13 </ b> A that is a rolling surface of the ball 13. When the cross section of the dense ball layer 13B is 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 suppresses damage to the raceway members (the outer ring 11 and the inner ring 12) due to vibrations and impacts caused by the combustion of fuel in the general-purpose engine 90, and the rolling elements (balls 13). ) To achieve a reduction in weight and improvement in seizure resistance. The impurities include inevitable impurities including those derived from raw materials or those mixed in the manufacturing process.

  Further, referring to FIG. 3, the region including the ball rolling surface 13 </ b> A that is the surface of the ball dense layer 13 </ b> B has a high ball density that is a layer having a higher density than the other regions in the ball dense layer 13 </ b> B. Layer 13D is formed. When the cross section of the ball height dense layer 13D 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. Thereby, the durability with respect to the rolling fatigue of the ball 13 is further improved, and the durability of the deep groove ball bearing 1 is further improved.

  In the present embodiment, the balls 13 constituting the deep groove ball bearing 1 may be composed of a sintered body mainly composed of β sialon and composed of the remaining sintering aid and impurities. By including a sintering aid, the porosity of the sintered body can be easily lowered, and the deep groove ball bearing 1 capable of stably ensuring sufficient durability can be easily provided. The impurities include inevitable impurities including those derived from raw materials or those mixed in the manufacturing process.

  Next, the manufacturing method of the rolling bearing for motor | power_engine in this Embodiment is demonstrated. FIG. 4 is a diagram showing an outline of a method for manufacturing a rolling bearing for a prime mover according to an embodiment of the present invention. Moreover, FIG. 5 is a figure which shows the outline of the manufacturing method of the rolling element which consists of (beta) sialon sintered compact in one embodiment of this invention.

  Referring to FIG. 4, in the method for manufacturing a rolling bearing for a prime mover 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 race member manufacturing process, the outer ring 11, the inner ring 12, and the like are manufactured. On the other hand, in the rolling element manufacturing process, balls 13 and the like are manufactured.

  And the assembly process of assembling the rolling bearing for motor | power_engine 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 rolling element manufacturing process is implemented using the manufacturing method of the rolling element which consists of the following (beta) sialon sintered compact, for example.

  Referring to FIG. 5, in the method for manufacturing a rolling element made of a β sialon sintered body 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. 5, 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 element is performed. Specifically, by applying a molding technique such as press molding, cast molding, extrusion molding, rolling granulation, or the like to the above β sialon powder or a mixture of β sialon powder and a sintering aid, the ball 13 Thus, a molded body formed into a general shape such as is produced.

  Next, a pre-sintering processing step is performed in which the surface of the molded body is processed so that the molded body is shaped to be closer to the shape of the desired rolling element after sintering. Specifically, by applying a processing method such as green body processing, the molded body is processed to have a shape closer to the shape of the ball 13 or the like after sintering. This pre-sintering processing step can be omitted if the shape is sufficiently close to the shape of the desired rolling element after sintering at the stage where the molded body is formed in the forming step.

  Next, referring to FIG. 5, a sintering step is performed in which the molded body is sintered. Specifically, for example, the molded body is heated and sintered by a heating method such as heating with an electromagnetic wave using microwaves or millimeter waves under a pressure of 1 MPa or less, so that the rough shape of the ball 13 or the like is obtained. A sintered body having the same 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 elements 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, the balls 13 as rolling elements are completed by polishing the surface of the sintered body produced in the sintering step. Through the above steps, the rolling element made of the β sialon sintered body in the present embodiment is completed.

  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. Thereby, a highly dense layer can remain in the region including the ball rolling surface 13A, and the rolling fatigue life of the ball 13 can be improved.

  The sintering step is preferably performed under a pressure of 0.01 MPa or higher in order to suppress the decomposition of β sialon, and more preferably performed under a pressure of atmospheric pressure or higher in consideration of cost reduction. Moreover, in order to form a dense layer while suppressing manufacturing costs, the sintering process is preferably performed under a pressure of 1 MPa or less. Further, in order to adjust the Young's modulus of the rolling element made of the β sialon sintered body to a desired value of 180 GPa or more and 270 GPa or less, for example, the z value of the β sialon powder prepared in the β sialon powder preparation step is set to 0. What is necessary is just to adjust in the range of 1 <= z <= 3.5. More specifically, the Young's modulus of the β sialon sintered body can be decreased by increasing the z value.

  Further, as the material of the outer ring 11 and the inner ring 12 in the above embodiment, for example, high carbon chromium bearing steel such as JIS standard SUJ2, alloy steel for machine structure such as SCM420, steel such as carbon steel for machine structure such as S53C, and the like. Can be adopted.

  In the above embodiment, the deep groove ball bearing has been described as an example of the rolling bearing for a prime mover of the present invention. However, the rolling bearing of the present invention is not limited to this, and various types of rolling bearings such as an angular ball bearing and a cylindrical roller bearing. Can be adopted. In the above embodiment, the case where the outer ring and the inner ring are employed as the race members of the rolling bearing of the present invention has been described. However, the race member is a shaft used so that the rolling elements roll on the surface. Or a member such as a housing. That is, the raceway member should just be a member in which the rolling surface for a rolling element to roll was formed.

  Embodiment 1 of the present invention will be described below. Rolling bearings having rolling elements made of β sialon sintered bodies having various z values were produced, and tests for investigating the relationship between the z value and the rolling fatigue life (durability) were conducted. The test procedure is as follows.

  First, a method for producing a test bearing to be tested will be described. First, β sialon powder prepared by a combustion synthesis method with a z value in the range of 0.1 to 4 is prepared, and is basically the same as the rolling element manufacturing method described in the above embodiment based on FIG. The rolling element whose z value is 0.1-4 by the method was produced. 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.

  Subsequently, after performing atmospheric pressure sintering as primary sintering for the molded body, the sintered spheres are obtained by performing HIP (Hot Isostatic Press) in a nitrogen atmosphere at a pressure of 200 MPa. Manufactured. Next, lapping was performed on the sintered spheres to obtain 3/8 inch ceramic spheres (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 (Example AJ). For comparison, a rolling element made of silicon nitride, that is, a rolling element having a z value of 0 was also produced in the same manner as the rolling element made of β sialon, and similarly assembled to a bearing (Comparative Example A).

Next, test conditions will be described. Maximum contact surface pressure P _max : 3.2 GPa, bearing rotational speed: 2000 rpm, lubrication: circulating oil supply of turbine oil VG68 (clean oil), test temperature: room temperature for the JIS standard 6206 model bearing manufactured as described above 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. In addition, after the test was stopped, the bearing was disassembled to confirm the damaged state of the rolling elements.

  Table 1 shows the test results of this example. In Table 1, the life in each Example and Comparative Example is expressed as a life ratio with the life in Comparative Example A (silicon nitride) as 1. The damage form is described as “peeling” when peeling occurs on the surface of the rolling element, and “wearing” when the surface is worn without peeling and the test is stopped.

  Referring to Table 1, Examples A to H of the present invention in which the z value is 0.1 or more and 3.5 or less have a life comparable to that of silicon nitride (Comparative Example A). Yes. Further, the form of breakage is “peeling” as in the case of silicon nitride. On the other hand, in Example I in which the z value exceeds 3.5, the life is shortened and wear is observed on the rolling elements. That is, in Example I in which the z value is 3.8, it is considered that although the rolling element finally peeled off, the life of the rolling element was affected by the wear of the rolling element. Furthermore, in Example J in which the z value is 4, the wear of the rolling elements proceeds in a short time, and the durability of the rolling bearing is further reduced.

  As described above, when the z value is in the range of 0.1 to 3.5, the rolling bearing provided with the rolling element made of β sialon sintered body has the durability of the rolling element made of the silicon nitride sintered body. It is almost equivalent to a rolling bearing with On the other hand, if the z value exceeds 3.5, the rolling elements are likely to be worn, resulting in a decrease in the rolling fatigue life. Furthermore, it has been clarified that when the z value increases, the cause of breakage of the rolling element made of β sialon changes from “peeling” to “wear”, and the rolling fatigue life is further reduced. Thus, it was confirmed that a rolling element made of a β sialon sintered body that is inexpensive and excellent in durability can be obtained by setting the z value to 0.1 or more and 3.5 or less.

  In addition, with reference to Table 1, in Example H in which the z value exceeds 3.5, a slight amount of wear has occurred in the rolling elements, and the service life has also decreased compared to Examples A to G. ing. From this, it can be said that the z value is desirably 3 or less in order to ensure sufficient durability more stably.

  From the above experimental results, the z value is preferably 2 or less, and more preferably 1.5 or less, in order to obtain durability (life) equal to or greater than that of a rolling element made of silicon nitride. On the other hand, in view of the ease of production of β sialon powder by a production process employing combustion synthesis, it is preferable to employ a z value of 0.5 or more at which a reaction due to self-heating can be sufficiently expected.

  Embodiment 2 of the present invention will be described below. A test for producing a rolling bearing having rolling elements made of β-sialon sintered bodies having various z values and investigating the relationship between the z value and the rolling fatigue life in an environment in which an impact is applied to the rolling bearing. Was done. The test procedure is as follows.

  First, a method for producing a test bearing to be tested will be described. First, β sialon powder prepared by a combustion synthesis method with a z value in the range of 0.1 to 3.5 is prepared, and the z value is 0.1 to 3.5 by the same method as in Example 1 above. A rolling element was produced. And the bearing of the JIS standard 6206 model number was produced in combination with the bearing ring produced using the various steel materials prepared separately as a raw material (Examples AJ). As steel constituting the race, JIS standards SUJ2, SCM420, SCr420, S53C, S45C, S40C and AISI standard M50 were adopted. For comparison, a rolling element made of silicon nitride, that is, a rolling element having a z value of 0 was also produced in the same manner as the rolling element made of β sialon, and similarly assembled to a bearing (Comparative Example A).

Next, test conditions will be described. For the bearing of the JIS standard 6206 model number manufactured as described above, the maximum contact surface pressure P _max : 2.5 GPa, the bearing rotation speed: 500 rpm, lubrication: turbine oil VG68 circulating oil supply, vibration conditions: 2500 N (50 Hz), Test temperature: An excitation shock fatigue test was performed under the condition of room temperature. The vibration of the bearing during operation is monitored by the vibration detection device, and the test is stopped when the bearing is damaged and the vibration of the bearing exceeds a predetermined value. Recorded as the lifetime of. In addition, after the test was stopped, the bearing was disassembled to confirm the damaged state of the bearing.

  Table 2 shows the test results of this example. In Table 2, the life in each example and comparative example is shown in the upper part of each column as a life ratio with the life of Comparative Example A (silicon nitride) as 1 when the material of the bearing ring is SUJ2. Yes. Moreover, the damaged part (bearing ring or ball) of the bearing is described in the lower part of each column.

  Referring to Table 2, Examples C to H of the present invention having a z value of 0.5 or more and 3.0 or less clearly have a longer life than silicon nitride (Comparative Example A). Yes. Here, as shown in Table 2, the damaged part was a track member (track ring) as in the case of silicon nitride, and the damaged form was delamination. On the other hand, in Examples I and J in which the z value exceeds 3.0, the life is shortened and the rolling element (ball) is damaged (peeled) first. That is, in Example I in which the z value is 3.25, it is considered that the bearing part (ball) made of the β sialon sintered body is damaged due to the impact and the life is shortened. Furthermore, in Example J in which the z value is 3.5, the rolling elements are peeled off in a shorter time, and the durability of the rolling bearing is further reduced.

  On the other hand, in Examples A and B in which the z value is smaller than 0.5, the lifetime is reduced to substantially the same level as in Comparative Example A, and the raceway member is preceded by breakage (peeling). That is, in Example B in which the z value is 0.25, the difference in physical properties from Comparative Example A in which the z value is 0 (silicon nitride) is reduced. Therefore, the collision between the ball made of the β sialon sintered body and the race member facing the ball unilaterally causes damage on the race member side, and the same as Comparative Example A employing the ball made of the silicon nitride sintered body. It is thought that the lifetime was reduced to

  Furthermore, referring to Table 2, even when the z value is 0.5 or more and 3.0 or less, when the hardness (surface hardness) of the opposite bearing ring is less than HV680, The life tends to be shorter than when the hardness is HV680 or higher. This is thought to be because when the hardness of the raceway is low, damage to the raceway member is likely to occur due to the collision between the ball made of β sialon sintered body and the raceway member facing the ball.

  As described above, when the z value exceeds 3.0, the bearing part itself made of the β sialon sintered body is easily damaged, whereas when the z value is less than 0.5, the contact surface pressure between the mating member is low. It increases, and damage to the mating member is likely to occur. And by making z value 0.5 or more and 3.0 or less, the balance of the intensity | strength of the raw material which comprises a rolling element and the reduction of the contact surface pressure between track members is ensured. As a result, it was confirmed that the life of a rolling bearing including a rolling element made of a β sialon sintered body is improved in an environment in which an impact is applied to the bearing. In particular, when the race member is made of steel, the physical properties of the race member and the physical properties of the rolling elements are well matched, and the occurrence of damage due to impact, vibration, or the like can be suppressed. Thus, the durability of the rolling bearing used in an environment in which an impact acts can be improved by setting the z-value of β sialon constituting the rolling element to 0.5 or more and 3.0 or less. confirmed.

  In addition, when the race member is made of steel, it was confirmed that the surface hardness of the race member is preferably HV680 or more in order to suppress damage to the race member.

  Embodiment 3 of the present invention will be described below. A test was conducted to investigate the formation state of the dense layer and the highly dense layer of the rolling elements made of β sialon constituting the rolling bearing for prime mover of the present invention. 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 was prepared, and the rolling element described in the above embodiment based on FIG. A cubic test piece having a side of about 10 mm was produced in the same manner as in the manufacturing method. A specific manufacturing method is as follows. First, a 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 having a pressure of 0.4 MPa (atmospheric pressure sintering).

  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. 6 is a photograph obtained by photographing the observation cross section of the test piece with oblique light from an optical microscope. FIG. 7 is an example showing a state in which the image of the photograph in FIG. 6 is binarized using a luminance threshold using image processing software. Further, FIG. 8 shows a region (evaluation region) where image processing is performed when the image of the photograph of FIG. 6 is binarized by the luminance threshold using image processing software and the area ratio of the white region is measured. FIG. In FIG. 6, the upper side of the photograph is the surface side of the test piece, and the upper end is the surface.

  With reference to FIGS. 6 and 7, the test piece in this example manufactured by the same manufacturing method as in the above embodiment has a layer having a white area smaller than the inside in the area including the surface. I understand. Then, as shown in FIG. 8, 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 of 150 μm or less from the outermost surface, 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 3 were obtained. In Table 3, 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. 8 as one field of view. Yes.

  Referring to Table 3, the area ratio of the white region in the present example was 18.5% 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 the present example produced by the above manufacturing method similar to the above embodiment, a dense layer and a highly dense layer having a white region less than the inside are formed in the region including the surface. It was confirmed.

  Embodiment 4 of the present invention will be described below. A test was conducted to confirm the rolling fatigue life of the rolling element made of the β sialon sintered body constituting the rolling bearing for a prime mover of the present invention. 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 was prepared, and the rolling element described in the above embodiment based on FIG. A 3/8 inch ceramic sphere having a diameter of 9.525 mm was produced in the same manner as the production method described above. A specific manufacturing method is as follows. First, a 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 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. By sintering, sintered spheres were produced. 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. Maximum contact surface pressure P _max : 3.2 GPa, bearing rotational speed: 2000 rpm, lubrication: circulating oil supply of turbine oil VG68 (clean oil), test temperature: room temperature for the JIS standard 6206 model bearing manufactured as described above 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 4 shows the test results of this example. Referring to Table 4, it can be said that the life of the bearings of the examples is all good considering 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 for motor of the present invention is excellent in durability. In the rolling bearing for motor of the present invention, the machining allowance of the rolling element made of β sialon sintered body is 0.5 mm or less, the life is improved by leaving the dense layer on the surface, and the machining allowance is 0.15 mm. It has been found that the lifetime is further improved by leaving a highly dense layer on the surface as follows.

  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 bearing for a prime mover of the present invention can be particularly advantageously applied to a rolling bearing for a prime mover that requires improved seizure resistance.

It is a schematic sectional drawing which shows the structure of the general purpose engine provided with the deep groove ball bearing in one embodiment of this invention. It is a schematic sectional drawing which shows the structure of a deep groove ball bearing. It is the general | schematic fragmentary sectional view which expanded and showed the principal part of FIG. It is a figure which shows the outline of the manufacturing method of the rolling bearing for motor | power_engine in one embodiment of this invention. It is a figure which shows the outline of the manufacturing method of the rolling element which consists of (beta) sialon sintered compact in one embodiment of this invention. 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. 6 with the brightness | luminance threshold value using image processing software. It is a figure which shows the area | region (evaluation area | region) which performs image processing.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Deep groove ball bearing, 11 outer ring, 11A outer ring rolling surface, 12 inner ring, 12A inner ring rolling surface, 13 balls, 13A ball rolling surface, 13B ball dense layer, 13C inside, 13D ball high dense layer, 14 cage, 90 general-purpose engine, 91 crankshaft, 91A outer peripheral surface, 92 crankpin, 93 connecting rod, 94 piston pin, 95 piston, 99 housing.

Claims (12)

A prime mover rolling bearing that rotatably supports a main shaft of a prime mover with respect to a member disposed so as to face the main shaft,
A track member;
A rolling element that contacts the raceway member and is disposed on an annular raceway,
The rolling element for a prime mover, wherein the rolling element is made of ceramics capable of suppressing an impact on the raceway member as compared with a case where the rolling element is made of silicon nitride.   The rolling element bearing for a prime mover according to claim 1, wherein the rolling element is composed of a sintered body mainly composed of β sialon and composed of remaining impurities.   The rolling bearing for a prime mover according to claim 1, wherein the rolling element is composed of a sintered body mainly composed of β sialon and comprising a remaining sintering aid and impurities. The β-sialon _is represented by the composition formula of _{Si 6-Z Al Z O Z} N 8-Z, satisfy 0.1 ≦ z ≦ 3.5, the rolling bearing for a motor according to claim 2 or 3. The β-sialon _is represented by the composition formula of _{Si 6-Z Al Z O Z} N 8-Z, satisfy 0.5 ≦ z ≦ 3.0, the rolling bearing for a motor according to claim 2 or 3.   The rolling bearing for a prime mover according to any one of claims 1 to 5, wherein a Young's modulus of the rolling element is 180 GPa or more and 270 GPa or less.   The rolling bearing for a prime mover according to any one of claims 1 to 5, wherein a Young's modulus of the rolling element is 220 GPa or more and 260 GPa or less. The track member is made of steel,
The rolling bearing for a prime mover according to any one of claims 1 to 7, wherein a surface hardness of the raceway member is HV680 or more.   9. The rolling element according to claim 1, wherein the rolling element has a dense layer that is a layer having a higher density than the inside in a region including a rolling surface that is a surface in contact with the raceway member. Rolling bearings for prime movers described in 1.   The rolling bearing for a prime mover according to claim 9, wherein an area ratio of a white region observed as a white region is 7% or less when a cross section of the dense layer is observed with oblique light of an optical microscope.   The rolling bearing for a prime mover according to claim 9 or 10, wherein a high-density layer, which is a layer having a higher density than other areas in the dense layer, is formed in a region including the surface of the dense layer. .   The rolling bearing for a prime mover according to claim 11, wherein an area ratio of a white region observed as a white region is 3.5% or less when a cross section of the highly dense layer is observed with oblique light of an optical microscope.