JP2016153147A - Silicon nitride roller, manufacturing method thereof, and inspection method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silicon nitride roller having a crowning formed therein and reliability higher than conventional one, a silicon nitride manufacturing method, and a silicon nitride inspection method.SOLUTION: A silicon nitride inspection method includes the step of preparing a plurality of columnar bodies 1 main components of which are silicon nitrides, a plurality of processing materials 2 main components of which are silicon nitrides, metal oxide powders lower in hardness than the columnar body 1, and a dispersion medium 3, the step of mixing the plurality of columnar bodies 1, the plurality of processing materials 2, the metal oxide powders, and the dispersion medium 3 to slide the columnar bodies 1 and the processing materials 2 into contact with each other, and the step of inspecting molded bodies obtained from the columnar bodies 1 in the slide-contact step. In the step of inspecting molded bodies, the presence of internal defects in the molded bodies are inspected by inspecting light passed through at least a part of the molded bodies by exposing light to the molded bodies.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a silicon nitride roller, a method for manufacturing a silicon nitride roller, and a method for inspecting a silicon nitride roller, and particularly, a silicon nitride roller suitable for a rolling element for a bearing, a method for manufacturing a silicon nitride roller, and an inspection of a silicon nitride roller Regarding the method.

Bearing steel is mainly used as the material of the rolling element for the bearing (bearing), but ceramics is used for applications that require characteristics such as high-speed rotation, insulation, heat resistance, and corrosion resistance. In general, silicon nitride (Si ₃ N ₄ ) having high strength, high toughness, and high hardness, and excellent heat resistance and corrosion resistance is used as a ceramic material for bearings.

  When the rolling element is a roller, excessive pressure (edge load) may be generated at the end of the outer diameter surface that contacts the raceway surface in the roller. When edge loading occurs, there arises a problem that the life of the roller is reduced. In order to avoid edge loading, crowning is generally formed at the end of the roller.

  As a method for forming the crowning on the roller, a method is generally employed in which a workpiece is ground using a diamond grindstone to form a roller to which the shape of the grindstone is transferred.

  In addition, as a method of forming the crowning on the roller, a crowning type threaded adjustment wheel having a curvature is used, and the crowning is transferred to the outer diameter of the tapered roller while intentionally changing the position of the tapered roller with respect to the grindstone. A method of grinding is known (Patent Document 1).

  In addition, when the rolling element is a roller, and it is necessary to sufficiently reduce the friction coefficient of the roller, mirror finishing (for example, super-finishing) is performed to mirror at least the outer diameter surface of the roller. ing.

JP 2010-284775 A

  That is, in the conventional method for manufacturing a roller, when it is necessary to sufficiently reduce the friction coefficient of the roller, it is necessary to perform a mirror finishing process such as a superfinishing process in addition to the crowning process. This is because it is difficult for the conventional crowning method to suppress the occurrence of irregularities such as scratches on the roller surface and polishing marks.

  However, since the conventional mirror surface processing is polishing processing using a grindstone, polishing marks or the like due to the mirror surface processing are generated on the surface of the roller. As a result, the roller manufactured by the conventional roller manufacturing method has a problem that the generation of irregularities such as surface scratches and polishing marks is not sufficiently suppressed.

  The silicon nitride roller used as a rolling element for a bearing preferably has no internal defect of a predetermined size or more. It is conceivable that the inspection of the internal defects of the silicon nitride roller is performed using the translucency of the silicon nitride roller.

  However, since the silicon nitride roller obtained by the conventional roller manufacturing method has the above-described irregularities, the area where the internal defect can be evaluated using the translucency of silicon nitride is limited to the area near the surface. There was a problem. Therefore, the silicon nitride roller obtained by the conventional roller manufacturing method includes a silicon nitride roller that does not have sufficiently high reliability due to internal defects formed in a region deeper than the vicinity of the surface. It was.

  The present invention has been made to solve the above-described problems. A main object of the present invention is to provide a silicon nitride roller in which crowning is formed and having higher reliability than the conventional one and a method for manufacturing the same.

  The method of manufacturing a silicon nitride roller according to the present invention includes a plurality of cylindrical bodies whose main constituent material is silicon nitride, a plurality of workpieces whose main constituent material is silicon nitride, and a hardness lower than that of the cylindrical body. A step of preparing a metal oxide powder and a dispersion medium, a plurality of the columnar body, a plurality of the processing materials, the metal oxide powder, and the dispersion medium by mixing the columnar body and the dispersion medium. A step of bringing the workpiece into sliding contact, and a step of inspecting the molded body obtained from the cylindrical body by the step of sliding contact. In the step of inspecting the molded body, the molded body is irradiated with light, and the light transmitted through at least a part of the molded body is detected to inspect for the presence of internal defects in the molded body.

  According to the present invention, it is possible to provide a silicon nitride roller in which crowning is formed and having higher reliability than the conventional one and a method for manufacturing the same.

FIG. 5 is a diagram for explaining the method for manufacturing the silicon nitride roller according to the first embodiment. FIG. 5 is a cross-sectional view for explaining a cylindrical body in the method for manufacturing the silicon nitride roller according to the first embodiment. FIG. 3 is a cross-sectional view for explaining the silicon nitride roller according to the first embodiment. 3 is a flowchart of a method for manufacturing the silicon nitride roller according to the first embodiment. 6 is a diagram for explaining cut crowning of a cylindrical body in the method for producing a silicon nitride roller according to Embodiment 2. FIG. 5 is a flowchart of a method for manufacturing a silicon nitride roller according to Embodiment 2. 6 is a cross-sectional view for explaining a silicon nitride roller according to a second embodiment. FIG. 5 is a flowchart of a method for manufacturing a silicon nitride sphere according to Embodiment 3. FIG. 10 is a diagram for explaining a spherical body inspection method in the method for manufacturing a silicon nitride spherical body according to Embodiment 3. FIG. 10 is a diagram for explaining a modification of the method for inspecting a sphere in the method for producing a silicon nitride sphere according to the third embodiment. 10 is a flowchart of a silicon nitride sphere inspection method according to Embodiment 4; 4 is a graph showing measurement data of a cross-sectional profile of a silicon nitride roller of an example in Example 1. 4 is a microscopic image of the surface of the boundary portion between the crowning and the outer diameter surface of the silicon nitride roller of Example 1 in Example 1. FIG. 2 is a microscopic image of an outer diameter surface of a silicon nitride roller of an example in Example 1. FIG. 2 is a microscopic image of an end face of a silicon nitride roller of an example in Example 1. FIG. 2 is a microscopic image of a crowning surface of a silicon nitride roller of an example in Example 1. FIG. 2 is a microscopic image of the surface of a boundary portion between a crowning and an outer diameter surface of a silicon nitride roller of a comparative example in Example 1. FIG. 2 is a microscopic image of an outer diameter surface of a silicon nitride roller of a comparative example in Example 1. FIG. 2 is a microscopic image of an end face of a silicon nitride roller of a comparative example in Example 1. FIG. 2 is a microscopic image of a crowning surface of a silicon nitride roller of a comparative example in Example 1. FIG. It is a graph which shows the measurement data of the cross-sectional profile of the cylindrical body after the cut crowning process of the Example in Example 2. FIG. 6 is a graph showing measurement data of a cross-sectional profile of a molded product after ball milling in an example in Example 2. 6 is a graph showing measurement data of a cross-sectional profile of a molded article after barrel polishing of a comparative example in Example 2.

  Embodiments of the present invention will be described below 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)
With reference to FIGS. 1-3, the manufacturing method of the silicon nitride roller which concerns on Embodiment 1 is demonstrated. Manufacturing method of rollers silicon nitride according to the first embodiment, the main constituent material is a plurality of cylindrical body 1 is a silicon nitride (Si 3 _{N 4),} the main constituent material is silicon nitride (Si ₃ N ₄₎ A plurality of workpieces 2, a metal oxide powder (not shown) having a hardness lower than that of the cylindrical body 1, and a dispersion medium 3 (S 10), and the plurality of cylindrical bodies 1 and the plurality of cylindrical bodies 1 A step (S20) of bringing the columnar body 1 and the workpiece 2 into sliding contact with each other by mixing the workpiece 2, the metal oxide powder, and the dispersion medium 3;

First, a plurality of cylindrical bodies 1 whose main constituent material is silicon nitride, a plurality of workpieces 2 whose main constituent material is silicon nitride (Si ₃ N ₄ ), and a hardness lower than that of the cylindrical body 1 A metal oxide powder and a dispersion medium 3 are prepared (step (S10)).

  The cylindrical body 1 is prepared, for example, by forming a raw material powder of silicon nitride into a spherical shape, and subjecting the molded body to pressure sintering or atmospheric pressure sintering. The cylindrical body 1 may be further polished with abrasive grains having a hardness higher than that of silicon nitride (for example, diamond, green silicon carbide (GC), white alumina (WA), etc.). The columnar body 1 contains 50% by volume or more of silicon nitride, for example, 80% by volume or more and 98% by volume or less of silicon nitride. The material constituting the cylindrical body 1 may contain, for example, a sintering aid.

  The columnar body 1 has an outer peripheral surface 1A and an end surface 1B. The outer peripheral surface 1A and the end surface 1B are orthogonal, for example. The dimensions (outer diameter, length, etc.) of the cylindrical body 1 may be any size, but are dimensions standardized by, for example, JIS standards and ISO standards as bearing rolling elements. In this step (S10), a plurality of columnar bodies 1 are prepared. At this time, it is preferable that the plurality of cylindrical bodies 1 have substantially the same dimensions.

  The cylindrical body 1 does not have to be provided in a complete cylindrical shape as long as it has an axis and the outer peripheral surface 1A is formed so as to surround the axis. For example, you may have the shape where the corner | angular part of the edge part (connection part with the end surface 1B) in the axial direction of 1 A of outer peripheral surfaces is rounded.

  The material constituting the workpiece 2 is mainly composed of silicon nitride, as is the case of the material constituting the cylindrical body 1 that is a workpiece. That is, the workpiece 2 contains 50% by volume or more of silicon nitride, for example, 80% by volume or more and 98% by volume or less of silicon nitride. The material constituting the processed material 2 may include, for example, a sintering aid.

  Although the processed material 2 should just have arbitrary shapes, from a viewpoint of the process variation reduction with respect to the cylindrical body 1, it is preferable that it is provided as a spherical body. In addition, the plurality of workpieces 2 may have different characteristics (silicon nitride content, shape, dimensions, etc.), but from the viewpoint of reducing processing variation with respect to the cylindrical body 1, the same shape and equivalent dimensions are provided. It is preferable to have. The processed material 2 is prepared by, for example, forming a silicon nitride raw material powder into a spherical shape, and subjecting the molded body to pressure sintering or normal pressure sintering. Further, the processed material 2 can be reused from the processed material 2 used in the method for manufacturing the silicon nitride roller according to the first embodiment.

  The cylindrical body 1 and the processed material 2 may be the same or different in content of silicon nitride, other contained elements, etc. as long as the main constituent material is silicon nitride. Also good. Further, the dimension (outer diameter, etc.) of the workpiece 2 may be an arbitrary size as long as it can be brought into sliding contact with the cylindrical body 1, and may be larger than the cylindrical body 1. Preferably, the dimension of the workpiece 2 is smaller than the dimension of the cylindrical body 1.

The metal oxide powder is a powder of a metal oxide having a hardness lower than that of silicon nitride, which is a main constituent material of the cylindrical body 1. The metal oxide powder has a lower hardness than the cylindrical body 1. The metal oxide powder is, for example, at least one selected from the group consisting of iron oxide (Fe ₂ O ₃ ), chromium oxide (CrO ₂ ), and cerium oxide (CeO ₂ ). The particle diameter (particle size) of the metal oxide powder may be any size generally handled as abrasive grains or loose abrasive grains, for example, but is preferably 1 μm or less. Note that the particle size distribution (particle size distribution) of the metal oxide powder need not be strictly limited because the metal oxide powder has a lower hardness than the cylindrical body 1.

  The dispersion medium 3 is a liquid in which the metal oxide powder is suspended. The dispersion medium 3 can be any liquid as long as the metal oxide powder can be suspended. For example, the dispersion medium 3 is a liquid having an OH group, such as water or alcohol.

  Next, the cylindrical body 1 and the workpiece 2 are brought into sliding contact with each other by mixing the plurality of cylindrical bodies 1, the metal oxide powder, and the dispersion medium 3 (step (S20)).

  In this step (S20), first, the plurality of cylindrical bodies 1, the plurality of workpieces 2, the metal oxide powder, and the dispersion medium 3 prepared in the previous step (S10) are accommodated in the container 10 (step (step ( S21)). The container 10 only needs to have an arbitrary shape and dimensions as long as it can accommodate a predetermined amount of the cylindrical body 1, the processed material 2, the metal oxide powder, and the dispersion medium 3. The container 10 has, for example, a cylindrical shape with a diameter of 200 mm and an axial length of 200 mm, and the material constituting the container 10 is polyethylene. In such a container 10, for example, 20 cylindrical bodies 1 having an outer diameter of 10.3188 mm (13/32 inches), 300 workpieces 2, 100 g of metal oxide powder, and dispersion medium 3 1.5L can be accommodated. At this time, it is preferable that the dispersion medium 3 and the metal oxide powder are accommodated in the container 10 and mixed at a rate of 60 g or more and 80 g or less per liter of the dispersion medium 3.

  In this step (S20), the number of workpieces 2 accommodated in the container 10 is preferably equal to or greater than the number of columnar bodies 1, for example, so that the columnar bodies 1 and the workpieces 2 are in sliding contact. Probability can be increased.

  The container 10 is rotatably provided so that the central axis C is a rotation axis. The container 10 is arrange | positioned, for example on the two rollers 11 arrange | positioned so that it may mutually extend in a horizontal direction. At this time, the central axis C of the container 10 is parallel to the rotation axis of the roller 11. The two rollers 11 are provided in a columnar shape, for example. That is, the container 10 and the roller 11 may be configured as a ball mill.

  Next, the cylindrical body 1, the processed material 2, the metal oxide powder, and the dispersion medium 3 are mixed by moving the container 10 (step (S22)). For example, the cylindrical body 1, the work material 2, the metal oxide powder, and the dispersion medium 3 accommodated in the container 10 are mixed by rotating the container 10 about the central axis C as the rotation axis. That is, in the step (S22), the cylindrical body 1, the processed material 2, the metal oxide powder, and the dispersion medium 3 are uniformly mixed by, for example, a ball mill. The processing conditions at this time are selected so that the cylindrical body 1 and the workpiece 2 can be brought into sliding contact. The rotation speed of the container 10 can be arbitrarily selected, and is, for example, 10 rpm or more and 100 rpm or less.

  Thereby, in this process (S20), the cylindrical body 1 and the workpiece 2 can be slidably contacted, and at the same time, the cylindrical body 1 and the metal oxide powder can be abraded.

  The silicon nitride roller 5 according to the first embodiment is manufactured by performing the steps (S10) to (S20). The silicon nitride roller 5 has a crowning 4 formed at both ends in the axial direction, and an outer diameter surface 5 </ b> A is formed in a region sandwiched between the both crowning 4. The outer diameter surface 5A includes a rolling surface in a rolling bearing having the silicon nitride roller 5 as a rolling element.

Next, functions and effects of the method for manufacturing the silicon nitride roller according to the first embodiment will be described. In the step of preparing (S10), similarly to the cylindrical body 1, a work material 2 whose main constituent material is silicon nitride, and a group consisting of Fe ₂ O ₃ , CrO ₂ , and CeO _{2 having a} hardness lower than that of silicon nitride. And at least one selected from the group consisting of metal oxide powders. In the sliding contact step (S20), the cylindrical body 1 is mixed in the processed material 2, the metal oxide powder, the dispersion medium 3, and the container 10 as described above.

  As a result, in the step of sliding contact (S20), the cylindrical body 1 is rubbed with the metal oxide powder and slidably contacted with the workpiece 2 and the dispersion medium 3 (water). As a result, it is considered that a mechanochemical reaction can be caused with high efficiency with respect to the convex portion of the cylindrical body 1. As a result, at both ends in the axial direction of the cylindrical body 1 that is easily slidably contacted or abraded with the work material 2, the dispersion medium 3, and the metal oxide powder, there are portions where the surface orientations change discontinuously. A smooth curved crowning 4 can be formed.

In addition, even when irregularities such as scratches and polishing marks are formed on the surface of the cylindrical body 1 whose main constituent material is silicon nitride, the silicon nitride, water, and metal oxide powder in the irregularities make SiO 2 _Two layers can be easily generated, and it is considered that the SiO ₂ layer can be easily removed from the surface of the cylindrical body 1 by friction when the cylindrical body 1 and the workpiece 2 are in sliding contact. . Actually, in the silicon nitride roller 5 obtained by the method for manufacturing the silicon nitride roller according to the first embodiment, the crowning 4 is formed, and the surface roughness (Ra) on the crowning surface 4A and the end surface 5B is a roller. It was confirmed that the surface roughness (Ra) was improved. Details will be described later.

  That is, according to the method for manufacturing the silicon nitride roller according to the first embodiment, the crowning 4 can be formed and the uneven portions on the surface can be relaxed or removed by the sliding contact step (S20). Therefore, in the preparing step (S10), a cylindrical body 1 is prepared which is processed to have a predetermined dimensional accuracy (roundness, etc.) and has irregularities such as scratches and polishing marks formed on the surface. In addition, the concavo-convex portions can be relaxed and removed simultaneously with the formation of the crowning 4 on the cylindrical body 1 in the sliding contact step (S20).

  In addition, since the cylindrical body 1 is not polished with abrasive grains made of a material harder than itself in the slidable contact step (S20), the surface of the cylindrical body 1 is not damaged in the step (S20). Generation of polishing marks can be suppressed.

  As described above, the silicon nitride roller 5 manufactured by the method of manufacturing the silicon nitride roller according to the first embodiment has the outer diameter surface 5A crowned 4 and the surface unevenness suppressed. The life reduction of the silicon nitride roller 5 can be suppressed, and the reduction of the bearing life of the rolling bearing provided with the silicon nitride roller 5 can be suppressed.

(Embodiment 2)
Next, with reference to FIG. 1, FIG. 5, FIG. 6 and FIG. 7, a method for manufacturing the silicon nitride roller according to the second embodiment will be described. The method for manufacturing the silicon nitride roller according to the second embodiment basically has the same configuration as the method for manufacturing the silicon nitride roller according to the first embodiment, but prior to the sliding contact step (S20), The difference is that the method further includes a step (S11) of forming the cut crowning 6 on the columnar body 1.

  The cut crowning 6 is a crowning in which both end portions in the axial direction of the cylindrical body 1 are formed with surfaces having a predetermined angle with respect to the outer peripheral surface 1A. That is, the cut crowning 6 includes at least one surface (first inclined surface 1 </ b> C) having a predetermined angle with respect to the axis of the cylindrical body 1. The first inclined surface 1C is connected to the outer peripheral surface 1A via a boundary portion 1E (a portion where the orientation of the surface changes discontinuously, for example, a connecting portion between the first inclined surface 1C and the outer peripheral surface 1A in FIG. 5). For example, an acute angle is formed with respect to the outer peripheral surface 1A (an obtuse angle with respect to the end surface 1B). Further, the first inclined surface 1C is connected to the end surface 1B. The first inclined surface 1C and the end surface 1B may be provided in a flat shape or may be provided in a curved shape.

  The crowning length L2 of the crowning 8 finally formed on the silicon nitride roller 7 is equivalent to the crowning length L5 of the cut crowning 6. In addition, the shape of the crowning 8 finally formed on the silicon nitride roller 7 is formed based on the shape of the cut crowning 6. That is, the shape and size of the cut crowning 6 can be arbitrarily selected according to the shape and size of the crowning 8 to be finally formed on the silicon nitride roller 7. In other words, by appropriately selecting the shape and dimensions of the cut crowning 6 formed on the cylindrical body 1, the crowning 8 having an arbitrary shape and dimension can be formed on the silicon nitride roller 8. A silicon nitride roller 8 having a crowning 8 having a crowning shape along it can be obtained.

  The cut crowning 6 has a crowning length L5 (distance between the boundary portion 1E and the end face 1B in the extending direction of the shaft)) with respect to a length L6 (see FIG. 3) of the bus bar in the extending direction of the shaft. The ratio is preferably 9% or more and 25% or less. If it does in this way, the crowning 8 of the silicon nitride roller 7 can be formed as a shape along a logarithmic curve.

  In the step (S11) of forming the cut crowning 6 on the cylindrical body 1, both end portions in the axial direction of the cylindrical body 1 prepared in the step (S10) of preparing the cylindrical body 1 (the outer peripheral surface 1A and the end surface 1B) ). In this step (S11), the cut crowning 6 may be formed by any method, and for example, a conventional crowning method may be used.

  In the conventional crowning processing method, for example, a grinding wheel shape is ground using a diamond grindstone whose grinding surface shape is provided in the crowning shape, so that the grinding surface shape is transferred to the cylindrical body to form a crowning shape. And a method of adjusting the angle between the columnar body and the grindstone and grinding the columnar body with the grindstone to form a crowning shape.

  In the former case, the shape of the grinding surface of the grindstone is provided in the same manner as the finished shape of the cut crowning 6, and the cylindrical body 1 is ground on the grinding surface of the grindstone, thereby forming the shape of the grinding surface. May be transferred to the cylindrical body 1 to form the cut crowning 6. Note that it is difficult to form the crowning 4 in the first embodiment and the crowning 8 in the second embodiment by such a conventional crowning method. For example, in the method of transferring the grinding wheel shape of a diamond grindstone, the processing efficiency is low because silicon nitride as the workpiece is very hard, and it is difficult to machine the crowning, outer diameter surface and end surface at the same time. The processing of the radial surface and the processing of the end surface are processed as separate processes. As a result, a boundary (boundary portion 1E) occurs between the outer diameter surface and the crowning.

  Moreover, although this process (S11) can be implemented using the conventional crowning processing method, it does not need to advance a process to the same extent as the conventional crowning processing method. In other words, in this step (S11), it is only necessary that the cut crowning 6 is formed to such an extent that a predetermined crowning shape can be formed in the subsequent step (S20).

  The cut crowning 6 formed in this step (S11) may be incomplete as the crowning shape as compared with the crowning formed by the conventional crowning method. For example, even if the boundary portion 1E remains significantly at the both ends in the axial direction of the cylindrical body 1 (with a smaller angle between the first inclined surface 1C and the outer peripheral surface 1A) than the conventional crowning shape, Good. Such a boundary portion 1E can be eliminated by the subsequent step (S20). At both ends in the axial direction of the silicon nitride roller 7 according to the second embodiment, a discontinuous surface portion is not formed in a cross section along the axial direction, and a smooth curved shape (preferably a logarithmic curved shape) ) Crowning 8 is formed. Details will be described later.

  Moreover, the uneven | corrugated | grooved part, such as a damage | wound and a grinding | polishing trace, may be formed in the surface of the cylindrical body 1 after a process (S11) process.

  Next, the cylindrical body 1 on which the cut crowning 6 is formed is brought into sliding contact (step (S20)). This step (S20) has the same configuration as the step (S20) of sliding contact in the first embodiment except that the cylindrical body 1 on which the cut crowning 6 is formed is a processing target.

  That is, the cylindrical body 1 in which the cut crowning 6 is formed is accommodated in the container 10 together with the plurality of processing materials 2, the metal oxide powder, and the dispersion medium 3 (step (S21)), and the container 10 is moved (rotated). Thereby, the cylindrical body 1, the processed material 2, the metal oxide powder, and the dispersion medium 3 are mixed (step (S22)).

  In this way, the silicon nitride roller 7 according to Embodiment 2 can be obtained. The silicon nitride roller 7 according to the second embodiment is manufactured by the silicon nitride roller according to the second embodiment, which includes a sliding contact step (S20) having the same configuration as the method of manufacturing the silicon nitride roller according to the first embodiment. Since it is produced by the method, the same effect as the silicon nitride roller 5 according to the first embodiment can be obtained. That is, the silicon nitride roller 7 according to the second embodiment is a silicon nitride roller whose main constituent material is silicon nitride, and includes an outer diameter surface 7A including a rolling surface and surrounding the shaft. And a crowning 8 is formed at each end of the outer diameter surface 7A in the extending direction of the shaft. Furthermore, since unevenness is suppressed on the outer diameter surface 7A and the surface of the crowning 8, it is possible to more effectively realize a reduction in the bearing life of the rolling bearing including the silicon nitride roller 7.

  Furthermore, according to the manufacturing method of the silicon nitride roller which concerns on Embodiment 2, since the process (S11) which forms the cut crowning 6 in the cylindrical body 1 is further provided before the process (S20) to slidably contact, The cylindrical body 1 is in sliding contact with the workpiece 2, and the surface of the cylindrical body 1 (including the cut crowning 6 (for example, the surface of the first inclined surface 1C and the first inclined surface 1D) and the end surface 1B) is a metal oxide. By rubbing with the powder, the radius of the cylindrical body 1 in the portion where the cut crowning 6 and the end face 1B are located in the axial direction can be reduced (dropped). As a result, it is possible to easily form the crowning 8 having a longer crowning length than the crowning 4 of the silicon nitride roller 5 according to the first embodiment.

  The crowning 8 formed in this way has an outer shape in a cross section along the axial direction of the silicon nitride roller 7 approximated to a logarithmic curve by appropriately selecting the shape and dimensions of the cut crowning 6, and from the viewpoint of avoiding edge loading Therefore, an ideal crowning shape can be formed. In other words, the boundary 1E is not formed on the crowning 8, and the outer diameter surface 7A and the end surface 7B are connected by the crowning surface 8A, which is a smooth curved surface. At this time, on the cross section of the silicon nitride roller 7 including the axis of the silicon nitride roller 7, the ratio of the crowning length L2 of the crowning 8 to the length L3 (see FIG. 3) in the extending direction of the axis of the bus is 9%. It is 25% or less.

  The silicon nitride roller 7 in which such a crowning 8 is formed has a reduced lifetime compared to the conventional silicon nitride roller, and therefore the rolling bearing provided with the silicon nitride roller 7 is compared with the conventional rolling bearing. Reduction of bearing life is suppressed.

  In the conventional crowning method as described above, the crowning shape such as the cut crowning 6 having the boundary can be formed relatively easily, but the crowning shape such as the above-described crowning 8 is formed. It was difficult.

  Therefore, conventionally, in order to form a crowning shape such as the crowning 8, a method of grinding the outer peripheral surface of a conical workpiece using a centerless cylindrical grinder has been adopted.

  However, when machining a workpiece whose main constituent material is silicon nitride, it is difficult to increase the machining efficiency, and many man-hours are required to form a crowning shape such as the crowning 8.

  On the other hand, in the method for manufacturing a silicon nitride roller according to the second embodiment, a general ball mill machine is used as the container 10 to relieve / remove irregularities such as surface scratches and polishing marks simultaneously with the formation of the crowning 8. Thus, the silicon nitride roller 7 can be manufactured. Therefore, the lifetime reduction of the silicon nitride roller can be suppressed easily and at low cost as compared with the conventional crowning method.

  That is, the silicon nitride roller 5 obtained by the silicon nitride roller manufacturing method according to the first embodiment has a crowning drop amount L1 and a crowning length L2 larger than those of the silicon nitride roller obtained by the conventional silicon nitride roller manufacturing method. Is provided. Therefore, the silicon nitride roller 5 according to the first embodiment can effectively avoid the edge load when used as a rolling element of a rolling bearing, and suppresses a decrease in the life, as compared with the conventional silicon nitride roller. Has been.

  Further, the silicon nitride roller 7 obtained by the method of manufacturing the silicon nitride roller according to the second embodiment is provided with a larger crowning length L2 than the silicon nitride roller 5 according to the first embodiment. Further, the crowning 8 of the silicon nitride roller 7 can have an ideal crowning shape or a shape approximate to this. Therefore, the silicon nitride roller 7 according to the second embodiment can avoid the edge load more effectively when used as a rolling element of a rolling bearing as compared with the conventional silicon nitride roller, and the lifetime is reduced. It is suppressed.

(Embodiment 3)
Next, with reference to FIGS. 8 and 9, a method for manufacturing the silicon nitride roller according to the third embodiment will be described. The method for manufacturing the silicon nitride roller according to the third embodiment basically has the same configuration as the method for manufacturing the silicon nitride roller according to the first embodiment, but is formed by the sliding contact step (S20). It differs in the point further provided with the process (S30) which test | inspects a body.

  In the step of sliding contact (S20) in the third embodiment, the columnar body 1 is processed into a molded body by forming the crowning 4 as in the step of sliding contact (S20) in the first embodiment. Here, the molded body corresponds to the silicon nitride roller 5 obtained by the slidable contact step (S20). However, as long as the irregular shape such as a scratch or a polishing mark on the surface of the silicon nitride roller is not newly formed, It may be a silicon nitride roller obtained by further performing an arbitrary finishing process after the step (S20).

  In the step of inspecting the molded body (S30), the molded body is irradiated with light, and the presence of internal defects in the molded body is inspected by detecting light transmitted through at least a part of the molded body.

  Referring to FIG. 9, the step (S30) of inspecting the molded body can be performed by visually inspecting the molded body irradiated with light using a magnifying glass such as the stereomicroscope 20.

  In addition, referring to FIG. 10, the step (S30) of inspecting the molded body may be performed by capturing a change in reflectance or absorptance from reflected light generated when the molded body is irradiated with laser light. Good. The inspection system at this time includes, for example, a light source 21, a reflecting mirror 22, a lens 23, a light receiving element 24, and a processing device 25. The light source 21 is provided so as to be able to irradiate the molded body with laser light. The reflecting mirror 22 causes the reflected light generated when the molded body is irradiated with laser light to enter the lens 23, and the lens 23 collects the reflected light on the light receiving element 24. The light receiving element 24 receives the reflected light and outputs a received light signal to the processing device 25. The processing device 25 processes the light reception signal received from the light receiving element 24 and outputs a processing result such as the presence or absence of an internal defect in the molded body.

  Since the molded body (silicon nitride roller) obtained by the slidable contact step (S20) has reduced irregularities such as scratches and polishing marks on the surface including the crowning 4, irradiation to such a molded body is performed. The reflected light is suppressed from being reflected, absorbed, refracted due to the unevenness on the surface of the molded body. Therefore, among the light irradiated to such a molded body, light (reflected light, transmitted light, refracted light, etc.) transmitted through at least a part of the molded body also travels from the inside of the molded body to the outside. Less susceptible to irregularities on the surface of the molded body. As a result, by capturing light (reflected light, transmitted light, refracted light, etc.) transmitted through at least a part of such a molded body, information such as the presence or absence of internal defects in a deeper region from the surface of the molded body can be obtained. It can be obtained with high accuracy. Thereby, the silicon nitride roller obtained by the silicon nitride roller manufacturing method according to the third embodiment has the crowning 4 formed as compared to the silicon nitride roller obtained by the conventional silicon nitride roller manufacturing method. In both the region and the region where the crowning 4 is not formed, the presence or absence of an internal defect is inspected with high accuracy from the surface to a deeper position.

  As described above, when the molded body is used as a rolling element for a bearing, the depth from the rolling surface of the region where the shear stress is maximum in the molded body is about 120 μm. In the method for manufacturing a silicon nitride roller, it is possible to manufacture a silicon nitride roller that has been inspected with high accuracy for internal defects in a region at such a depth.

  As a result, in the molded body that has been processed by the sliding contact step (S20), in a region where the depth from the surface of the molded body is shallower than 150 μm, there is no molded body having a defect having a maximum outer width of 25 μm or more. , It can be sorted out from other molded bodies. Suitable for rolling elements for bearings.

  Note that the semiconductor element manufacturing method according to the third embodiment may have a configuration in which the semiconductor element manufacturing method according to the second embodiment further includes a step (S30) of inspecting the molded body. That is, the semiconductor element manufacturing method according to the third embodiment further includes a step (S11) of forming the cut crowning 6 prior to the sliding contact step (S20), and the step (S30) is formed by the crowning 8. It may be a step of inspecting the formed body (corresponding to the silicon nitride roller 7). In this way, the molded body corresponding to the silicon nitride roller 7 can be inspected with high accuracy for the presence of internal defects.

(Embodiment 4)
Next, a silicon nitride roller inspection method according to Embodiment 4 will be described with reference to FIG. The silicon nitride roller inspection method according to the fourth embodiment includes a plurality of cylindrical bodies 1 whose main constituent material is silicon nitride, a plurality of workpieces 2 whose main constituent material is silicon nitride, and silicon nitride. A step (S40) of preparing a molded body obtained by mixing the metal oxide powder of low hardness and the dispersion medium 3 and bringing the cylindrical body 1 and the processed material 2 into sliding contact with each other; A step (S50) of inspecting the presence or absence of an internal defect in the molded body by irradiating the light and detecting light transmitted through at least a part of the molded body.

  First, a molded body is prepared (step (S10)). The molded body includes a plurality of cylindrical bodies 1 whose main constituent material is silicon nitride, a plurality of workpieces 2 whose main constituent material is silicon nitride, a metal oxide powder having a hardness lower than that of silicon nitride, It is obtained by bringing the cylindrical body 1 and the workpiece 2 into sliding contact with each other by mixing the dispersion medium 3. Before the cylindrical body 1 is slidably contacted with the workpiece 2, the process of forming the cut crown 6 similar to the method for manufacturing the silicon nitride roller according to the second embodiment is performed to form the cut crown 6. May be. That is, in this step (S10), a molded body on which the crownings 4 and 8 are formed is prepared. The surface roughness Ra value of the molded body at this time is, for example, less than 0.004 μm on any of the surfaces, outer diameter surfaces, and end surfaces of the crownings 4 and 8. Note that the molded body may be covered with a thin film whose surface is made of a light-transmitting material. In this case, irregularities such as scratches and polishing marks on the surface of a molded body whose main constituent material is silicon nitride and a thin film formed so as to cover the molded body are sufficiently reduced.

  Next, the molded body is irradiated with light, and the presence of internal defects in the molded body is inspected by detecting light transmitted through at least a part of the molded body (step (S50)).

  This step (S50) can be performed in the same manner as the step (S30) of inspecting the molded body in the method for manufacturing the silicon nitride roller according to the third embodiment. Specifically, as shown in FIG. 9, this step (S50) can be carried out, for example, by visually inspecting the molded body irradiated with light using a magnifying glass such as a stereomicroscope. Further, in this step (S50), as shown in FIG. 10, in the step (S30) of inspecting the molded body, a change in reflectance or absorptance is detected from reflected light generated when the molded body is irradiated with laser light. It may be implemented by capturing.

  The molded body prepared in the previous step (S40) has surface irregularities such as scratches and polishing marks reduced. Therefore, it is suppressed that the light irradiated with respect to such a molded object is reflected, absorbed, refracted due to unevenness on the surface of the molded object. The molded body has translucency because the main constituent material is silicon nitride. Therefore, light (reflected light, transmitted light, refracted light, etc.) transmitted through at least a part of the molded body due to the translucency of silicon nitride among the light irradiated on the molded body is reflected on the surface of the molded body. Scattering or the like due to the unevenness is suppressed. As a result, by capturing light (reflected light, transmitted light, refracted light, etc.) transmitted through at least a part of such a molded body, information such as the presence or absence of internal defects in a deeper region from the surface of the molded body can be obtained. It can be obtained with high accuracy.

  In other words, according to the inspection method of the present silicon nitride roller, the presence or absence of internal defects in a deeper region with respect to the entire surface of the silicon nitride roller including crowning is inspected with higher accuracy than the conventional inspection method of the silicon nitride roller. can do.

  In the silicon nitride roller manufacturing method according to the third embodiment and the silicon nitride roller inspection method according to the fourth embodiment, the inspection system shown in FIGS. is not. As long as it is possible to detect light transmitted through at least part of the molded body by irradiating the molded body with light, any method can be adopted.

  Here, although there is a part which overlaps with embodiment mentioned above, the characteristic structure of this invention is enumerated.

  (1) A method for manufacturing a silicon nitride roller according to the present embodiment includes a plurality of cylindrical bodies 1 whose main constituent material is silicon nitride, a plurality of workpieces 2 whose main constituent material is silicon nitride, A step of preparing a metal oxide powder having a hardness lower than that of the cylindrical body 1 and the dispersion medium 3 (S10), a plurality of cylindrical bodies 1, a plurality of workpieces 2, a metal oxide powder, and a dispersion medium 3; The step (S20) in which the cylindrical body 1 and the workpiece 2 are slidably contacted by mixing and the molded body (silicon nitride rollers 5, 7) obtained from the cylindrical body 1 by the slidable contact step (S20). (S30). In the step of inspecting the molded body (S30), the molded body is irradiated with light, and the presence of internal defects in the molded body is inspected by detecting light transmitted through at least a part of the molded body.

  Here, the main constituent material of the cylindrical body 1 is silicon nitride, which means that the material constituting 50% by volume or more of the cylindrical body 1 is silicon nitride. In other words, the cylindrical body 1 includes 50% by volume or more of silicon nitride, for example, 80% by volume or more and 98% by volume or less of silicon nitride. Moreover, making the cylindrical body 1 and the workpiece 2 slidably contact means putting the cylindrical body 1 and the workpiece 2 in a state where they are in contact with each other while sliding on each other. In the sliding contact step (S20), not only the cylindrical body 1 and the workpiece 2 are slid but also the cylindrical bodies 1 can be slid.

  In this way, referring to FIG. 1, in the sliding contact step (S20), the cylindrical body 1 is slid with the workpiece 2 or other cylindrical body 1 whose main constituent material is silicon nitride. When contacted, the surface is abraded by the metal oxide powder. At this time, depending on the type of the metal oxide powder, the cylindrical body 1 causes a chemical reaction with the metal oxide powder on the surface thereof. By such mechanical action and chemical action, the cylindrical body 1 can be crowned, and a molded body on which the crownings 4 and 8 are formed can be obtained. Furthermore, at the same time, the degree of the uneven portion generated on the surface (the outer peripheral surface 1A and the end surface 1B) of the cylindrical body 1 is reduced or the uneven portion is removed by the mechanical action and the chemical action. Can do. Further, when the outer peripheral surface 1A, the end surface 1B, and crowning 4, 8 begin to be formed in this step, the surface roughness of the crowning surfaces 4A, 8A can be reduced. In other words, the entire surface of the cylindrical body 1 can be processed simultaneously by mechanical action and chemical action.

  The light irradiated to the molded body in the inspection step (S30) is transmitted through the molded body due to the translucency of silicon nitride, and is reflected, absorbed, refracted by internal defects of the molded body. Here, in the case where irregularities such as scratches and polishing marks are formed on the surface of the molded body, the light transmitted through the molded body and reaching the surface of the molded body again is scattered by the irregularities on the surface. Or it is attenuated. Therefore, the silicon nitride roller manufactured by the conventional method of manufacturing a silicon nitride roller has a large surface roughness, and the region where the internal defect can be evaluated using the translucency of silicon nitride is limited to the region near the surface. It was.

  On the other hand, as described above, the molded body obtained by the slidable contact step (S20) has reduced irregularities such as scratches and polishing marks on the surface. The reflected light is suppressed from being reflected, absorbed, refracted due to the unevenness on the surface of the molded body. Therefore, among the light irradiated to such a molded body, light (reflected light, transmitted light, refracted light, etc.) transmitted through at least a part of the molded body also travels from the inside of the molded body to the outside. Less susceptible to irregularities on the surface of the molded body. As a result, it is possible to detect reflected light from a deeper position inside the molded body than in the prior art. For this reason, by capturing light (reflected light, transmitted light, refracted light, etc.) transmitted through at least a part of such a molded body, information such as the presence or absence of internal defects in a deeper region from the surface of the molded body It can be obtained with high accuracy.

  That is, according to the method for manufacturing a silicon nitride roller according to the present embodiment, silicon nitride roller 5 in which an internal defect in a deeper region has been inspected with high accuracy as compared with the conventional method for manufacturing a silicon nitride roller. 7 can be manufactured. For example, when the molded body is used as a rolling element for a bearing, the depth from the rolling surface of the region where the shear stress is maximum in the molded body is about 120 μm. It was not possible to manufacture silicon nitride rollers that were inspected with high accuracy for internal defects in such deep regions. On the other hand, in the manufacturing method of the silicon nitride roller, the silicon nitride rollers 5 and 7 in which the internal defects in the region at such a depth are also inspected with high accuracy can be manufactured.

(2) In the method for manufacturing a silicon nitride roller according to the present embodiment, the metal oxide powder is selected from the group consisting of iron oxide (Fe ₂ O ₃ ), chromium oxide (CrO ₂ ), and cerium oxide (CeO ₂ ). It is preferable that at least one selected.

Although the role of the metal oxide powder is not clear at present, the inventors of the present application presume as follows. Fe ₂ O ₃ , CrO ₂ , and CeO ₂ are considered to function as a catalyst for oxidizing the surface of silicon nitride. It is considered that the SiO ₂ layer can be formed by oxidizing the surface of the cylindrical body 1 by mixing the cylindrical body 1 whose main constituent material is silicon nitride and the metal oxide powder. In particular, at the boundary between the outer peripheral surface 1A and the end surface 1B formed in a convex shape on the surface of the columnar body 1 and the convex portions such as irregularities such as scratches and polishing marks, the probability of being scratched by the metal oxide Therefore, it is considered that the SiO ₂ layer is easily formed. Furthermore, since the convex portion has a high probability of being in sliding contact with the workpiece 2 and the other columnar body 1, it is considered that the SiO ₂ layer is easily removed. As a result, the step of sliding contact (S20) can perform crowning on the cylindrical body 1 and relieve irregularities such as scratches and polishing marks formed on the surface of the cylindrical body 1. It can be removed.

Further, Fe ₂ O ₃ , CrO ₂ , and CeO ₂ each have a lower hardness than silicon nitride (Si ₃ N ₄ ), and the cylindrical body 1 and the work material 2 that are mixed in the sliding contact step (S20). In addition, in the metal oxide powder and the dispersion medium 3, there is no material having a hardness higher than that of the cylindrical body 1 mainly composed of silicon nitride. Therefore, since it is suppressed that the said uneven part is newly formed in the surface of the cylindrical body 1 in this process (S20), the said uneven part can be relieve | moderated and removed more effectively.

  (3) In the manufacturing method of the silicon nitride roller according to the present embodiment, the step (S20) of sliding contact includes the cylindrical body 1, the processed material 2, the metal oxide powder, and the dispersion medium 3 in the container 10. It is preferable to include the step (S21) of housing the container 10 and the step (S22) of mixing the cylindrical body 1, the processed material 2, the metal oxide powder, and the dispersion medium 3 by moving the container 10.

  In this case, the silicon nitride roller is compared with the silicon nitride roller obtained by mixing the cylindrical body 1, the processed material 2, the metal oxide powder, and the dispersion medium 3 with a stirrer or the like without moving the container. Unevenness such as scratches on the surface and polishing marks, and surface roughness Ra value can be reduced.

  In addition, in the mixing step (S22), the container 10 includes the cylindrical body 1 while mixing the plurality of cylindrical bodies 1, the processed material 2, the metal oxide powder, and the dispersion medium 3 accommodated therein. As long as the workpiece 2 can be brought into sliding contact, the workpiece 2 can be arbitrarily moved, but is rotated, for example.

  (4) In the method of manufacturing a silicon nitride roller according to the present embodiment, the step (S30) of inspecting the molded body may be performed by visually inspecting the molded body irradiated with light using a magnifying glass. Good.

  Even in this case, the presence or absence of internal defects in the molded body can be inspected with high accuracy and easily.

  (5) In the method for manufacturing a silicon nitride roller according to the present embodiment, the step (S30) of inspecting the molded body is performed by changing the reflectance or the absorptance from the reflected light generated when the molded body is irradiated with laser light. May be implemented by capturing

  Even in this case, the presence or absence of internal defects in the molded body can be inspected with high accuracy and easily.

  (6) The silicon nitride spherical body inspection method according to the present embodiment includes a plurality of cylindrical bodies 1 whose main constituent material is silicon nitride, and a plurality of workpieces 2 whose main constituent material is silicon nitride. A molded body formed from the cylindrical body 1 by mixing the metal oxide powder having a hardness lower than that of the cylindrical body 1 and the dispersion medium 3 and bringing the cylindrical body 1 and the work material 2 into sliding contact with each other. A step of preparing, and a step of inspecting the molded body for an internal defect by irradiating the molded body with light and detecting light transmitted through at least a part of the molded body.

  In this way, since the irregularities such as scratches and polishing marks on the surface of the molded body to be inspected are sufficiently reduced, the light irradiated to such a molded body is on the surface of the molded body. Reflection, absorption, refraction, and the like due to unevenness are suppressed. Therefore, light (reflected light, transmitted light, refracted light, etc.) transmitted through at least a part of the molded body due to the translucency of silicon nitride among the light irradiated on the molded body is reflected on the surface of the molded body. Scattering or the like due to the unevenness is suppressed. As a result, it is possible to detect reflected light from a deeper position inside the molded body than in the prior art. For this reason, by capturing light (reflected light, transmitted light, refracted light, etc.) transmitted through at least a part of such a molded body, information such as the presence or absence of internal defects in a deeper region from the surface of the molded body can be obtained. It can be obtained with high accuracy.

  That is, according to the inspection method of the present silicon nitride roller, it is possible to inspect the internal defect in a deeper region with respect to the silicon nitride roller with higher accuracy than the conventional inspection method of the silicon nitride roller.

  (7) The silicon nitride rollers 5 and 7 according to the present embodiment are rollers whose main constituent material is silicon nitride, and have an outer diameter surface formed so as to surround the shaft including the rolling surface. In addition, crowning 4 and 8 are formed at both ends of the outer diameter surface in the extending direction of the shaft, respectively, and the maximum width of the outer shape is 25 μm or more in a region where the depth from the roller surface is shallower than 150 μm. There are no defects.

  When such silicon nitride rollers 5 and 7 are used as rolling elements for a bearing, the maximum shear stress in the silicon nitride rollers 5 and 7 when the bearing is used is in a region where the depth from the rolling surface is shallower than 150 μm. The area where the acts is included. Therefore, even when such maximum shear stress is applied to the silicon nitride rollers 5 and 7, the occurrence of cracks and the like starting from internal defects is suppressed. That is, in the region where the depth from the surface is shallower than 150 μm, the silicon nitride rollers 5 and 7 having no defect having a maximum outer width of 25 μm or more are suitable as rolling elements for bearings.

  In addition, since such silicon nitride rollers 5 and 7 are sufficiently reduced in irregularities such as surface scratches and polishing marks, a method of manufacturing a silicon nitride roller including the step (S30) of inspecting the molded body described above. Or obtained by carrying out an inspection method for silicon nitride rollers (can be selected).

  Next, examples will be described.

  With respect to the silicon nitride roller manufactured according to the method for manufacturing the silicon nitride roller according to the first embodiment, the dimensions and surface roughness of the crowning portion were measured.

(Sample 1 to Sample 3: Example 1)
First, a plurality of cylindrical bodies and processed materials made of silicon nitride were prepared. Specifically, the cylindrical body contains 80% by volume or more and 98% by volume or less of silicon nitride, and is polished by using diamond as abrasive grains. Both the outer diameter Φ and the length L of the cylindrical body were 13 mm. The prepared cylindrical body had a surface roughness (arithmetic average roughness) Ra value on the outer diameter surface of 0.0514 μm and a surface roughness Ra value on the end surface of 0.0475 μm.

  The processed material 2 was a spherical body containing 80% by volume to 98% by volume of silicon nitride. The outer diameter of the processed material 2 was 7 mm or more and 12 mm or less.

Next, as shown in FIG. 1, as an example, the prepared cylindrical body 1 is accommodated in a ball mill (container 10), and is rotated so that the cylindrical body 1, the work material 2, the dispersion medium 3, and the metal The oxide powder was mixed. Specifically, under the conditions shown in Tables 1 and 2, a plurality of cylindrical bodies 1, a plurality of processed materials 2, water as a dispersion medium 3, and iron oxide (Fe ₂ O ₃ ) as a metal oxide powder. , Chromium oxide (CrO ₂ ), and cerium oxide (CeO ₂ ) were housed in a ball mill container 10 and subjected to ball milling. As shown in Table 2, the ball mill container 10 was made of polyethylene as the container material. The shape of the ball mill container 10 was cylindrical, and the dimensions of the container were an inner diameter Φ200 mm and an axial length L200 m. The metal oxide powder was ball milled using iron oxide to obtain a silicon nitride roller 5 of Sample 1. Further, ball milling was performed using chromium oxide to obtain a silicon nitride roller 5 of Sample 2. Ball milling was performed using cerium oxide to obtain a silicon nitride roller 5 of Sample 3.

(Sample 4, Sample 5: Comparative Example 1)
Moreover, as a comparative example, in the same manner as Sample 1 to Sample 3 of Example 1, under the conditions shown in Table 1 and Table 2, the plurality of columnar bodies, the plurality of processed materials, and water as a dispersion medium, Aluminum oxide (Al ₂ O ₃ ) having a hardness higher than that of silicon nitride was accommodated in the ball mill container, and ball mill treatment was performed under the conditions shown in Table 2 to obtain a silicon nitride roller of Sample 4. In other words, the silicon nitride roller of sample 4 is manufactured by changing only the metal oxide powder with respect to the silicon nitride rollers of sample 1 to sample 3.

  In addition, as a comparative example, a plurality of the cylindrical bodies, a plurality of the processed materials, and water as a dispersion medium are accommodated in the ball mill container and shown in Table 1 without using metal oxide powder (metal Ball milling was performed under the conditions (only the amount of oxide powder contained was changed to 0 g) and the conditions shown in Table 2, and a silicon nitride roller of Sample 5 was obtained.

(Sample 6 to Sample 10; Comparative Example 2)
Further, as a comparative example, ball milling was performed in the same manner as in Example 1 and Comparative Example 2 using a processed material whose main constituent material was aluminum oxide, to obtain silicon nitride rollers of Sample 6 to Sample 10. That is, the silicon nitride rollers of Sample 6 to Sample 10 are manufactured under the same conditions as the silicon nitride rollers of Sample 1 to Sample 5 except for the processed material.

  Specifically, the cylindrical body contains 80% by volume or more and 98% by volume or less of silicon nitride, and is polished by using diamond as abrasive grains. The processed material 2 was a spherical body containing 80% by volume to 98% by volume of aluminum oxide. The outer diameter of the processed material 2 was 7 mm or more and 12 mm or less.

Further, similarly to the silicon nitride rollers of Sample 1 to Sample 4, under the conditions shown in Table 1 and Table 2, a plurality of cylindrical bodies, a plurality of processed materials whose main constituent material is aluminum oxide, water, One of Fe ₂ O ₃ , CrO ₂ , CeO ₂ , and Al ₂ O ₃ was accommodated in a ball mill container and subjected to ball mill treatment, thereby producing silicon nitride rollers of Sample 6 to Sample 9. Similarly to the silicon nitride roller of Sample 5, a plurality of cylindrical bodies, a plurality of workpieces whose main constituent materials are aluminum oxide, and water are accommodated in a ball mill container and subjected to a ball mill treatment. The silicon nitride roller of this was produced.

  With respect to the silicon nitride rollers of Samples 1 to 10 thus obtained, the roundness in the cross section perpendicular to the axial direction, the crowning drop amount L1 (see FIG. 2), the crowning length L2 (see FIG. 2), The surface roughness (Ra) of the outer diameter surface, the surface roughness (Ra) of the end surface, and the dimensions were measured. Furthermore, the ratio L2 / L3 of the crowning length L2 with respect to the length L3 of the outer diameter surface in the extending direction of the shaft was calculated. Table 3 shows the measurement results of the cylindrical body before the ball mill treatment described above with respect to the silicon nitride rollers of Sample 1 to Sample 5 subjected to ball mill treatment using a processing material whose main constituent material is silicon nitride. Shown together. Further, Table 4 shows the measurement results of the cylindrical body before the ball mill treatment described above with respect to the measurement results of the silicon nitride rollers of Sample 6 to Sample 10 which were subjected to the ball mill treatment using the processing material whose main constituent material is aluminum oxide. It shows together with a result. The crowning length and the crowning drop amount were calculated from the cross-sectional profiles obtained by obtaining the cross-sectional profiles of the silicon nitride rollers of Sample 1 to Sample 10 using a shape measuring instrument (using Mitutoyo Foam Tracer). FIG. 12 shows cross-sectional profile data of Sample 3. The vertical axis in FIG. 12 indicates the depth (unit: μm) from the reference plane in the direction perpendicular to the axial direction of the silicon nitride roller, and the horizontal axis is the distance (unit: mm) from the reference plane in the axial direction of the silicon nitride roller. Indicates.

  As shown in Table 3, the ratio of the crowning length L2 to the bus length L3 was 9.2%, 13.8%, and 11.5%, respectively. That is, the ratio of the crowning length L2 to the bus length L3 in the silicon nitride rollers of Samples 1 to 3 was 9% or more and 25% or less. That is, the silicon nitride rollers of Samples 1 to 3 were sufficiently crowned to avoid edge loading as rollers.

  Further, the surface roughness (Ra) of the outer diameter surface and the end surface of the silicon nitride rollers of Samples 1 to 3 are the same as the surface roughness (Ra) of the outer diameter surface and the end surface of the cylindrical body before the ball mill treatment. Compared with this, it was greatly reduced, and the surface roughness (Ra) sufficient for the roller was improved. On the other hand, there was no significant change in shape accuracy such as roundness before and after ball milling.

  In FIG. 13, the microscope image of the surface of the boundary part of a crowning and an outer diameter surface in the silicon nitride roller of the sample 2 is shown. FIG. 14 shows a microscopic image of the outer diameter surface of the silicon nitride roller of Sample 2. In FIG. 15, the microscope image of the end surface of the silicon nitride roller of the sample 2 is shown. FIG. 16 shows a microscopic image of the crowning surface of the silicon nitride roller of Sample 2. As a comparative example, the crowning of a silicon nitride roller on which FIGS. 17 to 20 are subjected to a crowning process using a diamond grindstone (specifically, a super-finish process using a diamond grindstone having a # 2000 grindstone count). The microscopic images of the surface of the boundary portion between the outer diameter surface and the outer diameter surface, the outer diameter surface, the end surface, and the crowning surface are shown.

  Compared to the conventional silicon nitride roller subjected to the crowning process, the silicon nitride roller of sample 2 has scratches on the surface of the boundary between the crowning and the outer diameter surface, the outer diameter surface, the end surface, and the crowning surface. It was confirmed that polishing marks were not noticeable.

  In contrast, the silicon nitride rollers of Sample 4 and Sample 5 have a crowning drop amount of less than 1 μm, and the ratio of the crowning length L2 to the bus bar length L3 is less than 1.0%. In order to avoid this, sufficient crowning was not formed. In particular, in the silicon nitride roller of Sample 5, no crowning was formed. The ratio of the crowning length L2 to the bus bar length L3 of the sample 4 silicon nitride roller was 0.8%, which was lower than that of the sample 1 sample 3 silicon nitride roller.

  Further, the surface roughness (Ra) of the outer diameter surface and the end surface of the silicon nitride roller of Sample 5 was slightly smaller than that before the ball mill treatment, but since it is 0.04 μm or more, the reduction in bearing life is suppressed. There was not enough improvement from the point of view.

  Further, in the silicon nitride roller of Sample 4, the surface roughness Ra value of the outer diameter surface was increased from 0.0514 μm before the ball mill treatment to 0.0522 μm, and the surface roughness Ra value of the end surface was 0. 0 before the ball mill treatment. It increased from 0475 μm to 0.0523 μm. This is because when the cylindrical body made of silicon nitride and the workpiece are slidably contacted, the surface of the cylindrical body is rubbed with high-hardness aluminum oxide, so that scratches and polishing marks are generated on the surface. Conceivable.

  That is, from the results of Example 1 and Comparative Example 1, the metal oxide powder having a hardness lower than that of the cylindrical body whose main constituent material is silicon nitride, and the main constituent material similar to the cylindrical body is silicon nitride. By performing a ball mill treatment with a certain workpiece, it is possible to produce a silicon nitride roller in which crowning is formed at both ends in the axial direction and irregularities such as scratches and polishing marks on the surface are sufficiently reduced. Was confirmed. In addition, a cylindrical body with a sufficiently high shape accuracy, such as roundness, is ball milled to achieve high shape accuracy and a crowning to sufficiently reduce scratches and polishing marks on the surface. It was confirmed that the obtained silicon nitride roller can be obtained.

  Further, as shown in Table 4, the silicon nitride rollers of Sample 6 to Sample 10 have a crowning drop amount of less than 1 μm, and the ratio of the crowning length L2 to the length L3 of the bus bar of the silicon nitride roller is 1 respectively. 0.5%, 1.5%, 1.5%, and 0.7%. That is, in the silicon nitride rollers of Samples 6 to 9, sufficient crowning was not formed to avoid edge loading as rollers. No crowning was formed on the silicon nitride roller of Sample 10. Furthermore, the surface roughness (Ra) of the outer diameter surface and the end surface of the silicon nitride rollers of Sample 6 to Sample 8 are the same as the surface roughness (Ra) of the outer diameter surface and the end surface of the cylindrical body before the ball mill treatment. Although it is slightly smaller than the above, since it is 0.03 μm or more, sufficient improvement was not seen from the viewpoint of suppressing reduction in bearing life. Further, the surface roughness of the silicon nitride rollers of Sample 9 and Sample 10 was equal to or larger than that before the ball mill treatment, and sufficient improvement was not seen from the viewpoint of suppressing reduction in bearing life.

  That is, from the results of Example 1 and Comparative Example 2, when the ball mill treatment was performed using a processed material whose main constituent material is aluminum oxide having a hardness higher than that of the columnar body, the type of metal oxide powder was changed. Regardless, it was confirmed that sufficient crowning was not formed and irregularities such as scratches and polishing marks on the surface could not be reduced sufficiently.

  With respect to the silicon nitride roller manufactured according to the method for manufacturing the silicon nitride roller according to the second embodiment, the dimensions and surface roughness of the crowning portion were measured.

(Sample 11: Example 2)
First, a plurality of cylindrical bodies and processed materials made of silicon nitride were prepared. Specifically, the cylindrical body contains 80% by volume or more and 98% by volume or less of silicon nitride, and is polished by using diamond as abrasive grains. Both the outer diameter Φ and the length L of the cylindrical body were 13 mm. The prepared cylindrical body had a surface roughness (arithmetic average roughness) Ra value on the outer diameter surface of 0.0514 μm and a surface roughness Ra value on the end surface of 0.0475 μm.

  The processed material 2 was a spherical body containing 80% by volume to 98% by volume of silicon nitride. The outer diameter of the processed material 2 was 7 mm or more and 12 mm or less.

  Next, cut crowning 6 was formed at both ends of the prepared cylindrical body 1 in the axial direction. The cut crowning 6 was formed by grinding the cylindrical body 1 using a diamond grindstone having a ground surface shape provided in the cut crowning shape, and transferring the grinding surface shape to the cylindrical body 1. In FIG. 21, the cross-sectional profile in the cut crowning 6 of the cylindrical body 1 is shown. The cross-sectional profile was acquired using a shape measuring instrument (using Mitutoyo Form Tracer).

Next, as shown in FIG. 1, the cylindrical body 1 on which the cut crowning 6 is formed is accommodated in a ball mill (container 10), and the cylindrical body 1, the work material 2, the dispersion medium 3, and the like are rotated. Metal oxide powder was mixed. Specifically, under the conditions shown in Tables 1 and 5, a plurality of cylindrical bodies 1, a plurality of processed materials 2, water as a dispersion medium 3, and iron oxide (Fe ₂ O ₃ ) as a metal oxide powder Was stored in a ball mill container 10 and subjected to a ball mill treatment. The ball mill container 10 was the same as the ball mill container 10 used in Example 1. As a result of the ball mill treatment, a silicon nitride roller 7 of Sample 11 was obtained. FIG. 22 shows the cross-sectional profile of the silicon nitride roller 7 in the crowning 8 and the cross-sectional profile of the cut crowning 6 of the cylindrical body 1 before the ball mill treatment shown in FIG.

  With respect to the silicon nitride roller of the sample 11 thus obtained, the roundness in the cross section perpendicular to the axial direction, the crowning drop amount L1 (see FIG. 3), the crowning length L2 (see FIG. 3), the outer diameter surface The surface roughness (Ra), end surface roughness (Ra), and dimensions were measured. Furthermore, the ratio L2 / L3 of the crowning length L2 with respect to the length L3 of the outer diameter surface in the extending direction of the shaft was calculated. Table 6 shows the measurement results for the silicon nitride roller of the sample 11 subjected to the ball mill treatment using the processing material whose main constituent material is silicon nitride, together with the measurement results of the cylindrical body before the ball mill treatment described above. .

  As shown in Table 6 and FIG. 22, the silicon nitride roller of Sample 11 has a crowning drop amount of 24 μm, and the ratio of the crowning length L2 to the length L3 of the bus bar of the silicon nitride roller is 10.8%. As a result, sufficient crowning was formed to avoid edge loading. Further, the ratio of the crowning length L2 to the bus bar length L3 of the silicon nitride roller of Sample 11 was larger than the ratio L2 / L3 of the silicon nitride rollers of Sample 1 to Sample 3 in Example 1.

  Referring to FIG. 22, the silicon nitride roller of sample 11 has a crowning shape that approximates a logarithmic curve as compared with the silicon nitride roller of sample 1 in Example 1, and a crowning having a more ideal shape is formed. It was. Further, the surface roughness (Ra) of the outer diameter surface and the end surface of the silicon nitride roller of the sample 11 is larger than the surface roughness (Ra) of the outer diameter surface and the end surface of the cylindrical body before the ball mill treatment. The surface roughness (Ra) was reduced to a sufficient level as a roller. On the other hand, there was no significant change in shape accuracy such as roundness before and after ball milling.

(Sample 12: Comparative Example 3)
Further, as Comparative Example 3, a silicon nitride roller of Sample 12 was obtained by barrel polishing. FIG. 23 shows a cross-sectional profile of the molded body of the sample 12. Compared to FIG. 22, the molded body of the sample 12 is rounded at the boundary between the outer diameter surface and the end surface, but the crowning like the molded body of the sample 11 is not formed. That is, the silicon nitride roller manufacturing method according to the first embodiment can easily form the crowning that has been difficult to form by the barrel polishing method conventionally employed as the crowning processing method.

  According to the method for manufacturing a silicon nitride roller according to the third embodiment, an appearance inspection was performed on the silicon nitride roller.

  First, four types of cylindrical bodies made of silicon nitride and having a length L of 13 mm and an outer diameter Φ of 13 mm were prepared. Specifically, the plurality of columnar bodies contained 80% by volume or more and 98% by volume or less of silicon nitride, and were polished using diamond as abrasive grains. The surface roughness (arithmetic mean roughness) Ra value of the cylindrical body was 0.01 μm. After the polishing process, a metal inclusion defect (stainless steel (SUS) powder having a maximum outer width of 45 μm was introduced at positions where the depth from the polished surface (surface) was 50 μm, 80 μm, 120 μm, and 150 μm, respectively. Four types of columnar bodies of sample 16 were prepared, and the position where the metal inclusion defect was introduced in each columnar body was at the above depth from the polished surface using an X-ray CT (Computed Tomography) apparatus. confirmed.

  It was evaluated whether or not internal defects could be detected by the following inspection methods for the cylindrical bodies of Sample 13 to Sample 16. As a first inspection method, as shown in FIG. 9, a method of visually inspecting the cylindrical bodies of Sample 13 to Sample 16 using a stereomicroscope 20 as a magnifier was adopted. Further, as a second inspection method, a method is used in which the change in the absorptance is captured from the reflected light generated when the cylindrical bodies of the samples 13 to 16 are irradiated with the laser beam using the inspection system shown in FIG. did.

  Further, ball milling was performed on the cylindrical bodies of Sample 13 to Sample 16 according to the step (S20) of sliding the cylindrical body and the workpiece in the silicon nitride roller manufacturing method according to Embodiment 1. The ball mill treatment includes a plurality of cylindrical bodies whose main constituent material is silicon nitride, including a cylindrical body of Sample 13 to Sample 16, a plurality of workpieces whose main constituent material is silicon nitride, and dispersion. Water as a medium and iron oxide as a metal oxide powder were accommodated in a ball mill container, and the conditions shown in Table 1 and Table 2 were used. The processed material was a spherical body containing 80% by volume to 98% by volume of silicon nitride. The outer diameter of the processed material 2 was 7 mm or more and 12 mm or less.

  It was evaluated whether or not internal defects could be detected by the first and second inspection methods in the same manner as before the ball mill treatment on the molded bodies (silicon nitride rollers) of Sample 13 to Sample 16 after the ball mill treatment. . Table 7 shows the inspection results.

  As shown in Table 7, for the cylindrical bodies of Sample 13 and Sample 14 where the surface depth of the metal inclusion defect is less than 80 μm, the first and second inspection methods are used even before ball milling. The metal inclusion defect could be detected. However, since the surface depth of the metal inclusion defect is deeper than 80 μm, both the first and second inspection methods detect the metal inclusion defect for the cylindrical body of the sample 15 and the sample 16 before the ball mill treatment. I couldn't.

  On the other hand, the metal inclusion defects could be detected by the first and second inspection methods for the molded bodies of the sample 15 and the sample 16 after the ball mill treatment. This is because, as described above, the cylindrical body before the ball mill treatment has irregularities such as scratches and polishing marks on the surface, and the internal defects exist at a deep position from the surface because the transmitted light is scattered and attenuated on the surface. In contrast, it is difficult to detect the surface of the molded body after ball milling, and the surface irregularities such as scratches and polishing marks are sufficiently reduced. It is considered that an internal defect existing at a deep position from the surface can be detected.

  In other words, from the result of Example 3, the surface of the molded body (silicon nitride roller) was measured by the method for manufacturing the silicon nitride roller according to the third embodiment and the method for inspecting the silicon nitride roller according to the fourth embodiment. It was confirmed that the presence or absence of internal defects could be inspected from a deeper position to a deeper position. Further, it was confirmed that the silicon nitride roller inspection method according to the fourth embodiment is particularly suitable as a silicon nitride roller inspection method for bearing rolling elements. Specifically, when a silicon nitride roller is used as a rolling element for a bearing, a shear stress acts on the silicon nitride roller from the rolling surface to a region of about 120 μm, so that the region has a metal inclusion defect or the like. Silicon rollers are not suitable for rolling elements for bearings that require high reliability. In contrast, by performing the silicon nitride roller inspection method according to the fourth embodiment (the method for manufacturing the silicon nitride roller according to the third embodiment), the depth from the rolling surface is at least about 150 μm. In the region where the depth from the rolling surface (roller surface) is at least about 150 μm, an internal defect of a predetermined size (for example, the maximum outer width is 25 μm or more) can be evaluated. It is possible to select silicon nitride rollers (or compacts) having no defects.

  Although the embodiment of the present invention has been described as above, the embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention is particularly advantageously applied to a silicon nitride roller used for a rolling element for a bearing and a method for manufacturing a silicon nitride roller.

  DESCRIPTION OF SYMBOLS 1 Cylindrical body, 2 Work material, 3 Dispersion medium, 4,8 Crowning, 5,7 Silicon nitride roller, 10 container, 11 roller.

Claims (7)

A plurality of cylindrical bodies whose main constituent material is silicon nitride, a plurality of workpieces whose main constituent material is silicon nitride, a metal oxide powder having a hardness lower than that of the cylindrical body, and a dispersion medium A preparation process;
A step of bringing the cylindrical body and the processing material into sliding contact by mixing the plurality of cylindrical bodies, the plurality of processing materials, the metal oxide powder, and the dispersion medium;
A step of inspecting a molded body obtained from the cylindrical body by the step of sliding contact,
In the step of inspecting the molded body, the molded body is irradiated with light, and the presence of internal defects in the molded body is inspected by detecting the light transmitted through at least part of the molded body. Manufacturing method of silicon nitride roller.   2. The method for producing a silicon nitride roller according to claim 1, wherein the metal oxide powder is at least one selected from the group consisting of iron oxide, chromium oxide, and cerium oxide. The step of sliding contact includes the step of accommodating the cylindrical body, the processed material, the metal oxide powder, and the dispersion medium in a container;
The method for producing a silicon nitride roller according to claim 1, comprising a step of mixing the cylindrical body, the processed material, the metal oxide powder, and the dispersion medium by moving the container.   The silicon nitride roller according to any one of claims 1 to 3, wherein the step of inspecting the molded body is performed by visually inspecting the molded body irradiated with light using a magnifying glass. Manufacturing method.   The step of inspecting the molded body is carried out by capturing a change in reflectance or absorptance from reflected light generated when the molded body is irradiated with laser light. 2. A method for producing a silicon nitride roller according to item 1. A plurality of cylindrical bodies whose main constituent material is silicon nitride, a plurality of workpieces whose main constituent material is silicon nitride, a metal oxide powder having a hardness lower than that of the cylindrical body, and a dispersion medium Preparing a molded body formed from the cylindrical body by mixing and slidingly contacting the cylindrical body and the workpiece; and
Inspecting the silicon nitride roller, comprising: irradiating the molded body with light and detecting the light transmitted through at least a part of the molded body to check for the presence of internal defects in the molded body. Method. When the main constituent material is silicon nitride,
Including a rolling surface and having an outer diameter surface formed to surround the shaft;
Crowning is formed at both ends of the outer diameter surface in the extending direction of the shaft,
A silicon nitride roller having no defect having a maximum outer width of 25 μm or more in a region where the depth from the surface of the roller is shallower than 150 μm.