JPH06229422A - Manufacture of ceramic rolling bearing member - Google Patents

Abstract

PURPOSE:To enhance the efficiency of grinding work on an end surface by forming a chamfer part in a peripheral edge part on the end surface of a compact when pressure molding is carried out, removing the sintered skin of the chamfer part by impact polishing after it is sintered, and grinding the end surface into a smooth surface while leaving the chamfer part. CONSTITUTION:A compact is sintered in a sintering furnace, and thus sintered body 12 is obtained. Because of tumbler processing, this sintered body 12 is inserted and rotated in a rotary drum together with an abrasive such as an alumina grain and water, and the surface is polished, and the skin forming a sintered surface of the sintered body 12 is removed. Thereby, both a chamfer part 21 and a recessed pit part 23 become the skin polished surfaces 21(X) and 23(X). Next, surface grinding is carried out only on a projecting surface 24(X) of an end surface of a sintered body 13 obtained by tumbler processing by a grinder, and an end surface interval distance as a cylinder roller 5 is adjusted, and a smooth end surface 24(Y) is molded, so that an end surface 52 of the cylinder roller 5 is formed. Lastly, precision grinding is carried out on a peripheral surface 31(Y) of a sintered body 14 whose end surface is ground, and a rolling travel surface 53 of the cylinder roller 5 is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a method of manufacturing a cylindrical roller for bearing made of ceramics and a bearing ring thereof.

[0002]

BACKGROUND OF THE INVENTION Since ceramics used for rolling bearing members have excellent hardness, wear resistance, heat resistance, and chemical resistance, alumina, silicon carbide, silicon nitride, etc. are used. Rolling bearing members such as cylindrical rollers and bearing rings are usually formed by pressure-compressing ceramic powder in a press die and firing the compact at high temperature to form a sintered body. It is manufactured by grinding the outer peripheral surface and the end surface.

[0003] These ceramic materials have poor moldability under pressure by a mold, and if there is a large spatial deviation in the compression ratio distribution of the powder compact pressed during mold molding, the molded product after release from the mold will have a large deviation. Cracks and defects are likely to occur. Therefore, conventionally, in the case of molding a cylindrical roller with a die, in order to make the compression ratio distribution uniform, the end surface of the roller is made a flat end surface, and after sintering, a chamfered portion is provided on the outer edge of the end surface by grinding. The entire end face was ground.

Further, a relatively long rod-shaped ceramic compact is molded by an isotropic pressure molding method (CIP) such as a rubber press, and after sintering, it is ground and cut to a predetermined length, and the end surface is edge-ground to form the outer edge of the end surface. A chamfer was formed on the.

[0005]

In the above-mentioned method for forming the end surface of the cylindrical roller made of ceramic, virtually all the end surfaces are ground.
Since the above-mentioned ceramic has a high hardness and is difficult to grind, it is difficult to increase the man-hour for grinding and the processing cost.

In order to reduce the grinding process, a method of forming a chamfered portion and sintering it in advance at the time of pressure molding and leaving only the chamfered portion and grinding only a relatively flat end face is considered. . In this case, the chamfered portion leaves a rough skin as it is as sintered, and the dust of the environment before or during the use of the bearing is retained in the surface recess of the sintered skin, and a part of the skin portion is used during use. Separated and mixed into the raceway groove of the bearing race,
The bearing life may be adversely affected. Therefore, even when the chamfered portion is formed in advance on the molded body, it is necessary to similarly grind the chamfered portion.

From the above point of view, the present invention provides a method for forming an end surface of a ceramic rolling bearing member such as a cylindrical roller.
An object of the present invention is to provide a method for manufacturing a rolling bearing member which reduces the surface area of an end surface to be ground after sintering and removes a harmful sintered skin by an appropriate method for treating an unground surface.

[0008]

According to a method of manufacturing a ceramic rolling bearing member for bearings of the present invention, a rolling bearing member is manufactured by sintering a cylindrical or ring-shaped compact formed by pressure molding from ceramic material powder. In the method, a chamfered portion is formed on the peripheral portion of the end surface of the molded body during pressure molding, and after sintering, at least the sintered skin of the chamfered portion of the sintered body is subjected to impact polishing of abrasive granules. A skin polishing step of removing, and a grinding step of grinding the end surface to a smooth surface leaving the chamfered portion,
It is characterized by performing.

Further, according to the present invention, a recess is formed in the center of the end face together with the chamfered portion of the peripheral edge portion on the end face of the molded body, and after sintering, at least the chamfered portion of the end face and the sintered skin of the recessed portion are ground particles. A skin polishing step of removing the material by impact polishing,
A method of manufacturing a cylindrical roller made of ceramics, which comprises performing a grinding step of grinding the end surface to a smooth surface while leaving the chamfered portion and the concave portion.

The rolling bearing member of the present invention includes a cylindrical roller as a rolling element interposed between an inner ring and an outer ring, which is a ring ring, and an inner ring and an outer ring. A ceramic material forming these bearing members is alumina. Silicon carbide or silicon nitride is adopted.

As the pressure molding method, a uniaxial pressure molding method is generally adopted. However, upper and lower punches are inserted into the hollow portion of a cylindrical die, and the punch end face is mixed with ceramic material in the hollow portion of the die by hydraulic means. The powder is pressed, and the punch end surface is shaped by shaping an end surface having a desired chamfered portion of the molded body. Since the peripheral surface of the mold die forms the peripheral surface of the molded body, the chamfered portion of the end surface is formed between the end surface and the peripheral surface. The cylindrical molded body is used for a cylindrical roller and includes both a solid body and a hollow body.

The molded body is sintered in a high-temperature firing furnace, the end surface of the sintered body is prepared by a skin polishing step and a grinding step,
The peripheral surface of the sintered body is subjected to grinding and precision grinding for forming a rolling surface to form a bearing member.

In the present invention, impact polishing of abrasive particles broadly includes tumbler treatment (barrel polishing, etc.), vibration polishing, shot blasting, air blasting and the like. All of them are intended to remove the sintered skin (sintered skin) of the ceramic sintered body by impact such as projection of a large number of independent abrasive grains on the surface of the sintered body, radiation, vibration contact, collision, etc. Particularly, the tumbler treatment and the vibration polishing have an advantage that many sintered bodies can be polished by one treatment.

[0014]

In the manufacturing method of the present invention, the end surface of the sintered body obtained by firing the compression molded body at a high temperature has a chamfered portion and a flat portion, so that a sintered surface of a rough surface with large irregularities is formed. Although it forms a skin, at least the chamfered portion has a sintered surface with less unevenness because the sintered skin is removed by impact polishing such as tumbler polishing. Therefore, only the remaining flat portion excluding the chamfered portion is ground by a grinder to form a smooth surface. Therefore,
The grinding area can be reduced and the working time can be shortened. On the other hand, impact polishing methods such as tumbler polishing or blasting process a large amount of sintered products all at once, and thus have a large polishing ability, so that the efficiency of the polishing / grinding process as a whole is improved.

The concave portion is formed in the center of the end surface of the molded body only by the end surface of the annular projection between the concave portion and the chamfered portion, which further reduces the grinding area. As a result, the efficiency of grinding is improved, while the recess is subjected to tumbler polishing at the same time as the chamfered portion.

The skin polishing process such as tumbler treatment or blast polishing and the grinding process may be performed before or after. After grinding the end face, including the unground chamfer and recess,
It is also possible to blast polish the end faces or tumbler polish the entire circumference of the sintered body. After that, precision grinding for forming a rolling surface may be performed.

Since the chamfered portion and the recessed portion are finished to have a certain fine surface as described above, it becomes difficult for dust or the like to adhere to the chamfered portion before or during the use of the bearing.

In particular, when the ceramic material is silicon nitride, coarse columnar crystals of β-Si ₃ N ₄ have developed on the surface of the sintered body after sintering, and the cylindrical roller The columnar crystals in the skin of the chamfer break and break into the rolling groove,
In particular, the rolling surface of the steel bearing ring will be damaged, but since the present invention removes the sintered skin by polishing, β-Si ₃
N ₄ columnar crystals are removed from the surface and are effective in protecting the rolling surface.

[0019]

EXAMPLES A method of manufacturing a ceramic rolling bearing member according to the present invention will be described below by taking an example of a cylindrical roller and an outer ring by selecting silicon nitride as a ceramic material. FIG. 3 shows a process chart.

FIG. 1 (A) is a press molding process for molding a mixed powder 10 containing silicon nitride powder and a small amount of a sintering aid such as alumina into a molded body 11 by a uniaxial pressure molding machine 7. The machine section is shown.

The pressing end surfaces of the pair of upper and lower punches 71, 72 to be inserted into the hollow portion of the floating die 73 of the molding machine 7 are preformed with a shape corresponding to the end surface shape of the molded body 11 made of powder. As shown in FIG. 1 (B), the molded body 11 after pressure molding has a chamfered portion 21 at the outer peripheral edge and a central portion at the end face 2 so as to approximate the shape of the cylindrical roller 5. A bottomed taper recess 23 is provided, and a flat annular protrusion 24 is formed between the chamfer 21 and the recess 23. The step portion 28 between the chamfered portion 21 and the peripheral surface 31 is provided for structurally strengthening the peripheral edges of the end faces of the punches 71 and 72, and is not always necessary for carrying out the method of the present invention. is not.

The compact 11 is fired at a high temperature of 1700 to 1900 ° C. in a sintering furnace (not shown),
Sintered body 12 is obtained. For tumbler treatment, this sintered body 12 is charged with an abrasive such as alumina particles and water in a rotary drum and rotated to rotate the surface as shown in FIG. 2 (A). Is ground to remove the skin that forms the sintered surface of the sintered body 12.
Therefore, both the chamfered portion 21 and the recessed portion 23 become the skin polishing surfaces 21 (X) and 23 (X).

Next, as shown in FIG. 2 (B), only the protruding portion 24 (X) on the end surface of the tumbler-treated sintered body 13 is subjected to surface grinding with a grinder to form an end surface as a cylindrical roller 5. When the smooth end face 24 (Y) is molded by adjusting the spacing distance, the end face 52 of the cylindrical roller 5 is obtained.

Finally, the sintered body 14 whose end face is ground
As shown in FIG. 2 (C), the peripheral surface 31 (Y) is precisely ground to form the rolling surface 53 of the cylindrical roller 5.

In FIG. 2, the alternate long and two short dashes line indicates the sintered body 12.
Shows a contour line of the skin before the removal of the skin, the reference sign X indicates a surface-polished surface, and the reference sign Y indicates a ground surface.

FIG. 4 shows a ceramic material made of silicon nitride Si ₃
A scanning electron micrograph of the surface texture of the chamfered portion 21 of the end face in the test in which the cylindrical roller 5 was molded using N ₄ -based ceramic is shown in FIG. 4 (A). It can be seen that a large number of coarse columnar crystals of β-Si ₃ N ₄ grow and remain.

FIG. 4B shows a surface crystal structure of the chamfered portion after the skin polishing step, in which coarse columnar crystals are removed. Therefore, the chamfered portion 21 (X) or the recessed portion 23 (X) is
Coarse columnar crystals can be removed by grinding the skin without grinding, so that damage to the raceway due to separation of the columnar crystals can be prevented.

An embodiment of the method for manufacturing the outer ring in the bearing ring is shown in FIG. 5 by the uniaxial pressure molding machine 7 shown in FIG. 5 (A).
A ring-shaped molded body 11 having chamfered portions 21 and 21 formed on the inner and outer peripheral edges of both end surfaces of the ring body as shown in FIG.

FIG. 6 is a sectional view of the sintered body 12 obtained by firing the pressure molded body 11 of FIG. 5B at a high temperature in each step of skin polishing and end face grinding. In this example, by tumbler polishing, the sintered skin is removed on almost the entire surface of the sintered body including the chamfered portions 21, 21 to form a skin-polished surface X (see FIG. 6).
(A)) Next, leaving only the chamfered portions 21, 21, only both end surfaces 24, 24 are ground to form a ground surface Y (FIG. 6).
(B)). Next, since the outer peripheral surface 31 and the inner peripheral surface 32 are ground to form the ground surface Y (FIG. 6C), the grinding step requires grinding processing for cutting and forming the chamfered portions 21, 21. Without it, it can be simplified and streamlined.

Finally, in this example, a concave curved surface 33 to be the rolling surface 633 of the outer ring is ground on the inner circumferential surface 32 of the inner ring to obtain a ceramic outer ring for a ball bearing (FIG. 6).
(C)).

[0031]

According to the method of manufacturing a ceramic rolling bearing member of the present invention, the chamfered portion and the recessed portion at the peripheral edge of the end face which are previously formed in the sintered body are made by the skin polishing, and the skin polishing process has a large processability. Moreover, since the end face grinding area can be reduced, the grinding time can be shortened and the grinding process can be made more efficient.

Since the surface of the chamfered portion and the recessed portion is removed to form a polished surface, dust and dust are unlikely to adhere to the bearing before or during use as a bearing, and rolling due to separation of the sintered surface skin. There is no risk of damaging the surface, especially the rolling surface of the steel bearing ring, which contributes to the improvement of the reliability of the ceramic bearing.

[Brief description of drawings]

FIG. 1 is a cross-sectional view (A) of a uniaxial pressure molding machine used to carry out the present invention and a cross-sectional view (B) of a molded cylindrical roller molded product.

FIG. 2 is a sectional view (A) of the sintered body for a cylindrical roller after polishing the surface of the sintered body for a cylindrical roller in the embodiment of the present invention, a sectional view (B) of the same after grinding the end surface, and a sectional view of the cylindrical roller after grinding the peripheral surface. Sectional view (C).

FIG. 3 is a manufacturing process drawing of the ceramic rolling bearing member of the present invention.

FIG. 4 is a scanning electron micrograph (magnification: 400) of the ceramic surface texture of the chamfered sintered skin (A) and the chamfered polished surface (B) of the chamfered sintered surface of the sintered body for silicon nitride cylindrical rollers (B).
0).

FIG. 5 is a view similar to FIG. 1 in the case of molding a ceramic outer ring.

FIG. 6 is a view similar to FIG. 2 when a ceramic outer ring is molded.

[Explanation of symbols]

 11 Pressure Formed Body 2 End Face 21 Chamfered Part 24 End Face (Protruding Part) 23 Recessed Part 31 Outer Surface 32 Inner Surface 5 Cylindrical Roller 6 Outer Ring 7 Uniaxial Pressure Forming Machine X Skin Polishing Surface Y Grinding Surface

Claims (2)

[Claims] 1. A method for manufacturing a rolling bearing member by sintering a cylindrical or ring-shaped molded body that is pressure-molded from ceramic material powder, wherein a chamfered portion is formed on the peripheral edge of the end surface of the molded body during pressure molding. After the sintering, after the sintering, a skin polishing step of removing the sintered skin of at least the chamfered portion of the sintered body by impact polishing of abrasive grains, and grinding the end face to a smooth surface leaving the chamfered portion. A method of manufacturing a ceramic rolling bearing member, comprising: performing a grinding step. 2. A cylindrical roller manufacturing method for manufacturing a cylindrical roller for a rolling bearing by sintering a cylindrical molded body that has been pressure molded from a ceramic material powder, and at the time of pressure molding, a peripheral edge of an end surface of the molded body. A chamfered portion and a recessed portion in the center of the end face, and a skin polishing step of removing at least the chamfered portion and the sintered skin of the recessed portion of the sintered body by impact polishing of abrasive granules after sintering, And a grinding step of grinding the end face into a smooth surface while leaving the chamfered portion and the recessed portion.