JP3082314B2 - Ceramics with good lubricity, ceramic mechanism members, and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic member having good lubricity used for a mechanical member of a friction portion such as a bearing or a sliding member requiring high speed rotation, a ceramic member using the same, and a method of manufacturing the same. .

[0002]

2. Description of the Related Art In recent machine tools, there is an increasing demand for improvement of machining efficiency and machining accuracy by high-speed rotation. To cope with this, the bearings such as angular contact ball bearings and sliding members have been reduced in weight by using silicon nitride and other ceramics to improve the load conditions on the bearings, thereby enabling high-speed rotation. Ceramics themselves are used in various fields as self-lubricating materials because they have good heat resistance and good seizure resistance compared to conventional materials. Is becoming a difficult situation. It is considered that the cause is that the contact surface is out of oil. Japanese Patent Application Laid-Open No. 61-28107 discloses the use of self-lubricating ceramics using silicon nitride for mechanical parts such as shafts and sliding films.
No. 3 discloses this. This ceramic is subjected to pulverization and mixing treatment of silicon nitride to which aluminum oxide and yttrium oxide have been added, and is then isostatically pressed to have interconnected voids to form a preformed porous article. Then, the preformed porous article is sintered to form a sintered porous article,
The gap is filled with a lubricant such as light mechanical oil or molybdenum disulfide to form a self-lubricating substance. In this self-lubricating substance using ceramics, the diameter of interconnected voids changes based on the particle size of silicon nitride particles and the molding pressure, so that controlled voids are formed only on the surface of the sintered porous article. It was difficult to do.

[0003]

SUMMARY OF THE INVENTION The present invention eliminates the above-mentioned drawbacks of the conventional ceramics and provides a ceramic having pores controlled only in the vicinity of the surface. The disadvantage of the mechanism member using a porous material is eliminated, the diameter of a number of pores provided near the surface of the sintered body constituting the mechanism member is controlled, the surface is made porous, and a lubricant is impregnated therein. By doing so, the occurrence of oil shortage in the sliding portion is prevented, and an object of the present invention is to provide a ceramic member having good lubricating properties corresponding to high-speed rotation of a machine tool or the like. Further, the present invention provides a method for producing a ceramic member having such a structure.

[0004]

A porous layer having controlled pores is provided near the surface of a nucleus portion of dense silicon nitride of ceramics. The core portion of the mechanism member is composed of a silicon nitride granulated powder having a controlled particle size, and a layer of a mixed powder of silicon nitride and boron nitride having a controlled particle size is applied around the core portion to form a CIP. By molding and sintering and processing the molded body, a ceramic member having a porous layer having controlled pores on its surface is created, and then the pores are impregnated with a lubricant to thereby improve lubricity. A good ceramic mechanism member is obtained.

[0005]

[Function] By providing pores whose diameter and porosity are artificially controlled only on the ceramic surface, mechanical strength can be maintained and porous ceramics can be provided on the surface. Impregnation with a lubricant can prevent running out of oil in the sliding portion.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below. The ceramics of the present invention comprises a core portion made of dense silicon nitride (Si ₃ N ₄ ) and a mixed powder (Si ₃ ) of silicon nitride and boron nitride (BN) having controlled pores covering the surface of the core portion. N ₄ -B
N) is a porous layer obtained by sintering. The starting materials of the ceramic of the present invention is a silicon nitride (Si ₃ N _4). After pulverizing the silicon nitride raw material, if necessary, a binder is mixed and the mixture is granulated to a desired particle size by a granulator. On the other hand, a mixed powder in which boron nitride powder is added at a ratio of 0.5 to 5 wt% to silicon nitride granulated powder is prepared and granulated to an appropriate particle size. A granule made of a mixed powder of silicon nitride and boron nitride is placed around a granule made of silicon nitride alone, and is pressed, baked, and then decomposed to remove boron nitride. A ceramic having a porous layer with controlled pores is manufactured. The principle of pore generation can be explained as follows. Since the sintering temperature of boron nitride is much higher than that of silicon nitride, sintering of silicon nitride particles proceeds during sintering, but sintering of the portion where boron nitride exists does not progress and each particle is not bonded to each other. Decomposition of this remaining, non-interconnected boron nitride by heating in the presence of water vapor or acid produces a continuous, constant depth pore. Since the pore diameter varies depending on the diameter of the silicon nitride granulated powder, the particle diameter of boron nitride, and the mixing ratio of the mixed powder, the diameter of the pores is controlled by controlling the particle diameter and the mixing ratio of each granulated powder. Can control.

Hereinafter, as Example 1, the production of an angular ball bearing 1 having a dense silicon nitride core portion 2 shown in FIG. 1 and having a porous layer 3 on the surface thereof will be described with reference to FIG.
First, a silicon nitride raw material is pulverized by a pulverizer, and then, if necessary, a binder is mixed and granulated to obtain a plain granulated powder. The particle diameter of the granulated powder is determined in consideration of the strength of the core required for the ceramic mechanism member 1 and the molding pressure.
This single-part silicon nitride granulated powder is formed into a spherical shape by an arbitrary molding method such as a pressure molding method, and a single-part portion 21 is obtained. On the other hand,
After mixing the powder of boron nitride with the powder of silicon nitride, the mixture is granulated to prepare a material for the porous layer. Simple part 21 molded earlier
A mixed powder 31 of silicon nitride and boron nitride is added as a nucleus and charged into the rubber mold 4. Then this rubber mold 4
Is placed in a cylinder 5 of a press machine filled with water or oil, and uniformly press-formed by a CIP method (rubber press method) in which pressure is applied by a piston 6 to obtain a preform. The preform is loaded into a normal firing furnace and fired. The fired silicon nitride spheres are finish-processed, and the boron nitride remaining on the surface portion is decomposed and removed by an ordinary method to form a porous layer 3 having controlled pores on the surface of the silicon nitride core portion 2. . After that, the pores are filled with a lubricant such as light mechanical oil or molybdenum disulfide under reduced pressure to produce an angular ball bearing 1 made of silicon nitride spheres having a porous layer with controlled pores on the surface. The decomposition and removal of silicon nitride can be performed continuously by heating in the presence of water vapor or acid in the latter half of the firing step, or can be performed after the completion of firing and before finishing. .

Next, as an example 2, a sliding member 8 for a shaft used in a high-temperature environment in which a porous layer 3 is provided on the surface of a core portion 2 made of dense silicon nitride as shown in FIG. This will be described with reference to FIG. A cylindrical partition plate 7 having a desired diameter is positioned inside a rubber press die 4 having a bottomed cylindrical shape. An annular space formed between the partition plate and the press die is filled with a mixed powder 31 of silicon nitride and boron nitride adjusted to a predetermined ratio and particle size by appropriately pressing the powder. In the internal space, a simple granulated powder of silicon nitride having a desired particle size 2
1 is filled by appropriately pressing. Then, after the partition plate 7 is removed and the upper part of the rubber mold is covered, it is loaded into a cylinder 5 of a press machine filled with water or oil, and pressure is applied by a piston 6 to perform CIP molding to obtain a preform. The preform is fired to form a porous layer 3 having controlled pores on the surface of the silicon nitride core 2. Thereafter, boron nitride is decomposed and removed, followed by grinding, to obtain a compact having a porous layer 3 having controlled pores on its surface and having a core portion 2 of dense silicon nitride. A lubricant such as molybdenum disulfide is filled under reduced pressure to obtain a lubricating ceramic shaft slide 8 having a porous layer having controlled pores on the surface. FIG. 6 is an enlarged view of the porous layer on the surface of the angular ball bearing 1 in FIG. According to this figure, the granular material 9 whose periphery is white is silicon nitride particles, and the respective particles are mutually bonded by sintering and have strength and friction resistance as a mechanical member,
The black portion 10 is a portion where the boron nitride located between the silicon nitride particles is decomposed and removed by heating to form interconnected pores, so that the effect of the present invention can be understood. FIG.
FIG. 2 is a sectional view near the surface of the angular ball bearing 1 in FIG. According to this figure, a porous layer 3 is formed on the surface of a core portion 2 made of dense silicon nitride, and the porous layer has silicon nitride particles 9 bonded to each other, and the porous layer 3 is located between the silicon nitride particles 9. It can be understood that pores generated by decomposing and removing boron by heating are connected to reach the surface.

[0009]

By controlling the mixing ratio and the particle size of the mixed powder of silicon nitride and boron nitride disposed on the surface of the core portion, the pore diameter and porosity of the porous layer can be freely controlled. At the same time, by arranging the layer of the mixed powder at an arbitrary position and an arbitrary thickness on the core, it is possible to easily and accurately form a porous layer having pores of controlled size and depth at any place on the ceramic surface. Can be formed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a ceramic angular contact ball bearing according to the present invention.

FIG. 2 is a conceptual diagram showing a method of manufacturing the ceramic angular contact ball bearing according to the present invention shown in FIG.

FIG. 3 is a sectional view of a ceramic shaft sliding member according to the present invention.

FIG. 4 is a cross-sectional view showing a process of manufacturing the ceramic shaft sliding member according to the present invention shown in FIG. 3;

FIG. 5 is a conceptual diagram showing a method of manufacturing the ceramic shaft sliding member according to the present invention shown in FIG. 3;

FIG. 6 is an enlarged view showing the state of the surface of the angular ball bearing obtained by the present invention shown in FIG. 1;

FIG. 7 is an enlarged sectional view showing a state of a section near the surface of the angular ball bearing obtained by the present invention shown in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Angular bearing 2 Dense core part made of silicon nitride 3 Porous layer 4 Rubber type 5 Press cylinder 6 Press piston 7 Partition plate 8 Shaft sliding body 9 Silicon nitride particles 10 Pores 21 Silicon nitride granules 31 Mixed powder

Continuation of front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B28B 3/00 102 C04B 41/87 F16C 33/62

Claims (13)

(57) [Claims] 1. A dense core portion obtained by sintering granulated silicon nitride powder, and a controlled diameter and control obtained by sintering a mixture of silicon nitride and boron nitride on the surface of the core. And a porous layer having pores of a given depth. 2. A dense core portion obtained by sintering silicon nitride granulated powder, and a controlled diameter and control obtained by sintering a mixture of silicon nitride and boron nitride on the surface of the core. Ceramic member comprising a porous layer having pores of a given depth, and a lubricant filled in the pores. 3. The ceramic mechanism member according to claim 2, wherein the ceramic mechanism member is an angular ball bearing. 4. The ceramic mechanism member according to claim 2, wherein the ceramic mechanism member is a shaft sliding member. 5. The mixture of silicon nitride and boron nitride has a concentration of 0.1%.
The ceramic mechanism member according to claim 2, wherein the ceramic mechanism member contains 5 to 5 wt% of boron nitride. 6. The ceramic mechanism member according to claim 2, wherein the lubricant is light mechanical oil or molybdenum disulfide. 7. A core comprising dense silicon nitride, a porous layer having pores of controlled diameter and depth disposed on the surface of the core, and a lubricant held by the porous layer. A method of manufacturing a ceramic mechanism member, wherein a granulated powder of silicon nitride having a controlled particle size is arranged in a central portion, and a mixed powder of silicon nitride and boron nitride having a controlled particle size is arranged on a surface portion thereof and pressure-formed. And a step of firing this molded body, a step of forming a porous layer having controlled pores by decomposing and removing unsintered boron nitride, and a step of filling the pores with a lubricant. A method for manufacturing a ceramic mechanism member. 8. The method according to claim 7, wherein the pressure forming step is a CIP method. 9. The method for manufacturing a ceramic mechanism member according to claim 7, wherein the ceramic mechanism member is an angular ball bearing. 10. The method for manufacturing a ceramic mechanism member according to claim 7, wherein the ceramic mechanism member is a shaft sliding member. 11. The mixture of silicon nitride and boron nitride comprises:
8. The method for manufacturing a ceramic mechanism member according to claim 7, comprising 0.5 to 5% by weight of boron nitride. 12. The method according to claim 7, wherein the lubricant is light mechanical oil or molybdenum disulfide. 13. The method according to claim 7, wherein the filling of the lubricant is performed under reduced pressure.