JPH06100226B2 - Ceramic bearing device - Google Patents

Description

The present invention relates to a hydrodynamic bearing device configured to perform high speed rotation, high precision rotation, or linear motion.

[Conventional technology]

Conventionally, there are many types of static pressure gas bearing devices, for example, one member for guiding rotation or linear motion is made of a metal material such as steel, and the bearing as the other member for receiving this one member is The body is made of metal such as steel, small holes with a diameter of about 0.5 mm are arranged at regular intervals as gas ejection parts, shallow grooves are formed on the surface, or a porous body made by sintering metal powder is used. The one arranged was used.

[Problems of conventional technology]

If a spout of a sintered metal porous body is used in such a bearing structure, the load applied to the member (shaft) can be increased as compared with other bearings having small holes, grooves, etc.
Moreover, although the shaft is less displaced under load, that is, the rigidity is high, when a porous body made of sintered metal is used, a predetermined pore size distribution is formed during surface processing to improve the bearing device. The pore size distribution on the surface of the porous body and the layer close to the surface change, and the desired gas flow rate cannot be obtained. Grinding, lapping, etc. are used for the surface processing of the porous body that is a sintered metal, but under normal processing conditions, there is a problem that the porous body plastically deforms due to the working force during processing and closes the fine pores. It has occurred.

In order to solve the problem of blockage of fine holes, it is possible to set the acting force at the time of surface processing to a slight force so that the material does not plastically deform, and to process for a long time, but this does not consist in terms of production cost.

Further, chips during processing, abrasive grains falling off from the grindstone, and the like are pressed into the porous surface layer, closing the fine holes. In order to solve this problem, it is possible to eject and remove the clogged foreign matter by the above processing method or compressed air, but it is difficult to completely remove it.

In addition to this, while corroding the surface layer of the porous body with a chemical solution and removing the blocked portion by dissolving, the gas flow rate, that is,
Pore size adjustments are being made. However, this method is effective in adjusting the gas flow rate, but has another problem in view of the accuracy of the bearing used for this purpose. That is, it is extremely difficult to maintain the general accuracy of the outer diameter of the movable body such as the rotating shaft and the radial clearance between the inside of the bearing portion and the inside of the bearing portion being 5 to 50 μm, and to adjust the ventilation amount to a predetermined value. .

Moreover, the depth of the blocking layer with respect to the micropores generated during processing is not stable.

Furthermore, in shafts and bearings made of metal materials, seizure occurs when overloaded, and the centrifugal force at high-speed rotation increases,
In the case of linear motion, the inertial force at the time of direction change during reciprocating motion is large, and there is a problem in strength with respect to material specific gravity, and it is difficult to maintain the accuracy of the bearing due to heat generated by other motion. In addition to the above, there were many inconveniences such as it was difficult to keep the machining accuracy constant on the axis.

[Means for solving problems]

In view of the above, the present invention configures one member for guiding rotation or linear motion with a ceramic material having high specific strength and specific rigidity and a small thermal expansion coefficient, and the gas ejection portion of the bearing which is the other member is a porous ceramic material. Composed of.

〔Example〕

 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a rotary type bearing, 1 is a rotary shaft made of ceramics, and this rotary shaft 1 is provided with a flange 1a which is integrally or separately formed as required. The rotary shaft 1 is connected to a drive source or a rotating body via a circular groove 1b for discharging fluid at the center of the rotary shaft 1.
Is provided.

A ceramic material such as alumina silicon nitride or silicon carbide is suitable for the constituent material of the rotating shaft 1.

On the other hand, the bearing is made up of a cylindrical porous body 3 surrounded by a casing 2. As the material of the porous body 3, the same ceramic raw material powder as that of the rotary shaft 1 is used and fired into a porous state. . In this case, in order to eject the fluid from the bearing, the optimal pores, porosity, etc. of the porous body 3 are set. However, the load characteristics for the bearing are not uniquely determined only by the characteristics of the porous body 3.

Therefore, as the porous body 3, those having an average pore diameter of 0.5 to 500 μm and a porosity of 20 to 50% are preferable from the viewpoints of easiness of production, cost and the like, and according to experiments, the average pore diameter is 0.5 μm.
If it is less than m, the ejection pressure is too high and clogging easily occurs,
On the other hand, if it is larger than 500 μm, the amount of ventilation is too large, which is inconvenient.

Further, the casing 2 is made of a ceramic having a thermal expansion coefficient similar to that of the porous body 3, and is provided with a fluid supply port 4 and an introduction hole 5. The introduction hole 5 is formed on the outer periphery of the porous body 3. Through one annular groove 3a and distribution hole 3b, the other annular groove
The fluid is also guided to 3a, and the fluid that has passed through the inner pores of the porous body 4 is jetted toward the outer peripheral surface including the flange 1a of the rotary shaft 1 and the gap between the outer peripheral surface of the porous body 4, It acts so as to receive the radial and thrust loads of the rotary shaft 1.

Further, a part of the fluid ejected toward the outer peripheral surface of the rotating shaft 1 is collected in the annular groove 1b, and the fluid delivery port 6 opened in the casing 2 through the discharge hole 3c formed in the central portion of the porous body 3. The fluid supplied to the inner surface of the flange 1a is discharged from the radial grooves (not shown) formed at both ends of the porous body 3.

In this way, the fine particles are efficiently ejected from the pores of the porous body 3 toward the outer peripheral surface of the rotating shaft 1. Therefore, in order to prevent the fluid from being ejected from an unnecessary portion, an adhesive layer, a glass or the like is formed on the surface of the porous body 4. A coating layer H such as a coating layer, a ceramic coating layer, and a metal coating layer is formed in advance. In this case, it is possible to apply a pressure or to solidify by heating, if necessary, and the glass coating layer and the ceramic coating layer have a thermal expansion coefficient close to that of the porous body 3 made of ceramics, and moreover, moisture resistance, The coating layer H having heat resistance can be formed.

Next, for the precision machining of the fluid ejection surface 3e facing the rotating shaft 1, the same grinding method as general ceramics can be applied. However, in comparison with machining of metal materials, ceramic materials generally have a higher rigidity. Since the metal porous body does not undergo plastic deformation, warpage and burrs do not occur during processing, and the pore blocking phenomenon that occurs in a metal porous body during processing is unlikely to occur.

Further, since the falling abrasive grains and grinding chips during processing are minute and are hard to adhere to the ceramic material, even if the fine pores of the porous body 3 are temporarily closed, it is easy to use an ultrasonic cleaner or the like. Can be removed. Therefore, it is possible to secure a predetermined amount of fluid ejection while maintaining the surface dimension of the porous body 3 with high accuracy, and since machining distortion does not remain, highly accurate machining can be easily achieved.

Next, as another embodiment according to the present invention, a linear motion bearing
As shown in the figure, the guide rail 10 which is one member for guiding the linear movement is made of a ceramic material, while in the movable body, the casing 20 is made of a dense ceramic material and the porous body 30 is made of a porous ceramic material. However, the movable body composed of the casing 20 and the porous body 30 is connected to a ball screw (not shown) or the like so as to perform a linear motion by the rotation of the ball screw. The fluid sent from the supply port 50 is made to jet out to the surface of the guide rail 10 through the internal fine holes of the porous body 30, and is the same as that of the rotary type shown in FIG. This is a static pressure gas bearing device.

〔The invention's effect〕

As described above, one member that guides rotation and movement is made of dense ceramic material, and the bearing is made of porous ceramic material.Therefore, the thermal expansion coefficient of both members is small, and the gap It is possible to provide a highly accurate and highly durable bearing device in which the amount of change is small, the amount of change is high, and seizure does not easily occur during overload.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a rotary type bearing device as an embodiment of the present invention, and FIG. 2 is a vertical sectional view of a linear motion type bearing device as another embodiment of the present invention. 1: rotating shaft 2: casing 3: porous body, H: coating layer 10: guide rail

 ─────────────────────────────────────────────────── ───Continued from the front page (56) References Shown 60-43724 (JP, U) Shown 55-106728 (JP, U) Shown 50-144146 (JP, U) Shown 57- 1170 (JP, Y2)

Claims (1)

[Claims] 1. A bearing device comprising one member for guiding rotation or linear motion and the other member having a gas ejection hole provided so as to surround the one member, wherein the one member is made of a dense ceramic material. At the same time, at least the inner peripheral portion of the other member is formed of a cylindrical porous ceramic material, and the entire inner peripheral surface excluding the opening of the porous ceramic material through a discharge hole is used as a gas ejection portion, and this gas ejection portion is A ceramic bearing device characterized in that a coating layer of a glass coat layer or a ceramic coat layer is formed on the surface of the porous ceramic material excluding the gas introduction part.