JPH07115947B2 - Ceramic hydrodynamic bearing member 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 constitutes a hydrodynamic bearing.
That to a method for producing Re hydrodynamic bearing member and this <br/> ceramic such journals.

[0002]

2. Description of the Related Art For example, in a hydrodynamic bearing, a ceramic journal having a hydrodynamic groove formed on its surface is used. A ceramic member having such an uneven surface is generally carbonized. It is obtained by pressing a powder material of silicon or the like under pressure, firing it, and then forming irregularities such as concave grooves on the surface of this sintered body.

By the way, since a sintered body obtained by firing is extremely hard and brittle, and it is difficult to form a groove or the like by a normal cutting process, the surface of the sintered body has been conventionally used. The irregularities are formed by a special surface processing method such as a sandblast method, a chemical etching method, an electric discharge machining method, a laser machining method.

[0004]

However, the conventional ceramic member obtained by forming the unevenness on the surface of the sintered body by such a surface processing method has the following problems.
In reality, there is a problem in strength, and its use is greatly limited.

That is, with regard to ceramics after sintering, the mechanical strength and chemical properties of the crystal grains, which are the constituent elements, and the grain boundaries between the crystals are completely different. Therefore, the sintered body is sandblasted or chemically etched. When the surface treatment is performed by the method, the degree of progress of crushing by sandblasting or corrosion by chemical etching differs between the crystal grains and the grain boundaries, and it is generally extremely difficult to obtain a surface roughness of 2 μRa or less. Therefore, for example, in a hydrodynamic bearing that uses a ceramic member obtained by performing such surface processing as a rotary journal, since the surface roughness of the hydrodynamic groove is large, the hydrodynamic bearing has a high rotational speed of more than 10 ⁴ rpm. In this case, the resistance due to the viscosity of air increases, the power loss and the amount of heat generation increase, and the undesirable phenomenon that the clearance between the journal and the bearing portion fluctuates due to thermal expansion easily occurs.

Further, in the case where the ceramic member is a sintered body subjected to surface processing such as electric discharge machining or laser machining, the machining accuracy of irregularities (particularly the machining accuracy of corners such as dynamic pressure generating grooves). ) Is low, and it is difficult to use in applications requiring a precise uneven surface as designed.

Further, in a ceramic member which has been surface-processed by a sandblasting method, a laser processing method or the like, a work-affected layer remains on the uneven surface, so that the proof stress against thermal shock is lowered and cracks or the like may occur. There is

Further, each of the above-mentioned surface processing methods requires complicated steps, and since it is probably a method for producing one product, it is easy and economical to manufacture a ceramic member having an uneven surface. Can not be done. Moreover, since the ceramic material that can be processed and the surface shape that can be formed are limited, the application of the obtained ceramic member is significantly limited. As described above, in the conventional case, a highly accurate dynamic pressure generating groove is used.
To obtain a ceramic hydrodynamic bearing member having
It was extremely difficult.

The present invention has been made in view of the above points, and is made of a ceramic having a highly accurate dynamic pressure generating groove having a small surface roughness and excellent thermal shock resistance and a small manufacturing error .
It is an object of the present invention to provide a hydrodynamic bearing member and a method of manufacturing the hydrodynamic bearing member easily and economically.

[0010]

The ceramic hydrodynamic bearing member of the present invention which has solved this problem is obtained by firing a ceramic molded body, and in particular, the ceramic molded body is a powdered ceramic material. The outer peripheral surface, which is the circumferential surface of the ceramic plastic body formed by pressure molding into a cylindrical or cylindrical shape,
Is a concave groove due to plastic deformation on the inner peripheral surface and does not become a dynamic pressure generating groove.
It is characterized in that a concave groove is formed. The ceramic member as the hydrodynamic bearing member includes not only a ceramic member in a narrow sense but also a sintered metal member obtained by molding and firing metal powder. Further, as the ceramic material, it is preferable to use carbide ceramics such as SiC, WC, TiC and B ₄ C. Also this
The method of the present invention for producing a hydrodynamic bearing member comprises the step of compacting a powdered ceramic material into a cylindrical or cylindrical cell.
After obtaining the lamic plastic body, the radial direction of this ceramic plastic body
While pressing the mold against the outer peripheral surface or the inner peripheral surface in the radial direction,
Relative rolling on the lamic plastic body creates a dynamic pressure generation groove.
After forming the concave groove,
This is to fire the plastic material. In addition to the final sintering treatment, the firing includes heat treatment and the like performed to remove molding aids such as a binder, a plasticizer, and a dispersant added at the time of molding the powder ceramic material.

[0011]

[Action] powder ceramic material a ceramic plastic body obtained by pressure-molding, since those having a plasticity some degree, the Ru <br/> are relatively rolls while pressing the formed shape type on the surface thereof is accurately formed uneven shape of the mold as the plastic deformation, so that the concave grooves <br/> surface roughness which substantially coincides with the surface roughness of the mold is formed.

Therefore, in this way, the concave due to plastic deformation is
By firing the ceramic formed body in which the grooves are formed, it is possible to obtain a ceramic member having concave grooves according to the processing accuracy and surface roughness of the forming die. Thus, it is easy to manufacture a molding die (for example, a die) with high precision and extremely small surface roughness. Therefore, by using such a molding die, an accurate shape as designed can be obtained. Available and extremely dense surface roughness (for example, 0.5 μRa or less)
Made of ceramic with dynamic pressure generating grooves on the outer or inner surface
The hydrodynamic bearing member can be obtained. Moreover, in the case of obtaining such a hydrodynamic bearing member, it no as as limitations mentioned in the introduction ceramic material or concave groove shape.

Further, the ceramic member, since the plastic working by sintering stage before is obtained by forming a concave groove,
Internal stress generated by forming a concave groove is relaxed in the firing step, in which hardly occurs even destroyed by various external forces such as cracks.

[0014]

EXAMPLES The following specifically described the present invention based on the embodiment shown in FIGS. 1 to 3 or Figure 4.

The first embodiment is one in which the present invention is applied to the case of manufacturing the journal 1 of the hydrodynamic bearing shown in FIG. In this hydrodynamic bearing, a hydrodynamic groove 1a formed on the outer peripheral surface of the journal 1 generates a hydrodynamic pressure between the opposing surfaces of the journal 1 and the radial bearing cylinder 2, so that both 1 and 2 can be operated at high speed and smoothly. It is configured to be capable of relative rotation.

That is, in the first embodiment, first,
A powder material (including an appropriate molding aid) such as silicon carbide or tungsten carbide is pressure-molded to obtain a solid axial ceramic plastic body 1 ′ corresponding to the shape of the journal 1.

Next, as shown in FIGS. 1 and 2, a molding die having a rotating body shape in which a ridge 3a having a shape corresponding to the dynamic pressure generating groove 1a is formed on the molding surface on the outer peripheral surface of the ceramic plastic body 1 '. Three
And the molding die 3 is relatively rolled while being pressed against the outer peripheral surface of the ceramic plastic body 1 '. As the mold 3,
Generally, a mold that has high processing accuracy and can reduce surface roughness is used.

Along with the relative rolling of the molding die 3, a concave groove 1'a is formed by the ridge 3a on the outer peripheral surface of the ceramic plastic body 1 '. The formation of the recessed groove 1'a is easily performed because the ceramic plastic body 1'is unfired and has a certain degree of plasticity.

When the molding die 3 makes one revolution, a concave groove 1'a corresponding to the dynamic pressure generating groove 1a is formed on the entire surface of the ceramic plastic body 1'in the circumferential direction, and a ceramic molded body to be fired is obtained. To be

Then, the ceramic compact is fired. That is, the low temperature firing for the removal treatment of the forming aid and the main firing at the sintering temperature are performed.

Thus, the journal 1 as a ceramic member having the dynamic pressure groove 1a formed on the outer peripheral surface as shown in FIG. 3 can be easily obtained.

By the way, in the hydrodynamic bearing shown in FIG. 3, the hydrodynamic groove 1a is not formed on the journal 1 side, but the hydrodynamic groove is formed on the inner peripheral surface of the radial bearing cylinder 2. Although it may be placed, according to the present invention, the cylindrical ceramic member having a concave groove on the inner peripheral surface in this manner can also be easily produced in the same manner as in the above embodiment.

That is, the second embodiment relates to an example of manufacturing such a radial bearing cylinder 2, in which a powder material is pressure-molded into a cylindrical shape corresponding to the radial bearing cylinder 2 to obtain a ceramic plastic body 2 '. As shown in FIG. 4, on the inner peripheral surface, the ridges 4a are relatively rolled while pressing the rotary mold die 4 having the ridges 4a having a shape corresponding to the dynamic pressure generating grooves. The concave groove 2'a corresponding to is formed over the entire surface, and thereafter, this is fired.

[0024]

[0025]

In each of the above-mentioned embodiments, the constituent members 1, 2, of the hydrodynamic bearing having the concave grooves 1a, 6a having a shallow groove depth.
In the present invention, since the irregularities on the surface of the ceramic member are plastically processed before firing, the shape of the molding die and the pressing form on the ceramic plastic body are changed. By doing so, it is possible to easily obtain a ceramic member having a surface shape and surface roughness according to the application. Of course, in the present invention, when forming the uneven surface, the surface shape such as the ceramic material, the groove depth, and the groove width is not particularly limited.
If the thickness is set to 200 μm (more preferably 50 μm or less), the effect of the present invention will be maximized.

[0027]

As is apparent from the above description, according to the present invention, a ceramic having excellent dynamic shock resistance and the like, which is exactly as designed, and which has an extremely precise dynamic pressure generating groove with surface roughness.
It is possible to provide a hydrodynamic bearing member made of metal . Further, it is so arranged to form a concave groove at a stage before firing with plastic, regardless of the material the material of the hydrodynamic with dynamic pressure generating grooves of the precision
The body bearing member can be easily manufactured, and the manufacturing cost can be significantly reduced by mass production. Moreover,
Mold shape, concave groove shape of machining accuracy, surface roughness of a member surface (groove depth, groove width, etc.), processing accuracy, Ru can freely change the surface roughness.

[Brief description of drawings]

Is a plan view showing the step of forming the concave groove in the first embodiment of the method according to the invention; FIG.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a sectional view of a hydrodynamic bearing using a ceramic member obtained by the same method.

4 is a perspective view showing a step of forming the concave groove in the method of the second embodiment.

[Explanation of symbols]

1 ... Journal ( dynamic pressure bearing member made of ceramic),
1a ... Dynamic pressure generating groove , 1 ', 2 ' ... Ceramic plastic body, 1
′ A, 2 ′ a ... concave groove ( concave groove that becomes a dynamic pressure generation groove ), 2 ... radial bearing tube (ceramic dynamic pressure fluid bearing member),
3, 4 ... Mold.

Claims (2)

[Claims] 1. A hydrodynamic bearing member made of ceramic by firing a ceramic molded body, wherein the ceramic molded body is formed by pressing a powdered ceramic material such as silicon carbide or tungsten carbide into a cylindrical or cylindrical shape. A ceramic groove formed by plastic deformation on the outer peripheral surface or the inner peripheral surface of the ceramic plastic body formed as described above, which is a dynamic pressure generating groove . Dynamic pressure fluid shaft
Receiving member. 2. A powdery ceramic material such as silicon carbide or tungsten carbide is molded into a cylindrical or cylindrical shape by pressure molding .
After obtaining the ceramic plastic body, the circle of this ceramic plastic body
While pressing the molding die against the outer peripheral surface or the inner peripheral surface, which is the peripheral surface
Relative rolling on the circumferential surface to form a dynamic pressure generation groove
After forming the groove, the ceramic in which the groove is formed
Ceramics characterized by firing a plastic body
For manufacturing a hydrodynamic bearing member manufactured by K.K.