JPH0729850B2 - Ceramic member of hydrodynamic bearing having a plurality of adjacent concave grooves on the surface 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 component part of a hydrodynamic bearing.
Materials, especially ceramics with a large number of closely spaced grooves on the surface
TECHNICAL FIELD The present invention relates to a ceramic member such as a journal made of quartz and a method for manufacturing the same.

[0002]

2. Description of the Related Art For example, in a hydrodynamic bearing, a ceramic journal having a large number of hydrodynamic grooves closely arranged in parallel is used. Generally, a ceramic member is obtained by press-molding a powder material such as silicon carbide and firing it, and then forming concave grooves on the surface of this sintered body.

By the way, a sintered body obtained by firing is extremely hard and brittle, and it is difficult to form a concave groove by a normal cutting process. Therefore, conventionally, the surface of the sintered body is sandblasted. The concave groove is formed by a special surface processing method such as a method, a chemical etching method, an electric discharge machining method, a laser machining method.

[0004]

However, the conventional ceramic member obtained by forming the concave groove on the surface of the sintered body by such a surface processing method has the following problems.
There is a problem in strength, so as a component of the hydrodynamic bearing.
The reality is that all uses are significantly limited.

That is, since the mechanical strength and chemical properties of the ceramics after sintering are completely different between the constituent crystal grains and the grain boundaries between the crystals, 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, when the ceramic member is a sintered body subjected to surface processing by electric discharge machining, laser processing, etc., machining accuracy of concave grooves (particularly machining of corners such as dynamic pressure generating grooves). Accuracy) is low, and it is difficult to use it as a component of a hydrodynamic bearing that requires precise groove formation as designed.

Further, in a ceramic member whose surface is processed by a sandblast method, a laser processing method, etc., a work-affected layer remains on the groove forming surface, so that the resistance to thermal shock is lowered and cracks are generated. May occur.

Further, all of the above-mentioned surface processing methods require complicated steps, and since they are probably one-piece production methods, it is easy and economical to manufacture ceramic members having concave grooves. Can not be done. Moreover, because there is a limit to the ceramic material that can be processed and the surface shape that can be formed,
The applications of the resulting ceramic component are severely limited.

[0009] The present invention has been made in view of the above, as well as providing a hydrodynamic ceramic member bearing a small Idi journals such fabrication error surface roughness and excellent small and thermal shock resistance, etc. , Such hydrodynamic bearing components
It is an object of the present invention to provide a method capable of suitably manufacturing a ceramic member as a material .

[0010]

Means for Solving the Problems] hydrodynamic bearing of <br/> ceramic member having a plurality of grooves on the surface proximate the present invention that solves this problem, silicon carbide, ceramic powder such as tungsten carbide Carbide obtained by pressure-molding a material <br /> On the surface of the ceramic plastic body, a molding die having one or more molding convex portions is repeatedly pressed while changing the pressing position on the plastic body surface, while allowing at least adjacent the groove is not formed at the same time, on which is formed a plurality of grooves adjacent a shall such by firing handle this. The ceramic member generally includes a ceramic member in a narrow sense and a sintered metal member obtained by molding and firing metal powder. However, in the present invention, the ceramic member is a dynamic pressure member.
That it is used as a component of fluid bearings
Taking into account, as a ceramic material, SiC, WC, Ti
C, and using a carbide ceramic B ₄ C and the like. In addition to the final sintering treatment, the firing treatment includes heat treatment and the like performed to remove the forming aids such as the binder, the plasticizer, and the dispersant added at the time of forming the powder ceramic material.

[0011]

[Function] Charcoal obtained by press-molding powder ceramic material
Since the ceramic ceramic plastic has a certain degree of plasticity, if a molding die is pressed against the surface and the molding convex part bites into the ceramic plastic body, the concave groove shape as the molding convex part is caused by plastic deformation. Is accurately formed, and a concave groove having a surface roughness substantially matching the surface roughness of the molding die is formed.

The step of forming the groove by biting the molding convex portion is repeated a plurality of times while changing the pressing position of the molding convex portion to the surface of the plastic body. Is designed so that at least adjacent grooves are not formed at the same time. That is, when the molding die has only one molding convex portion, naturally, in each concave groove forming step, adjacent concave grooves are not simultaneously formed, but the molding die has a plurality of molding convex portions. When a plurality of concave grooves are simultaneously formed by two or more molding convex portions in each concave groove forming step, for example, the pitch P of these molding convex portions may be a desired concave portion. The groove pitch is set to an integral multiple of the pitch p so that adjacent concave grooves at intervals of p are not formed at one time.

By the way, when the forming convex portion is made to bite into the surface of the ceramic plastic body, a material flow occurs at the biting portion, but when P = p, adjacent concave grooves are simultaneously formed in one concave groove forming step. When p is formed, since p is extremely small, the flow of the material due to the formation of the one concave groove and the flow of the material due to the formation of the other concave groove mutually interfere, and a smooth flow of the material is obtained. Hard to happen. For this reason, even though the ceramic plastic body is soft before firing, the bite resistance (deformation resistance of the plastic body) of the molding convex portion to the ceramic plastic body becomes large, and the bite is not sufficiently performed, The bite amount may become shallow, and the desired groove may not be obtained, and the plastic working accuracy may be reduced. If the pressing force of the forming die against the ceramic plastic body is increased more than necessary in order to obtain a sufficient bite, the ceramic plastic body may be deformed or broken, and the processing accuracy may be lowered.

However, as described above, the pitch P of the molding convex portions is
Is set to be larger than the pitch p of the concave groove, and even if the molding convex portion bites into the ceramic plastic body at a plurality of locations at the same time, the distance between the one biting portion and the biting portion adjacent thereto is sufficiently large. By so doing, the above-described material flow interference does not occur, and even if the pressing force of the forming die against the ceramic plastic body is not so large, the formation of the forming convex portion is sufficiently carried out by the forming convex portion. It is possible to form a highly accurate groove corresponding to the shape.

Therefore, by firing the ceramic molded body in which the grooves are formed by plastic deformation as described above, the ceramics in which the grooves corresponding to the processing accuracy and the surface roughness of the forming die are closely arranged at the predetermined pitch p. The member can be obtained. 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. Thus, it is possible to obtain a ceramic member having unevenness with a very dense surface roughness (for example, 0.5 μRa or less) on the surface. Moreover, in the case of obtaining such a ceramic member, the ceramic material and the shape of the concave groove are not limited as described at the beginning.

Further, since the above-mentioned ceramic member has concave grooves formed by plastic working in a stage before sintering,
At the same time that at least adjacent concave grooves are not formed at the same time to avoid interference of material flow, internal stress generated by forming concave grooves is relieved during the firing process, and various external forces such as cracks are generated. Destruction due to is also unlikely to occur.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on the embodiments shown in FIGS.

In this embodiment, the present invention is applied to the case of manufacturing the journal 1 of the hydrodynamic bearing shown in FIG. This hydrodynamic bearing has a plurality of concave grooves, which are adjacent to the outer peripheral surface of the journal 1 and are arranged in parallel. The hydrodynamic bearing 1a ... Is formed by the action of the hydrodynamic grooves 1a.
The dynamic pressure is generated between the opposing surfaces of the radial bearing tube 2 and the radial bearing tube 2 so that the both 1 and 2 can relatively rotate at high speed and smoothly.

First, a powder material (including an appropriate molding aid) such as silicon carbide or tungsten carbide is pressure-molded to form a solid shaft-shaped carbide ceramic plastic body corresponding to the shape of the journal 1. Get 1 '.

Next, as shown in FIGS. 1 and 2, both ends of the ceramic plastic body 1'are rotatably held by appropriate rotating jigs (not shown), and these jigs are formed into a long rectangular shape. By moving along the plate-shaped molding die 3, the ceramic plastic body 1 ′ is appropriately pressed against the molding surface 3 b, which is the upper surface of the molding die 3, while rolling on the molding surface 3 b. As the molding die 3, generally, a die that has high processing accuracy and can reduce surface roughness is used. The molding surface 3b is provided with a plurality of molding projections 3a ... Which are juxtaposed in parallel with each other in the rolling direction of the ceramic plastic body 1 '. Molded convex portion 3a
The shape and the number of are set corresponding to the dynamic pressure generating groove 1a to be formed. Thus, the pitch P of the forming protrusions 3a ... Is such that even if the plurality of forming protrusions 3a are bited at the same time, the material flow at each biting point is the material at the biting point adjacent thereto. It is set large enough so that it does not interfere with the flow. Specifically, the pitch P is an integral multiple (P = mp (m> 1)) of the pitch p of the dynamic pressure generating grooves 1a. By the way, the ceramic plastic body 1 ′ has the first molding convex portion 3 a.
When the first dynamic pressure generating groove 1a is formed by
It is necessary to rotate once or more from (A)) until all the dynamic pressure generating grooves 1a are formed.
Are arranged in parallel with each other at an equal pitch p and are arranged in parallel. Therefore, depending on the relationship between the number M of the dynamic pressure generating grooves 1a ... There may be a case where a new molding convex portion 3a bites into the formed dynamic pressure generating groove 1a again. When such a situation occurs, every time the ceramic plastic body 1 ′ makes one revolution, the newly formed dynamic pressure generating groove 1a is located at a position displaced from the previously formed dynamic pressure generating groove 1a. As it is formed, the position of the molding convex portion 3a for forming the new dynamic pressure generating groove 1a is shifted by a predetermined pitch. That is, some of the adjacent molding protrusions 3a, 3a
The pitch P ′ between them is set larger than mp. For example, when M is not divisible by m, in principle, the pitches P of the molding convex portions 3a ... Are all the same (P = mp), but when M is divisible by m, the "M / m" th and "M / m" th m + 1 "th," 2 (M / m) "th and" 2 (M
/ M) +1 "th," 3 (M / m) "th and" 3 (M / M)
m) +1 "th ............" (m-1) (M / m) "th and" (m-1) (M / m) +1 "th adjacent pitches P of the molding protrusions 3a, 3a. Let ′ be P + p = (m + 1) p. In this embodiment, as shown in FIGS.
M = 30, P = mp = 2p, and the fifteenth molding convex portion 3
The pitch P'between a and the 16th molding convex portion 3a is 3p.

When the ceramic plastic body 1'rolls, the first forming convex portion 3a bites into the surface of the plastic body to form the V-shaped dynamic pressure generating groove 1a (Fig. 1 (A)). After that, as the ceramic plastic body 1 ′ rolls, the dynamic pressure generating groove 1 is sequentially formed on the surface thereof in the rolling direction.
a ... are sequentially formed at a pitch of 2p (FIG. 1 (B))
reference). Then, after the ceramic plastic body 1'has rotated once, a new dynamic pressure generating groove 1a is sequentially formed between the adjacent dynamic pressure generating grooves 1a, 1a already formed (see FIG. 1).
(C) and FIG. 2) All the dynamic pressure generating grooves 1a ... Are formed at a desired pitch p by two rotations.

At this time, for example, as shown in FIG.
Even if biting by a plurality of molding convex portions 3a is performed at the same time, the interval P (= 2 between the biting points).
Since p) and P '(= 3p) are larger than the pitch p of the dynamic pressure generating grooves 1a, the material flow at each bite point does not interfere with the material flow at the bite point adjacent thereto. Therefore, the ceramic plastic body 1 '
In consideration of the fact that the ceramic plastic body 1'has a certain degree of plasticity before firing even if the pressing force on the molding surface 3b is not increased more than necessary, each molding convex portion 3a The biting into the plastic body 1'is performed smoothly and sufficiently, and the dynamic pressure generating groove 1a with high accuracy is formed while avoiding the deformation of the ceramic plastic body 1 '.

After all the dynamic pressure generating grooves 1a ... Are formed in the ceramic plastic body 1'in this manner, they are fired (low temperature firing and sintering temperature for removing the forming aid, etc.). Main firing), a journal 1 which is a ceramic member having dynamic pressure generating grooves 1a ... Which are arranged in parallel near the outer peripheral surface as shown in FIG. 3 is obtained.

The present invention is not limited to the above-mentioned embodiments, but can be appropriately improved and changed without departing from the basic principle of the present invention.

For example, as shown in FIG. 4, the dynamic pressure generating grooves 1a ... Can be formed by a molding die 3 having one molding convex portion 3a. Mold 3
As shown in FIG. 4 and FIG. 5, the arc-shaped molding surface 3b that can be abutted on the outer peripheral surface of the ceramic plastic body 1'is provided with a single protruding convex portion 3a having a V-shape. And
The ceramic plastic body 1'is intermittently moved in and out of contact with the ceramic plastic body 1 '. The ceramic plastic body 1'has a hollow shaft shape, is fitted and held by the core shaft 4, and is intermittently rotated at an angle corresponding to the pitch p of the dynamic pressure generating grooves 1a. ing.

That is, in this embodiment, after the forming die 3 is pressed against the ceramic plastic body 1'and the dynamic pressure generating groove 1a is formed by the forming convex portion 3a (see FIG. 4A), the forming die is once provided. 3 is separated from the ceramic plastic body 1 ′, the ceramic plastic body 1 ′ is rotated by an angle corresponding to the pitch p (see FIG. 2B), and the molding die 3 a is pressed against the ceramic plastic body 1 ′ again. By forming the dynamic pressure generating groove 1a adjacent to the previously formed dynamic pressure generating groove 1a ((C) of the same figure) and repeating this process, the ceramic plastic body 1'is arranged close to and in parallel with the outer peripheral surface thereof. The dynamic pressure generating grooves 1a are formed.

By thus forming one dynamic pressure generating groove 1a ..., the problem of material flow interference due to simultaneous intrusion of a plurality of molding convex portions does not occur, and
The dynamic pressure generating grooves 1a ... Can be formed smoothly and with high accuracy.
Of course, even when using the molding die 3 having a plurality of molding projections 3a ... As in the above embodiment, the value of m should be set appropriately in consideration of the diameter dimension of the ceramic plastic body 1 '. As a result, it is possible to always allow only one molding convex portion 3a to bite into the ceramic plastic body 1 '.

In a hydrodynamic bearing, a thrust bearing plate facing a lower end surface of a journal may be formed with a spiral hydrodynamic groove to receive a thrust load of the journal. A ceramic member, such as a thrust bearing plate or a seal ring in a dynamic pressure type mechanical seal, in which a plurality of concave grooves are formed close to each other on a non-rotating surface is also formed by the same method as shown in FIG. Grooves can be formed. For example, in manufacturing the thrust bearing plate 1 as shown in FIG. 7, as shown in FIG. 6, a ceramic plastic body 1 ′ formed in a disk shape corresponding to the thrust bearing plate 1 is made to correspond to the pitch p of the dynamic pressure generating grooves 1 a. The angle of rotation is intermittently rotated, and the dynamic pressure generating groove 1a is generated each time the rotation is performed.
The molding die 3 having the one molding convex portion 3a having a shape corresponding to is pressed.

In each of the above embodiments, the case where the ceramic member having the recessed groove 1a having a relatively shallow depth is manufactured has been described, but in the present invention, the recessed groove on the surface of the ceramic member is plastically worked before firing. Because I try to
By changing the molding surface shape of the molding die and the pressing form on the ceramic plastic body, it is necessary to use a ceramic member with a surface shape and surface roughness according to the application, that is, a hydrodynamic bearing component.
It is possible to easily obtain a ceramic member that can sufficiently exhibit the required function . Of course, when forming the concave groove, the surface shape of the ceramic material, groove pitch, groove depth, groove width, etc. depends on the type and function of the constituent members of the hydrodynamic bearing.
Although set appropriately, even if the groove pitch p is very small, when it is necessary to keep the groove depth of the groove and 1 to 200 [mu] m (more preferably 50μm or less), the effect of the present invention up to It will be limited.

[0030]

As apparent from the foregoing description, according to the present invention, excellent thermal shock resistance and the like, a very dense grooves of accurate and surface roughness as designed by chromatic on the surface, the dynamic Pressure fluid
An extremely excellent ceramic member can be provided as a constituent member of the bearing . Moreover, since the concave grooves are formed in the stage before firing having plasticity, and at least the adjacent concave grooves are not formed at the same time, even when the pitch of the concave grooves is small,
Regardless of the material used, the ceramic member can be manufactured with high accuracy and easily, and the manufacturing cost can be significantly reduced by mass production. In addition, the uneven shape (groove pitch, groove depth, groove width, etc.), processing accuracy, and surface roughness of the member surface can be freely changed depending on the shape of the molding die, processing accuracy, and surface roughness. For hydrodynamic bearings
The application can be expanded significantly.

[Brief description of drawings]

FIG. 1 is a side view showing a step of forming a groove in an embodiment of a method according to the present invention.

FIG. 2 is a plan view of the same.

FIG. 3 is a cross-sectional view of a hydrodynamic bearing using the ceramic member according to the present invention obtained by the same method.

FIG. 4 is a side view showing a step of forming a groove according to another embodiment.

FIG. 5 is a front view of a molding die used in this forming step.

FIG. 6 is a cross-sectional view showing a step of forming a groove according to still another embodiment.

FIG. 7 is a transverse plan view of the ceramic member thus obtained according to the present invention .

[Explanation of reference numerals] 1 ... Ceramic member of hydrodynamic bearing , 1
a ... Dynamic pressure generating groove (concave groove), 1 '... Carbide ceramic plastic body.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location F16C 17/02 A 8613-3J

Claims (2)

[Claims] 1. A molding die having one or a plurality of molding projections on the surface of a carbide ceramic plastic body obtained by pressure molding a powdered ceramic material such as silicon carbide or tungsten carbide. pressed repeatedly while changing the pressing position to the plastic surface, at least while allowing adjacent grooves are not formed at the same time, after having formed a plurality of grooves adjacent, characterized in that by firing handle this to, ceramic <br/> click member of the hydrodynamic bearing having a plurality of grooves on the surface proximate. 2. Powders of silicon carbide, tungsten carbide, etc.
Carbide ceramics obtained by pressure molding of powdered ceramic
On the surface of the plastic body with one or more
The shape is repeated while changing the pressing position on the plastic body surface.
Press back and press so that at least adjacent grooves are
Form multiple adjacent grooves while preventing them from being formed
In addition, it is characterized in that it is baked.
Of a hydrodynamic bearing having a plurality of adjacent grooves on the surface.
Manufacturing method of ceramic member.