JP3337289B2 - Hydrodynamic bearing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic pressure bearing for a low-viscosity working fluid.

[0002]

2. Description of the Related Art FIG. 6 is a perspective view of a conventional dynamic pressure bearing.
In the figure, 11 is a backing metal, 12 is a white, 13 is a journal, 14 is a wedge groove provided on the white, 15 is a dam formed on both sides and an end of the wedge groove, and H is a wedge groove. Inlet depth, D is the bearing diameter,
X is the load direction of the rotating body. The bearing is formed by embossing a white 12 on a steel backing 11 and a journal 1 of a rotating body.
3 are supported. There are various types of bearings that support the rotating body, but among the dynamic pressure bearings, the wedge groove bearing type as described above has been used as the type with the best load capacity and the floating characteristics of the rotating body. ing.

[0003] In the above bearing, a groove 14 is provided on the white sliding surface from the upstream side to the downstream side in the rotational direction as a wedge flow path for the lubricating working fluid, and dams 15 are provided on three sides around the groove. . The rotating body floats due to the pressure generated in the wedge channel, but with the rotation of the journal, the working fluid that has entered the wedge is prevented from flowing out to the outside by the dam. The advantage is that high load capacity can be obtained. Therefore, it is possible to quickly lift the rotating body with the rotation of the rotating body to form a working fluid film between the journal and the bearing, thereby avoiding damage to the journal and the bearing due to contact sliding.

The wedge flow path 14 and the dam 15 are formed by machining a white surface. In the case of lubrication with oil, the inlet depth H of the wedge groove is about 2/1000 of the bearing diameter D (a bearing having a diameter of 100 mm). In the case of about 0.2 mm).

[0005]

When a low-viscosity fluid other than oil (for example, a liquid such as water or alcohol or a gas such as air or nitrogen) is used as the working fluid for the bearing, the viscosity of the fluid film is low because the viscosity is low. If it is not small, a sufficient pressure (accordingly, load capacity) cannot be obtained. Even in a wedge groove bearing capable of providing a large load capacity in principle, the effect cannot be exhibited unless the entrance depth of the wedge groove is made shallow in proportion to the square root of the viscosity ratio. In other words, the entrance depth of the wedge groove H /
When the bearing diameter D is water: about 0.4 / 1000 (D = 100 mm and H
= About 0.004) In the case of air: about 0.1 / 1000 (H at D = 100 mm)
= About 0.001). It is difficult to accurately process such minute wedge grooves by using conventional materials and processing methods, and even if the latest processing method is used, it becomes very expensive.

An object of the present invention is to provide an inexpensive dynamic pressure bearing for a low-viscosity working fluid with high reliability by a new means for forming such fine wedge grooves.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems and relates to a dynamic pressure bearing having the following features. (1) In a dynamic pressure bearing that supports a rotating shaft, the depth of the bearing back metal gradually decreases from upstream to downstream in the sliding direction over substantially the entire surface except for both sides and downstream in the sliding direction. > and grooves wedge formed to be shallower s, the embedded surface of the elastomer after the hand covers the entire surface of the back metal in elastography Ma in the groove of the smooth and the wedge-shaped as a bearing sliding surface
The thickness of the elastomer other than the part
These parts also have a surface layer part that has been finished to a certain degree . (2) In the hydrodynamic bearing according to the above (1), the surface layer portion is a surface layer portion formed by smoothing the surface of the elastomer at a temperature of 100 ° C. to 200 ° C.

[0008]

When a slight pressure is generated between the sliding surfaces with the rotation of the rotating body, the elastomer starts to undergo an elastic compression change due to the pressure. Since the amount of compressive deformation is large when the elastomer is thick and small when the elastomer is thin, it is embedded in a wedge-shaped groove.
From the amount of compression deformation of the elastomer other than the part
The amount of compressive deformation of the elastomer buried in the wedge-shaped groove is
Since it becomes larger, the initially smooth bearing surface has a shape similar to a wedge groove provided with a conventional dam after deformation, and acts as a wedge groove bearing.

In the case where the wedge groove depth is insufficiently formed only by the pressure deformation, for example, when the weight of the rotating body is small, the pressure required for floating is small, and the depth of the wedge groove formation due to the amount of pressure deformation is small. And a step of smoothing the sliding surface under a high temperature (100 ° C. to 200 ° C.). The coefficient of linear expansion of an elastomer is larger than that of a metal, and at high temperatures, the surface of a thick portion of the elastomer becomes more convex than a thin portion. In this state, when the surface is smoothed and returned to room temperature, the thick portion of the elastomer can form a sliding surface similar to a wedge groove provided with a dent dam.

[0010]

FIG. 1 is a perspective view of a dynamic pressure bearing according to a first embodiment of the present invention. In the figure, 1 is a backing metal, 2 is a surface layer made of an elastomer provided on the inner surface of the backing metal, 3 is a journal, X is a rotating body load direction, and 2S (dashed line) is an elastomer surface layer after deformation by pressure. Shape. FIG.
Is a perspective view of the back metal before the elastomer coating, and 4 is a wedge groove formed on the inner surface of the back metal.

In this apparatus, first, an elastic resin (= elastomer) 2 is used instead of the conventional white in terms of material. Elastomers are generally richer in elasticity than metals such as white, and have a large elastic limit deformation. The linear expansion coefficient α is one order of magnitude greater, and this embodiment mainly uses the features.

Next, before coating the back metal 1 with the elastomer 2, a wedge groove processing 4 similar to the wedge groove 14 of the conventional wedge groove bearing is applied to the back metal in advance. The depth of the wedge groove processing 4 is about 10 times larger than that of the conventional wedge groove 14. After the elastomer coating is completed, the sliding surface of the elastomer is smoothed and, as shown in FIG.
The thickness of the elastomer 2 other than the part buried in the groove processing 4
Finish so that any part of the sliding surface is constant .

In the dynamic pressure floating bearing having the above-described structure, if any pressure is generated between the sliding surfaces as the rotation of the rotating body rises, the elastomer starts to undergo elastic compression change due to the pressure. The amount of compressive deformation is large the place thick elastomer, the thin place is reduced, part of the wedge grooves 4
Wedge groove from the amount of compressive deformation of the elastomer other than
The amount of compressive deformation of the elastomer in machining 4 was increased.
First, after the smooth bearing surface is deformed, it has the same shape as the conventional wedge groove + dam (the dashed line 2S in FIG. 1), and acts as a wedge groove bearing. In this bearing, pressure generation and deformation proceed simultaneously, and the rotating body floats.

If a thickness distribution of the elastomer is set in advance so that an optimum wedge groove depth determined by the viscosity of the working fluid is formed when a pressure level capable of causing the rotating body to float is generated, the working fluid with a low viscosity can be used. Wedge grooves of the required fine dimensions can be formed by deformation. Since the formation of the groove by the pressure deformation of the elastomer is completed instantly after the rotation rises, the rotating body can be floated very quickly and a large load capacity can be obtained.

In the case where the wedge groove depth is insufficiently formed by only the pressure deformation, for example, when the weight of the rotating body is small and the pressure required for floating is small and the formation depth of the wedge groove due to the amount of pressure deformation is small. Uses a step of smoothing the sliding surface under high temperature. This utilizes the characteristics of the above-mentioned elastomer at the time of finishing the sliding surface, heating the entire bearing and finishing it to a smooth surface at an appropriate high temperature (100 ° C to 200 ° C). When it is returned, a minute concave surface is formed in advance.

The coefficient of linear expansion of an elastomer is larger than that of a metal, and at a high temperature, the surface of a thick portion of the elastomer becomes more convex than a thin portion. In this state, when the surface is smoothed and returned to room temperature, the thick portion of the elastomer is dented, and a sliding surface having a wedge groove and a dam is formed. Since a certain amount of wedge grooves are already formed in the initial state of the bearing surface manufactured in this manner, it is possible to compensate for the lack of wedge groove formation due to pressure deformation during rotation, and to speed up the rotating body. Can be raised.

FIG. 1 shows an example of the dimensions of each part when PTFE (Teflon) is used as the elastomer and air is used as the working fluid in the embodiment of FIG.

Bearing specifications ・ Bearing diameter × width 10cm × 4cm ・ Bearing static load 150kg ・ Rated speed 20,000rpm To float a rotating body, a pressure of about 4kg / cm ² must be generated in the wedge groove on average. No. PTF at this pressure
In order for the amount of pressure deformation of E to be about 0.1 / 1000D = 0.001 cm, the thickness of PTFE may be set to 1.0 cm. In other words, when a wedge groove that gradually becomes shallower than 1.0 cm in the back metal is machined and coated with PTFE, an inner pressure of 4 kg / cm ² is applied to the back metal and the inlet depth is 0.001 cm due to deformation of PTFE.
As a result, a wedge groove bearing is formed.

Next, when the load capacity of the wedge groove bearing is calculated as described above, the load capacity is high even at a low speed, and a load capacity of 150 kg is generated at only a peripheral speed of 2.5 m / s to lift the rotating body. It turns out that it gets. The PV value (contact pressure × peripheral speed) at this floating rotation speed is 10 (kg / cm ² ) (m / s), which is 20 (kg), which is the limit value of a non-lubricated Teflon sliding bearing.
/ cm ² ) (m / s) before shifting from the sliding state to the non-contact fluid lubricating state, thereby avoiding damage to journals and bearings due to unlubricated sliding at high PV values. In addition, this floating peripheral speed is equivalent to 500 rpm in terms of the rotation speed of the rotating body.
Considering the start toward 000 rpm, it can be said that the rotating body floats immediately after the start. By selecting an elastomer having appropriate characteristics and adjusting the thickness of the elastomer coating, the above-described configuration and operation can be realized regardless of the bearing specifications.

Although FIGS. 1 and 2 show an embodiment in which the present invention is applied to a liner fixed journal shaft, the present invention is also applicable to a tilting pad type bearing or a thrust bearing. FIG. 3 is a perspective view of a liner fixed type thrust bearing according to a second embodiment of the present invention, FIG. 4 is a perspective view of a tilting pad type journal bearing according to a third embodiment of the present invention, and FIG. It is a perspective view of a tilting pad type thrust bearing concerning a 4th example. In the figure, 1 is a back metal, 2 is an elastomer, 4 is a wedge groove processed on the back metal, and 5 is a thrust collar.

In any case, as described above, the back metal 1 is subjected to the groove processing 4 corresponding to the wedge groove 14 of the conventional wedge groove bearing, and then coated with the elastomer 2. Therefore, in each of the embodiments, even when a low-viscosity working fluid is used, a large load capacity and good rotor floating characteristics unique to a wedge groove bearing can be obtained. Further, as in the first embodiment, the structure is a combination of the surface finishing under a high temperature (100 ° C. to 200 ° C.) using a large coefficient of linear expansion and the above-described pressure deformation.
Action is also possible.

As described in detail above, each of the above-described embodiments is based on the conventional technique based on the combination of the pressure deformation of the elastomer or the combination of the surface finishing and the pressure deformation at a high temperature (100 ° C. to 200 ° C.) utilizing a large linear expansion coefficient. Low-viscosity working fluid bearings, which were not feasible with the materials and processing methods described above, can be realized at low cost, and even when low-viscosity working fluids are used, they function as wedge groove bearings. Insufficient load capacity and contact damage due to poor floating characteristics of the rotor can be avoided.

[0023]

In the dynamic pressure bearing of the present invention, the depth of the bearing back metal surface extends from the upstream side to the downstream side in the sliding direction over substantially the entire surface except for both sides and the downstream side in the sliding direction.
And grooves wedge formed to be shallower gradually, is embedded surface of the elastomer to the entire surface of the back metal after hand coated elastography Ma in the groove of the smooth and the wedge-shaped as a bearing sliding surface
The thickness of the elastomer other than the part
Either part is provided with a surface layer part which is finished to a certain degree , or the surface part is formed by smoothing the surface of the elastomer at a temperature of 100 ° C. to 200 ° C., so that it is embedded in a wedge-shaped groove. Elast of the part other than the part
Error in the part buried in the wedge-shaped groove
The amount of compressive deformation of the stoma increases and the bearing slides smoothly at the beginning.
After the surface is deformed, it acts as a wedge groove bearing, so that a dynamic pressure bearing for a low-viscosity working fluid can be provided at low cost.

[Brief description of the drawings]

FIG. 1 is a perspective view of a dynamic pressure bearing according to a first embodiment of the present invention.

FIG. 2 is a partial perspective view of the embodiment.

FIG. 3 is a perspective view of a dynamic pressure bearing according to a second embodiment of the present invention.

FIG. 4 is a perspective view of a dynamic pressure bearing according to a third embodiment of the present invention.

FIG. 5 is a perspective view of a dynamic pressure bearing according to a fourth embodiment of the present invention.

FIG. 6 is a perspective view of a conventional dynamic pressure bearing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Backing metal 2 Elastomer 2S Elastomeric surface shape after deformation by pressure 3 Journal 4 Wedge groove processed on backing metal 5 Thrust collar

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) F16C 17/00-17/26 F16C 21/00-27/08 F16C 33/00-33/28

Claims (2)

(57) [Claims] 1. A hydrodynamic bearing for supporting a rotating shaft, its depth over substantially the entire surface, leaving the sides and downstream of the sliding direction of the bearing back metal surface gradually toward the downstream side from the sliding direction upstream side s and shallow so as groove formed wedge shape, the entire surface of the back metal to the surface of the elastomer after hand coated elastography Ma in the groove of the smooth and the wedge-shaped as a bearing sliding surface
The thickness of the elastomer other than the part to be buried
A dynamic pressure bearing comprising: a surface layer formed by uniformly finishing any part of a moving surface. 2. The dynamic pressure bearing according to claim 1, wherein the surface layer is a surface layer formed by smoothing the surface of the elastomer at a temperature of 100 ° C. to 200 ° C. .