JP2005163939A - Radial foil bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radial foil bearing capable of improving the stability under high-speed rotation of a rotating shaft and reducing the manufacturing cost. <P>SOLUTION: Two thin parts of low rigidity are formed in the circumferential direction of a main body part 17 of an ended circular top foil 2 at an interval, and cut and raised claws 12, 13 are formed on a bump foil 3 in a state that a length of the cut and raised claw 13 of a part corresponding to the thin part of the bump foil 3 mounted at an outer part in the radial direction of the main body part 17 is shorter than a length of the cut and raised claw 12 of a part not corresponding to the thin part. The main body part 17 of the top foil 2 and the main body part 10 of the bump foil 3 for backing up the main body part 17 have the shapes obtained by expanding side parts of an approximately regular triangle outward approximately in the circular arc shape to improve the stability under high-speed rotation of the rotating shaft 1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a radial foil bearing having a top foil, a bump foil, and an outer ring.

  Conventionally, as a radial foil bearing, there is one described in JP-A-11-247844 (Patent Document 1).

  As shown in FIG. 4, the radial foil bearing includes three top foils 31 (only two are shown in the figure) arranged on the outer side of a rotating shaft (not shown) with a bearing gap therebetween. There are provided three bump-shaped bump foils 32 (only two are shown in the figure) arranged on the outer side in the radial direction and an outer ring 35 arranged on the outer side in the radial direction of the bump foil 32.

  The outer ring 35 protrudes inward in the radial direction from the inner peripheral cylindrical surface 36, and has three T-shaped protrusions 37 (one protrusion 37 is shown in FIG. Only one is shown.) The circumferential length between adjacent protrusions 37 having a T-shaped cross section is substantially equal to the circumferential length of the top foil 31 and the bump foil 32.

  The top foil 31 and the bump foil 32 are inserted into the outer ring 35 by inserting both ends in the circumferential direction of the top foil 31 and the bump foil 32 into the concave portions 38 on the side of the two adjacent T-shaped protrusions 39. It is attached.

  In the conventional radial foil bearing described above, by attaching the top foil 31 to the outer ring 35 as described above, the shape of the inner peripheral surface of the three top foils 31 arranged on the inner side in the radial direction is changed to a substantially umbilical shape. A large dynamic pressure is generated at three predetermined locations on the circumference to improve the stability of the rotating shaft under high speed rotation.

However, the above-described conventional radial foil bearing can improve the stability of the rotating shaft under high-speed rotation. On the other hand, in order to fix the top foil 31 and the bump foil 32 to the outer ring 35, the outer ring 35 has a complicated cross section. A plurality of T-shaped protrusions 37 must be formed, and there is a problem that the manufacturing cost of the outer ring 35 is increased.
Japanese Patent Laid-Open No. 11-247844

  SUMMARY OF THE INVENTION An object of the present invention is to provide a radial foil bearing that can improve the stability of a rotating shaft under high-speed rotation and has a low manufacturing cost.

In order to solve the above problems, the radial foil bearing of the present invention is
A top foil disposed outside the rotating shaft with a bearing gap therebetween;
Bump foil disposed outside the top foil in the radial direction;
A radial foil bearing provided with an outer ring disposed on the outer side in the radial direction of the bump foil,
The top foil has an end and an annular portion,
Low-rigidity portions extending substantially in the axial direction are formed at a plurality of circumferentially spaced locations in the annular portion, and the annular portion has the low-rigidity portion as a vertex in the radial cross section. It is characterized by a substantially polygonal shape.

  The substantially polygonal shape includes a shape in which a side portion of the polygon is expanded outward in a substantially arc shape.

  According to the invention, since the low-rigidity portions extending substantially in the axial direction are formed at a plurality of locations spaced apart from each other in the circumferential direction of the annular portion, the bent portions are bent at the plurality of low-rigidity locations, In the radial cross-section, the annular portion becomes a substantially polygon having a plurality of locations with low rigidity as substantially vertices, and a side portion of the polygon is expanded outward in a substantially arc shape. Accordingly, the rotation shaft can be supported near the center of the arc-shaped bulge portion having high rigidity, and the movement of the rotation shaft can be limited to the inside in the radial direction near the center. The stability under high speed rotation can be improved.

  Further, in the radial foil bearing of one embodiment, the shape of the outer peripheral surface of the bump foil is a shape in which a polygonal side portion is expanded in a substantially arc shape on the outer side in the radial sectional view. It is a feature.

  According to the above embodiment, the shape of the outer peripheral surface of the bump foil is a shape in which the side of the polygon is expanded outward in a substantially arc shape in the radial cross-sectional view. It is possible to back up the top foil having a shape in which the side of the polygon is expanded in a substantially arc shape on the outside. Therefore, it is possible to further improve the stability of the rotating shaft under high speed rotation.

  Further, in the radial foil bearing according to one embodiment, the bump foil has a plurality of cut and raised claws, and the length of the cut and raised claws located in the vicinity of the vertex part of the polygon is in the vicinity of the vertex part. It is characterized in that it is shorter than the length of the above-mentioned cut-and-raised nail.

  According to the embodiment, since the length of the cut-and-raised claw located in the vicinity of the polygonal apex portion is shorter than the length of the cut-and-raised claw located outside the apex portion, the radial direction The shape of the bump foil in the cross section can be easily made into a shape in which the side portion of the polygon is expanded in a substantially arc shape on the outside.

  Moreover, the radial foil bearing of one Embodiment is characterized in that the low rigidity portion is a thin portion.

  According to the embodiment, since the low rigidity portion is a thin portion, the low rigidity portion can be easily and inexpensively manufactured by etching or the like.

  According to the radial dynamic pressure bearing of the present invention, the low-rigidity portions extending substantially in the axial direction are formed at a plurality of locations spaced apart from each other in the circumferential direction of the annular portion. In the radial cross section, the annular portion is bent into a substantially polygon having a plurality of locations with low rigidity, and the side portions of the polygon are expanded outward in a substantially arc shape. Shape. Therefore, the movement of the rotating shaft can be restricted to the inside in the radial direction near the center of the arc-shaped bulge portion having high rigidity, and the stability of the rotating shaft under high speed rotation can be improved.

  Further, according to the radial dynamic pressure bearing of the present invention, it is not necessary to form a complicated protruding portion for attaching the top foil and the bump foil to the outer ring, so that the manufacturing cost of the radial dynamic pressure bearing can be kept low.

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

  FIG. 1 is a radial cross-sectional view of an embodiment of a radial foil bearing of the present invention.

  This radial foil bearing includes a top foil 2, a bump foil 3, and an outer ring 4.

  As shown in FIG. 1, the top foil 2 is disposed on the outer side in the radial direction of the rotating shaft 1. The top foil 2 includes a main body portion 17 that is an end portion and an annular portion, and an attachment portion 18 that is continuous with one end in the circumferential direction of the main body portion 17 and is bent from the main body portion 17 in a substantially radial direction. . As shown in FIG. 1, the shape of the top foil 2 in the cross section in the radial direction of the main body portion 17 is a substantially umbilical shape (a shape in which a side portion of a substantially equilateral triangle is expanded in a substantially arc shape on the outside). .

  Actually, the shape of the main body portion 17 in the radial cross section is a rice ball shape close to a perfect circle shape. In the main body portion 17 shown in FIG. 1, the rice ball shape is exaggerated. .

  A bump foil 3 is disposed on the outer side in the radial direction of the main body portion 17 which is the annular portion. The bump foil 3 includes an end-shaped and annular main body portion 10 formed of a part of a substantially cylindrical surface, an attachment portion 11 extending from both circumferential ends of the main body portion 10 in a tangential direction of the both end portions, and the main body. Two types of cut-and-raised pawls 12 and 13 that extend in the tangential direction of portions other than both ends from the portions other than both ends in the circumferential direction of the portion 10 and have different sizes are provided.

  An outer ring 4 is arranged outside the bump foil 3 in the radial direction of the main body 10. The inner ring cylindrical surface of the outer ring 4 has one top foil engagement groove 5 extending in a substantially radial direction from one place on the inner circumferential cylindrical surface in the radial section, and the top foil engagement in the radial section. Two bump foil engagement grooves 8 extending in the substantially tangential direction of the inner peripheral cylindrical surface from adjacent portions on both sides in the circumferential direction of the joint groove 5 are formed.

  The top foil 2 has the mounting portion 18 engaged with the top foil engaging groove 5 of the outer ring 4, and the bump foil 3 has the mounting portion 11 engaged with the bump foil engaging groove 8. In this way, the top foil 2 and the bump foil 3 are fixed to the outer ring 4.

  FIG. 2 is a radial sectional view of the top foil 2 showing the top foil 2 in detail.

  The top foil 2 was formed into a cylindrical shape after forming the belt-like metal plate into a cylindrical shape without overlapping in the circumferential direction by roll processing so that both ends in one direction of the belt-like metal plate are adjacent to each other. One end of the metal plate is bent in the radial direction.

  As shown in FIG. 2, the top foil 2 is divided into three equal parts when the annular main body portion 17 is divided into three parts. It is getting thinner. The thin portions 28 and 29 having a small thickness are etched by 0.05 mm to 1.95 mm on the inner peripheral side of the two locations of the top foil 2 whose plate thickness is set to 0.1 mm to 2 mm. Is formed. The thin portions 28 and 29 are portions having low rigidity.

  FIG. 3 is a view showing the bump foil 3 before being molded into a cylindrical shape so as to be disposed on the inner circumferential surface of the outer ring 4.

  As shown in FIG. 3, the bump foil 3 is formed of a rectangular metal plate having elasticity. This rectangular metal plate has four substantially U-shaped slit grooves 20 (more precisely, slit grooves 20 having a shape obtained by removing the lower side from the periphery of the isosceles trapezoid) at the four corners of the rectangular metal plate. Two types of substantially U-shaped slit grooves 22, 24 having different sizes over 10 rows are formed in a portion excluding both ends in one direction of the rectangular metal plate indicated by an arrow A in FIG. (To be precise, slit grooves 22 and 24 having a shape obtained by removing the lower side from the periphery of the isosceles trapezoid) are formed.

  The substantially U-shaped slit grooves 20 at the four corners and the tongue pieces surrounded by the plurality of slit grooves 22, 24 arranged in the ten rows are respectively attached to the mounting portion 11 and the raised claws 12. , 13.

  The first, second, fifth, sixth, ninth, and tenth slit grooves from the end in the one direction in the substantially U-shaped slit grooves 22 and 24 arranged in the tenth row. The cut-and-raised claw 12 surrounded by 22 is formed in the same size, and is surrounded by slit grooves 24 in the third, fourth, seventh, and eighth rows from the end in the one direction. The cut and raised claws 13 are formed in the same size. The length of the mounting portion 11 in the one direction is larger than the length of the cut and raised pawl 12 in the one direction, and the length of the cut and raised pawl 12 in the one direction is cut and raised. The length of the pawl 13 is longer than the length in one direction.

  The mounting portion 11 surrounded by the substantially U-shaped slit grooves at the four corners is disposed so as to face the center in the one direction of the metal plate. Further, the cut and raised claws 12 are arranged in the end rows located at both ends in the one direction so as to face the end in the one direction, and the cut and raised claws are arranged in the row adjacent to the end example. 12 is arranged so as to face the center of the one direction. Subsequently, after arranging the raised claws 13 so as to face the end in the one direction, in a row adjacent to the row of the raised claws 12 arranged so as to face the center in the one direction, In the row adjacent to this example, the cut and raised claws 13 are arranged so as to face the center in the one direction. In this way, a pair of cut and raised claws 12 that form a pair with two and a pair of cut and raised claws 13 that form a pair with two are arranged alternately.

  In this embodiment, the thickness of the main body portion 10 of the bump foil 3 is set in the range of 0.05 mm to 1.0 mm, and the length of the cut claws 12 and 13 in the one direction is 0.5 mm to The range is set to 10 mm. The difference between the length of the cut and raised pawl 12 and the length of the cut and raised pawl 13 is set to 0.05 mm to 0.5 mm.

  Thus, by making the length of the cut-and-raised pawl 12 longer than the length of the cut-and-raised pawl 13, the size of the main body 10 rising from the inner peripheral cylindrical surface is changed depending on the location. The shape of the main body 10 in the radial cross-section is a shape in which the side of a substantially regular polygon that can stably support the rotating shaft under high-speed rotation of the rotating shaft is expanded outward in a circular arc shape (a rice ball shape) It is trying to become.

  In order to arrange the bump foil 3 inside the inner peripheral cylindrical surface of the outer ring 4, the body portion 10 of the bump foil 3 is molded into a substantially cylindrical surface so that both ends of the one direction of the metal plate are substantially matched. Thus, when the bump foil 3 is disposed on the inner peripheral cylindrical surface of the outer ring 4, the mounting portions 11 at the four corners protrude in the tangential direction of the cylindrical surface defined by the main body portion 10 of the bump foil 3, and It engages with the bump foil engaging groove 8.

  Further, when the bump foil 3 is disposed on the inner peripheral cylindrical surface of the outer ring 4, the cut and raised claws 12, 13 protrude in the tangential direction of the cylindrical surface defined by the main body portion 10 of the bump foil 3, The portion is brought into contact with the inner peripheral cylindrical surface, and the main body portion 10 is floated radially inward from the inner peripheral cylindrical surface.

  According to the radial foil bearing of the above-described embodiment, the top foil 2 is a thin-walled portion that is a portion having a low rigidity that is spaced apart from each other in the circumferential direction and extends substantially in the axial direction at two locations in the circumferential direction of the top foil 2. 28, 29, the thin-walled portions 28, 29 are bent, and the inner peripheral surface of the main body portion 17 of the top foil 2 is substantially circular with the side portion of the substantially equilateral triangle in the radial cross section. It becomes an arc-shaped shape (substantially rice ball shape). Accordingly, the rotary shaft 1 can be supported near the center of the arc-shaped bulge portion having high rigidity, and the movement of the rotary shaft 1 can be restricted to the inside in the radial direction near the center. Therefore, the rotating shaft 1 rotating at high speed can be stably supported.

  Further, according to the radial foil bearing of the above embodiment, the outer peripheral surface of the bump foil 3 is a cross-sectional view in the radial direction and has a substantially rice ball shape corresponding to the shape of the top foil 2. The foil 2 can be backed up. Therefore, the support capability of the rotating shaft 1 can be further improved.

  Further, according to the radial foil bearing of the above embodiment, a pair of cut and raised pawls 12 paired with two and a pair of cut and raised pawls 13 paired with two are alternately arranged. Since it is arranged, the distance from the inner peripheral cylindrical surface of the outer ring 4 of the body portion 10 of the bump foil 3 at two locations in the circumferential direction where the rows of the pair of raised claws 13 are arranged is a pair of raised and raised claws. It becomes smaller than the distance from the inner peripheral cylindrical surface of the outer ring 4 of the main body portion 10 of the bump foil 3 at two circumferential positions where 12 rows are arranged. From this, the shape of the main body portion 10 of the bump foil 3 in the cross section in the radial direction can be formed in a substantially arcuate shape with the sides of the substantially equilateral triangles outward, so that they are spaced apart at substantially equal intervals in the circumferential direction. The movement area of the rotary shaft can be limited to the inner side in the radial direction of the substantially central portion at the substantially central portions of the three arc portions, and the rotary shaft 1 rotating at high speed can be stably supported.

  Further, according to the radial foil bearing of the above embodiment, the low rigidity portions of the top foil 2 are the thin portions 28 and 29. Therefore, the low rigidity portions can be easily formed by etching.

  In the radial foil bearing of the above embodiment, the thin portions 28 and 29 having a low rigidity of the top foil 2 are formed at two locations on the main body portion 10 of the annular top foil 2, but the rigidity of the top foil is low. Thin portions may be formed on the main body of the annular top foil at a plurality of locations other than two at intervals in the circumferential direction (these multiple locations are equally spaced in the circumferential direction on the top foil main body). Are preferably separated from each other).

  Further, in the radial foil bearing of the above embodiment, the top foil 2 did not have an air vent hole penetrating between the inner peripheral side surface and the outer peripheral side surface, but in the radial foil bearing of the present invention, for example, An air hole that penetrates between the inner peripheral side surface and the outer peripheral side surface may be formed in a thin-walled portion having low rigidity. In this way, the dynamic pressure generated between the radial foil bearing and the rotating shaft can be made uniform with no variation, and the flying characteristics of the radial foil bearing can be further improved. it can.

  Further, in the radial foil bearing of the above embodiment, the portion having low rigidity of the top foil 2 is constituted by a thin portion. However, in the radial foil bearing of the present invention, the portion having low rigidity of the top foil is formed by the thickness of the top foil. The annular main body portion having substantially the same length may be locally subjected to heat treatment to constitute a portion where the heat treatment is performed.

  Further, in the radial foil bearing of the above embodiment, as shown in FIG. 3, three rows of a pair of long cut and raised claws 12, 12 and two rows of a pair of short cut and raised claws 13, 13 are circumferentially arranged. However, in the radial foil bearing of the present invention, a pair of long cut and raised pawls (m is a natural number of 4 or more) and a pair of short cut and pawl pawls (m-1). May be alternately arranged in the circumferential direction.

  Further, in the radial foil bearing of this embodiment, the body portion 10 having a shape in which the side portion of the regular polygon is expanded in a substantially arc shape by using two kinds of cut and raised claws 12 and 13 having different lengths. In the radial foil bearing according to the present invention, a large number of main body portions having a shape in which a side portion of a polygon is expanded in a substantially arc shape are arranged near the apex portion of an equilateral triangle. From a substantially vertex portion of a square (preferably a regular polygon) to the vicinity of the center of the arc portion on both sides of this vertex portion, a plurality of pairs of cut and raised claws are paired with Form the bump foil so that the length of the cut and raised pawl is less than or equal to the length of the cut and raised pawl of the pair far from the apex, and change the shape of the bump foil to the side of the polygon. In a substantially arc shape It may be formed in a sloppy shape. In addition, as an arrangement in which the length of the cut-and-raised claw of the pair closer to the vertex portion is equal to or shorter than the length of the cut-and-raised claw of the pair farther from the vertex portion, the arc portions on both sides from the above-mentioned vertex portion There are methods such as gradually increasing the length of the claws that form a pair with the two in the vicinity of the center. In this way, by introducing multiple cut-and-lift claws with different lengths, the length of the cut-and-raised claw of the pair near the vertex part is less than or equal to the length of the cut-and-raised claw of the pair far from the vertex part The bump foil body can be made more nearly symmetrical with respect to the center of the inner peripheral cylindrical surface of the outer ring in the radial cross section, and the floating characteristics of the radial foil bearing Can be made even better.

It is sectional drawing of the radial direction of the radial foil bearing of one Embodiment of this invention. It is a figure which shows the top foil with which the radial foil bearing of the said embodiment is provided. It is a figure which shows the bump foil with which the radial foil bearing of the said embodiment is provided. It is a fragmentary sectional view of the radial direction of the conventional radial foil bearing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotating shaft 2 Top foil 3 Bump foil 4 Outer ring 11 Attaching part 12, 13 Cut and raised claw 17 Body part 28, 29 Thin part

Claims (4)

A top foil disposed outside the rotating shaft with a bearing gap therebetween;
Bump foil disposed outside the top foil in the radial direction;
A radial foil bearing provided with an outer ring disposed on the outer side in the radial direction of the bump foil,
The top foil has an end and an annular portion,
Low-rigidity portions extending substantially in the axial direction are formed at a plurality of circumferentially spaced locations in the annular portion, and the annular portion has the low-rigidity portion as a vertex in the radial cross section. A radial foil bearing having a substantially polygonal shape. The radial foil bearing according to claim 1,
A radial foil bearing characterized in that the shape of the outer peripheral surface of the bump foil is a shape in which a polygonal side portion is expanded outward in a substantially arc shape in a radial sectional view. The radial foil bearing according to claim 2,
The bump foil has a plurality of raised claws,
The radial foil bearing according to claim 1, wherein a length of the cut-and-raised claw located in the vicinity of the vertex portion of the polygon is shorter than a length of the claw-and-raised claw located outside the vertex portion. In the radial foil bearing according to any one of claims 1 to 3,
The radial foil bearing according to claim 1, wherein the low rigidity portion is a thin portion.

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