JP2009074660A - Dynamic pressure gas bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make it possible to prevent, without increasing the number of parts, a gas film pressure from lowering due to wedge-shaped space width expansion resulting from upper foil deformation. <P>SOLUTION: There is provided the dynamical pressure gas bearing equipped with a foil portion that is provided between a stationary member to be mounted with a shaft and a pressure receiving rotating potion provided in the shaft and includes a basal portion whose whole portion can be spliced to the stationary portion and an elastic supporting portion having a plurality of projections which can be thrust elastically into the basal portion, an under foil arranged on a side of the stationary portion, and the upper foil that is spliced to the under foil and builds up a wedge-shaped space between itself and the pressure receiving rotating potion in order to form a gas film when the shaft rotates. In the dynamical pressure gas bearing, a form is held whose width gets smaller as proceeding to a downstream side of the gas film. Within an elastic supporting portion 51 of the under foil 5, an elastic coefficient of the projection 53 is made larger as proceeding to the downstream side of the gas film. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to bearings used in high-speed rotating machines such as aircraft air cycle machines, helium liquefaction equipment expansion turbines, automobile turbochargers, and the like, and in particular, a fixed member to which a shaft is attached and a rotational pressure provided on the shaft. The present invention relates to a dynamic pressure gas bearing that supports a load by a gas film formed between the first and second portions.

  As a bearing used for a high-speed rotating machine, for example, as shown in US Pat. No. 3,635,534, a wedge shape formed between a fixed member to which a shaft is attached and a rotary pressure receiving portion provided on the shaft. There is known a dynamic pressure gas bearing in which a thin gas film is formed between both members due to the space and the load is supported by the lubricating action of the gas film. Such a dynamic pressure gas bearing is applied to a thrust bearing.

As an example of such a conventional dynamic pressure gas bearing, a flexible annular foil locked to a fixed member is provided, and a swell portion is formed in a part of the foil so that the swell portion and the rotational pressure receiving member are formed. It is conceivable that the foil is bent by the pressure of the gas introduced into the gap between the rotary pressure receiving portion and the foil from the initial wedge-shaped space between the portions, and a plurality of wedge-shaped spaces are repeatedly formed between adjacent support protrusions. (See Patent Document 1).
JP 2007-92994 A

  By the way, in the structure of the said patent document 1, the cyclic | annular underfoil latched by the fixing member and the cyclic | annular upper foil which forms a wavy part in part are provided, The waviness part of this upper foil, and the said A configuration is adopted in which an initial wedge-shaped space is formed between the rotating pressure-receiving portion and a support base is provided in the space between the underfoil and the upper foil to support the upper foil.

  Thus, the upper foil is a thin plate-like member, and when the elastic coefficient and height of the underfoil and the support base are constant, the upper foil is greatly bent at a location where the gas film pressure is high, The space between the rotary pressure receiving part is increased. In that case, the malfunction that the gas film pressure in this space falls with expansion of this space generate | occur | produces. However, in the conventional configuration represented by the configuration of Patent Document 1, it is difficult to set the elastic coefficients of the underfoil and the support base for each part.

  The present invention is configured to solve the problems described above.

  That is, the dynamic pressure gas bearing according to the present invention includes a foil portion provided between a fixing member to which a shaft is attached and a rotation pressure receiving portion provided on the shaft, and the foil portion is the fixing member. An underfoil having an annular plate-like shape having an elastic support portion having a base portion that can be attached substantially entirely to the base portion and a plurality of protrusions that can be elastically projected and retracted with respect to the base portion. And an upper foil that forms a gas film including a wedge-shaped space between the rotating pressure receiving portion and the rotary pressure receiving portion so as to form a gas film when rotating the shaft. The under-foil elastic support portion has a mesh shape having a longitudinal element extending in the radial direction and a transverse element extending in the circumferential direction, and the protrusion is provided at a part or all of the intersection of the longitudinal element and the transverse element. That And butterflies.

  If this is the case, the elastic coefficient of the protrusion provided at each intersection can be set independently. For example, by increasing the elastic coefficient of the protrusion toward the downstream side of the gas film, the gas film The elastic force received by the upper foil increases toward the downstream side. That is, the upper foil is greatly separated from the fixing member on the downstream side of the gas film, and the width of the wedge-shaped space can be kept small. Furthermore, since the pressure received by each protrusion of the underfoil is independently received by each protrusion, the shape of each protrusion is not affected by the shape of the adjacent protrusion. Therefore, without causing an increase in the number of parts, it is possible to prevent the gas film pressure from decreasing due to the deformation of the upper foil and the expansion of the width of the wedge-shaped space.

  Further, as a configuration for enabling a gas film having a high load capacity to be configured, a distribution of a gas film thickness can be set according to a pressure distribution generated between the upper foil and the rotary pressure receiving portion in the elastic support portion. Examples are those in which the elastic coefficient in the elastic support part is distributed, and those in which the elastic coefficient of the protrusions of the part increases as it goes downstream of the gas film in the elastic support part. This is because, with such a configuration, the elastic coefficient of the portion where the pressure increases can be increased, and the shape of the wedge-shaped space formed between the upper foil and the rotary pressure receiving portion can be maintained. In particular, in the case of the latter, by increasing the elastic coefficient downstream of the wedge-shaped space formed between the upper foil and the rotary pressure receiving portion, the gas film thickness is reduced downstream of the wedge-shaped space. The shape which becomes small can be maintained.

  In addition, as a configuration for enabling the height of the point where the upper foil comes into contact with the under foil to be appropriately set, the protrusion width of the protrusion is changed according to the pressure distribution generated between the upper foil and the rotary pressure receiving portion. And the one in which the protrusion width of the protrusion of the portion increases in the elastic support portion toward the downstream side of the gas film. With such a configuration, by increasing the protrusion width of the protrusion at the portion where the pressure increases, and by causing the protrusion to sink greatly at the portion where the pressure increases, a large elastic biasing force is generated at the portion. This is because the wedge-shaped space formed between the upper foil and the rotary pressure receiving portion can be maintained. In particular, in the latter configuration, the protrusion width of the protrusion is set larger toward the downstream side of the gas film so that the protrusion sinks greatly toward the downstream side of the gas film. On the downstream side, the upper foil can receive a larger elastic biasing force from the underfoil. Therefore, as a whole, the shape in which the width of the wedge-shaped space becomes smaller toward the downstream side of the gas film can be maintained.

  In addition, as a mode for further increasing the elastic urging force received by the upper foil at a portion that receives a high gas film pressure and retaining the upper foil more effectively, it is generated between the upper foil and the rotary pressure receiving portion. The thing which changes the number per unit area of the protrusion of this part according to pressure distribution is mentioned.

  Further, as another aspect for further increasing the elastic biasing force received by the upper foil at a portion that receives a high gas film pressure and more effectively retaining the upper foil, for example, as it goes to the downstream side of the gas film, The thing which increases the number per unit area of the processus | protrusion of a site | part is mentioned.

  Then, as a mode for dealing with slight manufacturing errors in dimensions, changes in shape due to temperature changes, and contact with the rotating pressure receiving part, a reverse protrusion that protrudes toward the fixing member is provided on the underfoil. The protrusion can be projected and retracted by elastic deformation, and the elastic coefficient of the reverse protrusion is made smaller than the elastic coefficient of the protrusion in the elastic support portion. With such a configuration, a reverse protrusion can be provided at an arbitrary position using a portion where the lattice is not provided, so that an elastic coefficient different from the protrusion can be set over the entire surface of the underfoil. Because. And since the said protrusion and this reverse protrusion can be formed simultaneously, the manufacturing cost can also be reduced.

  According to the configuration of the dynamic pressure gas bearing according to the present invention, the pressure received by each protrusion of the underfoil is independently received by each protrusion, so that the shape of each protrusion is not affected by the shape of the adjacent protrusion. Therefore, without causing an increase in the number of parts, it is possible to prevent the gas film pressure from decreasing due to the deformation of the upper foil and the expansion of the width of the wedge-shaped space.

  Furthermore, if the elastic coefficient of the protrusion provided at each intersection is set independently, and the elastic coefficient of the protrusion is changed according to the pressure distribution of the gas film, for example, it goes to the downstream side of the gas film. As the elastic modulus of the protrusion increases, the elastic force received by the upper foil increases toward the downstream side of the gas film. That is, the upper foil is greatly separated from the fixing member on the downstream side of the gas film, and the width of the wedge-shaped space can be kept small.

  On the other hand, if the protrusion width of the protrusion is changed according to the pressure distribution generated between the upper foil and the rotary pressure receiving portion, for example, the protrusion width of the protrusion is set to be larger toward the downstream side of the gas film. As a result, the protrusions sink greatly toward the downstream side of the gas film, so that the upper foil can receive a larger elastic biasing force from the under foil on the downstream side of the gas film. Therefore, as a whole, the shape in which the width of the wedge-shaped space becomes smaller toward the downstream side of the gas film can be maintained.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

  As shown in a schematic front view in FIG. 1, the bearing according to the present embodiment includes a foil portion 4 provided between a fixing member 1 to which a shaft 2 is attached and a rotation pressure receiving portion 3 provided on the shaft 2. A gas film S including a wedge-shaped space is provided between the foil part 4 and the rotary pressure receiving part 3.

  As shown in FIG. 1, the foil part 4 includes an elastic support part having a base part 52 that can be almost entirely attached to the fixing member 1 and a plurality of protrusions 53 that can be elastically projected and retracted with respect to the base part 52. The gas film S including the wedge-shaped space is formed between the underfoil 5 having 51 and disposed on the fixing member 1 side and the rotary pressure receiving portion 3 in contact with the underfoil 5. And an upper foil 6. Here, FIG. 2 shows a plan view of the underfoil 5, and FIG. 3 shows a perspective view of a main part of the underfoil 5. Further, in FIG. 1, the under foil 5 and the upper foil 6 are shown to have a constant thickness in order to facilitate understanding of the shape. And is formed in an annular shape around which the shaft 1 is wound. In addition, the underfoil 5 and the upper foil 6 provided by the present invention are engaged with pins (not shown) implanted in the fixed part 1 with three recesses formed around the underfoil 5 and the upper foil 6, respectively. Guaranteed.

  The upper foil 6 has at least one, more specifically, three waviness portions (not shown) at intervals of 120 degrees, and the underfoil is between the waviness portion and the fixing member 1. 5 elastic support portions 51 are positioned. More specifically, the tips of the protrusions 53 of the underfoil 5 are in contact with the upper foil 6 respectively.

  On the other hand, the underfoil 5 has a longitudinal element 511 extending in the radial direction and a circumferential extension as shown in FIG. 2 and FIG. 3 and an enlarged view of the main part in FIG. The elastic support portion 51 is formed in a mesh shape having a transverse element 512 to be formed. In addition, the projection 53 is provided by projecting the intersection of the vertical element 511 and the horizontal element 512 upward. Further, the outermost peripheral portion of the underfoil 5 is an outer peripheral ring portion 56 having the same height as the base portion 52, and a shaft insertion hole through which the shaft 2 can be inserted is provided at the center portion, and the vicinity of the opening edge of the base portion 52 is provided. It is set as the inner peripheral ring part 57 which makes the same height. Here, the protrusion height of the protrusion 53 is reduced, for example, in a portion where the width of the gas film S including the wedge-shaped space is large, that is, a portion corresponding to the inlet. On the other hand, the protruding height of the protrusion 53 is increased in a portion where the width of the gas film S including the wedge-shaped space is small. The protrusion 53 can be protruded and retracted by elasticity, but the elastic coefficient is, for example, small at the portion where the width of the gas film S including the wedge-shaped space is large, that is, upstream of the gas film, and the width of the wedge-shaped space. The elastic modulus is increased in a small portion, that is, on the downstream side of the gas film (the side where the arrow R in FIG. 4 is directed). Of course, it is possible to adopt a configuration in which the protrusions have the same elastic modulus as they go to the downstream side of the gas film, and the protrusion height is made equal for all protrusions 53.

  Specifically, in this embodiment, the intermediate portion between the protrusions 53 and 53 is a recess 54 that is on the same plane as the flat portion 52, and the portion between the recess 54 and the protrusion 53 is an inclined portion 55. However, when changing the elastic coefficient, when reducing the elastic coefficient on the upstream side of the gas film, etc., the width of the inclined portion 55 is reduced, or the length is increased to reduce the elastic coefficient of the protrusion 53. In the case where the elastic coefficient is increased on the downstream side of the gas film or the like, the elastic coefficient of the projection 53 is increased by increasing the width of the inclined portion 55 or shortening the length, thereby reducing the gas. The elastic modulus is changed according to the pressure distribution of the membrane. In addition, when changing the protrusion height, for example, the pressure distribution of the gas film is reduced by decreasing the inclination on the upstream side to reduce the protrusion height and increasing the inclination on the downstream side to increase the protrusion height. The protrusion height can be changed according to the above. Further, as shown in FIG. 5, which is a sectional view taken along line xx in FIG. 2, the base 52 is provided with a reverse protrusion 59 that protrudes toward the fixing member 1 and can be retracted by elastic deformation. The reverse protrusion 59 abuts preferentially on the fixing member 1, and the elastic coefficient of the reverse protrusion 59 is smaller than the elastic coefficient of any protrusion 53 in the elastic support portion 51. That is, the reverse projection 59 is preferentially elastically deformed by the pressure of the gas film generated when the shaft 2 and the rotation pressure receiving portion 3 are rotated. In FIG. 4, only a part of the protrusion 53, the recessed portion 54, the inclined portion 55, and the reverse protrusion 59 are denoted by reference numerals, but the portion that is the protrusion 53, the portion that is the recessed portion 54, By attaching the same pattern to the portion that is the inclined portion 55 and the portion that is the reverse protrusion 59, the portions to which the respective patterns are attached are the protrusion 53, the concave portion 54, the inclined portion 55, and the reverse protrusion 59, respectively. I am trying to show that. 2 and 3, the portion corresponding to the protrusion 53, the portion corresponding to the recess 54, the portion corresponding to the inclined portion 55, and the portion corresponding to the reverse protrusion 59 are attached to FIG. 4. The same pattern is attached.

  Here, when the shaft 2 and the rotation pressure receiving portion 3 rotate, the air in the gap between the rotation pressure receiving portion 3 and the foil portion 4 is pulled by the viscosity of the air, and the gap between the rotation pressure receiving portion 3 and the foil portion 4 is gradually sandwiched. The pressure increases in the region of the wedge-shaped space. As a result of this pressure increase, the upper foil 6 is first subjected to a downward action. At this time, the upper foil 6 is brought into pressure contact with the protrusion 53 of the underfoil 5, and the underfoil 5 is subjected to a downward action. In response to this action, the reverse protrusion 59 is elastically deformed and the surface shape of the underfoil 5 is changed, and almost all of the protrusion 53 is in contact with the upper foil 6 and elastically deforms. On the other hand, the upper foil 6 receives an upward elastic force from the protrusion 53. This elastic force is, for example, a predetermined magnitude that is small at the inlet portion of the wedge-shaped space, that is, upstream of the gas film S, and larger than the elastic force at the inlet portion after the circumferential intermediate portion, that is, downstream of the gas film. It is. When the upper foil 6 receives such an elastic force from the protrusion 53, the shape of the gas film S including the wedge-shaped space is appropriate, for example, as the width decreases from the inlet portion to the downstream side. The shape is maintained, and an air pressure rise occurs in the upper portion of the elastic support portion 51. Due to this pressure increase, the bearing supports the rotary pressure receiving portion 3 in a non-contact manner.

  Therefore, if the structure of the bearing according to the present embodiment is employed, for example, the upper foil is increased by increasing the elastic coefficient of the protrusion 53 in the downstream portion of the gas film where the width of the wedge-shaped space is small and the air pressure is high. The thickness of the gas film S can be maintained at an appropriate value, for example, the subsidence of 6 can be suppressed.

  The underfoil 5 has an annular plate shape, and the elastic support portion 51 of the underfoil 5 is formed in a mesh shape having longitudinal elements 511 extending in the radial direction and transverse elements 512 extending in the circumferential direction. In addition, since the protrusion 53 is provided at the intersection of the vertical element 511 and the horizontal element 512, the elastic support portion 51 can be formed with a simple configuration only by press molding or the like.

  The underfoil 5 is provided with a reverse projection 59 that protrudes toward the fixing member 1, and the reverse projection 59 can protrude and retract by elastic deformation. Since the elastic modulus is smaller than the elastic coefficient, a slight manufacturing error in the dimensions of the underfoil 5 and the upper foil 6 and a shape change accompanying a temperature change can be absorbed by the elastic deformation of the reverse protrusion 59. Moreover, it can be made to follow the fluctuation | variation of the position of a rotary body.

  The specific configuration of each part is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

  For example, in the above-described embodiment, as shown in FIG. 6, the width dimension of the inclined portion 55 between the recess 54 and the protrusion 53 is increased toward the downstream side of the gas film (the side where the arrow R is directed). Thus, the elastic coefficient of the projection 53 may be increased as it goes downstream of the gas film. Further, for example, the elastic coefficient and the height of the protrusion may be changed in the radial direction. Further, as shown in the figure, a reverse protrusion 59 may be provided in the base 52 in a shape from the outer peripheral plate portion 56 toward the inner peripheral side.

  Further, in the above-described embodiment, as shown in FIG. 7 corresponding to FIG. 5, a cut may be provided in a part of the lateral element 512, and the reverse protrusion 59 may be provided in a portion near the cut end.

  In addition, the uneven portion of the underfoil may be formed in a mesh shape in which the vertical elements and the horizontal elements form a constant pitch, and protrusions may be provided only at some of the intersections. In this case, for example, a large number of convex portions may be set in a portion where the width of the wedge-shaped space is reduced. Further, as shown in FIG. 8, the density of the vertical elements 511 and the horizontal elements 512 is increased toward the downstream side of the gas film (the side to which the arrow R is directed), and projections are provided at all of these intersections to provide the gas film. The number of protrusions per unit area may be increased toward the downstream side.

  In addition, in the above-described embodiment, the protrusion is supported by the inclined portion extending in the radial direction and the inclined portion extending in the circumferential direction. However, the protrusion may be supported by only one of them. Further, the inclined portion may be configured to support such a protrusion in a cantilever manner. Of course, the elastic coefficient of each protrusion may be changed by changing the thickness of the inclined portion supporting each protrusion.

  Further, in the elastic support portion of the underfoil, for example, the protrusion height of the protrusion may be increased toward the downstream side of the gas film while setting the elastic coefficient of the protrusion to be equal. If configured in this way, the width of the wedge-shaped space in the portion corresponding to the downstream side of the gas film in the stage before the generation of the gas flow is small, and when the gas flow is generated, the pressure of the gas film increases on the downstream side, The protrusion on the downstream side sinks more and can give a strong elastic biasing force to the upper foil, and the protrusion height of the protrusion is large before the gas flow is generated, so the elasticity of the gas film and the underfoil is added. While balancing the power, it is possible to maintain a shape in which the width of the wedge-shaped space becomes smaller toward the downstream side of the gas film. Of course, the elastic modulus of the protrusion may be increased toward the downstream side of the gas film. In addition, change the height and elastic modulus in the radial direction, increase the height and elastic modulus in the downstream direction, and then reduce the height once again, so that an arbitrary change can be given so that an optimal gas film thickness can be formed. Also good.

  Further, the reverse protrusion may be provided by a method other than the aspect in which the transverse element is divided and provided separately in the outer peripheral portion as in the above-described embodiment, or when the temperature is provided in an environment where the temperature is substantially constant. Etc. may be omitted.

  In addition, various modifications may be made without departing from the spirit of the present invention.

The front view of the bearing which concerns on one Embodiment of this invention. The top view of the underfoil of the bearing which concerns on the same embodiment. The perspective view of the principal part of the underfoil of the bearing which concerns on the same embodiment. The figure which expands and shows the principal part in FIG. Xx sectional drawing in FIG. The top view of the underfoil of the bearing which concerns on the other embodiment of this invention. The figure corresponding to FIG. 5 which concerns on the other embodiment of this invention. The schematic plan view of the underfoil of the bearing which concerns on the other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fixed member 2 ... Shaft 3 ... Rotation pressure receiving part 4 ... Foil part 5 ... Underfoil 51 ... Elastic support part 52 ... Base 53 ... Protrusion 59 ... Reverse protrusion 6 ... Upper foil S ... Gas film

Claims (8)

A foil portion is provided between a fixing member to which a shaft is attached and a rotation pressure receiving portion provided on the shaft, and the foil portion includes a base portion that can be substantially entirely attached to the fixing member, and the base portion. An underfoil having an elastic support portion having a plurality of protrusions that can be elastically projected and retracted and arranged on the side of the fixing member, and an underfoil attached to the underfoil. An upper foil that forms a gas film including a wedge-shaped space between the rotation pressure receiving portion and the rotation pressure receiving portion to form a gas film during rotation, wherein the elastic support portion of the underfoil is radially provided A hydrodynamic gas bearing having a mesh shape having a longitudinal element extending and a transverse element extending in the circumferential direction, wherein the protrusion is provided at a part or all of an intersection of the longitudinal element and the transverse element. The elastic coefficient in the elastic support part is distributed so that the distribution of the gas film thickness can be set in accordance with the pressure distribution generated between the upper foil and the rotary pressure receiving part in the elastic support part. Item 1. A hydrodynamic gas bearing according to Item 1. 2. The dynamic pressure gas bearing according to claim 1, wherein the elastic coefficient of the protrusion of the portion is increased toward the downstream side of the gas film in the elastic support portion. 2. The hydrodynamic gas bearing according to claim 1, wherein a protrusion width of the protrusion is changed in accordance with a pressure distribution generated between the upper foil and the rotary pressure receiving portion. 2. The hydrodynamic gas bearing according to claim 1, wherein the protrusion width of the protrusion of the portion is increased toward the downstream side of the gas film in the elastic support portion. 6. The number of projections per unit area of the portion is changed according to a pressure distribution generated between the upper foil and the rotary pressure receiving portion. Dynamic pressure gas bearing. The dynamic pressure gas bearing according to claim 1, wherein the number of projections per unit area of the portion is increased toward the downstream side of the gas film. 8. A reverse projection that protrudes toward the fixing member is provided on the underfoil, and the reverse projection can be projected and retracted by elastic deformation. The hydrodynamic gas bearing described.

Images