Sliding Bearing and Pump Device Using the Same

Abstract

In a sliding bearing, load carrying capacity and bearing rigidity is increased without increasing a size of the bearing and the pressure of the fluid. The sliding bearing comprises a cylindrical-shaped sleeve supporting a rotatable shaft via fluid, and hydrostatic pressure pockets provided in the inner periphery of the sleeve. The hydrostatic pressure pockets constitute a plurality of rows of circumferentially disposed hydrostatic pressure pockets via orifices. At least one of the hydrostatic pressure pocket rows is arranged adjacently to each of both end portions of the inner periphery of the sleeve. And a circular cylindrical inner peripheral surface region without the hydrostatic pressure pockets is provided at a center portion of the sleeve. A width of the circular cylindrical inner peripheral surface region provided in the axial direction of the shaft is made wider than a sum of widths of the hydrostatic pressure pocket rows.

Description

CLAIM OF PRIORITY

[0001] The present application claims priority from Japanese application serial No. 2011-271887 filed on Dec. 13, 2011, the content of which is hereby incorporated by reference into this application

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a sliding bearing provided with a hydrostatic pressure bearing structure in which high pressure fluid is supplied into a gap between the outer periphery of a shaft and the inner periphery of a sleeve from the outside and which supports rotational movement of the shaft, and a pump device provided with a mechanism which supports, through the sliding bearing, the rotational movement of the shaft connected to an impeller.

[0004] 2. Description of the Related Art

[0005] As a large-sized pump device used in, for example, a circulative cooling system of a fast-breeder reactor, there has been generally used a mechanical-type vertical axial pump device in which an impeller attached to a longitudinal shaft is rotation-moved in a casing, to thereby transfer fluid, such as fluid metal, that is a cooling medium.

[0006] In this pump device, for the purposes of preventing impinging of the impeller on the casing or the like due to centrifugal whirling and/or earth quake, and suppressing vibration of the shaft, a journal bearing is arranged adjacently to the impeller of the shaft. As this journal bearing, there is often employed a sliding bearing. A shaft outer periphery is slid relative to a substantially cylindrical-shaped sleeve inner periphery of the sliding bearing while being lubricated via the fluid, whereby the rotational movement of the shaft is supported.

[0007] In the sliding bearing used in such a pump device, for the purpose of allowing thermal deformation and manufacturing tolerances of the shaft and casing, a gap between the shaft outer periphery and the bearing inner periphery is required to be increased relative to that in a general sliding bearing. Moreover, for the purpose of preventing the entrance of foreign material, fluid that can be used for the lubrication of the sliding bearing is limited to fluid of the same kind as the fluid to be transferred by the pump. In the pump device for the fast-breeder reactor, use of low-viscosity fluid metal or the like is required.

[0008] In the aforesaid situation, the sliding bearing itself which is used in the pump device is subjected to conditions where it is hard to obtain high dynamic pressure as compared to an oil lubricating sliding bearing used in a general mechanical device. Therefore, in order to stably support the shaft against high load even under such conditions, there has been often employed a hydrostatic pressure bearing structure in which high pressure fluid is introduced onto a sliding surface from the outside of the bearing and used to support a load.

[0009] Generally, in a journal bearing-type sliding bearing having the hydrostatic pressure bearing structure, several recess portions called "hydrostatic pressure pockets" are provided in a substantially circular cylindrical-shaped sleeve inner periphery in a circumferential direction or in a shaft axial direction and occupy the most part of the sleeve inner periphery. A passageway which communicates with an external pressure source is opened in each of the hydrostatic pressure pockets. High pressure fluid which is introduced via the passageways into the hydrostatic pressure pockets from the external pressure source fills hydrostatic pressure pocket interiors and a gap between the bearing and the shaft and flows to a low-pressure outside from an opened end portion of the gap.

[0010] If the shaft is radially pressed by a load and made eccentric in the bearing, a deviation of the gap is partially produced, so that the amount of fluid flowing out of a part of the gap present in an eccentric direction is reduced and pressure in the part rises, while the amount of fluid flowing out of a part of the gap present in a direction opposite to the eccentric direction is increased and pressure in the part drops. Pressure difference between both parts generates a restoring force tending to return the shaft to a center of the bearing, whereby the load of the shaft is supported.

[0011] In recent years, according to capacity enlargement of the pump device, demand has been raised for improving a load carrying capacity that is a supportable load for the sliding bearing, and a bearing rigidity that is a load carrying capacity change relative to a minimum gap change due to shaft eccentricity.

[0012] JP-A No. 61-236921 disclosing the background art in this technical field describes a hydrostatic pressure bearing which includes pockets in a bearing inner peripheral surface and in which high pressure oil is adapted to be supplied between the pockets and the outer peripheral surface of a rotating shaft. A plurality of pocket rows are formed in a circumferential direction arranged in an axial direction and the phases of the pockets between the respective rows are shifted in the circumferential direction.

[0013] According to the background art disclosed in JP-A No. 61-236921, the plurality of pocket rows in which the hydrostatic pressure pockets are formed in the circumferential direction is arranged in the axial direction and the phases of the pockets between the respective rows are shifted in the circumferential direction, whereby when the shaft is made eccentric in a certain radial direction, a force which acts in a radial direction perpendicular to this is cancelled and it can be anticipated that stability of the bearing at the time of high speed rotation is improved.

[0014] However, even if the phases of the hydrostatic pressure pockets are shifted in the circumferential direction and the pockets are merely arranged in the plurality of rows as described in the patent literature 1, this structure has little influence on the load carrying capacity and bearing rigidity of the bearing and it is hard for the structure to increase the load carrying capacity without increasing the pressure of an oil supplied from the outside, or without increasing the size of the bearing.

[0015] Moreover, JP-A No. 57-200699 describes a pump for fluid metal which is provided with a bearing for an impeller shaft, arranged just adjacently to an impeller provided between an inlet port and an outlet port in a casing and in which plural pockets are circumferentially arranged in a bearing inner surface and a portion of fuel metal pressed out by the impeller is introduced into the pockets, in which circumferential recess grooves that contain the fluid metal and allow the fluid metal to be present therein are provided in annular-band portions which axially interpose the pockets and are provided so as to be relatively-rotated with liquid sealing properties.

[0016] Moreover, JP-A No. 57-200699 describes a pump in which ring-shaped circumferential vacancies having the fluid metal always contained therein are additionally provided in annular-band portions which are provided so as to axially interpose the pockets constituting a hydrostatic pressure bearing for supporting the impeller and have liquid sealing properties.

[0017] According to the background art disclosed in JP-A No. 57-200699, the structure in which the circumferential recess grooves are provided in the annular-band portions that are provided so as to axially interpose the hydrostatic pressure pockets into which high pressure liquid metal is supplied from the outside is employed, whereby it is anticipated that even when metal contact is produced between the shaft and the bearing, the fluid metal is easy to be supplied to the circumference of the contacted portions and damage occurring due to seizure or the like is reduced by the effects of lubrication and cooling.

[0018] However, even if the circumferential recess grooves are provided in the annular-band portions as described in JP-A No. 57-200699, change in pressure distribution on a bearing inner periphery is small and the effects of improving the load carrying capacity and bearing rigidity of the bearing cannot be anticipated at all. Therefore, it is hard to improve the load carrying capacity without increasing the pressure of an oil supplied from the outside or without increasing the size of the bearing.

[0019] Moreover, JP-A No. 60-37329 describes a fluid bearing device in which a plurality of pressure generating band regions are formed in the circumferential direction of a bearing surface that supports an axial load and is provided at a bearing member fixed relative to a rotatable shaft member and each of the pressure generating band regions comprises a hydrostatic pressure generating portion including a pair of pockets formed so as to be axially spaced and having excretion mechanisms, a dynamic pressure generating portion including a land portion formed at a middle between the both pockets, and a supply groove formed along a side of the land which is parallel to axial lines of the both pockets, interconnecting the both pockets, and supplying pressure fluid to the both pockets via a throttle, and a bearing gap of the dynamic pressure generating portion is made smaller than a bearing gap of the hydrostatic pressure generating portion.

[0020] According to the fluid bearing device disclosed in JP-A No. 60-37329, it can be anticipated that in addition to the generation of hydrostatic pressure by the pressure fluid that is introduced into the external supply groove and also supplied to the pockets, the generation of the dynamic pressure in the dynamic pressure generating portion surrounded by the pockets and the supply groove can be also anticipated.

[0021] However, in the fluid bearing device disclosed in JP-A No. 60-37329, even if the dynamic pressure that is higher than the pressure of the pressure fluid supplied from the outside is produced in the dynamic pressure generating portion, the pressure is easy to escape through the supply groove and supporting by the dynamic pressure is restricted. Therefore, the load carrying capacity considerably depends upon the hydrostatic pressure.

[0022] Moreover, if the shaft is deformed or inclined to thereby make a certain part of the gap between the shaft and the bearing wider and an amount of fluid flowing out of the widened part of the gap is increased, an entire pressure in the pockets and the supply groove which communicate with each other is reduced and the load carrying capacity is easy to be lowered. In the vertical-type pump device, the shaft rotates in a state inclined relative to the bearing inner periphery in many cases. Therefore, it is difficult to apply the structures disclosed in the patent literatures to the vertical-type pumps or the like.

[0023] The present invention has been made with a view of the aforesaid background and it is an object of the present invention to provide a journal bearing-type sliding bearing provided with a hydrostatic pressure bearing structure in which high pressure fluid is supplied into a gap between an outer periphery of a shaft and an inner periphery of a substantially circular cylindrical shaped bearing from an outside and which supports rotational movement of the shaft, and a pump device having the sliding bearing enclosed, in which dynamic pressure produced in the gap at the time of rotation of the shaft is increased and utilized to the fullest, whereby it is possible to increase the load carrying capacity and bearing rigidity of the bearing without increasing a size of the bearing and the pressure of the fluid supplied from the outside.

SUMMARY OF THE INVENTION

[0024] In accordance with an aspect of the present invention, there is provided a sliding bearing which comprises a substantially circular cylindrical-shaped sleeve slidingly supporting a rotatable shaft via fluid in an inner periphery thereof, hydrostatic pressure supplying passages penetrating through the sleeve and supplying high pressure fluid into the sleeve inner periphery from an external pressure source, and hydrostatic pressure pockets provided in the inner periphery of the sleeve and having radially recessed shapes, the hydrostatic pressure supplying passages being opened in the hydrostatic pressure pockets, in which the hydrostatic pressure pockets constitute a plurality of rows of circumferentially disposed hydrostatic pressure pockets, at least one of the hydrostatic pressure pocket rows being arranged adjacently to each of both end portions of the inner periphery of the sleeve in an axial direction of the shaft, and a circular cylindrical inner peripheral surface region in which the hydrostatic pressure pockets are not present is provided at a center portion of the sleeve so as to be interposed between the hydrostatic pressure pocket rows.

[0025] In a sliding bearing according to a preferred embodiment of the present invention, a width of the circular cylindrical inner peripheral surface region without the hydrostatic pressure pockets which is provided in the axial direction of the shaft may be made wider than a sum of widths of the hydrostatic pressure pocket rows which is provided in the axial direction of the shaft.

[0026] In a sliding bearing according to a preferred embodiment of the present invention, hydrostatic pressure supplying passages communicating with hydrostatic pressure pockets belonging to the same hydrostatic pressure pocket row and hydrostatic pressure supplying passages communicating with hydrostatic pressure pockets belonging to a different hydrostatic pressure pocket row may be independently communicated with the pressure source supplying the high pressure fluid.

[0027] In a sliding bearing according to a preferred embodiment of the present invention, an arrangement-angle range of hydrostatic pressure pockets which extends in a circumferential direction may have a shape that is superposed on an arrangement-angle range of adjacent hydrostatic pressure pockets.

[0028] In a sliding bearing according to a preferred embodiment of the present invention, an arrangement-angle range of hydrostatic pressure pockets which extends in a circumferential direction may be located so as to be superposed on an arrangement-angle range of adjacent hydrostatic pressure pockets.

[0029] In a sliding bearing according to a preferred embodiment of the present invention, each of the hydrostatic pressure pockets may have a shape in which an outer side of the hydrostatic pressure pocket that is adjacent to an end portion of the sleeve extends to an upstream side relative to a rotational direction of the shaft as compared to an inner side of the hydrostatic pressure pocket that is remote from the end portion of the sleeve and the inner side of the hydrostatic pressure pocket that is remote from the end of the sleeve extends to a downstream side relative to the rotational direction of the shaft as compared to the outer side of the hydrostatic pressure pocket that is adjacent to the end portion of the sleeve.

[0030] In a sliding bearing according to a preferred embodiment of the present invention, a region of the sleeve inner periphery that has no hydrostatic pressure pockets may be formed with grooves in which the hydrostatic pressure supplying passages are not opened.

[0031] According to another aspect of the present invention, there is provided a pump device which comprises an impeller arranged at a midway of a fluid passage and transferring fluid according to rotational movement thereof, a shaft connected to an rotation power source and rotation-driving the impeller, a sliding bearing provided with a substantially circular cylindrical-shape sleeve slidingly supporting an outer peripheral surface of the shaft via the fluid, hydrostatic pressure supplying passages penetrating through the sleeve and supplying high pressure fluid into an inner periphery of the sleeve from an outlet side of the fluid passage.

[0032] The sliding bearing has hydrostatic pressure pockets which are provided in the inner periphery of the sleeve and have radially recessed shapes, the hydrostatic pressure supplying passages being opened in the hydrostatic pressure pockets, in which the hydrostatic pressure pockets constitute a plurality of rows of circumferentially disposed hydrostatic pressure pockets, at least one of the hydrostatic pressure pocket rows being arranged adjacently to each of both end portions of the inner periphery of the sleeve in an axial direction of the shaft, and a circular cylindrical inner peripheral surface region in which the hydrostatic pressure pockets are not present is provided at a center portion of the sleeve so as to be interposed between the hydrostatic pressure pocket rows.

[0033] In a pump device according to a preferred embodiment of the present invention, a width of the circular cylindrical inner peripheral surface region which is provided in an axial direction of the shaft may be made wider than a sum of widths of the hydrostatic pressure pocket rows which is provided in the axial direction of the shaft.

[0034] In a pump device according to a preferred embodiment of the present invention, hydrostatic pressure supplying passages communicating with hydrostatic pressure pockets belonging to a hydrostatic pressure pocket row and hydrostatic pressure supplying passages communicating with hydrostatic pressure pockets belonging to a different hydrostatic pressure pocket row may be independently communicated with the outlet side of the fluid passage.

[0035] In a pump device according to a preferred embodiment of the present invention, the fluid that flows through the fluid passage may be fluid metal.

[0036] According to the present invention, in the sliding bearing that comprises the substantially circular cylindrical-shaped sleeve slidingly supporting the rotatable shaft via fluid in the inner periphery thereof, the hydrostatic pressure supplying passages penetrating through the sleeve and supplying high pressure fluid into the sleeve inner periphery from the external pressure source, and the hydrostatic pressure pockets provided in the inner periphery of the sleeve and having radially recessed shapes, the hydrostatic pressure supplying passages being opened in the hydrostatic pressure pockets, the hydrostatic pressure pockets constitute the plurality of rows of circumferentially disposed hydrostatic pressure pockets, the at least one of the hydrostatic pressure pocket rows is arranged adjacently to each of both end portions of the inner periphery of the sleeve in the axial direction of the shaft, and the circular cylindrical inner peripheral surface region in which the hydrostatic pressure pockets are not present is provided at the center portion of the sleeve so as to be interposed between the hydrostatic pressure pocket rows.

[0037] Therefore, the shaft that is rotated in the inner periphery of the sleeve is supported by the hydrostatic pressure supplied in the hydrostatic pressure pockets from the outside and dynamic pressure produced on the circular cylindrical inner peripheral surface region. When the dynamic pressure is produced, large pressure is obtained as compared to the conventional example, and the loading capability and bearing rigidity of the entire sliding bearing can be increased.

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] FIG. 1 is a structure view of a vertical-type pump device according to an embodiment 1 of the present invention;

[0039] FIG. 2 is an enlarged view of a circumference of a sliding bearing in the vertical-type pump device according to the embodiment 1 of the present invention;

[0040] FIG. 3 is a perspective view of a sleeve in the sliding bearing according to the embodiment 1 of the present invention;

[0041] FIG. 4 is a graph showing a loading capability in the sliding bearing according to the embodiment 1 of the present invention;

[0042] FIG. 5 is a graph showing a bearing rigidity in the sliding bearing according to the embodiment 1 of the present invention;

[0043] FIG. 6 is a sectional view of a sliding bearing according to an embodiment 2 of the present invention;

[0044] FIG. 7 is a sectional view of a sliding bearing according to an embodiment 3 of the present invention;

[0045] FIG. 8 is a sectional view of a sliding bearing according to an embodiment 4 of the present invention;

[0046] FIG. 9 is a sectional view of a sliding bearing according to an embodiment 5 of the present invention; and

[0047] FIG. 10 is a sectional view of a sliding bearing according to an embodiment 6 of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0048] Embodiments of the present invention will be explained hereinafter with reference to the drawings.

Embodiment 1

[0049] An embodiment 1 of the present invention will be explained with reference to a vertical-type pump device 100 having a journal bearing-type sliding bearing according to the present invention incorporated therein.

[0050] FIG. 1 is a structure view of the vertical-type pump device 100 according to this embodiment. A passage 104 which communicates between an inlet port 102 and an outlet port 103 is formed in the interior of a casing 101. At the midway of the passage 104, an impeller 105 is provided at a tip end of a shaft 106 connected to an external rotation power source 107.

[0051] The shaft 106 is rotatably supported, on a side thereof adjacent to the rotation power source 107, by a bearing 108, and is rotatably supported, on a side thereof adjacent the impeller 105, by a sliding bearing 109. Supply of power from the rotation power source 107 causes the shaft 106 to be rotated to rotation-move the impeller 105, whereby fluid such as fluid metal which flows into an interior of the pump device 100 from the inlet port 102 is transferred through the passage 104 and then discharged out of the outlet port 103. Pressure head is produced at a downstream side of the passage 104 relative to the impeller 105, as compared to an upstream side of the passage 104 relative to the impeller 105, and pressure at the upstream side is increased.

[0052] The bearing 108 of the two bearings rotatably supports the shaft 106 and supports load produced in a vertical direction of FIG. 1, i.e., in an axial direction of the shaft 106. On the other hand, the sliding bearing 109 is fixed to a support portion 110 and suppresses centrifugal whirling of the shaft in a radial direction, to thereby suppress vibration produced according to the rotational movement of the shaft 106 and impeller 105, in addition to preventing impingement of the impeller 105 against a wall surface of the passage 104, the casing 101, etc.

[0053] FIG. 2 is an enlarged view of a circumference of a sliding bearing 109. In the sliding bearing 109, several hydrostatic pressure pockets 112A that have concavities recessed in the radial direction are formed in an inner periphery of a substantially circular cylindrical-shaped sleeve 111A. Hydrostatic pressure supplying passages 113 which penetrate through the support portion 110 and the sleeve 111A from the outlet port side of the passage 104 are opened in the respective hydrostatic pressure pockets 112A via orifices 114.

[0054] Thereby, portions of high pressure fluid that have been transferred to the downstream side of the passage 104 by the rotation of the impeller 105 pass through the hydrostatic pressure supplying passages 113 and the orifices 114, are introduced into the hydrostatic pressure pockets 112A, and fill a gap between the outer periphery of the shaft 106 and the inner periphery of the sleeve 111A.

[0055] The hydrostatic pressure pockets 112A constitute a plurality of rows of circumferentially disposed hydrostatic pressure pockets 112A in the inner periphery of the sleeve 111A. One row of hydrostatic pressure pockets is formed adjacently to each of the both end portions of the inner periphery of the sleeve 111A in the axial direction of the shaft 106. Moreover, a circular cylindrical inner peripheral surface region 115 in which a row of hydrostatic pressure pockets is not present is provided at a center portion of the inner periphery of the sleeve 111A so as to be interposed between the rows of hydrostatic pressure pockets.

[0056] FIG. 3 is a perspective view illustrating a detail of the sleeve 111A. The inner periphery of the sleeve 111A is provided at each of the both end portions thereof with the one row 116 of circumferentially disposed hydrostatic pressure pockets 112A, while the outer periphery of the sleeve 111A is provided with the hydrostatic pressure supplying passages 113.

[0057] A hydrostatic pressure supplying passage 113 communicating with one of the hydrostatic pressure pocket rows 116 and a hydrostatic pressure supplying passage 113 communicating with the other of the hydrostatic pressure pocket rows 116 are provided independently from each other and separately communicate with the downstream side of the passage 104 as also shown in FIG. 2.

[0058] The inventor of the present invention made the sliding bearing according to the present invention, performed an evaluation on loading capability and bearing rigidity, verified improvement effects of the loading capability and bearing rigidity by the application of the present invention, and investigated a relationship between the hydrostatic pressure pockets 112A capable of effectively achieving load reduction and effectively improving the bearing rigidity, and the circular cylindrical inner peripheral surface region 115 interposed by the hydrostatic pressure rows 116. Next, the results will be explained with reference to FIGS. 4 and 5.

[0059] FIG. 4 shows the loading capability of the bearing in a case where the pressure of the fluid supplied to the hydrostatic pressure pockets 112A is made constant and the widths of the hydrostatic pressure pockets 112A and the width of the circular cylindrical inner peripheral surface region 115 in the inner periphery of the sleeve 111A are varied. When the width of the circular cylindrical inner peripheral surface region 115 is increased relative to the sum of the widths of the hydrostatic pressure pocket rows 116 provided adjacently to the both ends of the sleeve 111A so as to interpose the circular cylindrical inner peripheral surface region 115 therebetween, the increase has resulted in particular in improvement of a loading capability increasing rate of the bearing as compared to a case of being equal to or lower than it.

[0060] FIG. 5 shows the bearing rigidity in the case where the pressure of the fluid supplied to the hydrostatic pressure pockets 112A is made constant and the widths of the hydrostatic pressure pockets 112A and the width of the circular cylindrical inner peripheral surface region 115 in the inner periphery of the sleeve 111A are varied. When the width of the circular cylindrical inner peripheral surface region 115 is increased relative to the sum of the widths of the hydrostatic pressure pocket rows 116 provided adjacently to the both ends of the sleeve 111A so as to interpose the circular cylindrical inner peripheral surface region 115 therebetween, the increase has resulted in particular in improvement of a bearing rigidity increasing rate as compared to a case of being equal to or lower than it.

[0061] When the hydrostatic pressure pockets rows 116 to be arranged adjacently to the both end portions of the inner periphery of the sleeve 111A and the circular cylindrical inner peripheral surface region 115 to be interposed between the hydrostatic pressure pocket rows 116 are formed, if the width of the circular cylindrical inner peripheral surface region 115 in the axial direction of the shaft 106 is increased, in this way, relative to the sum of the widths of the hydrostatic pressure pocket rows 116 interposing the circular cylindrical inner peripheral surface region, it has been verified that the load carrying capacity and the bearing rigidity can be more effectively increased.

Embodiment 2

[0062] The main purpose of providing the hydrostatic pressure pocket rows adjacently to the both end portions of the inner periphery of the sleeve lies in that pressure at the both ends of the circular cylindrical inner peripheral surface region arranged so as to be interposed between the hydrostatic pressure pocket rows is kept in a high state and a level of the dynamic pressure produced on the circular cylindrical inner peripheral surface region is kept.

[0063] FIG. 6 shows an embodiment 2 of a sleeve portion of a sliding bearing that more positively attains this purpose. Two hydrostatic pressure pocket rows 116 are arranged adjacently to each of the both end portions of the inner periphery of a sleeve 111B. In the two adjacent hydrostatic pressure pocket rows 116, hydrostatic pressure pockets 112B are arranged so as to be staggered in the circumferential direction.

[0064] A circular cylindrical inner peripheral surface region 115 in which the hydrostatic pressure pockets 112B are not present is formed at a center portion of the inner periphery of the sleeve 111B. The width of the circular cylindrical inner peripheral surface region 115 in the axial direction of the shaft 106 is wider than the sum of the widths of the four hydrostatic pressure pocket rows 116 interposing the circular cylindrical inner peripheral surface region 115 on the both sides thereof.

[0065] When such a structure is employed, at a circumferentially angular position in which the hydrostatic pressure pocket is not present in one hydrostatic pressure row 116, the hydrostatic pressure pockets 112B which belong to another adjacent hydrostatic pressure pocket row 116 are located, and the supply of the hydrostatic pressure by the hydrostatic pressure pockets 112B is uniformly successively performed in the whole circumferences of the both end portions of the sleeve 111B. Thereby, the pressure on the circular cylindrical inner peripheral surface region 115 is kept in a higher state and it is possible to provide high loading capability and bearing rigidity to the sliding bearing.

Embodiment 3

[0066] FIG. 7 shows an embodiment 3 of a sleeve portion of a sliding bearing which increases pressure on neighborhoods of the both end portions of a sleeve 111C, i.e., the both ends of the circular cylindrical inner peripheral surface region 115. Hydrostatic pressure pockets 112C have shapes asymmetrical in the circumferential direction and in the axial direction of the shaft 106. Hydrostatic pressure pocket-extending portions 117 are partially provided at the both ends of the hydrostatic pressure pockets 112C in the circumferential direction. Hydrostatic pressure pocket-extending portions 117 of a hydrostatic pressure pocket 112C are separated from hydrostatic pressure pocket-extending portions 117 of a circumferentially adjacent hydrostatic pressure pocket 112C but are partially superposed on them within a fixed circumferential arrangement-angle range.

[0067] Each hydrostatic pressure pocket 112C is formed with a hydrostatic pressure pocket-extending portion 117 extending to the upstream side of a rotational direction 118 of the shaft 106 on the outer side adjacent to the end portion of the sleeve 111C, and a hydrostatic pressure pocket-extending portion 117 extending to the downstream side of the rotational direction 118 of the shaft 106 on the inner side apart from the end portion of the sleeve 111C.

[0068] When such a structure is employed, the supply of the hydrostatic pressure by the hydrostatic pressure pockets 1120 is uniformly successively performed in the whole circumferences of the both end portions of the sleeve 111C. Thereby, the pressure on the circular cylindrical inner peripheral surface region 115 is kept in a high state and it is possible to provide high load carrying capacity and bearing rigidity to the bearing.

[0069] Moreover, small regions of the circumferential end portions of the hydrostatic pressure pockets 112C may be merely machined to thereby form the hydrostatic pressure pocket-extending portions 117, so that the manufacturing cost of this embodiment is reduced as compared to the embodiment of FIG. 6 in which the four hydrostatic pressure pocket rows in total are provided.

[0070] Moreover, the inner side of the sleeve 111C extends on the downstream side of the rotational direction of the shaft 106, so that a sucking force that tends to draw the fluid in the hydrostatic pressure pockets 112C toward the center side of the sleeve 111C acts according to the rotation of the shaft 106 and higher pressure is easy to be kept on the circular cylindrical inner peripheral surface region 115.

Embodiment 4

[0071] Similarly, FIG. 8 shows an embodiment 4 of a sleeve portion of a sliding bearing which increases pressure on neighborhoods of the both end portions of the inner periphery of a sleeve 111D, i.e., the both ends of a circular cylindrical inner peripheral surface region 115. Forming of hydrostatic pressure pockets 112D into rhombus shapes is performed in lieu of forming the hydrostatic pressure pocket-extending portions 117 at the hydrostatic pressure pockets 112D as in the embodiment shown in FIG. 7. The hydrostatic pressure pockets 112D are smoothly extended to the upstream side of the rotational direction 118 of the shaft 106, according to progressing toward the outer sides thereof that are adjacent to the end portions of the sleeve 111D, and are smoothly extended to the downstream side in the circumferential direction according to progressing toward the inner sides thereof that are remote from the end portions of the sleeve 111D.

[0072] When such a structure is employed, a sucking force that tends to draw the fluid in the hydrostatic pressure pockets 112D toward the center side of the sleeve 111D is easier to act as compared to the embodiment shown in FIG. 7, so that higher pressure is easy to be kept on the circular cylindrical inner peripheral surface region 115.

Embodiment 5

[0073] Moreover, FIG. 9 shows an embodiment in which foreign material discharging grooves 119 are formed in portions of the inner periphery of a sleeve 111E in which hydrostatic pressure pockets 112E are not present. The foreign material discharging grooves 119 are provided in a circular cylindrical inner peripheral surface region 115 occupying the center portion of the sleeve 111E, and regions of the both end portions of the sleeve 111E in which the hydrostatic pressure pockets 112E are not present. The foreign material discharging grooves 119 are grooves which are recessed in a radial direction different from a recessed direction of the hydrostatic pressure pockets 112E and in which the orifices 114 are not opened.

[0074] If any foreign material, wear particles, etc. flow into and remain in a gap between the outer periphery of the shaft 106 and the inner periphery of the sleeve 111E, the shaft 106 and/or the sleeve 111E may be subject to wear and/or damage. When the structure shown in FIG. 9 is employed, discharging of the foreign material, wear particles, etc. flowing into the gap between the outer periphery of the shaft 106 and the inner periphery of the sleeve 111E is facilitated.

[0075] The orifices 114 are not opened in the foreign material discharging grooves 119, and the foreign material discharging grooves 119 do not communicate directly with hydrostatic pressure supplying passages 113, so that dynamic pressure that is produced on the circular cylindrical inner peripheral surface region 115 escapes via the hydrostatic pressure supplying passages 113, resulting in less effect on the reduction in the pressure on the circular cylindrical inner peripheral surface region 115.

[0076] Moreover, the sizes of the foreign material, the wear particles, etc. flowing into the gap between the outer periphery of the shaft 106 and the inner periphery of the sleeve 111E are sizes at most equal to the size of the gap, so that the depths of the foreign material discharging grooves 119 may be also about equal to the size of the gap. Therefore, when the depths of the foreign material discharging grooves 119 are made about equal to the size of the gap, even if they extend up to the ends of the sleeve 111E, enlargement of clearance sectional areas in the end portions is small and escapement of the pressure through this route can be reduced.

[0077] Thereby, it is possible to configure a high reliable bearing in which the shaft 106 and/or the sleeve 111E is unlikely to be subject to damage due to the foreign material, the wear particles, etc., while providing high loading capability and bearing rigidity to the sliding bearing.

Embodiment 6

[0078] Moreover, FIG. 10 shows an embodiment 6 in which grooves 120 in which the orifices 114 are not opened are formed in the circular cylindrical inner peripheral surface region 115. Each groove 120 is extended, on the outer side thereof more adjacent to the end portion of a sleeve 111F, to the upstream side in the rotational direction 118 of the shaft 106, and is extended, on the inner side thereof away from the end portion of the sleeve 111F, to the downstream side in the rotational direction 118 of the shaft 106.

[0079] When such a structure is employed, a flow of the fluid is easy to become turbulence on the circular cylindrical inner peripheral surface region 115, or a sucking force that tends to draw the fluid toward the center portion of the sleeve 111F is easier to act according to the rotation of the shaft 106, so that an effect of generating dynamic pressure is increased.

[0080] Moreover, it is possible to configure a high reliable sliding bearing which may not be subject to the damage of the shaft 106 and/or sleeve 111F which occurs due to the accumulation of the foreign material, wear particles, etc. in the grooves 120.

[0081] As apparently noted from the above embodiments, the sliding bearing according to the present invention employs the structure in which the fixed circular cylindrical inner peripheral surface region is obtained at the center portion of the inner periphery of the sleeve and the hydrostatic pressure pocket rows are disposed at the both end portions of the sleeve so as to interpose the circular cylindrical inner peripheral surface region therebetween, whereby the pressure on the circular cylindrical inner peripheral surface region on which the dynamic pressure is produced at the time of the shaft rotation is increased and high pressure is kept by the circular cylindrical inner peripheral surface region, to thereby improve the loading capability and the bearing rigidity.

[0082] Moreover, the hydrostatic pressure supplying passages are independently provided at the both end portions of the sleeve and are separately communicated with the pressure source that can supply the adequate quantity of high pressure fluid, whereby the effect of the reduction of the pressure in the specific hydrostatic pressure pocket row on other pocket rows is restricted and high loading capability and bearing rigidity are obtained even if the shaft is brought to a state where it is inclined relative the inner periphery of the sleeve or deformed.

[0083] Moreover, the circular cylindrical inner peripheral surface region in the inner periphery of the sleeve is arranged so as to be interposed in the shaft axial direction by the hydrostatic pressure pocket rows, in which the pressure is higher than the pressure in the opened end portions of the sleeve, and the width of the circular cylindrical inner peripheral surface region is made wider than the sum of the widths of the hydrostatic pressure pocket rows that are provided in the shaft axial direction, whereby in addition to the increase in the pressure on the circular cylindrical inner peripheral surface region at the time of the shaft rotation, a ratio of dependency of the load carrying capacity on the pressure produced on the circular cylindrical inner peripheral surface region at the time of the eccentricity of the shaft is increased.

[0084] Therefore, even if the supply pressure from the outside is not increased, or even if the gap between the outer periphery of the shaft and the inner periphery of the sleeve is not made narrow, or even if the size of the sleeve is not increased, the loading capability and bearing rigidity of the entire sliding bearing can be effectively increased.

[0085] Moreover, according to the structure in which the hydrostatic pressure pocket rows are respectively provided adjacently to the both end portions of the sleeve, and the hydrostatic pressure supplying passages that are respectively communicated with the pocket rows are made independent from one another and connected to the pressure source capable of supplying the adequate quantity of high pressure, even if a specific part of the gap is widened by the inclination of the shaft and the pressure in the hydrostatic pressure pockets around the specific part of the gap is reduced.

[0086] The reduction does not effect on other hydrostatic pressure pocket rows, in addition to producing of a moment force tending to return the posture of the shaft to its original posture even if the shaft is inclined in the sleeve, so that it is possible to obtain high loading capability and bearing rigidity even at the time of the inclination of the shaft.

[0087] Moreover, the pump device according to the present invention has the structure which encloses the sliding bearing according to the present invention and supplies the pressure fluid to the hydrostatic pressure pockets from the outlet port side of the pump device, so that an additional pump device for supplying the pressure fluid to the hydrostatic pressure pockets is not required, thus making it possible to miniaturize the system.

[0088] Moreover, even if the gap between the outer periphery of the shaft and the inner periphery of the sleeve is made wider in a certain degree, or the shaft is inclined at a certain degree in the sleeve, it is possible to produce and keep, on the circular cylindrical inner peripheral surface region, the dynamic pressure higher than the pressure of the fluid supplied to the hydrostatic pressure pockets from the pump device.

[0089] Thereby, even in the large-sized pump device, in which the rotational movement of the shaft is required to be stably supported against the large thermal deformation, the manufacturing tolerances, etc., such as the vertical axial pump device used in the circulative cooling system of the fast breeder reactor, the high loading capability and bearing rigidity of the bearing can be obtained and the high reliability can be obtained.

[0090] For example, in the circulative cooling system of the fast breeder reactor, fluid such as liquid sodium or the like is often used as a cooling medium. In the pump device for transferring fluid metal, the same fluid metal is required to be used for lubrication in order that it is prevented from being mixed with other substances.

[0091] Generally, the fluid metal has a nature exhibiting a viscosity lower than that of a lubricating oil for a general machine or water at a high temperature, and is poor in lubricity.

[0092] Moreover, in the pump device, in addition to the requirement of making the shaft for rotating the impeller longitudinal in order to provide a shielding portion for radiation, it is hard to avoid the inclination and deformation of the shaft in a certain degree due to the thermal deformation and/or manufacturing tolerance since the pump device handles high temperature fluid metal.

[0093] In the pump device according to the present invention, the fluid that is brought into the high pressure by the impeller of the pump device is supplied to the hydrostatic pressure pockets of the sliding bearing enclosed, so that other substances may not get mixed with the cooling medium in the pump device.

[0094] Moreover, according to the structure in which the fixed circular cylindrical inner peripheral surface region is obtained at the center of the sleeve inner periphery in the sliding bearing and the hydrostatic pressure pocket rows are arranged at the both end portions of the sleeve so as to interpose the circular cylindrical inner peripheral surface region, the pressure on the circular cylindrical inner peripheral surface region on which the dynamic pressure is produced at the time of the shaft rotation is increased and the high pressure is kept by the circular cylindrical inner peripheral surface region, whereby it is possible to obtain the high load carrying capacity and bearing rigidity even in the case where a low viscosity fluid such as fluid metal which is poor in lubricity is used.

[0095] The load carrying capacity of the sliding bearing considerably depends upon the dynamic pressure particularly at the time when the shaft is made eccentric and it is unnecessary to externally install any device for particularly increasing the pressure of the fluid supplied to the bearing, in order to obtain the loading capability. Therefore, it is possible to make the pump device simple and small-sized.

[0096] Moreover, even if the gap between the shaft outer periphery and the sleeve inner periphery is made relatively wide, or in the case where the shaft is brought to the posture inclined relative to the sleeve inner periphery or deformed, the high loading capability and bearing rigidity are obtained, so that the thermal deformation and/or tolerance at the time of manufacturing are allowed and the stable supporting of the shaft rotation is performed.

[0097] Moreover, the hydrostatic pressure pockets are arranged adjacently to the end portions of the sleeve inner periphery, so that even in a case where excessive load acts on the shaft and the shaft that is inclined relative to the neighborhoods of the end portions of the sleeve inner periphery is directly brought into contact with the sleeve inner periphery, the fluid is supplied to the circumference to perform cooling and lubrication, thus making it to reduce damage due to wearing and/or seizure.

Claims

1. A sliding bearing comprising a substantially circular cylindrical-shaped sleeve slidingly supporting a rotatable shaft via fluid in an inner periphery thereof, hydrostatic pressure supplying passages penetrating through the sleeve and supplying high pressure fluid into the sleeve inner periphery from an external pressure source, and hydrostatic pressure pockets provided in the inner periphery of the sleeve and having radially recessed shapes, the hydrostatic pressure supplying passages being opened in the hydrostatic pressure pockets, wherein the hydrostatic pressure pockets constitute a plurality of rows of circumferentially disposed hydrostatic pressure pockets, at least one of the hydrostatic pressure pocket rows being arranged adjacently to each of both end portions of the inner periphery of the sleeve in an axial direction of the shaft, and a circular cylindrical inner peripheral surface region in which the hydrostatic pressure pockets are not present is provided at a center portion of the sleeve so as to be interposed between the hydrostatic pressure pocket rows.

2. The sliding bearing according to claim 1, wherein a width of the circular cylindrical inner peripheral surface region without the hydrostatic pressure pockets provided in the axial direction of the shaft is made wider than a sum of widths of the hydrostatic pressure pocket rows provided in the axial direction of the shaft.

3. The sliding bearing according to claim 1, wherein hydrostatic pressure supplying passages communicating with hydrostatic pressure pockets belonging to the same hydrostatic pressure pocket row and hydrostatic pressure supplying passages communicating with hydrostatic pressure pockets belonging to a different hydrostatic pressure pocket row are independently communicated with the pressure source supplying the high pressure fluid.

4. The sliding bearing according to claim 1, wherein an arrangement-angle range of hydrostatic pressure pockets which extends in a circumferential direction has a shape that is superposed on an arrangement-angle range of adjacent hydrostatic pressure pockets.

5. The sliding bearing according to claim 1, wherein an arrangement-angle range of hydrostatic pressure pockets which extends in a circumferential direction is located so as to be superposed on an arrangement-angle range of adjacent hydrostatic pressure pockets.

6. The sliding bearing according to claim 1, wherein each of the hydrostatic pressure pockets has a shape in which an outer side of the hydrostatic pressure pocket that is adjacent to an end portion of the sleeve extends to an upstream side relative to a rotational direction of the shaft as compared to an inner side of the hydrostatic pressure pocket that is remote from the end portion of the sleeve and the inner side of the hydrostatic pressure pocket that is remote from the end of the sleeve extends to a downstream side relative to the rotational direction of the shaft as compared to the outer side of the hydrostatic pressure pocket that is adjacent to the end portion of the sleeve.

7. The sliding bearing according to claim 1, wherein a region of the sleeve inner periphery that has no hydrostatic pressure pockets is formed with grooves in which the hydrostatic pressure supplying passages are not opened.

8. A pump device comprising an impeller arranged at a midway of a fluid passage and transferring fluid according to rotational movement thereof, a shaft connected to an rotation power source and rotation-driving the impeller, a substantially circular cylindrical-shape sleeve slidingly supporting an outer peripheral surface of the shaft via the fluid, hydrostatic pressure supplying passages penetrating through the sleeve and supplying high pressure fluid into an inner periphery of the sleeve from an outlet side of the fluid passage, and a sliding bearing having hydrostatic pressure pockets which are provided in the inner periphery of the sleeve and have radially recessed shapes, the hydrostatic pressure supplying passages being opened in the hydrostatic pressure pockets, wherein the hydrostatic pressure pockets constitute a plurality of rows of circumferentially disposed hydrostatic pressure pockets, at least one of the hydrostatic pressure pocket rows being arranged adjacently to each of both end portions of the inner periphery of the sleeve in an axial direction of the shaft, and a circular cylindrical inner peripheral surface region in which the hydrostatic pressure pockets are not present is provided at a center portion of the sleeve so as to be interposed between the hydrostatic pressure pocket rows.

9. The pump device according to claim 8, wherein a width of the circular cylindrical inner peripheral surface region which is provided in an axial direction of the shaft is made wider than a sum of widths of the hydrostatic pressure pocket rows which is provided in the axial direction of the shaft.

10. The pump device according to claim 8, wherein hydrostatic pressure supplying passages communicating with hydrostatic pressure pockets belonging to a hydrostatic pressure pocket row and hydrostatic pressure supplying passages communicating with hydrostatic pressure pockets belonging to a different hydrostatic pressure pocket row are independently communicated with the outlet side of the fluid passage.

11. The pump device according to claim 8, wherein the fluid that flows through the fluid passage is fluid metal.