Bearing

Abstract

Provided is a bearing having high slidability.　A bearing 5 is disposed on at least one among a substrate 2 and a rotating body 3 that rotates relative to the substrate 2, and the bearing 5 receives a thrust load between the substrate and the rotating body. A sliding surface 51 of the bearing 5 is provided with dynamic pressure generating grooves 10 for generating dynamic pressure by means of a surrounding fluid during the relative rotation.

Description

bearings

[0001] The present invention relates to a bearing, for example, a bearing that is disposed between a base material and a rotating body and supports a load in a thrust direction.

[0002] A radial bearing and a thrust bearing that rotatably support a rotating shaft of a rotary machine are arranged around the rotating shaft. For example, the bearings shown in Patent Document 1 are provided in a screw compressor. The screw compressor has a housing having an inlet and a discharge port, and a drive rotor and a driven rotor arranged in the housing. The drive rotor and the driven rotor each have spiral teeth that mesh with each other to rotate relative to each other. The rotation of each rotor pressurizes a pressurized fluid supplied from the inlet and sends it to the discharge port.

[0003] Both ends of each rotor are supported by bearings. The bearing at the end of each rotor on the discharge port side functions as a radial bearing, and the bearing at the end of each rotor on the suction port side functions as both a radial bearing and a thrust bearing. Each rotor moves toward the suction port due to the pressure difference between the pressurized high-pressure pressurized fluid and the low-pressure pressurized fluid before pressurization, but the thrust bearing can support the load in the thrust direction.

[0004] Japanese Patent Application Laid-Open No. 5-195972 (page 3, Figure 1)

[0005] However, with the bearing of Patent Document 1, as the rotational speed of each rotor increases and the pressure difference between the pressurized fluid on the discharge port side and the suction port side increases, the thrust load increases, resulting in an increase in the frictional force between the thrust bearing and each rotor.

[0006] The present invention has been made in view of these problems, and has as its object to provide a bearing with high sliding properties.

[0007] In order to solve the above problems, the bearing of the present invention is a bearing that is disposed on at least one of a substrate and a rotating body that rotates relative to the substrate, and receives a thrust load between the substrate and the rotating body, and the sliding surface of the bearing is provided with dynamic pressure generating grooves that generate dynamic pressure with a surrounding fluid during relative rotation.With this, the dynamic pressure generated by the dynamic pressure generating grooves can float the sliding surface and the other of the substrate and the rotating body in the axial direction, thereby improving the slidability between the sliding surface and the other of the substrate and the rotating body.

[0008] The dynamic pressure generating grooves may be in communication with a space where fluid exists on the outer diameter side of the sliding surface, thereby enabling the fluid to be efficiently introduced into the dynamic pressure generating grooves.

[0009] The dynamic pressure generating groove may be spiral in shape, which allows dynamic pressure to be generated efficiently.

[0010] The land of the sliding surface may be a flat surface, which allows dynamic pressure to be generated efficiently.

[0011] The bearing may be attached to one of the base material and the rotating body via an elastic member. In this case, when the bearing comes into contact with the base material or the rotating body, the elastic member can absorb the impact, thereby preventing damage to the bearing. In addition, the deformation of the elastic member makes it easier to maintain the parallelism of the sliding surfaces.

[0012] The elastic member may be a cup gasket fitted onto the bearing, and the bearing onto which the cup gasket is fitted may be fitted into a recess provided in one of the base material and the rotating body, thereby preventing damage to the bearing due to contact between the bearing and the side surface of the recess.

[0013] A bearing that slides relative to the bearing attached to one of the base material and the rotating body may be attached to the other of the base material and the rotating body. In this way, the pair of bearings slide relative to each other, resulting in excellent wear resistance.

[0014] The sliding surface and the other opposing surface of the substrate and the rotating body may be curved and fitted with each other in a concave-convex manner. This allows the axes of the substrate and the rotating body to be aligned. Dynamic pressure can be applied over a wide area between the sliding surface and the opposing surface.

[0015] Fig. 1 is a cross-sectional view showing a twin-screw compressor to which a bearing according to a first embodiment of the present invention is applied. Fig. 2 is an enlarged cross-sectional view of a main part showing the peripheral structure of the bearing according to the first embodiment. Fig. 3 is a view of the bearing from the axial direction. Fig. 4 is a schematic view showing a state in which dynamic pressure is generated in dynamic pressure generating grooves during relative rotation. Fig. 5 is an enlarged cross-sectional view of a main part showing the peripheral structure of a bearing according to a second embodiment of the present invention. Fig. 6 is an enlarged cross-sectional view of a main part showing the peripheral structure of a bearing according to a third embodiment of the present invention. (a) is a view of a bearing according to a fourth embodiment of the present invention from the axial direction, and (b) is a cross-sectional view taken along the line A-A in (a).

[0016] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A bearing according to the present invention will be described below with reference to the following examples.

[0017] A bearing according to a first embodiment will be described with reference to Figures 1 to 4. In this embodiment, a bearing applied to a fluid pump 1 will be described. In the description, the left and right sides of the page in Figure 1 correspond to the left and right sides of the fluid pump, and the top and bottom of the page correspond to the top and bottom sides of the fluid pump.

[0018] The fluid pump 1 of the first embodiment is a device that pressurizes a pressurized fluid such as air, oil, or refrigerant and sends it to downstream equipment, and is used in fields such as automobiles and general industrial machinery.

[0019] As shown in FIG. 1, the bearing structure of the fluid pump 1 is mainly composed of a housing 2 as a base material, a disk 3 and a rotating shaft 4 as rotating bodies, a first bearing 5, a second bearing 6, and multiple cup gaskets 7, 7′ (see FIG. 2) as elastic members.

[0020] The housing 2 is composed of a cylindrical main body member 21 with a bottom that opens on the left side, and a lid member 22 that closes the left opening of the main body member 21. A through hole 21a is provided in the bottom of the main body member 21. A space is formed within the housing 2 to accommodate the disc 3 in a rotatable manner.

[0021] A first bearing 5, which will be described later, is attached to the right side of the cover member 22, i.e., to the bottom of the housing 2. This first bearing 5 is a thrust bearing.

[0022] The disk 3 is fixed to the left end of the rotating shaft 4, which is inserted through the through-hole 21a of the housing 2. The rotating shaft 4 is inserted through the through-hole 21a of the housing 2 with some axial movement permitted. The rotating shaft 4 extends to the right side of the housing 2 and is connected to a driving means and an impeller (not shown). The rotating shaft 4 is supported by a radial bearing 8 disposed in the through-hole 21a.

[0023] A second bearing 6 (described later) is attached to the left end of the disk 3. The second bearing 6 is a thrust bearing and faces the first bearing 5.

[0024] As the rotating shaft 4 and disk 3 rotate, the fluid is pressurized by the impeller and transported downstream. The pressurized fluid flows into the housing 2 through the gap between the rotating shaft 4 and the inner surface of the housing 2 that defines the through-hole 21a. However, because the gap between the rotating shaft 4 and the inner surface of the housing 2 is small, when the fluid pump 1 is operating, the space on the impeller side (i.e., the space to the right of the housing 2) may become higher in pressure than the space within the housing 2. This pressure difference causes the disk 3 and rotating shaft 4 to move axially leftward. At this time, the thrust load acting from the disk 3 and rotating shaft 4 toward the cover member 22 of the housing 2 is supported by the first bearing 5 and second bearing 6, which face each other.

[0025] Next, the first bearing 5 will be described with reference to Figures 2 to 4. For the sake of convenience, the hydrodynamic grooves 10 are not shown in Figures 2 and 4.

[0026] As shown in FIGS. 2 and 3, the first bearing 5 is a ceramic molded product that is a low-friction member, and is formed in a substantially cylindrical shape.

[0027] As shown in FIG. 3, a plurality of dynamic pressure generating grooves 10 (nine in this embodiment) are arranged at equal intervals in the circumferential direction on the sliding surface 51 of the first bearing 5 .

[0028] The dynamic pressure generating groove 10 is a spiral groove that extends at an angle in the circumferential direction from the outer diameter side toward the inner diameter side of the first bearing 5. An outer diameter end 11 of this dynamic pressure generating groove 10 communicates with the space on the outer diameter side of the first bearing 5, i.e., the space inside the housing 2. An inner diameter end 12 of the dynamic pressure generating groove 10 has a shape that tapers toward the inner diameter side. The land 52 other than the dynamic pressure generating groove 10 on the sliding surface 51, more specifically the central circular portion and the portion between the dynamic pressure generating grooves 10, is a flat surface of the same height.

[0029] Returning to Figure 2, the first bearing 5 is attached to a recess 22b provided in an end surface 22d of the cover member 22 via a cup gasket 7. The cup gasket 7 is made of rubber. The cup gasket 7 is fitted onto the rear side, i.e., the left side, of the first bearing 5. Note that the cup gasket 7 is not limited to being made of rubber, and may be made of an elastic material such as synthetic resin.

[0030] A plurality of protrusions 7c protruding in the radially outward direction are formed on the outer peripheral surface of the side wall 7a of the cup gasket 7. The protrusions 7c fit into holes 22c formed in the side wall of the recess 22b, preventing the cup gasket 7 from falling out of the recess 22b and rotating in the circumferential direction.

[0031] When the first bearing 5 with the cup gasket 7 fitted thereon is attached to the recess 22 b of the cover member 22 , the sliding surface 51 is located to the right of the end surface 22 d of the cover member 22 .

[0032] Next, the second bearing 6 will be described.

[0033] 2, the second bearing 6 is a ceramic molded product that is a low-friction member and has a substantially cylindrical shape. A land 62 of a sliding surface 61 of the second bearing 6 is a flat surface.

[0034] This second bearing 6 is attached to a recess 32 provided in an end face 31 of the disk 3 via a cup gasket 7'. The cup gasket 7' has the same configuration as the aforementioned cup gasket 7. The cup gasket 7' is fitted onto the back side of the second bearing 6, i.e., onto the right side.

[0035] When the second bearing 6 fitted with the cup gasket 7 ′ is attached to the recess 32 of the disk 3 , the sliding surface 61 is located to the left of the end surface 31 of the disk 3 .

[0036] The first bearing 5 and the second bearing 6 are not limited to being made of ceramics, but may be made of SiC (hard material) or a combination of SiC (hard material) and carbon (soft material). Any sliding material used as a sliding material for thrust bearings can be used. Examples of SiC include sintered bodies using boron, aluminum, carbon, or other sintering aids, as well as materials consisting of two or more phases with different components and compositions, such as SiC with dispersed graphite particles, reaction-sintered SiC consisting of SiC and Si, SiC-TiC, and SiC-TiN. Examples of carbon include a mixture of carbonaceous and graphitic materials, resin-molded carbon, and sintered carbon. In addition to the above sliding materials, metal materials, resin materials, surface-modified materials (coating materials), composite materials, and the like can also be used.

[0037] Next, the states of the first bearing 5 and the second bearing 6 when the disk 3 is not rotating and when it is rotating will be described.

[0038] As shown in FIG. 2, when the disk 3 is not rotating, the sliding surface 51 of the first bearing 5 and the sliding surface 61 of the second bearing 6 are in contact with each other in the axial direction.

[0039] 3 and 4 , when the disk 3 rotates, the pressurized fluid in the dynamic pressure generating grooves 10 moves in the rotational direction of the second bearing 6 due to shear with the sliding surface 61. As a result, dynamic pressure is generated at the inner diameter end 12 of the dynamic pressure generating grooves 10, and the pressurized fluid in the housing 2 is introduced into the dynamic pressure generating grooves 10 from the outer diameter end 11.

[0040] The dynamic pressure generated at the inner diameter end 12 of the dynamic pressure generating groove 10 generates a force that moves the sliding surface 51 of the first bearing 5 and the sliding surface 61 of the second bearing 6 apart in the axial direction. As a result, the sliding surfaces 51 of the first bearing 5 and the sliding surfaces 61 of the second bearing 6 are slightly separated and do not come into contact with each other, or the thrust force acting between the sliding surfaces 51 of the first bearing 5 and the sliding surfaces 61 of the second bearing 6 is reduced, thereby improving slidability.

[0041] The dynamic pressure generated in the dynamic pressure generating groove 10 is highest at the inner diameter end 12 and gradually decreases toward the outer diameter side (see FIG. 4).

[0042] As explained above, the first bearing 5 is provided with dynamic pressure generating grooves 10, which generate dynamic pressure using the surrounding pressurized fluid during relative rotation, so that the sliding surface 51 of the first bearing 5 can be raised from the opposing sliding surface 61 of the second bearing 6, thereby improving the sliding properties between the sliding surfaces 51, 61. Furthermore, because the sliding surface 51 is raised from the sliding surface 61 using the pressurized fluid to be pressurized, there is no need to use a lubricating fluid, such as oil, separate from the pressurized fluid, and mixing of the pressurized fluid and the lubricating fluid can be avoided.

[0043] Furthermore, since the dynamic pressure generating grooves 10 communicate with the space in which the pressurized fluid exists, the pressurized fluid can be introduced efficiently, resulting in high dynamic pressure generating capacity.

[0044] Furthermore, the dynamic pressure generating groove 10 extends from the outer diameter side to the inner diameter side, and dynamic pressure is generated when the pressurized fluid moves to the center of the first bearing 5. Therefore, when the sliding surfaces 51, 61 are separated, the pressurized fluid between the sliding surfaces 51, 61 is less likely to escape to the outer diameter side, making it easier to maintain the state in which the sliding surfaces 51, 61 are separated.

[0045] Furthermore, since the dynamic pressure generating grooves 10 have a spiral shape extending downstream in the relative rotation direction of the sliding surfaces 51, 61, the pressurized fluid can easily move along the dynamic pressure generating grooves 10, thereby generating dynamic pressure efficiently. Furthermore, since the inner diameter ends 12 of the dynamic pressure generating grooves 10 are tapered in the extending direction, dynamic pressure can be generated even more efficiently.

[0046] Furthermore, since the land 52 of the sliding surface 51 is a flat surface existing on the same plane, it is possible to generate dynamic pressure more efficiently than with an uneven land. Furthermore, the sliding properties between the sliding surfaces 51 and 61 are stabilized.

[0047] Furthermore, the first bearing 5 and the second bearing 6 are made of ceramics, and therefore have excellent wear resistance.

[0048] Furthermore, the first bearing 5 is attached to the cover member 22 of the housing 2 via a cup gasket 7. With this, when the sliding surfaces 51, 61 come into contact with each other after the rotation of the disk 3 and the rotating shaft 4 has stopped, the cup gasket 7 can absorb the impact, preventing damage to the first bearing 5 and the second bearing 6, which are made of ceramics and are vulnerable to impacts. Furthermore, the elastic deformation of the cup gasket 7 makes it easy to maintain the parallelism of the sliding surfaces 51, 61.

[0049] Furthermore, since the cup gasket 7 is made of rubber with a high coefficient of friction, slippage between the cup gasket 7 and the housing 2, and between the cup gasket 7 and the first bearing 5 is suppressed, and co-rotation of the sliding surfaces 51, 61 can be restricted.

[0050] Furthermore, a cup gasket 7 is fitted onto the outside of the first bearing 5, preventing direct contact between the side surface forming the recess 22b of the housing 2 and the outer circumferential surface of the first bearing 5. In other words, because the cup gasket 7 is interposed between the recess 22b of the housing 2 and the first bearing 5, damage to the ceramic first bearing 5 can be prevented.

[0051] Furthermore, since the cup gasket 7' is also interposed between the second bearing 6 and the recess 32 of the disk 3, the same effect as above can be obtained.

[0052] Furthermore, since the first bearing 5 and the second bearing 6 are attached to the recess 22b of the housing 2 and the recess 32 of the disk 3, radial displacement is restricted, and the sliding surfaces 51, 61 can be maintained in a state in which they can slide relative to each other appropriately.

[0053] In this embodiment, the first bearing 5 and the second bearing 6 have the same diameter, but this is not limiting and they may have different diameters. Furthermore, the first bearing 5 and the second bearing 6 are not limited to being circular when viewed in the axial direction, and may be polygonal or elliptical when viewed in the axial direction, and the shapes can be freely changed.

[0054] Furthermore, although the inner diameter end of the dynamic pressure generating groove may extend to the center of the sliding surface, in order to efficiently exert the so-called "wedge effect" in which the pressurized fluid is introduced into the narrow gap between the sliding surfaces, it is preferable to leave a land in the center of the sliding surface and ensure that dynamic pressure is generated at the tip of the dynamic pressure generating groove, as in this embodiment.

[0055] Next, a bearing according to a second embodiment will be described with reference to Fig. 5. Note that the description of the same configuration as in the first embodiment will be omitted.

[0056] 5, the first bearing 250 has a sliding surface 251 that is concavely curved in cross section and circular when viewed in the axial direction, while the second bearing 260 has a sliding surface 261 that is convexly curved in cross section and circular when viewed in the axial direction.

[0057] The sliding surfaces 251 and 261 are fitted together in a concave-convex manner so as to be able to slide relative to each other. This allows the axes of the first bearing 250 and the second bearing 260 to be aligned when they rotate relative to each other, thereby maintaining a state in which the sliding surfaces 251 and 261 can slide relative to each other appropriately.

[0058] Furthermore, dynamic pressure can be generated between the sliding surfaces 251, 261, and the pressurized fluid between the sliding surfaces 251, 261 is less likely to escape to the outer diameter side, so the dynamic pressure generation effect is high.

[0059] Furthermore, since the sliding surfaces 251, 261 are curved, it is possible to ensure a wide sliding surface 251, 261, which enhances the dynamic pressure generation effect. Also, it is easy to smoothly align the axes of the first bearing 250 and the second bearing 260.

[0060] In this second embodiment, the sliding surface 251 is a concavely curved surface in cross section, and the sliding surface 261 is a convexly curved surface in cross section, but the sliding surface of the first bearing may be a convexly curved surface in cross section, and the sliding surface of the second bearing may be a concavely curved surface in cross section.

[0061] In addition, in Example 2, the sliding surface with a convex cross section and the sliding surface with a concave cross section are fitted together in a concave-convex manner, but this is not limited to this, and for example, a concave section with a rectangular cross section may be provided on one of the base material or the rotating body, and a convex section with a rectangular cross section may be provided on the other, and these may be fitted together in a concave-convex manner in the axial direction, with their flat bottom surfaces sliding relative to each other. Even in this case, the respective axes can be kept aligned.

[0062] Next, a bearing according to a third embodiment will be described with reference to Fig. 6. Note that the description of the same configuration as in the first embodiment will be omitted.

[0063] 6, a sliding surface 351 of a first bearing 350 of the third embodiment is configured to slide relative to an end surface 303a of a drive rotor 303. In other words, a second bearing is not attached to the drive rotor 303 side.

[0064] The bearing is not limited to being attached to the substrate, but may be attached to the rotating body, that is, it is sufficient that the bearing is attached to at least one of the substrate and the rotating body.

[0065] Furthermore, the third embodiment may be applied to the second embodiment.

[0066] Next, a bearing according to a fourth embodiment will be described with reference to Fig. 7. Note that the description of the same configuration as in the first embodiment will be omitted.

[0067] As shown in FIG. 7, the first bearing 450 of the fourth embodiment is composed of a base portion 450A and a sliding portion 450B.

[0068] The base portion 450A has a generally hexagonal shape when viewed in the axial direction. The sliding portion 450B has a generally cylindrical shape and is provided on the right side of the base portion 450A. The right surface of the sliding portion 450B serves as a sliding surface 451.

[0069] A recess 422b having a generally hexagonal shape when viewed in the axial direction is formed in the bottom 422 of the housing 420. A base 450A of a first bearing 450, on which a cup gasket 470 is fitted, is fitted in this recess 422b.

[0070] According to this, by fitting the recess 422b into the base 450A, when the first bearing 450 slides against the opposing surface of the other side, it is possible to reliably prevent the first bearing 450 from rotating together with the opposing surface of the other side.

[0071] In the fourth embodiment, the base portion 450A has a generally hexagonal shape when viewed in the axial direction, but this is not limited thereto, and may have any shape other than a circular shape when viewed in the axial direction, such as a polygonal shape or an elliptical shape when viewed in the axial direction. The shape of the sliding portion 450B may also be freely changed.

[0072] Furthermore, in this Example 4, an example was given of a configuration in which the first bearing 450 is composed of a base portion 450A and a sliding portion 450B, but for example, the first bearing may be composed of a hexagonal prism, the right surface of which may be used as the sliding surface.

[0073] Although the fourth embodiment exemplifies the configuration in which the base 450A and the sliding portion 450B are made of the same material, they may be made of different materials. For example, the sliding portion may be made of a highly wear-resistant ceramic, and the base may be made of a highly rigid metal.

[0074] Although the embodiments of the present invention have been described above with reference to the drawings, the specific configuration is not limited to these embodiments, and the present invention also includes modifications and additions that do not deviate from the gist of the present invention.

[0075] For example, in the first to fourth embodiments, the bearing is applied to a fluid pump, but the present invention is not limited to this and may be applied to a screw compressor or the like. Furthermore, the rotating body is not limited to a disk and can be freely changed. Furthermore, the bearing is not limited to a pump and may be applied to a compressor or the like.

[0076] Furthermore, in the first to fourth embodiments, the opposing surface facing the sliding surface of the bearing is a flat surface, but for example, dynamic pressure generating grooves may be formed on the opposing surface.

[0077] Furthermore, in Examples 1 to 4, the dynamic pressure generating grooves are spiral grooves, but this is not limited to this and may be Rayleigh steps or dimples, or may be arc grooves extending in the circumferential direction.

[0078] The pressurized fluid may be liquid or gas, or may be a mist of a mixture of liquid and gas.

[0079] In addition, in the above-described Examples 1 to 4, the elastic member is a cup gasket, but it may be a sheet-like elastic member, etc. It is preferable that the elastic member is disposed at least between the back surface of the bearing and the end surface of the base material or the rotating body.

[0080] Furthermore, in the first to fourth embodiments, the bearings are disposed in the recesses of the substrate or the rotor, but the bearings may be attached to a flat surface.

[0081] Furthermore, in the above-described Examples 1 to 4, the substrate is in a stationary state, but the substrate and the rotating body may both rotate in the relative rotation direction.

[0082] REFERENCE SIGNS LIST 1 fluid pump 2 housing (base material) 3 disk (rotating body) 4 rotating shaft (rotating body) 5 first bearing (bearing) 6 second bearing (other bearing) 7, 7' cup gasket (elastic member) 10 dynamic pressure generating groove 11 outer diameter end 12 inner diameter end 22b recess 32 recess 51 sliding surface 61 sliding surface (opposing surface) 52, 62 lands

Claims

1. A bearing that is disposed on at least one of a base material and a rotating body that rotates relative to the base material, and that bears the thrust load between the base material and the rotating body, wherein the sliding surface of the bearing is provided with dynamic pressure generating grooves that generate dynamic pressure with the surrounding fluid during relative rotation.

2. A bearing according to claim 1, wherein the hydrodynamic grooves communicate with a space on the outer diameter side of the sliding surface where fluid is present.

3. A bearing according to claim 1, wherein the hydrodynamic grooves are spiral-shaped.

4. A bearing according to claim 1, wherein the land of said sliding surface is a flat surface.

5. The bearing according to claim 1, wherein the bearing is attached to one of the base material and the rotating body via an elastic member.

6. A bearing as set forth in claim 5, wherein the elastic member is a cup gasket fitted onto the outside of the bearing, and the bearing onto which the cup gasket is fitted is fitted into a recess provided in one of the base material and the rotating body.

7. A bearing according to claim 5, wherein the other of said base material and said rotating body is fitted with another bearing that slides relative to the bearing fitted to one of said base material and said rotating body.

8. The bearing according to claim 1, wherein the sliding surface and the opposing surface of the other of the base material and the rotating body are curved surfaces that fit together in a concave-convex manner.

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