Standby pump and bearing device

Abstract

To prevent bearing seizure during pre-standby operation and to suppress the occurrence of excessive vibration during drainage operation.SOLUTION: A submerged bearing device 7 of the present embodiment includes: a sliding member 9 that is installed with a clearance on an outer peripheral side of a rotating shaft 5; a back metal 10 that holds the sliding member 9; a buffer member 11 that flexibly supports the back metal 10 in circumferential and radial directions; and a bearing housing 12 that holds the buffer member 11. The back metal 10 and the bearing housing 12 have contact portions 13 that abut on each other in the radial direction, and are configured such that a radial clearance δ of the contact portions 13 increases due to circumferential displacement of the back metal 10.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a standby pump and a bearing device suitable for preventing bearing burnout during standby operation and excessive vibration during drainage operation. [Background technology]

[0002] Patent Document 1 describes a standby pump equipped with a rotating shaft having an impeller fixed to its lower end and a plain bearing device that rotatably supports the rotating shaft. The plain bearing device includes a bearing disposed radially outward from the rotating shaft, a back metal disposed on the outer circumferential surface of the bearing, multiple elastic bodies disposed circumferentially on the outer circumferential surface of the back metal with gaps between them, and a bearing support disposed on the outer circumferential surface of the multiple elastic bodies (see Abstract). In this configuration, the multiple elastic bodies are disposed circumferentially on the outer circumferential surface of the back metal that holds the bearing, improving the heat dissipation of the bearing, which is a sliding member, and suppressing temperature increases in the bearing. This suppresses the progression of wear on the bearing and extends its lifespan (see paragraph 0026). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-170879 Summary of the Invention [Problem to be solved by the invention]

[0004] The advance standby pump of Patent Document 1 takes into consideration the heat dissipation properties of the bearing, which is a sliding member, and is able to suppress temperature increases in the bearing. Furthermore, an elastic body that acts as a buffer member is provided on the outer circumferential surface of the back metal that holds the bearing. When the shaft (rotating shaft) comes into contact with the sliding member (bearing) due to vibration of the shaft during advance standby operation, the buffer member (elastic body) deforms, reducing the contact load. This flexible structure is expected to prevent bearing burnout. However, during drainage operation, when a fluid excitation force acts on the impeller, shaft vibration can increase, and it is necessary to adequately suppress excessive vibration caused by the fluid excitation force.

[0005] An object of the present invention is to prevent bearing burnout during advance standby operation and to suppress the occurrence of excessive vibration during drainage operation. [Means for solving the problem]

[0006] In order to achieve the above object, the bearing device of the present invention comprises: The bearing comprises a sliding member that is installed with a gap on the outer circumferential side of a rotating shaft, a back metal that holds the sliding member, a buffer member that flexibly supports the back metal in the circumferential direction and the radial direction, and a bearing housing that holds the buffer member, The back metal and the bearing housing have abutment portions that abut in the radial direction, and are configured so that the radial gap of the abutment portions expands as the back metal is displaced in the circumferential direction. [Effects of the Invention]

[0007] According to the present invention, it is possible to prevent bearing burnout during advance standby operation and suppress excessive vibration during drainage operation. Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief explanation of the drawings]

[0008] [Figure 1]1 is an axial cross-sectional view of an advance standby pump according to an embodiment of the present invention, taken along the axial direction (vertical direction). [Figure 2] 1 is a cross-sectional view perpendicular to an axis, showing a bearing device (underwater bearing device) according to one embodiment (embodiment 1) of the present invention. [Figure 3] FIG. 3 is a cross-sectional view perpendicular to the axis showing the underwater bearing device in FIG. 2 when the shaft comes into contact with the sliding member during advance standby operation and the back metal is displaced in the circumferential direction. [Figure 4] This is a cross-sectional view perpendicular to the axis showing the underwater bearing device in Figure 2 when the shaft comes into contact with the sliding member during advance standby operation, the back metal is displaced in the circumferential direction, and a radial contact load is applied. [Figure 5] FIG. 2 is a cross-sectional view perpendicular to the axis showing a bearing device (submerged bearing device) according to one embodiment (embodiment 2) of the present invention. [Figure 6] FIG. 10 is a cross-sectional view perpendicular to the axis showing an underwater bearing device according to a modified example of the second embodiment. [Figure 7] FIG. 10 is a cross-sectional view perpendicular to the axis showing a bearing device (submerged bearing device) according to one embodiment (embodiment 3) of the present invention. [Figure 8] FIG. 10 is a cross-sectional view perpendicular to the axis showing a bearing device (submerged bearing device) according to one embodiment (embodiment 4) of the present invention. [Figure 9] FIG. 10 is a cross-sectional view perpendicular to the axis showing an underwater bearing device according to a modified example of the fourth embodiment. [Figure 10] FIG. 10 is a cross-sectional view perpendicular to the axis showing an underwater bearing device according to another modified example of the fourth embodiment. [Figure 11] FIG. 10 is a cross-sectional view perpendicular to the axis showing a bearing device (submerged bearing device) according to an embodiment (embodiment 5) of the present invention. [Figure 12] FIG. 10 is a cross-sectional view perpendicular to the axis showing a bearing device (submerged bearing device) according to an embodiment (embodiment 6) of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific embodiment of the advance standby pump and bearing device of the present invention will now be described with reference to the accompanying drawings. In each drawing, parts with the same reference numerals indicate the same or similar configurations.

[0010] A standby pump is a drainage pump designed to prevent urban flooding during torrential rainfall. Its standby operation begins before rainwater arrives, ensuring rapid drainage in emergencies. A standby pump primarily consists of a casing containing the liquid, an impeller that pumps the liquid inside the casing, and a shaft that transmits power to the impeller. The shaft is supported for free rotation by a thrust bearing device installed on top of the casing and a submerged bearing device installed inside the casing. The submerged bearing device is a water-lubricated bearing that is lubricated by rainwater during drainage operation, suppressing shaft vibration caused by fluid excitation forces acting on the impeller during drainage operation. While the impeller does not experience fluid excitation forces during standby operation before rainwater arrives, the submerged bearing device must support the shaft without lubrication, requiring a design that takes into consideration burnout caused by frictional heat generated by the shaft.

[0011] An embodiment of a front standby pump 1 to which a bearing device 7 according to the present invention is applied will be described with reference to Fig. 1. Fig. 1 is an axial cross-sectional view of the front standby pump 1 according to the embodiment of the present invention, taken along the axial direction (vertical direction).

[0012] The advance standby pump 1 comprises a casing 2 containing liquid, an impeller 3 that pumps the liquid inside the casing 2, an electric motor 4 that is installed at the top of the casing 2 and generates power, a shaft 5 that transmits the power of the electric motor 4 to the impeller 3, a thrust bearing device 6 that is installed at the top of the casing 2 and rotatably supports the shaft (rotating shaft) 5, and a submerged bearing device 7 that is installed inside the casing 2 and rotatably supports the shaft 5. In this embodiment, two submerged bearing devices 7 are installed: a first submerged bearing device 7a that is installed in the middle of the shaft, and a second submerged bearing device 7b that is installed above the impeller. Hereinafter, the term "submerged bearing device" may be simply referred to as the "bearing device."

[0013] An embodiment of the underwater bearing device 7 will be described below with reference to FIGS. 2 to 12. FIG. [Example 1] The underwater bearing device 7 of this embodiment will be described with reference to FIGS. 2 is a cross-sectional view showing a bearing device (submerged bearing device) 7 according to one embodiment (embodiment 1) of the present invention, taken along a plane perpendicular to the shaft 5. Note that arrow A in the figure indicates the direction of rotation of the shaft 5. The underwater bearing device 7 of this embodiment has a sliding member (bearing) 9 installed with a gap 8 on the outer periphery of the rotating shaft 5, a back metal 10 arranged on the outer periphery of the sliding member 9 to hold the sliding member 9, a buffer member (elastic body) 11 arranged on the outer periphery of the back metal 10 to flexibly support the back metal 10 in the circumferential and radial directions (diameter), and a bearing housing (bearing support) 12 arranged on the outer periphery of the buffer member 11 to hold the buffer member 11. The back metal 10 has a back metal abutment portion 13a that protrudes radially outward from its outer periphery, and the bearing housing 12 has a bearing housing abutment portion 13b that protrudes radially inward from its inner periphery.

[0014] The back metal abutment portion 13a and the bearing housing abutment portion 13b constitute the abutment portion 13 where the back metal 10 and the bearing housing 12 abut. A plurality of abutment portions 13 are provided spaced apart in the circumferential direction, and the buffer member 11 is disposed between adjacent abutment portions 13. A buffer member accommodating portion 11A that accommodates the buffer member 11 is formed between two abutment portions 13 that are spaced apart in the circumferential direction. The buffer member 11 is made of a flexible material such as rubber, and is accommodated in the buffer member accommodating portion 11A.

[0015] In the state shown in Figure 2, although a small radial gap δ (= δ0) is formed between the back metal abutment portion 13a of the abutment portion 13 and the bearing housing abutment portion 13b, radial displacement of the back metal 10 is almost restricted. Therefore, the back metal 10 is displaceable in the rotational direction relative to the bearing housing 12, but not in the radial direction. The abutment portion 13 is configured in a stepped shape, and the radii of the abutment surfaces 13a1 and 13b1 of the abutment portion 13 increase in a stepped manner in the rotational direction. Therefore, when the back metal 10 displaces in the rotational direction, the radial gap δ between the back metal abutment portion 13a of the abutment portion 13 and the bearing housing abutment portion 13b of the abutment portion 13 expands.

[0016] That is, the underwater bearing device 7 of this embodiment comprises a sliding member 9 installed with a gap on the outer periphery of the rotating shaft 5, a back metal 10 that holds the sliding member 9, a buffer member 11 that flexibly supports the back metal 10 in the circumferential and radial directions, and a bearing housing 12 that holds the buffer member 11. The back metal 10 and the bearing housing 12 have a contact portion 13 that abuts in the radial direction, and are configured so that the radial gap δ of the abutment portion 13 expands as the back metal 10 displaces in the circumferential direction.

[0017] In this case, the contact portion 13 is composed of a back metal contact portion 13a that protrudes radially outward from the back metal 10 and a bearing housing contact portion 13b that protrudes radially inward from the bearing housing 12.

[0018] Back metal abutment portion 13a has a contact surface 13a1 that abuts against bearing housing abutment portion 13b, and bearing housing abutment portion 13b has a contact surface 13b1 that abuts against back metal abutment portion 13a. Contact surface 13a1 of back metal abutment portion 13a and contact surface 13b1 of bearing housing abutment portion 13b form a radial gap of abutment portion 13, and the radii of each increase forward in the rotation direction of shaft 5.

[0019] Furthermore, the contact surface 13a1 of the back metal contact portion 13a and the contact surface 13b1 of the bearing housing contact portion 13b are formed in a stepped shape.

[0020] During the drainage operation, a water film is formed in the gap 8 between the shaft 5 and the sliding member 9, so that contact between the shaft 5 and the sliding member 9 does not occur, and no circumferential load due to contact friction is generated on the sliding member 9. As a result, the back metal 10 does not displace in the rotational direction, so the radial gap δ of the abutment portion 13 is maintained small (δ = δ0), and the bearing rigidity of the sliding member 9 is increased. As a result, during the drainage operation, vibration of the shaft 5 is reliably suppressed, and excessive vibration is prevented.

[0021] Next, the operation during advance standby will be explained using Figure 3. Figure 3 is a cross-sectional view perpendicular to the axis showing the underwater bearing device 7 when the shaft 5 comes into contact with the sliding member 9 during advance standby operation and the back metal 10 is displaced in the circumferential direction in Figure 2. Note that arrow B in the figure indicates the rotation direction of the back metal 10.

[0022] During advance standby operation, no water film is formed in the gap 8 between the shaft 5 and the sliding member 9, so when the rotating shaft 5 comes into contact with the sliding member 9, a frictional force in the rotational direction A is generated on the sliding member 9. As a result, the back metal 10 is displaced in the rotational direction B, and the step combination between the back metal abutment portion 13a and the bearing housing abutment portion 13b at the abutment portion 13 is misaligned. As a result, the gap δ at the abutment portion 13 expands to δ1 (δ1 > δ0).

[0023] In this case, by forming the contact surfaces 13a1 and 13b1 in a stepped shape, it is possible to firmly receive the bearing load and obtain a large gap δ even with a slight circumferential displacement of the back metal 10.

[0024] Figure 4 is a cross-sectional view perpendicular to the axis showing the underwater bearing device 7 in Figure 2 when the shaft 5 comes into contact with the sliding member 9 during advance standby operation, displacing the back metal 10 in the circumferential direction and applying a radial contact load C. The arrow C in the figure indicates the radial contact load.

[0025] 3, when the shaft 5 and the sliding member 9 are in contact with each other, the gap δ at the contact portion 13 expands to δ1 due to the rotational displacement of the back metal 10. In this state, when a radial load C is applied, the buffer member 11 can deform significantly, thereby reducing the bearing load on the sliding member 9 and preventing bearing burnout.

[0026] As a result, the underwater bearing device 7 of this embodiment can prevent bearing burnout during advance standby operation and suppress excessive vibration during drainage operation.

[0027] [Example 2] The submerged bearing device 7 of this embodiment will be described with reference to FIGS. FIG. 5 is a cross-sectional view taken perpendicular to the axis, showing a bearing device (submerged bearing device) 7 according to one embodiment (embodiment 2) of the present invention. The biggest difference between this embodiment and the first embodiment is that buffer members 11a with different rigidities are arranged. In this embodiment, buffer members (first buffer members) 11 and buffer members (second buffer members) 11a are arranged side by side in the circumferential direction. The rigidity of the buffer members 11 and 11a can be adjusted by changing the rubber components. By arranging buffer members 11a with different rigidities, the radial rigidity and circumferential rigidity of the buffer members 11 can be adjusted independently, and the movable range and bearing rigidity of the contact portion 13 can be appropriately set.

[0028] In this embodiment, the buffer member is configured by arranging a plurality of buffer members 11, 11a having different rigidities in the circumferential direction.

[0029] FIG. 6 is a cross-sectional view taken perpendicular to the axis, showing an underwater bearing device 7 according to a modified example of the second embodiment. The buffer members 11a having different rigidities may be provided at one location per buffer member 11 as shown in Fig. 5, or multiple buffer members 11a may be provided as shown in Fig. 6. In the modified example of Fig. 6, buffer members 11a are provided at both ends of one buffer member 11 in the circumferential direction.

[0030] [Example 3] The submerged bearing device 7 of this embodiment will be described with reference to FIG. FIG. 7 is a cross-sectional view taken perpendicular to the axis, showing a bearing device (submerged bearing device) 7 according to one embodiment (embodiment 3) of the present invention. The biggest difference between this embodiment and the first embodiment is that the contact surface of the contact portion 13 is not stepped but is inclined relative to the circumferential direction.

[0031] The opposing surface (contact surface) 13a1 of the back metal contact portion 13a that faces the bearing housing contact portion 13b is inclined at a predetermined angle θ1 (θ1 ≠ 0) with respect to a direction (line segment) D2 perpendicular to the radial direction D1 on the cross section of Figure 7. The opposing surface (contact surface) 13b1 of the bearing housing contact portion 13b that faces the back metal contact portion 13a is inclined at a predetermined angle θ1 (θ1 ≠ 0) with respect to a direction (line segment) D2 perpendicular to the radial direction D1 on the cross section of Figure 7. The opposing surfaces 13a1 and 13b1 are each formed as flat surfaces. Therefore, the opposing surfaces 13a1 and 13b1 can be called "inclined flat surfaces."

[0032] On the other hand, the opposing surface (contact surface) 13a1 of the back metal abutment portion 13a that faces the bearing housing abutment portion 13b in Examples 1 and 2, and the opposing surface (contact surface) 13b1 of the bearing housing abutment portion 13b that faces the back metal abutment portion 13a can be called a "step-like inclined surface" because the opposing surfaces 13a1 and 13b1 in Example 3 are formed in a step shape.

[0033] The "radial direction" described in this embodiment refers to the radial direction (radial line segment) passing through the center of the circumferential length L1 of the contact portion 13.

[0034] As described above, in this embodiment, the contact surface 13a1 of the back metal contact portion 13a and the contact surface 13b1 of the bearing housing contact portion 13b are formed as planes inclined at a predetermined angle θ1 with respect to the direction D2 perpendicular to the radial direction D1. Because the contact surfaces 13a1 and 13b1 are inclined, the gap δ (see FIGS. 2 and 3) of the contact portion 13 expands as the back metal 10 is displaced in the rotational direction, as in the first embodiment, preventing bearing burnout during advance standby operation and suppressing excessive vibration during drainage operation. The third embodiment has a simpler structure than the first embodiment and can be manufactured more inexpensively.

[0035] [Example 4] The underwater bearing device 7 of this embodiment will be described with reference to FIGS. FIG. 8 is a cross-sectional view taken perpendicular to the axis, showing a bearing device (submerged bearing device) 7 according to one embodiment (embodiment 4) of the present invention. The biggest difference between this embodiment and embodiment 3 is that the abutment surfaces 13a1, 13b1 of the abutment portion 13 are composed of flat portions 13a11, 13b11 formed without inclination relative to the circumferential direction, and inclined surface portions 13a12, 13b12 formed at the circumferential ends of the flat portions 13a11, 13b11.

[0036] 8, the contact surface 13a1 of the back metal contact portion 13a includes a flat portion 13a11 that is tangent in the circumferential direction and an inclined surface portion 13a12 that is inclined relative to the flat portion 13a11. The inclined surface portion 13a12 is formed on the rear end side of the flat portion 13a11 in the rotation direction A of the shaft 5, and is inclined relative to the flat portion 13a11 so that the closer it is to the rear end of the contact surface 13a1, the more it moves away from the bearing housing contact portion 13b that is disposed radially outward.

[0037] 8, the contact surface 13b1 of the bearing housing contact portion 13b includes a flat portion 13b11 that is tangent in the circumferential direction and an inclined surface portion 13b12 that is inclined relative to the flat portion 13b11. The inclined surface portion 13b12 is formed on the front end side of the flat portion 13b11 in the rotation direction A of the shaft 5, and is inclined relative to the flat portion 13b11 so that the closer it is to the front end of the contact surface 13b1, the more it moves away from the back metal contact portion 13a that is located radially inward.

[0038] During the drainage operation, the flat surface portion 13a11 of the back metal abutment portion 13a and the flat surface portion 13b11 of the bearing housing abutment portion 13b are disposed so as to face each other in the radial direction during the drainage operation.

[0039] During the advance standby operation, the back metal 10 is displaced in the rotation direction A by more than the width of the contact portion 13, so that the inclined surface portion 13a12 of the back metal contact portion 13a and the inclined surface portion 13b12 of the bearing housing contact portion 13b face each other in the radial direction, thereby expanding the gap δ (see FIGS. 2 and 3) of the contact portion 13 and reducing the bearing load. Meanwhile, the contact surfaces 13a1 and 13b1 of the contact portion 13 have flat surfaces 13a11 and 13b11, which more reliably suppresses vibration of the shaft 5 during the drainage operation. Furthermore, the inclined surface portions 13a12 and 13b12 are formed at the circumferential ends of the contact portion 13, and the radial gap δ (see FIGS. 2 and 3) continuously increases toward both ends of the contact portion 13. This allows the back metal 10 to reliably return to its initial position from the circumferentially displaced position, thereby reliably suppressing shaft vibration during the drainage operation.

[0040] FIG. 9 is a cross-sectional view taken perpendicular to the axis, showing an underwater bearing device 7 according to a modified example of the fourth embodiment. The shape of the circumferential end of the contact portion 13 may be curved (curved surface shape) as shown in Fig. 9. If the end of the contact portion 13 is curved, the back metal 10 can more reliably return to its initial position from the circumferentially displaced position. Also, as shown in Fig. 9, the buffer member 11 may be partially installed between the back metal 10 and the bearing housing 12. In other words, the buffer member 11 does not need to be installed over the entire buffer member accommodating portion 11A in the circumferential direction, but may be installed over only a part of the buffer member accommodating portion 11A.

[0041] By partially installing the buffer member 11, a gap is formed between the back metal 10 and the bearing housing 12, so that the frictional heat generated by the sliding between the shaft 5 and the sliding member 9 can be effectively cooled.

[0042] FIG. 10 is a cross-sectional view taken perpendicular to the axis, showing an underwater bearing device 7 according to another modification of the fourth embodiment. 10, inclined surface portions 13a12, 13b12 may be provided at both circumferential ends of the abutment portion 13. By providing inclined surface portions 13a12, 13b12 at both ends of the abutment portion 13, structural changes due to changes in the direction of rotation are not required, parts can be standardized, and installation errors can be prevented.

[0043] [Example 5] The submerged bearing device 7 of this embodiment will be described with reference to FIG. FIG. 11 is a cross-sectional view taken perpendicular to the axis, showing a bearing device (submerged bearing device) 7 according to an embodiment (embodiment 5) of the present invention. The biggest difference between this embodiment and the fourth embodiment is that a circumferential displacement suppression portion 14 for suppressing or restricting circumferential displacement of the back metal 10 is provided on the outer periphery of the back metal 10. That is, the back metal 10 of this embodiment has the circumferential displacement suppression portion 14 for the back metal 10 on its outer diameter portion.

[0044] In this embodiment, the circumferential displacement suppression portion 14 is provided as a protrusion that protrudes radially outward from the outer peripheral surface of the back metal 10, and the circumferential displacement of the back metal 10 is restricted by the circumferential displacement suppression portion 14 abutting against the bearing housing abutment portion 13b.

[0045] The circumferential displacement suppressing portion 14 can suppress excessive circumferential displacement of the back metal 10, thereby suppressing elastic deformation of the buffer member 11 and extending the life of the underwater bearing device 7.

[0046] [Example 6] The submerged bearing device 7 of this embodiment will be described with reference to FIG. FIG. 12 is a cross-sectional view taken perpendicular to the axis, showing a bearing device (submerged bearing device) 7 according to an embodiment (embodiment 6) of the present invention. The biggest difference between this embodiment and Example 5 is that a member 14 for suppressing circumferential displacement of the back metal 10 is provided on the inner periphery of the bearing housing 12. That is, the bearing housing 12 of this embodiment has a portion 14 for suppressing circumferential displacement of the back metal 10 on its inner diameter portion.

[0047] The circumferential displacement suppression portion 14 is provided as a protrusion that protrudes radially inward from the inner peripheral surface of the bearing housing 12. In this case, the circumferential displacement suppression portion 14 restricts the circumferential displacement of the back metal 10 by abutting against the back metal abutment portion 13a in the circumferential direction.

[0048] In this embodiment, as in embodiment 5, the circumferential displacement suppression member 14 can suppress excessive circumferential displacement of the back metal 10, thereby suppressing elastic deformation of the buffer member 11 and extending the life of the underwater bearing device 7.

[0049] The advance standby pump 1 of the present invention is an advance standby pump comprising a casing 2 containing liquid, an impeller 3 that pumps the liquid inside the casing 2, a shaft 5 that transmits power to the impeller 3, and an underwater bearing device 7 that is installed inside the casing 2 and supports the shaft 5 so that it can rotate freely, and the underwater bearing device has the underwater bearing device 7 of the above-mentioned embodiment and its modified example.

[0050] The present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and are not necessarily limited to those including all of the configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations. [Explanation of symbols]

[0051] 1...advance standby pump, 2...casing, 3...impeller, 5...shaft, 7...underwater bearing device, 9...sliding member, 10...back metal, 11, 11a...buffer member, 12...bearing housing, 13...abutment portion, 13a...back metal abutment portion, 13a1...abutment surface of back metal abutment portion 13a, 13b...bearing housing abutment portion, 13b1...abutment surface of bearing housing abutment portion 13b, 14...circumferential displacement suppression portion, δ...radial gap.

Claims

1. The bearing comprises a sliding member that is installed with a gap on the outer circumferential side of a rotating shaft, a back metal that holds the sliding member, a buffer member that flexibly supports the back metal in the circumferential direction and the radial direction, and a bearing housing that holds the buffer member, The back metal and the bearing housing have a contact portion that contacts radially, and the radial gap of the contact portion is expanded by circumferential displacement of the back metal.

2. 2. The bearing device according to claim 1, A bearing device characterized in that the abutment portion is composed of a back metal abutment portion protruding radially outward from the back metal and a bearing housing abutment portion protruding radially inward from the bearing housing.

3. 3. The bearing device according to claim 2, the back metal abutment portion has an abutment surface that abuts against the bearing housing abutment portion, the bearing housing abutment portion has an abutment surface that abuts against the back metal abutment portion, The abutment surface of the back metal abutment portion and the abutment surface of the bearing housing abutment portion form the radial gap of the abutment portion, and the radii of each increase toward the front in the rotation direction of the shaft.

4. 4. The bearing device according to claim 3, The bearing device according to claim 1, wherein the contact surface of the back metal contact portion and the contact surface of the bearing housing contact portion are formed in a stepped shape.

5. 4. The bearing device according to claim 3, A bearing device characterized in that the contact surface of the back metal contact portion and the contact surface of the bearing housing contact portion are configured as planes inclined at a predetermined angle with respect to a direction perpendicular to the radial direction.

6. 2. The bearing device according to claim 1, The bearing device is characterized in that the back metal has a portion for suppressing circumferential displacement of the back metal on its outer diameter portion.

7. 2. The bearing device according to claim 1, The bearing device is characterized in that the bearing housing has a portion for suppressing circumferential displacement of the back metal on its inner diameter portion.

8. 2. The bearing device according to claim 1, The bearing device is characterized in that the buffer member is configured by circumferentially arranging a plurality of buffer members having different rigidities.

9. A preceding standby pump includes a casing containing a liquid, an impeller that pumps the liquid inside the casing, a shaft that transmits power to the impeller, and an underwater bearing device that is installed inside the casing and rotatably supports the shaft, A preceding standby pump, comprising the bearing device according to any one of claims 1 to 8 as the underwater bearing device.

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