Centrifugal pump

Abstract

To easily adjust an impeller clearance without requiring adjustment by a shim.SOLUTION: A centrifugal pump 1 includes a clearance adjustment part 90 which is integral with a shaft 20 and in which bearing units 41, 42 on front / rear sides of the shaft slide in an axial direction. The clearance adjustment part 90 has a bearing housing 40 which is internally fitted to a rear part of a frame 50 in a slidable manner and in which the bearing unit 42 on a rear part of the shaft 20 is internally mounted. The bearing housing 40 can adjust an impeller clearance at a position of an adjustment arm 44 expanding on a lateral side of the housing itself and maintain the position, and includes a pressing spring 96 for assisting the sliding movement of the housing itself such that the spring applies a pressing force in a housing axis direction by being in contact with an opposite face 57 on the frame 50 side.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a centrifugal pump, and more particularly to a technique for adjusting the impeller clearance of a centrifugal pump. [Background technology]

[0002] The performance of a centrifugal pump changes depending on the size of the impeller clearance, which is the gap between the inner surface of the casing and the leading edge of the impeller blades.As the impeller inside the casing wears and the impeller clearance widens, pump performance decreases, so it is necessary to adjust the impeller clearance. Conventionally, when pump performance deteriorates, operators change the thickness of the clearance adjustment shim located in the bearing housing at the rear of the frame, thereby adjusting the axial position of the shaft and restoring pump performance. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-140875 Summary of the Invention [Problem to be solved by the invention]

[0004] In contrast to this, for example, the technology described in Patent Document 1 provides an adjustment mechanism that allows the shaft bearing housing to move axially relative to the frame, and adopts a configuration in which the shaft can be slid axially by moving the bearing housing at an adjustment position below the frame. This allows the operator to slide the shaft along the axial direction at an adjustment position below the axis of the frame and fix that position, eliminating the need for adjustment using a shim and improving the workability of the impeller clearance adjustment work.

[0005] However, when adjusting the sliding movement of the shaft at an adjustment position below the axis of the frame, as in the technology described in Patent Document 1, a tilting moment acts on the shaft according to the amount of protrusion at the adjustment position as the shaft slides along its axial direction, which hinders the smooth sliding movement of the shaft in the horizontal direction, resulting in a problem of reduced workability when adjusting the impeller clearance. The present invention has been made in light of the above-mentioned problems, and an object of the present invention is to provide a centrifugal pump that does not require adjustment using shims and allows the impeller clearance to be easily adjusted. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, a centrifugal pump according to one aspect of the present invention comprises a frame that rotatably supports a shaft, a casing fixed to the front surface of the frame, and an impeller housed within the casing and mounted coaxially at the tip of the shaft, wherein the impeller rotates within the casing when driven by the shaft, thereby sending fluid from an inlet port formed in the casing to a discharge port, and further comprises a clearance adjustment unit that is integral with the shaft and is configured to allow bearing units at the front and rear of the shaft to slide axially, and that adjusts impeller clearance, which is the gap between the inner surface of the casing and the leading edges of the impeller blades, and the clearance adjustment unit has a bearing housing that is fitted into the front or rear of the frame to be slidable axially, and in which a bearing unit at the rear of the shaft is housed, and the bearing housing has an adjustment arm that protrudes laterally from the bearing housing, allowing the impeller clearance to be adjusted and the position to be maintained, and a compression spring that assists the bearing housing's sliding movement is mounted so that it abuts against the opposing surface on the frame side to apply a pressing force in the axial direction. [Effects of the Invention]

[0007] According to the present invention, adjustment using a shim is not required and the impeller clearance can be easily adjusted. [Brief explanation of the drawings]

[0008] [Figure 1] 1A and 1B are explanatory views of an embodiment of a centrifugal pump according to an aspect of the present invention, in which FIG. 1A shows a cross section along the axis, and FIG. 1B shows a right side view of FIG. 1A. [Figure 2] 2A and 2B are explanatory views of the main parts of the centrifugal pump shown in FIG. 1, in which FIG. 2A is an enlarged view of the main parts at the rear of the frame in FIG. 1, FIG. 2B is a right side view of FIG. 2A, and FIG. 2C is a ZZ cross-sectional view of FIG. 2B. [Figure 3] 1 is an illustration of another embodiment of a centrifugal pump according to an aspect of the present invention, showing a cross section along the axis. FIG. [Figure 4] 1A and 1B are diagrams showing an example of a conventional centrifugal pump, in which FIG. 1A shows a cross section along the axis, and FIG. 1B shows a right side view of FIG. 1A. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the drawings are schematic. Therefore, it should be noted that the relationship between thickness and planar dimensions, ratios, etc. differ from the actual ones, and the drawings also include portions where the relationship and ratio of dimensions differ from each other. Furthermore, the embodiments described below are intended to exemplify devices and methods for embodying the technical ideas of the present invention, and the technical ideas of the present invention do not limit the materials, shapes, structures, arrangements, etc. of the components to the embodiments described below.

[0010] [Centrifugal pump] As shown in Fig. 1, the centrifugal pump 1 of this embodiment includes a frame 50 that rotatably supports a shaft 20. A casing 10 is fixed to a casing mounting surface 54 on the front side of the frame 50. A shaft seal 60 that seals the periphery of the shaft 20 is provided in the center of the rear of the casing 10. The casing 10 of this embodiment is a split type that is divided into two along a plane perpendicular to the shaft 20, and is configured to include a front casing 11 on the axial front side and a back casing 12 on the axial rear side. The upper front end of the frame 50 and the back surface of the casing mounting surface 54 are connected by a connecting rib 55 having a substantially T-shaped cross section.

[0011] The back portion of the back casing 12 is fixed to the casing mounting surface 54 of the frame 50 with fixing bolts 82. The front casing 11 is fixed to the front surface of the back casing 12 with bolts 72 of the fastening portion 70. The casing 10 has a suction port 10in at its front surface that juts out forward along the axial direction, and a discharge port 10out at its upper center. An impeller 30 is rotatably housed within the casing 10 and is coaxially mounted on the tip of a shaft 20. An output shaft of a motor (not shown) is connected to the rear end of the shaft 20 so as to transmit driving force. As a result, in the centrifugal pump 1 of this embodiment, the impeller 30 rotates within the casing 10 when driven by the shaft 20, and the pumped fluid is pumped from the suction port 10in formed in the casing 10 toward the discharge port 10out.

[0012] [Centrifugal pump shaft support] 1, the centrifugal pump 1 of this embodiment has a journal support 56 provided on the upper part of the frame 50. The journal support 56 of this embodiment includes a front journal support 56a and a rear journal support 56b that are spaced apart in the axial front and rear directions. The base end of the shaft 20 passes through the rear of the casing 10 and extends horizontally to the journal support 56, and the base end of the shaft 20 is supported horizontally and rotatably about its axis by the front and rear journal support portions 56a, 56b.

[0013] The axially front journal support portion 56a has a bearing unit 41, and the rear journal support portion 56b has a bearing unit 42. A front cover 83 is attached to the open end of the axially front front journal support portion 56a so as to cover the axial front end face. In this embodiment, the front bearing unit 41 is a duplex angular contact ball bearing consisting of two bearings 41 a, 41 b, and similarly, the rear bearing unit 42 is a duplex angular contact ball bearing consisting of two bearings 42 a, 42 b. In the centrifugal pump 1 of this embodiment, the rear bearing unit 42 serves as the adjustment work section of the clearance adjustment section 90.

[0014] [Clearance adjustment part] The clearance adjusting section 90 of this embodiment will be described in detail below. In the clearance adjustment section 90 of this embodiment, the cylindrical inner surface of the frame 50 at the support section 56 constituting the front support section 56a serves as a front guide surface 58 that supports the two front bearings 41a, 41b so that they can slide along the axial direction. The rear end face of the front bearing unit 41 abuts against the step portion of the shaft 20 in the axial direction, and when adjusting the impeller clearance, as the shaft 20 slides forward in the axial direction, it can slide axially within a predetermined range on the cylindrical inner surface of the frame 50.

[0015] Furthermore, in the clearance adjusting section 90 of this embodiment, as described above, the impeller clearance adjusting work section is provided in the portion that constitutes the rear bearing section 56b. 2, the clearance adjustment unit 90 of this embodiment has a hollow cylindrical bearing housing 40. The bearing housing 40 is fitted into the cylindrical inner surface of the frame 50 at a portion that constitutes the rear journal portion 56b so as to be slidable in the axial direction. In other words, the cylindrical inner surface of the frame 50 serves as a rear guide surface 59 that supports the bearing housing 40 so that it can slide in the axial direction.

[0016] The bearing housing 40 supports the bearings 42a, 42b with a predetermined fit tolerance in a cylindrical accommodation space formed inside the bearing housing 40, which has a step on the axial front side. The inner ring end faces of the bearings 42a, 42b are pressed and fixed from the rear against the step on the axial front side by a bearing fixing nut 47, restricting axial movement of the bearings 42a, 42b. The rear opening of bearing housing 40 is covered by housing cover 43, and dustproof gasket 49 is interposed between the housing cover 43 and the outer peripheral surface of shaft 20. Housing cover 43 is fixed to the back surface of bearing housing 40 with fixing bolts 45.

[0017] In this embodiment, an adjustment arm 44 that projects radially outward (in this example, downward from the center of the lower surface) is integrally formed with the bearing housing 40. An adjustment hole 48 that passes through the adjustment arm 44 in the axial direction is formed in a portion near the tip of the adjustment arm 44 as an adjustment bolt insertion hole. An adjustment bolt 92 is inserted into the adjustment hole 48, and the tip of the adjustment bolt 92 is screwed into an adjustment bolt fixing screw 53n formed on the rear surface of the frame 50. Furthermore, the adjustment bolt 92 has the adjustment arm 44 clamped between front and rear adjustment nuts (front nut and rear nut) 93, 94 via washers 95 from the front and rear of the adjustment hole 48 in the axial direction, making it possible to adjust and fix the axial position of the bearing housing 40. In particular, the clearance adjustment part 90 of this embodiment has a compression spring 96 that assists the sliding movement of the bearing housing 40. The compression spring 96 is attached so as to abut against the opposing surface 57 on the rear surface of the frame 50 side and to apply a pressing force to the bearing housing 40 in the axial direction.

[0018] The compression spring 96 of this embodiment is a cylindrical coil spring, and as shown in FIG. 2, is installed inside a mounting hole formed in an appropriate position in the bearing housing 40, and is interposed so as to be positioned between the front-facing surface of the bearing housing 40 and the opposing surface 57 on the frame 50 side, and the rear end surface is fixed from the rear in the axial direction by a spring fixing screw 91 that is threaded into a female threaded hole formed in the housing cover 43, so that the amount of deflection is adjusted and the spring is held in that state. In this embodiment, as shown in FIG. 1(b), the compression spring 96 and the spring fixing screw 91 are respectively arranged at two positions near the outer peripheral end in the radial direction of the bearing housing 40, namely, a first position at the top of the figure, which is slightly shifted clockwise as viewed from the back side based on the up-and-down direction of the adjustment hole 48, and a second position at the bottom of the figure, which is 180° circumferentially spaced from the first position.

[0019] It is possible to provide the compression spring 96 and spring fixing screw 91 at least in one location, the first position at the top of the figure. Furthermore, it is also possible to configure the compression spring 96 so that the amount of deflection is adjusted to a desired range by simply attaching the housing cover 43 itself, without providing the spring fixing screw 91. In the clearance adjusting section 90 of this embodiment, if the impeller 30 locks due to a problem with the liquid supply, the reaction force generated at that time may cause the bearing housing 40 to rotate, possibly bending the adjusting bolt 92 . Therefore, in this embodiment, as shown in Figures 2(b) and (c), in order to prevent damage to the adjustment bolt 92, a pair of anti-rotation pins 97 are inserted on the left and right sides from the rear in the axial direction so as to connect the frame 50 and the bearing housing 40, and by first hitting these pair of anti-rotation pins 97, damage to the adjustment bolt 92 is avoided.

[0020] Next, the operation and effects of the centrifugal pump of this embodiment will be described. In the centrifugal pump of this embodiment, the impeller 30 is rotated to increase the pressure of the fluid being pumped, and the fluid is transferred from the suction port 10in of the casing 10 to the discharge port 10out. In this type of centrifugal pump, the impeller clearance between the impeller and the housing changes over time, etc. However, in the conventional clearance adjustment unit 190 shown in Figure 4, for example, a shim 200 is interposed between the front end face of the bearing housing 140, which faces the shaft 120 in the axial direction, and the opposing face on the frame 150 side, to move the shaft 120 in the axial direction together with the front and rear bearing units 141, 142. However, this adjustment method requires the attachment and detachment of multiple fixing bolts 145, and also requires the time and effort of adjusting the thickness of the shim 200 to the desired thickness. Therefore, there is room for improvement in terms of efficient clearance adjustment.

[0021] In contrast to this, in the centrifugal pump 1 of this embodiment, instead of the adjustment method of interposing a shim, an adjustment arm 44 is provided that protrudes radially to the side of the bearing housing 40 (downward in this example), an adjustment bolt 92 is inserted into an adjustment hole 48 that passes through the adjustment arm 44, and its tip is screwed into a female thread 53n on the back surface (rear vertical surface 53) of the frame 50, and the adjustment arm 44 is clamped between adjustment nuts 93 and 94 from the front and rear of the adjustment hole 48 of the adjustment arm 44. As a result, according to the centrifugal pump 1 of this embodiment, the axial position of the bearing housing 40 can be adjusted and fixed by adjusting the position of the adjusting arm 44 that protrudes radially outward. Therefore, the impeller clearance can be adjusted by clamping the single adjusting bolt 92 and the pair of adjusting nuts 93, 94 that clamp it from the front and rear, without using a shim.

[0022] Here, when adjusting the impeller clearance at the position of the downwardly protruding adjustment arm 44, as the bearing housing 40 slides along the axial direction of the adjustment bolt 92, a tilting moment acts on the bearing housing 40 according to the amount of protrusion of the adjustment arm 44, which may hinder the smooth sliding movement of the shaft 20 in the horizontal direction. 2, the clearance adjustment section 90 of this embodiment has a compression spring 96 that assists the sliding movement of the bearing housing 40, and the compression spring 96 is attached so as to abut against the opposing surface 57 on the frame 50 side and apply a pressing force in the axial direction. As a result, according to the centrifugal pump 1 of this embodiment, the compression spring 96 can apply an axial pressing force that assists the sliding movement of the bearing housing 40 during clearance adjustment.

[0023] Therefore, according to the centrifugal pump 1 of this embodiment, even if the shaft 20 slides at the position of the adjustment bolt 92 that protrudes from the bearing housing 40 downward of the frame 50, the anti-tilt effect of the compression spring 96 provides an auxiliary pressing force in the axial direction, effectively preventing the bearing housing 40 from tilting, and allowing the shaft 20 to slide smoothly in the horizontal direction. Therefore, according to the centrifugal pump 1 of this embodiment, it is possible to efficiently adjust the clearance at one working position without using a shim, while preventing or suppressing the tilting moment that occurs in the bearing housing 40 during clearance adjustment [Invention 1].

[0024] Furthermore, according to the centrifugal pump 1 of this embodiment, the spring fixing screw 91 is provided coaxially behind the compression spring 96 in the axial direction (on the opposite side of the opposing surface on the frame side in the axial direction), thereby restricting the amount of axial deflection of the compression spring 96, which is more suitable as a structure for preventing or suppressing the tilting moment that occurs in the bearing housing 40 when adjusting the clearance. In other words, in this embodiment, a hexagon socket set screw (a so-called set screw) is used as the spring fixing screw 91, and the axial position and amount of deflection of the compression spring 96 can be regulated as desired, so this is an excellent structure in that the spring pressing force can be adjusted to an appropriate value by the amount of screwing in the spring fixing screw 91 [Invention 2].

[0025] Furthermore, even if the tilting moment acts excessively beyond the range of adjustment possible with the spring fixing screw 91 and the compression spring 96, causing the bearing housing 40 to become stuck, the centrifugal pump of this embodiment allows the spring fixing screw 91 and the compression spring 96 to be removed, and instead, a compression bolt can be screwed into the mounting holes from the rear side of the housing cover 43, which can be used for emergency adjustment to release the stuck state [Invention 3].

[0026] As described above, the centrifugal pump 1 of this embodiment can provide a centrifugal pump that does not require adjustment using shims and is equipped with a clearance adjustment mechanism that makes clearance adjustment easy. The centrifugal pump according to the present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the present invention. For example, in the above embodiment, an example has been shown in which the clearance adjustment unit 90 is disposed on the rear side of the frame 50, but this is not limiting, and the clearance adjustment unit 90 can also be disposed on the front side of the frame 50. Specifically, as shown in FIG. 3 , in a centrifugal pump 1 of another embodiment, the front bearing unit 41 serves as the adjustment working section for the clearance adjustment unit 90.

[0027] It should be noted that the other embodiment shown in the same figure is an example in which the clearance adjustment unit 90 can be arranged on the front side, so a description of the pump itself will be omitted, and components similar to or corresponding to those in the embodiment shown in Figure 2 described above will be given the same reference numerals, and descriptions thereof will be omitted as appropriate. In another embodiment of the clearance adjustment unit 90, the cylindrical inner surface of the frame 50 at the bearing portion 56 constituting the rear bearing portion 56b serves as a rear guide surface (58) that supports the two rear bearings (42a, 42b) so that they can slide along the axial direction, and the cylindrical inner surface of the frame 50 can slide axially within a predetermined range.

[0028] In another embodiment of the clearance adjustment unit 90, the bearing housing 40 is fitted into the cylindrical inner surface of the frame 50 at a portion that constitutes the front journal portion 56a so as to be slidable in the axial direction, and is supported so as to be slidable along the axial direction. Here, in the clearance adjustment unit 90 of this other embodiment as well, the housing cover 43 is fixed to the front surface of the bearing housing 40 with fixing bolts 45, as in the embodiment of FIG. 2 above. A compression spring 96 that assists the sliding movement of the bearing housing 40 is provided at a position above the opposing surfaces of the bearing housing 40 and the housing cover 43, and is fitted inside a mounting hole in the bearing housing 40. The compression spring 96 is attached so as to abut against the opposing surface on the front side of the frame 50 and apply a pressing force in the axial direction of the bearing housing 40. Note that other configurations of the clearance adjustment unit 90 in other embodiments are configured in the same manner as the embodiment in FIG. 2 above.

[0029] In this way, the clearance adjustment unit 90 of another embodiment can be provided on the front side of the frame 50, and with the clearance adjustment unit 90 of another embodiment, as with the embodiment in Fig. 2 above, instead of using an adjustment method that involves the interposition of a shim, the axial position of the bearing housing 40 can be adjusted and fixed by the position of the adjustment arm 44 that protrudes laterally in the radial direction. Therefore, the impeller clearance can be adjusted by clamping one adjustment bolt 92 and a pair of adjustment nuts 93, 94 that are clamped from the front and rear of the adjustment bolt 92, without using a shim. 2(b), when viewed from the axial direction of the bearing housing 40, the vertical direction of the adjustment hole 48 is defined as a reference line RL, the center line of the shaft 20 is defined as a rotation center CR, and the angle formed by the reference line RL, the rotation center CR, and a passing line PL passing through the center of the compression spring 96 is defined as θ. Furthermore, the centrifugal pump 1 may be configured so that the relationship 0°≦θ≦45° holds. Furthermore, if the angle between the reference line RL and a line passing through the rotation center CR and the center of one of the compression springs 96 (the compression spring 96 fixed by a spring fixing screw 91 positioned above the rotation center CR) is defined as θ1, and the angle between the reference line RL and a line passing through the rotation center CR and the center of the other compression spring 96 (the compression spring 96 fixed by a spring fixing screw 91 positioned below the rotation center CR) is defined as θ2, then the configuration may be such that the relational expression θ1-0.2θ1≦θ2≦θ1+0.2θ1 holds. That is, when the adjustment bolt 92 is operated, a rotational moment is generated in the bearing housing 40 due to the axial forces of the adjustment arm 44 and the adjustment bolt 92. At this time, the bearing housing 40 rotates on a plane (bearing housing rotation plane) defined by two parallel axes: the center line of the shaft 20 (center of rotation CR) and the center line of the adjustment bolt 92 (a straight line passing through the center of the adjustment hole 48). When the bearing housing 40 rotates, a moment is generated, and the compression spring 96 acts to counteract the moment generated by the rotation of the bearing housing 40 and correct the attitude of the bearing housing 40 . When the adjustment bolt 92 is operated in a direction that compresses the compression spring 96, the reaction force generated by the compression spring 96 against the operation of the adjustment bolt 92 increases, and a larger force is required to operate the adjustment bolt 92. For this reason, when the adjustment bolt 92 is operated, it is preferable that the reaction force generated by the compression spring 96 be small. In order to effectively reduce the reaction force generated by the compression spring 96 while maintaining the reaction force that corrects the posture of the bearing housing 40, the compression spring 96 needs to be positioned on or near the bearing housing rotation surface. As described above, if the relational expression 0°≦θ≦45° is satisfied, the reaction force generated by the compression spring 96 is reduced and the reaction force generated by the compression spring 96 is effectively utilized. Although it would be ideal for the compression spring 96 to be positioned at a position where θ is 0°, this is practically difficult due to the relationship with adjacent components (for example, the housing cover 43, etc.) For this reason, it is preferable to have a configuration where the relational expression 0°<θ≦15° holds, that is, a configuration where the compression spring 96 is positioned near the ideal position. Furthermore, as described above, in a configuration in which the compression springs 96 are arranged in two locations, it would be ideal for the two compression springs 96 to be arranged axially symmetrically with respect to the center line (center of rotation CR) of the shaft 20, but this is difficult in reality. For this reason, a configuration may be adopted in which the relational expression θ1−0.2θ1≦θ2≦θ1+0.2θ1 is established, and an allowable range (±20%) for axial symmetry is provided. [Explanation of symbols]

[0030] 1. Centrifugal pump 10 Casing 10in intake 10out outlet 11 Front casing 12 Back casing 20 shaft 30 impeller 40 Bearing housing 41a, 41b Bearings 42a, 42b Bearings 41,42 Bearing unit 43 Housing cover 44 Adjustable Arm 45 Fixing bolt 46 Female thread for push bolt 47 Bearing fixing nut 48 adjustment hole 49 Dustproof packing 50 frames 51 Front legs 52 Hind legs 53 Rear vertical surface 54 Casing mounting surface 55 Connecting rib 56 axis branch 56a Front axis support 56b Posterior shaft support 57 Opposite Surface 58 Front guide surface 59 Rear guide surface 60 Shaft seal 70 Fastening part 72 Fastening bolt 82 Fixing bolt 83 Front cover 90 Clearance adjustment part 91 Spring fixing screw 92 Adjustment bolt 93 Adjustment nut (front nut) 94 Adjustment nut (rear nut) 95 Washer 96 Compression spring 97 Anti-rotation pin

Claims

1. A centrifugal pump comprising: a frame that rotatably supports a shaft; a casing fixed to a front surface of the frame; and an impeller housed in the casing and provided coaxially at the tip of the shaft, wherein the impeller rotates within the casing when driven by the shaft, thereby sending fluid from an inlet port formed in the casing to a discharge port, a clearance adjustment unit that is integral with the shaft and allows front and rear bearing units of the shaft to slide in the axial direction, and that adjusts an impeller clearance that is a facing gap between the inner surface of the casing and leading edges of the blades of the impeller; the clearance adjustment portion has a bearing housing that is fitted into the front or rear portion of the frame so as to be slidable in the axial direction and that accommodates a bearing unit for the rear portion of the shaft; The bearing housing is characterized in that the impeller clearance can be adjusted and its position can be maintained by adjusting the position of an adjustment arm that protrudes laterally from the bearing housing, and a compression spring that assists the sliding movement of the bearing housing is attached so as to abut against an opposing surface on the frame side and apply a pressing force in the axial direction of the bearing housing.

2. 2. The centrifugal pump according to claim 1, wherein a fixing screw for the compression spring is coaxially attached to the compression spring on the axially opposite side of the opposing surface on the frame side, thereby restricting the amount of axial deflection of the compression spring.

3. 3. The centrifugal pump according to claim 2, wherein the fixing screw and the compression spring are removed, and instead a compression bolt is screwed in from the axially opposite side of the opposing surface on the frame side, so that the tip of the compression bolt can press the opposing surface on the frame side.

4. the bearing housing has a rear bearing unit that supports a rear portion of the shaft therein and is supported on the rear portion of the frame by a spigot-fit that is slidable in the axial direction; the adjustment arm is provided so as to extend downward to a position facing an adjustment bolt fixing screw formed on a rear end surface of the frame, and an adjustment bolt insertion hole, through which an adjustment bolt is inserted, is formed at a position coaxial with the adjustment bolt fixing screw, 4. The centrifugal pump according to claim 1, wherein the adjustment bolt adjusts and fixes the axial position of the bearing housing by tightening a front nut and a rear nut attached to the front and rear of the adjustment arm, thereby making it possible to adjust the impeller clearance.

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