JP2019206921A - pump - Google Patents

Abstract

To constitute a pump for favorably suppressing the leakage of fluid in a center part of a shroud by using a seal ring.SOLUTION: A pump comprises a closed pump rotor 43 which is rotatably accommodated in a pump space with a rotating axial core as a center, and has a shroud 43b, and a seal ring 52 which is movable along the rotation axial core coaxially with the rotating axial core with respect to a cylindrical part 43ba of the shroud 43b. The seal ring 52 has a pressure receiving face 52a opposing the shroud 43b, an abutment face 52b opposing an inner wall of the pump space at a side opposite to the pressure receiving face, an internal peripheral wall face 52c opposing an external periphery of the cylindrical part 43ba, and an external peripheral wall face 52d at the outside of the internal peripheral wall face. A recess G which is recessed toward a direction of the abutment face 52b from the pressure receiving face 52a of the seal ring 52 is formed over the whole periphery of the seal ring.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a pump having a closed type pump rotor having a shroud and having a structure for suppressing a back flow of fluid at an outer peripheral portion of the shroud.

  As a pump configured as described above, in Patent Document 1, a seal portion is provided between a casing and a shroud (front shroud in literature) of a pump rotor (impeller in literature) that is rotated by a driving force of a canned motor. The technology provided is shown.

  Further, in Patent Document 2, a seal ring having a double structure in the radial direction is externally fitted to the central portion of the shroud of the pump rotor, as judged from the description and drawings, and the end face of this seal ring A technique is shown in which the outer surface is brought into contact with the casing in the radial direction.

  This patent document 2 is intended to alleviate fluid leakage between a pump rotor (impeller in the literature) and a casing in a centrifugal pump, and the inner seal ring and the outer seal ring are relatively rotatable. It also describes that the sealing performance is improved by making one cross-sectional shape of the seal ring having a double structure L-shaped.

  Further, in Patent Document 3, a seal ring is externally fitted to the central portion of the shroud of the pump rotor (impeller in the literature), or the seal ring is inserted into the central portion, based on the description and drawings. A technique is shown in which the end portion of the seal ring is disposed so as to be able to contact the inner surface of the casing while being fitted.

  In this Patent Document 3, the object is to provide an impeller that minimizes suction loss by minimizing the distance between the suction part of the casing and the inflow part of the pump rotor, and the seal ring rotates integrally with the shroud, or A structure is described in which the seal ring is supported with respect to the shroud so as to be freely retractable in a direction along the axis.

JP 2009-221938 A Chinese Utility Model Registration No. 206129682 Korean Patent No. 10-1738910

  In the pumps disclosed in Patent Documents 1 to 3, while the pump rotor rotates, the fluid is sucked along the rotation axis of the pump rotor, and the centrifugal force generated by the rotation is used to fluid in a direction perpendicular to the rotation axis. It has the structure which sends out.

  In this type of pump, the central portion of the shroud is at a low pressure and the outer peripheral portion of the pump rotor is at a high pressure. Therefore, when the sealing performance between the outer periphery of the shroud and the casing is low, fluid from the outer periphery of the pump rotor Causes a phenomenon of flowing in the opposite direction toward the center side of the shroud, which decreases the pump performance.

  Considering the sealing performance, the one using the seal portion as shown in Patent Document 1 requires a gap to prevent resistance from acting on the rotation of the pump rotor, and the seal portion has a high dimensional accuracy in order to form this interval. Is required.

  Further, as shown in Patent Document 2, in the configuration in which the end surface of the seal ring is in contact with the inner surface of the casing, the outer seal ring of the double structure is held by the housing at the contact portion, and the inner seal ring is Since it rotates integrally with the shroud, it can be imagined that these speed differences become large and cause damage, and that the pump performance deteriorates due to the friction generated between them.

  Furthermore, as described in Patent Document 3, in the case where the seal ring is fitted to the shroud, it is possible to improve the sealing performance by bringing the end face of the seal ring into contact with the inner surface of the casing by the action of thrust accompanying rotation. It is. However, in this configuration, since the seal ring is movably fitted to the shroud, the phenomenon of fluid flowing in the gap between the shroud and the seal ring cannot be avoided. It was also possible to imagine that the sealing performance was lowered by the flow of fluid.

  For these reasons, there is a need for a pump that satisfactorily suppresses fluid leakage at the center of the shroud with a seal ring.

  A characteristic configuration of the pump according to the present invention includes a closed pump rotor having a shroud housed in a pump space inside a casing so as to be rotatable about a rotating shaft core, and the shroud is formed with a coaxial core with the rotating shaft core The cylindrical portion is provided with a seal ring that is coaxial with the rotating shaft core and is movable along the rotating shaft core. The seal ring has an annular pressure receiving surface that faces the shroud, and the opposite side. An annular contact surface facing the inner wall of the pump space, an inner peripheral wall surface facing the outer periphery of the cylindrical portion, and an outer peripheral wall surface opposite to the inner peripheral wall surface in the radial direction of the seal ring. In this seal ring, a recess recessed from the pressure receiving surface toward the contact surface is formed over the entire circumference.

According to this characteristic configuration, when the pump rotor rotates and the pressure on the outer periphery of the pump rotor rises from the inner space of the cylindrical portion of the shroud, this pressure acts on the pressure receiving surface of the seal ring, so that the seal ring Displacement is performed along the axis of rotation, and the contact surface of the seal ring contacts the inner wall of the casing. By abutting in this way, the fluid flowing from the discharge side to the suction side can be blocked at the abutting portion. In addition, since a recess that is recessed from the pressure-receiving surface of the seal ring toward the contact surface is formed, the inner peripheral wall surface is elastically deformed inward by the pressure of the fluid that has entered the recess, and the outer periphery of the cylindrical portion It is possible to make contact with the surface, preventing the flow of fluid between the inner peripheral wall surface and the outer peripheral surface of the cylindrical portion, and obtaining good sealing performance.
Therefore, the pump which suppressed the leakage of the fluid in the center part of a shroud favorably with a seal ring was comprised. Further, in this configuration, since the inner peripheral wall surface of the seal ring is elastically deformed and brought into contact with the outer peripheral surface of the cylindrical portion, these are highly accurate so as to reduce the distance between the inner peripheral wall surface and the outer peripheral surface of the cylindrical portion. It is not necessary to manufacture with.

  As another configuration, the seal ring is set such that a second thickness between the inner peripheral wall surface and the inner side surface of the recess is thinner than a first thickness between the outer peripheral wall surface and the outer side surface of the recess. May be.

  According to this, it is possible to greatly elastically deform the wall portion formed with the second thickness inside the concave portion in the radial direction from the wall portion formed with the first thickness outside the concave portion in the radial direction. The wall surface can be positively brought into contact with the outer peripheral surface of the cylindrical portion, and the sealing performance at this portion can be improved.

  As another configuration, the first thickness may be set to be thinner as the portion is closer to the opening of the recess.

  According to this, a portion close to the opening of the recess can be greatly elastically deformed in the wall portion formed with the first thickness, and the end portion of the inner peripheral wall surface of the seal ring can be easily provided on the outer peripheral surface of the cylindrical portion. It is possible to improve the sealing performance.

  As another configuration, a foreign matter discharge groove that allows fluid to flow in the radial direction of the seal ring may be formed on the contact surface of the seal ring.

  According to this, even when foreign matter is sandwiched between the contact surface of the seal ring and the inner wall of the pump space, it is possible to flow out together with the fluid through the foreign matter discharge groove. It is possible to eliminate the inconvenience that is caused to remain over time and cause a decrease in sealing performance.

  As another configuration, a rotation restricting portion that restricts the relative rotation between the seal ring and the shroud may be provided.

  According to this, by integrally rotating the cylindrical portion of the shroud and the seal ring, the mass of the pump rotor and the rotating member is increased, and stable rotation is possible without causing torque fluctuation.

It is sectional drawing of a water pump in the state in which a pump rotor rotates. It is sectional drawing of the site | part of the seal ring in the state spaced apart from the cover plate. It is sectional drawing of the site | part of the seal ring of the state contact | abutted to a cover plate. It is an expanded sectional view of the site | part of the seal ring of the state contact | abutted to a cover plate. It is a top view of a seal ring. It is a disassembled perspective view of a seal ring and a shroud. It is sectional drawing of the state which isolate | separated the site | part ranging from a 2nd casing to a rotor. It is sectional drawing of the ring part of a seal ring. It is sectional drawing of the ring part of the seal ring of another embodiment (a). It is sectional drawing of the ring part of the seal ring of another embodiment (b). It is sectional drawing of the ring part of the seal ring of another embodiment (c). It is a bottom view which shows the slit of the seal ring of another embodiment (c). It is sectional drawing of the ring part of the seal ring of another embodiment (d).

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
〔overall structure〕
In FIG. 1, a pump rotor 43 that rotates about a rotation axis X by a driving force of a motor unit M is housed in a casing C, and a suction cylinder 23 that sucks cooling water (an example of fluid), and sucked cooling water. A water pump P is shown as a specific example of a pump provided with a discharge cylinder 25 for feeding out a casing C in a casing C.

  The water pump P is configured as a centrifugal pump that sucks cooling water from the suction cylinder 23 into the pump space Sp as the pump rotor 43 rotates, and sends the sucked cooling water from the discharge cylinder 25 in the tangential direction of the pump rotor 43. ing.

  This water pump P is used in a form in which cooling water is circulated between an engine and a radiator in a vehicle such as an automobile. The pump having this configuration is not limited to the water pump P, and may be configured as a pump that sends out another fluid.

[Specific configuration of pump]
Although this water pump P can be used in any posture, in this embodiment, the vertical relationship will be described based on the posture shown in FIG.

  As shown in FIG. 1, the casing C is configured by connecting a first casing 10 made of resin, a second casing 20 made of resin, and a third casing 30 made of resin. In the casing C, the rotor 40 is accommodated in a space extending from the rotor space Sr formed in the first casing 10 to the pump space Sp formed in the second casing 20.

  A rotor space Sr that opens upward is formed in the first casing 10. The second casing 20 is formed with a bulging portion 22 that is cylindrical with the rotational axis X as a center and bulges upward, and a pump space Sp is formed in a region extending from the inside of the bulging portion 22 to the lower side.

  In order to connect the first casing 10 and the second casing 20 in a water-tight state, the first flange portion 11 and the first flange portion 11 correspond to each of the opposing portions of the first casing 10 and the second casing 20. Two flange portions 21 are formed, and these are connected by a technique such as heat welding or adhesion.

  As shown in FIG. 1, the first casing 10 has a rotor space Sr that is coaxial with the rotational axis X and has a bottom, and a stator 13 is embedded in a side wall portion 12 that surrounds the rotor space Sr. Further, the rotor space Sr is provided with a fixed shaft 14 that is coaxial with the rotation axis X in a form in which the base end portion is inserted into the bottom wall portion of the first casing 10.

  The stator 13 includes a core 13a in which magnetic steel plates are laminated, and a coil 13b made of a conductive wire wound around the core 13a. The stator 13 is embedded in the side wall of the first casing 10 by resin potting. The fixed shaft 14 has a circular cross-sectional shape, and an axial length is set so that the tip reaches the pump space Sp of the second casing 20.

  As shown in FIG. 2, a suction cylinder 23 is formed that protrudes upward from the upper wall 22 b of the bulging portion 22 of the second casing 20, coaxially with the rotational axis X. Further, a discharge cylinder 25 is formed in the second casing 20 in such a posture that fluid is sent in a tangential direction from an annular space surrounding the pump space Sp formed inside the bulging portion 22.

  As shown in FIG. 1, the third casing 30 is formed in a bowl shape in which the central portion swells downward in order to form a space for accommodating the control board 31. The third casing 30 is connected to the bottom of the first casing 10 by a technique such as heat welding or adhesion.

  A support portion 15 that protrudes downward is formed in the lower portion of the first casing 10, and the control board 31 is supported by the support portion 15.

  As shown in FIGS. 1 and 7, the rotor 40 has a bearing 41 that is rotatably fitted to the fixed shaft 14, and a lower motor rotor 42 and an upper closed pump rotor 43 are integrated. It is configured.

  A washer 44 and a bush 45 are externally fitted to the upper end of the fixed shaft 14, and these are supported by the fixed shaft 14 in a locked state by a retaining ring. With this structure, the upward movement of the rotor 40 is restricted.

  Although the bearing 41 assumes the cylindrical material which functions as a sliding bearing, you may comprise with a needle bearing etc. A plurality of permanent magnets 42 a are provided on the outer periphery of the motor rotor 42.

  The pump rotor 43 includes a base rotor 43a that protrudes upward toward the center side, a shroud 43b that is fixed to the upper surface side of the base rotor 43a at a predetermined interval, and an impeller 43c that is intermediate between them. Further, the shroud 43b is integrally formed with a cylindrical portion 43ba centered on the rotation axis X at the upper end.

  In addition, although the impeller 43c is comprised by the wing | blade body integrally formed in the lower surface side of the shroud 43b, you may integrally form in the state protruded on the upper surface of the base rotor 43a.

[Seal unit]
As the pump rotor 43 is driven to rotate, the water pump P creates a flow of cooling water from the central portion of the pump rotor 43 toward the outer peripheral side. As a result, the pressure at the central portion of the pump rotor 43 decreases, the cooling water is sucked from the suction cylinder 23, and the pressure at the portion close to the outer periphery of the pump rotor 43 in the pump space Sp rises. The cooling water is sent out from the discharge cylinder 25.

  Since a pressure difference is created in the pump space Sp in this way, the cooling water is caused to flow backward from a portion of the pump space Sp connected to the outer periphery of the pump rotor 43 toward an opening portion at the tip of the cylindrical portion 43ba of the shroud 43b. Pressure acts in the direction.

  And when rejection water flows backward by the effect | action of a pressure, the efficiency of the water pump P will be reduced. In order to suppress the backflow for this reason, in the present embodiment, the space between the cylindrical portion 43ba of the shroud 43b and the inner wall of the bulging portion 22 (the inner wall of the pump space Sp) facing the cylindrical portion 43ba. Is provided with a seal unit 50.

  As shown in FIGS. 1 to 4 and 6 to 8, the seal unit 50 includes a cover plate 51 that is press-fitted and fixed inside the bulging portion 22, and a seal ring 52 that is externally fitted to the tubular portion 43 ba of the shroud 43 b. And is configured.

  The cover plate 51 is formed into a shape that is generally annular and has a side wall portion that can be brought into close contact with the inner peripheral surface of the bulging portion 22 by press working of a stainless steel material. The cover plate 51 is press-fitted and fixed so that the upper wall portion thereof is in close contact with the lower surface of the upper wall 22 b of the bulging portion 22. By being fixed in this way, the lower surface of the cover plate 51 functions as an inner wall of the pump space Sp, and the contact surface 52b at the upper end of the seal ring 52 can be contacted.

  The seal ring 52 is molded into a ring shape with a material having high heat resistance and excellent durability like PPS (polyphenylene sulfide) resin. The seal ring 52 may be made of rubber or a resin material that can be flexibly deformed in order to improve sealing performance.

  As shown in FIG. 8, the seal ring 52 is generally annular, and as shown in FIG. 8, an annular pressure receiving surface 52 a that is the lower side facing the shroud 43 b and an upper side that faces the upper wall 22 b of the bulging portion 22 on the opposite side An annular contact surface 52b, an inner peripheral wall surface 52c facing the outer periphery of the cylindrical portion 43ba, and an outer peripheral wall surface 52d opposite to the inner peripheral wall surface 52c in the radial direction of the seal ring 52 (outside). A recess G that is recessed from the pressure receiving surface 52a toward the contact surface 52b is formed.

  That is, the seal ring 52 has a structure in which the outer wall portion 52S is arranged outside the recess G in the radial direction and the inner wall portion 52T is arranged inside the recess.

  In this seal ring 52, the inner peripheral wall surface 52c and the inner side surface of the recess G with respect to the first thickness T1 (thickness of the outer wall portion 52S) as the thickness between the outer peripheral wall surface 52d and the outer side surface of the recess G. The second thickness T2 (thickness of the inner wall portion 52T) is set to be thin. Furthermore, a notch groove 52e having a groove shape is formed on the entire periphery of the inner wall portion 52T exposed to the recess G. Further, as shown in FIG. 5, a plurality of foreign matter discharge grooves 52 ba having a posture along the radial direction of the seal ring 52 are formed in the portion of the contact surface 52 b.

  The seal ring 52 is supported so as to be movable in the vertical direction (the direction along the rotation axis X) with respect to the cylindrical portion 43ba of the shroud 43b. Further, a rotation restricting portion is formed between the seal ring 52 and the shroud 43b so that the seal ring 52 rotates integrally with the shroud 43b. The rotation restricting portion is formed by a plurality of restricting protrusions 43bt formed on the outer periphery of the cylindrical portion 43ba and a plurality of engaging grooves 52f formed on the inner wall portion 52T so as to engage with the restricting protrusions 43bt. Has been.

  As shown in FIG. 2, when the pump rotor 43 does not rotate, a part of the tubular portion 43ba comes into contact with the pressure receiving surface 52a of the seal ring 52, so that the pressure receiving surface 52a and the shroud 43b corresponding to the pressure receiving surface 52a. A gap D is formed between the upper surface and the upper surface.

  Since the seal unit 50 is configured in this manner, when the pump rotor 43 rotates in the direction indicated by the arrow in FIG. 6, the seal ring 52 rotates integrally with the cylindrical portion 43 ba and the pump rotor 43. The pressure generated by the rotation of the seal ring 52 acts on the pressure receiving surface 52a of the seal ring 52, and a force that moves (shifts) the seal ring 52 upward acts.

  Due to this movement, the contact surface 52b at the upper end of the seal ring 52 contacts the lower surface of the cover plate 51, and the clearance of this portion is eliminated, so that the tip of the cylindrical portion 43ba of the shroud 43b is connected from the portion connected to the outer periphery of the pump rotor 43. The flow of the cooling water which tries to flow backward toward the opening portion of the water is blocked, and the cooling water can be sent out with high efficiency (see FIG. 3).

  Further, when the seal ring 52 moves, cooling water is supplied through a gap D formed between the pressure receiving surface 52a of the seal ring 52 and the shroud 43b. For this reason, compared with the case where the gap D is not formed, the seal ring 52 can be quickly moved without causing a disadvantage that the pressure receiving surface 52a of the seal ring 52 is in close contact with the upper surface of the shroud 43b.

  In particular, the second wall thickness T2 of the inner wall portion 52T is formed to be thinner than the first wall thickness T1 of the outer wall portion 52S, and the notch groove 52e is formed in a portion of the inner wall portion 52T exposed to the recess G. The inner wall 52T has a structure that is easily elastically deformed.

  With this configuration, when the pump rotor 43 rotates, a part of the cooling water enters the recess G of the seal ring 52, moves the entire seal ring 52 upward, and makes the contact surface 52 b the lower surface of the cover plate 51. Abut. At the same time, as shown in FIG. 4, the inner wall 52T is elastically deformed inward by the pressure of the cooling water that has entered the recess G, and the inner peripheral wall 52c is brought into close contact with the outer periphery of the cylindrical portion 43ba. By sticking in this way, the sealing performance between the inner peripheral wall surface 52c and the cylindrical portion 43ba is enhanced, and the flow of cooling water at this portion is prevented. In FIG. 4, the amount of elastic deformation of the inner wall 52T is exaggerated.

  When the cooling water contains particulate foreign matter, the foreign matter can be discharged together with the cooling water through the foreign matter discharge groove 52ba formed on the contact surface 52b of the seal ring 52. Never stay in

[Another embodiment]
In addition to the above-described embodiments, the present invention may be configured as follows (the components having the same functions as those of the embodiments are given the same numbers and symbols as those of the embodiments).

(A) As shown in FIG. 9, a tapered portion 52 g that forms an inclined surface is formed so that the inner wall portion 52 </ b> T becomes thinner toward the opening side (lower side) of the recess G of the seal ring 52. By forming the tapered portion 52g at the lower end portion of the inner wall portion 52T as described above, the elastic deformation of this portion is easily performed, and the sealing performance between the inner peripheral wall surface 52c and the outer peripheral surface of the tubular portion 43ba is enhanced. Can do.

(B) As shown in FIG. 10, the notched groove 52e of the inner wall portion 52T is formed in a smoothly recessed shape, and the projecting region that projects smoothly along the notched groove 52e with respect to the inner peripheral surface facing this formation site. 52ca is formed over the entire circumference.

  With this configuration, not only the inner wall portion 52T of the seal ring 52 can be easily elastically deformed, but also the projecting region 52ca is brought into contact with the outer peripheral surface of the cylindrical portion 43ba, thereby sealing performance at this portion. It is also possible to increase.

(C) As shown in FIGS. 11 and 12, a plurality of slits 53 are formed in a vertical orientation with respect to the inner wall portion 52 </ b> T of the seal ring 52. These slits 53 are formed as cuts extending from the surface of the inner wall portion 52T facing the rotational axis X to the recess G, and are inclined to a virtual line passing through the rotational axis X in the bottom view shown in FIG. The posture is set.

  By forming the plurality of slits 53 in this way, the inner wall 52T is divided into a plurality of pieces, and the action of the cooling water that has entered the recess G with the rotation of the pump rotor 43 causes the inner wall 52T to Each piece can be easily elastically deformed inward. As a result, the inner peripheral wall surface 52c can be brought into close contact with the outer periphery of the cylindrical portion 43ba of the pump rotor 43 to further improve the sealing performance.

  In this alternative embodiment (c), it is assumed that the slit 53 is in a posture parallel to the rotation axis X and has a constant width. For example, as shown by a two-dot chain line in FIG. A modification example in which the slit width is enlarged and the slits 53a are formed is also conceivable. In the enlarged slit 53a of this modification, since the slit width is expanded toward the lower side (side closer to the shroud 43b), the width (length in the circumferential direction) of each piece of the inner wall portion 52T is decreased toward the lower side. Elastic deformation can be further facilitated to improve the sealing performance.

  In addition, the structure of this another embodiment (c) can also be combined with the structure of embodiment, and the structure of another embodiment (a), (b).

(D) As shown in FIG. 13, the seal ring 52 is formed by cutting out the inner periphery of the upper part of the seal ring 52 by a set thickness Tx. In this configuration, the upper wall thickness T4 of the contact surface 52b at the upper end of the seal ring 52 is made smaller than the total wall thickness T3 of the seal ring 52.

  That is, in the configuration of this another embodiment (d), the upper end portion of the inner wall portion 52T is cut away, so that the vertical dimension of the region where the stress acts when the inner wall portion 52T elastically deforms inward is shortened. As a result, when the inner wall 52T of the seal ring 52 is elastically deformed inward by the pressure of the cooling water that has entered the recess G with the rotation of the pump rotor 43, the stress acting in the direction that prevents this elastic deformation is reduced. As a result, the deformation can be easily performed, and the inner peripheral wall surface 52c can be brought into close contact with the outer periphery of the tubular portion 43ba of the pump rotor 43 to further improve the sealing performance.

  In addition, the structure of this another embodiment (d) can also be combined with the structure of embodiment, and the structure of another embodiment (a), (b), (c).

(E) It is conceivable that an engagement protrusion is formed on the seal ring 52 as the rotation restricting portion, and an engagement concave portion that engages with the engagement protrusion is formed on the shroud 43b. In the embodiment, the restriction projection 43bt is engaged with the engagement groove 52f of the inner wall portion 52T. Instead, the engagement groove 52f with which the restriction projection 43bt is engaged is formed in the outer wall portion 52S. It is also conceivable to configure so as to.

(F) The water pump P can be configured so that the shroud 43b and the seal ring 52 can rotate relative to each other without providing a structure for rotating the shroud 43b and the seal ring 52 integrally.

  INDUSTRIAL APPLICABILITY The present invention can be used for a pump having a closed type pump rotor having a shroud and having a configuration for preventing a back flow of fluid.

43 Pump rotor 43b Shroud 43ba Cylindrical part 52 Seal ring 52a Pressure receiving surface 52b Abutting surface 52ba Foreign matter discharge groove 52c Inner peripheral wall surface 52d Outer peripheral wall surface G Concave Sp Pump space T1 First thickness (first thickness)
T2 Second thickness (second thickness)
X rotation axis

Claims (5)

A closed type pump rotor having a shroud, which is housed in a pump space inside the casing so as to be rotatable around a rotation axis;
The shroud is provided with a seal ring movably along the rotation axis with the rotation axis and the coaxial core with respect to the cylindrical portion formed with the rotation axis and the coaxial core,
The seal ring includes an annular pressure receiving surface facing the shroud, an annular contact surface facing the inner wall of the pump space on the opposite side, an inner peripheral wall surface facing the outer periphery of the cylindrical portion, and the seal The inner circumferential wall surface is opposite to the inner circumferential wall surface in the radial direction of the ring, and a recess that is recessed from the pressure-receiving surface of the seal ring toward the contact surface is formed over the entire circumference. Pump.   The second thickness between the inner peripheral wall surface and the inner side surface of the recess is set to be thinner than the first thickness between the outer peripheral wall surface and the outer side surface of the recess. The pump according to 1.   3. The pump according to claim 2, wherein the first thickness is set to be thinner toward a portion closer to the opening of the recess.   The pump according to any one of claims 1 to 3, wherein a foreign matter discharge groove for allowing a fluid to flow in a radial direction of the seal ring is formed on the contact surface of the seal ring.   The pump as described in any one of Claims 1-4 provided with the rotation control part which controls these relative rotation between the said seal ring and the said shroud.

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