Abstract: A fluid machine includes a plurality of fluid dynamic plain bearings supporting a rotating member. The fluid dynamic plain bearings each include: a top foil; a bump foil; and a bearing housing. The top foil has a bearing surface that has one end portion and the other end portion in a circumferential direction of the bearing surface. The top foil has a fixed end and a free end respectively formed at the one end portion and the other end portion. A movement of the free end in an axial direction of the rotating member is regulated by a regulating member. A clearance through which a fluid flows is formed between the fixed end and the free end. The free end has a discharge passage through which a foreign substance contained in the fluid is discharged from the clearance. The discharge passage is formed through the free end.

Abstract: A foil bearing includes a bearing housing, a top foil, a bump foil, and two retaining portions. A holding groove is formed in the inner circumferential surface of the bearing housing to extend in an axial direction. The top foil and the bump foil each include an insertion plate portion, which is inserted into the holding groove and extends in the axial direction. Each of the retaining portions includes a facing surface that faces the insertion plate portion in the axial direction. In the axial direction, the distance between the facing surfaces of the two retaining portions is longer than the length of the insertion plate portion. At least one of the insertion plate portions includes a bent plate portion that is bent to contact the facing surface.

Abstract: A foil bearing includes a bearing housing, a top foil, and a bump foil. The bump foil has: a first portion, a second portion, and a third portion disposed at least between the first portion and the second portion and configured to come in contact with the top foil. The top foil applies a load to the second portion with displacement of the top foil in a radially outward direction of the bearing housing. The third portion is not in contact with the top foil when the load is equal to or lower than a predetermined load, and is in contact with the top foil with elastic deformation of the second portion when the load is higher than the predetermined load. The first portion is in surface contact with the inner peripheral surface.

Abstract: A turbo fluid machine includes a rotary shaft configured to rotate in one rotational direction, and a thrust foil bearing that includes: a plurality of bump foils each having a corrugated shape and a plurality of top foils each having a bearing surface that faces a thrust collar. Each bump foil is divided into an outer peripheral foil and an inner peripheral foil in a radial direction of the rotary shaft. Ridges on the outer peripheral foil are inclined in the other rotational direction of the rotary shaft while extending from an edge of the outer peripheral foil adjacent to an inner peripheral side toward an outer peripheral side, and the ridges on the inner peripheral foil are inclined in the other rotational direction while extending from an edge of the inner peripheral foil adjacent to the outer peripheral side toward the inner peripheral side.

Abstract: A turbo fluid machine includes a partition wall separating an inside of a housing into a compression space and a bearing space; and a foil bearing. The partition wall includes a support part having an end face raised toward a thrust collar in an axial direction. The support part has a groove formed in the end face and radially extending to an outer peripheral surface of the support part. Top foils of the foil bearing each have one surface facing the thrust collar and the other surface elastically supported by corresponding one of bump foils of the foil bearing. The foil bearing is mounted on the end face such that a position of the groove corresponds to a position of a gap between the bump foils and a position of a gap between the top foils and such that the groove faces the thrust collar in the axial direction.

Abstract: A turbo fluid machine includes a rotating member having a bearing-contact surface; an operating part configured to rotate together with the rotating member to compress and discharge a fluid; a housing accommodating the rotating member and the operating part; and a foil bearing having a bearing surface that faces the bearing-contact surface and supporting the rotating member such that the rotating member is rotatable relative to the housing. At least one of the bearing-contact surface or the bearing surface has thereon a coating layer. The coating layer comprises polyamide-imide serving as a binder resin and molybdenum disulfide serving as a solid lubricant. A mass ratio of molybdenum disulfide to polyamide-imide is 0.42 or more.

Abstract: A turbo fluid machine includes a rotary shaft configured to rotate in one rotational direction, and a thrust foil bearing that includes: a plurality of bump foils each having a corrugated shape and a plurality of top foils each having a bearing surface that faces a thrust collar. Each bump foil is divided into an outer peripheral foil and an inner peripheral foil in a radial direction of the rotary shaft. Ridges on the outer peripheral foil are inclined in the other rotational direction of the rotary shaft while extending from an edge of the outer peripheral foil adjacent to an inner peripheral side toward an outer peripheral side, and the ridges on the inner peripheral foil are inclined in the other rotational direction while extending from an edge of the inner peripheral foil adjacent to the outer peripheral side toward the inner peripheral side.

Abstract: A turbo fluid machine includes a rotary shaft configured to rotate in one rotational direction, and a radial foil bearing. The radial foil bearing includes: a bump foil formed of an elastic thin plate having a corrugated shape. The bump foil is divided into first and second foil portions located respectively on one side and on the other side in an axial direction of the rotary shaft. Ridges on the first foil portion are inclined in the other rotational direction of the rotary shaft while extending from an edge of the first foil portion adjacent to the other side toward the one side in the axial direction. The ridges on the second foil portion are inclined in the other rotational direction of the rotary shaft while extending from an edge of the second foil portion adjacent to the one side toward the other side in the axial direction.

Abstract: A fluid machine includes a rotating body, an operation body rotated integrally with the rotating body, a housing, hydrodynamic plain bearings rotatably supporting the rotating body relative to the housing, and a cooling passage arranged in the housing. The hydrodynamic plain bearings each include a resin coating layer at a portion that is opposed to the rotating body. The hydrodynamic plain bearings include at least one combination of hydrodynamic plain bearings. Each combination includes an upstream hydrodynamic plain bearing and a downstream hydrodynamic plain bearing located at different positions in a direction in which the fluid flows through the cooling passage. The coating layer of the upstream hydrodynamic plain bearing has a lower hardness than the coating layer of the downstream hydrodynamic plain bearing.

Abstract: A fluid machine includes a rotating body, an operation body rotated integrally with the rotating body, a housing, hydrodynamic plain bearings rotatably supporting the rotating body relative to the housing, and a cooling passage arranged in the housing. The hydrodynamic plain bearings each include a resin coating layer at a portion that is opposed to the rotating body. The hydrodynamic plain bearings include at least one combination of hydrodynamic plain bearings. Each combination includes an upstream hydrodynamic plain bearing and a downstream hydrodynamic plain bearing located at different positions in a direction in which the fluid flows through the cooling passage. The coating layer of the upstream hydrodynamic plain bearing has a lower hardness than the coating layer of the downstream hydrodynamic plain bearing.

Abstract: A motor-driven Roots pump includes a housing, a drive shaft and a driven shaft that have axial lines parallel with each other, and a gear chamber. The housing includes a first partition that has a first defining surface, a second partition having a second defining surface, and a relief recess. An addendum circle of the drive gear and an addendum circle of the driven gear intersect with each other at a first intersection point. A plane that includes both the axial lines is defined as an imaginary plane. The first intersection point is located on a side of the imaginary plane on which the drive gear and the driven gear start meshing with each other. An opening of the relief recess is opposed to the first intersection point and is arranged in a region on a side of the imaginary plane on which the first intersection point is located.

Abstract: A housing unit of a Roots pump includes a rotor housing, which includes a peripheral wall, and a cover member, which closes an opening of the rotor housing. At least one of a mating surface of the peripheral wall or a mating surface of the cover member includes an annular first groove accommodating a seal member. The rotor housing includes a bulging portion including a second groove. The seal member incudes first projections, which project from an annular seal body, and a second projection, which projects further radially inward from the seal body than the first projections. Each first projection includes a distal end that contacts a side surface on a radially inner side or on a radially outer side of the first groove. The second projection is arranged in the second groove to determine the position of the seal body in the first groove.

Abstract: A seal member includes pushing projections that project from a seal body toward at a groove inner-side circumferential surface and are arranged at intervals in a circumferential direction of the seal body. The pushing projections push the seal body against the groove inner-side circumferential surface and a groove outer-side circumferential surface between the groove inner-side circumferential surface and the groove outer-side circumferential surface. This reduces the gap between the groove outer-side circumferential surface and the seal member in the seal accommodating groove. Thus, salt water is unlikely to collect in the gap between the groove outer-side circumferential surface of the seal accommodating groove and the seal member. This improves the corrosion resistance of the housing and the seal member.

Abstract: A housing unit of a Roots pump includes a rotor housing, which includes a peripheral wall, and a cover member, which closes an opening of the rotor housing. At least one of a mating surface of the peripheral wall or a mating surface of the cover member includes an annular first groove accommodating a seal member. The rotor housing includes a bulging portion including a second groove. The seal member incudes first projections, which project from an annular seal body, and a second projection, which projects further radially inward from the seal body than the first projections. Each first projection includes a distal end that contacts a side surface on a radially inner side or on a radially outer side of the first groove. The second projection is arranged in the second groove to determine the position of the seal body in the first groove.

Abstract: A motor-driven Roots pump includes a housing, a drive shaft and a driven shaft that have axial lines parallel with each other, and a gear chamber. The housing includes a first partition that has a first defining surface, a second partition having a second defining surface, and a relief recess. An addendum circle of the drive gear and an addendum circle of the driven gear intersect with each other at a first intersection point. A plane that includes both the axial lines is defined as an imaginary plane. The first intersection point is located on a side of the imaginary plane on which the drive gear and the driven gear start meshing with each other. An opening of the relief recess is opposed to the first intersection point and is arranged in a region on a side of the imaginary plane on which the first intersection point is located.

Abstract: A seal member includes pushing projections that project from a seal body toward at a groove inner-side circumferential surface and are arranged at intervals in a circumferential direction of the seal body. The pushing projections push the seal body against the groove inner-side circumferential surface and a groove outer-side circumferential surface between the groove inner-side circumferential surface and the groove outer-side circumferential surface. This reduces the gap between the groove outer-side circumferential surface and the seal member in the seal accommodating groove. Thus, salt water is unlikely to collect in the gap between the groove outer-side circumferential surface of the seal accommodating groove and the seal member. This improves the corrosion resistance of the housing and the seal member.