Rotor for electric water pumps and sliding bearing device for water pumps
To provide a rotor for electric water pumps in which a sliding bearing formed of a thermoplastic resin composition can be produced at a low cost and has superior low friction and low wear property, and an inner diameter of the sliding bearing is hardly contracted by the insert-molding. A rotor 1 used for electric water pumps has a main body 2 that supports an impeller of the pump, a sliding bearing 3 that rotatably supports a shaft, and a magnet 4 disposed to face a stator. The sliding bearing 3 is an annealing treated body of a polyphenylene sulfide resin composition. The polyphenylene sulfide resin composition contains 5-30 vol % of carbon fiber, 1-20 vol % of polytetrafluoroethylene resin and 1-30 vol % of graphite relative to the whole volume of the polyphenylene sulfide resin composition. The main body 2 is an injection-molded body disposed by insert-molding a thermoplastic resin composition, which is different from the polyphenylene sulfide resin composition, at an outer diameter side of the sliding bearing 3.
1 . A sliding bearing device for water pumps, the sliding bearing device being configured to be used in a water pump having an impeller, a shaft that fixes the impeller, a cylindrical sliding bearing fixed to the impeller for rotatably supporting the impeller relative to the shaft, cylindrical thrust receivers that slide on respective end surfaces of the sliding bearing, and a casing and a cover that house the impeller and form a pump chamber, the water pump being configured to suck and discharge circulation water through the pump chamber using rotation of the impeller,
the sliding bearing device for water pumps comprising the sliding bearing and the thrust receivers,
wherein:
a land part serving as a sliding surface, and a lubrication groove that discharges the circulation water from an inner diameter side toward an outer diameter side are formed on a surface of at least one component of at least one end surface of the sliding bearing, and a thrust receiver of the thrust receivers,
the lubrication groove has an inclined surface inclined relative to the land part and is configured to generate dynamic pressure due to the relative rotation between the sliding bearing and the thrust receiver,
in a projection view of the surface on which the lubrication groove is formed, seen from a front side thereof, the lubrication groove is formed by a region surrounded by: a line A and a line B, where each of A and B extends on the surface from the inner diameter side to the outer diameter side; a circular arc C along an inner diametrical surface; and a circular arc D along an outer diametrical surface,
the lubrication groove has a groove width formed by the line A and the line B,
the line A and the line B are straight,
an extension of the line A passes through an axial center of the component on which the lubrication groove is formed,
the length of the circular arc C is more than the length of the circular arc D, wherein an angle between the line A and the line B is 0-15 degrees,
wherein the lubrication groove is a plurality of lubrication grooves, and the lubrication grooves are disposed on the respective surfaces of the at least one component at any intervals in the circumferential direction,
each of the lubrication grooves is disposed offset, from each line A, toward a downstream side in a direction of the relative rotation,
the lubrication grooves have a groove side surface formed by the line B, a groove bottom surface connected to the groove side surface and inclined toward the land part, and the groove bottom surface has a groove depth that becomes smaller toward the line A, and
an inclined surface, having a gradient steeper than the groove bottom surface, is formed on a boundary between an end portion of the groove bottom surface at an upstream side in a rotational direction and the land part.
2 . The sliding bearing device for water pumps as defined in claim 1 , wherein:
the line A is located at an upstream side relative to the line B in a direction of the relative rotation,
a sectional shape of the lubrication groove cut by any cutting plane orthogonal to the line A is generally a right triangle having a hypotenuse on the inclined surface, and
an inner angle relating to an apex defined by an intersection point between the line A and the cutting plane is 3-30 degrees.
3 . The sliding bearing device for water pumps as defined in claim 1 , wherein the maximum depth of the lubrication groove is 0.1-1.0 mm.
4 . The sliding bearing device for water pumps as defined in claim 1 , wherein:
the sliding bearing is an injection-molded body of a resin composition,
the sliding bearing has the lubrication groove on the at least one end surface thereof,
the sliding bearing has a gate mark on the outer diametrical surface, and
a weld part is formed within the lubrication groove and is not formed on the land part.