Water Pump

Abstract

A water pump includes a pump shaft surrounded by a pump housing having a tubular section. A pulley having a cylindrical section and a flange wall is mounted on an end section of the pump shaft. An impeller is mounted on the other end section of the pump shaft. A mechanical seal is coaxially disposed between the tubular section and the pump shaft. A bearing is coaxially disposed between the tubular section of the pump housing and the cylindrical section of the pulley. In this water pump, the pump shaft includes a coaxial small diameter shaft section located at its first part which is located axially between the mechanical seal and the flange wall. The small diameter shaft section has a diameter smaller than a diameter of a second part of the pump shaft on which the mechanical seal is disposed so as to form an annular step portion.

1 . A water pump comprising:
 a pulley including a cylindrical section located radially inward of an outer periphery of the pulley, the pulley being rotatable upon transmission of power from a driving force;   a pump shaft disposed radially inward of the cylindrical section of the pulley and fixed to the cylindrical section, the pump shaft having a first end section on which the pulley is mounted;   a first flange wall extending from a first axial end portion of the cylindrical section of the pulley in a direction of the pump shaft;   an impeller disposed at a second end section of the pump shaft;   a pump housing including a tubular section disposed to surround the pump shaft;   a mechanical seal disposed between a radially inward side of the tubular section of the pump housing and an outer peripheral surface of the pump shaft; and   a bearing disposed between an inner peripheral surface of the cylindrical section of the pulley and the tubular section of the pump housing to rotatably support the pulley on the tubular section of the pump housing;   wherein the pump shaft includes a coaxial small diameter shaft section located at its first part which is located axially between the mechanical seal and the flange wall, the small diameter shaft section having a diameter smaller than a diameter of a second part of the pump shaft on which the mechanical seal is disposed, the small diameter shaft section having an outer peripheral surface located radially inward of an outer peripheral surface of a third part of the pump shaft axially extending from the second part so as to form a first annular step portion.   
     
     
         2 . A water pump as claimed in  claim 1 , wherein the outer peripheral surface of the third part of the pump shaft and the outer peripheral surface of the small diameter shaft section are connected to each other through at least one annular face which is perpendicular to an axis of the pump shaft or tapered in a direction approaching the mechanical seal. 
     
     
         3 . A water pump as claimed in  claim 1 , wherein the tubular section of the pump housing includes a first portion defining thereinside a drain chamber for storing a liquid having a volume, and a second portion defining a drain hole for introducing liquid dropped from the annular step portion into the drain chamber, the drain chamber and the drain hole being located under the first annular step portion in a direction of gravity. 
     
     
         4 . A water pump as claimed in  claim 1 , wherein the outer peripheral surface of the small diameter shaft section of the pump shaft is cylindrical. 
     
     
         5 . A water pump as claimed in  claim 1 , wherein the small diameter shaft section of the pump shaft is formed at a part of the pump shaft, the diameter of the small diameter shaft section being smaller than a diameter of a fourth part of the pump shaft extending to the first end section of the pump shaft, the outer peripheral surface of the small diameter shaft section being located radially inward of an outer peripheral surface of the fourth part of the pump shaft so as to form a second annular step portion. 
     
     
         6 . A water pump as claimed in  claim 5 , wherein the outer peripheral surface of the fourth part of the pump shaft and the outer peripheral surface of the small diameter shaft section are connected to each other through at least one annular face which is perpendicular to an axis of the pump shaft or tapered in a direction away from the first flange wall. 
     
     
         7 . A water pump as claimed in  claim 3 , wherein the drain chamber is open to the atmosphere. 
     
     
         8 . A water pump as claimed in  claim 7 , wherein the tubular section of the pump housing includes a third portion defining thereinside an annular space chamber located around the outer peripheral surface of the small diameter shaft section, and a fourth portion defining a vent opening for venting vapor, the drain hole being formed above the annular space chamber in the direction of gravity, the vent opening being formed below the annular space chamber in the direction of gravity. 
     
     
         9 . A water pump as claimed in  claim 1 , wherein the pump shaft is formed continuously tapered in an axial direction of from side of the flange wall to side of the impeller, the outer peripheral surface of the third part of the pump shaft and the outer peripheral surface of the small diameter shaft section being connected through at least one annular face forming the first annular step portion, the annular face being perpendicular to the axis of the pump shaft. 
     
     
         10 . A water pump as claimed in  claim 1 , wherein the pulley includes a second flange wall extending from the cylindrical section at a second axial end portion opposite to the first axial end portion, and a belt installation section which axially extends from an outer peripheral portion of the second flange wall. 
     
     
         11 . A water pump as claimed in  claim 1 , wherein the pulley and the first flange wall are formed integral with each other. 
     
     
         12 . A water pump as claimed in  claim 11 , wherein the pump shaft and the first flange wall are formed separate from each other, the first end section of the pump shaft being fixed to the first flange wall. 
     
     
         13 . A water pump as claimed in  claim 1 , wherein the first flange wall is formed with a plurality of through-holes. 
     
     
         14 . A water pump as claimed in  claim 1 , wherein the first annular step portion is formed to have a plurality of annular step portions. 
     
     
         15 . A water pump as claimed in  claim 14 , wherein the small diameter shaft section includes a plurality of coaxial small diameter shaft sections so as to form a plurality of annular step portions. 
     
     
         16 . A water pump as claimed in  claim 1 , wherein the bearing includes an inner race, an outer race, and a bearing seal which is fixed to one of the inner and outer races and slidable to the other race. 
     
     
         17 . A water pump as claimed in  claim 1 , wherein the outer peripheral surface of the small diameter shaft section is located radially inward of the outer peripheral surface of the third part of the pump shaft by not less than 1 mm which corresponds to a height of the annular step portion. 
     
     
         18 . A water pump comprising:
 a pulley including a cylindrical section located radially inward of an outer periphery of the pulley, the pulley being rotatable upon transmission of power from a driving force;   a pump shaft disposed radially inward of the cylindrical section of the pulley and fixed to the cylindrical section, the pump shaft having a first end section on which the pulley is mounted;   a flange wall extending from an axial end portion of the cylindrical section of the pulley in a direction of the pump shaft;   an impeller disposed at a second end section of the pump shaft;   a pump housing including a tubular section disposed to surround the pump shaft;   a mechanical seal disposed between a radially inward side of the tubular section of the pump housing and an outer peripheral surface of the pump shaft; and   a bearing disposed between an inner peripheral surface of the cylindrical section of the pulley and the tubular section of the pump housing to rotatably support the pulley on the tubular section of the pump housing;   wherein the pump shaft includes a step portion located axially between the mechanical seal and the flange wall to restrict movement of adhering water transferred through the outer peripheral surface of the pump shaft from side of the mechanical seal in a direction toward the flange wall.   
     
     
         19 . A water pump comprising:
 a pump shaft having a first end section on which a pulley is disposed and a second end section on which an impeller is disposed;   a pump housing disposed surrounding an outer peripheral side of the pump shaft;   a bearing disposed to the pump housing to rotatably supporting the pump shaft; and   a mechanical seal fixed to the pump housing and to the pump shaft and having a seal section which makes sliding at a position nearer to the impeller than to the bearing in an axial direction of the pump shaft;   wherein a coaxial and annular groove is formed at the outer peripheral surface of the pump shaft and located at an axial position between the mechanical seal and the bearing to prevent adhering water from transferring in a direction toward the bearing.   
     
     
         20 . A water pump as claimed in  claim 19 , wherein the annular groove has an axial width of not less than 2 mm.