Patent Publication Number: US-6213063-B1

Title: Engine water pump structure

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a water pump for a water-cooled engine. 
     2. Description of Related Art 
     Japanese Utility Model Publication No. Hei 6-31197 discloses a structure of a water pump for a water-cooled engine of a motorcycle. In the water pump, an impeller is attached to one end of a hollow pump shaft, and a pump gear is attached to the other end of the pump shaft. The pump gear rotates in response to rotation of a crankshaft. The pump shaft is supported by a crankcase of the crankshaft. 
     The pump gear receives a thrust load from a pin. The pin has its opposite ends supported in the crankcase via the pump gear and is orthogonal to the crankcase. The pump gear is surface-supported by the crankcase. 
     In order to receive the thrust load by the pin, as described above, a drilling process and a force-fitting process are required in order to install the pin. Therefore, the number of components, including the pin itself, is increased. Further, the manufacturing and repair process is difficult. In order to support the pump shaft at the opposite ends thereof, the pump shaft should be centered very precisely. Therefore, the pump shaft is preferably supported at one end thereof 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to overcome one or more of the drawbacks associated with the background art. 
     It is a further object of the present invention to provide a water pump including a water pump shaft for rotatably supporting a water pump impeller, wherein the water pump shaft is directly and rotatably attached to a water pump body via a shaft support section. 
     It is a further object of the present invention to provide a water pump including a water pump shaft having an engaging portion formed at one end, opposite to an end where the impeller is supported. 
     It is a further object of the present invention to provide a method of forming a water pump shaft including a flange. 
     These and other objects are accomplished by providing a water pump for an engine comprising: a water pump body having an approximately cylindrical support section of a first diameter and a first length, wherein said first length is longer than said first diameter; a water pump shaft having a first end, a second end, and a second diameter, said second diameter being approximately equal to said first diameter, said water pump shaft lying within said cylindrical support section to be directly and rotatably attached to said water pump body; a water pump impeller included proximate said first end; and an engaging portion included proximate said second end for causing said water pump shaft and said water pump impeller to rotate relative to said water pump body. 
     Further, these and other objects are accomplished by providing an engine comprising: a crank case; a crank shaft rotatably mounted in said crank case; a driven member interacting with said crank shaft to rotate in response to rotation of said crankshaft; a first engaging member connected to said driven member to rotate therewith; a water pump body attached to said engine; a water pump shaft having a first end and a second end, said water pump shaft being directly and rotatably attached to said water pump body; a water pump impeller included proximate said first end; and a second engaging member included proximate said second end, said second engaging member being engaged by said first engaging member to cause said water pump shaft and said water pump impeller to rotate in response to rotation of said first engaging member. 
     Moreover, these and other objects are accomplished by providing a method of forming a water pump shaft of a water pump comprising the steps of: providing a die with a cylindrical opening of a first diameter formed therein; a punch having a circular groove formed in an end thereof with a protruding cylindrical portion inside the circular groove, the cylindrical protruding portion having a second diameter; and a hollow shaft with a third outer diameter approximately equal to the first diameter and a fourth inner diameter approximately equal to the second diameter; inserting one end of the hollow shaft into the circular opening of the die; inserting the cylindrical protruding portion into the hollow shaft until the hollow shaft seats into the circular groove; moving the punch toward the die; inserting the cylindrical protruding portion into the circular opening; and bending the hollow shaft in a radial direction at a point where the hollow shaft enters the die. 
     Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitative of the present invention, and wherein: 
     FIG. 1 is a cross sectional view of a water pump, in accordance with the present invention; 
     FIG. 2 is a partial cross sectional view of an engine in combination with the water pump of FIG. 1; 
     FIG.  3 ( a ) illustrates a first step in forming a water pump shaft of the water pump of FIG. 1; 
     FIG.  3 ( b ) illustrates a second step in forming the water pump shaft; 
     FIG.  3 ( c ) illustrates a third step in forming the water pump shaft; 
     FIG.  3 ( d ) illustrates a fourth step in forming the water pump shaft; and 
     FIG.  3 ( e ) illustrates a fifth step in forming the water pump shaft. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     An engine structure will be outlined with reference to FIG.  2 . The engine is a water-cooled four-cycle DOHC (double overhead camshaft) engine. The engine includes a crankcase  1 , a cylinder  2 , a cylinder head  3 , and a cylinder head cover  4  which is a part of the cylinder head  3 . A piston  5  is slidably housed in the cylinder  2  and is coupled to a crankshaft  6  (the center thereof is shown in FIG. 2) in the crankcase  1 . A combustion chamber is provided between the piston  5 , cylinder  2  and cylinder head  3 . 
     An inlet port  7  and an exhaust port  8  are provided on the cylinder head  3  and communicate with the combustion chamber. The inlet port  7  and exhaust port  8  are opened and closed by an inlet valve  10  and an exhaust valve  11 , respectively. The inlet valve  10  end exhaust valve  11  are driven by cams on camshafts  12  and  13 , which are rotated in synchronization with the crankshaft  6 . 
     A water jacket  14  is provided on the cylinder  2  and the cylinder head  3 , and receives cooling water from a water pump  15  disposed in the crankcase  1 . Water heated in a cooling process is fed to a radiator (not shown) via a thermostat  16  attached on the cylinder head  3 . The water is cooled by the radiator, and is then returned to the water pump  15 . 
     The thermostat  16  is provided with a bypass circuit including a bypass hose  17  connected to the water pump  15 . When a water temperature is below a predetermined value, a thermostat valve is switched over to the bypass circuit, so that cooling water heated by the engine is not fed to the radiator, but is directly returned to the water pump  15  via the bypass hose  17 . 
     In FIG. 2, an inlet pipe  18  receives cooling water, supplied from the radiator via a hose  18 A. The engine also includes an oil pan  19 , a starting motor  21 , and a speed sensor  22  connected to a transmission. The speed sensor  22  is disposed on a main shaft  23  of the transmission. Further, the engine includes a countershaft  24 , and a shift drum  25 . 
     A detailed structure of the water pump  15  will now be described with reference to FIG.  1 . The water pump  15  includes a pump body  30 , and a pump cover  31 , both of which are united by bolts  32 . The pump body  30  is coupled to the crankcase  1 . An impeller  34  is housed in a pump chamber  33  defined between the pump body  30  and the pump cover  31 . 
     The impeller  34  is force-fitted to one end of a pump shaft  35  in order to be connected thereto. The pump shaft  35  is hollow, has its one end blocked by the impeller  34 , and has its intermediate part received in a shaft support section  37  of a cylindrical part  36  formed in the pump body  30 . A length of the shaft support section  37  is larger than a diameter of the pump shaft  35 . In a prefeffed embodiment, the length is approximately three times the diameter of the pump shaft  35 . 
     The shaft support section  37  is constituted by an inner surface of a through hole formed in the cylindrical member  36 . The shaft support section  37  is partially and axially provided with an oil supplying groove  38 . The oil supplying groove  38  is blocked by a seal  39  at one end thereof, and communicates with one end of an oil supplying opening  41 , formed on an inner surface of the crankcase  1 , via a radial opening  40 . The oil supplying opening  41  communicates with an oil collecting recess  42  having an open top. Oil circulating, or dispersing, in the crankcase  1  is collected in the oil collecting recess  42 , and is supplied to the shaft support section  37  via the oil supplying opening  41  and the radial opening  40 . 
     An inner end of the cylindrical member  36  housed in the crankcase  1  is brought into contact with a flange  44  of the pump shaft  35  via a washer  43 . The flange  44  is radially formed on the pump shaft  35  by a bending, or beading, process, as will be described later. The flange  44  is integral with the pump shaft  35 . 
     The other end of the pump shaft  35  has a joint  45  in the shape of a notch. The joint  45  is engaged by a projecting of a driving shaft  46 , so that the driving shaft  46  and the pump shaft  35  rotate together. The driving shaft  46  is connected to a pump gear  47 . The pump gear  47  is supported by the crankcase  1  separately from the water pump  15 . The pump gear  47  rotates in response to rotation of the crankshaft  6 . 
     A mechanical seal  48  is provided between an outer surface of the pump shaft  35  and the pump body  30  at the end of the pump shaft  35  where the impeller  34  is attached. The mechanical seal  48  is in contact with the impeller  34  via a floating seat  49 . 
     Now reference will be made to FIGS.  3 ( a ) through  3 ( e ) to describe a method of forming the flange on the pump shaft  35 . In FIG.  3 ( a ), one end of a straight pipe material  50  is inserted into an opening  52  of a die, or dies  51 , and is held therein. The opening  52  has an inner diameter that is substantially equal to an outer diameter of the pipe material  50 . The opening  52  has a depth that is equal to a distance between one end of the pump shaft  35  and the flange  44 . 
     In FIG.  3 ( b ), the other end of the pipe material  50 , projecting from the dies  51 , is fitted into a punch  53 . The punch  53  has an annular groove  54  for engagement with the projecting end of the pipe material  50 . A portion  55  of the punch  53  inside the annular groove  54  is fitted into the pipe material  50 . A portion  756  of the punch  53  outside the annular groove  54  recedes from a tip  57  of the portion  56  by a size D. 
     FIG.  3 ( c ) illustrates a state when the punch  53  is pressed and moved toward the dies  51 . A part of the pipe material  50  that is not covered by the dies  51  and the punch  53  bends or projects radially to form the flange  44 . Thus, the pipe shaft  35  has the flange  44  extending around its circumference. The size of the flange  44  can be set as desired by adjusting the size D. 
     In FIG.  3 ( d ), the punch  53  is moved backward, which enables the water pump shaft  35  to be detached from the dies  51 . Thereafter, the joint  45  is formed on one end of the pump shaft  35 , and the pump shaft  35  is thermally treated and polished together with the joint  45 . The shaft support section  37  may also be thermally treated and polished. The pump shaft  35  is now completed. 
     Some of the advantages of the water pump, in accordance with the present invention, will now be described. The shaft support section  37  of the cylindrical part  36  is longer than the diameter of the pump shaft  35 . This enables the pump shaft  35  to be directly and rotatably attached to the pump body  30  by the long shaft support section  37 , rather than having the pump shaft  35  connected to the crankcase  1 , as in the background art. 
     The joint  45  is provided at an end of the pump body  30 , which is opposite to the end where the impeller  34  is arranged. The joint  45  removeably engages with the driving shaft  46 . This structure enables the pump shaft  35  to be supported at one end thereof, and dispenses with a heavy member, such as a gear, provided on the pump shaft  35 . This makes the water pump light weight. Further, this simplifies the manufacturing and repair processes, since the water pump can be made without having to attach the gear onto the pump shaft  35 , and since a water pump failure in the impeller section of the water pump can be fixed without having to replace the pump gear  47  operating in conjunction with the crankshaft  6 . 
     The oil collector  42 , oil supplying opening  41 , and opening  40  collect oil dispersing in the crankcase  1  and guide the oil to the oil supplying groove  38 . Each may be in the shape of a duct. This system is effective in reliably supplying lubrication oil to the shaft support section  37 , thus prolonging the life of the water pump. 
     The hollow pump shaft  35  also has several advantages. The pump shaft  35  is light weight and can be easily manufactured. Further, the flange  44  is integrally formed in the center of the pump shaft  35 , so that the pump shaft  35  can receive the thrust load of the mechanical seal  48  at the flange  44 . Still further, no pins are required to attach the flange  44 , and the pump shaft  35  will not be drilled in order to attach pins. The bending process to form the flange  44  can be easily performed and provides excellent precision in positioning the flange  44  on the pump shaft  35 . 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.