Patent Publication Number: US-9422936-B2

Title: Water pump in vehicle

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of the Patent Korean Application No. 10-2012-0017041, filed on Feb. 20, 2012, which is hereby incorporated by reference as if fully set forth herein. 
     BACKGROUND OF THE DISCLOSURE 
     1. Field of the Disclosure 
     The present invention relates to water pumps in vehicles, and more particularly, to a water pump in a vehicle, in which cooling water is guided to an inside of the water pump for dissipating heat. 
     2. Discussion of the Related Art 
     In general, the vehicle is provided with an engine cooling unit for maintaining a temperature of the engine to a proper level, and cooling the engine slowly to enable smooth operation of the engine. 
     The engine cooling unit includes a radiator, cooling fan, a thermostat, the water pump, and an operation belt, wherein the cooling water is drawn from the radiator by the water pump, circulates through an intake manifold, an exhaust manifold, and a water jacket in a cylinder head, and returns to the radiator again, to cooling down the engine. 
     In the meantime, the water pump in the vehicle itself also generates intense heat due to rotation of the rotor and so on, and there have been many researches for resolving the intense heat generated when the water pump in the vehicle is in operation. 
     SUMMARY OF THE DISCLOSURE 
     Accordingly, the present invention is directed to a water pump in a vehicle. 
     An object of the present invention, devised to solve above problem, is to provide a water pump in a vehicle, which does not require machining of a shaft to be projected from a rotor for rotation of the rotor. 
     Another object of the present invention is to provide a water pump in a vehicle, which has a stator enclosed from an outside to prevent foreign matter from infiltrating therein. 
     Another object of the present invention is to provide a water pump in a vehicle, which can prevent the water pump from being damaged by heat, and has an improved heat dissipation performance. 
     Another object of the present invention is to provide a water pump in a vehicle, which can dissipate heat from a driving unit of the water pump having the driving unit mounted thereto, easily. 
     Additional advantages, objects, and features of the disclosure will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
     To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a water pump in a vehicle includes a pump cover which forms an upper side exterior appearance of the pump for housing an impeller to be rotated, a hollow rotor coupled on the same axis with the impeller to rotate altogether, and a housing coupled to the pump cover to house the rotor and a stator therein, wherein the pump cover includes a first rotation shaft extended toward the hollow in the rotor passed through the impeller, the housing includes a second rotation shaft extended toward the hollow in the rotor, the first rotation shaft has a communication hole formed therein to be in communication with the hollow, and the rotor has a communication passage recessed in a lower end portion thereof to a predetermined depth. 
     The communication passage may be formed adjacent to the second rotation shaft. 
     The communication passage may be plural arranged spaced from one another. 
     The communication passage may be four arranged at 90 degree intervals. 
     The communication passage may be tapered such that the communication passage becomes the deeper as the communication passage goes toward an underside of the rotor the more. 
     The communication passage may include a moderately curved surface. 
     The water pump may further include an ancillary impeller on a side of the impeller facing the rotor for applying a pressure to water to move the water. 
     The first rotation shaft and the second rotation shaft may have the same rotation axis. 
     The first rotation shaft may be directed to one end of the hollow in the rotor, and the second rotation shaft may be directed to the other end of the hollow in the rotor. 
     The first rotation shaft and the second rotation shaft may be arranged spaced from each other. 
     In another aspect of the present invention, a water pump in a vehicle includes a pump cover which forms an upper side exterior appearance of the pump for housing an impeller to be rotated, a hollow rotor coupled on the same axis with the impeller to rotate altogether, a housing coupled to the pump cover to house the rotor and a stator therein, and a driving unit mounted to an underside of the housing for controlling the stator, wherein the pump cover includes a first rotation shaft extended toward the hollow in the rotor passed through the impeller, the housing includes a second rotation shaft extended toward the hollow in the rotor, the first rotation shaft has a communication hole formed therein to be in communication with the hollow, and the rotor has a communication passage recessed in a lower end portion thereof to a predetermined depth. 
     The communication passage may be formed adjacent to the second rotation shaft. 
     The communication passage may be plural arranged spaced from one another. 
     The communication passage may be tapered such that the communication passage becomes the deeper as the communication passage goes toward an underside of the rotor the more. 
     The communication passage may include a moderately curved surface. 
     The water pump may further include an ancillary impeller on a side of the impeller facing the rotor for applying a pressure to water to move the water. 
     The driving unit may include a driving unit body extended from the housing, and a driving unit cover for enclosing an inside space of the driving unit body. 
     The driving unit body may have a PCB mounted thereto. 
     The driving unit cover may have heat dissipation pins mounted thereto for dissipating heat. 
     The first rotation shaft may be directed to one end of the hollow in the rotor, and the second rotation shaft may be directed to the other end of the hollow in the rotor. 
     It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the disclosure and together with the description serve to explain the principle of the disclosure. In the drawings: 
         FIG. 1  illustrates a front view of a water pump in a vehicle in accordance with a preferred embodiment of the present invention. 
         FIG. 2  illustrates an exploded perspective view of the water pump in  FIG. 1 . 
         FIG. 3  illustrates a sectional exploded view of the water pump in  FIG. 2 . 
         FIG. 4  illustrates a sectional view of the water pump in  FIG. 1 . 
         FIG. 5  illustrates a plan view of a pump cover. 
         FIG. 6  illustrates a bottom view of a pump cover with a rotor mounted thereto. 
         FIG. 7  illustrates a front view of a water pump in a vehicle in accordance with another preferred embodiment of the present invention. 
         FIG. 8  illustrates an exploded perspective view of the water pump in  FIG. 7 . 
         FIG. 9  illustrates a sectional exploded view of the water pump in  FIG. 8 . 
         FIG. 10  illustrates a sectional view of the water pump in  FIG. 7 . 
     
    
    
     DESCRIPTION OF SPECIFIC EMBODIMENTS 
     Reference will now be made in detail to the specific embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
       FIG. 1  illustrates a front view of a water pump in a vehicle in accordance with a preferred embodiment of the present invention. The water pump in the vehicle in accordance with the preferred embodiment of the present invention will be described with reference to  FIG. 1 . 
     Referring to  FIG. 1 , the water pump in the vehicle includes a pump cover  10  which forms an upper side of an exterior appearance of the pump, and a housing  40  which forms a lower side of the exterior appearance of the pump. The housing  40  is mounted to an underside of the pump cover  10 . 
       FIG. 2  illustrates an exploded perspective view of the water pump in  FIG. 1 ,  FIG. 3  illustrates a sectional exploded view of the water pump in  FIG. 2 , and  FIG. 4  illustrates a sectional view of the water pump in  FIG. 1 . 
     Referring to  FIGS. 2 to 4 , the water pump includes the pump cover  10  for housing an impeller  18  to be rotated, a hollow rotor  30  coupled on the axis with the impeller  18  to rotate altogether, and the housing  40  for housing the rotor  30  and a stator  32  therein. 
     The rotor  30  has a cylindrical hollow formed therein, and the hollow has no outward shaft projected therefrom. That is, the rotor  30  has a cylindrical shape with the hollow with opened ends extended from a vacant inside. Particularly, the rotor  30  has a communication passage  31  recessed to a predetermined depth in a lower end portion thereof. 
     The stator  32  has a configuration identical to a stator used in a general water pump, of which description will be omitted. 
     It is preferable that the impeller  18  has a plurality of blades for applying rotation force to water to generate a water pressure, and a pass through hole formed in a center thereof. The water can move as the water is brought into contact with the blades. There is a first rotation shaft  12  to be described hereafter placed in the pass through hole in the impeller  18 . 
     And, there may an ancillary impeller  15  at a side of the impeller  18  facing the rotor  30  for applying a pressure to the water to make the water to move. The ancillary impeller  15  can make the water to move along a flow passage owing to the rotation force of the impeller  18 . In the meantime, the ancillary impeller  15  arranged to face the rotor  30  for applying the pressure to the water positioned on an upper side of the rotor  30 . 
     It is possible that the impeller  18  is fixed to the rotor  30  by insert injection molding, thermal bonding, or an adhesive so that the impeller  18  rotates at a speed the same with the rotor  30 . Of course, any structure may be employed as far as the structure can make the impeller  18  to rotate at the same time with the rotor  30  when the rotor  30  rotates, and to stop at the same time with the rotor  30  when the rotor  30  stops. Especially, it is possible to employ different structures that can connect the impeller  18  and the rotor  30  into a state in which the impeller  18  and the rotor  30  become one body. 
     In the meantime, the pump cover  10  includes the first rotation shaft  12  extended toward the hollow in the rotor  30  passed through the impeller  18 , and the housing  40  includes a second rotation shaft  44  extended toward the hollow in the rotor  30 . That is, the preferred embodiment of the present invention suggests providing no rotation shaft to the rotor  30  to make the rotor  30  to rotate, so that the rotor  30  has a simple structure of a substantially cylindrical shape, thereby enabling easy manufacturing of the rotor  30 . 
     The rotor  30  has both ends rotatably secured by the first rotation shaft  12  and the second rotation shaft  44 . In this case, it is preferable that the first rotation shaft  12  and the second rotation shaft  44  have the same rotation axis. It is because, in order to make the rotor  30  to be rotated stationary with respect to the first rotation shaft  12  and the second rotation shaft  44 , it is required that all of the rotor  30 , the first rotation shaft  12 , and the second rotation shaft  44  are coupled on the same axis. 
     In this case, the first rotation shaft  12  has a communication hole  16  formed therein in communication with the hollow in the rotor  30 . The communication hole  16  may be cylindrical which makes one end and the other end of the first rotation shaft  12  to be in communication with each other. That is, the communication hole  16  enables the water to move from the upper side of the first rotation shaft  12  to a lower side of the first rotation shaft  12 , allowing introduction of the water to an inside of the rotor  30 . 
     Of course, the first rotation shaft  12  is directed to the one end of the hollow in the rotor  30 , and the second rotation shaft  44  is directed to the other end of the hollow in the rotor  30 . One end of the rotor  30  at a center of the hollow is secured to the first rotation shaft  12 , and the other end of the rotor  30  at the center of the hollow is secured to the second rotation shaft  44 . In this case, since the first rotation shaft  12  and the second rotation shaft  44  are individual elements which are not in contact with each other, the rotor  30  is made to maintain a state in which the rotor  30  is secured to two points of the first rotation shaft  12  and the second rotation shaft  44 . 
     The housing  40  may include a housing cover  42  for housing the rotor  30 , and a housing body  46  for housing the housing cover  42 . It is possible that the housing cover  42  has a ‘T’ shape, substantially. 
     The housing cover  42  has the rotor  30  housed therein. Mounted between the housing cover  42  and the housing body  46 , there is the stator  32 . That is, in an enclosed space between the housing cover  42  and the housing body  46 , the stator  32  may be housed in an enclosed mode. 
     Provided on an upper side of the housing body  46 , there may be a flange  48  extended in a radial direction from a center of the housing body  46 . In this case, the flange  48  is coupled to an outside circumferential surface of the housing cover  42  for preventing the stator  32  housed in the housing body  46  from being exposing to an outside of the water pump. Since the housing cover  42  also has a ‘T’ shape on the whole, an outer portion of the housing cover  42  may coupled to the flange  48  at the housing body  46 . 
     That is, since the stator  32  can be housed in the space enclosed between the housing cover  42  and the housing body  46 , bringing into contact of foreign matter, such as water, to the stator  32  can be prevented. 
     Particularly, the second rotation shaft  44  can be provided to the housing cover  42 . In this case, the second rotation shaft  44  is extended toward the pump cover  10 , i.e., the other end of the rotor  30 . The housing cover  42  may have the rotor  30  housed therein, by rotatably securing one end of the rotor  30  to the second rotation shaft  44  projected a predetermined length from the housing cover  42 . 
     The first rotation shaft  12  and the second rotation shaft  44  are arranged spaced from each other. The first rotation shaft  12  is an element mounted to the pump cover  10 , and the second rotation shaft  44  is an element mounted to the housing cover  42  separate from the first rotation shaft  12 . Since the first rotation shaft  12  is not in contact with the second rotation shaft  44  directly, the inside of the rotor  30  may have a vacant hollow space which is not filled with the first rotation shaft  12  and the second rotation shaft  44 . The vacant hollow space in the rotor  30  as much as a space the first rotation shaft  12  and the second rotation shaft  44  are spaced away, the water pump of the embodiment can save material cost in comparison to a shape in which a rotation shaft is projected from both sides without the hollow in the rotor  30 . 
     Moreover, the first rotation shaft  12  and the second rotation shaft  44  have diameters smaller than a diameter of the hollow in the rotor  30 . This is because, in order to make the rotor  30  to rotate with respect to the first rotation shaft  12  and the second rotation shaft  44  with small friction, it is required to mount a first bearing  20  to the first rotation shaft  12  and a second bearing  50  to the second rotation shaft  44 . 
     The first rotation shaft  12  has the first bearing  20  provided thereto to make the rotor  30  to rotate at a rotation speed the same with the impeller  18 . The first bearing  20  may include first connection means  22  mounted to an outside circumferential surface of the first rotation shaft  12 , and a first friction preventive means  24  mounted to an outside circumferential surface of the first connection means  22 . 
     The first connection means  22  serves as a medium for preventing the rotor  30 , the impeller  18  and the first rotation shaft  12  from being in direct contact with one another. Since the first connection means  22  can rotate centered on the first rotation shaft  12 , the first connection means  22  enables the rotor  30 , and the impeller  18  to rotate independent from the first rotation shaft  12 , smoothly. It is possible that the first connection means  22  is formed of ceramic. 
     Though the first friction preventive means  24  also serves a function similar to the first connection means  22  substantially, the first friction preventive means  24  is different in that the first friction preventive means  24  is in direct contact to the rotor  30 . It is possible that the first friction preventive means  24  is formed of SiC. That is, the first friction preventive means  24  has strength stronger than the first connection means  22 , on the whole. 
     Of course, though  FIG. 3  discloses a mode in which the first bearing  20  makes the impeller  18  and the first rotation shaft  12  to be coupled coaxially, it is possible to change the mode such that the first bearing  20  is shifted down to a position lower than shown in  FIG. 3  to make the rotor  30  and the first rotation shaft  12  to be coupled coaxially. In this case, the first friction preventive means  24  may rotate in contact with an inside circumferential surface of the rotor  30 . 
     In the meantime, the second rotation shaft  44  has the second bearing  50  provided thereto for enabling the rotor  30  to rotate. It is possible that the second bearing  50  may include second connection means  52  mounted to an outside circumferential surface of the second rotation shaft  44 , and second friction preventive means  54  mounted to an outside circumferential surface of the second connection means  52 . In this case, the outside circumferential surface of the second friction preventive means  54  may be in contact with the inside circumferential surface of the rotor  30 . 
     The second connection means  52  serves as a medium for preventing the rotor  30  from being in direct contact with the second rotation shaft  44 . Since the second connection means  52  can rotate centered on the second rotation shaft  44 , the rotor  30  is made to rotate smoothly independent from the second rotation shaft  44 . It is possible that the second connection means  52  is formed of ceramic. 
     Though the second friction preventive means  54  also serves a function similar to the second connection means  52  substantially, the second friction preventive means  54  is different in that the second friction preventive means  54  is in direct contact to the rotor  30 . It is possible that the second friction preventive means  54  is formed of SiC. That is, the second friction preventive means  54  has strength stronger than the second connection means  52 , on the whole. 
     A reference number  14  denotes an O-ring for sealing a gap between the pump cover  10  and the housing cover  42  when the pump cover  10  is coupled to the housing cover  42 . In this case, the O-ring  14  may be formed of rubber seated in a seating groove  43  formed in the housing cover  42 . 
     In the meantime, it is preferable that the communication passage  31  formed in the rotor  30  is adjacent to the second rotation shaft  44 . Particularly, the communication passage  31  may be formed adjacent to the second bearing  50 . 
     The communication passage  31  may be tapered to make a depth thereof to become the deeper as the communication passage  31  goes toward the underside of the rotor  30  the more. That is, the depth of the communication passage  31  becomes the deeper as the communication passage  31  goes to the underside of the rotor  30  the more, resulting in a thickness of a portion of the rotor  30  to be the thinner as the communication passage  31  goes toward the underside of the rotor  30  the more. 
     Particularly, the communication passage  31  may include a moderately curved surface. That is, it is preferable that an outside circumferential surface of the communication passage  31  in a radial direction from a center of the rotor  30  is moderately curved. This is for making the water flowing through the communication passage  31  moves to the underside of the rotor  30  along the moderately curved surface, smoothly. 
       FIG. 5  illustrates a plan view of a pump cover. The communication hole will be described with reference to  FIG. 5 , in detail. 
     The communication hole  16  is formed to pass through the first rotation shaft  12  in a center of the first rotation shaft  12 . That is, the communication hole  16  provides an inlet of the water positioned on an upper side of the pump cover  10 , i.e., on an outside of the pump cover  10 , to be able to be introduced to a lower side of the pump cover  10 , i.e., to an inside of the water pump. 
     In the meantime, the first rotation shaft  12  can be secured by a bracket  13 . Since the first rotation shaft  12  has the communication hole  16  formed therein, a problem may take place in that strength of the first rotation shaft  12  becomes weak. Therefore, it is possible to secure the first rotation shaft  12  with a plurality of the brackets  13 , fixedly. 
       FIG. 6  illustrates a bottom view of a pump cover with a rotor mounted thereto. The communication passage will be described with reference to  FIG. 6 , in detail. 
     The communication passage  31  may be formed in plural in a lower end portion of the rotor  30 . In this case, the plurality of communication passages  31  may be arranged to space from one another at fixed angular intervals. Particularly, the communication passages  31  may be four arranged at 90 degree intervals. 
     Of course, if the communication passages  31  are three, the communication passages  31  may be arranged at 120 degree intervals. 
     An increased number of the communication passages  31  are advantageous in that a space increases, through which the water positioned in the rotor  30  is discharged to the underside of the rotor  30  through the communication passages  31 . However, unnecessary increase of the number of the communication passages  31  may cause a risk of securing force lost when the rotor  30  rotates coupled to the second rotation shaft  44 . Therefore, it is preferable that the communication passages  31  are about 3 to 4. 
     The operation of the water pump in accordance with the preferred embodiment of the present invention will be described. 
     Both ends of the rotor  30  are rotatably coupled on the same axis through axes of the first rotation shaft  12  and the second rotation shaft  44 , respectively. Owing to the first bearing  20  and the second bearing  50 , the rotor  30  can rotate without causing high friction with respect to the first rotation shaft  12  and the second rotation shaft  44 . 
     When the rotor  30  rotates, the impeller  18  can also rotates at the same speed with the rotor  30 . According to this, the water pressure generated by the impeller  18  enables the water pump to discharge or draw in the water. 
     Above description explains movement of the water for cooling different elements of the engine according to an original purpose of the water pump. Other than above operation, the water pump in accordance with the preferred embodiment of the present invention may also perform a function of cooling down the water pump by introducing the water to the inside of the water pump. 
     When the rotor  30  and the impeller  18  rotate, the movement of the water takes place. In this case, a portion of the water positioned on the upper side of the pump cover  10  passes through the first rotation shaft  12  through the communication hole  16 . 
     Then, the water moves to the inside of the rotor  30 , and reaches to the communication passage  31  as the water moves down to a lower side of the rotor  30 . 
     Since the rotor  30  rotates, the water positioned in the communication passage  31  moves to the underside of the rotor  30  owing to centrifugal force generated by rotation of the communication passage  31 . This is because the communication passage  31  has the moderately curved inside circumferential surface of the rotor  30  in the radial direction from the center of the rotor  30 , and becomes the deeper as the communication passage  31  goes to the underside the more. 
     In this case, since the moderately curved surface is smoothly curved, the water can move along the communication passage  31 , easily. 
     The water discharged to the outside of the rotor  30  from the inside of the rotor  30  through the communication passage  31  moves to the upper side of the water pump along an outside circumferential surface of the rotor  30 , again. In this case, since the impeller  18  is rotating, the ancillary impeller  15  under the impeller  18  is also rotating. Therefore, the ancillary impeller  15  enables the water positioned under the rotor  30  to move to the upper side of the rotor  30 , and therefrom, to the outside of the water pump, finally. 
     Thus, as the water is brought into contact with different elements of the rotor  30  and the water pump, the heat generated as the water pump is operated can transfer to the water. According to this, the water pump can be cooled down. 
     In the meantime, in the embodiment of the present invention, in order to make the water to move in the water pump smoothly, the communication passage  31  is formed to have a special shape, and the ancillary impeller  15  is provided, additionally. That is, since the communication passage  31  and the ancillary impeller  15  apply a pressure to the water while the communication passage  31  and the ancillary impeller  15  are rotating at the same time, the water in the water pump can move to a desired flow passage, smoothly. 
       FIG. 7  illustrates a front view of a water pump in a vehicle in accordance with another preferred embodiment of the present invention. The water pump in a vehicle in accordance with another preferred embodiment of the present invention will be described with reference to  FIG. 7 . 
     Referring to  FIG. 7 , the water pump includes a pump cover  10  which forms an upper side of an exterior appearance of the water pump, and a housing  40  which forms a lower side of the exterior appearance of the pump. The housing  40  is mounted to an underside of the pump cover  10 . 
     Particularly, the housing  40  has heat dissipation pins  70  on an underside of the housing  40  for dissipating heat generated at the water pump to an outside of the water pump. 
     In the meantime, since the water pump in accordance with another preferred embodiment of the present invention has the communication passage and the communication hole identical to the water pump in accordance with the preferred embodiment of the present invention,  FIGS. 5 and 6  will be referred to the same as the preferred embodiment of the present invention. Therefore, since description of the communication hole and the communication passage in the preferred embodiment of the present invention is the same with another preferred embodiment of the present invention, identical description will be omitted. 
       FIG. 8  illustrates an exploded perspective view of the water pump in  FIG. 7 ,  FIG. 9  illustrates a sectional exploded view of the water pump in  FIG. 8 , and  FIG. 10  illustrates a sectional view of the water pump in  FIG. 7 . 
     Referring to  FIGS. 8 to 10 , the water pump includes the pump cover  10  for housing an impeller  18  to be rotated, a hollow rotor  30  coupled on the same axis with the impeller  18  to rotate altogether, and the housing  40  for housing the rotor  30  and a stator  32  therein. 
     The rotor  30  has a cylindrical hollow formed therein, and the hollow has no outward shaft projected therefrom. That is, the rotor  30  has a cylindrical shape with the hollow with opened ends extended from a vacant inside. Particularly, the rotor  30  has a communication passage  31  in a lower end portion thereof. 
     The stator  32  has a configuration identical to a stator used in a general water pump, of which description will be omitted. 
     It is preferable that the impeller  18  has a plurality of blades for applying rotation force to water to generate a water pressure, and a pass through hole formed in a center thereof. The water can move as the water is brought into contact with the blades. There is a first rotation shaft  12  to be described hereafter placed in the pass through hole in the impeller  18 . The first rotation shaft  12  has a communication hole  16  formed therein to be in communication with the hollow in the rotor. 
     It is possible that the impeller  18  is fixed to the rotor  30  by insert injection molding, thermal bonding, or an adhesive so that the impeller  18  rotates at a speed the same with the rotor  30 . Of course, any structure may be employed as far as the structure can make the impeller  18  to rotate at the same time with the rotor  30  when the rotor  30  rotates, and to stop at the same time with the rotor  30  when the rotor  30  stops. Especially, it is possible to employ different structures that can connect the impeller  18  and the rotor  30  into a state in which the impeller  18  and the rotor  30  become one body. 
     In the meantime, the pump cover  10  includes the first rotation shaft  12  extended toward the hollow in the rotor  30  passed through the impeller  18 , and the housing  40  includes a second rotation shaft  44  extended toward the hollow in the rotor  30 . That is, another preferred embodiment of the present invention suggests providing no rotation shaft to the rotor  30  to make the rotor  30  to rotate, so that the rotor  30  has a simple structure of a substantially cylindrical shape, thereby enabling easy manufacturing of the rotor  30 . 
     The rotor  30  has both ends rotatably secured by the first rotation shaft  12  and the second rotation shaft  44 . In this case, it is preferable that the first rotation shaft  12  and the second rotation shaft  44  have the same rotation axis. It is because, in order to make the rotor  30  to be rotated stationary with respect to the first rotation shaft  12  and the second rotation shaft  44 , it is required that all of the rotor  30 , the first rotation shaft  12 , and the second rotation shaft  44  are coupled on the same axis. 
     Of course, the first rotation shaft  12  is directed to the one end of the hollow in the rotor  30 , and the second rotation shaft  44  is directed to the other end of the hollow in the rotor  30 . One end of the rotor  30  at a center of the hollow is secured to the first rotation shaft  12 , and the other end of the rotor  30  at the center of the hollow is secured to the second rotation shaft  44 . In this case, since the first rotation shaft  12  and the second rotation shaft  44  are individual elements which are not in contact with each other, the rotor  30  is made to maintain a state in which the rotor  30  is secured to two points of the first rotation shaft  12  and the second rotation shaft  44 . 
     The housing  40  may include a housing cover  42  for housing the rotor  30 , and a housing body  46  for housing the housing cover  42 . It is possible that the housing cover  42  has a ‘T’ shape, substantially. 
     The housing cover  42  has the rotor  30  housed therein. Mounted between the housing cover  42  and the housing body  46 , there is the stator  32 . That is, in an enclosed space between the housing cover  42  and the housing body  46 , the stator  32  may be housed in an enclosed mode. 
     Provided on an upper side of the housing body  46 , there may be a flange  48  extended in a radial direction from a center of the housing body  46 . In this case, the flange  48  is coupled to an outside circumferential surface of the housing cover  42  for preventing the stator  32  housed in the housing body  46  from being exposing to an outside of the water pump. Since the housing cover  42  also has a ‘T’ shape on the whole, an outer portion of the housing cover  42  may coupled to the flange  48  at the housing body  46 . 
     That is, since the stator  32  can be housed in the space enclosed between the housing cover  42  and the housing body  46 , bringing into contact of foreign matter, such as water, to the stator  32  can be prevented. 
     Particularly, the second rotation shaft  44  can be provided to the housing cover  42 . In this case, the second rotation shaft  44  is extended toward the pump cover  10 , i.e., the other end of the rotor  30 . The housing cover  42  may have the rotor  30  housed therein, by rotatably securing one end of the rotor  30  to the second rotation shaft  44  projected a predetermined length from the housing cover  42 . 
     The first rotation shaft  12  and the second rotation shaft  44  are arranged spaced from each other. The first rotation shaft  12  is an element mounted to the pump cover  10 , and the second rotation shaft  44  is an element mounted to the housing cover  42  separate from the first rotation shaft  12 . Since the first rotation shaft  12  is not in contact with the second rotation shaft  44  directly, the inside of the rotor  30  may have a vacant hollow space which is not filled with the first rotation shaft  12  and the second rotation shaft  44 . The vacant hollow space in the rotor  30  as much as a space the first rotation shaft  12  and the second rotation shaft  44  are spaced away, the water pump of the embodiment can save material cost in comparison to a shape in which a rotation shaft is projected from both sides without the hollow in the rotor  30 . 
     Moreover, the first rotation shaft  12  and the second rotation shaft  44  have diameters smaller than a diameter of the hollow in the rotor  30 . This is because, in order to make the rotor  30  to rotate with respect to the first rotation shaft  12  and the second rotation shaft  44  with small friction, it is required to mount a first bearing  20  to the first rotation shaft  12  and a second bearing  50  to the second rotation shaft  44 . 
     The first rotation shaft  12  has the first bearing  20  provided thereto to make the rotor  30  to rotate at a rotation speed the same with the impeller  18 . The first bearing  20  may include first connection means  22  mounted to an outside circumferential surface of the first rotation shaft  12 , and a first friction preventive means  24  mounted to an outside circumferential surface of the first connection means  22 . 
     The first connection means  22  serves as a medium for preventing the rotor  30 , the impeller  18  and the first rotation shaft  12  from being in direct contact with one another. Since the first connection means  22  can rotate centered on the first rotation shaft  12 , the first connection means  22  enables the rotor  30 , and the impeller  18  to rotate independent from the first rotation shaft  12 , smoothly. It is possible that the first connection means  22  is formed of ceramic. 
     Though the first friction preventive means  24  also serves a function similar to the first connection means  22  substantially, the first friction preventive means  24  is different in that the first friction preventive means  24  is in direct contact to the rotor  30 . It is possible that the first friction preventive means  24  is formed of SiC. That is, the first friction preventive means  24  has strength stronger than the first connection means  22 , on the whole. 
     Of course, though  FIG. 10  discloses a mode in which the first bearing  20  makes the impeller  18  and the first rotation shaft  12  to be coupled coaxially, it is possible to change the mode such that the first bearing  20  is shifted down to a position lower than shown in  FIG. 10  to make the rotor  30  and the first rotation shaft  12  to be coupled coaxially. In this case, the first friction preventive means  24  may rotate in contact with an inside circumferential surface of the rotor  30 . 
     In the meantime, the second rotation shaft  44  has the second bearing  50  provided thereto for enabling the rotor  30  to rotate. It is possible that the second bearing  50  may include second connection means  52  mounted to an outside circumferential surface of the second rotation shaft  44 , and second friction preventive means  54  mounted to an outside circumferential surface of the second connection means  52 . In this case, the outside circumferential surface of the second friction preventive means  54  may be in contact with the inside circumferential surface of the rotor  30 . 
     The second connection means  52  serves as a medium for preventing the rotor  30  from being in direct contact with the second rotation shaft  44 . Since the second connection means  52  can rotate centered on the second rotation shaft  44 , the rotor  30  is made to rotate smoothly independent from the second rotation shaft  44 . It is possible that the second connection means  52  is formed of ceramic. 
     Though the second friction preventive means  54  also serves a function similar to the second connection means  52  substantially, the second friction preventive means  54  is different in that the second friction preventive means  54  is in direct contact to the rotor  30 . It is possible that the second friction preventive means  54  is formed of SiC. That is, the second friction preventive means  54  has strength stronger than the second connection means  52 , on the whole. 
     A reference number  14  denotes an O-ring for sealing a gap between the pump cover  10  and the housing cover  42  when the pump cover  10  is coupled to the housing cover  42 . In this case, the O-ring  14  may be formed of rubber seated in a seating groove  43  formed in the housing cover  42 . 
     The water pump in a vehicle in accordance with another preferred embodiment of the present invention further includes a driving unit  60  mounted on an underside of the housing  40  for controlling the stator  32 . Of course, the driving unit  60  may control different elements of the water pump in addition to the stator  32 . 
     The driving unit  60  includes a driving unit body  62  extended from the housing  40 , and a driving unit cover  64  for enclosing an inside space of the driving unit body  62 . The driving unit body  62  is arranged under the housing body  46 , and, similar to the housing body  46 , has an inside space for housing different elements therein. Particularly, the driving unit body  62  may have a PCB (Printed Circuit Body) mounted thereto. 
     And, the driving unit cover  64  may have heat dissipation pins  70  mounted thereto for dissipation of heat. A plurality of the heat dissipation pins  70  may be provided in a variety of shapes along a side of the driving unit cover  64 . Of course, if there is a limitation in view of space, though the heat dissipation pins  70  may be projected from a portion of the driving unit cover  64 , it is preferable that the heat dissipation pins  70  are projected throughout an entire surface of the one side of the driving unit cover  64  for improving heat efficiency. 
     The operation of the water pump in a vehicle in accordance with another preferred embodiment of the present invention will be described. Since another preferred embodiment is different from the preferred embodiment in that another preferred embodiment suggests to provide the driving unit and the heat dissipation pins, only the driving unit and the heat dissipation pins will be described. 
     The driving unit  60 , particularly, the PCB  66 , generates heat as the water pump is driven to raise a temperature of the water pump, which is liable to damage the water pump. Therefore, in this case, the heat transfers from the driving unit body  62  to the driving unit cover  64 , and, therefrom, to an outside of the water pump through the heat dissipation pins  70 . 
     As has been described, the water pump in a vehicle of the present invention has the following advantages. 
     Since the rotor has no shaft manufactured to be projected therefrom, manufacturing and assembly of the rotor can be improved. 
     The stable heat dissipation regardless of heat generation at the time of the operation of the water pump permits to prevent the water pump from becoming out of order. 
     The stator, not exposed to an outside, but enclosed in the water pump permits to prevent the stator from being damaged by foreign matter infiltrated thereto. 
     The easy dissipation of the heat from the driving unit permits to prevent not only the driving unit, but also the water pump from being damaged by intensive heat. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.