Abstract:
A method for winding a coil on an object, wherein the coil includes a plurality of first coils and a plurality of second coils, may have winding the first coils on an exterior circumferences of the second coils, wherein an outer circumferences of the respective second coil is enclosed and in contact with outer circumference of at least three first coils, and wherein cross-sectional area of the second coil is smaller than that of the first coil, and wherein the outer circumference of the at least three first coils are in contact each other.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority to Korean Patent Application No. 10-2009-0118739 filed in the Korean Intellectual Property Office on Dec. 2, 2009, the entire contents of which is incorporated herein for all purposes by this reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a method for winding a coil on an object and a water pump of clutch type provided with the coil. More particularly, the present invention relates to a method for winding more coils on an object having a limited space, and to a water pump of clutch type provided with a coil securing a sufficient operation performance without increasing a size of the water pump of clutch type by using this method. 
     2. Description of Related Art 
     Generally, a water pump circulates coolant to an engine and a heater in order to cool the engine and heat a cabin. 
     The coolant flowing out from the water pump circulates a cylinder block and/or a cylinder head of an engine and cools the engine. In addition, the coolant circulates a heat exchanger and cools an exhaust gas of high temperature. At this time, temperature of the coolant rises, and the heated coolant is used for warming up a cabin of a vehicle. In addition, the heated coolant is cooled at a radiator and flows in the water pump again. 
     Such a water pump is largely divided into a mechanical water pump and an electric water pump. 
     The mechanical water pump is connected to a pulley fixed to a crankshaft of the engine and is driven according to a rotation of the crankshaft (i.e., a rotation of the engine). Therefore, coolant amount flowed out from the mechanical water pump is determined according to a rotation speed of the engine. 
     On the contrary, the electric water pump is driven by a motor controlled by a control apparatus. Therefore, the electric water pump can determines the coolant amount regardless of the rotation speed of the engine. Since components used in the electric water pump, however, is electrically operated, it is important for electrically operated components to have sufficient waterproof performance. If the components have sufficient waterproof performance, performance and durability of the electric water pump may also improve. In addition, the electric water pump has more components (a stator, a rotor, a water-proof means, and so on) than the mechanical water pump. So, manufacturing cost of the electric water pump is expensive and it is difficult to manufacture the electric water pump. 
     Recently, a mechanical water pump (e.g., water pump of clutch type) which selectively pressurizes the coolant according to a driving condition of the engine and supplies it to the engine has been developed. According to such a water pump of clutch type, a pulley is selectively connected to a shaft according to the driving condition of the engine, and the selectively connection of the pulley and the shaft is achieved by magnetic force generated by a coil wound on a coil case. 
     Hereinafter, a conventional method for winding a coil on a coil case of a water pump of clutch type will be described. 
       FIG. 4  is a cross-sectional view of a conventional coil, and  FIG. 5  is an enlarged view of  FIG. 4 . 
     As shown in  FIG. 4  and  FIG. 5 , coil layers  210  are wound on a coil case according to a conventional art. A coil  212  in the coil layers  210  is wound so as to form a plurality of rows. At this time, the coil  212  is wound as a rhombohedral packing. That is, cross-sectional centers of a plurality of coils forming a m-th row and a (m+1)-th row are arranged to form a zigzag shape, and an angle θ between the cross-sectional centers of the two neighboring coils forming the m-th row and one cross-sectional center of the coil forming the (m+1)-th row and contacting with the cross-sectional centers of the two neighboring coils is 60°. However, a pore  216  is formed among three neighboring coils  212  among a rhombohedral packing. Formation of the pore  216  restricts numbers of coils wound on the coil case. 
     Generally, magnetic force generated by the coil  212  is proportional to the numbers of coils  212  wound on the coil case. Therefore, it is very important for improving operation performance of a water pump of clutch type to wind more coils  212  on the coil case having a limited space. 
     The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art. 
     BRIEF SUMMARY OF THE INVENTION 
     Various aspects of the present invention are directed to provide a method for winding a coil on an object having advantages of generating strong magnetic force as a consequence of winding more coils on an object having a limited space and to provide a water pump of clutch type having advantages of securing sufficient operation performance without increasing size as a consequence of winding more coils on a coil case of the water pump of clutch type. 
     In an aspect of the present invention, a method for winding a coil on an object, wherein the coil comprises a first coil and a second coil, cross-sectional area of the second coil being different from cross-sectional area of the first coil, may have winding the first coil on an exterior circumference of the object or the second coil such that cross-sectional centers of a plurality of first coils form a row, and winding the second coil on the first coil such that cross-sectional centers of a plurality of second coils form a row, wherein winding the first coil and winding the second coil are repeated by predetermined numbers such that a plurality of rows of the first coil and the second coil is wound on the object, and wherein the cross-sectional centers of the first coil and the second coil are disposed to form a zigzag shape each other. 
     The cross-sectional centers of the first coils may be disposed to form a plurality of columns vertically disposed to the rows, wherein (m,n), (m,n+1), (m+1 and n+1), and (m+1,n) cross-sectional centers among the cross-sectional centers of the first coils are disposed to form a square, and wherein m and n are any natural numbers, and a (m,n) cross-sectional center means a cross-sectional center of the coil disposed at an intersecting point of a m-th row and a n-th column. 
     Cross-sectional area of the second coil may be smaller than that of the first coil, wherein each cross-section of the second coil is disposed in a pore formed among the (m,n), (m,n+1), (m+1 and n+1), and (m+1,n) cross-sections of the first coil, and wherein the cross-sectional area of the second coil is approximately 17% of or smaller than that of the first coil. 
     Current of the first coil may flow in an opposite direction of that of the second coil. 
     In another aspect of the present invention, a method for winding a coil on an object, wherein the coil comprises a plurality of first coils and a plurality of second coils, may include winding the first coils on an exterior circumferences of the second coils, wherein an outer circumferences of the respective second coil is enclosed and in contact with outer circumference of at least three first coils, and wherein cross-sectional area of the second coil is smaller than that of the first coil, wherein the outer circumference of the at least three first coils are in contact each other. 
     In further another aspect of the present invention, the water pump of clutch type which receives a coolant, pressurizes the coolant by a rotation of an impeller fixed to a shaft, and supplies the pressurized coolant to a cooling circuit may include a pulley connected to a crankshaft so as to rotate according to a rotation of the crankshaft, a hub at which the shaft is mounted so as to rotate together with the shaft, a pin selectively connecting the hub to the pulley, an elastic member always exerting elastic force on the pin, and a coil selectively applying magnetic force to the pin to an opposite direction of the elastic force, wherein the coil is wound on a case and includes first and second coils with different cross-sectional area, the first coil and the second coil are wound on the case by turns, and the first coil and the second coil are disposed to form a zigzag shape. 
     The first coil may be wound as a cubic packing, wherein the second coil is disposed in a pore among the first coils wound as the cubic packing, and wherein the cross-sectional area of the second coil is approximately 17% of or smaller than that of the first coil. 
     Current of the first coil may flow in an opposite direction of that of the second coil. 
     The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description of the Invention, which together serve to explain certain principles of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of a water pump of clutch type to which a coil according to an exemplary embodiment of the present invention is applied. 
         FIG. 2  is a cross-sectional view of a coil according to an exemplary embodiment of the present invention. 
         FIG. 3  is an enlarged view of  FIG. 2 . 
         FIG. 4  is a cross-sectional view of a conventional coil. 
         FIG. 5  is an enlarged view of  FIG. 4 . 
     
    
    
     It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment. 
     In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is/are intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims. 
     An exemplary embodiment of the present invention will hereinafter be described in detail with reference to the accompanying drawings. 
       FIG. 1  is a cross-sectional view of a water pump of clutch type to which a coil according to an exemplary embodiment of the present invention is applied. 
     As shown in  FIG. 1 , a water pump of clutch type  1  includes a pump housing  40 , a pump cover (not shown), a pulley  10 , a hub  80 , a shaft  20 , and a coil  110 . 
     The pump housing  40  has a disk shape and is provided with a penetration hole formed at a middle portion thereof. Coupling means for coupling the pump housing  40  with the pump cover are disposed at an external circumferential portion of the pump housing  40 . Generally, a bolt (not shown) is used as the coupling means. The shaft  20  is disposed in the penetration hole, and an impeller  30  is fixed to one end of the shaft  20 . A bearing for smoothly rotating the shaft  20  is disposed between the shaft  20  and the penetration hole. 
     The pump cover is coupled with the pump housing  40  so as to form a chamber (not shown) therebetween in which coolant is pressurized. The impeller  30  is disposed in the chamber. In addition, the chamber is connected to an inlet (not shown) so as to receive the coolant circulating a cooling circuit (not shown), and is connected to an outlet (not shown) such that the pressurized coolant is supplied to the cooling circuit. The impeller  30  rotates together with the shaft  20  and pressurizes the coolant flowing in the chamber. 
     The pump housing  40 , the pump cover, and the impeller  30  according to an exemplary embodiment of the present invention are similar to those according to conventional arts and are well known to a person of an ordinary skill in the art. Therefore, a detailed description thereof will be omitted. 
     The pulley  10  has an annular shape having an exterior circumference and an interior circumference. A belt (not shown) is mounted at the exterior circumference of the pulley  10 . The pulley  10  is connected to a crankshaft (not shown) through the belt. Therefore, the pulley  10  rotates according to a rotation of the crankshaft. Therefore, the pulley  10  always rotates when an engine operates. 
     The pulley  10  is provided with a friction pad  12  mounted at one surface thereof (a surface facing the pump housing  40 ), and a clutch disk  60  rubbing with the friction pad  12  is provided. The clutch disk  60  is always rotated together with the pulley  10  by frictional force of the friction pad  12 . A first hole  62  is formed at the clutch disk  60 . 
     The hub  80  has a disk shape, and a shaft mounting portion is formed at a middle portion thereof. The shaft  20  is mounted in the shaft mounting portion, and accordingly, the hub  80  rotates with the shaft  20 . In addition, a bearing  50  is disposed between the hub  80  and the interior circumference of the pulley  10  so as to permit relative rotation of the pulley  10  to the hub  80 . That is, the pulley  10  always rotates when the engine operates. However, the hub  80  is selectively connected to the pulley  10  and selectively rotates together with the pulley  10 . The bearing  50  includes an inner ring  52  fixed to the hub  80 , an outer ring  54  fixed to the interior circumference of the pulley  10 , and rolling elements  56  mounted between the inner ring  52  and the outer ring  54 . 
     A second hole  70  corresponding to the first hole  62  is formed at an external circumferential portion of the hub  80 . A pin  82  for selectively connecting the hub  80  with the pulley  10  is inserted in the second hole  70 . The pin  82  inserted in the second hole  70  is selectively inserted in or came out from the first hole  62  according to magnetic force generated by the coil  110  and elastic force of an elastic member  90  fighting against the magnetic force. If the pin  82  inserted in the second hole  70  is inserted in the first hole  62 , the hub  80  is connected to and rotates with the pulley  10 . If the pin  82  inserted in the second hole  70  is not inserted in the first hole  62  on the contrary, connection between the hub  80  and the pulley  10  is cut off and the hub  80  does not rotate. 
     The elastic member  90  is disposed between the hub  80  and the clutch disk  60  and applies the elastic force fighting against the magnetic force generated by the coil  110  to the hub  80 . A coil spring is mainly used as the elastic member  90 . 
     The coil  110  is wound on a coil case  100 . The coil case  100  has an annular shape, one surface thereof (a surface facing the pump housing  40 ) is open, so as to receive the coil  110 , the opened surface is blocked by a coil cover  120  after the coil  110  is wound on the coil case  100 . Therefore, the coil  110  wound on the coil case  100  is not uncoiled by the coil cover  120 . If the current is applied to the coil  110 , the magnetic force is generated at the coil  110 . The magnetic force pulls the pin  82  such that the pin  82  comes out from the first hole  62 . Therefore, if the current is applied to the coil  110 , the connection of the hub  80  with the pulley  10  is cut off. 
     Hereinafter, referring to  FIG. 2  and  FIG. 3 , the coil  110  according to the exemplary embodiment of the present invention will further be described. 
       FIG. 2  is a cross-sectional view of a coil according to an exemplary embodiment of the present invention, and  FIG. 3  is an enlarged view of  FIG. 2 . 
     As shown in  FIG. 2  and  FIG. 3 , the coil  110  includes a first coil  112  and a second coil  114 . Cross-sectional area of the first coil  112  is different from that of the second coil  114 . Herein, it is exemplarily described that the cross-sectional area A 2  of the second coil  114  is smaller than that A 1  of the first coil  112 . 
     The first coil  112  is wound on the coil case  100  or the second coil  114 , and the second coil  114  is wound on the first coil  112 . Cross-sectional centers of the first and second coils  112  and  114  form a row. In addition, the first and second coils  112  and  114  are wound by a predetermined numbers so as to form a plurality of rows. The first coil  112  and the second coil  114  are disposed to form a zigzag shape. In addition, the first coil  112  is wound as a cubic packing. That is, the cross-sectional centers of the first coil  112  are disposed to form a plurality of columns vertically disposed to the rows. Therefore, (m,n), (m,n+1), (m+1 and n+1), and (m+1,n) cross-sectional centers are disposed to form a square shape. That is, an angle θ between a connecting line of the (m,n) cross-sectional center with the (m,n+1) cross-sectional center and a connecting line of the (m,n) cross-sectional center with the (m+1, n) cross-sectional center is 90°, and length of one connecting line is the same as that of another connecting line. Herein, m and n are any natural numbers, and a (m,n) cross-sectional center means a cross-sectional center of the coil disposed at an intersecting point of a m-th row and a n-th column. 
     Generally, if the first coil  112  is wound as the cubic packing, porosity increases compared with a porosity if the first coil  112  is wound as the rhombohedral packing. However, the second coil  114 , the cross-sectional area A 2  of which is smaller than that A 1  of the first coil  112 , is disposed in the pore formed among the (m,n), (m,n+1), (m+1 and n+1), and (m+1,n) cross-sections of the first coil  112  according to the exemplary embodiment of the present invention. Therefore, porosity may be reduced. It is preferable that the pore among the first coil  112  is completely filled with the second coil  114 . Accordingly, the second coil  114  contacts with the first coils  112  surrounding it at four points P 1 , P 2 , P 3 , and P 4 . 
     If diameter of the first coil  112  is 1, the porosity is about 0.546. Therefore, diameter of the second coil  114  completely filling the pore (generally, density of the coil  110  is increased by pressing the coil  110 .) is about 0.417. Therefore, a ratio of the cross-sectional area A 1  of the first coil  112  to that A 2  of the second coil  114  is about 1,0.174. Therefore, it is preferable that the cross-sectional area A 2  the second coil  114  is 17% of or smaller than that A 1  of the first coil  112 . 
     Reduction in the porosity means that the numbers of the coils  110  wound on the coil case  100  increases. The magnetic force generated at the coil  110  is proportional to the numbers of the coils  110  wound on the coil case  100  and the numbers of the poles. Since the number of the coils  110  wound on the coil case  100  increases, the magnetic force generated at the coil  110  is stronger according to the exemplary embodiment of the present invention. 
     In addition, the current of the first coil  112  flows in an opposite direction that of the second coil  114 . Therefore, the number of the pores increases. 
     Further, since porosity of the coil  110  is reduced, the coils  110  are more pressed to each other. Therefore, slip of the coil  110  may be prevented, and accordingly, spread of adhesive for preventing slip of the coil  110  is unnecessary. 
     According to an exemplary embodiment of the present invention, a stronger magnetic force is generated at coils without increasing size of an object as a consequence of winding more coils on the object having a limited space. Therefore, capacity of devices (for example, a motor, a generator, a pump, and so on) generating the magnetic force by flowing current through the coil may increase without increasing size thereof. 
     For convenience in explanation and accurate definition in the appended claims, the terms “upper”, “lower”, “interior”, “exterior”, “inner”, and “outer” are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures. 
     The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.