Abstract:
A high-pressure fuel pump apparatus may include a housing, a camshaft that may be mounted in the housing and rotated by operation of an engine, an eccentric cam that may be disposed eccentrically with respect to the camshaft and integrally rotated with the camshaft, a piston that may be slidably mounted in the housing and engaged to the eccentric cam to move up/down in the housing to produce a pressured fuel with rotation of the eccentric cam, and a rotary member that may be disposed between the eccentric cam and the piston and has a rolling contact with the eccentric cam and the piston to convert rotation of the eccentric cam into a straight motion of the piston.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims priority to Korean Patent Application No. 10-2012-0104195 filed on Sep. 19, 2012, the entire contents of which is incorporated herein for all purposes by this reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a high-pressure fuel pump. More particularly, the present invention relates to a high-pressure fuel pump of which the weight and cost can be reduced and the performance can be improved. 
         [0004]    2. Description of Related Art 
         [0005]    In general, for a high-pressure fuel pump in a vehicle which is used to inject fuel, a camshaft is rotated by operating an engine and the rotation of the camshaft is converted into a straight motion of a piston. 
         [0006]    Describing the straight motion of the piston in detail, the piston is moved up by a cam integrally rotating with the camshaft and moved down by a spring disposed above the piston, thereby reciprocating straight. Further, a tappet moves up/down with the straight reciprocal motion of the piston, high-pressure fuel for fuel injection is produced. Further, a rotary member such as a roller is disposed between the cam and the piston such that the rotation of the camshaft is easily converted into the straight motion of the piston. 
         [0007]    In this configuration, the roller and the cam should be assembled in the same direction and the roller should be spaced at a predetermined distance from the camshaft. Therefore, manufacturing and assembling processes may be troublesome. 
         [0008]    On the other hand, abrasion and slip are generated on the outer circumferential surface of the roller and a portion that comes in contact with the outer circumferential surface of the roller. Further, abrasion may be generated on the inner side of a housing that comes in contact with the axial end surfaces of the roller. Further, the housing should be manufactured as large as the diameter of the roller. Therefore, the weight and cost of the high-pressure fuel pump may increase and the fuel efficiency of a vehicle may decrease. 
         [0009]    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 
       [0010]    Various aspects of the present invention are directed to providing a high-pressure fuel pump having advantages of being able to minimize abrasion of a rotary member and a portion that comes in contact with the rotary member. 
         [0011]    Further, the present invention provides a high-pressure fuel pump of which the weight and cost can be reduced and the performance can be improved. 
         [0012]    In an aspect of the present invention, a high-pressure fuel pump apparatus may include a housing, a camshaft that is mounted in the housing and rotated by operation of an engine, an eccentric cam that is disposed eccentrically with respect to the camshaft and integrally rotated with the camshaft, a piston that is slidably mounted in the housing and engaged to the eccentric cam to move up/down in the housing to produce a pressured fuel with rotation of the eccentric cam, and a rotary member that is disposed between the eccentric cam and the piston and may have a rolling contact with the eccentric cam and the piston to convert rotation of the eccentric cam into a straight motion of the piston. 
         [0013]    The rotary member is positioned inside the piston, and a portion of the rotary member protrudes from the piston to have the rolling contact with the eccentric cam. 
         [0014]    The piston is spaced with the eccentric cam by the rotary member to prevent direct contact between the eccentric cam and the piston. 
         [0015]    A guide groove is formed along an outer circumferential surface of the eccentric cam and receives the rotary member therein to guide rotation of the rotary member. 
         [0016]    The high-pressure fuel pump apparatus may further include an elastic member that provides an elastic force to the piston toward the camshaft. 
         [0017]    The piston may further have a support portion having a large diameter in comparison to an other portion thereof and having a lower portion formed in a hollow cylindrical shape, and a connector selectively fastened to the lower portion of the support portion, wherein the support portion and the connector are combined such that the rotary member is positioned inside the lower portion of the piston. 
         [0018]    A rotary member insertion hole is vertically formed through the connector, wherein a rotary member seat groove is formed in the support portion such that the rotary member is slidably seated thereon, and wherein the rotary member is disposed inside the piston while slidably covered by the rotary member insertion hole and the rotary member seat groove. 
         [0019]    A diameter of the rotary member is larger than a diameter of the rotary member insertion hole such that the rotary member is prevented from being separated from the piston. 
         [0020]    A portion of the rotary member protrudes down from the rotary member insertion hole to have the rolling contact with the eccentric cam. 
         [0021]    The connector is thread-fastened to the support portion. 
         [0022]    The rotary member may have a ball shape. 
         [0023]    The housing may include a hydraulic chamber into which the piston is slidably disposed, wherein a first pressure channel receiving a first pressured fluid and a second pressure channel supplying the pressured fluid to an injector are fluid-connected to the hydraulic chamber. 
         [0024]    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, which together serve to explain certain principles of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]      FIG. 1  is a view illustrating the configuration of a high-pressure fuel pump according to an exemplary embodiment of the present invention. 
           [0026]      FIG. 2  is a perspective view of a cam and a piston according to an exemplary embodiment of the present invention. 
           [0027]      FIG. 3  is a partial cross-sectional view of the piston according to an exemplary embodiment of the present invention. 
           [0028]      FIG. 4  is a perspective view of a connector for a piston according to an exemplary embodiment of the present invention. 
           [0029]      FIG. 5  is a perspective view of the piston with a support portion combined with the connector an exemplary embodiment of the present invention. 
       
    
    
       [0030]    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. 
         [0031]    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 
       [0032]    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 the 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. 
         [0033]    An exemplary embodiment of the present invention will hereinafter be described in detail with reference to the accompanying drawings. 
         [0034]      FIG. 1  is a view illustrating the configuration of a high-pressure fuel pump according to an exemplary embodiment of the present invention. 
         [0035]    As shown in  FIG. 1 , a high-pressure fuel pump according to an exemplary embodiment of the present invention includes a housing  16 , a camshaft  1 , a cam  10 , a piston  3 , a tappet  50 , a spring  52 , and a rotary member. 
         [0036]    The housing  16  is provided to receive the components of the high-pressure fuel pump. A hydraulic chamber  54  is formed in the housing  16 . The hydraulic chamber  54  receives and presses low-pressure fuel. Thereafter, high-pressure fuel produced in the hydraulic chamber  54  by the operation of the high-pressure fuel pump is supplied to an engine. The hydraulic chamber  54  is connected with a fuel tank by a low-pressure channel  56  to receive low-pressure fuel from the fuel tank. Further, the hydraulic chamber  54  is connected with an accumulator  60  by a high-pressure channel  58 . That is, the high-pressure fuel produced in the hydraulic chamber  54  is supplied to the accumulator  60  through the high-pressure channel  58 . In this configuration, check valves  7  and  8  may be disposed in the low-pressure channel  56  and the high-pressure channel  58 , respectively, to guide the fuel in one direction. 
         [0037]    On the other hand, the high-pressure fuel supplied to the accumulator  60  is supplied to an injector  70  and injected into a combustion chamber by the injector  70 . The accumulator  60  is a device that temporarily stores the high-pressure fuel. The accumulator  60  and the injector  70  are apparent to people of an ordinary skill in the art (hereafter, those skilled in the art) and the details are not described. 
         [0038]    The camshaft  1  is connected with the engine. Further, the camshaft  1  is disposed in the housing  16  and rotated by the operation of the engine. 
         [0039]    The cam  10  is formed or disposed on the camshaft  1  and integrally rotates with the camshaft  1 . That is, the camshaft  1  and the cam  10  have the same rotational axis  14 . Further, the cam  10  is eccentrically disposed about the camshaft  1 . 
         [0040]    Further, the housing  16  is combined with a hub to prevent the camshaft  1  and the cam  10  from separating from the housing  16 . That is, when one end of the camshaft  1  is inserted in the housing  16  and the cam  10  is positioned inside the housing  16 , the hub  18  is combined with the housing  16  at the other end of the camshaft  1 , such that the camshaft  1  and the cam  10  are prevented from separating. In this configuration, the camshaft  1  may be connected with the engine, through the hub  18 . That is, the hub  18  may be formed in a hollow cylindrical shape. Further, bearings  5  and  6  may be disposed, respectively, between the outer circumferential surface of the camshaft  1  and the inner circumferential surface of the hub  18  and between the outer circumferential surface of the camshaft  1  and the inner circumferential surface of the housing  16  such that the camshaft  1  smoothly rotates. 
         [0041]    The piston  3  moves up/down with the rotation of the eccentric cam  10 . That is, the piston  3  reciprocates straight up/down. Further, as the piston  3  moves up, the fuel in the hydraulic chamber  54  is compressed, such that high-pressure fuel is produced. 
         [0042]    The tappet  50  moves u/down with the piston  3 . Further, the piston  3  has a support portion  30  that is supported on the tappet  50 . Further, as the support portion  30  of the piston  3  moves up, the tappet  50  is pushed up by the support part  30 . That is, the support portion  30  may have a diameter larger than other portions of the piston  3 , corresponding to the size of the tappet  50 . The tappet  50  described herein may be a common tappet that converts the rotation of the cam into a vertical straight motion such that a fuel pump operates and fuel is supplied to an injection nozzle. Further, the common tappet may be an assembly of the tappet  50  and the piston  3  according to an exemplary embodiment of the present invention. Operating a fuel pump with the tappet  50  is apparent to those skilled in the art and the details are not provided. 
         [0043]    The spring  52  is provided to allow the piston  3  and the tappet  50  to smoothly move down. Further, the spring  52  is disposed higher than the tappet. 
         [0044]    The rotary member  4  is in rolling contact with the cam  10  and the piston  3  between the cam  10  and the piston  3 . That is, the rotary member  4  is disposed between the cam  10  and the piston  3  such that the rotation of the cam  10  is easily converted into a straight motion of the piston  3 . Further, the rotary member  4  prevents direct contact between the cam  10  and the piston  3 . Further, the rotary member  4  is formed in a ball shape to minimize the contact area. 
         [0045]    Meanwhile, a high-pressure fuel pump equipped with the rotary member  4  according to an exemplary embodiment of the present invention is not limited to the description referring to  FIG. 1  and the rotary member  4  may be applied to various high-pressure fuel pump that are operated by a camshaft with a cam  4  and a tappet assembly. 
         [0046]      FIG. 2  is a perspective view of a cam and a piston according to an exemplary embodiment of the present invention. 
         [0047]    As shown in  FIGS. 1 and 2 , the rotary member  4  is disposed inside the support portion  30  of the piston  3 . Further, the rotary member  4  partially protrudes from the piston  3  to be in contact with the cam  10 . The cam  10  has a guide groove  12 . 
         [0048]    The guide groove  12  is a groove formed around the outer circumferential surface of the cam  4  to guide the rotary member  4  being in contact with the cam  10 . Further, the guide groove  12  has a shape corresponding to the shape of the rotary member  4 . That is, the cross-section of the guide groove  12  may be an arc with the same radius as that of the rotary member  4  formed in a ball shape. Meanwhile, a lubricant may be supplied between the rotary member  4  and the guide groove  12 . 
         [0049]    The configuration and shape of the support portion  30  where the rotary member  4  is disposed are described hereafter in detail with reference to  FIGS. 3 to 5 . 
         [0050]      FIG. 3  is a partial cross-sectional view of the piston according to an exemplary embodiment of the present invention. 
         [0051]    As shown in  FIG. 3 , the piston  3  further includes a connector  20 . 
         [0052]    The connector  20  is combined with the support portion  30  such that the rotary member  4  is received inside the piston  3 . That is, the connector  20  is coupled to the lower portion of the support portion  30 . Further, the connector  20  has a rotary member insertion hole  24 . 
         [0053]    The rotary member insertion hole  24  is a hole vertically formed through the connector  20 . Further, the rotary member  4  is inserted in the rotary member insertion hole  24 . That is, the rotary member insertion hole  24  may be formed in a circle such that the ball-shaped rotary member  4  is inserted. Further, the inner diameter of the lower portion of the rotary member insertion hole  24  is made smaller than the diameter d of the rotary member  4  to prevent the rotary member  4  from separating from the connector  20 . That is, the rotary member  4  is inserted from above the rotary member insertion hole  24 . 
         [0054]    A rotary member seat groove  34  is formed in the support portion  30  such that the upper portion of the rotary member  4  is seated. That is, the rotary member seat groove  34  is formed on a connector contact surface  32  that is in contact with the connector  20  with the rotary member  4  inserted. In this configuration, the connector contact surface  32  is a surface that is in contact with the top  22  of the connector  20 . Further, the rotary member seat groove  34  may be shaped to correspond to a portion of the ball-shaped rotary member  4 . 
         [0055]      FIG. 4  is a perspective view of a connector for a piston according to an exemplary embodiment of the present invention. Further,  FIG. 4  shows the connector  20  with the rotary member  4  inserted therein. 
         [0056]    As shown in  FIG. 4 , the connector  20  is formed in a hollow cylindrical shape. In this structure, the hole is the rotary insertion hole  24 . The height h of the cylindrical connector  20  is made smaller than the diameter d of the rotary member  4 . Therefore, the rotary member  4  inserted in the rotary member insertion hole  24  may protrude up and down from the connector  20 . The portion of the rotary member  4  which protrudes upward from the connector  20  is seated in the rotary member seat groove  34  of the support portion  30  and the other portion protruding downward from the connector  20  comes in contact with the guide groove  12  of the cam  10 . Since the inner diameter of the lower portion of the rotary member insertion hole  24  is made smaller than the diameter d of the rotary member  4 , the rotary member  4  is prevented from separating from the piston  3 . 
         [0057]    Further, threads may be formed on the outer circumferential surface  26  of the connector  20 , for combination with the support portion  30 . 
         [0058]    Referring to  FIG. 3 , the lower portion of the support portion  30  is formed in a hollow cylindrical shape with the top closed and the bottom open. Further, the support portion  30  and the connector  20  are combined by inserting the connector in the hole of the lower portion of the support portion  30 . Further, threads corresponding to the threads of the connector  20  are formed on the inner circumferential surface  36  of the support portion  30 . That is, the connector  20  and the support portion  30  are thread-fastened. 
         [0059]    Tool insertion grooves  29  for a tool that fasten the connector  20  to the support portion  30  are shown in  FIG. 3 . The tool insertion grooves  29  may be formed on the underside  28  of the connector  20 . The shape of the tool insertion grooves  29  is not limited thereto and may be changed to correspond to tools by those skilled in the art. 
         [0060]      FIG. 5  is a perspective view of the piston with a support portion combined with the connector an exemplary embodiment of the present invention. 
         [0061]    As shown in  FIG. 5 , when the support portion  30  and the connector  20  are combined, a portion of the rotary member  4  protrudes outward from the connector  20  for the piston  3  to come in contact with the cam  10 . Further, the rotary member  4  can smoothly rotate with respect to the piston  3 . 
         [0062]    Referring to  FIG. 3 , the connector  20  can be turned by a tool that fits the tool insertion grooves  29  formed on the underside of the connector  20 . Further, the connector  20  is inserted into the hole at the lower portion of the support portion  30  by turning the connector  20  in the direction where the threads on the inner circumferential surface  36  of the support portion and the outer circumferential surface  26  of the connector  26  are fastened. The connector  20  can be inserted until the top  22  of the connector comes in contact with the connector contact surface  32 . The connector  20  is combined with the support portion  30 , with the rotary member  4  inserted in the rotary member insertion hole  24  of the connector  20 , such that the rotary member  4  is positioned inside the piston  3 . That is, the rotary member  4  is positioned inside the piston while covered by the rotary member insertion hole  24  and the rotary member seat groove  34 . On the other hand, a lubricant may be supplied between the rotary member  4 , the rotary member insertion hole  24 , and the rotary member seat groove  34  to minimize friction. 
         [0063]    As described above, according to an exemplary embodiment of the present invention, it is possible to minimize the contact surface of the rotary member  4 . Therefore, it is possible to improve durability by minimizing abrasion the rotary member and on the portion that comes in contact with the rotary member  4 . Further, as the rotary member  4  is positioned inside the piston  3  and guided by the guide groove  12  of the cam  3 , the rotary member  4  stably rotates without slip. Further, the performance of the high-pressure fuel pump can be improved. Further, as the space for the rotary member  4  is minimized, it is possible to reduce the weight and cost of the high-pressure fuel pump and to improve fuel efficiency of a vehicle. 
         [0064]    For convenience in explanation and accurate definition in the appended claims, the terms “upper”, “lower”, “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. 
         [0065]    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.