Patent Publication Number: US-8122811-B2

Title: Fuel injection pump and method for assembling the same

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is based on and incorporates herein by reference Japanese Patent Applications No. 2007-293596 filed on Nov. 12, 2007 and No. 2008-164965 filed on Jun. 24, 2008. 
     FIELD OF THE INVENTION 
     The present invention relates to a fuel injection pump for an internal combustion engine. The present invention further relates to a method for assembling the fuel injection pump. 
     BACKGROUND OF THE INVENTION 
     U.S. Pat. No. 6,615,799 B2 (JP-A-2002-310039) discloses a fuel injection pump including a camshaft, a cam, a sliding member, and a plunger. The cam is eccentric with respect to the camshaft. The sliding member is slidable and rotatable with respect to the outer circumferential periphery of the cam. The plunger is configured to pressurize and feed fuel in a compression chamber. 
     The cam is eccentric with respect to the center axis of the camshaft and rotatable integrally with the camshaft. The sliding member revolves around the center axis of the camshaft in conjunction with rotation of the camshaft. The plunger as a sliding member is slidable and configured to convert revolution of the sliding member into a reciprocal movement. In the present structure, the plunger conducts the reciprocal movement so as to pressurize and feed fuel in the fuel compression chamber. 
     More specifically, U.S. Pat. No. 6,615,799 B2 discloses a three-cylinder fuel injection pump including a housing, which has three cylinders and three fuel compression chambers, and three plungers each slidable in each cylinder and configured to pressurize and feed fuel drawn into the fuel compression chamber. The sliding member is in a ring shape and entirely surrounds the outer circumferential periphery of the cam. The sliding member is in a hexagonal shape having straight and arc-shaped outlines. The three plungers are located at intervals of 120 degrees, and having a straight outline slidably in contact with the sliding member. In the present structure, the sliding member has three sliding surfaces located at intervals of 120 degrees. The three plungers alternately pump fuel in the three compression chambers in conjunction with rotation of the camshaft. According to U.S. Pat. No. 6,615,799 B2, the outer circumferential periphery of the cam has a groove to lead lubricate oil into a sliding portion between the outer circumferential periphery of the cam and the sliding member. 
     In recent years, increase in discharge pressure of a fuel injection pump is demanded. When the discharge pressure is increased, surface pressure applied to the sliding portion between the cam and the sliding member becomes high. Therefore, supply of sufficient fuel is required to the sliding portion. However, in the structure of U.S. Pat. No. 6,615,799 B2, the sliding member is in a ring shape and entirely surrounds the outer circumferential periphery of the cam. Accordingly, it is hard to supply sufficient fuel to the sliding portion. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing and other problems, it is an object to produce a fuel injection pump configured to lead sufficient fuel into a sliding portion. It is another object of the present invention to produce a method for assembling the fuel injection pump. 
     According to one aspect of the present invention, a fuel injection pump comprises a housing having a cylinder and a compression chamber. The fuel injection pump further comprises a plunger slidable in the cylinder and configured to pressurize fuel in the compression chamber. The fuel injection pump further comprises a camshaft. The fuel injection pump further comprises a cam eccentric with respect to a shaft center axis of the camshaft and integrally rotatable with the camshaft. The fuel injection pump further comprises a sliding member slidable around an outer circumferential periphery of the cam and configured to revolve around the shaft center axis in conjunction with rotation of the camshaft. The plunger is slidable on the sliding member and configured to convert the revolution into a linear movement. The cam and the sliding member are accommodated in the housing. The sliding member has an opening through which the outer circumferential periphery is partially exposed. 
     According to another aspect of the present invention, a method for assembling a fuel injection pump, the method comprises inserting a cam of a camshaft into a sliding member. The method further comprises moving the cam around a shaft center axis and moving the sliding member around an outer circumferential periphery of the cam by applying moment caused by mass of the cam and the sliding member so as to position the cam and the sliding member at a specified rotative position. The method further comprises accommodating the cam and the camshaft in a housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings: 
         FIG. 1  is a longitudinal sectional view showing a fuel injection pump according to an embodiment; 
         FIG. 2  is an axial sectional view showing the fuel injection pump according to the embodiment; 
         FIG. 3A  is a perspective view showing a camshaft and a sliding member of the fuel injection pump, and  FIG. 3B  is an axial sectional view showing a cam and the sliding member; 
         FIGS. 4A ,  4 B are views each showing a sliding surface between the cam and the sliding member; 
         FIGS. 5A ,  5 B are partially sectional views each showing the sliding member assembled to the cam; 
         FIGS. 6A ,  6 B are views each showing the camshaft and the sliding member, which are assembled to each other; 
         FIG. 7  is an axial sectional view showing a modification of the fuel injection pump shown in  FIG. 2 ; 
         FIG. 8A  is a front view showing a first modification of the sliding member shown in  FIG. 2 , and  FIG. 8B  is a sectional view taken along the line VIIIB-VIIIB in  FIG. 8A ; 
         FIG. 9A  is a front view showing a second modification of the sliding member shown in  FIG. 2 , and  FIG. 9B  is a sectional view taken along the line IXB-IXB in  FIG. 9A ; 
         FIG. 10A  is a front view showing a third modification of the sliding member shown in  FIG. 2 , and  FIG. 10B  is a sectional view taken along the line XB-XB in  FIG. 10A ; 
         FIG. 11A  is an enlarged view showing the plunger in  FIG. 2 , and  FIG. 11B  is an axial sectional view showing a modification of the plunger shown in  FIG. 11A ; 
         FIG. 12  is a view showing a first modification of the plunger and the sliding member shown in  FIG. 4A ; 
         FIG. 13  is a view showing a second modification of the plunger and the sliding member shown in  FIG. 4A ; and 
         FIG. 14  is a partially sectional view taken along the line XIV-XIV in  FIG. 13 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Embodiment 
     As shown in  FIGS. 1 ,  2 , a fuel injection pump  1  is a single-cylinder fuel injection pump including a housing  2 , which has one cylinder  221  and one fuel compression chamber  222 , and a plunger  3 , which is for pressurizing and feeding fuel drawn into the fuel compression chamber. The fuel injection pump  1  includes a camshaft  5 , a cam  6 , and a sliding member  7 , in addition to the housing  2  and the plunger  3 . 
     The housing  2  includes a housing body  21 , a cylinder head  22 , and a bearing cover  23 . The cylinder  221  is defined in the cylinder head  22 . The fuel compression chamber  222  is defined by the inner surface of the cylinder head  22 , the end surface of a check valve member  411  of a check valve  41 , and the end surface of the plunger  3 . 
     The bearing cover  23  is fixed to the housing body  21  via a bolt. A metal bush  81 , which is accommodated in the bearing cover  23 , and a metal bush  82 , which is accommodated in the housing body  21 , configure a bearing of the camshaft  5 . The bearing cover  23  and the camshaft  5  therebetween define an oil seal. The camshaft  5  is accommodated in the housing body  21  and the bearing cover  23 . In the present structure, the camshaft  5  is rotatably supported by the metal bushes  81 ,  82 . 
     As shown in  FIG. 3A , the cam  6  has an outer circumferential periphery  61  as a cylinder lateral side substantially defining a circular cam profile. The cam  6  is eccentric with respect to a shaft center axis  5 A of the camshaft  5 . In the present structure, the shaft center axis  5 A of the camshaft  5  is shifted from a cam center axis  6 A of the cam  6 , and rotatable together with the camshaft  5 . Each of the inner walls of the housing body  21  and the bearing cover  23  is provided with an annular sliding plate  84 , which is slidable relative to the axial end surface of the cam  6 . 
     The sliding member  7  surrounds the outer circumferential periphery  61  of the cam  6 , and is rotatable and slidable relative to the outer circumferential periphery  61  of the cam  6 . As shown in  FIG. 3A , the sliding member  7  is substantially in a C-shape in cross section. The sliding member  7  is assembled to the cam  6  in the direction of arrow W along the shaft center axis  5 A. The sliding member  7  has an opening  72 , which is configured to partially expose a part of the outer circumferential periphery  61  of the cam  6  with respect to the circumferential direction of the sliding member  7 . That is, the opening  72  is provided in a portion of the sliding member  7  in the circumferential direction of the sliding member  7 . The opening  72  extends through the sliding member  7  in the direction of the shaft center axis  5 A. As shown in  FIG. 3B , the sliding member  7  has both tip ends  73  at the side of the opening  72 , and both the tip ends  73  extend along the outer circumferential periphery  61  of the cam  6 . In the present structure, the sliding member  7  surrounds a part of the outer circumferential periphery  61 , which is shown by the arrow R and longer than the semicircle thereof. 
     A metal bush (bearing member)  83  is press-fitted to the inner circumferential periphery of the sliding member  7  excluding the opening  72 . In the present structure, the sliding member  7  is slidable and rotatable relative to the outer circumferential periphery  61  of the cam  6 . In an actual structure, the sliding member  7  is press-fitted with the metal bush  83 , and thereafter the sliding member  7  together with the metal bush  83  is assembled to the cam  6 . In  FIG. 3A , the metal bush  83  is omitted so as to simplify the drawing. The metal bush  83  configures a part of a sliding member. The inner sliding surface of the metal bush  83  defines a sliding surface  831  as a rotary sliding portion between the outer circumferential periphery  61  of the cam  6  and the sliding member  7 . 
     The sliding member  7  has a sliding surface  71 , which is located on the opposite side of the opening  72  and slidably in contact with the plunger  3 . The sliding surface  71  is substantially in a planar shape and configured to reduce contact pressure when sliding relative to the part of the plunger  3 , which is in contact with the sliding surface  71 . As shown in  FIG. 2 , in the present structure including the camshaft  5 , the cam  6 , the metal bush  83 , and the sliding member  7 , the sliding member  7  revolves around the shaft center axis  5 A to perform an orbital motion in conjunction with the motion of the cam  6 , which is accompanied with the rotation of the camshaft  5 . The sliding member  7  is rotatable with respect to the cam  6 . The cam  6  rotates in the sliding member  7 , while the sliding member  7  is held by the plunger  3  and restricted from rotating. 
     The plunger  3  is biased from a spring  31  at the side of the sliding member  7 . In the present structure, the plunger  3  is in contact with the sliding surface  71  of the sliding member  7  such that the plunger  3  is slidable with respect to the sliding member  7  in the horizontal direction in  FIG. 2 . In the present structure, the plunger  3  moves in response to the revolution of the sliding member  7 , thereby converting the revolution of the sliding member  7  into the movement in the vertical direction in  FIG. 2 . Thus, the plunger  3  slides in the cylinder  221  in the vertical direction in  FIG. 1  and pressurizes fuel drawn from a fuel inlet passage  223  to feed the fuel into the fuel compression chamber  222  through the check valve  41 . The check valve  41  is configured to restrict fuel from reverse flowing from the fuel compression chamber  222  to the fuel inlet passage  223 . 
     The fuel pressurized in the fuel compression chamber  222  is supplied from a fuel discharge passage  224  to a common rail (not shown) through a fuel pipe. A check valve member  421  is provided to the fuel discharge passage  224  to configure a check valve. The present check valve is configured to restrict fuel from reverse flowing from the discharge passage  224  to the fuel compression chamber  222 . 
     In  FIG. 2 , the cam  6  and the sliding member  7  are accommodated in the housing body  21  of the housing  2 , and submerged in fuel as lubricant filled in the interior of a housing body  211 . As described above, the sliding member  7  is rotatable and slidable with respect to the outer circumferential periphery  61  of the cam  6  and provided with the opening  72 , through which the outer circumferential periphery  61  is partially exposed. In the present structure, the outer circumferential periphery  61  of the cam  6  at the lower side in  FIG. 4  can be directly submerged in the lubricating oil through the opening  72 . The lubricating oil being in contact with the outer circumferential periphery  61  at the lower side is directly fed to the sliding surface  831  between the outer circumferential periphery  61  of the cam  6  and the sliding member  7  accompanied with the rotation of the cam  6  with respect to the sliding member  7 . Whereby, the lubricating oil can be sufficiently fed to the sliding surface  831 . In  FIG. 4A , the camshaft  5  is indicated by the two-dot chain line in order to make the drawing easily viewable. 
     In addition, as described above, the opening  72  extends through a part of the sliding member  7 , the part being a portion of the sliding member  7  with respect to the circumferential direction of the sliding member  7 . The opening  72  extends substantially in the direction of the shaft center axis  5 A. As shown in  FIG. 5B , as the shaft center axis  5 A is shifted from the cam center axis  6 A and the camshaft  5  projects from the cam  6  with respect to the radial direction, the diameter of the circumscribed circle of the camshaft  5  becomes large. Even in this case, as shown in  FIG. 5B , the portion of the camshaft  5  may be projected from the cam  6  through the opening  72  to the lower side in  FIG. 5B , thereby being released through the opening  72 . Thus, the camshaft  5  does can be restricted from causing interference with the sliding member  7  when the sliding member  7  is mounted to the cam  6  along the arrow W. Therefore, in the present structure, the diameter of the circumscribed circle of the camshaft  5  may be enlarged. 
     Further, when the camshaft  5  is rotatably held by the housing  2 , the camshaft  5  automatically rotates around the shaft center axis  5 A toward the ground at the lower side in  FIG. 6A  by being applied with moment. The moment is caused by the mass of the cam  6  and exerted to the cam center axis  6 A as the center of gravity of the cam  6  around the shaft center axis  5 A. As described above, the opening  72  is located at the opposite side of the sliding surface  71 . In the present structure, the sliding member  7 , which is rotatable around the outer circumferential periphery  61  of the cam  6 , automatically (spontaneously) rotates by being applied with the moment caused by the mass of the sliding member  7 . Specifically, the center of the gravity of the sliding member  7  is applied with the moment, so that the sliding member  7  automatically rotates around the cam center axis  6 A, such that the sliding surface  71  is located at the side of the ground at the lower side in  FIG. 6A . Thus, as shown in  FIG. 6A , the rotation of both the cam  6  and the sliding member  7  results in automatically positioning of the sliding surface  71  steadily at the side of the ground at the lower side in  FIG. 6A  with respect to the shaft center axis  5 A. Therefore, the sliding surface  71  of the sliding member  7  can be automatically positioned with respect to the housing  2 . Thus, positioning work of both the plunger  3  and the sliding member  7  when the plunger  3  is mounted to the housing  2  can be omitted. In the present structure, the plunger  3  may be mounted from the lower side in  FIG. 6B  toward the sliding surface  71 , which is automatically positioned with respect to the housing  2 . 
     As described above, both the tip ends  73  of the sliding member  7  at the side of the opening  72  extend along the outer circumferential periphery  61  of the cam  6 . In the present structure, the sliding member  7  surrounds the part of the outer circumferential periphery  61 . The part of the outer circumferential periphery  61  is shown by the arrow R and longer than the semicircle of the cam  6 . In the present structure, the sliding member  7  can be steadily rotatable and slidable on the outer circumferential periphery  61  of the cam  6  without being detached radially from the cam  6 . 
     Further, as described above, the sliding surface  71  is located at the opposite side of the opening  72 . In the present structure, the plunger  3  can be steadily in contact with the sliding surface  71  of the sliding member  7 , while influence caused by the opening  72  is further reduced. Accordingly, revolution of the sliding member  7  can be further steadily converted into the sliding motion of the plunger  3 , so that fuel drawn into the fuel compression chamber  222  can be further steadily pressurized and fed. 
     As described above, the fuel injection pump  1  according to the present embodiment includes the housing  2 , which has the cylinder  221  and the fuel compression chamber  222 , and the plunger  3 , which is configured to slide in the cylinder  221  so as to pressurize and feed fuel drawn into the fuel compression chamber  222 . The fuel injection pump  1  further includes the camshaft  5 , the cam  6 , and the sliding member  7 . The cam  6  is eccentric with respect to the shaft center axis  5 A of the camshaft  5  and integrally rotatable with the camshaft  5 . The sliding member  7  surrounds the outer circumferential periphery  61  of the cam  6  and has the opening  72  through which the outer circumferential periphery  61  is partially exposed. The sliding member  7  is rotatable and slidable around the outer circumferential periphery  61  and configured to revolve around the shaft center axis  5 A in conjunction with rotation of the camshaft  5 . The cam  6  and the sliding member  7  are accommodated in the housing  2 . The plunger  3  is slidable on the sliding member  7  and configured to convert revolution of the sliding member  7  into the reciprocal movement (linear movement). 
     According to the present structure, the fuel injection pump, which can lead sufficient lubricating oil to the rotary sliding portion, can be produced. 
     Modification 
     In the above embodiment, a sliding surface  171 , on which the plunger  3  is slidable, is provided at the opposite side of the opening  72 . Alternatively, as shown in  FIG. 7 , a sliding member  17  may be provided instead of the sliding member  7 . The sliding member  17  has an opening  172  at a substantially right-angle position with respect to the sliding surface  171 . 
     In the present embodiment, the fuel injection pump  1  is a single-cylinder pump having the single cylinder, and hence the number of the sliding surface  71 ,  171  is one. In the present structure, the position of the opening is not limited to the position shown in  FIGS. 2 ,  7 , and may be determined at another position, as long as the sliding surface  71 ,  171  does not interfere with the opening  72 ,  172 . As described above, the opening  72  is preferably located at the opposite side of the sliding surface  71 . Alternatively, as shown in  FIG. 7 , the opening  172  may be located at the position other than the opposite side of the sliding surface  171 . In this case, influence caused by the opening  172  can be further reduced by increasing the thickness of the sliding member  17  in the radial direction, or elongating the portion shown by the arrow R in  FIG. 3B . Thus, in the present structure, the plunger  3  can be steadily maintained in contact with the sliding surface  171  of the sliding member  17 . 
     In addition, in the above embodiment, the opening  72 ,  172  extends through the part of the sliding member  7 , the part being the portion of the sliding member  7  with respect to the circumferential direction of the sliding member  7 . The opening  72  extends substantially in the direction of the shaft center axis  5 A. The opening is not limited to the structure described above. For example, as shown in  FIGS. 8A to 9B , a sliding member  27 ,  37  may be provided instead of the sliding member  7 ,  17 . The sliding member  7 ,  17  has an opening  272 ,  372 , which extends substantially perpendicularly to the shaft center axis  5 A through a part of the sliding member  27 ,  37 , the part of the sliding member  27 ,  37  being a portion in the direction of the shaft center axis  5 A. As shown in  FIG. 8B , the opening  272  is located substantially at the center of the sliding member  27  in the direction of the shaft center axis  5 A. As shown in  FIG. 9B , the opening  372  is located substantially at both ends of the sliding member  37  in the direction of the shaft center axis  5 A. 
     In the above-described sliding member  7 ,  17 , the sliding surface  831  is not defined throughout the circumference. By contrast, in the sliding member  27 , the sliding surface  831  is defined throughout in the circumferential direction at both end sides with respect to the direction of the shaft center axis  5 A, and hence the sliding member  27  entirely surrounds both the ends in the circumferential direction. In the sliding member  37 , the sliding surface  831  is defined throughout in the circumferential direction at the center with respect to the direction of the shaft center axis  5 A, and hence the sliding member  37  entirely surrounds the center in the circumferential direction. Therefore, lubricating oil can be sufficiently fed to the rotary sliding portion, compared with the sliding member  7 ,  17 , while the strength of the sliding member  27 ,  37  is enhanced. 
     In the above embodiments, the opening  72 , 172 , 272 , 372  extends in the direction of the shaft center axis  5 A or in the direction perpendicular to the shaft center axis  5 A. The direction of the opening  72 , 172 , 272 , 372  is not limited to the above embodiments. For example, as shown in  FIG. 10 , a sliding member  47  may be provided with an opening  472 , instead of the sliding member  7 ,  17 ,  27 ,  37 . The opening  472  does not extend throughout in both the direction of the shaft center axis  5 A and the direction perpendicular to the shaft center axis  5 A, i.e., the circumferential direction of the opening  472 . In the present structure, the substantially annular opening  472  extends through the sliding surface  831  substantially in the radial direction of the sliding surface  831 . Therefore, the sliding surface  831  is provided throughout the circumference excluding the opening  472 , and the sliding member  47  surrounds circumferentially throughout the sliding surface  831 . Therefore, lubricating oil can be sufficiently fed to the rotary sliding portion, compared with the sliding member  7 ,  17 , while the strength of the sliding member  47  is enhanced. 
     In  FIGS. 8 ,  10 , the opening  272 ,  372 ,  472  is provided on the opposite side of sliding surface  271 ,  371 ,  471 , on which the plunger  3  is slidable. The structure is not limited to that shown in  FIGS. 8 ,  19 . An opening may be provided as long as the sliding surface  271 ,  371 ,  471  does not interfere with the opening. 
     In the above embodiments, the plunger  3  is directly in contact with the sliding member  7  as shown in  FIG. 11A . The structure is not limited to that shown in  FIG. 11A . As shown in  FIG. 11B , a plunger  30  may be provided, instead of the plunger  3 . The plunger  30  includes a plunger body  32  and a tappet  33 , which are separate components. The tappet  33  is a converting member. The tappet  33  is in a C-shape in cross section. The tappet  33  is slidable on the sliding surface  71  of the sliding member  7 , thereby configured to convert the revolution of the sliding member  7  to the reciprocal movement. In addition, the tappet  33  is directly in contact with the plunger body  32 , thereby reciprocally moving the plunger body  32 . In the present structure, the tappet  33  is capable of suppressing stress exerted from the sliding member  7  to the plunger body  32  when the plunger  3  converts the revolution of the sliding member  7  into the reciprocal movement. 
     More specifically, the plunger  3  indicated in  FIG. 11A  receives the sharing force, which causes ineffective stress, directly from the sliding member  7  in the horizontal direction in  FIG. 11A . By contrast, in the plunger  3  indicated in  FIG. 11B , the tappet  33  receives the sharing force from the sliding member  7  in the horizontal direction in  FIG. 11B . In the present structure, the housing body  21  on both sides of the tappet  33  can receive the sharing force from the tappet  33 . Therefore, the tappet  33  is capable of suppressing the sharing force exerted from the sliding member  7  to the plunger body  32 . 
     In the above embodiments, the present structure is applied to the single-cylinder fuel injection pump  1  having a single-cylinder structure including the single plunger and the housing, which has the single cylinder and the single fuel compression chamber. The present structure is not limited to be applied to the single-cylinder fuel injection pump  1 . The present structure may be applied to a multi-cylinder fuel injection pump including a housing, which has multiple cylinders and multiple fuel compression chambers, and multiple plungers, which are for compressing fuel drawn into the fuel compression chambers and press-feeding the fuel. 
       FIG. 12  shows an example of the present structure applied to a two-cylinder fuel injection pump. The plunger  301  is slidably in contact with the sliding surface  571  of a sliding member  57 . A plunger  302  is slidably in contact with the sliding surface  573  of the sliding member  57 . The sliding surface  573  is located on the opposite side of the sliding surface  571 . As described above, the sliding member  57  rotates around the shaft center axis  5 A in conjunction with the rotation of the camshaft  5 . In the present structure, the plungers  301 ,  302  are slidably in contact respectively with the sliding surfaces  571 ,  573  of the sliding member  57 , thereby converting the revolution of the sliding member  57  into the reciprocal movement in the vertical direction in  FIG. 12 . The plungers  301 ,  302  reciprocate in the vertical direction in  FIG. 12 , thereby pumping fuel respectively drawn into two compression chambers (not shown) and press-feeding the fuel. 
     The opening  572  is located at the location substantially perpendicular to both the sliding surfaces  571 ,  573 . Specifically, the sliding surface of the sliding member  7  is located at a rotative position perpendicular to a rotative position of the opening  72 ,  172  with respect to the cam center axis  6 A of the cam  6 . In the present structure, the plungers  301 ,  302  are slidably in contact with the sliding member  57  respectively at the sliding surfaces  571 ,  573 , which are out of the opening  572  in the sliding member  57 . In the present structure, the plungers  301 ,  302  are configured to convert the revolution of the sliding member  57  into the reciprocal movement further steadily, while reducing influence of the opening  572 . 
     Even in the present two-cylinder fuel injection pump, the outer circumferential periphery  61  of the cam  6  can be partially submerged in lubricating oil directly through the opening  572 . Thus, lubricating oil can be sufficiently led to the rotary sliding portion between the outer circumferential periphery  61  of the cam  6  and the sliding member  57 . 
       FIGS. 13 ,  14  show an example of the present structure applied to a three-cylinder fuel injection pump. A plunger  301  is slidably in contact with a sliding surface  670  of a sliding member  67 . The plunger  302  is slidably in contact with a sliding surface  671  of the sliding member  67 . A plunger  303  is slidably in contact with a sliding surface  673  of the sliding member  67 . As described above, the sliding member  67  rotates around the shaft center axis  5 A in conjunction with the rotation of the camshaft  5 . 
     Therefore, the plunger  301  is slidably in contact with the sliding surface  670  of the sliding member  67 , thereby converting the revolution of the sliding member  67  into the reciprocal movement in the direction of a center axis  301 A of the plunger  301 . The plunger  302  is slidably in contact with the sliding surface  671  of the sliding member  67 , thereby converting the revolution of the sliding member  67  into the reciprocal movement in the direction of a center axis  302 A of the plunger  302 . The plunger  303  is slidably in contact with the sliding surface  673  of the sliding member  67 , thereby converting the revolution of the sliding member  67  into the reciprocal movement in the direction of a center axis  303 A of the plunger  303 . The plungers  301 ,  302 ,  303  respectively reciprocate in the directions of the center axes  301 A,  302 A,  303 A, thereby compressing fuel drawn into three compression chambers (none shown) and press-feeding the fuel. 
     An opening  672  is provided in the sliding surface  670 . The opening  672  is, for example, in an annular shape. Dissimilarly to the above embodiments, the plunger  301  is slidably in contact with the sliding member  67  at a portion of the sliding surface  670  in which the opening  672  is defined in the sliding member  67 . The present structure is defined, since the plunger is hard to be slidably in contact with the sliding member at a location out of the opening in the sliding member  67 , dissimilarly to the embodiments shown in  FIGS. 4A ,  12 . 
     In the present embodiment shown by  FIGS. 13 ,  14 , the center of the opening  672  is shifted from the center axis  301 A of the plunger  301  to the right side in  FIG. 14  so as to reduce influence caused by the opening  672 . In the present structure, the plunger  301  is capable of steadily in contact with the sliding surface  670  of the sliding member  67 . Thus, the outer circumferential periphery  61  of the cam  6  can be partially submerged directly into lubricate oil through the opening  672 . 
     Even in the present three-cylinder fuel injection pump, the outer circumferential periphery  61  of the cam  6  can be partially submerged in lubricating oil directly through the opening  672 . Thus, lubricating oil can be sufficiently led to the rotary sliding portion between the outer circumferential periphery  61  of the cam  6  and the sliding member  67 . 
       FIG. 14  is a partial cross sectional view showing cross sections of only the sliding member  67  and the metal bush  83  for simplifying the view. 
     The present invention may include a method for assembling the fuel injection pump. For example, the method includes inserting the cam  6  of the camshaft  5  into the sliding member  7 ; moving the cam  6  around the shaft center axis  5 A and the sliding member  7  around the outer circumferential periphery of the cam  6  by applying moment caused by mass of the cam  6  and the sliding member  7  so as to position the cam  6  and the sliding member  7  at a specified rotative position; accommodating the cam  6  and the camshaft  5  in the housing  2 ; and inserting the plunger  3  into the cylinder  221  of the housing z from the lower side of the housing  2  in the gravitation direction to make contact with the sliding surface of the sliding member  7  located at the lower side. 
     The above structures of the embodiments can be combined as appropriate. Various modifications and alternations may be diversely made to the above embodiments without departing from the spirit of the present invention.