Patent Publication Number: US-9422834-B2

Title: Roller lifter for internal combustion engine

Description:
CROSS-REFERENCE 
     This application claims priority to Japanese patent application no. 2012-138596 filed on Jun. 20, 2012, the contents of which are entirely incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to a roller lifter for internal combustion engines used in car engines or the like. 
     BACKGROUND ART 
     There are known pump lifters used for fuel supply pumps or valve lifters used for valve gears in internal combustion engines such as car engines or the like. 
     Some of these lifters include a roller at a portion directly contacting a cam lobe provided in fuel supply pumps or valve gear to reduce friction resistance against the cam lobe and to improve wear resistance of the surface contacting the cam lobe (hereinafter referred to as “roller lifter  9 ”). 
     The roller lifter  9  is configured, as shown in  FIG. 12 , with a roller  93  attached to a lifter body  92  having a sliding surface  924  that slides on the inner wall of a cylinder in which the roller lifter  9  is installed. To fabricate the roller lifter, the roller  93  is first placed between a pair of support portions  921  provided to the lifter body  92 . An axial support pin  94  of the roller  93  is inserted into support holes  922  formed in the support portions  921 , and both ends of the axial support pin  94  are compressed using a hydraulic press or the like to deform the ends to increase their diameters, to mechanically fasten the axial support pin  94  to the support portions  921 . 
     The roller  93  of the roller lifter  9  and the cam lobe are arranged such that their respective rotation axes are parallel, so as to minimize friction resistance between the roller and the cam lobe. For this reason, the lifter body  92  of the roller lifter  9  is formed with an anti-rotation retainer  923  to prevent displacement of the rotation axis of the roller  93 , i.e., to prevent the lifter body  92  from rotating relative to the inner wall of the cylinder (see Patent Document 1). 
     This anti-rotation retainer  923  is formed at one axial end of the lifter body  92  by cutting and bending processes using, for example, a cutting tool or a press. More specifically, the anti-rotation retainer  923  is formed by cutting off part of one end of a cylindrical metal member to form a protruding piece of a predetermined size axially protruding from one end of the lifter body  92 , and by bending the protruding piece to protrude radially outward. 
     The protruding piece needs to be bent largely outward in the radial direction from inside. Therefore, the radial part of the lifter body  92  opposite the protruding piece had to be largely cut off, except for the support portions  921 , to form the anti-rotation retainer  923 , as shown in  FIG. 12 . 
     PATENT DOCUMENT 
     
         
         Patent Document 1: JP-A-2010-1884 
       
    
     SUMMARY OF THE INVENTION 
     However, the roller lifter  9  shown in Patent Document 1 may have lower rigidity because part of the cylindrical metal member that is the component forming the lifter body  92  is largely cut off as mentioned above. Accordingly, there is a possibility that the lifter body  92  may deform when the axial support pin  94  is mechanically fastened to the support portions  921 , and the circularity accuracy of the sliding surface  924  may be lowered. 
     Moreover, as the lifter body  92  is largely cut off by cutting and pressing as mentioned above, the lifter body  92  tends to have a small length in the front to back direction (axial direction) of the region where the sliding surface  924  is formed. That is, the distance between the front end and the rear end of the sliding surface  924  (hereinafter referred to as “sliding length”) tends to be short. This may result in large cocking (wobbling) in the cylinder when the roller lifter  9  is installed in an internal combustion engine. Namely, the shorter the sliding length is, the larger the maximum inclination angle of the lifter body  92  becomes relative to the sliding axis, when the roller lifter  9  is installed in an internal combustion engine. The surface pressure between the lifter body  92  and the inner wall of the cylinder tends to be larger accordingly, and the increased friction resistance may impede smooth sliding of the roller lifter  9 . 
     To prevent the cocking in the cylinder, it is conceivable to design the lifter body  92  to have a longer sliding length in the sliding surface  924 . However, in a configuration in which the cut-off portion is located on the rear side in the axial direction as described above, increasing the length of the sliding surface  924  would simply increase the length in the front to back direction (axial direction) of the lifter body  92 , leading to bulkiness of the lifter body  92 . 
     The present invention was made in view of such problems and its object is to provide a roller lifter for internal combustion engines, which has higher rigidity of the lifter body, prevent cocking in the cylinder, and can achieve a size reduction. 
     One aspect of the invention resides in a roller lifter for internal combustion engines, including
         a cylindrical lifter body including a sliding surface on an outer circumferential surface thereof that slides on an inner wall of a cylinder; and   a roller rotatably attached to the lifter body via an axial support pin and making contact with a rotating cam lobe;   the lifter body further including a pair of support portions supporting the axial support pin, the axial support pin being mechanically fastened to the pair of support portions, with both ends thereof inserted in support holes formed in the support portions, and an anti-rotation retainer extending radially outward from the sliding surface, wherein   the sliding surface is formed on both front and rear sides in a sliding direction of the anti-rotation retainer (claim  1 ).       

     The anti-rotation retainer in the roller lifter for internal combustion engines extends radially outward from the sliding surface of the lifter body. Therefore, the lifter body need not be cut off largely to form the anti-rotation retainer. The lifter body can have higher rigidity accordingly, so that the circularity accuracy of the sliding surface can be maintained when the axial support pin is mechanically fastened to the support portions. 
     The sliding surface of the lifter body is formed on the front side and the rear side in the sliding direction of the anti-rotation retainer. Therefore, the distance (sliding length) between the front end and the rear end of the sliding surface of the lifter body can be made longer. As a result, the roller lifter can be prevented from cocking relative to the inner wall of the cylinder. 
     As the sliding length can be made sufficiently large without particularly increasing the axial length of the lifter body, a size reduction of the lifter body can also be achieved. 
     The invention can thus provide a roller lifter for internal combustion engines, which has higher rigidity of the lifter body, prevent cocking in the cylinder, and can achieve a size reduction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front view of a roller lifter in Embodiment 1; 
         FIG. 2  is a side view of the roller lifter in Embodiment 1; 
         FIG. 3  is a cross section along A-A of  FIG. 2  viewed from the direction of the arrow; 
         FIG. 4  is a cross section along B-B of  FIG. 2  viewed from the direction of the arrow; 
         FIG. 5  is a cross-sectional diagram illustrating a sliding mechanism where the roller lifter is used as a pump lifter in Embodiment 1; 
         FIG. 6  is a cross-sectional diagram illustrating a sliding mechanism where the roller lifter is used as a pump lifter in Embodiment 2; 
         FIG. 7  is a front view of a roller lifter in Embodiment 3; 
         FIG. 8  is a side view of the roller lifter in Embodiment 3; 
         FIG. 9  is a cross section along C-C of  FIG. 8  viewed from the direction of the arrow; 
         FIG. 10  is a front view of a roller lifter in Embodiment 4; 
         FIG. 11  is a side view of the roller lifter in Embodiment 4; and 
         FIG. 12  is a front view of a prior art roller lifter. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     The roller lifter for internal combustion engines can be used, for example, as a pump lifter for a fuel supply pump or a valve lifter for a valve gear in an internal combustion engine such as a car engine. 
     Herein, one side of the lifter body on which support portions are provided, i.e., the side that will make contact with the cam lobe, will be referred to as the rear side in the sliding direction, and the opposite side will be referred to as the front side in the sliding direction. 
     The sliding surface may preferably be split into a front sliding surface formed on the front side of the anti-rotation retainer and a rear sliding surface formed on the rear side of the anti-rotation retainer, and a small diameter part having a surface recessed radially inward from the sliding surface may be formed between the front sliding surface and the rear sliding surface, with the anti-rotation retainer extending from this small diameter part (claim  2 ). 
     This allows for highly accurate formation of the sliding surface. Namely, as the front sliding surface and the rear sliding surface are formed to the front and the back of the small diameter part where the anti-rotation retainer is formed, the anti-rotation retainer extending radially outward from the sliding surface does not get in the of when machining these sliding surfaces. The small diameter part, which cannot be easily polished as the anti-rotation retainer is formed there, need not be polished, as it is formed radially inward from the sliding surface and does not contact the inner wall of the cylinder. 
     The anti-rotation retainer may preferably have a contour formed at least partly by punching out part of the lifter body to extend radially outward (claim  3 ). The anti-rotation retainer can thus be formed integral with the lifter body by forging. The production cost can be reduced accordingly. Also, punching out part of the lifter body allows for highly accurate formation of end faces of the anti-rotation retainer. The anti-rotation retainer can thus provide its function of stopping rotation effectively. 
     EXAMPLES 
     Example 1 
     Specific embodiments of the roller lifter for internal combustion engines will be described below with reference to  FIGS. 1 to 5 . 
     The roller lifter  1  for internal combustion engines of this embodiment includes a cylindrical lifter body  2  having a sliding surface  24  on its outer circumferential surface that slides on an inner wall  51  of a cylinder  5 , and a roller  3  rotatably attached to the lifter body  2  with an axial support pin  4  and making contact with a rotating cam lobe  6 , as shown in  FIGS. 1 and 5 . 
     The lifter body  2  has a pair of support portions  21  for supporting the axial support pin  4 . 
     Both ends  40  of the axial support pin  4  are inserted in support holes  22  formed in the pair of support portions  21  and mechanically fastened thereto. 
     The lifter body  2  has an anti-rotation retainer  23  extending radially outward from the sliding surface  24 . The sliding surface  24  is formed both on the front and rear sides in the sliding direction of the anti-rotation retainer  23 . 
     The sliding surface  24  is split into two parts: a front sliding surface  241  formed to the front of the anti-rotation retainer  23  and a rear sliding surface  242  formed to the rear of the anti-rotation retainer  23 . 
     A small diameter part  243 , where the surface is recessed radially inward from the sliding surface  24 , is formed between the front sliding surface  241  and the rear sliding surface  242 . 
     The anti-rotation retainer  23  extends from the small diameter part  243 , as shown in  FIGS. 2 to 4 . The anti-rotation retainer  23  has a contour that is partly formed by punching out part of the lifter body  2  to extend radially outward. 
     The lifter body  2  is substantially cylindrical, and the sliding surface  24  has a cross section that is a perfect circle, or part of a perfect circle, in a direction orthogonal to the sliding direction. 
     The rear sliding surface  242  of the sliding surface  24  is formed near the rear end of the lifter body  2 , while the front sliding surface  241  extends from near the front end to around the center of the lifter body  2 . The small diameter part  243  is formed between the front sliding surface  241  and the rear sliding surface  242 . The small diameter part  243  has a length in the sliding direction that is shorter than that of the front sliding surface  241  but longer than that of the rear sliding surface  242 . The small diameter part  243  is recessed by about 100 μm or more, for example, inward relative to the sliding surface  24 . 
     The front end and the rear end of the lifter body  2  are chamfered. 
     The pair of support portions  21  extends from the rear end of the lifter body  2  to further than the front end of the small diameter part  243 . The pair of support portions  21  has flat outer surfaces parallel to each other. The outer surfaces of the support portions  21  are located on an inner side at least than the sliding surface  24 . 
     The anti-rotation retainer  23  is formed in the small diameter part  243 . The anti-rotation retainer  23  is formed by forging, such as to punch out part of the wall that forms the cylindrical lifter body  2 . More specifically, the rear end in the sliding direction of the anti-rotation retainer  23  is formed continuous with the small diameter part  243 , while the front end and a pair of side ends are cut out from the small diameter part  243 . The anti-rotation retainer  23  inclines such that the height of protrusion increases gradually from the rear end toward the front end. The front end of the anti-rotation retainer  23  protrudes radially outward from the sliding surface  24 . Thus, a front end face  230  and part of the pair of side end faces  231  of the anti-rotation retainer  23  are exposed from the small diameter part  243 . 
     The sliding surface  24  of the lifter body  2  is polished so as to have a perfect circular outline. 
     As shown in  FIG. 1 , the anti-rotation retainer  23  is formed by punching out part of the small diameter part  243  such as to have a triangular shape, with the side end face  231  extending therefrom, when viewed from a direction orthogonal to the side end face  231 . 
     To assemble the roller  3  to the lifter body  2 , as shown in  FIGS. 1 to 4 , the roller  3  is fitted in between the pair of support portions  21 , and the axial support pin  4  is inserted into the support holes  22  such that both ends  40  thereof protrude outward from the pair of support portions  21 . 
     The both ends  40  of the axial support pin  4  are then pressed axially by a hydraulic press or the like so that both ends  40  deform to increase their diameter, thereby to mechanically fasten the axial support pin  4  to the support portions  21 . 
     The roller lifter  1  of this embodiment may be used as a pump lifter  70 A for a fuel supply pump  7 A, for example, in an internal combustion engine such as a car engine, as shown in  FIG. 5 . 
     The roller lifter  1  of this embodiment may be installed, for example, such that the lifter body  2  having the sliding surface  24  slides on the inner wall  51  of a cylinder  5  in the fuel supply pump  7 A and that the roller  3  makes contact with a rotating cam lobe  6 , as shown in  FIG. 5 . 
     The fuel supply pump  7 A is configured to compress fuel F supplied from a fuel tank (not shown) to feed the compressed fuel F to an injector (not shown) in synchronism with the cam lobe  6  on a cam shaft  61  in a reciprocal engine, as shown in  FIG. 5 . 
     The pump lifter  70 A in the fuel supply pump  7 A is configured to slide inside the cylinder  5  arranged in a cylinder head  73  of the reciprocal engine, as the roller  3  is rotated by the rotating cam lobe  6 . 
     The pump lifter  70 A is configured to make contact with one end of a plunger  75  arranged slidable inside the cylinder head  73  to slide the plunger  75 , to compress the fuel F in a pressure chamber  76  formed inside the cylinder head  73  with the other end  750  of the plunger  75 . As shown in the  FIG. 5 , the pump lifter  70 A (roller lifter  1 ) is formed with a plate-like abutting portion  25  inside the lifter body  2  that has an annular cross-sectional shape. 
     A retainer  77  is secured to the outer circumference of the plunger  75  such as to make contact with the abutting portion  25 . A spring  78  is disposed between the retainer  77  and the cylinder head  73  to bias the pump lifter  70 A toward the cam lobe  6 . 
     As shown in the  FIG. 5 , the anti-rotation retainer  23  of the lifter body  2  fits in an anti-rotation groove  53  formed along the axial direction of the cylinder  5  in the cylinder head  73  such as to be slidable along the sliding direction. 
     The pressure chamber  76  is formed midway of a fuel supply passage  79  that runs inside the cylinder head  73  such as to communicate the fuel tank and the injector. 
     This embodiment has the following advantageous effects: 
     The anti-rotation retainer  23  in this embodiment extends radially outward from the sliding surface  24  of the lifter body  2 . Therefore, the lifter body  2  need not be cut off largely to form the anti-rotation retainer  23 . The lifter body  2  can have higher rigidity accordingly, so that the circularity accuracy of the sliding surface  24  can be maintained when the axial support pin  4  is mechanically fastened to the support portions  21 . 
     The sliding surface  24  of the lifter body  2  is formed on the front side and the rear side of the anti-rotation retainer  23  in the sliding direction of the lifter body  2 . Therefore, the distance (sliding length) between the front end and the rear end of the sliding surface  24  of the lifter body  2  can be made longer. As a result, the roller lifter  1  can be prevented from cocking relative to the inner wall  51  of the cylinder  5 . 
     As the sliding length can be made sufficiently large without particularly increasing the axial length of the lifter body  2 , a size reduction of the lifter body  2  can also be achieved. 
     The sliding surface  24  is split into the front sliding surface  241  formed to the front of the anti-rotation retainer  23  and the rear sliding surface  242  formed to the rear of the anti-rotation retainer  23 . The anti-rotation retainer  23  extends from the small diameter part  243 , which is recessed radially inward from the sliding surface  24  and formed between the front sliding surface  241  and the rear sliding surface  242 . 
     This allows for highly accurate formation of the sliding surface  24 . Namely, as the front sliding surface  241  and the rear sliding surface  242  are formed to the front and the back of the small diameter part  243  where the anti-rotation retainer  23  is formed, the anti-rotation retainer  23  extending radially outward from the sliding surface  24  does not get in the way of machining these sliding surfaces. The small diameter part  243 , which cannot be easily polished as the anti-rotation retainer  23  is formed there, need not be polished, as it is recessed radially inward from the sliding surface  24  and does not contact the inner wall  51  of the cylinder  5 . 
     The anti-rotation retainer  23  is formed by punching out part of the lifter body  2  so that its contour partly extends radially outward. The anti-rotation retainer  23  can thus be formed integrally with the lifter body  2  by forging. The production cost can be reduced accordingly. 
     When the anti-rotation retainer  23  is formed, a punch presses part of the lifter body  2  from inside and a die with an opening attached on the outside of the lifter body for the punched portion to escape serves as a receiver. Therefore, the anti-rotation retainer  23  can have shear cross sections as the side end faces  231  and the front end face  230 , i.e., the anti-rotation retainer  23  can have highly accurate end faces. Namely, if part of the lifter body  2  is protruded radially outward by plastic deformation instead of by punching to provide the anti-rotation retainer  23 , the contour of the anti-rotation retainer  23  would take a shape of a round boss protruded continuously from the lifter body  2 . It would be hard to control the contour of the anti-rotation retainer  23 , and to achieve a contour exactly as designed to conform to the anti-rotation groove  53 . Therefore, the anti-rotation retainer  23  would have to be subjected to another process such as cutting after the plastic deformation, in order to suitably function as the anti-rotation retainer. 
     By punching out part of the lifter body  2  to form part of the contour of the anti-rotation retainer  23 , the punched-out contour portions (side end faces  231  and the front end face  230 ) are cut out from the lifter body  2  and form shear cross sections. The punched out contour portions will not be curved, as mentioned above, like a round boss protruding continuously from the lifter body  2 . The contour of the anti-rotation retainer  23  is more controllable when forming the anti-rotation retainer  23 . As a result, the contour of the side end faces  231  and the front end face  230  of the anti-rotation retainer  23  can be easily and accurately made into a shape as designed. The anti-rotation retainer  23  can thus exhibit its function of stopping rotation effectively. Moreover, as punching allows collective formation of a plurality of anti-rotation retainers  23 , the number of process steps can also be reduced. 
     According to this embodiment, as described above, a roller lifter for internal combustion engines, which has higher rigidity of the lifter body, prevent cocking in the cylinder, and can achieve a size reduction, can be provided. 
     Example 2 
     This embodiment is an example in which the roller lifter  1  is used as a valve lifter  70 B in a valve gear  7 B of a reciprocal engine. 
     The roller lifter  1  itself is configured the same as the roller lifter  1  of Embodiment 1. 
     The valve lifter  70 B in the valve gear  7 B is configured to slide inside a cylinder  5  arranged in a cylinder head  73  of the reciprocal engine, as the roller  3  is rotated by the rotating valve gear cam lobe  6  formed on a cam shaft  61  of the reciprocal engine, as shown in  FIG. 6 . 
     The valve lifter  70 B abuts on a stem distal end  732  of a valve  730  in the reciprocal engine, and is arranged slidable up and down inside the cylinder  5  such as to open and close the valve  730  disposed to open and close an intake/exhaust port (intake port or exhaust port)  733 . 
     An abutting portion  25  is configured to abut on the stem distal end  732  of the valve  730 . 
     A retainer  77  is secured to the outer circumference of a stem part  731  of the valve  730 . A spring  78  is disposed between the retainer  77  and the cylinder head  73  to bias the valve lifter  70 B toward the cam lobe  6 . 
     The rest is the same as Embodiment 1, with similar advantageous effects. 
     Example 3 
     As shown in  FIGS. 7 to 9 , this embodiment is an example of the roller lifter  1 , in which one end in a direction orthogonal to the sliding direction of the anti-rotation retainer  23  is continuous with the small diameter part  243  while the other end extends radially outward from the sliding surface  24 . 
     The roller lifter  1  of this embodiment has a pair of anti-rotation retainers  23 . The respective ends of the anti-rotation retainers  23  that are continuous with the small diameter part  243  face each other, while the other ends (side end faces  231 ) are oriented to mutually opposite directions. 
     The side end faces  231  are formed such as to face the inner side face of the anti-rotation groove  53  (see  FIG. 5 ) when the roller lifter  1  is mounted to the cylinder  5 . 
     The rest is the same as Embodiment 1, with similar advantageous effects. 
     Example 4 
     As shown in  FIGS. 10 and 11 , this embodiment is an example of the roller lifter  1 , in which the small diameter part  243  is formed on the front side in the sliding direction of the support portions  21  of the lifter body  2 . One end in a direction orthogonal to the sliding direction of the anti-rotation retainer  23  is continuous with the small diameter part  243 , while the other end extends radially outward from the sliding surface  24 . 
     The front sliding surface  241  of the roller lifter  1  of this embodiment is formed shorter than the rear sliding surface  242 . 
     The rest is the same as Embodiment 3, with similar advantageous effects.