Abstract:
A tapered fuel injection pipe with a collar pressed and fitted below the neck is provided with a fine slit between the inside surface of the collar and the outside surface of a tapered part of the injection pipe in the free end zone of the collar. 
     By providing such fine slit, the strength against breakage is remarkably improved.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a collared fuel injection pipe for engines. 
     2. Description of the Prior Art 
     For a conventional fuel injection pipe for automobile engines, usually a drawn fine pipe of an outside diameter of 6 to 8 mm and inside diameter of 1.6 to 2 mm is used, a head 2 is made by a cold buckling method and a neck 3 is formed in the boundary part of the head hardened by buckling and the pipe shaft part not buckled. Generally, in case the injection pipe is vibrated, the neck 3 will become a fulcrum of the vibration and will be therefore often unavoidably broken. Therefore, since long ago, as a reinforcing measure, as shown in FIG. 1, the neck has been reinforced by the pressed contact of the curved surface 4 of the neck 3 and the curved surface 6 of a collar 5 with each other. However, as there is a clearance on the entire outside surface of the pipe except the pressed contact part between the curved surfaces 4 and 6, the fulcrum of the vibration will be located near the neck which will be thus likely to be broken. 
     If the collar 5 can be pressed and fitted to the outside surface of the pipe below the neck, even the conventional pipe will be able to be expected to be strengthened. However, it has been impossible due to a very high friction resistance to press and fit the collar 5 through the long pipe 1 extending below the neck. Shown in FIG. 2 is a type known as a Benz type having a step 7 on the pipe 1 near one end of the collar 5. It is shown together with the conventional product of FIG. 1 for comparison with the product of the present invention. 
     SUMMARY OF THE INVENTION 
     The present invention is to provide a collared fuel injection pipe for engines simple in the structure and high in the strength against breakage by eliminating such defects as are mentioned above. 
     According to the present invention, a collared fuel injection pipe for engines with a collar pressed and fitted below the neck is characterized by being provided with a fine slit between the inside surface of the collar and the outside surface of the injection pipe. 
     Further objects, advantages and features of the present invention will become more fully apparent from a detailed consideration of the arrangement and construction of the constituent parts as set forth in the following specification taken together with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1 and 2 are partly sectioned side view of conventional collared fuel injection pipes for engines. 
     FIG. 3 is a partly sectioned side view of a fuel injection pipe embodying the present invention. 
     FIG. 4 is a partly sectioned side view of a reference example for explaining the present invention. 
     FIG. 5 is a schematic view for explaining the operation of the present invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The present invention shall be explained with reference to FIGS. 3 and 4. 
     A pipe shaft part 1 of a tapered injection pipe having an outside diameter D has a head 2 and is fitted with a collar 5. 
     The curved surface 6 of the collar 5 and the curved surface 6 of a neck 3 of the injection pipe are pressed into contact with each other either by pressing and fitting the collar onto tapered part having the head 2 formed in advance or by fitting the collar 5 onto the tapered part and then forming the head 2. The outside surface 8 of the tapered part below the neck 3 and the inside surface 9 of the fitted collar are pressed into contact with each other toward the neck 3 with a boundary B as a limit and a fine slit 11 is provided toward the free end 10 of the collar 5. 
     By the way, in the drawings, l is the length of the collar, l 1  is the length below the neck of the tapered part of the injection pipe, W is the width of the slit 11 at the free end 10 and α is the angle of inclination of the tapered part. 
     Now, experiments were made by the method shown in FIG. 5 by making D=6 mm, α=52&#39;, W=0.04 to 0.08 mm and l 1  =10 mm, positioning the boundary B in the intermediate part of the collar 5, fastening and fixing the head 2 with a box nut 13 and varying the length l of the collar 5. The results are shown in the below mentioned table. 
     By the way, in the table, FIGS. 1 and 2 are of test values of conventional products. Each of the tested injection pipes was made by buckling a thick-walled fine pipe made by laminating six steel sheets and integrally bonding respective adjacent laminations with brazed layers. The strengths and test values shown in the following table were obtained by using such same material. The test value shows the number of repetitions until the product was broken by repeating vibrations in both ways in the following manner: 
     
         ______________________________________Length of the tested product (the lengthfrom the pressed contact boundary B tothe point P giving vibrations)                    115mmStress amplitude A        2mmRepeating rate           2.520 r.p.m.Box nut fastening torque 300cm-kg______________________________________ 
    
     
         __________________________________________________________________________Strength Tests (Numbers of repetations until breakage)Product illustrated            Product illustratedFIG. 1           in FIG. 2                         Product IllustratedInjection pipe   Benz type                         in FIG. 4Pressed contact      Standard            Pressed contact on                        Product illustrated in FIG.                                              Pressed contact onpart of the      type  the entire inside                        (Product of the present invention)                                              the entire insidecollar     Neck  surface     Tapered type          surfaceTest No. 1 10mm  10mm        16mm 13mm                                 10mm                                     8mm  6mm 8mm__________________________________________________________________________1          38.419            40.443      59.424                             54.790                                 85.176                                     71.239                                          67.460                                              45.3292          26.676            51.927      60.774                             64.880                                 88.553                                     53.591                                          57.053                                              39.4213          39.452            37.814      49.664                             70.027                                 71.820                                     73.417                                          51.530                                              46.6624          41.872            42.535      46.924                             50.024                                 86.486                                     57.119                                          61.820                                              52.6425          34.942            46.465      59.130                             60.417                                 76.074                                     74.264                                          48.848                                              48.7646          20.124            48.660      52.219                             65.046                                 81.274                                     70.227                                          55.818                                              40.2327          28.541            41.055      38.233                             51.256                                 72.450                                     55.355                                          55.129                                              46.9878          45.826            38.350      49.826                             63.852                                 80.615                                     67.297                                          64.407                                              39.2329          39.251            39.269      39.651                             70.343                                 89.460                                     62.208                                          48.913                                              38.25610         40.586            45.368      60.524                             60.036                                 70.157                                     58.782                                          60.812                                              47.442Average value      37.569            43.189      51.637                             62.067                                 80.206                                     64.350                                          57.279                                              44.496Differencebetween maximum      25.704            14.113      22.541                             19.087                                 19.303                                     18.909                                          16.812                                              13.386value andminimum value__________________________________________________________________________ 
    
     As understood from the above table: 
     (A) The type (FIG. 3) in which the fine slit 11 is provided toward the end 10 from the inner part of the collar 5 is stronger than the type (FIG. 4) in which the entire inside surface 9 of the collar is pressed into contact with the tapered outside surface 8 of the tapered injection pipe. Particularly, by comparing the type (l=8 mm) of FIG. 4 with the type (l=8 mm) of FIG. 3, the cause of the strengthening can be found. By the way, with the collars of other lengths l, the same results are obtained. 
     (B) In the type (FIG. 3) in which the fine slit 11 is provided toward the free end 10 from the inner part of the collar, the strength is different depending on the length of the collar 5 and shows a tendency to become higher as the free end 10 of the collar approaches the taper end 12 of the pipe. 
     By the way, in case the length l 1  of the tapered part below the neck was varied, as the l 1  became shorter than 10 mm, the strength was recognized to reduce but, on the contrary, even when it was somewhat longer, the same tendency as of the product of 10 mm was recognized. 
     The reason why the product of the present invention derives such effects is considered to be that, though the injection pipe and collar are respectively manufactured with the utmost care, as there are some manufacturing errors, in case the collar is fitted, the pressed contact boundary B on the inside surface 9 of the collar will not be in the plane intersecting the tapered part vertically to the pipe axis part and will be formed to be wave-shaped, the pressed contact surface of the inside surface 9 of the collar and the outside surface 8 of the tapered part will form the fine slit 11 in the lengthwise direction of the pipe of the tapered part, the contact boundary point will move with the slightest vibration and the stress repeating fulcrum on the tapered pipe side will be thereby three-dimensionally moved to develop a strengthening function. 
     Even if the present invention is applied to a conventional thick-walled drawn fine pipe instead of the laminated pipe having the above described brazed layers, the same effects will be recognized. 
     While the present invention has been described with reference to particular embodiments thereof, it will be understood that numerous modifications may be made by those skilled in the art without actually departing from the spirit and scope of the invention as defined in the appended claims.