Abstract:
A broach tool is provided for use in repairing a camshaft support bearing for operably supporting a camshaft in an internal combustion engine. The engine includes a cylinder head with bearing support towers that operably support journals on the camshaft at multiple aligned bearing locations. A broaching tool is provided that is adapted to be linearly pulled through the aligned bearing locations to reform the bearing support structures. Methods of repair include enlarging at least one camshaft support bearing to an oversized condition, such as by using the broach, optionally repairing the oversized camshaft support bearing by filling voids and galled areas with a thermal setting polymer, as needed, and optionally positioning a bearing insert on the camshaft, and positioning the camshaft including the bearing insert in the camshaft support bearing with the camshaft being rotatably supported in the bearing insert and the bearing insert being secured to the oversized camshaft support bearing.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of co-pending application, Ser. No. 09/301,629, filed Apr. 29, 1999, entitled BEARING INSERT FOR SUPPORTING ROTATABLE SHAFTS, METHOD OF REPAIR, AND RELATED BROACH TOOL. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to bearing inserts for operably supporting a rotatable shaft, such as a camshaft in an internal combustion engine, and further relates to a method for repairing spaced-apart bearing supports to receive the bearing inserts, and still further relates to a broaching tool for use in the method. 
     Modem internal combustion engines for passenger vehicles typically include a cylinder head and a camshaft rotatably supported at journals by the cylinder head at multiple aligned bearing locations. The cylinder heads include a bearing support structure (sometimes called “bearing housings”) at each of the bearing locations. An oil port is included in each bearing support structure for passing oil to journals on the camshaft. As engines age, the bearing surfaces on the cylinder head and the journals on the camshaft wear, such that these bearing locations sometimes need to be rebuilt. In extreme cases, galling and material deformation may occur, causing the camshaft to roughly rotate or even freeze up on the cylinder head. It is known to repair these bearing locations by welding on the cylinder head to reapply material to the support structure, and thereafter to machine away excess material to reform the bearing surfaces. It is also known to simply machine away material on the cylinder head to form an oversize bearing surface. A problem is that accurate alignment of the bearing locations along a camshaft is very important so that the camshaft is properly positioned for rotation without stress, and so that the intake and exhaust valves of the internal combustion engine work properly, set up for good alignment to re-cut the bearing locations is expensive and time consuming and can easily be done wrong. Further, the tools for cutting and machining the bearing locations can be expensive. Also, a plurality of different tools is required for each different bearing size, such that it requires significant capital investment for a repair shop. There are also the frustrations of not having (or not being able to find) the right size cutting tool for a particular size bearing. 
     It is known to cut away the bearing support structure and to locate a whole new massive outer bearing in the structure head to support the camshaft. Further, it is known to purchase new replacement camshafts having particular sized camshaft bearing surfaces. However, it is undesirable to cut away substantial material from the cylinder head of modern engines since this can affect their strength, operation, and heat flow in the cylinder head in adverse ways. Further, removal of large amounts of material can lead to mistakes that totally destroy cylinder heads. 
     Notably, broaching apparatuses and methods have been used to machine internal combustion engine components for many years. For example, see U.S. Pat. Nos. 5,224,804 and 5,435,676. U.S. Pat. No. 5,435,676 discloses a two-stage broaching method wherein the first broach is advanced through the bores, leaving unbroached ridges therebetween. A second broach then broaches the ridges that are left by the first broach. U.S. Pat. No. 5,224,804 discloses a tooling system and method for broaching engine components wherein the broach bar is forwardly passed through the engine block with the bearing bores being opened a progressively to their final diameter. Thus, there is a need for a one-stage broaching apparatus and method wherein the broach is pulled through the cam housings while accurately and ad efficiently machining the cam&#39;s bearing surface. 
     Accordingly, there is a need for a reliable bearing insert and a related method and tools that solve the aforementioned problems and that have the aforementioned advantages. 
     SUMMARY OF THE INVENTION 
     In one aspect, the present invention includes a broaching apparatus for use in a structural body having spaced-apart bearing supports with aligned holes defining an axis. The broaching apparatus includes an elongated broach having a longitudinally extending hole extending from end to end of the broach and having first threads formed along at least a portion of the longitudinally extending hole. The broach has a lead section, a cutting section, and a tail section. The cutting section is configured to enlarge the aligned holes from a smaller first diameter to a larger second diameter, and the lead and tail sections are configured to guide the broaching tool linearly through the aligned holes while maintaining accurate alignment with the aligned holes. The broaching apparatus further includes a motivating device including a broach puller and a holder rotatably receiving the broach puller. The broach puller has a shaft that extends through the holder with second threads on one end configured to mateably engage the first threads. The broach puller further has a configured end opposite the one end that is shaped to be engaged and rotatably driven by a machine or hand tool, such as an air impact wrench. The holder includes a first end section rotatably abutting the configured end of the broach puller and a second end section configured to abut the structural body. Thus, the aligned holes in the structural body can be broached by pulling the elongated broach through the aligned holes by rotating the broach puller. 
     In another aspect, the present invention includes a method of repair comprising steps of providing a cylinder head for an internal combustion engine having spaced-apart bearing housings configured to rotatably support a camshaft, one of the camshaft bearing housings having a galled, non-uniform bearing surface in need of repair; enlarging the non-uniform bearing surface to a slightly oversized condition to form an enlarged bearing housing and positioning a thin-walled insert on the camshaft and in the enlarged bearing housing and frictionally retaining the thin-walled insert in place in the enlarged bearing housing and rotatably supporting the camshaft in the thin-walled insert. 
     In another aspect, the present invention includes a method of repair comprising steps of providing a cylinder head having spaced-apart and aligned bearing housings configured to rotatably support a camshaft with at least one of the camshaft bearings being galled and in need of repair. The method further includes providing a broach configured to be pulled linearly through the aligned bearing housings to enlarge a diameter of the shaft bearing housing and broaching the galled camshaft bearing by pulling the broach linearly through the galled bearing housing. The method also includes applying polymeric compound to the galled camshaft bearing to fill in void areas. 
     In yet another aspect, the present invention includes a method of repair comprising steps of providing a cylinder head having spaced-apart and aligned bearing housings configured to rotatably support a camshaft, the camshaft bearings being in need of repair, and providing a broach configured to be pulled linearly through the aligned bearing housings to enlarge a diameter of the camshaft bearing housings. The method further includes broaching at least one of the camshaft bearing housings to an oversized diameter by pulling the broach linearly through at least one bearing housing and positioning at least one insert on the camshaft and in the at least one bearing housing with the camshaft being rotatably supported in the insert. 
     These and other features, advantages and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims and appended drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a cylinder head having a damaged front bearing, the bearing cap on the front bearing being exploded away to better show the front bearing; 
     FIG. 2 is an enlarged perspective view of a bottom housing portion of the damaged front bearing shown in FIG. 1, the front bearing structure potentially having the bearing cap (not specifically shown) having a similarly damaged surface; 
     FIG. 3 is a side view of an elongated broach for broaching aligned camshaft housings; 
     FIG. 3A is an enlarged side view of the circled area IIIA in FIG. 3; 
     FIG. 4 is a side view of the cylinder head, partially broken away (shown in FIG.  1 ), ax with the broach (shown in FIG. 3) positioned in the aligned bearing support structure ready to begin the broaching process; 
     FIG. 5 is a perspective view of the cylinder head after broaching and after filling galled areas with an epoxy filler, and including a release-agent coated sizer rod positioned in the bearing support structure to form the epoxy filler to a predetermined size; 
     FIG. 6 is an exploded perspective view of the bearing cap and bottom forming an epoxy/repaired bearing housing; 
     FIG. 7 is a perspective view of a camshaft bearing insert after the bearing insert has been installed in a camshaft housing and after the outward protruding minor section has been deformed and has taken a set; 
     FIG. 8 is an end view of the bearing insert shown in FIG. 7 as installed in a camshaft housing; 
     FIG. 9 is a plan view of a blank of thin sheet material for forming the insert shown in FIG. 7; 
     FIG. 9A is an end view of the blank from FIG. 9 formed into a generally circular shape, but that is slightly oval in shape and that is slightly open as to its slit; 
     FIG. 10 is a side perspective view similar to FIG. 4, but showing a modified bench-type broach puller; and 
     FIG. 11 is a side view of a modified broach similar to that shown in FIG. 3, but including multiple replaceable cutting sections forming the broaching tool. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A cylinder head  20  (FIG. 1) of an internal combustion engine comprises a machined casting  21 , such as aluminum or cast iron, that is particularly configured to operably support various engine components. Such cylinder heads and engine components, as well as the functions that each provide, are generally known in the art, such that they do not need to be described for an understanding of the present invention. The present cylinder head  20  includes a plurality of bearing support structures or cam housings  22  that defme multiple aligned cam bearing locations along a common axis. The bearing support structures  22  each define aligned holes configured to rotatably support a camshaft  23  on its journals  24 . The bearing support structures  22  include a bottom half  25  formed as part of the casting  21  of the cylinder head  20 , and further include a top half or bearing cap  26  secured to the bottom half  25 . A camshaft bearing insert  27  is constructed to friction fit into selected ones of (or all of) the bearing support structures  22  to rotatably support the camshaft  23 . The bearing insert  27  can be used in original castings  21  in new engines, such as to provide a more durable bearing housing at the journals  24 , or can be used in repair procedures to rebuild worn engines, as described below. 
     Bearing support structures  22  (FIG.  6 ), often called cam housings, each comprise a bearing top cap  26  secured to a bearing bottom half  25 . The illustrated top cap  26  includes tubular alignment projections  29  that engage mating locating holes  30  in the bottom half  25 . The illustrated top cap  26  is secured to the bottom half  25  by bolts that extend through tubular projections  29  threadably into the holes  30 . The top cap  26  and bottom half  25  include semi-cylindrical surfaces  31  and  32 , respectively, that join to form axially aligned holes across a top of the cylinder head  20 . The bottom half  25  includes an oil port  33  formed between its side edges that is operably connected to a source of engine oil. The oil port  33  is configured to deliver engine oil to the bearing location for lubricating the journal  24  on the camshaft  23  as the camshaft  23  rotates. The illustrated oil port  33  is circumferentially elongated, but it is noted that different oil port designs are known, including a single hole design or a design including spaced holes, and that the present inventive concepts will work with alternative designs. 
     Camshaft  23  (FIG. 1) is elongated and includes a main shaft  35  with a plurality of axially aligned journals  24  accurately positioned on and spaced apart along the main shaft  35 . Intake and exhaust cams  36  and  37 , respectively, are positioned along the main shaft  35  between the journals  24  for operating valve rockers (not shown) which in turn operate intake and exhaust valves (also not shown) on the cylinder head  20 . 
     As an engine is used, the bearing surfaces  31  and  32  (FIG. 1) and/or the journals  24  can become worn, such that the camshaft  24  no longer is accurately held and such that the camshaft  23  begins to vibrate during operation. In a worse case scenario, the material of the bearing surfaces  31  or  32  can become galled or scored, resulting in severe material removal and/or freezing of the camshaft  23  in the cam housings  22 . This is illustrated at locations  38  in FIG. 2 on the bearing surface  32  of the bottom half  25 . The present invention provides an insert  27 , repair methods, and tools that can be used to rebuild a worn cam housing  22 , as described below. 
     It is noted that many cylinder heads in modern vehicle engines are being made from aluminum and other alloys to reduce weight. Sometimes these new materials are not strong or durable enough to provide the service life desired. Also, many cylinder heads have reduced mass and structure, such that some new designs require a reinforcement in high stress areas, such as in the camshaft bearings. Still further, modern vehicles are being operated longer and a corresponding increase in engine life is desired. It is contemplated that the present bearing insert  27 , repair methods, and tools are usable in each of these circumstances. 
     Bearing insert  27  (FIG. 7) is provided for positioning in an oversized reformed cam housing  22  to reform or rebuild a cam housing  22 . The insert  27  is made from a phosphor bronze alloy having high durability and excellent properties for use as a bearing. When installed (see FIG.  8 ), the insert  27  is forced to take on a closed ring shape with opposing semi-cylindrical portions  40  and  41  joined by a short bulging section  42  on one side and a closed slit  43  on the other side. The short section  42  extends outwardly slightly from the circle of semi-cylindrical portions  40  and  41 , and is configured to engage a mating recess  44  (FIG. 6) located in the cam housing  22 , such as at a joint line between bearing surfaces  31  and  32 . The short section  42  is formed when the insert  27  is clamped in place in the cam housing  22  between housing halves  25  and  26 . A length of the blank  46  is closely controlled so that when edges  40 A and  41 A abut, there is excess material along a length of the bearing insert  27 . Therefore, as the cap half  26  is fully tightened, the short section  42  bulges outwardly to engage the recess  44  to act as an anti-rotation device to provide additional resistance against the torsional forces of the journals  24  as the camshaft  23  rotates within the bearing insert  27  on cam housings  22 . The forces are sufficient, such that after installation, the short section  42  takes on a permanent set, as shown in FIG.  7 . An oil port  45  is formed in a center of the illustrated semi-cylindrical portion  40  and extends circumferentially about halfway toward each end of the semi-cylindrical portion  40  or, in other words, about a total of 90 degrees in the insert  27 . Notably, the oil port  45  can be a single hole, two holes, a circumferential slot, a longitudinal slot, a “tear drop” shape, or any other configuration required for a particular cam housing design. 
     The illustrated bearing insert  27  is one piece and is preferably made from a blank  46  (FIG. 9) of flat stock of surface hardened phosphor bronze alloy material similar to that in the insert of U.S. Pat. No. 4,768,479, which has excellent memory and bearing properties. The blank  46  can be made in various ways, but in a preferred form the blank  46  is stamped and formed into a sleeve-like cylindrical shape close to the shape of bearing insert  27 . It is contemplated that the alloy material and thickness of the material of the blank  46  can be optimized for particular applications. Nonetheless, the illustrated insert  27  has a wall thickness of less than about 0.032 inches, and preferably that is about 0.008 inches to 0.020 inches, and most preferably that is about 0.016 inches. Further, the insert  27  is sized to a diameter and length of a camshaft journal, such as anywhere from about a 1.00 inch diameter to about a 2.00 inch diameter, and about 0.50 inches long to about 1.00 inches long for a journal for a camshaft in an internal combustion engine. The illustrated insert  27  is about one inch in diameter and is about ½ inch long. As formed, the insert  27  is formed with the slit  43  slightly opened up about ⅛ inches. The insert  27  is also formed to be slightly oblong or oval, such as about 0.125 inches longer in the dimension D 1  than in the dimension D 2  (FIG.  9 A). This oblong shape and the squareness of edges  40 A and  41 A cause edges  40 A and  41 A to abut on the camshaft journal  24  during installation, thus preventing problems with overlapping of edges  40 A and  41 A during installation. Further, wall of the insert  27  is resilient, such that the insert  27  can be flexed toward a more open condition and thereafter flexed to a more closed condition without kinking or breaking the insert  27 . This allows the insert  27  to be flexed open, such that the insert  27  can be snapped onto any one of the journals  24  from a side of the camshaft  23  without unacceptable distortion of the insert  27 . This is advantageous because the valve cams  36  and  37  (FIG. 1) are often larger than the journals  24 . Thus, the flexible insert  27  can be easily manually flexed and positioned on the camshaft  23 , even where the valve cams  36  and  37  are so large as to prevent slipping the insert  27  into position from an end of the camshaft  23 . After positioning the insert(s)  27  on the journal(s)  24  of the camshaft  23 , the camshaft  23  is set onto the bottom halves  25  with the oil ports  45  of each insert  27  being accurately aligned on the oil ports  33  on the bottom halves  25 . 
     Broach apparatus  50  (FIG. 4) includes a broach  51  and a motivating device that comprises a broach puller  52  and a puller holder  53 . The broach  51  is elongated and rod shaped and includes a lead section  54 , a cutting section  55 , and a tail section  56 . The lead and tail sections  54  and  56  are configured to guide the broach  51  through the aligned holes in the cam housings  22 , while accurately maintaining alignment of the broach  51  with an axial centerline of the cam housings  22 . Optimally, the lead section  54  has a diameter about equal to the diameter of the aligned holes in the cam housings  22  before they are broached by the cutting section  55 . Also, the tail section  56  has a diameter about equal to the diameter of the aligned holes in the cam housings  22  after they are broached by cutting section  55 . The illustrated tail section  56  has longitudinally extending relief areas  57  formed therein to reduce a risk of the tail section  56  dragging clips to scoring, marking, or scratching the re-cut aligned holes in the cam housings  22  as the tail section  56  is pulled therethrough. The cutting section  55  includes multiple circular knife edges  58 , five to eight of which are illustrated. Each knife edge  58  (FIG. 3 and 3A) is followed by a ring-shaped marginal surface  59  extending downstream of the knife edges  58 . The marginal surfaces  59  extend at an inward angle “A” from the knife edges  58 , and provide relief for the re-cut bearing surfaces  31  and  32  after each knife edge  58  passes over the bearing surfaces  31  and  32 . A relatively large ring-shaped undercut recess  60  is provided ahead of each knife edge  58  for receiving chips and cutaway material from the bearing surfaces  31  and  32 . A hole  61  extends through broach  51  from end to end and includes a threaded section  62  in the lead section  54 . The threaded section  62  includes Acme threads that are chosen to be relatively resistant to damage and resistant to binding from debris that may get into the threads. Nonetheless, it is contemplated that other threads could be used and still satisfy the functional requirements of the design. 
     The broach puller  52  (FIG. 4) includes an elongated threaded rod  64  shaped to threadably engage the thread section  62  in the broach. The broach puller  52  further includes a thrust bearing  65  and an enlarged hex head  66 . The puller holder  53  includes a tube  67  shaped to closely receive the threaded rod  64 , and further includes a first end  67 ′ shaped to abuttingly engage the thrust bearing  65  and a second end  68  shaped to abuttingly and stably engage an end of the cylinder head  20 . As shown in FIG. 4, the broach apparatus  50  is configured so that the broach  51  can be positioned in one end with the lead section  54  positioned in a first couple jO of the aligned cam housings  22  at one end of the cylinder head  20 . The rod  64  of the broach puller  52  is extended through the puller holder  53  at the other end of the cylinder head  20 , through all of the cam housings  22  and threadably into the broach  51 . An air impact wrench  69  with a socket  70  shaped to engage the hex head  66  of the broach puller  52  can be used to rotate the broach puller  52  to pull the broach  51  through the cam housings  22  of the cylinder head  20 . The puller holder  53  abuts the thrust bearing  65  and the enlarged head  66  of the puller  52  and also abuts the end of the cylinder head  20 , such that the broach  51  is forcibly pulled through the cylinder head  20  as the broach puller  52  is rotated. Further, it is noted that the puller holder  53  can be grasped by the repairman for stabilizing the arrangement during the manual broaching process. 
     A method of manual broaching the cam housings  22  of a cylinder head  20  is performed as follows. Initially, the cam bearing support structures or cam housings  22  are measured for warp. If the range of misalignment is too great, the cylinder head  20  is first straightened. Such procedures are known in the art. Next, the cam housings  22  are inspected for galling. If any of the cam housings  22  have galling (see FIG.  2 ), the damaged cam housing  22  can be repaired with epoxy putty, as noted below. The housing caps  26  are secured to the bearing bottom half  25  by torquing attachment bolts that extend through the tubular protrusions  29  threadably into the holes  30  to an appropriate specification, e.g., to about 16 ft/lbs. The lead section  54  of the broach  51  (FIG. 4) is placed in the last two cam housings  22  from a rear of the cylinder head  20 . The broach puller  52  and puller holder  53  are placed on an end of the cylinder head  20 , with an end of the rod  64  threaded into the broach  51 . A liberal amount of lubricant, such as WD- 40 ®, is applied to all bearing housings  22  and to the broach  51 . Using the air impact wrench  69  to rotate the broach puller  52 , the broach  51  is pulled through the housings  22 . The combination of the lead and tail sections  54  and  56  keep the broach  51  accurately aligned in the cam housings  22  as the cutting section  55  of the broach  51  reforms the cam housings  22 . Normally, it is contemplated that all cam housings  22  will be broached at a single time, although it is contemplated that a single cam housing  22  can be broached by pulling the broach  51  only far enough to reform the single cam housing  22 . 
     Severely galled cam housings  22  can be repaired as follows. The galled housing halves  25  and  26  (FIG. 6) are ground with a handheld die grinder and/or are broached to a depth of about 0.020 to 0.050 inches below the original housing surface. A shaft mold  75  (FIG. 5) is provided having a section with a particular diameter that has a release-agent coated or Teflon coated area corresponding to the cam housings  22 . The coated area of the rod-shaped shaft mold  75  has the desired final diameter of the repaired cam housings  22 ′. A suitable polymeric filler  76 , such as Devcon Titanium Putty, is mixed and applied to the ground cam housing  22  (or to the coated area on the shaft mold  75 ). With the housing caps  26  off, the shaft mold  75  is cradled in the cam housings  22 . The housing top caps  26  are then reattached to the bearing bottoms  25 , and the cap attachment bolts are appropriately torqued to a specification, e.g., about 16 ft/lbs. The putty is allowed to dry for an appropriate time, such as about four hours. Then the top caps  26  are disassembled and any excess putty is ground off. (See FIG. 6, which shows repaired surfaces  31 ′ and  32 ′ on the top cap  26  and bottom half  25 .) The oil ports  33  are cleaned out, such as with a hand drill. 
     To install the inserts  27  (FIG.  1 ), the bearing inserts  27  are flexed open and snapped onto journals  24  of a camshaft  23 , either from a side thereof or over an end of the camshaft  23 . The camshaft  23  is then positioned on the surface  32  of the bottom half  25  of the cam housing  22 , making certain that the oil slot  45  is aligned with the oil port  33  on the bottom half  25  of the cam housing  22 . The top caps  26  are placed in their order and assembled to the bottom halves  25  of the cylinder head  20 , including torquing them to an appropriate torque specification, e.g., 16 ft/lbs. The cam housing repair is complete. 
     It is contemplated that modifications can be made to the present inventive concepts while still being included in the present invention. For example, a bench-type broaching apparatus  80  (FIG. 10) can be used in place of the air impact wrench  69 . The bench-type apparatus  80  includes a stand  81  with spaced-apart blocks  82  and  83  holding a hydraulic cylinder  84 , and a stop  88  spaced from the front block  83 . An extendable/retractable rod  85  extends from the cylinder  84  and through the second block  83  and also through the stop  88  into an area where a cylinder head  20  is supported on a stand  86  against the stop  88 . A hydraulic fluid powering system  87  is attached to the cylinder  84  for motivating the extendable/retractable rod  85 . The broach  51  is positioned in the cylinder head  20  and is threadably connected to an end of the rod  85 . The broach  51  is pulled through the cylinder head  20  by operating the powering system  87  to move the broach  51 . It is contemplated that a semi-automatic powering system could also be configured to rotate, so that it could be used to rotate the broach puller  52  to pull the broach  51  by use of the rod  64 . 
     In yet another modification, a modified broach  51 ′ (FIG. 11) is provided with replaceable cutter sections  55 ′. It is contemplated that the cutter sections  55 ′ can be separate cutter rings as shown or can be a single modular unit. The illustrated cutter sections  55 ′ include a center body  89  having a nose  90  shaped to closely mateably engage a recess  91  on the structure upstream from the nose  90 , and further includes a recess  91  for receiving the nose  90  on a downstream adjacent structure. The cutter knife edges  58  extend from the structural rings  92  that extend radially from the center body  89 . In the illustrated modified broach  51 ′, the tail section  56 ′ is threaded. Thus, the tail section  56 ′ compresses the assembly of the lead, cutter, and tail sections  54 ′,  55 ′, and  56 ′, respectively, as the rod  64  pulls the broach  51 ′ through the cam housings  22 . Alternatively, the noses  90  and the recesses  91  can be threaded or friction fit to retain them together. In still another alternative, a long tubular mandrel (not specifically shown) extending from the lead section to the tail section (or visa versa) can be used to mount the cutter sections  55 ′. 
     The above description is considered that of the preferred embodiments only. Modification of the invention will occur to those skilled in the art and to those who make or use the invention. Therefore, it is understood that the embodiments shown in the drawings and described above are merely for illustrative purposes and not intended to limit the scope of the invention, which is defined by the following claims as interpreted according to the principles of patent law, including the doctrine of equivalents.