Patent Publication Number: US-6209507-B1

Title: Valve mechanism for internal combustion engine

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of our application 08/474,261 of the same title, filed Jun. 7, 1995, now abandoned which application is a division of our application Ser. No. 08/145,490, filed Oct. 29, 1993, now issued as U.S. Pat. No. 5,522,354, all assigned to the assignee hereof. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to a valve mechanism for an internal combustion engine and, more particularly, to an improved cylinder head and valve actuating system for an overhead camshaft internal combustion engine. 
     It is well recognized that the performance of internal combustion engines can be improved through the use of overhead valves operated by overhead mounted camshafts. When an overhead camshaft arrangement is employed, the cylinder head assembly trends to become much more complicated than with a conventional pushrod operated engine. This is because the cylinder head must, in addition to supporting the valves and the valve springs, provide support for the camshaft and for the actuators for the valves. Frequently, the valves are directly operated and this means that an arrangement must be provided for slidably supporting the thimble tappets that operate the individual valves from the camshaft. 
     If all of these functions are performed primarily by the cylinder head, then the cylinder head casting becomes extremely complicated. In addition, since it is necessary to machine the bearings for the camshaft provided by the cylinder head, and the bores for slidably supporting the tappets, than machining operations also add significantly to the cost of the cylinder head. Furthermore, there is the problem of assembly of all of components into such a unitary cylinder head assembly, and the problems of accessibility the various fasteners for securing the cylinder head to the cylinder block and the bearing caps to the cylinder head for journaling the camshaft. Of course, the problems mentioned above are complicated when the engine employs twin overhead camshafts. 
     It has been proposed, therefore, to employ a construction wherein the main cylinder head member itself does not have to perform all of these functions. For example, in U.S. Pat. No. 4,612,885, entitle Camshaft Bearing Arrangement For Overhead Cam Engine, issued Sep. 23, 1986, in the name of Masaaki Yoshikawa, and assigned to the assignee hereof, there is depicted a cylinder head arrangement wherein the main cylinder head assembly only supports the poppet valves for their movement and the return springs for the poppet valves. The camshafts and valve actuating tappets are supported in a separate cam carrier that is affixed to the cylinder head and thus can be machined and cast separately simplifying the aforenoted problems. However, with the arrangement shown in that Patent, the cam carrier forms the outer periphery of the cylinder head and the cam cover must sealingly engage it. In addition, the cam carrier must have a sealing arrangement around its outer periphery with the upper surface of the cylinder head to afford sealing. Hence, substantial addition machining operations are required. 
     It is, therefore, a principal object of this invention to provide an improved cylinder head assembly for an overhead camshaft internal combustion engine. 
     It is a further object of this invention to provide an improved cylinder head assembly for an overhead cam internal combustion engine wherein at least some of the valve actuating tappets and at least one of the camshafts are supported by a separate cam carrier member that is affixed to the cylinder head but in such a way that this cam carrier member need perform no sealing functions for the overall cylinder head assembly. 
     It is a further object of this invention to provide an improved and simplified cylinder head assembly for an internal combustion engine having an overhead camshaft wherein machining and assembly operations are considerably simplified. 
     In addition to the problems already noted, it is also desirable to ensure that the cam actuating tappets and camshafts are well lubricated. When a separate cam carrier member is provided, this can present additional difficulties in insuring that the camshafts are adequately lubricated as are the valve actuating tappets. 
     It is, therefore, a still further object of this invention to provide an improved cylinder head assembly including an improved arrangement for lubricating camshaft journals thereof. 
     SUMMARY OF THE INVENTION 
     A first feature of this invention is adapted to be embodied in a cylinder head assembly for an overhead camshaft engine that comprises a main cylinder head member which defines a lower sealing surface for sealing engagement with a cylinder block. At least one portion of the lower surface cooperating with a cylinder bore of the cylinder block to define a combustion chamber. The main cylinder head member further has an upper peripheral surface that surrounds a cam chamber and which is adapted to be sealingly engaged with a cam cover for enclosing the cam chamber. A cam and tappet carrier member is affixed to the main cylinder head member within the cam chamber. The cam and tappet carrier member defines at least one bearing surface for journaling a camshaft and at least one tappet bore for receiving at least one tappet actuated by the camshaft for operating a valve supported by the main cylinder head member. 
     Another feature of the invention is adapted to be embodied in an arrangement of the type described in the preceding paragraph. In accordance with this feature of the invention, the cam and tappet carrier member is formed with an oil gallery that extends along its length and which is served by an oil passage that extends through a lower surface of the cam and tappet carrier member for cooperating with an oil gallery formed in the cylinder head. 
    
    
     BREIF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partial to plan view of a cylinder head constructed in accordance with an embodiment of the invention, with the cam cover, camshaft bearing caps and other members removed so as to more clearly show the construction. 
     FIG. 2 is a cross sectional view taken along the line  2 — 2  of FIG. 1, but which also shows the remaining portions of the cylinder head assembly including the cam cover, bearing caps and the means of attachment to the cylinder block. 
     FIG. 3 is a cross sectional view taken along the line  3 — 3  of FIG. 1 showing all of the components illustrated in FIG. 2, and additional components where encompassed by this section line. 
     FIG. 4 is a cross sectional view taken along the line  4 — 4  of FIG. 1 again with certain of the missing components in place. 
     FIG. 5 is a partial top plan view with the components removed, in part similar to FIG.  1  and shows a further embodiment of the invention. 
     FIG. 6 is a cross sectional view taken along the line  6 — 6  of FIG.  1  and shows the components removed from FIG.  5 . 
     FIG. 7 is a cross sectional view taken along the line  7 — 7  of FIG.  5  and also shows the removed components. 
     FIG. 8 is a cross sectional view taken along the line  8 — 8  of FIG. 5 showing the removed components. 
     FIG. 9 is a partial top plan view with portions removed, similar to FIGS. 1 and 5, and shows yet another embodiment of the invention. 
     FIG. 10 is a cross sectional view taken along the line  10 — 10  of FIG.  9  and shows the removed components. 
     FIG. 11 is a cross sectional view taken along the line  11 — 11  of FIG.  9  and shows the removed components. 
     FIG. 12 is a cross sectional view taken along the line  12 — 12  of FIG.  9  and shows the removed components. 
     FIG. 13 is a partial top plan view, in part similar to FIGS. 1,  5  and  9 , with components removed, and shows another embodiment of the invention. 
     FIG. 14 is a cross sectional view taking along the line  14 — 14  of FIG. 13 with the removed components shown in position. 
     FIG. 15 is a cross sectional view taken along the line  15 — 15  of FIG. 13 showing the components in place. 
     FIG. 16 is a cross sectional view taken along the line  16 — 16  of FIG. 13 showing the components in place. 
     FIG. 17 is a partial top plan view with components removed, in part similar to FIGS. 1,  5 ,  9  and  13 , and shows yet another embodiment of the invention. 
     FIG. 18 is a cross sectional view taken along the line  18 — 8  of FIG. 17 with the removed components in place. 
     FIG. 19 is a cross sectional view taken along the line  19 — 19  of FIG. 17 with the removed components in place. 
     FIG. 20 is a cross sectional view taken along the line  20 — 20  of FIG. 17 with the removed components in place. 
     FIG. 21 is a partial top plan view with components removed, in part similar to FIGS. 1,  5 ,  9 ,  13  and  17 , and shows a still further embodiment of the invention. 
     FIG. 22 is a cross sectional view taken along the line  22 — 22  of FIG. 21 with the removed components installed. 
     FIG. 23 is a cross sectional view taken along the line  23 — 23  of FIG. 21, again, with the removed components installed. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION 
     In each of the embodiments illustrated, on a portion of the cylinder head of an internal combustion engine is depicted and this portion of the cylinder head is not shown in conjunction with the cylinder block, piston and remaining portions of the engine, which may be considered to be conventional. Also, it is not believed necessary to show all cylinders of the engine in the various embodiments because those skilled in the art will readily understand how the invention may be employed in conjunction with multiple cylinder engines. In addition, it is to be understood that the cylinder head depicted in the various embodiments may be the cylinder head for an in-line engine or for one bank of a V-type or opposed engine. Again, it is believed that those skilled in the art can readily understand how the invention can be applied to such engines. 
     Referring now in detail to the drawings and initially to the embodiment of FIGS. 1 through 4, a cylinder head assembly constructed in accordance with this embodiment is identified generally by the reference numeral  31 . The cylinder head assembly  31  includes a number of parts, to be described including a main cylinder head member  32  which is formed conveniently as a casting and may be made from a light weight material such as aluminum, aluminum alloys or the like. The main cylinder head member  32  has a lower sealing surface  33  that is adapted to be affixed to an associated cylinder block by means such as socket head screws  34  or the like. The socket headed screws  34  are disposed around a depressed control area  35  (FIGS. 3 and 4) of the cylinder head surface  33  that is adapted to cooperate with the associated cylinder bore to form the combustion chamber thereof, along with the piston and cylinder bore. 
     The main cylinder head member  32  is also provided with an upper peripheral sealing surface  36 , which surrounds a cam chamber  37  in which a valve actuating mechanism to be described is contained. 
     In this embodiment, like all of those, which will be described, the cylinder head assembly  31  is of the twin overhead cam type embodying a cross flow pattern. To this end, one side, the left side, of the cam chambers  37  comprises the intake side and the other side of the cam chamber  37  comprises the exhaust side. A plurality of intake valves  38  are supported for reciprocation in the main cylinder head member  32  by means of valve guides  39  that are pressed in place. In the illustrated embodiments, there are provided three intake valves for each combustion chamber recess  35 . It should be readily apparent to those skilled in the art, however, that the invention can be employed with engines having different numbers of intake valves. The invention, however, has particular utility with multiple valve engines because it easily facilitates the use of actuating mechanisms for such multiple valves. 
     Each intake valve  38  is biased toward its closed position by means of a coil compression spring  41  that bears against machined surfaces  42  of the main cylinder head member  32 . The other ends of the coil springs  41  acts against keeper retainer assemblies  43  that are affixed to the upper ends of the stems of the valves  38 . As a result of this construction, the intake valves  38  are all biased to a closed position, as is well known in this art. The intake valves  38  are opened in a manner, which will be described. 
     The heads of the intake valves  38  cooperate with valve seats  44  that are pressed or otherwise held in place in the cylinder head member  32  and which are formed at the termination of intake ports  45  that extend through the intake side of the main cylinder head member  32 . The intake ports  45  may be either individual for each intake valve  38  or may be Siamese in a desired grouping. 
     Turning now to the exhaust side of the main cylinder head member  32 , this includes a plurality of poppet type exhaust valves  46  which have there stems slidably supported in valve guides  47  that are pressed into the main cylinder head members  32 . In the illustrated embodiment, there are two exhaust valves per cylinder, but, like the intake valves, it is to be understood that the invention may be employed in conjunction with engines having any number of exhaust valves. As with the intake valves, however, the invention has particular utility with multiple valve engines. 
     Coil compression springs  48  encircle the stems of the exhaust valves  46  and engage at one end machined surfaces  49  of the main cylinder head member  32 . The opposite sides of these springs  48  are retained to the stems of the exhaust valves  46  by keeper retainer assemblies  51 . Single or Siamese exhaust ports  50  extend from the valve seats to an exhaust system (not shown). 
     The area between the intake and exhaust sides of the main cylinder head member  32  is provided with a plurality of spark plug wells  52 , one for each combustion chamber recess  35  to accommodate a spark plug  53  that is threaded into a tapped opening  54  formed at the base of the well so that the gap of the spark plug  53  will be disposed substantially centrally in the combustion chamber recess  35 . 
     The mechanism for actuating the intake valves  38  will now be described, and this includes a combined cam and tappet carrier member, indicated generally by the reference numeral  55  which may be formed as a casting from a light weight material such as aluminum or aluminum alloy. The carrier member  55  has tappet supporting portions  56  that are provided with machined bore  57  for receiving a tumble type tappets  58  associated with each of the intake valves  36 . Since the carrier member  55  is a separate piece, these tappet receiving bores  57  may be easily machined. 
     The carrier member  55  is also provided with cam lower bearing portions  59  which, in this embodiment, are disposed between adjacent cylinders and which provide bearing surfaces  61  (FIG. 2) for the rotatably journaling the baring portions of an intake camshaft  62  which has individual cam lobes  63  (FIG. 2) that cooperates with the thimble tappets  58  for opening the intake valves  38  in a well known manner. Individual bearing caps  64  are affixed to the carrier member  55  and also affixed this assembly to the cylinder block by means of bolts  65 . Locating pins  66  may be provided at spaced locations to facilitate alignment. 
     It should be noted that the cam bearing portions  59 , and, specifically, the bearing surfaces  61  overly the cylinder head hold down bolts  34 . In order to permit retorqueing of these bolts without removing the engine carrier assembly, the carrier member bearing surfaces  61  are provided with through bores  67  through which a tool may be passed so as to torque down the cylinder head fastener  34  on the intake side. 
     It should be readily apparent that the intake side of the cylinder head assembly  31  can be easily assembled by placing the intake valves in place with their springs  41  and retainers  43  before the carrier member  55  is installed. Although the upper lower and bearing surfaces  61  of the carrier member are parallel to the lower sealing surface  33  of the cylinder head while the tappet bores  57  are disposed at an angle, this later assembly presents no problem because the tappets  58  can be sized so that they can be in place in the carrier member  55  either before or after the carrier member  55  is placed on the cylinder head member  32 . The bores  57  are adequate in size so as to clear the valve spring assemblies during this installation. It should also be noted that the carrier member  55  is disposed inwardly of the cylinder head upper sealing surface  36  within the cam cavity  37  and, in this embodiment, does not extend above this surface. 
     Turning now to the exhaust side valve of the cylinder head assembly  31  and the actuation for the exhaust valves  46 , in this embodiment this is of the conventional type wherein the exhaust camshaft, to be described, and valve actuating thimble tappets are supported within the main cylinder member  32 . 
     The cylinder head member  33  on the exhaust side is provided with pairs of bosses  68  that are bored s to  69  so as to receive thimble tappets  71 . These thimble tappets engage the keeper retainer assemblies  51  for operating the exhaust valve  46 . An exhaust camshaft  72  having lobes  73  is journalled in the cylinder head member  32  by bearing portions  74  formed integrally with the exhaust side of the cylinder head assembly between the pairs of bosses  68  for the tappets for each cylinders. Bearing caps  75  are affixed to each of these bosses  74  by threaded fasteners  76  for engaging corresponding bearing surfaces on the exhaust camshaft  72  between the lobes  73  for journaling the exhaust camshaft. 
     The cam chamber  37  is covered by a cam cover  77  which carriers a sealing gasket  78  around its periphery and which sealingly engages the surface  36  of the cylinder head member  32  to close the cam chamber  37 . The cam cover  77  is also provided with an opening  79  aligned with the spark plug wells  52  so that spark plugs  53  can be installed and removed without removing the cam cover  77 . An “O” ring gasket  81  is provided around the openings  79  for sealing. 
     FIGS. 5 through 8 shows another embodiment of the invention which is generally the same as the embodiment of FIGS. 1 through 4 and for that reason parts which are the same or substantially the same as the previously described embodiment are identified by the same reference numerals and will be described again only in so far as is necessary to understand the construction and operation of this embodiment. The main difference between this embodiment and that previously disclosed is that the cam and tappet carrier  55  is provided with an extension  101  that extends from the tappet bosses  56  but toward the exhaust side of the engine and which is in registry with the spark plug well  52  of the cylinder head member  32  as best shown in FIG.  7 . This boss  101  has an opening  102  that is aligned with that of the cylinder head member  52  and also the corresponding opening  79  of the cam cover  77  so that the spark plugs  53  can be removed and installed without removing either the cam cover  77  or the cam and tappet carrier  55 . 
     The spark plug boss  101  is provided with a pair of lugs that have bored openings  103  so as to pass fasteners (not shown) which fasteners also secure the cam and tappet carrier  55  to the cylinder head member  32 . These threaded fasteners appear at  104  in FIG.  8  and it will be seen that certain of these fasteners extend over onto the exhaust side of the engine. 
     With this embodiment, a small O-ring seal  105  (FIG. 7) may be provided in the lower face of the bosses  101  for sealing with the cylinder head member  32  and the cam cover  77  also carriers gaskets  81  for sealingly engaging the upper surface of the bosses  101  rather than the cylinder head member  32  as in the previously described embodiment. 
     FIGS. 9 through 12 show another embodiment of the invention which is generally similar to the embodiment of FIGS. 5 through 8, and, for that reason, components of this embodiment which are the same or substantially the same as those of the preceding embodiment have been identified by the same reference numerals. The difference between the embodiment of FIGS. 9 through 12 and the embodiment of FIGS. 5 through 8 is that the exhaust camshaft and exhaust actuating tappets  72  and  71 , respectively, of this embodiment are also formed integrally with the cam and tappet carrier  55 . 
     To accomplish this, the spark plug boss portions  101  are provided with further extensions  151  that are bored at  152  so as to receive and slidably support the exhaust tappets  71 . In addition, an exhaust camshaft bearing lower half  153  is formed integrally between the bosses  151  for each cylinder and is connected to a box  154  formed from the spark plug boss  101 . Bearing caps  154  are affixed to the bosses  153  by threaded fasteners  155 . Hence, it should be apparent that this construction permits ease of formation of both tappet and bearings for both the intake and exhaust valves while retaining all of the advantages of the other embodiments. 
     FIGS. 13 through 15 show an embodiment which similar to the embodiment of FIGS. 9 through 12 and, for that reason, components of this embodiment which are the same as the embodiment of FIGS. 9 through 12 have been identified by the same reference numerals and will not be described again, except in so far as is necessary to understand the construction and operation of this embodiment. 
     This embodiment differs from that of FIGS. 9 through 12 in eliminating the spark plug boss portions  101  of the cam and tappet carrier  55  while still retaining the support for both intake and exhaust camshafts  62  and  72 , and all of the intake tappets  58  and exhaust tappet  71 . Thus, it is not necessary in this embodiment for the cam cover  77  or cylinder head member  32  to have any sealing relationship with the cam and tappet carrier  55 , thus limiting some of the machine surfaces on it. 
     In this embodiment, the intake cam bearing portions  59  of the cam and tappet carrier  55  have a pair of Y-shaped extensions  201  that extend toward the exhaust side of the cylinder head assembly  31  across the spark plug well  52  of the cylinder head member  32  and thus span it. These extensions carry integrally tappet supporting bars  202  that are formed with tappet receiving bores  203  for slidably supporting the exhaust tappets  71 . In addition, cam bearings bridges  204  are formed between the tappet bore  203  associated with each cylinder and form the lower bearing half for the exhaust camshaft  72 . A bearing cap  205  is affixed to each of the beams  204  by threaded fasteners  206 . 
     Referring now to the embodiment of FIGS. 17 through 20, this is an embodiment, which is similar to the embodiment of FIGS. 1 through 4, but shows a slightly different way in which the cam and tappet carrier  55  may be affixed to the main cylinder head  32 . In this embodiment, there is provided an additional boss  251  on the tappet carrying portion  56  of the cam and tappet carrier  55  between two of the tappet receiving bores  57 . This box receives a threaded fastener  252 , which serves to affix the cam and tappet carrier member  55  directly to the main cylinder head member  32 . In all other regards, this embodiment is the same as that of FIGS. 1 through 4 and, for that reason, further description of this embodiment is believed to be unnecessary. 
     FIGS. 21 through 23 show how the cam and tappet carrier of any of the previously described embodiments may also function so as to deliver lubricant to the camshaft bearings and, if desired, the tappet receiving bores thus further offering simplification of the cylinder head assembly. This embodiment is the same as that of FIGS. 1 through 4, but the intake and exhaust sides are reversed in the drawings. 
     Because the only difference between this embodiment and that of FIGS. 1 through 4 is the way in which the lubricant is delivered, all reference numerals applied to the embodiment of FIGS. 1 through 4 will be carried over with this embodiment and only the changes will be described. It should be understood that this concept may be used with all of the embodiments in addition to that of FIGS. 1 through 4. In this embodiment, more than one cylinder is depicted so as to show how the arrangement can be utilized to deliver lubricant to all of the camshaft bearing surfaces  61 , and also to the tappet bores  57 , if desired. 
     The portion of the engine not illustrated in the drawings is provided with a lubrication system and this includes a cam lubricant delivery passage that extend up through the cylinder block to the surface of the cylinder block that is sealingly engaged with the cylinder head surface  33 . This oil delivery passage is indicated by the arrow  301  in FIG.  22 . This passage communicates with a drilled passage  302  that extends through the main cylinder head member  32  from its cylinder block sealing surface  33  to a surface  303  that is engaged by one of the boss portions  59  of the cam and tappet carrier  55 . The lower surface of the cam and tappet carrier is formed with a corresponding drilling  304 , which is intersected by a longitudinally extending main gallery  305  that is easily formed through drilling the cam and tappet carrier  55 . One drilled, the ends of the gallery  305  are closed by plugs. The main gallery  305  is intersected by a plurality of supply passages  306 , which are drilled through the cam bearing surface  61  and, thus, deliver lubricant to the bearings of the camshaft  62 . If desired, similar cross drillings can be provided so as to communicate with the tappet bores  57 . 
     It should be readily apparent from the foregoing description of the described embodiments of the invention are very effective in providing a cylinder head assembly that can be easily machined and assembled and, nevertheless, will accommodate a large number of tappets and support the associated actuating camshaft or camshafts. Of course, the embodiments described are only preferred embodiments of the invention, and various changes and modifications may be made without departing from the spirit and scope of the invention, as defined by the appended claims.