Abstract:
A number of cylinder head arrangements that provide low cost and easy assembly of their various components with minimum labor and reduced necessity for line boring to reduce both manufacturing and assembly operation without adversely affecting performance.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This invention relates to reciprocating machines such as internal combustion engines or compressors of the type having a cylinder block having one or more cylinder bores that reciprocally support a piston or pistons that are connected a crankshaft at one end. The opposite end of these cylinder bores is closed by a cylinder head affixed to the cylinder block in a suitable manner. The flow into and out of the cylinder bores is controlled by valves reciprocally mounted in the cylinder head and operated by one or more camshafts journalled therein. Frequently the valves are operated from cams on the camshaft through pivotally supported rocker arms.  
         [0002]     Although this arrangement is generally effective, a substantial number of machining and assembly steps are required to complete the assembly. This adds to the cost and can, if not closely controlled, present alignment problems that can introduce inaccuracies and less than desirable operation.  
         [0003]     As an example of a prior art construction of this type, Japanese Published Application, Publication Number P2000-170506A shows a construction wherein an intake side camshaft and an exhaust side camshaft are journalled by underlying lower cam holders and overlying upper cam holders. The lower cam holders condition are fastened to the cylinder head via a first series of fasteners. In addition, the upper cam holder and lower cam holder are fastened to each other at positions spaced inward from the first fasteners. In addition the second fastening members each have a smaller diameter than the first fastening member.  
         [0004]     It is also stated therein that that size reduction of the cylinder head is possible and the first fastening members also serve to resist undesired cocking of the rocker shafts. However much fitting and precise location is required for machining and assembly.  
         [0005]     As a further disadvantage to this type of construction, to secure the positional accuracy of the rocker shaft support section formed on the lower cam carrier, line boring is necessary after the lower cam carriers are mounted independently on each cylinder head. Therefore, the scale of machining facilities for such line boring become larger.  
         [0006]     In addition, since the rigidity of hole machining tools needs to be secured to secure the machining accuracy, size reduction of the tool diameter is difficult. Therefore, weight saving and size reduction of the rocker shaft are difficult and in turn, weight saving and size reduction of the rocker arm are also difficult.  
         [0007]     Another prior art structure is shown in Japanese Patent Publication B 2537205. As shown therein each rocker shaft is configured to be supported pivotally on a respective one of a plurality of cam carriers. Therefore, when the cam carriers are assembled to the cylinder head, they need to be assembled in succession while rocker arms are fitted on the rocker shafts, causing complicated assembly work.  
         [0008]     In addition, each rocker shaft should not to overlap the opening that receives the respective spark plug insert. Therefore the support section for each of the rocker shafts needs to be separately machined for each cam carrier, making positional accuracy is difficult to obtain.  
         [0009]     Therefore it is a principal object of this invention to provide a simplified, low cost and easily manufactured and assembled arrangement for operating the valves of a multi cylinder and valve reciprocating machine.  
       SUMMARY OF THE INVENTION  
       [0010]     This invention is adapted to be embodied in a low cost, easily manufactured and assembled valve actuating mechanism for a reciprocating machine having a cylinder head adapted to be affixed in closing relation to at least one cylinder bore formed in a cylinder block. A cam shaft carrier is affixed to the cylinder head and defines a cam shaft bore for journaling a bearing surface of a cam shaft. A rocker shaft journal is formed by the cam shaft carrier in parallel relation to the cam shaft bore and extends on at least one side of the cam shaft bore. A rocker arm is journalled by the rocker shaft journal and has a follower surface engaged by a cam lobe of the cam shaft. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a top plan view of the cylinder head of a reciprocating machine constructed in accordance with a first embodiment of the invention, with the cam cover removed to more clearly show the construction.  
         [0012]      FIG. 2  is a further enlarged view of this embodiment, with the cam shafts removed.  
         [0013]      FIG. 3  is a side elevational view looking in the direction of the arrow  3  in  FIG. 2  showing the valves operated in phantom.  
         [0014]      FIG. 4  is a cross sectional view taken along the line  4 - 4  in  FIG. 3 .  
         [0015]      FIG. 5  is a cross sectional view taken along the line  5 - 5  in  FIG. 3 .  
         [0016]      FIG. 6   a  is an enlarged view taken generally along the line  6 - 6  in  FIG. 2  and shows the condition when the associated valve is closed.  
         [0017]      FIG. 6   b  is an enlarged view taken generally along the line  6 - 6  in  FIG. 2  and shows the condition when the associated valve is opened.  
         [0018]      FIG. 7  is a view in part similar to  FIG. 2  and shows another embodiment of the invention.  
         [0019]      FIG. 8  is a side elevational view looking in the direction of the arrow  7  in  FIG. 6  showing the valves operated in phantom.  
         [0020]      FIG. 9  is a top plan view, in part similar to  FIG. 1 , but with the cylinder head reversed, and shows still another embodiment of the invention.  
         [0021]      FIG. 10  is a further enlarged view of the embodiment of  FIG. 9 , showing one of the center cam shaft carriers with the cam shafts removed.  
         [0022]      FIG. 11  is a side elevational view looking in the direction of the arrow  11  in  FIG. 10  showing the valves operated and the operating cam lobes in phantom.  
         [0023]      FIG. 12  is a cross sectional view taken along the line  12 - 12  in  FIG. 11 .  
         [0024]      FIG. 13  is a top plan view, in part similar to  FIGS. 2, 7 , and  10  showing only the two cam carriers of this embodiment provided at the opposite ends of the cylinder head  
         [0025]      FIG. 14  is a cross sectional view of the embodiment of  FIG. 13  taken along a plane passing through the axes of the rocker arm journals. 
     
    
     DETAILED DESCRIPTION  
       [0026]     Referring now in detail to the drawings and initially to the embodiment of  FIGS. 1-6 , a multi-cylinder reciprocating machine is shown partially and is identified generally by the reference numeral  21 . As will be readily apparent to those skilled in the art, the invention may be applied to either reciprocating internal combustion engines or compressors. However to simplify the disclosure only engine applications are illustrated.  
         [0027]     In the illustrated embodiment of these figures ( FIGS. 1-6 ), a cylinder head, indicated generally at  22  is suitably affixed to a cylinder block (not shown). Basically any number of cylinders and any engine configuration may be employed such as in line, v type or opposed.  
         [0028]     In accordance with the invention, a plurality of cam carriers  23  are provided on the cylinder head  22  in a manner to be described shortly. The cam carriers  23  support for rotation an intake cam shaft  24  and an exhaust cam shaft  25  disposed parallel to each other. To this end, the cam carriers  23  are formed by a single lower piece  23   a  having lower bearing recesses  23   i  and  23   e  each associated with respective, axially spaced journal surfaces  24   b  and  25   b  of the respective intake and exhaust cam shafts  24  and  25   
         [0029]     To further complete the journaling of the cam shafts  24  and  25 , bearing caps  26   i  and  26   e  are affixed, in a manner to be described shortly, to the single lower piece  23   a  and the cylinder head  22 . These bearing caps have bearing surfaces  26   ib  and  26   eb  that are complementary to the lower bearing recesses  23   i  and  23   e . These bearing surfaces  26   ib  and  23   i  and  26   eb  and  23   e  embrace and journal the axially spaced cam shaft bearing sections  24   b  and  25   b  of the cam shafts  24  and  25 , respectively.  
         [0030]     The driven ends of the cam shafts  24  and  25  are also journalled directly in the end of the cylinder head  22  by end bearing caps also indicated by the reference numerals  26   ie  and  26   ee.    
         [0031]     Threaded fasteners  27  pass through bored holes  28  in the bearing caps  26   i , and  26   e  and aligned holes  29  formed in the single lower pieces  23   a  to fix the elements together. At the driven end of the camshafts  24  and  25  the end bearing caps  26   ie  and  26   ee  are bored to cooperate with tapped holes formed in the cylinder head at the driven end. Finally the lower ends  27   e  of all of these threaded fasteners  27  are threaded into tapped holes formed in the cylinder head  22  to complete the assembly.  
         [0032]     In addition a further pair of bored holes  28  are formed in axial alignment with the transverse center of the cylinder head  22  in the area of the single lower pieces  23   a  between the bearings  23   i  and  23   e  above tapped holes in the cylinder head  22  to receive further threaded fasteners  30  for additional security in retaining the lower pieces  23   a  when the bearing caps  26   i  and  26   e  are removed,  
         [0033]     Continuing to refer primarily to  FIG. 1 , the intake cam shaft  24  is formed with a plurality of intake cams  24   c , and the exhaust cam shaft  25  is formed with a plurality of exhaust cams  25   c . These pluralities of cams  24   c  and  25   c  are each adapted to operate the intake and exhaust valves, to be described shortly, through respective intake and exhaust rocker arms  31  and  32 .  
         [0034]     To this end, the single piece  23   a  of each of the cam carriers  23  is formed with an intake side rocker shaft journal opening  23   irj  and an exhaust side rocker shaft opening  23   erj  in a rocker shaft support section  23   ras  located between the intake cam shaft bearing  23   i  and the exhaust cam shaft bearing  23   e , as shown in  FIGS. 2 and 3 .  
         [0035]     Intake and exhaust rocker shafts  33 ,  34 , respectively, are supported by the rocker shaft support portions  23   ras , as shown in  FIGS. 1-4 . The rocker shaft support section  23   ras  is provided on both sides of the cam shaft bearings  23   i  and  23   e  and extends in the same direction as the cam shafts  24 ,  25  (see  FIG. 1 ).  
         [0036]     The rocker shaft journal openings  23   irj ,  23   erj  are formed in the cam carrier  23  as through-holes passing through the rocker shaft support section  23   ras . The rocker shafts  33 ,  34  are inserted in these rocker shaft through-holes  23   irj ,  23   erj.    
         [0037]     In addition to the structure as thus far described, the single lower piece  23   a  of each of the cam carriers  23  is formed with a hole  35  for a spark plug insert section between the intake rocker arm support  23   irj  and the exhaust rocker arm support  23   erj . This hole extends in a direction perpendicular to the axial direction of these shaft receiving sections  23   irj ,  23   erj , as shown in  FIGS. 1, 2  and  4 .  
         [0038]     A cylindrical collar  36  is fitted In the hole  35  for each ignition plug insert section formed in the cam carrier  23 , as shown in  FIG. 1 . Suitably mounted ignition plugs  37  serve the combustion chambers formed in part by the cylinder head  22  through the collars  36 .  
         [0039]     In addition to this purpose, the collars  36  also have the function of preventing the rocker shafts  33 ,  34  from slipping off the cam carrier  23 . This is accomplished by forming the rocker shafts  33  and  34  with notches  33   a  and  34   a , respectively to engage parts of the collar  36  for the prevention of their slipping-off.  
         [0040]     It is arranged so that the linear thermal expansion coefficient of the collar  36  is different (either larger or smaller) than that of the cam carrier  23 . This will insure that the collar  36  can be attached to and detached from the cam carrier  23  in a cold or a hot environment and subsequently the collar  36  will be prevented from slipping off the cam carrier  23  at room temperature. Such an arrangement improves handling properties of the cam carrier  23 , as well as its assembling properties, and a slipping-off prevention condition can be realized of a minimum amount of play as compared with mechanical fasteners such as bolts.  
         [0041]     As best seen in  FIGS. 2 and 4 , the cam carrier lower pieces  23   a  are formed with slots  23  as and intake side rocker arms  31  and exhaust side rocker arms,  32  are inserted in these slots  23  as. The rocker arms  31 ,  32  are formed with shaft insert holes  31   a ,  32   a , respectively for journaling rocker arms  31  and  32  in the lower pieces  23   a  on their shafts  33  and  34 .  
         [0042]     With the intake side rocker arms  31  fitted in the slots  23  as of the cam carrier  23 , the intake side rocker shaft  33  is inserted in the intake side rocker shaft through-holes  23   irj  and shaft insert hole  31   a . Likewise, with the exhaust side rocker arm  32  fitted in the slot  23  as of the cam carrier  23 , the exhaust side rocker shaft  34  is inserted in the exhaust side rocker shaft through-hole  23   erj  and shaft insert hole  32   a . The rocker shafts  33 ,  34  are supported independently for each cam carrier  23 , and pass through the rocker shaft support section  23   ras  of the cam carrier  23  and extend on both sides of the cam shaft bearing section  24   b  so as to be disposed parallel to the cam shafts  24 ,  25 . Thus the rocker arms  31 ,  32  are supported for rotation by the rocker shafts  33 ,  34  on both sides of the cam shaft bearing section  26   ib  of the cam carrier  23 .  
         [0043]     When the intake side cam shaft  24  and exhaust side cam shaft  25  are rotated, each of the intake side cams  24   c  and exhaust side cams  25   c  depresses each of the intake side rocker arms  31  and exhaust side rocker arms  32  for opening or the action of the springs, to be described, releases the depression and permits the rocker arms and associated valves to move to the closed positions.  
         [0044]     The cam carriers  23  are mounted approximately directly above each respective cylinder and configured such that all of the plurality of rocker arms  31 ,  32  supported on both sides of the cam shaft bearing section  26   ib  of the cam carrier  23 , correspond to that respective cylinder. Thus and as best seen in  FIG. 3 , each of the valves, indicated generally by the reference numeral  38 , serving a respective one cylinder are adapted to be opened/closed by the movement of the four rocker arms  31 ,  32  supported on the two rocker shafts  33 ,  34  of one cam carrier  23 .  
         [0045]     Referring now primarily to  FIGS. 2-5 , and  6   a  and  6   b , it will be seen that the upper bearing halves  26   ib  and  26   eb  have the aforementioned aligned holes  29  through which the threaded fasteners  27  pass along with the aligned bores  28  of the single lower piece  23   a  for the fastening of these assemblies to the cylinder head  22  in the desired relation to the associated cylinder.  
         [0046]     As another feature of the invention, the cam carriers  23  also cooperate to lubricate the valves and operating mechanism. To this end, the single lower piece  23   a  of each cam carrier  23  is formed with an oil passage, indicated generally at  39 , shown in  FIGS. 2, 3  and  6   a  and  6   b . This oil passage receives  39  pressurized oil from the engine lubricating system in a suitable manner and communicates with oil passages  41 ,  42 , respectively, extending toward the intake rocker shaft  33  and exhaust rocker shaft  34 . These passages  41  and  42  communicate respectively with coaxial oil passages  43 ,  44 , formed in the rocker arm shafts  33  and  34  respectively. To this end, the rocker shafts  33 ,  34  are each formed hollow inside and closed at both ends to form the oil passages  43  and  44 .  
         [0047]     The valve gear lubricating system also includes oil delivery notches  31   d  and  32   d  formed in the intake rocker arms  31  and exhaust rocker arms  32 , respectively. These oil delivery notches  31   d  and  32   d  are formed at the outer ends of delivery passages  43  and  44  that communicate with the rocker arm passages  41  and  42 , respectively and face toward the intake cams  24   c  and exhaust cams  25   c , shown partially in  FIGS. 6   a  and  6   b . As best seen in  FIG. 4 , the rocker shafts  33 ,  34  are retained axially by notches  33   a ,  34   a  formed therein that are engaged by the collar  36 .  
         [0048]     The valves  38  associated with the structure already described, their operation and construction will now be described in more detail by reference to  FIG. 3 . Each valve  38  is of the poppet type and has a valve stem  45  that is supported for reciprocation in the cylinder head  22  by a respective valve guide  42  pressed or otherwise secured to the cylinder head  22 . A valve head  46  at the lower end of the respective stem cooperates with a valve seat (not shown) fixed at the combustion chamber end of the cylinder head  22  to control the flow through a respective intake or exhaust port, not shown in this figure, but as well known to those skilled in this art.  
         [0049]     The valves  38  are normally retained in closed positions, as also known in the art, by return springs  47  of a desired type, with coil springs shown by way of example. These springs  47  are loaded between retainers  48  engaged with the cylinder head  22  and keeper retainers  49  fixed to the upper ends of the respective valve stem  45  to normally urge the valves  38  to their closed positions as shown in  FIGS. 3 and 6   a.    
         [0050]     As the respective cam shafts  24  and  25  rotate, their cam lobes  24   c  and  25   c  will act to drive the respective valves  38  to their opened positions as shown in  FIG. 6   b , with compression of the springs  47 . Upon continued rotation of the respective cam shaft  24  and  25  their lobes  24   c  and  25   c  will move away from the stems  45  and the springs  47  will close the valves  38 , as is well known in the art.  
         [0051]     As has also been noted, the oil delivery system for lubricating the valve train including the cam shafts  24  and  25  and specifically their respective cam lobes  24   c  and  25   c , the contacted surfaces of the rocker arms  31  and  32  and the stems of the operated valves insures adequate lubrication. However a system is also incorporated for controlling the amount of lubricant supplied to these areas so as to prevent excess oil flow. This system is described in connection with the exhaust valves but it should be understood that the intake valves are lubricated by the same type of flow controlling construction  
         [0052]     The oil or other lubricant is delivered continuously to the hollow interior of the respective rocker arm shaft, this being the passage  44  in the case of the exhaust valves  45  from the carrier base  23   a  through a delivery opening  44   i  that is continuously open since the rocker arm shaft  34  does not rotate. However the rocker arm  32  does rotate and its delivery passage  42  only overlaps a discharge opening  44   d  in the associated rocker arm  32  only at the time the associated rocker arm is moved toward the valve opening positions, as shown by comparing  FIG. 6   b  with  FIG. 6   a.    
         [0053]     To summarize the operation of this embodiment, as the engine  21  operates and the cam shafts  24 ,  25  and their plurality of cams  24   c ,  25   c  rotate, and the cams  24   c ,  25   c  depress will sequentially pivot the rocker arms  31 ,  32 , and the valve stems  33  are lowered along with their valve faces  32  air is taken in on the intake side and combustion gas is exhausted on the exhaust side as is well known in the art.  
         [0054]     In a like manner, when the cams  24   c ,  25   c  rotate beyond the condition of depressing the rocker arms  31 ,  32 , the valve stems  33  are raised by the action of the springs  47  and the valve faces  32  are also raised to close their respective seats (not shown) so that no air will be taken in on the intake side and no exhaust gas will be exhausted on the exhaust side. The lubrication of the operating mechanism is effected only when the valves are being operated so as to avoid excess lubrication.  
         [0055]     Thus, as should be readily apparent to those skilled in the art, the embodiment of  FIGS. 1-6  incorporates cam shafts  24 ,  25  having a plurality of cams  24   c ,  25   c  for depressing rocker arms  31 ,  32  journalled by a plurality of cam carriers  23  each formed integrally with cam shaft bearing sections  26   ib  and  26   eb  for supporting the cam shafts and rocker shaft support sections  23   irj  and  23   erj  for supporting rocker shafts  33  and  34 . The rocker shafts  33 ,  34  each supported independently by a cam carrier  23 , positioned in the rocker shaft support section  23   ras  of the cam carrier  23  and extending on both sides of the cam shaft bearing section  26   ib . Thus the axes of the cam shafts  24 ,  25 , support of the rocker arms  31 ,  32  on the rocker shafts  33 ,  34  on both sides of the cam bearing section  26   ib  of the cam carrier  23  are also parallel.  
         [0056]     Therefore, since a plurality of cam carriers  23  are provided and the rocker shaft  33 ,  34  are adapted to pass independently through respective of the rocker shaft support sections  23   ras  of the cam carriers  23 , not all the plurality of rocker shafts  33 ,  34  need be centered to facilitating assembly. Further, since the rocker shaft  33 ,  34  are divided for each cam carrier  23  and small in length, weight saving and size reduction can be effected. Further, smaller scale, machining facilities for the cam carriers  23  can be employed. In addition, the positional accuracy of the holes for supporting rocker shafts  33 ,  34  to the cam shaft bearing sections  26   ib    26   eb  can be obtained easily, resulting in improvement in reliability. Moreover, the work in mounting the rocker shafts  33 ,  34  to the arm carrier  33  is decreased.  
         [0057]     As added advantages, the rocker shaft support section  23   ras  extend on both sides of the cam shaft bearing section  26   ib  in the same direction as the cam shafts  24 ,  25  and is formed with slots  23  as for supporting the rocker arms  31 ,  32 . The rocker shaft support section  23   ras  is formed with through-holes  23   irj ,  23   erj  passing therethrough across the slots  23  as, and the rocker shafts  33 ,  34  are inserted in the through-holes  23   irj ,  23   erj . Therefore, since the rocker arms  31 ,  32  are held by the slots  23  as on both sides in the vicinity of the shaft insert holes  31   a ,  32   a , the rigidity of the mounting of the rocker arms  31 ,  32  along with accurate movement of the rocker arms  31 ,  32 , effecting higher rotation speed and improvement in reliability.  
         [0058]     As a further advantage, the cam carriers  23 , the rocker shafts  33 ,  34  and the rocker arms  31 ,  32  have passages  39 ,  41 ,  42 ,  43 ,  44  for oil supplied from the cylinder head  22  and the rocker shaft  33 ,  34  are hollow inside and closed at both ends with the notches  33   a ,  34   a  being covered by the collar  36 . Therefore, leakage of oil passing through the rocker shafts  33 ,  34  from the notches  33   a ,  34   a  can be suppressed. This structure allows the hollow portions inside the rocker shaft  33 ,  34  to be increased in size, effecting weight saving of the rocker shafts  33 ,  34 .  
         [0059]     Although in the multi-cylinder internal combustion engine  21  according to the embodiment of  FIGS. 1-6   b , the rocker shafts  33 ,  34  also pass through the rocker shaft support section  23   ras , this invention is not limited to that specific way the rocker shafts  33 ,  34  are supported. Also, although in this first embodiment, the rocker shafts  33 ,  34  extending on both axial sides of the cam shaft bearing section  26   ib  to be disposed parallel to the cam shafts  24 ,  25 , this invention is not limited to the foregoing embodiment.  
       Embodiment of FIGS.  7  and  8   
       [0060]     To this end,  FIGS. 7 and 8  show another embodiment of the invention. In describing this embodiment as well as those following, the same parts as in previous embodiments of the invention are designated by same reference numerals and description will not be repeated, except as necessary for those skilled in the art to understand and practice this and other additional embodiments to be described.  
         [0061]     This embodiment employs cam carriers identified generally by the reference numeral  123  (only one of which is shown). In this embodiment rocker shaft through-holes  123   e ,  123   i  are formed in respective rocker shaft support sections  123   erj  and  123   irj  positioned transversely outside a cam shaft bearing section, indicated generally at  124 . The central part of this cam shaft bearing section  124  includes a portion defining a cylindrical opening  125  for receiving a respective collar (not shown) like the collars  36  of the previously described embodiment to hold a respective spark plug. These components are formed so that the linear thermal expansion coefficient of the collar  36  is different (either larger or smaller) than that of the cam carrier  123 , as described in the previous embodiment. This will insure that the collar  36  can be attached to and detached from the cam carrier  123  in a cold or a hot environment and subsequently the collar  36  will be prevented from slipping off the cam carrier  123  at room temperature.  
         [0062]     In this embodiment, unlike that of  FIGS. 1-6  the spark plug collar receiving opening  125  is separated from the rocker arm support sections  123   irj  and  123   erj  by the remainder of the cam shaft bearing section  124 . Other effects and functions are substantially the same as in the first described embodiment of this  FIGS. 1-6 , except that while the rocker shafts  33 ,  34  on which the rocker arms  31 ,  32  rotate, are disposed inwardly in the first embodiment, they are dispose outwardly in this embodiment.  
       Embodiment of FIGS.  9 - 14   
       [0063]     Another embodiment of the invention is illustrated in  FIGS. 9-14 . Again where the elements of this embodiment are the same or substantially the same as components already described, those components have been identified by the same reference numerals as previously employed. Also and for the sake of brevity these components will be described only insofar as is necessary for those skilled in the art to practice this embodiment.  
         [0064]     The engine associated with this embodiment and more particularly a cylinder head assembly thereof is indicated generally by the reference numeral  201 . The cylinder head  201  of the multi-cylinder internal combustion engine in this embodiment is different from the multi-cylinder internal combustion engine  21  of first described embodiment of  FIGS. 1-6   b  in the following aspects and is also shown in a reversed position therefrom.  
         [0065]     Primarily, rather than operating all of the intake and exhaust valves associated with the same cylinder, the cam carriers, except for those at the ends of the of the cylinder head, as to be described shortly, operate one intake valve and one exhaust valve of pairs of the adjacent cylinders spanned by these paired, middle or central cam carriers, each of which is indicated generally by the reference numeral  223   m.    
         [0066]     Like the previous embodiments and as best seen in  FIGS. 10-12 , these middle cam carriers  223   m  are comprised of a single lower piece  223   ma  to which a pair of respective upper bearing halves  223   mib  and  223   meb  is affixed by threaded fasteners  227 . These middle cam carriers  223   m  are each disposed between adjacent centermost cylinders, as should be readily apparent from  FIG. 9 . The construction for the support at the ends of the cylinder head assembly  201  will, as has been noted, described later.  
         [0067]     Continuing to refer primarily to  FIGS. 10-12 , pairs of adjacent middle intake rocker arms  231   c  are supported on an intake pivot shaft  224  received in a suitable bore formed in single lower pieces  223   ma  of the middle cam carriers  223   m . The inner ends of these middle intake rocker arms  231   c  are retained in slots  223   mas  formed at one side of the single lower piece  223   ma.    
         [0068]     In a like manner adjacent middle exhaust rocker arms  232   c  are supported on an exhaust pivot shaft  234  recieved in a suitable bore formed in the single lower pieces  223   ma  of the middle cam carriers  223   m . The inner ends of these middle exhaust rocker arms  232   c  are also retained in slots  223   mas  formed in the single lower pieces  223   ma  of the middle cam carriers  223   m.    
         [0069]     The middle intake rocker arm shafts  224  and the middle exhaust rocker arm shafts  234  are retained in axial position in the slots  223   mas  and the single lower pieces  223   ma  of the middle cam carriers  223   m  in the manner now to be described. As with all of the embodiments described, threaded fasteners pass through bored holes in the respective components of the cam carriers of the embodiments. These bored holes in this embodiment are identified by the reference numerals  228 . As with the previously described embodiments, the body of the cylinder head ( 201  in this embodiment) has tapped holes to threadingly engage and retrain the threaded lower ends of the fasteners  227 . In addition and as best shown in  FIG. 12 , these fasteners  227  pass through a portion of the bores  228  which intersect the pivot shafts  224  and  234  and around which sleeves  229  are positioned to axially restrain them axially. These sleeves  229  are also received in notches  230  formed in the pins  224  and  234  to axially restrain them within their respective bores.  
         [0070]     From the description of this embodiment as already made, it should be obvious to those skilled in the art, that provision must be made for operating one intake valve and one exhaust valve for the cylinders at opposite ends of the cylinder head  201 . This structure may be best understood by reference to  FIGS. 13 and 14 . As already noted,  FIG. 13  is a top plan view showing only this portion of the structure of this embodiment and  FIG. 14  is a cross sectional view of the structure shown in  FIG. 13  taken through the pivotal axes of the rocker arms. The end intake rocker arms are identified by the reference numerals  231   e  and the end exhaust rocker arms are identified by the reference numeral  232   e.    
         [0071]     Referring now first to  FIG. 13  and remembering its relation to  FIG. 9 , at the respective left and right ends of the cylinder head  201 , end cam carriers  223   el  and  223   er  are provided to support the respective end intake rocker arms  231   e  and end exhaust rocker arms  232   e  for the cylinders provided at the left and right ends of the cylinder head  201 . These cam carriers  223   el ,  223   er  are each formed generally in the same shape as the middle cam carriers  223   m  but are shorter and less complex in some regards because they each only journal one intake rocker arm  231   e  and one exhaust rocker arm  232   e . Furthermore and as best seen in  FIG. 14 , the respective rocker shafts  224   e  and  234   e  are shorter in length than the rocker shafts  224  and  234  of the middle cam carriers since they only carry one rocker arm.  
         [0072]     Since the end cam carriers  223   el  and  223   er  journal respective ends of the camshafts  24  and  25  they are each provided with respective upper pieces  223   eib  and  223   eeb  that are fixed in place by the fasteners  227  in the manner as discussed with the other embodiments.  
         [0073]     The lubrication system associated with the end cam carriers  223   el  and  223   er  is generally the same as that for the middle cam carriers and their associated components, as shown in  FIG. 14 , except for the fact that it is only for two valves rather than four valves and thus it will not be described again in detail, but like components are identified by like reference numerals.  
         [0074]     In the multi-cylinder internal combustion engine of the previous embodiments the cam carriers have been associated respectively with a single cylinder. They have thus been centered over the axis of the associated cylinder bore of the cylinder block. Thus the collars  36  have passed through the central openings that receive them. Also, as has been noted, this affords the opportunity to use materials of different thermal expansion to assure retention. The same effect is obtained with this embodiment, as will now be described.  
         [0075]     As described, the middle cam carriers  223   m  are each mounted between adjacent cylinders. In addition these middle cam carriers  223   m  have a length that is somewhat less than the distance between adjacent cylinder axes. Thus there is in fact a gap between adjacent ends of the middle cam carriers  223   m . In addition there is a like gap between the end cam carriers  223   el    223   er  and their adjacent middle cam carriers  223   m . Thus the adjacent ends are formed with semi-cylindrical notches  241  that are complimentary to the lower portions of the cylindrical collars  36 . Therefore, even in the multi-cylinder internal combustion engine  201  having an ignition plug  37  dispose above each cylinder, the cam carriers  223   m  can be configured such that they don&#39;t obstruct the disposition of ignition plugs  37 . Thus, the degree of freedom in designing can be increased for the disposition of cam carriers  223   m  in the multi-cylinder internal combustion engine  201 .  
         [0076]     As has already been described in detail and thus to summarize, the connection between the collars  216 , cylinder head  201  and various cam carriers  223   m ,  223   el  and  223   er  as well as the interengagement between the various rocker arm shafts and the fasteners maintains all of the components in their desired relationship and reduces the labor and machining to produce the engines, as described  
         [0077]     Of course those skilled in the art will readily understand that the described embodiments are only exemplary of forms that the invention may take and that various changes and modifications may be made without departing from the spirit and scope of the invention, as defined by the appended claims.