Abstract:
An improved arrangement for controlling the valve operation of an internal combustion engine wherein the control valves are mounted within perpendicularly extending bores formed in the cylinder head and camshaft bearing cap with the bores being deep enough so that the valves do not project significantly beyond the cylinder head. In addition, one or more of the connecting passages are formed by grooves in the mating surfaces of the cylinder head and bearing cap to avoid the necessity of drillings and particularly of drilling blind bores.

Description:
BACKGROUND OF INVENTION 
     This invention relates to an internal combustion engine and more particularly to an improved, compact and easily manufactured, variable valve driving mechanism for such engines. 
     In order to improve the performance of internal combustion engines throughout their entire load and speed ranges, it has been proposed to employ a variable valve actuating mechanism that will vary the timing of one or more of the camshafts of the engine relative to the engine crankshaft and/or the degree of lift of the valve. By changing the valve timing and/or lift, it is possible to improve the performance for a variety of specific running conditions. 
     Conventionally, the variable valve timing mechanisms have employed some form of phase shifting mechanism in the drive of the camshafts so as to achieve the variation in the valve timing. These mechanisms are normally hydraulically operated and employ control valves that are mounted on the engine and which supply controlling pressure to the variable valve timing mechanism. Also the amount of valve lift can also be varied hydraulically. 
     Generally these control valves are comprised of a valve spool and a valve actuator, normally in the form of an electrically operated solenoid. It has been the practice to mount these valves in proximity to the camshafts so as to simplify the plumbing associated therewith and to avoid pressure losses. 
     One way this may be done is as shown in U.S. Pat. No. 6,289,861, assigned to the assignee hereof. As shown in that patent, the control valves are mounted so that they extend perpendicularly to the mating faces of the cylinder head and cam caps and in close proximity thereto. As shown in that patent, this results in, the positioning of the actuating solenoid in a vertically upstanding position and projecting substantially through the cam cover for the engine. Although this is acceptable in some applications, in many engine applications such projections are undesirable. 
     It is, therefore, a principal object to this invention to provide an improved actuating control valve mechanism for the variable valve actuating arrangement of an internal combustion engine. 
     It is another object to this invention to provide an improved and compact arrangement for mounting the control valve of a variable valve actuating mechanism for an internal combustion engine. 
     Normally the control valve receives oil from the engine lubricating system and delivers it through passages formed in the cylinder head and/or cam bearing cap to communicate with the variable valve actuating mechanism through passages that are formed in the camshaft and generally extend longitudinally there through. This requires the provisions of several passages including a supply passage and a return passage. The supply passage communicates to one of two chambers of the variable valve actuating mechanism and the return passage is connected to the other of these chambers of the valve actuating mechanism. The pressure in these chambers is varied to change the position of the variable valve timing mechanism to achieve the change in valve timing and/or lift. 
     Obviously, the provision of these multiple passages presents some problems and generally it has been the practice to form the passages primarily through drillings in the various engine components. This can give rise to several difficulties and also is costly. 
     It is, therefore, a still further object to this invention to provide an arrangement for the control valve communication with the variable valve timing mechanism wherein at least some of the supply passages can be formed in the interface between mating components without requiring drilling. 
     SUMMARY OF INVENTION 
     The features of the invention are adapted to be embodied in an internal combustion engine comprised of a cylinder head member adapted to be affixed in closing relation with at least one cylinder bore to form a variable volume combustion chamber with a piston reciprocating in the cylinder bore. At least one valve is supported for reciprocation in the cylinder head for serving the combustion chamber. A camshaft is journalled in the cylinder head and a cam cap that is affixed to the cylinder head for operating the valve. A hydraulically operated variable valve actuating mechanism operates the valves from an engine driven shaft and varies the timing and/or lift thereof. A control valve selectively controls the operation of the hydraulically operated variable valve actuating mechanism. The control valve has a spool portion and an operating portion for effecting reciprocation of the spool portion. 
     In accordance with a first feature of the invention, a fitting opening extends through the cam cap and is aligned with a corresponding fitting opening in the cylinder head. The fitting openings have their axes extending perpendicularly to facing and abutting surfaces of the cam cap and the cylinder head. The control valve is disposed in substantial part in the fitting openings with only a small portion of the control valve operating portion extending through an opening in an associated cam cover and outwardly of the area enclosed thereby. 
     In accordance with another feature of the invention, the control valve supplies fluid to and exhausts fluid from the variable valve timing mechanism through a plurality of passages formed in the internal combustion engine. At least one of these passages is formed by a recess formed in facing and abutting surfaces of the cam cap and the cylinder head. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is a cross sectional view taken along the line  1 — 1  of FIG.  2  and through the upper portion of one bank of an internal combustion engine constructed in accordance with an embodiment of the invention. 
     FIG. 2 is a top plan view of the cylinder head illustrated in FIG. 1 with the cam cover removed and portions broken away so as to more clearly show the construction. 
     FIG. 3 is a bottom view of the cam cap with the camshafts shown in phantom. 
     FIG. 4 is a further enlarged cross sectional view looking in the same direction and taken along the same plane as FIG.  1  and shows the lubricant flow path from the control valve. 
    
    
     DETAILED DESCRIPTION 
     Referring now in detail to the drawings, an internal combustion engine constructed in accordance with an embodiment of the invention is indicated generally by the reference numeral  11  and is shown only partially. That is, only the cylinder head assembly, indicated generally by the reference numeral  12 , of one bank of a V-type engine is illustrated because the invention deals primarily with the variable valve timing mechanism for the engine. Therefore, where any components of the engine  11  are not illustrated, those skilled in the art will readily understand that the construction may be of any desired or known type. 
     As noted, the engine  11  is of the V-type and for the aforenoted reasons only one cylinder bank is shown. It will be readily apparent to those skilled in the art that the invention can be utilized with engines having other configurations and with any number of cylinders. Also, the engine  11  is primarily intended for use in a vehicle such as an automobile or motorcycle and thus, must have a compact construction. 
     The cylinder head assembly  12  is comprised of a main cylinder head member, indicated generally by the reference numeral  13 , and which is formed from a suitable material such as aluminum or an aluminum alloy. A cam cover  14  is detachably affixed to the cylinder head member  13  in a known manner and encloses a cam chamber  15  in which the valve actuating mechanism, now to be described, is positioned. 
     As may be best seen in FIGS. 1 and 2, there are journalled in the cylinder head assembly  12  a pair of camshafts, each indicated generally by the reference numeral  16 , and one of which forms.an intake camshaft and the other which forms an exhaust camshaft. As seen in FIG. 2, each of these camshafts  16  is provided with a plurality of pairs of cam lobes  17  each associated with a respective cylinder of the engine for operating a respective pair of valves through thimble tappets  18 . In other words, the engine  11  is of the four valve per cylinder type. Although this type of valve actuating mechanism is described, it will be readily apparent to those skilled in the art that other forms of valve actuation and valve layouts can be employed in accordance with the invention. 
     The camshafts  16  and  17  are journal led in the cylinder head assembly  12  and specifically at spaced locations along their length by bearing caps  19  that are disposed between adjacent cam lobes  17  and which are affixed to the main cylinder head member  13  by threaded fasteners  21  in a manner well known in the art. 
     In accordance with the invention, there is further provided adjacent the forward ends of the camshafts  16  a common forward or main bearing cap  22  by which the ends of the cam shafts  16  are journaled in a manner that will be described shortly. This main bearing cap  22  and the cylinder head member  13  have facing surfaces  23  that are held in abutting engagement. This is accomplished by pairs of threaded fasteners at each side comprised of threaded fasteners  24  and  25 . These threaded fasteners  24  and  25  are threaded into appropriate tapped holes formed in the cylinder head member  13 . 
     Between the threaded fasteners  24  and  25 , the main bearing cap member  22  has bearing surfaces  26  that engage bearing surfaces for the camshaft  16 . In a like manner, the cylinder head member  13  is provided with complimentary bearing surfaces  27 . The rotational axes of the camshafts  16  defined by these bearing surfaces  26  and  27  are indicated by the center lines  28 . 
     Although any type of arrangement may be employed for transmitting drive from the engine crankshaft or another shaft or shafts which are rotated in time with the crankshaft, a timing drive, indicated generally by the reference numeral  30  is illustrated as one of many with which the invention can be utilized. This includes an engine shaft driven chain  29  that is entrained around a driven sprocket  31  fixed, in a manner to be described, to the camshaft  16  adjacent the valley between the cylinder banks. 
     This driven sprocket  31  includes a variable valve timing (VVT) mechanism of any suitable, hydraulically operated type so that the relative angular relationship of the camshaft  16  can be adjusted, in a manner to be described shortly. In addition, the sprocket  31  has a sleeve portion  32  which encircles the forward portion of the camshaft  16  and which terminates at its rear end in a driving sprocket  33 . 
     This driving sprocket  33  is contained within the valve chamber  15  and drives a timing chain  34  from which a further sprocket  35  is driven. The sprocket  35  has a cylindrical portion  36  which encircles the remaining camshaft  16  is journaled in the bearing cap  27 . At its forward end, this sprocket cylindrical portion  36  drives a second variable valve timing mechanism  37  by which the timing relationship of the associated camshaft  16  can be varied. In other words, the variable valve timing mechanism in the sprocket  31  drives and controls the timing of the right hand camshaft  16  shown in the figures while the variable valve timing mechanism  37  drives and controls the timing of the remaining of the camshafts  16 . 
     The variable valve timing mechanisms  31  and  37  each are of a type that employ a pair of hydraulic chambers which are selectively pressurized or communicated with a return to the oil reservoir in order to provide the axial shifting necessary to change the relative rotational position of the associated camshaft  16  relative to the engine crankshaft. The actual construction of these variable valve timing mechanisms can be of any known type and the invention deals primarily with the control valves for controlling their operation, indicated generally by the reference numeral  38  and the manner in which hydraulic fluid is delivered to and from these control valves. 
     Each control valve  38  is comprised of a lower valve portion  39  and an upper actuation portion  13 . The valve portion  39  includes a cylindrical sleeve  43  mounted in the cylinder head assembly  12  in a manner to be described and a sliding spool valve element  44 . As has been previously noted, the actuators  41  may be electrical solenoids which actuate the valve elements  44 . 
     Each valve portion  39  is mounted in a pair of aligned bores formed in the cylinder head member  13  and the main cam bearing cap  22 . These bores are indicated by the reference numerals  45  and  46 , respectively. These bores  45  and  46  collectively define a respective axis  47  that extends perpendicularly to a plane, indicated by the dot dash line  50  which passes through the mating surfaces  23  of the bearing cap  22  and cylinder head member  13 . The axes of rotation  28  of the camshafts  16  also lie on this plane. 
     The bores  45  and  46  are spaced low enough in the cylinder head member  13  so that only the upper peripheral edge of the actuating portion  41  extends through openings in the cam cover  14  that are sealed by sealing rings  48 . Thus, a very compact assembly is provided. A terminal end of the valves  38  is disposed externally of the cam cover  14  to receive a suitable electrical connector to transmit the control signals to the solenoid actuator  41 . 
     The oil supply to the control valves  38  will now be described. As is typical, the VVT mechanism contained within the elements  31  and  37  are operated by the lubricant from the engine and hence, an oil supply manifold  49  is crossed drilled through the cylinder head member  13  below the camshaft axes  28 . This communicates in a suitable manner with the engine oil pump, indicated schematically at  51 , through a conduit or conduits which are indicated schematically at  52 . 
     Cross drilled from the cylinder head surface  23  is a pair of supply passages consisting of lower smaller diameter portions  53  and upper larger diameter portions  54  with these upper portions extending to the cylinder head surface  23 . The upper bore portions  54  intersect the bores  45  of the cylinder head member  13  in which the valve sleeve  43  is positioned so as to communicate directly with inlet openings  55  formed in these valve sleeves  43  that cooperate with the lands on the valve spools  44 . This is true only at one side as i.e. the left hand side. The passage  55  at the other side communicates appropriately with the bore portion  54 . Removable oil filters  56  are positioned in recesses  60  formed in the cam bearing cap  22  for ease of servicing. That is, the filters  56  can be removed for cleaning or replacement merely by removing the bearing cap  22 . 
     A pair of passages  57  and  58  is formed along the length of the opposite sides of the valve sleeves  43  and these communicate with passages formed in the manner now to be described. First, there is an upper passage  59  formed by a drilling solely in the bearing cap  22  and this communicates with the bearing surface  26  formed therein and with a circumferential groove formed in the respective sleeve  32  and  36  and camshaft  16 . These grooves are shown in FIG.  2  and are identified by the reference numeral  61 . 
     The remaining passage is formed by a semi cylindrical, grooved passage, indicated by the reference numeral  61  and which is formed in the under surface  23  of the bearing cap  22  by a suitable machining operation, thus avoiding the necessity of drilling. The end of this slot  61  has a reducing diameter curved portion  62  which, in turn, communicates with a vertical passage  63  formed in the cylinder head member  13  and which communicates with the slot  57 . 
     The camshafts  16  each have a pair of longitudinally extending bores  64  and  65  which extend axially there through and communicate in a known manner with the variable valve timing mechanisms in the members  31  and  37 . 
     Not shown is a dump or return passage which is formed in the engine body so as to return oil from the selected one of the chambers back to the oil reservoir of the engine. 
     The control valves  38  are rigidly mounted to the cylinder head assembly and specifically to the bearing caps  22  by the threaded fasteners  24  or  25  and appropriate projections formed on the body of the valve portions  41 . 
     Thus, from the forgoing description it should be readily apparent that the described construction is not only compact but also greatly simplifies the formation of the passages for delivering and returning fluid from the VVT mechanisms and the engine lubricating system or other actuating oil supply. Although the embodiment specifically disclosed varies the valve timing, it should be readily apparent that the invention can also be employed with arrangements for varying the degree of valve lift or in systems where both timing and lift are hydraulically altered. Of course, the foregoing description is that of a preferred embodiment 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.