Abstract:
The present invention is related to a valve lifter for use in an internal combustion engine. The valve lifter comprises a body adapted to be reciprocally slidable within a valve lifter bore of an engine. The valve lifter includes a rotably mounted cam roller engaging the cam lobe of a cam-shaft where the cam lobe operates to drive the valve lifter body towards a valve open position. The valve lifter may also include an auxiliary roller rotatably mounted in the valve lifter body and engaging the cam roller where the force from the cam lobe is transferred to the lifter body through both the cam roller and auxiliary roller. The present invention includes a method of making a valve lifter by creating grooves in the walls of the recess to aid in the lubrication of the rollers.

Description:
RELATED APPLICATION  
       [0001]    The present application is a non-provisional application claiming the benefit of U.S. Provisional Application, Ser. No. 60/355,719 entitled VALVE LIFTER, filed in the United States Patent and Trademark Office on Feb. 7, 2002. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to high performance racing engines and more particularly, to an improved valve lifter for such racing engines.  
         BACKGROUND OF THE INVENTION  
         [0003]    Conventional camshaft internal combustion engines typically utilize valve lifters, push rods and valve springs along with rocker arms to open and close the valves of the engine to allow air and fuel to enter and exhaust to exit the cylinders of the engine during combustion. The valve lifter with a pushrod includes a cam roller, which rides on the lobes of a camshaft, which is rotated by the crankshaft. In typical roller type valve lifters, the force generated as the cam lobe drives the roller and associate valve lifter body to its valve opening position, is transferred to the valve lifter body through a pin that mounts the roller to the valve lifter body. The entire force imparted on the lifter body during reciprocation of the valve lifter is borne by the bearing and associated pin. As the lifter reciprocates up and down, the push rod seated in the lifter also reciprocates and transfers this up and down motion via a rocker arm to either an intake or exhaust valve.  
           [0004]    During the up stroke of the piston in the cylinder, the intake valve opens to allow fuel and air to enter the combustion chamber. Somewhere near the very top of the up stroke, both the intake and the exhaust valves close and the spark plug creates a spark to ignite the air-fuel mixture which is under compression by the piston. This results in a high temperature explosion which forces the piston downward, called the “power stroke,” thereby translating this movement via a connection rod to rotate the crankshaft which, in turn, translates this angular motion to the wheels of the vehicle via a set of gears. Near the bottom of the compression stroke, the exhaust valve opens to expel the burnt fuel mixture out of the cylinder. After the piston changes directions and begins the up stroke, the exhaust valve continues to remain open thereby forcing any remaining the spent gases out of the cylinder. However, during this same time, the intake valve begins to open to recharge the cylinder with fuel. It is not until the piston has started to travel upward that the exhaust valve closes. Thus, at various times during the compression cycle, both the intake and exhaust valves will be open and closed at the same time. The timing of the opening and closing of the valves is controlled by the physical design of the oval shaped lobes on the camshaft. As the valve lifter is pushed upward by the lobe of the camshaft, the valve lifter pushes the pushrod up which drives the rocker arm downward, causing the valve to open. Likewise, as the lifter and pushrod travel downward, the rocker arm raises and the valve closes due to the biasing action of the valve spring.  
           [0005]    In the operation of high-speed engines, measured as revolutions per minute (RPM), the valve train components are under extreme stress and high temperatures. This causes high frictional forces to be imparted on the cam roller via the cam lobe of the camshaft. Overall cam roller wear is a function of engine speed. High performance engines such as those used in drag racing applications produce extremely high engine speeds (6,000 to 13,000 RPM) over a short duration of time (i.e. less than 5 to 12 seconds). At these high engine speeds, it becomes difficult for the cam roller, pin and the associated bearings to withstand the stress of the engine and, therefore, subsequently fail. Cam rollers and associated pin often fail prematurely in racing situations due to this excessive force causing the valve lifter to be replaced between successive races. Therefore, there is a need for a valve lifter design that can withstand the stress of high performance engines used under racing conditions.  
           [0006]    In addition, inadequate oiling of the bearings will also result in excessive wear and may lead to failure of the bearings, and consequently failure of the valve lifter. A known approach to oiling the bearings is to provide oil feed bevels in the body of the valve lifter that houses the roller. This oil feed bevel allows oil to flow into the distal end of the valve lifter towards the shaft and bearings. While this method attempts to provide oil to the cam roller bearing, oil may not be present in this area or may be directed away from the shaft and bearing due to the rotation of the cam. Therefore, there is a need for a valve lifter design which improves the oiling of the cam roller bearings to prevent premature failure of the cam roller, especially in racing engines where high RPMs are obtained.  
         SUMMARY OF THE INVENTION  
         [0007]    The present invention relates to a valve lifter for an internal combustion engine, particularly for use in high performance in racing applications. The valve lifter includes a body adapted to be reciprocally slidable within a valve lifter bore forming part of the engine. The valve lifter also includes a cam roller and an auxiliary roller rotatably mounted in the lifter body. The cam roller engages the cam lobe of the cam-shaft for driving valve lifter body to open the associated valve. The auxiliary roller is mounted in the lifter body and engages the cam roller is such manner that the force of the cam lobe on the cam roller is transferred to both the cam roller and auxiliary roller such that neither roller bares the total force of the cam lobe individually.  
           [0008]    In a preferred embodiment, the cam roller and auxiliary roller are secured in the lifter body by pins. These pins allow the force from the cam lobe to be transferred from the rollers to the valve lifter body to open the associated valve.  
           [0009]    In another embodiment of the present invention, the valve lifter body includes a recess to house the cam roller. This recess includes grooves in the walls of the recess to allow oil to be directed into the recess. Oil is needed in this area of the lifter body to lubricate the bearings of the cam roller. In addition, an auxiliary roller can be included in the upper portion of the recess. The auxiliary roller is in rolling engagement with the cam roller. The grooves in the recess wall allow oil to be introduced to the upper region of the recess, which, in turn, allows the bearings of the auxiliary roller to be lubricated. This lubrication feature increases the life of the valve lifter.  
           [0010]    The present invention is also directed to a method of milling the recess of a valve lifter such that grooves remain on the walls of the recess for lubricating the bearings of the rollers. The method involves drilling holes in the body of the lifter where the recess is to be formed. A milling cutter is used to create the recess. The milling cutter does not mill to the outer edges of the holes, thus, upon completion grooves will remain at the four corners of the recess. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0011]    [0011]FIG. 1 is a perspective view of a valve lifter constructed in accordance with the preferred embodiment of the present invention.  
         [0012]    [0012]FIG. 2 is a fragmentary view, partially in section of a valve lifter constructed in accordance with the preferred embodiment of the invention shown in an operative position within an engine;  
         [0013]    [0013]FIG. 3 illustrates the positioning of, and force transfer between, rollers forming part of the valve lifter shown in FIG. 1;  
         [0014]    [0014]FIG. 4 shows an alternate positioning for the rollers shown in FIG. 3;  
         [0015]    [0015]FIG. 5 is a cross-sectional view of the valve lifter shown in FIG. 1, with the cam roller and auxiliary roller in their perspective positions;  
         [0016]    [0016]FIG. 6 is a cross-sectional view of the lifter body of FIG. 1, taken along line  6 — 6  of FIG. 5 with the auxiliary roller in the elevated position;  
         [0017]    [0017]FIG. 7 is a cross-sectional view of the lifter body of FIG. 1, taken along line  7 — 7  of FIG. 5 with the cam roller in the elevated position;  
         [0018]    [0018]FIG. 8 is an end view of a lifter body blank illustrating certain machining steps that are used to form the lifter body; and  
         [0019]    [0019]FIG. 9 is a cutaway view, partially in cross-section of the lifter body shown in FIG. 5, with the cam roller and auxiliary roller removed.  
     
    
     DETAILED DESCRIPTION  
       [0020]    [0020]FIGS. 1 and 2 illustrate the overall construction and use of a valve lifter  10  constructed in accordance with the preferred embodiment in the invention. The disclosed valve lifter  10  is especially suited for engine applications where high forces are encountered in opening the intake and exhaust valves. In particular, the disclosed valve lifter is especially useful in an overhead valve engine of the type that utilizes push rods for opening poppet-type intake and exhaust valves and valve springs for returning the valves to their closed positions. Generally the high forces referred to are encountered in competition engines used in drag racing and in particular to engines used in “top fueler competitions”. These engines utilize special fuels and superchargers to generate substantial horsepower for short intervals of time whereby vehicles are propelled from a stand still to speeds in excess of 300 mph in four or five seconds.  
         [0021]    As seen in FIGS. 1 and 2, the valve lifter  10  is mounted for reciprocating movement in a bore  14 , which is typically defined by an engine block  16 . As is conventional, the valve lifter  10  is driven generally upwardly to its valve opening position by a cam lobe  18   a , which forms part of a conventional cam shaft  18 . The valve lifter is urged downwardly, i.e., towards the cam shaft by valve springs (not shown) associated with each valve (not shown) which return the intake and exhaust valves to their closed positions.  
         [0022]    Each valve lifter  10  includes a cam roller  20  rotatably mounted at least partially within a valve lifter body  22 . Preferably, a set of needle bearing  24  rotatably supports the cam roller  20  on a fixed shaft  26  having ends secured in bores  28  forming part of the valve lifter body  22 . Optionally, the valve lifter  10  may incorporate an auxiliary roller  30  also positioned within recess  22   a.    
         [0023]    As seen best in FIG. 2, the cam roller  20  rides on an associated cam lobe  18   a  and the illustrated lifter  10  would be considered a “roller” type lifter. In conventional roller lifters, the force generated as the cam lobe drives the roller and associated valve lifter body to its valve opening position, is transferred to the valve lifter body through the pin that mounts the roller to the valve lifter body. The entire force is therefore borne by the bearing and associated pin.  
         [0024]    According to the invention, the valve opening force generated by the cam is partially transferred to the valve lifter body  22  by an auxiliary roller  30  which is also rotatably connected to the valve lifter body  22  by an associated pin  32  and needle bearing  34 . The pin  32  is rotatably held in associated bores  29  formed in the lifter body  22 . Again as seen best in FIG. 2, the auxiliary roller  30  is an operative contact and in rolling engagement with the cam roller  20 . As a result, the valve opening force generated cam lobe  18   a  as it drives the valve lifter  10  towards the valve opening position, is jointly transferred to the valve lifter body  22  by the roller pins  26 ,  32 . As a result, the valve opening force is distributed between the pins  26 ,  32  and no one pin or associated needle bearing bears all of the load.  
         [0025]    The proportion of the total valve opening force which is borne by the pins  26 ,  32  is determined in some part by the relative size of the rollers and the positioning of the roller support pins  26 ,  32 .  
         [0026]    The valve lifter body  22  includes a recess  22   a  in which the auxiliary roller  30  and a portion of the cam roller  20  are located. As is conventional, the upper part of the valve lifter body  22  includes a socket  40  for receiving the lower end of a push rod  44 . The socket  40  includes a relatively small bore  40   a  by which oil is conveyed to the socket  40  for providing lubrication to the associated rod  44 . In some designs, the push rods include a longitudinal oiling passage by which oil is delivered to the valve train (i.e. rocket shaft, rocker arm, and valve stems) located in the head of the engine.  
         [0027]    The disclosed valve lifter body  22  also includes an ear  22   b  to which a conventional anti-rotation bar (not shown) is attached. In general, an anti-rotation bar is attached to the ears of adjacent valve lifter and prevent the valve lifters from rotating within their associated bore and ensure that the cam roller  20  remains aligned with the cam lobe  18   a.    
         [0028]    [0028]FIG. 3 illustrates the relationship between the cam and auxiliary rollers  20 ,  30  and the cam force. In general, the cam lobe  18   a  contacts the cam roller  20  at a point on the cam roller  20  that is offset with respect to a center line  50  going through the centers of the shafts  26 ,  32 . As a result, the force exerted on the roller  20  by the cam lobe  18   a  has both a vertical and horizontal component (as viewed in FIG. 3). In other words, the vector of the force exerted on the cam roller  20  by the cam lobe  18   a  is not aligned with the longitudinal axis of the push rod  44  (see FIG. 2).  
         [0029]    [0029]FIG. 4 illustrates an alternate positioning of the rollers within the valve lifter body to at least partially compensate for the horizontal component of the valve opening force. In the FIG. 4 arrangement, a center line  56  for the auxiliary roller  30  is offset with respect to the center line  54  defined by the longitudinal axis of the push rod  44  and rotational center of the cam roller  20 . By offsetting the auxiliary roller  30 , some of the horizontal force is transferred to the auxiliary roller  30  and as a result, both the vertical and horizontal components of the valve opening force are shared i.e. split between the pins  26 ,  32 .  
         [0030]    FIGS.  5 - 9  illustrate the design of the lifter body in accordance with the present invention. As is conventional, the lifter body  22  contains a bevel  100  to allow oil to enter the lifter body  22  upon reciprocation. When the valve lifter is in motion, oil is splashed into the lifter, which in turns saturates the cam roller  20  with oil, thereby, oiling the set of needle bearings  24 . According to the present invention, in a preferred embodiment, grooves  110  are cut for the entire length of walls of the recess  22   a . The grooves  110  facilitate the introduction of oil into the recess  22   a . When the auxiliary roller is present, as shown in FIG. 5, the grooves  110  help introduce oil to the bearings  34  of the auxiliary roller  30 . This is best shown in FIGS. 6 and 7.  
         [0031]    The cam roller  20  and auxiliary roller  30  each contain a set of needle bearings  24  and  34 , respectively. The cross-sectional view of FIG. 5 illustrates the positions of the individual bearings when exposed to the grooves  110 . At any given time, two portions of each side of the set of bearings  24  and  34  in the cam roller  20  and the auxiliary roller  30  are exposed to the grooves  110 . These portions occur at opposite position of the same side of the rollers where the grooves are cut in the recess walls  22   c . As shown in FIG. 6 and  7 , recess walls  22   c  cover a portion of the set of bearings  24  and  34  while the uncovered portion is exposed to the grooves  110 . Preferably, in the completely exposed position, half of an individual bearing is covered by the recess walls  22   c  and half of the bearing is exposed to the groove  110 . Exposure to the grooves  110  occurs at only specific points within the recess  22   a . For example, individual bearings located in the 12 and 6 o&#39;clock positions of the auxiliary roller  30  and/or the cam roller  20  of FIG. 5 are covered by the recess walls  22   c  on both sides. When these two individual bearings are rotated to approximately either the 3 or 9 o&#39;clock positions, they are partially covered by the recess walls  22   c  and partially exposed to the grooves  110 . The set of bearings can contain either an even or odd number of individual bearings. In the case where there are an odd number of bearings, when a bearing occupies the 3 o&#39;clock position, the corresponding 9 o&#39;clock position is occupied by a section of two consecutive bearings and the interstitial space between them.  
         [0032]    When the valve lifter is in motion, the cam roller  20  and auxiliary roller, if present, rotates within the recess  22   a . This rotation, consequently, allows each of the individual bearings to be exposed to the grooves  110  and thus lubricated.  
         [0033]    [0033]FIG. 6 illustrates a sectional view of the lifter body  22  as shown from line  6 — 6  of FIG. 5, wherein the auxiliary roller  30  is shown half in elevation and half in a cut-away view. In the preferred embodiment, the grooves  110  are created for the entire length of the recess  22   a . The grooves  110  are created so that there is enough of the recess walls  22   c  between the grooves  110  such that needle bearings  24  and  34  of the auxiliary roller  30  or cam roller  20  in FIG. 7 remain in contact with the recess walls  22   c , thereby, securing the bearings in their relative positions. In a preferred embodiment, a portion of the set of the needle bearings  24  of the cam roller  20  and the needle bearings  34  of the auxiliary roller  30 , if present, are partially exposed in the grooves  110 , as described above. During normal engine operation, oil enters the lifter body  22  through the bevel  100  and travels in the grooves  110  thereby lubricating the roller cam  20 . When an auxiliary roller  30  is present, oil is moved up the grooves  110 , the entire length of the recess  22   a  to the auxiliary cam  30 , thus supplying the necessary lubrication to the needle bearings  34  of the auxiliary cam  30 .  
         [0034]    [0034]FIG. 7 illustrates a sectional view of the lifter body  22  as shown from line  7 — 7  of FIG. 5, wherein the roller cam  20  is elevated. The channels  110  are shown along with the bevel  100 . In a preferred embodiment, two bevels  100  are cut in the lifter body  22  each at opposite corners of the recess  22   a . The two bevels  100  ensure that oil is introduced to the inside of the lifter body  22  without regard to the direction of the roller cam  20  or auxiliary cam&#39;s  30  rotation. Once oil is present in the inside of the lifter body  22 , it can be introduced to the needle bearings  34  of the auxiliary roller  30  via grooves  110 . In addition, the valve lifter according to FIG. 7 can also be constructed to not include the auxiliary roller  30 . In this embodiment, the grooves  110  increase the introduction of oil to the bearings  24  of the cam roller  20 .  
         [0035]    [0035]FIG. 8 is an end view of a cylindrical blank or bar segment that is ultimately machined into the lifter body  22  shown in the other Figures. According to the present invention, the recess  22   a  can be created in any manner in which grooves are left in the walls of the recess  22   a . In the preferred embodiment, holes  110 ′ are drilled at the four corners of the recess  22   a.    
         [0036]    More specifically, the machining steps that may be performed in order to create the recess  22   a  (including sidewalls  22   c ) and the oiling grooves  110  are as follows. Four longitudinal bores  110 ′ are drilled into the cylindrical blank or bar. A drill or end mill is then used to drill a cylindrical bore  111  centrally with respect to the bores  110 ′. The bore  111 , as seen in FIG. 8, is substantially larger than the bores  110 ′ and is preferably slightly less than the spacing between opposite side walls  22   c . As an example, the bores  110 ′ may be 7/32 inches and the bore  111  may be 0.375 inches If an end mill is used to drill the bore  111 , it can then be moved laterally in order to mill out the rectangular recess  22   a . The milling bit mills the center stock of the recess  22   a ; the bit does not mill to the complete outer edge of the four corner holes  110 ′. Since the milling cutter only cuts through a portion of the bores  110 ′, the oiling grooves  110  are thus formed.  
         [0037]    This machining operation produces a recess  22   a  with straight sides  22   c  and small radial corners. It has been found that the holes  110 ′ produce grooves  110  that advantageously introduce lubrication to the needle bearings  24  of the cam roller  20  and needle bearing  34  of the auxiliary cam  30 . The resulting valve lifter body  22  with the recess  22   a  and grooves  110  can be used with either a cam roller or with a cam roller and auxiliary roller. It should be noted that if the bore  111  is machined with a drill, a milling cutter would then be introduced into the bore  111  to perform the milling operation. The same or a different milling cutter may be used to form a slot  113  (see FIG. 1) in which the roller  20  is positioned. As part of the step of milling the slot  113 , the bevels  100  may also be machined.  
         [0038]    [0038]FIG. 9 is a cutaway view of the lifter body  22  showing another view of the channels  110  in relation to the recess  22   a . Also shown are the bevel  100  and bores  28 . The channels  110  preferably run the entire length of the recess  22   a.    
         [0039]    It has been found that valve lifters constructed in accordance with the preferred embodiment of the invention have substantially improved life when used in competition engines of the type described above.  
         [0040]    Although the invention has been described with a certain degree of particularity, it should be understood that those skilled in the art can make various changes to it without departing from the spirit or scope of the invention as hereinafter claimed.