arm and a push rod

The present disclosure is directed to overhead valve engines, and more particularly to valve actuator

subassemblies .

Background

Overhead valve engines are internal combustion engines wherein the intake and exhaust valves are located in the cylinder head while the camshaft is placed in the cylinder block. The valves may be actuated by the camshaft through the intermediation of lifters, push rods and rocker arms, in that order. Lifters, also known as tappets or lash adjusters, can be hydraulic in nature and may serve to maintain zero valve clearance. A hydraulic lifter is able to take up valve train slack due to for example low engine temperatures, wear or incorrect adjustment, thereby reducing or eliminating tappet valve train noise.

Typically, a hydraulic lifter comprises a pressure chamber that is intermittently filled with engine oil from an oil gallery via a small drilling. When a valve associated with the lifter is closed, the lifter is free to fill with oil. When the valve is opening and the lifter is being operated by the camshaft, the oil feed is blocked. The blockage substantially seals the pressure chamber, and the lifter acts much like a solid one would, oil being virtually incompressible .

The push rod and rocker arm may be connected by a spherical joint and quite commonly lubricant is fed to that joint so as to facilitate smooth articulation of those components and to reduce wear. For instance, the rocker arm or push rod may be furnished with a lubricant supply for feeding lubricant to the interfacing surfaces of those components. In a known arrangement, a lubricant channel is formed through the rocker arm and has one opening in fluid communication with a lubricant supply and another opening disposed on or adjacent to the surface of the rocker arm arranged to cooperate with the pushrod.

As noted above, when the pressure chamber is in its sealed state, the virtually incompressible oil therein causes the lifter to behave much like a solid lifter. The effect of this is that the significant forces applied to the push rod and rocker arm by the cam shaft and valve springs, respectively, may also be transmitted through the push rod - rocker arm interface, e.g. a spherical joint. There may be very little clearance at that interface and the lubricant pressure may be insufficient adequately to drive the lubricant between the interfacing surfaces of those components. Consequently, lubricant may adopt a non- uniform flow across the push rod - rocker arm interface which may lead to uneven wear of those parts, thus reducing their life.

The present disclosure is directed, at least in part, to improving or overcoming some aspects of known push rod rocker arm assemblies.

Summary of the Invention

According to one aspect of the disclosure, there is provided a connection member for interconnecting a rocker arm and a push rod, the connection member comprising: a body attachable to one of the rocker arm and the push rod; one of a part-spherical head and a socket defined on the body and co- operable with the other of the part -spherical head and the socket defined on the other of the rocker arm and the push rod; and at least one groove provided on the part -spherical head or socket defined on the body so as to facilitate lubricant flow between said part-spherical head and the socket in use, wherein the part spherical head or socket defined on the body further defines a first contact area configured for cooperation with a corresponding second contact area defined on the other of the part spherical head or socket, the loads transmitted in use through the push rod and connection member being generally transmitted across those contact areas and wherein the or each groove lies substantially outside the first contact area.

Brief Description of the Drawings

Fig. 1 is a perspective view of an exemplary disclosed valve train;

Fig. 2 is a cross-sectional view through part of a first embodiment of the valve train shown in Figure 1;

Fig. 3 is a perspective view of a connection member shown in Figure 2 ;

Fig. 4 is a side view of the rocker arm and a

connection member as shown in Figs 1 and 2;

Fig. 5 is a bottom view of the rocker arm and the connection member as shown in Figs. 1 to 4;

Fig. 6 is a perspective view of the rocker arm and the connection member as shown in Figs 1 to 5 ;

Fig. 7 is a perspective view of a connection member according to a second embodiment of the disclosure; and Fig. 8 is a perspective view of a connection member according to a third embodiment of the disclosure.

Detailed Description

Fig. 1 illustrates an exemplary embodiment of a valve train 10 for use in an overhead valve engine (not shown) . For the purpose of this disclosure, valve train 10 is depicted as a valve train for use in a four-cylinder , four- stroke, inline internal combustion engine, having four valves per cylinder. One skilled in the art will recognize however, that valve train 10 may embody a valve train for use in other types of overhead valve engines with any number of cylinders in any configuration, for example an inline or V-configuration .

Valve train 10 may include a camshaft 11 of a

conventional design, having cam lobes 12. In total, the depicted camshaft 11 features eight cam lobes 12, two for each cylinder of the four-cylinder engine with which valve train 10 may be used. Lifters 13, such as hydraulic tappets, may abut camshaft 11 where cam lobes 12 are provided so that a rotating motion of the camshaft results in a periodical activation of the lifters. Each lifter 13 may support a first end 15 of an elongate push rod 14. A second end 16 of the push rod 14 may normally be in contact with a first end 31 of an associated rocker arm 30. The operable connection between the push rod 14 and the rocker arm 30 is facilitated by a connection member 40 and possibly secured by a push rod retainer 60 (see for more detail Fig 2) . Each rocker arm 30 may be pivotably mounted on a rocker shaft 32 in a conventional manner. An actuation end 33 of each rocker arm 30 - opposite the first end 31 - may mechanically operate a valve 20. In the general arrangement shown in Fig. 1, the actuation end 33 may engage a bridge 21 that may actuate a pair of valves 22. Each valve 22 may be provided on an end of a valve stem 23 that is slidably mounted within a valve stem guide 24. The upper end of a valve stem 23 may be connected to a valve spring 25 to bias the valve 22 towards its closed position, in touch with a valve seat.

Fig. 2 is a cross-sectional view of a rocker arm 30 and push rod 14 interconnected by the connection member 40 provided on the first end 31 of the rocker arm 30. The rocker arm - push rod connection may be provided with a push rod retainer 60 arranged partially to overlie the connection member 40 and the second end 16 of the push rod 14. Connection member 40 may include a shank 41 that may be inserted into a bore 37 provided through the first end 31 of the rocker arm 30. Shank 41 may be substantially cylindrical, though other shapes are conceivable as well. To enable a reliable connection, an upper portion of shank 41 may be provided with an outer thread (see Fig. 3) that may engage an inner thread (not shown) provided on a wall bounding the shank-receiving bore 37 in first end 31. A head 42 may be provided on a top end of the partly threaded shank 41, so as to allow the connection member 40 to be inserted and/or removed much like a screw or bolt.

Furthermore, this screw configuration may enable the position of the connection member 40 to be adjusted relative to the rocker arm 30, which may enable any slack in the valve train to be eliminated or reduced, which is particularly preferable in the absence of hydraulic lash adjusters. To this end, the head 42 may define at least one of an angular circumferential edge for engagement by a spanner and a socket 43 for engagement by a socket head wrench, a screwdriver or the like. In one arrangement, the shank 41 may be press fitted into the bore. In an

alternative arrangement, the connection member 40 may be integral to the rocker arm 30, such that they are cast, forged, machined or otherwise formed as a single item.

Connection member 40 further includes a pivot head 45 provided at a lower end of the shank 41. The pivot head 45 is at least partly spherically shaped and configured to cooperate with a socket 18 defined in the end of the push rod 14. The socket 18 comprises a part-spherical recess sized to receive at least part of the pivot head 45 so as to permit relative articulation between the rocker arm 30 and the push rod 1 . The forces applied by the valve springs 25 and the lifters 13 cause the pivot head 45 of the connection member 40 and the socket 18 at the end of the push rod 14 to engage . The regions on the pivot head 45 and socket 18 that bear the greatest loads are those having a tangential plane lying normal to the direction of those forces and will hereinafter be referred to as the contact areas 46.

Rocker shaft 32, rocker arm 30 and connection member 40 are all provided with passages to facilitate the delivery of lubricant, such as oil, to the pivot head 45. The connection member 40 has a lubricant channel 47 extending from an exit hole 48 in the centre of the contact area 46 and terminating blindly near the head 42. An annular recess 49 may be provided on the connection member 40, just below the head 42, and which may communicate with the blind end of the lubricant channel 47 via a radial drilling 50. The annular recess 49 may be configured to locate within the bore 37 of the rocker arm 30 and to communicate fluidly with the passage 36 in the rocker arm 30 regardless of the relative positions of the connection member 40 and the rocker arm 30. This configuration of passages may enable the effective delivery of lubricant to the exit hole 48 for lubricating the contact area 46 between pivot head 45 and the socket 18 of the push rod 14. The instantaneous contact region between the pivot head 45 and the socket 18 may vary as the relative orientation of the connection member 40 and push rod 14 varies. As such, the size of the contact area 46 may be sufficiently large to encompass the instantaneous contact regions of the pivot head 45 and socket 18 for all anticipated orientations of those components. The lubricant channels 36,35,47 may be arranged in their respective host members 30,32,40 such that a pressurized flow of lubricant may be effected from the rocker shaft 32 to the exit hole 48 during operation of valve train 10. There may be some delay after engine start, possibly about 30 seconds, before a constant supply of oil flows to the exit hole 48 and in which period reliance may be placed on any residual lubricant retained in the socket 18 of the push rod 14. The shank 41 of the connection member 40 may further define a constriction 52 for carrying the retainer 60 mentioned above. The constriction 52 may be provided in between a substantially square shoulder 53 and the pivot head 45. A tapering transition 54 between the rear annular face of the pivot head 45 and the constriction 52 may be concave and smooth.

Briefly, the retainer 60 may comprise a generally tubular base section 61 and four tapered projections 62 extending upwardly and inwardly from an upper edge 63 of the tubular base section 61. The four projections 62 are spaced equidistantly around the upper edge 63 and each may have a curved inside edge 64 having a point of curvature lying on the axis of the tubular base section 61.

Collectively, the curved inside edges 64 of the four projections 62 may define a segmented collar sized to locate around the constriction 52 while the tubular base section 61 may define an interior space to accommodate the pivot head 45 and the second end 16 of the push rod furnished with the socket 18. As such, the size and shape of the projections 62 and the tubular base section 61 may determine the size and shape of the segmented collar and interior space and therefore those parameters may be selected according to the characteristics of the push rod 14 and connection member 40 to which the retainer 60 is to be fitted.

With reference now to Figures 3 to 6, the pivot head 45 is provided with one or more groove 55 to promote the dispersion of lubricant between the part spherical surface of the pivot head 45 and the socket 18 of the push rod 14. The grooves 55 extend from the periphery of the contact area 46 towards a peripheral edge 56 of the pivot head 45, or at least to a free portion of the pivot head not generally disposed in use within the socket 18 of the push rod 14. In the particular arrangement shown in Figures 3 to 6, the grooves extend all the way to the periphery of the pivot head 45 so as to define indentations in the annular rear face of the pivot head. As such, the grooves 55 are in fluid communication with a low pressure region and thus define a low pressure path outside the contact area 46 to assist lubricant flow outwardly from the periphery of the contact area. Due to the little clearance B2012/050928

-12- between the pivot head 45 and the socket 18 inside the

contact area 46, the pressure of lubricant flowing

therethrough remains relatively high so as to create a film for bearing the loads transmitted through those components, much like a hydrodynamic bearing. Despite that high

pressure, the lubricant flow can be maintained due to the relatively small size of the contact area 46 and more

particularly, the pressure relief provided by the grooves 55.

The or each groove 55 may extend rectilinearly and or radially from the periphery of contact area 46 so as to define the shortest path to a free portion of the pivot head 45. The grooves 55 may also be spaced equidistant ly around the pivot head so as to provide equally accessible flow paths for lubricant disposed at any point in the

contact area 46 so as to promote a substantially uniform flow. In this embodiment there are five grooves, but the number of grooves may be selected according to the

characteristics of the valve train assembly: a greater

number of grooves 55 may increase the lubricant flow

between the components whereas a lesser number of grooves may increase the surface area so as better to distribute the load. 120S0928

-13-

The depth and or width of each groove 55 may increase away from the exit hole 48 so as to increase the cross- sectional area of the flow path. This may further reduce the pressure of the lubricant as it flows towards the outer end of the groove 55, thus causing it to spill over the peripheral lip defining the socket 18 of the push rod 14 and drain into the cast orifices (not shown) in the

cylinder head and engine block before returning to the

sump. In the absence of any such pressure relief features, jets of lubricant may squirt from the outer ends of the grooves and flood the engine breather with oil.

Figure 7 shows a second embodiment of the disclosure which is very similar to the first embodiment described above and as such like features have been accorded like reference numerals. The connection member 80 may be

provided with a shank 41, a pivot head 45 and a

constriction 52 disposed between those features. Grooves 55 are provided in the pivot head 45 and extend from the lower periphery of the constriction 52 defining a free

portion and the periphery of the contact area 46 located at the tip of the pivot head. The connection member may be connectable or integral to a rocker arm (not shown in

Figure 7) . As before, the socket 18 is part spherical and provided at the second end 16 of a push rod 81. In this arrangement, a lubricant channel 82 may extend

longitudinally through the push rod and have an exit hole 83 substantially in the centre of the socket. An annular contact area 84 is defined around the exit hole 83 in the socket 18 and which corresponds substantially to the contact area 46 defined by the grooves 55 on the pivot head . A further embodiment of the disclosure is illustrated in Figure 8. In this arrangement the connection member 100 is disposed on the upper end 101 of a push rod 102 and defines a socket 103 having grooves 104 that may be spaced uniformly therearound. The grooves 104 may extend from the periphery of the socket 103 inwardly towards the periphery of a contact area 105 defined substantially in the centre of the socket 103.

A portion 110 of the rocker arm is furnished with a pivot head 111 and a lubricant channel 112 having an exit hole 113 at the centre of the pivot head 111. A notional contact area may be defined around the exit hole 113 for cooperation with the contact area 105 defined on the socket 103. These contact areas may work in much the same way as those of the previous embodiments in that most of the loads transmitted in use through the push rod and rocker arm are likely to be transmitted across those contact areas and as such there is very little clearance between the surfaces defining those contact areas. Lubricant expelled through the exit hole may be dispersed across the contact areas to create a high pressure load bearing film. The grooves at least partially relieve the pressure of the lubricant at the peripheries of the contact areas as those grooves may provide flow paths to a low pressure zone not enclosed by the surfaces of the pivot head and the socket .

Industrial Applicability

The connection member is first attached to the rocker arm or push rod, if it is not integral to one of those components. The retainer 60 may be mounted to the

component furnished with the pivot head by presenting its curved edges 64 to the pivot head and moving those

components towards each other. As more force is applied, the increasing circumference of the spherically shaped pivot head temporarily urges the four projections 62 outward so as to enlarge the size of the segmented collar. When the segmented collar has become sufficiently large, the pivot head may pass fully therethrough and the projections 62 should rapidly return to their initial position so as to snap the retainer 60 in place. The constriction 52 behind the pivot head may limit relative axial and lateral movement of the retainer 60 while the tubular base section 61 may limit relative lateral movement of the push rod and the rocker arm. The components of the valve train may then be assembled in an appropriate manner.

During normal operation of the valve train 10, the camshaft 11 with the cam lobes 12 may rotate, which in turn may cause the lifters 13 reciprocally to move the push rods up and down. As a push rod moves up, the first end 31 of the associated rocker arm 30 may move up accordingly, and may cause the rocker arm to pivot around the rocker shaft 32. The pivoting motion of the rocker arm 30 may be such that the actuation end 33 of the rocker arm may move downward, pressing on the valve stem 23, against the action of the valve spring 25, to displace the valve 22 from its valve seat . As the push rod may move down again due to the continuing rotational motion of the cam lobe 12 that lifted it, the upward force on the push rod 14 may be relieved and the valve spring 25 may force the rocker arm 30 back into its starting position, thereby closing the valve. Thus, the valve train 10 may operate normally with push rod 14 reciprocally positioned between the lifter 13 and the first end 31 of rocker arm 30.

Meanwhile, a reasonably constant supply of lubricant, typically oil, is directed through the lubricant channel 47,82,112 and out through the exit hole 48,83,113 which is associated with the connection member 40,80,100 or another component (push rod or rocker arm) which cooperates with the connection member. The lubricant flows between the respective surfaces of the pivot head 45, 111 and socket 18, 103 and is initially under relatively high pressure while it flows over the contact areas 46,84,105. This results in the creation of a load bearing film that serves to reduce the wear on the interfacing surfaces. At the periphery of the contact areas much of the lubricant passes along the grooves 55,104 and outwardly towards a free area on the pivot head 45,111 or socket 18,103. The increasing cross-sectional area of the grooves 55, 104 causes a pressure drop in the lubricant as it flows further from the contact areas.

It will be apparent to those having ordinary skill in the art that various modifications can be made to the grooves 55,104 in the push rod 14,102,81 or rocker arm 30 - in particular the connection member 40,80,100 thereof - as disclosed herein. Other embodiments will be apparent to those having ordinary skill in the art from consideration of the specification. For instance, the connection member may comprise a socket provided with grooves and adapted for attachment to the rocker arm. It is intended that the specification and examples are considered as exemplary only. Other aspects, features and advantages will be apparent upon an examination of the attached drawings and appended claims.