BACKGROUND OF THE INVENTION
[0001] This invention relates to a camshaft lubricating system for an engine and more particularly
to an improved arrangement for insuring that the camshafts and valve train of an internal
combustion engine will be lubricated immediately upon starting of the engine.
[0002] The criticality of providing adequate lubrication to the moving components of an
internal combustion engine are well known. Even though the desirability of maintaining
adequate lubrication for the engine is well known, there are certain conditions of
engine operation wherein it is difficult if not impossible with present constructions
so as to insure adequate lubrication of the components. For example, when the engine
is running, it is a relatively simple matter to supply lubricant under pressure to
those components which should be lubricated. However, when the engine has been shut
down and then is restarted, there is normally some delay before the lubricant is delivered
to all of the moving components. The more remote the component is from the lubricant
reservoir and the lubricant pump, the more likely this component will not be adequately
lubricated upon initial start up. It is well known that a large proportion of the
wear of the components of the internal combustion engine occurs during start up.
[0003] One area wherein this lubricating problem is particularly acute is the lubrication
system for the valve train, particularly with overhead valve overhead camshaft type
engines. Normally the lubricant is supplied to the bearings and cam lobes and tappets
through a pressure system that delivers the oil to the cam bearings or camshaft frequently
through hollow internal passages in the camshaft. Because of the remote location,
these components can be subject to high wear on initial start up when the oil has
all drained from the cylinder head during long periods of inactivity.
[0004] It is, therefore, a principal object of this invention to provide an improved arrangement
for lubricating the camshafts and valve train of an internal combustion engine.
[0005] It is a further object of this invention to provide a system wherein it is insured
that the valve train or at least major components of it will be immersed in lubricant
even when the engine is not running so as to insure adequate lubricant delivery upon
start up.
[0006] It is a further object of this invention to provide an arrangement for trapping oil
around certain of the valve train components that may accumulate when the engine is
running and then will be available to lubricate these components when the engine is
restarted after shutdown.
SUMMARY OF THE INVENTION
[0007] This invention is adapted to be embodied in a cylinder head arrangement for an internal
combustion engine having first and second camshafts journaled for rotation relative
to the cylinder head for operating poppet valves reciprocating in the cylinder head.
Means are provided for delivering lubricant to the cylinder head for lubricating the
camshafts. In accordance with the invention, means are provided for forming a lubricant
dam to trap and retain a volume of lubricant in contact with the camshaft and at least
partially submerging the camshaft when the means for delivering lubricant ceases to
deliver lubricant due to stopping of the engine.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008]
Figure 1 is a cross-sectional view taken through the cylinder head of an internal
combustion engine constructed in accordance with an embodiment of the invention and
is taken generally along the line 1-1 of Figure 2.
Figure 2 is a top plan view of a portion of the cylinder head with the cam cover removed
and a portion broken away to more clearly show the construction.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION
[0009] Referring now in detail to the drawings, an internal combustion engine constructed
in accordance with an embodiment of the invention is shown partially and is identified
generally by the reference numeral 11. Since the invention deals primarily with the
valve train and lubricating system for it, only this portion of the engine has been
illustrated. The remaining components of the engine may be considered to be conventional
or those which are well known to those skilled in the art.
[0010] The engine 11 includes a cylinder block 12 that has one or more cylinder bore 13.
In the illustrated embodiment, the cylinder block 12 is disposed so that the cylinder
bores 13 are inclined to the vertical as in conjunction with a slanted engine or one
cylinder bank of a V type engine. Although the invention has particular utility in
conjunction with engines wherein the cylinder bores are so oriented. The invention
may also be employed in conjunction with engines having vertically aligned cylinder
bores, as will become apparent to those skilled in the art. In the illustrated embodiment
the engine 11 is slanted toward the front of an associated vehicle as indicated by
the arrow Fr.
[0011] Pistons 14 are slidably supported within the cylinder bores 13 and are connected
by means of connecting rods (not shown) to a camshaft in a well known manner.
[0012] A cylinder head assembly, indicated generally by the reference numeral 15 is affixed
to the cylinder block 12 in any known manner and is formed with individual recesses
16 that cooperate with each of the cylinder bores 13 and pistons 14 to form a combustion
chamber of any desired configuration.
[0013] The cylinder head assembly 15 includes a main cylinder head casting 17 in which the
recesses 16 are formed and which slidably support a plurality of intake valves 18.
In the illustrated embodiment, there are provided three intake valves per cylinder
bore 13. In addition, on generally the opposite side of the cylinder head 17 there
are slidably supported two exhaust valves 19. The intake valve 18 and exhaust valves
19 may be disposed in an orientation as shown and described in United States Letters
Patent 4,660,529, entitled "Four Cycle Engine", issued April 28, 1987 in the name
of Masaaki Yoshikawa and assigned to the Assignee of this application. It is to be
understood, however, that the invention may be employed with engines having other
numbers of intake and exhaust valves per cylinder.
[0014] The intake valves 18 have valve stems 21 that are slidably supported in guides 22
that are pressed into the cylinder head casting 17 and which control the flow of an
intake charge from a suitable charge former (not shown) through one or more intake
passageways 23 into the combustion chamber formed by the recess 16.
[0015] In a like manner, the exhaust valves 19 have stem portions 24 that are slidably supported
within guides 25 and which control the discharge of exhaust gases from the combustion
chamber 16 to the atmosphere through exhaust ports 25 and an appropriate exhaust system
(not shown).
[0016] The intake valves 18 are each surrounded by coil compression springs 26 that act
against the cylinder head casting 17 and a keeper retainer assembly 27 for urging
the intake valves 18 to their closed position. The intake valves 18 are opened by
means of an actuating mechanism, to be described, which includes thimble tappets 28
that are slidably supported within bores 29 formed in the cylinder head casting 17
and which cooperate with the tips of the valve stems 21 in a known manner.
[0017] In a similar manner, the exhaust valves 19 are urged to their closed position by
means of coil compression springs 31 that encircle their stems 24 and which act against
keeper retained assemblies 32 and the cylinder head casting 17 for urging the exhaust
valves 19 to their closed positions. Thimble tappets 33 are slidably supported in
bores 34 formed in the cylinder head casting 17 for opening the exhaust valves 19
in a manner which will be described.
[0018] An intake camshaft 35 is supported within the cylinder head assembly 15 and has individual
cam lobes 36, 37 and 38 which cooperate with the respective thimble tappets 28 associated
with each of the intake valves 21 of the respective cylinder bore 13. Bearing surfaces
are formed on the intake camshaft 35 between the cam lobes 36, 37 and 38 and bearing
assemblies 39 and 41 cooperate with these bearing surfaces so as to rotatably journal
the intake camshaft 35 in the cylinder head assembly 15.
[0019] The bearing assemblies 39 and 41 are formed respectively by bearing surfaces 42 and
43 formed integrally with the cylinder head casting 17 and with bearing caps 44 and
45 that are affixed to the cylinder head casting 17 by means of studs 46 and nuts
47.
[0020] In accordance with conventional practice, oil passages may be formed in the cylinder
head for delivering oil to the interior of the camshaft 35 where it is delivered to
the bearing assemblies 39 and 41 through cross drilled holes for lubrication of these
bearing assemblies. In addition, the lubricant will flow to lubricate the cam lobes,
36, 37 and 38 in a manner to be described.
[0021] It should be noted that the cylinder head casting 17 is provided with a construction
for forming an oil well 48 and associated with the cam lobes 36, 37 and 38 of each
cylinder. These wells 48 are formed by means of upstanding walls 49 formed integrally
with the cylinder head casting 17 and which cooperate with a wall 51 formed by the
bearing caps 44 and 45 so that the bearing caps 44 and 45 and wall 51 form a unitary
assembly. Lubricant will fill within the wells 48 to a level indicated by the line
52 when the engine is running so as to trap lubricant in the area of the cam lobes
36, 37 and 38 and tappets 28 for their lubrication. This oil is delivered from leakage
from the bearing assemblies 39 and 41 and will accumulate during engine running, as
aforenoted. Additional oil supplied during running will drain over the top of the
walls 51 and can be returned back to the lubricant sump through the normal return
drains in the cylinder head 17 (not shown)>
[0022] It will be seen that the cam lobes 36, 37 and 38 rotate through an arc indicated
by the line 53 in Figure 1 which will successively immerse and remove the cam lobes
36, 37 and 38 from this lubricant. In addition to providing lubrication when the engine
is running, when the engine is shut down, the wells 48 will trap lubricant. This trapped
lubricant will insure lubrication of not only the cam lobes 36, 37 and 38 and tappets
28 on start up, but also the bearing surfaces of the camshaft since it should be readily
apparent that they also are immersed.
[0023] An exhaust camshaft, indicated generally by the reference numeral 54 is journaled
within the cylinder head assembly 15 in a manner to be described and has pairs of
cam lobes 55 and 56 that cooperate with the thimble tappets 33 associated with the
exhaust valves 19 for opening these exhaust valves. The exhaust camshaft 54 is journaled
by individual bearing assemblies, indicated generally by the reference numeral 57
which cooperate with bearing surfaces formed between the individual cam lobes 55 and
56. These bearing assemblies include a bearing surface 58 formed integrally by the
cylinder head casting 17 and a bearing cap 59 that is affixed to the cylinder head
casting 17 by means of studs 61 and nuts 62. Since there is only one bearing assembly
57 associated with each cylinder of the exhaust camshaft 54 while there are two bearing
assemblies 39 and 41 with the intake camshaft 35 associated with each cylinder, the
studs 61 and nuts 62 are made of a larger diameter than the studs 46 and nuts 47 associated
with the intake camshaft 35 so as to insure good hold down relationship.
[0024] The valve assembly now described is contained within a cam tower recess 63 formed
by the cylinder head assembly and which is closed by means of a cam cover 64 that
is affixed to the cylinder head casting 17 in a known manner. The inclined configuration
of the cylinder head assembly 15 also forms a well 65 that is in proximity to the
bearings 59 and cam lobes 55 and 56 and in which lubricant which is delivered to the
camshaft bearing surfaces through the bearing assembly 59 can accumulate to a level
shown by the line 66 in Figure 1. Therefore, like the wells associated with the intake
camshaft tappets and bearing surfaces, lubricant will accumulate during running and
also will be maintained in this area when the engine is shut down so as to insure
immediate lubrication when the engine is restarted.
[0025] It is to be understood that the foregoing description is that of a preferred embodiment
of the invention 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.
1. A cylinder head arrangement for an internal combustion engine having first and
second camshafts journaled for rotation relative to said cylinder head for operating
poppet valves reciprocating in said cylinder head, means for delivering lubricant
to said cylinder head for lubricating said camshafts, and means for forming a lubricant
dam to trap and retain a volume of lubricant in contact with said camshafts and at
least partially submerging said camshafts when said means for delivering lubricant
ceases to deliver lubricant.
2. A cylinder head arrangement as set forth in claim 1 wherein a separate dam is formed
for each of the camshafts.
3. A cylinder head arrangement as set forth in claim 2 wherein the dams are formed
at least in part by integral walls of the cylinder head.
4. A cylinder head arrangement as set forth in claim 1 wherein the cylinder head is
disposed in an inclined relationship.
5. A cylinder head arrangement as set forth in claim 4 wherein the well associated
with one of the camshafts is formed in part by a peripheral surface of the cylinder
head assembly and the well associated with the other of the camshafts is formed at
least in part by a central upstanding wall of the cylinder head assembly.
6. A cylinder head arrangement as set forth in claim 5 wherein the camshafts are journaled
by bearing caps and the bearing caps associated with the other of the camshafts have
areas further defining the wells.
7. A cylinder head arrangement as set forth in claim 1 wherein the camshafts are journaled
on the cylinder head assembly by bearing caps.
8. A cylinder head arrangement as set forth in claim 7 wherein there are more bearing
caps associated with one of the camshafts than with the other of the camshafts.
9. A cylinder head arrangement as set forth in claim 8 wherein treaded fastening means
affix the bearing caps to the cylinder heads and wherein the threaded fastening means
associated with the camshaft having the greater number of bearings have a smaller
diameter.