An oil capacitor insert and an engine including such an oil capacitor insert

Abstract: An engine oil capacitor which allows a larger volume of oil to be used in an internal combustion engine without reducing fuel economy or increasing engine package size. Oil flow through the normal oil drainback holes (34) is partially restricted, resulting in a substantial quantity of oil being temporarily stored in the camshaft compartment (32), during engine operation.

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates generally to internal combustion engines, and more particularly to an engine oil capacitor which allows for a higher ratio of oil volume to engine volume. BACKGROUND OF THE INVENTION In an internal combustion engine, a supply of engine lubricant, such as petroleum oil, is provided in an oil pan at the bottom of the engine. During operation of the engine, a pump is used to carry the oil from the pan up into the working portions of the engine in order to lubricate the engine's moving parts. As oil is continuously supplied to these moving parts, excess oil drains back to the oil pan through various paths by the operation of gravity. In this way, oil is continuously circulated through the engine while it is operating. Referring to FIG. 1, there is illustrated a camshaft compartment of a prior art internal combustion engine, the camshaft compartment being indicated generally at 10. The compartment 10 includes end walls 12 and 24, as well as dividing walls 14-22. Each of the walls 12-24 includes a respective cam journal 26 formed therethrough. A camshaft 28 (shown in phantom in FIG. 2) is rotatably supported by the cam journals 26. Oil is supplied by the engine oil pump to the camshaft 28 in order to lubricate the camshaft 28 as it rotates in the cam journals 26. During this process, oil is continuously drained off of the camshaft 28 into the bottom of the compartment 10. This excess oil must be drained back into the oil pan so that it may once again be pumped into the lubrication circuit. The compartment 10 includes a plurality of large drainback holes 30 which allow the excess oil to drain back to the oil pan. As best illustrated in FIG. 2, the walls 14, 18 and 22 do not extend all the way to the bottom of the compartment 10, thereby forming three separate chambers 19, 21 and 23, each chamber having two drainback holes 30. Because the drainback holes 30 are large enough to allow a significant quantity of oil to pass therethrough, no appreciable quantity of oil remains in the compartment 10 during engine operation. All excess oil is immediately returned to the oil pan. Consumers who purchase internal combustion engines desire engines which contain a large volume of oil. The larger the oil volume, the longer the drain interval between required oil changes, and therefore the engine exhibits lower maintenance costs. The longer drain interval results from a lower duty cycle for each particular oil molecule when the total quantity of oil molecules is increased. However, if the oil pan is simply filled with more oil, the fuel economy of the engine is lowered. This results from the fact that the oil pan is situated immediately below the engine crankshaft. As the level of oil in the pan is increased, the rotating crankshaft interacts with the oil, causing drag on the crankshaft and windage losses which lower the efficiency of the engine. It is not feasible to provide a larger oil volume by simply increasing the size of the oil pan. This is because consumers also desire a small engine package size. In the past, therefore, engine designers have been forced to make trade-offs between oil volume, fuel economy and package size. Such trade-offs have been thought to be necessary when more oil is required, but more oil can't be added to the pan and the pan can't be made larger. There has therefore been a need in the prior art for a way to increase engine oil volume without lowering engine fuel economy or increasing engine package size. The present invention is directed toward meeting this need. DE-A-4,105,529 discloses an internal combustion engine having an intermediate reservoir which has one outlet line at its bottom which leads back to the oil sump and an overflow line which exits the intermediate reservoir at a location which is higher than the exit to the outlet line. The quantity of oil being discharged through the outlet line whilst the engine is running is smaller than that introduced into the intermediate reservoir. Hence the lubrication system stores oil in the intermediate reservoir as well as in the sump whilst the engine is running so that the volume of oil in the system can be larger than is usual. The oil in the intermediate reservoir drains back to the sump when the engine is turned off. DE-A-3,713,849 discloses such an intermediate oil reservoir formed at the top of a cylinder head for a camshaft. This reservoir is provided with a throttled lower outlet and an overflow over the top of the cylinder head at the upper edge of the reservoir. DE-A-2,140,840 and DE-A-2,643,628 both disclose such an intermediate oil reservoir which is a camshaft sump which is formed by an insert which closes the open bottom of a space which is formed in the engine block around the camshaft. The former is provided with overflow ports which are formed in the insert which is a dished plate whereas the latter, DE-A-2,643,628 has overflow ports formed in the engine block. SUMMARY OF THE INVENTION The present invention relates to an engine oil capacitor which allows a larger volume of oil to be used in an internal combustion engine without reducing fuel economy or increasing engine package size. Oil flow through the normal oil drainback holes is partially restricted, resulting in a substantial quantity of oil being temporarily stored in an engine compartment, such as the camshaft compartment, during engine operation. According to this invention there is provided an internal engine according to claim 1. Preferred features are claimed in the sub-claims. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a prior art camshaft compartment. FIG. 2 is a cross-sectional view of the prior art camshaft compartment of FIG. 1 FIG. 3 is a front perspective view of a first embodiment of the present invention. FIG. 4 is a rear perspective view of the first embodiment of the present invention. FIG. 5 is a cross-sectional view of a camshaft compartment including the first embodiment of the present invention. FIG. 6 is a perspective view of a second embodiment of the present invention. FIG. 7 is a front perspective view of a third embodiment of the present invention. FIG. 8 is a rear perspective view of the third embodiment of the present invention. FIG. 9 is a perspective view of a fourth embodiment of the present invention. FIG. 10 is a graph of brake specific fuel consumption versus engine oil level. DESCRIPTION OF THE PREFERRED EMBODIMENT For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the protection claimed in the claims is thereby intended, such alterations and further modifications in the illustrated device being contemplated as come within the protection claimed in the claims. The present invention allows for an increased quantity of oil to be used in an engine without increasing engine package size or reducing fuel economy. The present invention accomplishes this by changing the design of an upper engine compartment, such as the camshaft compartment, so that a significant quantity of oil is held in the camshaft compartment during engine operation. When the engine is started and oil is circulated by the oil pump, the camshaft compartment is filled with oil. When the oil in the camshaft compartment reaches a desired steady state level, excess oil is drained back to the oil pan. The present invention is therefore analogous to the charging of a capacitor in an electronic circuit. In one embodiment, a quantity of oil is retained in the camshaft compartment after engine shut down in order to prelubricate the camshaft at the next engine start. A first embodiment of the present invention is illustrated in FIGS. 3-5, and indicated generally at 84. The insert 84 allows for oil storage in the camshaft compartment without alteration of the existing block casting. The insert 84 mounts to the drainback holes 30 of the prior art camshaft compartment 10, by means of the integral tangs 86. The insert 84 mounts to the drainback holes 30 from inside the camshaft compartment 10, with the tangs 86 extending through the drainback holes 30 and gripping the opposite side of the wall in which the drainback holes 30 are formed. When the insert 84 is installed in the drainback hole 30, substantially all of the drainback hole 30 is obstructed. The insert 84 includes a small drainback hole 88 formed therethrough, but the rate at which oil drains through the hole 88 is much less than the rate at which oil is supplied to the camshaft compartment 10. Therefore, oil will accumulate in the camshaft compartment 10 until the oil level reaches the top 90 of the spill-over stack 92. At this level, the oil will spill over the edge 90 in a weir action. Referring now to FIG. 4, the insert 84 is shown from the opposite side. The oil flowing over the edge 90 exits the chute 94 through the drainback hole 30 and is drained back to the oil pan. The insert 84 includes a circumferential groove 96 into which is mounted an appropriate seal (not shown) in order to seal the insert 84 against the wall in which the drainback hole 30 is formed. Referring to FIG. 4, the inserts 84 are illustrated installed into the prior art camshaft compartment 10. It can be seen that the oil will rise to the level 98 during engine operation. The position of the level 98 is determined by the height of the stacks 92 of the inserts 84. After engine shut down, the oil will drainback to the oil pan through the small drainback holes 88 formed in the inserts 84. Referring now to FIG. 5, there is illustrated a second embodiment of the present invention, indicated generally at 100. The insert 100 is similar to the insert 84, and provides the same function within the camshaft compartment 10. However, the insert 100 has several features which are different from the insert 84. Like the insert 84, the insert 100 mounts through the drainback hole 30 via integral tangs 102 and thereby blocks the drainback hole 30 from draining oil. The insert 100 also includes a small drain hole 104 for draining the oil from the camshaft compartment 10 after engine shut down. Unlike the insert 84, the insert 100 includes a groove 106 which extends perpendicular to the plane of the drainback hole 30. A seal (not shown) placed within the groove 106 will therefore engage against the transverse surface of the drainback hole 30. Such an engagement of the seal is required in situations where the wall in which drainback hole 30 is formed is not planar, and therefore does not lend itself to engagement with a sealing surface. The insert 100 further includes a stack 108 which includes a T-shaped opening 110. The T-shaped opening 110 facilitates skimming of the oil when the engine is operated on a non-level surface, or if the engine is installed within the vehicle at a large angle from the horizontal. Referring now to FIGS. 7-8, a third embodiment of the present invention is illustrated and indicated generally at 112. The insert 112 is substantially similar to the insert 100 of FIG. 6, and the particular shape of the stack 108 and T-shaped opening 110 are better illustrated in FIG. 7. However, the integral tangs 102 of the insert 100 have been replaced in the insert 112 with a one piece metal clip 114 which is mounted to the insert 112 via a screw 116. The clip 114 is preferably formed from a resilient metal such as spring steel. Referring now to FIG. 9, there is illustrated a fourth embodiment of the present invention, indicated generally at 118. The insert 118 is substantially similar to the insert 112, with the exception that the spring clip 114 is mounted to the insert 118 via a molded post 120. The molded post 120 is formed from the same material as the remainder of the insert 118, which is preferably plastic, and is designed to have an interference fit with the mounting hole of the spring clip 114. Referring now to FIG. 10 there is illustrated experimental data which relates brake specific fuel consumption in an internal combustion engine with the level of oil in the oil pan, at various engine speeds. In order to obtain the data of FIG. 16 the oil level in the oil pan of the engine was measured ten minutes after engine shut down. It will be readily appreciated by those skilled in the art that the oil level has a marked influence on the amount of fuel consumption in an internal combustion engine. Particularly, at high engine speeds the parasitic loss from the interaction between the crankshaft and the engine oil in the oil pan is quite large. It will therefore be appreciated that use of the engine oil capacitor concept of the present invention will allow a significant quantity of oil (1-2 gallons) to be removed from the oil pan during engine operation and temporarily stored in the camshaft compartment. The removal of this quantity of oil from the oil pan during engine operation allows for an increased volume of oil to be used in the engine, thereby extending drain intervals, without the need to increase the size of the oil pan and without reducing fuel economy. Thus, for any particular existing engine design, an amount of oil equal to the amount of oil which can be stored in the camshaft compartment can be added to the oil pan without increasing the interaction between the crankshaft and the oil in the oil pan. It will be appreciated by those skilled in the art that, although the above embodiments of the present invention provide for oil storage in the camshaft compartment, such oil storage may be affected in any non-sump engine compartment. The principles of the present invention, as described hereinabove, may be applied to affect oil storage in any engine compartment by one having ordinary skill in the art following the teachings herein. While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the protection claimed by the claims are desired to be protected.

Claims: An oil capacitor insert (84,100,112,118) adapted to engage an oil drainback hole (30) formed in a wall of an engine compartment (10,32,42,48), said oil capacitor, insert (84,100,112,118) comprising: a body member having an opening therein; and at least one retention member (86,102,114) coupled to the body member, wherein the retention member (86,102,114) is operative to engage the wall such that the oil drainback hole (30) is filled in by the body member; characterised by a stack (92,108) coupled to the body member, the stack (92,108) having a stack opening (110) at a top surface (90) thereof and a hollow interior channel (94) coupling the stack opening (110) to the body member opening for fluid flow therebetween; wherein the stack opening (110) is at a level above a bottom of the oil drainback hole (30) when the oil capacitor insert (84,100,112,118) is engaged with the oil drainback hole (30), such that oil supplied to the engine compartment (10,32,42,48) accumulates therein until the oil reaches the level (90) of the stack opening (110) and flows through the interior channel (94) and through the oil drainback hole (30). An engine compartment (10,32,42,48) including at least one insert (84,100,112,118) according to claim 1, wherein the engine compartment (10,32,42,48) comprises a camshaft compartment. An engine including at least one insert (84,100,112,118) according to claim 1, further comprising: a secondary oil drainback hole (88,104) formed in the body member at a second level; wherein the stack opening level (90) is higher than the second level such that a quantity of oil is stored in the engine compartment (10,32,42,48) when the oil is at the stack opening level (90); and wherein a first flow capacity of the stack opening (110) is greater than a second flow capacity of the secondary oil drainback hole (88,104); and wherein the oil is supplied to the engine compartment (10,32,42,48) at a flow rate which is less than a combined first flow capacity of all said inserts (84,100,112,118) and greater than a combined second flow capacity of all said inserts (84,100,112,118). An insert (84,100,112,118) according to claim 1, wherein the at least one retention member comprises at least one tang (86,102) integrally formed with the body member. An insert (84,100,112,118) according to claim 1, wherein the at least one retention member comprises a spring steel clip (114). An insert (84,100,112,118) according to claim 1, wherein the stack opening is substantially rectangular. An insert (84,100,112,118) according to claim 1, wherein the stack opening (110) is substantially T-shaped. An engine according to claim 3, wherein the second level is substantially at a bottom of the body member, such that substantially no oil is stored in the engine compartment (10,32,42,48) when the oil is at the second level. An insert (84,100,112,118) according to claim 1, further comprising: a groove (96,106) formed in the body member; and a seal placed in the groove (96,108), wherein the seal engages the wall such that substantially no oil may flow past the seal.

Inventors: GUSTAFSON RICHARD J, HINDERLEIDER MARK B, LEONARD JAY F, GUSTAFSON, RICHARD J., HINDERLEIDER, MARK B., LEONARD, JAY F.
Applicants: CUMMINS ENGINE CO INC, CUMMINS ENGINE COMPANY, INC.
Application year: 1996
Main classification: F01M11
IPC codes: F01L1, F02F1, F01M11, F01M9