US 2989954 A
Description (OCR text may contain errors)
June 27, 1961 HULBERT 2,989,954
INTERNAL-COMBUSTION ENGINE Filed Sept. 21, 1959 Sheets Sneak TORQU 1.1 I
l G MIN.
TORQUE 61 I 9 k 62 i 66 g 6] I I Q 30 a T0 SUHP E 65 so I n TO BEARINGS 3| FIG.3.
INVENTOR. EDWARD A.HULBERT ATTORN EY United States Patent 2,989,954 INTERNAL-COMBUSTION ENGINE Edward A. Hulbert, Grosse Pointe, Mich., assignor to Continental Motors Corporation, Muskegon, Mich., a corporation of Virginia Filed Sept. 21, 1959, Ser. No. 841,145 Claims. (Cl. 12'3--'48) My invention relates to internal combustion engines and more particularly to an engine adapted for compression ignition and having a variable compression means facilitating engine operation on various types of fuels including medium octane gasoline.
The present invention is of particular value for, but not restricted to, engines used in military vehicles in which the engines must be of low bulk and weight since the engine compartment must be protected with heavy armor plate. Each extra cubic foot of engine bulk results in a large increase in total vehicle weight which in turn requires greater engine power in order to provide the requisite maneuverability. This increases fuel consumption and to carry sufficient fuel to provide the necessary vehicle range means still greater vehicle bulk and weight.
Heretofore, it has been the practice to use spark ignition engines for combat vehicles, partially because of their lower bulk and weight. The need for low fuelconsumption to increase vehicle range and to reduce logistical fuel requirements has led to increasing use of high economy compression ignition engines. However, conventional engines of this type are unsuitable for such use because of excessive bulk and weight and limitations on the attainment of high performance. Thus a need exists for a high performance, high economy engine for various applications.
The principal factor which limits the attainment of high performance in a compression ignition engine is the extremely high gas pressure developed in the cylinders on the firing stroke. Peak gas pressure is often more than twice as high as for a spark ignition engine of equivalent power, and the extremely high rate of pressure rise produces an impact effect which aggravates the destructive influence of high pressure on the engine structure.
For combat vehicles, it is highly desirable also that the engine operate on a wide variety of fuels including gasoline of medium octane which is available in greater abundance than other petroleum fuels. However, when gasoline is used in a compression ignition engine, the peak gas pressures and rate of pressure rise are still higher than with conventional compressionignition fuels.
One object of my invention is to facilitate cold weather starting of engines, particularly of the compression ignition type, by providing a means for varying the compression ratio of the engine.
Another object of the invention is to provide for more stable and smoother operation of engines at light loads by providing a means of automatically varying compression ratio in response to engine torque changes.
A further object of the invention is to reduce stresses and loads on the component parts of an engine when operated at high output by providing an improved variable compression means.
Yet another object of the invention is to facilitate construction of a high output multi-fuel engine having light weight and low bulk and yet provide long life under severe service conditions by utilizing an improved variable compression means actuated by automatically regulated changes in oil pressure.
Still another object of the invention is to provide an improved variable compression means for engines by uti-' lizing an eccentric piston wrist pin-to-connecting rod conice nection operated by a hydraulic actuating means carried entirely by the connecting rod.
A still further object of the invention is to provide a simplified variable compression means for engines by constructing an integrally formed connecting rod and hydraulic actuating means operable to vary the piston-tocrankshaft dimension while maintaining constant stroke.
For a more complete understanding of the invention, reference may be had to the accompanying drawings illustrating a preferred embodiment of the invention in which like reference characters refer to like parts throughout the several views and in which:
FIG. 1 is a fragmentary cross-sectional View of an engine crankshaft, piston and connecting rod assembly incorporating a preferred hydraulic means embodying the invention.
FIG. 2 is a fragmentary cross-sectional view taken substantially on the line 22 of FIG. 1.
FIG. 3 is a diagrammatic cross-sectional view of a preferred fluid pressure regulating system, and
FIG. 4 is a fragmentary cross-sectional view taken substantially on the line 44 of FIG. 2.
In FIGS. 1 and 2, a portion of an internal combustion engine crankshaft 10 is illustrated as having a crank 11 and as carried by a bearing assembly 12. A connecting rod 13 is rotatably carried by the crank 11 and supports a piston 14 having a wrist pin 15. Y
The piston-to-crank distance is adjustable by means of an eccentric element 16 rotatably carried by the connecting rod 13 on an axis A and rotatably supporting the piston wrist pin 15 on an axis B. The eccentric element 16 has a pair of arms 17 and 18 to which are respectively secured a pair of rods 19 and 20, preferably by means of universal joint connections 21. The rods 19 and 20 are actuated by plungers 22 and 23 respectively, being connected thereto preferably by means of universal joint connections 24. A stop element 28 is preferably mounted on the connecting rod 13 to limit movement of the arms 17 and 18.
The plungers 22 and 23 respectively reciprocate in single acting hydraulic cylinders 25 and 26 which are integrally formed with the connecting rod and whichare inclined outwardly as shown to facilitate drilling and reaming the cylinder bores. In operation, fluid pressure is directed to one and vented from the other of the cylinders 25 and 26, and to actuate the eccentric 16, shifting the position of the piston wrist pin axis B to alter the effective piston-to-crank dimension, thus varying the compression ratio of the engine. It will be seen that in the position shown in FIGS. 1 and 2, the plunger 22 is retracted and the plunger 23 extended, such that the piston 14 is at its lowest point, giving a relatively low compression ratio for normal engine operation. For starting and idling, however, fluid pressure will be directed to the cylinder 25 while cylinder 26 is vented, causing the plunger 22 to extend and plunger 23 to retract. The eccentric arm 17 will then be in the illustrated dotted line position, and the piston wrist pin axis will be raised or extended relative to the crank a distance of about /3 inch, which preferably eifects an increase in compression ratio, in the present case, from about 15 to 21. The long stroke of the pistons will be found to give adequate leverage against operating forces acting on the piston 14 tending to alter the position of the eccentric 16, and will be further assisted by the operation of a check valve hereinafter described.
Fluid pressure may be directed to the cylinders 25 and 26 by a hydraulic system such as the oil pressure system of the engine. In the preferred embodiment of the system, an oil pump 30, as indicated in FIG. 3, supplies oil under pressure through suitable passages 31 to the bearing 12, shown in FIG. 1, from whence it flows 3. through passages 32 provided in the crankshaft to a chamber 33 in the crank 11. The oil then passes through passages 34, at least one of which will register during rotation 'of the crankll with an arcuate' groove 35 'pro'- vided on the inner surface of a connecting'rod bearing 36"op'posite'"the shank of the connecting rod'. The oil will thuspas's through radial passages 37 through the bearin'gi36 to an annular groove 38in the connecting the passage 39 and operates against the compressionof springs 46 and 47 disposed in the shuttle valve 45'and tending to move the shuttle valve 45 to the position 'of FIG. 4. When oil pressure overcomes the spri'ngs'46' and '47, the shuttle valve 45 takes the position shownin FIG. 1. passage40 through a non return check valve 50 into a passage 51 and to anelongated annulargr'oo've 52' provided on the periphery of the shuttle valve 45, from which it is directed through a passage 53 to the cylinder 25. Apassage' 54 connected to the other cylinder 26 is'op'enly connected through the chamber 44 to vent openings 55 to relieve the pressure from the cylinder 26. This position of the shuttle valve thus gives the'higher compression ratio, the eccentric being moved to the position indicated by the dotted arm 17 position.
When oil pressure is lower, the springs 46 and 47 will movefthe shuttle valve 45 to the position of FIG. 4 in which the passage 54 leading to the cylinder 26-is registered'with the annular groove 52 of the valve 45, and oil pressure from the other cylinder 25'is vented throughthe other end of the distributing chamber 44 out vent ports 56 and 57. It will be noted that since the shuttle valve 45 is finely balanced between oil and spring pressure, its axis must be parallel to the axis of the piston wrist pin in order to prevent oscillating and reciprocating inertia losses of'the connecting rod 13 from biasing the shuttle valve 45 in either direction.
It will beapparent that the present system preferably requires two distinct oil pressures to provide for two distinct positions of the piston 14. The two oil pressures areprovided by utilizing a pressure regulating means as shown in FIG. 3, in which'the opening of a bypass passage 60connected with 'oil pressure passage 31 and vented to the engine sump is selectively regulated by means of a regulating valve 61, said regulating valve 61 having a cylindrical cavity 65 in which is inserted a compression spring'66, the' upper end of which reacts against a cup shaped piston 67 slidably mounted in cavity 65 of valve 61. A push rod 62 presses downwardon piston 67 and is actuated by a cam 63'provided on a fuel'control lever 64.' The fuel control lever 64 is actuated by any'desired linkage from conventional throttle controls and through a rotatableshaft 64A operatesthe enginefuel metering' valve (not shown) from the minimum torque position represented by the position of the lever 64 shown in solid to'th e maximum torque position represented by the dotted line position of the lever 64. In the minimum torque positionythat is; when the engine is" idling or being started, the spring 66 urges the valve '67 toward a closed position so that a relatively higher oil pressure is-neededto open the valve 61,- and the higher oil pressure-will-be directed to the shuttle valve mechanism 41,
in which case the force of the shuttle valve'springs'46': and!47--is overcomeand the oil pressure directedto the cylinder 25 to produce"the"higher compression'ratid as described previously.
In the maximum torque position of the lever 64, the
Oil under pressure will then flow from the spring 66 is lessercompressed and exerts a lower force on valve 61, venting more of the pumped oil to the sump so that the oil pressure reaching the shuttle valve mechanism is lower than the force of the shuttle valve springs 46 and 47, and the-oil'pressure is; directed-to the cylinder 26 to produce thelower compression ratio. I
The cam 63 is preferably contoured with 'ai'sharply sloping curve as shown so that the oil pressure change will be relatively rapid on moving the'fuel control lever 64 and can be effected at a desired intermediate stage between minimum and maximum lever torque positions.
It will also be noted that the use of the check valve 50betw'een passages 40 and 41 serves to lock the plunger 2 2'or 23 to which oil pressure is directed'in its upper'position; and in factinertia forces acting on-the piston and connecting rod' will be assisted by thecheck valve 50 when tending to actuate the piston 14 to its regulated position and opposed by the check valve 50" when tending to actuate the piston 14 out of the'actuat'ed position.
Although I 'have described only one preferred embodi ment of my invention, it will be apparent to one skilled in the ar'ttowhich the invention pertains that various changes and modifications maybe made therein without departing from the spirit of the invention or'the scope of the appended claims.
I claim: 7 p v 1. A variable compression means for an internal corn bustiori engine having a crankshaft, pistons each having a wrist pin, connecting rods respectively operably connecting said piston wrist pins to said crankshaft, and a fluid pressure system, said variable compression means comprising an adjusting means carried by each connecting rod andfoperable to vary the efliective crankshaft-to-piston dimension whereby to vary the compression ratioof said engine while retaining constant piston stroke, hydraulic means actuating said adjusting means and operated by said fluid pressure means in response to variations in pressurether'eof, and means regulating fluid pressure relative to engine torque, said connecting rod having an eccentric element rotatably carriedon' said piston wrist pin, said hydraulic means being connected with said eccentric element and being operable to rotate said eccentric to thereby vary thecrankshaft-to-piston dimension, said hydraulic means comprising a hydraulic cylinder carried by' said connecting rod, a plunger reciprocable in said cylinder and operably connected with said eccentric ele'rfierit'to rot-ate same, means connecting saidhydra'ulic cylinder with said fluid pressure means and having a valve" operable to-control fluid pressure flow to and from' bustion engine having a crankshaft, pistons each having a wrist pin, connecting rods respectively operably' connecting'jsaid pi'ston wrist pins to said crankshaft, and a fluid pressure system, said variable compression means comprising an adjusting means carried by each connecting rod and operable to vary the 'etfectivecrank shaft-t piston'dimension'whereby tovary the compression ratio of""said=engine"'while retaining constant piston stroke, hydraulic means actuating 'saidadjustin'g means and'operated by' said-"fluid pressure means in response tovar'iations 'in' pressure thereof, and means regulating fluid pres sure relative to engine torque,*said"connecting rod having an eccentric element rotatably carried on said piston wrist pin*,'-sa'id hydraulic'meansbeingconnected with said eccentric elementand being operable torotate'said ec-' centric to thereby vary the crankshaft-to-piston dimension, said hydraulic means comprising a pair of hydraulic cylinders carried by said connecting rod, a single action actuating plunger reciprocable in each hydraulic cylinder, said actuating plungers being operably connected to opposite sides of said eccentric element to rotate same in opposite directions, means connecting said hydraulic cylinders with said fluid pressure means and having a valve operable to control fluid pressure to and from said cylinders.
5. A variable compression means for an internal combustion engine having a crankshaft, pistons each having a wrist pin, connecting rods respectively operably connecting said piston wrist pins to said crankshaft, and a fluid pressure system, said variable compression means comprising an adjusting means carried by each connecting rod and operable to vary the effective crankshaft-topiston dimension whereby to vary the compression ratio of said engine while actuating constant piston stroke, hydraulic means actuating said adjusting means and operated by said fluid pressure means, said connecting rod having an eccentric element rotatably carried on said piston wrist pin, said hydraulic means comprising a hydraulic cylinder, an actuating plunger therein connected with said eccentric and operable to rotate said eccentric to thereby vary the crankshaft-to-piston dimension, said hydraulic means including fluid pressure passages in said connecting rod and connecting said hydraulic cylinder with said fluid pressure means, and a valve carried by said connecting rod and operable to control fluid pressure flow to and from said hydraulic cylinder.
6. The variable compression means as defined in claim 5 and having check valve means in said fluid pressure passages operable to trap fluid in said hydraulic cylinder to lock said engine piston in adjusted position against unfavorable inertia forces of said engine piston during operation.
7. The variable compression means as defined in claim 5 and in which said hydraulic cylinder is integrally formed with said connecting rod.
8. The variable compression means as defined in claim 7 and in which said hydraulic cylinder is inclined outwardly with respect to the axis of said connecting rod to facilitate easy boring of the inside of said hydraulic cylinder.
9. The variable compression means as defined in claim 5 and in which said valve comprises a casing integrally formed with said connecting rod and in which said hydraulic cylinder is integrally formed with said connecting rod.
10. The variable compression means as defined in claim 5 and in which said valve is disposed parallel to said wrist pin whereby motion of said valve is not biased by reciprocation and oscillation of said connecting rod.
References Cited in the file of this patent UNITED STATES PATENTS 2,120,012 Andreau June 7, 1938 2,134,995 Anderson Nov. 1, 1938 2,152,811 Michell Apr. 4, 1939 2,153,691 Hironaka Apr. 11, 1939 2,427,668 Gill Sept. 23, 1947 2,883,974 Heising Apr. 28, 1959