US2554336A - Variable compression ratio internal-combustion engine - Google Patents

Description

May 22, 1951 H. J. KRATZER VARIABLE COMPRESSION RATIO INTERNAL-COMBUSTION ENGINE 2 Sheet s-Sheet 1 Filed April 25, 1947 IN V EN TOR.

V R r K m I a T r T m A 5 m H? Y B H. J. KRATZER May 22, 1951 VARIABLE COMPRESSION RATIO INTERNAL-COMBUSTION ENGINE 2 Sheets-Sheet 2 Filed April 25, 1947 m. R mm H m m mJ 0 ELM Patented May 22, 1951 VARIABLE COMPRESSION RATIO IN TERNAL-CQMBUSTION ENGINE Herbert J. Kratzer, St. Louis, Mo.

Application April 25, 1947, Serial No. 743,751

4 C a ms.

The invention relates to internal combustion engines and more particularly to variable compression ratio engines of the kind described in Patent No. 2,399,276, issued April 30, 1946 to the present applicant.

The engine described in the above patent has a movable head to vary the cylinder volume for the more efficient combustion of fuel of approximately a given octane rating, and the compression ratio is varied automatically throughout a single range of head movement to compensate for different throttling effects. Different throttling may be due to manual throttling, decreased air density at higher altitudes, or throttling incidental to high engine speed. Any of these throttling effects starve the cylinders, i. e., results in the fuel charge being insufficient for an eflicient compression pressure. I The main object of the present invention is to. vary the operative ranges of compression ratios of a variable compression ratio engine to economically employ fuels of different octane ratings under the operating conditions mentioned above and, in addition, to compensate for temperature changes.

Another object is to readily vary the operative range of compression ratios by a conveniently located manual control.

Another object is to employ combustion chamber pressures to directly and automatically vary the combustion chamber volume of respective cylinders within a given range so that the combustion chamber volume approximately corresponds to the instant volumetric efliciency of the refueling operation.

, Another object is to provide the engine with simple means to adjust the combustion cham ber volume of each individual cylinder, inde pendently of the other cylinders, to compensate for manufacturing variations, carbon deposits, wear or other factors producing unequal combustion chamber performance.

Another object is to automatically select a predetermined minimum compression ratio for the duration of the engine starting operation.

Another object is to maintain all engine spark plug electrodes at the desired temperature during all operations, except at starting, of the engine by immersing the plug porcelains in an insulating coolant fluid, such as oil from the engine crank case, and to maintain this coolant fluid at a temperature sufficient to boil on condensation products and thus recondition the fluid and preserve its dielectric properties.

Another object is toposition the spark plugs 2 between the intake and exhaust valves and substantially centrally of the combustionchambers, irrespective of the prevailing compression ratio, to provide for reliable ignition and minimum flame travel.

Another object is to provide for the reliable ignition of economical fuel mixtures due to a minimum degree of new charge dilution with hot residual combustion chamber gases espe[-. cially at idle and light torque loads.

Another object is to cause turbulence within the combustion chambers to insure thorough mixing of the combustion chamber gases before ignition and to increase flame speed after ignition.

Another object is to cause turbulence during flow of combustion chamber gases to cylinder bores after ignition to facilitate combustion of the gases early in the expansion stroke.

These and other objects will be apparent to those skilled in the art from the following'description and accompanying drawings, in which:

Figure l is a plan view of an internal combustion engine constructed according to the invention.

Figures 2 and 3 are detail vertical transverse sections drawn to enlarged scale and taken approximately on the lines 22 and respectively, of Figure 1.

Figure 4 is a detail horizontal section taken approximately on the line 4- of Figure 3.

An internal combustion engine constructed according to the invention comprises a plurality of working cylinders I such as may be formed, for example, in a single block Ia. Each cylinder has a reciprocating piston 2 connected by a rod 3 to the engine crankshaft (not shown). A conventional intake valve ll and adjacent exhaust valve 5 are associated with each cylinder I.

A cylinder head 8 is mounted on block la and forms a water jacket with outer side walls 9. A vertical cylindrical bore IE3 through the head is above and partially overlaps each working cylinder I but is offset towards its associated valves 4 and 5. Slidable in each here is an inverted head piston I l. The bottom face of head 8 is recessed over valves 4 andfi to form pockets 4a and 5a (Figure 4). The bottom face of head piston II is recessed to form a pocket Ila. Pockets la, 5a and ilcr form the major portion of the cylinder combustion chamber 1, the walls of which converge towards the rem e side of he ork y nd r to form,

a restricted passageway Ia into the cylinder and, as so shaped, increase turbulence thereby promoting more complete combustion as early in the expansion stroke as possible.

Each head piston II is connected by a link I2 and pin I3 to a rocker arm I5 keyed to shaft I6 journalled in bearings I! on head 8. One rocker arm I5 has an extension it provided at its free end with an adjustable pin I9 engaging a saddle on the upper end of a helical coil spring 2| seated in the bottom of a hollow inverted piston 22 slidably in a spring cylinder 23 at the side of cylinder head 3. Preferably spring cylinder 23 is mounted on a bracket 24 including side walls and forming a pocket 33 for the purpose explained below.

During normal engine operation, the positions of head pistons II are determined'by the sum of l the pressures in all working cylinders I and by the thrust of compression spring 2| which resists and balances the working cylinder pressures. With small crankshaft torques, the sum of the pressures in working cylinders I is relatively small permitting spring 2| to move head pistons downwardly in cylindrical bores Ill and decrease the combustion chamber volume to provide higher compression ratios, At large crankshaft torques, the sum of the pressures in working cylinders is relatively large so that head pistons I move upwardly while compressing spring 2| and provide lower compression ratios due to the enlarged combustion chambers. This automatic determination of compression ratios provides for the optimum compression ratio at any prevailing speedtorque output of engine and compensates for barometric variations.

Oil from the crankcase is pumped through conduits 25, 25a in a block' 21, into spring cylinder 23 below spring piston 22 and piston 22 is raised from the solid line position shown inFigure 2 to other positions as indicated by the broken lines in Figure 2. The lower end of spring 2| is raised and its tension is increased, whereby head pistons II move downwardly in cylindrical bores l0 against the prevailing working cylinder pressures and decrease the volume of the combustion chambers to increase the compression ratios. The position of spring piston 22 in spring cylinder 23 is determined by a valve sleeve 26 slidably mounted in block 21 and extending upwardly into spring cylinder 23 and into a dome-shaped portion 28 of spring piston 22. The upper end of valve sleeve 26 is slotted at 30. Valve sleeve 26 may be raised or lowered relative to spring piston. 22 by an arm 29 pivoted in block 21 and link connected to valve sleeve 26. Spring piston 22 automatically moves to a position in spring cylinder 23 at the.

upper end of valve sleeve 26 and uncovers the lower portions of slots 3|] so that excess oil pumped into spring cylinder 23 escapes through slots 30 and flows through the interior of valve sleeve 26 into a cavity 21a in block 21 and through a conduit 3| to the crankcase.

Spring cylinder 23 has ports 32 in its upper.

sides so that oil leaking past spring piston 22 is returned to the crankcase through pocket 33, drain 34, cavity 21a and conduit 3|.

The most economical compression ratio for a particular fuel, irrespective of its octane rating, is the highest compression ratio which provides for smooth engine operation without knocking as evidenced by audible pinging. The engine may be economically adapted to fuel of any octane rating by operating lever 29 manually,

preferably from the dash of the car, to provide 4. maximum tension of spring 2| without causing the engine to knock.

For fuels of low octane rating, spring piston 22 is lowered in spring cylinder 23 and the tension of spring 2| is decreased to operate the engine in a range of decreased compression ratios. For fuels of high octane rating, spring piston 22 is raised in spring cylinder 23 and the spring tension is increased to operate the engine in a range of increased compression ratios.

A rib 43 on head 8 engages an adjustable screw 44 at the end of an extension 42 rigid with one of the rocker arms I5 and limits downward movement of head pistons and provides a maximum desired compression ratio for combustion chambers I. An adjustable stop Mi supported by a bracket 4| attached to head 8 engages the end of extension 42 and limits upward movement of head pistons I and provides a minimum desired compression ratio for combustion chambers I. In the event spring 2| breaks, the engine'would continue to function as a conventional engine at the minimum compression ratio. The maximum and minimum compression ratio stops preferably are adjusted to provide for a plurality of ranges of normal operating compression ratios for fuels of various octane ratings.

When the ignition circuit is opened and the engine is stopped, a plug valve 35 is moved to open position by an arm 35a, as shown by the solid lines in Figure 2, to quickly drain oil from spring cylinder 23 below spring piston 22 through conduit 25a, cavity 21a and conduit 3| to the crankcase, whereupon spring piston 22 moves rapidly to the solid line position shown in Figure 2, head pistons move downwardly until screw 44 engages stop 43, and spring 2| extends sub stantially to its free length.

During starting of the engine, when the crank shaft is being turned slowly by the starter, and

before anycyclic firing, only compression pressures contract spring 2| which offers but little II which move approximately midway between maximum and minimum combustion chamber volumes as determined by stops 4|! and 43. Initial ignition in combustion chambers I increases the sum of the combustion chamber pressures sufficiently to move headpistons upwardly to their maximum combustion chamber volume. After the motor operates through a few revolutions, intake manifold pressures and resulting combustion chamber pressuresdecrease, whereupon head pistons are moved downwardly by spring 2| approximately midway between maximum and minimum combustion chamber volumes. spring piston 22 is raised in spring cylinder 23 by oil under pressure from the engine lubricating system until slots 30 in valve sleeve 26 are uncovered. Displacement of spring 2| moves head pistons downwardly decreasing the combustion chamber volume until the spring tension is balanced by the sum of the cylinderpressures- With further operation of the engine,

other workingv cylinders. The volume of a compression chamber 1 may be decreased by loosening the nut on eye bolt [4 and tightening the nut on eye bolt Ma to shift element i511 aboutshaft l6 relative to.- keyed element 150; whereby head piston II is moved downwardly a short distance in head bore it. The nuts on eye bolts 14 and Ma then may be locked to retain head piston H in adjusted position.

Another of the arms l has an integral extension 50 provided with a bifurcated free end connected to one end of a link 5| by a pin 5Ia. The opposite end of link 5| is connected by a pin 5!?) to a dash pot piston 53 slidably mounted in an oil-filled dash pot cylinder 55. Cylinder 55 is attached to head 8 by webs 52. Dash pot piston 53 has a spiral Acme thread-shaped depression 54 about its circumference forming an elongated passageway bypassing the piston, thus enabling gradual movement of the dash pot piston in the dash pot cylinder. A plurality of equally spaced conduits 55 connect respective ends of cylinder 55 through upper and lower ports 51 and 58. Upper ports 5? normally are closed by the skirt portion of a cap 59 mounted rotatably on cylinder 55 and having apertures 5!! through the skirt portion. movable into registry with upper ports 51 to allow oil to flow freely through conduits 5B whenever more rapid adjustment of piston 53 is desired. The dash pot damps intercyclic firing impulses transferred to shaft 16 during normal engine operation so that the algebraic sum of the rapidly changing cylinder pressures will be counterbalanced by spring 2| whereby head pistons II and shaft It will move only when a change in engine torque occurs.

A spring 5! urges cap 59 against stop 62 in which position the cap closes ports 51. The cap may be moved to open said ports temporarily when the starter is actuated or when the throttle is opened quickly. This opening of ports 51 is effected through link 63 which has a rod 64 leading direct to the starter (not shown). Link 63 is connected to the throttle by a dash pot unit including a chamber 55, a piston 65a thrust towards the upper end of the chamber by spring 651) and a rod 650 connected to a lever 66 pivoted on the engine. A rod 66a leads to the throttle (not shown). The pin and slot connections between link 63 and the starter rod and the throttle rod enable the link to be moved by either rod independently of the other. When link 63 is moved from the solid line position shown in Figure 4 to the dotted line position by slow movement of the throttle, oil passes piston 65a and the position of link 63 is not changed. When the throttle is opened rapidly, oil in chamber 65 cannot pass piston 65a rapidly enough and chamber 65 is moved, thus shifting cap 59 to open ports 51 and allow oil in dash pot cylinder 66 to bypass piston 53 through ports 5'! and 58 so that head pistons H respond more rapidly to pressure changes in cylinder I.

The space H between working piston 2 at the top of its stroke and the overlying flat portion of cylinder head 8 preferably is a minimum. During the last part of the compression stroke of a working piston 2, the compressed gases above the piston are finally displaced from between the top of working piston 2 and the overlying portion of cylinder head 8 through passageway 1a into combustion chamber 1 with considerable velocity approximately in the directions indicated by the arrows in Figure 3, causing desirable turbulence of the gases in the combustion chamber to facilitate rapid flame travel from the spark gap through the combustion chamber as the working piston completes its upward compression stroke and starts downwardly on the expansion stroke. As the piston continues to accelerate in itsdownward movement, the ignited charge moves from the combustion chamber through the relatively narrow passageway la into working cylinder l' at an increased velocity. This downwardly directed flow of ignited gas causes further turbulence in the working cylinder and facilitates the continued rapid combustion causing maximum expansion pressure at the time the piston and crankshaft are positioned for maximum conversion of cylinder pressure into turning torque.

A spark plug i3 is threaded into the pocket portion of head piston H between the intake and exhaust valves so that the intake charge cools the spark gap electrodes. Plug '83 is positioned substantially centrally of the combustion chamber. The spark gap eiectrodes of spark plug 13 are maintained substantially at a desired temperature by immersing the plug head in coolant oil contained in head pistons II. The oil prevents hot spots on the portion of head pistons l I forming parts of the combustion chamber walls by convecting heat from these parts to the side walls of head pistons I l for transmission to water jacketed head bores in. The oil is maintained at a temperature sufficiently high to boil oif condensation products and thus reoondition the oil and maintain its dielectric properties to prevent short-circuiting over the plug porcelains. Oil from the crankcase may be circulated continuously through head pistons II as part of the oil filter system for continuously reconditioning the oil. High tension ignition cables [5 connect the immersed spark plugs 13 to the distributor (not shown).

The skirts of pistons ll always extend above the sides of head bores It to prevent oil seeping into combustion chambers 1 when the engine is stopped. A cover (not shown) may be provided for excluding dust and other injurious matter from the mechanism described. A raised rib 45 along the top periphery of head 8 directs spilt oil to drain into pocket 33 to be returned to the crankcase.

The details of the construction may be varied substantially without departing from the spirit of the invention, and the exclusive use of those modifications coming within the scope of the claims is contemplated.

What is claimed is:

1. In an internal combustion engine, a cylinder, a movable wall associated with said cylinder to change its compression ratio in accordance with cylinder pressures, a spring resisting the cylinder pressures and automatically positioning said wall during normal engine operation to determine the compression ratios within a predetermined range, a seat for said spring, hydraulic means to move said seat during engine starting operation to change the pressure of said spring, and manually adjustable means for controlling said hydraulic means to vary the seat position to change the spring pressure and thereby change the operative range of compression ratios.

2. In an internal combustion engine, a cylinder, a movable wall associated with said cylinder to change its compression ratio in accordance with cylinder pressures, a spring resisting the cylinder pressures and automatically positioning said wall during normal engine operation to determine the compression ratios within a predetermined range,

a piston seating said spring, a spring cylinder slidably receiving said piston, a hydraulic device actuated by fluid pressure, supplied by the normal operation of the engine, to move said spring seating piston in said spring cylinder to change the thrust of said spring, said device including a manually actuated positively adjustable ported sleeve control for varying the position of the spring seating piston and thereby varying the operative range of compression ratios.

3. In an internal combustion engine, a plurality of cylinders, a movable wall associated with each cylinder and movable inwardly and outwardly of said cylinder to change its compression ratios, means to resist the sum of the prevailing cylinder pressures and to automatically position said walls in unison during normal engine operation to determine the compression ratios, a pulsation eliminator to damp movement of said walls inwardly and outwardly of said cylinders, and means to render said pulsation eliminator substantially inoperative during rapid engine acceleration and during engine starting.

4. In an internal combustion engine, a cylinder, a movable wall associated with said cylinder to change its compression ratio in accordance with cylinder pressures, a spring resisting the cylinder pressures and automatically positioning said wall during normal engine operation to determine the compression ratios within a predetermined range, a seat for said spring, mechanism actuated automatically by the engine during its starting to move said seat to change the pressure of said spring, and manually adjustable means to vary the seat position to change the spring pressure and to change the operative range of compression rati s, 1

HERBERT J. KRATZER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 879,954 Fox Feb. 25, 1908 950,683 Stranahan Mar. 1, 1910 1,106,210 Halterman Aug. 4, 1914 1,437,929 Brockway Dec. 5, 1922 1,639,477 Wilson Aug. 16, 1927 1,757,907 Jameson et a1 May 6, 1930 1,795,309 Marshall Mar. 10, 1931 1,812,572 Talbot June 30, 1931 1,891,587 Wright Dec. 20, 1932 1,914,707 Wolf June 20, 1933 2,040,652 Gaty May 12, 1936 2,106,099 Jenkins Jan. 18, 1938 2,120,012 Andreau June 7, 1938 2,145,017 Tsundeda Jan. 24, 1939 2,157,486 Geisslinger et al May 9, 1939 2,399,276 Kratzer Apr. 30, 1946 2,420,117 Weatherup May 6, 1947 2,500,409 Hawkins Mar. 14, 1950 FOREIGN PATENTS Number Country Date 13,895 Austria Oct. 26, 1903 4,281 France Oct. 19, 1905 2,015 Great Britain Jan. 27, 1909 25,736 Great Britain Nov. 9, 1912 208,614 Great Britain Dec. 27, 1923

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