US2381895A - Compression control device - Google Patents

Description

Aug. 14, 1945.

D. F. FOSTERl COMPRESSION CONQKI'ROL DEVICE I Filed Aug. 23, 1945 2 Shee'tS-Sheet l Aug. 14, 1945.

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`Patterned Aug. 14, l1945 comaassron coN'mol. nevica Davia F. rotar, Na, can. application August es, im, semi No. 499,651

o sciame. (ci. 12s-4s) (Granted under the act of March 3 1883,.

The invention described herein may be manufactured and used by and for the Government .for governmental purposes. without the payment to me of any royalty thereon.

This invention vrelates to a compression control device for `internal combustion engines of the gasoline or Diesel fuel type and an object of the invention is to provide means operable manually or automatically for maintaining the engine compression pressure constant during changes in barometric pressure. The invention is particularly adapted for use withaircraft engines and is .de-

signed to prevent loss of engine `power output at high altitudes.

As is well. known, the compression pressure in an engine cylinder depends upon the compression ratio and the pressure of the fuelcharge in the cylinder when theI inlet valve has just closed. Compression ratio may be deflned as the ratio of the volume of the clearance space plus the volume swept by the piston to the clearance space.

The pressure of the charge in the cylinder at the beginning of the compression stroke is somewhat below atmospheric and increases-and -decreases with corresponding changes in the external atmospheric pressure. Hence, with the same compression ratio the lower the external atmospheric pressure. the lower will be the compression pressure and the engine power output. It is apparent, therefore, that a reduction in cylinder pressure due to change from a lower to a higher altitude, results in reducing the power of the engine. Even supercharged engines are susceptible to a loss of compression at high altitudes.

To compensate for the reduction in cylinder pressure due to the rareed atmosphere encountered at high altitudes andt'o provide uniform power outputfor all altitudes, the compression ratio must be varied with regard to changl ing altitude to keep the compression pressureconstant. The compression ratio maybe varied by increasing and decreasing the volume of the clearance space and it is to a compression control device operating onthisjprinciple that the present invention is directed. 'o

Specifically, the invention provides for varying the compression ratio of internal combustion engines by moving a flat plate into and out of the tiring chamber and across the inner surface of the cylinder head to vary the volume of the combustion chamber. The plate may have a rectilinear or a rotary sliding movement and is operated either manually.' or automatically by an altimeter or other barometer-controlled means. to

amended Api-n so. 192s; 31o o. Gf rs1) vary the compression ratio with regardto chang-v ing altitude.

The construction, operation, and advantages of the invention will be apparent from the following detailed description' thereof, reference being lmade to the accompanying drawings, wherein l `Figure 1 is a top plan view cfa cylinder construction embodying one form of the compression control device. I'

Figure 2 is a vertical longitudinal section on line 2-.2 of Figure 1 in'which the compression control member is shown-extended into' the com- -bustionchamber of `the engine cylinder.Y f

Figure 3 is a similar section inwhich'the compression control member is shown in the retracted Y or `high compression ratio condition.

Figure 4 is av top plan View of a'cylindei' con- 4 struction embodying a modified form ofthe-compression control member.

.Figure 5 is a section on line 5-5 of Figure 4,

Figure 6 is a schematic view of the operating Y mechanism for the compression control'member.

In the vdepicted cylinder construction, vthe pis- `Aton l is shown at'the top of its stroke i'n'the bore i Y of the engine cylinder 2 and in spaced relation tothe underside lof the cylinder head 3 to provide the usualvclearance space or combustion space l. The cylinder head preferably is of the detachable type. and for the purposes of the sub-Yl ject invention is modied from conventional r practiceto include in a side wall thereof a horizontal recess'l of substantial area and shallow depth. 'I'he recess or slot 5 is adapted to house the compression'control member 8 and is located near the top of the clearance space 4 into which it opens through the aperture 1; the upper sur'- face of the slot being a continuation of the undersurface of the cylinder head 3. The shape and size of the slot is in close accord with the corresponding features of the compression con- 'trol member so that the member, in its normally retracted position, is adapted to be wholly accommodated within the slot-and, when so accommodated, substantially 1111s the slot with edge pory tion 8 of the member in the vertical plane of the aperture 1. In the retracted position of the comthe compression ratio is at its minimum. When the compressioncontrol member is moved from its fully retracted position and is caused to extend into the clearance space, the volumetric capacity of the clearance space is reduced in dependence upon the extent of movement of the .compression control member, and -the compresaltitude; thereby maintaining the cylinder com` pression pressure constant with regard to changing altitude. Decreasing -the compression space results also in a proportionally larger fuel charge being drawn into the compression cylinder by the suction or intake action of the piston and linsures the proper degree of compression of the charge at the moment of combustion. 'I'he compression control member 8 is adapted, during its movement within the clearance space, to slidably engage the inner surface of the cylinder head 3 which in eiect provides a. rigid support or backl ing for the extended portion of the compression member. .The operation of the compression member may be initiated and regulated by any means or system of control, manual or automatic, which moves the member as the barometric pressure varies from sea level to ceiling altitude. The system of control may include electric, hydraulic, or mechanical unitsor a combination o! all three.

I'he construction shown in Figures 1 to 8 inclusive illustrate one'for'm or species of the invention in which the control member i .comprises a rectangular plate slidably mounted in the slot i; the latter being formed in an extension s of the cylinder head 3. Ring segments I and Il at the cylinder end o! the slot I, provide bearing supports and seals` for the compression control plate to prevent loss'oi compression between the clearance space and the slot. In the present instance, the compression control member is illustrated as being automatically operated and for this reason is provided at the outer end with a plunger l2 adapted to be reciprocated in a cylinder i3 forming an integral part o! the cylinder head extension l. Cylinder i3 is connected by pipes Il and I5 to a suitable source i6 of iluid supply, which source of iluid supply is adapted to be connected with and controlled by a barometer or altimeter I1 of an airplane as shown in Figure 2. In operation, as the airplane ascends to a higher altitude above sea level, the, expanding movement of the pressuresensitive element I8 of the altimeter is suitably transmitted to the piston I9 o! the hydraulic control; the piston l! being thereby moved in such manner as to cause the iluid in Pipe IB to be displaced in the direction of the plunger l2. The pressure exerted against the outer face of the plunger I2 by and during the displacement of the iluid in pipe II forces the `plunger inwardly of the cylinder il. This movement of the plunger causes the compression control plate 6 to be moved progressively outwardly o! the slot 5 so that a portion thereof extends beneath the inner surface of the cylinder head l and illls a portion of the space between the cylinder head and the piston I, thus reducing the volumetric capacity o! the clearance or compression space. The extent oi' movement of the compression cona,'ss1,sos'

trol plate is dependent upon the degree of displacement oi' the iluid in the control system and this is controlled by the expansion of the pressure-sensitive element I8. During descent of the airplane from a higher to a lower altitude, the contraction of the pressure-sensitive element of the barometer or altimeter is transmitted to the pistoni! in such manner that the movement of th'e latter, and the resultant direction of displacement of the fluid, is reverse to that which occurs when the airplane is ascending. Consequently, the pressure o! the fluid entering the cylinder i3 through the pipe M causes the pressure-control plate to be progressively retracted or withdrawn from the compression space. As the compression control plate is moved inwardly of the cylinder Il, any carbon which may have formed thereon is scraped therefrom by the ring segment I0.

A modied /form of compression control device is illustrated in Figures 4 to 6 inclusive. In this form, the compression control member comprises a sector-like disk which'is rotatably supported in the similarly shaped slot 5 by a vertical shaft 20 to the lower end of which the disk is attached. The shaft 20 has a bearing support in the' cylinder head 3 and terminates at its upper end within a casing 2| attached to or formed integral with the cylinder head. A rocker arm 22 is ailixed to the upper end of the shaft 20 and for the purpose of manual control has its tree end connected by linkage or other suitable means 23 to the hand lever 24. A tension element, such as the spring 25 anchored at one end to the casing 2| and attached at its other end to the rocker arm 22, normally positions the rocker arm at one limit of its stroke with the compression control disk 6 fully housed within the slot I. When the lhand lever is actuated to move the rocker arm against the tension o! the spring. the resultant turning movement of the shaft causes the compression control disk to rotate and be swung outwardly of the slot and-into the vcompression space; thereby reducj ing the volume oi' compression space and increasing the compression ratio. During reverse movement of the hand lever, the contraction of the spring causes the compression control disk to recede from the compression space with consequent increase in thevolume of the compression .chamber and decrease in the compression ratio. To provide for automatic operation of the compression control disk, the free'end of the rocker arm is engaged by the push rod 26 of a hydraulic piston 21; contact between the rocker arm and the push rod being substantially maintained by the action ot the spring 25. Piston 21 slides in acylinder formed integral with and within the casing 2l. The push rod oi' the piston 21 operates through the open inner end' of the cylinder 2l and is displaced outwardly against therocker arm 22 by the pressure of oil entering the outer end of cylinder through a conduit 2l leading from a suitable source of oil pres- -sure supply. The passage of the oil into and out of cylinder 28 is governed by a pressure control valve assembly 30 located in the conduit 29 and operated 'by a suitable electrical system 3|, such as a photo cell circuit, which in turn is controlled by an altimeter or barometer- 32 in an airplane. Any automatic control system suitable for the object in view may be employed with the subject invention .and the specific system herein disclosed is merely representative of one of many possible combinations of known del the photoelectric cell.

assises vices in general use adapted to provide for autov matic and progressive operation of the compressionv control member in accordance with changes in altitude of the aircraft. In the disclosed system, a graduated light screen 34 is ilxedly mounted on an extension 35 of the indicator shaft of the instrument 32 at the back ofthe latter'for rotation between a light source It and .a photoelectric cell 31; the screen 34 being a wofi' the.- instrument. The phlotoelectric cell is contained in an electric circuit including a sole-` noid '38 operatively associated with a rheostat control arm 39 for positioning the arm relative to the rheostat resistance coil 40 so as to increase and decrease thelresistance of the .valve-solenoid circuit 4|, and hence the strength of the soleniod 42, with increase and decreasel in the amount of light passing through the screen to The armature of the solenoid 42 is a needle valve 43 movable .to and from a valve seat in a by-pass passage 44 connected with the conduit 29 between the inletand outlet sides of the assembly 30 and leading that part of the conduit 29 between the piston 21 and the valve assembly 30, and the resultant displacement of the arm 22 is governed by the displacement of the by-pass controlvalve 43 relative to its seat, i. e., variations in the location of the valve between fully opened and closed positions, which in turn is controlled in an obvious manner from and by the altlmeter through the interconnecting electrical system. The altimeter .or barometerjenergizes the electrical mechanismy to operate the valve and control the flow of oil in response to variance in barometric pressure due to change in altitude whereby the e compression-control disk is moved inwardly of the compression space during-increase in altitude and vwithdrawn therefrom as the altitude decreases.

When the devicefembodiesl both manual and automatic means, as shown in of the cylinder and movable laterallyinwardly and outwardly of the clearance spacebetween -the piston and the cylinder head and in sliding contact. with the said head to vary the volumetric capacity of the clearance space, and barometric pressure-responsive means operatively connected with the compression control plate for moving the same to vary the volume of the clearance space in accordance with changes in barometric pressure due to changes in altitude whereby to maintain the compression pressure constant from sea level to ceiling altitude.

2. A 'compression control member for an in`- ternal combustion engine comprising, in combination with a cylinder and piston of the engine, a compression control plate mounted in the head of the' cylinder for movement laterally intov and out of the combustion chamber and 'adapted during such movement to slidably engage the inner surface of the cylinder head aboveethe piston,

an'd means for moving the said plate.

v back to the oil supply source. The pressure in Figure 6, a selectorcontrol such as the switch 33 may be provided for cutting out the autmatic means when manual operationis desired. Duringhthe withdrawal of the disk. any carbon formed thereon will bescraped therefrom by the.

edgesof the slot. l

From the foregoing, it will be obvious that by reducing the compression space in an aircraft engine cylinder as the barometric pressure varies from sea level to ceiling altitude, the compression pressure will be held constant for kall altitudes. The device, therefore, will permit sea level compression ratio, and operation of airplanes, at amr given altitude. By providing each cylinder head with a compression control member and synchronizing their movement with the operation of the altimeter, the compression ratios in all of the several explosion chambers of multicylinder engines may be properly and simultaneously varied to prevent loss ofenglne power at altitudes above sea level. t

Having thus described the invention, I claim: 1. A compression control fox` an internal combastion engine comprising. in combination with a cylinder and piston of the engine. a compreslsion control plate mounted flatwise in the headl 3. A compression` control for an internal combustion engine comprising the combination with a cylinder and piston of the engine, a head on the cylinder dening a clearance space above the piston and provided in a side wall thereof with a horizontal recess of substantial area and shall'ow depth ofl'set to but opening into the clearance space, a compression control member pivotally mounted in the said recess oi' the cylinder head for movement about an axis normal to the hori- Y zontal plane Vof the recess whereby'it is adapted to be moved laterally into and out of the clearance space between thepiston and the 'head of the cylinder, and means for moving .the said member.

, 4.- A compression control for an internalcom- Vbus'tion engine comprising the combination with a cylinder and piston of the engine, of a housing of substantial area and shallow depth in the head of the cylinder, and communicating with the clearance space between the piston and the head of the cylinder, a shaft rotatably mounted in the head of the cylinder with its inner end within the housing and its upper end externally thereof, a compression control member attached t'o the innerV end of the shaft and to be accommodated in the said housing, and means at the upper end of the shaft for turning the same to cause the compression, control member. to be moved inwardly or outwardly of the housing for lvarying the volumetric capacity of the clearance space. 5. A compression control for an internal combustion engine comprising, in combination. a cylinder, a piston therein. a cylinder head having e a recess in a side wall thereof forming a-substantially wide and shallow slot disposed in a plane normal to the axis of the cylinder and opening into the combustion chamber at the top making available the maximum volume capacity the inner surface of the cylinder head for reducof the clearance space or to be variously extended from the slot into the clearance space and across ing the volume capacity of the clearawspece. and means for positionably adjusting Y e plate.-

DAVID l'. FOSTER.

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