US1884480A - Internal combustion engine - Google Patents

Description

Oct. 25, 1932. L. M. wooLsoN.

INTERNAL COMBUSTION ENGINE Filed Oct. 25, 1930 D qu m WM N. mmm Wm w a hm. GNL/Am L wm@ mma mwN Wh OMF um; NE f i HM EyM M55 Ntmhw 88%, w L

, Sw mdmm Patented @et 25, 1932 UNrrED stars PATENT ori-Fics LIONEL Ill/L WOOLSON, DECEASED, LATE OF DETROIT, MICHIGAN, BY EMMA F. WOOLSON, EXECUTE-IX, 0F BLOOLVLFIELD VILLAGE, MICHIGAN, SSIGANOR 10 PACKARD MOTOR CAR COMPANY, GEL" DETROIT, MQHEGAN, A OBPORATION OF MICHIGAN INTERNAL COMBUSTION ENGINE Application filed October 25, 12930. Serial No. 491,254.

This invention relates to internal combustion engines of the compression ignition type and it is particularly adapted for use with marine engines and other engines of this nature which drive` steady loads of considerable n agnitude, such as ship propellers.

In Diesel engines of the type previously used in marine propulsion the ratio of weicht to power has been considerable and engines of this type have weighed from twenty-five to as much as several hundred pounds per horse power. Such weights of course are a distinct disadvantage, and have made the Diesel rengine impracticable except in relatively large installations. Much has been done in the edort to reduce this weight ratio, including the introduction into marine service of the .high speed Diesel engine.

In such `hioh speed engines, having speeds as high as 2000 R. P. M. it is necessary to have an early fuel injection, and the result is a much higher cylinder pressure, reaching valuesof 1200 pounds per square inch or more as compared with conventional maximum pressures of about 550 pounds per square inch in the prior low speed Diesel engines. True, this very high cylinder pressure is a peak pressure of short duration, occurring at the time of ignition, but it is ten times the average cylinder pressure during the working stroke of the engine, and more than twice the maximum pressure of other comparable engines. The 1200 pound peak pressure subjects the piston, connecting rods, crank shaft, cylinders and other aarts of the engine to terrific shock loads that must be taken and transmitted to the driven inember. ln the crank shaft these are not only in the form of direct blows delivered through the connecting rods, but also in the form `of high instantaneous torsional stresses caused by the lhigh acceleration given to the rotating parts, These parts have large inertia and particularly is this true of the engine flywheel, which is of considerable mass and which is necessary to proper idling of the engine.

Furthermore, Athese cylinder pressures, or the instantaneous peak .torques caused thereby,` constitute forcedy vibrations which synchronize 'at certain shaft speeds with the natural frequency of thecrank shaft, and induce vibrations therein which aggravate the original disturbance. rl`his results in a condition of resonance, and the resonant vibrations, when allowed to build up, grow rapidly and may promptly reach an amplitude such as to result in rupture of the shaft. Nor is this phenomenon always recognized, since vibrations which. are inappreciable to the senses may be accompanied by stresses easily sufficient to cause shaft failure.

It is not a sufficient answer 'to this problem to meet these stresses by increasing the size and strength of the crank shaft and other engine parts, since this necessarily involves a material increase in engine weight, and the reduction of weight is of prime importance. r:the overstressing of these crank shafts and other parts must be prevented in some other way.

The pres-ent applicant has discovered that such overstressing andy failure of the crank shafts of compression ignition engines of this type is due to a combination of the stresses resulting from peak cylinder pressures and resonant vibrations, and that a remedy fo-r this difficulty is not effected either by simple damping of the induced vibrations, or by cushioning the directly applied shocks, but that both damping and cushioning, jointly applied, do produce the. desired effect on the shaft, with the result that the shaft, and with it the connecting rods and other parts of the engine, may be greatly reduced in size and weight without fear of failure under maximum loads. y

The present invention, therefore, has for its principal object to provide means for cushioning or relieving stresses in the long crank shafts characteristic of engines of this type which will also damp torsional vibration induced therein.

Another object of the invention is to provide an engine shafthaving a vibration damper at each end thereof.

A further object of the invention is to provide apparatusof the character designated in which the connection of the crank shaft to its load and.l to its flywheel shall be through yieldable couplings providing mechanical damping friction without resilience.

Other' objects and features of novelty of the invention will be apparent from the description taken in connection with the drawing, in which:

Fig. 1 is a. longitudinal view, partially in sideV elevation and partiallj.' in vertical section through the crank shaft and the associated elements of a compression ignition engine, connected to drive a marine propeller, showing the application of this invention thereto;

Fig. 2 is a diagrammatic view showing the y general arrangement of the engine, propeller shaft and propeller illustrated in Fig. 1, and

Fig. 3 is a comparison of characteristic indicator diagrams of a low speed Diesel engine and a high speed compression ignition solid fuel injection engine of the type to which this invention relates.

Referring to the drawing, at 10 is indicated a marine engine of well known type, having a crank case 11 on which is mounted a cylinder block 12 comprising a number of cylinders such as 13 arranged in line. Each ofthe cylinders 13 is provided with a head 14 having air inlet and exhaust ports controlled by suitable valves 15, which are adapted to be operated in timed relation to the engine through any suitable valve operating mechanism (not shown).v A fuel nozzle 16 communicates with the interior of each of the cylinders and with suitable fuel pumps 17 which are also driven from the engine in timed relation thereto, there being a pump 17 for each of the engine cylinders. It will be understood that each of the pumps 17 operates to inject a measured charge of liquid fuel into its cylinder at the proper time in the engine cycle, but as the particular details of the fuel pump are not essential to an understanding of the present invention, further description thereof is unnecessary.

The crank shaft or driving system of this invention comprises the engine crank shaft proper with its flywheel and other associated masses. the propeller or other driven member, the propeller shaft or drive shaft, and the devices connecting these elements. In the embodiment illustrated, each of the engine c vlinders 13 is provided with a piston 18, and each of these pistons is connected by a con necting rod 19 with one of the cranks 21 of the crank shaft 22 in the usual way. The crank shaft is journaled in suitable bearings in the crank case 11, two of which are shown at 23, and it is provided with a driving flange 24 and a flywheel 25.

In the arrangement illustrated the flywheel 25 is located at the front end of the crank shaft and is journaled on a hearing sleeve 26 carried on a shaft extension 27. It is thus rotatably mounted on the shaft, but is connected thereto and driven therefrom by a yielding connection or clutch adapted to transmit the normal torque of the engine but to yield in response to peak torques of predetermined value. As illustrated, this connection comprises a number of radially disposed annular friction elements or plates 28, splined at their inner edges to the crank shaft, or to a sleeve 29 secured thereto, and interleaving with a number of similar plates 31 splined at their outer edges to the inside of the flywheel rim, as shown at 32. The plates are pressed axially into engagement by any suitable means such as the compression springs 33, arranged between the end plate 28 and a collar 34 carried by the shaft. The flywheel may be retained axially in position in any convenient manner, as by a washer and nut 36 threaded on the end of the shaft.

The other end of the shaft is adapted for operative connection with a driven or propeller shaft 37, through the driving flange 24. As shown, the end of the crank shaft is formed with a coaxial recess 38 in which is journaled the reduced forward end 39 of the propeller shaft 37. Adjacent the reduced portion 39, the propeller shaft is splined as shown at 4l to support a driven member or clutch hub 42 provided with spaced radially disposed driven plates 43. The side faces ot' the driven plates are provided with suitable friction lining 44 and are disposed between driving plates 46 which are arranged to turn together and with the crank shaft 22 in a manner well known in theart. To this end the plates 46 are associated in driving relation y a number of axially disposed driving pins 47 by which they are connected to the end or master plate 48 which is bolted or otherwise conveniently secured to the driving flange 24 integral with the crank shaft 22.

The plates 46 and the friction linings 44 of the plates 43 are urged axially into engagement by means of compression springs 49 which may be conveniently disposed between a pressure plate 51 and the nearer of the plates 46. This device is also preferably provided with radially disposed lever portions 52, fulcrumed on the pressure plate 51 and connected to the plates 46. The ends of the levers 52 may be actuated by a slidable bearing or collar 53 which is adapted to operate the levers 52 and move the pressure plate 51 against the action of the springs 49 through any suitable mechanism such as the clutch fork 54.

y It will be understood that the springs 49 are of a strength sutlicient to frictionally lock the plates 46 to the plates 43 for all ordinary or normal engine torques, but that the friction between the plates is insuflicient to rigidly connect the members upon a peak torque, such as occurs at the time of ignition as shown in Fig. 3. Under these circumstances the clutch plates 46 will slip with respect to the plates 43, thus relieving the driven Shaft llO 37 of the shocks imposed upon the system by the ignition torque of the engine.

The shaft 37 is usually of considerable length with respect to its diameter and is therefore highly resilient. It may be supported near its free end by a steadying bearing 55, formed on an arm G appropriately secured to the vehicle in which the engine is mounted (not shown). Adjacent the beari ing the shaft 37 is connected to its load,

which is shown in the form of a marine propeller 57 of well known construction. It will be evident from the foregoing description that the load represented by the propeller i 57 is connected to the crank shaft through a member having a considerable degree of resilience, by which it is caused to yield in torsion in accordance with the torque transmitted. It will also be understood that suitable transmission or change speed gearing of any type may be inserted in the drive 37 between the propeller 5'? and the driving flange 2st of the crank shaft, such gearing not affecting the invention. In the interest of simplicity,

however, a showing of such change speed f gearing has been omitted. The yielding contary peak torques and other shock loads such f as occur during the period of ignition. During the remainder of the cycle, the yieldable elements or couplings transmit the normal torque as though there were a. solid connection.

It will also be observed that this device provides a vibration damper, the crank shaft proper being in eect connected between a 1pair of suoli dempers. To prevent the resonant growth of such vibration as will be induced in the crank shaft system by reason of the forced vibrations, the present invention provides adequate damping for the entire system. Such damping is effected by the mechanical friction between the friction elements of the yieldable couplings or connections, that is between the plates 28 and 3l, and between plates 43 and 46; which friction serves to dissipate vibratory energy at a rate sumcient to prevent its resonant growth.

Thus it will be seen that the yieldable elements operate at any time when the maximum torque exceeds a predetermined amount, and further that the damping effect willcontinue as long as there is any relative movement between the crank shaft and the flywheel; that Although the invention has been describedl in connection with a specificl embodiment, the principles involved are susceptible of numer- 7i,

ous other applications which will readily occur to persons skilled in the art. The invention t-l'ierefore to be limited only as indicated by the scope ofthe appended claims.

Having thus described the invention, what is claimed and desired to be secured by Letters Al'ate-nt is: v

l. The combination with the cra-nk shaft of a compression ignition engine in which there is a very high maximum cylinder pressure at the moment of ignition, and a driven device such as a ship propeller, of a flywheel at one end only of said crank shaft, a somewhat yieldable propeller shaft from the other end of the crank shaft to said driven device, a friction clutch between said crank shaft and said propeller shaft capable of normally transmitting the engine torque without slipping but adapted to slip under very high instantaneous torque conditions, and a similar clutch between the. crank shaft and the flywheel.

2. The combination with the crank shaft of a compression-ignition engine in which there is a high instantaneous torque at the moment of ignition, and a driven device, of a flywheel on said crank shaft, a somewhat yieldable resilient drive shaft connected to said device, a friction clutch between the crank shaft and the drive shaft capable of normally transmitting the engine torque without slipping but adapted to slip under high instantaneous torque, and a similar clutch between the crank shaft and the flywheel.

8. The combination with the crank shaft.v of a compression ignition engine in which there is a high instantaneous torque at the moment of ignition, and a driven device, of a flywheel on said crank shaft, a somewhat yieldable resilient drive shaft connected to said device, a connection between the crank shaft and the drive shaft capable of transmitting the normal torque but adapted to yield under very high instantaneous torque, and a similar connection between the crank shaft,-l and the flywheel.

fl. The combination with the crank shaft of a compression ignition engine having a high momentary torque during the period of ignition, and a load driven by said engine, of agaflywheel for said crank shaft, a resilient shaft connected to said load, and separate means connecting said crank shaft between the resilient shaft and the flywheel including clutches yieldable to said high momentary torque. n

5. The combination with the crank shaft of a compression ignition engine having a high momentary torque during the period of ignition, and a load driven by said engine, of a flywheel for said crank shaft, a resilient shaft? connected to said load, and separate means to connect said crank shaft to the resilient shaft and to the ywheel, said means inc1uding friction couplings adapted to transmit the normal engine torque but to yield with a damping absorption of energy to said high Y momentary torque.

In testimony whereof, I have hereunto subscribed my name this 24th day of October,

EMMA F. WOOLSON,

Ewea'utr of the Estate of Lionel M.

Woolsow, Deceased.

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