US2349157A - Internal-combustion engine - Google Patents

Description

May 16, 1944.

Filed April 20, 1942 2 Sheets-Sheet l 9 d 0 l Z O JIM S \R- 2 .n l M l Z 4 7 W1 6 xx 3 f A o o 2 Q o H. FORD ETAL INTERNAL COMBUSTION ENGINE Filed April 20, 1942 May 16, 1944.

VIIII'IIWK7QrIII wIIIIIIIIIIII 2 Sheets-Sheet 2 ATTO RN ETS.

Patented May 16, 1944 Henry Ford, Dearborn, and Charles E. Sorensen,

Detroit, Mich, assignors to Ford Motor Company, Dearborn, Mich, a corporation of Delaware Application April 20, 1942, Serial No. 439,632

1 Claim.

This invention relates to internal-combustion engines and more particularlyto a drive for camshafts in such engines. I

At the present time. in the design of internalcombustion engines of large horsepower, notably aviation engines, provision is frequently made for separate activation of the exhaust and intake valves by individual camshafts. This system has certain advantages as, for instance, when two or more intake or exhaust valves are provided for each cylinder their operation by a single cam-,

- shaft would be complicated and cumbersome.

There are other circumstances in which the use of individual camshafts-is advantageous; but since the invention principally concerns the camshaft drive, they need not be listed here.

In the devices of the prior. art; whether single or multiple overhead camshafts were used to'operate the-intake and exhaust valves, the camshafts were driven -by gearing from the motor crankshaft. When multiple camshafts were used, this generally took the form of a bevel gear train from the crankshaft to one of the camshafts and a further gearing from the driven camshaft to the I other camshaft. Apart from th excessive weight and the inherently larger size of a bevel gear system, difliculty was encountered in providing suitable bearings. And since the system used a multiplicity of gears, the over-all efficiency was necessarily low.

'In addition to these difliculties, provision must be made on these engines to run a number of auxiliaries such as magnetos, injectors, and pumps in exact synchronization or in some fixed speed ratio with the motor. The preferred position for attaching thesev auxiliaries is in proximity to the driven end of the camshafts. The reasonfor this is that the camshaft is in synchronization with the motorfand being located at the top of the motor is readily accessible for such attachments. The driven end of the camshaft ispreferred because it avoids defects in synchronization caused by whip in the shaft. When the camshafts are driven as shown in this invention, the driven .end of each camshaft is available for the attachment of auxiliaries, a feature which does not appear in any other motor, to the applicants knowledge.

A further reference totheprior construction will make this point clear, In the usual construction. bevel gears are-attached to corresponding ends of the crankshaftand camshaft. A drive shafthaving bevel gears at each end is arranged between the crankshaft and camshaft, its gears meshing with those on the last-named shafts.

It follows that the drive shaft must be positioned a distance, .equal to at least one half the maior diameter of the bevel gear used, beyond the normal support for the crankshaft or camshaft. The auxiliaries used are generally of such size that they must be placed beyond the bevel gears on the drive shaft to clear them. This requires that the camshaft be extended a distance, equal to at least the major diameter of the bevel gear, to make operating connection withthe auxiliary. This is a substantial distance; and some provision for additional bearing for the shaft overhang,,as well as a support for the auxiliary must be made-a far from simple problem.

When pairs of camshafts are used, but one of them may be driven directly from the bevel drive.

The other camshaft is then driven by the first camshaft usually through conventional spur gearin-g. This involvesa further gear train with consequent greater weight, chance for mistiming, and a more complicated construction.

Another difliculty encountered when a bevel drive is used is in balancing the forces imposed on the drive shaft. As there is engagement on but one side thereof by the meshing gear'of the camshaft, any thrust must be taken care of by.

suitable bearings.

The present invention overcomes each of these disadvantages. .With the use of a worm gear system, the gear on the crankshaft, the drive shafts, and thegears on the camshafts are all substantially in one plane. The saving in space is at once apparent. The worm on the drive shaft is preferably placed between wheels on the two camshafts directly engaging with both of them; no further gearing being required between the two camshafts. As both are driven by the same work, there is no opportunity "for mistiming.

Since the drive and driven gears are in the same plane, no, difllculty is encountered in providing adequate bearings for the end of the camshaft as shown in Figure 3; and auxiliaries of whatever size desired can be attached to the end of a camshaft without an undue extension of the camshaft. Again, since thegearing does not cover the end of any camshaft, all the camshafts are available for the attachment of auxiliaries. A final advantage is that by engaging each camshaft fromopposite sides of the worm, the opposing forces on the worm therefrom are balanced. Compared ,to the older 7 system where one camshaft was driven by the worm and in turn drove the other, the tooth strength of the worm gear on the drive shaft need be but half as great, as the impressed force is directly divided between the two camshafts.

,' With this and other objects in view, our inven- .and head casting 29.

' crankshaft and the camshaft 'is 2:1.

tion consists of the arrangement, construction and combination of the various parts of our improved device, as described in this specification, claimed-in our claim and illustrated in the accompanying drawings in which:

Figure 1 is a transverse vertical section of an engine employing the invention.

Figure '2 is a partial sectional view taken on the I line 2-2 of Figure 1.

Figure 3 is a partial section on an enlarged scale taken on the line 3-3 of Figure l. v

Figure 4 is a partial transverse vertical section on an enlarged scale showing the upper end construction.

Figure 5 is a diagrammatic view showing the spline relationship.

Referring to Figure i, it indicates a V-type engine having the cylinder banks H with the usual pistons 2i connected by the rods 32 to the crankshaft i3. Overhead valve assemblies it are provided on top of the banks for each cylinder and are operated by the cam It on the camshafts it. This general construction is wellknown in the art and presents no novelty.

Separately spaced. camshafts it are provided for the intake and for the exhaust valves in each bank of cylinders. The intake valves, in 'the embodiment shown, are those located toward the interior of the V, and these are operated by the inner camshaft while exhaust valves-adjacent the outer side of the bank are operated .by the other camshaft. Instead of conventional.

manifolding, the space I! within the V serves -as the intake manifold and an intercooler l8 -is shown secured between the v for use with a supercharger to cool the entering air. The

shaft and the method used in assembling this structure. As shown, a worm wheel 22 is secured to. an extension 28 on the crankshaft l3 3 (see Figure 2) and, meshes with the two worms 2.4, shown here to be of the hour-glass or globoid type, which are secured to the drive shaft 25. This drive shaft is rotatably mounted at the lower end of the bearings 20 and at its upper end in a bearing 2! at the top of the block 28 adjacent to the division linebetween the block The quill II is splined to the drive shaft 25 and extends upwardly where,

I as best seen in Figure 4, it is splined to the upper worm 82. This worm, in turn, meshes with the two upper worm wheels 3 ch ar splined to the extension 34 of the. camshaft I.

In the present instance, a helix angle of approximately 45 degrees is used in designing the worm gearin and the speed'ratio' between the I Other angles and ratios may be chosen-as are required for the individual design, but those skilled in v the art will recognize thatin the interest of emciency, a helix angle approaching 45 degrees should be used.

Referring to Figure '2, it will also be noted that another gear 35 is'mounted. on the crankshaft extension ,2! and meshes with the pinion N spllned to the shaft-I1, extending rearwardly of the motor which serves as an additional accessory drive.

As best seen in Figure 3, a splined connection 38 is available at the end of each camshaft 'block casting is reinforced at its lower edge by cored box 19 which follows around the entire .the one-degree limit.

In practice, the two camshafts are adjusted to extension 34 which, together with the facing plates 39, for the ready attachment, and drive of such devices as timing gear, injection pump. magneto or other equipment which must be driven in exact synchronism with the motor. Further, as the lower worm is supported by bearings both above and below its point of engagement with the worm wheel and the upper worm is supported between two worm wheels, the side thrust ordinarily found in such constructions is obviated. In addition, the over-all length of the camshaft is reduced and the rigidity of attachmerit of accessories increased.

An extension of the invention is to be found in the method used for the assembly of the components. It is absolutely necessary that the phase angle of the camshaft be correct within 1 degree of the corresponding phase position of the crankshaft. The use of the worm at each Of course, the splines that co-operate with these.

namely'those in the upper worm 32 and the top of the drive shaft 28, respectively, are correspondingly similar in number.- Employing the Vernier characteristics of this differential spline,

the possible number of different positions numthe desired phase angle, the upper worm wheel 33 engaged with the upper'worms 32, and the assembl is locked and marked as shown at I to indicate alignment. It will be noted that the upper Worm 32 is supported in the upper bearing N and the lower bearing I so that it maintains itself in position during this step. The crankshaft is turned to its approximate angular location within the one-degree limit, which socordingiy moves the drive shaft 2| to a certain position. The quill SI is then dropped down through the upper worm l2 and its upper splines I mesh with the corresponding splines on the upper worm. Unless the alignment is exact, however, the lower splinesgfl will not mesh with corresponding splines in the drive shaft II. Accordingly, the quill is lifted upwardly until the spline l0 is-disengaged andis reinserted in another angular position. This is continued until all of the tooth combinations have been exhausted or-until a position is found in which-the quill readily engages the splines in both the worm and the drive shafts. In the event that Tit this matching is not obtained while the quill is moved from each tooth successively through crank position within the very narrow limits I which have been set. This permits a very close adjustment and one which is well-adapted to the assembly of this type of engine.

The advantages of this construction are manifold. The device is more compact and lighter than other conventional drives. It leaves the ends of all camshafts available to drive auxiliaries, and provides a secure and rigid base for the attachment of these auxiliaries. The drive to each pair of camshafts is direct, and as the drive shaft is positioned between the camshaft in the pair, the thrust forces are largely balanced. End bearings are provided for the camshaft, crankshaft and drive shaft and overhanging shafts avoided. Awide range of speed ratios is available without an undue increase in the sizeof the gear and, particularly when the hourglass or globoid worm is. used, the efficiency is extremely high. 7

Some changes may be made in the arrangement, construction, and combination of the various parts of the improved device without departing from the spirit of the invention. It is the intention to cover by the claims such changes as may be reasonably included within the scope thereof.

We claim as our invention:

In combination, in an internal-combustion agine of the v type, a camshaft drive, comprising. a pair of overhead camshafts rotatably mounted ,on each cylinder bank of said engine, a worm wheel disposed at one end of each camshaft, a main shaft having a worm wheel disposed at its corresponding end, a pair of intermediate shafts having worm gears disposed at each end thereof, means on said bank providing a camshaft bearing on each side of said worm wheel thereon and a facing plate in proximity thereto, said intermediate shafts being so arranged that the lower worm gears thereon mesh with said main shaft worm wheel on opposite sides thereof, and extending therefrom divergently to said camshaft pairs, the upper worm gears thereon each disposed between and meshing with.one of said worm wheel pairs, providing a drive means between said main shaft and said camshafts without obstruction at the ends of said camshafts permitting the attachment of auxiliaries thereto, said camshaft drive being substantially in one HENRY FORD. cnss. E. SORENSEN.

Images