Rotary-piston Internal-combustion Engine

Abstract

In a rotary-piston internal-combustion engine in which two sets of pistons rotate about a common axis while in sealing engagement with a cylindrical casing wall, and the two sets are connected so that the pistons of one set rotate at uniform speed and those of the other set rotate at cyclically varying speed to expand and contract combustion chambers circumferentially bounded by the pistons, the uniformly rotating pistons are fixedly fastened to the radial end walls of the casing, and motion is transmitted between the two sets by crankshafts journaled in a gear carrier fixedly fastened to one of the end walls and oscillating a mounting sleeve for the pistons of the other set. The crankshafts are rotated by respective gears meshing with a ring gear fastened to the normally stationary cylindrical casing wall.

Description

This invention relates to rotary-piston internal-combustion engines, and particularly to improvements in an engine which has at least two pairs of pistons mounted for rotation about a common axis while in sealing engagement with an engine casing and defining combustion chambers therebetween, the pistons of one pair being connected by a motion transmitting train to the pistons of the other pair for rotating the latter at cyclically varying speed when the pistons of the one pair rotate at uniform speed, and for thereby cyclically expanding and contracting the combustion chambers.

In known engines of the general type described above, the several pistons rotate in a stationary casing, and the uniformly rotating pistons are fastened to a main output shaft which extends over the entire length of the engine casing and of an axially adjoining gear casing which encloses the afore-mentioned motion transmitting train. In such an arrangement, the pistons rotating at varying speed must be mounted on two annular discs rotatably arranged on the main shaft, one of the discs being oscillated by the motion transmitting train. The bearings and the seals in the known engine present serious problems of design and maintenance, and the piston shapes must be selected with great care.

It has now been found that dimensional and other conditions are much less critical if a continuous main drive shaft is dispensed with, and if the radial end walls of the engine casing are mounted rotatably in the circumferential casing wall and fixedly fastened to the uniformly rotating pistons. In such an arrangement, the motion transmitting train may include a gear carrier fixedly fastened to one of the end walls, a crankshaft journaled in the carrier, an actuating mechanism for turning the crankshaft when the carrier rotates with the fastened end wall relative to the circumferential casing wall, and a connecting rod operatively interposed between the crankshaft and the pistons rotating at varying speed.

Other features, additional objects, and many of the attendant advantages of this invention will be appreciated readily as the invention becomes better understood by reference to the following detailed description of a preferred embodiment when considered in connection with the accompanying drawing in which:

FIG. 1 shows an internal combustion engine of the invention in section through its axis on the line I--I in FIG. 2;

FIG. 2 shows the engine of FIG. 1 in fragmentary radial section on the line II--II;

FIG. 3 shows elements of the engine of FIG. 1 in radial section on the line III--III; and

FIG. 4 shows a subassembly of the engine of FIG. 1 in radial section on the line IV--IV.

Referring initially to FIG. 1, there is seen a rotary piston engine of the invention whose combustion space is bounded in a radially outward direction by a cylindrical casing wall 1, and in two axial directions by radial, annular end walls 2,3 whose radial inner faces are fixedly fastened by screws 4' to two pairs of pistons 4, the pistons of each pair being diametrically opposite each other, as is better seen in FIG. 2, and the two pairs being offset from each other at right angles about the engine axis. In normal operation of the engine, the casing 1 is stationary, and the pistons 4 together with the end walls 2, 3 rotate at uniform speed about the engine axis which coincides with the axis of the casing 1.

The combustion space is bounded in a radially inward direction by an outer face of a mounting sleeve 6 which is coaxial with the casing 1 and carries four pistons 5 offset from each other at right angles. Hollow screws 7 extend through flats on the sleeve 6, best seen in FIG. 4, into the wide bases of the hollow wedge-shaped pistons 5 and thereby fixedly fasten the pistons 5 to the sleeve 6, one piston 5 and screw 7 being indicated in phantom view on the sleeve 6. The latter is coaxially mounted on a tumbler shaft 9 and secured against rotation on the shaft 9 by means of interengaged axial grooves and ribs 8.

A gear carrier 10 is fixedly fastened to the end wall 2 by means of screws 11. Three crankshafts 12 are equiangularly spaced on the carrier 10 about the engine axis, each crankshaft being received in a split bearing whose inner shell is integral with the carrier 10, the crankshaft being secured in the bearing by an outer shell 25 (FIG. 3) attached to the carrier 10. Only parts of two crankshafts are visible in FIG. 1, and only one has been shown in FIG. 3. The crankpin 13 of each crankshaft carries a connecting rod 14 whose free end is hingedly fastened to the enlarged head of the shaft 9. A spur gear 15 on each crankshaft 12 meshes with an internal ring gear 16 attached to a cylindrical gear housing 18 by screws 17. The screws also fasten an axially terminal cover 19 to the casing 18, the latter being fastened to the casing wall 1 by screws 18'.

When the carrier 10 and the pistons 4 rotate at uniform speed, the shaft 9, the mounting sleeve 6, and the pistons 5 oscillate relative to the pistons 4 to expand and contract combustion chambers 30 which are each bounded circumferentially by respective faces of a piston 4 and a piston 5. A fuel mixture is admitted to each combustion chamber through ports in the casing wall 1 in a manner well known in itself, and only partly indicated in the drawing at 31 in FIG. 1, and the mixture is ignited in the proper sequence by spark plugs not visible in the drawing. The combustion gases are discharged through ports in the casing wall 1. All elements bounding the combustion chambers are hollow and liquid-cooled in a conventional manner, the bores of the screws 7 serving as conduits for cooling liquid supplied to the pistons 5. The pistons 4, 5 are preferably made of a light metal alloy, such as an aluminum alloy, for its thermal properties, among other advantages, obvious in themselves.

A cylindrical hub portion 20 of the carrier 10 is journaled in a sleeve bearing 21 centered in the cover 19. The end of the circumferential casing wall 1 remote from the gear carrier 10 is fixedly fastened to another cover 23 by means of screws 24, and a sleeve bearing 22 centered in the cover 23 rotatably receives a hub portion of the end wall 3. The entire sub-assembly which rotates at uniform speed during engine operation is thus journaled in the stationary casing assembly by means of the bearings 21, 22.

The portion of the engine which rotates at a cyclically varying rate and mainly consists of the shaft 9, the mounting sleeve 6, and the pistons 5, is journaled in the uniformly rotating sub-assembly by means of a needle bearing 27 in a portion of the carrier 10 closely adjacent the end wall 2 and a needle bearing 28 interposed between the afore-mentioned hub portion of the end wall 3 and a fixed axial extension 26 on the sleeve 6.

Because the larger pistons 4 are secured to the end walls 2, 3 by axial screws 4', and the smaller oscillating pistons 5 are secured to the sleeve 6 by the radial screws 7, the shapes of the pistons in the radial plane of FIG. 2 may be chosen freely for optimum performance. The larger pistons 4 flare in a radially outward direction, and the smaller pistons 5 taper in the same direction.

Because of the cyclic variation in the acceleration of the pistons 5 during normal engine operation, the gears 15, 16 are subjected to loads having sharp peaks, and wear of the gears was initially found to be an important facter determining the useful life of the engine between overhauls. The maximum height of the peaks could be reduced significantly by offsetting a counterweight 14' on each crankshaft 12 relative to a plane through the axis of the shaft 12 which passes through the axis of the crankpin 13. In other words, a diameter drawn through the axis of the crankshaft 12 and through the center of gravity of the counterweight is offset by a small acute angle relative to a diameter drawn through the crankshaft axis and the center of gravity of the crank, the offset being opposite to the normal direction of crankshaft rotation. The optimum amount of the offset is a function of the crankshaft mass, the mass of the connecting rods 14, the inertia of the oscillating elements, and the like, and must be determined experimentally or otherwise for any given set of conditions.

The relatively simple construction of the engine of this invention is made possible by the absence of a main shaft extending over the entire length of the engine. The fixed connection between the pistons 4 and the end walls 2, 3 permits the use of an axially split main shaft whose axial parts are respectively constituted by the hub portion 20 of the gear carrier 10 and the corresponding hub portion of the end wall 3.

The three crank assemblies 12, 13, 14 linked to one axial end of the shaft 9 hold that end centered and coaxial with the engine axis without requiring a bearing, only the other axial end of the shaft 9 being secured to the sleeve 6 which itself is journaled in the uniformly rotating output assembly of the pistons 4 and associated elements. The load is thus distributed evenly on the three gears 15 without need for extreme precision in the dimensions of the oscillating elements.

If so desired, the sleeve 6 and shaft 9 may be combined in a unitary structure, and the bearing 27 may be dispensed with in the modified device. Dimensions, however, are more critical in the modified device than in the illustrated arrangement. This is offset, at least in part, by the simplicity of the modified device and by the smaller mass of the engine parts which move at varying speed, thus permitting the engine to operate at higher speed under otherwise unchanged conditions. Obviously, other sub-assemblies of the engine may be replaced by unitary bodies.

The cylindrical engine casing 1 and the fixedly connected end walls 2, 3 move relative to each other during engine operation, and the sleeve 6 similarly moves relative to the end walls 2, 3. Tight seals between these moving elements are necessary for most economical operation of the engine, and it is preferred to provide an annular groove in one element, and to back a sealing ring partly received in the groove by an undulating strip of spring steel interposed between the sealing ring and the bottom of the groove so as to bias the sealing ring outward of the groove and into sealing engagement with the other element.

Driven apparatus may be connected to any portion of the split main shaft in a conventional manner if the casing wall 1 and the gear housing 18 are held stationary by commonly used devices not explicitly shown. The cylindrical hub portion 20 of the gear carrier 10 is thus available as an output shaft in the illustrated apparatus.

Other modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

Claims

What is claimed is:

1. In a rotary-piston, internal-combustion engine having a casing, two pairs of pistons mounted for rotation about a common axis while in sealing engagement with said casing so as to define chambers therebetween, motion transmitting means connecting the pistons of one pair to the pistons of the other pair for rotating the pistons of said other pair at cyclically varying speed when the pistons of said one pair rotate at uniform speed and for thereby cyclically expanding and contracting said combustion chambers, the improvement which comprises:

a. said casing having a circumferential wall about said axis and two axially spaced, radial end walls rotatable relative to said circumferential wall,

b. each piston of said one pair being fixedly fastened in said casing to said end walls for rotation therewith,

c. said motion transmitting means including a gear carrier fixedly fastened to one of said end walls, a crankshaft journaled in said carrier, actuating means for turning said crankshaft when said carrier rotates with said one end wall relative to said circumferential wall, and a connecting rod operatively interposed between said crankshaft and the pistons of said other pair.

2. In an engine as set forth in claim 1, an output shaft fixedly connected to said carrier for joint rotation about said axis.

3. In an engine as set forth in claim 1, two bearings operatively interposed between the pistons of the one pair and said circumferential wall, and two additional bearings operatively interposed between the pistons of said one pair and the pistons of said other pair for rotation of the pistons of said pairs relative to each other and relative to said circumferential wall.

4. In an engine as set forth in claim 3, said actuating means including a first gear on said crankshaft in meshing engagement with a second gear fixedly fastened to said circumferential wall.

5. In an engine as set forth in claim 4, a counterweight fixedly fastened on said crankshaft in a position in which a diemeter drawn through the axis of said crankshaft and the center of gravity of said counterweight is offset by a small acute angle relative to a diameter drawn through the crankshaft axis and the center of gravity of the crank of said crankshaft.

6. In an engine as set forth in claim 4, said motion transmitting means further including two additional crankshafts journaled in said carrier, a gear on each additional crankshaft meshing with said second gear, and a connecting rod interposed between each additional crankshaft and the pistons of said other pair, the three crankshafts being equiangularly spaced about said axis.

7. In an engine as set forth in claim 6, a tumbler shaft mounted for rotation about said axis, said connecting rods connecting a first axial portion of said tumbler shaft to said crankshaft for oscillating the tumbler shaft in response to uniform rotation of said carrier, and mounting means on said tumbler shaft securing the pistons of said other pair to a second axial portion of said tumbler shaft axially remote from said first portion.

8. In an engine as set forth in claim 7, said mounting means including a sleeve member enveloping said tumbler shaft and fixedly fastened to said second axial portion, a part of said sleeve member spaced from said second portion toward said first portion being journaled in said one end wall.

9. In an engine as set forth in claim 8, a radially elongated fastener member engaging said sleeve member and each piston of said second pair for fastening the piston to said sleeve member.

10. In an engine as set forth in claim 9, said fastener member having a bore, and said piston of the second pair being hollow and communicating with said bore.