CA1097568A - Rocking-piston machine - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A rocking-piston machine is provided with at least one cylinder, wherein a skirtless rocking piston reciprocates. The rocking piston is con-nected rigidly with a connecting rod which is articulated to a crankshaft or eccentric shaft. The cylinder has a circular, oval, square, rectangular or any other suitable cross-section and is waisted substantially according to the rocking movement of the edge of the rocking piston. The rocking piston and connecting rod assembly comprise means for guiding said assembly in the cylinder under prestress, which prestress is at least partially controlled by a fluid and increases automatically with increasing speed of the machine.
The improved rocking-piston machine runs relatively smoothly and quietly com-pared to the prior art devices and gives superior guidance of the rocking pistons in their waisted cylinders.

Description

75~8 INTRODUCTION ANI~ BA~K~.~OUND OF Tl~ I~VENTIO~
The present invention relates -to improvements in rocking-piston machines~ i.e. rrlotors, compressors and pumps and particularly to combustion engines. This app]ication is a division of Application Serial No. 272,845, filed February 28, 1977.
The drawbacks of the existing trunk piston machines are the well-known, comparatively rough and noisy running due to their heavy pistons with piston slap, high oil drag due to their piston skirt and in general their complicated, heavy and expensive construction.
These drawbacks can be overcome in rocking-piston machines, for example as disclosed in Canadian Patent No. 927697 or the corresponding United States Patent No. 3,695,150 and United Kingdom Patents Nos. 1316775 and 1388904. However, the guiding of rocking pistons in their waisted cylinders is not without problems.
Accordingly one object of the present invention is to improve the guiding of rocking pistons and to improve the machines in other respects.
BRIEF SUMMARY OF THE_ NVENTION
The invention provides a rocking-piston machine, for example an engine or compressor or pump, with at least one cylinder, wherein a skirtless rocking piston reciprocates, this rocking piston being provided with periph-eral sealing means pressed hydraulically against the waisted cylinder wall, the piston also being connected rigidly to a connecting rod which is artic-ulated to a crankshaft or eccentric shaft. The cylinder may have a circular, oval, square, rectangular or any other suitable cross-section and is waisted according to the rocking movement of the periphery of the rocking piston.
Such rocking-piston machines have a piston without skirt and gudgeon pin, forming one piece with the connecting rod running in a short, waisted cylinder. The rocking movement causes the gas pressure to act 1(3~7568 alwa~s dircctly ;llong the ax;s of the conllecting rod, so that there is no latcral compollcllt of this load to callse piston slap and thercfore noise and wear.
Because the piston, as it moves between top and bottom dead centres, rocks back and forth in the cylinder, highly advantageous, asymmet-ric port timing can be readily adopted for two-stroke petrol or diesel engines, and the compressed gas is transferred from side to side of the combustion chamber, thus encouraging soft and complete combustion and low exhaust pollution in either two- or four-stroke engines. With a short rock-ing piston of very light weight, the primary and secondary vibration forcesare less than half as severe as those of a conventional engine, so fewer cylinders can be used without exceeding acceptable levels of vibration. The skirtless rocking piston causes low friction losses, because the oil drag is very low. This means higher mechanical efficiency and much easier cold starting than with the conventional piston. Experimental rocking-piston engines on test beds and in vehicles have confirmed these facts, but showed that in particular the longevity of the piston-guiding device was inadequate.
The object of this invention is to create a rocking-piston machine of the kind described above but which runs perfectly as an engine, compressor or pump over a long period of time.
According to the invention there is provided a rocking-piston machine, as an engine or a compressor or a pump, of the kind comprising a skirtless piston, a waisted cylinder in which said piston reciprocates, a connecting rod rigidly secured to the piston, and a crankshaft to which the connecting rod is articulated, characterised by the provision of guiding means on the piston to slidingly engage with variable guiding pressure against the internal boundary surface of the cylinder, said guiding means being responsive to variable fluid pressure for varying said variable

-2-~7568 guicling l~ress11re, i111d pu~ ir1g mea11s for creating sc1ic1 var:iable fluid pressure, the pl1mpi11g me.ll1s 1-eing s~1c11 th.lt the speed of operation thereof a11cd the variable fluic11~rc?ssure anc1 the var;able guidi.ng pressure increase and decrease in depen(1ence upon the speed of the machine.
Brief Description of the Drawing The following explanation describes a few simplified examples of execution, which have by no means optimal dimensions and whose individual features are interchangeable. In all these examples of execution the piston surface as well as the piston stroke is the same. Further details necessary for optimum running of the rocking-piston machine are briefly described and illustrated in the drawing:
The drawing shows in:
Figure l a cross-section of the middle part of an engine or compressor according to the invention, Figure 2 a horizontal section of its circular rocking piston, Figures 3 to 7 enlarged cross-sections of various piston edges, Figure 8 a cross-section of an engine or compressor with a rectangular cylinder, Figure 9 a horizontal section of this cylinder and rocking piston, Figures lO and ll a rocking-piston slide-valve engine in cross and longitudinal section, Figure 12 a plan view of the rectangular cylinder with horizontal section of the rocking-piston, Figures 13 and 14 a variation of this rocking-piston in half longitudinal and in half cross-section, Figure 15 an enlargement of the piston-guiding device of Figure 13, . -3~

5'6~

F`;~ures1~ to l9 enlar~red var ations o~ the piston edge in longi--tuAinal section, Figure~20 and 21 an application Or an engine approximately accord-ing to Figure 10 to 12 in a vehicle in elevation and plan view.
Detailed Description of the Preferred Embodiments Figure 1 shows a conventional engine or compressor equipped with a waisted cylinder and rockingj-piston 1 according to the invention. This is the first generation of the rocking-piston machine, where the lower part of the original cylinder is eliminated and thereby shortened cylinder 2 is ~ e rAp~A/~ ~R~ S~6~o~ Q~ 6 ~j~
1 ~ machined not cylindrically, as usual, but in a waisted shape\according to the rocking movement of the piston edge 3. This machining is more complicated, but less costly, because the length of the original cylinder is reduced by one-third or even a half and much greater tolerances are admissable. For this machining, a kinematic inversion can be used, whereby the boring tool is rotated in a fixed plane, and the cylinder block is fed up and down relative to it and, at the same time, rocked by means of a crank-and-cam mechanism. However, it is simpler to fix the cylinder block and machine it by means of a special boring spindle whose tool is fed radially, cyclically and automatically. This can be achieved by a three-dimensional cam or by numerical control. By this means the simultaneous machining of the top and bottom parts of the cylinder, i.e. cone 4, is possible. This cone 4 serves to fit and remove the rocking_piston 1 from below, which is normally pos-sible, sometimes even without having to dismantle the crankshaft. The con-version is even simpler in the case of exchangeable cylinder liners, for instance dry liners 5, wet liners or air-cooled individual cylinders, whose waisted surfaces can be machined for instance on a special lathe. Further-more~ tubes can be cold formed, i.e. waisted by lateral pressing and then cast in~ which makes for low costs. As is known from conventional cylinders ~_ - 4 _ and Wankel trochoids, t~le walls of the waisted cylinders can, if necessary, be coated wear-resi~tantly and ground, or honed by flexible tools like "Flexhone" reg. The geometrical shape of the waisted cylinders can be cal-culated very accurately, as explained in Figure 8.
The rocking_piston 1 of an Otto engine according to Figure 1 is welded to the connecting rod 6. The light construction reduces the primary inertia forces to about half those of a conventional trunk piston; the sec-ondary inertia forces are even mor~ reduced by the long connecting rod 6 with its upper rotating point 7 slightly under the piston crown 8. This is a very important feature for four-cylinder four-stroke in-line engines. These low inertia forces make it possible to use a light connecting rod cover ~ as well as a light counter-weight 10. The rotating point 7 travels not on the longi-tudinal axis of the cylinder, but preferably on an elongated loop 11. With the usual parallel valves, the rocking movement of the piston crown 8 after the top dead centre causes a violent intake swirl, provided that with clock-wise rotation of the crankshaft the inlet comes from the right. Super-imposed on this inlet swirl is a uniflow transfer 12 of the charge, which is generated by the rocking movement of the piston crown 8 on the region of the firing top dead centre. This causes a very intense mixing of the charge.
The sealing ring 13, which mainly takes up the combustion pressure, has a cambered edge, is fitted under radial prestress and has a considerable radial slide. The gas force acts in the centre of the sealing ring 13 and at right angles to its sealing plane, i.e. always in the direction of the crank pin 1~. Thereby, no notable lateral component of the gas force and therefore no piston slap is created. It is just this fact which makes it possible to dispense with the piston skirt and therefore to render the rocking-piston possible.

However, due to the inertia of the rocking-piston 1 and of the connecting rod 6, dynamic lateral forces are generated by the rocking move-ment and the figure-of-eight loop 11. These dynamic forces increase to the square of the increasing rotational speed and are zero at the stroke dead centres. The guiding ring 15, acting as a second sealing ring, has an edge cambered either uniformly or according to the rocking movement and is pre-stressed against the base 29 of its groove, in order to guide the rocking-piston 1 in the bore of the cylinder 2 without any play. This prestress has to be sufficient to take up the dynamic lateral forces mentioned above as well as the superimposed reactions of the friction forces due to the radial slide of the sealing ring 13 and the rotation of the crank pin.
According to the invention, the prestress is achieved by hydraulic means, for example by heat-resistant, oil-filled pressure tubes 16, 16', for example of P.T.F.E. material, arranged at the base 29 of the groove. According to Figure 2, each of the pressure tubes 16, 16' is on a different side of the cylinder plane 2 A and is for example bonded in the bore 17 located near the cylinder plane, while their free ends are closed in such a way that the opposite pressure tube 16' is locally supported and that the pressure tube 16, 16' seals the whole circumference of the guiding ring 15. Each bore 17 leads to a longitudinal duct 19 formed by the profile 20 of the connecting rod 6 and via a non-return valve 22 in the connecting rod big end to a pref-erably non-loaded zone of the big end bearing.
This system works as follows: after starting the engine, both oil columns in the ducts 19 are put under pressure in the region of the top dead centre by inertia. This pressure is transmitted to the pressure tubes 16, 16' and prestresses the rocking_piston via the guiding ring 15 against the wall of the cylinder 2. The height of the guiding ring 15, i.e. its interior surface, has to be such that the prestressing force is more or less the same as the dynamic lateral forces mentioned above. The oil pressure and with it 7~

the prestressing force rises to the square of the increase of the rotating speed and therefore in the ss;me proportion as the dynam;c lateral forces. As a result, the machine can run at any speed furthermore, it always works with a minimum of friction and wear, because the prestressing force behind the guiding ring 15 is never stronger than is necessary for a safe guiding of the rocking-piston. Furthermore, this prestressing force is independent of the wear of the guiding ring 15 and of the wall of the cylinder 2, because this wear is automatically adjusted by the creeping of the material of the oil tubes 16, 16', i.e. its permanent deformation. The non-return valve 22 hin-ders the oil from flowing down the ducts 19 under the influence of its inertiain the region of the bottom dead centre, where this force is relatively small. The sealing element 23 of the non-return valve is preferably conical and has about the same specific weight as the oil, i.e. may be of plastic material. This hydraulic piston prestressing device also functions automat-ically when the machine speed is reduced, whereby a certain untightness of the sealing element 23 with a soft spring and short stroke is favourable.
An oil scraper ring 24 with sharp edge is arranged in the third ring groove radially slideable and is radially prestressed. Its action may be improved by U-shaped oil-catching channels 25 with profile 26 on both sides of the connecting rod 6. The rocking-piston 1 needs very little lubrication oil, and its surface in contact with the wall of the cylinder 2 is only a few percent of the surface of a comparable, conventional trunk piston. This improves the mechanical efficiency and considerably reduces the oil drag under cold starting conditions, thereby, enabling the use of a smaller starter and a smaller battery.
Furthermore, this low friction makes for a very low, stable idling speed. Oil cooling of the rocking-piston 1 can easily be achieved by an oil flow through the centre 27 of the connecting rod 6, with oil return if nec-_ 7 _ 1~7~

essary.
The hydralllic piston-guiding device described above can be sim-plified by connecting the right pressure tube 16 to the end 18' of the left pressure tube 16' instead of to the bore 17. The resulting single tube 16/16' must be contracted at the point 18' so that the oil cannot flow freely to and fro between the right and left halves 16 and 16' of the pressure tube; other-wise, the piston guiding would be affected by interconnected prestressing.
In other words, each half relative to the cylinder middle plane 2 A of the piston guiding system must have its own prestressing.
There are further possibilities to simplify the hydraulic piston-guiding device. For instance, the right pressure tube 16, which has mainly to support the reactions of the friction forces mentioned above, can be filled with oil and closed at both ends. However, the automatic ad~ustment of the wear of the guiding ring 15 and the wall of the cylinder 2 takes place on the left hand side only, i.e. asymmetrically. A further simplification would be to omit both non-return valves 22, provided it is possible to use the hydrodynamic pressure differences in the connecting rod big-end bearing to establish the necessary oil flow and pressure conditions in the pressure tube 16, 16'. This could be the case with a rocking-piston 1 running at a constant speed, for e~ample in a compressor.
According to Figure 3, the pressure tube 16 is replaced by an elastic supporting and sealing ring 30 functioning like the pressure tubes 16, 16'. This variant simplifies the oil supply to the ring 30, which guides the rocking_piston during starting. Xowever, synthetic elastic materials have proved to be insufficiently heat-resistant for combustion engines.
As a variant, the pressure tubes 16, 16' can be stiffened, for instance by undulated steel springs or the like preferably arranged inside the tubes. These springs produce the necessary prestressing of the rccking_ ~0'~7~68 piston for starting the machine, i.e. in the absence of oil pressure in the pressure tubes 16, 16'.
In Figure 4, the guiding ring 15 with covered ~oint is replaced by two guiding rings 15 a with cambered edges arranged in one groove. The base of the groove is semi-circular and preferably grour.d, so that t'ne pressure tube 16 can oscillate in it when the guiding rings 15 a slide radially against each other due to the rocking movement of the piston 1. Similarly, ~hree or more thin guiding rings can be provided.
In Figure 5, the sealing ring 13 is arranged directly on top of the guiding ring 15. This causes a reduced radial slide of the sealing ring 13 and has proved to work very well. However, with this arrangement of the rings 13 and 15 in one groove, aLmost the full gas pressure acts on the pres-sure tube 16, which is additionally heavily loaded by high temperatures, in spite of an insulation strip 31.
According to Figure 6, this disadvantage is avoided by arranging a preferably very thin, flexible partition plate 32 between the sealing ring 13 and the guiding ring 15. This flexible partition plate 32 can extend over the whole piston surface and is covered by a separate piston crown 33, in the edge of which the sealing ring 13 is located. A separate feature of the guiding rings 15 b is -that they have a common camber or dome 34 which, how-ever, scrapes the oil on the wall of the cylinder 2 very strongly upwards.
Therefore, at least a double oil scraper ring 24 is necessary.
More and different possibilities are presented by rocking-piston engines of the second generation, which are not adaptations, but new designs.
These machines have circular, oval, square or rectangular cylinders and pref-erably a lubrication system which renders the oil scraper ring 24 super-fluous. Circular cylinders can normally be machined and the rocking_pistons fitted from below, whereby the cylinder and the cylinder head can be made in ~,.

75&8 one piece, possib]y together with half of the or the whole crankcase. This kind of` machine is, of course, very simple and light, the more so as the smooth running of the rocking_piston without piston slap and with a minimum of vibration allows for a very light, thin-wall construction.
Figure 7 shows, as an example of execution, a circular rocking-piston assembled from a piston crown 33, the partition plate 32 and a base plate 35 with a downward stepped rim in which the quiding ring 15 and the pressure tube 16 are located. The components 33, 32 and 35 can be assembled for instance by spot-welding and bonded to a hollow connecting rod 36 shaped to give an optimal strength-to-weight ratio and consisting for example of glass-fibre or carbon-fibre stratified plastics or of magnesium. The circu-lar cavity 37 may be used for oil-cooling and be connected to the pressure tube 16, the oil being taken from and returned to an encapsulated forced-feed lubrication as is shown in Figures 10 and 11. Such rocking-pistons and connecting rod assemblies are extremely ]ight and therefore need a corre-spondingly low prestressing.
Figures8 and 9 illustrate a rocking-piston machine as an engine or compressor with a rectangular cylinder 40 with side proportions of two to one and the long sides parallel to the crankshaft. This shape of cylinder is especially suitable for air-cooled machines with air-stream flowing parallel to the crankshaft, that is for example for compressors, stationary engines or moped and motorcycle engines installed longitudinally and having one cylinder or two cylinders in Vee or opposite configuration and preferably with cardan shaft drive to the rear wheel. Furthermore, this rectangular shape of the cylinder 40 allows very large, parallel valves 41 and 42, a central sparking plug 43 and a very short connecting rod 44, which can be forked if necessary. This shape of cylinder 40 is also particularly suitable for side valves or for a laterally arranged, long rotary valve with favour-~q7~

ably small dia~neter. The cylinder 40, the crankcase 45 and if possible thecylinder head are cas-t in onepiece of light metal with cooling ribs, its open and being closed by a cover 46. This layout enables the waisted cylin-der walls 47 and the flat rear wall 48 to be machined from the open end by tools guided by cams or m~merical control.
The waisted cylinder walls 47 are parallel to the theoretical cylinder curve 52 at a distance 51 which is the radius of the camber or dome of the guiding strip 49. The theoretical cylinder curve 52 is drawn by the upper ends of a "T" with a width 53 corresponding to the theoretical piston width and a height 54 corresponding to the length of the connecting rod 44 when the lower end of the "T" moves a circle 55 with a radius 56 cor-responding to half of the piston stroke. The theoretical cylinder curve 52 was first empirically and then mathematically researched. This led to the discovery that for a rocking-piston crank drive symmetrical to the cylinder axis, mathematically accurate cylinder curves 52 do in fact exist irrespec-tive of all the ratios of piston width 53, connecting rod length 54 and half piston stroke 56. However, for extreme ratios, these curves 52 oscillate too much, whereas for the usual geometric ratios of piston machines they are normally favourably shaped for waisted cylinders. A particularity of these theoretical cylinder curves 52 is that, for instance, an enlargement of the theoretical piston width 53 causes the curves to oscillate, whereas a further enlargement of the piston width causes these oscillations to disappear. An advantage of rectangular or square rocking-pistons is thæt they give mathe-matically accurate waisted cylinder walls 47, provided the crank drive is symmetrical to the cylinder axis. Circular rocking-pistons have no constant theoretical piston width 53 and therefore a compromise has to be found to minimalise the local radial inward and outward movements of the guiding ring 15, these ring movements being easily taken up by the pressure tubes 16. In 1~7S~B

order to firld the best possible compromise, a programme has been worked out which comprises about a thousalld punched cards of a big computer.
The waisted cylinder walls 47 and also the wall of a circular, waisted cylinder may differ slightly from the mathematica] shape to further improve the rocking piston running. For instance, the cylinder width can be slightly narrowed at the places where the dynamic lateral forces, due to the inertia of the rocking_piston 51 and connecting rod 44, are high, in order to locally increase the prestressing of the rocking-piston against the cylinder walls 47. Such a reduction of cylinder width can also be provided in the hotter region of the cylinder in order to compensate for thermal expan-sion.
The rocking-piston 57, shown in bottom centre position, has sup-porting ribs 58 and forms one piece with the connecting rod 44, for example in light metal; the rectangular piston crown 59 with the partition plate 60 is screwed or bonded to it. The piston ring 15 has to be superseded by a piston rectangle which is composed of two guiding strips 49 with the dome radius 51 and two sealing strips 50 with flat or domed edges. The strips 49 and 50 can be made in one piece to form identical corners, two of which make up the piston rectangle, ~these corners 49/50 act as a second piston seal due 20 to their overlapping ends and to the pressure tubes 61 and 62. On a clockwise rotating rocking_piston 57, preferably the right pressure tube 61 is filled with a liquid and closed at the ends, whereas the left pressure tube 62 has a connection 63 bonded to a bore in the rocking-piston. This connection 63 leads to a longitudinal bore 64 in the connecting rod 44 which bore is closed at both ends. The non-return valve 22 is pressed into the longitudianal bore 64, below which a gas-filled, elastic bubble 6-5 is located. The pressure tube 62 and the longitudinal bore 64 are filled with liquid which is under sufficient pressure from the compressed elastic bubble 65 to start the machine. ~hen the machine is runni~K, this pressure increases automatically under the influence of the inertia of the liquid column in the longitudinal bore 64 in the region of the top dead centre, thereby giving the hydraulic piston-guiding explained in Figure 1. ~lowever, in the ex&mple of execution according to Figures 8and 9, the hydraulic system is hermetically sealed and works without an oil feed from the crankshaft, whereby no forced-feed lubri-cation is necessary and no air can penetrate. In addition, there is a free choice of the hydraulic liquid with regard to its specific weight~ boiling and freezing point, viscosity etc.
To relieve the gas pressure on the guiding and sealing strips 49, 50 separate sealing strips 66 are provided above them ana are laterally slideable in the s&me way as the sealing ring 13. These separate sealing strips 66 are preferably constructed more or less in the same way as their counterparts 49, 50 and may be stamped out of sheet metal. These sealing corners have to be forced apart by suitable springs which replace the natural prestressing of the sealing ring 13, these springs being arranged for example in transverse grooves of the piston crown 59.
The layout of the crankcase 45 is similar to that of small two-stroke engines with for inst&nce a light-spring automatic inlet valve through which additional air is sucked in. This additional air is compressed inside the crankcase 45 and pushed into the cylinder through several transfer chan-nels 67 arranged at the bottom of the right cylinder wall 47. This occurs in the region of the bottom dead centre &nd according to the diagr&m 68, 69, asymmetrically to the dead centre. With compressors anti-clock~se rotation may be preferable so that less piston stroke is lost. Such compressors may have guiding and sealing strips 49, 50 made from plastic material, for in-stance on a P.T.F.E. base and possibly have no sealing strips 66, making them suitable for dry, unlubricated runnlng. The additional air mentioned above serves to cool tl~e connecting rod 44 and the rocking piston 57 and to in-crease the output o~ compressors and engines. With four-stroke Otto engines, the additional air is conducted to the exhaust gases at the end of the work-ing stroke which encourages the scavenging of the combustion chamber and later on an afterburning of the subsequent eYhaust gases. Furthermore, at the end of the intake stroke, during which an especially rich fuel-air mixture is drawn in from the top of the cylinder, additional air is fed in from below and forms an air layer on top of the rocking-piston, which produces a simple charge stratification with the rich mixture close to the sparking plug 43.
It is, of course, understood that the transfer channels 67 will be situated and shaped in the walls of quadrangular or circular cylinders in such way as to create the best possible conditions for increased output and/or charge stratification.
Even more promising is a combustion engine of the third generation as presented in Figures 10 to 12 in the bottom dead centre position. This is a small Diesel rocking-piston slide-valve engine working with two-stroke cycle and it uses all the inherent advantages of the rocking-piston, leading to a very simple, light and compact construction, reduced consumption and air pollution and particularly low running noise.
The housing of this in-line engine consists of a cylinder head 70, a cylinder block 71 and a crankcase half 72 in light metal or cast iron and is assembled with a minimum of parallel screws 73, 74. Here, too, the cylin-der has a rectangular shape again with the ratio of two to one, for instance, but unlike Figures 8 and 9, the short sides are parallel to a crankshaft 75.
The waisted running surfaces are now on the short sides of the rectangular cylinder and consist of separate, waisted cylinder inserts 76 or 77 which are installed in a rectangular cross-section aperture 78. This aperture is pre-cast in the cylinder block and broached and then possibly smoothed and cali-75i~

brated by a conical punch. The waisted cylinder insert 76 is of rigid con-struction and has a fixing bolt 79 friction welded to it. Simpler is a thin-wall insert 77, the top of which is bent to form a corner 80 which is clamped by a cylinder head 81. The waisted cylinder inserts 76 and 77 can be manu-factured easily by conventional methods of profile production and may be coated, as known for instance from the Wankel trochoids and ground in a simple manner, their coated and ground surfaces being, however, three times smaller than those of a comparable Wankel engine. The long, flat cylinder wall 82 can have a cylinder insert 83 made of flat sheet metal with a bent corner 84 and stamped gas ports 85. In this case, a tooth 86 or the like serves to seal and fix the corners 80 and 84 against each other until they are clamped by the cylinder head 81. In order to prevent the thin-wall cylinder inserts 77 and 83 from bending under thermal expansion, they must be bonded to the aperture 78 of the cylinder block 71 or pre-stressed outwards or be very flexible. All the cylinder inserts 76, 77 and 83 are exchangeable, if necessary, for easy engine overhaul. The very narrow cylinders give large cylinder interspaces 86 in which the exhaust ducts 87, inlet ducts 88 and transfer channels 89 are arranged and which allows even air-cooling.
The force-fed lubrication of the crankshaft by a usual oil pump is encapsulated with respect to the crankcase which requires the sealing of the crank pin 91 and the journal 92 bearings. The sealing of the crank pin 91 bearing is effected by tapered disc springs 93 which, for assembly, are diametrically split and run on tapered collars of the crank pin 91 and are therefore automatically prestressed axially when fitted. As variations, a C-shaped steel seal 95, preferably with plastic insert, is advantageous, particularly so if combined with a bearing shell 96. These sealing elements 93 and 95 abut against and seal the big-end of the connecting rod 97. The oil return from the crank pin 91 bearing takes place through a number of outwardly inclined bores 9O under centrifugal force into an annular space 99, into which also the oil from the ~ournal 92 bearing, i.e. the main bearing, escapes. The annular spaces 99 are sealed against the crank discs 100 by sealing rings 101 arranged in cir-cular grooves of the crank discs 100 and run in large-diameter bores of the cylinder block 71 and crankcase lower half 72. The big sealing rings 101 are for instance made from bent spring-steel strips may be for instance P.T.F.E. coated; their diameter may be considerably reduced by feeding the oil from the crankpin 91 bearing back through bores 102 inclined inwards.
This encapsulated, force-feed crankshaft lubrication, together with a tight and close crankcase, if necessary equipped with fillers, makes it possible to employ a simple two-stroke crankcase pump and thus eliminate a separate, noisy charger. It also serves to cool the rocking-piston 105 and connecting rod 97 assembly by air. In addition, this lubrication system largely avoids the pollution of the lubrication oil by combustion gases and carbon deposits especially with Diesel engines, thereby replacing highly undesirable oil change by simple and more economic topping-up. Another advantage of this encapsulated lubrication system is that it dispenses with oil-scraper rings which, as well known, produce great friction losses and have a highly varying efficiency. However, this feature cannot be used with conventional trunk pistons, the skirt of which need oil splash from the crankshaft.
The rocking-piston 105 and connecting rod 97 are made in one piece, for example as a light metal casting, the connecting rod cap 104 being preferably of steel to reduce the danger of big-end seizing at very low tem-peratures, which danger could of course be avoided by making the heavily dimensioned crankshaft 91/92/100 out of light metal as well. The rocking-piston 105 has two integral, asymmetric flat slides 106 which also stiffen 7~

the long piston sides. The connecting rod 97 has a cross-shaped 108 or alternatively ~I-shaped profile and is in one piece with one or more horizon-tal ribs 107 supporting the flat slides 106 and has on each side a vertical wall 109, all of which makes for a very stiff and easy-to-cast connecting-rod rocking-piston slide-valve assembly suitable for Diesel operation. The flat slides 106 dip in and out of local apertures 110 of the crank discs 100, provided the connecting rod 97 is not lengthened accordingly. The rocking-piston 105 has a rectangular, continuous groove strengthened, if necessary, in which guiding strips 111 and sealing strips 112 are located. Each guid-ing strip 111 and sealing strip 112 forms one piece, i.e. a guiding and sealing corner 111/112. Two such identical corners 111, 112 are arranged in one common groove with their ends abutting, forming a pair. Two such pairs are arranged on top of each other, with the abutting ends of the top pair diagonally opposite to the abutting ends of the lower pair, making for a very simple and effective sealing. This system of four identical sealing corners 111/112 has only four joints, all overlapping, whereas the simplest gas seal-ing of a rotary engine has fifteen partly different dealing elements with twelve open and six overlapping joints. Furthermore, the sealing length of a rocking-piston is 2.6 times less than that of a comparable rotary piston, and the dwell time of the gases is shorter. The guiding and sealing corners 111/112 should be made from convenient, wear resistant material or must be wear resistantly coated, especially the dome 113 of the guiding strips 111.
Such material and coating are well-known from trunk piston and rotary piston research.
The sealing strips 112 are prestressed against the flat cylinder walls 82, 83 for instance by ]ight undulated springs 114, whereas preferably the right guiding strips 111 are prestressed by a strong undulated spring 115. The opposite guiding strips 111 are prestressed again by oil pressure 1~756~

varying to the square of tile crankshaft speed, but with a mechanical trans-mittin6 device. This device consists of a half-moon shaped force-distributor 120 pushed against the rear s;de of the guiding strip 111 by a push rod 121, the free end of which is cut at an angle to form an oblique end 122 which is in contact with a small hydraulic piston 123, the end of which is cut at a corresponding, complementary angle. This piston 123 and the push rod 121 are cylindrica] and closely fitted in drillings of the rocking_piston 105, their oblique ends 122 being sliding surfaces and therefore for instance hardened and ground. The small hydraulic piston 123 can have sealing rings or the like and is actuated by an oil column in a longitudinal hole 124 of the con-necting rod 97. This oil column is put under pressure by its inertia in the region of the top dead centre, this pressure being maintained in the region of the lower dead centre by the non-return valve 125, as explained in Figure 1. The lower end of a longitudinal hole 124 is connected to the forced-feed lubrication of the crank pin 91. Alternatively, it may be closed as in Fig-ure 8. The longitudinal hole 124 is preferably formed by a steel tube 126 cast into the light-metal connecting rod 97, in order to prevent its undue thermal lengthening which would affect the position of the rocking-piston relative to the waisted cylinder. The drilling locating the small hydraulic piston 123 is endwise closed, its oil leakages as well as the gas leakages of the push rods 121 are evacuated downwards through a small venting port 127. The components 120 to 123 are symmetrically arranged and prestressed by a coil spring 128.
With this hydromechanic piston guiding system, the prestressing of the guiding and sealing strips 111 against the cylinder surface can be chosen at will, independent of the oil pressure, simply by varying the angles of the oblique ends 122. With a narrow angle of the oblique end 122 of the small hydraulic piston 123, which however must not be self-locking, high force ~75~8 multiplications can l)e achieved. As var;arlts, t:he small hydraulic piston l2a n~ay be lengthened and have several oblique ends 122 to activate several push rods 121, whereb~T the force distributors 120 can possibly be dispensed with. Furthermore, the -.trong undulated spring 115 can be omitted, rendering the prestressing system rigid. The same would be the case with syrnmetrically oblique ends 122, i.e. Vee-shaped ends acting on push rods 121 on both guid-ing and sealing strips 111, with the advantage that the automatic adjustment of all wear takes place on both sides, i.e. sym~.etrically to the longitudinal axis of the connecting rod 97.
The rocking-Eiston guiding and sealing corners 111, 112 are lubri-cated by leaks of the encapsulated, forced-feed lubrication of the crankshaft and/or by fresh-oil supply 130 arranged prefera.bly on the left side of the waisted cylinder, because the sealing strips 112, due to their rocking move-ment, always scrape the oil from left to right 5 when the engin~ rotat~s clockwise.
According to Fig~reslO and 11, the two-stroke rocking-piston slide-valve engine has an optimal reverse or loop scavenging with asymmetric timing of inlet 131, transfer 132 and exhaust 133 with considerable aftercharge, achieved by the rocking movement of the flat slides 106. With the narrow rocking-piston 105, the area of the interface between the transfer 132 and exhaust 133 gases is very small, so there is less interchange of heat and reduced mixing of the gases and therefore more complete scavenging. This engine is suitable as a petrol engine with carburettor, but a low-pressure fuel injection, for instance according to the arrow 13~, would be particu-larly attractive. Due to a comparatively low compression ratio and the absence of hot valves, low-octane and lead-free petrol can easily be used.
9~ ' J`p ~J6/2 1 ,4~
- However, with a high compression ratio, a ~er1~ combustion chamber 135, an injection nozzle 136 and a spark plug 137 arranged approx-R ~ 9 --75~

imntely as illus-trat,ed, multi-fuel running of the engine is possible. The in~ection nozzle 136 has for instance three jets at right angles, two of which are directed across the uniflow air-transfer 13O and one towards the sparking plug 137. Even with this direct injection, the uniflow air-transfer 138 produces a soft increase of combustion pressure, thanks to the supply of air continuing after top dead centre, therefore making for silent engine running. The direct fuel injection can be replaced by a precombustion or swirl chamber, which is suitable for Diesel or petrol operation with strat-ified charge and whose communicating holes are again directed across the uniflow air-transfer 13O.
At any rate, the rocking_piston offers new possibilities for fuel mixing and combustion, whereby the absence of hot exhaust valves and the inherent exhaust gas recycling strongly reduce the N0 content of the exhaust gases. The comparatively hot exhaust, possibly fitted with portliners, facilitates the afterburning of the CH. A further reduction of the exhaust pollution can be achieved by adding a turbocharger or pressure wave machine, which also increases the engine output.
As a variant~ Figures13 to 15 show a rocking_piston and connecting rod assembly for a thermally highly loaded engine, for instance for mopeds and motorcycles. Therefore, the rocking_piston 140 is an internally ribbed steel forging to which a flat slide, preferably sta~.ped from chrome steel, is spot welded. The connecting rod 142 is a steel forging as well and has a non-split big end 143 with roller bearing attached to a fabricated crank-shaft. The rocking-piston 140 is therefore screwed to the connecting rod 142 and can be withdrawn simply by dismantling the cylinder head. The exact alignment between rocking-piston 140 and connecting rod 142 is assured by flanges 144, and tight sealing of the flat slides 141 is achieved by pro-jections 144 of the connecting rod 142 to which they abut.

~ .

75~8 The double gllidine strips 11 are prestressed against the cylinder wall through force-distriblltors 120 by two push rods 121 with oblique ends 122, each of which is actuated b~ the corresponding, complementary oblique end of an actuating mass 1~5 arranged vertically. This actuating mass 145, due to its inertia in the region of the top dead centre, causes the necessary prestressing force on the guiding strips 111, which force automatically increases, as required, to the square of the increasing engine speed. In the region of the bottom dead centre, the actuating mass 145 is hindered from falling back by oil pressure built up in the region of the top dead centre and retained by a non-return valve 146 which is enclosed in a pocket 147 made, for instance, of P.T.F.E. material, as may be the ball 148. The pocket 146 is extended do~mwards through a passage in the housing 149 of the rocking-piston to form a liguid reservoir 150 and is hermetically sealed at its bot-tom end. This reservoir serves for re-adjustment of all wear and is put under light pressure by a surrounding, elastic tube 151. The hydromechanical rocking-piston prestressing device works in a different way to that in Figures 10 to 12, the prestressing force here being generated mechanically and sus-tained hydraulically. Furthermore, it is independent of any oil supply and confined to the rocking-piston, i.e. can easily be fitted and withdrawn with it. It is completely leak-proof, arranged in comparatively cool zone of the piston and allows a free choice of the liquid.
According to Figure 16, the guiding strips llla have no common dome so that they slide against each other due to the rocking movement of the piston 140. This sliding movement prevents the guiding strips llla and the sealing strips 112 from sticking in their grooves and is made possible by an oscillating member 155 being interposed between the guiding strips llla and push rods 121 or force-distributors 120 shaped accordingly. The oscillating member 155 is a semi-circular rod, the side of which abuts against the guid-~s~

75~

ing strips llla and is not flat, but double-Vee shaped as shown in the draw-ing. Obviously, the opposite groove of the rocking-piston 140 must have a semi-circular base and an oscillating member 155 as well. Three guiding strips llla are also possible, but with slightly different prestressing.
This is also the case in Figure 17 where four guiding strips lllb are arranged in one groove, the intermediate two being actuated by the oscil-lating member 155 slideable in an outer oscillating member 156 which actuates the top and bottom guiding strips lllb. Such an arrangement, consisting of eight identical guiding and sealing angles lllb/112b, with their abutting ends alternatively arranged in different corners of the rocking-piston, insures high gas-tightness between the rubbing surfaces of the guiding and sealing strips lllb, 112b and the cylinder walls.
The variant according to Figure 18 has a solid or hollow guiding roller 157 or needle located in a case 158 which is again actuated by push rods 121. The guiding roller 157 or needle rotates at least partially on the waisted walls of the cylinder inserts 76, 77, thus reducing friction and wear, especially so when its bearing surface on the case 158 is partially running on compressed gas.
Two or more guiding rollers 157 or needles may be arranged on top of each other analogous to Figure 16 and 17. Such an arrangement seems to be possible for example on the rocking-piston of a big or very big Diesel engine having square cylinders and heads with four parallel valves and approximately central fuel-injection and running in two-stroke or four-stroke cycle.
Figure 19 shows a particularly simple and versatile hydromechanical device for prestressing rocking-pistons aga~`nst their circular, rectangular or other convenient cylinder walls. This device can be incorporated in any of the examples of execution mentioned above, but is here explained with reference to Figures 2, 7 and 9. The piston crown 33, 59 can have a sealing ring 13 or sealing strip 66 and a flexible partition plate 32, 60. The guid-;.:

75~

ing ring 15 or guiding strip 49 is prestressed against the cylinder wall by the pressure tube 16, 62 which has a more or less cylindrical extension or pocket 160 preferably central to the cylinder plane 2A and is filled with liquid and closed at its ends in the region of the cylinder plane 2 A. The interior diameter o~ the pressure tube 16 diminishes towards these ends in order to reduce the hydraulic prestressing of the rocking-piston against the cylinder wall in regions where practically no dynamic forces must be sup-ported. Analogously, the same is the case with the pressure tube 62 which has also a central pocket 160 and a small interior diameter on its short sides with closed ends. The pockets 160 and therefore the pressure tubes 16, 62 are put under pressure by the inertia of a preferably cylindrical acutating mass 161 of convenient high and specific weight in the region of the top dead centre. This hydraulic pressure is maintained in the region of the bottom dead centre by a hydraulic cushion closed by the non-return valve 162, of plastic material, under which again a liquid readjustment reservoir 164 is located, which may be prestressed for instance by a coil spring located in an extension of the device housing 165 of the rocking-piston base 166. This pressure retaining device is again hermetically sealed in a pocket 167 made for instance in P.T.F.E. One or more of these devices 160 to 167 can be fitted to a rocking-piston and can easily be removed from above, to-gether with the other wearing parts. By pulling the pocket 167 downwards, the pressure in the tubes 16, 62 is released, making easy to fit the rocking-piston 140 from above. The plugs 163, 148 and 23 should be lignt, for exam-ple hollow or of foamed material, so that they float in the liquid in the non-return valves.
The elements of the described examples of embodiment are normally interchangeable with each other and are subject to detail modifications and refinements, while still remaining within the scope of this invention. The 5~

inventive rocking-piston prestressing devices are applicable to any type and size of rocking-pistolltnachines. They may even be indispensible in tiny rocking-pistons of, for instance, compressed-air motors for hand tools or household refrigerator compressors, superseding the possible use of elastomer 0-rings behind the guiding and sealing elements, the efficiency of which inevitably ceases over longer periods of time. Contrary to this, the inven-tive hydraulic or hydro-mechanical rocking-piston prestressing device has the unique advantage that the prestressing is reset under the influence of inertia forces with every revolution of the machine, i.e. is regenerated 10 permanentlY-As a last variant, especially suitable for tiny rocking_pistons as mentioned above, the pressure tubes 16 snd 61, 62 can run directly on the cylinder walls, their outer surface being strengthened and coated according-ly. Tiny rocking-piston connecting-rod assemblies are provided as one-piece plastic mouldings with a prestressing device somewhat as shown in Figures 8 and 19.
As already mentioned, for combustion engines, especially Diesel engines, a layout somewhat according to FigureslO to 12 seems to be most promising. This rocking-piston slide-valve engine has the same firing interval, i.e. true running as a four-stroke engine with double the number of cylinders and is extremely simple in construction and maintenance. Thanks - to its inherent soft combustion, successive opening of inlet and exhaust ducts, slap-free rocking-pistons with reduced oscillating masses, the absence of gears, camshaft and ralves and thanks to a highly compact and rigid engine housing, this engine may have unprecedentedly silent and smooth running with low starting friction, low idling speed, low specific fuel and oil consump-tion and low exhaust pollution. It is applicable as a stationary, boat or light-aircraft engine as well as a prime mover for any kind of motor and -- 2~ -~7568 agricultural vehicle, mak;ng for substantial secondary advantages. For instance, when fitted longitudinally or transversally to automobiles, it can normally be arranged horizontally with a luggage comparatment above it ana then can slide underneath the car in a crash, thus not shortening the crush zones. According to Figure 10, the direction of rotation is preferably clockwise, whereby the forces acting on the rocking_piston, i.e. its weight and the reactions of the connecting rod big end friction and of eccentric combustion pressure waves, due to an asymmetrically arranged combustion chamber, all act on the same, lower cylinder wall, which makes for a stable state, especially when starting.
As a particular example of adaptation, a two-cylinder, 1200 ccm engine is installed in a safety car and represented in Figures 20and 21 in elevation and plan view. Because of its extreme simplicity, light weight and relative freedom from vibration, noise and maintenance, this rocking-piston slide-valve engine 170 makes it practicable to adopt an underfloor, mid-engine car layout which is not longer dominated, as hitherto, by the engine installation, therefore giving spacious passenger and luggage compartments and 70 cm crush zones at front and rear with an overall length of only 400 cm. After tilting the back seat 171 forwards and the protection shield 172 rearwards, the engine 170 as well as the accessories 173 and the conventional automatic gearbox 174 are very accessible and can even be checked when the car is on the move.- A primary gear reduction 175 drives a short, transversal cardan shaft 176 and a very compact final drive 177 of a consequently light rear axle 178 which is laterally guided by the transversal cardan shaft 1'76.
By choosing the ratios of the spur gears 175 and 177 and the length of the trailing links 179 accordingly, the anticlockwise rotating, transversal cardan shaft 176 produces the desired antidive effect. For dismantling, the engine 170 can be supported and the right side of the car tilted upwards.

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Air-cooling ùirect to the up~er, hotter cylinder side can easily be achieved by a centrifugal blower fitted to the free end of the crankshaft. A cross-country reduction 175' and, thanks to the tyre-saving rigid axle 178, twin tyres loO can be fitted.
Bigger cars, vans trucks and the like have an engine with three or more cylinders and, if desired, a constant-velocity, sliding transversal propeller shaft with separate lateral guiding of the axle 178, whereas very small city-cars with three or four wheels have the back seat directly above a centrally located engine and perhaps a standard gearbox with direct top gear; otherwise, a chain-driven primary reduction 175 is necessary.
The rear-axle drive according to Figures 20 and 21 and variants can be supplemented by a semi-automatic gearbox, a safety differential lock or a uni~oint elastic axle according to earlier patents of the inventor. However, this rear, axle drive is also of interest for orthodox, trunk-piston engines, if necessary with a balance shaft l~l, or for any other type of suitable motor.

Claims (26)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A rocking-piston machine, as an engine or a compressor or a pump, of the kind comprising a skirtless piston, a waisted cylinder in which said piston reciprocates, a connecting rod rigidly secured to the piston, and a crankshaft to which the connecting rod is articulated, characterised by the provision of guiding means on the piston to slidingly engage with variable guiding pressure against the internal boundary surface of the cylinder, said guiding means being responsive to variable fluid pressure for varying said variable guiding pressure, and pumping means for creating said variable fluid pressure, the pumping means being such that the speed of the operation thereof and the variable fluid pressure and the variable guiding pressure increase and decrease in dependence upon the speed of the machine.

2. A machine according to claim 1, wherein said pumping means in-cludes a column of liquid and a non-return valve provided in association with said connecting rod, the fluid pressure being generated by the inertia of the said column when the piston is in the region of its top dead centre and substantially maintained by the non-return valve and increasing sub-stantially as the square of the engine speed.

3. A machine according to claim 1, wherein said pumping means in-cludes a movable solid mass in association with the piston and connecting rod to generate the fluid pressure when the piston is in the region of its top dead centre, the fluid pressure increasing substantially as the square of the engine speed.

4. A machine according to claim 3, comprising a non-return valve in a fluid system for substantially maintaining said fluid pressure.

5. A machine according to any one of claims 1 to 3, wherein said guiding means comprises flexible pressure tubes filled with fluid and arranged in the edge of the piston for co-operation of the guiding means at least with the portions of said boundary surface where the cylinder is waist-ed, the fluid in the flexible pressure tubes being subjected to said variable fluid pressure.

6. A machine according to claim 1, wherein said guiding means comprises at least one hydraulic piston acting through a push rod on a guid-ing and sealing element, the hydraulic piston being subjected to said variable fluid pressure.

7. A machine according to claim 6, wherein said push rod has an oblique end engaged by an oblique end of the hydraulic piston.

8. A machine according to claim 1, as a four-stroke internal combus-tion engine, said cylinder being of substantially rectangular cross-section having longer sides parallel to the crankshaft.

9. A machine according to claim 8, comprising a crankcase with an air-inlet reed-valve.

10. A machine according to claim 9, comprising a crankcase pump as in small two-stroke engines formed by the piston underside and having air trans-fer channels.

11. A machine according to claim 9 or 10, comprising means for pressure-feed lubrication of the crankshaft, sealing elements between the crankshaft and the crankcase, and sealing elements between the crankshaft and the con-necting rod.

12. A machine according to claim 1, 2 or 3, wherein the connecting rod is provided with passages for fluid and with valves for generating said var-iable fluid pressure.

13. A machine according to claim 1, 2 or 3, comprising at least one valve which is biased to open and allow substantially free flow of fluid towards the rocking-piston during periods of increasing engine speed and to substantially close and allow only restricted flow of fluid away from the rocking-piston during periods of decreasing engine speed.

14. A machine according to claim 1, 2, or 3, wherein the guiding means includes guiding and sealing elements extending around substantially the entire periphery of the rocking-piston and slidably located between parts of the rocking-piston.

15. A machine according to claim 1, as an engine, or other engine, in an engine and rear axle drive assembly for a road vehicle, comprising a gear-box arranged in the prolongation of the engine, said engine and gearbox being attached transversally to the vehicle in the vicinity of its rear axle, said gearbox comprising a first reduction gear arranged at the free end of said gearbox and driving via a transversal propeller shaft the spur gear final drive of said axle.

16. An axle drive assembly according to claim 15, wherein the gearbox is of a conventional manual type.

17. An axle drive assembly according to claim 15, wherein the gearbox is of a conventional automatic type.

18. An axle drive assembly according to claim 15, 16 or 17, wherein the first reduction gear is supplemented by a cross-country reduction gear.

19. An axle drive assembly according to claim 15, 16, or 17, wherein the propeller shaft is of a non-slidable cardan type in order to guide the rear axle laterally.

20. An axle drive assembly according to claim 15, 16 or 17, wherein the propeller shaft is of a constant-velocity and slidable type.

21. An axle drive assembly according to claim 15, 16 or 17, wherein the rear axle is of the rigid live type.

22. An axle drive assembly according to claim 15, 16 or 17, wherein the rear axle is of the elastic type with an intermediate joint.

23. An axle drive assembly according to claim 15, wherein the ratio of the final drive is adapted to the suspension geometry of the rear axle in such a way as to achieve a desired anti-squat effect of the vehicle.

24. An axle drive assembly according to claim 15, 16 or 17, wherein the engine has one or more horizontal or other cylinders arranged in line.

25. An axle drive assembly according to claim 23, wherein said cylinders are waisted in conformity with the rocking movement of skirtless pistons which are connected rigidly to their connecting rods.

26. An axle drive assembly according to claim 25, arranged beneath the rear seat of an automobile, said axle drive assembly being accessible from above by tilting the back seat forwards and a protection shield rearwards.