Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01B—MACHINES OR ENGINES, IN GENERAL OR OF POSITIVE-DISPLACEMENT TYPE, e.g. STEAM ENGINES
  • F01B9/00—Reciprocating-piston machines or engines characterised by connections between pistons and main shafts and not specific to preceding groups
  • F01B9/04—Reciprocating-piston machines or engines characterised by connections between pistons and main shafts and not specific to preceding groups with rotary main shaft other than crankshaft
  • F01B9/06—Reciprocating-piston machines or engines characterised by connections between pistons and main shafts and not specific to preceding groups with rotary main shaft other than crankshaft the piston motion being transmitted by curved surfaces
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
  • F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
  • F01L1/02—Valve drive
  • F01L1/04—Valve drive by means of cams, camshafts, cam discs, eccentrics or the like
  • F01L1/08—Shape of cams
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
  • F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
  • F01L1/30—Valve-gear or valve arrangements, e.g. lift-valve gear characterised by the provision of positively opened and closed valves, i.e. desmodromic valves
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16H—GEARING
  • F16H21/00—Gearings comprising primarily only links or levers, with or without slides
  • F16H21/10—Gearings comprising primarily only links or levers, with or without slides all movement being in, or parallel to, a single plane
  • F16H21/16—Gearings comprising primarily only links or levers, with or without slides all movement being in, or parallel to, a single plane for interconverting rotary motion and reciprocating motion
  • F16H21/18—Crank gearings; Eccentric gearings
  • F16H21/36—Crank gearings; Eccentric gearings without swinging connecting-rod, e.g. with epicyclic parallel motion, slot-and-crank motion
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
  • F02B75/00—Other engines
  • F02B75/16—Engines characterised by number of cylinders, e.g. single-cylinder engines
  • F02B75/18—Multi-cylinder engines
  • F02B2075/1804—Number of cylinders
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
  • F02B75/00—Other engines
  • F02B75/16—Engines characterised by number of cylinders, e.g. single-cylinder engines
  • F02B75/18—Multi-cylinder engines
  • F02B2075/1804—Number of cylinders
  • F02B2075/1812—Number of cylinders three
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
  • F02B75/00—Other engines
  • F02B75/32—Engines characterised by connections between pistons and main shafts and not specific to preceding main groups

Definitions

• This invention solves the known problem of the desmodromic, or positive, control of a reciprocating member comprising a pair of rollers riding on a uni-lobe cam.
• uni-lobe cam is meant a cam whose one rotation' corresponds to only one reciprocation of the reciprocating member.
• desmodromic or positive control is meant that if the one roller is in contact with the cam, the other roller is no more than the running tolerance away from the cam.
• the uni-lobe is simpler, smaller for the same stroke and can use counterweights, fixed on its shaft, for balancing inertia loads.
• a cam mechanism it is possible for a cam mechanism to employ a second camshaft to bear the thrust loads, or can bear the thrust loads on walls, immovable or rotatable to provide variable compression. [7] The latter needs not a gearing of high strength/high accuracy/small clearance to connect the cooperating camshafts, is cheaper to make and compact. [8] The uni-lobe cam must control desmodromicly the reciprocating member in both directions. Unless the necessary cam profile can be defined as strictly as to provide the demanded quality and accuracy of the reciprocation the control is impossible, the cam cannot meet the contemporary demands.
• the centers curve derives from the cam profile and the radius of the roller. Likewise, keeping the center of the roller on the centers curve and moving it along its successive positions, the roller defines the profiles of two cams, one external and one internal. If the axis of a milling cutter follows the centers curve, while removing material from a plate, it is machining the two cams mentioned.
• GB 891 ,490 the control of the reciprocation is provided by a uni-lobe cam whose geometiy is described in Page 3, lines 50 to 69, and in Fig. 5.
• the profile is defined as the union of two concentric circular arcs and two connecting curves such that the length of the line, defined by the contact point of the top roller and the contact point of the bottom roller, is constant.
• the distance between the centers of the rollers is constant; the distance between the contact points of the two rollers is substantially variable, varying from a minimum length, equal to the distance of the centers inus the sum of the radiuses of the two rollers, to a maximum which, depending on the roller size, may become more than 10% bigger than the minimum for reasonable size of roller.
• GB 891,490 although the two rollers ride on a common cam, it appears that the top roller diameter is larger, probably because of its heavier loads.
• the mathematical derivation of the cam profile makes it clear that it is impossible to control the piston desmodromicly with a common cam and rollers of different diameter.
• a camshaft comprising a first external cam, to constrain the reciprocation at one direction, and a second complementary external cam, to constrain the reciprocation at the opposite direction, provides more robust cams of reduced size, easier construction etc.
• the secondary external cam is selected to be a circle, while in Fig. 49 the general case is illustrated.
• the motion converting mechanism of Fig. 8 consists of a pair of counter-rotating shafts (7) and (8).
• the shaft (7) has double-disk cams (9) and (10) to allow room for the cam (11) of the shaft (8).
• harmonic it is meant a sft ⁇ ctly sinusoidal motion versus the time, i.e. versus the shaft-angle in the case of a single-lobe cam and versus the shaft-angle times the lobe-number for the cases of multi-lobe cams.
• the additional merit of the three-in-hne of the Fig. 8, as compared to the single or twin, is that besides being perfecdy balanced with respect to inertia forces and moments, i.e. the rocking moments along the shaft, it is also full balanced with respect to the inertia torques, i.e. the twisting moments about the shaft. This feature makes it as perfectly balanced as the Wankel rotary engine.
• Multi-lobe cams impact, as many times as the number of lobes, stronger momentary torques from combustion and even worse torque impacts from inertia, which means as many times stronger impacts for the whole mechanism, gearing included.
• Fig. 1 illustrates a way to derive a reciprocation by forcing a pin or a pair of pins to ride on a cam, in this case to produce a strictly sinusoidal reciprocation, called harmonic reciprocation.
• harmonic reciprocation As it is geometrically shown in Fig. 24, if the pin is kept in permanent contact with the cam, and the center of the pin can move along a line then, as the cam rotates about its axis the pin will perform a harmonic reciprocation.
• FIG. 2 depicts the necerney modification of the cam profile in order to add or subtract some higher order Fourier components to the displacement of the pin of the Fig. 1.
• a third order sinusoidal has been added and has been subtracted respectively to derive the other two profiles.
• the general way for the geometrical derivation of the appropriate cam profile is outlined in Fig. 24.
• Fig. 3 shows the way a single-lobe cam, which derives a harmonic reciprocation, needs to be modified if a different motion for the pin is, for some reason, more desirable than the harmonic motion. In most of the drawings, however, the design keeps on for cams deriving a harmonic reciprocation.
• Fig. 4 does compare the true dimensions, for the same stroke of the pin, of a three- lobe and a five-lobe cam, i.e. for identical harmonic reciprocation amplitude, e.g. piston stroke. Also Fig. 4 does compare the dimensions of the three-lobe cam with the dimensions of the single-lobe cam for the same stroke, again, to make it clear that only with a single-lobe cam reasonable dimensions are possible for specific stroke, either for the coaxial cams of Fig. 5 or for simply parallel cams or for the rest ways, here presented, deriving scissors-like action. [29] Fig. 5 shows one way to force the pin of Fig.
• Fig. 6 shows a second way to force the pin to ride on the cam control surface of Fig. 1 , i.e. by means of a second cam which is simply parallel, but not coaxial, to the cam of Fig 1.
• Fig. 7 proves that the pattern of Fig. 6 easily apply to a single piston.
• Fig. 8 illustrates a three cylinder twin-shaft engine.
• the cams are single-lobe and their counter-rotation takes place by means of a pair of gears (13) and (14).
• Fig. 9 is a cross section of the engine of Fig. 8 to reveal a piston arrangement.
• Fig. 10 is another cross section of the engine of Fig. 8 and a disassembly, to show the piston rod with its rollers
• Fig. 11 is a bottom view of the engine of Fig. 8 to show the two cams as they cooperate, the one being formed as a double-disk to allow a gap for the other cam to pass through, in order to keep them close to make the engine compact and the piston assembly strong, and the balance webs on the two shafts.
• Fig. 12 is a transparent view of the engine of Fig. 8 to show the three pairs of cams and the position of the respective pistons.
• Fig. 13, 14 and 15 depict a double-head piston four-cylinder or H-4 arrangement.
• Fig. 16 shows how a shuttle can be formed in a piston to house the cam throughout its rotation, i.e. to connect the reciprocating member with the rotating member desmodromicly, thereby provide an engine consisting of merely two moving parts, i.e. the rotating component and the reciprocating component.
• Fig. 17 shows the displacement of the piston of Fig. 16 as a result of the rotation of the single-lobe cam of Fig. 16.
• the single-lobe cam has full desmodromic control over the piston, i.e. complete control without any involvement of additional restoring means.
• Fig. 18 shows another way to force the pin of Fig. 1 to keep in contact with the control surface of the cam of Fig. 1, i.e.
• Fig. 19 shows the desmodromic control of a reciprocating roller trapped between a pair of non concentric cams and a pair of walls.
• Fig. 20 shows the wall version for a double-head piston and a X-type engine at right angle.
• Fig. 21 shows the mechanism at 12 successive angles of shaft rotation.
• the thrust rollers are coaxial to the rollers rolling on the frontal surface of the rotating cam-lobe. There are walls, not shown, where the thrust rollers roll on.
• Fig 22 shows an in line three cylinder engine having a single shaft with single-lobe cams, as well as the necüy immovable walls and the various parts disassembled.
• Fig 23 shows a shaft with a cam lobe and a piston assembly, with the piston at an offset from the axis of the shaft, as well as immovable walls for taking the thrust loads.
• Fig 24 and 25 show the geometrical construction of the cam lobe profile.
• Fig 26 shows two counter rotating cam lobes and immovable walls.
• the piston has a unique pin with rollers.
• Fig 27 is the mechanism of Fig 26 with the cam lobes rotating at the same direction.
• Fig 28 shows another realization of the mechanism with a unique cam lobe, immovable walls and the piston assembly.
• Fig 29 and 30 show a straight four balanced engine with a single shaft.
• Fig 31 shows the contact angle between roller and cam lobe.
• AU curves are for the same stroke and for sinusoidal reciprocation, i.e. harmonic.
• Fig 32 to 37 show a desmodromic valve control system.
• Fig 46 shows a mechanism similar to the one shown in Fig 28 to 30 with the difference that the piston has a connecting rod and the thrust rollers roll along paths which are rotatable for a few degrees about the main shaft, providing variable compression.
• Fig 47 to 49 show a mechanism based on a camshaft having two different complementary external cams. Each reciprocating roller cam follower rides on the external surface of its own cam.
• the two shafts counter-rotate by virtue of the equal gears (13) and (14).
• the cams on the shaft (7) are made as double-disk cam (9) and (10), to allow the cams (11 ) of the shaft (8) to pass through, so that no twisting moment is imparted to the piston assembly.
• the camlobes (9) and (10) of the shaft (7) and the camlobe (11) of the shaft (8) rotate.
• the rollers (5), (6) and (4) on the piston assembly (1) rolls along the peri phery of the camlobes, making the piston to reciprocate inside its cylinder.
• Adjusting means such as bolting, springs etc, known in the art, may be added to the rod assembly to provide the desirable clearances or preloading between the roller and the lobe.
• the rotation of the single-lobe cam is of the same order, i.e. frequency, as the reciprocation of the piston, thereby the webs (12) on die counter- rotating shafts suffice for the full balance of the forces and moments and, as the total kinetic energy of the three harmonically reciprocating members remain constant all along a revolution, there is no inertia torque altogether.
• the engine of Fig. 8 is as perfectly balanced as a rotary engine, e.g. Wankel rotary engine.
• the counterweight (12) are also to reduce the main bearing loads.
• FIG. 28, 29 and 30 illustrate an even simpler embodiment.
• the rail has the advantage of been easily adjustable.
• the even firing, straight four engine of Fig 29 has a single, one piece, shaft with a single-lobe cam for each cylinder.
• the engine is perfectly balanced as regards inertia forces and inertia moments.
• the rods connecting the upper part of the piston assembly to the lower part of the piston assembly could be just wires, as they are loaded with only tension loads.
• the thrust loads resulting from the mechanism are significantly stronger compared to the thrast loads of the conventional crank-rod mechanism.
• these strong thrust loads must be carried without losing excessive energy in friction.
• Fig 24 shows the way to create a cam lobe profile, given the amplitude of the sinusoidal, i.e. harmonic, reciprocation.
• the basic curve, upper left, has an eccentricity described as:
• a roller having its center on the periphery of the basic curve moves around the curve. Taking a circular disk, like the one shown in upped middle, and subtracting the roller as it rotates around the basic curve periphery, it results the upper right curve and finally the low middle curve. Holding two rollers, like the one used to subtract material from the circular disk, in a distance 2*a from center to center, shown in low middle, and pern ⁇ tting them to move only perpendicularly, die rotation of the cam lobe causes a harmonic reciprocation, along perpendicular axis, of the two rollers assembly, keeping both of them in permanent contact to the cam lobe. In the low right side is shown a groove made in similar way. Using a pair of counter rotating grooves, coaxial or parallel, it can result a reciprocation free from ⁇ irust loads.
• E(f) a + Y(f), where Y(f) is the desirable displacement along the perpendicular axis, relatively to the rotation angle, of the cam lobe.
• roller cam follower of radius Rl reciprocates with the piston and moves along an axis XL
• Another roller cam follower of radius R2 reciprocates with the piston and moves along an axis X2 parallel to XL
• the piston is controlled desmodromicly by the cam with the roller cam follower Rl at one direction, and with the roller cam follower R2 at the opposite direction.
• El is the centers curve of Rl roller while E2 is the centers curve of R2 roller.
• the angle between OAl and OBI is ⁇ , with ⁇ ⁇ ⁇ .
• ⁇ For each point of minimum eccentricity on the cam surf ace, there are two maximums at + ⁇ and - ⁇ angles, and for each point of maximum eccentricity on the cam surface there are two minimums at + ⁇ and - ⁇ , giving infinite maximums and minimums for random ⁇ as shown in Fig 42.

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Citations (5)

• 2003
  • 2003-10-29 GR GR20030100442A patent/GR20030100442A/el unknown
• 2004
  • 2004-10-29 WO PCT/GR2004/000052 patent/WO2005040558A1/en active Application Filing

Patent Citations (5)

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