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WO1992012337A1 - Moteur a rapport de compression variable - Google Patents

Moteur a rapport de compression variable Download PDF

Info

Publication number
WO1992012337A1
WO1992012337A1 PCT/GB1992/000006 GB9200006W WO9212337A1 WO 1992012337 A1 WO1992012337 A1 WO 1992012337A1 GB 9200006 W GB9200006 W GB 9200006W WO 9212337 A1 WO9212337 A1 WO 9212337A1
Authority
WO
WIPO (PCT)
Prior art keywords
piston
connecting rod
eccentric
gudgeon pin
engine
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/GB1992/000006
Other languages
English (en)
Inventor
Thomas Tsoi-Hei Ma
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Ford Werke GmbH
Ford France SA
Ford Motor Co Ltd
Ford Motor Co
Original Assignee
Ford Werke GmbH
Ford France SA
Ford Motor Co Ltd
Ford Motor Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ford Werke GmbH, Ford France SA, Ford Motor Co Ltd, Ford Motor Co filed Critical Ford Werke GmbH
Publication of WO1992012337A1 publication Critical patent/WO1992012337A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • 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
    • F02B75/04—Engines with variable distances between pistons at top dead-centre positions and cylinder heads
    • F02B75/045—Engines with variable distances between pistons at top dead-centre positions and cylinder heads by means of a variable connecting rod length
    • 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
    • F02B41/00—Engines characterised by special means for improving conversion of heat or pressure energy into mechanical power
    • F02B41/02—Engines with prolonged expansion
    • F02B41/04—Engines with prolonged expansion in main cylinders

Definitions

  • the present invention relates to a reciprocating piston internal combustion engine in which the distance between the piston crown and the centre of the crank pin, that is to say the effective length of the connecting rod, can be varied during engine operation.
  • GB-2 190 959 there is described a reciprocating piston internal combustion engine in which an eccentric sleeve is positioned between the crank pin and the connecting rod of the engine.
  • the eccentric sleeve is arranged to oscillate about the crank pin axis during rotation of the crankshaft by the action of a lever arm which is secured non-rotatably to the eccentric sleeve and is ovably linked to a control lever pivoted at its other end about a stationary anchoring pin.
  • the oscillation of the eccentric sleeve modifies the cranking motion and varies the compression ratio and the expansion ratio dynamically but the amount of oscillation and its phasing is limited by the geometry of the control linkage. It is necessary in this case to employ a complex external control system to match the compression ratio to the engine speed and load in order to ensure maximum efficiency and that the engine is not damaged by being operated with excessive compression ratio under high load.
  • GB 495,287 describes an engine in which bearings on the gudgeon pin for the piston are not concentric with the bearing for the connecting rod.
  • a cam is mounted on the gudgeon pin to rotate the eccentric bearing relative to the piston and thereby vary the compression ratio.
  • the cam is urged into a median position by a spring biassed cam follower which is mounted on the connecting rod.
  • the present invention seeks to provide an internal combus ⁇ tion engine in which the compression ratio can be varied by modifying the effective length of the connecting rod but which does not suffer from the disadvantages of the known prior art, as discussed above.
  • a reciprocating piston internal combustion engine having an eccentric arranged between each piston and its connecting rod and a spring acting between the inner surface of the piston and the outer surface of the connecting rod for applying a biassing torque to urge the point of maximum eccentricity on the eccentric to a rest position lying on a line transverse to the longitudinal axis of the connecting rod, the eccentric being free to oscillate about the rest position as a result of the forces acting between the piston and the connecting rod during engine operation so as to vary dynamically the instantaneous effective length of the connecting rod.
  • the gudgeon pin is provided with bearing surfaces for the piston and the connecting rod which are eccentric with respect to one another, the gudgeon pin being fitted to the piston by means of separate bearing sleeves or end caps as used to retain the cross of a universal joint in its forks.
  • the gudgeon pin has a concentric bearing for the connecting rod but is mounted in the piston by means of eccentric bearing rings which are fast in rotation with the gudgeon pin but can rotate relative to the piston.
  • Figure 1 is a section through a piston and the top end of a connecting rod of an en ine of the invention
  • Figure 2 is a section along the line I -II in Figure 1
  • Figure 3 is a section similar to that of Figure 1 through an alternative embodiment of the invention.
  • Figure 4 is a section along the line IV-IV in Figure 3.
  • a piston 10 is mounted on a connecting rod 12 by means of a gudgeon pin 14 which has a raised eccentric bearing 16 rotatably received within the connecting rod 12. Because the bearing 16 prevents the gudgeon pin 14 from passing through a bearing hole in the piston 10 having the same diameter as the end bearings 18 of the gudgeon pin 14, a larger hole is formed in the piston 10 at least at one end of the gudgeon pin 14 and the latter is retained in the piston 10 by means of a support sleeve or end cap 20 which is push fitted in the hole in the piston 10 but in which the gudgeon pin 14 can rotate freely.
  • a spring 22 is held in place by dimples 24 and 26 on the inner surface of the piston 10 and the outer surface of the connecting rod 12, respectively.
  • the arrangement described permits the gudgeon pin 14 to rotate freely relative to the connecting rod 12 and the piston 10.
  • the movement has two limit positions at which the maximum eccentricity lies on the longitudinal axis of the connecting rod (the line connecting the centres of the small end and beg end bearings), the compression ratio being increased in one limit position and decreased in the other.
  • the position adopted by the eccentric on the gudgeon pin 14 is determined by the forces acting between the piston and the connecting rod and the force of the spring 22.
  • the surir. 22 tends tc force the point of maximum eccentricity as far away from it as possible, that is to say to the 3 o'clock position as viewed in Figure 1.
  • dynamic forces act between the piston 10 and the connecting rod 12 which tend to realign the eccentric and dynamically vary the effective length of the connecting rod 12.
  • the piston has inertia and there is a reaction force when trying to make it reciprocate in the cylinder bore which varies generally sinusoidally with crank angle, being maximum upwards at top dead centre, maximum downwards at bottom dead centre of the crankshaft and negligible half way up the bore.
  • the movement of the piston is not exactly sinusoidal because of the finite length of the connecting rod but this approximation is adequate for an understanding of the invention.
  • the second force acting upon the piston is the reaction force from the compression of the gases in the combustion chamber. This force varies with the engine stroke and piston position, being maximum at top dead centre of the compression stroke and minimum at the bottom dead centre of the induction stroke.
  • the maximum eccentricity of the gudgeon pin will always tend to align away from the net force acting on it, this force being the resultant of the three dynamic force components and the static force of the spring 22.
  • the torque which causes this rotational motion is caused by the fact that the net force acts through the centre of the eccentric bearing 16 which is offset from the centre of rotation of the gudgeon pin 14 as determined by the end bearings 18.
  • the turning moment which is the product of the net force and the offset is enough to overcome any frictional torque on the bearing surfaces of the gudgeon pin 14.
  • the gudgeon pin will therefore naturally oscillate about its spring biased rest position as the engine operates in its various strokes.
  • the inertial force alone tends to increase the compression ratio towards the end of the compression stroke and exhaust stroke and to decrease compression (or increase expansion ratio) at the end of the power stroke and induction stroke. At low load, this force is dominant and this results in increased thermal efficiency and volumetric efficiency.
  • the combustion pressure can also bring about a rapid movement of the piston relative to the connecting rod if the combustion pressure is excessive and this limits the peak pressure and reduces the tendency to knock and the risk of resultant damage to the engine.
  • the arrangement can therefore be seen to achieve dynamic variation of the instantaneous effective length of the connecting rod which is beneficial not only during the compression and exhaust strokes but also during the intake and expansion strokes. Furthermore, the arrangement requires no external control being actuated by the forces which occur naturally during operation of the engine.
  • the oscillation of the gudgeon pin bearing 16 can be regarded as superposing on the reciprocating motion of the piston caused by the crank shaft a smaller amplitude oscillation of varying magnitude but which is always correctly synchronised with the crankshaft motion.
  • SAE 900229. the length of the connec ⁇ ting rod varies dynamically during an engine cycle whereas in the prior art the length is substantially constant during a cycle but may be varied from one cycle to the next.
  • the dynamic variation of the effective length of the connecting rod brings about a change in the working cycle of the engine which has four beneficial aspects.
  • Last, the maximising of the expansion ratio during induction increases the effective swept volume and the mass of the trapped intake charge.
  • the invention adds little to the reciprocating masses of the engine and does not require special lubrication or cooling.
  • the invention can furthermore be implemented inexpensively, in that it requires only minor modification to the piston/connecting rod assembly and does not add signi icantly to the component count nor to the complexity of. assembly.
  • the embodiment of Figures 3 and 4 operates in the same manner as that of Figures 1 and 2 and differs only in the manner in which the mutually eccentric bearings are formed and assembled.
  • the piston 10 and connecting rod 12 can, as in the case of the first embodiment, be conventional.
  • the gudgeon pin 14' can itself also be conventional but instead of being a push fit into the connecting rod 12 it is required to acts as a bearing for the connecting rod.
  • the ends of the gudgeon pin 14' have eccentric sleeves 20' which are a push fit over the ends of the gudgeon pin 14' .
  • the sleeves 20' are free to rotate relative to the piston 10 and are assembled in situ onto the gudgeon pin 14' in a jig which ensures that their points of maximum eccentricity are aligned with one another.
  • the only additional components required over and above a conventional engine are the two eccentric sleeves 20' and the spring 22.
  • the holes in the piston and the connecting rod are of course also dimensioned differently but that does not affect the manufacturing cost.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Output Control And Ontrol Of Special Type Engine (AREA)
  • Shafts, Cranks, Connecting Bars, And Related Bearings (AREA)
  • Pistons, Piston Rings, And Cylinders (AREA)

Abstract

On décrit un moteur à combustion interne, à piston à mouvement alternatif, comprenant un excentrique (16) placé entre chaque piston (10) et sa bielle (12) ainsi qu'un ressort (22) appliquant un couple poussant l'excentrique (16) vers une position de repos se trouvant sur une ligne transversale par rapport à l'axe longitudinal de la bielle, position dans laquelle le point d'excentricité est au maximum. L'excentrique peut osciller librement autour de la position de repos en raison des forces agissant entre le piston (10) et la bielle (12) au cours du fonctionnement du moteur, et cela fait varier de façon dynamique et instantanément la longueur utile de la bielle.
PCT/GB1992/000006 1991-01-05 1992-01-03 Moteur a rapport de compression variable Ceased WO1992012337A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9100202A GB2251457A (en) 1991-01-05 1991-01-05 I.c.engine with variable compression ratio
GB9100202.2 1991-01-05

Publications (1)

Publication Number Publication Date
WO1992012337A1 true WO1992012337A1 (fr) 1992-07-23

Family

ID=10688003

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1992/000006 Ceased WO1992012337A1 (fr) 1991-01-05 1992-01-03 Moteur a rapport de compression variable

Country Status (2)

Country Link
GB (1) GB2251457A (fr)
WO (1) WO1992012337A1 (fr)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB9408373D0 (en) * 1994-04-23 1994-06-15 Ford Motor Co Engine with variable compression ratio
DE102011111816B4 (de) 2011-08-27 2021-07-08 Volkswagen Aktiengesellschaft Vorrichtung mit Exzenter-Kolbenbolzen zur Erzielung eines variablen Verdichtungsverhältnisses in einem Hubkolbenmotor
CN103615316B (zh) * 2013-11-29 2016-06-01 东风小康汽车有限公司重庆分公司 活塞连杆链接总成

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE536393C (de) * 1928-05-15 1931-10-22 Anton Loer Steuerung fuer Zweitaktbrennkraftmaschinen
FR965917A (fr) * 1948-04-29 1950-09-26 Moteur avec un piston à course variable
FR1087991A (fr) * 1953-09-16 1955-03-02 Perfectionnements aux moteurs à combustion interne à quatre temps
EP0219634A2 (fr) * 1985-10-25 1987-04-29 Toyota Jidosha Kabushiki Kaisha Dispositif pour changer le rapport de compression utilisant un palier excentrique dans un moteur à combustion interne

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB473887A (en) * 1936-04-15 1937-10-15 Yasusaburo Hironaka Improvements in and relating to an internal combustion engine with means for varyingthe compression ratio
GB495287A (en) * 1937-03-22 1938-11-10 Charley Jonville Improved means for varying the piston stroke of internal combustion engines

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE536393C (de) * 1928-05-15 1931-10-22 Anton Loer Steuerung fuer Zweitaktbrennkraftmaschinen
FR965917A (fr) * 1948-04-29 1950-09-26 Moteur avec un piston à course variable
FR1087991A (fr) * 1953-09-16 1955-03-02 Perfectionnements aux moteurs à combustion interne à quatre temps
EP0219634A2 (fr) * 1985-10-25 1987-04-29 Toyota Jidosha Kabushiki Kaisha Dispositif pour changer le rapport de compression utilisant un palier excentrique dans un moteur à combustion interne

Also Published As

Publication number Publication date
GB9100202D0 (en) 1991-02-20
GB2251457A (en) 1992-07-08

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