Classifications

• • 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
  • F01L7/00—Rotary or oscillatory slide valve-gear or valve arrangements
  • F01L7/06—Rotary or oscillatory slide valve-gear or valve arrangements with disc type valves
• • 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
  • F01L13/00—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations
  • F01L13/0015—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations for optimising engine performances by modifying valve lift according to various working parameters, e.g. rotational speed, load, torque
• • 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
  • F01L7/00—Rotary or oscillatory slide valve-gear or valve arrangements
  • F01L7/02—Rotary or oscillatory slide valve-gear or valve arrangements with cylindrical, sleeve, or part-annularly shaped valves
  • F01L7/021—Rotary or oscillatory slide valve-gear or valve arrangements with cylindrical, sleeve, or part-annularly shaped valves with one rotary valve
• • 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
  • F01L7/00—Rotary or oscillatory slide valve-gear or valve arrangements
  • F01L7/12—Rotary or oscillatory slide valve-gear or valve arrangements specially for two-stroke engines
• • 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
  • F02B75/02—Engines characterised by their cycles, e.g. six-stroke
  • F02B2075/022—Engines characterised by their cycles, e.g. six-stroke having less than six strokes per cycle
  • F02B2075/025—Engines characterised by their cycles, e.g. six-stroke having less than six strokes per cycle two

Definitions

• the invention relates to a two-stroke engine, comprising one or more cylinders, in each of which the scanning is delayed by means related to the rotation of the crankshaft.
• Two-stroke engines conventionally comprise at least one cylinder in which a piston delimiting a combustion chamber moves, a pump casing situated at one end of said cylinder and separated from said combustion chamber by said piston, at at least one transfer opening in the combustion chamber, at least one transfer duct connecting said combustion chamber to said pump casing, and at least one opening for exhausting the burnt gases from the combustion chamber.
• the piston when the piston reaches the end of its travel near the bottom dead center, it discovers the exhaust lights (or openings) thus letting escape the combustion gases from the combustion chamber, then the piston discovers the transfer lights (or openings) located at a different level from the exhaust lights so that fresh air compressed by the piston in the pump housing can then escape from the pump cartel, and be introduced into the combustion chamber via the transfer conduits.
• the introduction of fresh air or fuel mixture from the pump housing into the combustion chamber is therefore directly linked to the opening by the piston of the transfer lights.
• the operations taking place in the cylinder are essentially the introduction of air or a fuel mixture into the cylinder, the ignition, the combustion and then the discharge of the burnt gases out of the cylinder where combustion took place. All these operations must take place in a precise order, in extremely short times which vary according to the power at which the engine operates.
• Sweeping that is to say the movement of gases in the combustion chamber When replacing the burnt gases with fresh gases, is therefore very important since its smooth running ensures good combustion of the gases, i.e. -to say a good performance of the engine.
• the present invention aims to provide a 2-stroke engine of the type defined at the head of the description, of simple design therefore reliable and which, because of its simplicity, is a very reasonable cost price, while ensuring high efficiency and by limiting the discharge of hydrocarbons to the atmosphere as much as possible.
• the motor according to the invention allows an improvement in the sweeping efficiency, in particular at low speeds.
• the sweeping time in the combustion chamber is relatively long so that all of the gas dynamics carrying out in the first part of the combustion cycle, part of the fresh gases leaves towards the exhaust without having been burned. This phenomenon is also called “direct short circuiting of unburnt fuel at the exhaust”.
• the start of the sweep should not be delayed too long because at high speeds.
• the sweep is done in a very short period of time, if all the fresh gases arrive too late, the chamber will contain less fresh gas, the engine will have a lower power, which is not desirable.
• the present invention therefore relates to an engine of the type defined at the head of the description and which also comprises means placed at the level of the transfer duct, driven in rotation by the crankshaft and intended to close said channel at certain moments of the cycle, so to delay The sweep in the combustion chamber.
• the means for periodically closing the transfer duct consist of at least one coaxial flange and fixed to the crankshaft, the means being provided with at least one cutout at the periphery, the cutout allowing at certain moments in the cycle, the exhaust of fresh gases from the pump housing to the combustion chamber via the transfer duct.
• the closure means consist of at least one valve linked to the crankshaft and provided with cutouts at the periphery.
• the engine according to the invention may include means intended to modify the shape of the cutting of the flange or of the valve according to the speed of rotation of the flange.
• the means for modifying the shape of the peripheral cutout consist of at least one annular sector (s) movable relative to the flange and which react to the action of the centrifugal force exerted on the flange.
• the means for selectively closing the transfer duct consist of a rotary plug placed in the transfer duct. More precisely.
• the rotary valve is placed near a transfer opening.
• the present invention relates to both "loop scanning” type motors and “transverse scanning” type motors, the definition of which will be given below.
• the invention will be better understood on reading the description which follows, given by way of indication and in no way limiting, with reference to the appended drawings, according to which:
• FIG. 1 is a vertical section view of a two-stroke engine according to one of the embodiments of the invention, showing the piston near bottom dead center,
• Figure 2 is a vertical sectional view of a two-stroke engine according to one of the embodiments of the invention, showing the piston at the dead top
• Figure 3 is a front view of a flange according to the invention
• FIG. 4 is a front view of another embodiment of the flange according to the invention.
• FIG. 5 is a front view of a device allowing variable opening of the transfer lights as a function of the engine speed
• FIG. 6 shows in section a transverse scanning motor equipped with a shutter means according to the invention
• FIG. 7 is a diagram showing the opening law of the transfer lights according to the invention and conventionally, around the bottom dead center of the piston.
• Figures 1 and 2 show in vertical section a first embodiment of the invention, where only appear the parts essential to understanding the invention.
• the cylinder 1 is closed in the upper part by a cylinder head 2.
• a piston 3 moves inside the cylinder between the top dead center as shown in FIG. 2 and the bottom dead center as shown in FIG. 1.
• the piston 3 thus delimits a combustion chamber 4 of variable volume, between its upper surface 31 and the lower surface of the cylinder head 21.
• Cooling fins 10 can be provided on the outside face of the cylinder 1. Such fins can also be made on the outside face of the cylinder head 2. Any other cooling means, such as cooling by a liquid, can of course be provided without departing from the scope of the invention.
• a pump housing 5 is arranged in the extension of Chamber 4, below the piston 3.
• the pump housing 5 is crossed by the axis of the crankshaft 6 to which is linked for example a flywheel 7.
• a connecting rod 8 connects the piston 3 to the flywheel 7.
• the wall of the cylinder 1 is traversed, preferably in its lower part, by openings or lights 9 called “transfer” which each communicate via a conduit or transfer channel 11 with the interior volume of the pump housing 5 which also comprises appropriate openings 51.
• the wall of the cylinder 1 also comprises so-called exhaust openings 12 intended for the evacuation of the gases burned in the combustion chamber 4.
• the motor illustrated in FIGS. 1 and 2 is of the loop scanning type because the transfer openings 9 create, by their orientation, a movement of the fresh gases in the cylinder. Thereby.
• the scanning is carried out as indicated by the arrows 13 in FIG. 1, that is to say in the form of a loop.
• the transfer 9 and exhaust 12 openings are conventionally closed and uncovered by the piston at different times of the operating cycle. According to Figures 1 and 2, the start of the exhaust will take place before the start of the injection of fresh air or fuel mixture since the upper level of the exhaust lights 12 is located above the upper level of the lights 9. The difference in the heights of the aforementioned lights allows per ⁇ to intervene on the moments of exhaust and intake.
• the piston is, in known manner, the only element controlling the opening of the transfer lights 9 and the exhaust lights 12.
• flanges or valves 14 are connected, by any means known per se, to the axis of the crankshaft 6.
• the flanges of the crankshaft are cut to obtain disc shapes cut at the periphery.
• a part is preferably attached to the crankshaft 6.
• This part has the form of a disc provided with cutouts at the periphery and cooperates with the opening 51 to form a valve.
• FIG. 3 shows an exemplary embodiment of a closure means according to the invention.
• a cut is made in the form of a ring portion on the periphery of the flange.
• the width of the ring portion here is substantially equal to the height H of the opening 51 of the transfer duct on the pump housing side, so that at certain times of the cycle, the flange discovers the opening 51 thus authorizing the passage of non-carburetted air in the transfer duct 11.
• FIG. 3 only the left half of the transfer light 51 is uncovered.
• the opening of the transfer duct is therefore not controlled only by the piston 3 but also by the flange 14.
• the cut in the flange defines the moment of opening of the transfer duct.
• the shape of the cutout can define how the opening will be made.
• FIG. 4 shows another possible form of the cut, according to which the opening of the transfer light 51 will take place gradually since the flange first discovers the outermost zone of La then the entire height H of the light.
• FIG. 7 shows the curves defined by the opening of the transfer lights as a function of the angle of rotation of the crankshaft when the piston is near the bottom dead center.
• Curve 70 in solid lines shows the law of opening the transfer lights obtained in a known manner, that is to say when only the piston controls the opening of the lights.
• Curves 71 and 72 drawn respectively in lines mixed and dotted each show a law of opening of the lights, obtained according to the invention.
• Curve 71 was obtained for a first setting, that is to say a first law of opening of the flange or of the valve while curve 72 relates to a second setting different from the first.
• the duration of the sweep in the combustion chamber is different depending on the engine speed.
• the constraints at the sweeping level are different, even contradictory depending on the speed of rotation and the load of the motor.
• FIG. 5 illustrates a possible embodiment of such a system, according to which each annular sector 20 has an arm 23 and cooperates with a return spring 22.
• the centrifugal force thus tends to counteract the action of the return spring 22, it that is to say to bring the annular sectors 20 on the uncut surface of the flange, as shown in dotted lines.
• This device is a nonlimiting example, known per se, which will therefore not be described further here. Any other means capable of varying the opening angle of the flange as a function of the engine speed is of course conceivable without departing from the scope of the invention.
• FIG. 6 illustrates another embodiment of the invention applicable to so-called transverse scanning motors.
• the exhaust duct 61 opens into the combustion chamber 4 in a zone diametrically opposite to the transfer lumen 9. Therefore.
• the scanning is carried out in the direction indicated by the arrows 62, that is to say by crossing the combustion chamber 4 along a diametrical plane.
• the means intended to close off The transfer duct at certain moments of the cycle consists, for example, of a rotating plug 63 placed in the transfer channel 11 near the transfer lumen 9 located on the side of the combustion chamber.
• the plug 63 can be placed near the transfer light 51 on the pump housing side.
• the rotary plug 63 is mechanically connected to the rotation of the crankshaft 7 by a chain or a toothed belt 64 in order to transmit the rotation of the engine to the rotary plug, thereby making it possible to close the transfer duct 11 as a function of the rotation of the crankshaft.
• This device therefore performs the same function as the flanges provided with cutouts described above in the case of loop scanning motors.
• the advantages brought to the engine have therefore already been mentioned above.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Cylinder Crankcases Of Internal Combustion Engines (AREA)

Applications Claiming Priority (2)

Publications (1)

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ID=9403807

Family Applications (1)

Country Status (3)

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Family Cites Families (13)

• 1990
  • 1990-12-28 FR FR9016441A patent/FR2671137A1/fr active Pending
• 1991
  • 1991-12-19 WO PCT/FR1991/001035 patent/WO1992012332A1/fr not_active Application Discontinuation
  • 1991-12-19 EP EP19920902729 patent/EP0517887A1/de not_active Withdrawn

Non-Patent Citations (1)

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