FR2734317A1 - Twin stroke I.C. engine with integral gas scavenging - Google Patents

Abstract

The engine has a cylinder (1) with a reciprocating piston (2) linked to a crank (5) by two rods (6) situated on either side of the cylinder. A pre-compression chamber (11) is formed between the base of the piston and a cover (13) on the lower end of the cylinder. Intake ports (15,16) link the pre-compression chamber to a combustion chamber (17) via a transfer chamber (8) controlled by a non-return valve (7). The piston has two heads and a central transverse axle (4) which passes through elongated slots in the cylinder walls to join the connecting rods (6). During operation the expansion of the gases in the combustion chamber causes the piston to compress the gases for the next charge in the precompression chamber.

Description

 The present invention relates to the production of an internal combustion engine, with reciprocating piston, whose mechanical two-stroke cycle is mainly achieved by a precompression chamber disposed in the part of the cylinder opposite the combustion chamber. The invention relates to this device aiming to improve the scanning of gases to ensure self-supercharging of the 2-stroke engine.

 Two-cycle thermal engines do not provide all the power they should, compared to 4-stroke engines. The main reason is the gas inertia phenomenon which is opposed to the relatively short intake and exhaust times, linked to the two-stroke cycle. On the other hand, these engines have a fairly limited operating speed range; power is often developed at high revs. Add the absence of torque and engine brake and the use of 2-stroke is reserved for very specific cases (motorcycles, outboard, chainsaws, karting ...). Their performance is also affected by excessive fuel and lubricant consumption. Indeed, these unseparated cycles, hampered by the gas flow speed; this will result in significant pollution, resulting from imperfect combustion and the fact that the oil used to lubricate the moving parts in the engine, ends up being burnt beech with the fuel mixture. This type of lubrication does not give all the satisfactions because it often remains too important at low revs and causes excessive fouling of the engine. When at high speed, it tends to be insufficient and causes seizure or premature wear. Finally, note that this wear and tear, on all reciprocating piston engines, occurs in particular on the big end bearing, the engine being in bottom dead center. The main reason for this localized wear is due to the fact that practically no precompression phenomenon does not interfere with the linear speed of the piston when approaching bottom dead center. The crankshaft completely collects the balance constraints of the engine.

 The present invention aims to remedy these drawbacks to a large extent and relates to this end, as a new industrial product, a 2-stroke heat engine, characterized because it comprises a cylinder, piston, cylinder head and valve device , which allows the design of a precompression chamber, ensuring the self-supercharging of this engine.

Greater suction and gas entry outside the crankcase, an energetic sweeping of the used gases allow a more regular running at different speeds as well as a better harmony of the different parameters of consumption, energy efficiency and mechanical robustness.

 The device, object of the invention, comprises a cylinder head -10- single cover, as on other 2-stroke engines, comprising a spark plug or an injector, see a decompressor to facilitate start-up; this for information only.

An engine cylinder -1- pierced with an exhaust light -12-, opening approximately flush with the piston head at bottom dead center. Facing it approximately in the cylinder, there is an inlet light -16- possibly less important in passage of gas. And finally, an inlet light -15- feeds the decompression chamber 11- fitted out thanks to the cover -13- on the side of the cylinder opposite the cylinder head. This cylinder also comprises in these sides two oblong slots of a length equivalent to the stroke of the piston, to let the piston pin -14- connect at its ends on 2 connecting rods -6- (1 on each side). It is important to specify that at no time during the cycle should these two lights communicate with the interior chambers -17- and -11- of the engine.

A hollow cylindrical piston -2- provided with segments arranged near these heads, closed by added lids having the role of caps, crossed approximately in the middle by an axis -14-.

The length of this piston is determined approximately by the dimension between the precompression cover -13- and the bottom of the ports -12- and -16-.

A transfer box -8- which tightly connects the intake lights -15- and 16- with each other and itself equipped with non-return valves -7- which regulate the supply between the engine and the device power supply, carburetor as an example.

The combustion chamber -17- as well as the cylinder head -10- can be cooled by an air or water system -9-.

The connecting rods -6- transmit their force on a conventional crankshaft where their anchor points are separated by a bearing -4- located just in the vertical axis of the piston, pledge of solidity of the bottom of this engine.

Lubrication can be carried out by any means suitable for the device, as a nonlimiting example: by oil pan. Although it may be necessary to add a very small amount of oil to the fuel of this type of engine, according to the invention.

The device according to the invention is given by way of nonlimiting example in the attached drawings, in which
Figure - I- is a cross-sectional elevation view of the various parts of this engine; This to show the realization of the cylinder, biché on one side by a classic cylinder head; but also as a device specific to the invention, this bottom cylinder cover, partition between the crankcase crankcase and this precompression chamber ensuring self-supercharging of the engine.

We can also see on this drawing, the three lights (minimum) which participate in the flow of gases, as well as the cover connecting the two of these collaborating lights at the intake; a real tunnel connecting the two chambers arranged in opposition in the same cylinder. This transfer case is supplied with fresh gas through non-return valves supporting the pressure of the precompression. Finally, note the oblong bores on the side of the cylinder, shown in dotted lines in the drawing, and which, arranged parallel to the connecting rods, open two passages in the cylinder, over a length corresponding to the stroke of the piston and its axis.

Figure -H- is a longitudinal sectional elevation view of the main engine members at bottom dead center. This drawing reveals the axis system which runs right through the piston at the same time as the cylinder to connect as soon as possible to the connecting rod feet. The square figure which surmounts the piston in the drawing is a representation of the exhaust light fully discovered at this point in the cycle (bottom dead center). We can also see the importance of the central bearing, located between the connecting rods, in the distribution of the forces and stresses of the piston on the crankshaft.

Figure -III- is a side view of the upper part of the engine on which we can see the cylinder -1- with its oblong hole provided for the passage of the piston pin -14- and which does not reveal at any time of the cycle a passage with one of the two combustion or precompression chambers. Note also that the transfer case -8- as well as the exhaust duct -18- open higher in the cylinder and are when they are discovered, at bottom dead center. Despite all this, the piston -2- is visible in this drawing, through the oblong bore.

Figure -N- is a schematic representation showing the start of compression of the fresh gases which fill the combustion chamber -17-. During this ascending phase of the piston -2-, the intake valve is then opened, allowing the fuel mixture to enter the precompression chamber - l 1-.

Figure -V- is a schematic representation which very briefly shows the piston -2- in the downward phase or engine time compressing the fresh gases in the precompression chamber -l 1-, the valve -7- being closed.

The figure -VI- is a schematic representation which shows the end of the engine time, the moment when the precompressed gases will leave the precompression chamber -11-, by the lights -15-, -16- and expel the burnt gases by the exhaust light -12- from the combustion chamber -17-. The supply valve is then closed due to the pressure in the transfer case -8-.

 Figure -II- shows the different parts of the engine, the piston being in bottom dead center. We will describe, below, its operation in a two-stroke mechanical cycle, indicating the successive phases of the distribution, mainly concerning the suction, transfer of gases, exhaust and compressions; shown schematically, by way of example, in the figures -IV -, - V- and -VI-.

At bottom dead center, the precompression chamber -l 1- reduced to its smallest volume is emptied of the precompressed fresh gases which then fill the chamber -17-.

The piston -2- in its ascending phase (Figure IV) again compresses this gas mixture in the combustion chamber -17- as soon as the lights -16- and -12- are blocked. The vacuum created by this translation of the piston makes it possible to fill the precompression chamber -l 1- at the same time through the open valve -7- and the light -15-. The lower piston head (the one opposite the cylinder head) fitted with segments ensures a large intake of fresh air or gas.

Shortly before the piston moves to top dead center, the gases are ignited. Under the effect of this sudden increase in pressure, the piston -2- is visibly pushed back towards the bottom dead center (Figure V) in the same way as another internal combustion engine.

This moment is the engine time, when the energy developed by the explosion must produce a force transmitted to the crankshaft via the connecting rods. But it is also the time to compress the fresh gases admitted to the precompression chamber -11- during the previous phase of the cycle; the non-return valve -7- being closed automatically at the start of precompression.

The exhaust gases, fully expanded, begin to evacuate through the exhaust port -12- gradually discovered by the piston -2- (Figure VI). Then it will be the turn of the intake light -16- whose opening will cause the transfer of gases between the precompression chamber -11- and the combustion chamber -17- through the light -15- and the housing transfer -8-; thus ensuring by their pressure a complete sweeping of the burnt gases. The different phases of the two-stroke mechanical cycle are obtained by two successive strokes of the piston, requiring a full revolution of the crankshaft. The ratio between the volumes of the chambers -11- and -17- and the transfer case -8- plays a key role in the efficiency of filling the combustion chamber -17-. In fact, these volumes determine the quantity of fresh gas admitted into this engine and therefore determines the power and the character of this engine.

 Furthermore, the invention is not limited to the device described above; it is obvious that other embodiments can be conceived without departing from the scope of the invention; as an example: the cooling, the lubrication mode, the type of non-return valve, the number, the shape and the location of the segments, the volumetric ratio of the precompression chamber, see the distribution diaphragms.

 This combustion engine device, object of the invention, can be used to replace conventional 2 or 4-stroke engines and seems particularly well suited to the propulsion of boats, in a six-cylinder version, arranged flat, in particular.

Claims (9)

 1) Internal combustion engine, of the type composed of a cylinder -1-, in which a piston -2- slides, the said piston being connected to a crankshaft -5- by two connecting rods -6-, arranged on the side and d 'other of the cylinder -1-, a precompression chamber -11- being arranged thanks to the cover -13- fixed to the base of the cylinder and the lower head of the piston. Characterized in that the intake element consists of lights -15- and -16 which communicate the precompression chamber -11- and the combustion chamber -17-; interconnected by a transfer box -8-, itself controlled by a non-return valve -7-. Characterized in that the piston -2- has two heads for compressing gases. Characterized by the axis -14- of this piston passing through the walls of the cylinder -1- by oblong bores.  2) Engine according to claim -1- characterized by a cylinder -1- pierced with at least three lights -12-15-16- necessary for the passage of gases; closed at both ends by a cylinder head -10- and a cover -13-; also pierced with oblong bores intended for the passage of the piston pin.  3) Engine according to claim -2- characterized by a cover -13- precompression chamber -11- closing the side of the cylinder opposite to the cylinder head -10-.  4) Motor according to claim -3- characterized by a precompression chamber -11- opening into a transfer housing -8- by a light -15- located at the base of the cylinder -1-.  5) Engine according to claim -4- characterized by a transfer box -8- connecting the intake lights -15- and -16-, allowing the transfer of gases between the precompression chambers -11- and combustion -17 - itself being controlled by a non-return valve device -7- managing the entry of gases into the engine.  6) Motor according to claim -1- characterized by a cylinder -1- drilled right through at the level of the piston pin -14- but of which these openings do not open in any case inside the chambers -11- and -17-; and are closed at each moment of the cycle by the piston -2-.  7) An engine according to claim -1- characterized by a piston -2- double acting with two heads provided with segments both for compressing gases.  8) Motor according to claim -1- characterized by an axis -14- of a length greater than the diameter of the piston it supports, also passing through the cylinder by two oblong slots provided for this purpose, allowing it to rest on the two connecting rod feet, this, immediately on its exit from each side of the cylinder.  9) Engine according to claim -3- whose piston pin transmits its force on two connecting rods arranged parallel to each side of the cylinder.