US 2890688 A
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June 16, 1959 Filed 001;. 28, 1953 J. R. GOIOT 2,890,688
INTERNAL COMBUSTION ENGINES 2 Sheets-Sheet 1 June 16, 1959 J. R. GOIOT INTERNAL COMBUSTION ENGINES 2 Sheets-Sheet 2 Filed Oct. 28, 1953 u w Q..
INTERNAL C@USTiN ENGINES Jean Roger Goiot, Nantes, France Application October 28, 1953, Serial No. 388,752
Claims priority, application France December 4, 1952 Claims. (Cl. 123-48) The present invention relates to a spark operated two stroke combustion engine. In spark operated two-stroke engines it is usual to adopt a high volumetric compression ratio and this necessitates, on the one hand, the provision of a very powerful ignition device to overcome the resistance of the overcompressed air, and, on the other hand, the provision of a crankshaft with a fly wheel having a great reserve of inertia to ensure the provision of the necessary compression when the engine turns at low speed.
It has been found that engines running at low speeds, even when equipped with such means, operate irregularly and with some roughness; in the case of a two-stroke engme, in particular, this irregularity involves a serious drawback which consists in that the engine shows, at low speed, a tendency to operate according to the four stroke cycle method.
The invention has for its object to overcome this drawback in a spark operated two stroke engine.
According to the present invention a spark operated two-stroke internal combustion engine having a high compression, comprises an auxiliary chamber connecta-ble with the main combustion chamber by means of a valve which through a mechanical, pneumatical, hydraulical or electromagnetical connection is controlled by a member controlling the engine over its whole working range, the said connection being controlled by said member in such a manner that when such member is moved to the position which corresponds to slow running of the engine the said connection causes the opening of the valve, while as soon as the control member is removed from its slow running position the said connection causes the closure of the valve.
On account of this mode of connection in which the auxiliary chamber is automatically connected to the combustion chamber by bringing the said control member into its position which corresponds to slow running condition, the volumetric compression ratio is reduced and ensures a smooth running of the engine. Furthermore as at slow running conditions the compression ratio is reduced it is possible to reduce the size of the fly-wheel together with the power of the ignition device.
By way of example several forms of embodiment of the object of the invention are described hereafter and illustrated in the annexed drawing, in which:
Figure 1 illustrates partly, in diametral section, the upper part of a cylinder in the carter of which has been provided the auxiliary chamber.
Figure 2 is a view similar to the View of Figure l, the valve mounted between the cylinder of the engine and the auxiliary chamber being shown as lifted from its seat, and
Figures 3, 4, 5, 6 illustrate alternative embodiments of the control lover of the valve.
In Figures 1 and 2, the numeral 1 designates the main combustion chamber in the cylinder head 2 into which is also drilled a threaded hole 3 to receive the spark plug 4.
The cylinder head, preferably in the part adjoining the 2,890,688 Patented June 16, 1959 drilling for the spark plug 4, is provided with a recess or pocket 5 covered by means of a cover 6 held in position by suitable fixing means (not shown). This auxiliary chamber 5 is isolated from the combustion chamber 1 by a socket 7 with a solid bottom 8, screwed or forced into the part 9 of the cylinder head. The bottom 8 of the socket is bored with ports ill, 11 opening in the auxiliary chamber 5 and its forward lip forms a seat 12 for the head 13 of the valve, the stem 14 of which is guided by a bore 15 in the bottom of the socket 7 and extends beyond the boss 16 of the cover 6, passing through a stufiing box including a tightening nut 17. This nut 17 includes a hollow portion 18 in which is arranged a compression spring 19 surrounding the stem 14 of the valve and bearing, by one of its ends, upon the bottom 20 of this hollow portion and by its other end upon a washer 21 mounted on the stem M and fixed by means of the setpin 22.
On an arm or bracket 23 of the boss 16 is pivoted in 24 a lever 24, the nose 25 of which is near the end 26 of the stem 14, the other end 27 of thislever being, through mechanical hydraulic, pneumatic or electromagnetic connection, appropriately connected, for example by known arrangements.
This connection is carried out so that, when the said member is brought into a position which corresponds to slow running condition of the engine, the lever 24 revolves to apply the nose 25 to the end 25 of the stem 14; the stem is thereby pushed towards the combustion chamber and moves the head 13 of the valve apart from the seat 12, thus permitting the auxiliary chamber 5 to communicate with the combustion chamber l. The ratio of volumetric compression is thereby reduced and allows the engine running slowly, but it allows, due to the low volumetric ratio, to reduce the size of the flying-wheel and the power of the ignition equipment.
According to the embodiment of Figure 3, the end 26 of the stem 14 of the valve bears upon the surface of a cams 28 mounted on an axis 29, the nose of which is designated by 30. To lift the valve 13 from its seat 12, and thereby connect the combustion chamber 1 with the auxiliary chamber 5, the cam is moved from the position shown in Figure 3 to the position shown in Figure 4, the nose 3% thrusting back the stem 14 against the action of spring 19. This rotary motion of the cam is obtained by moving the member controlling the engine over its whole working range, for example the throttle control lever or handle into its position which corresponds to the slow running condition of engine. For that purpose, the handle or lever will, when brought to a position which corresponds to slow running condition, actuate a Bowden wire, which in turn will act, in any suitable manner, on the cam 28, to bring this cam into a position corresponding to Figure 4. According to an alternative embodiment, the cam 23 can be driven directly by the Bowden cable controlling the fuel supply on motorcycles; the wire will rotate the shaft of the cam when the lever or twist grip of the motor-cycle controlling the fuel supply is actuated, and in this case the cylindrical surface of the cam will correspond to the normal or fast working conditions of the engine while the peripherical length of the nose corresponds to the slow running conditions. Instead of the Bowden wire for actuating the lever 24' or the cam 28, one can use a system of rods, slidably arranged or connected to each other by means of 'bellcrank levers.
In the alternative embodiment of Figure 5, the end 26 of the stem 14 of the valve is operated for the opening of the valve 13 by means of an hydraulic device including a first cylinder 31 in which is arranged a piston 32 on which acts a spring 33, the rod 34 of this piston being in alignment with the stem 14 of the valve 13. The cylinder 31 is connected by a duct 35 with a 3 second cylinder 36 in which slides the piston 37, the rod 38 of which is operated by one of the above said control members controlling the engine of its whole working range. The chambers 39, 40 of the cylinders 36, 31 and the duct 35 are filled up with an incompressible liquid which transmits the stress F generated by piston 37 to the piston 32 which is thereby pressed back towards the right and causes, through the rod 34, the opening of the valve 13 as soon as one of the said control members is moved into its position which corresponds to the slow running position of the engine.
In the form of embodiment of Figure 6, the stem 14 of the valve 13 is pressed back in the position giving rise to the opening of the valve 13 by means of a lever 24', arranged as in Figure l but operated by an electro magnetic device. For this purpose, the magnetic core 39 of an electro magnet 39 is hinged at 27 on lever 24 pivoting around the axis 24 and having its nose located in front of the end 26 of the stem 14. The electro magnet 39' is fed, for instance, by the dynamo D of the engine and its supply circuit is controlled by a switch 40, the closing of which is synchronized with one of the control members controlling the engine over its Whole working range in such a manner that as soon as one of such member is brought into a position corresponding to slow running condition, switch 40 is closed causing lifting of the valve 13. The switch 40 can, for instance, be associated with the throttle lever 41 of the engine and will include a fixed contact 42 placed on the path of a movable contact 43 carried by the lever and adapted to close the circuit of the electro magnet When this lever is in the position corresponding to the slow running conditions.
Although the example above described and illustrated shows a single auxiliary chamber controlled by a single valve, the present invention includes also the embodiments including one or several auxiliary chambers, controlled by one or several valves or similar devices.
What I claim is:
1. A spark-operated two-stroke internal combustion engine comprising a cylinder, means defining an auxiliary chamber provided with means for communicating with said cylinder to reduce the compression ratio in the cylinder, valve means normally closing said communicating means between the cylinder and the auxiliary chamber, and automatic means maintaining the valve means in position to close said communicating means during operation of the engine at high and medium speeds but acting upon said valve means to open said communicating means when said engine operates at low speeds normally resulting in erratic engine operation to open said auxiliary chamber into communication with said cylinder at such low speeds.
2. A spark-operated two-stroke internal combustion engine as defined in claim 1, wherein said communicating means between the auxiliary chamber and the cylinder comprises a socket member having a seat for the valve means and a plurality of ports of restricted cross section communicating with the auxiliary chamber.
3. In a spark operated two-stroke internal combustion engine including a gas handle controlling the engine over its whole working range, a cylinder, a cylinder head defining therewith a main combustion chamber, a pocket formed in said cylinder head, said pocket being closed outwardly and communicating with the main combustion chamber by an aperture formed as a valve seat, a valve cooperating with said seat and having a stem slidably disposed in said cylinder head, the free end of the stem projecting outwardly from the cylinder head spring means acting on said stem and thereby applying the valve against the seat during normal working condition of the engine, a cam rotatably mounted adjacent the free end of the stem, a peripheral nose on said earn, a Bowden cable operatively connecting the gas handle and the cam to cause, as soon as the said gas handle is brought into its position which corresponds to slow working condition of the engine, rotation of the cam in a direction bringing the nose thereof in contact with the free end of the stem whereby the valve is unseated and allows free communication of the main combustion chamber and the pocket, while as soon as the gas handle is removed from its position which corresponds to slow working condition of the engine, the cam is rotated in the reverse direction whereupon the valve is seated on account of the action of the spring.
4. A spark-operated two-stroke internal combustion engine as defined in claim 1 in which the automatic means are controlled by a Bowden cable.
5. In a spark-operated two-stroke internal combustion engine including a throttle lever controlling the engine over its whole working range, a cylinder, a cylinder head defining therewith a main combustion chamber, a pocket formed in said cylinder head, said pocket being closed outwardly and communicating with the main combustion chamber by an aperture formed as a valve seat, a valve cooperating with said seat and having a stem slidably disposed in said cylinder head, the free end of said stem projecting outwardly from the cylinder head, spring means acting on said stem and thereby applying the valve against the seat during normal working condition of the engine, a lever pivoted intermediate its ends and having a magnetic core pivotally connected to the other end of said lever, an electro-magnet arranged in front of said core, a current supply circuit for said magnet including a switch, a movable contact carried by the throttle lever and adapted as soon as the throttle lever is brought into its position which corresponds to slow running conditions to close the supply circuit of the electro-magnet and to actuate the core whereby the pivoted lever is rotated in a direction to act upon the free end of the stem and to unseat the valve which allows free communication of the main combustion chamber and the pocket, while as soon as the throttle lever is removed from its position which corresponds to slow working conditions of the engine, the switch returns in its inoperative position allowing the closure of the valve on account of the action of the spring.
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