US2148249A - Internal combustion engine - Google Patents

Description

web. 21, x39., M -WOMAS 2,148,249

IINTERINHL COMBUSTION ENGINE Filed Aug. l0, 1936 KURT vous ATTURA/[Y Patented Feb. 21, 1939 UNITED STATES INTERNAL COMBUSTION ENGINE Kurt Thomas, Gaggenau/Baden, signor, by mesne assignments, Armstrong Whitworth & Co.

Germany, asto Sir W. G. (Engineers) Limited, Newcastle-upon-Tyne, England Application August 10, 1936, Serial No. 95,072 In Germany August 9, 1935 Claims. `(Cl. 123-65) (Granted under the provisions of sec. 14, act of 4 March 2, 1927; 357 0. G. 5)

'I'his invention relates to two-stroke cycle lnternal combustion engines wherein at least a substantial portion of the burnt gases leaves the cylindex' at a speed much higher than that obtaining when an adiabatic iiow only 'is involved, and' in such a short interval of time that it is discharged as a mass leaving a depression behind it, which is utilised in introducing a fresh charge into the cylinder by opening the inlet orifice with the required delay after the opening of the exhaust orifice to ensure that the burnt gases are then moving outwardly through the exhaust orifice or duct, and thata suction eifect is exerted at the inlet orifice as a consequence of the exit of the said mass.

When the burnt gases leave the cylinder as a mass in the manner stated above, they leave a l depression which may approach a complete vacuum behind them in the cylinder and in the exhaust duct close to the cylinder. The volume of this depression will depend upon the distance to which the mass of burnt gases travels away from the cylinder. Thereafter this outward movement is reversed in direction and a return of the gases towards the cylinder takes place. Consequently if the inlet orifice is opened while the exhaust. orifice is open and the burnt gasesare moving outwardly through the exhaust orifice or duct and a suction effect is exerted at the inlet orifice, the charge will enter into a substantially void space and may, therefore, if desired be introduced by atmospheric pressure alone.

If the reversal in direction of motion of the burnt gases occurs while the exhaust orifice is still open, burnt gases may re-enter the cylinder. This objectionable eiTect may be avoided by closing the exhaust orifice of the cylinder before the return of the burnt gases into the cylinder occurs. However if a crank angle is selected for exhaust closure which is suitable for a low engine speed, this will result in exhaust being closed at higher speeds not onlybefore the return of the burnt gases occurs but while a depression still exists in the cylinder and in the exhaust pipe close to the cylinder. Thus, special provision will have to be madeyfor completing the charge if maximum results are to be obtained.

According to the present invention the closure. of exhaust is regulated in such a Way that the suction eiiect created by the mass exit of the burnt gases from the cylinder is utilised as completelyas possible` at all engine speeds, and at the same time the return of the burnt gases into the cylinder is prevented.

, For this purpose'a regulating device is provided dit? which permits a shifting of the exhaust closure in relation to the commencement of exhaust or in relation to the crank, more particularly in such way that the exhaust closure occurs relatively ater at high speeds than at low speeds.` 5

In the drawing the invention is illustrated in various embodiments.

Figure 1 shows a diagram of pressures existing rin the exhaust pipe of a two-stroke Diesel engine during the exhaust period.A

Figure 2 is a longitudinal section through such an engine with `a rotary valve, and

lFigures 3 and leach show a rotary valve control.

In Figure 1 the base line :c denotes a develop- 15 ment of a portion of the crank circle, and at the same time the zero line for the `pressures. The lines n1, nz and n3 represent the variation of the pressure in the exhaust connection after the opening of the exhaust and during the scavenging and 20 charging operation at speeds of 111:900, n2: 1200 and n3 =1400 R. P. M. 'I'he diagram shows that with a varying period of delay after the opening of the exhaust (1li) the pressure at rst rises rapidly, indicating the mass exit of the burnt gases 25 but then falls just as rapidly, and descends below zero. After this, in the diagram illustrated, in about the region of the lower dead centre Tu of the piston movement, a pressure above zero occurs again denoting the return of the burnt gases 30 towards the cylinder. As will be seen, with varying engine speeds, the particular moment at which the return occurs is shifted very considerably, in such a way that at high speeds the return occurs later and at low speeds already occurs correspondingly earlier in accordance with the longer time available for a definite crank angle. Now if the inlet and exhaust apertures are controlled by the piston at all speeds invariably and symmetrically in relation tothe lower dead centre (as indicated by the vertical lines yi, y2, ya and 114 of the diagram in Figure 1) and if the exhaust closure is adjusted to the normal high speed, the scavenging and charging of the cylinder is very materially hindered in the lower range of spe'eds,-since a return of the burnt gases and the Vrecurrence of the raised pressure occurs substantiallyearlier at a lower speed than at the normal upper speed. Thus for example, it will be seen from the diagram represented, that at 900 R. P. M. the return of the burnt gases occurs at the lower dead centre, Whereas at a speed of 1400 R. P. M. the return vunly occurs at about 30 after the lower dead centre. On the other hand with an earlier` invariable closing of the as the mass of burnt cylinder. At low speeds, therefore, the exhaust must be closed earlier (for instance at n==900 at the lower dead centre) than at higher speeds (for example 30 after the lower dead centre at Within the ambit of the invention there may be .employed any desired mechanical, pneumatic, hy-

draulic or electrical regulating device, known in itself, which is dependent upon the speed of revolution, in conjunction with any desired shut-oil member, such as a rotary valve, a tubular valve, a piston valve, a lift valve or the like.

In Figure 2 the invention is illustrated as ap plied to a two-stroke Diesel engine, l denoting the cylinder, 2 kthe piston and 3 the inlet directly connected to the atmosphere without a blower, and 4 the outlet controlled by the piston like the inlet. As a supplementary controlling device Afor the exhaust there is also provided a rotary valve 5, which is connected according to Figure 3, with a shaft 6, which in its turn is provided with oblique keys or wedges 1 in the nature of inclined teeth. In the latter there mesh the twisted grooves 8 of a slide valve bush 9 which carries non-rotatably a driving toothed wheel I0, driven by the engine, and which can be displaced from time to time to left or right, directly or indirectly, for instance by means of a centrifugal governor to which it is connected by a lever I l. The angle of adjustment of the slide valve 5 is thereby shifted in the cylinder in relation to its drive lll, and therefore the control aperture l2 thereof is adjusted in relation to the exhaust port 4, so that the slide valve closes the exhaust port earlier at a lower speed, for instance about 20 after the lower dead centre in relation to the line n2 in Figure i, and correspondingly later at higher speeds.

The device according to Figure 4 acts in the same manner, except that here, instead of a bush provided with twisted grooves, a helical wheel E@ displaceable along lreys i3 is provided. Means may also be provided for enabling the adjusting to be effected by hand.

I claim:

l. ln an internal combustion engine, a cylinder having an inlet port subjected to substantially constant pressure, and an outlet port, means for opening said outlet port for momentarily reducing the pressure within said cylinder below atmospheric pressure and means for closing said outlet port before the pressure in said cylinder reaches said constant pressure, irrespective of the speed of the engine, said last means including means responsive to the speed of the engine.

2. In an internal combustion engine of the kind described having a cylinder, a piston adapted to reciprocate in said cylinder, an inlet opening in said cylinder adapted to supply scavenging air at substantially atmospheric pressure thereto, an

outlet opening in said cylinder for the exhaust of the burnt gases, said openings being so positioned in said cylinder that the piston reciprocating therein opens said exhaust outlet before the admission inlet, whereby when the admission begins the mass of exhaust gases escaping through said outlet has produced a vacuum or high depression in the cylinder for sucking in the scavenging air, and means for closing said v`exhaust before the pressure in said cylinder equals that of the incoming air, irrespective of engine speed, said last means including means responsive to the speed of the engine.

3. The combination according to claim 1 in which the means for closing the outlet port comprises a rotary sleeve valve, means for driving said valve from said engine, and a speed-change mechanism responsiveto speed of the engine interconnecting the valve and said driving means.

4. The combination according to claim 2, in which said last means comprises a rotary slide valve, means adapted to rotate said slide valve in accordance with the speed of the engine, and means intermediate said engine and valve for adjusting said rotary slide valve, said means being responsive to the speed of the engine Aand so constructed and arranged that the outlet is closed relatively early for slow engine speeds and relatively late at higher engine speeds.

5. The combination according to claim 2 in which said last means comprises a rotary slide valve, a driving wheel for the same driven by the engine, a coupling device interconnecting said wheel and valve comprising two meshing wheels with oblique teeth, one rotating with said valve and the other with said wheel, and means responsive to the speed ofthe engine for varying the meshing of said wheels.

6. A method of controlling two-stroke cycle inn ternal combustion engines, which comprises establishing communication between the exhaust system and the cylinder during the ring stroke, providing for the issuance of the gases at high speed as a compact mass leaving a high degree of vacuum in the cylinder, admitting a fresh charge when a suction effect is exerted in the cylinder and while the burnt gases are moving outwards through the exhaust system as a compact mass, cutting off the communication between the exhaust system and cylinder in relation with the movement of the burnt gases through the exhaust system as a compact mass, and varying the instant at which the said communication is cut oft in relation with the engine speed.

7. A method of controlling two-stroke cycle internal combustion engines, which comprises establishing communication between the exhaust system and the cylinder during the ring stroke, providing for the issuance of the gases at high speed as a compact mass leaving a high degree of vacuum in 'the cylinder, admitting a fresh charge I when a suction effect is exerted in the cylinder and while the burnt gases are moving outwards through the exhaust system as a compact mass, cutting off the communication between the ex haust system and cylinder in relation with the movement of the burnt gases through the exhaust system as a compact mass, and varying the instant at which the said communication is cut off in dependence upon engine speed, for producing an earlier closure of exhaust at lower speeds and a later closure of exhaust at higher speeds.

8. A method of controlling two-stroke cycle internal combustion engines, which comprises establishing communication between the exhaust system and the cylinder during the firing stroke, providing for the issuance of the gases at high speed as a compact mass leaving a high degree of vacuum in the cylinder, admitting a fresh charge when a suction effect is exerted in the cylinder and while the burnt gases are moving outwards A through the exhaust system as a compact Vsaid exhaust being closed mass, cutting oil' the communication betwee the exhaust system and cylinder in relation with the movement of the burnt gases through the exhaust system as a compact mass. so that the said communication is cut off before the return of the said mass of burnt gases to the cylinder, and varying the instant at which the said communif cation-ls cut oil.' in dependence upon engine speed, for producing an earlier closure of exhaust at lower speeds and a later closure of exhaust at higher speeds.

9. In a variable speed two-stroke cycle internal combustion engine oi the kind described, the combination with a cylinder, an exhaust system and an exhaust port leading to the exhaust system,

of means for varying the crank angle occupied by the exhaust period.

10. In a variable speed two-stroke cycle internal combustion engine of the kind described. the combination with a cylinder, an exhaust system, an exhaust port leading to the exhaust system, of means 4for opening and closing the exhaust port and means for increasing the crank angle between exhaust opening and exhaust closure as the engine speed increases and i'or decreasing said crank' angle as the engine speed decreases,

at all speeds over adeaired range of speeds immediately before the return of the burnt gases to the cylinder occurs.

11. In a variable speed two-stroke cycle internal combustion engine of the kind described, the combination with a cylinder, an exhaust system. an exhaust port leading to the exhaust system, of means for opening the exhaust port at a nal combustion engine of the nal combustion engine of the exhaustport, of means for constant crank angle and means for closing said exhaust port at a variable crank angle.

12. In a variable speed two-stroke cycle interkind described, the combination with a cylinder, an exhaust system, an exhaust port leading to the exhaust system, of a rotary exhaust valve, means for driving said valve in phase with the engine and means i'or adjusting said valve in relation to its driving means for varying the instant of exhaust closure.

13. Apparatus as claimed in claim 10, wherein said adjusting-means comprises an axially displaceable helical member and speed responsive means for axially displacing said member.

14. In a variable speed two-stroke cycle interkind described, the combination with a cylinder, an inlet orifice, means for opening the inlet orice and for closing the inlet orifice at a xed crank angle after the opening thereof, an exhaust system and an exhaust port leading to the exhaust system, of means for varying the crank angle occupied by the exhaust period.

15. In a variable speed'two-stroke cycle internal combustion engine of the kind described, the combination with a cylinder, an inlet oriilce, means for opening the inlet oriilce, an exhaust system, an exhaust port leading to the exhaust system, and means for opening and closing the varying the crank angle between exhaust Opening and exhaust closure and means for closing the inlet orice after the closure of the exhaust port.

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