US2283594A - Internal combustion engine - Google Patents

Description

y 9,1942. F. M. ASPIN 2,283,594

INTERNAL COMBUSTION ENGINE Filed July 6, 1936 4 Sheets-Sheet l FIG. I.

[221/612 [01' 5am? M /mif 4072/2 5y 121's Alia/"my May 19, 1942. EM. ASPIN 2,283,594

INTERNAL COMBUSTION ENGINE Filed July 6, 1936 4 Sheets-Sheet 2 FIG. 4.

May I9, T942.

F. M. ASPIN 2,283,594 INTERNAL COMBUSTION ENGINE Filed July 6, 1936 4 Sheets-Sheet 3 5y leis Alfonzey Illll HIH [122/612 [or F/aYM" 4/6222? 145 0272 May 19, 1942M F. M. ASPIN I 2,283,594

INTERNAL COMBUS TION ENGINE Filed July 6, 1936 4 Sheets-Sheet 4 flu/612101 Patented May 19, 1942 INTERNAL COMBUSTION ENGINE Frank Metcalf Aspin, Bury, England Application July 6, 1936, Serial No. 89,115 In Great Britain July 23, 1935 Claims.

This invention relates to internal combustion engines of the kind comprising a rotary valve member having a chamber formed therein which constitutes part of the combustion space, is always in communication with the engine cylinder through an opening in the direction of its axis of rotation and has a lateral port adapted to register with inlet and/or exhaust passages.

There are two main considerations in designing an internal combustion engine. One is the horsepower obtainable for a given size or cubic capacity of piston displacement and the other is efficiency, including particularly thermal efliciency. The difficulty is to improve the one (i. e. either power or efficiency) without loss of the other.

The power of, or horsepower developed by, an internal combustion engine increases initially with increase of engine speed, due to a greater number of impulses per minute thus obtained.

As the engine speed increases, however, other factors come into operation which act to reduce the increase of power thus obtainable until eventually a peak is reached and the power output thereafter actually decreases with increase of engine speed. These factors are principally, the rate of propagation of the combustion and the resistance to the entrance and exit of the gases. There are also purely mechanical problems and all this is well known.

As regards the resistance to the entrance'and exit of the gases, which depends upon the design of ports and valves, it is obvious that, provided lubrication and gas sealing problems can be overcome, a rotary valve member of the kind to which this invention relates, has many advantages over the poppet valve.

As regards rate of propagation of combustion, it is well known that the rate of propagation under ideal, or any, conditions increases with increase of compression ratio, and this also increases the thermal efficiency by producing quicker and more complete combustion, but in an internal combustion engine of the kind in which the explosive mixture is obtained from a carbureter, pre-ignition is liable to occur and is the chief limiting factor which prevents increase of compression ratio where standard fuels are to be used, because the engine power and efiiciency' fall olf when pre-ignition occurs. Therefore, it is a fact that, in standard engines, using standard petrol or like fuel, the compression ratio seldom exceeds 7 to l. Of course, preignition can to some extent be reduced by employing an over-rich explosive mixture, but with such method, not only is thermal efficiency lowered and carbon deposit increased, but the rate of flame propagation and the resultant explosive pressure is lowered, both of which factors limit the power output, especially at the higher speeds. It is known that pre-ignition can be caused by local hot-spots with which the gases come into contact, such as an overheated plug or exhaust valve, but it is also known that, theoretically, the temperature of compressed gases rises proportionally with the compression ratio so that, apart from local hot-spots, the gases should reach the flash point of ordinary petrol-air mixture at about 7 to 1 compression. To exceed such compression ratio, therefore, it has always been assumed that special fuels, generally known as dope have to be used.

As regards thermal efficiency, while combustion efficiency can also be improved by increasing the compression ratio, there is the factor of heat losses to be considered. If the compression ratio is raised without reducing in substantially the same ratio the area of surface exposed to the gases, the increased temperature of the gases, which follows with the increase of compression, causes proportionally increased heat losses, quite apart from any other result obtained. The use of a compact volume of compression, ideally a spherical chamber, enables such increase of heat losses to be avoided by reducing the exposed surface area substantially with increase of compression ratio. It is also known that thermal efficiency can be increased, and tendency to preignition reduced, by encouraging turbulence within the gases, so that combustion spreads more uniformly through them. I

With all the above knowledge, however, it has been considered impossible, with ordinary fuels and in engines for ordinary use, to provide a compression ratio greater than 7 to 1, and/or that such ratio represented the useful limit, above which little advantage, if any, would be obtainable.

There are therefore only two principal ways 'of increasing the power or efficiency or both of an internal combustion engine, namely (1) To raise the compression ratio if pre-ignition can be avoided, and thermal losses kept down.

(2) To reduce resistance to flow of gases.

The object of the invention is an improved construction and arrangement of the parts of an internal combustion engine to reduce the effect of the limiting factors and conditions above explained, thereby enabling development in the above two principal ways to increase the power and eificiency of an engine of a given size or cubic capacity of piston displacement.

The internal combustion engine of this invention comprises a rotary valve member having within itself a chamber of compact volume always in communication with the engine cylinder through an opening in the direction of its axis of rotation, the chamber constituting a very large part of the compression space when the piston is at the end of its compression stroke and being further characterized in that the whole or a major portion of the chamber and the whole or a major portion of the opening therein are positioned on one side of the axis of rotation of the valve member. By compact volume is meant a dome-like shape, as, for example, partly spherical, in contrast with a fiat or thin shape. The piston, cylinder and the chamber in the valve member are so proportioned and arranged that when the piston is in position producing maximum compression (at the end of its compression stroke), the chamber constitutes substantially all of the compression space. The piston may be arranged to rise to the top of the cylinder in such close proximity to the cylinder head to provide a thin space or clearance, for example, 0.01 inch in thickness or depth, the combustion space at maximum compression being within the space of the valve chamber and the thin clearance space. The engine of the invention operates efiiciently and without pre-ignition at high compression ratios 12 to 1 and higher. The chamber may advantageously, for example, constitute 90 per cent or more of the compression space. The valve member has a port connecting the chamber with one or more gas passages, and preferably the wall of the chamber extends to, and practically merges with, the edges of the port.

In the accompanying drawings- Fig. 1 is a sectional elevation of the cylinder head portion of one example of engine made in accordance with the invention;

Fig. 2 is a sectional elevation showing a modification of the arrangement shown in Fig. 1;

Fig. 3 is a sectional elevation through the inlet and exhaust ports showing an alternative gas sealing device;

Fig. 4 is a sectional elevation of the cylinder head portion of a modified form of the invention;

Fig. 5 is a sectional elevation of a complete engine showing the latest and preferred form of the invention;

Fi 6 is a sectional elevation on line 6-6 of Fig. '7; and

Fig. 7 is a sectional plan on line 1-1 of Fig. 5.

As shown in Fig. 1, the dome-shaped compression and combustion chamber or space 43 is formed in the exteriorly dome-shaped rotary valve-member 44 of a slightly larger diameter than the engine cylinder with a tubular extension 45 at its upper end to carry the bearing on which it revolves, such bearing consisting of a ring 46 secured to the extension 45 against conical half rings 41 and supported by a double-thrust arrangement of ball bearings 48, and other races 49 and 50 of which are adjustable by means of shims 5| and 52, respectively, for clearance and for raising or lowering of the member 44. The ring 46 is secured to the extension 45 by a screwed collar 53 and lock nut 54. between which is secured a pinion wheel 55. The axis of the domed valve-member 44 is preferably coincident with the axis of the cylinder and rotates within a liner 56 fixed in the lower part of the cylinder head,

and a gas-tight joint is provided by a sleeve 51 engaged by rings 58 at the base of the tubular extension 45. The cylinder head is made in two parts and secured in the upper part is a depending tubular member 59 screwed at its lower end for a sparking plug and having rings 60 to form a gas-tight joint within the extension 45. The compression and combustion chamber 43 and the opening therefrom to the cylinder are off-set from the axis of rotation of the member 44, so that they are practically wholly on one side of such axis. At the same time, the member 44 is drilled and plugged or filled with aluminum to balance it about its axis of rotation, the plugging being effected to assist conduction and distribution of heat, which might be adversely affected if the holes were not plugged or filled. This chamber 43 is of compact volume and practically spherical in shape except where it merges into a port 6| on one side of the domed part of the member where in section at such part it closely resembles the section of a bent pipe. The port 6| is located in a wall portion of the chamber 43 which is remote from the valve axis. The uppermost part of the port 6| preferably extends to the full height of the uppermost part of the inner wall of the chamber 43 and the curved wall of chamber 43 preferably extends to the outer edge of the port 6|, thereby facilitating the smooth flow of gases from the chamber through the port. Also, at the top of the chamber 43 and co-axial with the axis of revolution of the member 44 is a passage 62, merging smoothly into the wall of the chamber, the lower part of which passage is shaped to receive the extreme end of the sparking plug and which thereafter widens out into the tubular extension 45 above referred to. The inlet passage 63 is partly shown in Fig. 1, while there is also shown a gas sealing strip 64 and spring 55 behind the same and a lower ring 66 to retain the strips of which there are two more, one on each side of the port 6|. The ring 66 also forms the gas seal at the lower end as the member 44 is proportioned with a small working clearance at its diameter. Lubrication is obtained by passages 61 leading to an annular groove 68, vertical grooves 69 leading to an annular space 10 and further grooves H leading to each sealing strip. The space 10 supplies lubrication to the rings 60. Oil is supplied under pressure to the ball bearings from which it reaches the above enumerated passages and rises to and lubricates the driving gear. Cooling is obtained by arranging for a substantial circulation of the oil.

The driving gear for the extension 45 consists of straight or helical pinion 55 with an idle wheel 13 and vertical shaft 74 carrying the pinion 12, such shaft being driven from the engine crankshaft.

The lower edge of the wall forming the chamber 43 where the chamber opens into the top of the engine cylinder, may be rounded off, bevelled or otherwise shaped, and the underside of the cylinder head and the top of the piston may be domed or made conical, or as may be found most effective for turbulence and generally directing the passage of the charge between the engine cylinder and the compression and combustion chamber.

In operation, in the construction shown, the gases are substantially entirely compressed within the compact space of chamber 43, with suitable turbulence, leaving only a small thi space or working clearance above that part of the top of the piston not immediately under the lower opening of the said space. A compression ratio of approximately to 1 is provided by the pro? spark ignition and fed by a carburetor. It will be observed also that as the member 44 forms the cylinder head, and rotates, the gases are subjected to surface friction between it and the piston as they first emerge from the combustion chamber and as they are being compressed. The axial adjustment for the member 44, which is provided at the bearings, enables the working clearance to be adjusted as between the domeshaped member 44 and its surrounding housing. About .0015 inch difference of diameter will generally be found to be suflicient on the size of parts above described. Furthermore, as the member 44 is suspended from above, it will expand downwardly, at the same time as outwardly, and the domed shape enables the clearance to be kept substantially uniform at all temperatures. The domed outer shape may be modified to be conical or some other tapered shape to give this effect more accurately. By using a domed shape of a suitable true radius, the sealing strips 84 around the springs for cooling and lubrication purposes.

As' shown in Fig. 4, the rotary valve-member 86 in which is formed the off-set compression and combustion chamber 81 is formed with a depending extension 88 adapted to be engaged by gas sealing rings 89 in the wall of the upper end of the cylinder liner 90 in which the piston 9| operates. .As compared with Fig. 1, the overall height is thus considerably reduced. The extension 88 is formed with gear teeth 88a and the rotation of the member 86 is effected through gear wheels 92, 93 and 94, the latter being secured to a vertical shaft 95 driven from the engine crankshaft. The arrangement shown in Fig. 4 was designed for use with a crankcase of an engine originally fitted with an overhead cam shaft and the wide spacing of the vertical shaft 95 necessitated the use of the intermediate gear wheels 92 and 93. The same remark applies to the gearing shown in Fig. 1. The rotary member 86 is conical and is rotatably journaled parts.

in a liner 94a fixed in the cylinder head, which in this instance is not made in two separable The conical surfaces are accurately ground to form a gas-tight bearing surface. Relative difference of expansion between the rotary can be made from segments cut from a standard piston ring. The member 44 could be split or partly split as is the practice with pistons, to allow it to fit resiliently within its housing, but this, though successful for improving the fit was not found to be so satisfactory as it increased the oil consumption and resulted in some loss of compression.

Instead of constructing the mounting for the member 44 so as to provide and maintain a working clearance, it has been found practicable to make the outer surfaces of conical or dome or other tapered shape and to permit axial movement and provide a spring or other means to keep them resiliently in contact, at the same time maintaining oil lubrication for the surfaces.

This arrangement allows automatic compensation for wear and for expansion and contraction and examples thereof are described later with reference to Figs. 2, 4, 5, 6 and '7.

As shown in Fig. 2, the rotary valve-member 14 in which is formed the compression and combustion chamber is maintained in contact with the liner '15, in which it rotates, by means of a spring 18 engaging between a collar 11 and a thrust race 18, the collar 11 being secured to the extension 19, of the member 14. A driving pinion 88 is also secured to the extension 19, by a collar 8|.

As shown in Fig. 3, the rotary valve member 82 is conical and is mounted with a running clearance as in the arrangement shown in Fig. l. Instead of providing sealing strips in the rotary member 82, sliding sleeves 83 are provided in the inlet and exhaust passages, each sleeve having a collar 84 engaged by a spring 85 acting to press the inner end of the sleeve against the periphery of the member, thus obtaining a gas-tight seal at the ports while providing a minimum area of surface in frictional contact. Lubricating oil would .be circulated member 86 and the liner 94a is provided for by allowing for axial displacement of the rotary member 86 against a retaining spring 95a. Lubrication for the conical bearing surface is provided by an annular oil space 98 to which oil is fed under high pressure while the rings 89 are cooled and lubricated by oil circulation through suitable oil passages, not shown. The driving gearing will, of course, be lubricated from the pressure lubrication system at the same time.

The engine and details thereof shown in Figs. 5, 6 and '7 represents the preferred form of the invention embodying the latest modifications and improvements. Apart from the substantial construction of the crankcase, the main bearings and the connecting rod and big end bearing, there is nothing in the lower part of the engine which differs from conventional practice. Some idea of the increase of strength which has been considered necessary may be gathered from the fact that the four holding down bolts for the cylinder head are proportioned to withstand collectively tons tension and this strength has been found necessary. Such question of the proportions and strength of the various parts is of course an ordinary matter of engineering design.

The cylinder body 91, of aluminum alloy, is fitted with a steel liner 98. The cylinder head 99 shown separately in Fig. 6 is made with a detachable cover I00 which is fitted after the driving-gearing, described later, has been assembled.

In the head 99 which is also of aluminum alloy, is a fixed liner Illl, conically shaped internally to receive the conical rotary valve member I02 in which is formed the oil-set substantially spherical combustion chamber I03 of compact volume. A single fiat gasket I04 provides the only gas-tight joint required between the liner 98 and the liner llll, the lower end of the member I82 being just short of such gasket to allow of relative expansion and downward movement of such member. The ground conical surface of the rotary member I02 provides both the hearing surface and the only gas-tight joint required as between the combustion chamber H13, the cylinder space above the piston I05 and the inlet port I06 and exhaust port I01. As compared with the previous examples, no gas sealing rings or strips are required. The said conical surfaces are maintained in contact by a. spring I08 acting through a driving spindle I 09 secured by a pin IIO to the upper end of the member I02. This driving spindle carries a gear wheel III and is supported at its lower end ina ball bearing H2, and at its upper end in a bush II 3 in the cover I so that the member I02 is relieved of any lateral stresses from the gearing. The ballbearing II2 also acts as a thrust race for the spring.- The substantially spherical shape of the compression and combustion chamber is to be seen from Fig. 5, and outlined by the circular dotted line in Fig. 6, while the shape of the port is also seen in Fig. 6 as indicated by the outline II4 which is flat at the top and bottom with straight inwardly inclined sides, all corners being of course slightly rounded. The size and position shown of the inlet and exhaust ports I06 and I0! relative to the port in the rotary member I02 and the position of the sparking plug hole II5 (see Fig. 7) are shown to actual scale but they are of course a matter of engineering design according to the timing required. It may be observed however, that the arrangement shown provides an unobstructed port area of 1.75 sq. inches, which is very large for an engine of 250 cc. capacity, having a combustion space of 1800. or 1.1 cubic inches.

As shown in Figs. 5 and 7, respectively lubrication for the cylinder head is provided under high pressure through the oil pipe IIG from which it passes to a-distribution passage III. Leading from the passage II! are two ducts H8 and H9, the entrance to each of which is controlled by an adjustable screw I20. These ducts H8 and H9 lead to the upper and lower 'ends of rotary valve-member I02 to supply lubrication thereto at high pressure. Lubrication supplied at the smaller diameter of the tapered valve member will tend to spread over the tapered surface by centrifugal force and effective lubrication is thus ensured. At one end of the passage II! is a valve seating against which is a spring-loaded ball valve I2I, the loading of which is adjustable by means of the screw I22 and determines the pressure of the oil feed to the ducts H8 and II9. The surplus oil, which is released by the ball valve passes by the duct I23 to the space above the rotary member which it fills, and finally flows over the gearing and down the easing of the shaft drive for the gearing to return to the crankcase. An oil container, supplementary to the crankcase is preferably included in the oil circuit in accordance with the usual present day practice.

By the use of the invention it is possible with a compact combustion chamber to obtain larger valve ports by reason of the larger diameter of the valve body and its greater peripheral speed,

to obtain improved flame propagation due to the turbulence produced by the eccentric travel of the combustion space in the valve and of the cylinder entrance port and to obtain improved scavenging due to the effect of centrifugal force on the exhaust gases.

Obviously the invention is not limited to all the details of the constructional forms above described, as modification thereof other than as herein proposed is clearly possible without departing from the nature of the invention, for example the shape and speed of rotation of the valve member in which is formed the compression and combustion chamber may be varied as a matter of design according to the cycle and number of ports provided.

The ports may be shaped so that the inlet gases are scooped into the valve body and also to assist turbulence, as by relative inclination of the leading and trailing edges of the ports in the valve and the ports in the housing surrounding the valve, so as to give for instance, an initial entry at the top of the port and initial exit at the bottom.

Certain features of the apparatus illustrated and described in this application are more particularly described and claimed in my copending application Serial No. 258,224, filed February 24, 1939, as a continuation-in-part of this application.

What I claim is:

1. An internal combustion spark-ignition engine comprisng a cylinder, a piston reciprocally mounted in the cylinder, a rotary valve member operatively mounted on the head-end of the cylinder, a dome-like-shaped combustion chamber in the valve member having curved walls and an opening into the cylinder, the major portion of the chamber and of the opening being positioned on one side of the axis of rotation of the valve member, and a port in a wall portion of the chamber remote from the axis of the valve member and serving to permit the exhaust of gas from the chamber; said curved walls merging into the outer edges of the port, said piston, cylinder and chamber being so proportioned and arranged that when the piston is in the position producing maximum compression the chamber constitutes substantially all of the compression space.

2. An internal combustion spark-ignition engine comprising a cylinder, a piston reciprocally mounted in the cylinder, a. rotary valve member operatively mounted on the head-end of the cylinder, a dome-like-shaped combustion chamber in the valve member having an opening into the cylinder, the major portion of the chamber and of the opening being positioned on one side of the axis of rotation of the valve member, a port in the valve member opening into the chamber and located in a wall portion of the chamber remote from the valve member axis, and an exhaust passage adapted to communicate with said port, said piston, cylinder and chamber being so proportioned and arranged that when the piston is in the position producing maximum compression the chamber constitutes approximately all of the compression space, the upper edges of the port and passage extending substantially to the full height of the chamber thereby facilitating the smooth flow of gases from the chamber through the port, said engine being constructed to attain a speed sufliciently high to create a centriiugal force assisting in producing efiective scavenging when the port is open for exhaust.

3. An internal combustion spark-ignition engine comprising a cylinder, a piston reciprocally mounted in the cylinder, a rotary valve member operatlvely mounted on the head-end of the cylinder, a dome-like-shaped combustion chamber in the valve member having a curved top wall and an opening into the cylinder, the major portion of the chamber and of the opening being positioned on one side of the axis of rotation of the valve member, a port in the valve member opening into the chamber and located in a wall portion of the chamber remote from the valve member axis, said curved wall merging into the upper edge of the port, and an exhaust passage adapted to communicate with said port, said piston, cylinder and chamber being so proportioned and arranged that when the piston is in the position producing maximum compression the chamber constitutes approximately all of the compression space, said engine being constructed to attain a speed sufliciently high to create a centrifugal force assisting in producing effective scavenging when the port is open for exhaust.

4. An internal combustion spark-ignition engine comprising a cylinder, a piston reciprocally mounted in the cylinder, a rotary valve member operatively mounted on the head-end of the cylinder and having its axis of rotation coincident with the cylinder axis, a dome-like-shaped combustion chamber of compact volume in the valve member having an opening into the cylinder, the major portion of the chamber and of the opening being positioned on one side of the axis of rotation of the valve member, a port in the valve member opening into the chamber and located in a wall portion of the chamber remote from the valve member axis, and an exhaust passage adapted to communicate with said port, said piston, cylinder and chamber being so proportioned and arranged that when the piston is in the position producing maximum compression the chamber constitutes approximately all of the compression space, the upper edges of the port and passage extending to the full height of the chamber thereby facilitating the smooth flow of gases from the chamber through the port, said engine being constructed to attain a speed sufliciently high to create a centrifugal force assisting in producing eflective scavenging when the port is open for exhaust.

5. An internal combustion spark-ignition engine comprising a cylinder, a piston reciprocally mounted in the cylinder, a rotary valve member operatively mounted on the head-end of the cylinder, a combustion chamber of compact volume in the valve member having the top wall curved and an opening leading directly into the cylinder, said chamber wall being flared outwardly at the juncture of the chamber and the cylinder, the major portion of the chamber and of the opening being positioned on one side of the axis of rotation of the valve member, and a port in a wall portion of the chamber remote from the axis of the valve member and serving to permit the exhaust of gas from the chamber, the curved wall merging into the upper edge of the port, said piston, cylinder and chamber being so proportioned and arranged that when the piston is in the position producing maximum compression the chamber constitutes substantially all of the compression space.

FRANK METCALF ASPIN.

IKUL/lvl

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