US2842107A - Internal combustion engine - Google Patents

Description

July 8, 1958 H. TEEGEN INTERNAL COMBUSTION ENGINE Filed Deb. 27, 1955 I 7 E M g Mow m B r e a United States Patent INTERNAL COMBUSTION ENGINE Hermann Teegen, Bielefeld, Germany, assignor to Diesel Engine Company of Texas, Houston, Tex, a corporation of Texas Application December 27, 1955, Serial No. 555,675

4 Claims. (Cl. 123-43) The invention relates to an internal combustion engine of the self-ignition type compressing an air-fuel mixture, the compression ratio of said engine being variable, which enables the ignition point to be adapted to the respective operating conditions. In known engines of this type it has already been proposed to arrange adjusting members in the cylinder head, which vary the volume of the combustion chamber. Furthermore, it has also been proposed to separately vary said members in their position dependent on the respective cylinder wall temperature, in that outside of the cylinder a thermo-responsive regulating element is provided, the variations of which being transmitted, through a lever arrangement, to the adjusting member which determine the capacity of the combustion chamber. Engines of such kind have the disadvantage that the control is insufiicient and that furthermore a complicated construction of the cylinder head is necessary.

The invention eliminates the above mentioned deficiencies in that according to the invention a control piston is provided opposite the piston operating in the cylinder, the combustion chamber being formed between said two pistons. The control piston, through means .of a sealing ring, sealingly bears against the inner walls of the cylinder. Immediately on the upper end of the cylinder, means are provided which upon variation of the position of the control piston affect the capacity of the combustion chamber, said means being responsive to the temperature in the combustion chamber.

Due to the arrangement of the thermo-responsive means for the shifting of the control piston immediately on the upper cylinder end a very favorable heat flow is secured. The distance to be bridged for the heat transfer is very short so that the arrangement is very sensitive and even small temperature changes in the combustion chamber result in an immediate adaption of the chambers capacity.

The thermo-responsive means are preferably formed of outer rings and inner rings which are arranged immediately on the shaft of the control piston. The inner rings have a different coefficient of thermal expansion than the outer rings, i. e. the inner rings and the outer rings consist of different material having different coeflicients of thermal expansion. t

On the sides facing each other the inner rings and the outer rings are provided with tapered support surfaces which bear against each other. An expansion of the outer rings, caused by a temperature rise results in a more or less deep axial interlocking of the inner rings with the outer rings and thus in an axial shifting of the control piston which bears against the cylinder cover through means of said rings.

In accordance with the invention a sealing ring has been provided between the control piston and the cylinder wall which consists of a helical strip material. On their inner sides the screw-like threads form a tapered seat into which fits the control piston provided with a correspondingly tapered rim. Through means of the combustion pressure or of a correspondingly arranged spring 2,842,107 Patented July 8, 1958 III the control piston is pressed into the seat of the sealing ring which is expanded to an extent so that a pressing action against the inner cylinder wall and thus a positive sealing action results.

Further details of the invention are specified in the following text and illustrated in the appended drawing, of which Fig. 1 is a longitudinal sectional view through a singlecylinder two-stroke cycle internal combustion engine in which the air-fuel mixture is compressed in the crank case and transferred into the cylinder,

Fig. 2 is a sectional view through the lower part of the control piston, on an enlarged scale,

Fig. 3 is a top plan view on the sealing ring employed in combination with the control piston.

In the cylinder 1, which on its outer side is provided with wedge-like ribs 2, a piston 3 operates. The piston pin 4 carries the connecting rod 5 which on the other side is supported on the crank pin 6.

In the crank case 7 the crank shaft 8 with the crank webs 9 is journalled in suitable ball or roller bearings. A fly-wheel 10 or a pulley, respectively, has been secured to the crank shaft 8 in known manner.

The air-fuel mixture is prepared either inside or outside the crank case 7. Through channels 12 in the cylinder 1 the air-fuel mixture which has been precompressed in the crank case, is passed to the combustion chamber above the piston 3 in the cylinder 1.

At the upper end the combustion chamber is closed by a control piston 13, the outer circumference of which being tapered. On this tapered portion a sealing ring 14 is arranged.

Construction of the seal and its arrangement can be seen clearly from Figs. 2 and 3. The seal is formed of a helical material strip of a length to form several screwlike threads. The section of the strip material has been selected so that the individual screw threads with their fiat surfaces rest closely on each other and that the seal on its outside forms a cylindrical body engaging the inner walls of the cylinder 1. The thread portion between the ends of the screw-like threads are offset so that the seal has a shape as can be seen from Fig. 3

The sealing ring formed of the screw-like threads consists of a resilient material. Inside, the sealing ring forms a tapered seat into which fits the piston 13. By more or less pressing of the piston 13 into the seal 14 this is more or less expanded and thus blocked in the cylinder 1. Since the sealing ring 14 forms several screwlike threads which leave no gap an absolutely safe sealing action is effected.

In the upper part of the cylinder 1 an enlarged chamber 15 is provided into which extends the control piston 13 with its shaft in. On the shaft 16, in the chamber 15, thermo-responsive means are provided which affect a displacement of the control pistonllS in the cylinder 1. In the embodiment illustrated, these means comprise three inner rings 17, 18, and 19, inovably arranged on the shaft 16. Said three rings are arranged one after the other with a certain play and provided with tapered. surfaces on their outer circumference. The material of these inner rings has a low c-oeflicient of thermal expansion.

Between the inner rings 17, 13, or 3.9, respectively, outer rings 20 or 21, respectively, are arranged consisting of a material having a high coeiheient of thermal expansion. On their insides the rings 2i and 21 have tapered surfaces corresponding to those on the inner rings 17 or 19, respectively, so that the inner and outer rings 17, 2t), 18, 21,. and 19 bear against each other through means of these tapered surfaces.

The ring 1'7 has a collar 22 through means of which it rests on the upper side of the sealing ring 14, whilst the ring 19 has a collar 23 and is movably guided in the cyl- 3 inder cover 24. The cover 24 is fixedly bolted to the cylinder through means of bolts 25 and 26 and closes the upper end of the chamber 15. On the other hand, the cover 24 has a cup-shaped indentation 27, which extends into a recess 28 in the shaft 16 of the control piston 13.

In the center of the shaft 16 a bolt 29 is formed on the piston 13 which passes through the chamber 27 and which forms a screwed-onspring back-rest 30 for a compression spring 31 outside said chamber 27, said spring being passed over the bolt 29 and arranged in the chamber 27.

The compression spring tends to pull the control piston 13 against the cylinder cover 24 as soon as the expansible rings 20 and 21 allow for such movement, i. e. as soon as the rings 20 and 21 expand due to a rise in temperature so that they no longer support the inner rings 17 to 19 which then have axial play. On the other hand, the spring 31 presses the control piston 13 into the sealing ring 14 and thus tightly closes the upper end of the cylinder 1.

Both pistons 3 and 13 have a recess 32 and 33, respec- 'tively, on the sides facing each other, whereby the combustion chamber is formed.

Operation of the arrangement is as follows: Both pistons 3 and 13 have approached each other so that only a small gap 34 remains between them, and the air-fuel mixture is compressed only in this gap and the chamber 32 or 33, respectively. The size of this combustion chamber at first is not varied, since the control piston 13 is pressed into the sealing ring 14 and thus remains in its position in the cylinder 1. As soon as the temperature rises, the increasing heat is transmitted to the rings 20 and 21. The material of these rings has a high coefficient of thermal expansion which results in a corresponding expansion of the rings. Thus the rings 17, 18, and 19 lose their axial support. Due to the combustion pressure and the additional action of the spring 31 the control piston 13 now can be displaced outwardly for a certain distance which depends upon the respective temperature, i. e. the combustion chamber capacity is automatically increased and thus adapted to the new operating conditions. On the other hand, when the temperature decreases, the rings 20, 21 are contracted and the inner rings 17, 18, and 19 are pressed apart in axial direction, the control piston 13 is pushed into the cylinder 1 and the capacity of the combustion chamber is reduced.

Iclaim:

1. An internal combustion engine having a cylinder and a piston movable in said cylinder, and including, a control piston in one end of the cylinder, the space between the first piston and the control piston forming a combustion chamber, means for adjusting the position of the control piston relative to the cylinder to thereby vary the area of the combustion chamber in accordance with temperature changes, said last-named means comprising a plurality of inner rings surrounding the control piston and constructed of a material having a relatively low coefficient of expansion, one of said rings engaging a pro jection on the control piston whereby movement of the rings in a direction parallel to the control piston axis will permit movement of said control piston relative to the cylinder, a plurality of outer rings disposed alternately between the inner rings and constructed of a material having a relatively high co-efiicient of expansion, the bores of the outer rings engaging the outer peripheral surfaces of the inner rings with the engaging surfaces of the rings being inclined, where-by radial expansion and contraction of the outer rings permits the inner rings to move up and down relative to the axis of the cylinder, and a fixed support for confining the inner rings between said fixed support and the end of the cylinder, whereby as the outer rings expand and contract, the inner rings undergo movement to change the position of the control piston with respect to the cylinder.

2. An internal combustion engine as set forth in claim 1, together with resilient means constantly acting upon the control piston to urge said piston in a direction which will maintain the projection on said control piston in contact with one of the inner rings to assure movement of piston upon a movement of the inner rings.

3. An internal combustion engine having a cylinder and a main piston reciprocable therein and including a control piston closing the power end of said cylinder and slida'ble therein, the area between the main piston and the control piston forming a combustion chamber, said control piston comprising a main cylindrical body portion and a reduced shaft portion, a series of inner rings surrounding the shaft portion with one end ring of said series engaging the body portion of the piston, a fixed support engaging the other end ring of the series, whereby said rings are confined between the fixed support and the body portion, and a plurality of outer rings at least partially interposed between and engaging the inner rings, the bore of each outer ring and the surfaces of adjacent engaged inner rings being tapered, whereby expansion and contraction of the outer rings allows movement of the inner rings relative to each other and to the fixed support in a direction upwardly and downwardly relative to the axis of the cylinder, whereby the position of the control piston with respect to the main piston maybe changed to thereby vary the area of the combustion chamber, the inner rings being constructed of a material having a lower co-eflicient of expansion than the outer rings whereby temperature variations Will result in adjustments of the control piston.

4. An internal combustion engine as set forth in claim 3, together with an extension on the shaft portion of the control piston extending through the fixed support, and a spring means surrounding the extension and confined between the fixed support and an enlargement on the extension for constantly urging the control piston in a direction which urges the series of inner rings in a direction toward the fixed support.

References Cited in the file of this patent UNITED STATES PATENTS 1,812,572 Talbot June 30, 1931 1,874,682 Woolson Aug. 30, 1932 FOREIGN PATENTS 495,218 Great Britain Nov. 9, 1938 727,345 Germany Oct. 31, 1942

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