US2497977A - Two-cycle scavenging engine - Google Patents

Description

Feb. 21, 1950 CARR|E 2,497,977

THO-CYCLE SCAVENGING ENGINE Filed March 16, 1948 3 Sheets-Sheet 1 fis.

7710mm 6". (ARR/5 Feb. 21, 1950 T. CARRIE TWO- CYCLE SCAVENGING ENGINE? 3 Shee't-Sheet 2 Filed March 16, 1948 Feb. 21, 1950 T. G. CARRIE 2,497,977 TWO-CYCLE SCAVENGING ENGINE Filed March 16, 1948 3 Sheets-Sheet 3 F/qz 223 222 Fig.4

O 226 2 224 awe/wan THOMHS 6. CARR/E flflowwu Patented Feb. 21, 1950 UNITED STATES PATENT OFFICE.

4 Claims. 1

Introduction This invention relates to internal combustion engines and more specifically to Diesel engines.

In the applicant's co-pending application Serial No. 573,650, filed January 20, 1945, of which this application is a continuation-in-part, now Patent No. 2,448,079, August 31, 1948, there is described an engine operating on a two-cycle uniflow scavenging principle and introducing new features of design and operation. Briefly, this engine included a frame, a cylinder block carried by said frame, a cylinder head on said cylinder block, at least one cylinder carried by said block, a valve chamber in said cylinder head having'a smaller diameter than the cylinder and in alignment therewith, a piston in said cylinder and a piston valve in said valve chamber, a wrist pin on said piston, a crank shaft provided with a crank, a connecting rod forming an operative connection between said wrist pin and said crank, said connecting rod having a portion surrounding said wrist pin and provided with outwardly extending parts constituting journals, a yoke connected to the piston valve, side rods connected to said yoke, a pair of rocker arms iulcrummed on said frame, each of said rocker arms being connected at one end to one of said side rods, and a. drag link connecting the other end of each rocker arm to one of said outwardly extending parts. Certain refinements are also provided in the nature of a lubricating system and a cooling system in which passages are provided in the rocker arms and drag links, and cooling and lu bricating fluids are circulated through said passages.

The invention The present appllcation deals with improvements particularly applicable to engines of this type. In accordance with the present invention, the piston crown includes a downwardly extending frustro-conical section, the lower portion of which includes an opening. A socket bearing having a spigot held in this opening is adapted to bear upon the top end of the connecting rod. In accordance with this structure, the jets from the sprayers are deflected by the conical section to the piston walls rather than on the piston head. Moreover, the thrust from the piston is transmitted directly from the piston head through the frustro-conical section and. the socket bearing to the top of the connecting rod as well as through the walls of the piston to the wrist pin. According to a refinement of the preferred structure. the connecting rod includes a separate piston pin bearing fitted in the eye of the connecting rod and having portions extending outwardly from the eye of the rod to constitute the journals for the drag links. According to a further refinement the top portion of the piston valve chamber is connected with the scavenging air manifolds whereby the piston valve acts as an auxiliary air compressor.

Detail description The invention will be more fully understood by reference to the accompanying drawings illustrating a preferred embodiment and in which- Figure 1 is a vertical elevation partly in section of :1 Diesel engine constructed in accordance with this preferred embodiment taken from one en Figure 2 is a fragmentary cross section through the engine in a direction transverse to Figure 1, showing particularly the piston, connecting rod, drag link and crank shaft structure and arrangement, and illustrating also the piston cooling ar-' rangement, socket bearing, and lubricating arrangement.

Figure 3 is an elevation partly in section of the cylinder head of the engine shown in Figures 1 and 2.

Figure 4 is an elevation partly in section of the cylinder head shown in Figure 3 but in a trans verse direction.

Figure 5 is a plan view in half section of the cylinder head and cylinder shown in Figures 1 to 4 showing the piston valve and cylinder and internal exhaust header.

Referring more particularly to the drawings, the engine shown in an 8 cylinder unit of H inch bore and 13 inch stroke designed to develop 1000 H. P. at 460 R. P. M.

Referring to the drawings, the engine includes 3 major castings. A base plate 20!, a crank case 202 and a cylinder block 203 are rigidly tied together by tie rods 2 into a single unit. The tie rods are placed two at each end of the engine and two between each pair of cylinders. The tie rod diameter is graduated so that they form dowel pins 205 between the respective castings. The tie rods are anchored to the under-side of the base plate cross members by a split square collar 200 which fits into a recess or groove and bolted to the bottom end of the rod. The rods are then drawn up rigidly by the nut at the top end of the tie rod.

Base plate The base plate consists of two angle sections with double web cross members which carry the crank shaft in Babbitt lined steel shells. A single 55 web 201 provided with slots or windows 208 for 00 tank.

Crank case The crank case is a rectangular box section with double web cross members that conform with the double web cross members of the base plate. Bosses as cast between the webs of the cross members to contain the fulcrum pins Zlll of the linkage rocker arms. The spaces between each pair of cross members at back and front of the crank case are enclosed by sheet metal doors 2| 1 and secured by rectangular steel bars secured by two studs located between the crank case doors. The crank case doors extend edge to edge the whole length of the engine and practically all the full height of the crank case allowing easy across to the working parts.

Cylinder block The cylinder block 203 is of rigid box section. Cylinder jackets H2 and scavenging air spaces M3 are completed when the liners 2 are inserted. The lower part of the block forms the water header Eli; and like the scavenging air manifolds is common to all cylinders. Sleeves 2H3 are cased in the water header to receive the cylinder liners. Rubber sealing rings prevent leakage from the cylinder jackets to the air spaces. The water header is self-contained and sealed by the sleeves 21s carrying the cylinder liners 2H3. The cylinder jackets 2!? which form the top of the cylinder block are separate and individual to the several cylinders. Sleeves ill? for housing the side or valve rods are cast on each side of the cylinder block. Ample doors for cleaning out water and air spaces are provided. Each cylinder is provided with scavenging air ports M8 cast in the cylinder liner at the bottom of the piston stroke and since no exhaust ports are required in the cylinder liner the scavenging air ports fill the entire periphery.

Cylinder head The cylinder heads are cast singly and contain the piston valve cylinder M9 and exhaust manifolds 220 in a common water jacket. The piston valve chamber forms the center and is cast between the exhaust manifolds which extend across the back and front of the cylinder head.

Cross passages 22H encasing the exhaust ports extend round the side of the piston valve chamber making both manifolds common. The exhaust ports 222 fill the entire periphery of the piston valve chamber. The flanges of the exhaust manifolds 226 at the sides of the cylinder heads are machined at an angle so that a wedge-shaped gap is left between the flanges of the adjacent cylinder heads when bolted down. Wedge-shaped flanges 226 fitted with asbestos inserts on each face are inserted into the wedge-shaped gap between the flanges and drawn up by two bolts 225 which pass through bridge pieces 226 spanning the a'tflacent heads. The exhaust manifolds thus become continuous the whole length of the en- 4 Crankshaft The chank shaft journals and crank pins are drilled and plugged at each end 232. Connecting holes 233 drilled through the crank webs and plugged at the ends form a continuous passage through the crank shaft. Two smaller feeder holes 234 diametrically opposite are drilled d1- agonally from center of the crank shaft journal to communicate with the center hole and one oll outlet hole 235 is likewise drilled diagonally from the periphery of the crank pin to the center hole. The crank shaft thus becomes an auxiliary or secondary lubricating oil header, fed through the main bearings from the supply pipes of the lube oil header.

- Piston The piston is fitted with a socket bearing 235 which bears directly on the top end of the connecting rod 231, The socket bearing is anchored by a spigot 236A and is carried on the rectangular flange 2363 at the bottom of the inverted conical section 246 extending down from the top of the piston encasing the under-side of the piston crown. The area of the bearing surface of the socket bearing and piston pin hearing are equal so that only one-half of the unit stress of the piston thrust is effective on the piston pin thus preventing any tendency to piston pin deflection.

Lubricating oil system Forced feed lubrication is used throughout. Oil is pumped from the sump tank and delivered through an oil cooler and regulating valve to the lubricating oil header 238 which extends along the front of the engine inside the crank case. Branch or supply pipes 239 from the header are connected to each main bearing. Oil from the supply pipes is forced through the feeder holes 231A drilled in the periphery of the crank shaft journals to the secondary lube oil header formed by the hollow crank shaft and fed through the holes 235 drilled from the periphery of the crank pin to the crank bearing and up through a passage 2373 in the connecting rod to the piston pin 246 and socket bearing 236 at the top end of the connecting rod.

By using the crank shaft as a secondary lube oil header no particular bearing is dependent on its own particular supply pipe. The clogging or stoppage of one or several of the supply pipes would have little or no effect on the eificient lubrication of the engine and crank shaft cooling is obtained by passing oil directly from the coolers through the hollow crank shaft.

Piston cooling 245. The sprayers are located at the top of the drag links a little to the side of the center line so that the oil ejected from the sprayers is equally distributed by the oscillation of the drag links. The cooling oil spray jets are deflected to the piston walls by the inverted conical section 246 extending from the top of the piston which prevents the cooling oil Jets from striking the hot piston crown.

The piston cooling and lubricating oil pumps are of sufllcient capacity to supply both systems so that the engine can operate at full capacity with the partial or total breakdown of either one of the pumps. Cross connectingvalves are provided for this purpose.

Cooling system The cooling water enters the water header 2|! at the bottom of the cylinder block through a manually controlled regulating valve. Two external pipes 241, one at back and one in front of the engine lead the water from the header to the bottom of the respective cyclinder jackets 2l2. These pipes discharge into the cylinder jackets on diagonally opposite sides so as to impart a spiral flow to the water passing upwards round the liner. Another external pipe 248 leads the circulating water from the top of the cylinder jacket to the top of the piston valve chamber where it passes downwards between the piston valve chamber and the inner walls of the exhaust manifold, across the bottom of the cylinder head and upwards round the outside walls of the exhaust manifolds discharging into a cross-connecting pipe 249 from each side of the top of the cylinder head into a common overboard discharge pipe 250. The discharge pipe from each cylinder is provided with a thermometer and a conveniently located regulating valve 25! to control the now of water through each cylinder. A small pipe 252 leading from the extreme top of the cylinder Jacket and having a separate discharge supplies water to the cylinder cover of the piston valve chamber and prevents air locks in the cylinder heads.

Working parts A crank shaft 253 having cranks is suitably supported in the crank case 202. A piston 254 is mounted, for movement within each cylinder liner 2. To the piston is connected, through a wrist pin 240 a connecting rod 237 which in turn is to be driven from the piston.

Mounted for travel in the valve chamber is a piston valve 255 in the form of an inverted piston. The piston valve is connected through a rod 250 with a yoke 251. To each end of the yoke is connected a downwardly extending valve or side rod 258 which operate respectively at the back and front of the engine. Carried on fulcrum pins 2l0 on the main casting at each side of the connecting rod is a rocker arm 243 located inside the crank case. The rocker arms are designed to transmit one-half the piston stroke to the piston valve. A drag link 2 connects the inner end of each rocker arm directly to the top end of the connecting rod and operates on journals 259 formed by the projecting ends of the piston pin bearing 260 at the side of the eye of the rod. The piston ring bearing is a separate part fitted into the eye of the rod.

By the arrangement described, the piston valve is so connected to the connecting rod that upward movement of the piston valve is translated through the yoke, side rods, rocker arms and drag links to a downward thrust on the connecting rod. Thus, a modified opposed piston effect is obtained in a trunk piston engine with a single crank. Moreover, since the drag links operate inside the piston eliminating the use of a piston rod, cross-head and guide bars, the weight and height of the engine is greatly reduced, and a more even balance of the working parts obtained.

Placing the valve or side rods at back and front of the engine allows for a conventional cylinder pitch. an important factor in a. multi-cylinder ensine.

Operation In operation, the piston valve begins to open the exhaust ports before bottom dead center or 20 before the piston begins to open the scavenging ports. Between the position exhaust opening" and scavenging opening," i. e. 20 of the crank orbit the piston valve has uncovered the exhaust, greatly reducing the cylinder pressure which is further reduced by the rapid cooling of the exhaust gases as they escape from the cylinder due to the extensive cooling surface of the exhaust manifolds. The scavenging ports begin to open 47 before bottom dead center or 20 after the exhaust port opening has greatly reduced the cylinder pressure, allowing a large volume of air at low pressure to enter the scavenging air ports and flow through the cylinder in a single direction expelling the remaining burnt gases out through the exhaust ports an as the piston valve is operated from the connect g rod the closing of the scavenging air and exhaust ports are in the same relation to the crank as the opening, but reversed in order, the scavenging ports closing 20 before the exhaust ports.

Since the piston valve is operated directly from the connecting rod and travels only one-half the piston stroke it follows that, in operation, only one-half the load on the piston valve is transmitted to the engine by the connecting rod and is effective for twice the length of the valve travel, 1. e. the whole length of the piston stroke.

Inversely, only one-half the compression load on the piston valve during the compression stroke is effective on the engine, thereby allowing the engine to operate at a high compression ratio with the increased cylinder volume added by the opposed piston eflect of the piston valve.

Advantages piston" effect with a single crank and without 7 eccentrics or cam shafts.

(2) The elimination of a piston rod, cross head and guide bars greatly reduces the over-all engine height and weight allowing for higher speeds.

(3) Practically perfect scavenging is obtained by the unique design of the cylinder head in which the "piston valve chamber and the exhaust' manifold form an integral part and communicate directly without extended or restricted exhaust passages. This design allows a free and uninterrupted flow of the exhaust gasses from the cylinder to the exhaust manifolds, and

provides a very extensive area of cooling surfaces,

thus further increasing scavenging efllciency by the rapid cooling of the exhaust gases as they are expelled from the cylinder.

(4) Smooth running is ensured by the inherent 1s balance of the engine and centering the major stresses low in the engine housing. Only onehalf of the cylinder pressure is exerted on the cylinder head while the load on the piston valves is taken up by the fulcrum pins located between the double web frame of the crank case.

Only half the load on the piston valve is exerted on the engine and is effective the whole length of the piston stroke, thereby allowing the engine to operate at a high compression ratio with increased cylinder volume due to the opposed piston effect of the piston valve.

(6) Since the load on the piston valve is transmitted directly to the connecting rod by the drag links, it exerts no stress on the piston or piston pin. The load on the drag links is always equal and opposed in force and direction, therefore balancing and eliminating side thrust, or cross-head effect on the piston.

(7) The area of the bearing surface of the socket bearing at the top end of the connecting rod is equal to the bearing surface of the piston pin bearing thereby reducing the unit stress of the piston thrust on the piston pin by one-half.

(8) The load on the piston valve is taken by the fulcrum pins of the rocker arms so that only one-half the cylinder pressure is effective on the cylinder head and since the tie rods and main bearing bolts are anchored under the base plate cross members, all major stresses are kept low in the engine housing. Aluminum alloy pistons and cast iron piston valves give a perfect balance to the engine ensuring smooth running at high speeds.

(9) Work is performed on the engine by the piston valve which develops, in one preferred form of engine, approximately 22% of the rated engine horse power.

(10) The elimination of all spring return cam and roller operated valves.

A greater .piston valve travel and a reduction in cylinder pitch is obtained by eliminating an eccentric, while the width of the engine is reduced by eliminating secondary crank shafts with accompanying gear chain drives.

It will be understood that, without departing from the spirit of the invention or the scope of the claims, various modifications may be made in the specific expedients described. The latter are illustrative only and not offered in a restricting sense, it being desired that only such limitations shall be placed thereon as may be required by the state of the prior art.

The sub-titles used throughout the specification are merely to simplify reference thereto and should otherwise be disregarded.

I claim:

1. An internal combustion engine, comprising in combination, a frame, a cylinder carried by said frame, a valve chamber having a smaller diameter than the cylinder and in alignment therewith, a piston in said cylinder and a piston valve in said valve chamber, a wrist pin on said piston, a crank shaft provided with a crank, a connecting rod forming an operative connection between said wrist pin and said crank, said connecting rod having a piston pin bearing fitted in its eye, said bearing having parts extending outwardly from the eye to constitute journals, a yoke connected to the piston valve, side rods connected to said yoke, a pair of rocker arms fulcrumed on said frame, each of said rocker arms being connected at one end to one of said side rods, a drag link connecting the other end of each rocker arm to one of said outwardly extending parts.

2. An internal combustion engine, comprising in combination, a frame, a cylinder carried by said frame, a valve-chamber having a smaller diameter than the cylinder and in alignment therewith, a piston in said cylinder and a piston valve in said valve chamber, 'a wrist pin on said piston, a crank shaft provided with a crank, a

connecting rod forming an operative connection between said wrist pin and said crank, said connecting rod having a portion surrounding said wrist pin and provided with outwardly extending parts constituting journals for the drag links, a yoke connected to the piston valve, side rods connected to said yoke, a pair of rocker arms fulcrumed on saidframe, each of said rocker arms I being connected at one end to one of said side rods, a drag link connecting the other end of g each rocker arm to one of said outwardly extending parts, said piston crown having a downwardly extending conical section, the lower portion of said section including an opening, a socket bearing having a spigot held in said openings, said socket bearing bearing on the top end of the connecting rod.

3. An internal combustion engine, according to claim 2, in which connecting oil passages are provided in the rocker arms and drag links, sprayers are provided in the drag links adjacent the underside of the piston and are connected with said passages, the jets from said sprayers adapted to be deflected by the conical section to the piston walls.

4. An internal combustion engine, comprising, a cylinder block, a cylinder head mounted on said cylinder block, a cylinder within said cylinder block, a valve chamber having a smaller diameter than the cylinder and mounted in alignment therewith, in said cylinder head, exhaust headers within said cylinder head one at each side of said valve chamber, exhaust ports leading directly from said valve chamber to said exhaust headers, a scavenging air manifold within said cylinder block, scavenging ports leading directly from said scavenging air headers to said cylinders, said piston including a wrist pin, a crank shaft having a crank, a connecting rod forming an operative connection with said wrist pin and said crank, said connecting rod having a portion surrounding said wrist pin and provided with outwardly extending parts constituting journals for the drag links, a pair of rocker arms fulcrumed on said frame, each of said rocker arms being connected at one end to one of said side rods, and a drag link connecting the other end of each rocker arm to one of said outwardly extending parts, the top portion of the piston valve chamber being connected with the scavenging air manifolds whereby the piston valve acts as an auxiliary air compressor.

THOMAS G. CARRIE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,126,376 Curtis Aug. 9, 1938 2,220,173 Olsson Nov. 5, 1940 FOREIGN PATENTS Number Country Date 203,516 Switzerland of 1939

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