US3174762A

US3174762A - Piston and fire ring construction

Info

Publication number: US3174762A
Application number: US169514A
Authority: US
Inventors: Donald M Hesling; Laverne W Kibbey; Lewis M Davis
Original assignee: Sealed Power Corp
Current assignee: SPX Corp
Priority date: 1962-01-29
Filing date: 1962-01-29
Publication date: 1965-03-23
Anticipated expiration: 1982-03-23
Also published as: DE1776219B2; DE1476105A1; GB957885A; DE1776219C3; DE1776219A1

Description

March 1965 D. M. HESLING ETAL 3,

PISTON AND FIRE RING CONSTRUCTION Filed Jan. 29, 1962 2 Sheets-Sheet 1 F15. s Fm. 4

WENTORS DONALD M. HESLING, LAVERNE KIBBEY 6; LEWIS M. DAvls ATTORNEYS MarCh 1965 D. M. HESLING ETAL 3,174,762

PISTON AND FIRE RING CQNSTRUCTIDN Filed Jan. 29, 1962 2 Sheets-Sheet 2 I 1 TORS 44 DONALD M. HESLING, LAVERIWE MFYIBBEY 6c LEWIS M. DAV/5,

A a. M

ATTORNEYS United States Patent 3,174,762 PISTGN AND FREE RHNG fIQNSTRUfITlGN Donald M. Heeling, Laverne W. Kibbey, and Lewis M.

Davis, Muskegon, Mich, assignors to Sealed Power Corporation, Muskegon, Mich, a corporation of Michigan Filed Jan. 29, N62, Ser. No. 169,514 Claims. (Cl. 277-193) This invention relates to a piston and fire ring construction for use in internal combustion engines, particularly diesel engines.

Sticking of the top compression ring and bore scuffing have been problems in diesel engines, particularly in engines which have been modified, run at higher speeds or turbocharged in order to increase the horsepower output of the engines.

The piston configuration and piston ring arrangement normally used in these heavy duty engines is such that the top compression ring is placed a considerable distance from the top surface of the piston, leaving an unusually wide head land. This is especially true in open chamber type diesels where part or all of the combustion chamber is in the head of the piston. The large mass of metal in the head land in the top ring groove area becomes very hot since it is exposed to the flame of the combustion process. However, fuel and lubricating oil are only partially burned in tins area and consequently a hard deposit forms. Bore scutfing can result when the deposit on the head land becomes sufficiently thick to take up the normal clearance provided between the land and the cylinder wall. Scufiing can also occur when carbon deposits from partially-burned fuel and lubricating oil fill up the normal clearance between the inside diameter of the top compression ring and the root diameter of the piston groove, or between the side of the ring and the side of the groove. In both of the latter cases, when the ring operating clearances are taken up the outside diameter of the ring is permanently exposed beyond the piston lands. Therefore, when the piston rocks slightly during its normal operation, a very high pressure condition will exit between the ring face and the cylinder bore and hence scuifing will result.

An object of the present invention is to provide an improved piston and fire ring assembly for protecting the head land of the piston as well as the top compression ring thereof located at the conventional position on the piston.

Another object is to provide an improved fire ring and piston assembly operative to shield or bafile the area below the fire ring from the flame front without becoming clogged by carbon deposits in the fire ring groove.

A further object is to provide an improved piston and fire ring assembly operative to keep the cylinder wall scraped free of deposits that might otherwise work their way into the compression ring grooves located below the fire ring groove.

In the accompanying drawing:

FIG. 1 is a fragmentary vertical section of a piston and ring assembly in a cylinder with the piston and ring assembly constructed in accordance with the present invention.

FIG. 2 is a plan view of a fire ring segment of the present invention.

FIG. 3 is a fragmentary enlarged view of a portion of FIG. 1 illustrating two fire ring segments assembled in the fire ring groove of the piston in accordance with the present invention.

FIG. 4 is a fragmentary sectional view corresponding to that of FIG. 3 but reduced in scale therefrom, illustrating a modified piston groove construction for aluminum pistons provided with the present invention.

FIG. 5 is a fragmentary sectional View similar to that of FIG. 4 illustrating a still further modified piston groove construction.

amass Patented Mar. 23, 1965 "Ice FIGS. 6 and 7 are fragmentary sectional views similar to that of FIG. 3 but enlarged thereover to illustrate the operation of the piston and fire ring assembly of FIG. 3.

Referring to FIG. 1, the piston and fire ring construction of the present invention is shown applied to a conventional heavy duty piston 10 mounted for reciprocation in a cylinder 12 of a conventional diesel engine, not otherwise shown.

circumferential ring grooves

14, 16 and 18 for respectively receiving conventional top and middle compression rings 20 and 22 and a conventional oil ring 24. Piston It? is designed for open chamber type diesel engines and hence a large recess 26 is provided in the head of the piston to form part or all of the combustion chamber. As a result the top compression ring 20 is placed a considerable distance from the top surface 28 of the piston, leaving an unusually wide head land 30 indicated by the bracket in FIG. 1.

In accordance with the present invention, a circumferential ring groove 32 is provided in head land 30 which preferably is located as close as possible to the top end surface 28 of piston 14) consistent with the strength of the land material disposed between groove 32 and top surface 23. An improved fire ring assembly 34 is inserted in groove 32 which preferably comprises two

steel segments

36 and 38 as more clearly shown in FIG. 3.

Fire ring segments

36 and 38 are identical and each comprise an annular ring (FIG. 2) with a parting gap 39 and an outer peripheral cylinder scraping surface 40 which may be either plain, chrome plated, or coated or plated with some other wear resistant substance. The fire ring segments may be made in a conventional manner by coiling up suitable steel stock into the circular ring configuration of FIG. 2, heat treating the ring to 800 F. to relieve coiling stress and, if desired, plating the outer periphery of the ring to provide the scraping surface 40 and then reheating to relieve plating stress. While two

fire ring segments

36, 38 are preferred, fire ring assembly 34 may comprise a multiplicity of such segments or only one of such segments.

One critical feature of the piston and fire ring assembly of the present invention resides in the dimensional relationship of the fire rin' assembly 34 relative to the fire ring groove 32 and to the diameter of the bore of cylinder 12. The total axial width of the two fire ring segments 36, 3S, i.e., the dimension of the segments which is parallel to the axis of the piston, is considerably less than the corresponding axial width of fire ring groove 32. This provides a relatively great amount of side or axial clearance, such as that shown in FIG. 3 between the top surface 41 of fire ring segment 36 and the top wall 42 of groove 32, as compared to the axial clearance normally specified for a conventional compression ring (usually .002-.004 inch). The width of groove 32 is the distance between top wall 42 and bottom wall 44 of groove 32. It has been found that the best results are obtained when the two

fire rings

36, 38 are axially dimensioned to provide a total axial clearance ranging from .003 to .012 inch. The preferred range is from .003 to .006 inch. The other important dimensional characteristic of

fire ring segments

36, 38 is their outside and inside diameters in the free or expanded condition thereof, the outside diameter being substantially the same as the inside diameter of the bore of cylinder 12 so that these segments when installed in piston it within cylinder 12 exert little or no radial force against the cylinder wall. The inside diameter of

fire ring segments

36, 38 is greater than the root diameter of piston groove 32 so that the segments do not contact or bottom against the back wall 43 of the groove during normal operation of the engine.

It will thus be seen that the fire ring assembly 34 has what normally would be thought of as a sloppy Piston 10 is provided with suitable lit in piston groove 32. However, in accordance with the present invention fire ring assembly 34 is not intended to provide a 100percent seal as is expected from a compression ring. Rather, the purpose of these fire rings is to battle or shield the area below them from the flame front and also to keep the cylinder wall scraped free of deposits that might otherwise Work their way into

compression ring grooves

14 and 16.

Theoperation of

fire ring segments

36 and 38 is best shown in F168. 6 and 7. Due to the axial clearance in the ring groove and the lack of radial pressure against the wall of cylinder 12, the

fire ring segments

36 and 38 can rotate and shift axially in groove 32 relative to piston 10.

This movement is induced by reciprocation of the piston in the cylinder and results in a cleaning action between the top and

bottom walls

42 and 44 of groove 32 and the respectively adjacent surfaces of

fire ring segments

36 and 38. Since the fire ring segments do not completely seal compression, no great pressure is built up behind the segments and they are not forced out against the cylinder wall with extreme pressures. Preferably, the

fire ring segments

36, 38 have a high radial thickness to axial width ratio, such as about six to one, as compared to the usual ratio of about two and one quarter to one for conventional compression rings, and are relatively lightweight. This tends to reduce ring groove pounding due to inertial forces.

Due to their relatively sloppy fit in groove 32,

fire ring segments

36 and 38 have room in the groove to dish (movement of the ring segment from a planar to a conical shape) between the inclined positions illustrated in solid lines respectively in FIGS. 6 and 7. The dishing movement results from the net combined effect of gas pressure, inertial and momentum forces and friction between the

first ring segments

36, 38 and the wall of the cylinder during reciprocation of the piston. For example, on the intake stroke of a four-cycle engine the

ring segments

36, 38 assume the upwardly dished position of FlG. 6 The downwardly dished position shown in solid lines in FIG. 7 is a transient condition at the beginning of the compression stroke. During the remainder of the compression stroke, the combustion stroke and the exhaust stroke the

ring segments

36, 38 lieflat against the bottom side 44 of groove 32 as indicated in broken lines in FIG. 7. This dishing movement produces what may be termed a windshield wiper action between the

fire ring segments

36, 38 and the wall of cylinder 12 which assists in sweeping the cylinder wall clean. The dishing movement also causes the mutually adjacent surfaces of

fire ring segments

36, 38 to move radially relative to one another, thereby assisting in keeping fire ring assembly 34 clean so that the'fire

segments

36, 38 thereof remain free to move radially independently of one another to insure maximum contact of each fire ring scraping sur-. face 40 with the wall of cylinder 12.

When it is desired to install a fire ring assembly in accordance with the present invention in a piston made of aluminum, or some other relatively soft material, it

is preferred'to use the modified piston groove construetion illustrated in FIGS. 4 and 5. In FIG. 4 an alurnlnum piston 50 is partially shown which generally corresponds to piston in configuration and in the location of top compression ring 20 and a groove 14 therefor. However, 7

instead of casting or machining a 'firc ring groove directly in the material of the piston, an .annularcast iron insert 54 is placed in the piston mold and the molten aluminum is poured around the insert. A fire ring groove 56 1s then machined'in the cast iron insert 54 to receive fire :ring assembly 34, it being understood thatthe dimensional relationship between the fire ring assembly, insert groove 56 and the bore of cylinder 12 is as specified in the previously described embodiment. Alternatively, as shown in FIG. 5, the aluminum piston 50 may be cast with an even larger cast iron insert 60 therein which encompasses the location of the compression ring 20 as well as fire ring assembly 34. Both a fire ring groove '62 and a compression ring groove 64 are then machined of axial clearances between fire ring assembly 34 and groove 32 are intended to apply to a range of piston sizes currently employed in known diesel engines of the heavy duty type. Also, the lower limit of the aforementioned axialclearance range is more critical than the upper limit. If less than the specified minimum clearanceis provided, ring sticking will be found to occur as in prior art fire ring construction. If more clearance is provided than that specified for the upper limit of said range, the fire ring assembly would still be operable to serve as a baffle to shield the compression rings therebelow from the flame front and thereby reduce sticking, but the excessive sloppiness of such a fit would cause hammering of the fire assembly in the fire ring groove and result in excessive wear of the ring groove.

By way of example and not by way of limitation, a piston and fire ring construction operable in accordance with the invention may be constructed according to the following specifications:

Maximum individual axial width of

firering segments

36, 38 as installed Axial width of groove 32 Cylinder bore diameter Free outside diameter of

fire ring segments

36, 38

.0310 inch. 0.68O.69 inch. About 4.000 to 5.125 in.

Substantially equal to Individual radial thickness of cylinder bore diameter.

fire ring segments

36, 38 .l67.l73 inch after Clearance between inside diplating.

meter of ring 24 and root diameter of piston groove 32 Distance across gap 39 at free CD. of fire ring segments Material offire ring segments- .032-.042 inch.

0.25 to .065 inch.

Similar to S.A.E-l070 hardened and tempered reduce carbon deposits on the head land of'the piston and in the top compression ring groove to thereby enable an internal combustion engine to operate for a considerably longer period even at wide open throttle without stickin of either the compression of the fire rings. It is to be understood that the piston and fire ring construction disclosed herein may also be applied in accordance with the present invention to diesel engines other'th-an the open chamber'type as well as to gasoline or gas engines if the above mentioned problems are being encountered.

We claim:

1. In combination: a piston adapted for'reciprocation in an internal combustion engine cylinder, said piston having a transverse end surface adapted to form a movable said end surface including first and second grooves re-' spectively constituting the closest and next closest grooves to said end surface of said plurality of grooves, and 'a head land bounded by said end surface and said second V groove; a set of piston rings individually disposed in all but said first groove of said plurality of grooves including a parted first compressionring disposed in said second groove having a free state outside diameter greater than the diameter of the cylinder whereby said compression ring is adapted to be radially compressed by the cylinder wall to develop compression sealing contact therewith; and a parted fire ring disposed in said first groove and constituting the sole ring element disposed in said first groove, said fire ring being dimensioned axially relative to said first groove to provide a predetermined axial clearance therebetween sufiicient to permit said fire ring to dish and move axially in said first groove in response to piston reciprocation in the cylinder, said fire ring having a free state inside diameter greater than the root diameter of said first groove to permit rotation of said fire ring relative to the piston in response to piston reciprocation and said fire ring having a free state outside diameter substantially equal to the diameter of the cylinder such that said fire ring has a relatively low unit pressure contact with the cylinder wall compared to that of said first compression ring whereby said fire ring has a mere wiping rather than sealing contact with the cylinder wall.

2. The combination set forth in claim 1 wherein said axial clearance between said fire ring and said first groove is greater than the axial clearance provided between said compression ring and said second groove.

3. The combination set forth in claim 1 wherein said axial clearance between said fire ring and said first groove falls within a range from about .003 to .012 inch.

4. The combination set forth in claim 1 wherein said axial clearance between said fire ring and said first groove falls within a range from about .003 to .006 inch.

5. In combination: a piston adapted for reciprocation in an internal combustion engine cylinder, said piston having a transverse end surface adapted to form a movabl wall of the cylinder combustion chamber, a cylindrical peripheral surface having a plurality of circumferential grooves therein spaced axially from one another and from said end surface including first and second grooves respectively constituting the closest and next closest grooves to said end surface of said plurality of grooves, and a head land bounded by said end surface and said second groove; a set of piston rings individually disposed in all but said first groove of said plurality of grooves including a parted first compression ring disposed in said second groove having a free state outside diameter greater than the diameter of the cylinder whereby said compression ring is adapted to be radially compressed by the cylinder wall to develop compression sealing contact therewith; and a plurality of parted fire rings disposed in said first groove and constituting the sole ring elements disposed in said first groove, said fire rings each being dimensioned axially relative to one another and to said first groove to provide a predetermined axial clearance between the combined axial dimension of said fire rings and the axial dimension of said first groove sufi'icient to permit said fire rings to dish and move axially in said first groove in response to piston reciprocation in the cylinder, said fire rings each having a free state inside diameter greater than the root diameter of said first groove to permit rotation of said fire rings relative to the piston in response to piston reciprocation, said fire rings each having a free state outside diameter substantially equal to the diameter of the cylinder such that said fire rings each have a relatively low unit pressure contact with the cylinder wall compared to that of said first compression ring whereby said fire rings each have a mere wiping rather than sealing contact with the cylinder wall.

References Cited by the Examiner UNITED STATES PATENTS 765,033 7/04 Myers 277-63 XR 2,118,433 5/38 Goodyear 277193 2,294,519 9/42 Starr 277-224 XR 2,938,758 5/60 Phillips 277227 XR FOREIGN PATENTS 456,618 5/48 Canada.

119,828 10/63 Sweden.

EDWARD V. BENHAM, Primary Examiner.

WALTER A. SCHEEL, Examiner.

Claims

1. IN COMBINATION: A PISTON ADAPTED FOR RECIPROCATION IN AN INTERNAL COMBUSTION ENGINE CYLINDER, SAID PISTON HAVING A TRANSVERSE END SURFACE ADAPTED TO FROM A MOVABLE WALL OF THE CYLINDER COMBUSTION CHAMBER, A CYLINDRICAL PERIPHERAL SURFACE HAVING A PLURALITY OF CIRCUMFERENTIAL GROOVES THEREIN SPACED AXIALLY FROM ONE ANOTHER AND FROM SAID END SURFACE INCLUDING FIRST AND SECOND GROOVES RESPECTIVELY CONSTITUTING THE CLOSEST AND NEXT CLOSEST GROOVES TO SAID END SURFACE OF SAID PLURALITY OF GROOVES, AND A HEAD LAND BOUNDED BY SAID END SURFACE AND SAID SECOND GROOVE; A SET OF PISTON RINGS INDIVIDUALLY DISPOSED IN ALL BUT SAID FIRST GROOVE OF SAID PLURALITY OF GROOVES INCLUDING A PARTED FIRST COMPRESSION RING DISPOSED IN SAID SECOND GROOVE HAVING A FREE STATE OUTSIDE DIAMETER GREATER THAN THE DIAMETER OF THE CYLINDER WHEREBY SAID COMPRESSION RING IS ADAPTED TO BE RADIALLY COMPRESSED BY THE CYLINDER WALL TO DEVELOP COMPRESSION SEALING CONTACT THEREWITH; AND A PARTED FINE RING DISPOSED IN SAID FIRST GROOVE AND CONSITUTING THE SOLE RING ELEMENT DISPOSED IN FIRST GROOVE, SAID FIRE RING BEING DIMENSIONED AXIALLY RELATIVE TO SAID FIRST GROOVE TO PROVIED A PREDETERMINED AXIAL CLEARANCE THEREBETWEEN SUFFICIENT TO PERMIT SAID FIRE RING TO DISH AND MOVE AXIALLY IN SAID FIRST GROOVE IN RESPONSE TO PISTON RECIPROCATION IN THE CYLINDER, SAID FIRE RING HAVING A FREE STATE INSIDE DIAMETER GREATER THAN THE ROOT DIAMETER OF SAID FIRST GROOVE TO PERMIT ROTATION OF SAID FIRE RING RELATIVE TO THE PISTON IN RESPONSE TO PISTON RECIPROCATION AND SAID FIRE RING HAVING A FREE STATE OUTSIDE DIAMETER SUBSTANTIALLY EQUAL TO THE DIAMETER OF THE CYLINDER SUCH THAT SAID FIRE RING HAS A RELATIVELY LOW UNIT PRESSURE CONTACT WITH THE CYLINDER WALL COMPARED TO THAT OF SAID FIRST COMPRESSION RING WHEREBY SAID FIRE RING HAS A MERE WIPING RATHER THAN SEALING CONTACT WITH THE CYLINDER WALL.