US2864660A - Internal combustion engine piston and oil ring for same - Google Patents

Description

Dec. 16, 1958 H. M. SEUBERT, JR 2,864,660

INTERNAL COMBUSTION ENGINE PISTON AND OIL RING FOR SAME Filed April 11, 1956 l0 INVENTOR. HARRY M. SEUBERT JR.

ATTORNEY Unite tates Pater INTERNAL COMBUSTION ENGINE PISTON AND 01L RING FOR SAME Harry M. Seubert, .lr., Toledo, Ohio Application April 11, 1956, Serial No. 577,608

Claims. (Cl. 309-45) This invention relates to internal combustion engines, but more particularly to pistons and oil rings used in internal combustion engines.

There are two major problems encountered by designers of pistons for internal combustion engines. In the first place the differential in thermo expansion between the piston head and the piston skirt due to temperature differential that exists in these two areas during engine operation, constitutes one of these problems. The other problem is concerned with the differential in thermo expansion between the piston pin bosses and the piston wall 90 from these bosses due to the difference in the amount of piston mass located in each of these areas.

The endeavors to cope with these problems have involved the tapering of the piston so that the piston head is smaller in diameter than the upper skirt of the piston. Additionally a metallic band has been cast in the piston at the highest thermo expansion point, the metal being of a lower coefi'icient of expansion and supposedly decreasing the pistons rate of expansion in this particular area. These efforts have been directed to overcome the problem of the differential in thermo expansion as above mentioned.

The eflforts to cope with the second problem above mentioned, i. e. the differential in thermo expansion between the piston pin bosses and the piston wall, has resulted in slotting the piston skirt in horizontal and vertical planes and also the proportioning the mass of the piston to achieve the optimum expansion characteristics.

Additional problems are faced by the unequal piston skirt wear and poor oil control and in an endeavor. to solve these problems, the piston skirt has been cam ground and the skirt has been made of a flexible nature. The type of cam profile employed is dependent upon the nature of the piston design and engine application and is quite a costly operation.

The important item in all of these endeavors is to maintain a clearance between the piston and the cylinder wall at all engine speed-load conditions. Too much clearance causes excessive piston slap at low speeds and too little clearance results in piston scufiing and seizing.

It is a desideratum to provide a practical and economical solution to the above problems, eliminating all costly efforts and produce a piston designed with sufficient clearance to satisfy the high speed-load demands and employ a low friction piston oil ring in the skirt area of the piston, properly preloaded so as to be in contact with the cylinder wall at the lowest operational temperature expected for engine operation.

An object is to overcome the above difliculties and to produce a piston and oil ring assembly which satisfactorily copes with the several problems and which is efficient and economical.

Another object is to produce a new and improved piston structure equipped with a rotating oil ring having the unique features of construction and operation hereinafter described.

Other objects and advantages of the invention will hereinafter appear, and for purposes of illustration but not of limitation, an embodiment of the invention is shown on the accompanying drawing in which Figure 1 is a somewhat diagrammatic view partly in elevation and partly in vertical section of a piston disposed within an engine cylinder and equipped with the oil ring in accordance with this invention;

Figure 2 is an enlarged fragmentary transverse section substantially along the line 22 of Figure 1;

Figures 3, 4 and 5 are diagrammatic views showing different positions of the rotating oil ring in different positions of the piston;

Figure 6 is a diagrammatic view showing a portion of the piston and adjacent cylinder wall and illustrating by broken lines operational characteristics of the rotating oil ring;

Figure 7 isa view somewhat similar to Figure 6 showing the elastic deformation of the oil ring due to piston side thrust load, and

Figure 8 is a diagrammatic view similar to Figure 6 illustrating the oil metering action of the rotating oil ring.

The illustrated embodiment of the invention comprises a piston 10 having a head 11 at the upper end thereof equipped with the usual rings 12. Depending from the head 11 is a separate segmental skirt 13 suitably fixed to the head by an integral connection 14 providing bosses to receive the connecting rod wrist pin 15. The piston is reciprocable within an engine cylinder 16.

Formed in the outer side of the piston skirt 13 is a cylindrical channel 17 which is long tudinally elongate and the inner wall of which is parallel to the Wall of the cylinder receiving the piston. Disposed within and embracing the channel 17 is an endles garter-type oil ring 13 which is of an helical wire of metal or other suitable material. The diameter of the wire forming the continuous helix and the spacing between adjacent convolutions determine the amount of oil which will be metered in the operation of the piston and also the amount of piston side thrust which the oil ring can absorb. For greater load absorbing properties, a larger wire diameter is necessary thereby increasing the space between the adjacent convolutions and also resulting in an increase in the quantity of oil which will be metered. Preferably the wire form ng the oil ring is round in cross section in order to facilitate the rotating action of the ring in the operation of the piston.

Figures 3, 4 and 5 show different positions of the rotating oil ring 18 during the reciprocatory movement of the piston 10. Thus it will be observed that the oil ring moves from one end to the other of the channel 17 and during such movement rotates and as indicated on Figure 8 in which the arrow 19 indicates the direction of piston movement, the oil ring moving in the direction of the arrow 20 and at the same time rotating. In such rotational movement, the oil is metered adequately to lubricate the cylinder walls as indicated on Figure 8.

Referring to Figure 6 it will be understood that as the piston moves to the left of the figure at a given velocity, the oil ring travels in the same direction but only at one-half the piston velocity. Thus it will be manifest that although the piston velocity actually varies continually during the stroke, the oil ring 18 also varies its velocity and at the same rate. In view of the fact that the linear velocity is equal to the distance divided by time, linear velocity is directly proportional to the distance traveled. As a consequence the distance traveled by the piston (the stroke) is twice the distance covered by the oil ring 18. As indicated on Figure 6, 21 des gnates the distance traveled by the oil ring 18 and this distance is always one-half of the piston stroke.

Figure 7 illustrates the elastic deformation of the oil ring 18 which absorbs and softens the piston load transferral to the wall of the cylinder, the oil ring being designed to rotate under load. In this figure, the broken line 22jillustrates the reduction. of clearance due to side thrust load on the piston, such thrust being absorbed by the oil ring which is resilient and is accordingly deformed but without militating against its ability to rotate.

In view of the resilience of the oil ring 18, the piston can be cylindrical with the same clearance for the skirt 13 as at the head 11, variations in piston diameter along the length of the piston due to thermo distortion and load deformation being absorbed by the oilrings helical deflection, such deflection being illustrated on Figure 2.

It will be manifest that due to the above structure,

cold piston slap is prevented due to the initial prcl-oatb ingimparted to the oil ring 18. As the engine begins to warm up, the piston begins to expand unequally in the skirt area. Such unequal expansion is elastically absorbed by the helical deformation of the low-friction rotating oil ring 18 without ditficulty. At the same time,

the major and minor thrust forces on the wrist pin 15 are cushioned by the oil ring 18 against the cyl'nder wall, thereby substantially reducing wear. Due tothe one-half speed characteristic of the oil ring 18 as above pointed out, oil is metered and spread more uniformly over the cylinder wall a the oil ring rolls up and down in phase with the piston but only at one-half of its velocity. The normal sliding friction between the cylinder and piston is substantially reduced by a factor of one-, fifth to one-tenth. Reduction in engine wear and frictional horsepower loss is also appreciable due to this structure.

Numerous changes in details of construction, arrangement and choice of materials may be effected without departing from the spirit of the invention, especially as defined in the appended claims.

What I claim is:

l. A piston assembly for internal combustion engines comprising a piston head, a skirt depending from the head and having an inwardly extending channel extending around the skirt, and an endless helix of resilient wire-like material embracing said channel and rotatable therein during its travel from one end of the channel to the other during piston reciprocation.

2. A piston assembly for internal combustion engines comprising a piston head, a skirt depending from the head and having an inwardly extending channel extending around the skirt, and an endless helix of resilient wire-like material embracing said channel and rotatable therein during its travel from one end of the channel to the other during piston reciprocation, said helix being preloaded when in engagement with the wall of the cylinder receiving the piston.

3. A piston assembly for internal combust on engines comprising a piston head, a skirt depending from the head and having an inwardly extending channel extending around the skirt, and a preloaded, resilient helix embracing said channel, rotatable and translatorily movable in the channel during reciprocatory piston movements with the outer portion of the helix engageable with the walls of the cylinder receiving the piston.

4. A piston assembly for internal combustion engines comprising a piston head, a skirt depending from the head and having an inwardly extending channel extending around the skirt, and an endless helix of resilient wire-like material embracing said channel and rotatable therein during it travel from one end of the channel to the other during piston reciprocation, said wire-l ke material being round in cross section and the spacing of the adjacent convolutions predetermining the amount of oil to be metered during piston movement.

5. A piston assembly for internal combustion engnes comprising a piston head, a skirt depending from the head and having an inwardly extending channel extending around the skirt, and an endless helix of resilient wire-like material embracing said channel and rotatable therein during its travel from one end of the channel to the other during piston reciprocation, the diameter of the wire-like material being predetermined and the spacing of adjacent convolutions predeterminng the amount of oil to be metered during piston operation and the amount of piston side thrust to be absorbed.

References Cited in the file of this patent UNITED STATES PATENTS 31,847 Young Mar. 26, 1861 207,871 Horton Sept. 10, 1878 391,956 Frager Oct. 30, 1888 417,321 Gresham Dec. 17, 1889

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