GB2226097A

GB2226097A - A piston ring for an internal combustion engine

Info

Publication number: GB2226097A
Application number: GB8827252A
Authority: GB
Inventors: Jose Milton Magri Laugenio
Original assignee: COFAP Companhia Fabricadora de Pecas Ltda
Current assignee: Marelli Cofap do Brasil Ltda
Priority date: 1987-05-11
Filing date: 1988-11-22
Publication date: 1990-06-20
Also published as: IT8847915A0; GB8827252D0; BR8702563A; IT1234996B; FR2639682B1; DE3814769A1; FR2639682A1

Description

1 A PISTON RING FOR AN INTERNAL CWBUSTION ENGINE The invention relates to

piston ring for an internal combustion engine.

multi-piece oil control rings have been known for a long time having tyn steel rail rings chromium plated at the peripheral surface thereof to provide a wear resistant coating, a self-tensioned ring with slots and adequate peripheral surfaces and a corrugated expander spring located behind it.

The aforementioned multi-piece oil control ring is known by the piston ring industry and has been part of the state of the ar4,- at least since 1963, according to the Goetze Catalogue, publication 1zo. 776, Issued June 1963.

Besides helping the scraping of oil from the cylinder wall, the intermediary ring also has the function of providing oil flow to the crankcase through slots performed in its body at the same time that it a-s as a separator for the pair of rails. However, in such a cIL construction there are no torsional effects in the intermediary ring and the assembly fails to promote adequate sealing of the rails towards 20 the walls of a piston groove in the control ring is located.

Such action is necessary to pre,;ent the oil from being breathed and burnt in the combustion chamber.

Therefore, it is desirable to provide the side sealing of rails against the piston groove through torsional movement of an intermediary ring. It is also desirable to control an oil film at the cylinder wall to allow suitable lubrication of relevant engine parts therein.

1 z According to one aspect of the present invention there is provided a piston ring for a piston of an internal combustion engine, comprising an annular ring having substantially axially extending internal and external peripheral surfaces, at least one of which surfaces has a cut away portion at one edge thereof for effecting a torsional twist in the piston ring.

According to another aspect of the present invention there is provided an internal combustion engine including a piston ring for apiston of an internal ccmbustion engine, comprising an annular ring having substantially axially extending internal and external peripheral surfaces, at least one of which surfaces has a cut away portion at one edge thereof for effecting a torsional twist in the piston ring.

The invention will now be described by way of example with reference to the accompanying drawings, in which:- Fig. I is a fragmentary radial and axial cross-sectional view of a piston ring, piston and cylinder; control ring according to the present inventioin; Fig. ii is a front view of an intermediary ring according to the present invention, Fig. III A and B are respectively front and plan views of an expander for use with the piston ring according to the present invention.

Fig. IV A and B and Fig. V A and B show fragmentary radial and axial cross-sectional views of a piston assembly operatively installed in a piston groove with the positive and reverse twist, respectively.

Referring more specifically to the drawings the structural detail of an intermediary piston ring of a multi-piece oil control ring is best illustrated in Fig. I in which is represented a cylinder wall 1 having a reciprocatable piston 6 mounted therein and an oil ring groove 4 around the piston.

1 1 1 The multi-piece oil control ring is located in the groove 4 and comprises two steel rails 2, an intermediary piston ring 3 and a corrugated expander 5.

Fig. II shows the intermediary ring 3 in more detail with the ring 3 having top and bottom edges 7 which are arranged to engage the cylinder wall 1 one at a time, an outer peripheral tapered surface 9, upper side face 10, bottom side face 11, cutaway portions 12 and 14, inside peripheral surface 13 and slots 8 in the side faces.

Fig. III shows a top view of an expander A with side face slots 15, whilst Fig. III B is a plan view of said expander of Fig. III A illustrating the corrugations thereof which are effective to force the rails 2 against the cylinder wall.

Fig. IV A and B are fragmentary radial and axial cross sectional views showing the intermediary piston ring 3 of the present invention located in a piston groove with an operative positive twist.

As shown in view A of both Figs IV and V the outer peripheral rounded surface of the rails 2 have a wear resistant coating. Figs. IV 3 and V B show the outer peripheral surface of rails 2 with contoured edges also having a wear resistant coating.

Fig. V A and B are fragmentary radial and axial cross sectional views similar to those of Figs. IV and V showing the intermediary piston ring 3 of the present invention located in a piston groove but having an operative necative twist.

The intermediary rings of this invention operate as follows: The expander 5 presses the rails 2 against cylinder wall 1 thus scraping the oil which returns to the crankcase through a gap between piston and cylinder wall or through the slots 8 of the intermediary ring and slots of the expander (see view of Fig. III).

1 The intermediary ring 3 features cutaway portions 12, 14 which allow the ring to be a twist ring, providing an alternate movement during operation in such mannerthat the rails 2 act against the piston groove 4 prcmoting side sealing therewith.

Cutaway portion 12 may be located at the intersection of the upper or bottcm side faces and the inner peripheral axially extending surface of the intermediary ring 3. If cutaway portion 12 is located in the upper side face 10, the torsion of the intermediary ring 3 will be positive, pranoting major sealing at the outer upper corner of the piston ring and the inside bottom corner of the piston groove, as indicated by arrows on both views of Fig. IV.

When cutaway portion 12 is located in the bottom face 11 of ring 3, the torsional force of ring 3 will be negative, promoting major sealing at the outside bottom corner 7 and at the inside uPper corner of the piston groove according to arrows on both views of Fig. V. The cutaway portion 14 also promotes positive twist of the intermediary ring 3. With this cutaway portion 14 of napier type and tapered outer peripheral surface, the intermediary ring 3 provides oil control at the cylinder wall 1 during upward or downward strokes of the piston and particularly so that a film of oil is maintained between the ring 3 and cylinder wall 1 for lubricating the piston during upward movenent of the piston 6, and scraping the oil during downward action.

1

Claims

CLAIMS:

1. A piston ring for a piston of an internal combustion engine, comprising an annular ring having substantially axially extending internal and external peripheral surfaces, at least one of which surfaces has a cutaway portion at one edge thereof for effecting a torsional twist in the piston ring.

2. A piston ring as claimed in claim 1, wherein the said cutaway portion is located at one or the other edge of the said internal peripheral surface.

3. A piston ring as claimed in claim 1, wherein a cutaway portion is located at the lower edge of the outer peripheral surface of the piston ring.

4. A piston ring as claimed in any one of the preceding claims, wherein the outer peripheral surface is tapered.

5. A piston ring as claimed in any one of the preceding claims, including slots in one or other of side faces of the piston ring extending between the said internal and external peripheral surfaces for allowing oil to flow towards the crank case in use.

6. An internal combustion engine having a piston ring as claimed in any one or more of the preceding claims.

7. A piston ring substantially as hereinbefore described with reference to, and as illustrated in, Figs. I, II and IV; or Fig. V of the accompanying drawings.

8. An internal canbustion engine substantially as hereinbefore described with reference to, and as illustrated in, Figs. I, II and IV; or Fig. V of the accompanying drawings.

1 Published 1990 atThe Patent office. State House. 66'71 High Ho'born. London WCIR 4TP. Further copies mky be obtainedfrorn The Patent Office Wes Branch. St Ma:7; Cray. Orpington. Kent BR5 3RD- Printed by Multiplex techniques ltd. St Mary Cray. Ke,-.. Cor. 187