GB2216985A

GB2216985A - A piston ring arrangement for an internal combustion engine

Info

Publication number: GB2216985A
Application number: GB8904680A
Authority: GB
Inventors: Jose Milton Magri Laugenio
Original assignee: COFAP Companhia Fabricadora de Pecas Ltda
Current assignee: Marelli Cofap do Brasil Ltda
Priority date: 1988-04-08
Filing date: 1989-03-01
Publication date: 1989-10-18
Anticipated expiration: 2009-03-01
Also published as: GB2216985B; DE3836796A1; BR8801752A; IT8821958A0; ES2012657A6; FR2629870A1; IT1232347B; GB8904680D0; JPH02185654A; FR2629870B1

Abstract

An oil and compression piston ring assembly for internal combustion engines features a pair of rails 10 located in the same ring groove of a piston, the rails are separated by an intermediate compression ring 20 with at least a portion of it peripheral surface 23 contactable with a cylinder wall C of an engine. The pair of rails are urged radially outwards against the cylinder wall by a bridging spring element 30 located inside the ring groove CA. This construction arrangement makes it possible to use pistons having only two ring grooves, so the pair of rails act like an oil ring, while the intermediate separator ring acts in oil control as in blow-by. <IMAGE>

Description

h 2216985 A PISTON RING ARRANGEMENT FOR AN INTERNAL COMBUSTION ENGINE This

invention relates to a piston ring arrangement for an internal combustion engine.

In the motor vehicle engine art, the usual number of piston rings for each piston of modern internal combustion engines comprises three rings which have the following requirements:

1. TO provide an effective seal to combustion gases (blow-by control); A typical ring set known in the art for Otto motors may be assembled with a compression ring in the first ring groove having a 1.5mm ring width; an intermediary ring at the second ring groove also having a 1.5mm ring width, and an oil ring at the third ring groove of 25 the piston, the oil ring ccimprising two or three parts together having 3.0 mm rirxg width.

2. To prevent excess of lubricating oil from reaching the combustion chamber (oil control), and 3. To provide a heat conduction path from the piston to the cylinder water jacket.

The first and third functions are effected solely by the compression rings, but the second one is a combined effort of both compression - and oil control rings.

In past years and before the introduction of modern technology, ring sets were canposed of more than three rings for a piston, with ring widths up to two times greater than that described above.

n I- The necessity to reduce the weight, width, moving masses and friction of internal combustion engines, led to a reduction in rina quantity and ring width per piston.

Therefore it is desirable to provide an arrangement of oil - and compression rings for internal combustion engines in which a reduction in axial height of the piston is achieved without compromising engine performance.

According to the present invention there is provided an oil and compression piston ring assembly for an internal canbustion engine, canprising a pair of rails arranged to be located inside a ring groove of a piston of an internal caTbustion engine, each rail being located adjacent to a respective side wall of the ring groove with a peripheral c the engine; surface of the rails arranged to contact the cylinder wall of an intermediate ccmpression ring locatable between the pair of rails for maintaining the rails of each pair in an axially spaced configuration -ive side wall of.

relative to the piston and engagable against a respect the ring-groove, the ring having at least a portion of its peripheral surface engagable with the cylinder wall; and biasincf means located inside the ring groove and being supported simultaneously by the piston and the pair of rails for biasing the pair of rails radially outwardly against the cylinder wall of the engine.

In one embodiment in accordance with the present invention there is provided a ring arrangement of the above mentioned type which allows for a reduction in piston ring grooves without a corresponding reduction of rings necessary for appropriate piston operation.

one preferred embodiment of a piston ring in accordance with the present invention has a compression piston ring assembly for each piston of an internal combustion engine, said arrangement featuring:

(a) tyn rails engable in a piston ring groove, each rail being located adjacent to a corresponding side wall therein with its peripheral surface contacting the cylinder wall of the engine block, and 1-1 1 1 - t (b) an intermediate compression ring installed between the pair of rails so as to maintain them separated one from the other and located against the pertinent side wall of the piston groove, the intermediate compression ring having at least a portion of its outer periphery contacting the cylinder wall; and a spring element arranged at the bottom of the groove and supported, simultaneously at the groove and at the pair of rails, so as to move the pair of rails radially outwardly against the cvlinder wall.

The above mentioned one embodiment defines an assembly which not only embodies the present invention but also performs the rail function of the prior art and is located at the second and third piston ring grooves, thus combining these grooves and allowing use of the pistons with only two grooves and, consequently, lower axial height.

With the proposed arrangement, the pair of rails,pressed against ' the engine block through the spring element, acts as the cylinder wall o'. an oil ring, while the intermediate ring, which promotes the separation between the tyn rails, acts as much in oil consumption control as in blow-by.

An Embodiment of the present invention will now be disclosed by wa of example with reference to the accompanying drawings, in which:

Y 1 Figure 1 is a fragmentary radial cross-sectional view of a portion of an engine showing one of the cylinders having installed therein a piston ring assembly in accordance with the present invention, Figure 2 is a fragmentary cross-sectional view of a rail of a pair of rails used in the arrangement of Figure 1, Figures 3 to W are both fragmentary cross-sectional views of portions of the intermediate ring exemplifying different features to be used in the arrangement of the present invention, and Figures 4 to 4C are top plan views of different configurations exemplifying a spring element used in the arrangement of this invention.

t ' Referring to Figure 1, there is shown a piston ring arrangement featuring a pair of rails 10 preferably of steel, having a surface coating or treatment, or anti-wear thermo chemical treatment. Each rail is manufactured in a conventional manner as illustrated in Figure 2, with its peripheral surface 13 defining a cylindrical surface portion which is urged against cylinder wall C of the engine.

ibe pair of rails 10, are installed in the ring groove CA of piston P of the engine, thus superseding the known second and third ring grooves.

According to Figure 1, each rail 10 is installed adjacent a corresponding side wall of ring groove CA, its inside surface 14 apart from bottom wall of the groove CA and its peripheral surface 13 contacting the cylinder wall C of the engine.

Between the pair of rails 10, is located an intermediary compression ring 20, usually of cast iron or steel, and dimensioned so as to have at least a portion of its side surfaces 21 contacting the corresponding side surfaces 11 of the pair of rails 10, so as to hold them axially seated against the adjacent side walls of ring groove CA. The intermediate compression ring 20 is designed to have its inside surface 24 moved radially outwardly with reference to the alignment of inside surfaces 14 of the pair rails 10 and still its peripheral surface 23 having at least a portion contacting the cylider wall C of the engine.

in other Ynrds, the intermediary compression ring 20 has maximal size diameter applicable at least to a portion of its peripheral surface 23 equal to the internal diameter of cylinder C.

Figures 3 to W illustrate different configurations of the construction of intermediary compression rings 20. Figures 3, 3A,3B,3D,3E and 3P show intermediary canpression rings with the following features:

taper-faced, of the positive twist type 20 straight-faced 20a taper-faced 20b S 7 (.0 k_ straight-faced, of the positive twist type 20c taper-faced, of the negative twist type 20d half keystone ring 20e napier ring 20f According to figures to 3G to 3U, these intermediary compression rings feature radial bevel surfaces 26,26ap26b,26c,26d,26e and 26f on its bottom faces, or radial bevel surfaces. 27, 27a, 27b, 27c, 27d, 27e and 27f on its top faces.

The fourth and last element of the assembly is defined by an expander spring element 30 located in the ring groove CA so as to bear simultaneously, in the case of springs illustrated in Figures 4A to 4C, upon the bottom wall of ring groove CA and the inner surface 14 of the pair of rails 10, to radially press the pair of rails outwards against the cylinder wall C of the engine. In the case of the spring according to Figure 4, the spring bears simultaneously upon the side wall of the groove CA and the inner surface 14 of the pair of rails 10.

As illustrated in Figures 4 to 4C, these expander springs 30 can be of different configurations. The springs are of a strip of metallic material having a substantially rectangular cross-section throughout its length and may or may not provide transverse bending along its length so as to apply a radial outward pressure upon the pair of rails 10.

The expander spring 30 illustrated in Figure 4A to 4C is guided by side walls of ring groove CA touching the bottom wall and the inside the surface 14 of the pair of rails 10 at a plurality of points angularly spaced, while according to the configuration as shown in Figure 4 there is no contact with the bottom wall of ring groove CA. However, it must be understood that other spring elements may be provided which exert the same force upon the pair of rails 10.

i

Claims

1. An oil and compression piston ring assembly for an internal combustion engine, comprising a pair of rails arranged to be located inside a ring groove of a piston of an internal combustion engine, each rail being located adjacent a respective side wall of the ring groove with a peripheral surface of the rails arranged to contact the cylinder wall of the engine; an intermediate compression ring locatable between the pair of rails for maintaining the rails of each pair in an axially spaced configuration relative to the piston and engagable against a respective side wall of the ring groove, the ring having at least a portion of its peripheral surface engagable with the cylinder wall; and biasing means located inside the ring groove and being supported simultaneously with the piston and the pair of rails for biasing the pair of rails radially outwards aaainst the cylinder wall of the engine.

2. An assembly as claimed in claim 1, wherein the biasing means is supported simultaneously on the bottom wall of the ring groove and inner peripheral edge surface of the pair of rails.

3. An assembly as claimed in claim 2, wherein the biasing means engages the bottom wall of the ring groove and an inner peripheral edge surface of the pair of rails at a plurality of angularly spaced points.

4. An assembly as claimed in any one of the preceding claims, wherein the biasing means is arranged to touch one of the side walls of the ring groove.

5. An assembly as claimed in any one of the preceeding claims, wherein the biasing means is guided axially by the side wall of the ring groove.

6. An assembly as claimed in any one of the preceeding claims, wherein biasing means is defined as a metallic band.

7. An assembly as claimed in claim 6, wherein the metallic band is treated with a coating, or an anti-wear surface treatment or an anti-war thermochemical treatment.

j 1 -11

8. An assembly as claimed in any one of the preceding claims, wherein a corresponding ring groove is located in the region of the second ring groove of a conventional piston having three ring grooves.

9. An assembly as claimed in any one of the preceding claims, wherein the inner surface of the intermediate compression ring is displaced radially outwards relative to the aligrffnent of peripheral surfaces of the pair of rails.

10. An assembly as claimed in any one of the preceding claims, wherein the intermediate compression ring is arranged to contact the adjacent side faces of the pair of rails through surface portions of or another side face of the intermediate compression ring.

11. An assembly as claimed in claim 8, wherein one of the side faces of the intermediate compression ring includes radial bevels.

12. An assembly as claimed in any one of the preceding claims wherein the intermediate compression ring includes one of the following contructions: taper-faced, of the positive twist type; straight-faced; taper faced; straight-faced, of the positive twist type; taper-faced, of the negative twist type; half keystone ring; and napier ring.

13. An engine including a piston having two piston ring grooves, one of which grooves is adapted to receive and oil and compression piston rincr assembly, comprising a pair of rails arranged to be located inside a ring groove of each piston, each rail being located adjacent a respective side all of the ring groove with a peripheral surface of the rails arranged to contact the cylinder wall of the engine; an intermediate compression ring locatable between the pair of rails for maintaining the rails of each pair in an axially spaced configuration relative to the piston and engageable against a respective side wall of the ring groove, the ring having at least a portion of its peripheral surface engagable with the cylinder wall; and biasing means located inside the ring groove and being supported simultaneously with the piston and the pair of rails for biasing the pair of rails radially outwards against the cylinder wall of the engine.

14. An oil and cempression piston ring assembly substantially as herein before described with reference to, and as illustrated in, Figures 1 and 2,or Figure 1 as modified by any one of of Figures 3 to 3u; or Figure 1 as modified by any one of Figures 4 to 4C of the accompanying drawings.

Published 1989 at The Patent Office. State House, 8&'71 High Holbora, LondonWClR 4TF. Further copies maybe obtainedfrom The Patent Offloe. Sales Branch, St Mary Cray, Orpir4ton, Kent BR5 3RD. Printed by Multiplex techniques ltd, St Mary Cray, Kent, Con. 1/87 -i tZ