GB2175065A

GB2175065A - Oil control ring for piston

Info

Publication number: GB2175065A
Application number: GB08512512A
Authority: GB
Inventors: Edward J Murray
Original assignee: AE PLC
Current assignee: AE PLC
Priority date: 1985-05-17
Filing date: 1985-05-17
Publication date: 1986-11-19
Also published as: GB2175065B; GB8512512D0; JP2756785B2; EP0222864B1; DE3666277D1; EP0222864A1; WO1986006810A1; US4759266A; JPS62502849A

Description

1 GB2175065A 1

SPECIFICATION

Multiple part oil-control ring for piston The present invention relates to a multiple-part 70 oil control ring for a piston e.g. in an internal combustion engine.

A known construction of a ring of this type comprises an expander or spring ring and one or more lamellar rings or rails supported by 75 the expander.

The composite ring is located in a groove in the piston and the expander is arranged to urge the rails both radially outwards against the cylinder wall and axially against the walls of the groove.

The expander may take many forms though one form frequently encountered comprises a ring formed by folding a flat strip with a series of alternate cut-outs along each edge form a U-shaped channel section and subse quently bending the channel section into a generally U-sectioned ring.

In the motor industry, engine designers wish to reduce engine dimensions to improve car body profiles and to reduce engine weight.

One way of achieving this is to reduce the engine block dimension in the direction of the engine cylinders, however, it is generally pre ferable to do so without affecting the cylinder capacity and compression parameters. This can be done by reducing the height of the piston, and indeed this is frequently an objec tive sought by piston designers.

One of the drawbacks of the folded-strip form of expander described above resides in the fact that its minimum axial thickness, in practice, tends to be quite large if it is to perform its spring/support function effectively.

It is therefore an object of the present invention to provide an oil control ringhaving a comparatively small dimension in the axial direction of the piston, in order to reduce the piston height.

According to the invention, there is provided a multiple-part oil-control ring for a piston which comprises an expander ring and at least one lamellar rail supported by the expander, the expander being formed from a flat strip of spring material having a first series of notches 115 along one edge and a second series of notches alternating with the first series along the other edge, the material between the notches of the first series and the other edge of the strip being deformed to provide lugs standing proud of the surface of the strip, the strip being bent to form the expander ring with the one edge at the outer circumference of the ring and the other edge at the inner circumference of the ring, whereby the lugs provide a series of supports for the lamellar rail.

The fact that the expander ring is not folded in the axial sense means that its axial thick ness may be less than that of a comparable 130 to 85 expander of the known type described above.

Preferably, the control ring includes two rails, one on either side of the expander ring, in which case the lugs should protrude on both sides of the expander ring to support the two rails. Preferably, the lugs are punched from the strip material to protrude alternately from each surface of the expander ring.

Preferably, there are protrusions from the surface of the expander ring between the notches of the second series and the outer circumference, which act to space an annular rail from the expander ring surface. These protrusions preferably extend from both surfaces of the expander ring to space one annular rail from each surface of the expander ring and may be punched from the strip material to protrude alternately from each surface of the expander ring, to space an annular rail from each surface of the sxpander ring.

These protrusions, in spacing the rails from the expander ring, improve drainage from between the rails to the piston groove, which might otherwise be reliant upon the second series of notches.

Alternatively, there may be only one rail associated with the expander ring, this rail preferably being on the top or piston crown side of the expander ring. In such a construction, the lugs and protrusions on the expander ring preferably extend on one side only of the expander ring.

In a preferred embodiment the notches may be shaped to have neck widening to an open- ing extending towards the opposite edge of the strip. In the case of the second series of notches, these may be curved towards the outer circumference which helps to achieve a more equal spring resistance around the notch periphery and also assists in allowing a sufficient amount of material to be deformed in forming the lugs. The free ends of the expander ring 11 preferably form a butt joint.

There may be extensions on the inner cir- cumference of the expander ring, particularly if the piston groove is comparatively deep, in order to help ensure that the composite ring is correctly located, and in order to help prevent "popping out" of the composite ring as the piston is positioned in the cylinder. The extensions may be formed integrally at the inner circumference of the expander ring, or may be separately attached. They may be present at spaced intervals between the notches of the second series, or may be present between each and every notch in which case each extension should take up a part only of the space between the notches.

In order to adjust or regulate the resilience of the expander ring, cut-away portions may be provided at the inner circumference of the expander ring at positions corresponding to positions of the notches of the first series.

The expander ring may be of stainless steel preferably with a hardness in the range 2 GB2175065A 2 HV300-350 or may be of a suitably tempered carbon steel to give the required spring properties. It will be appreciated that the strip from which the expander ring is formed may be stamped out and subsequently deformed by bend punching to form the lugs and protrusions.

It has been found that a strip thickness of 0.020 inches (0.51mm) is preferable though this may be as low as 0.0 15 inches (0.38mm) or as high as 0.025 inches (0.64mm). The rails used may be 0.018 (0.46mm) or 0.020 inches (0.51mm) in thickness though they may have thicknesses in the range 0.015 inches (0.38mm) to 0.025 inches (0.15mm). The lugs may protrude from the surface of the expander ring by from 0.012 inches (0.30mm) to 0.020 inches (0. 51mm). The protrusions may protrude from the surface of the expander ring by from 0.006 inches (0.15mm) to 0.010 inches (0.25mm). In a preferred embodiment, the strip thickness is 0.020 inches (0.51mm), the rails are 0. 018 inches (0.46mm) in thickness, the lugs protrude by 0.015 inches (0.38mm) and the protrusions by 0.008 inches (0.046mm); this gives an overall com posite ring thickness of 0.072inches (1.82mm).

The invention may be carried into practice in various ways and some embodiments will now be described by way of example with reference to the accompanying drawings in which:

FIGURE 1 is an isometric sketch of a portion of an expander ring in accordance with the 100 present invention; FIGURE 2 is a view similar to FIGURE 1 but with two rails in position, forming a compo site ring; FIGURES 3 to 6 are sections on the succes- 105 sive radial planes 111-111, IV-IV, V-V and VINI shown in FIGURE 2; and FIGURE 7 is a view similar to FIGURE 1 showing an alternative embodiment.

Figure 1 shows a portion of an expander ring 11, which is formed from a flat strip of spring steel, having two series of notches 12,13 extending into the strip alternately from its outer circumference 14 and its inner cir- cumference 15 respectively. The notches 12,13 have narrow necks 16,17 which widen into larger apertures 18,19 respectively. This arrangement leaves lands 21 of material be tween the apertures 18 and the inner circum ference 15 and lands 22 of material between 120 the apertures 19 (which are somewhat curved), and the outer circumference 14.

The lands 21 are bend punched axially in alternate opposite directions to form a series of lugs 23 protruding from one surface of the 125 ring 11 and an alternating series of lugs 24 protruding from the other surface. These lugs 23,24 provide ledges 25,26. The lands 22 have dimples 27,28 punched axially in alter- nate opposite directions.

FIGURE 2 shows an assembled composite ring comprising the expander ring 11 of FIGURE 1 together with a pair of lamellar rails 31,32. The rail 31 is supported on the]edges 25 and is spaced from the expander ring surface by the dimples 27. Similarly, the rail 32 is supported on the]edges 26 and is spaced from the expander ring surface by the dimples 28. This is illustrated in FIGURES 3 to 6 which show the composite ring in a groove 33 of a piston 34.

At the position shown in FIGURE 3, the rail 31 is spaced by dimple 27. At the position shown in FIGURE 4, the rail 32 is supported on the ledge 26 of the lug 24. At the position shown in FIGURE 5, the rail 32 is spaced by the dimple 28. At the position shown in FIGURE 6, the rail 31 is supported on the ledge 25 of the lug 23.

The ledges 25,26 actually provide an arcuate support which, in conjunction with the internal diameter of the rails, has the effect of causing a small axial force on the rails 31,32 at their inner peripheries. This provides side sealing so that angling of the flat base is not necessary although an angle of 2' to 10' may be provided by some pressing means, should this be required to provide additional side sealing force.

The outward load on the rails 31,32 which enables them to remove oil from the cylinder wall is obtained by compressing the expander ring 11 when the composite ring, mounted in the piston groove 33 is forced into the cylinder bore. Drainage for oil scraped from the cylinder wall between the rails 31,32 is provided by the notches 12 which communicate with drainage passages in the groove 33 and also via the spaces between the rails 31,32 and the ring surfaces, these spaces being maintained by the dimples 27,28.

FIGURE 7 shows an expander ring 41 having two alternative features.

The first of these is the provision of cut- away portions 42 in the lugs 23,24 beneath the apertures 18. This may be helpful in tailoring the resilience of the expander ring as a whole and also, more particulary, to make the local resilience more nearly equal to that of the remainder of the expander ring.

The second alternative feature is the provision of extensions 43 on the inner circumference of the expander ring. These may be formed integrally when the original strip is pressed or punched out or may be attached at a later stage. They may even be of a hard wax-like material which will disappear in use since one of the main purposes is to prevent -popping out- during assembly by spacing the composite ring correctly relative to the piston groove.

Claims

1. A multiple-part oii-control ring for a pis- ton which comprises an expander ring and at 3 GB2175065A 3 least one lamellar rail supported by the expander, the expander being formed from a flat strip of spring material havng a first series of notches along one edge and a second series of notches alternating with the first series along the other edge, the material between the notches of the first series and the other edge of the strip being deformed to provide lugs standing proud of the surface of the strip, the strip being bent to form the expander ring with the one edge at the outer circumference of the ring and the other edge at the inner circumference of the ring, whereby the lugs provide a series of supports for the lamellar rail.

2. A control ring as claimed in Claim 1 in which the strip is deformed from both sides to provide lugs protruding from both axial surfaces of the ring, and in which two annular rails are provided, one supported by the lugs associated with one surface of the expander ring and the other supported by the lugs associated with the other surface of the expander ring.

3. A control ring as claimed in Claim 2 in which the lugs are punched from the strip material to protrude alternately from each surface of the expander ring.

4. A control ring as claimed in any preced- ing claim including protrusions from the surface of the expander ring between the notches of thesecond series and the outer circumference, which act to space an annular rail from the expander ring surface.

5. A control ring as claimed in Claim 4, including protrusions from both surfaces of the expander ring to space one annular rail from each surface of the expander ring.

6. A control ring as claimed in Claim 4 or Claim 5 in which the protrusions are punched from the strip material to protrude alternately from each surface of the expander ring, to space an annular rail from each surface of the expander ring.

7. A control ring as claimed in any preceding claim in which the notches are shaped to have a neck widening to an opening extending towards the opposite edge of the strip.

8. A control ring as claimed in any preced- ing claimincluding extensions on the inner circumference of the expander ring.

9. A control ring as claimed in any preceding claim including cut-away portions at the inner circumference of the expander ring at positions corresponding to positions of the notches of the first series.

10. A multiple-part oil-control ring for a piston constructed and arranged substantially as herein specifically described with reference to and as shown in FIGURES 1 to 6 optionally modified in accordance with FIGURE 7.

Printed in the United Kingdom for Her Majesty's Stationery Office, Dd 8818935, 1986, 4235. Published at The Patent Office, 25 Southampton Buildings, London, WC2A 'I AY, from which copies may be obtained.