US3249094A

US3249094A - Lubricating sealing means for rotary combustion engines

Info

Publication number: US3249094A
Application number: US315280A
Authority: US
Inventors: Hoppner Ernst; Lechler Rolf; Hoffmann Gunter
Original assignee: Wankel GmbH; NSU Motorenwerke AG
Current assignee: Wankel GmbH; Audi AG
Priority date: 1962-10-13
Filing date: 1963-10-10
Publication date: 1966-05-03
Anticipated expiration: 1983-05-03
Also published as: DE1187854B; GB1017568A

Description

May 3, 1966 E. HOPPNER ETAL LUBRICATING SEALING MEANS FOR ROTARY COMBUSTION ENGINES Filed (kit. 10, 1963 3 Sheets-Sheet 1 Ill [sir/ gr INVENTORS ERNST HOPPNER RqLF LECH LER @1259? HOFFMANN ATT'URNLY y 1966 E. HOPPNER ETAL 3,249,094

LUBRICATING SEALING MEANS FOR ROTARY COMBUSTION ENGINES Filed Oct. 10, 1963 5 Sheets-Sheet 2 INVENTORS 'l= l g z 2 ERNST HOPPN ER RQLF' LECHLER GUNTER HOFFMANN NEY y 3, 1966 E. HGPPNER ETAL 3,249,094

LUBRICATING SEALING MEANS FOR ROTARY COMBUSTION ENGINES Filed Oct. 10, 1965 3 Sheets-Sheet 5 TE-7 141m IIIFJVENTORS ERNST HOPPNER RQLF LECH LER GUNTER HOFFMANN BY ATT NEY United States Patent 3 2495994 LUBRICATING SEALING MEANS FOR ROTARY CGMBUSTION ENGINES Ernst Hiippner, Lindau (Bodensee), Rolf Lechler, Bad Friedrichshall-Kochendorf, and Giinter Hoifmann, Neudenau (.l'agst), Germany, assignors to NSU Motoreuwerke Aktiengesellschaft, N eckarsulm, Germany, and Wankel G.m.b.H., Lindau, Germany Filed Oct. 10, 1963, Ser. No. 315,280 Claims priority, application Germany, Oct. 13, 1962, N 22,209 13 Claims. (Cl. 123-8) This invention relates to internal combustion engines, in particular to those of the rotary piston type, and is directed to improved sealing means between relatively moving parts of such engines.

In general, engines of this type comprise an outer body formed by a peripheral wall interconnected by a pair of parallel end walls thereby defining a cavity whose peripheral shape preferably is basically an epitrochoid. A rotatably mounted rotor is supported for eccentric movement on a shaft within the cavity "and has a plurality of circumferentially-spaced apex portions with radially movable seal strips mounted therein for sealing engagement with the inner surface of the peripheral wall, thereby forming Working chambers which upon relative rotation of the outer body and rotor vary in volume. An in take port is provided for admitting a fuel-air mixture to the combustion zone of said engine, and an exhaust port is provided for expelling the burnt gases. Any suitable method of igniting the fuel-air mixture may be used, whereupon the stages of intake, compression, expansion and exhaust may be carried out. A lubrication'system for the engine shaft and bearings generally includes means for supplying lubricating oil also to the interior of the. rotor for cooling purposes.

A rotary combustion engine of the character referred to above is described in US. Patent No. 2,988,065, granted June 13, 1961, to Felix Wankel et al.

As is well known in the operation of internal combustion engines, it is necessary to prevent the lubricating oil from leaking past the piston into the zone of the engine where combustion gases are present, in order to minimize oil consumption and avoid fouling. Heretofore, in rotary combustion engines of this type an oil seal ring has been mounted in the rotor side walls for resilient sealing contact with the inner faces of the corresponding end walls of the engine housing. However, because of possible distortion of the housing side walls incident to high combustion temperatures, and/or roughness or uneven character of these walls, the usual piston seal ring does not always make leak-proof contact between the piston and housing. In such instances, oil lubricant may pass into the operating chambers, especially during the induction cycle. A further disadvantage of this arrangement is that this oil-seal ring, which is in direct heatconducting relation to the piston, often includes in part a non-metallic rubber-like material which deteriorates gradually at piston temperatures, thereby limiting the useful life of such rings. Summarizing briefly, the usual oilseal rings interposed directly between the coacting walls of the piston and housing involve material difficulties that have not entirely been overcome.

A principal object of this invention therefore is to provide new and improved lubricant sealing means for a rotary combustion engine of the character described, wherein an oil sealing device is interposed between the engine shaft structure and the piston for preventing leakage of oil from the transmission area past the piston into the operating chambers.

A further object of the invention is to provide in a preferred form new and improved sealing means wherein oil sealing ring structure is carried by and rotatable with the shaft structure for directly engaging the piston and avoiding the sealing difficulties previously referred to.

In particular, the present invention provides primary and secondary oil sealing means, both preferably carried by the conventional shaft eccentric. The primary sealing means engages directly the piston side walls for sealing the shaft, transmission and bearing areas containing the pressurized lubricant with respect to the piston, and the secondary sealing means likewise carried by the eccentric (or cam) makes a shaft-housing seal for the comparatively low-pressure exhaust lubricant, thereby preventing leakage of lubricant along the housing side walls to the piston along a path lay-passing the shaft piston seal.

The invention will be more fully set forth in the following description referring to the accompanying drawings, and the features of novelty will be pointed out with particularity in the claims annexed to and forming a part of this specification.

Referring specifically to the drawings:

FIGURE 1 is a simplified sectional view of a rotary combustion engine of the type to which the present invention is applicable;

FIGURE 2 is a detailed sectional. view of the engine taken generally along the line 2-2 of FIGURE 1 showing application of the invention thereto;

FIGURE 2A is an enlarged detail view of the piston seal shown in FIGURE 2;

FIGURE 3 is a sectional view taken along the line 3-3 of FIGURE 2 showing the piston drive and shaft eccentric structure of the engine;

FIGURES 4, 5 and 6, 7 are separate detail views of the seal discs of FIGURE 2 that are mounted on opposite sides of the engine shaft eccentric; and

FIGURES 8, 9 and 10 are detail views in section showing alternative forms of the piston seal.

In FIGURES l and 2 there is shown a rotary combustion engine having an outer body or housing generally designated at 1 composed of a pair of

end walls

3 and 4 interconnected by a peripheral wall 2. The housing defines a cavity therein having a transverse axis M1. As shown, for example in FIGURE 1 the profile of the inner wall 2 is basically a two-lobed epitrochoid. A shaft 6 is rotatably mounted in the housing co-axial with the axis M1 and has an eccentric portion 7 formed thereon. A rotor 8 is rotatably mounted on the eccentric and has three circumferentially spaced apex portions 12, FIG- URES l and 2, which are in sealing cooperation with the inner surface 2 to form a plurality of working chambers 5 which upon relative rotation of the wall 2 and rotor 8 vary in volume. Seal strips 12 as indicated are mounted in each apex portion and extend from one end face of the rotor to the other end face, FIGURE 2, for continuous sealing engagement with the inner surface 2, thereby sealing the working chambers 5.

End face seals 3 and 4' are also provided in each end or side face of the rotor and are in sealing engagement with the

housing side walls

3 and 4 at surfaces 311 and 4a respectively, to prevent leakage of the gases from the working chambers 5 past the rotor in known manner.

A suitable bearing 9 is supported in the rotor 8 for rotatively supporting the rotor on the eccentric 7. Suitable bearings 6a and 6b are also mounted in the

end walls

3 and 4. as shown in FIGURE 2 for supporting the rotating shaft 6 in the housing.

The rotor (piston) drive connection with the shaft comprises an externally-toothed gear or pinion 10 that is secured to the shaft journal box at the wall 4 in meshing engagement with an internally-toothed gear 11 which constitutes an end-portion of the rotor inner bearing ring 11'.

The gears and 11 serve to r-otatively position the rotor with respect to the epitrochoidal surface of the peripheral wall 2. In the embodiment, FIG. 1, illustrating a two-lobed epitrochoid and a threelobed rotor, the ratio of rotation of the eccentric 7 and its shaft 6 with respect to the rotor is 3:1, i.e., for each rotation of the rotor about its axis M2, which corresponds to the center of the eccentric 7, the eccentric and shaft 6 rotate three times around the shaft axis M1. The eccentricity E of the cam 7 represents the piston throw or stroke.

Illustration of the other engine operating features including a fuel-air mixture intake port, ignition or spark plug and exhaust port for the combustion gases is unnecessary for a complete understanding of the invention and therefore is omitted; an adequate description thereof is in the Wankel et al. Patent 2,988,065 referred to above.

The lubrication system for the essential bearings and gears including the main shaft bearings 6a and 6b, the piston-eccentric bearings 9 and the piston position gearing 10-11, comprises interconnecting passages in the housing, shaft structure and piston hereinafter described through which a lubricating medium referred to as oil, is circulated. The oil is applied as indicated by direction arrows so as both to lubricate the main shaft bearings and the transmission and drive parts, and also to cool the interior of the piston.

In order to confine the oil to the shaft and transmissiondrive areas and prevent its leakage past the piston into the operating chambers 5, the main oil seal is made essentially between the shaft eccentric and the piston itself, rather than between the engine side walls and piston ac cording to prior practice as explained above. To this end, there is secured to the shaft eccentric 7 at least one seal-carrying

member

14 or 15, as the case may be, located between one side of the eccentric and the corresponding housing side wall. Specifically, the member 14 (or 15) may be of disc-like form having its center coincident with the center of the eccentric 7 which also defines the axis of rotation M2 of the piston. As shown in FIGURE 3, the disc 15 is cut away at 21 to form a crescent for rotation clearance at the piston internal ring gear 11, companion fixed gear 10 and shaft 6.

Although as will be apparent, a single disc may be used for sealing purposes at one side of the piston in accordance with the invention (the piston in such case having a conventional ring seal at its opposite side and being axially biased toward that side of the housing) a preferred construction includes two

discs

14 and 15 secured as by bolts to opposite sides of the eccentric, FIGURES 2 and 3, for rotation with-the shaft 6. The disc peripheries are located respectively opposite a recess wall 18 formed at each side of the piston, FIGS. 2 and 2A.

As the annular seals carried by the discs for wiping the piston side walls are essentially similar, a description with special reference to FIG. 2A of the seal ring 16 carried by the disc 14 will be suflicient. This ring is composed of a suitable metal and has a generally U-shape cross-section. It is retained within the outer part of the disc 14 by a transverse flange thereof 14', so as to be concentric of the piston axis M2 and movable axially, -i.e., toward and away from the piston side wall 80. The ring is resiliently biased toward the piston wall by an annular spring 17 positioned between the inner side of the disc and the ring as shown. The ring may have an annular shoulder on its inner periphery at the disc side for retaining the spring.

A fluid-tight seal between the ring 16 and disc flange 14 is provided by an O-ring 16a of rubber-like material enclosed under compression within the U of the ring. Accordingly, the ring 16 which is biased laterally to make annular wiping engagement with the adjacent piston side wall 80 completes a seal between that piston wall surface 8a and the shaft eccentric and disc structure.

The normally oil-containing passages and spaces referred to above for lubricating and cooling purposes are formed in part by the sealing

discs

14 and 15. As shown 4 in FIGURES 2 and 3, the oil enters the housing by a passage a formed inthe end wall 4 and communicates with the gearing 10-11 through an annular passage b formed in the corresponding main bearing housing. The cut-away part of the disc 15 at 21 admits oil from passage b to all the gearing 1041 during rotation of the piston around the fixed gear 10. From passage b the oil flows through radiating passages c formed in the disc 15 to the piston-eccentric bearings 9, and through passage 0! in the ring gear and piston into the hollow piston cooling pas-' sage e.

The disc 15 is provided with a circular flange or hub portion 22a, FIGURES 2 and 5, that makes an oil seal at 22b with the housing end wall 4 as shown, thereby sealing the piston at its side 8b from oil in the annular passage b.

The oil outlet from the piston cavity e includes another passage 1 in the piston and ring gear which communicates with a generally circular space g formed in part between a crescent-shape portion 14' of the disc 14, FIGURES 2, 6 and 7, and the surrounding wall of the piston at its inner-periphery. This space in turn opens into the cylindrical hub extension 22 of the disc which extends over a smaller diameter hub 3' formed on the bearing housing and constituting part of the engine side wall. The space therebetween defines an annular passage h leading to the oil exhaust port k.

For the purpose of sealing the disc hub 22 and hence the oil passage 11, with respect to the housing wall 3, the hub which is rotatable within the end wall 3, is provided, as in the case of the hub 22 of disc 15, with an oil seal, such as spiral grooves 23 formed in the outer surface of the hub. Thus, oil from the shaft area is prevented from leaking into the clearance space between the housing side wall 3a and that side of the piston.

Alternative forms of seals used according to the invention are shown by FIGURES 8, 9 and 10. In FIG- URE 8, a resilient seal ring 16 is carried by disc 14 for example, within an annular groove 16" and is biased by suitable spring means axially outward rather than inward, to make the piston seal. For this purpose a metal companion ring or annulus 25 overlapping and surround ing the disc periphery is mounted on the piston itself to form an extension of its side wall along the housing wall. Specifically, the ring has a radially extending flange 26 with a re-entrant edge 26' that fits within 2. corresponding groove in the disc 14 to form a supplemental labyrinth-type seal. The annular clearance gap 27 between the disc 14 and ring- 25 is in communication with the oilcooling space e in the piston and slants radially outward as shown. Accordingly, oil from the passage 2 tending to enter the clearance gap is flung back into the piston cavity by centrifugal force due to the higher rotative speed of the disc 14. Oil from the piston space e is thereby prevented from leakage past the disc into the piston-housing clearance and so into the engine operating chambers 5.

In FIGURE 9, the sealing ring 16' of FIGURE 8 is dispensed with and in lieu thereof a so-called gap-seal is used. Here, the disc 14 and piston ring 25 have close tolerance clearance surfaces that may have a generally Z-shape form as shown. The radially extending part 28 of the clearance gap has a minimum length H to prevent leakage of oil from the piston cavity e past the disc. This length depends on engine design factors affecting the centrifugal force available to force back oil into the piston cavity, including the maximum oil level in the piston cavity, the spacing of the radially extending outer end of the gap from the eccentric (disc) axis of rotation M2, and the piston throw E. A further consideration is that oil entering the radial passage 28 be given to maximum extent the rotative speed of the disc. To this end, the aforesaid tolerance should be as small as possible and the gap surface area of the higher speed disc be made rough and that of the lower speed piston ring 25 be made smooth.

FIGURE shows a variation of the gap-seal wherein labyrinth sealing between the disc 14 and piston at 29 is used. Here, the piston ring and the disc 14 overlap radially and have a staggered tongue and groove mating configuration to form a labyrinth along the clearance gap.

Although the disc-piston sealing action is herein described as generally axial, it will be understood that radial sealing between the discs and piston is contemplated as being within the spirit of the invention.

It will also be understood that the

discs

14 and 15, though preferably concentric with the piston axis of rota.- tion M2, may have a slight eccentricity with resepct to this axis where the seal of FIGURE 2, for example is used. This eccentricity can be advantageous for widening the seal-wiped area of the piston wall where the seal tends to abrade and wear a groove in the piston.

It should be understood that this invention is not limited to specific details of construction and arrangement thereof herein illustrated, and that changes and modifications may occur to one skilled in the art without departing from the spirit of the invention.

What is claimed is:

1. In an internal combustion engine of the rotary piston type having a housing, a piston mounted for eccentric rotation within said housing successively to form with said housing walls variable-volume operating chambers, a rotatable power output shaft mounted in said housing, and transmission drive means between said piston and shaft provided with continuous lubrication, improved means for preventing passage of the transmission lubricant into the aforesaid operating chambers comprising means secured to said shaft for rotation therewith, and sealing structure concentric of the axis of rotation of the piston interposed between said shaft-secured means and a side wall of the piston and mounted in one of them for preventing leakage of the lubricant past the piston side wall into said operating chambers.

2. Apparatus as specified in claim 1 wherein the shaftsecured means is a rigid member, generally in a plane parallel to a side wall of the piston, said member and a generally similar member being rotatable with the shaft and extending along opposite side walls respectively of the piston, each member having means for retaining its respective sealing structure for engaging a corresponding side wall of the piston.

3. Apparatus as specified in claim 1 wherein the shaftsecured means also has a hub portion surrounding the shaft for engaging in sealing relation the engine housing side wall for sealing the lubricant within that part of the housing enclosing the shaft.

4. Apparatus as specified in claim 3 wherein the hub portion of the shaft-secured means is rotatable within a cylindrical portion of the corresponding housing side wall and has oil sealing grooves formed at the outer surface thereof to constitute a seal between the shaft and housing side wall.

5. Apparatus as specified in claim 1 wherein the sealing structure comprises a sealing ring mounted in said shaftsecured means and biased in a direction parallel to the shaft axis into sealing engagement with a side wall of the piston.

6. Apparatus as specified in claim 5 wherein the shaftsecured means is a disc concentric with the piston axis of rotation and rotatable with the shaft, said disc having a peripheral flange portion formed to retain said sealing ring in sealing. contact with the piston.

7. Apparatus as specified in claim 5 wherein the sealing ring is composed of metal and a resilient non-metallic ring is mounted between the metal ring and shaft-secured means for sealing the engaging surfaces thereof.

8. Apparatus as specified in claim 5 wherein the piston has an annular metal sealing annulus forming an extension of the piston side wall overlapping and surrounding in close tolerance the sealing ring, and the sealing ring is biased axially outward into engagement with said annulus.

9. Apparatus as specified in claim 1 wherein the sealing structure constitutes a split seal ring forming a narrow clearance slot extending radially with respect to the piston axis whereby centrifugal force due to rotation of said shaft-secured means tends to prevent passage of lubricant through said slot toward the shaft.

10. Apparatus as specified in claim 1 wherein the sealing structure comprises an annular metal sealing annulus forming an extension of the piston side wall, and the shaft-secured means is a disc, the peripheral portion of said disc being surrounded in close tolerance by said annulus to form a gap-seal and the disc and annulus surfaces defining a generally Z-shape gap having a radially extending portion through which leakage of oil toward the shaft is opposed by centrifugal force incident to rotation of said disc.

11. Apparatus as specified in claim 1 wherein the sealing structure constitutes a split-seal ring, one part of which is attached to a piston edge at the housing side wall, the other part being attached to the shaft-secured means, the clearance gap between said parts defining a close tolerance labyrinth.

12. In an internal combustion engine of the rotary piston type having a housing, a piston mounted for eccentric rotation within said housing successively to form with said housing walls variable-volume operating chambers, a rotatable power output shaft mounted in said housing, and transmission drive means including an eccentric between said piston and shaft provided with continuous lubrication, a member secured to said eccentric for rotation therewith, and sealing means interposed axially between a peripheral part of said member and a side wall of the piston and mounted in one of them to preclude leakage of lubricant from the shaft and transmission areas past the piston at said side wall into said operating chambers. I

13. Apparatus as specified in claim 12 wherein the eccentric-secured member is a disc secured to the eccentric at one side thereof and extends adjacent to a piston side wall, and the sealing means constitutes a ring-type seal surrounding the shaft concentrically of the piston axis of rotation and mounted between the respective side walls of the disc and piston to be sealed for making, together with said disc, an axial seal between the shaft and the aforesaid piston side wall.

No references cited.

SAMUEL LEVINE, Primary Examiner.

F. T. SADLER, Assistant Examiner.

Claims

1. IN AN INTERNAL COMBUSTION ENGINE OF THE ROTARY PISTON TYPE HAVING A HOUSING, A PISTON MOUNTED FOR ECCENTRIC ROTATION WITHIN SAID HOUSING SUCCESSIVELY TO FORM WITH SAID HOUSING WALLS VARIABLE-VOLUME OPERATING CHAMBERS, A ROTATABLE POWER OUTPUT SHAFT MOUNTED IN SAID HOUSING, AND TRANSMISSION DRIVE MEANS BETWEEN SAID PISTON AND SHAFT PROVIDED WITH CONTINUOUS LUBRICATION, IMPROVED MEANS FOR PREVENTING PASSAGE OF THE TRANSMISSION LUBRICANT INTO THE AFORESAID OPERATING CHAMBERS COMPRISING MEANS SECURED TO SAID SHAFT FOR ROTATION THEREWITH, AND SEALING STRUCTURE CONCENTRIC OF THE AXIS OF ROTATION OF THE PISTON INTERPOSED BETWEEN SAID SHAFT-SECURED MEANS AND A SIDE WALL OF THE PISTON AND MOUNTED IN ONE OF THEM