US3185387A

US3185387A - Apex sealing means

Info

Publication number: US3185387A
Application number: US265252A
Authority: US
Inventors: Paschke Hanns-Dieter
Original assignee: NSU Motorenwerke AG
Current assignee: Audi AG
Priority date: 1962-03-31
Filing date: 1963-03-14
Publication date: 1965-05-25
Anticipated expiration: 1982-05-25
Also published as: DE1223614B; GB990709A

Description

y 25, 1965 HANNS-DIETER PASCHKE 3,185,387

APEX SEALING MEANS Filed March 14, 1963 2 Sheets-Sheet 1 HANNE-DETER E X EHKE ATTORNEY y 1965 HANNS-DIETER PASCHKE 3,185,387

APEX SEALING MEANS Filed March 14, 1965 2 Sheets-Sheet 2 INVENTOR. HANNEI-DIETER F'AEILJHKE.

BY f 773mm (0. ATTEIRNEW United States Patent 2 Claims. oi. 230-445 The present invention relates broadly to the art of rotary mechanisms and is particularly directed to sealing means for such rotary mechanisms.

The invention is particularly useful in connection with rotary mechanisms similar to that disclosed in United States Patent Number 2,988,065, although as will become apparent, this invention is not limited to this specific type of rotary mechanism. In the following description the invention is described in relation to an internal combustion engine, but the invention .is also suitable to other forms of rotary mechanisms such as fluid pumps and fiuid motors.

A rotary engine as disclosed in said patent comprises an outer body or housing having a cavity therein and an inner body or rotor disposed therein rotatable relative to the outer body, about an axis laterally spaced from, but parallel to the axis of said cavity. The inner body is journaled on an eccentric portion of a shaft which is co-axial with the outer body and journaled in bearings carried by the outer body end Walls. The outer body has axially-spaced end walls and a peripheral wall interconnecting the end walls to form said cavity; the inner surface of the cavity peripheral wall having a multi-lobed profile which preferably is basically an epitrochoid.

The inner body or rotor has end faces carrying end-face seal means and intermediate seal elements disposed adja cent to said outer body end walls for sealing cooperation therewith, and has a peripheral surface with a plurality of circumferentialiy-spaced apex portions, each carrying a radially-movable seal for sealing engagement with the multi-lobed inner surface of the outer body peripheral wall to form a plurality of working chambers between the two bodies which vary in volume upon relative rotation of the two bodies.

Each apex seal of the inner body is received within an outwardly-facing groove running axially from one end face to the other of the inner body at its associated apex portion on the inner body thereby separating the adjacent Working chambers. Each apex seal fits within its apex groove with a clearance between the apex seal side faces and the groove sidewalls so that the apex seal is radially movable. The operating pressures in the working chambers are difierent from one another so that there is a differential pressure across each apex seal between each two adjacent chambers which urges the apex seal against one side wall and away from the opposite side wall of its apex groove. Gas from the chamber with the higher pressure enters the bottom of the apex groove through the gap between the apex seal side face and apex groove side wall which are adjacent to said chamber. The gas pressure urges said apex seal against the opposite apex groove side' wall adjacent to the working chamber with the lower pressure and also urges the apex seal radially outwardly so that its outer edge is in sealing engagement with the peripheral wall inner surface.

Prior combustion engines of this type have apex seals which are rectangularin their cross-section and with a uniform thickness measuring only a small fraction of the radial height of the apex seal so that the pressure of the operative medium on the underside of the apex seal may not be sufficient to urge the apex seal radially outwardly counter to the frictional force acting between the side face of the apex seal and its adjacent groove sidewall; Hence, in such prior engines it may be necessary to add relatively strong spring means under the apex seal whereby the wear of the radially outer edge of the apex seal is increased.

An object of the present invention comprises the provision of a rotary combustion engine in which a novel apexrseal arrangement for the working chambers is provided to maintain continuous and improved sealing during engine operation.

Specifically, instead of providing apex seals of uniform thickness, this invention provides apex seals with recesses on both side faces in the region within their apex grooves, with the recesses in opposite side faces of each apex seal communicating with one another.

Other objects of the invention will become apparent upon reading the annexed detail description in connection with the drawings in which:

FIG. 1 is a schematic, transverse, sectional view of a rotary combustion engine;

FIG. 2 is a partial, longitudinal, sectional view through the rotor apex portion and groove showing to a greatly enlarged scale the apex seal in accordance with the invention;

FIG. 3 is a cross-sectional view, as taken on line 33 of FIG. 2;

FIG. 4 is a cross-sectional view, as taken on line 4-4 of FIG. 2;

FIG. 5 is a perspective view of an end portion of the rotor apex portion with the apex seal omitted;

FIG. 6 is a view similar to that of FIG. 3 with the spring omitted and showing an additional form of apex seal in accordance with the invention.

Referring to the drawings, the housing or outer body of a rotary combustion engine comprises spaced

end walls

10 and 12, and a peripheral Wall 14 disposed between the interconnecting said end walls to form a cavity therebetween. The inner surface 16 of the peripheral wall 14 preferably has a multi-lobed profile in cross section which preferably is basically an epitrochoid.

Inside and eccentric to the housing is disposed an inner body or rotor 18, having a plurality of circumferentiallyspaced apex portions 20 about its outer periphery to form a plurality of working chambers 32 between the inner and outer bodies which vary in volume upon rotation of the inner body relative to the outer body.

Each of said apex portions 20 has radially-movable apex seal strip means 22 received within a single outwardly-facing groove 24 extending in a direction parallel to the rotor axis from one end face to the other of the rotor 18 and urged radially outward by spring means 26 and by gas pressure from the adjacent working chamber having the higher pressure into sealing engagement with the peripheral wall inner surface.

The inner body 18 also has end faces having end-face seal means 28 and intermediate seal elements 30 disposed in sealing engagement with the

end walls

10 and 12 which together with the apex seals 22 form a continuous seal about the working chambers 32.

The bottom of each apex groove 24 has an enlarged cylindrical bore portion at each end of the groove, and an axially-movable intermediate seal element 30 is slidably fitted within such cylindrical bore portion and urged axially against the

adjacent end wall

16 or 12 by gas pressure within said groove. means 22 is in sealing cooperation with an intermediate seal element 30. Between the intermediate seal elements 30, disposed at the rotor apex portions 20 on each end face of the rotor 18 adjacent to the rotor periphery are end face seal strips 28, each of which extends from one Each end of the apex sealv intermediate seal element 30 to an adjacent element 30 and is received in a groove 24 in its rotor end face.

During rotation of the inner body 18, the apex seal means 22 slide continuously along their outer edges in bearing against the inner surface 16 of the peripheral wall 14 and the intermediate seal elements 30 and end-face seal strips 28 slide continuously along the flat inner surfaces of the end walls and 12.

During engine operation, the working chambers 32 have varying gas pressures. The pressure differential between each two adjacent working chambers 32 urges the apex seal strip 22 therebetween laterally toward one side face or the other of its grooves 24 for sealing engagement therewith thereby leaving a slight clearance 33 (FIG. 3) at the other side face of said groove. As a result, gas pressure from the adjacent working chamber is transmitted through said clearance 33 into the bottom of the associated groove 24 whereby said pressure urges the two intermediate seal members at the ends of said groove axially into sealing engagement with the

end walls

10 and 12 of the outer body and also adds to the force of the spring 26 urging said apex seal strip 22 radially outwardly.

The pressure differential urges the apex seal 22 in hearing against the sidewall 34 or 36 of the apex groove 24, and also causes a frictional force which acts counter to the forces on the apex seal 22 urging the apex seal radially outwardly against the peripheral wall 14.

The engine so far described is substantially similar to the engine disclosed in the aforementioned United States Patent Number 2,988,065 and for additional description reference is made to said patent. The seal arrangement so far described is substantially similar to the seal arrangement disclosed in United States Patent Number 3,033,180 and reference is made to said patent.

The pressure differential acting across each apex seal strip means 22 between its two adjacent chambers 32 urges said apex seal toward the chamber with the lower pressure, pressing the seal face in bearing against the adjacent groove side wall. According to the invention, as illustrated in FIG. 2, both side faces 38 and of each apex seal 22 are respectively provided with recesses 42 and 44 in the region within its apex groove 24. The recessed portions 42 and 44 of the two seal faces are in communication with each other, preferably through openings 46 in each said apex seal 22, so that the contact pressure and friction between the contacting side face 38 or 40 of each said apex seal 22 and the contacted sidewall 34 or 36 of its apex groove 24 is reduced whereby each said apex seal 22 can move toward the inner surface 16 of the peripheral wall 14. As the frictional force equals the product of the pressure-impinged area, the pressure on said area and the coefficient of friction; the frictional force is minimized by providing recesses 42 and 44 in the side faces 38 and 40 of each said apex seal 22 which are in communication with one another. Thus, the pressure acting on one side face 33 in the region of its recess 42 is annulled by the equal pressure acting on the opposite side face 40 of each said apex seal 22 in the region of its recess 44. The recesses 42 or 44 leaves ridges 48 or 50 about the recesses on the side faces 38 or 40 of the apex seals 22. Each said ridge 48 and 50 is a raised portion of its side face 38 or 40 with a preferably flat surface in contact with its adjacent groove sidewall 34 or 36 whereby the contacting area of said ridge 48 or 50 becomes the sole pressure-impinged area. Each ridge or raised portion 48 or 50 forms a border around its recess 42 or 44 and covers the edge or corner of the apex groove 24 in order to seal off one chamber from its adjacent chamber 32.

The recesses 42 and 44 extend to the radially inner edge of each said apex seal strip 22, as illustrated in FIG. 1, whereby the recesses 42 and 44 on opposite side faces 38 and 40 of each said apex seal 22 may be in communication with each other. In addition, however, openings or apertures 46 are preferably also provided in the apex seal strip 22 communicating with said recesses 42 and 44,

thereby providing a more rapid equilibrium of the gas pressures on opposite side faces 38 and 40 of the apex seal 22 in the region of their recesses 42 and 44. The number and size of the openings 46 in each apex seal strip 22 are such that the cross-sectional area of the opening provided thereby between the recesses 42 and 44 is sufficient relative to the size of the recesses 42 and 44 to provide for rapid equalization of the pressures in said recesses without said openings causing undue weakening of the apex seal strip 22.

As illustrated in FIG. 2, the radial depth of the portion of each apex groove 24 between the bores for the intermediate seal elements 30 preferably is made less than the radial depth at said seal elements. This construction serves to minimize the volume of each apex groove 24 so that the pressure below each apex seal strip 22 is able to more rapidly conform to pressure variations, particularly the pressure variations in the adjacent working chamber 32 having the higher pressure.

Considering the forces acting on each said apex seal strip 22, by analogy, each said seal strip 22 may be regarded as a two-armed lever having a fulcrum formed by the outer corner 52 of its apex groove sidewall 34 or 36 against which the apex seal 22 bears. The gas forces that act on the portion of the apex seal strip 22 extending outside of its apex groove 24 tend to tip the strip 22 about said groove corner 52; while the gas forces that act on the portion of the apex seal strip 22 within its apex groove 24 act counter to said tipping forces. In order to minimize any such tipping of an apex seal strip 22, the portion of the surface area of each side face of an apex seal strip bounded by the ridges 48 or 50, other than the surface area of the recesses 42 or 44, and which is disposed within its apex groove 24 is so formed and shaped that each of these surface portions has a substantial surface area with the center of area of each said surface portion having a substantial moment arm from the groove outer edge such that the turning moment of the gas forces on said surface area portions of an apex seal strip is greater than the opposing turning moment of the gas forces on the portion of the apex seal strip disposed outside its apex groove 24 and tending to tip the seal about the outer edge of said groove.

In some regions of the inner surface 16 of the peripheral wall 14, there is a frictional force between the seal strip outer edge or crest 54 and said inner surface 16 which acts together with the forementioned forces and causes a tilting of each said apex seal strip 22. Such a frictional force, which is represented by the arrow, and letter P in FIG. 3, is opposite to the direction in which the inner body 18 is turning as indicated by the arrow, and letter D.

In order to increase the moment acting counter to such tipping forces and to avoid any such tipping of the apex seal strip 22, a substantial portion of each ridge 48 and 50 is preferably disposed near the radially inner portion of its apex seal strip 22 so that the pressure-impinged area of the contacting ridge surface has a lever arm which is as long as possible whereby its countertilting moment is as large as possible. With such a shape to the ridges 48 and 50 at each side face 38 and 40 of each said apex seal 22, the center of gravity of its pressureimpinged area is as far as possible from the corner 52 of its groove side wall 34 or 36 and its counter-tilting moment is as large as possible.

As illustrated in FIG. 5, the inner body 18 preferably has a cut-out groove 56 in each end portion of each apex groove 24 running substantially normal to said apex groove. In addition, each said apex seal strip 22 preferably has a pocketlike recess 58 in each side face 38 and 40 of the apex seal strip 22 adjacent said cut-out groove 56 as illustrated in the left side of FIG. 2. The pocketlike recess 53 together with the gap 60 between the rotor end face and the

housing end wall

10 or 12 in FIG. 4, or the cut-out groove 56 in FIG. 5. form a continuous passage to vent the region adjacent to said pocketlike recess 58 to i the working chamber 32 with the lower gas pressure,

thereby providing improved bearing of the ridge 48 or 50 against the end portions of the groove side wall 34 or 36. In FIG. 6, the outer crest or'edge 54a of the apex seal strip 22a is formed by a tenon-like extension 62, or tonguelike protrusion on the apex seal strip 22, which contacts For ease of understanding, the parts of FIG. 6 corresponding to the parts of FIGS. 1 through 5 have been designated by the same reference numerals but with a subscript -a added thereto. On each side of the tenon-like extension 62, the apex seal strip 22a has a cut-back step whereby there is always a portion A of the overall width of the apex seal strip 22a, which is exposed to that adjacent chamber 32a having the lower pressure. Thus, there is a residual area against which the gas pressure can act to force the seal strip 22a radially outwardly.

As illustrated in FIG. 6, the higher gas pressure in one chamber 32a urges the apex seal strip 22a against the groove sidewall 36a adjacent to the chamber 32a with the lower gas pressure. The higher gas pressure acts against the underside 64a of the seal strip 22a, and against the side face 33a of the seal strip 22a adjacent to the higher pressure chamber 31a and also against the portion of the outerside area which is on the high pressure side of the line of contact. The gas pressure on a portion of the underside area is annulled by the similar gas pressure on a corresponding outerside area. However, the lower gas pressure acts on another portion indicated by the width A of the outerside area, which is on the low pressure side of the line of contact. Hence, in all regions of the peripheral-wall inner surface 16a, the apex seal 22a has a residual portion of the underside area, which is opposite to the low-pressure portion A of theouterside area, against which the gas pressure acts to force the seal strip 22a radially outwardly. Moreover, with such construction of the apex seal strip 22a, as illustrated in FIG. 6, the spring is preferably omitted as the gas pressure on the underside 64a of the apex strip 22a overcomes the counteracting friction at the groove sidewall 36a, and forces the apex seal strip 22a radially outwardly.

While I have described my invention in detail in its present preferred embodiment it will be obvious to those skilled in the art after understanding my invention that various changes and modifications may be made therein without departing from the spirit or scope thereof. It is intended by the appended claims to cover all such modifications.

What is claimed is:

1. A rotary mechanism comprising an outer body having spaced end walls and a peripheral wall forming a cavity therebetween; an inner body having axially-spaced end faces and disposed within said outer body cavity between the end walls thereof for rotation relative to said outer body with each of said end faces adjacent to an end wall; said inner body having a plurality of circumferentially-spaced apex portions having sealing cooperation with the inner surface of the peripheral Wall of said cavity to form between the inner and outer bodies a plurality of working chambers wherein varying fluid pressures cyclically occur; and a plurality of seal strips, one for each of said apex portions and each received in a groove in an apex portion extending from one end face to the other of the inner body; each said seal strip having a width in the circumferential direction which is slightly less than the width of its associated groove whereby the fluid in that one of the two adjacent working chambers having the higher pressure urgesv said seal strip against the opposite side of its groove and enters the groove and acts on the radially inner edge ofthe seal strip to urge it radially outward into sealing engagement with the inner surface of the outer body peripheral wall; each said seal strip having at least one recess in each of its side faces disposed within a region of said side face which is disposed entirely within its apex portion groove, said recess extending over a substantial area of said side face, the recesses on opposite sides of said seal strip being of substantially equal area, said seal strip having at least one passage therethrough interconnecting said recesses; each of said seal strips having an additional recess in each of its side faces adjacent at least one end of said strip, each said additional recess being disposed inwardly of the outer edge of the associated groove for said seal strip and extending to said adjacent end of said seal strip.

2. The combination recited in claim 1, wherein the end face of said inner body adjacent saidadditional recesses in said seal strip is slightly out back in the axial direction in the apex region to vent said additional recesses to the adjacent working chambers.

References Cited by the Examiner UNITED STATES PATENTS FOREIGN PATENTS 22,712 of 1911 Great Britain. 732,394 6/55 Great Britain.

JOSEPH H. BRANSON, JR., Primary Examiner.

Davin l03135

Claims

1. A ROTARY MECHANISM COMPRISING AN OUTER BODY HAVING SPACED END WALLS AND A PERIPHERAL WALL FORMING A CAVITY THEREBETWEEN; AN INNER BODY HAVING AXIALLY-SPACED END FACES AND DISPOSED WITHIN SAID OUTER BODY CAVITY BETWEEN THE END WALLS THEREOF FOR ROTATION RELATIVE TO SAID OUTER BODY WITH EACH OF SAID END FACES ADJACENT TO AN END WALL; SAID INNER BODY HAVING A PLURALITY OF CIRCUMFERENTIALLY-SPACED APEX PORTIONS HAVING SEALING COOPERATION WITH THE INNER SURFACE OF THE PERIPHERAL WALL OF SAID CAVITY TO FORM BETWEEN THE INNER AND OUTER BODIES A PLURALITY OF WORKING CHAMBERS WHEREIN VARYING FLUID PRESSURES CYCLICALLY OCCUR; AND A PLURALITY OF SEAL STRIPS, ONE FOR EACH OF SAID APEX PORTIONS AND EACH RECEIVED IN A GROOVE IN AN APEX PORTION EXTENDING FROM ONE END FACE TO THE OTHER OF THE INNER BODY; EACH SAID SEAL STRIP HAVING A WIDTH IN THE CIRCUMFERENTIAL DIRECTION WHICH IS SLIGHTLY LESS THAN THE WIDTH OF ITS ASSOCIATED GROOVE WHEREBY THE FLUID THAT ONE OF THE TOW ADJACENT WORKING CHAMBERS HAVING THE HIGHER PRESSURE URGES SAID SEAL STRIP AGAINST THE OPPOSITE SIDE OF ITS GROOVE AND ENTERS THE GROOVE AND ACTS ON THE RADIALLY INNER EDGE OF THE SEAL STRIP TO URGE IT RADIALLY OUTWARD INTO SEALING ENGAGEMENT WITH THE INNER SURFACE OF THE OUTER BODY PERIPHERAL WALL; EACH SAID SEAL STRIP HAVING AT LEAST ONE RECESS IN EACH OF ITS SIDE FACES DISPOSED WITHIN A REGION OF SAID SIDE FACE WITH IS DISPOSED ENTIRELY WITHIN ITS APEX PORTION GROOVE, SAID RECESS EXTENDING OVER A SUBSTANTIAL AREA OF SAID SIDE FACE, THE RECESSES ON OPPOSITE SIDES OF SAID SEAL STRIP BEING OF SUBSTANTIALLY EQUAL AREA, SAID SEAL STRIP HAVING AT LEAST ONE PASSAGE THERETHROUGH INTERCONNECTING SAID RECESSES; EACH OF SAID SEAL STRIPS HAVING AN ADDITIONAL RECESS IN EACH OF ITS SIDE FACES ADJACENT AT LEAST ONE END OF SAID STRIP, EACH SAID ADDITIONAL RECESS BEING DISPOSED INWARDLY OF THE OUTER EDGE OF THE ASSOCIATED GROOVE FOR SAID SEAL STRIP AND EXTENDING TO SAID ADJACENT END OF SAID SEAL STRIP.