US3113526A

US3113526A - Slit apex seals

Info

Publication number: US3113526A
Application number: US186710A
Authority: US
Inventors: Paschke Hanns-Dieter
Original assignee: NSU Motorenwerke AG
Current assignee: Audi AG
Priority date: 1961-04-13
Filing date: 1962-04-11
Publication date: 1963-12-10
Anticipated expiration: 1980-12-10

Description

Dec- 10, 1963 HANNs-DIETER PAscHKE 3,113,526

sLIT APEX SEALs Filed April 11, 1962 INVENTOR. HANNEx-DIETER FAEEHKE ATTFINEY United States Patent O 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 US. Patent No. 2,988,065, although as will become apparent, this invention is not liniited to this specic 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 for fluid purnps and uid motors.

A rotary engine as disclosed in said patent comprises an outer body 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 or housing has axially-spaced end walls and a peripheral wall interconnecting the end walls to form said cavit 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 disposed adjacent to said outer body end walls for sealing cooperation therewith and has a peripheral surface with a plurality of circumferentially-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 runs axially from one end face to the other of the inner body.

Prior combustion engines of this type have had a groove at each apex portion of the inner body in which single radially-movable seal strip was disposed, said seal strip separating the adjacent working chambers. The full depth of the apex strip, as measured radially, is composed of a partial depth received in its groove, plus the remaining strip depth exposed to the combustion gases in the working chambers, this exposed portion extending between the inner-body apex-portion surface and the inner surface of the outer body. During operation of the engine the apex seal strips may be subjected to uneven heating because the radially-inward part of the apex seal strip which is situated in the groove in the rotor apex portion is able to dissipate a part of its heat through the groove wall to the rotor, whereas the radially-outward part f the apex seal strip that projects beyond the rotor has no direct contact with either the inner or outer body except along its outer edge and therefore said projecting portion of the apex seal strip becomes hotter than the remainder of the apex seal strip. As a result, the edge portion of the apex seal strip projecting from the rotor acquires an outwar ly convex shape to produce gaps between the end portions of the strip and the outer-body peripheral wall thereby impairing the sealing engagement of the strip with the outer body peripheral wall and causing leakage of gases between the Working chambers.

In addition, such a convex seal strip may rock about its point of contact with the peripheral wall as the en- Mice gine operates. Any such rocking movement can lead to injury to the peripheral-wall inner surface.

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

Speciiically, instead of providing only a single seal element at each apex portion, acting as a partition between the two adjacent Working chambers, this invention provides at least two seal strips in each apex groove, and extending over the entire width of the rotor, with at least one or" the seal strips in each apex groove having a plurality of slits that extend inwardly from its radially-outward edge and with the other seal strip covering said slits. Preferably each apex seal strip has slits extending inwar ly from its outer edge and also has slits extending outwardly from its inner edge. Such a slit apex seal strip will more nearly contact the inner surface of the outer body notwithstanding non-uniform temperatures of said seal strip or deformation of said inner surface.

Such a slit apex seal strip has the further advantage in that the slits provide the seal strip with a substantial flexibility in its longitudinal direction. As a result of this flexibility each apex seal strip can be made to sealingly engage the outer body end walls without danger of becoming clamped therebetween because of expansion of said seal strips relative to the outer body. Accordingly, a further object of the present invention resides in the provision of novel apex seal constructions in which the apex seal strips have longitudinal ilexibility to insure sealing at the ends of these seals.

A further object of the invention resides in a novel construction of the apex seal strips for reducing the manufacturing costs. ln accordance with the invention, the slits are non-symmetrically spaced in an identical manner along each seal strip. With this seal construction, each pair of seal strips in a groove can be oppositely disposed so that each strip covers the slits in the adjacent strip notwithstanding the fact that the seal strips are slit in an identical manner.

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

FIG. l is a partial, longitudinal, sectional view through a rotor apex portion and groove showing a prior art form of unslit apex seal strip;

FIG. 2 is a View similar to FIG. l, except showing the slit apex seal strip in accordance with the invention, and as taken along line Z-Z of FlG. 3;

FG. 3 is a partial View of the rotor apex portion and a pair of slit seal strips as taken along line 3*-3 of FIG. 2;

FlG. 4 is an enlarged, front-elevation view of a pair of slit apex seals in accordance with the invention;

FIG. 5 is a top View of a pair of slit apex seals as taken along line 5 5 of FIG. 4;

FIG. 6 is an enlarged, partial, front-elevation View of a pair of slit apex seals.

Referring to the drawings, as illustrated in FIG. 1, the housing of a rotary combustion engine comprises spaced end walls ll and l2, and a peripheral Wall 13 disposed between and interconnecting said end walls. The inner surface lll of the peripheral wall ll3 preferably has a multi-lobed profile in cross-section which is basically an epitrochoid. Inside and eccentric to the housing is disposed an inner body or rotor l5, having preferably spaced apex portions le at each of which is an outwardly-facing apex groove 17 recei ing a radially-movable seal strip itl for separating adjacent working chambers lll. The prior art form of unslit seal strip i8 is urged outwardly in sealing cooperation with the inner surface lltof the peripheral wall 13, partly by spring means 2l) and also by gas pressure coming into the groove 17 from an adjacent working chamber 19. Each end of the apex seal strip 18 is in sealing cooperation with an intermediate sealing element 21, which is also received within the apex groove 17 at its ends. This intermediate sealing element 21 is axially movable 'and is in sealing cooperation with the adjacent surface o' the outer-body end wall l1 or l2. Between the intermediate sealing elements 2l, disposed on each end face of the rotor 15 and associated with a working chamber 19, are end-face-sealing strips 22. All of these seal elements and strips act to seal the working chambers 19.

In the prior art form of radially-movable, unslit, apex seal strip 18 as illustrated in FIG. l, particular difficulties may arise when the medium in the working chamber 19 has a high temperature, as in the case of a rotary combustion engine. The temperature of the unslit seal strip l becomes unevenly distributed across the seal strip because the radially-inward or inner edge 23 of the strip i3, which is received in its apex groove 17, loses heat to the rotor l5 mostly by conduction and acquires a lower temperature than the radially-outward or exposed outer edge 24 of the strip l8r. The temperature difference between the part of the outer edge 24 and the part at the inner edge 23 of the strip 18 can amount to 150 C. to 200 C. in the case of apex seal strips in certain rotary combustion engines.

Because of the temperature difference between the

edges

23 and 24, the apex seal strip 18 becomes deformed, assuming a new shape, with the outer edge 24 l'acquiring an outwardly-curved convex profile. As a result of this thermal distortion, the strip lt! bears against the inner surface of the peripheral Wall 14 only at the middle portion of the strip i8, as illustrated in FIG. l, during engine operation, and gaps 25 me formed on both sides of the middle portion, which impairs the sealing. The magnitude of the gaps l5 has been greatly exaggerated in the drawing for purpose of illustration.

In addition, because of said thermal distortion, each end face 26 of the apex seal strip i8 becomes slanted relative to the surface of the outer-body end wall l1 and 12, as illustrated in FlG. l, so that the outer corners of the strip, which are located at the intersection of the outer edge 24- and the end face 25, dlg into the outerbody end walls ll and l2. As a result, the radial movement of the strip i8 may become restricted and its sealing cooperation with tie inner surface of the peripheral Wall 14 and with the end wall lll and l2 also may become impaired.

Another diiiiculty with the prior art form of unslit apex seal strip i8 also results from outwardly-curved convex profile of the strip 1S as mentioned above and the limited contact only at the middle portion of the outer edge 24 of the strip l. This added difculty is that the apex seal strip 18 may rock about its point of Contact with the peripheral wall 133 as the engine operates. Any such rocking movement can lead to injury to the inner surface of the peripheral wall 14 of the outer body.

As shown in FlGS. 2 and 3, in accordance with the invention, two radially-movable, slit, apex seal strips 27 :and 28 are disposed side-by-side in each rotor apex groove 17 in place of the prior art form of the single :strip 1S as shown in FIG. l.

Each such apex seal strip 27 and 2d has a plurality of spaced slits 29 and 3i) respectively which extend inered by the adjacent seal strip 27.

Such a slit

apex seal strip

27 and 22 will because of r4 its flexibility more nearly contact the inner surface of the outer body ld notwithstanding non-uniform temperatures oi said

seal strip

27 and 23 or deformation of said inner surface i4. A

The radially outward edge 24 of each slit apex seal strip will still become deformed slightly due to the nonuniform temperatures, but instead of the outer edge 24 assuming an outwardly-curved convex profile over the strip length as in the case of the prior art form of unslit strip 18, as illustrated in FlG. l, the outer edge 24 of each

slit strip

27 and 28 will assume a prolile of a plurality of small, outwardly-curved arcs between the slits as illustrated in FIG. 6. Each small are is much smaller in height and the total arc is of much less outward curvature than that of the above mentioned convex proiile of the unslit strip 18; with the result that the outer edge 24 over the length of the

slit strips

27 and 28 will more nearly Contact the inner surface 14 of the outer body. Also, since the

strip

27 and 28 are slit, the corners do not become slanted and thus do not dig into the end walls l1 and 12.

Accordingly, as illustrated in FIGS. 2 and 6, the outer edge 24 of the slit strips 27 and 223 will bear against the inner surface i4 substantially along the entire length of the strip and not just at the middle portion of the strips. As a result there are no substantial sealing gaps between the strips 27 and 2S and the outer body, and in addition the aforementioned rocking movement of said prior art unslit seal strips is avoided.

Furthermore, the plurality of slits 29 and 3i) give the apex seal strips 27 and 23 a substantial longitudinal ilexibility compared to that of the usual unslit strip, which insures sealing engagement of its end faces 26 with the end walls l1 and l2, provides for control of the frictional contact with said end walls, and avoids clamping of the

strips

27 and 23 by the end walls ll and l2.

Due to the elasticity of the

strips

27 and 28 the friction between the end faces 2e and the end walls l1 and l2 can substantially be determined so that this friction restraint on the radial movement of the apex seal strip is known and the apex seal strip spring 2d can be desinned to insure radially outward movement of the seal strips against the inner surface i4.

Also, due to the greater elasticity of the slit strips 27 and 2S, they can better adapt to the deformations of the inner surface of the peripheral wall 1.4.

To increase the longitudinal flexibility of each

seal strip

27 and 28, each of these strips has a slit adjacent to at least one of its ends. Thus, one of the slits 29, designated 2%, in the strip 27 is disposed adjacent to one end of the strip, and similarly one of the slits 30, designated 39a, in the strip 23 is disposed near one end of this strip. The slits 29a and Stk run parallel to the adjacent edges 26 of their

respective strips

27 and 28. in this way, a sort of yieldable lip 33 is formed at one end of each seal strip 27 and 2E by their respective slits 29a and 39a. The gas pressure which enters the slits 22a and 33a forces the adjacent lip 33 into sealing engagement with the adjacent outer-body end Walls 1l and l2.

For the purpose of increasing the elasticity of the apex seal strips 27 and 28, there are preferably also provided in addition to the outer edge slits, a plurality of spaced slits 3l and 32 extending outwardly part way from their inner edge 23 with said, latter, inner-edge slits being covered by the wall of the apex groove i7. The increased elasticity of the slit strips 27 and 28 improves sealing of their end faces 26 with the end walls l1 and l2- and of their outer edge with the peripheral-wall inner surface 14.

ln order to simplify manufacture, it is possible to make all the slit apex seal strips 27 and 2S with outer-edge slits 29, 29a, Si) and 30a as identical parts. In each apex groove 17, there is a pair of slit seal strips 27 and 2S with the strips of each pair having outer-edge radiallyinward slits 29, 29a, 30 and 30a of identical non-symmetrical spacing, but with said pair of

strips

27 and 28 being oppositely disposed in the groove 17, so that each

strip

27 and 28 covers the outer-edge radially-

inward slits

29, 29a, 30 and 30a in the other of said pair. That is, the slits of the rst strip 27 are covered by the other adjacent strip 28 because, during assembly of the strips in their groove 17, the other strip 28 is turned one hundred eighty degrees (180) about its middle before being placed in the groove adjacent to the rst strip 27.

Both of the above seal strips 27 and 28 in each groove 17 are slit. It is also possible to provide an unslit seal strip in the groove to cover the slits of the adjacent slit seal strip.

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 modications may be made therein without departing from the spirit or scope thereof.

What is claimed is:

A rotary mechanism comprising an outer body having spaced end walls and a peripheral Wall forming a cavity therebetween; an inner body disposed within said outer body for rotation relative to said outer body; said inner body having a plurality of circumferentially-spaced 25 grooves about its periphery; each of said grooves receiving a pair of radially-movable, side-by-side seal strips for sealing cooperation with the inner surface of said peripheral wall to form a plurality of Working chambers between said bodies which vary in volume upon relative rotation of said bodies; the pair of apex seal strips in each groove extending from one end face to the other of the inner body, and having a plurality of spaced slits extending inwardly part Way from the radially outer edges of said strips and having an identical non-symmetrical spacing but with said pair of strips being oppositely disposed in the groove so that each strip covers said inwardly extending slits in the other of said pair.

References Cited in the le of this patent UNITED STATES PATENTS 1,617,863 Planche Feb. 15, 1927 2,027,594 Hutt Jan. 14, 1936 2,633,292 Voznica Mar. 31, 1953 3,064,880 Wankel Nov. 20, 1962 FOREIGN PATENTS 123,352 Great Britain Feb. 17, 1919 864,855 France May 7, 1941