Side Gas Seal Means For Rotary Mechanisms

Abstract

The improved side gas seal comprises a seal strip disposed in a groove in the rotor face adjacent each of the flank portions of the rotor. The seal strip is resiliently biased in a direction outwardly of the groove by a spring means. The radially outer surface of the seal strip is provided with at least one recess for communicating the interstices between the rotor face and housing wall with the space between the bottom of the groove and the anti-seal side of the seal strip to thereby pass pressurized gas to the space behind the seal strip. This pressurized gas provides a force supplementing the force of the spring means acting against the seal strip and assists in urging the seal strip outwardly of the groove and into sealing abutment against the adjacent housing wall surface.

Description

DISCLOSURE

This invention relates to rotary mechanisms and, more particularly, to seal means for sealing the interstices between the rotor faces and the adjacent housing wall surfaces.

BACKGROUND OF THE INVENTION

In rotary mechanisms, such as rotary internal combustion engines of the Wankel type as disclosed in the U.S. Pat. No. 2,988,065 to Wankel et al., it is customary to provide in each of the end faces of the rotor an annular oil seal and gas seals disposed outwardly of the oil seals. The gas seals of the segmental type disposed adjacent each of the flank portions of the rotor usually coact at their opposite ends with an apex seal assembly which includes an apex pin to effect thereby a substantially complete fluid seal between each of the rotor faces and the associated housing surfaces. Each of the segmental gas seals is located in an arcuate groove and is resiliently biased in a direction outwardly of the groove by a spring means. Many side seal designs have been developed to increase the sealing effectiveness, some of such development effort is exemplified in the following United States Patents:

Wankel et al U.S. Pat. No. 2,880,045 Bentele U.S. Pat. No. 2,979,042 Wankel U.S. Pat. No. 3,064,880 Bentele U.S. Pat. No. 3,033,180 Hurley U.S. Pat. No. 3,081,745 Schlor U.S. Pat. No. 3,102,520 Scherenberg et al U.S. Pat. No. 3,131,945 Simonsen U.S. Pat. No. 3,139,233 Froede U.S. Pat. No. 3,142,439 Bentele U.S. Pat. No. 3,176,910 Paschke U.S. Pat. No. 3,251,541.

In some of these patents the side seals are shown spring biased toward the housing end wall while as shown in the Paschke patent, side seals are biased by gas pressure.

Accordingly, an object of this invention is to provide an improved gas seal means for a rotary mechanism which reduces gas leakage rates from the working chambers and provides a rotary mechanism with improved power output and fuel economy.

Summary

Accordingly, the present invention contemplates an improved gas sealing means for a rotary mechanism of the Wankel type, which gas sealing means comprises an elongated seal strip disposed within a groove in the face of the rotor and extending adjacent each flank portion of the rotor. A resilient biasing means, as for example a wavy metallic strip or ribbon, is disposed between the seal strip and the bottom of the groove to urge the seal strip in a direction outwardly of the groove and into engagement with the adjacent housing wall. The seal strip is provided with at least one notch in the radially outer surface of the strip so as to define with the radially outer surface of the groove a passageway. The passageway functions to communicate the space between the rotor face and the adjacent housing wall with the space between the seal strip and bottom of the groove so that the seal strip surface opposite from its sealing surface (hereinafter referred to as the "anti-sealing surface") is subjected to gas pressure. This relatively high gas pressure assists the resilient biasing means in urging the seal strip into abutment against the adjacent housing wall.

Another feature of the present invention is the provision of a chamfer along the radial outer edge of the sealing surface of the seal strip. This chamfer is dimensioned in relation to the depth of the notch so that seal strip maintains uninterrupted sealing engagement with the housing wall as the seal strip tilts or rocks within the groove under varying gas pressures to which the seal strip is subjected. By maintenance of continuous sealing contact of the seal strip with the housing wall, gas from the interstice between the housing wall and rotor face radially outwardly of the seal strip is prevented from bypassing the seal strip through the notch.

In a more limited aspect the present invention provides a plurality of arcuate-shaped notches so that gas communicates with the anti-sealing surface of the seal strip via a plurality of passageways.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood from the following detailed description thereof when considered in connection with the accompanying drawing wherein but one embodiment of the invention is illustrated by way of example, and in which:

FIG. 1 is a diagrammatic transverse view of a rotary mechanism having side gas seals according to this invention;

FIG. 2 is an enlarged fragmentary view showing in elevation a portion of the side gas seals of this invention shown in FIG. 1;

FIG. 3 is a cross-sectional view taken substantially along line 3--3 of FIG. 2, shown somewhat on an enlarged scale; and

FIG. 4 is a view similar to FIG. 3 showing the side gas seal in a tilted position.

Description of the Preferred Embodiment

Now referring to the drawings and, more specifically to FIG. 1, the reference number 10 generally refers to a side gas seal according to this invention for a rotary mechanism of the Wankel type, such as an internal combustion engine of the kind disclosed in the U.S. Pat. No. 2,988,065.

As illustrated, rotary mechanism 10 comprises a rotor 12 which is supported for eccentric rotation within a cavity formed by a housing 14. The housing 14 of a single rotor mechanism comprises two end walls 18 held in spaced relationship to each other by an intermediate wall 20 which defines an epitrochoidal peripheral inner surface 22. The rotor 12 has one more apex portion than the number of lobes formed by the housing cavity so that in the rotary mechanism 10 herein illustrated, the rotor has two opposite generally triangular shaped faces 23 each of which has three apex portions 24, while the cavity has two lobes. The rotor has three peripheral surfaces or flanks 26 which define with the housing cavity three working chambers A, B, and C which successively expand and contract in volumetric size as rotor 12 rotates within housing 14.

As shown, if rotary mechanism 10 is an internal combustion engine, an inlet port 28 may be provided to admit a mixture of fuel and air into chamber A. An exhaust port 30 may be provided to communicate with chamber B to pass spent products of combustion from the engine. An ignition means 32, such as a spark plug, may be provided to ignite the compressed fuel and air mixture in chamber C so that the expanding products of combustion rotatively drive rotor 12 in a counterclockwise direction.

The mechanism 10 is provided with sealing means to seal the interstices between rotor 12, epitrochoidal surface 22, and the inner surface 16 of end walls 18 to minimize intercommunication between chambers A, B and C. As is conventional, each apex portion 24 of rotor 12 is provided with an apex seal 34 which projects radially from rotor 12 to engage the epitrochoidal surface 22. The space 36 between each rotor face 23 and the adjacent surface 16 of end walls 18, which space 36 communicates with chambers A, B, and C, is sealed by gas seal means according to this invention. To prevent leakage of oil into the chambers A, B, and C, from an area adjacent the crankshaft 38, an oil seal 40 is carried in each of the faces 23 of the rotor.

The gas seal means according to this invention comprises a plurality of arcuate-shaped seal strips 42, each of which is disposed for slidable movement in a groove 44 formed in each face 23 and adjacent each flank 26 of the rotor. A resilient biasing means of any suitable type, such as a wavy spring steel strip or ribbon 46, is disposed between the bottom of groove 44 and the anti-seal side 48 of seal strip 42 to urge the seal strip 42 into abutment against surface 16 of end wall 18 (see FIG. 3). A plurality of spaced, arcuate-shaped notches or recesses 50 are provided in the radially outer surface 52 of the seal strip so as to communicate space 36 between rotor face 23 and surface 16 of the adjacent end walls 18 with the space between the bottom of groove 44 and anti-seal side 48 of seal strip 42. With the space behind seal strip 42 in unrestricted communication with space 36 and, hence the gas pressures in working chambers A, B and C, the anti-seal side 48 of seal strip 42 is subjected to those gas pressures. Since the area on the sealing side of seal strip 42 exposed to the gas pressures in space 36 is less than the area of anti-seal side 48 of seal strip 42, the net force exerted by the gas pressure is in a direction urging seal strip 42 toward surface 16. This gas exerted force supplements the force of spring 46 to maintain seal strip 42 in sealing engagement with surface 16.

As best illustrated in FIG. 4, each of the seal strips 42 is subjected to tilting or "rolling" about its cross-section centroidal axis and within the limits permitted by the tolerances between the dimensions of groove 44 and seal strip 42. To insure that under this movement of seal strip 42 an uninterrupted seal between the seal strip and surface 16 is maintained, the radially outer edge of seal strip 42 is provided with a chamfer 54. This chamfer 54 extends in the sealing surface of the seal strip, from a point at or below the deepest part of recesses 50 in surface 52 of the seal strip, to radial outer surface 52. The chamfer 54 presents to surface 16 an uninterrupted contact line 56 (see FIG. 2) in the tilted position of the seal strip so that gas in space 36 cannot bypass the seal strip through the recesses 50 which bypassing would occur in absence of chamfer 54 and the line contact 56.

In tests comparing gas seal strips 42 having seven recesses 50 with conventional gas seal strips (only spring biased), substantial reductions in gas leakage rates have been achieved by gas seal strips 42 according to this invention. More specifically, at 3,000 rpm of the test engine, the gas leakage rate was 31 percent less than the leakage rate of the conventional seal strips, at 4,000 rpm the gas leakage rate was 42 percent of the leakage rate of the conventional seal strips, and at 5,500 rpm the gas leakage rate was reduced by 54 percent. Under wide open throttle conditions of engine operation, the gas leakage rate was 54 percent less than the leakage rate when conventional seal strips were employed in the engine.

It is believed now readily apparent that the present invention provides an improved gas seal strip for a rotary mechanism which substantially reduces gas leakage through the interstice between the rotor face and housing end walls. It is a gas seal which has the effect of improving the power output of the mechanism.

Although but one embodiment of the invention has been illustrated and described in detail, it is to be expressly understood that the invention is not limited thereto. Various changes can be made in the arrangement of parts without departing from the spirit and scope of the invention as the same will now be understood by those skilled in the art.

Claims

What is claimed is:

1. An improved side gas seal assembly for a rotary mechanism having a rotor comprising opposite face portions and a plurality of peripheral flank portions, the rotor being supported for eccentric rotation in a cavity formed in a housing defining a peripheral trochoidal surface and wall surfaces adjacent each of said rotor face portions, the side gas seal assembly comprising:

a. a groove in each rotor face extending adjacent each flank portion of said rotor;

b. a seal strip for each groove having a sealing side, an anti-sealing side, and radial inner and outer surface portions;

c. each of said seal strips being disposed in each of said grooves with the sealing side projecting from said groove and the anti-sealing surface adjacent the bottom portion of said groove;

d. resilient biasing means for each seal strip disposed in said groove to urge the associated seal strip in a direction outwardly from its associated groove and the sealing side into abutment against the adjacent wall surface;

e. recess means in each of said seal strips to communicate the space between the rotor face and the adjacent housing wall surface and the space between the anti-sealing surface of the seal strip and the bottom of the associated groove to conduct pressurized gas to the latter space and thereby exert a force on said seal strip directed outwardly of its associated groove; and

f. the sealing side of the seal strip is provided with a chamfered portion which extends from at least the depth of the recess means to provide an uninterrupted sealing line engaging the adjacent wall surface and extending the full length of the seal strip when the seal strip tilts relative to its associated groove to thereby prevent pressurized gas from by-passing the seal strip.

2. The apparatus of claim 1 wherein said seal strip is substantially rectangular in cross-section.

3. The apparatus of claim 1 wherein said recess means is located in the radial outer surface portion of said seal strip to define with the groove a passageway means.

4. The apparatus of claim 1 wherein said recess means is a plurality of spaced notches in the radial outer surface portion of the seal strip to define with the groove a plurality of passageways.

5. The apparatus of claim 4 wherein each of said notches is arcuate in shape and extend from the sealing side to the anti-sealing side of the seal strip.