US3847517A - Rotary piston for a rotary internal combustion engine - Google Patents

Abstract

The rotor for a rotary internal combustion engine has in each of its flank portions an elongated recess or pocket which is substantially narrower in width than the rotor flank so as to define between the recess and the rotor side faces two relatively large land portions in the flank surface. A plurality of ribs are circumferentially spaced with respect to the hub portion and radially extending between and interconnecting the flank surfaces along the sides and bottom walls of the pockets and the hub portion to thereby define a plurality of axially extending cooling fluid passageways adjacent the sides and bottom walls of each of the pockets. The bottom wall of each pocket has an extension integrally formed with said bottom wall and projecting axially from one side thereof to a point beyond the end of the surface of the hub portion adjacent said side of the bottom wall and which extension serves as a baffle for directing cooling fluid into said fluid passages.

Description

United States Patent [1 1 Hermes et al.

[4 1 Nov. 12, 1974 l54l ROTARY PISTON FOR A ROTARY INTERNAL COMBUSTION ENGINE [75] Inventors: Walter L. Hermes, Cedar Grove;

' Howard R. Corwin, North Caldwell; Murray Berkowitz, Woodcliff Lake; Harold D. Lamping, Oakland, all of NJ.

[73] Assignee: Curtiss-Wright Corporation,

Wood-Ridge, NJ.

22 Filed: Dec. 26, 1973 2! Appl. No.: 428,109

Related US. Application Data [63] Continuation of Ser. No. 253,319, May 15, 1972,

abandoned.

[56] References Cited UNITED STATES PATENTS 3,253,580 5/1966 Eberhard et a1, 123/8 FOREIGN PATENTS OR APPLICATIONS Germany 418/91 Primary Examiner-Charles J. Myhre Assistant ExaminerW. Rutledge, Jr. Attorney, Agent, or Firm-Arthur Frederick 57 ABSTRACT The rotor for a rotary internal combustion engine has in each of its flank portions an elongated recess or pocket which is substantially narrower in width than the rotor flank so as to define between the recess and the rotor side faces two relatively large land portions in the flank surface. A plurality of ribs are circumferentially spaced with respect to the hub portion and radially extending between and interconnecting the flank surfaces along the sides and bottom walls of the pockets and the hub portion to thereby define a plurality of axially extending cooling fluid passageways adjacent the sides and bottom walls of each of the pockets. The bottom wall of each pocket has an extension integrally formed with said bottom wall and projecting axially from one side thereof to a point beyond the end of the surface of the hub portion adjacent said side of the bottom wall and which extension serves as a baffle for directing cooling fluid into said fluid passages,

3 Claims, 10 Drawing Figures AXIAL VELOCITY COMPONENT HXIRL VELOCITY COMPONENT INTO OUT OF ROTOR POCKET PATENTEI] NOV 1 2 I974 ROTOR POCKET IN FEET PER SECOND IN FEET PER SECOND SIEEI 30$ 5 NARROW POCKET 5THNDQRD POCKET BTC 50 50 IO TDC I0 50 50 ATC l I BEFORE TOP CENTER IN DEGREES HFTER TOP CENTER IN DEGREES 'i AIENIEuNuv 12 1314 3.847351 7 BACKGROUND OF THE INVENTION With the necessity for reducing air pollution it has become more and more essential to produce internal combustion engines of increased fuel combustion efficiency to minimize harmful exhaust emissions. Considerable effort has been exerted to increase the fuel burning efficiency of rotary piston engines of the Wankel type by modifications in rotor design as is exemplified in the following U.S. Pats:

Froede et al. No. 3,097,632 Turner No. 3,359,955 Bentele No. 3,359,956 Jones No. 3,405.695 Yamamoto No. 3,584,607 Hamada et al. No. 3,606,602 Hejj No. 3,610,209 Hamada No. 3,249,095 Liebel No. 3,292,600 Meurer No. 3,244,!59

It has been found that there is a direct correlationship between the completeness of fuel combustion and the degree of intimate mixing achieved between the fuel and air. Therefore, increased turbulence within the combustion chamber can be expected to increase the intermixing of fuel and air, and hence result in more complete combustion of fuel. It is particularly difficult I to achieve optimum fuel combustion in rotary piston engines of the Wankel type having a combustion system consisting of unthrottled air intake and controlled fuel injection into the combustion chamber adjacent an ignition device, such stratified charge fuel combustion systems being disclosed in the U.S. Pats. to Bentele, N0. 3,246,636 and Jones No. 3,393,667. In such stratified charge systems, the larger the volumetric size of the working chamber and/or the greater the speed of rotor rotation the more difficult it is to provide substantially complete combustion of fuel. Thus, the proper stoichiometric mixing of fuel and air within the very short period of time available after fuel injection commences is dependent upon the establishment of a high degree of turbulence within the combustion chamber.

Accordingly, it is an object of this invention to provide in a rotary piston, internal combustion engine, an improved rotor which is capable of producing high turbulence within the combustion chamber to thereby achieve intimate mixing of fuel and air and substantially complete combustion of fuel.

Another object of the present invention is to provide in a rotary piston, internal combustion engine, an improved rotor which creates high gaseous fluid velocities within the working chamber to thereby provide a proper stoichiometric mixing of air and fuel and the efficient combustion of the fuel.

SUMMARY OF THE INVENTION Now, therefore, the present invention contemplates,

in a rotary piston engine of the Wankel type, an improved rotor which coacts with the engine housing to provide within the combustion chamber a high degree of turbulence to obtain improved mixing of air and fuel and hence substantially complete combustion of the latter.

The rotor according to this invention comprises in each peripheral surface or flank thereof a recess of pocket which is relatively long, narrow and deep in configuration. The pocket is dimensioned in width and positioned so that a relatively wide flank surface portion of flank land extends on opposite sides of the pocket. These two flank lands coact with the walls, defining the engine cavity within which the rotor rotates, to compress the gaseous fluid (air and fuel) in the combustion chamber and impart to the gaseous fluid a high velocity in a direction axially toward and away from the pocket. With the gaseous fluid cascading into and out of the pocket at high velocity, a high turbulence is cre ated within the pocket thereby rapidly effecting intimate mixing of fuel and air.

Preferably, each pocket in each flank is of generally rectangular configuration extending substantially the length of the rotor flank and located substantially midway between the opposite side faces of the rotor. The pocket is also preferably constructed in width to be slightly greater than one-third the dimensional width of the rotor flank so as to provide the relatively large land portions on opposite sides of the pocket. I

The depth of each pocket is determined by the volumetric size that the pocket must be to achieve a desired compression ratio and, of course, taking into account the structural strength requirements of the rotor to resist the thermal and mechanical stresses to which it is subjected. Also, the rotor provides separation of the hub from the flank so as to provide axially extending, cooling fluid flow passageways between the bottom wall of the pocket and the hub of the rotor to cooland pocket walls, the hub and flank being connected by radial ribs coextensive with the stiffening ribs.

In one embodiment of this invention the depth of the pocket is optimized relative to the strength requirements and the designed compression ratio by tapering the pocket side walls inwardly toward each other to thus provide stiffening ribs interconnecting the hub with the rotor side walls of a size necessary to achieve the desired structural strength.

In another embodiment, the narrow pocket includes two shallow grooves extending from opposite sides of the leading portion of the pocket and beyond the pocket toward the leading apex portion of the piston. These grooves function todefine with the peripheral inner housing surface shooting passages or channels for directing high velocity streams of fuel and air into the expansion combustion chamber.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objectives and advantages of the present invention will appear more fully hereinafter from a consideration of the detailed description which follows when taken together with the accompanying drawings wherein three embodiments of the invention are illustrated and in which;

FIG. 1 is a side elevational view of a rotary piston engine having a rotor according to this invention with parts broken away for illustration purposes only;

FIG. 2 is a plan view of the rotor shown in FIG. 1 showing one of the flank portions of the rotor;

FIG. 3 is a view in crosssection taken along line 3-3 of FIG. 2;

FIG. 4 is a cross-sectional view taken along line 44 of FIG. 2;

FIG. 5 is a fragmentary plan view of the rotor having the fuel injection spray impingement pattern shown thereon;

FIG. 6 is a graph showing the axially directed velocities induced in the working chamber by a rotor according to this invention as compared with a standard rotor;

DESCRIPTION OF PREFERRED EMBODIMENTS Now referring to the drawings and more particularly to FIGS. 1 to 6, 10 generally designates a rotary piston or rotor for a rotary piston internal combustion engine of the Wankel type, such as disclosed in the US. Pat. No. 2,988,065 to Wankel et al and No. 3,246,636 to Bentele. As is conventional in such engines, the rotor 10 has a body portion having opposite side faces 12, a hub portion 14 and a periphery consisting of a plurality of flanks 16. Each of the flanks 16 has a slightly curved surface extending between the apex seals 18 disposed in the apex portions of the rotary piston. The rotary piston is mounted on an eccentric portion 11 of a shaft 13 for rotation within a cavity formed by the engine housing 15. The cavity is partially defined by an inner trochoidal shaped peripheral wall 20. The peripheral surface 20 may have a multi-lobe profile and, preferably, is an epitrochoid having one less lobe than the number of flanks 16 of rotor 10. Suitable intake and exhaust ports 21 and 23 are provided in the housing 15 to pass air or air and fuel mixture into the combustion chamber formed by the cavity walls'and the flanks and exhaust spent products of combustion from the combustion I chambers. In a stratified charge fuel combustion system, as exemplified in the US. Pats. to Bentele, No. 3,246,636 and Jones, No. 3,393,667, the fuel is introduced into the combustion chambers by a fuel injector 17 (see FIG. 1) for admixture with air.

In accordance with this invention, rotor 10 has in each flank 16, an elongated, narrow and relatively deep recess 22. The recess 22 is preferably rectangular in shape, when viewed in plan as shown in FIG. 2, with a length less than the length of the flank between adjacent apex seals 18 and with a width substantially less than the width of flanks 16 between opposite side faces 12. As illustrated, the recess width may be aboutone third the width of flank 16. The recess 22 is preferably located in flank 16 midway between side faces 12 and in slightly closer spaced relation to the trailing apex seal 18 than the space between the recess and the leading apex seal 18 relative to the direction of rotation as shown by arrow A. The recess 22 forms in flank 16 two relatively wide land portions 24 on opposite sides of the recess.

As best shown in FIGS. I, 3 and 4, recess 22 is defined by two spaced, parallel walls 26 and 28 and a flat bottom wall 30 which, as viewed in FIG. 1, is slightly inclined at the opposite ends 32 outwardly toward and into merger with the flank surface. The walls 26 and 28 extend perpendicularly to the surface of flanks 22 and bottom wall 30. As best shown in FIG. 3, side faces 12 and flanks 22 are interconnected by integrally formed, radially extending stiffening ribs 25. The depth of recess 22 is not critical and is only a function of its dimensional width and the compression ratio desired. In other words, the smaller the width of recess 22 the greater the depth to retain the same compression ratio.

In operation of rotor 10 and its rotation within the housing cavity relative to trochoidal surface 20, the air or mixture of fuel and air is compressed or squeezed between flank surface 16 and trochoidal surface 20. This compression of the fluid in the combustion chamber imparts to the fluid an axially directed velocity inwardly toward and outwardly of the recess. These axially directed velocities vary as rotor 10 approaches and passes top dead center (represented by the line B in FIG. 1 as is graphically illustrated in FIG. 6. As shown in the graph of FIG. 6, the relatively wide land portions 24 provide at 6,000 RPM axially directed velocities of high magnitude as compared with a rotary piston having a standard recess or pocket which is of relatively wide, shallow configuration such as the type shown in the US. Pat. to Bentele, No. 3,359,956 and Lamm et al. No. 3,398,724. Thesev high axial velocity components produce a high degree of turbulence in the combustion chamber and hence improved intermixing of fuel and air and more complete fuel combustion.

As best shown in FIG. 3, the flanks 16, including the walls 26, 28 and 30 are radially separated from hub 14 and interconnected by circumferentially spaced radially extending ribs 27, the ribs 27 being coextensive with stiffening ribs 25. The bottom wall 30 and hub 14 define between ribs 27 a plurality of axial cooling fluid flow passageways 29 through which a cooling fluid, such as oil, can flow to cool the walls 26, 28 and 30 of pocket 22 and thereby prevent deterioration of the rotor flanks due to excessive heating. The addition of passageways 29 to the rotor provides ribs 27 with flexibility which compensates for the thermal growth of rotor 10 without distortion of the bearing seat in hub portion 14 of the rotor. To better direct cooling fluid flow into passageways 29, bottom wall 30 is provided with annular extensions 31 which project axially beyond the plane containing the end surfaces 33 of hub 14.

This improved fuel combustion is particularly evident when rotary piston 10 is employed in conjunction with a Stratified charge type of fuel combustion system wherein fuel is injected into air trapped in the combustion chamber by a fuel injector 17 which emits fuel in a plurality of streams past an ignition means, such as a spark plug 19. Particularly excellent results were achieved when fuel was injected so as to form the impingement patterns 36 shown in FIG. 5. This fuel spray pattern together with the high turbulence in the combustion chamber provides intimate fuel mixing and vaporization of fuel and, hence efficient fuel combustion. The best high power combustion efficiency has been achieved by using a multi-stream fuel injector spray pattern wherein some of the fuel streams are directed counter to the direction of the rotor rotation. The position of pocket 22 in flank surface 14 closer to the trailing" apex 18 than the leading" apex 18 was selected in relation to fuel injection and ignition to minimize the amount of air passing ahead of the initiation of fuel injection and to provide for completely painting" the surface of pocket 22 and land portions 24 with fuel and thereby obtain intimate mixing of fuel and air inside the pocket to thus achieve optimum fuel combustion.

In FIGS. 7 and 8 is shown a second embodiment of this invention wherein increased structural strength is achieved over rotor I0 shown in FIGS. 1 to 6. The rotor 40 of this second embodiment functions to provide the same high magnitude of axial velocities as rotor 10 and therefore has an elongated, narrow pocket or recess in each of the flanks of the rotor. Like parts of rotor 40 corresponding to the parts of rotor 10 will be designated by the same reference number but with the suffix A added thereto.

As illustrated in FIGS. 7 and 8, rotor 40 has a narrow pocket or recess 22A in each flank 16A of the rotary piston. The recess 22A is essentially the same as recess 22 except that side walls 26A and 28A of recess 22A have lower portions 42 which incline toward each other in a direction toward bottom wall 30A. As best shown in FIG. 7, the hub portion .14A is connectedto flanks I the lower portions 42 of recess side walls 26A and 28A than if side walls were straight as in rotor 10 (see FIG. 3) or as shown by the phantom lines 48 in FIG. 7. Thus, with thicker ribs 48, rotor has greater structural strength to resist the thermal and mechanical stresses imposed on the rotary piston. Of course, as compared with recess 22, recess 22A will have to be slightly greater in width than the width of recess 22 to permit rotor 40 to achieve the same compression ratios as obtained by rotor 10.

In FIG. 9 is shown a third embodiment of the present invention which comprises a rotor 50 having in each flank surface a pocket or recess 22B differing from the pocket or recess 22A of rotor 40 shown in FIGS. 7 and 8 in that the pocket 228 includes two relatively shallow, tapering grooves 52. The grooves 52 extend on opposite sides of the leading portion of the pocket and forwardly of the latter toward the leading end of flank surfaces 16 relative to the direction of rotor rotation. In view of the close similarity of rotor 50 to pis-.

tons l0 and 40, parts of rotor 50 corresponding to like parts of pistons 10 and 40 have been designated by the same number but with the suffix B added thereto.

As shown in FIG. 9, each groove 52 is preferably arcuate shaped in cross-section and taper forwardly to a point where is merges with the flank surface 168.

It has been found that in order to improve fuel consumption at high power output in an engine having a stratifled charge type fuel combustion system and rotors l0 and 40, there must be increased utilization of the air within the combustion chamber for fuel combustion. This increased utilization of air for burning fuel which otherwise would be unburned is attained by use of rotor 50 because of grooves 52 which form with the inner peripheral surface of the housing (not shown), similar to peripheral surface 20 (FIG. l),

shooting channels or passages. These shooting.

channels conduct presurrized fuel and some air at high velocity into the fuel starved, expansion combustion chamber (space to the right of the lobe shown in FIG. 1) in advance of the compression-combustion chamber (space to the left of the lobe shown in FIG. 1) relative to the direction of piston rotation A. These two high velocity fluid streams injected by grooves 52 into the expansion working chamber accomplishes, in effect, a recovery of air which has passed into the expansion chamber before fuel injection by causing the air to mix with the fuel and, hence, cause the latter to burn. which fuel would otherwise remain unburned for lack of air and/or sufficient time to mix with air in the compression-combustion chamber.

It is believed now readily apparent that the present invention provides a rotor for a rotary piston internal combustion engine which coacts with the engine housing to provide improved turbulence within the combustion chamber and, hence, rapid and intimate mixing of fuel and air for optimum combustion of the fuel.

Although but three embodiments of the invention have been illustrated and described in detail, it is to be 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.

What is claimed is:

l. A rotor for a rotary piston, internal combustion engine comprising:

a. a body portion having a hub portion, opposite side faces and a plurality of contiguous flank surfaces spaced radially outward of the hub portion;

b. said hub portion having opposite end surfaces each of which lie in a plane axially and inwardly spaced from the plane of the associated side face;

c. a pocket in each of the flank surfaces;

d. each of said pockets being generally rectangular in shape and having opposite side walls and a bottom wall;

e. a plurality of ribs circumferentially spaced with respect to the hub portion and radially extending between and interconnecting the flank surfaces along the sides and bottom walls of the pockets and the hub portion;

f; said ribs defining with the hub portion and the flank surfaces a plurality of axially extending cooling fluid flow passageways adjacent the side and bottom walls of each of the pockets; and

g. the bottom wall of each pocket has an extension integrally formed with said bottom wall and projecting axially from one side thereof to a point beyond a radial plane containing the end surface of the hub portion adjacent said side of the bottom wall and which extension serves as a baffle for directing cooling fluid into said fluid passageways.

2. The apparatus of claim 1 wherein the bottom wall .of each pocket has a second integral extension which projects axially from the opposite side of the bottom wall from said first extension and extends beyond the radial plane containing the opposite end surface of the hub portion to direct cooling fluid flow relative to said fluid passageways.

3. A rotor for a rotary piston internal combustion engine comprising:

a. a body portion having a hub portion, side faces and a plurality of contiguous flank surfaces spaced radially outward of said hub portion;

h. each of said end surface of the hub portion being in a plane axially inwardly spaced from the plane of the associated side face;

c. a pocket in each of said flank surfaces;

d. each of said pockets having an elongated configu ration and a width substantially less than the total width of the associated flank surface extending between said opposite side faces so as to form two relatively wide land portions of the flank surfaces on the opposite sides of the pocket;

e. each of said pockets being of generally rectangular shape and having opposite side walls and bottom wall; f. a plurality of ribs circumferentially spaced with respect to the hub portion and radially extending between and interconnecting the flank surfaces along the side and bottom walls of the pockets and the hub portion;

g. said ribs defining with the hub portion and the flank surfaces a plurality of axially extending cooling fluid passageways adjacent the side and bottom walls of each of the pockets; and

h. extension portions formed integrally with the bottom walls of each of said pockets and projecting axially from opposite sides of the bottom wall to points beyond radial planes containing the end surfaces of the hub portion adjacent said opposite sides of the bottom wall to direct cooling fluid into and from said fluid passageways.

Claims (3)

1. A rotor for a rotary piston, internal combustion engine comprising: a. a body poRtion having a hub portion, opposite side faces and a plurality of contiguous flank surfaces spaced radially outward of the hub portion; b. said hub portion having opposite end surfaces each of which lie in a plane axially and inwardly spaced from the plane of the associated side face; c. a pocket in each of the flank surfaces; d. each of said pockets being generally rectangular in shape and having opposite side walls and a bottom wall; e. a plurality of ribs circumferentially spaced with respect to the hub portion and radially extending between and interconnecting the flank surfaces along the sides and bottom walls of the pockets and the hub portion; f. said ribs defining with the hub portion and the flank surfaces a plurality of axially extending cooling fluid flow passageways adjacent the side and bottom walls of each of the pockets; and g. the bottom wall of each pocket has an extension integrally formed with said bottom wall and projecting axially from one side thereof to a point beyond a radial plane containing the end surface of the hub portion adjacent said side of the bottom wall and which extension serves as a baffle for directing cooling fluid into said fluid passageways.

2. The apparatus of claim 1 wherein the bottom wall of each pocket has a second integral extension which projects axially from the opposite side of the bottom wall from said first extension and extends beyond the radial plane containing the opposite end surface of the hub portion to direct cooling fluid flow relative to said fluid passageways.

3. A rotor for a rotary piston internal combustion engine comprising: a. a body portion having a hub portion, side faces and a plurality of contiguous flank surfaces spaced radially outward of said hub portion; b. each of said end surface of the hub portion being in a plane axially inwardly spaced from the plane of the associated side face; c. a pocket in each of said flank surfaces; d. each of said pockets having an elongated configuration and a width substantially less than the total width of the associated flank surface extending between said opposite side faces so as to form two relatively wide land portions of the flank surfaces on the opposite sides of the pocket; e. each of said pockets being of generally rectangular shape and having opposite side walls and bottom wall; f. a plurality of ribs circumferentially spaced with respect to the hub portion and radially extending between and interconnecting the flank surfaces along the side and bottom walls of the pockets and the hub portion; g. said ribs defining with the hub portion and the flank surfaces a plurality of axially extending cooling fluid passageways adjacent the side and bottom walls of each of the pockets; and h. extension portions formed integrally with the bottom walls of each of said pockets and projecting axially from opposite sides of the bottom wall to points beyond radial planes containing the end surfaces of the hub portion adjacent said opposite sides of the bottom wall to direct cooling fluid into and from said fluid passageways.

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