Patent Description:
Combustion chambers of a rotary engine, such as a Wankel engine, are delimited radially by the rotor and rotor housing and axially by the two end walls. The end walls facing the combustion chamber are subjected to high pressure and thermal loads. On the other hand, the end walls must provide the running surface for the rotor's side seals.

<CIT> and <CIT> disclose side housings for rotary piston machines according to the preamble of claim <NUM>.

In accordance with one aspect of the present invention, there is provided a side housing for a rotary internal combustion engine, comprising: a side wall; a side plate having a rotor-engaging side facing away from the side wall and a back side opposite the rotor-engaging side and facing the side wall, the side plate defining first threads located on the back side, the first threads extending circumferentially around a central axis of the side plate; and a nut rotatable relative to the side wall about the central axis of the side plate and axially locked to the side wall relative to the central axis, the side plate secured to the side wall via a threaded engagement between the first threads of the side plate and second threads defined by the nut.

The side housing may include any of the following features, in any combinations.

In some embodiments, the first threads are defined by a protrusion extending from a back face of the side plate.

In some embodiments, the protrusion is monolithic with a remainder of the side plate.

In some embodiments, the side wall defines a bore bounded by a bore peripheral face, an annular recess extending radially outwardly from the bore peripheral face relative to the central axis, a retaining member received within the annular recess.

In some embodiments, the nut has a peripheral flange, the peripheral flange being in axial abutment against the retaining member.

In some embodiments, the retaining member includes annular ring segments circumferentially distributed about the central axis and received within the annular recess.

In some embodiments, the nut has a web extending radially inwardly to a radially-inner edge, lugs protruding inwardly from the radially-inner edge, the lugs engageable by a tool for rotating the nut about the central axis.

In some embodiments, the web is free of contact with the back side of the side plate.

In some embodiments, the side plate is made of aluminum, the rotor-engaging side being coated with a coating, such as a hard coating (i.e. harder than aluminium), such as silicon carbide, aluminum nitride, chromium carbide, tungsten carbide.

In some embodiments, the side plate extends radially from a central hole sized for receiving a shaft of the rotary engine to a peripheral edge, the first threads located radially between the peripheral edge and the central hole.

In accordance with another aspect of the present invention, there is provided a rotary internal combustion engine comprising: a rotor; a housing circumscribing a rotor cavity, the rotor received within the rotor cavity and rotatable within the rotor cavity relative to the housing, the housing having a peripheral wall extending circumferentially about a central axis, side housings mounted to the peripheral wall, the rotor cavity extending axially between the side housings, a side housing of the side housings having: a side wall secured to the peripheral wall, a side plate having a rotor-engaging face facing the rotor cavity and in contact with the rotor, and a back face opposite the rotor-engaging face and facing the side wall, and a protrusion extending from the back face, the side plate secured to the side wall via the protrusion, the protrusion located radially inwardly of the peripheral wall, the protrusion extending circumferentially about the central axis.

The rotary internal combustion engine may include any of the following features, in any combinations.

In some embodiments, a nut is axially locked to the side wall and rotatable relative to the side wall about the central axis, the protrusion threadingly engaged to the nut.

In some embodiments, the nut is axially locked to the side wall via a retaining member.

In some embodiments, the side wall defines a bore bounded by a bore peripheral face, an annular recess extending radially outwardly from the bore peripheral face relative to the central axis, the retaining member received within the annular recess.

In some embodiments, the web is free of contact with the back face of the side plate.

In some embodiments, the side plate has a peripheral section extending circumferentially around the central axis, the peripheral section disposed axially between the side wall and the peripheral wall, an axial gap between the peripheral wall and the rotor-engaging face of the side plate at the peripheral section.

In some embodiments, the protrusion and the side plate are two parts of a single monolithic body.

Referring to <FIG>, a rotary internal combustion engine, referred to simply as a rotary engine <NUM> below, which may be a Wankel engine, is schematically shown. The rotary engine <NUM> comprises an outer body <NUM> having axially-spaced side housings <NUM>, which each includes a side wall <NUM> and a side plate <NUM> mounted to the side wall <NUM>, with a peripheral wall <NUM> extending from one of the side housings <NUM> to the other, to form a rotor cavity <NUM>. In <FIG>, the side wall <NUM> is indicated with a dashed line because it sits below the side plate <NUM>. The inner surface of the peripheral wall <NUM> of the cavity <NUM> has a profile defining two lobes, which may be an epitrochoid.

The outer body <NUM> includes a coolant circuitry 12A, which may include a plurality of coolant conduits 18B defined within the peripheral wall <NUM>. As shown more clearly in <FIG>, the coolant conduits 18B extends from one of the side housings <NUM> to the other. The coolant circuitry 12A is used for circulating a coolant, such as water or any suitable coolant, to cool the outer body <NUM> during operation of the rotary engine <NUM>. Although only two coolant conduits 18B are shown, it is understood that more than two coolant conduits 18B may be used without departing from the scope of the present disclosure.

An inner body or rotor <NUM> is received within the rotor cavity <NUM>. The rotor <NUM> has axially spaced end faces <NUM> adjacent to the side walls <NUM>, and a peripheral face <NUM> extending therebetween. The peripheral face <NUM> defines three circumferentially-spaced apex portions <NUM>, and a generally triangular profile with outwardly arched sides <NUM>. The apex portions <NUM> are in sealing engagement with the inner surface of peripheral wall <NUM> to form three rotating combustion chambers <NUM> between the rotor <NUM> and outer body <NUM>. The geometrical axis of the rotor <NUM> is offset from and parallel to the axis of the outer body <NUM>.

The combustion chambers <NUM> are sealed. In the embodiment shown, each rotor apex portion <NUM> has an apex seal <NUM> extending from one end face <NUM> to the other and biased radially outwardly against the peripheral wall <NUM>. An end seal <NUM> engages each end of each apex seal <NUM> and is biased against the respective side wall <NUM>. Each end face <NUM> of the rotor <NUM> has at least one arc-shaped face seal <NUM> running from each apex portion <NUM> to each adjacent apex portion <NUM>, adjacent to but inwardly of the rotor periphery throughout its length, in sealing engagement with the end seal <NUM> adjacent each end thereof and biased into sealing engagement with the adjacent side plates <NUM> of the side housings <NUM>. Alternate sealing arrangements are also possible.

Although not shown in the Figures, the rotor <NUM> is journaled on an eccentric portion of a shaft such that the shaft rotates the rotor <NUM> to perform orbital revolutions within the rotor cavity <NUM>. The shaft may rotate three times for each complete rotation of the rotor <NUM> as it moves around the rotor cavity <NUM>. Oil seals are provided around the eccentric to impede leakage flow of lubricating oil radially outwardly thereof between the respective rotor end face <NUM> and side housings <NUM>. During each rotation of the rotor <NUM>, each chamber <NUM> varies in volumes and moves around the rotor cavity <NUM> to undergo the four phases of intake, compression, expansion and exhaust, these phases being similar to the strokes in a reciprocating-type internal combustion engine having a four-stroke cycle.

The engine includes a primary inlet port <NUM> in communication with a source of air and an exhaust port <NUM> In the embodiment shown, the ports <NUM>, <NUM> are defined in the peripheral wall <NUM>. Alternate configurations are possible.

In a particular embodiment, fuel such as kerosene (jet fuel) or other suitable fuel is delivered into the chamber <NUM> through a fuel port (not shown) such that the chamber <NUM> is stratified with a rich fuel-air mixture near the ignition source and a leaner mixture elsewhere, and the fuel-air mixture may be ignited within the housing using any suitable ignition system known in the art (e.g. spark plug, glow plug). In a particular embodiment, the rotary engine <NUM> operates under the principle of the Miller or Atkinson cycle, with its compression ratio lower than its expansion ratio, through appropriate relative location of the primary inlet port <NUM> and exhaust port <NUM>.

Referring now to <FIG>, one of two side housings <NUM> of the outer body <NUM> is illustrated. As briefly introduced above, the side housings <NUM> include the side walls <NUM> that are secured to the peripheral wall <NUM>. Each of the side walls <NUM> has a portion located proximate an outer perimeter P (<FIG>) of the side wall <NUM> and configured to be in abutment against the peripheral wall <NUM> for defining the rotor cavity <NUM>.

In the embodiment shown, each of the side walls <NUM> is configured to be secured to a respective one of opposed ends of the peripheral wall <NUM>. The side housings <NUM> further include side plates <NUM> located on inner sides of the side walls <NUM>. The side plates <NUM> define rotor-engaging faces 16A on which the side seals <NUM> and the corner seals <NUM> of the rotor <NUM> are in abutment during rotation of the rotor <NUM>. The side plates <NUM> further define back faces opposite the rotor-engaging faces 16A. The back faces of the side plates <NUM> face the side walls <NUM>.

The side walls <NUM> may be made of aluminum, more specifically an aluminum alloy, due to its light weight and high thermal conductivity. However, it may be required that the surfaces of the side walls <NUM> in contact with the seals <NUM>, <NUM> be coated to provide a wear-resistance surface. In the embodiment shown, the side plates <NUM> are made of aluminum and coated with a hard (or harder) material such as silicon carbide, aluminum nitride, chromium carbide, tungsten carbide, and so on. Any suitable wear resistant coating applied by thermal spray or any other suitable method may be used. The side walls <NUM> and the side plates <NUM> will be described in more details below. Although the text below uses the singular form, the description may be applied to both of the side walls <NUM> and to both of the side plates <NUM>.

Referring more particularly to <FIG>, the side wall <NUM> includes a peripheral section 14A, which is in abutment with the peripheral wall <NUM>, and a center section 14B, which is circumferentially surrounded by the peripheral section 14A. In the disclosed embodiment, the peripheral section 14A of the side wall <NUM> is secured to the peripheral wall <NUM>. The center section 14B of one of the side walls <NUM> faces the center section 14B of the other of the side walls <NUM>. The side walls <NUM> are secured to the peripheral wall <NUM> with any suitable means known in the art. As shown, a sealing member <NUM> is located between the peripheral wall <NUM> and the peripheral sections 14A of the side walls <NUM> for limiting coolant from leaking out. The sealing member <NUM> may be a O-ring. The sealing member <NUM> may be received within an annular recess, which may be defined by one or more of the peripheral wall <NUM> and the side wall <NUM>.

The side wall <NUM> defines a recess 14C for receiving the side plate <NUM>. The peripheral section 14A of the side wall <NUM> extends from the outer perimeter P to the recess 14C. As shown, a surface 14D of the peripheral section 14A of the side wall <NUM> that faces the peripheral wall <NUM> is axially offset from a surface 14E of the center section 14B of the side wall <NUM>. A magnitude of the offset corresponds to a depth of the recess 14C and may correspond to a thickness t of the side plate <NUM> plus any axial gap defined between a rotor-engaging face of the side plate <NUM> and the peripheral wall <NUM>. The side plate <NUM> is therefore in abutment with the surface 14E of the center section 14B of the side wall <NUM>. In other words, a sealing surface of the side plate <NUM>, located on a side of the side plate <NUM> that faces the rotor cavity, may be aligned with the peripheral section 14A of the side wall <NUM>.

The side wall <NUM> defines an abutment surface 14F. The abutment surface 14F is defined by a shoulder created by the offset of the surfaces 14D, 14E of the peripheral and central sections 14A, 14B of the side wall <NUM>. The side wall <NUM>, via its abutment surface 14F, limits radial movements of the side plate <NUM> relative to the axis of rotation of the rotor <NUM>.

In a particular embodiment, a gap may remain between a peripheral section of the side plate <NUM> and the abutment surface 14F of the side wall <NUM>. In other words, and in the embodiment shown, the side plate <NUM> may be spaced apart from the abutment surface 14F. A size of the gap may change during operation of the rotary engine <NUM> as the side wall <NUM> and the side plate <NUM> may expand at different rates with an increase of a temperature in the rotor cavity <NUM>. In other words, the space between the side plate <NUM> and the abutment surface 14F of the side wall <NUM> may allow relative thermal expansion between the side plate <NUM> and the side wall <NUM> so that thermal stress transferred from the side plate <NUM> to the peripheral wall <NUM> and the side wall <NUM> might be minimized.

To limit axial movements of the side plate <NUM> relative to the axis of rotation of the rotor <NUM> (<FIG>), a periphery of the side plate <NUM> is contained axially between the peripheral wall <NUM> and the side wall <NUM>. In other words, the periphery of the side plate <NUM> is sandwiched between the side wall <NUM> and the peripheral wall <NUM>. A sealing member <NUM> is located at the periphery of the side plate <NUM> for limiting the combustion gases to leak out of the rotor cavity <NUM> and for limiting the cooling fluid from leaking into the combustion chamber <NUM> (<FIG>). As shown more specifically in <FIG>, the sealing member <NUM> is contained within a recess 16B defined by the side plate <NUM>. The sealing member <NUM> may be a O-ring. Any suitable sealing member may be used.

In a particular embodiment, the sealing member <NUM> and the abutment surface 14F of the side wall <NUM> allows the side plate <NUM> to move radially relative to the side wall. Such a movement, along a radial direction relative to the axis of rotation of the rotor <NUM>, may be required in a configuration in which the side wall <NUM> is made of a material having a coefficient of thermal expansion different than that of the side plate <NUM> and/or because the different components may be exposed to different temperatures and, thus may exhibit different thermal expansions.

The side wall <NUM> further defines a pocket <NUM> that may circumferentially extend a full circumference of the side wall <NUM>. In other words, the pocket <NUM> is annular. More than one pocket may be used. The pocket <NUM> may not cover an entirety of the center section 14B of the side wall <NUM>. The pocket <NUM> is configured for circulating a liquid coolant, such as water for cooling the side plate <NUM>. The pocket <NUM> may be part of the coolant circuitry 12A and is in fluid flow communication with the coolant conduits 18B that are defined in the peripheral wall <NUM>. The pocket <NUM> extends from the surface 14E of the center section 14B and away from the rotor cavity <NUM>. A depth D (<FIG>) of the pocket <NUM> is defined by a distance along the axis of rotation of the rotor <NUM> between the surface 14E of the center section 14B and a bottom surface <NUM> of the pocket <NUM>.

As shown in <FIG>, the peripheral section 14A of the side wall <NUM> defines a plurality of ribs 14I that are circumferentially distributed around the rotor cavity. The ribs 14I defines the abutment surface 14F and a portion of the surface 14E of the center section 14B of the side wall <NUM>. Consequently, and in the depicted embodiment, the abutment surface 14F is defined by a plurality of surfaces defined by the ribs 14I. The ribs 14I may be configured to support a pressure load imparted by a combustion of a mixture of air and fuel within the combustion chambers <NUM>.

Cavities or spaces 14J are defined between the ribs 14I. More specifically, each pair of two consecutive ones of the ribs 14I defines a space 14J therebetween. The spaces 14J are in fluid communication with the pocket <NUM> and with the coolant conduits 18B of the peripheral wall <NUM>. Stated otherwise, the coolant conduits 18B are in fluid communication with the pocket <NUM> via the spaces 14J between the ribs 14I. The spaces 14J may allow the liquid coolant to flow from the pocket <NUM> to the coolant conduits 18B of the peripheral wall <NUM>. It is understood that the liquid coolant may be circulated in closed loop and through a heat exchanger. The heat exchanger may be used to dissipate heat to an environment outside the engine; the heat transferred from the engine to the liquid coolant.

As shown in <FIG> and <FIG>, a flow F1 of the liquid coolant circulates within the pocket <NUM>. The flow F1 is divided in sub-flows F2; each of the sub-flows F2 circulating within a respective one of the spaces 14J and within a respective one of the coolant conduits 18B of the coolant circuitry 12A. The liquid coolant may be circulated out of the outer body <NUM> and within a heat exchanger for extracting the heat. The liquid coolant may then be reinjected in the coolant circuitry 12A for further heat extraction.

Referring now to <FIG>, another embodiment of the outer body is generally shown. For the sake of conciseness, only elements that differ from the outer body <NUM> of <FIG> are described. In the embodiment shown, the recess 118C that receives the sealing member <NUM> is defined by the peripheral wall <NUM> instead of by the side plate <NUM>.

Referring to <FIG>, as mentioned above, the side plate <NUM> may be made of aluminum and is coated with a hard (or harder) material such as silicon carbide or another suitable material such as chromium carbide. The coating of the side plate <NUM> defines the rotor-engaging face 116A on a rotor-engaging side of the side plate <NUM>. The coating may be applied with plasma spray, high velocity oxygen fuel (HVOF), or any other suitable coating technique. The rotor-engaging face 116A may be enhanced by other techniques such as electro deposited plating (e.g., nanocrystalline CoP, Nickasil) and conversion coatings (e.g., silicon saturation). In the embodiment shown, the side plate <NUM> has a flared portion 116P that flares away from an end face 118D (<FIG>) of the peripheral wall <NUM>. The flared portion 116P extends away from a plane containing a remainder of the side plate <NUM>. The flared portion 116P extends toward the side wall <NUM>. The flared portion 116P is shown as being a chamfer, but may alternatively be a roundover or any other suitable shape. A first coating <NUM> is deposited on the side plate <NUM>. The first coating <NUM> extends up to a coating edge <NUM>. The coating edge <NUM> is located on the flared portion 116P. Therefore, a gap or spacing is provided between the coating edge <NUM> and the end face 118D of the peripheral wall <NUM> such that the coating edge <NUM> is distanced from the end face 118D of the peripheral wall <NUM> by the spacing. The coating edge <NUM> is therefore free of contact with the end face 118D of the peripheral wall <NUM>. The first coating <NUM> may have a substantially uniform thickness up to the coating edge <NUM>. Or, in the alternative, the first coating <NUM> may tapers down toward the coating edge <NUM>. It may tapers down to zero in thickness. In other words, the thickness of the first coating <NUM> may decrease toward the coating edge <NUM>. The thickness may decrease below its nominal thickness where it covers the flared portion 116P. The first coating <NUM> therefore follows the shape of the flared portion 116P.

The flared portion 116P may have a first edge and a second edge located outwardly of the first edge relative to the rotation axis of the rotor <NUM>. The first edge is located inwardly of an inner face 118A (<FIG>) of the peripheral wall <NUM>. The first edge is thus overlapped by the end face 118D of the peripheral wall <NUM>. The first edge is located between the inner face 118A of the peripheral wall <NUM> and an outer face of the peripheral wall <NUM>; the outer face facing away from the rotor cavity <NUM>. Therefore, a start location of the flared portion 116P, which corresponds to the first edge, is aligned with, or is overlapped by, the peripheral wall <NUM> and may be offset from a coating deposited on the inner face 118A of the peripheral wall <NUM>. Thus, the first coating <NUM>, located on the flared portion 116P, may be free of contact with the coating <NUM> of the peripheral wall <NUM>. More detail about this coating arrangement is provided in <CIT>, the entire contents of which are incorporated herein by reference.

In the embodiment shown, the coating edge <NUM> ends at a peripheral groove <NUM>. A radial gap is therefore present between the side plate <NUM> and the abutment surface 14F of the side wall <NUM> at the peripheral groove <NUM>. The side plate outer edge geometry may alternatively include only of a simple chamfer or radius.

In some cases, the side plate may be in intimate contact with the peripheral face. Thus, when the engine stack is clamped during assembly some preload may be transferred to the coating surface. During engine operation additional loads may be imposed to the side plate and relative slip between the mating parts may occur. After some engine running time, the coating edge area on the side plate may be progressively worn by the coating on the peripheral wall. This may initiate coating cracks and eventually coating edge spalling on the side plate. Moreover, a relatively high internal oil consumption may be exhibited due to difficulty of controlling deformations of the side plate during operation. The side plate may be fixed on the side housing with several small bolts pulling near the central portion and potentially creating local depressions on the final coated surface located on the other side of the side plate, and therefore further increasing the oil consumption because of the difficulty of the rotor side sealing grid to follow this locally deformed surface closely enough to avoid oil leaks. Also, the side plate is put in sandwich between the side wall and the peripheral wall. This creates two highly loaded axial interfaces on both sides of the side plate and may present potential areas of concern for surface fretting damage. Also, on the engine level, introducing several components in the axial stack increases the variability in positioning the bearing centers. The part geometry may be complicated at least part due to cooling passages that may be machined in the side plate to allow coolant to flow from the side wall to the peripheral wall. Fitting all these features on the side plate may limit the available design space and drives thin wall thickness at many locations. These locations may become stress risers and become potential weaker point for the part resistance to fatigue damage.

Referring now to <FIG>, features of the side plate <NUM> of the present disclosure may at least partially alleviate these drawbacks. The side plate <NUM> has a rotor-engaging side that defines a rotor-engaging face 116A facing the rotor cavity <NUM> and in contact with the rotor <NUM>, and a back side that defines a back face 116B opposed to the rotor-engaging face 116A. The back face 116B faces away from the rotor cavity <NUM> and away from the rotor <NUM>. The back face 116B faces the side wall <NUM> and may be in contact with the side wall <NUM>. The back side of the side plate <NUM> defines threads. In the embodiment shown, these threads are defined by a protrusion 116C, which may also be referred to as a threaded member, that extends from the back face 116B and that extends away from the back face 116B and away from the rotor-engaging face 116A. In the present embodiment, and as will be explained later, the side plate <NUM> is secured to the side wall <NUM> via the protrusion 116C. The side plate <NUM> is non-rotatable relative to the side wall <NUM>. The protrusion 116C and the side plate <NUM> may be two parts of a single monolithic body. In other words, the protrusion 116C may monolithically protrude from the back face 116B.

Any suitable means for securing the side plate <NUM> to the side wall <NUM> is contemplated. For instance, the protrusion 116C may define one of dog(s) and slot(s) whereas the side wall <NUM> may define the other of dog(s) and slot(s). The dog(s) engageable to the slot(s) to axially lock the side plate <NUM> to the side wall <NUM>. The protrusion 116C is herein shown as being annular and extending circumferentially a full circumference. It will be appreciated that the protrusion 116C may include a plurality or protrusion sections circumferentially distributed about the rotation axis and spaced apart from one another. The protrusion 116C may be removable from the side plate <NUM>.

Referring to <FIG>, the protrusion 116C defines first threads 116D, which are herein located on a face of the protrusion 116C that faces a radially-inward direction. Herein, the first threads 116D are located on an outer face of the protrusion 116C, but other configurations are contemplated. The protrusion 116C is circular and extends circumferentially a full circumference around an axis of the rotary engine <NUM>. This axis may correspond to a rotation axis of the rotor <NUM>. In an alternate embodiment, the protrusion 116C may include a plurality of protrusion segments circumferentially distributed about the axis. The segments may be spaced apart from one another and each may define threads. The side plate <NUM> defines a central hole 116E. The central hole 116E is circumscribed by the protrusion 116C. The protrusion 116C defines an annular groove 116F (<FIG>) sized for receiving a sealing member <NUM> (<FIG>), such as an O-ring. The sealing member <NUM> is biased radially between the protrusion 116C within the annular groove 116F and a bore peripheral face <NUM> (<FIG>) that circumscribes a bore <NUM> (<FIG>) of the side wall <NUM>. The sealing member <NUM> may be alternatively an axial or corner O-ring.

Referring to <FIG>, the side housing <NUM> further includes a nut <NUM> that is used for securing the side plate <NUM> to the side wall <NUM>. The nut <NUM> includes a central section 117A that defines second threads 117B and that extends axially relative to the axis of rotation of the rotor <NUM>, a flange 117C that extends radially outwardly from a first axial end of the central section 117A, and a web 117D that extends radially inwardly from a second opposite axial end of the central section 117A. In the embodiment shown, the second threads 117B are located on a face of the central section 117A that faces a radially-outward direction. When viewed in cross-section, the nut <NUM> has a Z-shape. The second threads 117B of the nut <NUM> are threadingly engageable to the first threads 116D of the protrusion 116C of the side plate <NUM>. The nut <NUM> may be made of aluminum or any other suitable material. The second threads 117B may be UNJ type threads or any other suitable threads. Pockets may be introduced in the web 117D of the nut <NUM> for weight reduction and to allow oil to contact the back face 116B of the side plate <NUM> to contribute in providing an even temperature distribution along the side plate <NUM>. Thread locking features such as, but not limited to, Spiralock (e.g., self-locking) thread pattern, plastic insert or a pin system may be incorporated for the nut.

Referring more particularly to <FIG>, the nut <NUM> is axially locked to the side wall <NUM> and is rotatable relative to the side wall <NUM> about its central axis. The second threads 117B of the nut <NUM> are threadingly engageable to the first threads 116D of the protrusion 116C of the side plate <NUM>. Therefore, rotation of the nut <NUM> about its central axis translates in an axial movement of the side plate <NUM> along direction D1 and relative to the side wall <NUM> until the side plate <NUM> is seated in the recess 14C defined by the side all <NUM>.

As shown in <FIG>, the nut <NUM> is axially locked to the side wall <NUM> via a retaining member <NUM>. The retaining member <NUM> is received within an annular recess <NUM> that extends radially outwardly from the bore peripheral face <NUM>. Therefore, the retaining member <NUM> is blocked axially relative to the side wall <NUM> by being partially received within the annular recess <NUM>. The flange 117C of the nut <NUM> is disposed axially rearward of the retaining member <NUM>. In other words, the flange 117C and the retaining member <NUM> radially overlap one another; the retaining member <NUM> being located axially between the flange 117C and the side plate <NUM>. Axial movements of the nut <NUM> are therefore blocked by the flange 117C axially abutting against the retaining member <NUM>, which is itself blocked axially by a shoulder 14N that bounds the annular recess <NUM>; the shoulder 14N facing an axial direction relative to the axis.

In the embodiment shown, the retaining member <NUM> includes a plurality of ring segments 119A circumferentially distributed about the central axis of the side plate <NUM>. Each of the ring segments 119A may be inserted axially into the bore <NUM> of the side wall <NUM> until it becomes axially aligned with the annular recess <NUM>. Then, the ring segments 119A may be moved radially outwardly until they are inside the annular recess <NUM> and at least partially radially overlapping the shoulder 14N. A shim <NUM> may then be inserted until it axially overlaps the ring segments 119A. The shim <NUM> may have a frustoconical shape to help pushing the ring segments 119A within the annular recess <NUM>. The shim <NUM> may be fully circumferential and may be used to maintain the ring segments 119A properly seated within the annular recess <NUM>. Holes or slots may be machined in the ring segments 119A to ease manipulation. A number of the ring segments 119A may be determined to ease assembly while providing the adequate retention of the nut <NUM>. A thickness of the flange 117C is carefully designed to fit inside the side wall <NUM> and to allow enough deflection under load to keep a proper contact pattern height and to avoid or limit edge contact with the annular ring segments.

As shown in <FIG>, once the side plate <NUM> is secured to the side wall <NUM>, a first gap G1 remains between the web 117D of the nut <NUM> and the back face 116B of the side plate <NUM>. The first gap G1 extends axially between the web 117D of the nut <NUM> and the side plate <NUM>. The web 117D is therefore free of contact with the back face 116B of the side plate <NUM>. A recess may be machined in the side plate <NUM> and/or in the web 117D to avoid contact between the side plate <NUM> and the nut <NUM>. Moreover, as shown in <FIG>, a peripheral section of the side plate <NUM> is sandwiched between the side wall <NUM> and the peripheral wall <NUM>. A second axial gap G2 is disposed between the peripheral wall <NUM> and the rotor-engaging face 116A of the side plate <NUM>. Thus, the rotor-engaging face 116A of the side plate <NUM> may be free of contact with the peripheral wall <NUM>. This may limit potential damage that could be imparted to the coating of the side plate by the internal edge of the rotor housing <NUM>.

In the embodiment shown, the first threads 116D defined by the protrusion 116C are centered relative to the side plate <NUM>. The first threads 116D may extend annularly a full circumference around a central axis of the side plate <NUM>. The first threads 116D may be located radially between the central hole 116E used for receiving a shaft of the rotary engine <NUM> and a peripheral edge of the side plate <NUM>. Thus, in the present embodiment, the side plate <NUM> is secured to the side wall <NUM> via a retaining force exerted on the side plate <NUM> via the protrusion 116C and the nut <NUM>. The retaining force may be substantially uniformly distributed around a central axis of the side plate <NUM>. The retaining force may be centered relative to the side plate <NUM>. This may allow to achieve a uniform retaining force that may allow to overcome the aforementioned drawbacks (e.g., local depression in the side plate impairing sealing).

Referring now to <FIG>, the nut <NUM> is shown in greater detail. The nut <NUM> further includes lugs 117E protruding inwardly from a radially-inner edge 117F of the web 117D. The lugs 117E are engageable by a tool for rotating the nut <NUM> about its central axis. Slots <NUM> are interspaced between the lugs 117E. In an alternate embodiments, the lugs 117E may be replaced by teeth or any other suitable means for being engaged by a tool. The radially-inner edge 117F may define a polygonal shape (e.g., hexagonal) able to be engaged by a tool to transmit a torque to the nut <NUM> for securing the side plate <NUM> to the side wall <NUM>. The lugs 117E are designed to withstand the assembly tooling torque with sufficient margin while avoiding them to block the oil scavenging flow area. This is why the lugs are radially recessed inwardly from the central hole 116E (<FIG>) of the side plate <NUM>. In other words, the lugs 117E are recessed radially outwardly from the central hole 116E (<FIG>) such that the whole area of the central hole 116E is accessible to a flow of oil to reach the back face 116B of the side plate <NUM>. The lugs 117E are located to avoid being intersected by this flow of oil.

The disclosed side plate <NUM> may allow to transfer axial preload from the nut <NUM> to the side plate <NUM> via the first thread 116D machined on the protrusion 116C of the side plate <NUM>. A reaction on the face of the nut <NUM> is taken by the retaining member <NUM> engaged in the annular recess <NUM> of the side wall <NUM>. A diameter of the protrusion 116C is selected to be kept close to the surrounding annular support face on the side wall <NUM> to minimize the lever arm effect that to minimize bending of the side plate <NUM>. Stated differently, the protrusion 116C via which the side plate <NUM> is secured to the side wall <NUM> may be located to be as close as possible to where the side plate <NUM> abuts the side wall <NUM> to minimize bending of the side plate <NUM>. This may minimize the side plate bending deformation under preload. The geometry of the ring segments 119A and of the annular recess <NUM> is chosen to limit their tilting and to minimize contact stress concentration at an edge the side housing groove edge. The ring segments 119A installation may be facilitated by the shim <NUM>.

In the present embodiment, a ratio of a diameter of the protrusion 116C at the first threads 116D to the diameter the sealing member received within the annular groove 116F ranges from <NUM> to <NUM>, preferably <NUM>. A ratio of the diameter of the protrusion 116C at the first threads 116D to a diameter of the central hole 116E of the side plate <NUM> ranges from <NUM> to <NUM>, preferably <NUM>. A ratio of a diameter of the protrusion 116C at the first threads 116D to an internal diameter of the nut <NUM>, that is, at the slots <NUM>, ranges from <NUM> to <NUM>, preferably <NUM>. A ratio of a radius of the protrusion 116C at the first threads 116D to a radial distance between the central axis of the side plate <NUM> and a pressure relieve aperture <NUM> ranges from <NUM> to <NUM>, preferably <NUM>. This pressure relieve aperture <NUM> is fluidly connected to an environment outside the rotary engine <NUM> and is used to allow combustion gases accumulating between the seals <NUM> and ring seals located on the end faces <NUM> (<FIG>) of the rotor <NUM>. In other words, during operation, some combustion gases may flow past the seals <NUM> and reach a cavity defined axially between an end face <NUM> of the rotor <NUM> and a side plate <NUM>, and radially between the seals <NUM> and ring seals (not shown) located on the end face <NUM>. To avoid pressure build-up, it may be required to allow the combustion gases to flow out of this cavity. The pressure relieve aperture <NUM> is used for that purpose and allows the combustion gases to be drained to the environment outside the rotary engine <NUM>.

A ratio of a first thickness of the side plate <NUM> taken at a location radially outward of the protrusion 116C to a second thickness of the side plate <NUM> taken at a location radially inward of the protrusion 116C ranges from <NUM> to <NUM>, preferably <NUM>. A shape of the pressure relieve aperture <NUM>, which may be referred to as a blow-by hole, may have a height taken in a radial direction of <NUM> inch (<NUM>) and a width taken in a circumferential direction of <NUM> inch (<NUM>). A ratio using minimal tolerance to maximal tolerance ranges from <NUM> to <NUM>.

To assemble the side housing <NUM>, the nut <NUM> is inserted first into the bore <NUM> of the side wall <NUM>. Then, the ring segments 119A are each inserted into the annular recess <NUM>. The shim <NUM> may be used to bias the ring segments 119A into the annular recess <NUM>. This shim <NUM> may be omitted in some configurations. Then, the side plate <NUM> may be inserted. To do so, the side plate <NUM> is moved toward the bore <NUM> and the first threads 116D of the protrusion 116C are threadingly engaged with the second threads 117B by rotating the nut <NUM> about its central axis. This may be done by engaging the lugs 117E of the nut <NUM>. The nut <NUM> is thus rotated. This translates into a movement of the side plate <NUM> along the direction D1 until the side plate <NUM> is properly seated within the side wall <NUM>. In some other embodiments, self-locking thread pattern, plastic insert, or a pin system may be incorporated in the nut <NUM>.

Referring now to <FIG>, in accordance with another embodiment a side housing <NUM>, the retaining member <NUM> may be a retaining ring <NUM> (e.g., circlip). This retaining ring <NUM> may be deformed radially and inserted axially until it registers with the annular recess <NUM>. The retaining ring <NUM> may then be allowed to expand radially to sit inside the annular recess <NUM> to thereby axially lock the nut <NUM> via the flange 117C. Understandably, the nut <NUM> is inserted first then the retaining ring <NUM> is installed in the position depicted in <FIG>. In such a configuration, the shim may be omitted. In some embodiments, two or more retaining rings <NUM> may be axially stacked upon one another.

Referring now to <FIG>, in accordance with another embodiment of a side housing <NUM>, the nut <NUM> has longer lugs 217E that extends radially inwardly beyond the central hole 116E of the side plate <NUM>. This may allow a tool to have direct access to the nut <NUM> for rotating the nut <NUM> to thereby threadingly engage the nut <NUM> to the protrusion 116C of the side plate <NUM>.

Referring now to <FIG>, the rotor-engaging face 116A may require to be ground to obtain a suitable surface finish for mating with the rotor seals and have an acceptable wear life. This grinding step may however induce deformation in the side plate <NUM>, which may in turn create areas of non-uniform coating thickness. Thus, deformation of the side plate <NUM> during the coating process may be managed by carefully designing the clamping fixture of the side plate during a grinding operation. This may allow to obtain a final coating having a substantially uniform thickness.

In the embodiment shown, the side plate <NUM> may be supported at the back face 116B both radially inwardly of the protrusion 116C and radially outwardly of the protrusion 116C. To do so, a first support S1 and a second support S2 may be used. The first support S1 may abut the back face 116B of the side plate <NUM> at a location radially outward of the protrusion 116C whereas the second support S2 may abut the back face 116B of the side plate <NUM> at a location radially inward of the protrusion 116C. The first and second supports S1, S2 may define annular abutting faces that may extend a full circumference. These annular abutting faces may abut the back face 116B of the side plate <NUM>. The first and second supports S1, S2 may be parts of a single support to allow the machining of the two supporting planes on the same machine and with the same setup. This may maximize the accuracy of their height difference. Stated differently, when designing the grinding fixture that provides the supports S1 and S2 within a single monolithic piece of material, it is possible to finish the two surfaces contacting the back side of the side plate <NUM> at the same time. These two surfaces are located at two different axial locations (height difference) and are radially offset from one another: one radially inwardly of the protrusion 116C and the other radially outwardly of the protrusion 116C. If the first and second supports S1 and S2 are made of two different parts, they will have to be part of an assembly. This may induce accuracy issues in the height difference of these two surfaces. Ideally, the supports S1 and S2 would contact the back of the side plate <NUM> simultaneously. In reality, manufacturing errors may cause the side plate back face to contact one of them first.

This technique may ensure a relatively flat (e.g., <NUM>-<NUM> inch (<NUM>-<NUM>)) rotor-engaging face 116A at the grinding stage with minimal clamping load (e.g., few hundred pounds of force). The clamping load at this stage may be minimized since it may result in top surface post-grinding deformations when releasing the clamping load. A support nut S3 may be used to apply the clamping on the first and second supports S1, S2. The second support S2 may define external threads to mate with the threads of the protrusion 116C.

The disclosed side housing <NUM> including the nut <NUM> and the side plate <NUM> may provide a uniform clamping force on the side plate <NUM>. The disclosed side housing <NUM> may improve rotor sealing, robustness, and durability of the coating. The coated surface of the side plate <NUM> may remain non-deformed when the engine tie bolts are preloaded to clamp the peripheral wall <NUM> to the side walls <NUM> because of the second gap G2 (<FIG>) defined between the side plate <NUM> and the peripheral wall <NUM>. It may simplify the design of the outer body <NUM> of the rotary engine <NUM>, may be easier to machine, to coat, and to grind. The back face 116B of the side plate <NUM>, by being flat, may enhance the possibility to grit blast the side plate <NUM> on both sides before coating. It may permit control and minimize initial side plate bent shape that may occur when coating a relatively thin plate on one side only. The grit blasting described above may be beneficial to the side plate back face since it may: increase surface roughness to minimize relative slip and surface fretting/wear damage at contacts with the side housing <NUM>. It may enhance heat transfer with coolant, and may reduce compressive residual stresses that may increase the plate surface resistance to fretting and fatigue, etc..

The disclosed design of the side plate <NUM> may allow quick and easy strip and recoat operations by allowing to remove the coating over the full surface, such as with any basic surface grinder, instead of a precise contouring. This may avoid the need to re-machine the surrounding lip. This may be particularly useful for restoring the side plate surface at engine overhaul. The disclosed design may eliminate the risk of aluminum lip fretting and wear since there is no more lip on the rotor side of the side plate <NUM>. This is possible by sandwiching the peripheral section of the side plate <NUM> between the peripheral wall <NUM> and the side wall <NUM>. The proposed design may increase durability of the outer body <NUM> without compromising engine cooling efficiency. This may be possible by providing the space gained by removing the lip at the outer edge of the side plate <NUM> with the flared portion 116P (<FIG>). As discussed above, the flared portion 116P may avoid having the rotor housing edge contacting the peripheral wall <NUM> too close to the coating edge. This may eliminate the coating edge spalling risk. The disclosed design may ease the initial coating grinding operation by eliminating the protruding coating "ridge" built on the top of the surrounding aluminum lip, which may force additional grinding passes. The grinding operation may produce a smoother and uniform side plate surface that may promote proper rotor side seals contact and may therefore significantly lower the engine internal oil consumption.

Claim 1:
A side housing (<NUM>;<NUM>;<NUM>) for a rotary internal combustion engine (<NUM>), comprising:
a side wall (<NUM>);
a side plate (<NUM>;<NUM>) having a rotor-engaging side (16A; 116A) facing away from the side wall (<NUM>) and a back side (116B) opposite the rotor-engaging side and facing the side wall (<NUM>), characterised by
the side plate (<NUM>;<NUM>) defining first threads (116D) located on the back side (116B), the first threads (116D) extending circumferentially around a central axis of the side plate (<NUM>;<NUM>); and
a nut (<NUM>;<NUM>) rotatable relative to the side wall (<NUM>) about the central axis of the side plate (<NUM>;<NUM>) and axially locked to the side wall (<NUM>) relative to the central axis, the side plate (<NUM>;<NUM>) secured to the side wall (<NUM>) via a threaded engagement between the first threads (116D) of the side plate (<NUM>;<NUM>) and second threads (117B) defined by the nut (<NUM>;<NUM>).