HK1230690B - Rotary engine rotor - Google Patents

Description

Rotating engine rotor

Technical Field

The present invention relates to a rotary engine rotor, and in particular, but not exclusively, to a Wankel engine rotor.

Background Art

Rotary internal combustion engines are commonly used to power automobiles, aircraft, boats, stationary engines and compressors.A rotary internal combustion engine comprises a rotating piston or rotor rotatably mounted within a cavity in a housing or stator.

A Wankel engine is a specific form of rotary internal combustion engine in which the stator comprises a two-lobed, outwardly extending rotating bore and end plates located at opposite longitudinal ends of the bore, defining a cavity therein. The walls of the cavity are provided with inlet and exhaust ports for air and exhaust gases, respectively. The rotor of a Wankel engine comprises three rotor perimeters having a generally equilateral triangular cross-sectional shape with outwardly curved sides.

The rotor is mounted on an eccentric journal on the main shaft and is geared to rotate in a planetary manner within a cavity at one-third of the main shaft's rotation. The rotor's gearing is typically provided by an insert housed within a positioning hole provided in the inner surface of the main body. The insert includes a bearing portion and an indexing gear, which is configured to engage with a fixed gear carried by one of the engine's end plates. The engagement of the indexing gear with the fixed gear constrains the rotor's rotation to one-third of the main shaft. The insert needs to be securely fixed to the main body of the rotor to prevent rotational or axial movement of the insert relative to the rotor body.

Vertex seals are positioned at each of the rotor's three vertices, configured to engage the inner wall of the outer rotating aperture. As the rotor rotates relative to the stator, the vertex seals displace relative to the inner wall of the outer rotating aperture, but maintain sealing engagement with it throughout the rotor's rotational cycle. The rotor thus divides the cavity into multiple working chambers, which vary in volume and position as the rotor rotates relative to the stator.

The shape of the outer surface of each rotor perimeter has historically been selected to maximize the engine's compression ratio. This results in an outwardly curving, arcuate perimeter that is symmetrical about an axial plane perpendicularly bisecting the perimeter. It is also known to form a shallow, dished recess substantially centrally within the perimeter, with the base of the recess curving inward at its leading and trailing edges. Similar to the arcuate perimeter, the shape, size, and location of these recesses are typically selected to maximize the engine's compression ratio.

Summary of the Invention

According to the present invention there is provided a rotary engine rotor as described in the accompanying claims.

According to the present invention, viewed from a first aspect, there is provided a rotary engine rotor comprising three rotor peripheries arranged in a generally equilateral triangle shape, each rotor periphery having a leading edge and a trailing edge, the leading edge of at least one of the rotor peripheries comprising an elongated lip extending the entire axial length of the rotor periphery.

Applicants have discovered that rotors according to the present invention improve engine performance, for example by providing increased power and reducing temperatures. This performance improvement can be attributed to increased efficiency in converting the expansion of combustion gases into torque. This mechanism of improved engine performance is contrary to established design practice in the industry, where any improvement in engine performance is typically achieved by improving the engine's compression ratio.

Preferably, said at least one rotor periphery comprises a generally outwardly curved profile from said lip to a trailing edge of said rotor periphery.

The lip preferably includes a front surface and a rear surface. The front surface preferably points outward relative to the circumferential center of the rotor periphery, which is defined as a circumferential position equidistant between the front and rear surfaces of the rotor periphery. The rear surface preferably points inward toward the circumferential center of the rotor periphery. Since the lip is located at the leading edge of the rotor periphery, pointing the rear surface of the lip inward toward the circumferential center of the rotor periphery ensures that the normal of the surface of the rear lip points in a direction circumferentially opposite to the direction of rotation of the rotor, thereby providing efficient conversion of the expanding gas pressure into torque on the rotor.

The front surface of the lip is preferably curved radially outwards.The radius of curvature of the front surface of the lip is preferably substantially equal to the radius of curvature of at least one rotor periphery near its trailing edge.

The rear surface of the lip may be curved radially inwards. Preferably, the radius of curvature of the rear surface of the lip is substantially smaller than the radius of curvature of the front surface of the lip and/or the radius of curvature of at least one rotor periphery near its rear edge. The radius of curvature of the rear surface of the lip is preferably between 0.2 and 9.0 mm, preferably between 1.0 and 8.0 mm, preferably between 2.0 and 7.0 mm, or preferably between 3.0 and 6.0 mm. Surface elements of the rear surface of the lip adjacent to its front surface preferably include a normal in a direction substantially opposite to the direction of rotation of the rotor. Surface elements of the rear surface of the lip remote from its front surface preferably include a normal pointing substantially radially, i.e. substantially perpendicular to the direction of rotation of the rotor. Alternatively, the rear surface of the lip may have a stepped profile. Preferably, the stepped profile may include steps.

The curvature of the rear surface of the lip between two of the aforementioned surface elements is preferably substantially uniform. Alternatively, the curvature of the rear surface of the lip between two of the aforementioned surface elements preferably increases with increasing distance from the front surface of the lip.

Alternatively, the rear surface of the lip may be substantially planar.The normal to the rear surface of the lip is preferably directed substantially opposite to the direction of rotation of the rotor.

The rotor preferably includes a central bore for receiving the stator shaft. The central bore preferably has a ring gear disposed on its inner surface, and the stator shaft preferably includes a pinion gear. The ring gear preferably has a radius greater than a radius of the pinion gear, such that the ring gear is configured for eccentric movement about the pinion gear.

Preferably, the radial extent of the leading edge of at least one rotor periphery relative to the central bore of the rotor is substantially equal to the radial extent of the trailing edge of at least one rotor periphery. Thus, the lip in this embodiment is defined in part by a recess formed in the outer surface of the rotor periphery and extending the entire axial length of the rotor periphery. It will be appreciated that in this embodiment, the leading surface of the recess is equivalent to the trailing surface of the lip.

The cross-section of the lip is preferably substantially uniform.

The longitudinal axis of the lip is preferably substantially parallel to the axial direction of the rotor.The lip preferably extends over less than 30% of the circumferential length of the rotor periphery, more preferably less than 10% of the circumferential length of the rotor periphery.

Preferably, each rotor periphery includes a lip as described above.

Preferably, the rotor is a Wankel engine rotor.

According to the present invention, viewed from a second aspect, there is provided a rotary engine rotor comprising three rotor peripheries arranged in a generally equilateral triangle shape, each rotor periphery having a leading edge and a trailing edge, at least one rotor periphery comprising a cavity having a leading edge and a trailing edge, wherein at least a portion of the base of the cavity proximate its trailing edge is curved outwardly.

The applicant has found that the rotor according to the second embodiment of the present invention improves the performance of the engine in which the rotor is installed, for example by providing increased power and reduced temperature. This performance improvement is attributable to the increased efficiency of converting the expansion of combustion gases into torque.

The radius of curvature of the base of the cavity near its trailing edge is preferably between 100 mm and 170 mm, more preferably about 150 mm.

The base preferably blends into the rotor periphery at the trailing edge of the cavity.Preferably, there is a tangential blend between the base and the trailing edge of the cavity.

A portion of the base proximate the leading edge of the cavity may be substantially planar.

Alternatively, a portion of the base near the leading edge of the cavity may be curved radially inwardly. In this embodiment, the radius of curvature of the base near the leading edge of the cavity is preferably substantially smaller than the radius of curvature of the base near the trailing edge of the cavity.

In another alternative embodiment, a portion of the base near the leading edge of the cavity may be curved radially outward about a center of curvature displaced from the center of curvature of a portion of the base near the trailing edge of the cavity to define a longitudinal valley bounded by the convex sidewalls.

The cavity preferably extends over between 80% and 95% of the axial length of the rotor circumference and is preferably located substantially axially centrally.

At least one of the rotor peripheries may include a secondary cavity having a first portion formed in a base of the first cavity and a second portion formed in the rotor periphery.

Preferably, each rotor periphery includes a cavity as described above.

Preferably, the rotor is a Wankel engine rotor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a perspective view of a rotating engine rotor according to an embodiment of the present invention;

FIG2 is a cross-sectional view through the rotating engine rotor shown in FIG1;

3 is a cross-sectional view through a rotary engine rotor according to a second embodiment of the present invention;

FIG4 is a perspective view of a rotary engine rotor according to a third embodiment of the present invention; and

FIG5 is a perspective view of a rotary engine rotor according to a fourth embodiment of the present invention.

DETAILED DESCRIPTION

1 and 2 of the drawings, there is shown a rotary engine rotor 10 according to a first embodiment of the present invention.

The rotor 10 comprises a body 11 formed by three rotor peripheries 12 arranged in a substantially equilateral triangle shape.

The rotor body 11 may include or consist of cast iron, aluminum, aluminum alloy, titanium nickel, cobalt or cobalt alloy. Preferably, the rotor body 11 is composed of cast iron.

The rotor body 11 may be formed by casting, machining from a billet, sintering or additive manufacturing. Additive manufacturing includes three-dimensional printing. Preferably, the rotor body 11 is formed from iron as a single-piece casting.

Each rotor periphery 12 comprises a radially outwardly directed outer surface 13, a radially inwardly directed inner surface 14 and generally axially directed first and second side surfaces 15. Each rotor periphery 12 comprises a leading edge 16 and a trailing edge 17 defined relative to the direction of rotation of the rotor peripheries 12 (only the uppermost rotor periphery 12 is marked in FIG. 1 ).

A recess 18 is formed in the outer surface 13 of each rotor periphery 12. Recess 18 extends from the trailing edge 17 of the corresponding rotor periphery 12 over approximately 95% of the circumferential length of the corresponding rotor periphery 12. It is also contemplated that each rotor periphery 12 may include a recess 18. Recess 18 includes a front surface 19 and a rear surface 20 defined relative to the direction of rotation of the rotor periphery 12. The front surface 19 of the recess 18 is inwardly curved, preferably having a radius of curvature between 0.2 and 9.0 mm, preferably between 1.0 and 8.0 mm, preferably between 2.0 and 7.0 mm, or preferably between 3.0 and 6.0 mm. The rear surface 20 of the recess 18 is outwardly curved, having a radius of curvature that is orders of magnitude greater than the radius of curvature of the front surface 19, for example, approximately 150 mm. However, the radius of curvature may vary circumferentially about the corresponding rotor periphery 12. In particular, the radius of curvature may increase toward the trailing edge 17 of the corresponding rotor periphery 12. In the illustrated embodiment, the inwardly curved front surface 19 merges into the outwardly curved rear surface 20, such that both can be considered a single surface having a varying circumferentially varying curvature. Axially, the recess 18 extends the entire axial length of the respective rotor periphery 12. Thus, an elongated lip 21 is defined at the leading edge 16 of the respective rotor periphery 12, extending the entire axial length of the respective rotor periphery 12. It is also contemplated that each rotor periphery 12 may include a lip 21. The longitudinal axis of the lip 21 is substantially parallel to the axial direction of the rotor periphery 12, and the cross-section of the lip 21 relative to this axis is substantially uniform across the entire length of the lip 21. It is also contemplated that the lip 21 may have a form in which the normal to the rear surface of the lip is oriented substantially opposite to the direction of rotation of the rotor.

The lip 21 includes a front surface 22 and a rear surface 23 defined relative to the direction of rotation of the rotor periphery 12. The front surface 22 of the lip 21 is outwardly curved, with a radius of curvature substantially equal to the radius of curvature of the rear surface 20 of the recess 18. The rear surface 23 of the lip 21 is provided by the front surface 19 of the recess 18 and is therefore inwardly curved. The center of curvature of the rear surface 23 of the lip 21 is located inboard of the surface 23 relative to the circumferential midpoint of the rotor periphery 12. Therefore, the circumferential vector component of the normal to the rear surface 23 of the lip 21 points in a direction opposite to the direction of rotation of the rotor 10. The precise direction of the normal to the rear surface 23 of the lip 21 depends on the surface elements of the surface 23 that take into account the inwardly curved profile of the surface; surface elements located proximal to the front surface 22 of the lip 21 have larger circumferential vector components than surface elements located distal to the front surface 22 of the lip 21.

The inner surface 14 of each rotor periphery 12 includes a locating portion 24 located at the midpoint of the periphery 12, the locating portions 24 together partially defining a locating aperture 25. The inner surface 14 of each periphery 12 also includes a cooling channel portion 26 located at each end of the periphery 12. The cooling channel portions 26 together define three cooling channels 27 that extend axially through the rotor 10 in the region of each vertex of the rotor 10. Each respective cooling channel 27 is partially cylindrical and is provided with cooling fins 28 arranged to increase the surface area of the cooling channel 27. In an alternative embodiment (not shown) in which the rotor is not air-cooled, the air cooling channels 27 and other corresponding features are absent.

The side surface 15 of each rotor periphery 12 is provided with a respective sealing strip receptacle arranged to receive a respective side sealing strip 29. Additional sealing strip receptacles 30 are provided at the apex of each rotor periphery 12, these strip receptacles 30 being arranged to receive a respective axial sealing strip (not shown).

Insert 31 is positioned in locating hole 25 and coupled to rotor periphery 12 via retaining pins (not shown) extending through corresponding retaining sockets (not shown) formed in rotor periphery 12 and insert 31. Insert 31 is formed as a forging of a suitable bearing steel or is forged from a bar of bearing steel. Insert 31 circumferentially encloses cooling passages 27 defined in inner surface 14 of rotor periphery 12 to define cooling ducts 32 extending the entire axial length of rotor 10. Cooling ducts 34 allow air to flow through rotor 10, thereby providing engine cooling.

Insert 31 includes a bearing portion 33 and an indexing gear. The indexing gear includes a machined ring gear 34 arranged to eccentrically rotate around a central pinion (not shown) of a stator (not shown). The axial length of ring gear 34 is less than the entire axial length of rotor body 11, and ring gear 34 is arranged at one axial end of rotor 10.

The rotor 10 is mounted in a cavity (not shown) in a stator (not shown) on an eccentric journal of a main shaft (not shown). The cavity is defined by a two-lobed outboard rotating bore closed at each end by an end plate (not shown). The ring gear 25 is arranged to engage with a fixed pinion (not shown) in a planetary manner, with the rotor 10 rotating at one-third of the rotation of the main shaft. The rotor 10 and the walls of the cavity are shaped so that a working chamber is formed when the rotor 10 rotates, and the walls of the cavity are also provided with inlets and exhaust ports (not shown) for air and exhaust gases, respectively. In use, each side sealing strip 29 forms a seal between the side 14 of the rotor body 11 and the wall of the cavity provided by the stator (not shown). Similarly, each axial sealing strip 29 forms a seal between the corresponding vertex of the rotor periphery 12 and the wall of the cavity to divide the cavity into a plurality of working chambers.

In a given working chamber, the expansion of the gas contained therein exerts a force on the outer surface 13 of the corresponding rotor periphery 12. The expanding gas pressure is converted into torque over the circumferential length of the rotor periphery 12. However, due to the orientation of the vector surface of the lip's rear surface 23, the efficiency of this conversion of the expanding gas pressure into torque is much greater at the lip's rear surface 23 than over the remainder of the rotor periphery 12's outer surface 13. Thus, the lip 21 provides a substantial contribution to the overall efficiency of the conversion of the expanding gas pressure into torque without substantially compromising the engine's compression ratio.

A second embodiment of the invention is shown in Figure 3. The rotor 110 of this embodiment is similar to the rotor 10 of the first embodiment with the following modifications. The same reference numerals are used for corresponding features.

In this embodiment, the front surface 19 of the recess 18 and, consequently, the rear surface 23 of the lip 21 are substantially planar, as opposed to being inwardly curved. The normals to the surfaces 19, 23 are directed substantially opposite to the direction of rotation of the rotor 10. Thus, the surfaces 19, 23 are optimally oriented for converting the expansion of the combustion gases into torque.

In an alternative embodiment (not shown), the direction of the normal to surfaces 19, 23 may not be substantially opposite to the direction of rotation of rotor 10: lip 21 will provide an increase in the efficiency of converting the expansion gas pressure into torque, assuming the circumferential component of the normal to surfaces 19, 23 is opposite to the direction of rotation of rotor 10. However, this alternative embodiment will not provide the same increase in the efficiency of converting the expansion gas pressure into torque as the embodiment shown in FIG3 .

A third embodiment of the invention is shown in Figure 4. The rotor 210 of this embodiment is similar to the rotor 10 of the first and second embodiments with the following modifications. The same reference numerals are used for corresponding features.

In this embodiment, the recess 18 extends approximately 75% of the circumferential length of the respective rotor periphery 12. The recess 18 is positioned toward the leading edge 16 of the rotor periphery, but is spaced therefrom such that the recess 18 is defined at the leading edge 16 of the rotor periphery.

The recess 18 formed in the outer surface 13 of each rotor periphery 12 does not extend the entire axial length of the corresponding rotor periphery 12. Instead, the recess 18 extends approximately 90% of the axial length of the rotor periphery and is axially centrally located. Unlike the embodiment shown in Figures 1 to 3, the outer surface 13 of each rotor periphery 12 therefore does not include a lip. Furthermore, unlike the embodiment shown in Figures 1 to 3, the recess is therefore completely defined at its axial and circumferential edges and thus defines a cavity having a base and sidewalls 35.

The side wall 35 is substantially planar, with the normal to the side wall 35 being in the axial direction. In an alternative embodiment (not shown), the side wall has a radius of curvature preferably between 0.2 and 9.0 mm.

Similar to the embodiment shown in Figures 1 and 2, the base of recess 18 includes a front surface 19 and a rear surface 20 defined relative to the direction of rotation of rotor periphery 12. Front surface 19 of recess 18 is inwardly curved, including a radius of curvature between 0.2 and 9.0 mm, preferably between 1.0 and 8.0 mm, preferably between 2.0 and 7.0 mm, or preferably between 3.0 and 6.0 mm. Rear surface 20 of recess is outwardly curved, including a radius of curvature that is orders of magnitude greater than that of front surface 19, for example, approximately 150 mm. However, the radius of curvature may vary circumferentially about the corresponding rotor periphery 12. In particular, the radius of curvature may increase toward the trailing edge 17 of the corresponding rotor periphery 12. In the illustrated embodiment, the inwardly curved front surface 19 blends into the outwardly curved rear surface 20, such that both can be considered a single surface having a varying, circumferentially varying curvature. Furthermore, the rear surface 20 of the base of the recess 18 merges into the outer surface 13 of the rotor periphery 12 at the trailing edge of the recess 18 .

A fourth embodiment of the invention is shown in Figure 5. The rotor 310 of this embodiment is similar to the rotor 210 of the third embodiment with the following modifications. Like reference numerals are used for corresponding features.

In this embodiment, the recess 18 provided in the outer surface 13 of the rotor periphery 12 is substantially the same as the recess 18 of the embodiment shown in FIG4 , except that a secondary cavity 36 is provided in each rotor periphery 12. The secondary cavity 36 includes a first portion 37 having a generally rounded rectangular shape and a second portion 38 having a shape similar to the blade of a shovel. The first portion 37 spans the base of the recess 18 and the rotor periphery 12, while the second portion is formed only in the rotor periphery 12.

In an alternative embodiment (not shown), the rotor periphery 12 shown in FIG. 1 may also have a secondary cavity 36 as described in the fourth embodiment.

In another alternative embodiment (not shown), the front surface of the recess may be substantially planar, for example the recess may have a cross-section similar to the cross-section of recess 18 shown in FIG. 3 .

Claims (19)

1. A rotary engine rotor comprising three rotor peripheries arranged in a generally equilateral triangular shape, each rotor periphery having a leading edge and a trailing edge. Wherein, at least one of the rotor peripheries includes an elongated lip extending the entire axial length of the rotor periphery, characterized in that... The at least one rotor periphery includes a generally outwardly curved profile from the lip to the trailing edge of the rotor periphery. 2. The rotary engine rotor according to claim 1, wherein the lip includes a front surface and a rear surface. 3. The rotary engine rotor according to claim 2, wherein the front surface of the lip points outward relative to the circumferential center of the rotor. 4. The rotary engine rotor according to claim 2, wherein the rear surface of the lip points inward toward the circumferential center of the rotor. 5. The rotary engine rotor according to any one of claims 2 to 4, wherein the front surface of the lip is curved outward. 6. The rotary engine rotor of claim 5, wherein the radius of curvature of the front surface of the lip is substantially equal to the radius of curvature of the at least one rotor periphery near its trailing edge. 7. The rotary engine rotor according to claim 2, wherein the rear surface of the lip is radially inwardly curved. 8. The rotary engine rotor according to claim 2, wherein the rear surface of the lip is substantially planar. 9. The rotary engine rotor according to claim 2, wherein the rear surface of the lip has a stepped profile. 10. The rotary engine rotor according to claim 1, wherein the lip extends from the leading edge of the rotor periphery by less than 30% of the circumference of the rotor periphery. 11. The rotary engine rotor according to claim 1, wherein the at least one rotor periphery includes a recess formed in an outer surface, the recess including a leading edge and a trailing edge and extending axially through the entire length of the rotor periphery, the lip being defined between the leading edge of the rotor periphery and the leading edge of the recess. 12. A rotary engine rotor comprising three rotor peripheries arranged in a generally equilateral triangular shape, each rotor periphery having a leading edge and a trailing edge, at least one rotor periphery including a cavity having a leading edge and a trailing edge, at least a portion of the base of said cavity near its trailing edge being outwardly curved, characterized in that... The cavity is partially located in a recess extending from the leading edge of the rotor's periphery. 13. The rotary engine rotor according to claim 12, wherein the radius of curvature of the base of the cavity near its trailing edge is between 100 mm and 170 mm. 14. The rotary engine rotor of claim 12, wherein the base is fused into the rotor periphery at the trailing edge of the cavity. 15. The rotary engine rotor according to any one of claims 12 to 14, wherein a portion of the base near the leading edge of the cavity is substantially planar. 16. The rotary engine rotor of claim 12, wherein a portion of the base near the leading edge of the cavity is radially inwardly bent. 17. The rotary engine rotor of claim 16, wherein the radius of curvature of the base near the trailing edge of the cavity is substantially greater than the radius of curvature of the base near the leading edge of the cavity. 18. The rotary engine rotor of claim 12, wherein the cavity extends between 80% and 95% of the axial length of the rotor periphery and is substantially axially centered. 19. The rotary engine rotor of claim 12, wherein the at least one rotor periphery includes a secondary cavity having a first portion formed in a base of a first cavity and a second portion formed in the rotor periphery.