GB2388405A

GB2388405A - Counterbalanced rotor seal

Info

Publication number: GB2388405A
Application number: GB0203960A
Authority: GB
Inventors: James Black
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-02-20
Filing date: 2002-02-20
Publication date: 2003-11-12
Also published as: GB0203960D0

Abstract

A sealing device 40 for a rotor 20 of a rotary engine having a centre of rotation and a peripheral surface. The sealing device 40 comprises at least one sealing member 46 provided at the peripheral surface, and a seal retraction means adapted to urge each sealing member 46 substantially towards the centre of rotation when the rotor (20, Fig 1) is rotating, counteracting the tendency of the seal 46 to move outwards due to the centrifugal force generated when the rotor (20, Fig 1) is rotating. Also disclosed is an engine speed limiting device that operates by allowing the passage of fuel between the seal 46 and the housing 12 while the seal 46 is being urged towards the centre of rotation.

Description

1 2388405

1 Counterbalanced Rotor Seal 3 The present invention relates to a seal for a 4 rotating member. In particular, but not 5 exclusively, the invention relates to a 6 counterbalanced seal for a rotor of a rotary engine.

8 An alternative to the piston and cylinder internal 9 combustion engine is the rotary engine. This type 10 of engine utilises a triangular rotor contained 11 within a housing. The rotor is mounted on a 12 stationary gear connected to the housing, and also 13 the eccentric lobe of an output shaft. The 14 stationary gear causes the rotor to orbit the 15 stationary gear as it rotates. The housing for the 16 rotor is epitrochoidal in shape and so the apices of 17 the rotor remain in contact with the housing as the 18 rotor rotates. The four strokes of combustion all 19 take place in the chambers defined by the inner 20 surface of the housing and the side faces of the 21 rotor.

1 It is necessary for the apices of the rotor to 2 remain in contact with the housing as the rotor 3 rotates. For instance, should contact be lost at 4 either apex associated with the chamber in which the 5 air and fuel mixture is compressed, the mixture can 6 escape from the chamber and this causes inefficient 7 combustion. Seals such as metal blades are often 8 provided at the apices of the rotor. To accommodate 9 any small errors in alignment, the seals are often 10 sprung to provide a biasing force that maintains the 11 contact between the seals and the housing.

13 The seals can be subject to substantial wear, -

14 particularly at higher engine speeds. Rotation of 15 the rotor generates a centrifugal force acting on 16 the seal and spring that is a function of the speed 17 of the engine. The centrifugal force causes -

18 extension of the spring and the contact force 19 between the seal and housing is increased. At a 20 sufficient magnitude, this contact force can cause 3 21 degradation and damage to the seal.

23 According to a first aspect of the present 24 invention, there is provided a sealing device for a 25 rotor having a centre of rotation and a peripheral 26 surface, the sealing device comprising: 27 at least one sealing member provided at the a 28 peripheral surface; and 29 seal retraction means adapted to urge the or 30 each sealing member substantially towards the centre 31 of rotation when the rotor is rotating.

1 Preferably the seal retraction means is operated by 2 the centrifugal force generated from rotation of the 3 rotor.

5 Preferably the sealing device further comprises 6 biasing means to urge the sealing member away from 7 the centre of rotation of the rotor. Preferably the 8 biasing means is connected to the rotor and the 9 sealing member is connected to the biasing means.

10 Preferably the biasing means comprises a spring.

12 Preferably the seal retraction means comprises at 13 least one retractor that is rotatably supported 14 about an axis of rotation relative to the rotor.

15 Preferably the or each retractor has an asymmetrical 16 distribution of mass with respect to its axis of 17 rotation. Preferably the axis of rotation and the 18 centre of mass of the or each retractor are offset 19 such that the centrifugal force causes the or each 20 retractor to rotate relative to the rotor.

21 Preferably the or each retractor co-operates with 22 the or each sealing member such that the or each 23 sealing member is urged substantially towards the 24 centre of rotation as the centrifugal force causes 25 the or each retractor to rotate relative to the 26 rotor.

28 Preferably the rotor comprises at least one aperture 29 and the or each retractor is rotatably mounted in 30 the or each aperture. ?eerably the or each 31 retractor is substantially cylindrical and has a 32 cut- out. Preferably the cut-out is a volume defined

( 1 by one quadrant of the circular face of the cylinder 2 through the depth of the cylinder.

4 Preferably the or each sealing member comprises a 5 flange portion and the or each retractor applies a 6 retracting force to the flange to urge the or each 7 sealing member substantially towards the centre of 8 rotation. Preferably a face of the retractor 9 defined by the cut-out acts upon the flange.

11 Preferably the rotor is a rotor of a rotary engine.

12 Preferably the rotor is substantially triangular.

13 Preferably a sealing member is provided at each apex 14 of the rotor.

16 Preferably the rotor rotates within a housing.

17 Preferably the sealing member seals the rotor within 18 the housing.

20 The force applied by the biasing means may be 21 greater than the retracting force. Alternatively 22 the retracting force is greater than the force 23 applied by the biasing means at relatively high 24 speeds of rotation of the rotor.

26 According to a second aspect of the present 27 invention, there is provided a rotor having a centre 28 of rotation and a peripheral surface, the rotor 29 comprising: 30 a sealing device comprising at least one 31 sealing member provided at the peripheral surface 32 and seal retraction means adapted to urge the or

1 each sealing member substantially towards the centre 2 of rotation when the rotor is rotating.

4 Preferably the seal retraction means is operated by 5 the centrifugal force generated from rotation of the 6 rotor.

8 Preferably the sealing device further comprises g biasing means to urge the sealing member away from 10 the centre of rotation of the rotor.

28 Preferably the rotor comprises at least one aperture 29 and the or each retractor is rotatably mounted in 30 the or each aperture. Preferably the or each 31 retractor is substantially cylindrical and has a 32 cut-out. Preferably the cut-out is volume defined

1 by one quadrant of the circular face of the cylinder 2 through the depth of the cylinder.

4 Preferably the rotor is a rotor of a rotary engine.

5 Preferably the rotor is substantially triangular.

6 Preferably a sealing member is provided at each apex 7 of the rotor.

9 Preferably the rotor rotates within a housing.

10 Preferably the sealing member seals the rotor within 11 the housing. -

13 Preferably the or each retractor applies a 14 retracting force to the or each sealing member to 15 urge the or each sealing member substantially 16 towards the centre of rotation. The force applied 17 by the biasing means may be greater than the 18 retracting force. Alternatively the retracting 19 force is greater than the force applied by the 20 biasing means at relatively high speeds of rotation 21 of the rotor.

23 According to a third aspect of the present 24 invention, there is provided an engine comprising: 25 a rotor having a centre of rotation and a 26 peripheral surface; 27 a sealing device comprising at least one 28 sealing member provided at the peripheral surface 29 and seal retraction means adapted to urge the or 30 each sealing member s,,bsa.-- a'2-. -.-ads the centre 31 of rotation when the rotor is rotating.

5 Preferably the sealing device further comprises 6 biasing means to urge the sealing member away from 7 the centre of rotation of the rotor.

9 Preferably the seal retraction means comprises at 10 least one retractor that is rotatable supported 11 about an axis of rotation relative to the rotor.

12 Preferably the or each retractor has an asymmetrical 13 distribution of mass with respect to its axis of 14 rotation. Preferably the axis of rotation and the 15 centre of mass of the or each retractor are offset 16 such that the centrifugal force causes the or each 17 retractor to rotate relative to the rotor.

18 Preferably the or each retractor co-operates with 19 the or each sealing member such that the or each 20 sealing member is urged substantially towards the 21 centre of rotation as the centrifugal force causes 22 the or each retractor to rotate relative to the 23 rotor.

25 Preferably the rotor comprises at least one aperture 26 and the or each retractor is rotatably mounted in 27 the or each aperture. Preferably the or each 28 retractor is substantially cylindrical and has a 29 cut-out. Preferably the cut-out is a volume defined 30 by one quadrant of the irc,.:lar face Of the -blinder 3l through the depth of the cylinder.

1 Preferably the rotor is a rotor of a rotary engine.

2 Preferably the rotor is substantially triangular.

3 Preferably a sealing member is provided at each apex of the rotor.

6 Preferably the rotor rotates within a housing.

7 Preferably the sealing member seals the rotor within 8 the housing.

10 Preferably the or each retractor applies a 11 retracting force to the or each sealing member to 12 urge the or each sealing member substantially 13 towards the centre of rotation. The force applied 14 by the biasing means may be greater than the 15 retracting force. Alternatively the retracting 16 force is greater than the force applied by the 17 biasing means at relatively high speeds of rotation 18 of the rotor.

20 According to a fourth aspect of the present 21 invention, there is provided a speed limiting device 22 for a rotary engine comprising: 23 a rotor having a centre of rotation and a 24 peripheral surface, the rotor being rotated by 25 combustion of fuel within the rotary engine; 26 a housing for housing the rotor; 27 a sealing device comprising at least one 28 sealing member provided at the peripheral surface 29 for sealing the peripheral surface of the rotor and 30 the housing, and seal retraction means adapted to 31 urge the or each sealing member substantially

f 1 towards the centre of rotation when the rotor is 2 rotating, 3 wherein, at a predetermined speed of rotation 4 of the rotor, the urging of the sealing member 5 allows passage of the fuel between the sealing 6 member and the housing such that the speed of 7 rotation of the rotor decreases or remains constant.

9 Preferably the seal retraction means is operated by 10 the centrifugal force generated from rotation of the 11 rotor. 13 Preferably the sealing device further comprises 14 biasing means to urge the sealing member away from 15 the centre of rotation of the rotor.

17 Preferably the biasing means is adapted to 18 predetermine the speed of rotation such that the 19 retracting force is greater than the force applied 20 by the biasing means at relatively high speeds of 21 rotation of the rotor.

23 Preferably the seal retraction means comprises at 24 least one retractor that is rotatably supported 25 about an axis of rotation relative to the rotor.

26 Preferably the or each retractor has an asymmetrical 27 distribution of mass with respect to its axis of 28 rotation. Preferably the axis of rotation and the 29 centre of mass of the or each retractor are offset 30 such that the centrifugal force causes the or each 31 retractor to rotate relative to the rotor.

32 Preferably the or each retractor co-operates with

f 1 the or each sealing member such that the or each 2 sealing member is urged substantially towards the 3 centre of rotation as the centrifugal force causes 4 the or each retractor to rotate relative to the 5 rotor.

7 Preferably the rotor comprises at least one aperture 8 and the or each retractor is rotatable mounted in 9 the or each aperture. Preferably the or each 10 retractor is substantially cylindrical and has a 11 cut-out. Preferably the cut-out is a volume defined 12 by one quadrant of the circular face of the cylinder 13 through the depth of the cylinder.

15 Preferably the rotor is substantially triangular.

16 Preferably a sealing member is provided at each apex 17 of the rotor.

19 An embodiment of the present invention will now be 20 described, by way of example only, with reference to 21 the accompanying drawings, in which: 23 Fig. 1 shows a side view of an engine in accordance 24 with a third aspect of the present invention; 26 Fig. 2 shows a side view of a rotor in accordance 27 with a second aspect of the present invention; 29 Fig. 3 shows a side view of a sealing device in 30 accordance with a 'ire; ;; i 31 invention; and

1 Fig. 4 shows another side view of the sealing device 2 of figure 3.

4 Referring to Fig. 1, there is shown a rotary engine 5 10. The engine comprises a housing 12 and a rotor 6 20 mounted within the housing 12. The rotor 20 is 7 substantially triangular and has an aperture 22 at 8 its centre. The aperture is provided with number of 9 internal gear teeth (not shown) around its 10 circumference. A stationary gear 30 is connected to 11 the housing 12. The stationary gear 30 is provided 12 with external teeth (not shown) and these mate with 13 the teeth of the rotor 20. The rotor 20 and gear 30 14 co-operate such that, as the rotor 20 rotates, it 15 orbits the stationary gear 30. Therefore, there is 16 vertical and horizontal movement of the rotor 20 17 relative to the stationary gear 30.

19 The internal surface 14 of the housing 12 is adapted 20 such that it is always in close proximity to the 21 apices of the rotor 20 as it rotates. This is 22 achieved using an epitrochoidal shape for the 23 internal surface 14.

25 At each apex of the rotor 20 is a sealing device 40.

26 The sealing device 40 seals the gap between the 27 rotor 20 and the internal surface 14 of the housing 28 12. Thus separate chambers 16, 17, 18 are created 29 within the housing 12. It should be appreciated 30 that these chambers 16, 17, 18 change in position 31 and volume as the rotor 20 rotates.

1 The engine 10 also includes an inlet port 60 and an 2 outlet port 62, which are connected to an air intake 3 system (not shown) and an engine exhaust system (not 4 shown) respectively.

6 A mixture of air and fuel (not shown) enters the 7 housing 12 via the inlet port 60 due to expansion in 8 volume of the respective chamber 16 as the rotor 20 9 rotates. Following further rotation of the rotor 10 20, the chamber 16 is no longer in communication 11 with the inlet port 60 and the volume of the chamber 12 16 decreases, causing compression of the mixture.

14 The engine further includes spark plugs 70 that are 15 used to ignite the mixture of air and fuel when the 16 chamber 17 is substantially at a minimum volume.

17 Two spark plugs 70 are provided to ensure efficient 18 combustion of the mixture.

lg 20 Combustion causes expansion of the mixture and this 21 is the driving force for the rotor 20. With further 22 rotation of the rotor 20 the chamber 17 increases in 23 volume and the leading apex of the rotor 20 reaches 24 and then passes the outlet port 62. Further 25 rotation causes the chamber 18 to decrease in volume 26 and this forces the combusted mixture to exit the 27 housing 12 via the outlet port 12.

29 The rotor 20 is shown in greater detail in Fig. 2 30 though the sealing device 40 is not included in this 31 figure. At each apex of the rotor 20 is a socket 26 32 adapted to receive the sealing device 40. The

( 1 socket 26 comprises two substantially circular 2 apertures 27 and a longitudinal slot 28. The slot 3 28 extends from the apex substantially in the 4 direction of the centre of the rotor 20 and extends 5 beyond the two apertures 27.

7 Figs. 3 and 4 show one apex of the rotor 20 in 8 greater detail, and the sealing device 40 is also 9 included. In Fig. 3 the sealing device 40 is shown 10 in a first position. In Fig. 4, the sealing device 11 40 is shown in a second position.

13 The sealing device 40 comprises two retractors in 14 the form of cylinders 42 loosely mounted in each of 15 the socket apertures 27. Each cylinder 42 has a cut 16 out which is defined by one quadrant of the circular 17 face of the cylinder 42 through the thickness. This 18 cutout defines two planar surfaces 44.

20 Each cylinder 42 rotates about the centre point 45 21 of the circular face of the cylinder 42. The cut 22 out of the cylinder 42 entails that the centre of 23 mass of each cylinder 42 is offset from its centre 24 of rotation 45. The centre of mass and the centre 25 of rotation 45 for each cylinder 42 are offset along 26 a first axis 90 which is in the direction of the 27 centre of rotation of the rotor 20 and along a 28 second axis normal 92 to the first axis.

30 The sealing device further comprises a sealing 31 member 46 which extends from a location near to the 32 base of the longitudinal slot 28 and he'yon.d the apex

( 1 of the rotor 20. A first end 47 of the sealing 2 member 46 is in contact with the internal surface 14 3 of the housing 12. A spring 48 connects the second 4 end of the sealing member 46 to the base of the 5 longitudinal slot 28. The spring 48 urges the 6 sealing member 46 towards the housing 12.

8 In the first position of the sealing device 40, the 9 planar surface 44 of the cylinder 42 makes contact 10 with the flange 50 of the sealing member 46.

12 The sealing member 46 includes a waisted portion 52 13 which extends between the main body of the sealing 14 member 46 and a flange 50. A portion of each of the 15 cylinders 42 extends into the waisted portion 52 and 16 a portion of the planar surface 44 is in contact 17 with the under-surface of the flange 50. The urging 18 of the spring 48 also causes the flange 50 of the 19 sealing member 46 to act upon the planar surface 44 20 of each cylinder 42. The cylinders 42 are therefore 21 caused to be in a first orientation.

23 Figure 4 shows the sealing device 40 in a second 24 position. In this position, the cylinders 42 are in 25 a second orientation. Rotation of the cylinders 42 26 has caused substantially only an edge of the planar 27 surface 44 of each cylinder 42 to act upon the 28 flange 50 of the sealing member 46. The sealing 29 member 46 is urged towards the base of the 30 longitudinal slot 28 and We spring 48 is 31 compressed. The waisted portion 52 ensures that no

( 1 other portion of the cylinder 42 will make contact 2 with the sealing member 46.

4 In this embodiment of the invention, urging of the 5 sealing member 46 causes a passage 80 between the 6 sealing member 46 and the housing 12. Therefore the 7 gases in one chamber may flow through the passage 80 8 and into another chamber. The result of this is 9 that compression and combustion of the mixture of 10 air and fuel will be reduced. In consequence, the 11 driving force on the rotor 20 will decrease, as will 12 the speed of rotation of the rotor 20. The present 13 embodiment therefore acts as a speed limiting device 14 within the engine.

16 In use, the sealing device 40 seals the rotor 20 and 17 the housing 12 such that a number of chambers 16 are 18 formed within the housing 12. When the rotor 20 is 19 stationary, or the speed of rotation of the rotor 20 20 is moderate, the urging of the sealing member 46 by 21 the spring 48 will maintain the cylinders 42 in a 22 first orientation.

24 At relatively high speeds of rotation of the rotor 25 20, a relatively greater centrifugal force will act 26 upon the sealing device 40. As the centre of 27 rotation 45 for each cylinder 42 is offset from its 28 centre of mass along both the first 90 and second 92 29 axes, the centrifugal force will urge the cylinders 30 42 towards a position r.- hich its centre of mass is 31 furthermost from the centre of rotation of the rotor 32 20 such that the centres of mass and rotation are

1 aligned along the first axis 90. A portion of the 2 cylinder 42 will act upon the flange 50 of the 3 sealing member 46 thereby urging the sealing member 4 towards the base of the slot 28.

6 The degree of rotation of the cylinders 42 is 7 dependent on the mass of the cylinders 42, the speed 8 of rotation of the rotor 20 and the stiffness of the 9 spring 48, as well as the offset distance (along the 10 first 90 and second 92 axes) between the centre of 11 mass and the centre of rotation 45 of each cylinder 12 42, and the distance between the cylinders 42 and 13 the centre of rotation of the rotor 20. If these 14 factors are predetermined such that the urging force 15 from the cylinders 42 is greater than the urging 16 force from the spring 48, then the cylinders 42 will 17 rotate until they are in the second orientation 18 shown in Fig. 4. This will allow the passage 80 to 19 form between the chambers.

21 It should be appreciated that the factors given 22 above can be predetermined such that the passage is 23 formed at a particular speed of rotation of the 24 rotor 20. The escape of the mixture of air and fuel 25 from one chamber to another will reduce the driving 26 force on the rotor 20 causing the rotor speed to 27 decrease. This decrease in speed will reduce the 28 centrifugal force acting on the sealing cylinders 42 29 and so reduce the urging force on the sealing member 30 46 provided by the sealing cylinders 42. This 31 urging force will therefore be of a lesser magnitude 32 than the urging force provided by the spring 4 8, and

1 the sealing member 46 will be brought into contact 2 with the housing 12, eliminating the passage 80. In 3 practice, the speed of rotation of the rotor 20 will 4 reach equilibrium. The sealing device 40 is 5 therefore acting as a speed limiting device.

7 Alternatively, the properties can be predetermined 8 so that, within an expected range of rotation speed, 9 no passage will form between the sealing member 46 10 and the housing 12. In this embodiment of the 11 present invention, there will be significantly less 12 rotation of the cylinders 42. However, the urging 13 of the sealing member 46 towards the base of the 14 slot 28 will reduce the contact force between the 15 sealing member 46 and housing 12 and so lengthen the 16 life of the sealing member 46.

18 Various modifications and improvements can be made 19 without departing from the scope of the present 20 invention. In particular, the sealing cylinders 42 21 may be of any suitable geometry in which the centre 22 of mass and the centre of rotation of the cylinders 23 42 are offset along at least the second axis 92.

24 The offset distance may be increased by using a 25 centre of rotation of the cylinders 42 other than 26 the centre-point of the cylinder 42. Although the 27 sealing device 40 has been described with two L 28 retractors, or sealing cylinders 42, it is to be At 29 understood that one retractor only may be provided.

Claims

1 Claims

3 1. A sealing device for a rotor having a centre of 4 rotation and a peripheral surface, the sealing 5 device comprising: 6 at least one sealing member provided at the 7 peripheral surface; and 8 seal retraction means adapted to urge the or 9 each sealing member substantially towards the centre 10 of rotation when the rotor is rotating.

12

2. A sealing device as claimed in Claim 1, wherein 13 the seal retraction means is operated by the 14 centrifugal force generated from rotation of the 15 rotor. 17

3. A sealing device as claimed in either Claim 1 18 or 2, wherein the sealing device further comprises 19 biasing means to urge the sealing member away from 20 the centre of rotation of the rotor.

22

4. A sealing device as claimed in any preceding 23 claim, wherein the seal retraction means comprises 24 at least one retractor that is rotatably supported 25 about an axis of rotation relative to the rotor.

27

5. A sealing device as claimed in Claim 4, wherein 28 the or each retractor has an asymmetrical 29 distribution of mass with respect to its axis of 30 rotation.

1

6. A sealing device as claimed in Claim 4 or 5, 2 wherein the axis of rotation and the centre of mass 3 of the or each retractor are offset such that the 4 centrifugal force causes the or each retractor to 5 rotate relative to the rotor.

7

7. A sealing device as claimed in any of Claims 4 8 to 6, wherein the or each retractor co-operates with 9 the or each sealing member such that the or each 10 sealing member is urged substantially towards the 11 centre of rotation as the centrifugal force causes 12 the or each retractor to rotate relative to the 13 rotor.

15

8. A sealing device as claimed in any of Claims 4 16 to 7, wherein the rotor comprises at least one 17 aperture and the or each retractor is rotatably 18 mounted in the or each aperture.

20

9. A sealing device as claimed in any of Claims 4 21 to 8, wherein the or each retractor is substantially 22 cylindrical and has a cut-out.

24

10. A sealing device as claimed in Claim 9, wherein 25 the cut-out is a volume defined by one quadrant of 26 the circular face of the cylinder through the depth 27 of the cylinder.

29

11. A sealing device as claimed in any of Claims 4 30 to 10, wherein the or each sealing member comprises 31 a flange portion and Oh_ or each retractor applies a 32 retracting force to the flange to urge the or each

1 sealing member substantially towards the centre of 2 rotation. 4

12. A sealing device as claimed in any preceding 5 claim, wherein the rotor is a rotor of a rotary 6 engine. 8

13. A sealing device as claimed in any preceding 9 claim, wherein the rotor is substantially triangular lo and rotates within a housing, and a sealing member 11 is provided at each apex of the rotor to seal the 12 rotor within the housing.

14

14. A sealing device as claimed in any of Claims 3 15 to 13, wherein the retracting force is greater than 16 the force applied by the biasing means at relatively 17 high speeds of rotation of the rotor., 18 ''

19

15. A rotor having a centre of rotation and a 20 peripheral surface, the rotor comprising: 21 a sealing device comprising at least one 22 sealing member provided at the peripheral surface 23 and seal retraction means adapted to urge the or 24 each sealing member substantially towards the centre 25 of rotation when the rotor is rotating.

27

16. An engine comprising: 28 a rotor having a centre of rotation and a 29 peripheral surface; 30 a sealing device comprising at least one 31 sealing member provided at the peripheral surface 32 and seal retraction means adapted to urge the or

4

17. A speed limiting device for a rotary engine 5 comprising: 6 a rotor having a centre of rotation and a 7 peripheral surface, the rotor being rotated by 8 combustion of fuel within the rotary engine; 9 a housing for housing the rotor; 10 a sealing device comprising at least one ll sealing member provided at the peripheral surface 12 for sealing the peripheral surface of the rotor and 13 the housing, and seal retraction means adapted to 14 urge the or each sealing member substantially 15 towards the centre of rotation when the rotor is 16 rotating, 17 wherein, at a predetermined speed of rotation, '.

18 of the rotor, the urging of the sealing member 19 allows passage of the fuel between the sealing 20 member and the housing such that the speed of 21 rotation of the rotor decreases or remains constant.