ROTARY POSITIVE-DISPLACEMENT FLUID MACHINES

Abstract: A rotary positive-displacement fluid machine comprising a rotor (12) eccentrically mounted in a casing (14, 15) for rotation about an axis (30), the rotor having recesses (33) respectively receiving vanes (21) which oscillate in the recesses as the rotor rotates. Each vane (21) is connected by a crank (27) to an arm (28) for oscillation about a vane axis (35) which is located inwards of the outer extremity of the tip which itself has a clearance fit within the casing (14, 15). The tip of each vane is preferably curved about a vane axis (35). The machine may be connected to the crankshaft of an internal combustion engine and driven by the pressure difference between the ambient air and that at the engine inlet manifold. Alternatively the device may operate as a heat pump.

Description: ROTARY POSITIVE-DISPLACEMENT FLUID MACHINES This invention relates to rotary positive-displacement fluid machines. According to one aspect o f the invention a rotary positive-displacement fluid machine comprises a rotor eccentrically mounted in a casing for rotation about an axis, the rotor having recesses respectively receiving vanes which oscillate in the recesses as the rotor rotates, each vane being connected by a crank to an arm for oscillation thereon about a vane axis, which arm can oscillate about an axis offset from the rotor axis, the vane axis being radially inwards of the radial inner surface of the casing and the vane tip being curved about said vane axis. Accord ing to another aspect of the invention a rotary positive-displacement f luid machine comprises a rotor assembly eccentrically mounted in a casing, the rotor assembly comprising end members between which is a rotor having movable vanes, a drive shaft extending through one end member and connected to the other end member so as to support the rotor assembly. The vanes may be radially slidable. The vanes may be mounted in recesses in the rotor for oscillation in the end members. The casing may have an end member extending towards another casing end member and supported on the drive shaft. The vanes may be connected by cranks to arms which can oscillate with respect to the vanes on an axis offset from the rotor axis provided by an element supported in the other casing end member and which is supported by the rotatable drive shaft. According to another aspect of the invention a rotary positive-disp lacement f luid machine comprises a rotor assembly rotatable in a casing and comprising a rotor having recesses receiving vanes which are connected by cranks to arms which can oscillate relative to the cranks and to an axis offset from the rotor assembly axis, the rotor being between end members which have axially inner and outer parts respectively having a seal and a bearing between them and a shaft of the respective vane Each invention can be used with the others. According to another aspect of the invention an internal combustion engine has a positive-displacement rotary device coupled to the crankshaft and driven by the pressure difference between ambient air and the engine inlet manifold, and exhaust gas from the engine is fed to the inlet to the rotary device. The invention may be performed in various ways and one specific embodiment with possible modifications will now be described by way of example with reference to the accompan\ ιng drawings, somewhat diagrammatic, in which Fig. 1 is a perspective view part cut away of a rotary machine; Fig. 2 is a schematic section of a machine; Fig. 3 is a schematic axial view of a rotor; Fig. 4 is an exploded perspective view of a rotor disc; Fig. 5 is a perspective view of part of the disc; Fig. 6 is an axial view of the disc; Fig. 7 shows a modification; Fig. 8 shows another modification; Fig. 9 illustrates a heat pump, and Fig. 10 shows an engine; Fig. 1 1 shows a control plate; Fig. 12 is a flow diagram; and Fig. 13 is an enlarged view of part of a modified rotor vane. A rotary positive-displacement fluid machine 10 has an outer stator assembly 1 1 within which can rotate an eccentrically mounted rotor assembly 12. The stator assembly 1 1 has a first end plate 13, a two-part radially stepped casing part 14, 15 and a second end plate 16, the assembly being held together by bolts 17, with f luid- tight seals as appropri ate (not shown) , and prov iding an expansion/compression chamber 70. The ro tor assembly 1 2 comprises a rotor 20 with angularly spaced peripheral recesses 33 receiving respective vanes 21. Each vane 21 is integral with end shaf ts 22, 23 mounted respectively for rotation (oscillation) about axis 32 on bearings 24a, 25a in a first rotor disc 24 and a second rotor disc 25 secured to the rotor 20 by bolts 26 (only one shown). The shafts 23 are pivotally connected by respective integral crank arms 27 to oscillating arms or spokes 28 which can oscillate (about an axis 30) on a common shaft 29 which is fixed in the second end plate 16. The arms 28 rotate with the rotor and also oscillate on the shaft 29. The arms 27 oscillate about axes 35. A drive shaft 40 with an axis 41 offset from the axis 30 is held by bolts 26 to the rotor assembly. With this arrangement, the vanes 21 oscillate about axes 32 in the recesses 33 to produce a compression region 43 and an expansion region 44 wi th the outer surf ace 45 o f the vanes 21 disposed with very small clearance with respect to the inner surface 46 of the casing 14. The v ane surf aces 45 are machined to maximum tolerance and the vane surface has a very small running clearance with surface 46. Suitable bearings 50 are provided as required. In the present case the rotor assembly 12 is supported on the drive shaft 40. The end wall 13 is extended axially at 51 its central region towards the end wall 16 with interposed bearings 52, 53. The pressure load on the rotor assembly is thus largely taken on bearings 52, 53 so as to be axially distributed rather than being cantilevered at an end of the drive shaft The drive shaft 40 is received at 42 in the shaft 29 which improves balance and the shaft 29 is thus supported at both its ends and has less bending load than a cantilevered shaft and can thus be smaller, reducing weight. The shaft 29 can be integral with plate 16. The shafts 29, 40 can be assembled by relative axial movement. This feature can be used in machines with vanes which slide radially in and out in the rotor. In the present case the axes 35 of relative angular movement between the arms 27 and 28 are radially inwards of the casing surface 46 and of the outer surfaces or tips 45 of the vanes, which are curved about or around the axes 35 (part-circular). Compared with an arrangement in which the axis 35 is coincident with the surface 46 and the surface 45 is effectively an edge about which the vane 21 pivots as it rotates in the casing, the present arrangement provides a curved surface for the vane tip which rolls as the vane is oscillated about axis 35 thus reducing tip wear. The curved vane tip is easier to make, is stronger, and improves maintenance of tip clearance The lengths of arms 27 and 28 are also less thus reducing weight and providing for a smaller overall machine diameter. For ease of manufacture and assembly the rotor disc 25 is formed from two parts 54, 55 Fig. 4 which are assembled by relative axial movement. The part 54 has radial portions 56 with concave ends which are received in radial recesses 57 in part 55 to form apertures 58 for the shafts 23 and have recesses 59 in one face which receive projections 60 of part 55 with ribs 61 received in slot 62 between projections 60, the whole providing aperture 63 for rotor portion 20a. The shafts 23 are placed in apertures 58 in part 55 before the part 54 is moved axially into position. In this case the rotor surface 20b Fig. 2 can extend the axial extent of disc 25. If the rotor is cut away to provide flange 64 the part 55 has an end recess for receipt of flange 64 on shaft 40. Rotor disc 24 can be made as two pieces formed by a circular split line passing through apertures in disc 24 for receiving shafts 22 and assembled by relative axial movement. One wall surface 65 (the trailing surface) of the recess 33 generally conforms to a surface 66 of the respective vane 21 and the curved surface 45 means that at one limit of the oscillating movement of the vane 21 there will be a small volume 67 Fig. 3 not occupied by the vane. As shown in Fig 7 this can be reduced by appropriately shaping the rotor portion 68 at 69. This reduces loss of compression. As shown i n Fig. 8 , one way o f sealing the expansion/compression chamber 70 against entry of lubricating oil is to split the discs 24, 25 into two axially spaced parts 71 , 72 bolted together at their radial outer ends and provide bearing 73 for part 72 and seal 74 for part 71 engaging a ring 75 on the shaft 40. The gap 76 between parts 71 , 72 can act as an air vent and oil drain. In this case the parts 71 , 72 can each be in two parts connected by a circular face passing through apertures 58, and the arrangement of Fig. 6 is not needed A close sleeve 77 Fig. 2 can be located on shaft 29 between part 16 and disc 25 and the arms 28 can oscillate on the sleeve 77 with interposed bearings 78. This distributes the radial loading along the sleeve (the radial loading on arms 28 varies as they rotate). The sleeve 77 rotates at a speed between the rotor speed and the oscillation speed of the arms 28. In one example, Fig. 9, the device is used as a heat pump Angularly spaced inlet ports 90, 91 and outlet ports 92, 93 communicate with the interior 70 of the casing. Radiators 94 and94a are selectively connectable by switching 94b to ports 90, 93; and radiators 95, 95a are selectively connectable by switching 95b to ports 91 , 92. Fluid is circulated in a closed circuit. Radiators 94a and 95a are inside the house and radiators 94, 95 are outside the house In summei , radiators 94a, 95 are not used. Hot fluid leaving port 93 is cooled in radiator 94 by outside air and further cooled fluid leaving port 92 cools radiator 95a. In winter radiators 94 and 95a are not used; cold air leaving port 92 is heated in radiator 95 by outside (less cold) ambient air, and the heated fluid from port 93 heats the house via radiator 94a. If the device is used for example as a throttle loss recovery turbine in an internal combustion engine 131 Fig 10, the device 100 replaces a butterfly valve between the air intake 101 and the inlet manifo ld 1 02 , being driven by the pressure di fference between ambient and the inlet manifold which is at a pressure less than ambient and thus driving belt 103 and crankshaft pulleys 104 to put energy into the crankshaft. In this case, as rotor speed increases, the fluid mass flow is increased For example as shown in Figs 3 and 1 1 , an angularly extending air inlet port 120 is formed in casing 14, and angularly slidable in the casing to enlarge or reduce the angular extent of the inlet port is a plate 123 which can move from its position illustrated with full lines in Fig 1 1 , at idling speed to a position 123a illustrated with dotted lines at maximum rotor speed (full throttle) At idling speed the air inlet port 120 extends from A to B in Figs. 3 and 1 1 , but plate 123 moves to position 123a at full throttle thus to extend the air inlet to position D The flow to the engine inlet manifold, shown at G, is via a port which is open between positions E and A. The distance between consecutive or adjacent vanes 21 thus defining the extent of chambers 70, is illustrated diagrammatically bv B to C and D to E in Fig. 3. The movement of the plate 123 can be controlled by mechanism 124 (for example a cable) in response to movement of an engine accelerator pedal 125 (Fig. 10). In a modification shown in Fig. 12, some of the exhaust gas passing through an exhaust pipe 130 from the internal combustion engine 131 is passed to the air inlet 120 of the rotary device 100 and is thus then fed back to the engine air inlet to reduce the nitric oxide content of the exhaust gas passing to atmosphere. The pressure of this exhaust gas is normally less than or equal to that of the ambient air. Fig. 13 shows another arrangement intended for use at high speeds. Point X indicates the point of the tip which is closest to the casing when t he v ane is closed up (compartment at least volume), point Z indicates the point of the tip which is closest to the casing when the vane is fully open (compartment at maximum volume); and point Y is between points X and Z. Lines 200, 201 , 202 are tangents to the casing surface opposite points X, Y, Z respectively. As the vane tip pivots during operation, the part of the vane tip closest to the internal surface of the casing moves from point X to point Z. Between point Y and Z the mechanism stresses are at their highest and the normal tip clearance (calculated at X) reduces Typical lv t he linkage mechanism between the vane and the drive shaft, which causes the vane to oscillate, stretches and/or twists (including bearings, crank arm) and the tip clearance is reduced. If the reduction is greater than the available clearance, this will produce tip-rub. At high speeds e.g. 6000 rpm there is a relatively large tip movement between points Y and Z. To prevent a heavy rub on the tip, the tip profile is modified to a more flattened shape as shown by the broken line 203. This may follow the curvature of the casing at every increment, or for practical purposes, the line 203 could be two flats 204, 205 machined on the tip at right angles to the radii 206, 207 at points Y and Z respectively.

Claims: CLAIMS 1. A rotary positive-displacement fluid machine comprising a rotor eccentrically mounted in a casing for rotation about an axis, the rotor having recesses respectively receiving vanes which oscillate in the recesses as the rotor rotates, each vane being connected by a crank to an arm for oscillation thereon about a vane axis, which arm can oscillate about an axis offset from the rotor axis, the vane axis being located radially inwards of the radial inner surface of the casing. 2. A rotary positive-displacement fluid machine according to Claim 1 , wherein the vane tip is curved around said vane axis. 3. A rotary positive-displacement fluid machine according to Claim 1 or Claim 2, wherein the casing has axially spaced end members one of which extends towards the other and is supported on a drive shaft. 4. A rotai y positive-displacement fluid machine according to Claim 3, wherein the rotor axis is provided by an element supported in said other casing end member, which element is supported by the drive shaft. 5. A rotai y positive-displacement fluid machine according to any preceding cl aim , whei ein the rotor is positioned between rotor end members having axially inner and outer parts respectively having a seal and a bearing between them and a shaft of the respective vane. 6. A rotary positive-displacement fluid machine according to Claim 3, wherein the casing is mounted upon bearings supported on the drive shaft and located between the two casing end members. 7. A rotary positive-displacement fluid machine according to Claim 2 or Cl a im 3 , wherein each v ane is mounted within a respective radially disposed recess on the rotor, at least one wall defining each recess being curved partially to follow the curved tip of the respective vane whereby to reduce volume of space between the curved tip and the adjacent radial inner surface of the casing at one limit of oscillatory movement of the respective vane. 8. A rotary positive-displacement fluid machine comprising a rotor assembly eccentrically mounted in a casing, the rotor assembly comprising end members between which is a rotor having movable vanes, a drive shaft extending through one end member and connected to the other end member to support the rotor assembly. 9. A rotary positive-displacement fluid machine according to Claim 8, wherein the vanes may oscillate about a vane axis located radially inwards of the radial inner surface of the casing, the vane tip being curved about said vane axis. 10. A rotary positive-displacement fluid machine according to Claim 8, wherein the vanes are mounted to be radially slidable in recesses in the rotor for oscillation with respect to the end members. 11. A rotary positive-displacement fluid machine according to Claim 5 to Cl aim 8 , wherein one of said rotor end members is formed from two parts adapted to be assembled by relative axial movement. 12. A rotary positive-displacement fluid machine according to any preceding claim, coup led to the crank shaft o f an internal combustion engine and driven by the pressure difference between the ambient air and that in the engine inlet manifold. 13. A rotary positive-displacement fluid machine according to Claim 12, wherein exhaust gas from the engine is fed to the inlet of the rotarv positive-displacement fluid machine. 14. A rotary positive-displacement fluid machine according to any preceding claim, when used as a heat pump with angularly spaced inlet ports and outlet ports communicating with the interior of the casing, fluid being circulated in a closed circuit. 15. A rotary positive-displacement fluid machine according to any preceding claim, including, in the casing, a fluid inlet port and a fluid outlet port, chambers between adjacent vanes serving repeatedly and alternately as compression and expansion chambers. 16. A rotai y positive-displacement fluid machine according to Claim 15, wherein said inlet port is adjustable in size. 17. A rotary positive-displacement fluid machine according to Claim 16, wherein said inlet port is adjustable automatically according to changes in fluid mass flow. 18. A rotary positive-displacement fluid machine according to Claim 2, wherein the prof i le of the curved tip of each vane is modified to a more flattened shape to ensure clearance from the casing at high rotor speeds. 19. A rotary positive-displacement fluid machine according to Claim 18, wherein the modified profile comprises one or more flats. 20. A rotary positive-displacement fluid machine coupled to the crankshaft of an internal combustion engine and driven by the pressure difference between ambient air and that at the engine inlet manifold, and wherein exhaust gas from the engine is fed to the inlet of the rotary device.

Inventors: DAVIDSON DAVID PETER, DRIVER RONALD WILLIAM, DAVIDSON, DAVID, PETER, DRIVER, RONALD, WILLIAM
Applicants: DAVIDSON DAVID PETER, DRIVER RONALD WILLIAM, DRIVER TECHNOLOGY LTD, DAVIDSON, DAVID, PETER, DRIVER TECHNOLOGY LIMITED, DRIVER, RONALD, WILLIAM
Application year: 1998
Main classification: F01C1
IPC codes: F01C1