WO2001020132A1

WO2001020132A1 - A rotary positive-displacement fluid machine

Info

Publication number: WO2001020132A1
Application number: PCT/GB2000/003440
Authority: WO
Inventors: Ronald William Driver
Original assignee: Driver Technology Limited
Priority date: 1999-09-11
Filing date: 2000-09-08
Publication date: 2001-03-22
Also published as: GB9921458D0

Abstract

A rotary positive-displacement fluid machine comprising a rotor (12) eccentrically mounted in a casing (11) for rotation about an axis (29), the rotor having angularly spaced vanes (21) which divide the interior of the casing into a plurality of chambers (33) which vary in capacity as the rotor rotates eccentrically within the casing. Thus the machine may act as a turbine or supercharger. Each vane (21) is mounted on a shaft (23) by way of a splined connection (81, 84), the splines (84) on the shaft (23) being divided into circumferentially spaced segments (93) joined by thin-walled sections (94) to constrain the splined segments to expand concentrically and uniformly by means of a draw bolt (91) or clamp pin (95) to ensure axial alignment of the shaft with the vane.

Description

A ROTARY POSITIVE-DISPLACEMENT FLUID MACHINES

THIS INVENTION relates to rotary positive-displacement fluid machines.

Such a machine is known typically in WO 98/57039 which describes and illustrates 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 extending parallel

to the axis between a pair of axially spaced side disc. The vanes oscillate in the recesses as the rotor rotates. Each vane has a vane tip which maintains a clearance fit within the casing, and is

connected by a crank to an arm for oscillation about a vane axis which is located inwards of the outer extremity of the vane tip. The tip of each vane is preferably curved about the vane axis. The rotor is mounted on a shaft at its axis. The driven shaft of 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.

In such a machine each vane is mounted on a shaft which is connected by the

crank to the arm, and the vane and shaft may be integrally formed or connected together as

separate parts where the shaft passes into or through a bore in the vane and is bonded thereto

using a proprietary bonding agent. -2-

In some cases the vanes are attached to their respective shafts before assembly

of the rotor, which requires that the rotor side discs be constructed in separate parts, thus rendering the assembly process cumbersome and expensive. Also, under certain operating

conditions and where temperature may vary considerably there is a risk that where the vanes and

shafts are bonded together, the vanes may become detached from the shafts or that the two parts

may have some relative movement which will interfere with the accuracy and performance of

operation of the machine.

According to the present invention, 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 shaft and a crank to an arm for oscillation thereon about a vane axis; is characterised in that each vane is connected to its associated shaft by inter-engaging

splines and in that the splines are provided in angularly spaced segments around the shaft, the

segments being partially joined thus to ensure concentric expansion thereof for engagement of

the shaft and the vane in a locking relationship.

Expansion of the spline segments in the shaft may be achieved by a tapered

draw bolt or by a tapered clamp pin which is self-locking.

The clamp pin may include sprung fingers or lugs which locate behind

shoulders when the two parts are locked together. An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:-

Fig. 1 is a perspective view part cut away of a rotary positive-displacement

fluid machine to which this invention applies;

Fig. 2 is a schematic section of the machine;

Fig. 3 is a schematic axial view of a rotor;

Fig. 4 is a cross-sectional view of the mode of attachment of a vane to its associated shaft and being a section taken on line A- A of Fig. 5;

Fig. 5 is an end view of the splined connection of the shaft to the vane;

and Fig. 6 is a view of a clamp pin which may be used for attachment of the parts

together.

A rotary positive-displacement fluid machine 10 has an outer casing assembly

11 within which can rotate an eccentrically mounted rotor assembly 12. The casing assembly

11 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 fluid-tight seals as appropriate (not

shown), and providing an expansion/compression chamber 70. (Fig. 3) The rotor assembly 12 comprises a rotor 20 with angularly spaced peripheral

recesses 33 receiving respective vanes 21. Each vane 21 is attached to an end shaft 23 mounted respectively for rotation (oscillation) about an axis 32 on bearings 24a, 25a in axially spaced

rotor side discs 24 and 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 a common axis on a 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 attached to the rotor

assembly.

Referring now to Fig. 3, with this arrangement, the vanes 21 oscillate about

their pivotal axes 32 in the recesses 33 to produce a compression region 43 and an expansion

region 44 with the outer tip surface 45 of each vane 21 disposed with very small running

clearance with respect to the inner surface 46 of the casing 14.

During rotation of the rotor, each vane 21 also oscillates about a vane axis 35

spaced inwardly from the vane tip 45.

Referring now to Figs. 4 to 6, and in accordance with the invention there is

shown the means of attachment of the shaft 23 to its associated vane 21. The vane is shown as

having a central bore 80 internally splined at 81 in its end region to which the shaft 23 is to be -5- attached and has an outer sleeve 82 at the same end around which is a bearing 83 by which the

vane is rotatably mounted in the rotor disc 25. The shaft 23 which is a separate piece to be

attached within the bore 80 of the vane, is complementarily splined at 84 thus to become

inter-engaged with the splines 81 in the end region of the bore 80. The crank 27 is integrally

formed with the shaft 23 and a bore 88 is defined within the inner radial end of the crank 27 and

the shaft 23, the outer end of the bore having a parallel section 89 which expands into a diverging

section 90. An enlarged open recess 85 is provided at the end of bore 88 remote from diverging

section 90.

To lock the parts together with the splines 81 and 84 inter-engaged, a tapered

draw bolt 91 may pass through the bore 88 and be drawn tight by a nut 92 to expand the shaft 23 in the region of the splines 84. For this purpose the splined part of the shaft 23 is divided into

four segments each having an angular extent of about 20°, as illustrated at 93 in Fig. 5, this

arrangement being produced by cut-outs 98 as indicated in dotted lines in Fig. 4.

If the segmental parts of the splined end of the shaft 23 were discontinuous but

for their roots then tightening of the draw bolt may cause the splines to be expanded

non-concentrically i.e. biassed towards one side, due to differential frictional bearing between

the draw bolt 91 and the splined section. This would cause the shaft 23 and crank 27 to be off-sei

from the central axis of rotation of the vane and cause erratic operation of the machine.

Therefore, the segmental sections 93 are connected together, i.e. they have peripheral continuity

by way of thin-walled sections 94, and it is these thin-walled sections which maintain and constrain the splined segments to expand concentrically and uniformly as the draw bolt 91 is

tightened.

Referring now to Fig. 6 in place of the draw bolt 91 and nut 92 there may be

provided a clamp pin 95 having a shallow angle of taper at 99 to provide a self-locking push fit

within the tapered bore of the shaft 23. Preferably flange 27 locates against the inner end face of the shaft, while two or more integral and segmental sprung fingers 96 pass through bore 88

and having end tabs 97 which locate against an outer face within the recess 85 otherwise

occupied by the nut of the draw bolt.

The manner of attachment and locking of the shafts 23 to their respective vanes

21 as described herein renders the assembly of this part of the machine more readily attained and

with accuracy by lesser skilled personnel.

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 shaft and a crank to an arm for oscillation thereon about a vane axis; characterised in

that each vane is connected to its associated shaft by inter-engaging splines; and in that

the splines are provided in angularly spaced segments around the shaft; and in that the

segments are partially joined thus to ensure concentric expansion thereof or engagement

of the shaft or the vane in a locking relationship.

2. A rotary positive-displacement fluid machine according to Claim 1 , wherein each vane

includes a central bore internally splined in an end region to which the shaft is to be

attached.

3. A rotary positive-displacement fluid machine according to Claim 1 or Claim 2, wherein

each vane has a sleeve in an end region to which the shaft is to be attached, around

which sleeve is located a bearing by which the vane is rotatably mounted in the rotor.

4. A rotary positive-displacement fluid machine according to any preceding claim,

wherein the shaft is externally splined in an end region to which the vane is to be

attached. 5. A rotary positive-displacement fluid machine according to any preceding claim,

wherein the crank is integrally formed with the shaft and defines a central bore for receiving locking means for attachment of the shaft to the vane.

6. A rotary positive-displacement fluid machine according to Claim 5, wherein the

central bore has a parallel section and a diverging section for receipt of tapered means

for locking the shaft to the vane.

7. A rotary positive-displacement fluid machine according to any preceding claim,

wherein the shaft is divided into four splined segments each having an angular extent

of about 20° there being cut-outs between the segments.

8. A rotary positive-displacement fluid machine according to any preceding claim,

wherein the splined segments of the shaft are joined by thin walled sections extending circumferentially between the splined segments thus to maintain and constrain the latter

to expand concentrically and uniformly into engagement with the corresponding splines

of the vane.

9. A rotary positive-displacement fluid machine according to any preceding claim,

including a tapered draw bolt which may be tightened to expand the splined segments

of the shaft. 10. A rotary positive-displacement fluid machine according to Claim 9, wherein the tapered

draw bolt has a tapered section and a parallel section.

11. A rotary positive-displacement fluid machine according to any one of Claims 1 to 9,

including a tapered clamp pin which is self-locking within a central bore of the shaft.

12. A rotary positive-displacement fluid machine according to Claim 11, wherein the

tapered clamp pin is flanged to become located against an inner face of the shaft and

includes a plurality of sprung fingers having locking tabs adapted to engage an outer

face of the shaft.