GB2085094A - Hydraulic motors - Google Patents

Abstract

A hydraulic motor has a cylindrical stator portion 3 which has a number of peripheral reentrant portions 18. In each reentrant portion is a roller element 19. The rotor 2 has a surface 23 which defines with the periphery of the stator portion, a number of generally crescent-shaped spaces. The stator and rotor are provided with passages 14, 15, 17, 21, 22 and 16, 20 respectively which cooperate cylically during rotation of the rotor to conduct hydraulic fluid to and from the reentrant portions. Pressurised hydraulic fluid is conducted to a reentrant portion only when the distance between the surface 23 and the stator in the proximity of the reentrant portion is increasing. This urges the roller disposed in that reentrant portion against the surface 23, thus causing the rotor to rotate. A hydraulic motor driven electric generator is also provided by the invention. <IMAGE>

Description

SPECIFICATION Hydraulic Motors This invention relates to hydraulic motors.

More especially though not exclusively the invention relates to such motors suitable for driving electric generators to provide electric power in aircraft.

Thus it is an object of the present invention to provide a hydraulic motor which is small, light, and extremely reliable in accordance with the criteria of aeronautical design. It is a further object of the present invention to provide a form of hydraulic motor driven electric generator suitable for use in an aircraft.

According to one aspect of the invention a hydraulic motor comprises: a stator having a substantially cylindrical portion which has a multiplicity of peripheral reentrant portions, a rotor which has a surface defining with the surface of said stator portion a plurality of circumferentially extending generally crescent-shaped spaces, and a multiplicity of roller elements each disposed in a respective said reentrant portion, the stator and rotor being provided with passages which cooperate cyciically during rotation of the rotor to conduct hydraulic fluid to and from the reentrant portions, pressurised hydraulic fluid being conducted to a reentrant portion only when the distance between the said rotor surface and stator portion surface in the proximity of said reentrant portion is increasing, thereby urging the roller disposed in that reentrant portion against the said rofor surface and causing the rotor to rotate.

Preferably the generally crescent-shaped spaces are evenly distributed around the cylindrical stator portion. The forces within the motor are then symmetrically distributed and the loading on the roller elements and on the rotor bearings is therefore substantially balanced.

Consequently the roller elements and rotor bearings may be of a light concentration, frictional wear is minimised and very high hydraulic pressures may be employed within the motor.

Three or more crescent-shaped spaces may be incorporated in a motor in accordance with the invention. Preferably, however, there are only two crescent-shaped spaces.

The said surface of the rotor preferably has the shape of constantly accelerating curves between cylindrical extremes.

According to a further aspect of the invention in a hydraulic motor driven electric generator, the generator comprises an annular stator coaxially surrounding a permanent magnet rotor, and the motor comprises a rotor coaxially surrounding a stator, the generator rotor being secured to the exterior of the motor rotor so that the motor effectively constitutes the hub of the generator.

In a generator in accordance with the invention, the motor is suitably of the form provided by the first aspect of the invention.

One hydraulic motor driven electric generator in accordance with the invention incorporating a hydraulic motor in accordance with the invention will now be described with reference to the accompanying drawings in which: Figure 1 shows a sectional elevationtthe generator along the line X-X in Figure 2, Figure 2 shows a part sectional elevation along the line B-B of the generator shown in Figure 1, Figure 3 shows a part sectional elevation along the line A-A of the generator shown in Figure 1, and Figure 4 shows a part sectional elevation along the line D-D of the generator shown in Figure 1.

Referring to Figures 1 and 2 of the drawings, the generator has a casing comprising two end plates 7 and 10 between which is clamped the stator 29 of the aiternator, the stator being of annular form and comprising laminations and windings encapsulated in expoxy resin.

The hydraulic motor comprises a stator 1 disposed coaxially within the casing and surrounded by the motor rotor 2. The stator 1 includes a shaft 3 one end of which locates in a circular recess in the inner surface of the end plate 7. The shaft is secured to the end plate 7 by means of a union 8 having a threaded male portion 9 which extends through an aperture in the end plate 7 and is screwed into a threaded aperture in the adjacent end of the shaft 3. At its other end the shaft 3 carries a centrally apertured disc 5 which locates in a circular recess in the inner surface of the end plate 10, the disc 5 being retained on the shaft by a nut 11 which screws onto the end of the shaft 3.

Between the disc 5 and a radial abutment 1 2 on the shaft 3 there is clamped a spacer plate 4, the plate having eight reentrant slots extending radially into it from its outer periphery at equally spaced positions around its circumference, the slots and the adjacent abutment 12 and disc 5 thus forming eight chambers 18.

The motor rotor 2 is carried on the part of the shaft 3 between the abutment 1 2 and the end plate 7, the curved surface of the shaft being circumferentially grooved to reduce friction.

Bearing rings 33 are provided at either end of the rotor to restrict its axial movement.

As described in detail below, the rotor is caused to rotate by the supply of hydraulic fluid, e.g. oil, under pressure to the chambers 1 8. In each chamber 1 8 there is located a roller 1 9 which fits closely within its associated chamber to minimise loss of fluid. The fluid periodically urges the rollers outwardly against the adjacent surface 23 of the rotor which, as further described below, is so shaped that the periodic outward forces exerted by the rollers cause the rotor 2 to rotate on the shaft 3.

The rotor of the alternator comprises a pure iron annular core 27 secured around the motor rotor 2 and a plurality of permanent magnets 28 secured at equally spaced positions around the outer surface of the core 27.

Hydraulic fluid at high pressure is supplied to the motor via a passage 1 5 in the union 8 to an axial bore 13 in the shaft 3 which communicates via two holes 1 3A at its inner end with an annular manifold 14 formed by a circumferential groove in the shaft 3 and the adjacent surface of the rotor 2 (see also Fig. 4). In the rotor 2 there are two passages 1 6 which at one end communicate with the manifold 14, and into which high pressure fluid therefore passes. At its other end each of the passages 16 communicates sequentially, during rotation of the rotor, with successive ones of eight passages 1 7 in the shaft 3, each passage communicating at its other end with a respective one of the chambers 1 8, the passages 1 6 communicating with diametrically opposite ones of the passages 1 7.Thus, as the rotor relates, high pressure fluid is supplied in turn to each pair of diametrically opposite ones of the chambers 1 8.

A route for discharge of fluid from the chambers 18 via the passages 1 7 is provided by a further pair of passages 20 in the rotor. At its end nearer the end plate 10 each of the passages 20 communicates sequentially with successive ones of the passages 1 7, as the rotor rotates, in similar manner to the passages 1 6. At their other end the passages 20 communicate with the space surrounding the rotor 2, and thence with a passage 21 in the end plate 7 and a passage 22 in a further union 35 secured to the end plate 7, whereby hydraulic fluid is discharged.As illustrated in Figures 3 and 4, the passages 1 6 and 20 are disposed alternately around the rotor so that as the rotor relates any given passage 1 7 and its associated chamber 18 is alternately connected to the high pressure source of fluid via a passage 16 and via a passage 20 to the discharge passages 21,22. Furthermore, due to the disposition of the passages 1 6 and 20, while high pressure fluid is being admitted to one pair of diametrically opposite chambers 18, fluid is being discharged from the orthogonally positioned diametrically opposite chambers 18, and the remaining chambers 1 8 are effectively shut off.

In the drawing passages which carry pressurised fluid are marked P and passages which carry discharge fluid are marked R. The passages 17, which carry pressurised and discharge fluid alternately are unmarked.

The shape of the motor rotor surface 23 is illustrated in Figure 2 which shows a section along the line B-B of Figure 1. This surface has two cylindrical 20C sections having a second, greater radius, these sections being alternately disposed at quadrants around the surface. The surfaces between these cylindrical sections have the shape of constantly accelerating curves providing a smooth transisition between the different radii.

Pressurised hydraulic fluid isdelivered in operation to opposed pairs of chambers 18 when their associated rollers 19 are situated at the start of two opposing constantly accelerating curved regions adjacent to the sections 25 having the smaller radii. The rotor is urged to turn as the rollers move towards the sections 26 having the greater radii. The supply of pressurised fluid is maintained until the rollers reach the sections 26.

The pressurised fluid in the opposed pairs of chambers is discharged while the rotor passes from the sections 26 to the sections 25. The chambers 18 are closed off and hydraulic pressure remains static therein while the rollers cooperate with the cylindrical sections 25 and 26 so that seizure due to hydraulic lock of the engine does not occur. At least two of the eight rollers are therefore driving the rotor at any instant.

It will be appreciated that since the whole of the interior of the generator casing is filled with hydrualicfluid, 'O' rings 31 are provided at appropriate locations to prevent leakage of fluid. It will be noted- in this connection that the conservation of the generator does not involve the provision of any rotating seals with consequent improvement in reliability of the generator.

Claims (9)

Claims

1. A hydraulic motor comprising: a substantially cylindrical stator portion which has a multiplicity of peripheral reentrant portions, a rotor which has a surface defining with the surface of said stator portion a plurality of circumferentially extending generally crescent-shaped spaces, and a multiplicity of roller elements each disposed in a respective said reentrant portion, the stator and rotor being provided with passages which cooperate cyclically during rotation of the rotor to conduct hydraulic fluid to and from the reentrant portions, pressurised hydraulic fluid being conducted to a reentrant portion only when the distance between the said rotor surface and stator portion surface in the proximity of said reentrant portion is increasing, thereby urging the roller disposed in that reentrant portion against the said rotor surface and causing the rotor to rotate.

2. A hydraulic motor according to Claim 1 in which the generally crescent-shaped spaces are evenly distributed around the cylindrical stator portion.

3. A hydraulic motor according to Claim 2 in which there are two crescent-shaped spaces.

4. A hydraulic motor according to any preceding claim in which the said surface of the rotor has the shape of constantly accelerating curves between cylindrical extremes.

5. A hydraulic motor according to any preceding claim in which pressurised hydraulic fluid is conducted via a manifold to a first plurality of passages in the rotor each of which communicates sequentially, during rotation of the rotor, via successive ones of passages in the stator, with each of said reentrant portions, and a discharge route for the fluid is provided by a second plurality of passages in the rotor which communicate sequentially during rotation of the rotor via successive ones of said passages in the stator with each of said reentrant portions to conduct discharge fluid through a space surrounding the rotor to an outlet passage.

6. A hydraulic motor according to Claim 5 in which said first plurality of passages comprises two passages which simultaneously communicate with a diametrically opposite pair of said reentrant portions, and said second plurality of passages comprises two passages which at the same time simultaneously communicate with another diametrically opposite pair of said reentrant portions.

7. A hydraulic motor substantially as hereinbefore described with reference to the accompanying drawings.

8. A hydraulic motor driven electric generator wherein the generator comprises an annular stator coaxially surrounding a permanent magnet rotor.

and the motor comprises a rotor coaxially surrounding a stator, the generator rotor being secured to the exterior of the motor rotor so that the motor effectively constitutes the hub of the generator.

9. A hydraulic motor driven electric generator according to Claim 8, in which the motor isof the form according to any one of Claims 1 to 7.