GB2325279A

GB2325279A - Hydraulic vane machine axial sealing arrangement

Info

Publication number: GB2325279A
Application number: GB9801970A
Authority: GB
Inventors: Lars Martensen; Gunnar Lyshoj Hansen; Henry Madsen Moeller
Original assignee: Danfoss AS
Current assignee: Danfoss AS
Priority date: 1997-01-29
Filing date: 1998-01-29
Publication date: 1998-11-18
Anticipated expiration: 2018-01-29
Also published as: FR2758858A1; ITTO980072A1; GB2325279B; GB9801970D0; DE19703114C2; DE19703114A1; FR2758858B1

Abstract

A hydraulic vane machine comprising a rotor 3, several radially movable vanes, a stator 2 having a stator bore, in which the rotor is arranged rotatably, and whose internal wall is made as a guide contour 4 on which the vanes bear, and a respective sideplate arrangement 18 on the axial side faces of rotor and stator, which bound the vane cells 17 together with the rotor, the vanes and the stator. For this purpose, the sideplate arrangements are fixed on the rotor and rotate together with the rotor in relation to the stator. Hydraulic pressure pockets 23 connected via a channel 24 to the vane cells press the inner cell 19 against the stator to ensure fluid tightness, and the area 22 may be coated in low friction material.

Description

1 - Hydraulic vane machine 2325279 This invention concerns a hydraulic

vane machine with a rotor, which rotor has several radially movable vanes, with a stator having a stator bore, in which the rotor is arranged rotatably, and whose internal wall is made as a guide contour on which the vanes bear, and with a respective sideplate arrangement on the axial side faces of rotor and stator, which sideplate arrangements, together with the rotor, the vanes and the stator bound the vane cells.

Such machines can be made both as motors (US 4,376,620 and US 3,254,570) and as pumps (US 3,255,704). On rotor rotation relative to the stator, the vanes move radially inwards and outwards, the movement being controlled by the guide contour. For this purpose the guide contour has nonworking (or "rest") sections, in which the stator bore has a diameter only slightly larger than the outside diameter of the rotor, and working sections, in which the stator bore has a larger diameter. Commutation areas are arranged between the non-working areas and the working areas, in which the vanes are moved radially from the inside to the outside or from the outside to the inside, respectively. Here, the bearing of the vanes on the guide contour is effected by springs. However, in most cases an additional hydraulic support is used to increase the bearing pressure of the vanes on the guide contour.

Even though the principle, as mentioned above, can be used for both pumps and motors, the following description is, for convenience, based on a motor.

In the working areas, the high pressure side of the vanes is acted upon by hydraulic fluid under increased pressure. The low pressure side of the vanes is exposed to a lower pressure. The pressure difference across the vanes produces the required torque for driving the motor. In some cases, it may happen that a closed vane cell is placed - 2 between the high pressure connection and the low pressure connection of the machine. In this case, the pressure difference across two or more vanes will apply.

As in all hydraulic machines, it is important that internal leakages are kept small, that is, that the machine is also fluid-tight inside. In this connection, areas in which sealing between movable parts is required cause particular problems.

In a vane machine, this is primarily the case with the bearing of the vane on the guide contour. Additionally, the vane cells must also be sealed towards the side. In the known cases, there is both friction between the rotor and the sideplates and friction between the vanes during their radial movement and the side plates. As considerable pressures are applied to obtain fluid-tightness, each of these movements causes wear and thus deterioration in performance, particularly when hydraulic fluids are used, the lubricating effect of which is poorer than that of the synthetic hydraulic oils used until now. Such a fluid could, for example, be water.

It is an object of the invention to improve the performance of a hydraulic vane machine.

The present invention provides a hydraulic vane machine with a rotor, which rotor has several radially movable vanes, with a stator having a stator bore, in which the rotor is arranged rotatably, and whose internal wall constitutes a guide contour on which the vanes bear, and with a respective sideplate arrangement on the axial side faces of rotor and stator, which sideplate arrangements, together with the rotor, the vanes and the stator, bound the vane cells, wherein the sideplate arrangements are fixed on the rotor and rotate together with the rotor in relation to the stator.

In a hydraulic vane machine of the kind mentioned in the introduction, the above-mentioned object is achieved in

3 that the sideplate arrangements are fixed on the rotor and rotate together with the rotor in relation to the stator.

This construction does not prevent friction between moving parts. However, at least, different kinds of movement are partly isolated from each other. Until now, the rotor with its vanes rotated in relation to the sideplates. This caused friction between the rotor side face and the sideplate. In the present construction, the sideplate now rubs on the stator side face. However, with the friction of the vanes it is a different matter. Until now, the vanes did not have to make simply a purely radial movement in relation to the sideplates. This radial movement had also superimposed on it the rotational movement, so that in principle the vanes had to brush across the whole sideplate surface. Extremely precise manufacturing of the vanes and the sideplates with corresponding mutual adjustment was required to keep friction at a low level. This is not the case any longer. The vanes make a purely radial movement in relation to the sideplates, whereas the sideplates make a purely rotational movement in relation to the side face of the stator. This means that these two movements are strictly isolated from each other. Accordingly, the mutual positioning of the individual parts can be improved, so that better fluid-tightness is achieved. A superimposed movement of the vanes in relation to the stator will also occur. However, this movement is restricted to a relatively small area, so that it is no longer so critical. In total, these design measures lead to somewhat reduced wear, which again gives improved operation of the machine. Particularly in the case of a motor, the reduced friction also gives improved starting torque or generally a better starting behaviour.

In a preferred embodiment, each sideplate arrangement has an inner plate and an outer plate, a hydraulic pressure pocket arrangement being formed between inner and outer - 4 plate. By means of the pressure pocket arrangement, pressure forces acting in the axial direction can be exerted on stator and rotor by the sideplate arrangement. While the sealing forces for the rotor could also be achieved by tightening up using mechanical fixing elements, this is more difficult with the contact surface facing towards the stator. However, the hydraulic forces which can be produced in the pressure pocket arrangement are sufficient to provide a seal also in this area. Here the outer plate can be used as abutment, on which the pressure in the pressure pockets is "supported", to press the inner plate against rotor and stator.

In this case, it is particularly preferred for the pressure pocket arrangement for each vane cell to have at least one pressure pocket connected with the vane cell. When the vane cell is exposed to pressure, such a permanent connection ensures that the same pressure will also prevail in the pressure pocket. On the other hand, it is also ensured that the pressure in the pressure pocket will drop when there is no pressure in the vane cell. Accordingly, the sealing forces are only built up when required. in the unloaded vane, cells sealing forces are not required. Therefore a sealing force is not produced here, and wear JL kept small.

Preferably, the pressure pocket has a larger pressure area than the vane cell in the axial direction. Irrespective of the magnitude of the pressure in the vane cell, this measure provides that the contact force of the sideplate on the stator is larger than the force attempting to lift the sideplate from the stator owing to the pressure in the vane cell. This measure is relatively simple. However, it ensures the fluid- tightness of the machine.

Advantageously, each pressure pocket has a seal. This reduces the requirement for accuracy when machining the inner and outer plates. The fluid-tightness is no longer - 5 provided only by the bearing of these two plates against each other. Fluid-tightness is assisted by the seal.

In this connection, it is particularly preferred that the seal be made by means of a sealing ring under bias arranged between inner plate and outer plate in the pressure pocket. Such a sealing ring, for example, made as round-section sealing ring or 0-ring is inexpensive and easy to mount.

It is particularly preferred that the inner plate has a recess, in the region of which the sealing ring does not bear on the inner plate in the axial direction. This measure provides that the hydraulic fluid under pressure can also reach an area between inner plate and sealing ring. In this way, penetration in one spot is sufficient. Then the hydraulic fluid, as it were, successively lifts the sealing ring from the inner plate and presses it against the outer plate. Thus, the total area of the pressure pocket is available for taking-up the hydraulic pressure and production of the corresponding forces, and not merely the space surrounded by the sealing ring. The arrangement can therefore also be used when only limited installation space is available.

In an alternative embodiment, the seal can also be formed by a membrane connected with the inner plate. The membrane is pressed against the outer plate through an admission of pressure to the pressure pocket, and thus produces the required contact forces. The membrane can, for example, be coated on the inner plate when a plastics coating is available here.

Preferably, a small gap is arranged in the area of the pressure pockets between inner plate and outer plate. As stated above, the inner plate and the outer plate need no longer be precisely adapted to each other. It may even be contemplated to leave a small gap between them on purpose. The width of the gap is in the range from a few hundredths 6 the sealing deformation to 3/10 mm. It is no problem to seal such a small gap with ring or the membrane, and a disadvantageous of the seal will not occur. However, the gap has the advantage that a possible unbalanced loading of the outer plate can be compensated. Such an unbalanced loading leads to a, though small, inclination of the outer plate in relation to the inner plate. Without the gap, this would directly cause the outer plate to act on the inner plate and press it with a relatively large force against the stator, causing increased wear. Primarily, this can be absorbed by the gap, as the gap permits a small inclination of the outer plate in relation to the inner plate. Furthermore, the gap simplifies mounting. The torque required for tightening the bolts keeping rotor and sideplate arrangement together need not be exactly the same for all bolts. However, it can be higher than without the gap, as drawing together the sideplates will not immediately cause bearing on the rotor.

Advantageously, the inner plate is provided with a friction-reducing plastics material, at least on the area bearing on the stator. Such a plastics material provides low-friction co-operation with -the material of the stator, for example, stainless steel. Particularly suited are plastics materials from the group of high-strength thermoplastic plastics materials on the basis of polyaryl ether ketones. These materials could be for example, polyether ether ketones, polyamides, polyacetals, polyaryl ethers, polyethylene terephthalates, polyvinylene sulphites, polysulphones, polyether sulphones, polyether imides, polyamide-imides, polyacrylates, phenolic resins, such as novolak resins etc., wherein glass, graphite, polytetrafluoroethylene or carbon, especially in fibre form, can be used as fillers. In this connection, especially the material polyether ether ketone (PEEK) has proved to be useful. When - 7 using such materials, even water can be used as hydraulic fluid.

In a preferred embodiment, a channel connected with a low pressure connection is provided between the inner plate and the rotor, which channel runs adjacent to the vane cells and the moving areas of the vanes. In spite of all precautions, it normally cannot be prevented that hydraulic fluid reaches areas in which it is not wanted. Even though it is only a question of small quantities, such a leakage during operation can lead to a pressure build-up corresponding to the operating pressure of the hydraulic machine. When the leaking hydraulic fluid reaches the area between rotor and sideplate it must be ensured that this hydraulic fluid does not cause separation of the sideplates, which would lead to further leakage. This is the reason for providing the channel. In the radial direction, it bounds as large an area as possible around the centre of the rotor. Of course, the size is limited on one hand by the vane cells and on the other hand by the moving areas of the vanes, also having hydraulic areas, which contribute to the control of movement of the vanes. In any case, the channel helps ensure that the area lying radially inside the channel is kept pressure-free. Any hydraulic fluid reaching the channel cannot move further inwards but is drained away to the low pressure connection through the channel. Thus the fixing means keeping the sideplates and the rotor together in the axial direction, for example, bolts, can be kept relatively small, thus simplifying dimensioning.

Advantageously, the inflow and outflow of hydraulic fluid takes place from the radial direction. This means that the sideplate arrangements are free from control tasks. They no longer have to perform proper commutation of the hydraulic fluid. They need only ensure that the - 8 vane cells remain fluid-tight. This is a considerable simplification of the machine design.

Preferably, the supply connections for inflow and outflow are arranged in the guide contour. In other words, both the pump connection and the tank connection or the high pressure connection and the low pressure connection, respectively, open out into the inner wall of the stator bore. Commutation then takes place automatically as the vanes pass by. These are then supplied with the corresponding pressures in the right position.

Preferably, the guide contour has working and nonworking sections, between which the commutation sections are arranged, the beginning and end of each commutation section having a supply connection with the same direction. The commutation areas or sections are the only sections in which the vanes move. With the arrangement of a supply connection both at the beginning and at the end of each commutation area, both connections having the same direcare not loaded with a into and extension from pump or high pressure ends of a commutation Correspondingly, two tank connections or low pressure connections are provided at the ends of the commutation section in which the vanes retract. The fact that the vanes are not loaded with a pressure difference on extension and retraction also ensures that they are not pressed against the rotor. Friction between rotor and vanes is thus kept as low as possible in the commutation sections. This also reduces wear and improves performance.

A hydraulic vane machine constructed in accordance with the invention will now be described by way of example only with reference to the accompanying drawings, in which:

tion, it is ensured that the vanes pressure difference on retraction the rotor. Thus, for example, two connections can be provided at the section in which the vanes extend.

9 - Fig. 1 is a longitudinal section through a hydraulic vane motor; Fig. 2 shows an enlargement of the detail A marked in Fig. 1; Fig. 3 is a schematic view of a sealing arrangement; Fig. 4 shows the section IV-IV marked in Fig.

Fig. 5 shows the section V-V marked in Fig. 1; and Fig. 6 shows the section VI-VI marked in Fig. 1 Referring to the accompanying drawings, a vane motor 1 has a stator 2 in which a rotor 3 is rotatably arranged. For that purpose, the stator has a stator bore whose inner wall creates a guide contour 4. The guide contour 4 has two diametrically opposed non-working sections 5 in which the stator bore diameter is only slightly larger than the rotor, and also two diametrically opposed working sections 6 in which the stator bore diameter is larger. Transition or commutation areas 7, 7a are arranged between the nonworking sections 5 and the working sections 6.

The rotor 3 has several, in this case eight, vanes 8, which are pressed radially outwards and thus against the guide contour 4 by means of a respective spring 9.

The principal mode of operation of such a motor 1 can be explained on the basis of Fig. 4. Pump channels 10 and tank channels 11 are provided in the stator. For reasons of clarity, Fig. 4 shows the pump channels 10 and the tank channels in the same plane. In reality, however, as shown in Fig. 1, they lie on planes displaced axially in relation to each other.

As the design of the machine is rotation symmetrical, only one working section 6 is explained in the following.

The pump channel 10 is connected with the stator bore via two pump bores 12, 13 arranged at the beginning and the end of the commutation section 7, that is, the pump bores 12, 13 open into the guide contour 4. The tank channel 11 is also connected with the stator bore via tank bores 14, 15, that is, the tank bores 14, 15 also open into the guide contour 4 at the beginning and the end of the commutation section 7a following the commutation section 7.

When the rotor 3 rotates in the direction of the arrow 16, a vane 8 first passes the pump bore 12. As hydraulic fluid is also supplied through the pump bore 13 with the same pressure, the vane 8 is exposed to the same pressure on both sides in the rotation direction. Thus, it can extend radially outwards under the force of the spring 9, without being pressed against the rotor by hydraulic pressures. If required, the force of the spring 9 can also be supported by hydraulic pressures (not shown).

As soon as the vane 8 has passed the second pump bore 13, hydraulic fluid is supplied only to its high pressure side. The high pressure side is the rear side in the movement direction. As soon as the preceding pump vane 8a has passed the tank bore 14, the hydraulic fluid on the low pressure side of the vane 8 flows into the tank bore. This causes a pressure difference between the two sides of the vane 8, which produces the torque required to drive the rotor 3.

Again in the following commutation section 7a, the vane 8 is exposed to the same pressure on both sides, namely, the tank pressure. Consequently, it is not loaded by a pressure difference of the hydraulic fluid, when it is retracted into the rotor 3 again through the effect of the guide contour 4.

Vane cells 17 are formed between the individual vanes. From Fig. 4 can be seen that these vane cells are bounded by the rotor 3 and the stator 2 (in the radial direction) and by neighbouring vanes 8, 8a in the circumferential direction. From Fig. 1 it is seen that, for sealing the vane cells 17 in the axial direction, sideplate arrangements 18 are provided on both axial side faces of rotor 3 and stator 2. These sideplate arrangements 18 bound the vane cells 17 in the axial direction.

The sideplate arrangements 18 comprise an 19 and an outer plate 20. The two sideplate 18 and the rotor 3 are fixed to each other by bolts 21, that is, the sideplate arrangements together with the rotor 3 in relation to the inner plate arrangements means of 18 rotate stator 2. together with the rotor 3, the vanes 8 can always be moved radially inwards and outwards at the same place in relation to the sideplates. Friction in the direction of rotation occurs in areas 22 between the inner plate 19 and the stator 2. To produce the required fluid-tightness here, the inner plate 19 must be pressed against the stator 2 with a certain force. This force is produced by means of a respective hydraulic pressure pocket 23 connected via a channel 24 with the associated vane cell 17. The cross-sectional area of the pressure pocket 23 in the axial direction is larger than the cross-sectional area of the vane cell 17 in the same direction. Correspondingly, the force working axially from the outside to the inside is larger than the force working axially from the inside to the outside. The inner plate 19 is thus pressed against the stator 2 with a positive force.

The contact force only appears, however, when hydraulic fluid under pressure is available in the vane cell 17. However, a seal will only be needed in this case. When the corresponding vane cell 17 is in a nonworking section 5, a As the sideplate arrangements 18 rotate - 12 contact force is not produced, neither is it required, as there is no hydraulic fluid, for which sealing is required.

At least in the area 22, the inner plate 19 has a surface with a frictionreducing plastics material, for example, polyether ether ketone (PEEK). In many cases, however, it will be advantageous to cover the whole inner plate 19 with the plastics material, or even to make it of this plastics material, wherein reinforcements of stainless steel can be provided.

The outer plate 20 is made of a more stable material, for example, of stainless steel. rials also permits the use of This combination of matewater as hydraulic fluid.

Between the inner plate 19 and the outer plate 20, at least in the area of the pressure pockets 23 there is a small gap 25. This gap 25 can have a width ranging from few hundredths to approximately 3/10 mm. It serves the purpose of compensating for a possible tilt of the outer plate 20 in relation to the inner plate 19, that is, to prevent a possible tilt, which might. for example, occur through an uneven loading of the outer plate 20, from causing a correspondingly higher contact force of the 1'- nner plate 19 against the stator 2. It also facilitates mounting. The bolts can be tightened with a relatively high torque, which need however not be uniform, the risk of jamming of the stator being normally rather small.

To seal this gap 25 (and of course to seal the pressure pocket 23 towards the outside), a seal in the form of a sealing ring 26 is provided, which is made as a roundsection sealing ring or O-ring. This sealing ring bears on both inner plate 19 and outer plate 20 under a certain bias (compression). An additional feature is, however, that the whole length of the sealing ring 26 does not bear on the inner plate 19. On the contrary, a recess 27 is provided, in whose area the sealing ring 26 is spaced a small distance from the inner plate 19. In this recess 27, the hydraulic fluid entering the pressure pocket 23 can now get under the sealing ring 26. The hydraulic fluid can then propagate along the length of the sealing ring 26, thus pressing the sealing ring 26 axially against the outer plate 20. This increases the effective cross-section of the pressure pocket 23. This appears from Fig. 3 showing a schematic view of the mode of operation.

Fig. 3a shows the embodiment without the recess 27. Here the hydraulic fluid could act on the sealing ring 26 only in the radial direction, as shown schematically by means of arrows. This will also provide some sealing, as the sealing ring 26 is deformed and seals the gap 25. However, basically only the area within the sealing ring 26 is available for pressure to act on the inner plate 19.

When, as shown in Fig. 3b, the hydraulic fluid can also get under the sealing ring 26 through the recess 27, it presses the sealing ring 26 against the plate 20 also in the axial direction, so that a larger pressure application surface will be available due to the corresponding counterpressure on the inner plate 19. Moreover, the fluidtightness is improved.

Alternatively, sealing of the pressure pocket 23 can also be effected in a way not shown, in that each pressure pocket has a membrane, made in one piece with the inner plate 19. This embodiment is especially advantageous, when the inner plate 19 has a coating of a plastics material. In this case, the membrane can be made together with the plastics material coating.

Fig. 5 shows the side of the inner plate 19, on which the pressure pockets 23 are arranged. Fig. 6 shows the opposite side of the inner plate 19.

Figs. 2 and 6 show that in the area of the vane cells 17 the inner plate 19 has pockets 28. By means of these pockets, it is possible to achieve equilibrium between the hydraulic forces on the axial inside and the axial outside - 14 of the inner plate 19. This is particularly important in the commutation areas 7, 7a, as here the cross-section of the vane cells 17 changes. However, the pockets 28 ensure that a constant pressure surface is available.

On the inside of the inner plate 19 shown in Fig. 6, a channel 29 is provided, following the vane cells, or rather the pressure pockets 28, closely. Furthermore, it surrounds the moving area of the vanes 8, here shown as a radial groove 30. Among other things, this radial groove 30 can also be used for transporting hydraulic fluid to the base 31 of the vanes 8 to intensify the hydraulic pressure to the outside. Further, this radial groove 30 can also be used for hydraulic relief of the vanes 8 on movements in the radial direction, which leads to a reduction in friction.

The purpose of the channel 29 is the draining of hydraulic fluid penetrating (radially) inwards between the rotor and the side plate arrangements 18 in spite of all sealing efforts. This provides a chamber, in the area radially inside the channel 29, to which the pressure of the hydraulic fluid is not admitted. Accordingly, the bolts 21 can be kept so small that they fit in between the individual vane cells 8.

When the inner plate 19 has a coating of a plastics material or is made of a plastics material, all channels shown in Figs. 5 and 6 can be made when moulding the plate, simply by providing a corresponding negative mould.

Claims

C L A I M S:

1. A hydraulic vane machine with a rotor, which rotor has several radially movable vanes, with a stator having a stator bore, in which the rotor is arranged rotatably, and whose internal wall constitutes a guide contour on which the vanes bear, and with a respective sideplate arrangement on the axial side faces of rotor and stator, which sideplate arrangements, together with the rotor, the vanes and the stator, bound the vane cells, wherein the sideplate arrangements are fixed on the rotor and rotate together with the rotor in relation to the stator.

2. A machine according to claim 1, wherein each sideplate arrangement has an inner plate and an outer plate, a hydraulic pressure pocket arrangement being formed between the inner and outer plates.

3. A machine according to claim 2, wherein the pressure pocket arrangement for each vane cell has at least one pressure pocket connected with the vane cell.

4. A machine according to claim 3, wherein the pressure pocket has a larger pressure area than the vane cell in the axial direction.

5. A machine according to claim 3 or 4, wherein each pressure pocket has a seal.

6. A machine according to claim 5, wherein the seal is made by means of a sealing ring under bias arranged between the inner and outer plates in the pressure pocket.

7. A machine according to claim 6, wherein the inner plate has a recess, in the region of which the sealing ring does not bear on the inner plate in the axial direction.

8. A machine according to claim 5, wherein the seal is formed by a membrane connected to the inner plate.

9. A machine according to any one of claims S to 8, wherein a small gap is arranged in the area of the pressure 16 - pockets between the inner plate and the outer plates.

10. A machine according to any one of claims 1 to 9, wherein the inner plate is provided with friction-reducing plastics material, at least on the area bearing on the stator.

11. A machine according to any one of claims 1 to 10, wherein a channel connected with a low pressure connection is provided between the inner plate and the rotor, which channel runs adjacent to the vane cells and the moving areas of the vanes.

12. A machine according to any one of claims 1 to 11, wherein the inflow and outflow of hydraulic fluid takes place, in use, from the radial direction.

13. A machine according to claim 12, wherein the supply connections for inflow and outflow are arranged in the guide contour.

14. A machine according to claim 12 or 13, wherein the guide contour has working and non-working sections, between which commutation sections are arranged, the beginning and end of each commutation section having a supply connection with the same direction.

15. A hydraulic vane machine substantially as herein described with reference to, and as illustrated by, the accompanying drawings.