GB2111127A - Rotary positive-displacement fluid-machines - Google Patents

Abstract

In a hydraulic machine that may be a pump of the sliding-vane type (as shown) a transverse pressure- balancing channel 21 is provided in the rotor 9 so as to equalize the pressures in liquid-filled gaps 18, 19 between the rotor end- faces and the adjacent housing walls 3, 11. Alternative forms of the channel(s) are described with reference to Figs. 2 and 3 (not shown). <IMAGE>

Description

SPECIFICATION Arrangement for the axial positioning of a rotor of a hydraulic displacement machine The present invention relates to an arrangement for the axial positioning of a rotor of a hydraulic displacement machine, the rotor being composed of a shaft with a rotor body arranged thereon, and the rotor end faces forming together with associated stationary housing walls variable interconnected sealing gaps.

In consequence of the axial movability of the rotor (rotary piston), there result in such arrangements axial gap widths of different amount at both end faces of the rotor. When one gap increases and the other decreases in consequence, the distribution of pressure over the width of the smaller gap will change due to friction influences and variations in the viscosity, as well as due to an elastic deformation of the components and thus of the gap geometry. Thereby a surplus force will be caused on the side of the larger gap which displaces the rotor still further in the direction of the smaller gap and thus decreases the latter still more. Said surplus force will be compensated by a mechanical counterforce which has as a result a high contact pressure between rotor end face and the abutting stationary side wall of the housing.Caused by this, the surfaces sliding on each other will no longer be separated by a lubricating film, and mixed friction will occur between the parts concerned. Since such a gap is susceptible to contaminants, high temperatures will result due to hydraulic fluid lacking what-together with the high contact pressure and the low viscosity of the lubricant and the contami nantscan result in seizing of the respective parts.

Various solutions have been proposed so far to obtain a stable centred position of the rotor between the housing end walls respectively between frontally arranged control discs. However, despite expensive and complicated design arrangements, these solutions bear considerable disadvantages: In a hydrostatic bearing, there occur high radial losses in leakage oil, and the functional reliability is comparatively limited in spite of great and costly efforts made in the manufactire of the nozzles.

Even when employing control grooves uniform in dimension and location on both sides of the rotor, disadvantages will arise which essentially consist in that no exact defined control and no precise centered position of the rotor are possible, as a result whereof there is increased danger of seizing on account of unilateral axial abutment of the rotor. In addition, expensive material combinations (bronze) are required in the area of the control discs, and there result a larger quantity of radial leakage oil and thus a lower volumetric efficiency.

When the control surfaces on the lateral discs are of varying size, the above disadvantages will even be potentiated.

Finally, it is known to arrange for short-time connections to the leakage oil chambers by means of small control grooves which will be actuated once per rntationfor a short interval.

Though this affords the advantage that the bearings will be supplied with oil more uniformly, there may likewise ensur a unilateral abutment of the rotor and thus the disadvantages described hereinabove as well as considerable pressure pulsations which imply additional noise.

To overcome the disadvantages occasioned by the varying width of the sealing gaps, an arrangement of the type initially referred to has already been proposed in German printed and published patent application 28 46 841, wherein the two sealing gaps are connected via channels containing invariable hydraulic resistances to the high pressure side of the displacement machine in such manner that a positioning control circuit will be formed for the axially symmetric position of the rotor which comprises the sealing gaps on both sides and the invariable resistances, the said circuit being of the kind of a hydraulic bridge circuit. In the event of the axial position of the rotor drifting from.the centered position, this arrangement has as a consequence a compulsory resetting so that there are constantly provided equal gap widths on both end faces of the rotor.Admittedly, a like arrangement fulfils the fundamental preconditions for a sufficient lubrication of the bearing on account of an exact centered position of the rotor, however, design and manufacture thereof are comparatively costly because of the various connecting bores required.

It is therefore an object of the present invention to improve an arrangement of the type initially referred to such that its design and manufacture can be considerably simplified.

According to the present invention there is provided an arrangement for the axial positioning of a rotor of a hydraulic displacement machine, the rotor being composed of a shaft with a rotor body arranged thereon, and the rotor end faces forming with associated stationary housing walls variable interconnected sealing gaps, wherein the rotor contains at least one connecting channel to interconnect the sealing gaps.

This permits to obtain an exact centered position of the rotor while minimal and uniform radial leakage, for example, oil is attained. Moreover, sufficient lubrication of the bearing will be ensured when a good volumetric efficiency is provided. In addition, unilateral control pockets can be arranged in the arrangement which leads to a simpler con struction. The arrangement enables further more an exact control and thus causes less noise. There is no need for special material combinations.

In a preferred embodiment of the present invention, the connecting channel extends transversely through the shaft carrying the rotor body. In this case, the connecting channel advantageously includes ports in the area between the rotor body and sliding bearings, which latter support the shaft and are contained in the housing. Due to these transverse connecting bores in front of the sliding bearings, a pressure balance takes place between the chambers of the displacement machine so that the rotor (rotary piston) will always be urged to assume its centered position. Besides, the two sliding bearings will be uniformly supplied with leakage oil independently of the instantaneous position of the rotor.

Instead of the transversely extending connecting channel, there may be likewise provided a connecting channel including a radial portion on each side of the rotor body and a portion along the axis of the shaft, the latter portion connecting the said radial portions.

According to another embodiment of the invention, the connecting channel may likewise extend through the rotor body parallel to the shaft.

The present invention will be described in more detail in the following by way of embodiments illustrated in the accompanying drawings.

In the drawings, Figure 1 is a longitudinal sectional view of a hydraulic displacement machine with a connecting channel extending transversely through the rotor; Figure 2 is a partial longitudinal sectional view of a displacement machine with the connecting channel that extends through the rotor having a different location, and Figure 3 is a partial longitudinal sectional view of a hydraulic displacement machine with the connecting channel in the rotor body having a third location.

The displacement machine 1 illustrated in Fig. 1 is a vane-type rotary pump having a pump housing 2 which is closed by a cap 3 secured thereto. The housing 2 and the cap 3 contain bores 4 and 5 receiving the sliding bearings 6 and 7, the said bores being in alignment with one another. Supported in the latter bearings is a shaft 8 to which a discshaped rotor body 9 is fitted. Said rotor body can be integrally designed with the shaft 8 of the rotor-as is illustrated.

An annular chamber 10 is provided in the pump housing 2 to receive the rotor body 9.

Besides the rotor body 9, said annular chamber 10 accommodates an intermediate disc 11. The pump housing 2 contains a pressurefluid inlet bore 1 2 and a pressure-fluid outlet bore 1 3. Terminating in these bores 1 2 and 1 3 are paraxial channels 14 and 1 5 which extend likewise through the intermediate disc 11 and which establish connection to the vane compartments 1 6 of the displacement machine 1. Said vane compartments 1 6 are formed by vane elements not shown which are slidable to and fro in radial slots designed in the rotor body 9 and which abut with their outer edge on a control ring 1 7.

To connect a sealing gap 1 8 disposed between the rotor 8, 9 and the intermediate disc 11 with a sealing gap 1 9 disposed between the rotor 8, 9 and the oppositely lying inner surface of the pump housing 2, a throughchannel having the shape of a bore 21 extends transversely through the rotor 8, 9.

Said bore 21 contains a port 22 in the area between the sliding bearing 7 and the rotor body 9 as well as a port 23 between the sliding bearing 6 and the rotor body 9, in each case in the transition area between the rotor body 9 and the shaft 8.

In the embodiment illustrated in Fig. 2 in which the essential components of the displacement machine 24 correspond to those of the displacement machine 1, a through-channel 28 is arranged in the rotor shaft 27 to interconnect the sealing gaps 25 and 26 which correspond to the sealing gaps 1 8 and 1 9 in Fig. 1, the said through-channel 28 comprising two radial portions 29 and 30 on both sides of the rotor body 34 which terminate each in the area between the sliding bearings 32 and 33 and the rotor body 34 into the sealing gaps 25 and 26 and which are interconnected by an axial portion 31 that extends along the axis of the shaft 27.

The displacement machine 36 illustrated in Fig. 3 in turn is substantially identical with the displacement machines 1 and 24. However, to connect the sealing gaps 37 and 38, this method provides for at least one bore 40 to extend through the rotor body 41 in parallel to the shaft 39, the said bore terminating in the area of the chambers in front of the sliding bearings 32, 33 and by this establishing a connection to the sealing gaps 37, 38.

If the rotor body 9 is weakened too much due to bore 21 or 28 or 40, the said may also extend through the pump housing 2.

Claims (6)

1. An arrangement for the axial positioning of a rotor of a hydraulic displacement machine, the rotor being composed of a shaft with a rotor body arranged thereon, and the rotor end faces forming with associated stationary housing walls variable interconnected sealing gaps, wherein the rotor contains at least one connecting channel to interconnect the sealing gaps.

2. An arrangement as claimed in claim 1, wherein the connecting channel extends transversely through the shaft which carries the rotor body.

3. An arrangement as claimed in claim 2, wherein the connecting channel includes ports in the area between the rotor body and sliding bearings the latter supporting the shaft and being contained in the housing.

4. An arrangement as claimed in claim 1, wherein the connecting channel includes a radial portion on each side of the rotor body and a portion extending along the axis of the shaft and connecting the radial portions.

5. An arrangement as claimed in claim 1, wherein the connecting channel extends through the rotor body parallel to the shaft.

6. An arrangement substantially as hereinbefore described with reference to and as illustrated in Fig. 1, Fig. 2 and Fig. 3 of the accompanying drawings.