EP2147222A2

EP2147222A2 - Hydrodynamic bearing with asymmetrical lobes

Info

Publication number: EP2147222A2
Application number: EP08805841A
Authority: EP
Inventors: Michel Wendling
Original assignee: Flender Graffenstaden SAS
Current assignee: Flender Graffenstaden SAS
Priority date: 2007-05-24
Filing date: 2008-05-23
Publication date: 2010-01-27
Also published as: WO2008149038A2; FR2916498B1; WO2008149038A3; FR2916498A1; US20100092115A1

Abstract

Hydrodynamic bearing with four lobes (l_1, l_2, l_3, L4) with centres of curvature that are eccentric relative to its geometrical centre, said lobes (L1, L2, L3, L4) being separated by oil feed grooves (5, 6, 7, 8), characterized in that the lobes (L1, l_2, L3, L4) are asymmetrical and include: - angular apertures of at least two different values; - at least two different eccentricities relative to the geometrical centre (O) of the bearing; the centres (01, 03; 02, 04) of two opposing lobes (L1, L3; L2, L4) being aligned with the geometrical centre (O) of the bearing.

Description

Hydrodynamic pad with asymmetrical lobes.

The present invention relates to a four-lobe hydrodynamic bearing intended to operate at high loads and at high speeds while having a stable operation when empty. Its specific capabilities are particularly sought after in the case of gear shafts of gearboxes or gear multipliers with high power gears.

The use of hydrodynamic bearings with symmetrical lobes is well known and widespread. The said lobes constitute four identical cylindrical sliding surfaces obtained by boring at diameters slightly greater than the assembly diameter of the pad, as shown in FIG. 1.

The angular apertures of the lobes are identical, and four oil feed grooves are machined between the lobes. Such a configuration, in which the centers of the lobe bores are eccentric with respect to the geometric center of the pad, makes it possible to obtain four precharge effects on the shaft. These effects are particularly advantageous for improving the hydrodynamic stability of the shaft-carrying film in the case of low radial load and high speed operation, or in the case of operation of rapid tree lines with critical dynamic behaviors.

The symmetrical arrangement of the lobes further allows the shaft to rotate in both directions of rotation with identical lift. Assuming the choice of important values of lobe eccentricity to produce high precharges, it is also possible to guarantee that, whatever the angular direction of the load, the shaft will never come into position on a groove. oil distribution, which would have the effect of causing a fall in lift of the shaft or hydrodynamic vibration instabilities. The use of a symmetrical lobe pad is therefore particularly well suited to high speed operation cases. sliding and for variable radial loads of low or moderate level, angular orientation also variable.

In this configuration, taking into account the space required for the distribution of oil to the friction surfaces, the angular aperture of each of the feed grooves is of the order of 20 °, which limits the angular aperture of each of the bearing surfaces at about 70 °. This value explains the low load capacity of a standard four-lobed pad in comparison with, for example, that of a pad with two fixed lobes whose active openings are greater than 150 °. The object of the present invention is, by modifying the angular apertures of each of the four lobes, to allow high load capacities to be obtained, while maintaining the aforementioned advantages of the symmetrical four-lobed pad. For this purpose, the hydrodynamic pad of the invention, also provided with four lobes with centers of curvature eccentric with respect to its geometric center, said lobes being conventionally separated by oil supply grooves, is mainly characterized in that that the lobes are asymmetrical and present:

angular openings of at least two different values;

at least two different eccentricities with respect to the geometric center of the pad; the centers of two opposing lobes being aligned with the geometric center of the pad.

In this new configuration, the four lobes do not perform the same functions, hence their different geometry. It is thus possible to assign to one of the lobes a much larger angular aperture than that of the others, so as to obtain a maximum lift surface.

In this case, this lobe is the charge lobe. The high value of its angular aperture makes it possible, with the same applied force, to obtain lower pressure point values in the oil wedge and higher oil film thicknesses. This improved bearing performance results in an improvement in endurance resistance of the anti-corrosion metal. friction of the sliding surface and a reduction of the temperature where the thickness of the film is minimal. The eccentricity, relative to the geometric center of the bearing, the center of the maximum angular aperture lobe and the value of the load angle are chosen so as to have the optimum conditions of lift of the oil film.

The other three lobes, of smaller angular aperture, are lobes of maintenance and stabilization. For this reason, the offsets of their center have values much higher than the eccentricity of the center of the load lobe. The choice of offsets and angular apertures of the active surfaces of the four lobes ensures continuity of guiding of the shaft. As in the case of a symmetrical four-lobe bushing, the shaft can not come into contact with the lubricating and cooling devices arranged between the end of the active sliding surface of a lobe and the beginning of the active zone. of the next lobe. The lobes may also have at least two different axial widths.

According to the invention, for a shaft centered at the geometric center of the bearing, the minimum clearance points of two opposing lobes are aligned with the geometric center of the bearing. In this case, these points are located on a circle whose diameter corresponds to the assembly diameter of the pad. This arrangement makes it possible to preserve for the asymmetrical lobe pad the ease of dimensional control of the assembly diameter of the symmetrical four-lobe bearings. The pad of the invention may consist of two half-shells angular opening of 180 ° each.

More specifically, each of these half-shells may comprise two lobes and two grooves. The joint plane of the bushing is angularly oriented so that the nominal load is directed on the load lobe. The invention will now be described in more detail with reference to the various figures for which:

- Figure 1 is a sectional view of a bearing with symmetrical four lobes constituting the prior art; FIG. 2 represents a pad with four asymmetrical lobes, which is the subject of the present invention.

With reference to FIG. 1, the four lobes (1, 2, 3, 4) are symmetrical, that is to say that they have the same angular aperture and the same radius of curvature. Thus, the four centers (01, 02, 03, 04) of the arcs that constitute them are arranged symmetrically with respect to the geometric center (O) of the pad, which is in practice located at the intersection of the diagonals of the square constituted by said points. (01 to 04). The lobes (1, 2, 3, 4) are separated by grooves (5, 6, 7, 8) provided for the oil supply.

The circle (9) represented in FIG. 1 in dashed lines passes through the four points which appear at the place where the arrows schematizing the four lobes (1, 2, 3, 4) point at the intersection between said lobes.

(1, 2, 3, 4) and the lines respectively (01, 03) and (02, 04). The diameter of this circle corresponds to the assembly diameter of the pad.

As already mentioned, such a pad is adapted to operating hypotheses with high sliding speed and variable radial loads of low to moderate level.

One of the advantages of this configuration can be seen in the fact that this pad works in the same way in both possible directions of rotation. However, it has limitations in case of high load and high speed operation.

The pad appearing in FIG. 2, which is the object of the present invention, overcomes these drawbacks and proposes a configuration which is perfectly suited to high loads, even in the case of high speed. This pad is asymmetrical, that is to say that the angular sectors covered by each of the lobes (L1, L2, L3, L4) are different. As a corollary, the eccentricities of the centers (01, 02, 03, 04) with respect to the geometric center (O) of the bearing are also variable from one lobe to the other. The lobe (L1) is the lobe of charge. Its angular aperture is therefore much higher than that of the lobe (L2), so as to obtain a maximum lift surface. The pad is in this case constituted by two half shells (10, 11). The lobes (L1) and (L2) are located in the half-pad (10), while the lobes (L3) and (L4) are arranged in the other half-pad (11).

The joint plane is oriented angularly so that the nominal load is directed on the lobe (L1). The angular sector of the lobe (L1), as well as the radius of curvature and consequently the eccentricity of (01) with respect to (O) allows optimum lift of the oil film resulting in particular from a decrease in peak values. pressure in the oil wedge, as well as an increase in oil film thicknesses at the lobe (L1). The anti-friction metal of the sliding surface has a better mechanical endurance due to these increased lift performance.

The lobes (L2) to (L4) are stabilization and holding lobes with greater eccentricities of the points (02) to (04) than that of the lobe (L1).

The choice of these eccentrations as well as the choice of the angular openings of the active surfaces of the four lobes ensure the continuity of the guidance of the tree. In this configuration, it can not come into contact with the lubrication and cooling devices placed between two successive lobes. It should be noted that, in this configuration, even the oil supply grooves (5) to (8) can be asymmetrical, angularly and in axial width.

This solution, in addition to the clear improvement of the lift of the oil film at the level of the load lobe, makes it possible to size the sliding surfaces of the unfilled lobes so as to optimize the cooling of the bushing and to reduce the friction losses.

Claims

1. Hydrodynamic pad with four lobes (11, 12, 13, 14) with eccentric centers of curvature with respect to its geometric center, said lobes (L1, 12, 13, L4) being separated by grooves (5, 6, 7). , 8) for supplying oil, characterized in that the lobes (L1, 1-2, L3, L4) are asymmetrical and have:

angular openings of at least two different values;

at least two different eccentricities with respect to the geometric center (O) of the pad; the centers (01, 03, 02, 04) of two opposite lobes (L1, L3, L2, L4) being aligned with the geometric center (O) of the pad.

2. Hydrodynamic pad with four lobes (L1, L2, L3, L4) according to the preceding claim, characterized in that the lobes (L1, L2, L3, L4) have at least two different axial widths.

3. hydrodynamic pad with four lobes (L1, L2, L3, L4) according to the preceding claim, characterized in that, for a shaft centered at the geometric center (O) of the pad, the minimum clearance points of two opposing lobes (L1 , L3, L2, L4) are aligned with the geometric center (O) of the pad.

4. Four-lobe hydrodynamic pad (L1, L2, L3, L4) according to one of the preceding claims, characterized in that the minimum clearance points of the four lobes (L1, L2, L3, L4), when the shaft is centered at the geometric center (O) of the pad, are located on a circle (9) whose diameter corresponds to the assembly diameter of the pad.

5. hydrodynamic pad with four lobes (L1, L2, L3, 4) according to any one of the preceding claims, characterized in that it consists of two half-shells (10, 1 1) of angular opening of 180 ° .

6. hydrodynamic pad with four lobes (L1, L2, L3, L4) according to the preceding claim, characterized in that it comprises two lobes (L1,

L2; L3, L4) and two grooves (5, 8; 6, 7) per half shell (10, 1 1).