RADIAL SPIRAL-GROOVE BEARING

Abstract: A radial bearing comprising a cylindrical bearing bush (1) and a shaft arranged therein, the bush (1) and the shaft being rotatable with respect to each other and one of the cooperating bearing surfaces of the bush and the shaft being provided with a pattern of shallow lubricant-pumping grooves (3) (4) which, during relative rotation between the bush (1) and the shaft, build up a pressure in a lubricant present between the shaft and the bush (1). In one axial zone of the bush or the shaft the relevant bearing surface is provided along one half of its circumference with a groove pattern (3) which is arranged to pump in one circumferential direction, and along the other half of its circumference with an identical groove pattern (4) which is arranged to pump in the opposite circumferential direction.

Description: The invention relates to a radial bearing comprising a cylindrical bearing bush and a shaft arranged therein, the bush and the shaft being rotatable with respect to each other and one of the cooperating bearing surfaces of the bush and the shaft being provided with a pattern of shallow lubricant­ pumping grooves which, during relative rotation between the bush and the shaft, build up a pressure in a lubricant present between the shaft and the bush. A radial bearing of the kind described above is described in the Netherlands Patent Application 7609817 (PHN.8508) laid open to public inspection. In this known bearing, the shaft or the bush is provided with at least three patterns of shallow lubricant-pumping grooves located in successive axial zones, the two outer patterns having grooves which exert their pumping effect in the same direction and the intermediate pattern having grooves pumping in the opposite direction. The result of this is that upon rotation of the shaft in one direction a pressure is built up in the lubricant present in the area of one outer pattern of grooves and the inner pattern of grooves, while upon rotation in the opposite direction a pressure is built up in the lubricant present at the area of the other outer pattern of grooves and the inner pattern of grooves. Thus, the bearing operates both upon rotation in one direction and upon rotation in the other direction. A disadvantage of this known bearing is that with the different directions of rotation disturbing tilting moments occur in such a bearing. This is due to the fact that in one direction of rotation journalling takes place in one axial zone and in the other direction of rotation journalling takes place in another axial zone. Especially with self-adjusting bearings and more particularly with relatively heavily loaded bearings, patterns of grooves of the kind mentioned herein before cannot be used. The invention has for its object to provide a hearing of the kind mentioned in the opening paragraph, which is suitable for two directions of rotation and in which the said disturbing tilting moments do not occur. The radial bearing according to the invention is characterized in that in an axial zone of the shaft or the bush the relevant bearing surface is provided along one half of its circumference with a pattern of grooves which is arranged to pump in one circumferential direction, and along the other half of its circumference with an identical pattern of grooves with is arranged to pump in the opposite circumferential direction. Thus, a bearing is obtained in which both upon rotation in one direction and upon rotation in the other direction a pressure is built up in the lubricant, i.e. in the same axial zone, so that a varying tilting moment does not occur. In this configuration of the pattern of grooves, however, it has to be ensured that the load vector has a constant direction with respect to the pattern of grooves. This means that with a rotating load (imbalance) the patterns of grooves have to be formed in the shaft, and with a load vector which always has the same direction the patterns of grooves have to be formed in the bush. In a further embodiment of the bearing according to the invention, the grooves of the two patterns are so formed that the bottoms of the grooves extend eccentrically about the axis of the bearing so that the depth of each groove varies gradually from a maximum at the area where the patterns adjoin each other along one axially extending side of each pattern to a minimum at the area where the patterns of grooves adjoin each other along the other axially extending side. Thus, extremely high loads can be transferred by means of a lubrication film formed hydrodynamically. The grooves in the bearing surfaces mainly serve as supply grooves for the lubricant, while in the substantially smooth (ungrooved) bearing part an optimum lubrication film is formed by means of the wedge effect, which film keeps the shaft and the bush separated from each other. A further embodiment of the bearing is characterized in that the groove patterns are each bounded at their two axially spaced ends by a lubricant-collecting groove provided in the shaft or in the bush. Lubricant is pumped into the latter grooves from the bearing gap over one half of the circumference from these grooves into the bearing gap, in which a pressure is then built up. The invention will be described more fully with reference to the drawings. Figures 1 and 2 show in axial sectional view and in end elevation a radial bearing suitable for two directions of rotation, the bearing being provided with grooves having the same depth throughout their length; Figures 3, 4 and 5 show in a tranverse sectional view and in two axial sectional views, respectively, taken on the lines IV-IV and V-V, respectively, a radial bearing suitable for two directions of rotation, the bearing being provided with grooves of varying depth. In Figures 1 and 2, reference numeral 1 designates a bearing bush in which a shaft 2 can be rotatably journalled. For the sake of clarity, the shaft is omitted from Fig. 1. The bearing bush 1 is provided at its inner circumference with two patterns of helically extending grooves 3 and 4, the pattern 3 extending along the right-hand half of the circumference, as viewed in the drawings, and the pattern 4 extending along the left-hand half thereof. When the shaft 2 rotates in the direction indicated by the arrow 5, (Fig. 2), lubricant will be pumped in the groove pattern 3 towards the area 6 of the circumference of the bearing bush. Upon rotation of the shaft 2 in the other direction indicated by the arrow 7, lubricant will be pumped through the grooves of the pattern 4 towards the area 6. In both directions of rotation, the bearing gap between the bush 1 and the shaft 2 will consequently always be filled at 6 with lubricant under pressure. It is assumed that the load vector is directed constantly towards the area 6. To collect lubricant the patterns 3 and 4 are each bounded at their two axially spaced ends by grooves 8 and 9, respectively. The grooves 8 and 9 are bounded at their sides remote from the groove patterns by rings 10 and 11, respectively. The rings 10 and 11 under certain circumstances may also form part of the bearing bush 1. Upon rotation of the shaft 2, lubricant from the store of lubricant in the grooves 8 and 9 is drawn along one half of the inner circumference through the other groove pattern. Upon reversal of the direction of rotation of the shaft, the latter situation also changes. Figures 3, 4 and 5 show diagrammatically a radial bearing with a shaft 2 and a bearing bush 1. The bearing bush, as in the preceding embodiment, is provided with two patterns 13 and 14 of shallow lubricant-pumping grooves. However, the grooves are now so formed that the bottoms of the grooves extend somewhat eccentrically about the axis of the bearing so that the depth of each groove varies gradually from a maximum at 15 where the two groove patterns adjoin each other along one axially extending side of each pattern to a minimum, even approaching zero at 16 where the patterns adjoin each other along the other axially extending side. The result of this is that upon rotation of the shaft 2 in the direction of the arrow 17, the groove pattern 13 pumps lubricant to the area 16 of the bearing gap and a high hydrodynamic pressure is built up in the lubricant there due to the wedge effect so that high loads can be absorbed. Upon rotation of the shaft 2 in the direction of the arrow 18, the groove pattern 14 pumps lubricant to the area 16. Thus, a spiral-groove radial bearing is obtained which ensures satisfactory journalling during rotation of the shaft in each of the two directions. However, in this case the load should, of course, always be directed towards the area 16. In the case of a load vector following the rotation of the shaft, the groove patterns must therefore be provided not in the bearing bush but on the shaft.

Claims: 1. A radial bearing comprising a cylindrical bearing bush and a shaft arranged therein, the bush and the shaft being rotatable with respect to each other and one of the cooperating bearing surfaces of the bush and the shaft being provided with a pattern of shallow lubricant-pumping grooves which, during relative rotation between the bush and the shaft, build up a pressure in a lubricant present between the shaft and the bush, characterized in that in an axial zone of the bush or the shaft the relevant bearing surface is provided along one half of its circumference with a groove pattern which is arranged to pump in one circumferential direction, and along the other half of its circumference with an identical pattern of grooves which is arranged to pump in the opposite circumferential direction. 2. A radial bearing as claimed in Claim 1, characterized in that the grooves of the two patterns are so formed that the bottoms of the grooves extend eccentrically about the axis of the bearing so that the depth of each groove varies gradually from a maximum at the area where the patterns adjoin each other along one axially extending side of each pattern to a minimum at the area where the groove patterns adjoin each other along the other axially extending side. 3. A radial bearing as claimed in Claim 1 or 2, characterized in that the groove patterns are each bounded at their two axially spaced ends by a lubricant-collecting groove provided in the shaft or the bush.

Inventors: TIELEMANS, LEONARDUS PETRUS MARIA, VAN ROEMBURG, FRANCISCUS MARIA JOHANNES
Applicants: N.V. PHILIPS' GLOEILAMPENFABRIEKEN
Application year: 1986
Main classification: F16C33
IPC codes: F16C33, F16C17