DE102008050412A1 - Multiplane slide bearing for rotatory mounting of spindle motor, has bearing bush with multiple sliding surfaces and has shaft, where sliding surface has lubrication groove, compression surface and plateau surface - Google Patents

Abstract

The multiplane slide bearing has a bearing bush (1) with multiple sliding surfaces and has a shaft (2). The sliding surface has a lubrication groove (4), a compression surface (5) and a plateau surface (6). The plateau area has a bearing gap (3) of certain width and the compression surface has an additional gap of largest width. The multiplane slide bearing has three sliding surfaces and the diameter of the shaft is 2-3 millimeter. An independent claim is included for a spindle motor with a stator and a rotor arranged in a housing of a hard disk drive.

Description

Field of the invention

The Invention relates to a multi-surface sliding bearing, in particular for the rotary mounting of a spindle motor. Such bearings are also called polygonal plain bearings or n-lobes bearings with n> = 2 ("Lemon bearing" for n = 2) designated.

State of the art

The characteristic feature of a multi-surface bearing is that of usual cylindrical plain bearings deviating, non-circular shape of the bearing bore, which consists of two or more sliding surfaces in the form of circular arcs consists.

Of the Radius of the sliding surfaces is larger by a certain amount than the radius of the shaft, which causes a bearing gap results, which with a suitable lubricant filled is. From this difference in radius between shaft and sliding surface arises in each arc a wedge-shaped gap, called the compression area is and each with its greatest width at an axially in the bearing bush incorporated lubrication groove begins. The narrowest point of the Bearing gap is usually in the middle of the sliding surface in one so-called plateau area. At the onset of rotation of the shaft Due to its adhesion to the shaft and sliding surfaces, the lubricant becomes weaker the well-known lubrication theory in the direction narrowed in the direction of rotation Bearing gap pulled. In the bearing gap between shaft and bearing bush builds up a pressure mountain, which on reaching a certain Value the shaft lifts off the bearing bush. Shaft and bearing bush are thus separated from each other by the intervening bearing gap separated, d. H. the wave is running in the field of hydrodynamic lubrication.

Mehrflächengleitlager are characterized by high load capacity, suitability for high speeds and low friction losses.

By Adaptation of the lubricant toughness, the shaft peripheral speed and the shape of the bearing gap, the height of hydrodynamic load capacity and the bearing friction varies and thus adapted to the respective requirements.

Disclosure of the invention

It The object of the invention is a multi-surface sliding bearing in terms Optimize bearing friction and concentricity.

These The object is achieved by the Characteristics of the independent Claim 1 solved.

preferred Embodiments of the invention and further advantageous features arise from the dependent ones Claims.

The Mehrflächengleitlager includes a bearing bush with several sliding surfaces and one in the bearing bush rotatably mounted shaft, wherein the sliding surfaces each have a lubricating groove, a compression surface and a plateau area where g is the width of the bearing gap in the area of the plateau surface and H an additional Width of the gap in the area of the compression surface is. According to the invention, H = a + b · g, where the value a is between 0.2 and 0.6, the value b between 0.2 and 0.6 and the gap width g of the bearing gap between 0.5 microns and 5 microns.

With the specified dimensioning of the size H results in an optimization of the multi-surface plain bearing in terms of concentricity, shock and bearing friction, such as Studies have shown. The multi-surface sliding bearing according to the invention may preferably used for pivotal mounting in a spindle motor, which in turn for Drive a hard disk drive is used. Hard disk drives have memory disks that are read out by read / write heads. An important Measure is here the track error (off track error), d. H. the deviation of the Read / write head of the respective data track, on which the Data is recorded. This deviation arises inter alia by inaccuracies of the concentricity of the storage system, so that the Read / write head deviates from the optimum track in the radial direction. The described multi-surface sliding bearing was optimized for this tracking error.

According to the invention in particular multi-surface plain bearings with three sliding surfaces and a shaft diameter between 2 and 3 mm as well as multi-surface plain bearings with five sliding surfaces and a shaft diameter of 3 to 5 mm. At a Multi-surface sliding bearing according to the invention with five sliding surfaces are the value for a preferably between 0.1 and 0.4, the value of b preferably between 0.1 and 0.4 and the value g of the gap width between 0.5 microns and 5 microns.

Preferably is the gap width of the bearing gap g between 1.8 to 2.5 microns.

Preferably is the area fraction the lubrication groove on the sliding surface 5 to 15%. The preferred area percentage the compression surface on the sliding surface is 20 to 75% of the total sliding surface.

Of the preferred area proportion the plateau surface on the sliding surface is 20 to 45%.

embodiments The invention will be explained in more detail with reference to the drawings. Out The drawings and the following description will become apparent Further features and advantages of the invention.

Short description of the drawing

1 schematically shows a plan view of an inventive multi-surface sliding bearing.

1a shows enlarged a section of the bearing in the region of the bearing gap.

2 shows a diagram of the gap width H as a function of the bearing gap width g for certain values of a and b.

3 shows a diagram of the area ratio of the plateau surface as a function of the gap width g for an optimized bearing.

4 shows in a diagram a family of curves of the size of the additional gap width H as a function of the circumferential angle for a sliding bearing with three sliding surfaces.

5 shows the same as 4 for a sliding bearing with five sliding surfaces.

6 shows by way of example the tracking error of the multi-surface sliding bearing according to the invention as a function of the gap width g.

Description of preferred embodiments the invention.

1 shows a plan view of a multi-surface sliding bearing according to the invention. The bearing comprises a bearing bush 1 with a non-circular bearing bore, in which a shaft 2 is rotatably mounted. Between the inner wall of the bearing bush and the outer circumference of the shaft 2 there remains a bearing gap 3 , which is filled with a bearing fluid, such as a bearing oil. In the example shown is a Mehrflächengleitlager with a total of five on the bearing bush 1 trained sliding surfaces shown. Each sliding surface covers a circumferential angle of 72 ° (360 ° / 5) and includes a lubrication groove 4 , in the longitudinal direction, ie parallel to the axis of rotation, in the bearing bush 1 is introduced. The wave 2 turns in the direction of the arrow 7 counterclockwise and is completely cylindrical. Starting from the lubrication groove 4 each sliding surface closes in the direction of rotation 7 a compression surface whose area in 1 with the numeral 5 is designated. This compression surface 5 forms together with the surface of the shaft 2 a wedge gap with decreasing bearing gap width. At the area of the compression surface 5 closes a plateau area 6 on, which forms the narrowest point of the bearing gap and in which the bearing gap has a constant gap width g.

1a shows an enlarged view of a portion of the bearing in the region of the bearing gap 3 , wherein for simplicity the surfaces of the bearing bush 1 and the wave 2 not arcuate but are shown as straight lines. You can see the lubrication groove 4 , in the direction of movement 8th of the bearing fluid, which also the direction of movement 7 the wave 2 corresponds to the compression range 5 followed. In the area of the compression surface, the width of the bearing gap is reduced from its greatest width g + H to its smallest width g. In the area of the plateau area 6 the bearing gap width g remains constant. When using the rotary motion of the shaft 2 becomes the bearing fluid due to its adhesion to wave 2 and the sliding surfaces of the bearing bush 1 in the direction of rotation narrowing bearing gap 3 pressed. It builds between wave 2 and bearing bush 1 a pressure mountain, which makes the camp viable. The running accuracy and bearing friction depends in particular on the viscosity of the lubricant but also on the shape of the bearing surfaces. It has been found that, in particular, the width g of the bearing gap plays a role in comparison to the additional width H of the compression gap. The optimized additional gap width H in the compression area 5 can be expressed by the multiplication of the bearing gap width g with a proportionality factor b and addition with a value a: H = a + bg

2 shows diagrams of the additional gap width H in relation to the gap width g. The curve 10 applies to a 3-surface plain bearing with H = 0.397 + 0.41 × g. The curve 11 applies to a 5-surface sliding bearing with H = 0,124 + 0,204 × g.

For example arises for a 5-surface sliding bearing and a typical gap width g of 2 to 3 microns optimized additional Gap width of 0.5 to 0.7 microns. For a 3-surface plain bearing is the extra Slit width H at the same bearing gap width g must be set much higher.

In addition to the size of the additional gap width H in relation to the bearing gap width g still plays the surface portion of the plateau surface 6 relative to the total area of the sliding surface a role for the optimization of the storage properties.

3 shows the optimal area proportion of the plateau section 6 on the total surface part of a sliding surface in relation to the bearing gap width g for bearings with five or three sliding surfaces. Curve 12 applies to a Mehrflächengleitlager with three sliding surfaces, it can be seen that with increasing gap width g of the bearing gap and an increasing surface portion of the plateau section should be provided. With a bearing gap width of about 4 μm, the area fraction has reached its maximum at about 28% and again drops slightly for larger widths of the bearing gap. In a bearing with five sliding surfaces, the required area for an optimal bearing increases up to a gap width of about 3 microns to about 27% and dwells even for larger gap widths to about 5 microns at this level, the optimization in this area strong noise (up to ± 3%).

4 shows a family of curves for the parameter bearing gap width and the associated optimal additional gap width H as a function of the circumferential angle. Up to a circumferential angle of about 15 ° is the lubricating groove 4 , so that here the additional gap width H increases sharply up to its maximum at about 15 ° circumferential angle. From this circumferential angle of 15 ° reduces the additional gap width H for all bearing gap widths steadily up to a circumferential angle of about 85 to 100 °. From here, the additional gap width H is equal to zero and the plateau area adjoins, which runs up to 120 ° circumferential angle. The representation in 4 applies to a plain bearing with three sliding surfaces, ie each sliding surface has a total circumferential angle of 120 °.

5 shows a representation of a sliding bearing with five sliding surfaces, each sliding surface having a total circumferential angle of 72 °. Here too, a set of curves is shown for corresponding bearing gap widths of 1 micrometer to 5 micrometers, which shows the associated optimum additional gap width H as a function of the circumferential angle. The lubrication groove is located up to a circumferential angle of 10 °. From the circumferential angle of 10 ° the compression area runs. With bearing gap widths of 1 micrometer to 3 micrometers, the additional gap width h remains approximately the same or slightly increases up to a circumferential angle of approximately 30 °, and then drops steadily to a circumferential angle of approximately 55 to 60 °. From here then the plateau area extends to the end of the circumferential angle of the sliding surface of 72 °. The curves for a bearing gap width g of 4 microns and 5 microns show a similar course, but larger deviations, for H in the compression region depending on the circumferential angle.

6 shows the tracking error as a function of the gap width g for spindle motors for driving hard disk drives. The curves for plain bearings with three or five sliding surfaces are shown. It can be seen that the tracking error increases correspondingly with increasing gap width g, namely for slide bearings with three surfaces, curve 16 , less than for sliding bearings with five sliding surfaces, curve 17 ,

1

bearing bush

2

wave

3

bearing gap

4

lubrication

5

compression surface

6

plateau surface

7

direction of rotation the wave

8th

flow direction lubricant

10

Curve (3-area bearing)

11

Curve (5-surface bearing)

12

Curve (3-area bearing)

13

Curve (5-surface bearing)

14

curves (3-area bearing)

15

curves (5-surface bearing)

16

Curve (3-area bearing)

17

Curve (5-surface bearing)

Claims (10)

Multi-surface plain bearing with a bearing bush ( 1 ) with several sliding surfaces and one shaft ( 2 ), wherein the sliding surfaces each have a lubricating groove ( 4 ), a compression surface ( 5 ) and a plateau surface ( 6 ), where g is the width of the storage gap ( 3 ) in the area of the plateau surface ( 6 ) and H the largest width of an additional gap in the area of the compression surface ( 5 ), characterized in that it has three sliding surfaces, where: H = a + b * g, where 0.2 <= a <= 0.6 and 0.2 <= b <= 0.6 and 0.5 microns <= g <= 5 microns. Multi-surface sliding bearing according to claim 1, characterized in that the diameter of the shaft ( 2 ) Is 2-3 mm Multi-surface plain bearing which has a bearing bush ( 1 ) with several sliding surfaces and one shaft ( 2 ), wherein the sliding surfaces each have a lubricating groove ( 4 ), a compression surface ( 5 ) and a plateau surface ( 6 ), where g is the width of the storage gap ( 3 ) in the area of the plateau surface ( 6 ) and H the largest width of an additional gap in the area of the compression surface ( 5 ), characterized in that it has five sliding surfaces, where: H = a + b * g, where 0.1 <= a <= 0.4 and 0.1 <= b <= 0.4 and 0.5 microns <= g <= 5 microns. Multi-surface sliding bearing according to claim 3, characterized in that the diameter of the shaft ( 2 ) Is 3-5 mm. Mehrflächengleitlager according to one of the claims 1 to 4, characterized in that the gap width g is preferably 1.8-2.5 microns. Multi-surface sliding bearing according to one of claims 1 to 5, characterized in that the surface portion of the lubricating groove ( 4 ) at the sliding surface is 5-15%. Multi-surface sliding bearing according to one of claims 1 to 6, characterized in that the surface portion of the compression surface ( 5 ) at the sliding surface is 20-75%. Multi-surface sliding bearing according to one of claims 1 to 7, characterized in that the surface portion of the plateau surface ( 6 ) at the sliding surface is 20-45%. Spindle motor with a stator and a rotor, the by means of a multi-surface plain bearing according to claims 1 to 8 is rotatably supported relative to the stator, and an electromagnetic Drive system for driving the rotor. Hard disk drive with a housing in which a spindle motor according to claim 9 is arranged, at least one disk, the spindle motor is driven in rotation and a read-write device for writing and reading Data to and from the disk.