NL1011003C2 - Rolling bearing with non-uniform distances between the rolling elements. - Google Patents

Description

Reversible leather with non-uniform mutual distances between the revolving elements

The invention relates to a rolling bearing comprising an inner ring, an outer ring, a series of rolling elements which contact the raceways of said rings, and a cage which provides mutual distances between the rolling elements, of which a plurality of said mutual distances are not uniform.

Such a rolling bearing is known from US-A-5483744. According to this document, a bearing with irregular or semi-rhythmic spacing is provided. Such semi-rhythmic mutual distances can for instance be formed by alternating mutual distances of only two different sizes. In particular, that document proposes a method aimed at providing an adapted bearing suitable for a particular application.

As an example, it has been indicated that a bearing can be obtained by this method, which offers a better vibration behavior. According to a further example, a bearing can be obtained which has improved anisoelastic properties.

That method comprises a first step of selecting irregular mutual distances for the rolling elements. Subsequently, for example by means of a calculation, it is determined whether these irregular mutual distances provide a desired result.

If that desired result is not obtained, the mutual distances are adjusted, until finally a better vibration behavior or an improved anisoelastic property is obtained.

This known method has the drawback that it is rather laborious and time-consuming. For each specific bearing, complete tests are performed with modified cages, or simulated by calculation. No general teaching can be derived from these tests or from that calculation regarding the behavior of a series of bearings of a corresponding type.

The vibration and sound quality, or the acoustic comfort of bearings, is becoming increasingly important in certain areas of machine engineering. As an example are mentioned the noise daf generated by electric motors in household appliances, which depends on the quality and design of the bearings.

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Depending on shape errors, for example the waveform and local imperfections of the raceways and rolling elements, geometry, speed, mounting, load and lubrication conditions, the bearing excitation spectrum may show sharp peaks. As a result, unacceptable levels of vibration and / or noise can occur.

As an example, it should be mentioned here that machine sounds with very clearly audible tones, ie with a high tonality, are perceived as more disturbing by the human ear than louder sounds with less clearly recognizable tones, ie than sounds with a lower tonality.

The so-called yawing phenomenon is mentioned as a further example of disturbing or dangerous noises in the 10 bearing applications. That phenomenon is caused by an interaction between a resonance of the bearing system and the lubricant distribution on the raceways and the elements.

The object of the invention is to provide a bearing which offers better behavior with regard to these phenomena, without however having to perform calculations or tests for specific bearings. This object is achieved in that at least two of these non-uniform spacings have different sizes.

The invention is based on the insight that an improved lower vibration spectrum is obtained if care is taken to choose different sizes for the mutual distances. Those sizes of the spacing should not exceed certain minimum and maximum values, in order to ensure a sufficient thickness for the cage bars separating the cage cavities, or to avoid unacceptable mechanical instability caused by a large distance between two adjacent balls.

Preferably, all mutual distances of the rolling elements differ from each other. In that case, no spacing is equal to another spacing, giving a completely equal distribution in a histogram.

In terms of statistics, the spacings between neighboring rolling elements must be evenly distributed in a histogram. This means that all distances are different sizes. However, an uneven histogram distribution is also possible. For example, 10 1 1 Π ft 7 3 acceptable results can still be obtained if two of the distances are equal.

Different sizes of the mutual distances provide a vibration spectrum, the highest peaks of which in the upper frequency range 5 are considerably reduced. In addition, additional low amplitude sideband frequencies are generated.

The "flattened" lower excitation spectrum thus obtained results in vibrations with less pure tones. While the additional sideband frequencies also generate sound, the overall impression of such a "flattened" and "spread" vibration spectrum, also referred to as "white sound", is much more pleasant to the human ear.

The spacing of different sizes according to the invention also solves the problem of yawing by suppressing the unstable behavior caused by the interaction between the lubricant distribution and a resonance. In other words, the interaction between the lubricant and the vibration behavior of the bearing application (e.g. a gearbox) that causes the yaw phenomenon is disrupted.

It is pointed out that the term "spacing" in this application refers to the distance between two adjacent cage cavities. Such spacing or space could also be expressed in terms of degrees, gradians or radians, in combination with the radius on which the cage cavities are located.

The invention also relates to a cage for a bearing as described above. Said cage comprises a number of cage cavities which are mutually spaced, some of the mutual distances between the cage cavities being non-uniform. According to the invention, at least two of the non-uniform spacings are of different sizes.

The invention will now be further described with reference to the graphs shown in the figures.

Figure 1 shows a schematic cross section of a ball bearing cage according to the invention.

Figure 2 shows a histogram concerning the mutual distances of the cage cavities of the cage according to Figure 1.

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Figure 3 shows a graph with the measured frequency spectrum of a standard ball bearing.

Figure 4 shows a graph of the measured frequency spectrum of a first embodiment of a ball bearing according to the invention.

Figure 5 shows a graph of the measured frequency spectrum of a second embodiment of the ball bearing according to the invention.

Figure 6 shows a generalized histogram concerning the mutual distances of the cages according to the invention.

The cage 1 shown in Figure 1 has a total of eight cage cavities 2.

10 Other versions with more or less cage cavities are also possible. The cage cavities are separated from each other by means of cage bars 3, which are connected to cage rings 4 at both ends.

The mutual distance between two adjacent cage cavities 2 is determined by the pitch angle 5 (Δφΐ), as shown in figure 1. By means of the radius R, 15 which determines the distance between the origin of the axis of the cage 1, and the center of the cage cavities 2, the mutual distance or distance S between two cage cavities can be derived.

The pitch angles Δφϊ between all cage cavities of the embodiment of figure 1 are mutually different. In other words, no specific pitch angle Acpj is equal to another pitch angle Acpk. This is shown graphically in Figure 2, which represents a histogram of those pitch angles Δφϊ in degrees.

By means of a standard test device, the frequency spectrum according to the graph of figure 3 can be obtained. In this standard cage, all cage cavities have equal spacing or equal pitch angles. The spectrum includes several sharp peaks, not only in the lower frequencies, but also in the higher frequencies.

The graph of Figure 4 shows the frequency spectrum of a ten-cavity cage whose spacing between adjacent cage cavities increases monotonically. It is clear that such non-uniform mutual distances lead to lower peaks, especially in the high frequencies, and also to the generation of additional frequency lines, the so-called sideband frequencies. As a result, the spectral density increases. It is important to note, however, that the highest peaks in the frequency range above 150 Hz are significantly reduced 1 o 1 1 η n 3 5 compared to the frequency spectrum of the standard cage as shown in Figure 3: note the difference in scale from the vertical axes.

The same applies to the frequency spectrum in figure 5, concerning a cage in which the mutual distances or spaces between the cage cavities all differ from each other, but are randomly distributed (figure 2).

The frequency spectra of Figures 4 and 5 clearly show that the cage design according to the invention particularly affects the vibrations excited by wave orders of a larger size or at least of the same order size, such as the number of rolling elements in the bearing. A flattened lower-10 exit spectrum is obtained, in other words, the energy concentrated in the sharp spectral peaks of the standard cage design is spread to other frequency lines.

As a result, the content of "pure" tones in the overall sound generated by the bearing is much lower for the cage bearings according to the invention. The lower sound has a lower tonality and is more like a sound such as a "white sound".

The histogram of figure 6 concerns a generalized example of the pitch angles in a cage 1 according to the invention. The horizontal centerline includes a number of different pitch angles Δφΐ between adjacent cage cavities 5, expressed in 20 degrees, radians or gradians. The vertical axis includes the number of each stitch angle available in a cage 1.

In the example, only one of each pitch angle Δφ2, Δφ5, Δφ8, .. is available. There is no pitch angle Δφ ,, Δφ3, Δφ8, but the pitch angles Δφ4 and Δφ7 occur twice.

25 Each pitch angle Δφΐ should be understood to include pitch angles with a deviation less than the manufacturing tolerances, as indicated by the width t.

A Λ A A Λ Λ 7

Claims (22)

Rolling bearing comprising an inner ring (13), an outer ring (12), a series of rolling elements (11) which contact the raceways of those rings (12, 5, 13), and a cage (1) providing spacing between the rolling elements (11), of which a plurality of said mutual distances (5) are not uniform, characterized in that at least two of said non-uniform mutual distance (5) have different sizes. The rolling bearing according to claim 1, wherein a number of at least a third of the total number of spacings (5), or the next higher integer of that 1/3 number of total spacings, is not uniform. Rolling bearing according to claim 1 or 2, wherein at least half of the total number of spacings (5), or the next higher integer of half the number of total spacings, is not uniform. Rolling bearing according to claim 1, 2 or 3, wherein all non-uniform mutual distances (5) have different sizes. 20 Rolling element bearing according to claim 1, 2 or 3, wherein all mutual distances (5) are not uniform. Rolling element bearing according to one of the preceding claims, wherein the non-uniform and mutually different mutual distances (5) increase monotonically in the circumferential direction. Rolling element bearing according to any one of claims 1-5, wherein the non-uniform and mutually different mutual distances (5) are distributed irregularly in circumferential direction. Rolling element bearing according to claim 7 or 8, wherein the increments of the mutual distances have an identical size. i 1011003 Rolling element bearing according to claim 7 or 8, wherein the increments of the mutual distances are of different sizes. Rolling element bearing according to any one of the preceding claims, wherein the difference between the non-uniform mutual distances (5), expressed in degrees of a circle of 360 °, is at most 360 * -x 1.5 n, where n is the number of rolling elements. 10 Rolling bearing according to any one of the preceding claims, wherein the differences in the spacing (5) size exceed the manufacturing tolerances (t). 12. Cage (1) for a rolling bearing, said cage comprising a number of cage cavities (2) which are mutually spaced, and a multiple of the mutual distance (5) between said cage cavities (2) is not uniform, with characterized in that at least two of said non-uniform spacing (5) have different sizes. 20 Cage (1) according to claim 12, wherein a number of at least one third of the total number of mutual distances (5), or the next higher integer of that one third number of total mutual distances, is not uniform. Cage (1) according to claim 12 or 13, wherein at least half of the total number of spacings (5), or the next higher integer of half the number of total spacings, is not uniform. Cage (1) according to claim 12, 13 or 14, wherein all non-uniform spacings (5) have different sizes. 1011003 Cage (1) according to claim 12, 13, 14 or 15, wherein all mutual distances (5) are not uniform. Cage (1) according to claims 12-16, wherein the non-uniform and mutually different distances (5) increase monotonically in the circumferential direction. Cage (1) according to claims 12-17, wherein the non-uniform and mutually different mutual distances (5) are distributed irregularly in the circumferential direction. The cage (1) according to claim 17 or 18, wherein the increments of the spacings are of identical size. The cage (1) according to claim 17 or 18, wherein the increments of the spacings are of different sizes. 15 Cage (1) according to claims 12-20, wherein the difference between the non-uniform mutual distances (5), expressed in degrees of a circle of 360 °, is at most 360 f - x 1.5 n 20, wherein n is the number of rolling elements. Cage (1) according to claims 12-21, wherein the differences in the spacing (5) size exceed the manufacturing tolerances (t). 1011003