JPH04321816A - Gear box bearing of helicopter - Google Patents

Abstract

PURPOSE:To enable formation of an excellent lubricating film on a rolling surface even in cases where synthetic oil of low viscosity is used as lubricating oil by forming a slightly rough surface where a number of tiny independent recesses are randomly arranged on the surface of rolling elements of a bearing or on the rolling surface of an inner and an outer bearing ring. CONSTITUTION:A number of cylindrical rolling elements 14 are built in between an inner ring 12 and an outer ring 13 in a gear box bearing of a helicopter, e.g. a cylindrical roller bearing 11. At least one of the surface of the cylindrical rolling elements 14, the rolling surfaces of the inner ring 12 and the outer ring 13 is formed to be slightly rough where a number of independent tiny recesses of concave shape are randomly arranged. The slightly rough surface is set so that the parameter SK value of surface ruggedness may be minus, and the ratio of the surface area of the tiny recesses may range between 10% and 40%. And the average surface area of the respective tiny recesses is set so as to range between 35 and 150mum<2> when rearrangement is made so that the recesses of the equivalent diameter of 3mum phi or less may be omitted. This constitution allows satisfactory oil film formation of the rolling surface.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a bearing for a helicopter gearbox.

0002

2. Description of the Related Art As shown in FIG. 11, a helicopter gearbox 1 has an input shaft 2 connected to a jet engine.
The rotation is transmitted to the output shaft 3 by various gears, and in order to support the input shaft 2 and output shaft 3, various bearings 4 such as cylindrical roller bearings, tapered roller bearings, spherical roller bearings, and ball bearings are used. etc. are used built-in.

[0003] It is necessary to supply lubricating oil to each of the bearings 4, and since the gearbox 1 of the helicopter is connected to a jet engine, the same lubricating oil used in the jet engine is used in the gearbox 1. .

By the way, low-viscosity synthetic oils are used as lubricating oils for jet engines because of the need for starting in cold regions and their lubricating properties at high temperatures.

[0005]

[Problems to be Solved by the Invention] Since jet engines operate at high speeds and low loads, even low-viscosity synthetic oil can form an oil film between the raceways and rolling elements in bearings in jet engines. There is no problem with the durability of the product.

On the other hand, the bearing 4 in the gearbox 1 is often used at low speeds and high loads, and if the bearing 4 under these conditions is lubricated with low viscosity synthetic oil, the gap between the raceway and the rolling elements will be reduced. The problem is that the formation of an oil film is insufficient, causing wear, flaking, peeling damage, etc., and shortening the bearing life.

Therefore, the present invention provides a gearbox for a helicopter that can advantageously form an oil film between the bearing ring and the rolling elements and extend the life of the bearings even when a low-viscosity synthetic oil is used as the lubricating oil. Our goal is to provide bearings for

[0008]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a bearing for use in a helicopter gearbox, in which at least one of the surfaces of the rolling elements of the bearing or the rolling surfaces of the inner and outer races is Then, a countless number of small independent depressions are randomly provided, and the surface roughness of the surface on which these depressions are provided is set such that the surface roughness parameter SK value is negative, and the surface area ratio occupied by the micro depressions is 1
A configuration in which the ratio is 0 to 40% is adopted.

[0009]

[Operation] A countless number of independent minute depressions are randomly formed on the surface of the rolling element or at least one of the raceway surfaces of the inner and outer raceway rings, and the surface roughness with the depressions is determined by the parameter SK value being negative. The surface area ratio is 10~
40%, the small depressions act as lubricating oil reservoirs and buckets for replenishing contact areas, preventing the formation of an oil film between the raceways and rolling elements even if the lubricating oil is a low-viscosity synthetic oil. This improves bearing efficiency, eliminates wear, delamination, and peeling damage, and extends the lifespan of bearings that are incorporated into helicopter gearboxes.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a cylindrical roller bearing 11 as a bearing for the helicopter gearbox shown in FIG.
It has a structure in which a large number of cylindrical roller rolling elements 14 are incorporated between an inner ring 12 and an outer ring 13.

FIG. 2 also shows the ball bearing 15, with the inner ring 16
It has a structure in which a large number of steel ball rolling elements 18 are incorporated between the outer ring 17 and the outer ring 17.

In the cylindrical roller bearing 11 and the ball bearing 15, at least one of the surfaces of the rolling elements 14 and 18 or the raceway surfaces of the inner rings 12 and 16 and the outer rings 13 and 17 has countless independent minute concave depressions. It is formed on randomly arranged micro-rough surfaces, and this micro-rough surface has a surface roughness parameter SK.
The value is negative, for example -1.6 or less.

[0014] The surface processing treatment for obtaining the above-mentioned surface roughness conditions can be performed by special barrel polishing to obtain the desired finished surface.

The parameter SK value refers to the degree of skewness (SKEWNESS) of the surface roughness distribution curve.A symmetric distribution such as a Gaussian distribution has an SK value of 0, but the parameter SK value is -1.6. The following setting values are in a range where the shape and distribution of the surface recesses are favorable for oil film formation.

[0016] In the case of the micro-rough surface, which is the surface of the cylindrical roller rolling element 14 or the raceway surfaces of the inner rings 12, 16 and outer rings 13, 17, the parameter SK value is -1.6 in both the axial direction and the circumferential direction.
It is as below.

[0017] The surface area ratio occupied by the minute depressions on the above-mentioned minute rough surface is in the range of 10 to 40%, and the average area of the minute depressions is 35 to 150 μm2 when the equivalent circle diameter of 3 μm or less is excluded. ing.

FIG. 3 shows the finished surface condition of the standard roller.
Figure 4 shows a comparison of the finished surface conditions of micro-roughening applied to the rolling element surface or the raceway surfaces of the inner and outer rings. As shown in FIG. 4, the micro-rough surface of the present invention is a special surface in which recesses are formed in a plane and no protrusions protrude from the plane.

In order to quantitatively measure the minute depressions, the surface of the rolling element or the rolling surface can be enlarged, and the image can be quantified using a commercially available image analysis system.

[0020] White parts of the image are analyzed as surface flat parts, and minute depressions are analyzed as black parts. For example, L from Pierce Co., Ltd.
When analyzed using the A-525 image analysis system, the shading of the original image is first clarified using an emphasis filter, and then very fine black parts with an equivalent circle diameter of 3 μm or less are removed using a noise eraser.

[0021] The size and distribution of minute depressions left after removal with a noise eraser, and the surface area ratio of the minute depressions are determined to evaluate the rolling element surface or inner and outer ring raceway surfaces.

Next, we will introduce a conventional ball bearing in which the surfaces of the inner and outer rings and the surfaces of the steel ball rolling elements are superfinished, and a conventional ball bearing in which the surfaces of the inner and outer rings are superfinished and the surfaces of the steel ball rolling elements are made with indentations in random directions. The results of a life test conducted using a ball bearing of the present invention formed with a micro-rough surface will be explained.

The surfaces of the superfinished inner and outer rings and steel ball rolling elements are 0.2 μmRmax or less, and the micro-rough surfaces in random directions are 2 μmRmax.

The test equipment used was a radial load tester 21 as shown schematically in FIG.
Test bearing A is attached to 2 and a load is applied to perform the test.

[0025] The test conditions are as follows.

Radial load 500Kgf rotation speed
3500rpm lubricant
Turbine oil Figure 6 shows the results of a rolling element life test conducted on each test bearing under the above conditions.

As is clear from the above test results, 10
% failure probability is 45 hours for conventional ball bearings,
The ball bearing of this invention exhibited a significantly longer life of 125 hours.

In general, there is a relationship between the oil film parameter and the oil film formation rate as shown in Figure 7, and it is said that the larger the oil film parameter is, the better from the viewpoint of service life. cannot be explained by Λ alone.

[0029] Confirmation of oil film formation on the finished surface of the steel ball rolling element and peeling resistance were carried out using a two-cylinder testing machine.
Accelerated peeling tests were conducted under free rolling conditions using cylindrical specimens with the same surface finish as the test bearing steel balls of the present invention and the conventional test bearing steel balls described above. The status of oil film formation was confirmed using a direct current method.

Test conditions Maximum contact pressure 227Kgf/mm2
Circumferential speed 4.2m/se
c (2000rpm) Lubricant
Turbine oil (10cst under test conditions) Number of repeated loads: 4.8 x 105 (4h
r) The oil film formation rate in this test is as shown in Figures 8 and 9, and the oil film formation rate on the finished surface of the test bearing of the present invention was 20% at the start of operation compared to the conventional test bearing. The oil film formation rate was improved to a certain degree.

[0031] Also, the number of repeated loads is 1.2 x 105
It was confirmed that the finished surface specimen of the present invention almost completely formed an oil film.

Further, in the finished surface of the conventional test bearing, many occurrences and progress of peeling of about 0.1 mm in length were observed, whereas no damage was observed in the finished surface of the present invention.

As mentioned above, compared to the normal rolling of a bearing ring with a super-finished surface and a steel ball rolling element, the ball bearing of the present invention with a super-finished bearing ring and minute depressions in the steel ball rolling element has , Figure 10 (
As shown in A) and (B), if the countless minute depressions a act as lubricant reservoirs and buckets for replenishing the contact area, and the direction of the surface roughness is perpendicular to the direction of oil b flow, then This will increase the oil film thickness.

Therefore, even in bearings where low-viscosity synthetic oil is used as lubricating oil, such as in helicopter gearboxes, the oil film formation rate between the raceway and the rolling elements is improved and the life of the bearing is extended. Can be done.

[0035] If the area ratio of minute depressions is 30% or more and the average surface is 120 μm2 or more, the effective contact length tends to decrease and the long life effect tends to decrease.

Further, in the illustrated embodiment, cylindrical roller bearings and ball bearings are illustrated as bearings, but the present invention can be applied to all bearings used in helicopter gearboxes, such as tapered roller bearings and spherical roller bearings.

[0037]

[Effects] As described above, according to the present invention, in a bearing that is installed and used in a helicopter gearbox, at least one of the surfaces of the rolling elements or the raceway surfaces of the inner and outer rings is formed into a random micro-rough surface, Since the surface roughness parameter SK value is negative and the surface area ratio occupied by minute depressions is set to 10 to 40%, it is advantageous for oil film formation on the raceway surface, and the lubricating oil is a low-viscosity synthetic oil. It is also possible to increase the thickness of the oil film between the bearing ring and the rolling elements, thereby preventing wear and peeling damage and extending the life of helicopter gearbox bearings.

[Brief explanation of drawings]

[Figure 1] Cross-sectional view of a cylindrical roller bearing

[Figure 2] Cross-sectional view of ball bearing

[Figure 3] Schematic diagram showing the finished surface condition of the conventional rolling element surface

[
FIG. 4 Schematic diagram showing the finished surface condition of the rolling element surface of this invention

[Figure 5] Schematic diagram of test equipment

[Figure 6] Graph showing the results of life test

[Figure 7] Relationship diagram showing oil film parameters and oil film formation rate

[Figure 8] Graph showing oil film formation rate in conventional ball bearings

[Figure 9] Graph showing the oil film formation rate in the ball bearing of this invention

[Figure 10] (A) and (B) are schematic explanatory diagrams showing micro-rough surfaces and oil flow.

[Figure 11] Schematic diagram showing the gearbox of a helicopter

[Explanation of symbols]

11 Cylindrical roller bearing 12, 16 Inner ring 13, 17 Outer ring 14 Cylindrical roller rolling element 15 Ball bearing 18 Steel ball rolling element

Claims (2)

[Claims] Claim 1: In a bearing used in a helicopter gearbox, countless small independent depressions are randomly provided on at least one of the rolling element surface of the bearing or the raceway surfaces of the inner and outer raceway rings, and the depressions are formed at random. The surface roughness of the provided surface is such that the surface roughness parameter SK value is negative, and the surface area ratio occupied by the minute depressions is 10 to 4.
A helicopter gearbox bearing characterized by 0%. [Claim 2] The average area of minute depressions is 35 to 150 μm2, excluding those with an equivalent circular diameter of 3 μmφ or less.
The bearing for a gearbox of a helicopter according to claim 1.