High-speed bearings with grooved and cylindrical raceways

Abstract

A high-speed shaft assembly includes: a shaft formed of a first material; and an external member formed of a second material and arranged around the shaft, the shaft or the external member being rotatable around an axis. The two materials have significantly different coefficients of thermal expansion so that the shaft and / or the external member can move relative to each other along the axis at temperatures exceeding 250°F and at temperatures less than 0°F. The inner ring of the bearing is arranged around the shaft and has an inner raceway, which is a cylindrical surface or an annular groove. The outer ring of the bearing is arranged around the inner ring and is coupled to the external member. The outer ring has an outer raceway, which is the other of a cylindrical surface and a groove. During relative displacement of the shaft and the external member, a plurality of balls arranged between the raceways can be displaced axially along the cylindrical raceway surface.

Description

Technical Field

[0001] The present invention relates to a bearing, and more particularly to a bearing used in high-speed shaft applications. Background Art

[0002] Typically, bearings used in relatively high-speed applications such as gas turbine engines include one or more rows of cylindrical rollers. When there is relative axial displacement between the components supported by such cylindrical roller bearings (which may be half the length of the rollers), the rollers must slide axially along the contact line between the rollers and the bearing raceways. Summary of the invention

[0003] The present invention is a high-speed shaft assembly, the high-speed shaft assembly comprising: a shaft formed of a first material and having a central axis; an outer member formed of a second material and arranged around the shaft. At least one of the shaft and the outer member can rotate around the central axis, and the thermal expansion coefficient of the second material is substantially different from the thermal expansion coefficient of the first material. In this way, at a temperature greater than 250 degrees Fahrenheit and at a temperature less than 0 degrees Fahrenheit, one of the shaft and the outer member can be displaced along the central axis relative to the other of the shaft and the outer member. An inner ring of a bearing is arranged around the shaft and coupled to the shaft, the inner ring having a circumferential outer surface providing an inner raceway, the inner raceway being a generally cylindrical surface or an annular groove. An outer ring of a bearing is arranged around the inner ring and coupled to the outer member, the outer ring having a circumferential inner surface providing an outer raceway, the outer raceway being the other of a generally cylindrical surface and an annular groove. Furthermore, a plurality of balls are arranged between the inner race and the outer race so as to rotatably couple the inner ring and the outer ring, each ball being axially displaceable along a cylindrical race surface during relative axial displacement of the shaft and the outer member. BRIEF DESCRIPTION OF THE DRAWINGS

[0004] The above summary of the invention and the detailed description of the preferred embodiments of the invention will be better understood when read in conjunction with the accompanying drawings. For the purpose of illustrating the invention, presently preferred schematic embodiments are shown in the accompanying drawings. However, it should be understood that the invention is not limited to the precise arrangements and means shown. In the accompanying drawings:

[0005] Figure 1 is an axial cross-sectional view of a high-speed shaft assembly according to the present invention, showing a high-speed bearing having a deep groove inner raceway and a cylindrical outer raceway;

[0006] Figure 2 is shown separated from the shaft and outer member Figure 1 Axial cross-sectional view of a high-speed bearing;

[0007] Figure 3 yes Figure 2 an enlarged broken-away portion of

[0008] Figure 4 is an axial cross-sectional view of a high-speed shaft assembly according to the present invention, showing a high-speed bearing having a cylindrical inner raceway and a deep groove outer raceway;

[0009] Figure 5 is shown separated from the shaft and outer member Figure 4 Axial cross-sectional view of a high-speed bearing;

[0010] Figure 6 yes Figure 5 an enlarged cutaway portion of;

[0011] Figure 7 is an enlarged cutaway axial cross-sectional view of a high-speed bearing having two inner rings and one outer ring;

[0012] Figure 8 is an enlarged cut-away axial cross-sectional view of a high-speed bearing having an inner ring with two raceways;

[0013] Fig. 9 is an enlarged cut-away axial cross-sectional view of a high-speed bearing having an inner ring and two outer rings; and

[0014] Fig.10 is an enlarged cut-away axial cross-section of a high-speed bearing having an outer ring with two raceways. DETAILED DESCRIPTION

[0015] The use of specific terms in the following description is for convenience only and is not limiting. The words "inwardly", "inwardly" and "outwardly", "outwardly" refer to directions toward and away from a designated centerline or geometric center of the described element, respectively, and the specific meanings are readily apparent from the context of the specification. In addition, as used herein, the words "connected" and "coupled" are intended to include a direct connection between two components (without any other components interposed between them) and an indirect connection between components (with one or more other components interposed between them). The terminology includes the words specifically mentioned above, their derivatives and words of similar meaning.

[0016] Referring now to the drawings in detail, wherein like reference numerals are used to refer to like elements throughout, Figures 1 to 10A high-speed shaft assembly 10 including a bearing 11 is shown, and the high-speed shaft assembly 10 is used in a gas turbine engine, a compressor, or other devices (such as): wherein the assembly has a rotation speed of more than one thousand revolutions per minute (1000 rpm) and can reach tens of thousands of rpm (e.g., 10,000 rpm, 30,000 rpm, etc.), and operates at low temperatures (e.g., as low as negative one hundred degrees Fahrenheit (-100°F)) or high temperatures (e.g., up to six hundred degrees Fahrenheit (600°F)). The shaft assembly 10 mainly includes a shaft 12, an outer member ( / external member) 14 (e.g., a seat ( / bearing seat) (housing) or seat assembly), an inner ring 16, an outer ring 18, and a plurality of balls 20 (i.e., spherical rollers), the rings 16, 18 and the balls 20 forming the bearing 11, and the bearing 11 also includes a cage 21. The shaft 12 is formed of a first material (such as 4140 steel, 4340 steel, 9310 steel, etc. for the "cold section" and nickel alloys and similar materials for the "hot section"), is preferably hollow (as depicted), and has an outer surface 12a and a central axis A C The outer member 14 is formed of a second material (eg, magnesium or Inconel (hot section), titanium (cold section)), is disposed around the shaft 12, and has a circumferential inner surface 14a.

[0017] At least one of the shaft 12 and the outer member 14 may be rotatable about the central axis A. C Rotates at a relatively high rotational speed as described above. In certain applications, the shaft 12 rotates relative to the fixed outer member 14, in other applications, the outer member 14 rotates relative to the fixed shaft 12, and in still other applications, both the shaft 12 and the outer member 14 rotate at different speeds and / or in different angular directions. In addition, the thermal expansion coefficient of the second material forming the outer member 14 is significantly ( / greatly) different from the thermal expansion coefficient of the first material forming the shaft 10, and the thermal expansion coefficient of the second material forming the outer member 14 is significantly greater than or significantly less than the thermal expansion coefficient of the first material forming the shaft 10. In this way, at a temperature greater than two hundred and fifty degrees Fahrenheit (250°F) and at a temperature less than zero degrees Fahrenheit (0°F), at least one of the shaft 12 and the outer member 14 can be relative to the other of the shaft 12 and the outer member 14 along the central axis A C Displaceable. As described below, due to the sizing of the shaft assembly 10 and components of a machine incorporating the shaft assembly 10 (eg, a gas turbine engine, a compressor, etc.), the relative axial displacement of the shaft 12 and the outer member 14 is relatively large.

[0018] In addition, the inner ring 16 of the bearing is arranged around the shaft 12 and is coupled to the shaft 12, and has a circumferential inner surface 17A and a circumferential outer surface 17B providing an inner raceway 22. The inner raceway 22 is a generally cylindrical surface 24 ( Figure 4-Figure 6 , Fig. 9 and Fig.10 ) or annular groove ( / groove) (groove) 26 ( Figure 1-Figure 3 , Figure 7 and Figure 8 ), the annular groove 26 extends radially inward from the outer surface 17B, and the inner raceway 22 is preferably formed as a "deep groove" raceway known to those skilled in the art of bearings. The bearing outer ring 18 is arranged around the inner ring 16 and is connected to the outer member 14. The outer ring 18 has a circumferential inner surface 19A that provides the outer raceway 28 and an opposing circumferential outer surface 19B, and the circumferential outer surface 19B is preferably press-fitted against the inner surface 15 of the outer member 14 or the circumferential inner surface of an intermediate member (for example, a sleeve ( / bushing), a spacer, etc.; not shown). The outer raceway 28 is formed as the other of a generally cylindrical surface and an annular groove; in other words, when the inner raceway 22 is formed as an annular groove 26, the outer raceway 28 is a cylindrical bearing surface 30 (provided by the circumferential inner surface 19A) ( Figure 1-Figure 3 , Figure 7 and Figure 8 ), or when the inner raceway 22 is formed as a cylindrical surface 24, the outer raceway 28 is formed as an annular groove 32 ( Figure 4-Figure 6 , Fig. 9 and Fig.10 ).

[0019] In either case, a plurality of balls 20 are arranged between the inner raceway 22 and the outer raceway 28, respectively, to rotatably couple the inner ring 16 and the outer ring 18, respectively, and thereby also rotatably couple the shaft 12 and the outer member 14. During the relative axial displacement of the shaft 12 and the outer member 14, each of the plurality of balls 20 can be displaced axially along the cylindrical raceway surface 24 or 30. Therefore, by forming the inner raceway 22 or the outer raceway 28, respectively, as a cylindrical bearing surface 24 or 30, the balls 20 can be rollably displaced axially during the relative axial displacement of the shaft 12 and the outer member 14 due to thermal expansion at an elevated temperature or thermal contraction at a reduced temperature. Since the balls 20 make point contact with the cylindrical bearing surface 24 or 30, rather than line contact as a cylindrical roller, such axial displacement of each ball 20 occurs with significantly lower friction than a cylindrical roller. Although the axial displacement of the balls 20 may be approximately the entire width w of the cylindrical raceway surface 24 or 30, the axial displacement of the balls 20 may be approximately the entire width w of the cylindrical raceway surface 24 or 30. C ( Figure 2 and Figure 5), but since under normal operating ( / running / working) conditions, the ball 20 is preferably positioned substantially in the center ( / middle) of the surface 24 or 30, the axial displacement is preferably at most about one-half of the cylindrical surface width w C .

[0020] Reference Figure 2 and Figure 5 , bearing 11 is a "high speed" bearing defined by having a DN factor or DN value greater than one million, where the DN value is defined as the product of the bearing diameter and the rotational speed of the bearing. Specifically, Figure 2 and Figure 5 As shown, the inner ring 16 includes a generally cylindrical annular body 40 having a bore 42 having an inner diameter ( / inner diameter) ID. The annular body 40 of the inner ring 16 is sized such that the product of the rotational speed of the shaft 12 or the rotational speed of the outer member 14 and the value of the bore diameter ID expressed in millimeters is greater than one million; in other words, DN value = rotational speed × ID ≥ 1,000,000. Since the tangential velocity and stress in a "larger size" bearing are significantly higher than a relatively smaller size bearing rotating at a similar rotational speed (e.g., a bearing incorporated into a dental drill), the DN value or DN factor is used to represent the higher speed of the bearing.

[0021] Reference Figure 7-10 The bearing 11 may include two or more inner rings 16 having raceway grooves 26 ( Figure 7 ), single ( / single) (single) inner ring 16 having two or more grooves 26 ( Figure 8 ), two outer rings 18 each having a groove 32 ( Fig. 9 ) or a single outer ring 18 having two or more grooves 32 ( Fig.10 ), the inner ring 16 with the groove 26 is coupled to a single outer ring 18 with a cylindrical raceway surface 30 as appropriate ( Figure 7 and Figure 8), or the outer ring 18 having the groove 32 is coupled with the single inner ring 16 having the cylindrical raceway surface 24 as the case may be, and the bearing 11 includes the second group (or the third group or more) of balls 20. More specifically, for the bearing 11 having the outer raceway 28 formed as the cylindrical raceway surface 30, the inner ring 16 may be the first inner ring 50 having the first raceway groove 51, and the bearing 11 further includes the second inner ring 52 having the second raceway groove 53 (and the bearing 11 may include three or more inner rings), the first group of balls 54 are arranged between the first groove 51 and the cylindrical outer raceway surface 30, and the second group of balls 55 are arranged between the second groove 53 and the outer raceway surface 30. As an option, the inner ring 16 may be formed with: two (or more) annular grooves 26, specifically the first groove 56, the second groove 58, etc., which are spaced apart in the axial direction on the outer surface 17B of the (inner) ring and have the first group of balls 54 and the second group of balls 55, respectively. In either case, the axial length of the outer race 18 is dimensioned so that the race 18 extends beyond the axial ends of the two races 50 , 52 or the single inner race 16 a sufficient distance to allow for axial displacement of the two sets of balls 54 , 55 .

[0022] Furthermore, for a bearing 11 having an inner raceway 22 formed as a cylindrical raceway surface 24, the outer ring 18 may be a first outer ring 60 having a first raceway groove 61, and the bearing 11 further includes a second outer ring 62 having a second raceway groove 63 (and may include three or more outer rings), a first set of balls 64 being arranged between the first groove 61 and the cylindrical inner raceway surface 24, and a second set of balls 65 being arranged between the second groove 63 and the inner raceway surface 24. As an alternative, the outer ring 18 may be formed with: two (or more) annular grooves 32, specifically a first groove 66, a second groove 68, etc., which are axially spaced apart on the inner surface 19A of the (outer) ring and have a first set of balls 64 and a second set of balls 65, respectively. In either case, the axial length of the inner ring 16 is dimensioned so that the ring 16 extends beyond the axial ends of the two rings 60, 62 or a single outer ring 18 by a sufficient distance to allow axial displacement of the balls 64, 65.

[0023] Some advantages of any of the above multi-row designs are that the multi-row ball 20 will allow for a lower radial footprint than a single-row ball 20, and the resistance or compliance to moment loading can be adjusted by increasing the spacing between the rows.

[0024] Preferably, both the inner ring 16 and the outer ring 18 are made of an aerospace grade steel material such as M50, M50 NiL, 440C stainless steel, Pyrowear 675, or any other material of similar strength and having similar properties. The cage 21 is preferably made of hardened 4340 steel with 0.001"-0.002" silver plating and is preferably balanced to five (5) grams per cubic centimeter or tighter to optimize high speed performance. In addition, the balls 20 are preferably made of ceramic or silicon nitride materials, but can be made of the same aerospace grade steel material as the rings 16, 18.

[0025] In addition, each of the bearing inner race 16 and the bearing outer race 18 is preferably heat treated to prevent significant dimensional changes between negative one hundred degrees Fahrenheit (-100° F) and six hundred degrees Fahrenheit (600° F). Such heat treatment may be through-hardening, carburizing, nitriding, carbo-nitriding, or a combination of these or other treatment processes.

[0026] In addition, the various components of the high-speed bearing 11 are preferably formed to relatively high precision or tolerances, most preferably meeting or exceeding the requirements of the American Bearing Manufacturers Association (ABMA) ABEC5 grade. In addition, the bearing components (particularly the inner ring 16) are assembled in the shaft assembly 10 with tighter tolerances to prevent the potential adverse effects experienced by the "high-speed" rotation as described above. Preferably, the inner ring 16 is connected to the shaft 12 or an intermediate member (such as a sleeve, spacer, etc.) arranged between the ring 16 and the shaft 12 by an interference fit, and the interference fit generates a hoop stress of at least ten thousand pounds per square inch (10,000 psi) in the inner ring 16. In this way, the effect of centrifugal growth during high-speed rotation is significantly reduced.

[0027] The high speed bearing 11 of the present invention has many advantages over previously known bearings for similar applications. Current bearings with cylindrical rollers are prone to skidding / sliding, tilting or skewing at high rotational speeds ( / rotational speed) due to light radial loads, and therefore, intentional ( / deliberate) "out of round" must usually be combined to apply artificial radial loads to prevent such skidding damage. Compared to cylindrical rollers, in the present invention, the ball 20 is significantly more stable at higher rotational speeds, and friction is significantly reduced when the ball 20 is displaced axially. In addition, the ball 20 has a significantly larger radius than the corners ( / corners) of cylindrical rollers, and by having the ball 20, the high speed bearing 11 does not have the same misalignment problems as bearings including cylindrical rollers. In addition, with the preferred ball 20 formed of a ceramic material, since ceramics are much harder than steel, the potential damage during assembly of the ball 20 into the rings 16, 18 is significantly reduced, and the lubrication requirements are greatly reduced.

[0028] The representative, non-limiting embodiments of the present invention are described in detail above with reference to the accompanying drawings. This detailed description is only intended to teach those skilled in the art more details for practicing the preferred aspects of the present teachings, and is not intended to limit the scope of the present invention.

[0029] In addition, the combination of features and steps disclosed in the above detailed description may not be necessary to practice the invention in the broadest sense, but are merely taught to specifically describe representative examples of the invention. In addition, the individual features of the above representative examples and the following individual independent and dependent claims may be combined in a manner not specifically and explicitly listed to provide additional useful embodiments of the present teachings.

[0030] All features disclosed in the specification and / or claims are intended to be disclosed separately and independently from each other for the purpose of original written disclosure and for the purpose of limiting the claimed subject matter, regardless of the combination of features in the embodiments and / or claims. In addition, all value ranges or indications of entity groups are intended to disclose every possible intermediate value or intermediate entity for the purpose of original written disclosure and for the purpose of limiting the claimed subject matter. The present invention is not limited to the above-described embodiments and may vary within the scope of the appended claims.

Claims

1. A high-speed shaft assembly, comprising: a shaft formed of a first material and having a central axis; an outer member formed of a second material and disposed about the shaft, at least one of the shaft and the outer member being rotatable about the central axis, the second material having a coefficient of thermal expansion that is substantially different than the coefficient of thermal expansion of the first material such that at temperatures greater than 250 degrees Fahrenheit and at temperatures less than 0 degrees Fahrenheit, at least one of the shaft and the outer member is displaceable along the central axis relative to the other of the shaft and the outer member; a bearing inner ring disposed about the shaft and coupled to the shaft, the inner ring having a circumferential outer surface providing an inner raceway, the inner raceway being one of a generally cylindrical surface and an annular groove; a bearing outer ring disposed about the inner ring and coupled to the outer member, the outer ring having a circumferential inner surface providing an outer raceway, the outer raceway being the other of a generally cylindrical surface and an annular groove; as well as a plurality of balls arranged between the inner raceway and the outer raceway so as to rotatably couple the inner ring and the outer ring, each ball being axially displaceable along the cylindrical raceway surface during relative axial displacement of the shaft and the outer member, Each of the bearing inner race and the bearing outer race is heat treated to prevent significant dimensional changes between negative one hundred degrees Fahrenheit (-100° F) and six hundred degrees Fahrenheit (600° F).

2. The shaft assembly according to claim 1, characterized in that The inner ring has a bore having a diameter, and the product of the rotational speed of the shaft or the rotational speed of the outer member and the value of the bore diameter in millimeters is greater than one million.

3. The shaft assembly according to claim 1, characterized in that The cylindrical surface has a width, and the relative axial displacement of the shaft or the relative axial displacement of the outer member is at most about one-half of the width of the cylindrical surface.

4. The shaft assembly according to claim 1, characterized in that Each ball of the plurality of balls is formed of a ceramic material.

5. The shaft assembly according to claim 1, characterized in that One of the inner ring and the outer ring having an annular groove includes another annular groove, and the shaft assembly also includes another plurality of balls, which are arranged in the other annular groove and can roll circumferentially around the axis and can roll axially along the cylindrical raceway surface.

6. The shaft assembly according to claim 1, characterized in that The inner ring is connected to the shaft or an intermediate member disposed on the shaft by an interference fit, and the interference fit generates a hoop stress of at least ten thousand pounds force per square inch (10,000 psi) in the inner ring.

7. The shaft assembly according to claim 1, characterized in that Each of the bearing inner race and the bearing outer race is at least one of hardened, carburized, nitrided, and carbonitrided.

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