GB2355770A

GB2355770A - Cylindrical roller bearing

Info

Publication number: GB2355770A
Application number: GB0022159A
Authority: GB
Inventors: Yukio Ohura; Naoki Matsuyama; Yu Koiwa
Original assignee: NSK Ltd
Current assignee: NSK Ltd
Priority date: 1999-09-13
Filing date: 2000-09-11
Publication date: 2001-05-02
Anticipated expiration: 2020-09-11
Also published as: GB2355770B; JP3289711B2; JP2001082464A; GB0022159D0

Abstract

The gyro moment "S" of the cylindrical roller 6 is taken to be equal to or larger than the sum of the moment "U" which occurs due to dynamic unbalance of the cylindrical rollers, and the moment "C" which occurs due to fluctuation on the skew angle of the cylindrical rollers, that is, S / U + C. At the same time, when the cylindrical rollers are skewed, so that the end faces of the cylindrical rollers come in rubbing contact with the inner surfaces of the rims, the product Q Ò V of the force "Q" which is applied in the direction of pressure between the end faces of the cylindrical rollers 6 and the inner surfaces of the rims 8 at the points of sliding contact due to the moments "S", "U" and "C", and the sliding velocity "V" at the point of sliding contact is 60 kgf Ò m/s or less.

Description

2355770

Title of the InKention

Cylindrical Roller Bearing Field of the Invention

This invention relates to a cylindrical roller bearing for supporting a rotating shall that rotates at high speed and wl-deli is installed in high-speed rotating illachaiery such as a gas turbine, jet engine, or machine tools such as a machining center.

Backaround of the Invention

Cylindrical roller beariDgs, such as disclosed in Japanese Patent Publication No. Tokukai Bei 7-12119, have been widely used for suppotting various kinds of rotating parts such as the rotatb3g shaft of a gas turbine.

JFig. 1 shows one example of a cylindrical roller bearing that has been widely known and disclosed. This cylinddcal roller bearbig I coniprises an inner race 3 which bas an inner ring raceway 2 around its outer surfacc, an outer race 5 which has mi outer ring raceway 4 around its inner surface, a plurality of cylindrical rollers 6 which are located in between the iniver ring raceway 2 and outer ring I raceway 4 suct) that they rotate freely, and a retainer 7 which is provided to rotate freely between the inner ring raceway 2 and outer ring raceway 4 With the plurality of cylindrical rollers 6 held therein, A pair of rims 8 are fon-ned on both ends ofthe inner ring raceway 2. The space between the riins 8 is slightly larger than the dimension in the axial direction (left and right in Fig. 1) of the cylindrical rollers 6. Each of the cylindrical rollers 6 is held in the axial direction by and between these firns 8 to prevent them from (Usplacernent in the axial direction. Moreover, each of the cylindrical rollers 6 is fornied with charnfercd sections 11 between the rolling surf ace 9 and both end faces 10 it) the axial direction, When the cylindrical roller bearing 1, constructed ag described above, is in use, the inner race 3 fits, for example, around the center of a rotating sbaft (not shovn), and the outer race 5 fits inside a housing (not shown), Wien the rotatiTIg shaft.rotates., the cyl.indrical. rollers 6 roll to allow the inner ra-ce 3 to rotate inside the outer race 5.

However, when the cylindrical roller bearing I is in use, it is impossible to avoid the occurrence of so-called "skew", where the cylindrical -rollers 6 rotate as are with the center axis of each of the cylindrical rollers 6 not being parallel with 2 flie center axes of the itmer race 3 and outer race 5. Wien this kind of skew occurs rubbing occurs between the outer peripheral cdge of both end faces of the cylindrical roUers 6 and the rims 8, so that unless special countermeasures are taken, extreme wear of the cylindrical. rollers 6 and the ritus 8 may occur under poor conditions such as poor lubrication.

Particularly in the case of a high-speed cylindrical roller bearing that is used in. conditions where the product d.-n of the pitch circle diameter d,,, (mm), and the rotational speed n (rpin) exceeds 1.5 million, it is easy for problems such as abnormal wcar or seizure to occur, and this becomes a barrier for high-speed use. Especially in the field of macliining equipment where supplying only a small amount of lubricant is mainstream., this problem occurs easily.

Therefore, conventionally in the case ofjet lubrication that is used for jet engines, gas turbines and the like, the inner surfaces of the rij-ns are inclined, and the edges of the rim.s and end faces of the cylindrical rollers are rounded (edges R are formed).

Furtlicn-nore, as disclosed in US Patent No. 4 3 18,1574,, the angle of inclination of the inner surface. of the dins changes in the middle, or as disclosed in US Patent No. 4,027,930, the inner surface of the rinas is made coinvex baving 3 a specified radius of curvatUre.

With these techniques, when the cylindrical rollers skc',V, a film of lubrication oil is Banned between the ends of the cylindrical rollers aad the riins, by a wedge effect, and this makes it possible to prevent the aforementioned abnormal wear or seizure. Moreover, by decreasing the dynamic unbalance of the cylindrical rollers, it becomes more difficult for skew to occur.

The prior art as described above for preventing abnorinal wear or seizure due to skew was not sufficient for operation under very extreme conditions. In other words, in order to improve the performance of machining tools, it is desired to further increase tbe rpin of the shaft that is supported by the cylindrical roller bearing such that it rotates freely, and it is also desired to red-Lice tbe ainount of lubricant that must be supplied to the cylindrical rollerbearing in order to reduce the rotation resistance that occurs as the speed is increased.

A cylindrical roller bearing for supporting large radial loads is not used in conditions where it receives unifonn loading all the way around its circurnference. In oflier words, during use, part of the cylindrical roller bearing in the circumferential direction, or load area, supports the radial loa.d, and (lie opposite side in the radial direction, or noload aTea, does not receive the radial load.

4 Moreover, when the cylindrical roller bearing is i 6peration in a revolution type niotion, each cylindrical roller alternately passes the load area and no-load area, Also, since the cylindrical rollers are &-aly supported between the inner ring raceway and outer ring raceway when positimied on the load area, there is almost no change in position (skew angle), and revolves around the shaft while it rotates around its own axis in a stable condition. On the other hand, when the cylindrical rollers ae positioned on the non-load area, the posture changes comparatively freely withaut being constrained by the himer ring raceway and outcr ring raceway.

Moreover., when the posture of the cylindrical rollers c.banges when positioned on the no-load side, due to a inoment which occurs because of dynamic unbalance of the cylindrical rollers, or because of a Moment which occurs due to changes in the skew angle of the cylindrical rollers that accompanies the revolving motion of the cylindrical rollers, the rotating and revolving motion of (be cylindric4l, rollers become unstable. As a result, friction between the end faces of the cylindrical rollers and the rims becomes large, which makes it easy for abnonnal wear or seizure to occur.

Sunu-nar y of (be Invention Aji objective of this invention is to provide a. cylindrical roller bearing that is cap,able of effectively promfitig abnormal wear or seizure due to skew, even under severe (high-speed rotation, little ILtbrication) conditions.

Btief Description of the Drg-mings

Fig, I is a partial, cross sectional view of a first example of the cylindrical roller bearing which. is the ob ect of the present invention. j Fig. 2 is a diagranunatic view to explain the gyro moment applied to the cylindrical rollers during operation of a cylindrical roller bearing.

Fig. 3 is a diagranunatic view to explain the inertia moment of a cylindrical roller.

Fig. 4 is a graph to show the range where gyro moment acts in a direction to make the skew augle larger when a cylindrical roUcT is skewed, Fig. 5 is a diagrammatic view to explain the dynamic unbalance of a cylindrical roller.

Fig. 6 is a graph to show a -relation between a gyro mament added to a cylindrical roller and flie i-noment caused with a change in skew angle in the cylindrical roller.

6 kig. 7 is a partial, pross sectional view t6 show a cylindrical 'roller in the skew state.

Fig. 8 is a top plain view of the cylindrical roller of Fig, 7.

Fig. 9 is a side elevational view of the cylindrical roller of Fig.7.

Fig. I OA is aii end view of an example of the end face of the cylindrical roller in wear state.

Fig. IOB is an end view of an example of the end face of the cylindrical roller in wear state.

Fig. I I is a graph to show the range of the present invention..

Fig. 12A is a partial, cross sectional view of an example of the cylindrical roller bearing used in experiment conductcd to confirm the effects of the present invention.

Fig. 12B is a partial, cross sectional view of an example of the cylindrical roller bearing used in experiment conducted to confirm the effects of the present invention, Fig. 13 is a graph to show the results of the cxperiment conducted to confirm Ilie effects of the present invention.

Detailed Descrip-tioll of Prefcffed Embodiments 7 The cylindrical roller bearing of this inveution, in the same nianner as the aforemeritioned prior cylindrical bearing, comprises an inner race that has a cylindrical inner ring raceway formed arotaid its OUter peripheral surface, an outer race that has a cylindrical outer ring raceway formed around its inner peripheral surface,, a plurality of cylindrical rollers that a:re located between the miner ring raceway and outer ring raceway such that they cmi rotate freely, and a. pair of rims that are.fornied on botli sides of either the ftiner ring raceway or outer ring raceway such that they folin a space that is slightly larger than the length of the cylindrical roflers. In addition, the outer race is stationary and the inner race is rotated during use.

Particularly, with the cylindrical roller bearilig of this invention, (lie gyro moment " S" is taken to be equal to or larger than the sum of the moment ". U" which occurs due to dynamic unbalance of the cylindrical rollers, and the moment C" which occurs due to fluctuation, on the skew angle of the cylindrical rollers, that is, S _>_ U + C. At the same thne, when the cylijidrical rollers are skewed, so that the end faces of the cylindrical rollers corne in rubbfiig contact with the inner surfaces of the rims, the product Q - V of flic.force " Q" which is applied in thq direction of pressure between the end faces of the cylindrical rollers and the inner a surfaces of the rims at the points of sliding'contact due to the three moments "S", CV, and,c,,, and the sliding velocity "V" at tbe point of sliding contact, is equal to or less flian 60 kgf -i-nls- Of the tLu-ee moments "S", "U' and "C", the gyro moinent. "' S" is expressed by the following equation.

S = 1, - Sill 4) - (I., - JQ - CO C 2. sin 4) - Cos (b where, "Ix" is die moment of inertia around the "Y' axis of rotation of the cylindrical rollers; is the inornent of inertial around the "T' axis which runs through the center point of the cylindrical rollers and is orthogonal to the "X' axis of rotation of the cylindrical. rollers; It (0 "' is the angular velocity of revolution of the cylindrical rollers; Co is the angular velocity of rotation of the cylindrical rollers, 0 is the skew angJe of the cylindrical rollers, "A (A " is the change in skew angle during one rotation of Ole cylindrical, rollers, and f eTU" is the monient around the axis which rans through the center point of Ole cylindrical roller and whicli is orthogonal to the axis of rotation of the cylindrical 9 rollers and which occurs due to t1je dynamic unbalance of the cylindrical rollers.

tilen - ui naxilli -n value "U" of the moment around the "Z axis that Moreover, occurs due to the dynamic unbalance of the cylindrical roffers is expressed by the equation:

U = lu 0 CO J3 Furthermore, when as the cylindrical rollers skew, the end fa-ces of the cylindrical rollers coine in sliding contact with the inner surfaces of the rims, and when the cylhidrical rollers rotate, the inaxinium value "C" of the inoment t1lat occurs due to the change 11i skew angle of the cylindrical rollers is expressed by the equation:

C = Iz. Z\ (1) - (0 B In the cylindrical roller bearirig of this iovention, constructed as described 6bove,, the gyro motnent "S" is equal to or greater flian the sum of the inaxii-nurn value "U' of the moment around the 'T' axis which occurs due to the dynan-& unbalance of the cylindrical rollers, and the maximum value "C" of the moinent which occurs due to the change in the skew angle of the cylindrical rollers, so that the gyro nionient "S" keeps the posture of the cylindrical rollers stable.

Moreover, the product Q -V of the force "Q"' that acts at the point of sliding contact between the end:faces of the cylindrical rollers mid the inner surfaces of the rims in the direction that they push each other, and the sliding velocity "V" at the point of sliding contact, is equal to or less than 60 kgf - 1111s. jn other words, since the gyro moment "S" is prevented from becoming excessively large, it is possible to keep ffiction to a minfinum. at fjl.e point of sliding contact and to prevent abnonnal wear and scizure.

These points will be explained in detail below, The following exphination is for tbe case when the rims 8 are fonned on the outer peripheral sufface of the inner race 3. However, the explanation is similar when the rims, are fon-ned on the inner peripheral surface of the outer race 5.

First, the gyro moment "'S" is taken to be equal to or greater than the sum of the maximum value "U" of the moment and the maximum value "C" of the moment, that is, S _2: U + C. And then, the explanation will center oil stabilizing the posture of the cylindrical rollers. In other words, this invention actively uses the gyro motnent that occurs due to the skew of the cylindrical rollers, as a. control factor for stabilizing the posture of the cyWidrical rollers when they are positioned on the no-load side.

As mentioned above, in the case of the cylindrical roller bearing I as shown I I in Fig. 1, whicb is the object Of this invention, the space between the pair of rims 8. that are fonned on both ends around the outer peripheral surface of the inner race 3, is slightly larger than the length in the axi,-:d direction of the cylindrical rollers 6.

Therefore, a sniall gap exists between both ends in the axial direction of the cylindrical rollers 6 and the inner surfaces of the rfins 8, arid due to this gap, the cylindrical rollers 6 revolve while rotating in a skewed condition. As a result of the cylitidneal rollers 6 revolving around the shaft in this way w1lile rotating around its own axis in a skewed state, the cylindrical roffer begin to have precession motion sucli as that shown in Fig. 2, and a gyro moment "S" with a iriaLn,iitude of that given by Equation (1) acts on the cylindrical rollers 6.

S =I., Co'; - Sill 0 - Cos 4) --- (1) ]n this Equation (1), as shown in Fig. 3, is the momerit of inertia around the "X" axis of rotation of the cylindrical rollers 6, "J," is the moment of inertial around the "E' axis which passes through the cemer point of the cylindrical rollers 6 and which is orthogonal to the "Y' axis of rotation,- " o),3" is the angular velocity of rotatio.i) of the cylindrical rollers 6, " w, " is the angular velocity of revolution of the cylinch-ical rollers 6, mid " 0 " is the skew angle of the 12 cylindrical rollers 6 and has a positive value ( (1) > 0).

Also, in Fig. 2, "11" indicates the angular monientum (vector) when t1le cylindrical rollers 6 are under precession. Also, as mentioned above, is tile angular velocity of orbital revolution of the cylindrical rollers 6.

On the other hand, witli the iiormal dimensions of the conventional cylindrical roller bearing 1, wben the cylindrical roller bearing I is used in a state such that the outer race 5 is stationary and the inner raue is rotated, then /((0 Cos > Tlierefore, when the extenial forccs (forces other than the gyro nionient "S") are not taken into consideration., then when the cylindrical rollers 6 are skewed, this gyro mornent "S" acts in the same direction as the skew of the cylindrical rollers 6) in other words, acts in a direction that proinotes the skew, and increases the skew angle " 0 ".

In Fig. 4, the range f I - J.;, / 1,:-:Ei co 13 /( co cos 4))) in wilicli the gyro nioinent "S" acts in the direction that increases the skew migle " 0 " when the cylindrical rollers 6 are skewed, and the rwige T,, / I., '-- 0, is shown by the sliaded area.

in Fig, 4, the horizontal axis is the ratio 1, / 1, of the moments or inertia of 13 th e cyliudrical rollers 6, and the vertical axis i, (0 / ( C'O cos (1) ;-' 73 On. the other hand, a awaient "U,," duG to the dyDamic unbalance that occur-s around the "T' axis acts on the cyl indrical rollers 6 with a in g i d iveln a 11 tu e that is gi by Equation 2a below.

U., = 13 - cos ( (k) T3 ---(2a) Also, the maximurn. value "U" ofthe inornent "U, " in this Equation (2a) is given by Equation (2b).

Tj = lu a CO 13 2 (2b) In Equation (2b), is the monizit of inertia related to dynarnic unbalance, of t4c cylindrical rollers 6, and " (,) 13" is the angular velocity of rotation of the cylindrical rollers 6. The moment oC inertia "lu" is expressed by Equation (3) below.

T,. = (M6/2) - e - L (3) In Equation (3), "M,," is the mass of each cylindrical roller 6. In addition, as shown in Fig. 5, the center of gravity of the cylindrical rollers 6 is shifted frorn the geometrical center, and "e" is the aniount of eccentricity fii the radial direction o:f the cylindrical rollers 6 when this shifted component is assunied to exist on both ends of the cylindrical rollers 6, and '-'L" is the leiigtli. in tile axial direction of the cylindrical rollers 6.

14 Rutherinore7 when the cylindrical rollers 6 are skewed, they revolve around the shaft while rotating around its own axis with the outer peripheral edges on both end faces in the axial direction are pressed against the inner surfaces of the rims 8.

As a result,, a moment "C, '% that occurs due to the change in the ske'w angle 4; "' because of the change in shape of the cyUuldrical rollers 6 and rims 8, acts on the cylindrical rollers 6 with a magnitude as given by Eqtiation (4a) below.

Cl,=C - COS(COBt+ 0) --- (4a) in ti:iis j-7.quatioya (4a), 11 0 11 is the phase difference o-ri-noment "C, " with respect to the 11101lient 'U,, ". Also, in Equation (4a), the inaximuni value "C" of the moment "C, " is expressed by Equation (4b).

C-4-Aq) - con 2 (4b) In this equation (4b), ",L 0 " is the change in skew angic " 0 "'during one rotation of a cylindrical roller 6, and " co is the angular velocity of rotation o F the cylindrical rollers 6.

Now, it is assumed that the cylindrical rollers 6 rotate arotuid its own axis witli the outer peripheral edges on bodi end faces of the cylindrical rollers 6 in contact with the inner sutfaces of the rinis 87 and by taking the skew moment that the cylindrical rollers 6 receive ftorn the rinis 8 to be "T". then the eqiation below related to the skew angle " 0 " of the cylindrical rollers 6 is obtained, where the skew moment that is applied to the cylindrical rollers 6 frorn both the inner ring raceway 2 and outer ring raceway 4 is sinall and is ignored.

Iz - (d2 q) / dt?) n- S U, - T --- (5) The left side of the Equation (5) is:

J,, - (d 20 / dt') 17, - d7/ dt' (A 0 nt + 0)Ij- - -(-ZSo -COB 2. Cos ((0,3t+ 0)) CIV Therefore., Equation (5) can be rewrftten by Equation (6).

T = S + U, + C, --- (6) Now, when considering e = 0, in other words, when the phases of "U,," and r.r.C.CC match, then Equation (6) becoines:

T = S + (U + C) -cos (co It) --- (7) The skew moment "T" fliat the cylindrical rotlers 6 receive from the rinis 8, changes periodically during o-ne rotation of the cylitidrical. rollers 6. This is shown. in Fig. 6.

Ilie skew inoinent "T" that the cylindrical rollers 6 receive from the rinis 8 16 becomes a immimum when the cylindrical rollers 6 are puslied back by the rims in a direction such that the skew angle " 4) " becomes snialler in the state where the cyhndiical rollers 6 are the most skewed between the rinis 8, and when the cylindrical rollers 6 are pressed the most to the rims 8 due to the skew moment CCU re , caused by the unbalance of the cylindrical rollers 6 in the state where the cylindrical rollers 6 are the most skewed between the rims 8.

The skew inornent "T"' that the cylindrical rollers 6 receive from tlienirns 8 becomes a inininium when the moment "C, " acts on the cylindrical rollers 6 in a direction stich that the cylindricalrollers 6 separate from the rims 8 upon the time wlien the skew angle ",0 " of the cylindrical rollers 6 becomes larger from the statc wbere the skew angle " 0 " or the cylindrical rollers becomes the srnallest and when the skew nionient "U." acts on the cylindrical rollers 6 in a direction sucli that the cylindrical rollers 6 separate from the rims 8 in the state where the skew angle " d) " of tbe cylindrical rollers 6 becomes a tnininium.

The monients "S", "U"and "C" will be explained for the case that satisfies 'S U + C as mentioned above. From Equation (7), T 4 0 constantly kept, so the cylindrical rollers 6 have a skew angle in a constant direction and are constantly pressed toward the rims 8. Ili otber words, the cylindrical rollers 6 revolve aroinid. the shaft being guided by the rinis 8 and do not separate from the rims 8. In this way, the cylindrical rollers 6 are guided by the rims 8, and since they revolve around the shaft while rotating around its own axis in a stable state, the cylindrical rofler bearing I can be operated stably even wlicn. used in a state where the cylindrical roller bearing 1 has a no-load area as desclibed above.

In other words, wben passing this no-load arca, tile cylindrical rollers, 6 revolvc around the shaft wIffle rotating around its own. axis with both end faces iii the axial direction being pressed against the inner surfaces of the nms 8 and enter the load area again with the same posture (the direction of the skew angle 11 61 has not changed). 'llierefore, the niotioD of the cylindrical rollers 6 does not become unstable during one revolution.

In addition to the moments "U V wid "CV" being causes of a force that changes the skew angle of the cylindrical rollers 6 during operation of the cylhidrical roller bearing 1, are misaligtunent of the iniler race 3 and outer race 5, or a skew moment caused by shape ciror (inclination) of the imier ring raceway 2 or outer riDg raceway 4, 1--lowever the skew moments caused by these are smaller than the moments "S", (CU31 and"C" that occur when the bearing is used at high speed such. that the aniount of "din - il" exceeds 1.5 million, as is the object of 18 this invention. There is no sl-.)ecial problem. even when the skew moments caused due to misalignment or shape error are not considered- Next, suppressing die friction at the sliding contact point and preventing abnormal wear or seizure ftorn occurring is expi ained for when the product "Q V- of the force "Q" that acts in a direction that presses the cylindrical rollers 6 against the inner surfaces of the rinis 8 at the sliding contact point of the axial end faces of the eyffiidrical rollers 6 and the inner surfaces of the rims 8, and the sliding velocity "V" at tile sliding contact point, is taken to be 60 kgf -ni/s or less.

As described above, wben the gyro nionient "S" is equal to or greater than the sLun of the maximum values of the moments "U" and "C", then the operation of (he-cylindrical rollers 6 is stable, and froin that aspect, it is possible to prevent abnon-nal wear or seizure from occurring. However, when thegyro moment "S is too large, (lie force "Q" that presses botb end faces in the axial direction of the cylindrical rollers 6 against the inner surraces of the rinis 8, becomes too large.1 As a result of this force "Q" becoming excessiveJy large, tile product "Q V" at tl-ie sliding contact point becomes large as shown in Equation (8) belovv, aiid it becomes easy for abnotnial wear or seizure to occur.

19 Q - V -- (m/B) - V --- (8) in Equation (8), "Q" is a force (kgt) that acts in a direction that presses the outer peripheral edges at both end faces in the axial direction of the cyliodrical rollers 6 against the imer suLfaces of the rims 8 at the point of contact "G" between fliern, when the cylindrical rollers 6 skew as shown in Figs. 8 and 9, and i c4v" is the sliding velocity (m/s) betwceii the outer peripheral edges at both ends in the axial direction of the cylin(bical rollers 6 and the inner surfaces of the rijus 8 at the point of contact "G". Also, "M" is the skew moment (kgf -m) that acts in a direction that makes the skew angle 15 " of the cylindrical rollers 6 smallcr, and is the sum of the moments "S", "U" and "C", described -above. That is, (M S + U + Q. As sbown in Fig. 9, "B" is the leligh (m) of the area of contact betwcen the end faces of the cylindrical roller 6 and the inner surfaces of the rim 8 when the cylindrical roller 6 is skewed.

With these kinds of asstimptions, the inventors perfonned tests to learn what effects that the product Q - V has an wear of the end faces of the cylindrical rollers 6 and the inner surflaces of the rims 8. When the prodLLCt Q -V is equal to or 60 kgf -mls or less, that is, Q - V '-5; 60 kgf -nVs, there was no abnomial wear or seizure of the end faces in the axial direction of the cylimirical rollers 6 and the,- imacr surfaces of the rims 8, With the relationship of moments "S", "U"' and e.CC25, described above, therange of the invention is S ->-- U + C, and the upper Ihnit of the product Q - V due to the sum of these moments S + U 4 C is 60 kgf - ni/S.

In Fig. 11, the range of the invention that satisfies these two conditions, is shown by the grid area. The horizontal axis in Fig. 11 is tile component of the product Q - V that is caused by the gyro moment "S", ,and likewise the vertical axis is the component of tbe product Q - V that is caused by the sum U + C of the moments "U", and '-'C"'.

In Fig. 11, of the part that is not pail of (lie range of the invention shown by the grid area, in the area that is shown by Ibe diagonal lines where (U + C) > S, there is eccentTic wear on the end faces of the cylindrical rollers 6 as shown by the diagonal lines in Fig. I O(A). Iii other words, in the are where (U + C) > S, the cylindrical rollers 6.move unstably as the cylindrical roller bearing I operates, so Ihat there is eccentric wear on both end faces in the axial direction of the cylindrical rollers 6.

On the other liand, in Fig. II in the range of dotted area where S -!: U + C but Q - V > 60 kgf - m1s, the motion of the cylindrical rotlers 6 is stable as the 21 cylindrical roller bearing 1. operates, so that both end faces in the axial direction of the cylindrical rollers 6 wear nii a concentric c1rcular shape as shown by the diagonal lines in Fig. I O(B). However, even though the wear is in a concentric circular shape, as long as Q - V > 60 kgf - ro/s, the amount of wear will be large and there is a possibility of seizure.

In the present invention, by satisfying the conditions of the range of grid area shown by the grid in Fig. I I where S _k U + C, and Q - V:-S 60 kgf -ni/s, the motion of the cylindrical rollers 6 is stabilized while the cylindrical roller bearing I is operating in, the range, as well as wear is suppressed and the danger of seizure is reduced. lt is fliought that a cylindrical roller bearing I that satisfies both of these two conditions S --' U + C, and Q - V _f:5 60 kgf - m/s can be realized by using short rollers whose length 'Vin the axial direction is stualler than the diameter (outer diameter) "D" of the rolling surface, that -is, L/D < 1.

1-imbodinients Next, testing that was perfornied to cbeck the effect of the invention will be explained. Ilie test was perfornied for a cylindrical roller bearing la, shown in 22 Fig. 12(A),. that is outside the range of this invenuon and which has cylindrical rollers 6a whose rolling-surf-ace diameter (outer diameter) "Y' is equal to die length "L" (see Fig, 5 for D, L) in the axial direction, that is, L/D = 1, and for a cylindrical roller beariDg I b, shown in Fig. 12(B), that is included fil the range of the invention and which has cylindrical rollers 6b whose length "L", in the axial direction is sinaller than rolling-saiface diameter (outer dian-leter) "D", (flat is, L/D < 1. The cylindrical rollers 6a are a so-called "equal length and diameter roller"wbile the cylindrical rollers 6b are a so-called "short roller". The cylindrical rollerbearings I a, I b comply to model number KI 014, with all outer diameter of 110 nirn,, inner diameter of 70 imn, and width o-F 20 mm. Also, 18 cylindrical rollers were used, respectively. The filner race 3of the cylindrical roller bearings I a, I b was rotated tinder conditions of a minute amoLmt of hibricatiou (oil-air lubrication), and the rpm when seizure occtirred was measured. The results are shown in Fig. 13- In the test results shown in Fig. 13, the markings 0 show the test results -for cqual length and diameter cylindrical rollers carbonitrided steel made of as disclosed in the cylindrical roUer bearing of Japanese patent Publication No. Tokukai Hei 11-6526, and the -markings D show the test results for short 2.3 cylindrical rollers made of carbonitrided steel, As can be clearly seen from the tests, wben the short rollers are used, the rise in the temperature of the outer race is small, which improves the witi-seizure capability.

The opposing inner surfaces of flie pair of rims 8fion.-ned in the cylindrical roller bearing I are inclined in a direction such that. the space between them increases moving in a direction outward in the radial direction, and when the cylindrical rollers 6 are skewed, so that the outer peripheral edges of both end faces of the cylindrical rollers 6 come in contact with the OLLter rims 8,, there is a possibility tbat a solid ofl. layer will be securely formed at the point of sliding contact due to the wedge effect of the oil when outer peripheral edges of the end faces cot= in contact with the inclined inncr surfaces. 'Ihercfore,- it is possible to more effectively prevent abnorn-lal wear or seizure even under condition of rainute lubrication at high speed.

Finally, the cylindfical roller bearing of this invention as described above where the cylindrical rollers that satisfy the conditions: S -!-: U + C, and Q - V 60 kgf -mls, can be realized by regUlatiDg the Enciisions, of each of tile COMPOJICDtSajid operating conditions of the cylindrical roller bearing etc., for exainple, as -follows:

- Outer diameter "D" (m.rn) of the cylindrical roller x Length "U' (mill) in tlif-- 24 axial direction: (1) 9 X 9 - Size of the space between the end faces in flit axial direction of a cylindrical roller and the inner surfaces of the rims -. Approx- 0.04 (mm) - The heiglit "'h" of the rims from the inner ring raceway or the outer ring raceway (see Fig. 1): 2.6 (rain) Inclination angle, of the inner surface of the briiin (open outward) witli reference to the vertical surfaces: Approx. 40 minutes Unbal ance of the cylindrical rollers 20 (mg - min) or less - Squareness of the end faces in the axial direction of tbe cylftidtical rollers 0.003 (nim) or less - Operating condition of the cylindrical rofler bearing: 30,000 (rpm.) or less The cylindrical roffer bearing of Mis invention, con. structed and functioning as described above, makes it possible to prevent abnornial wear and seizure of the end faces of the cylindrical rollers and the inner surfaces of the rims, as well as makes it possible to improve durability and reliability of tb.c mechanical device in wliich tbe cylindrical roller bearing is installed.

Claims

What is claimed is:

L A cylindrical roller bearing comprising a rotatable inner race that has an outer peripheral surface formed with a cyliiidrical iluier ring raceway, a stationary outer race that has an inner peripheral surface fomied with a cyfindrical outer ring raceway, and a plurality of cylindrical rollers that are rotatably located between the fimer ring raceway and outer ring raceway, one of the inner ring raceway and outer ring raceway being formed with a pair of rims on both sides thereof such that a space slightly larger than tbe length of the cylindrical. rollers is fon-ned between the rims, wherein the gyro moment "S" is expressed by the following equation: S=L - coo - COB -sino-(I'- 1") -CO'.2 Sin 0 -cos where "Ix" is the monient of inertia around the "Y' axis of rotation of the cylindrical rollers; is die moment of inertia around the "Z" axis which runs through the center point of the cylindrical rollers and is orthogonal to the 'W' axis of rotation of the cylindrical rollers; is the angular velocity of orbital revolution of the cylindrical rollers; (o is the anguLar velocity of rotation of the cylindrical rollers, 0 is the skew angle of tI)e cylindrical rollers, 2(,=.

AIL 0 " is the change in skew angle during one rotation of the cylindrical rollers, wherein the maximum value "'U" afthe moment arou-nd the "T' axis that occurs due to the dynamic unbaiance of the cylhidrical rollers is e4ressed by the equationU= III - (013 where is the inoment of inertia related to the dynainic, unbalance of the cylindrical rollers, around the axis which runs tlu-ough the center point of the cylindrical roller and which is orthogonal to the axis of rotation of the cylindrical rollers, wherein,, the maximum value "C" of the moment that occurs due to the change in skew angle of the cylindrical rollers when the end faces of the cylindrical roUers coine in sliding contact with the inner surfaces of the rims, while the cylilidrical rollers rotate because the cylindrical rollers skew, is expressed by the equation: C=Iz-'L(P -COB2 wherein the gyro moment "S" is taken to be equal to or larger than the sum of the maxitnum moment "U' and the maximum mornent "'C"', and wherein when Lhe cylindrical rollers are skewed, so that the end faces of the 277.

cylindrical rollers come in rubbing contact with-die inner surfaces of the rims, tht'.. pi-oduct Q V of the force "Q" which is applied in tl-ie direction of pressing the wid faces of the cylindrical rollers and the inner surfaces of the rims to eac,11 offier at the point of sliding contact due to the three moments "S", "U' and "C", and the sliding velocity "V" at the point of sliding contact, is equal to or less than 60 kgf - m1s.
2. The cylindrical roller bearing of Claim 1, wlierein flie pair of rims have opposing inner surfaces which are inclined in a direction such that the space between the opposing wrier surfaces increases toward the tip end edge in the radial direction of the rims, and when the cylindrical rollers are skewed, so that the outer peripheral edges of both end faces of the cylindrical rollers come in contact with the rims., the outer petipheral edges of Ole end faces come in contact with the inclined iiiner surfaces at a portion closer to die base end than the tip end edge.

21S.