DE2152309A1 - ball-bearing - Google Patents

Description

Patent attorneys

Dipl. Ing. H. Heuck Dipl. Phy *. W. Schmitz

ΓβΙ. 5380586

Societe Nationale d ¹ Etude

et de Construction de Moteurs

d'Aviation

150 Blvd. Haussmann

75 - Paris, France ¹⁸ October 1971

Attorney File M-1736

ball-bearing

The invention relates to a device for storing a rotating component, in particular the rotor of a turbomachine (for example an aircraft jet engine), the can be loaded by an arial thrust of different sizes and directions

The roller bearings and especially the ball bearings for higher speeds have for reasons of production, assembly, Puncture mode and lubrication necessarily have an internal radial play. In the rest position and at low speeds Therefore, the axis of the rotor shifts due to gravity with respect to the theoretical axis of the bearing something down; if with increasing speed the centrifugal force, which the rotor due to its low but exposed to unavoidable imbalance, the same size

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and then becomes greater than the weight of the rotor, the axis of the rotor moves around the axis of the bearing This has the consequence that machines such as turbo machines, whose rotor running on ball bearings is relatively light and large Speed rotates, can be set in dangerous vibrations.

This applies to rolling bearings that are only exposed to radial forces are. The ball bearings, on the other hand, which have to absorb an axial thrust and act, for example, as thrust bearings, center in operation again. In fact, the radial play of the bearings due to the relative axial movement between the inner and outer races wrestle by eliminating their axial play, whereby the contact between the Balls and the raceways of the races takes place at a certain angle. With a large axial thrust, the vibrations are thus switched off. In the case of turbo machines, their axial thrust changes with the speed, however, the risk of oscillation remains with no load or low load This is particularly true of aerospace turbomachines, such as gas turbine jet engines, which have significant Changes in the axial thrust (even a change in direction of the axial thrust) depending on the plug state of the das Engine-carrying aircraft are exposed.

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It is possible to expose the bearing to an axial force which always points in the same direction regardless of the operating state of the rotor by placing an additional on the bearing Biasing force is exerted which is greater than the maximum possible oppositely directed axial thrust of the rotor is. However, this solution has the disadvantage that the load on the bearing is increased, resulting in larger dimensions of the bearing requires.

It is already known to arrange two or more ball bearings side by side in order to keep the rotor in the same place, for example at the end of the shaft, to be supported; but also in this case requires the use of an additional Preload force an oversizing of the bearings.

The object of the invention is to create a device of the type specified in the introduction, in which the radial play of the two supporting the rotor in the entire operating range Ball bearings eliminated and thus any vibrations avoided without overloading the ball bearings. This is achieved by the features specified in claim 1.

In the device according to the invention need the opposing Preload forces not to be very large. It is sufficient,

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that they eliminate the axial play of the ball bearings in the rest position. They can be applied by any suitable means be, for example by preloaded elastic components (for example V-shaped springs or disc springs) or hydraulic devices (for example servomotors »which are operated with the pressure of the lubricating oil of the ball bearings will).

In a preferred embodiment of the invention

the two inner or outer races of the ball bearings, which are mounted with axial play, are preloaded by a elastic member biased so that they are pushed away from each other. This is enough to get on the two races exert opposing pretensioning forces.

In the rest position or in the lower speed range, this elastic component exerts a certain axial force on at least one of the ball bearings, so that the rotor is centered in this ball bearing ψ , whereby the internal radial play of this ball bearing by eliminating its internal axial play (or in other words by the relative axial movement between the inner and outer races under the effect of this axial force) is eliminated. This axial force, which is initially exerted by the elastic component, is subsequently in a certain way replaced by that of the rotor, to the extent that; how it increases with speed. From the moment the axial thrust of the

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Rotor exceeds the maximum force exerted by the elastic member, the ball bearings are the effect of this Axial force is no longer exposed and they work together to take up the axial thrust of the rotor.

This axial thrust of the rotor can then be evenly distributed between the ball bearings due to a particularly advantageous embodiment of the invention, which consists in the displacement of the arranged with axial play To limit races against the effect of the biasing force acting on it by a stop.

A preferred exemplary embodiment of the invention is explained in more detail with the aid of the drawings. Show it:

Fig. 1 is a half-axial section through an inventive Device with two ball bearings, the outer race © of which is built into a stator with axial play and are urged away from each other by a spring, and their inner races are axially locked on the rotor shaft are. The camp is at rest.

Fig. 2 is a partial section along the line H-II in Fig. 1,

3 is a view corresponding to FIG. 1, showing the position of the ball bearings when the shaft is one from the left, is exposed to a certain axial thrust directed to the right,

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FIG. 4 is a view corresponding to FIG. 3 showing the The position of the ball bearings shows when the axial thrust of the rotor is applied to the races has reached or exceeded the maximum pre-tensioning force,

Figure 5 shows the changes in position of the ball bearings during a 5a and 5b

Acceleration.

The device shown serves to support the shaft of a rotor 3 in a stator 1. It has two identical ones Ball bearings 4.5, the inner races 4a, 5a without any Clearance are attached to the shaft 2 and their outer races 4b, 5b with low friction (i.e. with a low diametrical play of the order of, for example, a few hundredths of a millimeter) and axially sliding are arranged displaceably in the rotor 1. You are through openings 6,7 of the stator to avoid contact corrosion lubricated. The ball bearings themselves are lubricated by means not shown

A ring 8, which forms a spacer sleeve, provides a constant axial distance between the inner races 4a and 5a safe. The entire structure of the races 4a, 5a and the spacer sleeve 8 is between a shoulder 2a of the

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Shaft and one screwed with a thread 2b of the shaft Nut 9 held · The outer race 4 "b is provided with projections 10 that engage in grooves 1a of the stator, and the outer race 5b has a grooved flange 11 (Pig x 2), in the grooves of which projections 12 engage. The projections 12 are each provided with a fixing pin 12a which is pressed into a blind hole 13 of the stator is. The projections 12 are formed by a threaded ring 14 held, the versehraubt with an internal thread 1b of the stator is. The flange 11 is less thick than the projections 12, so that the race 5b to the left of the nut can slide in the stator. The outer races 4b and 5b are by an annular preloaded spring 15 with U-shaped cross-section, the two legs of which facing each other Form stop surfaces 15a, 15b, pushed away from each other.

Fig, 1 shows the storage device in the rest position. the outer races 4b, 5b, which are biased by the spring 15, have a greater distance than that between the Stops 2a, 9 clamped inner races 4a, 5a, the distance between which is determined by the spacer sleeve 8. The spring 15 pushes the outer races 4b, 5b over the Balls 4c, 5c against the inner races 4a, 5a. In this Position the races 4b and 5b on the shoulder 1c of the

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Stator and the threaded ring 14; the shoulder 1e and the Threaded ring 14 must not limit the distance between the outer races, which, as explained above, are not allowed to limit

support via the balls on the inner race rings " must be able to.

The contact of the balls 4c with the raceways of the races 4a and 4b takes place on a rotationally symmetrical cone (L · with the angle oL, which runs through the center points of the balls and whose axis coincides with the axis XX ^{1 of} the bearings »takes place in the same way the contact of the balls 5 on a cone C ₂ »which has the same angle CL ^ , but is directed opposite to the cone Cj Races 4b, 5b are exerted in the opposite direction. When the outer races are moved apart, the spring moves in a symmetrical manner the lines of contact of the balls of the two ball bearings by exerting a preload force on the ball bearings, whose internal radial play is eliminated in this way will.

In this rest position, the stop surfaces 15a and 15b of the spring 15 are separated from one another _{by a play J 1.}

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The mode of operation of the bearing device during commissioning and acceleration of the rotor 3 is now examined, it is assumed that the rotor is subjected to an axial thrust which can become zero and change its direction, which, however, is initially directed from left to right.

This from left to right (i.e. in the direction of arrow P the pign. 3, 4) directed axial thrust is transferred from the race 4a via the balls 4c of the ball bearing 4 to the race 4b transfer. The race 4b is thus on the one hand the axial thrust directed from left to right and on the other hand the biasing force directed from right to left, exerted on it by the spring 15 acting on the raceway 5b is suspended. The axial thrust is thus transmitted from the leather 15 to the race 5b. It follows that from This axial thrust occurs on the threaded ring 14 as Stop acts and the axial thrust of the race 5b on the Stator 1 transmits. In the illustrated embodiment, the race 5b was already with the threaded ring 14 in touch; so it does not move. If, however, when assembling a certain play between the race 5b and the threaded ring 14 were provided, the rotor and the two ball bearings 4, 5 would be from the one shown in FIG Move position together to the right until the race 5b rests against the threaded ring 14.

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As long as the axial thrust remains less than the preload of the spring 15, the races 4a, 4b and 5a, 5b also remain in the position shown in FIG. When the axial thrust becomes greater than the bias of the spring 15, the spring deforms so that the rotor 3 shifts to the right, taking the inner races 4a, 5a with it, while the race 4a takes the race 4b with it via the balls 4c. The race 5b, which still rests on the threaded ring 14, is no longer pressed against the balls 5c. Fig. 3 shows the position of the components when the axial thrust has reached a value at which the play Jp between the stop surfaces 15a and 15b of the spring half the size of the game J ₁ in FIG. 1. The balls 5c are held by the centrifugal action against the outer race 5b and do not touch the inner race 5a because of the inner radial play of the ball bearing 5. The ball bearing 5 is no longer loaded and could therefore be the cause of vibrations if it were to support the shaft 2 alone; the shaft 2, however, remains centered by the loaded ball bearing 4. The outer race 4b of the ball bearing 4 follows the displacement of the inner race 4a by moving away from the shoulder 1c, against the increasing tension force exerted on it by the spring 15, the spring being attached to the threaded ring 14 adjacent race 5b is supported. The WinkelQL of the cone C ₁ remains in

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essentially the same oil .. The ball bearing 5 does not matter more, and the ball bearing 4 alone and without play carries the entire axial thrust of the shaft 2.

If the axial thrust of the rotor increases with the speed, the races 4a, 5a and 5b slide further to the right and compress the spring 15 until the race 5a is supported by the balls 5c on the race 5b, which is permanently on the threaded ring 14 is present. In this position, which is shown in Pig. 4, the contact of the balls 5c with the raceways of the races 5a and 5b on a rotationally symmetrical cone O ₅ , which is oriented like the cone C. The rotor cannot move any further to the right (apart from the elasticity of the balls and the races), so that the pretensioning force of the spring 15, which cannot be compressed any further, has reached a maximum. The axial thrust of the rotor is transmitted to the rotor partly via the ball bearing 4 (through the race 4b _f, the spring 15, the race 5b and the threaded ring 14) and partly via the race 4a, the spacer sleeve 8, the ball bearing 5 and the threaded ring 14 . The axial thrust is thus distributed to the two ball bearings and the internal radial play of both ball bearings is eliminated.

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So that the ball bearing 5 can assume the position shown in Figure 4, it is obviously necessary that the play Ja between the Aaschlagflachen 15a and 15h of the spring (Figure 1) is at least equal to the inner axial play of the ball bearing 5 (ie equal to the inner Axial play of each of the ball bearings, as the ball bearings are identical). If the play J ^ were greater than the inner axial play, the part of the axial thrust transmitted by the ball bearing 4 could not be greater than the maximum prestressing force exerted by the spring 15, the remaining part of the axial thrust would have to be transmitted by the bearing 5. Thus, the maximum axial thrust of the rotor can be distributed almost evenly between the two ball bearings by precisely selecting the force of the spring. Preferably, however, the play J .. is given a value which is equal to the inner axial play of each of the ball bearings, so that the stop surface 15a rests against the Aaschlagflache 15b when there are large axial forces (FIG. 4). In this way, the force of the spring can be reduced, as a result of which the preloading force transmitted by the spring to the ball bearings and thus their wear at low speeds are reduced. As soon as the axial thrust of the rotor is greater than the maximum preload force of the spring (FIG. 4), the race 4b rests positively on the threaded ring 14 (since the stop surfaces 15a and 15b lie against one another), while the ball bearing 5 simultaneously does its part of the axial thrust

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takes over and its internal axial play is eliminated in the same sense as that of the ball bearing 4. The great axial forces are thus evenly distributed over the two ball bearings.

The FIGS. 5, 5a and 5b show in a schematic and exaggerated manner the displacement of the races between the positions of FIG. 3? Ign. 1, 3 and 4. When the distance between the races 4a and 5a is L, the distance between the races 4b and 5b in FIGS. 1 and 5 the value L + J ₁ , in FIGS. 3 and 5a, the value of L + _J1 / 2 and in Figs. 4 and 5b the value L

Since the two ball bearings are arranged symmetrically to each other in the rest position, the mode of operation is the Storage device in the case of an axial thrust directed from right to left is the same as that described above, the displacements take place from right to left and the roles of the ball bearings 4 and 5 are reversed. The ball bearing 5 carries only the small axial forces and transmits them to the race 4b resting on the shoulder 1c; the internal axial play the ball bearing 4 is then "consumed" with increasing load in the same direction as that of the ball bearing 5, and the load is distributed over the two ball bearings. The axial play between the flange 11 and the shoulder 1d of the

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Stator (Fig.1) must be so large that the Race 5b can move to the left until the ball bearing 4 absorbs part of the load.

It goes without saying that numerous modifications of the exemplary embodiment described are possible without the frame to leave the invention. In particular, the elimination of the internal, which takes place in the opposite direction Axial play of the two ball bearings can be realized by other means. For example, those with axial play arranged outer races are axially pressed against each other instead of being pushed away from each other. With Races arranged with axial play could also be the inner races, while the outer races are axially immovable to be ordered. In addition, the outer race of one of the ball bearings and the inner race of the other ball bearings can be arranged with axial play, these two races in the same direction ™ are elastically pretensioned.

The bearing device could have more than two ball bearings, for example a third ball bearing, its inner race with the race 4a and the outer race with the race 4b is firmly connected.

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Claims (2)

Claims. 11.) Device for mounting a rotating component, in particular the rotor of a turbo machine, which is driven by an axial thrust of different sizes and directions is resilient, with at least two ball bearings arranged next to each other, whose internal axial play in opposite directions Direction is eliminated by two preload forces acting on the axially slidably mounted inner or attack outer races of the two ball bearings, characterized in that each of the races (4b, 5b) is pressed by the biasing force acting on it against a first stop (1c, 14), and that the Displacement of the slidingly mounted raceway (4b, 5b) at least one of the ball bearings against the action of the biasing force acting on it is limited to a value by a second stop (15a, 15b) -16- 209819/0940 is equal to the internal axial play of the other ball bearing (J ₁ ). 2. Apparatus according to claim 1, "in which the" two ball bearings are designed identically and the "two axially slidingly mounted - inner or outer - races are pushed away from each other by a pretensioned spring or other elastic means, characterized in that that the second stop consists of stop surfaces (15a, 15b) formed on the spring (15) which are mutually can be moved into the system in order to limit the tension of the spring to a value that is equal to the inner axial play (J ..) each of the ball bearings is » 209819/0940 Blank page