WO1997007347A1

WO1997007347A1 - Autobalancing unit and a method and a tool for manufacturing such a unit

Info

Publication number: WO1997007347A1
Application number: PCT/SE1996/001012
Authority: WO
Inventors: Bo Göransson; Ratomir Lazic; Jonas NILSAGÅRD
Original assignee: Aktiebolaget Skf (Publ)
Priority date: 1995-08-18
Filing date: 1996-08-14
Publication date: 1997-02-27
Also published as: SE9502884D0; SE9502884L; SE506579C2; AU6760196A

Abstract

An autobalancing unit arranged to produce automatically in a rotary system, with which the unit is associated, a static and/or dynamic balancing effect, and incorporating in combination an outer race ring (2) with a circumferential inner race track (7), an inner race ring (3) positioned in the bore of the outer race ring (2) concentric therewith and having an outer circumferential surface (8) confronting the race track (7) of the outer race ring (2), cover members (4, 5) fitted between the race rings, thereby spacing apart the race rings and sealing of an annular chamber (6) between themselves and the race rings, and a number of rolling bodies (10) positioned in said chamber and being of a diameter smaller than the radial size of the annular chamber (6), whereby the race track (7) of the outer race ring (2) and the rolling bodies (10) have substantially the same hardness and/or yield strength.

Description

AUTOBALANCING UNIT AND A METHOD AND A TOOL FOR MANUFACTURING SUCH A UNIT

The present invention refers to an autobalancing unit, i.e. a machine element arranged and adapted to produce automati¬ cally a static and/or dynamic balancing effect on rotary systems during operation.

Such machine elements comprise an annular outer race ring with a circumferential inner race track, and an annular inner race ring with a circumferential outer surface. The two race rings are positioned coaxially, with the inner race ring situated concentric within the outer race ring thus that the said race track of the outer race ring together with the said outer surface of the inner race ring encompass an annular space, in which annular space are provided a number of rolling bodies, which have smaller diametrical measure than the radial height of the annular space, thus that the rolling bodies are movable within said annular space. The side openings of said annular space being covered by sealing annular cover members, thus forming a sealed annular chamber between said race rings and said cover members . In order to dampen the said movement of the rolling bodies, the said annular chamber is preferably filled at least partially with a dampening fluid, e.g. oil.

The function of the unit is to compensate for unbalance appearing in the rotary system to which the unit is mounted, thereby allowing the rolling bodies entrapped in the annular chamber to move freely to arrange themselves in angularly displaced clusters or in spaced apart relations, with the rolling bodies contacting the race track of the outer race ring. The unit is not subjected to loads comparable e.g. to the load supported by a rolling bearing of comparable size, and for this reason some of the components of the unit must not be dimensioned and manufactured to withstand the high stresses appearing in a comparable rolling bearing. However the rolling bodies and the race track of the outer race ring must have sufficient strength to withstand the forces acting between them during operation and primarily the wear occurring during operation.

UK-832,048 refers to such a balancing device for rolling bodies wherein, for reducing the leak problem at the joints between side covers and race rings, it is suggested to use race rings, which are been made integral with one of the side covers, whereby the leak problem is reduced to the joints between the side edges of inner and outer race and the other side cover, which is connected in any appropriate manner to the remainder of the unit, formed as a ring having a C-shaped cross section. This certainly eliminates the leak problem at one^' axial side of the unit, but manufacture of the C-shaped body of the unit is expensive, particularly in view of the fact that the inner race ring must not have the material properties required for the outer race ring.

The purpose of the present invention is to provide an autobalancing unit of the type referred to, which functio¬ nally is superior to the known devices of this type, and which is still simple and less expensive to manufacture than earlier known comparable balancing units, and this has been achieved according to the invention in that the autobalancing unit has been given the features defined in the accompanying claims .

The invention furthermore refers to a novel method for manufacturing the autobalancing unit according to the invention, and this method is characterized by the features defined in claim 5, whereas an assembly tool also encompassed by the invention is defined in claim 10.

Hereinafter the invention will be further described by way of a non-limiting example with reference to the accompanying drawings . Fig. 1 shows a diametrical cross section of an autobalancing unit according to the invention,

Fig. 2 is a cross section of a side cover member forming part of the unit according to Fig. 1, Fig. 3 illustrates in cross section a portion of the outer race ring of the unit,

Fig. 4 is a cross sectional portion of the inner race ring of the unit, whereas

Fig. 5 and 6 are larger scale views of the portions encircled in Fig. 4, and

Fig. 7 shows in cross section a diagrammatical view of a pressing tool for mounting the auto-balancing unit according to Fig. 1.

Fig.s 8 and 9 show some alternative embodiments of the auto- balancing unit according to the invention.

Fig. 1 shows in cross section an auto-balancing unit 1 in accordance with the invention, and comprising an annular outer race ring 2, an annular inner race ring 3 positioned in the bore of the outer race ring and coaxial therewith, first and second annular side cover members 4 and 5 resp., fitted between the race rings and acting to keep the race rings 2, 3 spaced apart and sealing off an annular chamber 6 formed between the confronting circumferential inner and outer surfaces of said race rings 2, 3 and said side cover members 4, 5 resp. In its interior circumferential surface, the outer race 2 ring has a race track 7, whereas the inner race ring 3 has a circumferential outer surface 8 and an inner axial bore 9 concentric with the race track 7. In the annular chamber 6 is positioned a number of rolling bodies, in the example shown balls 10, which are of a diametrical size smaller than the radial distance between the said race track 7 and circumferential outer surface 8. The number of rolling bodies 10 furthermore is so small that the rolling bodies - the balls - are movable both radially - due to the smaller diameter dimension - and angularly, thus being able during operation to cluster or be spaced apart automatically against the race track 7, and anywhere along the circumfer¬ ence of the annular chamber 6 for compensating unbalance ten- dencies in a rotary system with which the auto-balancing unit is associated. The annular chamber is also, at least partial¬ ly filled with a damping liquid 11, e.g. oil.

In this case both race rings 2 and 3 are shaped as annular members, which can be easily produced by cutting from tubular material, and subsequent turning or rolling. As the working conditions result in rather small loads acting upon the inner race ring, this ring could be made from a material of lower quality, and it needs not have the properties of the race track 7 of the outer race ring 2, which is subjected to the load and wear from the rolling bodies 10 contacting it.

The race track 7 of the outer race ring and the rolling bodies 10 shall preferably have a high hardness/yield strength for giving as good balancing properties and wear resisting ability as possible, but experience has proven that an increase in these properties for anyone of these compo¬ nents will not necessarily improve the properties mentioned. Instead it has proven that it is more essential for obtaining good properties in these respects, that the, preferably, high values are matched in a proper manner, i.e. that their hardness/yield strength are so close to each other as possible, i.e. a better result is obtained by giving both cooperating components the same values in this respect, than by maintaining this value for one component and increasing it for the other.

The side cover members 4, shown in cross section in Fig. 2, and 5 are identic in size and shape and can be considered as annular washers having in one side face a shallow, slightly curved recess 12 facing the interior of the annular chamber in mounted position and thereby giving space in axial direction for the rolling bodies.

Fig. 3 shows in bigger scale a section of the outer race ring 2, as seen in cross section prior to assembly of the auto¬ balancing unit. From this view can be seen how the race ring 2 in both areas axially outside the race track 7 has circum- ferential grooves 13, which can be produced e.g. by rolling. In a similar manner the inner race ring 3, with its external circumferential surface 8 and interior bore 9, has one circumferential groove 14 positioned at each axial side of the surface 8, the closer shape of the grooved portion V being shown in larger scale in Fig. 5, and the axial edge VI of the bore 9 being shown in larger scale in Fig. 6.

As shown in Figs . 4 and 5 the circumferential groove 14 is positioned in a flat portion 15 of the ring 3 of smaller diameter than the circumferential surface 8 and situated at a distance from the side face of the ring. As can be seen in Figs. 4 and 6, the bore 9 has a bevelled opening for facili¬ tating mounting of the unit on a shaft .

The grooves 13 of the outer race ring 2 are positioned and shaped in a manner corresponding to the grooves 14 in the inner race ring 3.

Fig. 7 shows in a diagrammatical cross section a mounting tool 17 for assembly of the auto-balancing unit according to the invention. The mounting tool 17 incorporates a frame 18 rigidly attached to a bedding and carrying a press bed 19, which supports an annular, planar press plate 20 centred in its central bore about a mandrel 21, which is supported in the frame 18 thus that it by means of a spring 22 is elastically biased in axial direction. The press bed 19 is arranged in a ring 23 mounted in a "floating" manner in the frame 18, and projecting with the inner circumferential wall above the plane of the planar press plate 20.

The assembly tool furthermore incorporates a plunge 24 driven in a manner and by conventional means not further shown, and which carries a cold upsetting die 25, having arranged through it a central mandrel 26 biased in axial direction by a spring 27. The cold upsetting die 25 is surrounded and guided by an annular guiding collar 28 rigidly connected to the plunge 24, which collar 28 with its side remote from the plunge projects axially outside the cold upsetting die 25. The projecting portion of said collar 28 has an outer diameter equal to or somewhat bigger than the inner diameter of the floating ring 23. The bore of the floating ring 23 and the outer end surface of the guiding collar 28 are both provided with corresponding chamfers illustrated at 29. The inner diameter of the guiding collar 28 is substantially equal to the outer diameter of the outer race ring 2 of the auto-balancing unit to be assembled in the tool.

The procedure at assembly of the auto-balancing unit is the following: The outer race ring 2 is positioned on the planar press plate 20. The inner race ring 3 is positioned on the same planar press plate thus that the frame-supported mandrel 21 centres it. By this positioning of the two race rings 2, 3 on the same planar press plate 20 it is ascertained that the^' side faces of the two race rings are located in parallel. A cover member 4 is positioned over the upper annular opening between the two race rings. The plunge 24 thereupon is caused to move axially towards the press plate 20, whereby the plunge-borne mandrel 26 with its free end enters the bore of the inner race ring 3, whereas the end of the guiding collar 28 projecting outside the die 25 with its inner bore encloses and guides the outer race ring 2, and with its outer chamfered wall contacts the floating ring 23 urging this downwards during increased radially inner tensioning gene- rated by the contact between the chamfers 29. Thereby the outer race ring 3 is pretensioned radially as the cold upsetting die 25 reaches the cover member 4, thereby causing this to be cold-headed in its position, whereby the material of the contact edge of the cover member will float and penetrate into the grooves 13, 14 of the rings 2 and 3 respectively (see Figs. 3 and 4), thereby creating a strong and tight joint.

Thereupon the sub-unit, consisting of race rings 2, 3 kept together by one side cover 4, is turned upside-down and positioned on the press plate 20 with the bore of the inner race ring 3 centred by the frame-supported mandrel 21, whereupon rolling bodies are inserted in the space between inner ring outer ring and said one cover member. A part of the remaining volume of the gutter-shaped sub-unit then is filled up with a suitable, preferably viscous fluid, and the second cover member is positioned and the plunge 24 is again caused to cold-head the second cover member to the sub-unit under pre-tension and in the same manner as for the first cover member, thereby forming a completely encased auto¬ balancing unit .

This completed auto-balancing unit 1 then is subjected to final treatment in that the bore 9 of the inner race ring 3 is ground to be concentric with the race track of the outer race ring. During grinding of the bore of the inner race ring a surface which is concentric with the race track 7 of the outer race ring is preferably used as a reference. Such an external surface could for instance be the envelope surface of the outer race ring or a surface produced in the same operation as the race track. The faces of the inner ring are subjected to a grinding operation after the cold-heading operation.

The invention is not limited to the embodiment shown in the accompanying drawings and described with reference thereto but modifications and variations are possible within the scope of the appended claims. Although the autobalancing unit throughout the description and in the drawings has been shown comprising a^' separate outer race ring and a separate inner race ring it is thus possible to use an inner race ring formed e.g. integrally in the material of a shaft or a race ring forming an axial extension of a bearing inner race ring, etcetera.

Fig. 8 thus illustrates how a shaft 30 on which the unit 1 according to the invention shall be arranged can be provided with the inner race ring 3' of the unit machined or formed directly in the material of the shaft.

Fig. 9 further shows how the inner race ring 3' ' of the auto¬ balancing unit 1 can be constituted by a cylindrical flange extending axially from a the inner race ring of a bearing 31. Although nothing specifically has been said about the materials in the different components of the autobalancing unit according to the invention beside their mechanical properties, it is of course possible to use different materials, e.g. in inner race ring and outer race ring, whereby the inner race ring, which is not subjected to load and only minor wear, even may be e.g. a wooden inner race ring, whereas the outer race ring and the rolling bodies are made of materials with higher hardness and/or yield strength. It is further not necessary that the materials of the outer race ring and of the rolling bodies are the same, but different combinations of materials such as different metallic materials, plastics or ceramic materials may be used for these components, as long as their hardness and/or yield strength substantially match each other.

Claims

1. An autobalancing unit arranged to produce automatically in a rotary system, with which the unit is associated, a static and/or dynamic balancing effect, and incorporating in combination an outer race ring (2) with a circumferential inner race track (7) , an inner race ring (3,3', 3'') posi¬ tioned in the bore of the outer race ring (2) concentric therewith and having an outer circumferential surface (8) confronting the race track (7) of the outer race ring (2) , cover members (4, 5) fitted between the race rings, thereby spacing apart the race rings and sealing of an annular chamber (6) between themselves and the race rings, and a number of rolling bodies (10) positioned in said chamber and being of a diameter smaller than the radial size of the annular chamber (6) , c h a r a c t e r i z e d t h e r e i n, that the race track (7) of the outer race ring (2) and the rolling bodies (10) have substantially the same hardness and/or yield strength.

2. An autobalancing unit as claimed in claim 1, c h a r a c t e r i z e d t h e r e i n, that the race track (7) of the outer race ring (2) and the rolling bodies (10) have the same, high hardness and/or yield strength, whereas the inner race ring (3, 3', 3'') has lower hardness and/or yield strength.

3. An autobalancing unit as claimed in claim 1 or 2 , c h a r a c t e r i z e d t h e r e i n, that the side covers (4, 5) of the unit are annular washers, securedly fitted to the outer race ring (2) axially outside the race track (7) and to the inner race ring (3, 3' , 3'') axially outside the said circumferential outer surface (8) thereof.

4. An autobalancing unit as claimed in claim 3, c h a r a c t e r i z e d t h e r e i n, that the race rings (2; 3, 3' ,3' ') have circumferential grooves (13, 14) wherein said side covers (4, 5) are secu¬ redly fitted.

5. A method for producing an autobalancing unit such as claimed in claim 1, c h a r a c t e r i z e d i n, positioning an outer race ring (2) in an assembly apparatus

(17) , positioning an inner race ring (3,3', 3'') coaxially with the outer race ring (2) inside this, securedly fitting a first annular cover plate (4) between said outer and inner race rings (2, 3, 3',3'') at a position axially outside the said race track (7) in the outer race ring, introducing rolling bodies (10) in the space between the said outer and inner race rings, preferably filling, at least partially the gutter-formed annular space between the race rings and the said first cover plate (4) with a damping liquid, and securedly fitting a second annular cover plate (5) between said outer and inner race rings at a position axially outside said race track (7) in the outer race ring on the opposite axial side as compared to the position of said first cover plate (4) .

6. A method as claimed in claim 5, c h a r a c t e r i z e d i n, subjecting the completed autobalancing unit (1) to a final treatment whereby the bore (9) of the inner race ring (3,3'') is ground to be concentric with the race track (7) of the outer race ring.

7. A method as claimed in claim 6, c h a r a c t e r i z e d i n using an surface as a reference during grinding of the bore of the inner race ring (3, 3' ') , such as the envelope surface of the outer race ring or a syurface produced in the same machining operation as the race track of the outer race ring.

8. A method as claimed in anyone of claims 5 to 7, c h a r a c t e r i z e d i n subjecting the completed autobalancing unit (1) to a further treatment, whereby the side faces of the inner race ring are ground to be perpendicular to the race track (7) of the outer race ring, and using as a reference a detail on an external surface, such as the side face of the outer race ring.

9. A method as claimed in anyone of claims 5 - 8, c h a r a c t e r i z e d i n securedly fitting the cover plates (4, 5) in their positions by using a cold upsetting technique.

10. An assembly tool for manufacturing an autobalancing unit as claimed in claim 1, c h a r a c t e r i z e d t h e r e i n that it incorporates a frame (18) carrying a press bed (19) , which supports an annular, planar press plate (20) centred in its central bore on a mandrel (21) supported in the frame (18) , but elastically biased in axial direction, the press bed (19) being arranged in a ring (23) mounted in a floating manner in the frame (18) , and projecting with the inner circumferential wall above the plane of the planar press plate (20) , a driven plunge (24) carrying a cold upsetting die (25) , having arranged through it a central mandrel (26) biased in axial direction and being surrounded and guided by an annular guiding collar (28) rigidly connected to the plunge (24) , which collar (28) with its side remote from the plunge projects axially outside the cold upsetting die (25) , the projecting portion of said collar (28) having an outer diameter equal to or somewhat bigger than the inner diameter of the floating ring (23) , the bore of which floating ring (23) and the outer end surface of the guiding collar (28) both being provided with corresponding chamfers (29) , whereby the inner diameter of the guiding collar (28) is substan¬ tially equal to the outer diameter of the outer race ring (2) of an auto-balancing unit to be assembled in the tool.