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WO1998001733A1 - A method for controlling vibration amplitude in rotary systems - Google Patents

A method for controlling vibration amplitude in rotary systems Download PDF

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Publication number
WO1998001733A1
WO1998001733A1 PCT/SE1997/001216 SE9701216W WO9801733A1 WO 1998001733 A1 WO1998001733 A1 WO 1998001733A1 SE 9701216 W SE9701216 W SE 9701216W WO 9801733 A1 WO9801733 A1 WO 9801733A1
Authority
WO
WIPO (PCT)
Prior art keywords
imbalance
rotary
mass
rotary system
vibration amplitude
Prior art date
Application number
PCT/SE1997/001216
Other languages
French (fr)
Inventor
Jonas NILSAGÅRD
Peter Kinde
Lars NORDSTRÖM
Original Assignee
Aktiebolaget Skf
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Aktiebolaget Skf filed Critical Aktiebolaget Skf
Priority to AU36382/97A priority Critical patent/AU3638297A/en
Publication of WO1998001733A1 publication Critical patent/WO1998001733A1/en

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
    • B24D5/00—Bonded abrasive wheels, or wheels with inserted abrasive blocks, designed for acting only by their periphery; Bushings or mountings therefor
    • B24D5/16—Bushings; Mountings
    • B24D5/165—Balancing means
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B23/00—Portable grinding machines, e.g. hand-guided; Accessories therefor
    • B24B23/02—Portable grinding machines, e.g. hand-guided; Accessories therefor with rotating grinding tools; Accessories therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B41/00—Component parts such as frames, beds, carriages, headstocks
    • B24B41/04—Headstocks; Working-spindles; Features relating thereto
    • B24B41/042—Balancing mechanisms
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
    • F16F15/00—Suppression of vibrations in systems; Means or arrangements for avoiding or reducing out-of-balance forces, e.g. due to motion
    • F16F15/32—Correcting- or balancing-weights or equivalent means for balancing rotating bodies, e.g. vehicle wheels
    • F16F15/36—Correcting- or balancing-weights or equivalent means for balancing rotating bodies, e.g. vehicle wheels operating automatically, i.e. where, for a given amount of imbalance, there is movement of masses until balance is achieved
    • F16F15/363—Correcting- or balancing-weights or equivalent means for balancing rotating bodies, e.g. vehicle wheels operating automatically, i.e. where, for a given amount of imbalance, there is movement of masses until balance is achieved using rolling bodies, e.g. balls free to move in a circumferential direction
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M1/00—Testing static or dynamic balance of machines or structures
    • G01M1/30—Compensating imbalance
    • G01M1/36—Compensating imbalance by adjusting position of masses built-in the body to be tested

Definitions

  • the present invention refers to a method for controlling vibration imparted on different types of rotary systems following imbalance in said systems. For minimizing such imbalance tendencies it has since long been provided mechanisms, which automatically outbalance the vibrations and allow the system to operate at a substantially reduced vibration level. This is achieved by means of rolling bodies freely movable in paths concentric with the axis of the rotary system, which rolling bodies at rotation of the system automatically will find their appropriate angular positions along the path to compensate for the inherent imbalance of the system. Such mechanisms are commonly referred to as auto-balancing units, and the method itself is called auto-balancing.
  • the purpose of the present invention is to provide a solution of this problem and to suggest a method for controlling vibration amplitude in rotary systems, whereby is obtained a rapid and appropriate automatic positioning of the balancing rolling bodies in their path, and this is achieved with the features defined in the accompanying claim 1.
  • Fig. 1 a diagrammatical illustration over a mechanical system appropriate for being equipped with an autobalancing unit.
  • Fig. 2 is a diagram showing the vibrational characteristics for a discrete system with initial eccentricity ⁇ .
  • FIG. 3 illustrates in a schematical side view an autobalancing unit in out-balanced position.
  • Fig.s 4a and 4b illustrate schematically the forces acting upon a rolling body in an autobalancing unit at different amplitudes
  • Fig. 5 illustrates schematically an autobalancing unit provided with an artificial imbalance in accordance with the present invention.
  • FIG. 1 which very schematically shows a housing 1, being resiliently connected to a base 2, as illustrated with a symbolic spring 3, and being provided with a shaft 4 having a rotating mass 5.
  • the stationary vibration level i.e. the vibration level resulting after a long time and at different rotational speeds, for the rotating mass, (continuous line), and for the machinery housing (dash-line), when the rotating mass has an eccentricity ⁇ relative to its shafting point.
  • Fig. 3 is schematically illustrated in a side view an autobalancing unit, intended to be connected concentric to the rotary shaft or the like, which shall be outbalanced, and comprising an inner ring 6, an outer race ring 7 positioned about the inner ring 6 and concentric thereabout and a number of rolling bodies 8, preferably balls, but being of such a number that they occupy only a part of the volume contained between the two 0 rings 6 and 7.
  • rolling bodies 8 preferably balls, but being of such a number that they occupy only a part of the volume contained between the two 0 rings 6 and 7.
  • the space between the rings 6, 7 is closed off externally by means of not shown end plates, and the free volume between rings and endplates, not occupied by the rolling bodies 8 is usually filled with a medium, e.g. oil exerting a dampening and pulling-along effect on the rolling bodies.
  • a medium e.g. oil exerting a dampening and pulling-along effect on the rolling bodies.
  • the unit in this figure is shown in out-balanced condition, whereby an out-off-balance effect is illustrated in the upper right hand quadrant of the outer race ring at OOB.
  • the rolling bodies 8 here have taken up spaced apart positions along the outer race ring distributed about the position opposite to the position for the OOB, and thereby the disturbing out- off-balance OOB is compensated, and the centrifugal force F c acting on the rolling body and the normal force F N acting perpendicularly towards the race track are equal and directed in opposite directions and through the centre of rotation RC and the geometrical centre GC, which thereby coincide. Therefore there is no resulting force causing imbalance when the system is running.
  • the out-off-balance symbol OOB is illustrated as a rather small area, representing a comparatively small mass, and the rolling bodies 8 thereby are distributed over quite a long portion of the race track. If the size of the OOB and/or the distance between the position for OOB and the geometrical centre GC should increase, then the rolling bodies of course should become more concentrated opposite to the position for OOB, until they finally should be positioned close to each other.
  • the autobalancing principle requires that there is about 180° phase shift between the centre of gravity of the rotating mass and its deflection, i.e. when the centre of gravity of the rotating body 5 is pointing upwards on the body, then its shaft centre is in its lowermost position.
  • This phase difference can be seen in the Fig. 2 diagram, as a "negative amplitude", i.e. the continuous line is in the appropriate area situated below the axis representing the rotational speed.
  • the rotational speed is generally in the intermediate area, i.e. on the plateau of the continuous line in Fig. 2.
  • the balancing bodies are influenced in a manner so as to help them initially to start finding their correct balancing positions, and this is done by intentionally increas- 10 ing the forced vibration amplitude U f .
  • this can be achieved by increasing the ratio between the rotating imbalance m.-,, * ⁇ and the total mass m Iot , which last mentioned is m rot + m h , i.e. the rotating mass together with the mass of the housing supporting the rotating mass.
  • FIG. 4a With reference to Fig.s 4a and 4b it is schematically shown that at a system with imbalance there is a distance between the geometrical centre GC and the rotating centre RC, and this distance causes a resulting force F R .
  • Fig. 4a is shown how a small distance al _- causes a small resulting force F R
  • a larger distance a2 shown in Fig. 4b causes a bigger force F R .
  • the difference between heavy and light systems can be found in the size of the vibration amplitude.
  • the resulting force F R causing the balancing bodies (balls) in the balancing — unit to change their positions can be considered to be proportional to the vibration amplitude. This is shown to be lower for heavy machines, such as floor-anchored grinding machines, as compared to light machines, e.g. hand-held angular grinders.
  • the balls thus will experience a lower resulting force at lower vibration amplitude, and if this is too low the balls will not be able to overcome the internal resistance of the system, such as moment of inertia, resistance from the oil provided in the housing of the autobalancing unit as a medium dampening the motion of the balls and carrying them along, and this means that the balls will not move to try to find their optimum positions from a balancing point of view.
  • the internal resistance of the system such as moment of inertia, resistance from the oil provided in the housing of the autobalancing unit as a medium dampening the motion of the balls and carrying them along, and this means that the balls will not move to try to find their optimum positions from a balancing point of view.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • General Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Aviation & Aerospace Engineering (AREA)
  • Testing Of Balance (AREA)
  • Turbine Rotor Nozzle Sealing (AREA)

Abstract

A method for controlling vibration imparted on different types of rotary systems following imbalance in said systems, using in a manner known per se, an auto-balancing unit comprising an encased annular track (7) mounted to the rotary system and having a number of rolling bodies (8) freely moveable along said track for compensating imbalance in the rotary system, whereby an additional increased forced vibration amplitude (uf) is intentionally applied to the autobalancing unit.

Description

A METHOD FOR CONTROLLING VIBRATION AMPLITUDE IN ROTARY SYSTEMS
The present invention refers to a method for controlling vibration imparted on different types of rotary systems following imbalance in said systems. For minimizing such imbalance tendencies it has since long been provided mechanisms, which automatically outbalance the vibrations and allow the system to operate at a substantially reduced vibration level. This is achieved by means of rolling bodies freely movable in paths concentric with the axis of the rotary system, which rolling bodies at rotation of the system automatically will find their appropriate angular positions along the path to compensate for the inherent imbalance of the system. Such mechanisms are commonly referred to as auto-balancing units, and the method itself is called auto-balancing.
Autobalancing mechanisms used e.g. for hand-held angle grinders have proven thenv selves to operate very well, whereas trials with corresponding mechanisms provided at big, floor-mounted grinding machines have given a very poor function. It furthermore has been found that at comparatively low rotational speeds and/or in combination with only slight out-of-balance in the system to be balanced, the balancing bodies will have difficulties to move to their optimum balancing positions, i.e. they will have a tendency to "float around" in the system without being able to find and stay in positions where they give the best possible balancing effect.
The purpose of the present invention is to provide a solution of this problem and to suggest a method for controlling vibration amplitude in rotary systems, whereby is obtained a rapid and appropriate automatic positioning of the balancing rolling bodies in their path, and this is achieved with the features defined in the accompanying claim 1.
Hereinafter the background to and the solution of the present invention will be described with reference to the accompanying drawings, showing schematically in
Fig. 1 a diagrammatical illustration over a mechanical system appropriate for being equipped with an autobalancing unit. Fig. 2 is a diagram showing the vibrational characteristics for a discrete system with initial eccentricity ε .
c Fig. 3 illustrates in a schematical side view an autobalancing unit in out-balanced position.
Fig.s 4a and 4b illustrate schematically the forces acting upon a rolling body in an autobalancing unit at different amplitudes, and
10
Fig. 5 illustrates schematically an autobalancing unit provided with an artificial imbalance in accordance with the present invention.
Most mechanical systems which are considered appropriate as applications for auto- - r balancing can be schematically described as in the accompanying drawing Fig. 1 , which very schematically shows a housing 1, being resiliently connected to a base 2, as illustrated with a symbolic spring 3, and being provided with a shaft 4 having a rotating mass 5.
Q Such a system has a vibration characteristic in accordance with the graph shown in Fig.
2, wherein is indicated the stationary vibration level, i.e. the vibration level resulting after a long time and at different rotational speeds, for the rotating mass, (continuous line), and for the machinery housing (dash-line), when the rotating mass has an eccentricity ε relative to its shafting point.
5
In Fig. 3 is schematically illustrated in a side view an autobalancing unit, intended to be connected concentric to the rotary shaft or the like, which shall be outbalanced, and comprising an inner ring 6, an outer race ring 7 positioned about the inner ring 6 and concentric thereabout and a number of rolling bodies 8, preferably balls, but being of such a number that they occupy only a part of the volume contained between the two 0 rings 6 and 7. Although not shown in this figure the space between the rings 6, 7 is closed off externally by means of not shown end plates, and the free volume between rings and endplates, not occupied by the rolling bodies 8 is usually filled with a medium, e.g. oil exerting a dampening and pulling-along effect on the rolling bodies. The unit in this figure is shown in out-balanced condition, whereby an out-off-balance effect is illustrated in the upper right hand quadrant of the outer race ring at OOB. The rolling bodies 8 here have taken up spaced apart positions along the outer race ring distributed about the position opposite to the position for the OOB, and thereby the disturbing out- off-balance OOB is compensated, and the centrifugal force Fc acting on the rolling body and the normal force FN acting perpendicularly towards the race track are equal and directed in opposite directions and through the centre of rotation RC and the geometrical centre GC, which thereby coincide. Therefore there is no resulting force causing imbalance when the system is running. In this figure the out-off-balance symbol OOB is illustrated as a rather small area, representing a comparatively small mass, and the rolling bodies 8 thereby are distributed over quite a long portion of the race track. If the size of the OOB and/or the distance between the position for OOB and the geometrical centre GC should increase, then the rolling bodies of course should become more concentrated opposite to the position for OOB, until they finally should be positioned close to each other.
The autobalancing principle requires that there is about 180° phase shift between the centre of gravity of the rotating mass and its deflection, i.e. when the centre of gravity of the rotating body 5 is pointing upwards on the body, then its shaft centre is in its lowermost position. This phase difference can be seen in the Fig. 2 diagram, as a "negative amplitude", i.e. the continuous line is in the appropriate area situated below the axis representing the rotational speed.
For most applications of autobalancing , e.g. for angle grinders, the rotational speed is generally in the intermediate area, i.e. on the plateau of the continuous line in Fig. 2.
Experiments have shown that the balancing function is dependent on a forced vibration amplitude Uf (intentional or caused by the design of the system), which can be expressed with the formula uf = mro/mtot «ε • Φ (ω/ω0 ) wherein mm = the rotating mass of the system mtot = the total mass of the system ε = the eccentricity ω = the rotational frequency ω0 = the resonance frequency 5 Φ (ω/ω 0) =* goes against 1 the higher above the rotational frequency the system gets. According to the present invention it is now suggested that the above problem is solved in that the balancing bodies are influenced in a manner so as to help them initially to start finding their correct balancing positions, and this is done by intentionally increas- 10 ing the forced vibration amplitude Uf.
In accordance with the formula given hereabove this can be achieved by increasing the ratio between the rotating imbalance m.-,,*^ and the total mass mIot , which last mentioned is mrot + mh , i.e. the rotating mass together with the mass of the housing supporting the rotating mass.
15
This theory is further confirmed by the above mentioned finding that small hand held rotary implements are much more sensible to autobalancing functions than large machinery which are furthermore often anchored in a large and heavy fundament, thereby having a substantially lower ratio mro/mto( than the small hand-held tool.
20
With reference to Fig.s 4a and 4b it is schematically shown that at a system with imbalance there is a distance between the geometrical centre GC and the rotating centre RC, and this distance causes a resulting force FR. In Fig. 4a is shown how a small distance al _- causes a small resulting force FR , whereas a larger distance a2 shown in Fig. 4b causes a bigger force FR.
The difference between heavy and light systems can be found in the size of the vibration amplitude. The resulting force FR causing the balancing bodies (balls) in the balancing — unit to change their positions can be considered to be proportional to the vibration amplitude. This is shown to be lower for heavy machines, such as floor-anchored grinding machines, as compared to light machines, e.g. hand-held angular grinders. The balls thus will experience a lower resulting force at lower vibration amplitude, and if this is too low the balls will not be able to overcome the internal resistance of the system, such as moment of inertia, resistance from the oil provided in the housing of the autobalancing unit as a medium dampening the motion of the balls and carrying them along, and this means that the balls will not move to try to find their optimum positions from a balancing point of view.
It now consequently is suggested to increase the imbalance in the system by adding an artificial imbalance to the system.
Experiments have proven that by imparting such an imbalance upon the system it is achieved also at comparatively low rotational speeds and/or at low "normal" or inherent imbalance in the system, that the balancing bodies rapidly and safely will find their proper positions for giving a satisfactory balancing effect to the system. It thus must be seen as a un-expected technical effect that by imparting upon a rotary system an increased artificial imbalance, an autobalancing unit associated with the rotary system will give a more satisfactory, and, above all, a more rapid balancing result than without such additional artificial imbalance.
For achieving this it is suggested, e.g. to provide the autobalancing unit with an additional artificial imbalance body, as shown schematically in Fig. 5, where the outer race ring 7 is provided with a weight 9 increasing the "normal" imbalance in the system, and thereby initially increasing the resulting force FR, whereby this will safely exceed the resistance in form of rolling resistance etcetera, and make die rolling bodies rapidly find- ing their appropriate positions.
Of course it is also possible to increase the "normal" imbalance within the system not by adding an extra weight, but also by removing weight at a proper position. Such a method for increasing the imbalance can have further advantages, as thereby no extra weight is added to the system as such. The invention is not limited to the embodiments schematically shown in the drawings and described with reference thereto but modifications and variants are conceivable within the scope of the appended claims.

Claims

1. A method for controlling vibration imparted on different types of rotary systems following imbalance in said systems, using in a manner known per se, an auto-balancing 5 unit comprising an encased annular track (7) mounted to the rotary system and having a number of rolling bodies (8) freely moveable along said track for compensating imbalance in the rotary system, characterized in intentionally applying an additional increased forced vibration amplitude (Uf) to the 0 autobalancing unit.
2. A method as claimed in claim 1 , characterized in applying an additional increased forced vibration amplitude by intentionally increasing 5 the ratio between the rotating imbalance (m.0, *ε) incorporated in the system and the total mass (m,ot) of the system, i.e. the combined mass of the rotating mass and the mass of the stationary members supporting the rotating mass of the system.
3. A method as claimed in anyone of the preceding claims, β characterized in adding an artificial imbalance (OOB) to the inherent, natural imbalance of the system by altering the mass of the rotary system at at least one position offset from the geometrical axis of the rotary system.
5 4. A method as claimed in claim 3, characterized in applying an artificial imbalance weight (9) to the rotary system for adding artificial imbalance.
0
5. A method as claimed in claim 3, characterized in removing weight from a position offset from the geometrical axis of the rotary system for adding artificial imbalance.
PCT/SE1997/001216 1996-07-09 1997-07-04 A method for controlling vibration amplitude in rotary systems WO1998001733A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU36382/97A AU3638297A (en) 1996-07-09 1997-07-04 A method for controlling vibration amplitude in rotary systems

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE9602706-5 1996-07-09
SE9602706A SE510266C2 (en) 1996-07-09 1996-07-09 Method for controlling vibration amplitude in rotating systems

Publications (1)

Publication Number Publication Date
WO1998001733A1 true WO1998001733A1 (en) 1998-01-15

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SE (1) SE510266C2 (en)
WO (1) WO1998001733A1 (en)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2341811A (en) * 1998-09-05 2000-03-29 Michael Cole Centrifugal evaporator with load sensor
GB2345655A (en) * 1998-11-12 2000-07-19 Michael Cole Centrufugal evaporator
DE10320974B4 (en) * 2003-05-09 2005-12-01 Siemens Ag Method for reducing an imbalance and use of an electro-rheological fluid for reducing an imbalance
DE10320973B4 (en) * 2003-05-09 2006-04-27 Siemens Ag Imaging tomography apparatus and method for reducing an imbalance on a tomography device
DE102006050207B3 (en) * 2006-10-25 2008-05-29 Ab Skf Drive or airplane model or toy, has automatic balancing system that has housing with circularly processed receiving space around axis of rotation, where number of balancing weight are arranged
DE102007034382A1 (en) 2007-07-24 2009-01-29 Schaeffler Kg Autobalancing device for unbalance compensation in separators or centrifuges and separator or centrifuge with such a Autobalancing device
US20100069216A1 (en) * 2008-09-16 2010-03-18 Hanlab Corporation Control method of automatic balancing centrifuge using balancer
US7942801B2 (en) * 2008-07-09 2011-05-17 Hanlab Corporation Automatic balancing centrifuge using balancer
US10818450B2 (en) 2017-06-14 2020-10-27 Black & Decker Inc. Paddle switch

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4075909A (en) * 1976-01-29 1978-02-28 Deakin James E Automatic shaft balancer

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4075909A (en) * 1976-01-29 1978-02-28 Deakin James E Automatic shaft balancer

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2341811A (en) * 1998-09-05 2000-03-29 Michael Cole Centrifugal evaporator with load sensor
GB2341811B (en) * 1998-09-05 2002-04-17 Michael Cole Control of weight during evaporation of samples
GB2345655A (en) * 1998-11-12 2000-07-19 Michael Cole Centrufugal evaporator
DE10320974B4 (en) * 2003-05-09 2005-12-01 Siemens Ag Method for reducing an imbalance and use of an electro-rheological fluid for reducing an imbalance
DE10320973B4 (en) * 2003-05-09 2006-04-27 Siemens Ag Imaging tomography apparatus and method for reducing an imbalance on a tomography device
DE102006050207B3 (en) * 2006-10-25 2008-05-29 Ab Skf Drive or airplane model or toy, has automatic balancing system that has housing with circularly processed receiving space around axis of rotation, where number of balancing weight are arranged
DE102007034382A1 (en) 2007-07-24 2009-01-29 Schaeffler Kg Autobalancing device for unbalance compensation in separators or centrifuges and separator or centrifuge with such a Autobalancing device
US7942801B2 (en) * 2008-07-09 2011-05-17 Hanlab Corporation Automatic balancing centrifuge using balancer
US20100069216A1 (en) * 2008-09-16 2010-03-18 Hanlab Corporation Control method of automatic balancing centrifuge using balancer
US8292793B2 (en) * 2008-09-16 2012-10-23 Hanlab Corporation Control method of automatic balancing centrifuge using balancer
US10818450B2 (en) 2017-06-14 2020-10-27 Black & Decker Inc. Paddle switch

Also Published As

Publication number Publication date
SE9602706L (en) 1998-01-10
AU3638297A (en) 1998-02-02
SE510266C2 (en) 1999-05-03
SE9602706D0 (en) 1996-07-09

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