Classifications

• • 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
  • G01M1/365—Compensating imbalance by adjusting position of masses built-in the body to be tested using balancing liquid
• • 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
  • G01M1/32—Compensating imbalance by adding material to the body to be tested, e.g. by correcting-weights
  • G01M1/323—Compensating imbalance by adding material to the body to be tested, e.g. by correcting-weights using balancing liquid

Definitions

• the present invention concerns a method for balancing wheel comprising pneumatic tyres containing a viscous balancing composition, as well as an apparatus capable of carrying out the method.
• DE 38 23 926 Al describes a method for carrying out quality control of tyre manufacture, the method involving mounting the tyre on a measuring rim comprising measuring means, pressing the tyre at a fixed distance against a measuring drum comprising force measuring means, and rotating the rim/tyre combination together with the drum by driving one of them with a motor.
• the document does not envisage using the procedure for balancing tyres, just as there is no description of introducing a balancing composition into the tyre during the procedure .
• the object of the invention is therefore to provide a method for balancing a wheel using a viscous balancing composition so that an initial driving distance, with its reductions in road safety and drive comfort, can be eliminated.
• a further object is to provide an apparatus useful in carrying out the method of the invention.
• one aspect of the invention is a method for balancing automobile wheel assemblies comprising pneumatic tyres, said method comprising
• the force F and the time T being sufficient to cause the balancing composition to be distributed inside the tyre, thereby balancing the wheel assembly.
• the invention concerns an apparatus comprising a rotatable assembly on which a wheel assembly comprising a rim and a pneumatic tyre may be mounted; a rotatably mounted drum having an axis of rotation essentially parallel to that of the rotatable wheel assembly, the axes drum and/or the rotatable wheel assembly being capable of being moved in a direction towards and away from one another;
• spring means and/or dampening means mounted between the axis of rotation of the rotatable wheel assembly and the ground and/or between the axis of rotation of the drum and the ground.
• the balancing composition introduced into the tyre is suitably of the thixotropic types described the above-mentioned US patent 4,867,792 as well as in US patent 5,431,726, the content of both hereby being incorporated by reference.
• the wheel and the drum can have one of at least two relative arrangements.
• the axis of the drum is outside the circumference of the tyre and the axis of the tyre is outside the circumference of the drum, i.e. that the tyre tread is in contact with the outside surface of the drum; this is the preferred embodiment and will be described in more detail below.
• the second possible arrangement is that where the entire tyre is inside a hollow drum, and the tyre tread is in contact with the inside surface of the drum.
• Skilled persons in the field of automobile and tyre testing equipment will be able to envisage other possible ways of effecting contact between a tyre and a drum intended to simulate the tyre moving along a road surface, and all such arrangements are comprised within the scope of the present invention.
• the diameter of the drum may in principle be from a fraction of the tyre diameter, such as a roller of 5-10 cm diameter, to several times the diameter of the tyre such as the road wheel drums used in the testing of car suspension systems and having diameters of up to 5 meters .
• the drum/wheel diameter ratio is in the range from 0.1 to 1.
• the rotational speed of the wheel is preferably so that the peripheral speed is at the most 70 m/s, preferably at least 10 m/s such as 30-40 m/s. Since thixotropic balancing compositions primarily exert their balancing effect when the tyre is subjected to vibrational forces that exceed the flow limit of the composition in question, the speed at which the wheel assembly rotates should be such that the imbalances of the wheel cause it to be subjected to strong harmonic oscillations. The exact speed for that condition will depend on a number of factors such as weight and size of the wheel/tyre assembly, stiffness of the tyre, etc. The skilled art worker will be able, through simple experimentation, to determine the conditions at which the harmonic oscillations appear.
• the force F with which the tyre and drum act on one another can vary widely but is preferably of a magnitude which simulates the wheel loading of an actual vehicle and is then in particular dependent on whether the tyre in question is for a passenger vehicle or for a truck or cargo vehicle.
• the term "simulates" is intended to mean that the force F between the tyre and the drum is between 50% and 200% of the weight load on each of the wheels of the vehicle for which the wheel is being balanced.
• a typical load force will be from around 1500 N to around 8000 N, and in the case of a truck or bus a typical load force may be in the range from 20000 N to 50000 N.
• the force may be produced by any means known to the skilled person such as hydraulic means; arrangements using weights; springs; pneumatic means; magnetic, e.g. electromagnetic, means; electromechanical means or the like.
• the time period T is of a length which allows the wheel assembly to become balanced by the balancing composition inside the tyre.
• the actual magnitude of T will depend on a number of factors, i.a. to what extent oscillations of the wheel assembly are obtained under the actual method conditions.
• experiments have indicated that T can be brought down to as short as 2 minutes or less.
• rotatable wheel assembly and/or the drum are suspended using spring means and/or dampening means .
• the term "spring means" is intended to mean any device capable of providing a spring action, i.e. an increase in a force as a result of an increase in translational shift of the object suspended.
• the spring means may be mentioned spiral or disc springs made from steel or fibre-reinforced plastics; pneumatic cylinders; magnetic repulsion devices; or the like.
• the means producing the force F are constituted by devices producing a spring action, it is conceivable that the spring means of the suspension can form part of the means producing the force F.
• the spring characteristics of the spring means may suitably be in the range of 10-1000 N/mm, preferably in the range of 50-100 N/mm.
• dampening means is intended to mean any device or arrangement capable of performing a dampening effect on vibrations of object to be dampened such as the wheel assembly or drum.
• dampening means may be mentioned oil-based viscosity dampers such as those commonly used in the wheel suspension in automobiles, or suitable electromagnetic arrangements.
• the characteristics of the dampening means may suitably have dampening characteristics providing a dampening factor between the drum and the tyre of from 500 to 5000 Ns/m, preferably from 800 to 2000 Ns/m, such as around 1000 Ns/m for a passenger vehicle; and a dampening factor of from 800 to 8000 Ns/m for a truck.
• wheel assembly suspension unit and the drum suspension unit may each be suspended in relation to a base using spring and dampening means as described above.
• a measuring means connected to the suspension of the wheel assembly.
• a measuring means may be a device measuring the acceleration or movement of the wheel shaft or the forces acting on the wheel shaft.
• the measuring means may be an accelerome- ter device, a mechanical, electromechanical or optical displacement measurement device, or a strain gauge or piezoelectric force measurement device.
• the vibrations may be applied to the wheel assembly and/or the drum and are intended to superimpose a dynamic force F d on the static force F. If vibrations are applied to both the wheel assembly and the drum, the vibrations may be applied to them independently of one another. Furthermore, the vibrations on any one of the wheel and the drum may be applied independently in two directions at right angles to one another.
• vibrations may be at a frequency of at the most 100 Hz, preferably at the most 50 Hz, in particular at the most 30 Hz, and an amplitude of at the most ⁇ 50 mm.
• useful amplitudes are up to around ⁇ 0.1 mm at 100 Hz, up to ⁇ 10-20 mm at 30 Hz, and up to ⁇ 50 mm at 10 Hz.
• the vibrations may suitably be induced in a direction essentially parallel with a line connecting the centre of the axis of rotation of the wheel assembly and the centre of the axis of rotation of the drum, and essentially at right angles with said axes, and/or being induced essentially at right angles with a line connecting the centre of the axis of rotation of the wheel assembly and the centre of the axis of rotation of the drum, and essentially at right angles with said axes.
• the vibrations may be induced by any conventional vibration- inducing means known to the skilled person.
• the balancing composition inside the tyre is usually dependent on the temperature of the composition, and the speed at which balancing is attained would therefore be expected to be greater at increased composition temperature
• a further embodiment of the invention is contemplated in which the composition inside the tyre is subjected to heating, e.g. by means of microwaves emitted from a standard microwave transmitter or by means of radio frequency heating.
• the balancing composition may suitably be heated to a temperature typical of the operating temperature of a tyre, such as around in the range of 70-90°C.
• a preferred embodiment is that which further comprises measuring means for monitoring the balance of the wheel assembly.
• Such measuring means may be as described above.
• the apparatus comprises means for inducing vibrations, the nature of the vibrations being as described above.
• useful vibration- inducing means include mechanical means such as an excentric linkage mechanism; hydraulic means comprising a piston and cylinder arrangement and associated hydraulic pumps and valves as well as pump control means; electromagnetic means.
• a preferred type of vibration- inducing means are excentric linkage mecha- nisms, such as those in which a cylindrical rotary member having a non-circular generator curve, e.g. an elliptical, cylindrical rotary member, is arranged between the two assemblies between which a relative vibrating movement is to be induced.
• the two assemblies are cyclically forced away from one another and allowed to approach one another (usually under the influence of spring means and optionally associated dampening means) , thereby inducing a vibrating relative movement.
• the characteristics of the vibrations are preferably as described above.
• Fig 1 shows a wheel 3 comprising a pneumatic tyre 3' mounted on a rim 3''. Prior to mounting, the tyre has had a viscous balancing composition placed inside it.
• the wheel 3 is mounted on a rotatable assembly mounted on a base, and the wheel is driven by a motor (M) 6 via a belt or chain drive or similar.
• a rotatable drum 4 is pressed against the tread surface of the tyre with a force F.
• the assembly 8 comprising the drum 4 is able to move in the direction of the force F using bearing elements indicated by means of the rollers 7.
• the generally vertical member 10 supporting the drum 4 is journalled on an axis 9 and is further supported relative to the assembly 8 through spring and dampening means indicated schematically and symbolically at 5.
• the assembly 2 is connected to the ground or base plate 1 through spring and dampening means 5' .
• the embodiment in fig 2 corresponds to that of fig 1 with the difference that instead of the wheel assembly 3 being driven by a motor 6, it is the drum 4 being driven by the motor.
• the base plate 1 is subdivided into a plate 1' and another, separate plate 1' ' . Each of these are connected to a base plate or the ground 12 through spring means 13.
• a vibrating means 11 is placed, here shown schematically as an elliptical rotary member rotating at an angular speed of ⁇ .
• vibrating means 11' and 11'' are placed, here also shown schematically as elliptical rotary members rotating at an angular speed of ⁇ ' and ⁇ ' ' , respectively.
• the various elliptical rotary members are driven by respective motors (not shown) .

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Testing Of Balance (AREA)

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Citations (3)

• 1997
  • 1997-05-12 DE DE1997119886 patent/DE19719886A1/de not_active Withdrawn
• 1998
  • 1998-05-11 WO PCT/IB1998/000699 patent/WO1998052009A1/en active Application Filing
  • 1998-05-11 AU AU70711/98A patent/AU7071198A/en not_active Abandoned

Patent Citations (3)

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