Patent Description:
In a second aspect, the present invention also relates to a system for high-speed harmonic forces testing and balancing tire and wheel assemblies.

The present invention pertains to the technical field of quality assurance devices and methods. In particular, the present invention pertains to the technical field of vibration reduction for tire and tire/wheel assemblies at critical speeds of a car.

Such a method according to the preamble is also known from <CIT>. JP '<NUM> aims to reduce the problem of high speed vibrations of a tire wheel assembly at high speeds. JP '<NUM> describes a method wherein a first mass is mounted onto a tire/wheel assembly at a specific phase, after which said tire/wheel assembly is spun at high speeds and tested for uniformity. Based on a tire uniformity vector calculated during uniformity testing, a second mass and a second phase are computed. The method of JP '<NUM> is iterative, requiring multiple tries in order to attain balancing of a tire/wheel assembly.

A similar iterative process for balancing a wheel is disclosed in <CIT>. US '<NUM> is limited in that both static and dynamic balancing are tested only at low speeds. This practice disadvantageously obscures other relevant wheel unbalance factors. This results in wheels which are balanced inadequately for use in field conditions, causing a higher risk of poor riding experience or even malfunction of the wheels or vehicles onto which said wheels are assembled. The running balancing and tire uniformity process are carried out separately with no correlation between both processes. Furthermore, and missing link to the driving performance of the car.

<CIT> discloses an apparatus for measuring uniformity and dynamic balance of a tire, comprising: a spindle rotatably supported in a rigidly-supported spindle housing, said tire being fixedly mounted on said spindle, said spindle being rotated when measurement is performed; and at least one piezoelectric force sensor mounted on a surface of said spindle housing, said at least one piezoelectric force sensor detecting a force generated by rotation of the tire as said spindle is rotated.

<CIT> discloses a high-speed uniformity adjustment system for a tire wheel assembly includes: a high-speed uniformity machine for measuring the high-speed uniformity of the tire wheel assembly; and a calculation device for calculating the mass and installment topology of a balance weight such that the magnitude of a vector expressed as a sum of a vector of the measured high-speed uniformity and the vector of the centrifugal force applied to the balance weight attached against the tire wheel assembly is smaller than the magnitude of the vector of the measured high-speed uniformity.

<CIT> discloses a method wherein the mass of a tire/wheel assembly is altered to apply a static imbalance to the assembly in a manner which aims to reduce the overall tendency of the assembly to cause vibration in the plane perpendicular to its axis of rotation when in use.

The known methods are not particularly suited to address performance affecting factors associated with more complex systems including, for example though not limited to, reciprocating motions.

Tire/wheel assembly performance depends on the value and position of the balancing and tire uniformity force influence on the tire/wheel assembly during driving. Due to the introduction of bigger sizes of tires, the standard balancing method has no impact evaluation of the tire deflection due to the increase of car load. This effect is further aggravated by the increased battery weight and extra motors on hybrid/electrical cars.

The present invention aims to resolve at least some of the problems and disadvantages mentioned above. The invention thereto aims to provide a method and system which permit efficient and effective balancing of tire/wheel assemblies such that the resulting balanced tire/wheel assemblies are safe and provide enough comfort in real field conditions.

The present invention and embodiments thereof serve to provide a solution to one or more of above-mentioned disadvantages. To this end, the present invention relates to a method for high-speed tire/wheel assembly uniformity balancing according to claim <NUM>. The method as disclosed in claim <NUM> advantageously results in faster processing times as well as increased driving comfort at the critical speed of the car when the risk level of vibrations is higher.

Preferred embodiments of the device are shown in any of the claims <NUM> to <NUM>.

In a second aspect, the present invention relates to a system for tire/wheel assembly uniformity balancing according to claim <NUM> with which to apply the method according to claim <NUM>.

The following description of the figures of specific embodiments of the invention is merely exemplary in nature and is not intended to limit the present teachings, their application or uses. Throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

The present invention concerns a method and system for high-speed tire and wheel assembly uniformity balancing. The present inventions advantageously allows for balancing a tire/wheel assembly for multiple unbalancing factors in a single station, this advantageously permits not only a higher throughput but also lower rate of rejections during any further inspection or auditing steps.

Whereas the terms "one or more" or "at least one", such as one or more or at least one member(s) of a group of members, is clear per se, by means of further exemplification, the term encompasses inter alia a reference to any one of said members, or to any two or more of said members, such as, e.g., any ≥<NUM>, ≥<NUM>, ≥<NUM>, ≥<NUM> or ≥ <NUM> etc. of said members, and up to all said members.

Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to a person skilled in the art from this disclosure, in one or more embodiments.

In a first aspect, the invention provides a method for high-speed tire/wheel assembly uniformity balancing comprising the steps of:.

In this method, the measured vibration forces are used to compute a vibration force vector, which vector is a vectorial sum of a static vibration force and a torque imbalance force vector. The static vibration force is the vectorial sum of a tire uniformity first harmonic radial force variation vector and a static imbalance vector. The first harmonic radial force variation vector and a static imbalance vector are measured on each of at least two planes of the tire/wheel assembly, said planes being perpendicular to the axis of the tire/wheel assembly. The torque imbalance vector corresponding to the dynamic imbalance of the tire/wheel assembly, the first harmonic radial force variation vector and a static imbalance vector measured on each plane being used to calculate a torque imbalance force vector. By preference each plane is equipped with at least two 3D sensors. Most preferably, said sensors are mounted on a trunnion supporting axis of the rotatable fixture. Known methods consider only the mass distribution of the tire/wheel assembly when balancing for dynamic imbalance. The present method advantageously incorporates the effects of mass distribution of the tire/wheel assembly as well as tire uniformity harmonics in the dynamic imbalance vector, here designated torque imbalance vector. In this way, non-uniformities in tire elasticity around the perimeter of the tire are also advantageously compensated for. In order to compensate for both the static vibration force and a torque imbalance force vector, the method includes a step of calculating and providing a mass and location for the balancing weights to be placed on the surface of the rim of the tire/wheel assembly. More preferably, the calculated location of the balancing weights is on the interior perimeter surface of the rim, facing the axis of the tire/wheel assembly. This surface advantageously permits a continuous range of placement options instead of only two planes. The possibility of using said interior perimeter surface of the rim permits also the use of a single balancing weight, which weight is protected against displacement due to impacts while driving. Most preferably, the step of calculating and providing a mass and location for the balancing weights includes only one mass and one location for a single weight to be placed on the interior perimeter surface of the rim. Said single weight is most preferably cut to weight from a continuous balancing weight stock. Most preferably, said balancing weights are also cut to shape, In this way allowing for the most advantageous mass placement and distribution when applied to the tire/wheel assembly, therefore, permitting superior balancing of said assembly when compared to known methods.

By preference, two of the at least two measurement planes are distanced at least <NUM> from each other, more preferably <NUM>, <NUM>, <NUM>. More preferably, at least one of the at least two measurement planes is located coincident with a first outer edge of the wheel, more preferably still, a second plane is located coincident a second outer edge of the wheel, said second outer edge being located opposite to said first outer edge. In this way, the combined first harmonic radial force variation vector and a static imbalance vector measured on each plane can be used to more accurately calculate a torque imbalance force vector, which torque imbalance force vector relates to the dynamic imbalance of the tire/wheel assembly. By preference, the 3D sensors used are high definition 3D piezo electric sensors, more preferably, said sensors can detect variations of less than <NUM> N, preferably less than <NUM> N, most preferably less than <NUM> N.

In a further embodiment, the vibration force vector is a vectorial sum of the tire uniformity first harmonic radial force variation vector and the static imbalance vector and a torque imbalance force vector. By preference, the application of the balancing weight is carried out as an automated process. In this way, a more precise and faster placement of the weights is attained. The higher speed at which the tire/wheel assembly is tested advantageously permits detecting and balancing for a broader range of unbalance factors that would otherwise be obscured by radial force variation if testing at low-speed. For example, tangential and lateral force variations due to uniformity and mass unbalance, as well as radial run-out are advantageously more strongly represented in the measured vibration forces. In a further preferred embodiment, the measured vibration force vector is a vectorial sum of the tire uniformity first harmonic radial force variation vector and the static imbalance vector for each of at least two planes of the tire/wheel assembly and a torque imbalance force vector. The more complex composition of the vibration force vector advantageously increases the number of factors which are addressed during the step of balancing a tire/wheel assembly, therefore reducing the number of quality nonconformities.

In a further embodiment, before the step of bringing the testing drum in contact with the tire of the tire/wheel, at least one load value is calculated based a mass distribution of a car. By preference, a range of load values is calculated. More preferably, this range of load values reflect different mass distributions related to number and location of passengers and luggage loads inside a vehicle. More preferably, the range of load values should consider a range of roll and pitch angles from -<NUM>° to <NUM>°. In a further embodiment, during the vibration force vector measurement step, the force applied to the tire by the testing drum is equal to at least one of the calculated load values. In this way, the balancing of each tire/wheel assembly can be tailored to the preferred type of driving circumstances and experience required by a customer.

In a further embodiment, the step of computing mass and location of at least one balancing weight includes computation of the location and magnitude of the vibration force vector. By preference, computation of the location and magnitude of the vibration force vector is carried out using vibration values measured by at least two sensors, more preferably three, most preferably at least four 3D sensors. In this way, vibration is advantageously detected and measured across multiple axis, allowing for a more precise computation of the direction and magnitude of the vibration force vector.

In most common cases, balancing weights are provided in a range of standard masses. Therefore, it is unlikely that a standard balancing weight having a mass exactly the same as the computed mass for the balancing weight is readily available. In a further embodiment, the computed mass of the balancing weight is approximated to the mass of a nearest available standard weight. By preference, the computed mass of the balancing weight is approximated to the mass of a combination standard balancing weights. More preferably, said combination of standard weights includes divisible adhesive tape weights, yet more preferably, said divisible adhesive tape weights have a tolerance of <NUM>, <NUM>, <NUM> most preferably, <NUM>. In this way, the computed mass for the balancing weight can be used for further computations.

In a further embodiment, the position of the at least one balancing weight is given as an angle and distance from the wheel axis. This position refers to the center of mass of the at least one balancing weight. In this way, the position of the at least one balancing weight is made clear, enabling easy assembly by either an operator or by automated weight application means, such as but not limited to a robotic arm equipped with an end effector configured to apply balancing weights. In some situations, such as but, not limited to, tire/wheel assemblies with a torque imbalance force, at least one balancing weight in each of at least two planes may be necessary to adequately balance said tire/wheel assembly. Therefore, the position of the at least one balancing weight includes also a plane where said weight is to be placed. In this way, the vibration forces are addressed more effectively.

According to the method of the invention, the position of each balancing weight is computed based on the mass of the at least one balancing weight, and the magnitude and location of the vibration force vector. This permits balancing the tire/wheel assembly even if multiple standard balancing weights are used. By preference, the position of each balancing weight is computed considering also the dimensions of each of the at least one balancing weights. In this way, overlapping of the balancing wights is avoided and thereby ensuring that each balancing weight can be properly assembled.

In order to filter out tire/wheel assemblies which, after the step of placing balancing weights, fail to meet the desired performance standards, a step of auditing the balanced tire/wheel assembly for any residual imbalance is necessary. For this purpose, an imbalance limit is calculated, which limit is used to determine if the audited tire/wheel assemblies meet the desired quality. Therefore, in a further embodiment, the method further comprises a step of auditing the balanced tire/wheel for any residual imbalance while the tire/wheel assembly is still mounted onto the tire uniformity machine. This advantageously permits reducing setup times that would otherwise be necessary should the tire/wheel assembly have to be mounted onto another tire uniformity testing machine. Another significant advantage relates to the reduced factory space required when using only a single machine to carry all the measuring, balancing and testing of a tire/wheel assembly. As an alternative to this embodiment, the step of auditing the balanced tire/wheel for any residual imbalance is performed on a second tire uniformity machine. In this way, the throughput of the tire uniformity machine is increased as the delay caused by the step of balancing the tire/wheel assembly and the step of auditing is advantageously transferred to other workstations. This permits also the use of tire uniformity machines for the auditing step, which machines may have, for example, have a lower cost or different number and type of sensors.

A second aspect of the invention relates to a system for balancing a tire/wheel assembly comprising:.

By preference, only the first axis is movable relative to the second axis. By preference, the first axis is moved by means of at least one threaded spindle and load drive set driving the first frame. More preferably, at least one sensor is provided connected between the distal end of the threaded spindle and the first frame. Said sensors being strain gauges, more preferably, the sensors being piezo-electric sensors. In this way, the signals captured by the at least one sensor connected to the spindle and the first frame can advantageously be used to accurately control and monitor the load pressure put upon a tire by the drum before and during system operation. The second axis preferably comprises two coaxially aligned parts movable relative to each other along their longitudinal axis, each of said parts comprising a flange, each flange being configured to support one side of a tire/wheel assembly. In this way, the tire/wheel assembly is supported from both sides, which advantageously eliminates false non-uniformity and/or unbalancing readings due to deformation of the second axis while under the load caused by the drum. More preferably, each part of the second axis is independently movable relative to each other. This permits using a conveyor to bring a tire/wheel assembly in alignment with the second axis, thus avoiding the need to lift said tire/wheel assembly while also making the ingress of said tire/wheel assembly into the machine substantially faster. Most preferably, each part of the second axis is movable by means of at least one electric actuator. In this way, a longer first motion of each part of the second axis can be carried out followed by a second shorter motion of each of said second axis parts. This advantageously permits a faster installation of a tire/wheel assembly while maintaining said assembly firmly supported.

In a further embodiment, at least one of the at least four 3D sensors is rigidly attached to the housing of the tire/wheel fixture, said tire/wheel fixture being a clamp adaptor configured to hold the tire/wheel assembly. In a further embodiment, at least one of the at least four 3D sensors are rigidly attached to the second axis. The sensors used are, by preference but not limited to, accelerometers (piezoelectric), velocity sensors, proximity probes (capacitance or eddy current) and/or laser displacement sensors. More preferably, at least two of the sensors mounted on either the frame and/or the second axis are of the same type. In this way, computation errors due to different sensors being affected differently by changing environmental conditions are advantageously avoided.

According to the system of the invention, at least one of the processing units of the calculation unit are configured to run the steps of:.

By having a processing unit run the aforementioned steps, the testing parameters are advantageously kept consistent from test to test. By preference, all the parameters (e.g. tire/wheel assembly speed, load pressure, tire pressure) are controllable by an operator by means of the at least one user input device. More preferably, all parameters and measured values are associated to an individual test reference code, which parameters, values and code and are stored in at least one of the memory units. Also by preference, said stored information includes the mass and location of at least one balancing weight. In this way, test parameters, measured values and the computed mass and location of the one or more balancing weights associated to an individual test are advantageously made available for use in other processes (e.g. balancing the wheel/tire assembly) and for quality control. However, it is obvious that the invention is not limited to this application. The method according to the invention can be applied in all sorts of wheels which must be balanced by the addition of mass.

The present invention will be now described in more details, referring to examples that are not limitative.

With as a goal illustrating better the properties of the invention the following presents, as an example and limiting in no way other potential applications, a description of a number of preferred applications of the method for high-speed tire/wheel assembly uniformity balancing based on the invention, wherein:.

Claim 1:
A method for high-speed tire/wheel assembly uniformity balancing comprising the steps of:
receiving a pressurized tire/wheel assembly (<NUM>);
mounting the tire/wheel assembly onto a rotatable fixture of a tire uniformity testing machine (<NUM>), said fixture being configured to receive and rigidly attach to a tire/wheel assembly;
bringing a testing drum (<NUM>) in contact with the tire of the tire/wheel assembly such that a predetermined force is applied upon said tire;
running the tire uniformity testing machine, bringing the perimeter of the testing drum to a critical speed while measuring vibration forces by means of at least four 3D sensors;
computing mass and location of at least one balancing weight (<NUM>); and balancing the tire/wheel assembly by applying said at least one balancing weight;
characterized in that, the measured vibration forces are used to compute a vibration force vector (<NUM>) which vector is a vectorial sum of a static vibration force (<NUM>) and a torque imbalance force vector (<NUM>), the static vibration force (<NUM>) being the vectorial sum of a tire uniformity first harmonic radial force variation vector (<NUM>) and a static imbalance vector (<NUM>), the first harmonic radial force variation vector and a static imbalance vector being measured on each of at least two planes of the tire/wheel assembly, said planes being perpendicular to the axis of the tire/wheel assembly, said torque imbalance force vector corresponding to the dynamic imbalance of the tire/wheel assembly, the first harmonic radial force variation vector and a static imbalance vector measured on each plane being used to calculate said torque imbalance force vector, the position of each balancing weight is computed based on the mass of the at least one balancing weight, and the magnitude and location of the vibration force vector.