Device for measuring a static imbalance in a tyre

Abstract

The invention relates to a device (10) for measuring a static imbalance in a tyre (P), the measuring device (10) comprising a weighing table (12) that comprises a horizontal measuring plane (14) mounted on at least three weighing units arranged at regular intervals around the same reference circle, a device for the automated positioning of a tyre on said weighing table, the positioning device allowing the tyre (P) to be placed on one of its sidewalls on the measuring plane (14) of the weighing table and the tyre (P) to be centred in an automated manner relative to the centre of the reference circle of the weighing units, and a processing unit (28) connected to each weighing unit.

Description

DEVICE FOR MEASURING STATIC UNBALANCE IN A TIRE

[0001] The present invention relates to the measurement of a static imbalance in a tire.

[0002] Application EP3901603 describes a machine for measuring an imbalance in a wheel comprising a rotating shaft on which the wheel is mounted, a sensor for measuring the imbalance forces generated during the rotation of the shaft, an angular sensor measuring the angular position of the shaft, and electronic means for determining from the information returned by the sensors the values ​​and positions of the corrective masses to be affixed to the wheel to eliminate the imbalance forces.

[0003] Furthermore, application EP3901603 also provides a device projecting a light point onto the wheel to indicate the position of the corrective masses to be applied.

[0004] The rotary machine described in application EP3901603 is particularly intended for measuring unbalance in a wheel, that is to say in the assembly formed by a rim and a tire mounted on this rim.

[0005] If such a rotary machine is used to measure unbalance in a single tire, for example as part of a quality control immediately after manufacturing the tire, it is necessary to first mount the tire on a rim that must be perfectly balanced, and it is also necessary to inflate the tire to the correct pressure. In addition, it is generally also necessary to lubricate the tire beads to correctly mount the tire on its rim.

[0006] Finally, once the unbalance measurement has been carried out, the tire must be removed from its rim.

[0007] While fitting and removing a passenger vehicle tire from its rim can be carried out relatively easily by an operator, this is not the case for tires intended for heavy goods vehicles or aircraft.

[0008] In the case of these large and heavy tires, the operations of mounting and removing the tire from a rim take longer for an operator to carry out, even if this operator is assisted by automated gripping and mounting / removing devices.

[0009] Ultimately, the machine described in application EP3901603 is more particularly intended for measuring unbalance in a wheel as it will be mounted on the vehicle, or for measuring unbalance in a tire which has just been manufactured but preferably of the passenger car type.

[0010] The present invention aims to overcome the drawbacks of prior art rotary unbalance measuring machines.

[0011] To this end, the invention relates to a device for measuring a static imbalance in a tire, the measuring device comprising a weighing table comprising a horizontal measuring plane and mounted on at least three load cells arranged at regular intervals on the same reference circle contained in a horizontal plane, a device for automated positioning of a tire on this weighing table, the positioning device making it possible to automatically place the tire on one of its sidewalls on the horizontal measuring plane of the weighing table, the positioning device making it possible to automatically center the tire relative to the center of the reference circle of the load cells, and a processing unit connected to each scale so that each scale communicates to the processing unit the value of the mass that it supports when a tire is placed motionless and centered on the measuring plane of the weighing table.

[0012] Thanks to the weighing table measurement, the measuring device according to the invention makes it possible to avoid mounting the tire on a rim or equivalent support. In addition, thanks to the weighing table measurement, the measuring device according to the invention is easily and quickly adaptable to tires of different dimensions. Indeed, it is no longer necessary to change the rim or tire support when the dimensions of the tire to be measured change.

[0013] Thanks to the automated positioning device, manual handling of tires is eliminated. This is particularly advantageous for implementing unbalance measurement in large and heavy tires such as tires intended for aircraft or heavy goods vehicles, particularly as part of quality control of these tires in their manufacturing plant.

[0014] According to another advantage, the measuring device according to the invention makes it possible both to identify the position of an imbalance in a tire and also to know the mass of this tire, which is useful for implementing quality control at the end of manufacturing.

[0015] Advantageously but not necessarily, the invention may also provide that: - the device for positioning a tire on the weighing table is a robotic arm or an automated gantry equipped with a device for gripping a tire with internal or external jaws, - the measuring device is equipped with a system for acquiring the arrival position of the tire, - the measuring device comprises a device for marking the position of the static unbalance determined by the processing unit on the tire, preferably with a red dot, - the device for marking the position of the static unbalance comprises an output conveyor receiving the tire to be marked and a robotic arm equipped with a marker, preferably pneumatic, - the measuring device comprises a tire arrival conveyor and an intermediate tire conveyor, the positioning device making it possible to automatically pick up a tire from the arrival conveyor to take it and place it automatically on the measuring plane of the weighing table, and to automatically pick up a tire from the measuring plane of the weighing table to take it and place it automatically on the intermediate conveyor.

[0016] The invention also relates to methods for measuring a static imbalance in a tire using the device for measuring a static imbalance in a tire according to the invention.

[0017] According to a first method, the tire is automatically placed a first time on the measuring plane of the weighing table by the positioning device, then automatically removed from the weighing table to be automatically placed there again a second time with better centering relative to the reference circle. load cells, and then the load cells carry out at least one measurement of the mass they support for at least one position of the tire on the measuring plane of the weighing table and they transmit this information to the processing unit.

[0018] For example, in this first method, the tire is picked up and placed back down several times, preferably at least three times, automatically by the positioning device on the measuring plane of the weighing table before the scales measure the mass they are supporting.

[0019] According to a second method, the measuring device being equipped with a system for acquiring the arrival position of the tire, the arrival position of the tire is acquired by the measuring device before the tire is picked up by the positioning device, then the tire is brought automatically onto the measuring plane of the weighing table by the positioning device, the centering of the tire on the measuring plane of the weighing table being obtained by prior acquisition of the arrival position of the tire, and then the scales carry out at least one measurement of the mass that they support for at least one position of the tire on the measuring plane of the weighing table and they transmit this information to the processing unit.

[0020] In the context of the implementation of the measuring method according to the invention, it may also be provided that: - the scales take a measurement after a non-zero delay after the tire has been placed on the measuring plane of the weighing table, - the scales measure the mass they support for several positions of the tire on the measuring plane of the weighing table taken around the center of the reference circle of the scales, - the scales measure the mass they support for X positions of the tire on the measuring plane of the weighing table, each position being separated from the following position by an angle in degrees equal to 360 / (X+l).

[0021] Other characteristics and advantages of the invention will appear in the description which follows. This description, given by way of example and not as a limitation, refers to the attached drawings in which: - [Fig.l] is a schematic perspective view of a device for measuring static unbalance in a tire according to the invention, - [Fig.2] is a schematic top view of a device for measuring static unbalance in a tire according to the invention, - [Fig.3] is a schematic front view of a device for measuring static unbalance in a tire according to the invention.

[0022] The invention relates to a device 10 for measuring a static imbalance in a tire such as that which is for example illustrated in Figure 1.

[0023] This measuring device 10 is suitable for measuring static unbalance in all types of tires.

[0024] Measuring the unbalance in a tire allows us to know whether the measured unbalance is within the tolerances of the tire manufacturer or within the tolerances of the future user of the tire, such as an aircraft manufacturer for example. Measuring the mass and position of an unbalance in a tire also allows us to add a patch, i.e. a mass of rubber, opposite the position of the unbalance in the tire. Finally, measuring the mass and position of an unbalance in a tire allows the tire to be mounted on a rim in such a way that the unbalance of the tire is located opposite the unbalance of the rim on which it is mounted.

[0025] According to the invention, the device 10 for measuring a static unbalance in a tire comprises a weighing table 12 comprising a horizontal measuring plane 14 and mounted on at least three load cells 16 arranged at regular intervals on the same reference circle 18 contained in a horizontal plane PH, such as the measuring plane 14 for example.

[0026] Load cells are centrally supported load cell type load cells.

[0027] At least three load cells are required to measure a static unbalance in a tire. If the weighing table includes three load cells, these load cells are arranged at 120° to each other. However, the weighing table could also include four or more load cells. In all cases, all the load cells on the weighing table are preferably arranged at regular intervals on the same reference circle 18 contained in a horizontal plane PH.

[0028] In more detail, the weighing table 12 comprises a frame 20 supporting a mounting plane 22 on which the load cells 16 are mounted around their reference circle 18. The measuring plane 14 takes the form of a circular plate 24 mounted flat on the load cells 16 and centered relative to the reference circle 18 of the load cells.

[0029] In order to avoid handling a tire by an operator, the device 10 for measuring a static imbalance in a tire comprises an automated device 26 for positioning a tire P on the weighing table 12.

[0030] To enable the position and mass of a static unbalance to be determined from the information sent by the load cells, the tire to be measured must be placed on one of its sides on the measuring plane 14 and the tire thus placed must be centered in relation to the reference circle 18 of the load cells.

[0031] Also, the positioning device 26 makes it possible to automatically place the tire to be measured on one of its sides on the horizontal measuring plane 14 of the weighing table, and the positioning device 26 also makes it possible to automatically center the tire P relative to the center of the reference circle 18 of the load cells 16. For this purpose, the positioning device 26 knows the position of the center of the reference circle 18 of the load cells 16. For example, the positioning device 26 has previously acquired the position of the center of the reference circle 18 of the load cells 16 by learning using a calibration template.

[0032] For estimating the position and mass of a static unbalance in the tire P placed and centered on the measurement plane 14, the device 10 for measuring a static unbalance in a tire comprises a processing unit 28 connected to each scale 16 so that each scale 16 communicates to the processing unit 28 the value of the mass that it supports when a tire P is placed immobile and centered on the measurement plane 14 of the weighing table.

[0033] For example, the positioning device 26 of a tire P on the weighing table 12 is a robotic arm 30 equipped with a gripping device 32 for a tire with internal jaws 34. The robotic arm 30 may be a robotic arm with 3, 4 or 5 axes of mobility. The gripping device 32 for a tire comprises, for example, three internal jaws 34 intended to grip the tire from the inside, that is to say at the level of the tire rods. The inner jaws 34 are mounted on a star-shaped support 36 comprising as many branches as there are inner jaws. For example, an inner jaw 34 comprises a movable hook 38, and for example mounted tilting, at its lower end to grip the tire by one of its rods.

[0034] Alternatively, the positioning device 26 may be an automated gantry allowing the gripping device 32 to be moved on several axes (this variant not being shown in the figures).

[0035] Alternatively to the internal jaws, the gripping device 32 can be equipped with external jaws (variant not shown) which grip the tire from the outside.

[0036] In order to avoid deformation of the tires by the positioning device, provision may be made for regulation of the tightening torque of the jaws of the gripping device 32. Indeed, such deformations may impact the centering of the tire on the weighing table and distort the determination of the mass and position of a static imbalance in the tire.

[0037] In order to allow the addition of a patch, that is to say a mass of rubber, opposite the position of the imbalance in the tire or to mount the tire on a rim such that the imbalance of the tire is located opposite the imbalance of the rim on which it is mounted, the measuring device 10 may comprise a device 46 for marking the position of the static imbalance determined by the processing unit on the tire, preferably with a red dot.

[0038] For example, the device 46 for marking the position of the static unbalance comprises an output conveyor 48 receiving the tire to be marked and a robotic arm 50 equipped with a marker 52, preferably pneumatic. For example, the output conveyor 48 is a belt conveyor.

[0039] For the arrival and transport of a tire P to be measured to the weighing table 12 and from the weighing table to the output conveyor 48, the measuring device 10 may comprise an arrival conveyor 54 for a tire and an intermediate conveyor 56 for a tire, the positioning device 26 making it possible to automatically pick up a tire from the arrival conveyor 54 to take it and place it automatically on the measuring plane 14 of the weighing table 12, and to automatically pick up a tire P from the measuring plane of the weighing table to take it and place it automatically on the intermediate conveyor 56. For example, the arrival conveyor 54 and the intermediate conveyor 56 are belt conveyors.

[0040] Ideally, to facilitate the flow of tires, the inlet conveyor 54, the intermediate conveyor 56 and the outlet conveyor 48 are arranged one behind the other and in this order.

[0041] To enable the transfer of the tires P between the three conveyors in the event of a breakdown of the weighing table 12 or the positioning device 26, the weighing table 12 is arranged parallel to the three conveyors. Preferably, the weighing table 12 is arranged parallel to the intermediate conveyor 56.

[0042] Alternatively, the measuring device 10 may comprise only one inlet conveyor and one outlet conveyor (this variant not being shown in the figures). In this case, the weighing table is aligned with the two conveyors and located between these two conveyors.

[0043] In order to identify the arrival position of the tire P, for example on the arrival conveyor 54, the measuring device 10 may be equipped with a system 60 for acquiring the arrival position of the tire P. For example, this acquisition system 60 is a camera 62 supported by the positioning device 26. The arrival position of the tire P is the position in which the tire P is gripped by the gripping device 32 when it arrives at the input of the measuring device. Alternatively, the acquisition system 60 may be mounted on a support independent of the positioning device 26.

[0044] According to the invention, the measurement of a static unbalance in a tire P consists of identifying the eccentricity of the center of gravity of the tire due to the presence of an unbalance in this tire. With the measuring device 10 according to the invention, the measurement of a static unbalance in a tire P consists of identifying the position, and therefore the eccentricity, of the center of gravity of this tire relative to the center of the reference circle 18 of the load cells. The eccentricity of the center of gravity of the tire is determined by the processing unit 28 from the information transmitted by the load cells 16, namely the mass supported by each load cell. Then, knowing this eccentricity of the center of gravity and the distance at which a patch (mass of rubbery rubber) can be applied to the tire, for example inside this tire, the processing unit 28 can determine the mass of the patch.The relationship used by the processing unit is as follows: Unbalance (in gm) = Total mass of the tire (in g) x Eccentricity (in m). In the context of the present invention, the mass and position of the static unbalance are calculated in the median plane of the measured tire.

[0045] The invention also relates to methods for measuring a static imbalance in a tire P using a measuring device 10 according to the invention.

[0046] According to a first measuring method, the tire P is automatically placed a first time on the measuring plane 14 of the weighing table by the positioning device 26, then automatically removed from the weighing table 12 to be automatically placed there again at least a second time with better centering relative to the reference circle 18 of the weighing cells.

[0047] In order to further improve the centering of the tire P on the measuring plane of the weighing table, the tire P can be picked up and placed back down several times, preferably at least three times, in an automated manner by the positioning device 26 on the measuring plane of the weighing table 12. With each new pick-up, the tire is located closer and closer to a perfectly centered position on the weighing table.

[0048] Following this or these operations of removing and redepositing the tire P on the weighing table, the scales 16 carry out at least one measurement of the mass that they support for at least one position of the tire P on the measuring plane 14 of the weighing table and they transmit this information to the processing unit 28.

[0049] According to a second measuring method aimed at avoiding the operation(s) of picking up and redepositing the tire P on the weighing table, the arrival position of the tire is acquired by the measuring device 10 before the tire is picked up by the positioning device 26, in particular using the acquisition system 60, then the tire is brought automatically onto the measuring plane 14 of the weighing table by the positioning device, the centering of the tire P on the plane of measurement of the weighing table being obtained by prior acquisition of the arrival position of the tire, and then the scales 16 carry out at least one measurement of the mass that they support for at least one position of the tire on the measurement plane 14 of the weighing table and they transmit this information to the processing unit 28.

[0050] In either of these measuring methods and in order to prevent the measurement made by each load cell from being distorted by vibrations, it may be provided that the load cells 16 carry out a measurement after a non-zero delay after the tire P has been placed on the measuring plane 14 of the weighing table. This non-zero delay corresponds to a stabilization time for the measurement transmitted by the load cells, this stabilization time being variable depending on the size and rigidity of the tire. For example, the load cells 16 carry out a measurement from 2 to 40 seconds after the tire P has been placed on the measuring plane 14 of the weighing table.

[0051] In order to determine more precisely and more certainly the position of the center of gravity of the tire P and always in one or other of two measuring methods, it can be provided that the load cells 16 carry out a measurement of the mass that they support for several positions of the tire P on the measuring plane of the weighing table taken around the center of the reference circle 18 of the load cells. Thus, the possibility of a calculation error due to the random position of the unbalance relative to the load cells is limited. The tire P having to remain centered on the measuring plane of the weighing table, between two different measuring positions, the tire P is simply moved in rotation around the center of the reference circle of the load cells 16 by the positioning device 26. When the position of the tire on the weighing table changes, the positioning device preferably picks up and then redeposits the tire on the weighing table.It may also be possible to provide for several picking-up and re-depositing operations during each change of position of the tire on the weighing table, and / or to carry out a measurement with the scales only after a non-zero delay after the tire P has been re-deposited in a new position on the measuring plane 14 of the weighing table.

[0052] In more detail, the load cells 16 carry out a measurement of the mass that they support for X positions of the tire P on the measuring plane of the weighing table, each position being separated from the following position by an angle in degrees equal to 360 / (X+l). For example, between 3 and 9 positions of the tire P on the measuring plane of the weighing table are used for the determination of a static unbalance in each tire.

Claims

Claims 1. Device (10) for measuring a static unbalance in a tire (P), the measuring device (10) comprising a weighing table (12) comprising a horizontal measuring plane (14) and mounted on at least three load cells (16) arranged at regular intervals on the same reference circle (18) contained in a horizontal plane, an automated positioning device (26) for a tire on this weighing table, the positioning device making it possible to automatically place the tire (P) on one of its sides on the horizontal measuring plane (14) of the weighing table, the positioning device making it possible to automatically center the tire (P) relative to the center of the reference circle (18) of the load cells,and a processing unit (28) connected to each scale (16) so that each scale communicates to the processing unit the value of the mass that it supports when a tire (P) is placed immobile and centered on the measuring plane (14) of the weighing table., 2. Device (10) for measuring a static unbalance in a tire according to claim 1, in which the device (26) for positioning a tire on the weighing table is a robotic arm (30) or an automated gantry equipped with a device (32) for gripping a tire with internal (34) or external jaws.

3. Device (10) for measuring a static imbalance in a tire according to one of the preceding claims, the measuring device (10) being equipped with a system (60) for acquiring the arrival position of the tire (P).

4. Device (10) for measuring a static unbalance in a tire according to one of the preceding claims, further comprising a device (46) for marking the position of the static unbalance determined by the processing unit on the tire, preferably with a red dot.

5. Device (10) for measuring a static unbalance in a tire according to claim 4, in which the device (46) for marking the position of the static unbalance comprises an output conveyor (48) receiving the tire to be marked and a robotic arm (50) equipped with a marker (52), preferably pneumatic.

6. Device for measuring a static imbalance in a tire according to one of the preceding claims, further comprising an arrival conveyor (54) for a tire and an intermediate conveyor (56) for a tire, the positioning device (26) making it possible to automatically pick up a tire (P) from the arrival conveyor (54) to take it and place it automatically on the measuring plane (14) of the weighing table, and to automatically pick up a tire (P) from the measuring plane of the weighing table to take it and place it automatically on the intermediate conveyor (56).

7. Method for measuring a static unbalance in a tire (P) using a device (10) for measuring a static unbalance in a tire according to one of the preceding claims, in which the tire (P) is automatically placed a first time on the measuring plane (14) of the weighing table by the positioning device (26), then automatically removed from the weighing table to be automatically placed there again a second time with better centering relative to the reference circle (18) of the load cells, and then the load cells (16) carry out at least one measurement of the mass they support for at least one position of the tire (P) on the measuring plane of the weighing table and they transmit this information to the processing unit (28).

8. Method for measuring a static unbalance in a tire according to claim 7, in which the tire (P) is picked up and redeposited several times, preferably at least three times, in an automated manner by the positioning device (26) on the measuring plane of the weighing table (12) before the scales carry out a measurement of the mass that they support.

9. Method for measuring a static unbalance in a tire (P) using a measuring device (10) for measuring a static unbalance in a tire according to one of claims 1 to 6, in which, the measuring device (10) being equipped with a system for acquiring the arrival position of the tire, the arrival position of the tire is acquired by the measuring device (10) before the tire is gripped by the positioning device (26), then the tire is brought automatically onto the measuring plane (14) of the weighing table by the positioning device, the centering of the tire (P) on the measuring plane of the weighing table being obtained by prior acquisition of the arrival position of the tire,and then the scales (16) carry out at least one measurement of the mass that they support for at least one position of the tire on the measuring plane of the weighing table and they transmit this information to the processing unit (28)., 10. Method for measuring a static imbalance in a tire according to one of claims 7 to 9, in which the load cells (16) carry out a measurement after a non-zero delay after the tire (P) has been placed on the measuring plane (14) of the weighing table.

11. Method for measuring a static imbalance in a tire according to one of claims 7 to 10, in which the load cells (16) carry out a measurement of the mass that they support for several positions of the tire (P) on the measurement plane of the weighing table taken around the center of the reference circle (18) of the load cells.

12. Method for measuring a static unbalance in a tire according to claim 11, in which the load cells carry out a measurement of the mass that they support for X positions of the tire on the measurement plane of the weighing table, each position being separated from the following position by an angle in degrees equal to 360 / (X+l).

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