FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10, rule 13)
1. Title of the invention: AN INTEGRATED SYSTEM FOR MEASURING TIRE
UNIFORMITY AND TIRE NOISE
2. Applicant(s)
NAME NATIONALITY ADDRESS
CEAT LIMITED Indian RPG HOUSE, 463, Dr. Annie Besant Road, Worli, Mumbai -Maharashtra 400 030, India
3. Preamble to the description
COMPLETE SPECIFICATION
The following specification particularly describes the invention and the manner in which it
is to be performed.

TECHNICAL FIELD
[0001] The present subject matter relates, in general, to testing of a tire to be installed in a vehicle and, particularly but not exclusively, to system for measuring tire uniformity and tire noise.
BACKGROUND
[0002] When a vehicle travels on a road there can be many types of excitation sources. These excitation sources lead to noise and vibrations. The vibrations produced can cause a state of discomfort to users of the vehicle and hence can reduce ride quality. Contact between the tires of the vehicle and the road is a source of the noise and the vibrations in the vehicle. There are various internal factors that can excite tire noise and vibrations, such as, tire imbalance, tire uniformity, tread pattern design and tire cavity resonance and the like. Therefore, it is essential to identify the contributions and reasons of tire noise and vibration.
[0003] Primary cause of vibrations originating from the tire running on a smooth road is non-uniformity of the tires. Tire uniformity mainly refers to characteristics of tires that may include, but are not limited to, symmetric mass distribution along the axis of rotation, geometry of the tire (e.g., radial and lateral tire runout), and force generated when the tire rotates around its axis. Non-uniformity in the tire is generally caused by manufacturing anomalies. Lack of uniformity in the tire generates variation in forces exerted in the lateral, radial and longitudinal directions during the rotation of the tire around its axis. Non-uniformity in the tires running at various speeds can be quantified by testing them on a high-speed uniformity machine. The machine provides the information on the force variation generated by the tyre in radial, lateral and longitudinal direction.
[0004] When the tire rolls on the road, the interaction between tire surface and road generates noise which propagates to the driver, occupants and the passers-by around the vehicle and creates discomfort. Thus, it is important for tire

manufacturers to quantify and study tire noise for better design of tires which produces lesser noise. Measurement of tire noise at source (using microphones in close proximity to the site of generation of noise – tire/road interface) is used for the same. Noise measurement on tires at an indoor test lab is conducted in a sound proof room called semi anechoic chamber.
[0005] To identify the root cause of ride disturbances caused by the vibrations generated due to non-uniformity of the tire and the noise during the movement of the tire on the road, tires, having been manufactured, must be tested for non-uniformity and noise generation.
BRIEF DESCRIPTION OF DRAWINGS
[0006] The detailed description is described with reference to the accompanying
figures. In the figures, the left-most digit(s) of a reference number identifies the
figure in which the reference number first appears. The same numbers are used
throughout the drawings to reference like features and components.
[0007] Fig. 1 illustrates the directions of force variation generated by a tire, when
rolled on a surface or road.
[0008] Figs. 2 illustrates an integrated system 100 for measuring tire uniformity
and tire noise, in accordance with an implementation of the present subject matter.
[0009] Fig. 3 illustrates top view of the integrated system 100, in accordance
with an embodiment of the present subject matter.
[0010] Fig. 4 illustrates cross sectional view of the integrated system 100, in
accordance with another embodiment of the present subject matter.
DETAILED DESCRIPTION
[0011] The present subject matter relates to aspects relating to measuring tire uniformity and tire noise simultaneously by providing an integrated system to measure tire force uniformity and tire noise.
[0012] Tire uniformity and tire noise measurement have individual characteristic requirements and are thus measured on different test systems/setup conventionally.

Tire force variation measurement at high speeds to evaluate the non-uniformity in the tires is performed on a high-speed uniformity machine at controlled conditions such as load, speed, temperature, inflation pressure and the like. The tire is mounted on a spindle of the high-speed uniformity machine. The tire mounted on the spindle is loaded to a drum of the high-speed uniformity machine or to a surface providing a road like surface for the rotation of the tire. The drum rotating at realistic road speeds, rotates the tire. Accordingly, the high-speed uniformity machine provides the information on the force variations generated by the tyre in radial, lateral and tangential directions as shown in Fig. 1. Lateral forces (FL) are exerted in a direction perpendicular to the plane in which the tire rotates. Tangential forces (FT) are exerted tangentially to the circumference of the tire. While, radial forces (FR) act along a radius of the tire.
[0013] Further, noise measurement on tires is carried out in a semi anechoic chamber. The semi anechoic chamber provides ideal condition with lowest ambient noise levels for measurement and identification of noise generated by the tire running on a surface, wherein the surface is normally a drum surface which simulates the road.
[0014] Tires having lack of uniformity produces higher force variations resulting in more vibrations. Consequently, more noise at various tire frequencies is generated at the tire road interface. To establish a correlation between the tire uniformity and tire noise, it is required to measure tire force variations and tire noise simultaneously. Tire force variation measurement at high speeds requires a high-speed uniformity machine or the other machine equipped with a force measuring spindle which can measure tire force variation during tire rotation. Tire force variations measurement on high speed uniformity machine are affected by some mechanical arrangements, which may include but are not limited to, torque applied for mounting tire on the spindle, sequence in which the bolts are tightened and orientation and alignment of the wheel holding the tire with respect to the mounting spindle. The force variations

of the same tire measured with a change in set up with respect to changes in these arrangements may be different. Consequently, a correlation between the force variations and the tire noise cannot be established, when both of these measurements are performed on separate setups. Also, more space and cost are required for setting up individual indoor facilities for tire uniformity measurement and tire noise measurement. Further, tire noise measurement requires a semi anechoic chamber housing a drum surface for loading and rotating tires. Thus, it also requires a set up for mounting and loading the tires on to the drum as required in case of measurement of the force variations. Accordingly, a separate space and setup for tire noise measurement and tire uniformity measurement is not required. An integrated setup is needed for the measurement of tire uniformity and tire noise simultaneously to accurately correlate the tire uniformity and tire noise so that an improvement in the design of the tire can be performed. Also, space requirements and cost associated with setting up individual facilities for the measurement of tire uniformity and tire noise can be avoided through an integrated setup for both the measurements. Further, in case of using two individual setups for measuring uniformity and noise, extra efforts and time are also required to demount a tire from a present setup and then to mount the tire on a second setup, in order to measure another parameter, e.g. uniformity or noise.
[0015] In the conventional setups of noise measurement and uniformity measurement of the tire, the drum required for loading and rotating the tire is placed inside a housing under the ground, with small portion of the drum protruding out of the ground. In such setups, tire to be tested is mounted to a spindle. The tire is placed vertically above the protruding portion of the drum and is loaded towards the drum surface. The semi-anechoic chamber involved in the noise measurement of the tire generally comprises its wall and ceiling equipped with absorbing material to absorb the reflections of sound/noise. The sound reflections only come from the

floor/ground. Thus, in the setup of noise measurement of the tire, the drum is placed under the ground from where the reflections of sound come from. [0016] The present invention coalesces the requirements of tire uniformity measurement and tire noise measurement and discloses an integrated system for simultaneously measuring tire uniformity and tire noise at controlled conditions of load, speed, inflation pressure, ambient temperature and ambient noise. In an embodiment, the integrated system overcomes the above-described problems associated with the conventional approach of measuring the tire uniformity and tire noise on separate setups.
[0017] In accordance with an embodiment of the present subject matter, an integrated system for simultaneously measuring uniformity and noise of a tire may include a semi-anechoic chamber and a high-speed uniformity machine forming a vibro-acoustic chamber. The semi-anechoic chamber comprises a ground portion, a ceiling portion and four side walls. The high-speed uniformity machine is placed along one side wall from amongst the four side walls of the semi-anechoic chamber. The high-speed uniformity machine may comprise a drum capable of rotating at high speed and a spindle. The tire can be mounted on the spindle and loaded to the drum at a predefined load. The tire can freely rotate around the axis of the spindle, along with the rotation of the drum. In an example, a surface having a predefined asperity is fastened to the drum. The tire rotates against this surface along with a rotation of the drum at a predefined speed. The surface fastened to the drum provides a road like surface against which the tire mounted on the spindle can be rolled or run. The high¬speed uniformity machine may further comprise a force and uniformity measurement hub to measure force variations and the uniformity of the tire during rotation of the tire. The spindle of the high-speed uniformity machine houses the force and uniformity measurement hub. Output from the force and uniformity measurement hub is recorded. The system may comprise a noise measurement system located

inside the vibro-acoustic chamber for measuring a noise generated, when the tire rolls against the drum at a particular speed and load.
[0018] In an exemplary implementation, the ground portion, the ceiling portion and any three of the four side walls of the semi anechoic chamber except from the one side wall along which the high-speed uniformity machine is placed are covered with noise absorbing wedges and are thus, capable of absorbing any reflection of the sound. The high-speed uniformity machine may be placed along the side wall of the semi anechoic chamber which is not covered with noise absorbing wedges and is thus, capable of reflecting noise/sound. The tire to be tested is mounted on the spindle of the high-speed uniformity machine and is loaded horizontally towards the drum, i.e., in a direction perpendicular to an axis of rotation of the tire. [0019] In another embodiment of the present invention, a tire to be tested for uniformity and noise may be mounted on the spindle of the high-speed uniformity machine. The tire may then be loaded to the drum of the high-speed uniformity machine at a predefined load using mechanical arrangement. The drum can be rotated at predefined speed. The tire also rotates along with the drum since it is loaded on to the drum. The speed and load of the tire may be allowed to stabilize for some time, e.g., for 1 min. The noise measurement system located inside the vibro-acoustic chamber measures the tire noise, when the tire rotates along with the drum against the surface of the drum. During noise measurement the force variations of the tire in the lateral, radial and longitudinal direction are measured at the spindle using the force and uniformity measurement hub. The high-speed uniformity machine also comprises a laser measuring head for measuring tire run outs in lateral and radial directions. The geometric measurements of the rotating tire are thus captured during noise measurement of the tire using the laser measuring head on the high-speed uniformity machine. After measuring the force variations and noise, the spindle is retracted to its original position, i.e., where it was before loading the tire to the drum and the rotation of the drum is brought down to a standstill condition.

[0020] Thus, the integrated system disclosed in the present invention facilitates simultaneous measurement of the tire uniformity and tire noise at controlled conditions of load, speed, inflation pressure, ambient temperature and ambient noise. This achieves higher accuracy in measurements. Further, since both the measurements, i.e., the tire uniformity and the tire noise are conducted simultaneously on the same system, the variation in measurements of force variations, that may otherwise be induced because of differences in mechanical arrangements like torque applied to the spindle, tightening of bolts and alignment of the tire axis, when the same tire is placed on individual setups for measuring uniformity and noise, can be avoided. This establishes a highly accurate correlation between the tire force variation and tire noise at various frequency bands, since effect of tire uniformity on tire noise can be simultaneously captured and analyzed. With the use of the integrated system, a separate space for tire noise measurement or tire uniformity measurement is not required. This provides effective space utilization and saves infrastructure and operational cost for setting up individual indoor facilities for tire uniformity and tire noise measurement. Also, using a single integrated system for measuring tire uniformity and tire noise saves time and effort for conducting two separate tests.
[0021] The above and other features, aspects, and advantages of the subject matter will be better explained with regard to the following description and accompanying figures. It should be noted that the description and figures merely illustrate the principles of the present subject matter along with examples described herein and, should not be construed as a limitation to the present subject matter. It is thus understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the present disclosure. Moreover, all statements herein reciting principles, aspects, and examples thereof, are intended to encompass equivalents thereof. Further, for the sake of simplicity,

and without limitation, the same numbers are used throughout the drawings to reference like features and components.
[0022] Fig. 1 illustrates the directions of force variation generated by a tire, when rolled on a surface or road, in accordance with another implementation of the present subject matter. Fig. 2 illustrates an integrated system 100 for simultaneously measuring tire uniformity and tire noise.
[0023] The integrated system 100 for simultaneously measuring tire uniformity and tire noise, in an implementation of the present subject matter, comprises a high¬speed uniformity machine 101 and a semi anechoic chamber 102. The high-speed uniformity machine 101 and the semi anechoic chamber 102 together forms a vibro-acoustic chamber for the measurement of the tire uniformity and tire noise. The semi anechoic chamber 102 comprises a ground portion, a ceiling portion and four side walls. The high speed non-uniformity machine 101 may comprise a drum 104 capable of rotating at high speed and a spindle (not shown in Fig) for mounting a tire.
[0024] In an example, a surface (not shown in figures) having a predefined asperity is fastened to the drum 104 such that the surface rotates with the drum and the tire rotates along with a rotation of the drum 104 at a predefined speed. The surface is provided along periphery of the drum 104 for imparting characteristics of a road like surface for the rotation of the tire 103. In an example, the asperity of the surface of the drum 104 induces vibrations and the noise at the interface of the tire and the surface of the drum 104 during rotation of the tire. Asperity of the surface can be varied based on an asperity of a road in real time. The high-speed uniformity machine 101 may further comprise a force and uniformity measurement hub 105. The force and uniformity measurement hub 105 may be housed in the spindle of the high-speed uniformity machine. The high-speed uniformity machine 101 may also comprise a laser measuring head (not shown in figures) for measuring tire run outs in lateral and radial directions. The system may comprise a noise measurement system

106 located inside the vibro-acoustic chamber for measuring a noise generated, when the tire 103 rolls against the drum 104 at a predefined speed and load. [0025] In an example, the ground portion, the ceiling portion and any three of the four side walls of the semi anechoic chamber 102 are covered with plurality of noise absorbing wedges 107 and thus, absorb any reflection of the noise or sound. One of the four side walls of the semi anechoic chamber 102 is not covered with the noise absorbing wedges 107 and thus, reflect noise. The high-speed uniformity machine 101 is placed above a ground and along the side wall of the semi anechoic chamber 101 which is not covered with noise absorbing wedges 107. In another example, at least the drum 104 of the high-speed uniformity machine 101 is placed above the ground along said one side wall of the semi-anechoic chamber 102, which is not covered with noise absorbing wedges 107 and a portion housing the drum 104 is placed below the ground.
[0026] In operation, a tire 103 to be tested is mounted on the spindle of the high¬speed uniformity machine 101 and is loaded at a predefined load horizontally towards the drum 104, i.e., in a direction perpendicular to an axis of rotation of the tire 103 (as indicated by the arrow 108 in Fig. 2) using mechanical arrangements to enable the tire 103 to interface with the drum 104. The drum 104 is rotated at a predefined realistic road speed. The tire 103 is also rotated around its axis, along with the drum 104. The noise measurement system 106 located inside the vibro-acoustic chamber measures the tire noise, when the tire rotates along with the drum against the surface fastened to the drum 104. In an example, the noise measurement system 106 measures three components of the noise, i.e., trailing edge noise TEM, side noise SM and leading-edge noise LEM. During noise measurement the force variations of the tire 103 in the lateral, radial and longitudinal direction are measured at the spindle using the force and uniformity measurement hub 105. The geometric measurements of the rotating tire 103 are also captured during noise measurement of the tire using the laser head on the high-speed uniformity machine 101.

[0027] Thus, the integrated system 100 for simultaneously measuring tire uniformity and tire noise disclosed herein obviates the need of setting up two individual indoor facilities for the measurement of tire uniformity and tire noise. This results in saving of space and infrastructural cost associated with setting up individual facilities for both the measurements. The operational cost, time and efforts required for running two individual facilities and conducting two separate tests on respective facility are also eliminated. Further, the force and uniformity hub 105 and noise measurement system 106 simultaneously capture the force variation exerted by the tire and noise generated, when the tire rolls against the surface of the drum 104 at the predefined speed and load. No discrepancy in the force variation exerted by the tire 103 and noise generated on the same speed and load can arise that may otherwise occur when the same tire is subjected to test at different setups for the measurement of uniformity and noise because of the difference in mechanical arrangements like torque applied to the spindle, tightening of bolts and alignment of the tire axis and the like. Accordingly, an effect of the force variation on the noise generated can be accurately identified and a precise correlation between the force variation and the noise can be established.
[0028] In an example, experiments were conducted to test various tires of different sizes such as tires A, B, C, D and tire E with various tread patterns such as pattern 1, 2 and 3 using the presently disclosed integrated system for simultaneously measuring uniformity and noise of a tire. The experiment was conducted for various frequency ranges such as 500-4000 Hz and 300-500Hz and at different speed values such as 60 kmph and 80 kmph. Tire C has also been loaded at 60% and 80% to the drum of the high dpeed uniformity machine. Table 1 specifies the correlation matrices (R-square values) between the various components of noise (LEM, SM and TEM) and force variations in radial and tangential direction for various frequency ranges.

Frequency Range Tyre Size LEM vs RF SM vs RF TEM vs RF LEM vs TF SM vs TF TEM vs TF
500 -4000Hz 60 kmph

Tyre A 0.02 0.59 0.05 0.03 0.54 0.03

Tyre B (CEAT Tire) 0.25 0.84 0.21 0.17 0.75 0.09

Tyre C - 60% load -0.01 0.65 0.10 -0.02 0.52 0.05

Tyre C - 80% load 0.12 0.77 0.16 0.05 0.69 0.04

80 kmph

Tyre A -0.01 0.64 0.10 0.13 0.65 0.16

Tyre B (CEAT Tire) 0.13 0.82 0.18 0.37 0.86 0.35

Tyre C - 60% load 0.06 0.77 0.22 0.23 0.74 0.23

Tyre C - 80% load 0.06 0.75 0.19 0.11 0.74 0.18
300 -500Hz 60 kmph

Tyre D (CEAT Tire) 0.18 -0.88 -0.54 0.74 -0.24 -0.17

Tyre E Pattern 1 0.73 0.70 -0.52 -0.47 -0.23 0.19

Tyre E Pattern 2 0.75 0.64 0.51 -0.65 -0.31 -0.53

Tyre E Pattern 3 0.85 0.65 0.23 -0.25 -0.02 -0.02

80 kmph

Tyre D 0.47 -0.54 -0.01 0.62

Tyre A (CEAT Tire) 0.80 0.07 0.29 -0.62 -0.43 -0.26

Tyre B -0.03 0.60 0.16 -0.64 -0.86 -0.66
Table 1: R-square values of correlation between various channels of noise and forces [0029] Following conclusions can be drawn from the data revealed above in Table 1. Any correlation R-square value above 50% is considered to be significant.

(1) In 500-400 Hz region, a good positive correlation is seen between the side mic noise to radial forces and tangential forces. So as the forces increase, the noise in this frequency range also increases.
(2) It can be see that, a better R-square value is obtained at higher load (e.g., if comparison is made between 60% load and 80% load).
(3) As the speed increases to 80kmph, the R square values increase indicating a better correlation than that at 60kmph.
(4) In 300-500 Hz region, better correlation is seen in leading edge mic noise to radial force.
[0030] The integrated system for simultaneous measurement of tire noise and uniformity enables the measurement of tire noise and uniformity (forces – RF and TF) in the same time domain, thus making the correlation exercise shown in Table 1 possible. These correlation trials are not possible with two separate facilities for tire uniformity measurement and tire noise measurement, since the measurements would not happen at the same time. Similar studies on various patterns, sizes, brands of tires may enable the creation of a database with various conclusions. Using data science, prediction algorithm can be created which can be used to predict the effect of forces generated by the tire on tire noise.
[0031] Figs. 3 and 4 illustrate 3 illustrates a top view and cross-sectional view, respectively, of the integrated system 100, in accordance with an implementation of the present subject matter.
[0032] In another embodiment of present subject matter, the integrated system 100 may also comprise HVAC (heating, ventilation, and air conditioning) system to maintain the ambient temperature of tire uniformity and tire noise measurement space. Further, the smoothness of the surface fastened to the drum on which tire rolls can be changed to, for example, smooth, medium and coarse, to provide the realistic road conditions during measurement of the tire uniformity and noise. This is

achieved using road shells of different asperity or roughness (fine, medium or coarse) which can be attached to the otherwise smooth drum of the machine. [0033] According to another embodiment of the present invention, the system 100 is also equipped with the impact noise testing capability and tire/wheel balancing capabilities. For impact noise testing, cleats which are protruding obstructions mounted parallel to the direction of rotation of the drum are used. A tire loaded on the drum runs over the cleats at various speeds, when the drum rotates, simulating impact. The noise produced during the impact of cleats on the tire, called as impact noise is measured. The cross section of the cleats used for impact noise testing can be triangular, trapezoidal, semicircular, circular, step or any combination of these cross sections.
[0034] Although implementations for an integrated system 100 for simultaneously measuring tire uniformity and tire noise are described, it is to be understood that the present subject matter is not necessarily limited to the specific features of the systems described herein. Rather, the specific features are disclosed as implementations for the integrated system 100 for simultaneously measuring tire uniformity and tire noise.

I/We Claim:
1. An integrated system 100 for simultaneously measuring uniformity and noise
of a tire 103, the integrated system 100 comprising:
a semi-anechoic chamber 102 comprising a ground portion, a ceiling portion and four side walls;
a high-speed uniformity machine 101 placed along one side wall from amongst the four side walls of the semi-anechoic chamber 102, the high-speed uniformity machine 101 comprising:
a drum 104 capable of rotating at high speed, wherein the tire 103 is
to interface with the drum 104, such that the tire 103 rotates along with a
rotation of the drum 104; and
a force and uniformity measurement hub 105 to measure force
variations and the uniformity of the tire 103 during rotation of the tire 103;
a noise measurement system 106 located inside the semi-anechoic chamber 102 to measure a noise generated upon rotation of the tire 103.
2. The system 100 as claimed in claim 1, wherein the ground portion, the ceiling portion and three side walls from amongst the four side walls of the semi-anechoic chamber 102 except from the one side wall along which the high-speed uniformity machine 101 is placed, are covered with noise absorbing wedges 107.
3. The system 100 as claimed in claim 1, wherein the high-speed uniformity machine 101 comprises a spindle, the tire 103 being mounted on the spindle, and wherein the spindle houses the force and uniformity measurement hub 105.
4. The system 100 as claimed in claim 1, wherein the tire 103 is to be loaded horizontally towards the drum 104 at a predefined load in a direction perpendicular to an axis of rotation of the tire 103 to enable the tire 103 to interface with the drum 104.

5. The system 100 as claimed in claim 1, wherein at least the drum 104 of the high-speed uniformity machine 101 is placed above a ground along said one side wall of the semi-anechoic chamber 102, which is not covered with noise absorbing wedges 107.
6. The system 100 as claimed in claim 1, wherein a surface having a predefined asperity is fastened to the drum 104, and wherein the tire 103 rotates against said surface along with a rotation of the drum 104 at a predefined speed.
7. The system 100 as claimed in claim 6, wherein the asperity of the surface of the drum 104 induces vibrations and the noise at the interface of the tire 103 and the surface of the drum 104 during rotation of the tire 103.
8. The system 100 as claimed in claim 1, wherein the high-speed uniformity machine 101 comprises a laser measuring head to measure tire run outs in a lateral and a radial direction.
9. The system 100 as claimed in claim 1, wherein the integrated system 100 comprises a heating, ventilation, and air conditioning HVAC system to maintain the ambient temperature of the semi-anechoic chamber 102.
10. The system as claimed in claim 1, wherein the noise measurement system 106 is to measure a trailing edge noise TEM, a side noise SM and a leading-edge noise LEM.