FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See Section 10; rule 13)
TITLE OF THE INVENTION Non Obstructive Particle (lamping for hollow structure in a vehicle
APPLICANTS
TATA MOTORS LIMITED, an Indian company
having its registered office at Bombay House,
24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001 Maharashtra, India
INVENTORS
Prasanth B, Sachin Wagh and Ganesh Iyer
an are Indian Nationals
of TATA MOTORS LIMITED an Indian company
having its registered office at Bombay House,
24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001 Maharashtra, India
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is performed.

FILED OF INVENTION
This invention relates to the method of damping applied to the cradle of a passenger car to improve the NVH performance of the vehicle.
BACKGROUND OF INVENTION
The technique used in automobiles for NVH is one of the key parameter for customer comfort. The incab noise can be broadly classified into airborne noise and structure borne noise. The source of the structure borne noise is the energy transferred from the engine to the body through the different attachments. A cradle is generally employed to mount the engine, gearbox to the vehicle. The cradle can be either a sub frame on which a part of the power train is mounted or a cradle where the whole engine and transmission unit is attached. In either of the cases the energy from the engine will get transferred to the body through the cradle which is a primary transfer path for the structure borne noise at the incab. If proper care is not taken at the time of design of the cradle, it can act as a poor transfer path for the noise and vibrations to the body structure. To improve the structural characteristics of the cradle, different modifications where thought off, the major one's being increase in stiffness, adding mass etc. These modifications didn't give the expected benefit and overall cost also increases. Visco-elastic materials have wide range of applications in vibration damping in normal environment but loose their effectiveness in varying or extreme temperature and environmental conditions and will also degrade over time. Damping can be a good method to improve the structural characteristics of cradle with out affecting the cost targets.
OBJECTS OF THE INVENTION
Main objective of this invention is to improve the structural performance of the cradle and to reduce the energy transfer from the power train to the vehicle body and thus improve the incab noise performance of the vehicle.

Another object of the invention is to provide a solution at low cost which is reliable in all operating conditions of the vehicle, which can be easily implemented in production with out many modifications to the process.
SUMMARY OF INVENTION
Accordingly the present invention discloses the Non Obstructive Particle Damping (NOPD) for hollow structure in a vehicle comprising of plurality of hollow structural members configured for supporting the major vehicle components generating vibration; at least one type of damping particles configured to be filled in said plurality of hollow structural members and sealed to constitute the structural members of the vehicle to facilitate damping the vibration in the automobiles and for supporting the major vehicle components generating vibration.
The plurality of hollow structural member comprises of cradle, chassis sections, cross members, driveline components etc The cradle is configured to be mounted on the vehicle body through plurality of mounting locations viz. three front mounting locations (1) and two rear mounting locations (2). The major vehicle components generating vibration comprises of the engine, gearbox and the suspension systems configured to be mounted on said cradle. The cradle is made of at least four tubes fastened to each other.
The damping particles configured for NOPD are Lead particles and/or Steel/Cast Iron particles and/or Gravel/ Sand and/or Saw dust and/or Rubber granules or any other material used for damping.
The damping particle size/diameter and/ or shape are configured on the basis of its application and the amount of damping required.
The particle damping is configured for achieving high damping by converting kinetic energy of the structure to heat energy. The maximum size of the particles is configured to limit to l/5th of size of the section in which they are to be inserted.

The damping particles configured to be in spherical shape. The NOPD is configured to increase said damping properties of the structure by 50% and improvement in the frequencies above 200 Hz.
Non Obstructive Particle Damping (NOPD) for hollow structure in a vehicle comprises of plurality of hollow structural members configured to support the major vehicle components generating vibration; at least one type of damping particles configured to be filled in plurality of pockets with optimized/predetermined quantity of said particles and sealed; wherein said plurality of pockets are configured to be filled in said hollow structural members into various strategic locations along the structure for localized damping of said structures.
BRIEF DESCRIPTION OF DRAWING
Figure 1 shows a cradle used for the particle damping application. Figure 2 shows the damping comparison with damping particles and without damping particles.
Figure 3 shows a cradle with 5 locations points for mounting it on the body of vehicle.
Figure 4 shows experimental modal analysis of superior damping observed at all attachment locations above 200 Hz.
DETAILED DESCRIPTION
Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only, and not for the purpose of limiting the same.
The present invention relates to the method of damping applied to the cradle of a passenger car to improve the NVH performance of the vehicle. This method uses particles for damping NVH of vehicles to improve the structural characteristics of a

cradle or any such member which transfers or causes structure borne noise in a vehicle. The vehicle can be any vehicle as for example a passenger car or a commercial vehicle. Non obstructive particle damping (NOPD) is a vibration damping technique entailing placement of numerous loose particles by either of the following methods: (i) inside the structure cavity (ii) attached separately onto the structure at strategic locations such as anti-nodal points determined by experimental or CAE techniques. A passive damping methodology for structures, where energy dissipation occurs due to friction and impact between particles; NOPD performance is unaffected by temperature and hence can be used in cryogenic or high temperature environments.
Selection of appropriate materials for different applications are important as damping required is dependent on type of material. Particles having highest density give superior damping. Some of the particles generally used for NOPD are: Lead particles, Steel/Cast Iron particles, Gravel/ Sand, Saw dust, Rubber granules, etc. Particle size/diameter also plays an important role in damping of vibration in the vehicles. Spherical particles are generally preferred. Depending on the application and the damping required, size of the particles can be optimized. As a rule of thumb the maximum size of the particles not to exceed l/5th of section size.
Said damping particles are filled in different quantity in hollow structural member such as cradle, chassis sections, cross members, driveline components etc. The damping particles comprises of sand and/or steel powder and/or saw dust or lead or any other material used for damping. In spite of particles metal balls of small sizes can also be used.
The cradle as mentioned in this invention is a vital (hollow) member that supports the rear un-sprung mass and the power train (which is attached on to the cradle at three mounting locations as indicated). The cradle is mounted on the body through 5 attachment locations as indicated in Figure 3 viz. three front attachments

locations (1) and two rear attachment locations (2). The cradle itself is hence a major transfer path for the vibrations and structure borne noise transferred into the body. The cradle here mounts the engine at (3), gearbox and the suspension systems at (4). The cradle is made of four tubes welded to each other.
The sand was filled into all the four tubes and sealed. The damping properties of the structure have shown almost 50% increase with particle damping applied. The frequency analysis and modal data has shown a quantum improvement in the frequencies above 200 Hz (Ref: Figure 4).
According to present invention particle damping method increases the structural damping by inserting particles to a vibrating structure. The particles absorb the kinetic energy of the structure and convert it into heat through in elastic collisions between the particles and the enclosure. Additional energy dissipation may also occur due to frictional losses and inelastic particle-to-particle collisions amongst the particles. The unique aspect of particle damping is that high damping is achieved by converting kinetic energy of the structure to heat as opposed to the more traditional methods of damping where the elastic strain energy stored in the structure is converted into heat.
Particle damping has the advantage of being a better damping material with minimal impact on cost and yet a consistent performance through out the life cycle.
A boom is observed in vehicle at a low frequency range which can be attributed to the engine firing orders. Majority of the incab noise issues in the vehicle is due to the structure borne excitation. In said vehicle a cradle is employed to mount the engine, transmission unit and the suspension systems. Accordingly the energy is transferred through the path with least resistance. Here the energy transferred to the body from the engine and other system mounted to the cradle, is the major source of structural excitation contributing to the incab noise. The root cause analysis has also indicated that the cradle as the key transfer path for the excitation to the body.

The excitations from the engine mounts, road input and other excitations from the suspension side are amplified by the cradle if it is poorly designed.
The cradle is made up of hydro-formed tubes welded together. The cross member towards the front of the vehicle holds the suspension semi-trailing arm, and C-mount. The longitudinal members of the cradle have locations to mount the A and B mounts. The cradle is mounted to the body at 5 locations including one attachment to the body near the C-mount attachment. Particle damping was tried out on the cradle helps in improving the modal characteristics of the cradle with a very nominal increase in the cost. Furnace sand is used as the damping material since the density is very high. The hollow section of the cradle was filled with sand through the sides and was sealed.
Measurements were done on the cradle to quantify the improvements in the damping characteristics and the modal improvements. The cradle with and without damping particles was subjected to modal analysis with cradle in free-free condition. The modified cradle was also fitted on a vehicle level to access the improvements in the vehicle level.
The particle damping in cradle helps in reducing the amplitude of the low frequency peaks responsible for the boom. The modal analysis has indicated a reduction in the modal frequencies by 10 to 15 Hz along with the reduction in the amplitude with the particle damping applied. The main advantage comes up in the frequency region above 200 Hz region where all the peaks get damped completely. The improved cradle has potential to show improvement in incab noise of the vehicle both subjectively and objectively. The main improvements are observed for the problems in the higher frequency range.
Localized damping of structures is also possible by optimizing the quantity of particles used for filling the structure by inserted pockets of damping particles into various strategic locations along the structure instead of the entire structure.

Advantages:
■ Improved NVH Performance.
■ Also used for chassis sections, cross members, driveline components etc
■ Implemented on all types of automobile vehicles
■ Minimal cost of implementation.
■ No Major Structural Modification required.
■ Implementation possible even at the final stage of vehicle development.
■ Can be used as an alternative for Tuned Mass Dampers.
■ Material cost is very less.

WE CLAIM
1. Non Obstructive Particle Damping (NOPD) for hollow structure in a vehicle comprises of plurality of hollow structural members configured for supporting the major vehicle components generating vibration; at least one type of damping particles configured to be filled in said plurality of hollow structural members and sealed to constitute the structural members of the vehicle to facilitate damping the vibration in the automobiles.
2. The NOPD for hollow structure in a vehicle as claimed in claim 1 wherein said plurality of hollow structural member comprises of cradle, chassis sections, cross members, driveline components etc
3. The NOPD for hollow structure in a vehicle as claimed in claim 2 wherein said cradle is configured to be mounted on the vehicle body through plurality of mounting locations viz. three front mounting locations (1) and two rear mounting locations (2).
4. The NOPD for hollow structure in a vehicle as claimed in claim 1 wherein said major vehicle components generating vibration comprises of the engine, gearbox and the suspension systems configured to be mounted on said cradle.
5. The NOPD for hollow structure in a vehicle as claimed in claim 2 wherein said cradle is made of at least four tubes fastened to each other.
6. The NOPD for hollow structure in a vehicle as claimed in claim 1 wherein said damping particles configured for NOPD are Lead particles and/or Steel/Cast Iron particles and/or Gravel/ Sand and/or Saw dust and/or Rubber granules or any other material used for damping.
7. The NOPD for hollow structure in a vehicle as claimed in claim 1 wherein said damping particle size/diameter and/ or shape are configured on the basis of its application and the amount of damping required.

8. The NOPD for hollow structure in a vehicle as claimed in claim 1 wherein said particle damping is configured for achieving high damping by converting kinetic energy of the structure to heat energy.
9. The NOPD for hollow structure in a vehicle as claimed in claim 1 wherein the maximum size of the particles is configured to limit to l/5th of size of the section in which they are to be inserted.
10. The NOPD for hollow structure in a vehicle as claimed in claim 1 wherein said damping particles configured to be in spherical shape.
11. The NOPD for hollow structure in a vehicle as claimed in claim 1 wherein said NOPD is configured to increase said damping properties of the structure by 50% and improvement in the frequencies above 200 Hz.
12.Non Obstructive Particle Damping (NOPD) for hollow structure in a vehicle comprises of plurality of hollow structural members configured to support the major vehicle components generating vibration; at least one type of damping particles configured to be filled in plurality of pockets with optimized/predetermined quantity of said particles and sealed; wherein said plurality of pockets are configured to be filled in said hollow structural members into various strategic locations along the structure for localized damping of said structures.