WO2022239031A1

WO2022239031A1 - Brake linings with improved nvh for commercial vehicles

Info

Publication number: WO2022239031A1
Application number: PCT/IN2022/050459
Authority: WO
Inventors: Muthukumar M.; Savitha S.; Balaji SRINEVASAN
Original assignee: Rane Brake Lining Limited
Priority date: 2021-05-14
Filing date: 2022-05-11
Publication date: 2022-11-17

Abstract

A brake lining (10) for a commercial vehicle drum brake system is provided. The brake lining (10) includes a brake shoe, a first layer (15), and a frictional layer (16). The frictional layer (16) improves the friction and wear performances of the vehicle drum brake system. The frictional layer (16) is attached to the brake shoe such that the first layer (15) is in between the brake shoe and the frictional layer (16). The first layer (15) and the frictional layer (16) are moulded together using a binder. The first layer (15) with enhanced thermomechanical properties improves the Noise Vibration and Harshness (NVH) characteristics of the brake lining (10).

Description

BRAKE LININGS WITH IMPROVED NVH FOR COMMERCIAL VEHICLES

FIELD OF THE INVENTION

The present invention relates to the field of vehicle drum brake system. More particularly, the present invention relates to noise, vibration and harshness (NVH) improvement of brake lining for commercial vehicles drum brake system.

BACKGROUND OF THE INVENTION

Generally, brake shoe is a part of a braking system which carries a brake lining in a drum brake used in a vehicle. The brake shoe carries the brake lining, which is riveted or glued to the brake shoe. When the brake is applied by driver, the brake shoe moves and presses the brake lining against the inside of the drum, friction generated between the brake lining and the drum provides the braking effort which helps driver to control the vehicle. The brake linings are composed of a relatively soft but tough and heat-resistant material with a high coefficient of dynamic friction, which is mounted to a solid metal backing using high-temperature adhesives or rivets. The complete assembly including the brake lining and the solid metal backing is then often called a brake shoe.

Since the brake lining is the portion of the braking system, which converts vehicle's kinetic energy into heat, the brake lining must be capable of withstanding high temperatures.

Brake linings for commercial vehicles like bus, truck etc., has unique combination of multiple materials to achieve desired performance. The specific performance parameter may include good friction (high performance), low wear (high life), and good NVH (noise free braking), among others. However, such asbestos free brake linings have relatively lower strength than asbestos type brake lining.

Original equipment manufacturers (OEM) prefer high friction characteristics in asbestos free brake lining. These are demanding requirements considering the new regulation on overloading of vehicles approved by Government bodies in existing vehicles. Hence, high friction characteristics in brake lining lead to Noise, Vibration and Harshness (NVH) issues leading to discomfort. In addition, high friction characteristics of brake lining can also lead to reduction in life of the product. Hence, brake lining while in service has to withstand such severity in duty conditions due to very high thermo-mechanical stresses under repeated braking events leading to elongation of the rivet hole compromising the strength of the brake lining. The loosening of the liner can lead to a noise issue.

Improvement of NVH by formulation design affects other properties like friction and wear characteristics in addition to being a costlier option because of specialty NVH additives that has to be used to improve NVH performance. More specifically, the improvements for NVH in brake lining will effect friction or wear characteristics or other properties of the product which are essential characteristics of a brake lining in deceleration or stopping the vehicle.

In view of the above discussion, none of the conventional methods comprehensively address all the key issues like performance, life & NVH of brake lining equally. Hence, there is a need for improved technique to address the above mentioned problems of the existing brake lining implements.

OBJECTS OF INVENTION

The primary object of the present invention is to provide noise, vibration and harshness (NVH) improvement of brake lining for commercial vehicle drum brake system apart from meeting the performance & life requirements. This is achieved by introducing an NVH friendly high strength composite layer to solve the problems associated with commercial vehicle brake lining used in the drum brake system.

It is another object of the present invention to provide a brake lining to overcome several aspects of brake system related issues like no riveting crack during fitment, and no liner loosening while in service.

It is another object of the present invention to provide brake linings riveted to a brake shoe of the commercial vehicles drum brake system with improved NVH performance.

It is another object of the present invention, wherein the high strength composite layer enhances NVH performance due to the inclusion of unique combination of materials and their resultant product properties. It is another object of the present invention, wherein by introducing the high strength composite layer, the NVH characteristic of the brake lining is improved together with the strength of the product without affecting the friction (braking performance) or wear (life) characteristics of the brake lining thereby improving the durability of the product without premature removal before end- of-life in service leading to overall cost economics.

SUMMARY OF THE INVENTION

One or more of the problems of the conventional prior art are overcome by various embodiments of the present invention.

In one aspect of the invention, a brake lining for a vehicle drum brake system is provided. The brake lining for a commercial vehicle drum brake system includes a brake shoe, a first layer and a frictional layer. The first layer enhances the NVH performance while the frictional layer improves the friction and wear performance of the vehicle drum brake system.

It is another aspect of the present invention, wherein the frictional layer is attached to the brake shoe such that the first layer is in between the brake shoe and the frictional layer.

It is another aspect of the present invention, wherein the first layer and the frictional layer are moulded together using a binder without any adhesive or glue for bonding.

It is another aspect of the present invention, wherein first layer and the frictional layer are integrally moulded under a temperature range of 125°C to 175°C, by applying a pressure ranging between 15MPa to 25MPa, for duration of 20minutes to form the brake lining.

It is another aspect of the present invention, wherein the brake lining when riveted using a plurality of rivets to the brake shoe of the vehicle drum brake system results in crack free performance during retro-fitment and in service.

It is another aspect of the present invention, wherein the first layer reduces the noise, vibrations and harshness of the vehicle drum brake system and withstands thermo mechanical stresses. It is another aspect of the present invention, wherein the first layer is composed of natural rubber based on butadiene and synthetic rubber based on copolymers of acrylates, styrene, butadiene, acrylonitrile, isocyanates, polyols and silicones.

It is another aspect of the present invention, wherein the first layer is composed of natural fibres and synthetic fibres for high strength characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

The manner in which the features, advantages and objects of the invention, as well as others which will become apparent, may be understood in more detail, more particular description of the invention briefly summarized above may be had by reference to the embodiment thereof which is illustrated in the appended drawings, which form a part of this specification. It is to be noted, however, that the drawings illustrate only a preferred embodiment of the invention and is therefore not to be considered limiting of the invention's scope as it may admit to other equally effective embodiments.

Fig. 1 illustrates an exploded view of a brake assembly fitted on an axle of a vehicle, in accordance with an embodiment of the present invention;

Fig. 2 illustrates the rivets used for riveting of brake linings to the brake shoe, in accordance with an embodiment of the present invention.

Fig. 3 illustrates the drill holes in brake linings for riveting, in accordance with an embodiment of the present invention;

Fig. 4 illustrates the drill holes are matched with the brake shoes for riveting, in accordance with an embodiment of the present invention;

Fig. 5 illustrates the brake linings are riveted to the brake shoes, in accordance with an embodiment of the present invention;

Fig. 6 illustrates the brake shoe assembly, in accordance with an embodiment of the present invention;

Fig. 7 illustrates the cross-section of a conventional brake lining, according to the prior art; and Fig. 8 illustrates the cross-section of the brake lining, in accordance with an embodiment of the present invention.

DESCRIPTION FOR DRAWINGS WITH REFERENCE NUMERALS:

(1) Brake chamber (2) Slack adjuster

(3) Brake camshaft

(4) S-cam brake

(5) Brake shoes

(6) Return spring

(7) Brake drum

(8) Rivets

(9) Drill holes

(10) Brake linings

(11) Brake shoe assembly

(12) Cracks

(13) Angular hole (prior art)

(14) Conventional brake lining

(15) First layer

(16) Frictional layer

(17) Angular hole (present invention)

DETAILED DESCRIPTION OF THE INVENTION

It is to be understood that the present disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. This particular form is only an exemplary embodiment and is not intended to be taken restrictively to imply any limitation on the scope of the present invention. The present disclosure is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

The present invention relates to the field of drum brake system. More particularly, the present invention relates to noise, vibrations and harshness (NVH) improvement of brake linings for commercial vehicles. Advantageously the present invention relates to a NVH improvement of a commercial vehicle brake lining having enhanced thermo mechanical properties for improved durability when riveted to a brake shoe. Fig. 1 illustrates an exploded view of an S-cam brake assembly fitted on an axle of a vehicle, in accordance with an embodiment of the present invention; the brake assembly includes brake chamber (1), slack adjuster (2), brake camshaft (3), S-cam brake (4), brake shoes (5), return spring (6) and brake drum (7).

The S-cam brake (4) is a foundation brake used on commercial vehicles with air brake systems. The S-cam brake is a drum brake that uses air brake chambers (1) and slack adjusters (2) to press the brake shoes (5) against the surface of the brake drum (7).

The brake chamber (1) is a component of a drum brake system. It is located in each wheel and connected to slack adjuster (2) through which force is transferred to the brake shoes (5). The function of the brake chamber is to exert force onto the brake shoes (5) so as to bring them into contact with the brake drum (7) and stop the vehicle with friction.

The slack adjuster (2) is a vital part of the foundation brake. It acts as a lever, forming the connection between the actuator and the brake camshaft (3). The function of the slack adjuster (2) is to compensate for wear in both brake lining and brake drum (7), while maintaining a constant stroke of the actuator.

In the drum brake system, the return spring (6) connects the two brake shoes (5) through angular hole (13). The primary function of the spring is to return the brake shoes (5) to its original position when the brakes are released.

Fig. 3 illustrates the drill holes (9) in brake linings (10) for riveting, in accordance with an embodiment of the present invention. The brake lining rivets (8), as shown in Fig. 2, are used to secure brake shoes (5) and brake linings (10) on the drum brake system of the vehicle. The drill holes (9) are machined in brake linings (10) to match with the brake shoes (5), as shown in Fig. 4 for riveting. The brake linings (10) are riveted to the brake shoes (5), as shown in Fig. 5 are attached to the brake shoe assembly (11), as shown in Fig. 6.

Fig. 7 illustrates the cross-section of a conventional brake lining (14), according to the prior art. The brake lining (14) includes a main frictional layer. Enhancing the main frictional layer for NVH through addition of NVH additives (rubber particles etc.,) will affect the strength or friction or life characteristics of the brake lining (14).

In an embodiment, an asbestos free brake lining have limited strength, this approach of NVH improvement further reduces the mechanical strength leading to stresses and cracks (12) during retro fitment or liner loosening or angular hole (13) elongation or drill hole (9) elongation as shown in Fig. 7, during service. Introduction of special materials (synthetic organic fibres etc.,) enhances the mechanical properties as well as NVH characteristics of the brake lining (14) and are not cost effective. Thus, these approaches of improving a brake lining (14) are not practical solutions for NVH resolution and have limitations on industrial applicability and commercial acceptance.

In contrast to Fig 7, the Fig. 8 illustrates the cross-section of the brake lining (10), in accordance with an embodiment of the present invention. The brake lining (10) for a vehicle drum brake system includes a brake shoe (5) as shown in Fig. 1, a NVH layer (also referred to as first layer in the claims section) (15) and a frictional layer (16). The frictional layer (16) improves friction and wear performance of the vehicle drum brake system while the first layer with improved thermo mechanical properties improves the NVH performance of the brake lining.

In an embodiment, the NVH layer (15) is made of a combination of materials for enhancing the NVH characteristics and improved strength of the brake lining (10). The NVH layer combined with the frictional layer (16) enhances the brake lining (10) performance. The performance includes strength, friction, life and noise characteristics and by enhancing these performance characteristics, the durability of the brake lining is greatly enhanced.

In an embodiment, the NVH layer (15) comprises of selected materials from a regular friction layer (16) material composition to enhance the mechanical characteristics of the brake lining (10). By selection of critical materials and increasing the dosage of such materials the NVH characteristics as well as mechanical characteristics of the brake lining (10) are improved. If such materials are increased in the frictional layer (16) itself, it will have negative impact on friction performance or life or noise. By formulating with special additives which has better NVH characteristics along with the selected materials from the frictional layer (16) as mentioned above, different combinations of NVH layers (15) are obtained by varying the properties as shown in Table 1. Table 1:

NVH improvement of commercial vehicle brake lining with improved durability

Formation of NVH Layer: NVH 1 to NVH5 is a composition based on different NVH additives as shown in Table 1. Illustrative examples of NVH additives includes the following materials: particles of natural rubber based on butadiene and synthetic rubber based on copolymers of acrylates, styrene, butadiene, acrylonitrile, isocyanates, polyols, silicones etc., but are not limited to these materials. By varying the combination of these materials and its dosages, particle size and shape etc., different product (called as brake lining) characteristics can be achieved as illustrated through examples NVH1 to NVH5.

In an embodiment, the thickness of the NVH is in the range of 4.5mm to 6.5 mm. the exact thickness of the NVH layers (15) may depend on the specific requirements of the brake lining (10) as per the product (vehicle type) requirement and the application as shown in Table 1.

In an embodiment, the NVH layer (15) is made of materials with high strength characteristics like natural fibres and synthetic fibers, among other high strength material suitable for such applications. The composition of the NVH layer (15) may be determined based on the strength requirements.

In an embodiment, the NVH layer is made of fibers, include but are not limited to fibres of synthetic types made from a polyamine, acyl chloride, acrylonitrile and polysaccharides, among other synthetic fibers. The fibers may be obtained by addition, condensation, carbonization or melting of minerals of silica, alumina, and zirconia, among others. Additionally, the NVH layer fibers may include fibres which are treated or coated or impregnated with special additives or polymers for improving the adhesion properties or surface tension, among other properties.

In an embodiment, the NVH layer (15) during manufacture of brake lining (10) for the vehicle drum brake system, the frictional layer (16) is attached to the brake shoe (5) such that the NVH layer (15) is in between the brake shoe (5) and the frictional layer (16). The NVH layer (15) and the frictional layer (16) are moulded together using a binder, under a temperature range of 125°C to 175°C, by applying a pressure ranging between 15MPa to 25MPa, for a duration of 20minutes depending upon the product being moulded and the combination of materials used in the NVH layer (15) and friction layer (16) to form the brake lining (10) as shown in Fig. 8.

In an embodiment, the brake lining (10) is riveted using a plurality of rivets (8) as shown in Fig. 2 to the brake shoe (5) of the vehicle drum brake system.

The NVH layer (15) in combination with frictional layer (16) is evaluated for special characteristics related to mechanical and NVH related properties. By comparing with the mechanical and NVH properties of the frictional layer (16), the enhancement by the NVH layer (15) is established well.

The NVH layer (15) has additional features like high strength characteristics leading to improved resistance to thermo-mechanical stresses during fitment and in service. The improved resistance results in crack free fitment during manual riveting of brake lining to shoes and also there will be no liner loosening or no angular hole (17) elongation during brake application as shown in Fig. 8. In contrast, the prior art as disclosed in Fig. 7 lacks all these advantages.

In an embodiment, the frictional layer (16) engages with the rotating drum (7) during brake application remains unchanged; and the friction or wear characteristics of the frictional layer (16) remain unchanged.

The present invention is clearly advantageous in providing a technical solution to the problems of the prior art. The present invention is advantageous in improving the NVH of the brake lining. Further, it is also advantageous in providing high strength characteristics to the brake lining leading to improved resistance to thermo-mechanical stresses during fitment and in service. Further, it is also advantageous in providing improved resistance resulting in crack-free fitment during manual riveting of brake lining to the brake shoes, and also there will be no liner loosening or no drill hole elongation or angular hole elongation during brake application. Thus, the overall performance of the brake lining is greatly enhanced leading to better durability in service.

Claims

WE CLAIM:

1. A brake lining for a vehicle drum brake system, comprising: a brake shoe; a first layer; and a frictional layer to improve friction and wear performance of the vehicle drum brake system, characterized in that, the frictional layer is attached to the brake shoe such that the first layer is in between the brake shoe and the frictional layer, and wherein the first layer reduces the noise, vibrations and harshness (NVH) of the vehicle drum brake system and withstands thermo mechanical stresses.

2. The brake lining according to claim 1, the first layer and the frictional layer are moulded together using a binder.

3. The brake lining according to claim 2, wherein first layer and the frictional layer are moulded under a temperature range of 125°C to 175°C, by applying a pressure ranging between 15MPa to 25MPa, for a duration of about 20 minutes to form the brake lining.

4. The brake lining according to claim 3, wherein the brake lining is riveted using a plurality of rivets to the brake shoe of the vehicle drum brake system.

5. The brake lining according to claim 1, wherein the first layer is made of natural rubber based on butadiene, and synthetic rubber based on copolymers of acrylates, styrene, butadiene, acrylonitrile, isocyanates, polyols and silicones.

6. The brake lining according to claim 1, wherein the first layer is composed of natural fibres and synthetic fibres for high strength characteristics.

7. The brake lining according to claim 1, wherein the thickness of the first layer is in the range of 4.5mm to 6.5 mm.

8. The brake lining according to claim 1, wherein the first layer together with the frictional layer improves the NVH performance characteristics and withstands thermo mechanical stresses leading to crack free performance while riveting and in service without affecting the friction and wear characteristics of the frictional layer thereby leading to enhanced durability in service.