TITLE:

HIGH PERFORMANCE BRAKE FOR PASSENGER CAR AND LIGHT COMMERCIAL VEHICLES

FIELD OF THE INVENTION

This invention in general relates to the scientific field of mechanical engineering and relates to an automobile brake system. More particularly the present invention relates to drum brakes for vehicles and a high braking performance in the drum brake system for passenger cars and light commercial vehicles where the drum brakes are used in the rear axle.

BACKGROUND OF INVENTION

It has been found that in the braking system In passenger cars and light commercial vehicles, generally front wheels are fitted with calipers and rear axle with drum brakes.

During the brake application, the pressurized fluid operates the caliper and drum brakes to generate a force and con-espondingly stop the vehicle or hold it in a stationary or parked position.

To cater to the increasing vehicle weights, increasing speeds and to offer improved braking performance, drum assemblies have increased In size from 180mm dia meter to 295 dia meter till date to cater passenger car and utility vehicle application. However regarding the braking system for passenger cars and light commercial vehicles several innovations and attempts have proved ineffective in maintaining high performance of the braking system.

Several attempts have been made to provide an effective braking system for vehicles in general. However such efforts have not been conducive to passenger cars and light commercial vehicles. Firstly the proposal of bigger diameter brakes has resulted in increased cost and also packaging bigger brakes with in the available wheel size has been a problem.

Secondly proposing bigger diameter wheel cylinders has caused higher fluid volume displacement and has lead to increased pedal travel. Finally usage of high mu linings for higher performance has lead to brake squeal, high fade and lining wear.

The relevant prior art methods, which will deal with enhanced performance of the braking system, are as follows Canadian Patent Application No CA 2548197 describes a brake shoe key for attaching a railroad car brake shoe to a brake head has a stop which engages the brake head to limit the insertion of the key into the brake head's keyway. The stop is located on the key so that when it engages the brake head the knee of the key will engage the lug of the brake shoe and the tang of the key will be spaced from the brake head. This correctly positions the key for retaining the brake shoe while leaving space between the tang and brake head to permit access with a prying tool for subsequent safe removal of the key.

France Patent Application FR 2892534 discloses a brake assembly that consists of a clutch pedal, a brake pedal, and an accelerator pedal, each comprising a shoe plate and a connection unit that connects the shoe plate to a floor pan of a motor vehicle. The connection unit laterally extends with respect to the shoe plate while leaving a space located between the plate and the floor pan such that the unit is viewed from a driver seat. An energy absorbing padding is associated to each pedal. The padding Is located at the front and facing the space in a running direction of the vehicle,France Patent Application FR 2893687 claims a brake shoe that has a web integrated to an inner periphery of an arched rim and a lining integrated to an outer periphery of the rim, where the rim is made of friction material. The rim has reinforcing ribs on the inner periphery for modifying the rigidity of the rim along its length so as to obtain a uniform distribution of a braking pressure of the brake shoe on the entire width of the rim.

Japan Patent Application JP 10267061 describes a brake shoe for a magnetically levitating vehicle. In a nonmagnetic metal-made back plate tightened to a brake shoe mounting part of a vehicle, a plate-shaped friction material is layered to present a slide friction surface. The material is formed in plate shape by a carbon fiber reinforced carbon composite, layered in a surface of a heat absorbing plate, and is provided with a slide friction plate presenting the slide friction surface and a ceramic composite material-made friction suppressing block dispersedly arranged in the slide friction plate, so that a tip end surface carries partly the slide friction surface.

Japan Patent Application JP 2002081477 claims a brake shoe for a bicycle having braking performance improved in wet conditions, preventing a rim, when decelerated or stopped, from being excessively worn by the brake shoe for a bicycle while maintaining good performance in the wet conditions. The brake shoe for a bicycle, which has a rim contact portion with a braking face formed out of a non-sulfur cross linked polymeric compound cross linked by zinc methacrylate, is provided for solving means, and the brake shoe for a bicycle, which has a rim contact portion with a braking face formed of one polymeric compound selected from the group consisting of a butadiene rubber cross linked by peroxide and metallic ion cross linking structure and an acrylonitrile butadiene rubber, is provided for solving means.

Japan Patent Application JP 2002349615 discloses a brake shoe, of which the weight is reduced by reducing the amount of lining to be abandoned, while maintaining present brake performance by reducing the lining remained on a shoe rim, when used to the limit of abrasion thickness.
Japan Patent Application JP 56122883 claims a brake shoe having excellent braking performance and exhibiting an effect of inhibiting brake squeak, by blending collagen with a rubber friction material. 5-50pts.wt., pref, 20- SOpts.wt. Collagen is blended with lOOpts.wt. Rubber friction matehal. The mixt is molded with heating under pressure to obtain the desired caliper brake shoe for bicycles.

United States Patent Application US 20040129513 discloses a vehicle brake shoe assembly incorporating a plurality of extensions which projects through the brake friction material matrix to the outer friction surface of the brake shoe assembly. Each extension is configured to cooperate with the brake friction material matrix to engage a surface of an opposing friction element, increasing the static and dynamic friction performance of the assembly beyond that achieved from the engagement of the brake friction material matrix and the surface of the opposing friction element alone.

United States Patent Application No US 20020139439 describes as a vehicle brake shoe assembly having a rigid backing plate incorporating a plurality of extension which project through the brake friction material matrix to the outer friction surface of the brake shoe assembly .Each extension is configured to operate w\Xh the brake friction material matrix to engage a surface of an opposing friction element simultaneously with the friction element simultaneously with the friction material , increasing the static and dynamic friction performance of the assembly during initial use beyond that achieved from the application of either the brake friction material or the projections alone.

United States Patent Application US 4603763 claims a drum brake with two internal expanding brake shoes pivoted at substantially diametrically opposite axes. It incorporates the negative feedback of the brake shoe sliding friction forces to oppose the applied hydraulic brake actuating forces for the purpose of reducing variant in brake torque due to random or uncontrolled variations in the coefficient of friction between brake shoe and brake drum. The required brake shoe friction force feedback is accomplished by eliminating the normally leading brake shoe with its undesirable lock-up prone positive feedback and replacing it with a brake shoe pivoted about an axis diamethcally opposite the pivot axis of the normally trailing brake shoe. The location of the shoe pivots is chosen to establish the required feed back magnitude by use of lever ratios whose adequacy is verified by the force equilibrium equations of the brake system. The resulting unconventional location of the brake shoe pivots permits the sliding fiction forces between shoes and drum at both shoes to be applied as forces acting in a direction opposite the applied brake actuating hydraulic forces for forward vehicle motion.

The above prior art does not address the issue of an effective braking system for passenger cars and light commercial vehicles. It also does not solve the problem of enhancing safety by creating high torque output in such light vehicles but instead seeks to remedy peripheral issues of the braking system such as brake parts' wear and tear and brake sound. Further there is no effort to solve the issue of obtaining sufficient torque for the braking operation in a passenger car or light commercial vehicle.

The present invention differs from the various prior art and overcomes these problems by reconstructing the current design brake geometry for improving brake performance without modification in the brake size, wheel cylinder size and change in friction material.

Further it will be apparent to those skilled in the art that the objects of this invention have been achieved by providing this high performance braking system. Various changes may be made in and without departing from the concept of the invention. Further, features of some stages disclosed in this application may be employed with features of other stages. Therefore, the scope of the invention is to be determined by the terminology of the following description and the legal equivalents thereof.

SUMMARY OF THE INVENTION

This present Invention may be summarized, at least in part, with reference to its objects.
The foremost object of this invention is to present high performance brake for passenger car and light commercial vehicles.

Another object of this invention is to optimize the brake size so that packaging of rear brakes in passenger cars and light commercial vehicles is easy.

Another object of this invention is to handle higher braking performance, without any abnormal change in the dimensions or weight or cost associated with the normal, know drum brake assembly.

Another object of this invention is to maintain an adequate and effective brake torque even with unfavorable conditions of brake shoe friction.
Another object of this invention is to obtain higher torque through modifications in the existing brake system without any increased cost.

Yet another object of this invention is to obtain higher torque through modifications in the existing brake system and eliminating any increased pedal travel.

A further object of this invention is to obtain higher torque through modifications in the existing brake system without generating any marginal concerns such as brake squeal, high fade or lining wear.

These and other objects and advantages and features of the present invention will be more readily apparent when considered in reference to the following description.

Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention.

DESCRIPTION OF THE DRAWING

Figure 1 is a cross sectional diagram of the present invention which is used as reference for the following description and claims.

DETAILED DESCRIPTION OF THE INVENTION

The following description is presented to enable any person skilled in the art to make and use the invention, and is provided in the context of particular applications of the invention and their requirements. The present invention can be configured as follows:

The drum brake assembly consists of a back plate (1), lined leading shoe (2), lined trailing shoe (3), wheel cylinder assembly (4), auto adjuster assembly (5), hand brake lever (6), shoe hold down springs (7) and shoe return springs (8). The wheel cylinder assy is bolted to the backplate (1) and the lined leading shoe (2) and lined trailing shoe (3) are assembled onto the backplate (1) with the help of shoe hold down springs (7) and shoe return springs (8). When the wheel cylinder assembly (4) is pressurized, pistons in wheel cylinder push the lined leading shoe (2) and the lined trailing shoe (3) and because of the drag force, torque is generated.
The efficiency or Brake factor of drum brake is given by = Tangential drum force / input force for the conventional brake geometry, Theoretically from brake geometry calculation, the distance between the brake center and the shoe butting point on the back plate abutment will have an influence in the torque output of the brake.

The present invention inserts an elongated back plate locating plate (10) made of Fe540 and heat treated material into the existing brake assembly instead of the present backplate locating plate, An extension is provided for supporting the lined leading shoe (2) and the lined trailing shoe (3). This results in reduction of distance between the brake centre and the brake shoes on the backplate location plate (10). This results in high performance brake.

The above insertion of a backplate locating plate (10) and subsequent reduction in the distance between the brake center and the shoe butting point on the back plate abutment leads to the increased torque output. Compared to a conventional brake assembly, the present invention generates more torque for the same input pressure.

To validate the efficacy of the present invention, prototype samples of 180 dia x 40 mm hydraulic auto adjust service; fonward pull brake assemblies containing the features of the present invention, was developed for the test purpose. A conventional 180 dia x 40 mm hydraulic auto adjust service, forward pull drum brake assembly was taken up for testing to compare the differences in brake output torque. The wheel cylinder diameter, friction lining area, grade and test inertia for both designs above were maintained at constant. Inertia dynamometer test was then carried out on the conventional design and on the present invention
to compare the input / output relationships.

Dynamometer tests were further carried at various vehicle speed and pressures. The input hydraulic pressure and torque output at each speed / pressure level was recorded.

The pressure and brake output torque for the conventional design and the present invention at vehicle equivalents speeds of 20 kmph 40 kmph, and 105 kmph respectively was calculated. An average increase of around 30% in brake torque output in the present invention for the same pressure input was observed. The increase in output agrees with the premises of the present invention and marginal difference can be attributed to friction material sensitivity, fractional losses etc.

Low mu linings can be used with the present invention thereby reducing noise, fade, and grabbing. The present invention can be incorporated into any type of drum brake.

While there has been shown and described what is considered to be preferred embodiments of the invention, it will, of course, be understood that various modifications and changes in form or detail could readily be made without departing from the spirit of the invention. It is therefore intended that the invention be not limited to the exact forms described and illustrated, but should be constructed to cover all modifications that may fall within the scope of the above description.

It will be apparent to those skilled in the art that the objects of this invention have been achieved by providing the above invention. However various changes may be made in the structure of the invention without departing from the concept of the invention. Therefore, the scope of the invention is to be determined by the terminology of description and the legal equivalents thereof.

CLAIMS

What is claimed is:

1. A high performance brake for passenger car and light commercial vehicles comprising of a drum brake assembly containing a back plate (1), lined leading shoe (2), lined trailing shoe (3), wheel cylinder assembly (4), auto adjuster assembly (5), hand brake lever (6), shoe hold down springs (7) and shoe return springs (8) characterized in that said drum brake assembly contains an elongated back plate locating plate (10) made of Fe540 material with heat treatment for locating said lined leading shoe (2) and lined trailing shoe (3).

2. The high performance brake for passenger car and light commercial vehicles as claimed in Claim 1 wherein an extension is provided for supporting said lined leading shoe (2) and said lined trailing shoe (3) resulting in reduced distance between the brake centre and the brake shoes on said backplate locating plate (10).

3. The high performance brake for passenger car and light commercial vehicles as claimed in Claim 1 wherein said brake assembly contains low mu linings.

4. The high performance brake for passenger car and light commercial vehicles as claimed in Claim 1 wherein said elongated back plate locating plate (10) is made of Fe540 material with heat treatment.

5. The high performance brake for passenger car and light commercial vehicles as claimed in Claim 1 wherein a wheel cylinder assy is bolted to said backplate (1) situated on said elongated back plate locating plate (10).

6. The high performance brake for passenger car and light commercial vehicles as claimed in Claim 1 wherein said lined leading shoe (2) and said lined trailing shoe (3) are assembled onto said backplate (1) situated on said elongated back plate locating plate (10) with the help of said shoe hold down springs (7) and said shoe return springs (8).

7. The high performance brake for passenger car and light commercial vehicles as claimed in Claim 1 wherein the pressure and brake output torque for the conventional design and said high performance brake at vehicle equivalents speeds of 20 kmph 40 kmph, and 105 kmph respectively yields an average increase of around 30% in brake torque output in high performance brake.