Title of Invention

IMPROVED BRAKE SYSTEM FOR AUTOMOBILES

Abstract

This invention relates to improved brake system for automobile comprises of a brake pedal with pedal motion sensor, compressed air source, circular disc with holes fitted at the end of valve assembly of vacuum booster, at least two flexible hoses are connected to said circular disc, one free end of said hoses is open to atmosphere and other free end is communicating to the air from intercooler via non-return valve, air reservoir & control valve. Brake pedal is connected to the booster purshrod with the help of clevis pin. In accordance with this invention the compressed air from the compressed air source is bled through a non return valve and stored inside the reservoir. A non return vale is provided to replenish and store air in the reservoir when some amount of air is used during braking. Air reservoir is provided with fins for further cooling the stored compressed air.

Full Text

FORM 2 THE PATENTS ACT 1970 (39 of 1970) & THE PATENTS RULES, 2003 COMPLETE SPECIFICATION (See Section 10; rule 13) TITLE OF THE INVENTION Improved Brake System For Automobiles 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 Mr. Anshuman Gupta, Mr. Badal G Bisen, both 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 to be performed. FIELD OF INVENTION This invention relates to the brake system of an automobile and more particularly it relates to hydraulic brake system with vacuum booster. BACKGROUND OF INVENTION All automobiles are provided with brake system to reduce risk of any mishap. Hydraulic brake system is one of the commonly used brake systems in cars, Utility Vehicles (UV) and Light Commercial Vehicle (LCV)s. Hydraulic brake circuit mainly consist of a brake pedal, vacuum booster, tandem master cylinder, fluid reservoir, disc/ drum brakes and bundy tubes. The force applied by the driver gets amplified and acts on the disc/ drum to stop the vehicle. There has to be a good co-relation/ relationship between the pedal effort applied, pedal travel, deceleration level achieved and stopping distance for "good brake feel". Brake feel also depends upon the time lag between the force applied on brake pedal and the response of braking system. Hence "brake feel" can be improved by reducing the response time of the brake system. Many vehicles are having "poor brake feel" complaints, pertaining to the above -mentioned reasons. Apart from modifications/ analysis done on disc/ drum brakes, brake pedal etc, the analysis of the brake booster has always being done considering the vacuum pump side of the diaphragm with modifications being suggested for the same like increasing the vacuum pump size or adding a vacuum reservoir. WO9605091 teaches pneumatic brake booster for motor vehicle which is able to dispense with a pressure reservoir for a brake booster that works with pneumatic overpressure and is actuated by means of a brake pedal, which consists of first 2 chamber on the brake pedal side of a movable wall which divides the booster housing into two chambers having a continuous connection with a compressed-air source and that when actuated, a control valve controlling the pneumatic pressure differential acting on the movable wall establishing a connection to the atmosphere for the second chamber on the side of the movable wall facing away from the brake pedal. The drawbacks associated with above said prior art is that in this case specially designed booster is required and it cannot be easily accommodated on the existing normal boosters and this prior art does not teach anything about knee point position, reaction time of braking system and stopping distance of the automobile. OBJECTS OF THE INVENTION The main object of this invention is to provide a brake system having better response time to enhance the "brake feel" of the automobile. Another object of this invention is to provide a brake system with an increased knee point position so as to increase the range of operation of booster and tandem master cylinder. Yet another object of this invention is to provide a brake system, which is simple in construction and cost effective. BRIEF DESCRIPTION OF INVENTION Improved brake system for automobile in accordance with this invention basically comprises of a brake pedal with pedal motion sensor, compressed air 3 source, circular disc with holes fitted at the end of valve assembly of vacuum booster, at least two flexible hoses are connected to said circular disc, one free end of said hoses is open to atmosphere and other free end is communicating to the air from intercooler via non-return valve, air reservoir & control valve. Brake pedal is connected to the booster pushrod with the help of clevis pin. When the brake pedal is pressed, due to inward motion of the booster pushrod, the valve assembly opens the passage between the diaphragm and external environment and simultaneously the control valve opens by taking the signal from the pedal motion sensor provided at brake pedal; because of which the compressed air enters into the push rod side of the diaphragm through the circular disc, which allows the translatory motion of the pushrod without any leakage of air because of provision of seals. The control valve opens only when there is forward motion of the brake pedal and all other times the valve is in closed position. The motion of diaphragm pushes the pistons of TMC to generate the required level of hydraulic pressure. The compressed air enters the booster axially and then flows radially outwards in a uniform fashion. In case of any failure in pressurized air circuit, said hose which is open to atmosphere takes care in supplying the desired quantity of air at atmospheric pressure for operation. This invention aims at reducing the response time of the brake circuit and thereby reducing the stopping distance and improving the "brake feel" of an automobile. The pressure on the push rod side of the brake booster has been increased to that above atmospheric pressure using a compressed air from the engine itself after getting cooled in intercooler. This invention would therefore enable the increase of differential pressure across the chamber of the brake booster, thereby improving the overall brake system performance. Also this 4 invention aims at reducing the size of booster & TMC assembly by keeping same performance characteristics. In accordance with this invention the compressed air from the turbocharger of the engine is bled through a non return valve and stored inside the reservoir. A non return valve is provided to replenish and store air in the reservoir when some amount of air is used during braking. Air reservoir is provided with fins for further cooling the stored compressed air. DETAILED DESCRIPTION OF INVENTION 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, Fig.l shows the layout of brake system in accordance with the invention Fig. 2 shows the close view of the valve body with circular disc and pushrod Fig. 3 shows a graph showing position of knee point and reaction time by this system as compared to conventional system Fig. 4 shows a graph showing stopping distance of automobile with this system as compared to conventional system for same pedal efforts Now referring to figs. 1 and 2 improved brake system comprises of a brake pedal (17) with pedal motion sensor (21), turbocharger (22) with intercooler (3), circular disc with holes (20) fitted at the end of valve assembly (19) of vacuum booster (7), flexible hoses (23,16) are connected to the said circular disc with holes. Free end of said hose (16) open to atmosphere and free end of said hose (23) is communicating to the air from intercooler (3) via non-return valve (4) , air reservoir (5) & control valve(6). 5 Brake pedal (17) transfers motion to vacuum booster (7) through a clevis pin (15) via pushrod (18). Said pushrod (18) slides through the circular disc (20) and actuates the valves present in valve body (19) thereby allowing air inside the booster axially. Intercooler (3) gets the compressed air from turbocharger (22) which consisting of a turbine (1) and compressor (2). The vacuum booster (7) in vehicles is used to give the required assist or boost during braking. It works on the principle of differential pressure. A diaphragm (8) separates the two chambers inside the brake booster (7). The push rod side of the brake booster (7) has a provision for air inlet and the other side is connected to the tandem master cylinder (12). When the engine is running, the vacuum pump (11) helps in maintaining equal level of vacuum on both sides of the diaphragm (8). Vacuum booster (7) is connected to vacuum pump (11) through a vacuum hose (10) and a non return valve (9). When the brake pedal (17) is applied, the push rod (18) of the brake booster (7) moves in through the sealing ring (24) of the circular disc (20) thereby closing the valve between the two chambers and allowing atmospheric air to come into the push rod side of the diaphragm (8). This creates a pressure difference between the two chambers and therefore the diaphragm (8) is pushed forward, giving an assist to the brake force applied by the driver. Vacuum booster (7) is connected to tandem master cylinder (12), which generates hydraulic pressure due to forward movement of booster pushrod (18). This hydraulic pressure gets divided into two hydraulic circuits (13,14) giving clamping force to brake assembly to stop the automobile. The compressor (2) of the turbocharger (22) compresses the atmospheric air to a relatively high value which then enters the intercooler (3) where the temperature of the compressed hot air is brought down. In this invention, some amount of air coming out of the intercooler (3) is bled and sent through the non return valve (4) to the finned air reservoir (5). Further cooling of compressed air is achieved with 6 the help of fins provided on the outer surface of the air-reservoir (5). A separate compressor or any other source of compressed air can also be used for supplying the compressed air. When brake pedal (17) is pressed, the push-rod (18) opens a valve in valve body (19), allowing compressed air from finned air reservoir (5), via hose (23), to enter the booster (7) on one side of the diaphragm (8) while sealing off the vacuum. This increases pressure on diaphragm (8) and assist the push rod (18), which in turn pushes the piston in the tandem master cylinder (12). The compressed air entering through the valve body (19) flows radially outwards inside the booster chamber in a uniform fashion leading to equal pressure application on the diaphragm (8) area. As the brake pedal (17) is released, the valve returns to its original position and prevents entry of outside air supply. This restores vacuum to both sides of the diaphragm (8). Due to compressed high pressure air on one side of diaphragm (8) and vacuum on other side, high differential pressure is created and hence pushrod (18) operates faster as compared to the earlier system of using air at atmospheric pressure at the pushrod side of vacuum booster (7). This higher differential pressure will lead to obtaining better brake booster characteristics in terms of response time as well as improved brake feel. As differential pressure between compressed air from finned air reservoir (5) and vacuum level in vacuum booster (7) is higher than the differential pressure between compressed air from finned air reservoir (5) and atmospheric air from hose (16), the air continues to travel from finned air reservoir (5) to vacuum booster (7) without any leakage. 7 A pedal motion sensor (21) is a potentiometer or brake light switch and is used to give brake pedal (17) position input signal to the control valve (6). Normally during NO brake application, this control valve (6) remains in closed and prevents entry of compressed air from reservoir (5) to hose (23). As soon as the brake pedal (17) is pressed, the control valve (6) opens taking signal from pedal motion sensor (21). This helps is minimizing the load on engine by optimally using the compressed air. Fig 3 shows a graph comparing conventional & brake system in accordance with this invention in relation to hydraulic pressure generation w.r.t time. Clearly there has been marked reduction in the response time of the brake system. This reduction of response time leads to "improved brake feel". Further, there has been increase in knee point and maximum pressure generation with this brake system leading to increase in the working range of TMC. Fig 4 shows a graph comparing conventional & brake system in accordance with this invention in relation to automobile stopping distance w.r.t time. Clearly there has been marked reduction in automobile stopping distance under same testing conditions. Since automobile stopping distance is related to the deceleration level achieved hence, driver will get a feedback of more deceleration level generation for same pedal efforts and would perceive improvement in "brake feel" The foregoing description is a specific embodiment of the present invention. It should be appreciated that this embodiment is described for purpose of illustration only, and that numerous alterations and modifications may be practiced by those skilled in the art without departing from the spirit and scope of the invention. It is intended that all such modifications and alterations be 8 included insofar as they come within the scope of the invention as claimed or the equivalents thereof. WE CLAIM 1. Improved brake system for automobiles comprises of master cylinder assembly, foundation brakes, fluid reservoir, vacuum pump, vacuum booster assembly, brake pedal, pedal motion sensor, control valve, compressed air source, circular disc with holes and at least one flexible hose wherein said circular disc is fitted at the end of valve assembly of said vacuum booster assembly, said at least one flexible hose is connected to said circular disc, free end of said hose is communicating to the air from said compressed air source through control valve, said brake pedal is provided with pedal motion sensor and is connected to the pushrod, said control valve is interfaced with pedal motion sensor. 2. Improved brake system for automobiles as claimed in claim 1 wherein said at least one flexible hose is connected to said circular disc near push rod of vacuum booster in order to have radial outward flow of air inside vacuum booster. 3. Improved brake system for automobiles as claimed in claims 1 and 2 wherein said compressed air source is turbocharger with intercooler of engine or air compressor unit. 4. Improved brake system for automobiles as claimed in claims 1 to 3 wherein said pedal motion sensor is a potentiometer or brake light switch. 5. Improved brake system for automobiles as claimed in claims 1 to 4 wherein said circular disc is further connected to at least one flexible hose and free end of said hose is open to atmosphere. 10 6. Improved brake system for automobiles as claimed in claims 1 to 5 wherein said vacuum booster assembly comprises of diaphragm, pressure disc and piston, push rod, valve assembly. 7. Improved brake system for automobiles as claimed in claims 1 to 6 wherein said compressed air source is connected to hose through nonreturn valve and air reservoir. 8. Improved brake system for automobiles as claimed in claim 7 wherein said air reservoir is provided with fins on outer surface to cool the compressed air. 9. Automobiles fitted with improved brake system as claimed in claims 1 to 8. 10. Improved brake system for automobiles substantially as herein described with reference to accompanying drawings. Dated this 24th day of September 2007. 11 ABSTRACT Title: Improved Brake System For Automobiles This invention relates to improved brake system for automobile comprises of a brake pedal with pedal motion sensor, compressed air source, circular disc with holes fitted at the end of valve assembly of vacuum booster, at least two flexible hoses are connected to said circular disc, one free end of said hoses is open to atmosphere and other free end is communicating to the air from intercooler via non-return valve, air reservoir & control valve. Brake pedal is connected to the booster pushrod with the help of clevis pin. In accordance with this invention the compressed air from the compressed air source is bled through a non return valve and stored inside the reservoir. A non return valve is provided to replenish and store air in the reservoir when some amount of air is used during braking. Air reservoir is provided with fins for further cooling the stored compressed air. Fig.l

Documents:

1876-mum-2007-abstract.doc

1876-mum-2007-abstract.pdf

1876-MUM-2007-CLAIMS(AMENDED)-(10-1-2012).pdf

1876-MUM-2007-CLAIMS(AMENDED)-(8-10-2014).pdf

1876-MUM-2007-CLAIMS(MARKED COPY)-(8-10-2014).pdf

1876-mum-2007-claims.doc

1876-mum-2007-claims.pdf

1876-MUM-2007-CORRESPONDENCE(20-11-2007).pdf

1876-mum-2007-correspondence-received.pdf

1876-mum-2007-description (complete).pdf

1876-mum-2007-drawings.pdf

1876-MUM-2007-FORM 13(10-1-2012).pdf

1876-MUM-2007-FORM 18(20-11-2007).pdf

1876-MUM-2007-FORM 8(20-11-2007).pdf

1876-MUM-2007-FORM 9(20-11-2007).pdf

1876-mum-2007-form-1.pdf

1876-mum-2007-form-2.doc

1876-mum-2007-form-2.pdf

1876-mum-2007-form-26.pdf

1876-mum-2007-form-3.pdf

1876-MUM-2007-GENERAL POWER OF ATTORNEY(10-1-2012).pdf

1876-MUM-2007-MARKED COPY(10-1-2012).pdf

1876-MUM-2007-REPLY TO EXAMINATION REPORT(10-1-2012).pdf

1876-MUM-2007-REPLY TO HEARING(8-10-2014).pdf

1876-MUM-2007-SPECIFICATION(AMENDED)-(10-1-2012).pdf

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