F O R M 2
THE PATENTS ACT, 1970 (39 of 1970)
COMPLETE SPECIFICATION (See section 10 and rule 13)
1. TITLE OF THE INVENTION
ELECTRONIC HYDRAULIC CONTROL UNIT ASSISTED HYDRAULIC BRAKE SYSTEM
2. APPLICANT(S)
(a) NAME FORCE MOTORS LIMITED
(b) NATIONALITY INDIAN Company
(c) ADDRESS MUMBAI-PUNE ROAD,
AKURDI, PUNE 411 035,
MAHARASHTRA INDIA

FIELD OF INVENTION
The present invention relates to uni-booster (Hydraulic Booster) assisted Brake system with additional assistance in Fail Safe mode. More particularly, the present invention provides additional Brake assistance in case of fail safe mode through EHCU Hydraulic Brake assist feature.
BACKGROUND OF THE INVENTION
Brake system being used on the Vehicle is Uni-Booster (Hydraulic Booster) assisted. The assistance is taken from the hydraulic boost (ABS system feature) to reduce the pedal effort required for generation of pressure. Accumulator is used for fail safe mode to apply fluid under pressure to Uni-booster in case of pump / Engine fail or input loss condition.
In the prior art an U.S. Pat. No. 6,634,723 disclose an electro hydraulic control unit includes a valve body having a recess formed in a surface thereof and a circumferential wall which extends around the recess. The wall includes at least one widened portion. An electronic control unit is mounted over the recess. The electronic control unit carries a circuit substrate which extends over the widened portion of the valve body wall such that widened portion of the valve body wall forms a heat for an electronic component carried by the circuit substrate, including a motor connector extending into the recess. A pump motor is mounted upon the valve body surface opposite from the electronic control unit. An electronic connector extends from the motor through the bore formed in the valve body and connects to the motor connector mounted upon the circuit substrate.
In another prior art an U.S. Pat. No. 8,651,587 B discloses a hydraulic brake system equipped for anti-slip control and for active brake interventions has a self-priming pump. A pressure retention valve prevents the brake system’s low pressure accumulator and the wheel brake brakes from being evacuated below atmospheric pressure during sensitive brake operations. A two position valve deactivates the bias of the pressure retention valve by opening a fluid path from the low pressure accumulator to the pump when it is desired that the wheel brakes be retracted farther to reduce drag and excessive wear of the brake friction elements.
SUMMARY OF INVENTION
The objective of invention is to have additional Brake assistance for delivering high Brake Fluid pressure to Primary and secondary circuit lines in case of fail safe mode.

Brake system being used on the Vehicle is Uni-Booster (Hydraulic Booster) assisted. Accumulator is used for fail safe mode to apply fluid under pressure to Uni-booster in case of pump / Engine fail or input loss condition.
Therefore such as herein described there is provided an electronically controlled hydraulic brake system comprising: a driver operated brake foot pedal and uni booster for assistance to reduce the pedal effort for generating required pressure in master cylinder, displacing brake fluid into a brake circuit; a plurality of front and rear wheel brakes (LF, RF, LR, RR) with Brake Calipers; a dual discharge pump; a brake fluid (Dot 4) reservoir fitted with level sensor for brake fluid level and Uni booster reservoir filled with mineral oil; a plurality of wheel speed sensors (front and rear) configured for sensing the speeds of front and rear wheels in real time; a high pressure accumulator configured for storing the fluid under pressure. Pressurized fluid is supplied under pressure in case of fail safe mode, When no assistance is available from Uni Booster; a plurality of circuit / lines (primary and secondary) configured for supplying fluids to front and rear wheels respectively; wherein one side of the said discharge pump, pressurized fluid is used for Steering system for power steering assistance, while other side of the discharge pump, pressurized fluid is used for Hydraulic brake booster (uni-booster); and wherein electronically controlled hydraulic unit (ECHU) is configured for automatically modulating the pressure in the Primary and secondary circuit with respect to input / output pressure required to avoid slip at wheels. Pressure fluid is supplied to the Calipers at each wheel end, thereby generating the required torque to decelerate / stop the vehicle.
In other embodiment due to metal to metal sealing in uni-booster in case of pump fail condition, the input pressure to the uni-booster will be provided by accumulator but the fluid under pressure will reduce with respect to time due to fluid leakage through the metal to metal seal to output and finally to reservoir. This will reduce the assistance thus increasing the pedal effort to generate brake fluid pressure at Master Cylinder outlet.
To overcome the issue, HBA feature available in EHCU is used. EHCU senses the Brake pedal status whether Brake pedal is pressed / depressed, if pressed then sensor available in the EHCU will sense master cylinder pressure. In case there is no master cylinder pressure or reduction in the system pressure with respect to time, the EHCU will automatically generate the pressure in the Primary and secondary circuit through inbuilt pump and motor and will supply the pressurized fluid to the Caliper and thereby generating the brake torque in order to stop the vehicle.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 is a basic circuit diagram of uni-booster assisted Brake system with Dual Discharge pump in accordance with the present invention;
Figure 2 is a basic circuit diagram of uni-booster assisted Brake system with ABS in accordance with the present invention;
Figure 3 is a circuit depicting the use of HBA for pressure generation in Fail safe mode in accordance with the present invention;
DETAILED DESCRIPTION OF INVENTION
The present invention relates to the use of Hydraulic Brake Assist feature available in EHCU to assist Braking in uni-booster in fail-safe mode. EHCU senses the Brake pedal status, if pressed then sensor available in the EHCU will sense master cylinder pressure. In case there is no pressure or reduction in the system pressure with respect to time, the EHCU will automatically generate the pressure in the Primary and secondary circuit through inbuilt pump and motor and will assist the driver to decelerate or hold the vehicle.
Basic Foundation Brake system with uni-booster assistance can be easily explained with the help of following circuit diagram described in Fig 1. Uni-booster assistance is developed with the help of Dual discharge pump. One side of the pump pressurized fluid is used for Steering system for power steering assistance, while other side of the pump pressurized fluid is used for Hydraulic brake booster (uni-booster). This pressurized fluid assists the foundation brakes system to achieve the deceleration with lesser input pedal effort.
Figure 2 depicts the working of Foundation brake circuit and ABS (Antilock Braking system) control Unit. The pedal is applied by the driver to decelerate / stop the vehicle. Pressure in the tandem master cylinder is generated in proportion to the pedal leverage. This increases the force availability for generating brake system pressure. Then the assistance is provided by uni-booster (hydraulic booster) through pressurized fluid (Mineral Oil) being supplied by Engine driven dual discharge pump. When Brake pedal is pressed, Fluid path to the uni booster reservoir is blocked and back pressure is generated inside the chamber, which translates the Booster piston with high effort as per boost ratio of 21:1. It means the input force at push rod exclarated by booster ratio to give input to master cylinder.

From master cylinder the Brake fluid (Dot 4) under pressure is supplied to the EHCU through primary / secondary circuit. This pressurized fluid is input to the Electronic hydraulic control unit (EHCU). EHCU senses the Wheel speeds through wheel speed sensor and modulates the Pressure to avoid slip. H circuit is being used on the vehicle; Primary line supplies the fluid under pressure to Front, while secondary to the rear respectively.
In addition to the hydraulic assistance, accumulator is also provided on the uni-booster. This accumulator stores the fluid under pressure. Fluid from uni-booster enters the accumulator and compresses the nitrogen gas available on the other side of the diaphragm. Fluid under pressure gets stored in the accumulator. In case of failsafe (No uni-booster assistance), the one way valve at accumulator outlet allows fluid to enter the uni-booster thus providing the assistance for Brake system. Fluid under pressure will remain in the accumulator until fluid is delivered from accumulator for fail sade mode.
There is metal to metal sealing in uni-booster since rubber sealing cannot sustain high pressures and fatigue loading condition. Due to metal to metal sealing in case of pump fail condition, the input pressure to the uni-booster will be provided by accumulator but the fluid under pressure will not be able to stay permanently. The pressure will reduce with respect to time due to fluid leakage through the metal to metal seal to output and finally to reservoir. This reduction in pressure will reduce the assistance thus increasing the pedal effort to generate brake fluid pressure at Master Cylinder outlet. In Fig 1 Brake system with uni-booster is shown, the assistance is taken from the hydraulic boost to reduce the pedal effort required for generation of pressure. Accumulator is used for fail safe mode to apply fluid under pressure to uni-booster in case of pump fail or input loss condition.
The circuit as depicted in Fig 3 shows the basic working of Hydraulic brake assist feature. The present invention relates to the use of Hydraulic Brake Assist feature available in EHCU to assist braking in uni-booster in fail-safe mode.
EHCU senses the Brake pedal status whether Brake pedal is pressed / depressed, if pressed then sensor available in the EHCU will sense master cylinder pressure. In case there is no master cylinder pressure or reduction in the system pressure with respect to time, the EHCU will automatically generate the pressure in the Primary and secondary circuit through inbuilt pump and motor and will supply the pressurized fluid to the Caliper and thereby generating the brake torque in order to stop the vehicle. This way the Hydraulic brake assist feature assists the driver to decelerate or hold the vehicle as additional function in case of fail safe mode after accumulator.

Although the foregoing description of the present invention has been shown and described with reference to particular embodiments and applications thereof, it has been presented for purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the particular embodiments and applications disclosed. It will be apparent to those having ordinary skill in the art that a number of changes, modifications, variations, or alterations to the invention as described herein may be made in complete specification, none of which depart from the spirit or scope of the present when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.

WE CLAIM:
1. An hydraulic brake system assisted by electronically controlled hydraulic unit to generate the hydraulic pressure in the primary / secondary circuit automaticlaly in case of Fail safe mode (No assistance from hydraulic booster. Hydraulic brake system comprising:
a driver-operated pedal and uni-booster for assistance to reduce pedal effort for generating pressure in master cylinder and displacing brake fluid into a brake circuit;
a plurality of front and rear wheel brakes (LF, RF, LR, RR) with Brake Calipers;
a dual discharge pump; wherein one side of the said discharge pump supplies pressurized fluid for Steering system for power steering assistance, while other side delivers pressurized fluid for Hydraulic brake booster (uni-booster);
a brake fluid reservoir fitted with level sensors for brake fluid level and uni-booster reservoir, filled with mineral oil;
a plurality of wheel speed sensors (front and rear) configured for sensing the speeds of front and rear wheels in real time;
a high pressure accumulator configured for storing the fluid under pressure; Pressurize fluid is supplied in case of failsafe condition, when no assistance is available from uni-booster;
a plurality of circuit / lines (primary and secondary) used for supplying fluids to front and rear wheels respectively;
Wherein electronically controlled hydraulic unit (ECHU) is configured for automatically modulating the pressure in the Primary and secondary circuit with respect to input and output pressure required to avoid slip at wheels. Pressurized fluid is supplied to the calipers at each wheel end thereby generating the required brake torque to decelerate / stop the vehicle.

2. The hydraulic brake system, according to claim 1, wherein the pressurized fluid from Dual discharge pump is supplied to Uni Booster and hydraulic boost assists the brakes system of the vehicle to achieve the deceleration / stop the vehicle with lesser input pedal effort.
3. Wherein the said EHCU senses the wheel speeds through wheel speed sensor and modulates the fluid pressure to avoid slips. Inbuilt parts in EHCU - Pump, motor, accumulator and dump valves are used to reduce / generate the pressure output to caliper to avoid slip.
4. The hydraulic brake system, according to claim 1, wherein the said accumulator is configured for fail safe mode and to apply fluid under pressure to uni-booster in case of pump fail or input loss condition.
5. The hydraulic brake system, according to claim 1, wherein the uni-booster is having metal to metal sealing in order to sustain high pressures and fatigue loading condition. In case of pump fail condition, the input pressure to the uni-booster will be provided by accumulator but the pressure will reduce with respect to time due to fluid leakage through the metal to metal seal to output and finally to reservoir. This will reduce the assistance thus increasing the pedal effort to generate brake fluid pressure at Master Cylinder outlet.
6. The hydraulic brake system, according to claim 1, Wherein the assistance is taken from the hydraulic boost, a feature available in EHCU to reduce the pedal effort required for generation of pressure.
7. The hydraulic brake system, according to claim 1, wherein the said EHCU senses the brake pedal status, if pressed, then the sensor available in the EHCU senses the master cylinder pressure.

8. The electronically controlled hydraulic brake system, according to claim 1, wherein under condition that there is no pressure or reduction in the system pressure with respect to time, the EHCU is configured to automatically generate the pressure in the Primary and secondary circuit through inbuilt pump and motor and configured for assisting the vehicle to decelerate or hold / stop.