Title of Invention

A DEVICE WHICH ENHANCES THE RESPONSE OF THE VACUUM ASSISSTED SERVO BRAKING SYSTEM OF AN AUTOMOBILE IN A PANIC BRAKE CONDITION

Abstract ABSTRACT An electronic device, which enhances the response of the vacuum assisted servo braking system of an automobile in a panic brake condition, consisting of a pedal force rate sensor positioned between a top plate and bottom plate and fixed on to the brake pedal. The electronic circuit device takes decision depending on the sensor input, to energise or de-energise an electromagnetic dc operated normally closed solenoid valve, which on energizing allows the atmospheric air to the rear shell of the servo and collapses the vacuum.
Full Text

This invention pertains to the field of automobile industry and more particularly relates to braking system of automobiles.
While braking of an automobile, under normal condition the output force from the servo output rod is proportional to pedal effort and boost ratio of the servo. When the rate of force generated on the brake pedal exceeds the normal rate, the boost ratio of the servo comes down drastically. So the driver feels that the pedal is hard in such panic conditions. In other words, the brake force developed at the wheels for a given pedal effort is lower in panic conditions compared to normal braking conditions. Hence the brake force generated at the ground due to brake hydraulic pressure will be less than the available ground reaction force in panic conditions due to the time lag in pressure build up. The brake force developed at the tire to the road contact patch is directly proportional to the hydraulic brake pressure which in-turn depends on the force exerted by the servo output to the master cylinder input rod. The brake force naturally depends on the driver's response and skill, which are entirely individualistic and cannot be dependable during panic braking. Hence the stopping distance of an automobile will be more in panic brake conditions. To dynamically reduce the time lag in developing the brake force at the vehicle wheels of an automobile, a fast responding intelligent brake booster system is needed. The said device is a fast responding electronically actuating system servo.
It is to be noted that the prior art description gives in detail Information of the technology, method, process and system known in the art. It explains

the deficiency in the related art and the object of the invention being to overcome or surmount the problem associated with the prior art. This forms the essential feature and the object of the invention.
A search for patents in the relevant area of technology using various data bases was conducted. From the search the following documents were identified. A thorough examination of patents has been done. The results of the finding are summarized below :
A cited US Patent application US 5,590,937 dot. Jan 09, 1997 filed by Lucas Industries public limited company, United Kingdom relates to an invention having an electromagnetically operated valve located in the valve body and requires modification of existing brake booster unit and uses the output from a load sensor to actuate the valve. In the present invention, the electromagnetically operated valve is not located in the valve body and hence requires no modification of the brake booster, except drilling a hole in the booster shell. Also, the actuation of the electromagnetic valve is through the signal from a pedal rate sensor located outside the servo unit unlike the load sensor fitment inside the booster in the cited patent.
A cited US Patent application US 6,044,750 dot. Apr 04, 2000 filed by Lucas Industries public limited company, United Kingdom relates to an invention having an electromagnetic actuation unit received in the control valve housing having an insert made of diamagnetic material for improving magnetic flux.

A cited US Patent application US 6,272,969 Bl dot. Aug. 14, 2001 filed by Lucas Industries pick (GB) relates to an invention having an electromagnetically operated valve located in the valve body and requires modification of existing brake booster unit.
A cited US Patent application US 5,735,581 dot. Apr 7, 1997 filed by Lucas Industries public, Sol hull, United Kingdom relates to an invention of a pneumatic brake booster having an additional valve seat, which provides an additional ventilation duct.
In order to eliminate the deficiencies in the related prior art, the applicant had made elaborate research and invented an electronically assisted vacuum servo comprising a brake booster having an electromagnetically operated dc normally closed solenoid valve arrangement, an electronic control device which permanently senses the signals from the pedal rate sensor, compares the rate with a predetermined value and suitably actuates the electromagnetic solenoid valve during a panic brake application, a pedal rate sensor connected with the electronic control device for sensing pedal travel rate.
Therefore it is the principal object of the invention to provide a device to boost the hydraulic brake pressure of an automobile in panic condition by collapsing the vacuum in the rear shell of the servo by an external agency. In accordance with the aforesaid objective, there is provided a device that enhances the response of the vacuum assisted servo braking system of an automobile in a panic brake condition. The vacuum is collapsed in emergency condition to assist/ boost effectively the drivers' input brake pedal force by an air solenoid. The air solenoid is dc operated one port, two position normally closed valve. The solenoid is consisting of a plunger guided in a metallic member, which upon excitation opens the port to allow atmospheric air inside the servo shell during the control brake cycle of an automobile containing vacuum assisted servo.

The said device, according to the invention is an electronically assisted vacuum servo, in which a pedal rate sensor (9) gives a voltage output across the points (1) and (2) to the electronic circuit (11) depending upon the rate of pedal application. The circuit decides to energies or reenergize the solenoid valve (13) fitted on to the rear shell (12). In normal condition both the front and rear chambers are connected to the vacuum source (engine or vacuum pump) in vacuum assisted servos. When brake is applied, the front and rear shells first get isolated by a valve and further pressing of the pedal opens one more valve to allow atmospheric air into the rear shell. The pressure difference between front and rear shell of the servo will give a boost ratio. But in panic conditions due to the lower rate in airflow from atmosphere to the rear shell compared to the pedal travel rate, the boost ratio will be less.
The said device wilt sense the pedal rate, take decision and send signals (5) & (6) to energies or de-energies the air solenoid valve (13) fitted on to the servo shell of the servo (12). It opens or closes the orifice (20) and allows or stops the atmospheric air to flow from hole (21) in to the servo rear shell (12) through the port (22). Hence an enhancement in the response of the servo is observed under panic conditions. Hence a parallel path exists to the existing manually operated valve for the airflow and hence a boost in the boost ratio is observed. The electronic control circuit will be energized by vehicle battery + eV terminal (3) and -eV terminal (4).

The invention will now be described, by way of example, with reference to the accompanying drawing in which, the construction of the device is as shown in Fig.l and the arrangement of the internal parts of the solenoid are shown in Fig.2.
The solenoid is a dc operated one port, two position normally closed valve (13) consisting of a plunger (14) guided in a metallic member (15) and a spring (16) housed in a base (17) surrounded by an electromagnetic coil (18) covered with a magnetic material (19). Upon excitation of the electromagnetic coil (18) from a dc power source opens the orifice (20) against the spring (16) to allow atmospheric air inside the shell of the servo during the control brake cycle of an automobile containing vacuum assisted servo.
During brake application the pedal rate sensor (9) gives a voltage output across the points (1) and (2) of the electronic circuit (11) depending upon the rate of pedal application. The pedal rate sensor (9) is positioned between a top plate (7) and bottom plate (8) and fixed on to the brake pedal (10). The sensor generates a voltage directly proportional to the rate of change of force. It is fitted on to the brake pedal such that when a brake is applied, the force is passed on to the brake pedal through the sensor. The electronic circuit conditions the input signal, amplifies & compares it with a set panic rate level. If the sensor output rate is more than the set level, then it sends signals (5) &. (6) to energies the air solenoid valve (13). An electromagnetic air solenoid valve (13) fitted on to the servo shell of the servo (12). On energizing, it opens the orifice

(20) and allows the atmospheric air to flow from hole (21) in to the servo rear shell (12) through the port (22). Hence an enhancement in the response of the servo is observed under panic conditions. Therefore a parallel path exists to the existing manually operated valve for the airflow and hence a boost in the boost ratio is observed.
The invention has been explained in relation to specific embodiment. It is inferred that the foregoing description is only illustrative of the present invention and it is not intended that the invention be limited or restrictive thereto. Many other specific embodiments of the present invention which come within the scope of the claims are to which the present invention is readily susceptible without departing from the spirit of the invention.
The scope of the invention should therefore be determined not with reference to the above description but should be determined with reference to appended ciaim along with full scope of equivalents to which such claims are entitled.


I/We claim ;-
1) An electronically assisted vacuum servo comprising a brake booster
having an electromagnetically operated dc normally closed solenoid
valve arrangement, an electronic control device which permanently
senses the signals from the pedal rate sensor, compares the rate with
a predetermined value and suitably actuates the electromagnetic
solenoid valve during a panic brake application, a pedal rate sensor
connected with the electronic control device for sensing pedal travel
rate.
2) An electronically assisted vacuum servo as claimed in claim-1 wherein
the said pedal rate sensor is fitted on to the brake pedal.
3) An electronically assisted vacuum servo as claimed in claim-1, wherein
the said electronic control circuit takes input voltage from the sensor,
and controls the servo output,
4) An electronically assisted vacuum servo as claimed in claim-1, wherein
the said air solenoid valve is fitted on to the servo
shell of the servo.
5) An electronically assisted vacuum servo as herein described with
reference to the accompanying drawings.


Documents:

0786-mas-2001 abstract.pdf

0786-mas-2001 claims.pdf

0786-mas-2001 correspondence-others.pdf

0786-mas-2001 correspondence-po.pdf

0786-mas-2001 description (complete).pdf

0786-mas-2001 drawings.pdf

0786-mas-2001 form-1.pdf

0786-mas-2001 form-19.pdf


Patent Number 198667
Indian Patent Application Number 786/MAS/2001
PG Journal Number 08/2007
Publication Date 23-Feb-2007
Grant Date 25-Jan-2006
Date of Filing 21-Sep-2001
Name of Patentee BRAKES INDIA LIMITED
Applicant Address PADI, CHENNAI - 600 050 TAMIL NADU
Inventors:
# Inventor's Name Inventor's Address
1 H. RAMASUBRAMANIAN DIVISIONAL MANAGER (ADVANCED ENGG.) BRAKES INDIA LIMITED PADI, CHENNAI - 600 050 TAMIL NADU
PCT International Classification Number B60T13/68
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA