-2-
FIELD OF INVENTION
This invention relates to an electronic parking brake system. The system
can be operated manually/automatically to prevent locking of rear
wheels in dynamic condition by applying optimum braking force for
vehicles without "wheel speed sensor and their controlling mechanism to
judge 86 control wheel locking".
BACKGROUND/PRIOR ART
Parking brake system of vehicle is classified into mechanical and
electronic parking brake system. Said mechanical system comprises a
lever, which occupies space between front seats and also requires effort
for its operation with no offer of features for automatic
application/Automatic release/Hill Hold.
The above system may lead to locking of rear wheels during sudden
application of parking brake in dynamic condition, thereby causing
unstability in the vehicle dynamic behavior.
In order to obviate the aforesaid shortcomings, electronic parking brake
system was introduced in the automobile industry. However, this
electronic system has been devised taking into consideration maximum
vehicular mass (when the vehicle is loaded to maximum). Therefore
maximum vehicle loading is used to determine the braking force.
Hence, higher braking force in accordance to maximum vehicle mass is
applied on the rear wheels, which is unnecessary and therefore reduces
useful life span of the system.
Further, the known electronic parking brake system is installed with Anti
lock braking system (ABS)/Electronic Stability Program (ESP) to check
rear wheels locking. These additional features render the system
expensive, therefore finding space particularly in high end vehicles.
-3-
In view of the above, there is a need to develop an electronic parking
brake system which can overcome limitations of the prior arts and at the
same time can function efficiently being cost effective.
Now, reference may be made to the following Publication/Patent:
A known art discloses a method involving driver-independent applying of
an increasing drive moment to holding wheels during presence of a
standstill. An electrical parking brake is arranged at the holding wheels.
Brake torque of a service brake is reduced at the holding wheels by
simultaneously measuring wheel acceleration and/or wheel speed or
wheels e.g. front left wheel. The parking brake at the holding wheels is
activated, when the measured wheel acceleration and/or the wheel speed
at the holding wheels is lowered below a preset holding threshold level at
the service brake.
This takes into account maximum mass of the vehicle without estimating
actual mass. Therefore maximum value of the mass is utilized to obtain
required braking torque.
JP 2008298016:An ECB (Electronically Controlled Brake) device applies
or releases a parking brake by the drive of a motor. The ECB device
controls a braking force applied to a vehicle based on an operation input
by a driver. A battery supplies electric power to an EPB (Electronic
Parking Brake) device and the ECB device. A capacitor is for use in the
back-up of the battery and commonly used for the EPB device and the
ECB device. A vehicle speed restriction demand part determines whether
electric power necessary for stopping the travelling vehicle by the ECG
device and operating the parking brake by the EPB device is charged to
the capacitor or not, and requests an engine ECU to restrict vehicle
speed if it is determined that the electric power is not charged.
-4-
This involves estimation of vehicle mass to manipulate the electrical
system of vehicle responsible for braking, wherein mass of vehicle is
measured by means of sensor.
None of the above can fulfill requirements of the present invention.
Hence the present invention has been proposed.
OBJECTS OF THE INVENTION
A primary object of the present invention is to propose an electronic
parking brake system which addresses issues related to prior arts.
Another object of the present invention is to propose an electronic
parking brake system which automatically engages/disengages parking
brake according to requirement.
Still another object of the present invention is to propose an electronic
parking brake system which is cost effective and reliable.
Further object of the present invention is to propose an electronic
parking brake system, which can be operated in automatic as well as in
manual mode.
Yet another object of the present invention is to propose an electronic
parking brake system which takes into account actual mass of the
vehicle to obtain optimum braking force to be applied on rear wheels to
prevent rear wheel locking in dynamic state and increase useful life
span of system.
Still another object of the present invention is to propose an electronic
parking brake system which is workable without ABS/ESP system and
can support ABS/ESP system.
-5-
SUMMARY OF THE INVENTION
The system is directed to electronically operated parking brake system
which works independent of ABS/ESP in a manual transmission or
automatic transmission vehicle. It receives input from a system of
sensors to control parking brake force and provide additional driver
assist functions like automatic operation and release of parking brake,
holding the vehicle (avoiding roll back) on an inclined plane when there is
no driver intent to move. The system is developed taking into account
inputs from various sensors to judge vehicle condition and decide the
amount of force in the parking brake cable connected to rear wheels.
Certain inputs are also taken from the ECU of vehicle according to the
requirement. The type of control is closed loop control and the whole
system is monitored by an internal microcontroller i.e. ECU of EPB
System.
The EPB system of instant invention applies required amount of braking
force on rear wheels by making use of actual mass of vehicle thereby
improving system's life span.
This system prevents the rear wheel lock during parking brake
application in dynamic condition of the vehicle by applying optimum
amount of braking required for any loading condition. The said feature
thereby increases the safety and improves the stability of the vehicle.
Independent claim indicates inventive features and dependent claims
indicate various other features of present invention.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Further objects and advantages of this invention will be more apparent
from the ensuing description when read in conjunction with the
accompanying drawings of exemplary embodiments of invention and
wherein:
Fig. 1 shows: Block diagram of present invention.
Fig. 2 shows: Flow chart regarding operation of parking brake
system of present invention.
DETAIL DESCRIPTION OF THE PRESENT INVENTION WITH
REFERENCE TO THE ACCOMPANYING DRAWINGS;
The invention embodies electronic parking brake system with a
procedure (software) for the application of parking brake in the
static/dynamic condition of the vehicle. The procedure is established so
as to prevent the wheel lock due to parking brake application in dynamic
condition. The vehicle in discussion is not based on ABS/ESP and hence,
the procedure is devised taking into consideration non availability of
wheel speed sensors and other ABS/ESP hardware and software. It
determines the current mass of the vehicle from the acceleration of the
vehicle, the driving force acting on the vehicle and the gradient of road
surface on which motor vehicle is moving. The acceleration data and
gradient data are obtained from the internal sensing mechanisms in the
vehicle and the driving force on the vehicle through Electronic Control
Unit (ECU) of vehicle or can be obtained from clutch output torque.
Based on the total vehicular mass, the vehicle rear axle loading can be
determined. This is carried out through an internal map which contains
the data of variation of the rear axle loading with total vehicular mass.
Once the vehicle mass/rear axle loading is determined, braking force is
controlled so that system lifespan increases and rear wheel lock can be
prevented during the sudden application of parking brake in dynamic
condition.
The system takes input from several internal sensors like accelerator
pedal sensor/clutch pedal sensor, inclination sensor, vehicle speed
sensor and other inputs from vehicle ECU to automatically
engage/disengage the parking brake whenever necessary. The amount of
braking force that is to be applied on the cable can be deduced via mass
of vehicle and road gradient so as to obtain only the minimum required
braking i.e. optimum braking force which can hold vehicle in static
condition and which can maintain the vehicle in a stable condition while
braking in dynamic condition.
Now referring to fig. 1, Actuator Assembly (1) comprises of Electronic
Control Unit (ECU) (2) connected to Hardware part of Electronic Parking
Brake (3). Hardware part (3) comprises of motor &, gear mechanism along
with other internal sensors 8& necessary elements .Electronic control unit
(ECU) (2) of actuator assembly (1) is provided in connection with
accelerator pedal (A) and clutch pedal (B) to receive electronic command
regarding position of accelerator and clutch respectively.
Further, the electronic control unit, ECU(2) is also provided in
communication with ECU of vehicle through communication network
such as CAN Line (C) for the receipt of Driving force on vehicle/clutch
torque output, vehicle speed/engine speed and gear position as input
signal.
Further, there is connectivity of inclination and acceleration sensor (5)
with the electronic control unit (2) for being fed with angle of inclination
(6) of road surface on which motor vehicle is drivenand acceleration (a) of
the vehicle respectively.
Alternatively, single sensor can be used to give both acceleration and
gradient information.
-8-
Thus, the electronic control unit (2) is networked with various sensors to
retrieve input variables therefrom.
The above inputs regarding driving force on the vehicle, speed of vehicle,
gear position, accelerator position, clutch position, inclination (9) and
acceleration of vehicle are processed through electronic control unit (2) of
actuator assembly to obtain optimum braking force by using actual mass
of vehicle following which the electronic control unit (ECU) (2) actuates
hardware part (3) of (EPB) by means of actuation signal. Upon actuation,
the EPB unit apply/release the optimum braking force on the rear
wheelsso as to prevent locking of the wheels (R) in dynamic state of
vehicle and increase lifespan of system.
Actual mass of the vehicle relies on the following factors:
- Driving force (F)
- Current Acceleration (a)
- Inclination (9) of vehicle with the ground.
As can be seen in the figure, the clutch pedal (B) in connection with
clutch (H) located between Transmission (T) and Engine (E).
Transmission (T) connected to front wheel (F) through respective drive
shaft (S).
There is provision of a means in the form of switch (4) for using parking
brake system of invention in manual/automatic mode for which
reference may be made to fig. 2, which is self explanatory particularly to
a person skilled in the art regarding operation of the present system in
manual as well as in the auto mode. However, following can be
summarized from the flow chart.
Auto Mode: Auto Mode is meant for Static Condition only.
System monitors all input variables and determines Vehicle mass, M
depending upon driving Force, F current acceleration, a and road surface
inclination,9.
-9-
Upon checking existing vehicle conditions, inclination,9 and total
mass,M system modulates motor working to apply/release optimum
parking brake force, Bf
Manual Mode: Manual Mode can be used for Static/ Dynamic condition.
Upon receiving driver input in manual mode, System checks for vehicle
speed to decide whether it is Static Braking or Dynamic Braking case.
Static Braking - System works similar to Auto mode by Checking
variables (road surface inclination,9) and determining Total mass,M to
modulate motor working to apply/ release optimum parking brake
force, Bf
Dynamic Braking - For Dynamic braking condition, system determines
total masSjM based on input variables. Rear axle loading.Mris estimated
from total mass so as to apply safe value of braking force, Bfd to prevent
rear lock 85 maintain vehicle stability.
The present invention can be made compatible with anti brake locking
system (ABS)/Electronic stability program (ESP).
Advantageous Features
- Cost effective
- Long life span
- Safe in the absence of ABS/ESP (Electronic Stability Program) by
preventing locking of rear wheels in dynamic condition.
It is to be noted that the present invention is susceptible to
modifications, adaptations and changes by those skilled in the art. Such
variant embodiments employing the concepts and features of this
invention are intended to be within the scope of the present invention,
which is further set forth under the following claims:-

WE CLAIM:
1. An electronic parking brake system comprising a novel actuator
assembly, which processes various input variables for optimum
braking force to be applied on the rear wheels of vehicle to
prevent locking thereof in dynamic condition and maintain
stability of vehicle.
2. An electronic parking brake system as claimed in claim 1,
wherein the actuator assembly comprising an electronic control
unit installed with a software provided in communication with
hardware part of electronic parking brake unit, which is
connected to rear wheels by means of parking cable.
3. An electronic parking brake system as claimed in claim 1 or 2,
wherein the hardware part is mounted on the rear wheels.
4. An electronic parking brake system as claimed in any of the
preceding claims, wherein the electronic control unit is
connected to accelerator pedal, clutch pedal, inclination and
acceleration sensor, and electronic control unit of vehicle for
being fed with input variables namely, position of accelerator,
clutch position, inclination and acceleration and driving force
on vehicle/clutch torque output, vehicle speed/ engine speed,
gear position.
5. An electronic parking brake system as claimed in any of the
preceding claims, wherein vehicle acceleration and road surface
gradient can be measured by using same/separate sensors.

6. An electronic parking brake system as claimed in any of the
preceding claims, wherein the electronic control unit processes
said input variables to obtain optimum braking force such as
herein described.
7. An electronic parking brake system as claimed in any of the
preceding claims, wherein the electronic control unit actuates
hardware part of electronic parking brake unit by means of
actuation signal to apply/release optimum braking force on the
rear wheels.
8. An electronic parking brake system as claimed in any of the
preceding claims, comprising a provision in the form of switch
for operating the parking brake system in manual/automatic
mode as in fig. 2.
9. An electronic parking brake system as claimed in any of the
preceding claims, wherein the Driving Force is available in
vehicle ECU, which can also be obtained by using Clutch
Torque output available in vehicle ECU or by using accelerator
position, clutch position and other variables.
10. An electronic parking brake system as claimed in any of the preceding
claims, wherein the automatic mode applies or releases parking
brake force without driver intervention by detecting vehicle
condition by using various inputs like vehicle speed/ engine
speed, accelerator pedal position, inclination of road surface,
gear position, driving force on vehicle.

11. An electronic parking brake system as claimed in any of the
preceding claims, which is basically devised for Motor vehicle
without ABS (Anti-Lock Braking system)/ESP (Electronic
stability Program), which can be made compatible with Motor
vehicle with ABS/ESP systems as well.
12. An electronic parking brake system as claimed in any of the
preceding claims is associated with the advantageous features
such as herein described.