U.S. patent application number 09/784757 was filed with the patent office on 2001-09-27 for parking brake system for motor vehicles.
Invention is credited to Engelhard, Willibald.
Application Number | 20010023799 09/784757 |
Document ID | / |
Family ID | 7630955 |
Filed Date | 2001-09-27 |
United States Patent
Application |
20010023799 |
Kind Code |
A1 |
Engelhard, Willibald |
September 27, 2001 |
Parking brake system for motor vehicles
Abstract
A parking brake system for a motor vehicle has a control for
activating the parking brake, an electrical parking brake control
unit for controlling braking devices which are assigned to the
parking brake, a brake booster function control unit for
controlling brake booster functions which promote traveling comfort
and safety. When the control is activated at a vehicle velocity
above a predefined minimum velocity, the braking devices assigned
to the service brake are controlled by the brake booster function
control unit.
Inventors: |
Engelhard, Willibald;
(Wernberg-Koblitz, DE) |
Correspondence
Address: |
LERNER AND GREENBERG, P.A.
Post Office Box 2480
Hollywood
FL
33022-2480
US
|
Family ID: |
7630955 |
Appl. No.: |
09/784757 |
Filed: |
February 15, 2001 |
Current U.S.
Class: |
188/151R ;
303/10; 303/89 |
Current CPC
Class: |
B60T 13/74 20130101;
B60T 8/3255 20130101; B60T 7/107 20130101; B60T 8/32 20130101; B60T
8/4809 20130101 |
Class at
Publication: |
188/151.00R ;
303/89; 303/10 |
International
Class: |
B60T 011/10; B60T
017/16 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 15, 2000 |
DE |
100 06 656.9 |
Claims
I claim:
1. A parking brake system for a motor vehicle, comprising: a
braking device; a control for activating a parking brake function;
a first control unit for activating said braking device and
assigned to a parking brake, said first control unit connected to
said control; a second control unit for activating said braking
device and assigned to a service brake, said second control unit
connected to said control and controlling brake booster functions
which promote traveling comfort and safety, if said control is
activated at a vehicle velocity above a predefined minimum velocity
and below a predefined maximum velocity, said braking device is
activated by said first control unit and by said second control
unit, one of braking pressures and braking forces being predefined
by said second control unit as a function of a braking effect
achieved by said first control unit.
2. The parking brake system according to claim 1, wherein said
second control unit is programmed to: initiate and control an
electrical stability program; initiate and control a traction
control function; and initiate and control an electrical
differential locking function.
3. The parking brake system according to claim 1, including: a
first signal line connecting said control to said first control
unit; and a second signal line connecting said control to said
second control unit.
4. The parking brake system according to claim 1, including a first
signal line connecting said control to said first control unit; and
a second signal line connecting said first control unit to said
second control unit, a parking brake request signaled by activating
said control being transmitted from said first control unit to said
second control unit through said second signal line.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to a parking brake system for motor
vehicles. The parking brake system has a control for activating a
parking brake function, a first control unit for activating a
braking device and assigned to a parking brake, and a second
control unit for activating the braking device and assigned to a
service brake. The second control unit controls brake booster
functions that promote traveling comfort and safety.
[0003] In addition to a known service brake system (service brake)
which is actuated by a foot pedal, legislation requires a parking
brake system (parking brake)--frequently also referred to as a
handbrake. Such a parking brake is configured so as to be largely
independent of the service brake of the motor vehicle and is used,
on the one hand, to secure the motor vehicle in a stationary state
(static activation) and on the other hand to brake the vehicle
while traveling (dynamic activation). Dynamic activation may be
necessary when the service brake fails, for example. Conventional
vehicles are predominantly equipped with manually activated parking
brakes. The parking brake is engaged or released in a metered
fashion by a Bowden cable using a brake lever that is usually
disposed in the center console. Foot-activated parking brakes that
are engaged in a metered fashion by a foot pedal and released
instantaneously by a release lever are also known. Metered release
of the parking brake is not possible with foot-activated
systems.
[0004] Both manually activated and foot-activated parking brakes
have the disadvantage that the operator of the motor vehicle must
apply an appreciable force at least to engage the parking brake. In
addition, the brake lever or the foot pedal takes up a large amount
of space in the center console or in the pedal region.
[0005] In order to overcome this disadvantage, electrical parking
brakes--referred to below as electrical parking brakes or EPB for
short--are known which are activated with little application of
force by controls, for example by switching a key. The controls are
advantageously disposed in the dashboard region or steering wheel
region. Such an electrical parking brake is known from Published,
Non-Prosecuted German Patent Application DE 198 38 886 A1.
[0006] When the parking brake is activated dynamically, that is to
say the control is activated while the vehicle is traveling,
controlled braking of the vehicle must be ensured even when the
vehicle is traveling at a high velocity and wheel slip is
occurring. The parking brake must therefore by necessity be
controlled as a function of the travel situation. For this purpose,
in the known parking brake the wheel speeds are transmitted to the
control unit of the parking brake and evaluated there. Effective
control can be achieved in such a case only by complex algorithms
such as are known in anti-lock braking systems. However, this
entails high additional costs.
[0007] Published, Non-Prosecuted German Patent Application DE 198
26 687 A1 discloses an electrically activated brake system for
motor vehicles in which, by activating a parking brake control, the
service brake system is activated above a predefined vehicle
velocity and the parking brake system is activated below the
predefined vehicle velocity.
SUMMARY OF THE INVENTION
[0008] It is accordingly an object of the invention to provide a
parking brake system for motor vehicles which overcomes the
above-mentioned disadvantages of the prior art devices of this
general type, in which controlled braking of the motor vehicle is
ensured at low cost when the parking brake is activated
dynamically.
[0009] With the foregoing and other objects in view there is
provided, in accordance with the invention, a parking brake system
for a motor vehicle. The parking brake system includes a braking
device, a control for activating a parking brake function, a first
control unit for activating the braking device and assigned to a
parking brake, the first control unit is connected to the control,
and a second control unit for activating the braking device and
assigned to a service brake. The second control unit is connected
to the control and controls brake booster functions which promote
traveling comfort and safety. If the control is activated at a
vehicle velocity above a predefined minimum velocity and below a
predefined maximum velocity, the braking device is activated by the
first control unit and by the second control unit. The braking
pressures or braking forces are predefined by the second control
unit as a function of a braking effect achieved by the first
control unit.
[0010] In order to achieve continual improvements in safety and to
increase the traveling comfort and operating convenience, more and
more vehicles are being equipped with brake booster functions such
as an electrical stability program (ESP), a traction control system
(ASR) or electrical differential lock (EBS) system. Such booster
functions can also be used to generate a braking force or a braking
pressure at the braking device of the service brake, and thus
achieve a braking effect, without activating the service brake
pedal. Evaluations, for example of the wheel speeds, which permit
the motor vehicle to be braked as a function of a travel situation,
are carried out in any case in the control units of such brake
booster functions. According to the invention, when the parking
brake control is activated while the vehicle is traveling the
braking device assigned to the service brake is activated by the
control unit of such a brake booster function. In order to do this,
the brake actuators which are responsible for generating the
braking force or the braking pressure at the brake device are
controlled. As a result, the parking brake function is easily
assumed by the service brake while the vehicle is traveling.
However, in particular the functionality of the control unit of the
brake booster function is utilized to control the actuators for the
braking device on an individual basis and as a function of a travel
situation.
[0011] In accordance with an added feature of the invention, the
second control unit is programmed to: initiate and control an
electrical stability program; initiate and control a traction
control function; and initiate and control an electrical
differential locking function.
[0012] In accordance with an additional feature of the invention, a
first signal line connects the control to the first control unit,
and a second signal line connects the control to the second control
unit.
[0013] In accordance with a concomitant feature of the invention, a
first signal line connects the control to the first control unit,
and a second signal line connects the first control unit to the
second control unit. A parking brake request signaled by activating
the control is transmitted from the first control unit to the
second control unit through the second signal line.
[0014] Other features which are considered as characteristic for
the invention are set forth in the appended claims.
[0015] Although the invention is illustrated and described herein
as embodied in a parking brake system for motor vehicles, it is
nevertheless not intended to be limited to the details shown, since
various modifications and structural changes may be made therein
without departing from the spirit of the invention and within the
scope and range of equivalents of the claims.
[0016] The construction and method of operation of the invention,
however, together with additional objects and advantages thereof
will be best understood from the following description of specific
embodiments when read in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a block circuit diagram of a parking brake system
with a hydraulic service brake according to the invention; and
[0018] FIG. 2 is a block circuit diagram of the parking brake
system for a motor vehicle with an electric service brake.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0019] In all the figures of the drawing, sub-features and integral
parts that correspond to one another bear the same reference symbol
in each case. Referring now to the figures of the drawing in detail
and first, particularly, to FIG. 1 thereof, there is shown a
parking brake system according to the invention. The parking brake
system has a control 1 for activating a parking brake function. The
control 1 may be embodied, for example, as a single push-button key
that merely discriminates between the states "activated" and "not
activated". Likewise, the control 1 may also be embodied as a
double push-button key with the states "engage", "release" and a
"home position". The selection of the control 1 here is mainly
dependent, as is its configuration in the interior of the vehicle,
on criteria relating to comfort and ergonomics. For safety reasons,
the motor vehicle is preferably equipped with a further control
(redundancy principle) which is not illustrated. A parking brake
request from a driver which is signaled by activating the control 1
is transmitted through a signal line 2 to a first control unit 3
being an electrical parking brake control unit or EPB control unit
3 for short. The parking brake request of the driver is transmitted
from the control 1 through a signal line 4 to a second control unit
5 being a brake-booster function-control unit or BAF control unit 5
for short. As an alternative to parallel reading-in of the parking
brake request by the EPB control unit 3 and the BAF control unit 5,
the parking brake request can also be passed on from the EPB
control unit 3 to the BAF control unit 5 via a further signal line
20, for example in the form of a controller area network (CAN) bus
shown by the dashed line in FIG. 1.
[0020] Brake booster functions which promote safety or comfort,
such as for example an electrical stability program and/or a
traction control (ASR) and/or an electrical differential lock
(EDS), are controlled using the BAF control unit 5. To control such
brake booster functions, further signals which characterize the
travel situation, for example the wheel speeds, are necessary. This
information is transmitted to the BAF control unit 5 from sensors
(not illustrated) or other control units via one or more signal
lines 6. A variable which characterizes a velocity of the motor
vehicle, for example wheel speeds or the actual velocity of the
vehicle calculated therefrom, is transmitted from the BAF control
unit 5 to the EPB control unit 3 through one or more signal lines 7
(redundancy principle). The BAF control unit 5 controls a service
brake actuator 8 by which a desired brake pressure or a desired
braking force is set at a braking device 9. When the service brake
is a hydraulic one, the service brake actuator 8 is embodied for
example as a hydraulic unit via which the hydraulic pressure at the
braking device 9 is controlled. The braking device 9 can be
embodied here as disc brakes or drum brakes. For reasons of
clarity, only a single braking device 9 is illustrated in FIG. 1 by
way of example. However, in reality, each wheel of the motor
vehicle is preferably assigned its own braking device 9.
[0021] In motor vehicles with a hydraulic service brake,
mechanically activated parking brakes are generally used. In such
brakes, the EPB control unit 3 controls a parking brake actuator 10
which is connected to at least two of the braking devices 9 of the
motor vehicle via Bowden cables. The braking devices 9 in question
here are usually those that are mounted on the two front wheels or
on the two rear wheels. The parking brake actuator 10 is embodied,
for example, as an inexpensive D.C. brush motor with a self-locking
spindle gear mechanism. The self-locking of the spindle gear
mechanism also ensures the securing effect of a parking brake with
mechanical devices as is legally required.
[0022] In motor vehicles with an electric service brake (FIG.
2)--also referred to using the term "brake by wire"--there is no
need for separate actuators for activating the service brake and
the parking brake. Both the EPB control unit 3 and the BAF control
unit 5 are connected to a wheel brake actuator 11 in such brake
systems. For the sake of simplification, only a single wheel brake
actuator 11 with the associated braking device 9 is illustrated in
FIG. 2. The wheel brake actuators 11 are usually embodied as
self-locking electric motor/gear mechanism units that are
preferably disposed directly on the wheels. A brake system with
such wheel brake actuators is known, for example, from German
Patent DE 196 15 186 C1.
[0023] The function of the parking brake system according to the
invention is explained in more detail below.
[0024] After the control 1 is activated for a brief time in the
stationary state of the motor vehicle, the braking devices 9
assigned to the parking brake are engaged with a predefined time
profile and with a predefined maximum force using the EPB control
unit 3 by use of the parking brake actuators 10--or the wheel brake
actuators 11 in the case of electric brake systems. In order to
prevent the motor vehicle from rolling away, for example when
parked on an incline, a high actuator speed, which causes the
braking devices 9 to be engaged quickly, is predefined here. The
maximum force is advantageously specified as a function of the
angle of inclination of the slope. After the control 1 is activated
again for a brief time, the braking devices 9 assigned to the
parking brake are instantaneously released. In order to avoid the
parking brake from being released unintentionally in the stationary
state, the state of the ignition device, for example, may
additionally be evaluated in the EPB control unit 3.
[0025] After the control 1 has been briefly activated at a vehicle
velocity below a predefined minimum velocity (for example in the
range from 3 to 5 km/h), the braking devices 9 assigned to the
parking brake are engaged in a way analogous to the activation of
the control 1 in the stationary state. After the control 1 is
activated again (system off), the braking devices 9 are
instantaneously released. The minimum velocity can be predefined
here on a vehicle-specific basis, but is dependent on the measuring
range of the velocity or wheel speed sensors used. With future
active sensors, i.e. ones which sense velocities as far as 0 km/h,
it is also possible to strictly separate the activation of the
parking brake in the "stationary state" and while "traveling". To
do this, the minimum velocity is simply fixed at the value 0
km/h.
[0026] After the control 1 has been activated at a vehicle velocity
above the predefined minimum velocity, the braking devices 9
assigned to the service brake are engaged over the duration of the
activation by the BAF control unit 5 by the service brake actuator
8--or the wheel brake actuators 11 in the case of electric brake
systems. Here, the braking pressure or the braking force is
specified individually for the individual braking devices 9 as a
function of the wheel speeds and of the wheel slip that occurs. In
this way, controlled braking of the motor vehicle is ensured even
when the control 1 is activated at relatively high vehicle
velocities. As soon as the control 1 is no longer activated, the
braking devices 9 are instantaneously released. In a further
embodiment, the braking devices 9 that are assigned to the service
brake can also be engaged after a brief activation of the control
at a vehicle velocity above the predefined minimum velocity by the
BAF control unit 5 by use of the service brake actuators 8 or the
wheel brake actuators 11. In this case, the braking devices 9 are
not released again until the control 1 is activated again.
[0027] The braking devices 9 assigned to the parking brake are
advantageously additionally activated by the EPB control unit 3
when the control 1 is activated at a vehicle velocity above the
predefined minimum velocity but below a predefined maximum velocity
(for example in the range from 7 to 10 km/h). Here, the
functionality of the BAF control unit 5 is utilized to the effect
that the braking pressures defined by the BAF control unit 5 or the
predefined braking forces are specified as a function of the
braking effect achieved by the EPB control unit 3. Such an
overlapping control of the actuators for the braking device 9 has
the advantage that communication, for example for mutual functional
monitoring, between the EPB control unit 3 and the BAF control unit
5 is not necessary.
* * * * *