U.S. patent application number 10/816604 was filed with the patent office on 2005-10-06 for use of ecu to control brake valve actuator.
Invention is credited to Bennett, Mark A., Eberling, Charles E., Hatipoglu, Cem.
Application Number | 20050218719 10/816604 |
Document ID | / |
Family ID | 34963413 |
Filed Date | 2005-10-06 |
United States Patent
Application |
20050218719 |
Kind Code |
A1 |
Hatipoglu, Cem ; et
al. |
October 6, 2005 |
Use of ECU to control brake valve actuator
Abstract
A brake valve actuator (BVA) of a vehicle is controlled by an
electronic control unit (ECU) to provide automatic traction control
(ATC), roll stability (RS) and yaw stability (YS) functions for the
vehicle, by actuating the dual brake valve without driver
intervention. The ATC function is provided by making braking
pressure available at the driven wheels only of the vehicle. This
may be done by selectively controlling the modulators for the
driven wheels and the non-driven wheels of the vehicle. The ATC
function in this manner can be provided for a straight truck or
bus, or for a tractor and trailer, without the need for an ATC
solenoid. In another embodiment, a yaw control function is
provided, without the need for ATC solenoids or for pressure
sensors in the delivery lines. In yet another embodiment, yaw
control benefits are provided with an additional sensor.
Inventors: |
Hatipoglu, Cem; (Rocky
River, OH) ; Eberling, Charles E.; (Wellington,
OH) ; Bennett, Mark A.; (Grafton, OH) |
Correspondence
Address: |
CALFEE HALTER & GRISWOLD, LLP
800 SUPERIOR AVENUE
SUITE 1400
CLEVELAND
OH
44114
US
|
Family ID: |
34963413 |
Appl. No.: |
10/816604 |
Filed: |
April 2, 2004 |
Current U.S.
Class: |
303/188 |
Current CPC
Class: |
B60T 15/045 20130101;
B60T 8/1755 20130101; B60T 8/246 20130101; B60T 8/24 20130101; B60T
2230/03 20130101; B60T 8/175 20130101 |
Class at
Publication: |
303/188 |
International
Class: |
B60T 008/60 |
Claims
Having described the invention, we claim:
1. A method of controlling the braking function of a vehicle having
a first braking circuit associated with driven wheels of the
vehicle and having a second braking circuit associated with
non-driven wheels of the vehicle, said method comprising the steps
of: sensing a vehicle condition for which braking of the driven
wheels is desired independently of operator demand; in response to
said sensing step, electrically actuating a dual brake valve of the
vehicle thereby to direct braking pressure to both the first and
second braking circuits of the vehicle; and controlling a plurality
of modulators in the vehicle to inhibit delivery of braking
pressure to the non-driven wheels of the vehicle.
2. A method as set forth in claim 1 wherein said sensing step
comprises sensing wheel spin of at least one of the driven wheels
of the vehicle, and said controlling step comprises controlling the
plurality of modulators in the vehicle to enable delivery of
braking pressure to the at least one driven wheel of the
vehicle.
3. A method as set forth in claim 1 wherein said step of
electrically actuating a dual brake valve of the vehicle includes
directing braking pressure through a relay valve associated with
the driven wheels of the vehicle and said controlling step includes
controlling modulators associated with the driven wheels of the
vehicle to selectively control delivery of braking pressure to the
driven wheels of the vehicle.
4. A method as set forth in claim 1 wherein the vehicle braking
system includes an electrically energizable actuator associated
with the dual brake valve for actuating the dual brake valve in
response to said sensing step, the actuator being manually
energizable in response to an operator signal independently of the
foot of the vehicle operator, and wherein said step of electrically
actuating the dual brake valve comprises electrically energizing
the actuator thereby to actuate the dual brake valve.
5. A method as set forth in claim 1 wherein said sensing step
comprises sensing roll stability condition of the vehicle, and said
controlling step comprises controlling the plurality of modulators
in the vehicle to enable delivery of braking pressure to the at
least one driven wheel of the vehicle.
6. A method as set forth in claim 5 wherein the dual brake valve
has a mechanical override feature by which driver actuation of the
vehicle brake pedal by a sufficient amount can override the brake
valve actuator.
7. A method as set forth in claim 5 wherein said controlling step
comprises controlling the plurality of modulators in the vehicle to
enable delivery of braking pressure to all the wheels of the
vehicle.
8. A method of making available braking pressure to wheels of a
moving vehicle having an air braking system that includes a dual
brake valve for, when actuated, simultaneously applying braking
pressure to both first and second braking circuits of a vehicle,
the dual brake valve being proportionally actuatable by the foot of
an operator of the vehicle, said method comprising the steps of:
determining the existence of a dynamic vehicle condition for which
it is desired that braking pressure be made available to the
vehicle wheels independently of driver braking demand; and, in
response, electrically actuating the dual brake valve thereby to
make available braking pressure to the vehicle wheels.
9. A method as set forth in claim 8 wherein said determining step
comprises determining the existence of wheel spin of at least one
driven wheel of the vehicle, and said actuating step comprises
braking the at least one driven wheel to regain traction for the
driven wheel.
10. A method as set forth in claim 9 further comprising the step of
controlling a plurality of modulators in the vehicle to enable
delivery of braking pressure to one or more driven wheels of the
vehicle and to inhibit delivery of braking pressure to one or more
non-driven wheels of the vehicle.
11. A method as set forth in claim 8 wherein said determining step
comprises determining the existence of a possible rollover
condition of the vehicle, and said actuating step comprises braking
selected ones of the vehicle wheels to slow the vehicle to prevent
rollover of the vehicle.
12. A method as set forth in claim 8 further comprising the step of
controlling a plurality of modulators in the vehicle to selectively
control delivery of braking pressure to the wheels of the
vehicle.
13. A method as set forth in claim 12 wherein said controlling step
includes controlling the modulators to enable delivery of braking
pressure to one or more driven wheels of the vehicle and to inhibit
delivery of braking pressure to one or more non-driven wheels of
the vehicle.
14. A method as set forth in claim 8 wherein the vehicle braking
system includes an electrically energizable actuator associated
with the dual brake valve for actuating the dual brake valve in
response to said determining step, the actuator being manually
energizable in response to an operator signal independently of the
foot of the vehicle operator, and wherein said step of electrically
actuating the dual brake valve comprises electrically energizing
the actuator thereby to actuate the dual brake valve.
15. A vehicle braking system for a vehicle having a first braking
circuit associated with driven wheels of the vehicle and having a
second braking circuit associated with non-driven wheels of the
vehicle, said system comprising: a dual brake valve for, when
actuated, simultaneously applying braking pressure to both the
first and second braking circuits of the vehicle, said dual brake
valve being proportionally actuatable by the foot of an operator of
the vehicle; a manually energizable actuator for actuating said
dual brake valve independently of the foot of the vehicle operator;
at least one sensor for sensing a dynamic vehicle condition for
which it is desired that braking pressure be made available to at
least one of the vehicle wheels independently of driver braking
demand; and a controller responsive to said sensor for energizing
said actuator electrically to make available braking pressure to
the at least one vehicle wheel.
16. A system as set forth in claim 15 wherein said sensor is
operative to sense wheel spin of a driven wheel of the vehicle, and
said system is operative to make braking pressure available to the
driven wheel of the vehicle.
17. A system as set forth in claim 16 further comprising a
modulator between said dual brake valve and the driven wheel, said
controller being operative to control said modulator to selectively
make braking pressure available to the driven wheel.
18. A system as set forth in claim 17 further comprising a
modulator between said dual brake valve and a non-driven wheel of
the vehicle, said controller being operative to control said
modulator to block the application of braking pressure to the
non-driven wheel.
19. A system as set forth in claim 15 wherein said sensor is
operative to sense a rollover condition of the vehicle, and said
system is operative to make braking pressure available to selected
ones of the wheels of the vehicle.
20. A system as set forth in claim 19 wherein said system is
operative to make braking pressure available to all the wheels of
the vehicle.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a braking system for a
vehicle. In particular, the present invention relates to the
provision of an automatic traction control (ATC) function and a
roll stability (RS) function with a vehicle braking system.
[0002] A typical vehicle braking system for a straight truck, bus,
tractor, or trailer, includes a source of pressurized air along
with valves for selectively directing the air to brake chambers at
the wheels of the vehicle. Many such vehicle braking systems
provide an antilock braking system (ABS) function, by which an
electronic control unit (ECU) selectively releases and applies
braking at individual wheels to prevent wheel lockup.
[0003] Some vehicle braking systems also provide an automatic
traction control (ATC) function. In one aspect of ATC, an
electronic control unit (ECU) selectively applies braking at
individual wheels to match wheel speeds side to side to help
control wheel spin that occurs in response to driver demand via the
accelerator pedal. This control is typically effected by
controlling a wheel end modulator associated with the wheel. The
modulator provides an air flow path to the wheel that can be
rapidly opened or closed by a solenoid under the control of the
ECU.
[0004] In order to provide the ATC function, high pressure air must
be made available at the modulators in the absence of driver
demand. This is typically done by having a constant supply of high
pressure air from the reservoir to an ATC solenoid that is
associated with the modulators on the driven axle. In an ATC event,
the ATC solenoid is energized under the control of the ECU to
direct the high pressure air from the reservoir to the modulators.
The modulators are then controlled by the ECU selectively to apply
and release braking force to the wheels, to control any wheel
spin.
[0005] As one example, FIG. 1 shows schematically some portions of
a prior art vehicle braking system that is operative to provide ATC
on a straight truck, or bus. The system is also ABS effective. The
system includes a foot brake valve (FBV) that normally provides
driver demand proportioned air pressure as a control air flow to a
relay valve (designated ATC) associated with the driven wheels of
the vehicle. The relay valve includes an ATC solenoid that is
controlled by an ECU. The ATC solenoid is normally de-energized, in
which case driver demand proportioned air is used as the control
pressure on the relay valve, to control the flow of air from the
reservoir to the rear axle modulators. When the ECU determines that
the traction control function is desired, the ECU energizes the ATC
solenoid on the relay valve, which opens the relay valve
immediately, in spite of the lack of driver demand controlled
pressure. Reservoir air pressure is provided to the rear
modulators. The rear modulators, under the control of the ECU, use
that air to modulate brake pressure in the brake actuators, thus
controlling the spinning of the rear wheels.
[0006] Vehicle air brake systems typically include a primary
circuit, which is often used for driven wheels, and a secondary
circuit, which is often used for non-driven wheels. The vehicle has
a dual brake valve, or foot brake valve (FBV), which is a valve in
both the primary circuit and the secondary circuit that is
controlled by the foot pedal (brake pedal) of the vehicle in
response to driver demand for braking. The dual brake valve is
supplied with high pressure air from one or more reservoirs. When
the valve is actuated by driver applied force on the brake pedal,
this high pressure air is directed into the primary and secondary
braking circuits of the vehicle.
[0007] Some vehicles with dual brake valves also have a brake valve
actuator (BVA), which is an actuatable device interposed between
the valve and the brake pedal that applies enough force to the
brake valve so that the brake valve's output (delivery pressure to
the primary and secondary circuits) is at least 85 psi. The BVA is
operated (piloted by, or receives a pneumatic control signal from)
either (a) a pneumatic on/off control valve actuated by the
driver's hand like a switch, or (b) an on/off solenoid valve
controlled by an on/off electrical switch operated by the driver's
hand. The BVA is used to conduct a pre-trip inspection, in which
the brakes are set and held in an applied condition so that the
driver can check the braking system of the vehicle without having
to be in the cab pressing on the brake pedal. U.S. Pat. No.
6,659,244 shows the use of a brake valve actuator in a vehicle air
braking system.
SUMMARY OF THE INVENTION
[0008] In accordance with the invention, the brake valve actuator
(BVA) of a vehicle is controlled by an ECU to provide ATC, yaw
stability (YS) and ESP functions for the vehicle. These functions
require supply (reservoir) air to be available to the vehicle's
wheel end modulators in the absence of driver demand (brake pedal
movement). In accordance with the invention, this is effected by
having the ECU control the BVA to actuate the dual brake valve
without driver intervention.
[0009] In one embodiment, the ATC function is provided by making
braking pressure available at the driven wheels only of the
vehicle. This may be done by blocking the modulators for the
non-driven wheels so that no braking effect is provided at the
non-driven wheels. At the same time, the modulators for the driven
wheels are controlled to enable selective braking, under control of
the ECU, of the driven wheels. The ATC function in this manner can
be provided for a straight truck or bus, or for a tractor and
trailer, without the need for an ATC solenoid. For a tractor and
trailer, there is a need to be able to stop pressure delivery to
the trailer, which is typically met by a standard modulator
controlling the trailer delivery directly from the brake ECU.
[0010] That is, since the modulators for the non-driven wheels can
hold, and not allow any new pressure to go to their associated
brakes, the system can supply full air pressure to them, and allow
the modulators to block it. The system can use the existing brake
valve (under control of the BVA) to provide the supply air, and so
there is no need for an ATC valve for either the driven or
non-driven wheels.
[0011] In another embodiment, the RS function is provided, without
the need for ATC solenoids or for pressure sensors in the delivery
lines.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The foregoing and other features of the present invention
will become apparent upon consideration of the following
description of the invention with reference to the accompanying
drawings, in which:
[0013] FIG. 1 is a schematic illustration of a prior art braking
system for a straight truck or bus, having an ATC capability;
[0014] FIG. 2 is a schematic illustration of a braking system in
accordance with a first embodiment of the invention for a straight
truck or bus, having an ATC capability;
[0015] FIG. 3 is a schematic illustration of a braking system in
accordance with a second embodiment of the invention for a tractor
and trailer, having an ATC capability;
[0016] FIG. 4 is a schematic illustration of a prior art braking
system for a straight truck or bus, having an RS capability;
[0017] FIG. 5 is a schematic illustration of a braking system in
accordance with a third embodiment of the invention for a straight
truck or bus, having an RS capability;
[0018] FIG. 6 is a schematic illustration of a prior art braking
system for a tractor and trailer, having an RS capability; and
[0019] FIG. 7 is a schematic illustration of a braking system in
accordance with a third embodiment of the invention for a tractor
and trailer, having an RS capability.
DETAILED DESCRIPTION OF THE INVENTION
[0020] The present invention relates to a braking system for a
vehicle. In particular, the present invention relates to a vehicle
braking system that provides an automatic traction control (ATC)
function. The invention is applicable to braking systems of
differing constructions. For example, the invention is applicable
braking systems for vehicles having only two axles, with either one
or both axles being driven; to vehicles having more than two axles
with one or more being driven; and to vehicles (such as trailers)
having no driven axles. As representative of the invention, FIG. 2
illustrates a vehicle braking system 10 constructed in accordance
with a first embodiment of the invention.
[0021] The braking system 10 forms a part of a vehicle 12 having
non-driven wheels 14 and driven wheels 16. The illustrated vehicle
12 is a rear wheel drive vehicle and so a forward direction in the
vehicle is indicated by the arrow 18. The arrangement of driven
wheels 16 and non-driven wheels 14 could be different in other
vehicles, for example, in a front wheel drive vehicle.
[0022] Two ABS wheel end modulators 20 are associated with the
non-driven wheels 14. Two ABS wheel end modulators 22 are
associated with the driven wheels 16. All of the modulators 20 and
22 are controlled by an ECU 30.
[0023] The vehicle includes a foot brake valve 32 for controlling
flow of pressurized air from one or more reservoirs (not shown) to
the modulators 20 and 22. The foot brake valve 32 is actuated by
the vehicle brake pedal 34.
[0024] The foot brake valve 32 has a primary chamber 36 that is
located in a primary circuit 38 of the vehicle braking system 10.
The primary circuit 38 also includes a relay valve 40, between the
foot brake valve 32 and the modulators 22. The primary circuit 38
controls braking on the driven wheels 16. Specifically, when the
brake valve 32 is actuated, air at a pressure determined by the
amount of actuation of the brake pedal 34 is directed from the
primary chamber 36 to the relay valve 40 as control air to actuate
the relay valve. The relay valve 40, when actuated, directs air
from a primary reservoir (not shown) to the modulators 22 of the
driven wheels 16.
[0025] The foot brake valve 32 has a secondary chamber 42 that is
located in a secondary circuit 44 of the vehicle braking system 10.
The secondary circuit 44 controls braking on the non-driven wheels
14. Specifically, when the brake valve 32 is actuated, air from a
secondary reservoir (not shown) flows through the secondary chamber
42 to the modulators 20 of the non-driven wheels 14, at a pressure
determined by the amount of actuation of the brake pedal 34.
[0026] The system 10 includes a brake valve actuator (BVA) 50. The
BVA 50 is an actuatable device interposed between the brake valve
and the brake pedal. The BVA 50 is controlled by a BVA controller
52 that is provided with supply air.
[0027] The BVA controller 52 is operated (piloted by, or receives a
pneumatic control signal from) an actuator 54 that may be either a
pneumatic on/off control valve actuated by the driver's hand like a
switch, or (b) an on/off solenoid valve controlled by an on/off
electrical switch operated by the driver's hand. The controller 52,
when actuated, directs supply air to the BVA 50 to actuate the BVA
and, thereby, actuate the dual brake valve 32.
[0028] The BVA 50 may be used in a known manner for conducting a
pre-trip inspection, in which the brakes are set and held in an
applied condition so that the driver can check the braking system
of the vehicle without having to be in the cab pressing on the
brake pedal 34.
[0029] In accordance with a feature of the present invention, the
BVA controller 52 is also operated by the ECU 30. Specifically, the
ECU 30 is operative to actuate the BVA controller 52, independently
of controller actuation (described above) that results from driver
input.
[0030] The ECU 30 is provided with inputs from one or more sensors
for sensing a dynamic vehicle condition for which it may be
desirable to make braking pressure available to the driven or
non-driven wheels of the vehicle, independently of driver demand.
Specifically, the ECU 30 may be provided with input from one or
more wheel spin sensors 31, associated with the driven wheels of
the vehicle and the non-driven wheels of the vehicle. The ECU 30
may also be provided with input from one or more rollover condition
sensors 33 that are operative to sense conditions such as lateral
acceleration that are indicative of a possible rollover condition
of the vehicle. Other types of sensor inputs may be provided, in
addition or alternatively.
[0031] Should wheel spin at the driven wheels 16 be sensed, the ECU
30 may determine that the automatic traction control (ATC) function
of the system 10 should be provided to stop the wheel spin. If such
a determination is made, the ECU 30 electrically actuates the BVA
controller 52. The BVA controller 52 directs supply air to the BVA
50, thereby actuating the BVA. The BVA 50 actuates the dual brake
valve 32.
[0032] When the dual brake valve 32 is thus actuated by the ECU 30,
air from the secondary reservoir flows through the secondary
chamber 42 to the modulators 20 of the non-driven wheels 14. The
ECU 30 when in the ATC mode controls the modulators 22 to block
flow of air to the brake chambers of the non-driven wheels 14.
Therefore, no braking effect is provided at the non-driven wheels
14, as is desired.
[0033] When the dual brake valve 32 is thus actuated by the ECU 30,
air under pressure is directed from the primary chamber 36 to the
relay valve 40 as control air, thus actuating the relay valve. The
relay valve 40 when actuated directs air from the primary reservoir
to the modulators 22 of the driven wheels 16. The ECU 30 when in
the ATC mode selectively controls the modulators 22 associated with
the driven wheels 16 to enable flow of air to the brake chambers of
the driven wheels. Braking effect is provided as desired at the
driven wheels 16, to stop the wheel spin. The braking effect can be
applied and released under the control of the ECU 30.
[0034] The application of braking effect to the driven wheels 16 is
done without any driver input, that is, without pressing on the
brake pedal 34. Thus, the automatic traction control function is
provided. Because the brake valve actuator 50 is used to energize
the primary braking circuit 38, a standard relay valve 40 can be
used in the primary circuit, rather than a relay valve with an ATC
solenoid.
[0035] This feature of the invention thus takes advantage of the
fact that the vehicle 12 already has a device (the BVA 50) which is
operative to energize the vehicle braking system 10 in the absence
of brake pedal actuation. Putting this device 50 under the control
of the ECU 30 enables the provision of braking effect under
computer control and thus enables the provision of the automatic
traction control function, without the need for the more complex
and expensive ATC hardware shown in FIG. 1.
[0036] Being able to control the BVA 50 with the ECU 30 provides
additional advantages. The ECU 30 can control operation of the BVA
50 so that it is not erroneously actuated, for example by the
pre-trip solenoid when the vehicle 12 is moving.
[0037] The service brakes can also be applied using the ECU 30 to
control the BVA 50. Some vehicles include an "Autobrake" function
by which service brakes are automatically applied by actuating the
BVA 50, in certain circumstances. For example, the service brakes
of a school bus might be automatically applied when the school bus
door is opened with the lights flashing. In such a vehicle, the ECU
30 can be programmed to disable this function when it is not safe
to have it in effect--for example, while the vehicle is moving.
Other BVA functions can also be disabled in such circumstances, for
example, the pre-trip function, or any other brake actuation other
than the one provided for by the driver's foot or hand control.
Thus, putting the BVA 50 under control of the ECU 30 adds
functionality to the BVA in the form of a safety interlock to
prevent misuse of the brakes via the BVA.
[0038] FIG. 3 illustrates schematically a vehicle braking system
10a constructed in accordance with a second embodiment of the
invention. The braking system 10a is similar to the braking system
10 (FIG. 2) and parts that are the same or similar in function are
given the same reference numerals with the suffix "a" added.
[0039] The system 10a is used on a tractor-trailer combination. The
parts of the system 10a that are used for braking control on the
tractor are the same as those shown in FIG. 2. In addition, an
extra air line 60 is taken off the delivery from the secondary
circuit 44a, going back to a double check valve 62 normally found
in a conventional tractor trailer protection valve. Another air
line 64 is taken off the delivery from the primary circuit 38a,
going back to the double check valve 62. The higher of these two
lines 60 and 64, at the double check valve 62, provides the
input/control to the trailer, in a known, standard manner.
[0040] The pressure that is passed through from the double check
valve 62 goes to a solenoid-controlled trailer control valve 66
that is an on-off valve. During an ATC event, the ECU 30 controls
the valve 66 to block application of braking effect to the wheels
of the trailer. When an ATC event is not in progress, the ECU 30a
controls the valve 66 to enable application of braking effect to
the wheels of the trailer in the usual manner.
[0041] With the system 10a, the vehicle brake lights are controlled
through the ECU 30a, during an ATC event. This prevents energizing
the brake lights due to brake actuation, when the vehicle is 12a
not being slowed.
[0042] In accordance with another aspect of the invention, just as
the ECU 30a blocks the front axles from braking when traction
control is desired, the ECU can in an ATC situation selectively
block braking effect at all of the tractor's axles, thus allowing
braking effect only to the trailer's axles.
[0043] The other advantages of the system 10 apply also to the
system 10a. For example, as with the system 10 (FIG. 2), the system
10a (FIG. 3) does not need the conventional ATC solenoid, and
retains the pre-trip inspection capability of the BVA.
[0044] In accordance with another aspect of the invention, a roll
stability control or roll stability (RS) function can be provided
for a straight-truck or bus having a BVA, with reduced cost and
complexity compared to standard braking systems that provide such a
function.
[0045] FIG. 4 shows one prior art hardware arrangement that is used
for obtaining RS on a straight truck or bus (no trailer). The
primary circuit of the dual brake valve provides driver control
pressure to a relay valve (designated ATC) having an ATC solenoid,
associated with the driven wheels. Supply air from the primary
reservoir (not shown), as passed by the relay valve, goes to the
vehicle's rear (to the right as viewed in FIG. 4) ABS wheel end
modulators. The solenoid on the relay valve, and the modulators,
are under the control of the ECU.
[0046] The secondary circuit of the dual brake valve provides
driver control pressure to a relay valve having an ATC solenoid,
associated with the non-driven (front) wheels. Supply air from the
secondary reservoir (not shown), as passed by the relay valve, goes
to the vehicle's front ABS wheel end modulators. The solenoid on
the relay valve, and the modulators, are under the control of the
ECU. Because both the front and rear relay valves are controllable
by ATC solenoids, they have reservoir air going to them, bypassing
the dual brake valve, and so they can be actuated at any time with
or without driver intervention, to brake the wheels.
[0047] In the prior art system shown in FIG. 4, the rear wheels (or
driven wheels) are controllable in this manner for ABS and ATC and
electronic stability functions, and also for the RS function (to be
described below). When the RS function is initiated, braking effect
is provided at all wheels, and the ABS function is used
simultaneously to prevent wheel lockup. The front wheels (or
non-driven wheels) are controllable in this manner for ABS and yaw
stability functions only.
[0048] The prior art system shown in FIG. 4 also includes a
pressure sensor in the secondary delivery line and a pressure
sensor in the primary delivery line. These sensors sense the
pressure at the delivery of the brake valve, to indicate driver
demand, and deliver that indication as input to the ECU to use in
controlling the event. This also indicates the potential pressure
that can be delivered to the brake chambers, so that the ECU can
select between driver requested pressure and RS requested pressure.
This prior art system thus requires, on top of the ABS hardware,
two pressure sensors and two ATC solenoids, in order to be able to
perform RS function robustly.
[0049] If sufficient pressure is present, that generally means the
driver is trying to make a controlled stop, and therefore ATC
should be disabled. Similarly, for RS, if the driver requested
pressure exceeds the autonomous pressure being applied by the RS
system, full braking control is given to the driver. As such, the
higher of the driver requested pressure and the RS requested
pressure is always provided to the wheels.
[0050] When the ECU senses an event, it controls the two ATC
solenoids thereby to provide braking pressure to the modulators
associated with the primary and secondary circuits of the service
brake system, in spite of no driver demand. The ECU controls all
wheel end modulators to control all of the wheels independently
front/back and left/right to provide the needed braking action to
slow and/or stabilize the vehicle.
[0051] FIG. 5 illustrates schematically a vehicle braking system 70
constructed in accordance with a third embodiment of the invention.
The system 70 provides an RS function on a straight truck, or bus,
using BVA actuation.
[0052] The braking system 70 forms a part of a vehicle 72 having
non-driven wheels 74 and driven wheels 76. The illustrated vehicle
is a rear wheel drive vehicle and so a forward direction in the
vehicle is indicated by the arrow 78. The arrangement of driven
wheels 76 and non-driven wheels 74 could be different in other
vehicles, for example, in a front wheel drive vehicle.
[0053] Two ABS wheel end modulators 80 are associated with the
non-driven wheels 74. Two ABS wheel end modulators 82 are
associated with the driven wheels 76. All of the modulators 80 and
82 are controlled by an ECU 90.
[0054] The ECU 90 is provided with inputs from one or more sensors
for sensing a dynamic vehicle condition for which it may be
desirable to make braking pressure available to the driven or
non-driven wheels of the vehicle, independently of driver demand.
Specifically, the ECU 90 may be provided with input from one or
more wheel speed sensors 91a, associated with the driven wheels of
the vehicle and the non-driven wheels of the vehicle. The ECU 90
may also be provided with input from one or more rollover condition
sensors 93a that are operative to sense conditions such as lateral
acceleration that are indicative of a possible rollover condition
of the vehicle. Other types of sensor inputs may be provided, in
addition or alternatively.
[0055] The vehicle includes a foot brake valve 92 for controlling
flow of pressurized air from one or more reservoirs (not shown) to
the modulators 80 and 82. The foot brake valve 92 is actuated by
the vehicle brake pedal 94.
[0056] The foot brake valve 92 has a primary chamber 96 that is
located in a primary circuit 98 of the vehicle braking system. The
primary circuit also includes a relay valve 100, between the foot
brake valve 92 and the modulators 82. The relay valve 100 does not
have an ATC solenoid. The primary circuit 98 controls braking on
the driven wheels 76.
[0057] The foot brake valve 92 has a secondary chamber 102 that is
located in a secondary circuit 104 of the vehicle braking system
70. The secondary circuit also includes a relay valve 106, between
the foot brake valve 92 and the modulators 80. The relay valve 106
does not have an ATC solenoid. The secondary circuit 98 controls
braking on the non-driven wheels 74.
[0058] The system 10 also includes a brake valve actuator (BVA) 110
interposed between the brake valve 92 and the brake pedal. The BVA
110 is controlled by a solenoid valve 112 that is capable of
proportional pressure application.
[0059] In accordance with one aspect of the present invention, the
BVA controller 112 is operated by the ECU 90. The ECU 90 actuates
the BVA 110 to provide braking pressure to all the modulators 80
and 82. Specifically, it provides the potential for braking
pressure to reach all four modulators 80 and 82 via the relay
valves 100 and 106. The operation is different for ATC and for
RS.
[0060] For ATC operation, in the event of sensed wheel spin during
acceleration, the ECU 90 actuates the BVA 110. The ECU 90 controls
the modulators 82 on the driven axle, in a manner to apply braking
effect so as to keep all wheels 76 on the driven axle spinning
together, in the following manner. (This function is provided in
the prior art system (FIG. 4) by energizing the ATC valves to apply
the brakes on the driven wheels.)
[0061] First, the ECU 90 controls the modulators 80 on the
non-driven wheels 74 so as to block air flow to the brake chambers
on the non-driven wheels. Next, the ECU 90 controls the BVA 110 to
apply air to both the primary and secondary circuits 98 and 104.
Because the secondary circuit modulators 80 are already blocked
when this application of air is provided, no braking occurs at the
non-driven wheels 74. The primary circuit modulators 82 receive air
just as if it were coming from an ATC valve, and they control
braking of the driven wheels 76 in the known manner to provide the
automatic traction control function.
[0062] To provide an RS function in the system 70, the ECU 90 may
determine, in a known manner, the need to slow the vehicle to
mitigate a rollover risk. The ECU 90 cuts the vehicle throttle and
applies the vehicle brakes strongly, in a manner as described
below. (This function is provided in the prior art system (FIG. 4)
by energizing the ATC valves to apply the brakes on the driven
wheels.)
[0063] The brake application in the system 70 of FIG. 5 is effected
by the ECU 90 actuating the BVA 110. The actuation of the BVA 110
pulls down the brake pedal 94, proportionally. The ECU 90 controls
the modulators 82 on the driven axle to provide the desired ATC
function at the driven wheels 76.
[0064] If the RS function is active and the driver steps on the
brake pedal 94 strongly, the system 70 can abort the RS function
and return full braking control to the driver. This happens because
of the "mechanical override" feature of the BVA 110, which
transfers control of the dual brake valve 92 from the BVA to the
brake pedal 94 when the brake pedal is depressed enough to indicate
a demand for more pressure than is being provided by the
BVA-controlled brake valve.
[0065] Because of this "mechanical override" feature, the system 70
does not need any pressure sensors or brake pedal sensors or
switches to effect an RS abort in response to sudden driver demand.
In this manner, the added cost and complexity of the prior art
system shown in FIG. 4 is eliminated. The two ATC solenoids and two
pressure sensors are replaced with one BVA (which may already be
present on the vehicle) and one solenoid.
[0066] The ECU 90 may be operative to block braking effect at all
wheels except one, in a situation in which a low pressure test
pulse is provided to that one wheel to help detect imminence of a
rollover situation.
[0067] In accordance with another aspect of the invention, a roll
stability control or roll stability (RS) function can be provided
for a tractor-trailer vehicle having a BVA, with reduced cost and
complexity compared to standard braking systems that provide such a
function.
[0068] FIG. 6 shows a prior art system that is used for obtaining
RS on a tractor-trailer. The system is similar to the system shown
in FIG. 4 for obtaining RS on a straight truck or bus. The parts
that are used for braking control on the tractor are the same as
those shown in FIG. 4. No brake valve actuator is used. An air line
is taken off the delivery from the dual brake valve secondary
circuit, going back to a double check valve. Another air line is
taken off the delivery from the dual brake valve primary circuit,
going back to the double check valve. The higher of these two lines
provides the input/supply to the trailer, in a known, standard
manner.
[0069] In the prior art system shown in FIG. 6, the pressure that
is passed through from the double check valve goes to a trailer
control module or solenoid. During an ATC event, the ECU controls
the solenoid to block application of braking effect to the wheels
of the trailer. When an ATC event is not in progress, the ECU
controls it to enable application of braking effect to the wheels
of the trailer in the usual manner.
[0070] This system requires, on top of the ABS hardware, two
pressure sensors and two ATC solenoids, in order to be able to
perform the RS function.
[0071] FIG. 7 illustrates schematically a vehicle braking system
70a constructed in accordance with a fourth embodiment of the
invention. The system 70a provides an RS function on a tractor
trailer combination 72a, using BVA actuation.
[0072] The system 70a is similar to the system 70 shown in FIG. 5
for obtaining RS on a straight truck or bus, and parts that are the
same or similar in function are given the same reference numerals
with the suffix "a" added. The parts that are used for braking
control on the tractor are the same as those shown in FIG. 5,
including a BVA 110a.
[0073] An air line 120 is taken off the delivery from the secondary
circuit 104a, going back to a double check valve 122. Another air
line 124 is taken off the delivery from the primary circuit 96a,
going back to the double check valve 122. The higher of these two
lines 120 and 124 provides the input/control to the trailer.
[0074] The pressure that is passed through from the double check
valve 122 goes to a trailer control module or solenoid 126. During
an ATC event, the ECU 90a controls the solenoid 126 to block
application of braking effect to the wheels of the trailer. When an
ATC event is not in progress, the ECU 90a controls it to enable
application of braking effect to the wheels of the trailer.
[0075] The present invention is also applicable to ESP (electronic
stability program). This function includes roll stability functions
and hardware and can apply independent wheel end braking for yaw
stabilization. In this case, it is necessary to provide a sensor
for determining the driver's braking intention, or amount of
intervention, which is not needed in the cases mentioned above.
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