Fluid-pressure and analogous brake systems – Electric control
Reexamination Certificate
1999-11-24
2001-11-06
Schwartz, Christopher P. (Department: 3613)
Fluid-pressure and analogous brake systems
Electric control
C073S756000
Reexamination Certificate
active
06312061
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates in general to electro-hydraulic brake systems and in particular to a structure for mounting a cluster of pressure sensors upon an electro-hydraulic brake system control unit.
An electro-hydraulic brake system (EHB) combines the advantages of an electric braking system with components of a conventional hydraulic brake system. Thus, an EHB can be considered as an intermediate hybrid system which includes features of both a conventional hydraulic brake system and a brake by wire system (BBW). By utilizing conventional hydraulic brake components, development and conformance costs and times are reduced.
Referring now to
FIG. 1
, there is shown, generally at
10
, a typical EHB. The EHB
10
includes a pedal unit
11
which is hydraulically connected to a hydraulic control unit (HCU)
12
. The hydraulic control unit
12
forms an interface between the pedal unit
11
and a pair of conventional hydraulically actuated vehicle front wheel brakes
13
and a pair of conventional hydraulically actuated vehicle rear wheel brakes
14
.
The pedal unit
11
includes a tandem master cylinder
15
which is supplied with brake fluid from a master cylinder reservoir
16
. The master cylinder
15
is connected by a conventional mechanical linkage to a vehicle brake pedal
17
. The brake pedal
17
also is coupled to a displacement transducer
18
which generates an electrical signal having an amplitude which is proportional to brake pedal travel. One chamber of the master cylinder
15
is connected by a first hydraulic brake line
19
while the other chamber of the master cylinder
15
is connected to a second hydraulic brake line
20
. The pedal unit
11
also includes a normally closed valve
21
which connects the first brake hydraulic brake line
20
circuit to a pedal travel simulator
22
. The pedal travel simulator
22
is an electro-hydraulic device which is operative during operation of the EHB
10
to provide brake pedal resistance and force as feedback to the vehicle operator.
The HCU
12
includes a first normally open isolation valve
23
which is connected between the first hydraulic brake line
19
and one of the front wheel brakes
13
and a second normally open isolation valve
24
which is connected between the second hydraulic brake line
20
and the other of the front wheel brakes
13
. Each of the front wheel brakes
13
is connected through an isolator piston
25
to a pair of proportional control valves
26
whose purpose will be explained below. The second valve of each pair of proportional control valves
26
is connected to a corresponding rear wheel brake
14
. The isolator pistons
25
hydraulically isolate the front wheel brakes
13
from the rear wheel brakes
14
. As shown in
FIG. 1
, the front wheel brakes
13
are hydraulically connected through a first balance valve
27
. Similarly, the rear wheel brakes
14
are hydraulically connected through a second balance valve
28
.
The HCU
12
further includes a motor driven pump
35
as a source of pressurized brake fluid for actuation of the wheel brakes
13
and
14
. The pump
35
has an intake port which draws brake fluid through a hydraulic line
36
from the master cylinder reservoir
16
. The pump
35
also has a discharge port which is connected through each of the proportional control valves
26
to a corresponding front or rear wheel brake
13
or
14
. Each of the proportional control valves
26
includes a discharge port which is connected though a hydraulic discharge line
38
to the master cylinder reservoir
16
. The discharge port of the pump
35
also is connected through a relief valve
39
to a high pressure accumulator
40
.
A plurality of pressure sensors are included in the EHB
10
. The pressure applied to the HCU
12
by the master cylinder
15
is monitored by a brake actuation pressure sensor
45
which is illustrated in
FIG. 1
as being mounted in the first hydraulic brake line
19
between the master cylinder
15
and the first isolation valve
23
. Alternately, the brake actuation pressure sensor
45
can be mounted in the second hydraulic brake line
20
between the master cylinder
15
and the second isolation valve
24
(not shown). The brake actuation pressure sensor
45
is rated to measure relatively low pressures which are on an order of magnitude of 60 bar (900 psi). A wheel brake pressure sensor
47
is included in each hydraulic line connecting each proportional control valve
26
to the associated wheel brake. The wheel brake pressure sensors
47
monitor the pressure being applied to the associated wheel brake and are rated to measure relatively high brake actuation pressures which are on an order of magnitude of 200 bar (3,000 psi). An accumulator pressure sensor
48
is connected to the high pressure accumulator
40
and monitors the output pressure of the accumulator
40
. When the pump pressure exceeds the accumulator pressure or when the relief valve
39
is open, the accumulator pressure sensor
48
measures the pump output pressure. The accumulator pressure sensor
48
is also rated to measure relatively high pressures which are on an order of magnitude of 200 bar (3,000 psi).
The solenoid valves and pressure sensors are electrically connected to a microprocessor (not shown) which is included in an Electronic Control Module (ECU) (not shown). The ECU can either be mounted upon the HCU
12
or located remotely from the HCU
12
. The ECU microprocessor is programmed with appropriate software to monitor the output signals from the pressure sensors
45
,
47
and
48
and the brake pedal transducer
18
. The microprocessor is responsive to the sensed pressures and displacement of the brake pedal transducer
18
to energize the pump
35
and to selectively actuate the proportional control valves
26
to supply pressurized hydraulic fluid for actuation of the wheel brakes
13
and
14
.
The operation to the EHB
10
will now be described. During vehicle operation, the microprocessor associated with the HCU
12
continuously receives electrical signals from the brake pedal transducer
18
and the pressure sensors
45
,
47
and
48
. The microprocessor monitors the condition of the brake pedal transducer
18
and the pressure signals from the brake actuation pressure sensors
45
for potential brake applications. When the vehicle brake pedal
17
is depressed, the brake pedal displacement transducer
18
generates a displacement signal. Simultaneously, the brake actuation pressure sensor
45
generates a signal which is proportional to the force applied to the brake pedal
17
. The microprocessor is operative to combine the displacement and force signals into a brake command signal. The microprocessor software is responsive to the brake command signal to actuate the pump motor and close the isolation valves
23
and
24
to separate the master cylinder
15
from the wheel brakes
13
and
14
. The microprocessor then selectively operates the proportional control valves
26
in the HCU
12
unit to cyclically relieve and reapply hydraulic pressure to the wheel brakes
13
and
14
. The hydraulic pressure applied to the wheel brakes is adjusted by the operation of the proportional control valves
26
to produce adequate brake torque to decelerate the vehicle in accordance with the brake command signal generated by the vehicle operator.
If the EHB
10
should fail, the isolation valves
23
and
24
return to their normally open positions to provide unassisted push though braking by allowing direct hydraulic communication between the master cylinder
15
and the front wheel brakes
13
.
SUMMARY OF THE INVENTION
This invention relates to a structure for mounting a cluster of pressure sensors upon a control unit for an electro-hydraulic brake system.
As shown in
FIG. 1
, a typical electro-hydraulic brake system (EHB)
10
includes a plurality of pressure sensors
45
,
47
and
48
. In the past, vehicles have included pressure sensors for measuring engine manifold absolute pressure or barometric pressure, both of which have relati
Darnell Charles
Hornback Edward R.
Lowman Clark E.
Schliebe Paul M.
Bartz C. T.
Kelsey-Hayes Company
MacMillan Sobanski & Todd LLC
Schwartz Christopher P.
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