U.S. patent application number 09/814055 was filed with the patent office on 2001-10-25 for vehicular brake conrol device.
Invention is credited to Hamada, Toshiaki, Nitta, Hirofumi, Tanaka, Wataru.
Application Number | 20010034574 09/814055 |
Document ID | / |
Family ID | 18597972 |
Filed Date | 2001-10-25 |
United States Patent
Application |
20010034574 |
Kind Code |
A1 |
Tanaka, Wataru ; et
al. |
October 25, 2001 |
Vehicular brake conrol device
Abstract
The present invention provides a vehicular brake control device
which makes it possible to detect a failure or malfunction in
closing an electromagnetic valve which is placed between a master
cylinder and each of wheel cylinders. The vehicular brake control
device includes a pressure application device which is capable of
applying a hydraulic pressure automatically, i.e., regardless of a
brake pedal depression, to each of wheel cylinders by way of a
hydraulic pressure control device 17 from a master cylinder 20 and
an ECU 18 which drives the pressure application unit 12 and the
hydraulic pressure control device 17 to adjust a braking force of
each of wheels. The hydraulic pressure control device 17 includes a
set of pressure-maintaining and pressure-reducing valves for each
wheel. The ECU 18 has a pressure application check division 77
which begins to check the pressure application at a predetermining
timing.
Inventors: |
Tanaka, Wataru; (Anjo-shi,
JP) ; Hamada, Toshiaki; (Okazaki-shi, JP) ;
Nitta, Hirofumi; (Obu-shi, JP) |
Correspondence
Address: |
BURNS DOANE SWECKER & MATHIS L L P
POST OFFICE BOX 1404
ALEXANDRIA
VA
22313-1404
US
|
Family ID: |
18597972 |
Appl. No.: |
09/814055 |
Filed: |
March 22, 2001 |
Current U.S.
Class: |
701/70 ;
303/122 |
Current CPC
Class: |
B60T 8/4036 20130101;
B60T 8/88 20130101; B60T 8/4845 20130101; B60T 8/885 20130101; B60T
2270/406 20130101 |
Class at
Publication: |
701/70 ;
303/122 |
International
Class: |
B60T 008/88 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 22, 2000 |
JP |
2000-080969 |
Claims
What is claimed is:
1. A vehicular brake control device comprising: a master cylinder
which is capable of generating a brake fluid pressure in response
to a brake pedal depression force; hydraulic pressure control means
for controlling a brake fluid pressure which is transmitted from
the master cylinder to each of wheel cylinders of respective
wheels; pressure application means which is capable of
automatically applying a hydraulic pressure to each of the wheel
cylinders independent of a brake pedal depression by way of the
hydraulic pressure control means: and control means for controlling
a braking force of each of the wheels by driving the pressure
application means, the hydraulic pressure control means, or both
the hydraulic pressure control means including a first
electromagnetic valve for establishing and interrupting fluid
communication between the master cylinder and each of the wheel
cylinders and a second electromagnetic valve for establishing and
interrupting fluid communication between a reservoir and each of
the wheel cylinders, the control means including pressure
application check means which makes all the first electromagnetic
valves of the respective wheels and all the second electromagnetic
valves of the respective wheels closed and opened, respectively, at
a predetermined timing and which initiates a pressure application
check for judging whether or not the automatic pressure application
is made successfully by controlling the pressure application means,
the pressure application check means including electromagnetic
valve abnormal condition judging means which judges whether the
first electromagnetic valve of one of the wheel cylinders fails to
be kept opened if the rate of change of the hydraulic pressure
applied by the pressure application means increases after an elapse
of a fixed time duration (KT1) from the initiation of the pressure
application check.
2. A vehicular brake control device as set forth in claim 1,
wherein the pressure application check means judges, if the master
cylinder pressure increases to a predetermined value (KP1) before a
fixed time duration (KT2) elapses after the initiation of the
pressure application check, whether the pressure application means
and the first electromagnetic valve of each of the wheels are in
normal condition.
3. A vehicular brake control device as set forth in claim 1,
wherein the pressure application check means includes pressure
application abnormal judging means and pump regenerative voltage
check means, the pressure application abnormal judging means
judging temporarily whether the pressure application means is
abnormal if more than a fixed time duration (KT2) from the
initiation of the pressure application check is required for the
master cylinder pressure to increase to a predetermined value
(KP1), the pump regenerative voltage check means driving a pump for
a short time duration in order to suck the brake fluid, after the
temporal judgment, which enters the reservoir by way of the second
electromagnetic valve of each of the wheel cylinders, the pump
regenerative voltage check means judging whether, if the
regenerative voltage of the pump after its driving is less than a
predetermined value (KVP), the first electromagnetic valve of one
of the wheel cylinders fails to be kept open.
4. A vehicular brake control device as set forth in claim 3,
wherein the pump regenerative voltage check means judges whether,
if the regenerative voltage of the pump after its driving is not
less than the predetermined value (KVP), each of the first
electromagnetic valves is normal and the pressure application means
is abnormal.
Description
[0001] This application is based on and claims priority under 35
U.S.C. .sctn. 119 with respect to Japanese Application No.
2000-080969 filed on Mar. 22, 2000, the entire content of which is
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention is directed to a vehicular brake
control device which makes it possible to apply a brake fluid
pressure to each of wheel cylinders irrespective of a brake pedal
operation.
BACKGROUND OF THE INVENTION
[0003] One of the prior art vehicular brake control devices of the
kind, as is well known, includes a hydraulic pressure generation
means which makes it possible to cause a master cylinder to
generate a master cylinder pressure in response to a brake pedal
depression force which is, for example, boosted by a booster, a
hydraulic pressure supply means which supplies the master cylinder,
as a brake fluid pressure, to a wheel brake cylinder of each of
wheels, and a pressure application means which introduces a
hydraulic pressure into a pressure application chamber in the
hydraulic pressure supply means. In addition, the aforementioned
known vehicular brake control device includes a control means which
controls the pressure application means to automatically adjust the
master cylinder pressure and which drives the hydraulic pressure
supply means to control a braking force to be applied to each of
the wheels. The hydraulic pressure generation means has a normally
opened electromagnetic valve, as a pressure-maintaining valve,
which establishes and interrupts a fluid communication between the
master cylinder and each of the wheel cylinder and a normally
closed electromagnet valve, as a pressure-decrease valve, which
establishes and interrupts a fluid communication between the master
cylinder and a reservoir.
[0004] In the foregoing conventional or prior art brake control
device, when the master cylinder pressure is automatically
increased, if the wheel cylinders are for front-wheels as driven
wheels of an FR-vehicle under traction control, the pressure
retaining valve is required to close which is provided between the
master cylinder and each of such wheel cylinders in order to
prevent an increase of the brake fluid pressure of each of the
wheel cylinders.
[0005] However, if the pressure retaining valve malfunctions or has
trouble remaining in its opened state, the wheel cylinder which is
never increased in hydraulic pressure is pressurized. Thus, for
example, despite traction control for starting or accelerating the
vehicle, a problem occurs such as prevention of starting the
vehicle due to the brake fluid application into the wheel cylinder,
or so-called `brake drag`.
[0006] Thus, a need exists to provide a vehicular brake control
device, for overcoming the aforementioned problem, which make it
possible to detect a malfunction of an electromagnetic valve
wherein its opened state remains unchanged or can not be shifted to
its closed state.
SUMMARY OF THE INVENTION
[0007] The present invention has been developed to satisfy the
request noted above and a first aspect of the present invention is
to provide a vehicular brake control device which comprises:
[0008] a master cylinder which is capable of generating a brake
fluid pressure in response to a brake pedal depression force;
[0009] hydraulic pressure control means for controlling a brake
fluid pressure which is transmitted from the master cylinder to
each of wheel cylinders of respective wheels;
[0010] pressure application means which is capable of automatically
applying a hydraulic pressure to each of the wheel cylinders
independent of brake pedal depression by way of the hydraulic
pressure control means; and
[0011] control means for controlling a braking force of each of the
wheels by driving the pressure application means and/or the
hydraulic pressure control means,
[0012] the hydraulic pressure control means including a first
electromagnetic valve which establishes and interrupts fluid
communication between the master cylinder and each of the wheel
cylinders and a second electromagnetic valve which establishes and
interrupts fluid communication between a reservoir and each of the
wheel cylinders,
[0013] the control means including pressure application check means
which makes all the first electromagnetic valves of the respective
wheels and all the second electromagnetic valves of the respective
wheels closed and opened, respectively, at a predetermined timing
and which initiates a pressure application check for judging
whether or not automatic pressure application is made successfully
by controlling the pressure application means,
[0014] the pressure application check means having an
electromagnetic valve abnormal condition judging means which judges
that the first electromagnetic valve of one of the wheel cylinders
fails to be kept opened if a changing rate of the hydraulic
pressure applied by the pressure application means increases after
a fixed duration (KT1) has elapsed from the initiation of the
pressure application check.
[0015] In accordance with a first aspect of the present invention,
the first electromagnetic valve and the second electromagnetic
valve are closed and opened, respectively, if a failure or
malfunction is found in closing the first electromagnetic valve
(i.e., the first electromagnetic valve fails to shift from its open
position to its closes position), the brake fluid flows into the
reservoir through the second electromagnetic valve, the consumed
amount of the brake fluid at each of the wheel cylinders increases.
Thus, the increasing speed of the hydraulic pressure becomes slower
which is introduced by the pressure application means after
initiation of the pressure application check, which results in that
immediately when the reservoir is filled with the brake fluid the
increasing speed of the hydraulic pressure changes drastically,
which is introduced by the pressure application means. Therefore,
if a speed change is found to be increased in the increasing speed
of the hydraulic pressure which is introduced by the pressure
application means within a fixed time duration (KT1), measured from
the initiation of the pressure application, the electromagnetic
valve abnormal judging means makes it possible to detect, with
great accuracy, a failure or malfunction in closing the first
electromagnetic valve.
[0016] A second aspect of the present invention is to provide a
vehicular brake control device, as a limited version of the first
aspect, wherein the pressure application check means judges, if the
master cylinder pressure increases to a predetermined value (KP1)
before a fixed time duration (KT2) elapses after the initiation of
the pressure application check, that the pressure application means
and the first electromagnetic valve of each of the wheels are in
normal condition.
[0017] In accordance with the second aspect of the present
invention, if the hydraulic pressure which is introduced by the
pressure application is increased to a fixed value (KP1) until a
fixed time duration (KT2) elapses after initiation of the pressure
application check, it becomes possible to judge that the pressure
application means and the first electromagnetic valve of each of
the wheels are in good order or in normal condition.
[0018] A third aspect of the present invention is to provide a
vehicular brake control device, as a limited version of the first
aspect, wherein the pressure application check means includes
pressure application abnormal judging means and pump regenerative
voltage check means, the pressure application abnormal judging
means judging temporarily that the pressure application means is
abnormal if more than a fixed time duration (KT2) from the
initiation of the pressure application check is required for the
master cylinder pressure to increase to a predetermined valve
(KP1), the pump regenerative voltage check means driving a pump for
a short time duration in order to suck the brake fluid, after the
temporal judgment, which enters the reservoir by way of the second
electromagnetic valve of each of the wheel cylinders, the pump
regenerative voltage check means judging that if the regenerative
voltage of the pump after its driving is less than a predetermined
value (KVP) the first electromagnetic valve of one of the wheel
cylinders fails to be kept open.
[0019] In accordance with the third aspect of the present
invention, if the master cylinder pressure requires a fixed time
duration (KT2) measured from the initiation of the pressure
application check for reaching a predetermined value (KP1), it is
impossible to judge whether the pressure application means is
abnormal or the first electromagnetic valve is in failure in its
closing operation. Thus, the pressure application means is
temporarily judged to be abnormal. Thereafter, if the pump
regenerative voltage is found to be not greater than the
predetermined value (KVP) after driving the pump for a short time
duration, the brake fluid flows into the reservoir by way of the
second electromagnetic valve due to a failure or malfunction im the
first electromagnetic valve, which makes it possible to judge that
the pump inertia force of the pump upon its termination is used to
discharge the brake fluid and therefore the pump regenerative
voltage lowers temporarily. Thus, in such a case, it can be judged
that a failure or malfunction is found in closing the first
electromagnetic valve of any one of the wheel cylinders.
[0020] A fourth aspect of the present invention is to provide a
vehicular brake control device, as a limited version of the third
aspect, wherein the pump regenerative voltage check means judges
that if the regenerative voltage of the pump after its driving is
not less than the predetermined value (KVP), each of the first
electromagnetic valves is normal and the pressure application means
is abnormal.
[0021] In accordance with the fourth aspect of the present
invention, if the regenerative voltage of the pump after its
driving is not less than a fixed value (KVP) the first
electromagnetic valve is normal and the brake fluid fails to flow
into the reservoir by way of the second electromagnetic valve.
Thus, the foregoing pump inertia force is not used to discharge the
brake fluid when the pump stops, i.e., the pump has no load, which
makes it possible to judge that the first electromagnetic valve is
normal and the pressure application means is abnormal.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The foregoing and additional features and characteristics of
the present invention will become more apparent from the following
detailed description considered with reference to the accompanying
drawing figures in which like reference numerals designate like
elements and wherein:
[0023] FIG. 1 illustrates a diagram of a vehicular brake control
device in accordance with an embodiment of the present
invention;
[0024] FIG. 2 illustrates a hydraulic pressure circuit diagram with
which the vehicular brake control device shown in FIG. 1 is in
association;
[0025] FIG. 3 illustrates a flowchart which is indicative of how
the vehicular brake control device, which is shown in FIG. 1,
operates;
[0026] FIG. 4 illustrates a flowchart of a sub-routine shown in
FIG. 3; and
[0027] FIG. 5 illustrates a flowchart of a sub-routine shown in
FIG. 4.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
[0028] Hereinafter, a vehicular brake control device with automatic
pressure application function in accordance with an embodiment of
the present invention will be explained in detail with reference to
FIGS. 1 to 4 inclusive.
[0029] First of all, as shown in FIG. 2, the vehicular brake
control device includes a pressure generating device 11 which
generates and issues a brake fluid pressure and a pressure
application unit 12 which automatically applies a hydraulic
pressure to the pressure generating device 11. In addition, the
vehicular brake control device includes a hydraulic pressure
control device 17 which regulates the brake fluid pressure which is
transmitted from the pressure generating device 11 to wheel
cylinders 13, 14, 15, and 16 which are provided on a front-right
wheel FR, a front-left wheel FL, a rear-right wheel FR, and a
rear-left wheel RR, and a rear-left wheel RL, respectively, and an
electronic control unit 18 (cf. FIG. 1) which controls braking
forces of the respective front-right wheel FR, front-left wheel FL,
rear-right wheel RR, and rear-left wheel RL.
[0030] The pressure generating device 11 has a vacuum booster 19
and a master cylinder 20. The master cylinder 20 is illustrated in
a schematic fashion for simplification wherein seal members and
other members are omitted. In the pressure generating device 11,
when a brake pedal 21 is depressed, the resultant depression force
is amplified at a lever ration in a link mechanism (not shown).
Then, the amplified force is transmitted to an operating rod 22,
thereby pushing the same. The force transmitted to the rod 22 is
further amplified at the vacuum booster 19 and the resultant force
is transmitted to a first piston 23 of the master cylinder 20.
Then, the first piston 23 is urged in the left direction in FIG. 2
from the illustrated original position against a biasing force of a
spring, which results in that a fluid communication between the
reservoir 25 and a first pressure chamber 24 of the master cylinder
20 is interrupted, thereby generating or developing a hydraulic
pressure in the first pressure chamber 24. The resultant hydraulic
pressure urges a second piston 26 in the left direction in FIG. 2
from the original position against a biasing force of a spring,
with the result that a fluid communication between the reservoir 25
and a second pressure chamber 27 of the master cylinder 20 is
interrupted, thereby generating or developing a hydraulic pressure
in the second pressure chamber 27.
[0031] Thus, when the first piston 23 is urged by the pedal
depression force after being amplified by both the link mechanism
and the vacuum booster 19, the brake fluid pressure, viz., a brake
input pressure Pmcin is generated in the first pressure chamber 24
which depends on the pedal depression force. In addition, the brake
fluid pressure generated in the first pressure chamber 23 urges the
second piston 26 to generate the brake fluid pressure also in the
second pressure chamber 27. It is to be noted that hereinafter the
phrase `the pressure increased at the vacuum booster 19` includes
the lever-ratio amplified pressure at the link mechanism.
[0032] In addition, in the master cylinder 20, a third pressure
chamber 28 is defined at a side of the first piston 23 which is
opposed to the vacuum booster 19 in order to receive the hydraulic
pressure generated at the pressure generate unit 12. When this
hydraulic pressure or a third chamber pressure P3 causes the first
piston 23 to move forward, a hydraulic pressure or a third chamber
servo pressure Pmc3 is generated in the first pressure chamber 24
which is an amplification of the third chamber pressure P3 at a
pressure receiving area ratio A of the first piston 23, where
pressure receiving area ratio A is defined as a ratio between a
pressure receiving area of the first piston which opposes the first
pressure chamber 24 and a pressure receiving area of the first
piston which opposes the third pressure chamber 28. Thus, the
master cylinder 20 is expected to issue a master cylinder pressure
Pmc which is made up two components: one is the pedal input
pressure Pmc3 which depends on the pedal depression force which is
amplified at the vacuum booster, the other is the third chamber
pressure Pmc3 which depends on the hydraulic pressure which is fed
from the pressure application unit 12.
[0033] The pressure application unit 12 includes a pump 29 which
supplies a brake fluid stored in the reservoir 25 after
pressurizing the brake fluid to the third pressure chamber 28, an
electric motor 30 which drives the pump 29, and a linear valve 31
whose open degree changes and varies with a voltage value of an
input signal (a control signal) in order to relieve the brake fluid
under pressure which is discharged from the pump 29 to the
reservoir 25. Thus, if the electronic control unit (ECU) 18 issues
the control signal which is indicative of the current value to the
linear valve 31, hydraulic-current characteristic (i.e., adjusting
characteristic of pressure application) of the linear valve 31
causes the third pressure chamber 28 to introduce therein the
hydraulic pressure which is in proportion to the value of the
control signal (current value). This introduced hydraulic pressure
is the difference between the pressure of the brake fluid
discharged from the pump 29 and a pressure decrease of the brake
fluid at the linear valve 31 which is discharged from the pump
29.
[0034] The brake fluid pressure generated at the master cylinder 20
is applied to the wheel cylinders by way of front-wheel side and
rear-wheel side piping systems. That is, the hydraulic control
device 17 which establishes fluid pressure control between the
master cylinder 20 and each of the wheel cylinders 13 through 16
includes front and rear hydraulic circuits.
[0035] The brake fluid pressure generated at the first pressure
chamber 24 of the master cylinder 20 is fed to a main passage 32
which is in fluid communication with the wheel cylinders 13 and 14
by way of the front hydraulic circuit. That is, the main passage 32
has two branching passages in which pressure-maintaining valves 33a
and 34a are provided which are in fluid communication with the
wheel cylinders 13 and 14, respectively. In addition, a passage
between the wheel cylinder 13 and the pressure-maintaining valve
33a is in fluid communication with a reservoir 38 by way of a
pressure-decrease valve 33b, while a passage between the wheel
cylinder 14 and the pressure-maintaining valve 34a is in fluid
communication with the reservoir 38 by way of a pressure-decrease
valve 34b.
[0036] On the other hand, the brake fluid pressure generated at the
second pressure chamber 27 of the master cylinder 20 is fed to a
main passage 37 which is in fluid communication with the wheel
cylinders 15 and 16 by way of the rear hydraulic circuit. That is,
the main passage 37 has two branching passages in which
pressure-maintaining valves 35a and 36a are provided which are in
fluid communication with the wheel cylinders 15 and 16,
respectively. In addition, a passage between the wheel cylinder 15
and the pressure-maintaining valve 35a is in fluid communication
with a reservoir 39 by way of a pressure-decrease valve 35b, while
a passage between the wheel cylinder 16 and the
pressure-maintaining valve 36 is in fluid communication with the
reservoir 39 by way of a pressure-decrease valve 36b.
[0037] Each of the pressure-maintaining valves 33a, 34a, 35a, and
36a is in the form of a normally opened electromagnetic valve,
while each of the pressure-decrease valves 33b, 34b, 35b, and 36b
is in the form of a normally closed electromagnetic valve. Each of
these valves 33a, 34a, 35a, 36a, 33b, 34b, 35b, and 36b is made ON
(energized) upon receipt of the hydraulic pressure control (control
current) issued from the ECU 18.
[0038] Thus, in case where the pressure-maintaining valve 33a and
the pressure-decrease valve 33b, which are for the front-right
wheel FR which is explained representatively as an example,
selected r43ecipon, while both the pressure-maintaining valve 33a
and the pressure-decrease valve 33b are made OFF (deenergized), the
wheel cylinder 13, which is isolated from the reservoir 38, is in
fluid communication with the master cylinder 20, thereby making a
wheel cylinder pressure-increase condition. Under a
pressure-increase condition, the hydraulic pressure of the wheel
cylinder 13 can be increased. While both the pressure-maintaining
valve 33a and the pressure-decrease valve 33b are made ON
(energized), the wheel cylinder 13, which is isolated from the
master cylinder 20, is in fluid communication with the reservoir
38, thereby making a wheel cylinder 13 pressure-decrease condition.
Under a pressure-decrease condition, the hydraulic pressure of the
wheel cylinder 13 can be decreased. While the pressure-maintaining
valve 33a and the pressure-decrease valve 33b are made ON
(energized) and OFF (deenergized), respectively, the wheel cylinder
13 is isolated from both of the master cylinder 20 and the
reservoir 38, thereby making a wheel cylinder 13
pressure-maintaining condition under which the brake fluid pressure
in the wheel cylinder 13 is, without being increased or decreased,
kept at a predetermined value.
[0039] Bringing each of the wheel cylinders into any one of the
aforementioned three states can be made by changing the signal (ON
or OFF) which is fed to the pressure-maintaining valve and the
pressure-decrease valve which correspond to each of the wheel
cylinders, which results in that the brake fluid pressure which is
applied to each of the wheel cylinders 13, 14, 15, and 16 can be
varied or adjusted, thereby making it possible to establish an
individual braking force control for each of the wheels FR, FF, RF,
and RR.
[0040] In the front hydraulic circuit, there are provided return
passages 47 and 48 which makes it possible to return the brake
fluid from the wheel cylinders 13 and 14, by passing the
pressure-maintaining valves 33a and 34a, respectively, to the
master cylinder 20. In the return passages, there are provided
check valves 49 and 50 so that the brake fluid may not flow back to
the wheel cylinders 13 and 14, respectively. Similarly, in the rear
hydraulic circuit, there are provided return passages 51 and 52
which makes it possible to return the brake fluid from the wheel
cylinders 15 and 16, by bypassing the pressure-maintaining valves
35a and 36a, respectively, to the master cylinder 20. In the return
passages, there are provided check valves 53 and 54 so that the
brake fluid may not flow back to the wheel cylinders 15 and 16,
respectively.
[0041] In the main passage 32, there is provided a hydraulic
pressure gauge or sensor 62 for determining the master cylinder
pressure Pmc which is generated, as a brake fluid pressure, at the
master cylinder 20. The wheels FR, FL, RR, and RL are provided with
wheel speed sensors 63, 64, 65, and 66 for measuring wheel speeds
thereof, respectively. The brake pedal 21 is in association with a
stop lamp switch (SLS) 67. The stop lamp switch 67, which acts as a
brake pedal depression detection means, issues a first signal (e.g.
an ON signal) and a second signal OFF (e.g. OFF signal) when the
brake pedal 21 is depressed and the brake pedal is released,
respectively.
[0042] Referring back to FIG. 1 for explaining a detailed structure
of the ECU 18, in response to or depending on the brake pedal
depression force or a vehicle condition, the ECU 18 controls the
braking force applied to each of the wheels by driving the ECU 18
and by causing the pressure application unit 12 to establish an
automatic increase of the master cylinder pressure such that the
pressure application unit 12 adjusts the control signal to be fed
to the linear valve 31 which results in adjusting the hydraulic
pressure to be introduced into the third pressure chamber 28 of the
master cylinder 20 (the third pressure chamber pressure P3).
[0043] The ECU 18 is in the form of a micro-computer based
electronic control device. In detail, the ECU 18 is made up of a
CPU (Central Processing Unit) 70, a RAM (Random Access Memory) 71,
a ROM (Read Only Memory) 72, an input circuit division 73, an
output circuit division 74, and others.
[0044] The input circuit division 73 is connected with the
hydraulic pressure sensor 62, the stop lamp switch 67, and the
wheel speed sensors 63, 64, 65, and 66. In addition to these
sensors, the input circuit division 73 is also connected with a
steering angle sensor 81 which detects a steering angle, a
vehicular acceleration sensor 82 which detects vehicle-body
lengthwise and lateralwise accelerations, a yaw rate sensor 83
which detects a yaw rate of the vehicle body, and other devices.
Moreover, the input circuit division 73 is connected with the motor
30 and the linear valve 31 of the pressure application unit 12, the
pressure-maintaining valves 33a, 34a, 35a, and 36a and
pressure-decrease valves 33b, 34b, 35b, and 36b, the motor 40, and
others.
[0045] The ECU 18 includes a vehicle stability control division 75,
an automatic pressure application control division 76, and a
pressure application check division 77 as a pressure application
check means. These divisions are designed to function on the basis
of calculation results at the CPU 70.
[0046] The vehicle stability control division 75 executes vehicle
stability control which controls the braking force of each of the
wheels individually for decreasing a deviation of the vehicle body
under, e.g., steering for turn from a target line to be as small as
possible on the basis of a vehicle condition which is detected by
the wheel speed sensors 63-66, the sensors 81-83, and others such
as a vehicle condition (vehicle condition amount) under steering
for turn. For such a purpose, the vehicle stability control
division 75, depending on the detected vehicle condition amount,
controls the motor 30 of the pressure application unit 12 and an
amount of the control signal (current amount I) to be supplied to
the linear valve 31 of the pressure control unit 12.
Simultaneously, the vehicle stability control division 75 controls
the pressure-maintaining valves 33a, 34a, 35a, and 36a, and the
pressure-decrease valves 33b, 34b, 35b, and 36b, and others.
[0047] Other than the vehicle stability control division 75, the
ECU 18 includes an anti-skid control division 90 and a traction
control division 91. The anti-skid control division 90, for the
purpose of preventing the wheel from being locked upon brake
application, controls the hydraulic pressure control device 17 so
as to adjust the braking force to be applied to each of the wheels.
The traction control device 91, for preventing the driving wheels
from slipping when the vehicle is driven, controls the pressure
application unit 12 and the hydraulic pressure device 17 for
applying braking force to each of the driving wheels.
[0048] The automatic pressure application control division 76
causes, when it controls the control signal to be fed to the linear
valve 31 of the pressure application unit 12, the pressure
application unit 12 to adjust the hydraulic pressure introduced
into the third pressure chamber 28 of the master cylinder (the
third chamber pressure P3) for establishing an automatic pressure
application of the master cylinder pressure. For such a purpose,
the automatic pressure application control division 76 adjusts the
hydraulic pressure (the third chamber pressure P3) above a maximum
master cylinder pressure Pmc which is obtained when the vacuum
booster 19 is operated by the fully depressed brake pedal 21 and
automatically adjusts the master cylinder pressure Pmc by the third
chamber servo pressure Pmc3 which depends on the resulting
hydraulic pressure.
[0049] The pressure application check division 77 checks whether or
not the aforementioned automatic pressure application is made, at a
predetermined timing, when the vehicle begins to travel, on the
basis of an output signal from the stop lamp switch 67 and the
master cylinder pressure Pmc which is detected by the hydraulic
pressure sensor 62. In detail, when the vehicle begins to travel,
the pressure application check division 77 controls the pressure
application unit 12 to increase the master cylinder pressure by
closing all of the pressure-maintaining valves 33a, 34a, 35a, and
36a which constitutes a first electromagnetic valve device and by
opening all of the pressure-decrease valves 33b, 34b, 35b, and 36b
which constitute a second electromagnetic valve device, thereby
beginning to check whether or not the foregoing automatic pressure
application is established.
[0050] The pressure application check division 77 has a
pressure-maintaining valve abnormal judging portion 78 which judges
whether one of the pressure-maintaining valves 33a, 34a, 35a, and
36a of the respective wheels is in failure in the closing movement
during the changing speed of the master cylinder pressure when a
fixed time duration (KIT) elapses after initiation of the pressure
application check.
[0051] The pressure application check division 77 also has a
pressure unit abnormal judging portion 79, as a pressure
application abnormal judging means, which temporarily judges that
the pressure application unit 12 is abnormal or malfunctioning when
a fixed time duration (KT2) is required after initiation of the
pressure application check for the master cylinder to reach a
predetermined value (KP1). Moreover, the pressure application check
division 77 has a pump regenerative voltage check means, which
judges, subsequent to the temporary judgment, that one of the
pressure-maintaining valves 33a, 34a, 35a, and 36a of the
respective wheels is in failure in the closing movement when a pump
regenerative voltage is less than a predetermined value (KW) after
driving the pump 41 (42) for a short time, during which the pump
sucks the brake fluid from the reservoir 38 (39) which has flowed
therein from the pressure-decrease valves (i.e. the second
electromagnetic valve device) 33b and 34b (35b and 36b).
[0052] Hereinafter, with reference to FIGS. 3 to 5 inclusive, an
operation of the vehicular brake control device according to the
present embodiment will be described, together with an explanation
of a content which is executed by the ECU 18.
[0053] A main routine, which follows a flowchart shown in FIG. 3,
starts upon engine starts-up which results from turning on a
vehicular ignition switch (not shown). After doing a required
initialization, at step S100, an input procedure and a calculate
procedure are executed in such a manner that the input procedure
reads the signals from the hydraulic pressure sensor 62, the stop
lamp switch 67, the wheel speed sensors 63, 64, 65 and 66, the
steering angle sensor 81, the vehicular acceleration sensor 82, the
yaw rate sensor 83, and other sensors, and the calculate procedure
calculates a master cylinder pressure change speed dPmc according
to the following formula:
dPmc=Pmc'-Pmc
[0054] where Pmc' and Pmc are the current and the latest master
cylinder pressures.
[0055] Next, at step S101, wheel and vehicular condition amounts
are calculated such as a wheel speed of each wheel, a wheel
acceleration of each wheel, each estimated vehicle body speed at a
vehicle position, and a real slip rate of each wheel.
[0056] Thereafter, the control goes to step S102, where it is
checked whether the initiation condition of the pressure
application check is checked or the pressure application check has
been terminated. If the result is false (NO) and true (YES), step
S103 is executed and step S104 is executed by jumping step S103,
respectively.
[0057] The initial condition of the pressure application check is
established at a timing when the stop lamp switch 67 is made OFF by
releasing the brake pedal 21 while the brake pedal 21 is being
depressed which causes the stop lamp 67 to be made ON after turning
on the ignition switch for starting the vehicle. Thus, so long as
the brake pedal 21 is being depressed, the initiation cognition
fails to be established. In addition, the termination of the
pressure application check means that a flag is set (e.g. the flag
is made `1`) for indicating that the pressure application has been
terminated.
[0058] Now, the brake pedal 21 is released for starting the
vehicle, the initiation condition of the pressure application check
is established, which makes the pressure application check
termination flag `0`, and the control goes to step S103 to perform
a pressure application check procedure whose flowchart is depicted
in FIG. 4.
[0059] In the pressure application check procedure, as the
flowchart in FIG. 4 shows, first of all, at step S202, it is
checked whether or not the pressure application check is being
made. If so, the control goes to step S204. If not, i.e., if the
pressure application procedure has been terminated, the control
goes to step S222.
[0060] Since the pressure application is now being made, the
control goes to step S204, at which all of the pressure-maintaining
valves 33a, 34a, 35a, and 36a of the respective wheels are
energized to close, all of the pressure-decrease valves 33b, 34b,
35b, and 36b of the respective wheels are de-energized to open, the
control current to the linear valve 31 is caused to increase, the
pump 29 is driven (i.e., is made ON) by the motor 30, and a timer
CTCHECK is initiated to increase or count-up while the pressure
application check. Thus at step S204, the brake fluid is prevented
from being fed to each of the wheel cylinders 13, 14, 15, and 16 by
closing all of the pressure-maintaining valves 33a, 34a, 35a, and
36a of the respective wheels, the pressure-decrease valves 33b,
34b, 35b, and 36b of the respective wheel are opened, and
concurrently the pressure application unit 12 is controlled to
increase the master cylinder pressure, which results in the
initiation of the automatic pressure application. Thus, during the
resultant condition, the master cylinder pressure increases speed
while the resultant condition becomes later than that while the
pressure-decrease valves 33b, 34b, 35b, and 36b are being closed.
This means that the slope of the pressure increase is
decreased.
[0061] Thereafter, at step S206, it is checked whether or not the
fixed time duration KT2 has elapsed from the initiation of the
pressure application check, i.e., the count value of the counter
CTCHECK is in excess of KT2. If the result is false, the control
goes to step S208. If the result is true, the control goes to step
S216.
[0062] If the control goes to step S208 before the fixed time
duration KT2 has not elapsed when measured from the initiation of
the pressure application check, it is checked whether or not the
master cylinder pressure is in excess of the predetermined value
KP1. If the master cylinder pressure Pmc is equal to or less than
the predetermined value KP1, the control goes to step S218. When,
just after the pressure application check, the master cylinder
pressure Pmc is low, the control goes from step S208 to step
S210.
[0063] At this step S210, it is checked whether or not the fixed
time duration KT1 has been elapsed from the initiation of the
pressure application check, i.e., the count value of the counter
CTCHECK is in excess of KT1 (KT1<KT2). If the count value of the
counter CTCHECK is less than or equal to KT1, the control goes to
step S104. If the count value of the counter CTCHECK is in excess
of KT1, the control goes to step S212.
[0064] At step S104 which is to be executed when the counter
CTCHECK indicates a value of not greater than KT1, a control mode,
such as anti-skid control and its corresponding slip rate, are
set.
[0065] Thereafter, the control goes to step S105. In a hydraulic
pressure servo control at step S105, in response to the set control
mode, the pressure application unit 12 and the hydraulic pressure
control device 17 are so driven as to control the braking force to
be applied to each of the wheels. Thereafter, the control returns
to step S100 to execute steps S100, S101, and S102. At step S102,
if the aforementioned pressure application check initiation
condition is not established, which is indicates the pressure
application check procedure is being made, the control goes step
S103 to continue pressure application check procedure.
[0066] In the pressure application check procedure, after executing
steps S202, S204, and S206, at step S208, if the fixed time
duration KT1 elapses from the initiation of the pressure
application check before the master cylinder pressure exceeds the
fixed value KP1 and the fixed time duration KT2 elapses the,
control goes to step S212 from step S210.
[0067] At this step S212, it is checked whether or not an increase
is found in the master cylinder pressure change speed dPmc which is
calculated at step S100. If the result is true and false, the
control goes to step S214 and step S104, respectively. In detail,
if the master cylinder pressure change speed dPmc is found to have
increased, this indicates that the master cylinder pressure change
speed dPmc has rapidly increased immediately upon a full brake
fluid introduction into the reservoir 38 and/or the reservoir 39 by
way of the pressure-decrease valves 33b, 34b, 35b, and/or 36b
resulting from a failure or malfunction in closing at least one of
the pressure-maintaining valves 33a, 34a, 35a, and/or 36a. Thus, if
the fixed time duration KT1 elapses and the master cylinder
pressure change speed dPmc is increased until the master cylinder
pressure Pmc reaches the predetermined value KP1, the control goes
to step S214 from step S212.
[0068] At step S214, a pressure-maintaining valve abnormal
condition judging procedure 3 is executed. In this procedure, when
a failure or malfunction is judged in closing at least one of the
pressure-maintaining valves 33a, 34a, 35a, and 36a, a procedure is
made which causes a lamp to be lit for indicating the resultant
malfunction to a driver along with setting an inhibit flag, and an
inhibit procedure is made for inhibiting the control in each
control mode. Thereafter, the control goes to step S220.
[0069] In addition, during the pressure application check, if the
master cylinder pressure Pmc exceeds the predetermined value KP1
before elapse of the fixed time duration KT2 when measured from the
initiation of the pressure application check, the automatic
pressure application is considered to be normal or made
successfully by the pressure application unit 12 and others. Thus,
in such a case, the control goes from step S208 to step S220 by way
of stop S218 which executes a procedure which is indicative of the
normal or successful automatic pressure application.
[0070] If an elapse of the predetermined time duration KT2 is found
before the master cylinder pressure Pmc exceeds the fixed value
KP1, it is impossible to detect whether a malfunction of the
pressure application unit 12 or malfunction in closing at least one
of the pressure-maintaining valves 33a, 34a, 35a, and 36a causes
the unsuccessful execution of the automatic pressure application.
Thus, in such a case, the control goes to from step S206 to S220 by
way of step S216 in which the pressure application unit 12 is
judged to be temporarily abnormal.
[0071] It is to be noted that, during the pressure application
check procedure step, S220 is also executed when the result of step
S202 is false or NO, rather than execution of one of steps S214,
S216, and S218.
[0072] At step S220, an outside pressure application procedure is
executed. In this outside pressure application procedure, all of
the pressure-maintaining valves 33a, 34a, 35a, and 36a of the
respective four wheels are de-energized (made OFF) to open, all of
the pressure-decrease valves 33b, 34b, 35b, and 36b of the
respective four wheels are de-energized (made OFF) to close,
outputting of the control signal to the linear valve 31 is
interrupted (made OFF), the pump 29 is terminated (made OFF), and
the timer counter CTCHECK is rest. Thereafter, the control goes to
step S222 to execute a pump regenerative voltage procedure.
[0073] In this pump regenerative voltage procedure, step S300 shown
in the flowchart in FIG. 3 determines, on the basis of the result
of step S216, whether or not the pressure application unit 12 is
found to be temporarily abnormal or not. If the result of step S300
indicates that the pressure application unit 12 is temporarily
abnormal, the control goes to step S304. If not, i.e., the step 300
is executed after executing steps S202, S214 (or S218), S220 and
S222, the control goes to step S302 to reset or clear a pump
regenerative voltage check timer counter CTPCHECK.
[0074] At step S304, it is checked whether or not a pump
regenerative voltage check is terminated. If the result is true,
the control terminates the routine depicted in FIG. 5 to return to
step S104 shown in FIG. 3. If not, the control goes to step
S306.
[0075] At step S306, the pump regenerative voltage check timer
counter CTPCHECK is incremented or is initiated to count. Then the
control goes to step S308. At this step S308, it is checked whether
or not the pump regenerative voltage check timer counter CTPCHECK
is indicative of a first fixed value KPT1. When, just after
initiation of the pump regenerative voltage check timer counter,
its indication is less than the value KPT1, the control goes to
step S310 to cause the motor 40 to drive or turn on the pumps 41
and 44.
[0076] After this driving operation, if the indication of the pump
regenerative voltage check timer CTPCHECK is equal to or greater
than the first fixed value KPT1, the control goes from step S308 to
step S312 to check whether or not the indication of the pump
regenerative voltage check timer CTPCHECK is less than a second
fixed value KPT2. When, that just after that the indication of the
pump regenerative voltage check timer CTPCHECK reaches the first
fixed value KPT1, the indication of the pump regenerative voltage
check timer CTPCHECK is less than the second fixed value KPT2, the
control goes to step 314 to terminate or turn off the pumps 41 and
44.
[0077] Thereafter, if the indication of the pump regenerative
voltage check timer CTPCHECK is in excess of the second fixed value
KPT2, the control goes from step S312 to step S316 to check whether
or not a pump regenerative voltage Vpomp is less than a
predetermined value KVP.
[0078] Executing steps S308, S310, S312, S314, and S316 activates
the pumps 41 and 44 for a short time period which is substantially
equal to the fixed value KPT1 after initiation of the increment of
the timer counter CTPCHECK, and the resulting pump regenerative
voltage Vpomp is compared to the fixed value KPT1. It is to be
noted that the pump regenerative voltage Vpomp is a monitoring
value which is indicative of the voltage at an upstream side of
each of the pumps 41 and 44.
[0079] Due to a full brake fluid introduction into the reservoir 38
and/or the reservoir 39 by way of the pressure-decrease valves 33b,
34b, 35b, and/or 36b resulting from a failure or malfunction in
closing at least one of the pressure-maintaining valves 33a, 34a,
35a, and/or 36a, the inertia force of each of the pumps 41 and 44
upon termination thereof is used to discharge (i.e. suck) the brake
fluid, which causes the pump regenerative voltage Vpomp to lower
temporarily, resulting in that the pump regenerative voltage Vpomp
is made less than the fixed value KVP. Thus, in such a case, the
control goes from step S316 to S318 during the failure or
malfunction in closing at least one of the pressure-maintaining
valves 33a, 34a, 35a, and 36a of the respective wheel cylinders 13,
14, 15, and 16, and a procedure is executed to indicate the
detected malfunction to the driver by lighting a lamp and set an
inhibit flag, and a procedure is executed to inhibit subsequent
each of various control modes. Thereafter, the control goes to step
S322 to terminate the pump regenerative voltage check
procedure.
[0080] This termination makes the result of step S224 shown in FIG.
4 YES and the control goes to step S226 to execute a pressure
application check termination procedure, in which a pressure
application termination flag is set (i.e., is made `1`).
Thereafter, the control goes to step S104 (FIG. 3).
[0081] On the other hand, if the pump regenerative voltage Vpomp is
equal to or greater than the fixed value KVP, no failure or no
malfunction is detected in closing the pressure-maintaining valves
33a, 34a, 35a, and 36a, which fails to introduce the brake fluid
into the reservoir 38 by way of the in-series pressure-maintaining
valve 33a and the pressure-decrease valve 33b, and by way of the
in-series pressure-maintaining valve 34a and the pressure-decrease
valve 34b, and which fails to introduce the brake fluid into the
reservoir 39 by way of the in-series pressure-maintaining valve 35a
and the pressure-decrease valve 35b, and by way of the in-series
pressure-maintaining valve 36a and the pressure-decrease valve 36b.
Thus, no brake fluid is stored in both the reservoirs 38 and 39,
respectively, which results in that at termination of driving of
each of the pumps 41 and 44, the inertia force thereof is not used
for sucking the brake fluid (i.e. each pump is of no load), thereby
not lowering the pump recovery voltage Vpomp temporarily.
Therefore, in such a case, the control goes from step S316 to step
S320, when it is judged that each of the pressure-maintaining
valves 33a, 34a, 35a, and 36a is in good order but the pressure
application unit 12 is in malfunction, a procedure is executed to
indicate the detected malfunction of the pressure application unit
12 to the driver by lighting a lamp and set an inhibit flag, and a
procedure is executed to inhibit each of various subsequent control
modes. Thereafter, the control goes to step S322 to terminate the
pump regenerative voltage check procedure.
[0082] As explained above, upon starting the vehicle, the pressure
application check procedure and the pump regenerative voltage check
procedure are executed and, after executing the pressure
application check termination procedure at step S226 in FIG. 4, the
routine depicted in FIG. 3 is performed for doing various controls
depending on the vehicle conditions during vehicle movement such
that steps in FIG. 3, except for step S102, are executed.
[0083] The aforementioned vehicular brake control device in
accordance with the present embodiment provides the following
advantages.
[0084] If an increase is found in the master cylinder pressure
change speed dPmc after elapse of the fixed time duration KT1 when
measured from the initiation of the pressure application check
(i.e., if the result of step S110 is YES), it become possible to
judge a failure or malfunction in closing at least any one of the
pressure-maintaining valves 33a, 34a, 35a, and 36a.
[0085] Thus, detecting such the failure or malfunction makes it
possible to issue an alarm to the driver by lighting a lamp and to
inhibit a control in each of various modes. This means that
drawbacks can be prevented in advance, such as an impossibility of
starting a vehicle due to brake fluid pressure application to a
wheel cylinder for a wheel (e.g. a front wheel as the driven wheel
of FR vehicle which is in traction control) and the brake fluid
application into the wheel cylinder or so-called `brake drag`.
[0086] During the pressure application check procedure (i.e., upon
initiation of the pressure application check) which is indicated at
step S204 in FIG. 4, the pressure-decrease valves 33b, 34, 35b, and
36b of the respective wheel cylinders 13, 14, 15, and 16 are opened
while the pressure-maintaining valves 33a, 34a, 35a, and 36b are
closed, and the consumed amount of brake fluid in each of the wheel
cylinders 13, 14, 15, and 16 increases. Thus, the master cylinder
pressure increasing speed becomes slower (i.e. the slope of
pressure increase is lowered), which makes it possible to increase
detecting accuracy of a failure or malfunction in closing the
pressure-maintaining valves 33a, 34a, 35a, and 36a.
[0087] If the master pressure is in excess of the predetermined
value KP1 (i.e. if the result of step S208 is YES) before the timer
CTCHECK indicates it has reached the second predetermined value KT2
when measured from the initiation of the pressure application
check, which is indicative of the successful or normal execution of
the automatic master cylinder pressure application, it is thereby
possible to judge the condition of the pressure application unit 12
and each of the pressure-maintaining valves 33a, 34a, 35a, and 36a
of the respective wheels.
[0088] If the timer counter indicates more than the second
predetermined time duration KT2 (i.e. if the result of step S206 is
YES), it is not impossible to make a decision whether the pressure
application unit 12 is in malfunction or each of the
pressure-maintaining valves 33a, 34a, 35a, and 36a is in failure in
its closing operation, thereby making a temporary decision that the
pressure application unit 12 is in malfunction. Then, the pumps 41
and 44 are driven for a short time duration and thereafter, if the
resultant pump regenerative voltage Vpomp is smaller than the fixed
value KVP (i.e., the result of step S316 in FIG. 5 is YES), at
least one of the pressure-maintaining valves 33a, 34a, 35a, and 36a
can be found in failure in its closing operation.
[0089] If the resultant pump regenerative voltage Vpomp is in
excess of the fixed value KVP (i.e. the result of step S316 in FIG.
5 is NO), it is possible to judge whether the pressure application
unit 12 is in malfunction.
MODIFICATIONS
[0090] The present invention allows the aforementioned embodiment
to be modified as follows.
[0091] In the foregoing embodiment, it is possible to light a lamp
for indicating the result of each of steps S318 and S320 in FIG.
5.
[0092] The pressure application unit is not limited to the
aforementioned unit 12 and any type of pressure application unit is
available so long as it makes it possible to establish an automatic
control of the master cylinder pressure by being controlled by the
ECU 18.
[0093] Instead of the stop lamp switch 67 as a means for the
depression of the brake pedal 21, other structures are available
such as stroke sensor which is made ON after the brake pedal 21
strokes through a distance and a depression force sensor which is
in the form of a gauge sensor which outputs an ON-signal when the
operating rod 22 is applied with a depression force whose magnitude
is equal to or greater than a fixed value.
[0094] Instead of the front and rear piping in the hydraulic
pressure control device 17 which connects the master cylinder 20 to
each of the wheel cylinders 13, 14, 15, and 16 of the respective
wheels in the foregoing embodiment, a diagonal piping is
available.
[0095] Instead of the tandem type master cylinder 20 in the
foregoing embodiment, a single type master cylinder is
available.
[0096] Instead of the pressure application unit 12 which applies a
hydraulic pressure to the master cylinder pressure, another
pressure application unit is available which is disclosed in one of
Japanese Patent Laid-Open Print No. Hei. 7(1995)-246923 and
Japanese Patent Laid-Open Print No. Hei. 8(1996)-230634 in order to
detect a failure or malfunction of each of the pressure-maintaining
valves in its closing operation.
ADVANTAGES OF THE PRESENT INVENTION
[0097] As apparent from the foregoing description, it is possible
to detect a failure or malfunction in closing the first
electromagnetic valve which is disposed between the master cylinder
and each of the wheel cylinders of the respective wheels. In
addition, opening the second electromagnetic valve makes lower the
increasing speed of the introduced hydraulic pressure (i.e. the
pressure increase slope declines), thereby increasing the accuracy
in judging whether or not the pressure-maintaining valve is in
failure in its closing operation.
[0098] In accordance with another aspect of the present invention,
it is possible to judge that the pressure application means and the
first electromagnetic valve of each of the wheels are in good order
or in normal condition.
[0099] In accordance with another aspect of the present invention,
it is possible to judge a failure or malfunction in closing the
first electromagnetic valve of each of the wheel cylinders of the
respective wheel.
[0100] In accordance with yet another aspect of the present
invention, it is possible to judge that the pressure application
means is in an abnormal condition or in malfunction and the first
electromagnetic valve of each of the wheels is in good order or in
normal condition.
[0101] The principles, preferred embodiments and modes of operation
of the present invention have been described in the foregoing
specification. However, the invention which is intended to be
protected is not to be construed as limited to the particular
embodiments disclosed. Further, the embodiments described herein
are to be regarded as illustrative rather than restrictive.
Variations and changes may be made by others, and equivalents
employed, without departing from the spirit of the present
invention. Accordingly, it is expressly intended that all such
variations, changes and equivalents which fall within the spirit
and scope of the present invention as defined in the claims, be
embraced thereby. Each of the aforementioned documents are
incorporated by reference herein in their entireties.
* * * * *