U.S. patent application number 13/241017 was filed with the patent office on 2012-03-29 for vehicle brake system.
This patent application is currently assigned to ADVICS CO., LTD.. Invention is credited to Masahiro Matsuura, Masayuki Naito, Akitaka NISHIO.
Application Number | 20120074767 13/241017 |
Document ID | / |
Family ID | 45869923 |
Filed Date | 2012-03-29 |
United States Patent
Application |
20120074767 |
Kind Code |
A1 |
NISHIO; Akitaka ; et
al. |
March 29, 2012 |
VEHICLE BRAKE SYSTEM
Abstract
A vehicle brake system is provided with a hydraulic brake
device, a regenerative brake device incorporating a generator
motor, and a brake control device. The control device includes a
section for calculating a driver target brake force for each wheel
corresponding to a manipulation amount of a braking manipulation
member, a section for enabling the brake control device itself to
set compensation brake forces for respective wheels, a section for
selecting a larger one of the driver target brake force and the
compensation brake force for each wheel and for subtracting a base
hydraulic brake force from the selected brake force to set
differences for respective wheels as compensated target brake
forces for the wheels, and a section for controlling the
distribution of the compensated target brake force for each wheel
to a controlled hydraulic brake force for each wheel and a
regenerative brake force for each driving wheel.
Inventors: |
NISHIO; Akitaka;
(Kariya-shi, JP) ; Matsuura; Masahiro;
(Chiryu-shi, JP) ; Naito; Masayuki; (Aichi-ken,
JP) |
Assignee: |
ADVICS CO., LTD.
Kariya-shi
JP
|
Family ID: |
45869923 |
Appl. No.: |
13/241017 |
Filed: |
September 22, 2011 |
Current U.S.
Class: |
303/3 |
Current CPC
Class: |
B60T 2270/604 20130101;
B60L 2210/40 20130101; B60L 7/26 20130101; B60W 10/188 20130101;
B60L 7/14 20130101; Y02T 10/64 20130101; Y02T 10/72 20130101; B60L
2240/423 20130101; B60T 13/586 20130101; B60W 2710/182 20130101;
Y02T 10/7072 20130101; B60W 20/13 20160101; B60T 8/4059 20130101;
B60T 13/686 20130101; B60W 20/00 20130101; B60W 10/08 20130101;
B60W 2540/12 20130101; B60W 2720/406 20130101; B60L 50/16 20190201;
B60L 15/2009 20130101; B60W 2710/18 20130101; B60T 1/10 20130101;
Y02T 10/70 20130101; B60L 2250/26 20130101; B60W 30/18127 20130101;
B60W 2710/083 20130101; B60T 8/4872 20130101 |
Class at
Publication: |
303/3 |
International
Class: |
B60T 13/58 20060101
B60T013/58; B60T 13/74 20060101 B60T013/74 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 24, 2010 |
JP |
2010-213201 |
Claims
1. A vehicle brake system comprising: a hydraulic brake device
having a master cylinder for generating a base hydraulic pressure
corresponding to a manipulation amount of a braking manipulation
member, a pump for generating a controlled hydraulic pressure, and
a hydraulic control unit for adding a base hydraulic brake force
corresponding to the base hydraulic pressure and a controlled
hydraulic brake force corresponding to the controlled hydraulic
pressure to apply the added brake forces to wheels; a regenerative
brake device for applying a regenerative brake force to driving
wheels which are included in the wheels and are driven by a
generator motor; and a brake control device for cooperatively
controlling the hydraulic brake device and the regenerative brake
device; wherein the brake control device includes: a driver target
brake force calculation section for calculating a driver target
brake force for each wheel corresponding to the manipulation amount
of the braking manipulation member; a compensation brake force
setting section for enabling the brake control device to set
compensation brake forces for the respective wheels independently
of the driver target brake force; a selection compensation section
for selecting a larger one of the driver target brake force and the
compensation brake force for each wheel and for subtracting the
base hydraulic brake force from the selected one brake force to set
a compensated target brake force for each wheel; and a distribution
control section for controlling the compensated target brake force
for each wheel to be distributed to the controlled hydraulic brake
force for each wheel and the regenerative brake force for each
driving wheel.
2. A vehicle brake system comprising: a hydraulic brake device
having a master cylinder for generating a base hydraulic pressure
corresponding to a manipulation amount of a braking manipulation
member, a pump for generating a controlled hydraulic pressure, and
a hydraulic control unit for adding a base hydraulic brake force
corresponding to the base hydraulic pressure and a controlled
hydraulic brake force corresponding to the controlled hydraulic
pressure to apply the added brake forces to wheels; a regenerative
brake device for applying a regenerative brake force to driving
wheels which are included in the wheels and are driven by a
generator motor; and a brake control device for cooperatively
controlling the hydraulic brake device and the regenerative brake
device; wherein the brake control device includes: a driver target
brake force calculation section for calculating a driver target
brake force for each wheel corresponding to the manipulation amount
of the braking manipulation member; a compensation brake force
setting section for enabling the brake control device to set
compensation brake forces for the respective wheels independently
of the driver target brake force; an addition compensation section
for adding the compensation brake force for each wheel to the
driver target brake force to obtain a sum and for subtracting the
base hydraulic brake force from the sum to set a compensated target
brake force for each wheel; and a distribution control section for
controlling the compensated target brake force for each wheel to be
distributed to the controlled hydraulic brake force for each wheel
and the regenerative brake force for each driving wheel.
3. The vehicle brake system as set forth in claim 1, wherein: the
wheels are four wheels including two front wheels and two rear
wheels; the driving wheels are selected as the two front wheels or
the two rear wheels; and the distribution control section includes:
a left right comparison section for comparing a right side sum made
by adding the compensated target brake forces for the front and
rear wheels on a right side with a left side sum made by adding the
compensated target forces for the front and rear wheel on a left
side, each of the compensated target brake forces being calculated
by the selection compensation section; a left light equal-time
distribution control section being operable when the right side sum
and the left side sum are equal, for applying to the generator
motor a demand regenerative brake force which is obtained by the
addition of the compensated target brake forces for the four
wheels, acquiring the executed regenerative brake force which was
executed by the generator motor, and subtracting a value which is
obtained by dividing the executed regenerative brake force by four,
from each of the compensated target brake forces for the four
wheels to set respective differences as the respective controlled
hydraulic brake forces; and a left light unequal-time distribution
control section being operable when the right side sum and the left
side sum differ, for applying to the generator motor a demand
regenerative brake force which is obtained by doubling a smaller
one of the right side sum and the left side sum, acquiring the
executed regenerative brake force which was executed by the
generator motor, and subtracting a value which is obtained by
dividing the executed regenerative brake force by four, from each
of the compensated target brake forces for the four wheels to set
respective differences as the respective controlled hydraulic brake
forces.
4. The vehicle brake system as set forth in claim 1, wherein the
distribution control section includes: a regeneration demand
section for applying to the generator motor a demand regenerative
brake force calculated by multiplying a smallest value of the
compensated target brake forces for the driving wheels calculated
by the selection compensation section, by the number of the driving
wheels; a regeneration acquisition section for acquiring the
executed regenerative brake force which the generator motor
executed based on the demand regenerative brake force; and a
regeneration reflecting section for controlling the distribution of
the controlled hydraulic brake force to each wheel based on the
executed regenerative brake force.
5. The vehicle brake system as set forth in claim 2, wherein: the
wheels are four wheels including two front wheels and two rear
wheels; the driving wheels are selected as the two front wheels or
the two rear wheels; and the distribution control section includes:
a left right comparison section for comparing a right side sum made
by adding the compensated target brake forces for the front and
rear wheels on a right side with a left side sum made by adding the
compensated target forces for the front and rear wheel on a left
side, each of the compensated target brake forces being calculated
by the addition compensation section; a left light equal-time
distribution control section being operable when the right side sum
and the left side sum are equal, for applying to the generator
motor a demand regenerative brake force which is obtained by the
addition of the compensated target brake forces for the four
wheels, acquiring the executed regenerative brake force which was
executed by the generator motor, and subtracting a value which is
obtained by dividing the executed regenerative brake force by four,
from each of the compensated target brake forces for the four
wheels to set respective differences as the respective controlled
hydraulic brake forces; and a left light unequal-time distribution
control section being operable when the right side sum and the left
side sum differ, for applying to the generator motor a demand
regenerative brake force which is obtained by doubling a smaller
one of the right side sum and the left side sum, acquiring the
executed regenerative brake force which was executed by the
generator motor, and subtracting a value which is obtained by
dividing the executed regenerative brake force by four, from each
of the compensated target brake forces for the four wheels to set
respective differences as the respective controlled hydraulic brake
forces.
6. The vehicle brake system as set forth in claim 2, wherein the
distribution control section includes: a regeneration demand
section for applying to the generator motor a demand regenerative
brake force calculated by multiplying a smallest value of the
compensated target brake forces for the driving wheels calculated
by the addition compensation section, by the number of the driving
wheels; a regeneration acquisition section for acquiring the
executed regenerative brake force which the generator motor
executed based on the demand regenerative brake force; and a
regeneration reflecting section for controlling the distribution of
the controlled hydraulic brake force to each wheel based on the
executed regenerative brake force.
Description
INCORPORATION BY REFERENCE
[0001] This application is based on and claims priority under 35
U.S.C. 119 with respect to Japanese Application No. 2010-213201
filed on Sep. 24, 2010, the entire content of which is incorporated
herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a vehicle brake system
provided with a hydraulic brake device and a regenerative brake
device. More particularly, it relates to a brake control device for
cooperatively controlling the hydraulic brake device and the
regenerative brake device.
[0004] 2. Discussion of the Related Art
[0005] In hybrid vehicles which are provided with an engine and a
generator motor as travelling drive sources, it has become
widespread to heighten the fuel efficiency by regenerating motion
energy to electric energy by the generator motor and storing the
electric energy at the time of a braking operation. In this sense,
the generator motor is regarded as a regenerative brake device that
applies the regenerative brake force to driving wheels. The
regenerative brake device alone is unable to generate a sufficient
brake force and thus, is usually used in combination with a
conventional hydraulic brake device which operates under
pressurized oil. Therefore, a cooperative control is required for
the hydraulic brake device and the regenerative brake device, and
there have been proposed various cooperative control technologies
like that described in US 2007/0272457 A1 (equivalent of
JP2007-308005 A).
[0006] A vehicle disclosed in the United State publication is
provided with a combustion engine, an electric motor, battery
means, fluid-operated brake means (hydraulic brake device), demand
brake force setting means, and brake control means. The
fluid-operated brake means is able to output a brake force based on
a manipulation pressure (base hydraulic pressure), corresponding to
the driver's manipulation and a negative pressure in the combustion
engine, and an additional pressure (controlled hydraulic pressure)
given by pressurizing means. Further, when a brake demand
manipulation is performed, the brake control means executes a
control to compare a sum of a regenerative brake force by the
electric motor and a manipulation brake force corresponding to the
manipulation pressure with a demand brake force and judges the
necessity of a brake force depending on the additional pressure.
The control makes it possible that even when the negative pressure
in the combustion engine goes down, a demand brake force is
acquired correctly by suppressing an uncomfortable feeling which is
liable to be felt by the driver.
[0007] Further, although the hydraulic brake device usually
operates in response to the braking manipulation by the driver and,
in addition to this function, is often to have a function of
automatically adjusting the brake force to be increased or reduced.
Such an automatic brake control function is realized in a
combination of an electronic control device, incorporating a
computer and being operable by software, and sensors for acquiring
various information such as braking manipulation amount, wheel
speeds and the like. For example, in an active cruise control (ACC)
function, a following distance (i.e., a distance to a vehicle
ahead) is kept to be longer than a predetermined value by
generating a brake force in dependence on the situation where a
braking manipulation is not performed or the amount of the braking
manipulation is insufficient though a detected following distance
decreases. In a brake assist (BA) function, it is discriminated
based on a braking manipulation amount and a manipulation speed
whether or not a braking manipulation is an urgent braking
manipulation, and an additional brake force is added to the brake
force corresponding to the braking manipulation force. Further, in
an antilock brake system (ABS) function, when a wheel is locked at
the time of an urgent braking manipulation, the hydraulic pressure
in the hydraulic brake device is automatically adjusted to regulate
the brake force thereby to suppress the slipping of the wheel.
Those belonging to this category are a traction control (TRC)
function that controls the driving force to be effectively exerted
on the road surface by adding a brake force when the slipping
amounts of the driving wheel are large, and an electronic stability
control (ESC) function that keeps the stability in travelling by
regulating the braking amounts of respective wheels during the
travelling.
[0008] In systems provided with a hydraulic brake device and a
regenerative brake device as typically described in the
aforementioned United State publication, when a braking
manipulation is done, the regenerative brake device is additionally
operated whereas, during an automatic brake control function such
as the ACC function, the BA function or the like, the brake force
is regulated only by the hydraulic brake device with the
regenerative brake device held out of operation. That is, a stage
that the regenerative brake function by a generator motor can be
utilized takes place unless the driving wheels are being driven
when the brake force is generated by the automatic brake control
function. However, during the automatic brake control function, the
regenerative brake function has heretofore not been utilized for
the reason that the utilization of the regenerative brake function
at that stage complicates the distribution of brake forces to
respective wheels, and the like. As a result, the hydraulic brake
device only has been used even at the stage that the regenerative
brake device can be inherently utilized, and thus, the opportunity
to enhance the efficiency in regeneration has been lost.
SUMMARY OF THE INVENTION
[0009] Accordingly, it is a primary object of the present invention
to provide an improved vehicle brake system which when generating a
brake force by an automatic brake control function, is able to
distribute a part of the brake force to a regenerative brake
device, thereby enhancing the efficiency in regeneration.
[0010] Briefly, in a first aspect of the present invention, there
is provided a vehicle brake system, which comprises a hydraulic
brake device having a master cylinder for generating a base
hydraulic pressure corresponding to a manipulation amount of a
braking manipulation member, a pump for generating a controlled
hydraulic pressure, and a hydraulic control unit for adding a base
hydraulic brake force corresponding to the base hydraulic pressure
and a controlled hydraulic brake force corresponding to the
controlled hydraulic pressure to apply the added brake forces to
wheels; a regenerative brake device for applying a regenerative
brake force to driving wheels which are included in the wheels and
are driven by a generator motor; and a brake control device for
cooperatively controlling the hydraulic brake device and the
regenerative brake device. The brake control device includes a
driver target brake force calculation section for calculating a
driver target brake force for each wheel corresponding to the
manipulation amount of the braking manipulation member; a
compensation brake force setting section for enabling the brake
control device to set compensation brake forces for the respective
wheels independently of the driver target brake force; a selection
compensation section for selecting a larger one of the driver
target brake force and the compensation brake force for each wheel
and for subtracting the base hydraulic brake force from the
selected one brake force to set a compensated target brake force
for each wheel; and a distribution control section for controlling
the compensated target brake force for each wheel to be distributed
to the controlled hydraulic brake force for each wheel and the
regenerative brake force for each driving wheel.
[0011] With the construction in the first aspect of the present
invention, the brake control device which cooperatively controls
the hydraulic brake device and the regenerative brake device
selects a larger one of the driver target brake force corresponding
to the manipulation amount of the braking manipulation member and
the compensation brake force set by the brake control device itself
for each wheel, subtracts the base hydraulic brake force from the
selected one brake force to set a compensated target brake force
for each wheel, and distributes the compensated target brake force
to the controlled hydraulic brake force for each wheel and the
regenerative brake force for each driving wheel. Thus, when the
compensation brake force exceeds the driver target brake force, at
least a part of the brake force which part corresponds to a surplus
is distributed to the regenerative brake device. This results in
bringing the regenerative brake device into operation though the
same has heretofore not been operated when the compensation brake
forces set by the brake control device itself are generated during
an active cruise control function or the like, and therefore, the
efficiency in regeneration can be enhanced.
[0012] In a second aspect of the present invention, there is
provided a vehicle brake system, which comprises a hydraulic brake
device having a master cylinder for generating a base hydraulic
pressure corresponding to a manipulation amount of a braking
manipulation member, a pump for generating a controlled hydraulic
pressure, and a hydraulic control unit for adding a base hydraulic
brake force corresponding to the base hydraulic pressure and a
controlled hydraulic brake force corresponding to the controlled
hydraulic pressure to apply the added brake forces to wheels; a
regenerative brake device for applying regenerative brake forces to
driving wheels which are included in the wheels and are driven by a
generator motor; and a brake control device for cooperatively
controlling the hydraulic brake device and the regenerative brake
device. The brake control device includes a driver target brake
force calculation section for calculating a driver target brake
force for each wheel corresponding to the manipulation amount of
the braking manipulation member; a compensation brake force setting
section for enabling the brake control device itself to set
compensation brake forces for the respective wheels independently
of the driver target brake force; an addition compensation section
for adding the compensation brake force for each wheel to the
driver target brake force to obtain a sum and for subtracting the
base hydraulic brake force from the sum to set a compensated target
brake force for each wheel; and a distribution control section for
controlling the compensated target brake force for each wheel to be
distributed to the controlled hydraulic brake force for each wheel
and the regenerative brake force for each driving wheel.
[0013] With the construction in the second aspect of the present
invention, the brake control device which cooperatively controls
the hydraulic brake device and the regenerative brake device adds
the driver target brake force corresponding to the manipulation
amount of the braking manipulation member and the compensation
brake force set by the brake control device itself for each wheel
to obtain the sum, subtracts the base hydraulic brake force from
the sum to set the compensated target brake force for each wheel,
and distributes the compensated target brake force to the
controlled hydraulic brake force for each wheel and the
regenerative brake force for each driving wheel. Thus, at least a
part of the compensation brake force is distributed to the
regenerative brake device. This results in bringing the
regenerative brake device into operation though the same has
heretofore not been operated when the compensation brake forces set
by the brake control device itself are generated during a brake
assist function or the like, and therefore, the efficiency in
regeneration can be enhanced.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
[0014] The foregoing and other objects and many of the attendant
advantages of the present invention may readily be appreciated as
the same becomes better understood by reference to the preferred
embodiments of the present invention when considered in connection
with the accompanying drawings, wherein like reference numerals
designate the same or corresponding parts throughout several views,
and in which:
[0015] FIG. 1 is a schematic view showing the construction of a
vehicle brake system in a first embodiment according to the present
invention;
[0016] FIG. 2 is a circuit diagram showing the detailed
construction of a hydraulic brake device shown in FIG. 1;
[0017] FIG. 3 is a graph showing the operation property at an
ordinary time of the vehicle brake system;
[0018] FIG. 4 is a flow chart showing a control processing executed
by a brake ECU in the first embodiment;
[0019] FIG. 5 is a combination of graphs schematically exemplifying
the result that the brake ECU attains in the control processing
shown in FIG. 4 during the operation of an active cruise control
function;
[0020] FIGS. 6(A)-6(D) are schematic diagrams for explaining
specific examples of distribution controls in which a left right
equal-time distribution control means or section executes the
distribution of brake forces to respective wheels;
[0021] FIGS. 7(A)-7(B) are schematic diagrams for explaining
specific examples of distribution controls in which a left right
unequal-time distribution control means or section executes the
distribution of brake forces to the respective wheels;
[0022] FIG. 8 is a flow chart showing a control processing executed
by the brake ECU in a second embodiment; and
[0023] FIGS. 9(A)-9(D) are explanatory views for showing specific
examples of distribution controls in which brake forces are
distributed to the respective wheels in the second embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
First Embodiment
[0024] Hereafter, a vehicle brake system in a first embodiment
according to the present invention will be described with reference
to FIGS. 1-7. FIG. 1 is a schematic view showing the construction
of a vehicle brake system 1 in the first embodiment according to
the present invention. As shown in the figure, the vehicle brake
system 1 is composed of a regenerative brake device A, a hydraulic
brake device B, a hybrid ECU 50, a brake ECU 60 and the like. The
vehicle brake system 1 is equipped on a front-drive, four-wheel
hybrid vehicle and is usually operated in dependence on a stepping
manipulation of a brake pedal 21 by the driver. In addition
thereto, the system 1 has a function in which the brake ECU
automatically sets and regulates a brake force for each wheel in
dependence on the vehicle travelling state.
[0025] The regenerative brake device A is constituted by a
generator motor 20 incorporated therein and includes an inverter
device and a battery device (both not shown). The generator motor
20 operates as electric motor by being driven by the inverter
device which converts a direct current voltage of the battery
device into an alternating current voltage, and drives a front
right wheel 7FR and a front left wheel 7FL both being driving
wheels. Further, the generator motor 20 operates as generator by
being driven by the front right wheel 7FR and the front left wheel
7FL and charges the battery device through the inverter device. At
this time, the reaction force from the generator motor 20 applies a
regenerative brake force to the front right wheel 7FR and the front
left wheel 7FL, and thus, this function is generally called the
regenerative brake device A. The front right wheel 7FR and the
front left wheel 7FL are on a common axle connected to the
generator motor 20 and thus, generate regenerative brake forces
which are almost the same in strength. In a modified form, a
generator and an electric motor may be individually provided in
substitution for the generator motor 20, and the generator may be
provided with the function of operating as the regenerative brake
device A.
[0026] The hybrid ECU 50 is an electronic controller for
controlling the whole of a power train for the hybrid vehicle and
cooperatively controls an engine (not shown) and the generator
motor 20. The hybrid ECU 50 is connected to the inverter device and
controls the regenerative brake device A.
[0027] The hydraulic brake device B uses operating oil as operating
fluid and as shown therein, is composed of a brake pedal 21, a
vacuum brake booster 22, a master cylinder 23, a hydraulic control
unit 25 and the like. In the hydraulic brake device B, the stepping
force given by the stepping manipulation of the brake pedal 21 is
boosted by the vacuum booster 22, a base hydraulic pressure is
generated by operating the master cylinder 23, and a controlled
hydraulic pressure is added to the base hydraulic pressure by
operating pumps 37, 47 (FIG. 2) in the hydraulic control unit 25,
so that the hydraulic pressure so added is applied to respective
wheel cylinders WC2, WC3, WC4 and WC1 of the front right wheel 7FR,
the front left wheel 7FL, a rear right wheel 7RR and a rear left
wheel 7RL. Hereafter, the hydraulic brake device B will be
described in detail with reference to FIG. 2.
[0028] FIG. 2 is a circuit diagram showing the detailed
construction of the hydraulic brake device B shown in FIG. 1. The
brake pedal 21 is a member corresponding to a braking manipulation
member and operates the vacuum booster 22 in correspondence to the
stepping manipulation amount. A stroke amount being the
manipulation amount of the brake pedal 21 is detected by a pedal
stroke sensor 21a and is outputted as detection signal to the brake
ECU 60. The vacuum booster 22 boosts the stepping force by the
stepping manipulation of the brake pedal 21 by utilizing a negative
pressure supplied from the engine (not shown) and operates the
master cylinder 23.
[0029] The master cylinder 23 is of a tandem type and is
constituted by a housing 23a taking the shape of a bottomed
cylinder and first and second pistons 23b, 23c arranged in line in
the housing 23a to be fluid-tightly and slidably. A first hydraulic
chamber 23d is formed between the first piston 23b and the second
piston 23c, while a second hydraulic chamber 23f is formed between
the second piston 23c and a bottom portion of the housing 23a. The
first and second pistons 23b, 23c are driven by the vacuum brake
booster 22 to generate a base hydraulic pressure in the first and
second hydraulic chambers 23d, 23f. Further, a reservoir 24 has a
function of regulating the quantities of the operating oil in the
first and second hydraulic chambers 23d, 23f by communicating with
the same when the first and second pistons 23b, 23c are not being
operated.
[0030] The hydraulic control unit 25 is constructed by packaging
into a single case hydraulic control valves 31, 41; pressure
increase control valves 32, 33, 42, 43 and pressure reducing
control valves 35, 36, 45, 46 which constitutes ABS control valves;
pressure regulating reservoirs 34, 44; pumps 37, 47; and a motor M.
As shown in FIG. 2, the brake piping passage of the hydraulic brake
device B in the present embodiment is configured to take an
X-piping fashion which has a first piping passage L1 for applying a
hydraulic brake force to the front right wheel 7FR and the rear
left wheel 7RL and a second piping passage L2 for applying the
hydraulic brake force to the front left wheel 7FL and the rear
right wheel 7RR. The master cylinder 23 is connected to the second
pipe passage L2 at the first hydraulic chamber 23d and to the first
piping passage L1 at the second hydraulic chamber 23f.
[0031] First of all, description will be made regarding the
construction of the first piping passage L1 of the hydraulic
control unit 25. The first piping passage L1 is provided thereon
with the hydraulic control valve 31 constituted by a differential
pressure control valve. The hydraulic control valve 31 is
switchable into a communication state and a differential pressure
state in response to a command from the brake ECU 60. The hydraulic
control valve 31 is usually held in the communication state, but by
being switched into the differential pressure state, is able to
maintain an oil passage L12 on the wheel cylinder WC1, WC2 sides at
a pressure which is higher by a predetermined differential pressure
than the base hydraulic pressure of an oil passage L11 on the
master cylinder 23 side. This differential pressure is a controlled
hydraulic pressure and can be generated from a discharge pressure
of the pump 37, as referred to later.
[0032] The oil passage L12 branches into two, and one branched is
provided thereon with the pressure increase valve 32 for
controlling the pressure increase of the brake hydraulic pressure
to the wheel cylinder WC1 for the rear left wheel 7RL. The other
branched is provided thereon with the pressure increase valve 33
for controlling the pressure increase of the brake hydraulic
pressure to the wheel cylinder WC2 for the front right wheel 7FR.
Each of the pressure increase valves 32, 33 is configured as a
two-position valve which is controllable by the brake ECU 60 to be
switched into a communication state and a blocked state. Thus, when
the pressure increase control valves 32, 33 is held in the
communication state, each of the wheel cylinders WC1, WC2 can be
supplied with either the base hydraulic pressure of the master
cylinder 23 or a hydraulic pressure which is made by adding a
controlled hydraulic pressure built by the operation of the pump 37
to the base hydraulic pressure.
[0033] Further, the oil passages L12 between the pressure increase
control valves 32, 33 and the respective wheel cylinders WC1, WC2
are in communication with a reservoir hole 34a of the pressure
regulation reservoir 34 through respective oil passages L13. The
oil passages L13 respectively have the pressure reducing valves 35,
36 arranged thereon, each of which is controllable by the brake ECU
60 to be switched into a communication state and a blocked
state.
[0034] In a usual operation state that the ABS function is not
being executed, the pressure increase control valves 32, 33 remain
in the communication state, while the pressure reducing control
valves 35, 36 remain in the blocked state. With the execution of
the ABS control, a pressure reducing mode is executed to close the
pressure increase control valves 32, 33 and to open the pressure
reducing control valves 35, 36. Thus, the operating oil is
discharged to the pressure regulation reservoir 34 through the oil
passages L13, and the hydraulic pressure in the wheel cylinders
WC1, WC2 are reduced to prevent the front right wheel 7FR and the
rear left wheel 7RL from becoming a tendency to be locked. In a
pressure increase mode at the time of the ABS function, the
pressure increase control valves 32, 33 are opened, while the the
pressure reducing control valves 35, 36 are closed. Thus, the
hydraulic pressure in the wheel cylinders WC1, WC2 is increased to
increase the brake forces of the front right wheel 7FR and the rear
left wheel 7RL. The pressure increase control valves 32, 33 are
provided with respective safety valves (one-way valves) 32a, 33a in
parallel thereto. The safety valves 32a, 33a operate to return the
operating fluids in the wheel cylinders WC1, WC2 to the reservoir
24 when the brake pedal 21 is not stepped further during the ABS
function.
[0035] Further, the pump 37 together with a safety valve 37a is
arranged on an oil passage L14 which connects the reservoir hole
34a of the pressure regulation reservoir 34 to the oil passages L12
extending between the hydraulic control valve 31 and the pressure
increase control valves 32, 33. A damper 38 arranged on the
discharge side of the pump 37 absorbs the pulsation in pressure in
the discharged operating oil to urge the same to be supplied to the
oil passages L12 without such pressure pulsation. The suction side
of the pump 37 is connected to the reservoir hole 34a of the
pressure regulation reservoir 34. Further, an oil passage L15 is
provided which makes another reservoir hole 34b of the pressure
regulation reservoir 34 communicate with the oil passage L11, so
that the pressure regulation reservoir 34 is in communication with
the master cylinder 23.
[0036] The pump 37 is able to adjust its discharge flow volume
since the drive current to the motor M is regulated by a command
from the brake ECU 60. The pump 37 operates at the time of the
pressure reducing mode in the ABS control and draws the operating
oils in the wheel cylinders WC1, WC2 or the operating oil in the
pressure regulation reservoir 34 to return the drawn operating oil
to the master cylinder 23 through the hydraulic control valve 31
held in the communication state. Further, the pump 37 operates to
generate a controlled hydraulic pressure in performing the
functions that control the vehicle to be stable in posture, such as
the traction control function, the electronic stability control
function and the like, in addition to the active cruise control
function and the brake assist function.
[0037] That is, in order to generate a differential pressure across
the hydraulic control valve 31 having been switched to the
differential pressure state, the pump 37 draws the operating fluid
in the master cylinder 23 through the oil passage L11 and the oil
passage L15 and discharges the drawn operating fluid to each of the
wheel cylinders WC1, WC2 through the oil passages L14, L12 and
further through the pressure increase valves 32, 33 held in the
communication state to apply a controlled hydraulic pressure
thereto. Further, also in the case that a sufficient regenerative
brake force cannot be performed by the regenerative brake device A,
and the like, the pump 37 is operated to generate a differential
pressure and applies a controlled hydraulic pressure to each of the
wheel cylinders WC1, WC2.
[0038] Further, the oil passage L11 is provided thereon with a
pressure sensor P for detecting the base hydraulic pressure
generated by the master cylinder 23, and the detected signal is
transmitted to the brake ECU 60. The positions of the first and
second pistons 23b, 23c in the master cylinder 23 are grasped from
the base hydraulic pressure detected by the pressure sensor P, and
this makes it possible to know the manipulation amount of the brake
pedal 21. The pressure sensor P may be provided on the oil passage
L21 of the second piping passage L2.
[0039] Further, the second piping passage L2 in the hydraulic
control unit 25 takes the same construction as the aforementioned
first piping passage L1 and is composed of oil passages L21-L25.
The same is true with valves and the like, and the second piping
passage L2 is provided thereon with the hydraulic control valve 41
and the pressure regulation reservoir 44. One of branching oil
passages L22 is provided thereon with the pressure increase control
valve 42 for controlling the pressure increase of the brake fluid
in the wheel cylinder WC3 of the front left wheel 7FL, while the
other of the branching oil passages L22 is provided thereon with
the pressure increase control valve 43 for controlling the pressure
increase of the brake fluid in the wheel cylinder WC4 of the rear
right wheel 7RR. Further, the pressure reducing control valves 45,
46 are provided on oil passages L23 respectively branching from the
oil passages 22, and the pump 47 is provided on an oil passage
L24.
[0040] The hydraulic control unit 25 is able to apply the base
hydraulic pressure from the master cylinder 23 and the controlled
hydraulic pressure which is built by driving the pumps 37, 47 and
by controlling the hydraulic control valves 31, 41, to the wheel
cylinders WC1-WC4 of the respective wheels 7RL, 7FR, 7FL, 7RR. When
supplied with the base hydraulic pressure and the controlled
hydraulic pressure, the respective wheel cylinders WC1-WC4 operate
brake means BK1-BK4 to apply a base hydraulic brake force FB and a
controlled hydraulic brake force FC to each of the wheels 7RL, 7FR,
7FL, 7RR. As the brake means BK1-BK4, there are used disc brakes,
drum brakes or the like, in which friction members like the brake
pads, brake shoes or the like restrict rotations of disc rotors,
brake drums or the like which are bodily provided on the
wheels.
[0041] The brake ECU 60 is an electronic controller for controlling
the whole of the vehicle brake system 1 in cooperation with the
hybrid ECU 50. The brake ECU 60 controls the openings/closings of
the valves and the like in the hydraulic control unit 25 and also
controls the driving of the motor M to control the pumps 37, 47.
Further, the brake ECU 60 is connected to receive detection signals
from the pedal stroke sensor 21a and the pressure sensor P.
Further, the brake ECU 60 is connected to receive a detection
signal form a following distance sensor (vehicle-to-vehicle sensor)
61. The following distance sensor 61 is a sensor which uses a laser
beam to detect the following distance to a vehicle traveling ahead,
and the detection signal of the following distance is used in
executing the active cruise control function.
[0042] The brake ECU 60 calculates a driver target brake force FT
corresponding to the manipulation amount of the brake pedal 21,
subtracts a base hydraulic brake force FB therefrom and distributes
the remainder for use as a controlled hydraulic brake force FC and
a regenerative brake force (executed regenerative brake force FG).
At this time, the brake ECU 60 supplies the hybrid ECU 50 with a
command indicating the strength of a demand regenerative brake
force FR being a target of the regenerative brake force. The hybrid
ECU 50 controls the regenerative brake device A in response to the
command and feeds back an actually generated regenerative brake
force, that is, an executed regenerative brake force FG. Upon
receiving the executed regenerative brake force FG, the brake ECU
60 finally controls the distribution of the controlled hydraulic
brake force FC to each wheel. The hybrid ECU 50 and the brake ECU
60 cooperatively control the hydraulic brake device B and the
regenerative brake device A and correspond to the brake control
device in the claimed invention.
[0043] Further, the brake ECU 60 has a function of automatically
setting compensation brake forces FD for the respective wheels by
itself in dependence on the vehicle travelling situation and
controlling the distribution thereof, as exemplified hereinafter.
For example; in the active cruise control function, when the
detected following distance decreases, the brake ECU 60 sets the
compensation brake forces FD to keep the following distance longer
than a predetermined value. When each compensation brake force FD
exceeds the driver target brake force FT, the brake ECU 60 executes
a control to automatically compensate the difference. Further, in
the brake assist function, when recognizing an emergency braking
manipulation from the braking manipulation amount and the
manipulation speed, the brake ECU 60 sets another compensation
brake force FE which should be added to the driver target brake
force FT. The brake ECU 60 automatically executes a control to
generate a brake force on which the compensation brake force FE is
added to the driver target brake force FT.
[0044] Heretofore, the brake force being a surplus over the driver
target brake force FT has been realized as a result that the brake
ECU 60 drives the pumps 37, 47 of the hydraulic control unit 25 to
increase the controlled hydraulic pressure and hence, to increase
the controlled hydraulic brake force FC. The present embodiment is
designed to make the regenerative brake device A generate at least
a part of the brake force being the surplus over the driver target
brake force FT.
[0045] FIG. 3 is a graph showing the operation property of the
vehicle brake system 1 at an ordinary time. In FIG. 3, the axis of
abscissas indicates the manipulation amount of the brake pedal,
while the axis of ordinates indicates brake force. The solid line
curve in the figure represents the driver target brake force FT
corresponding to the manipulation amount of the brake pedal 21, and
the broken line curve represents the base hydraulic brake force FB
which corresponds to a base hydraulic pressure the master cylinder
23 generates in correspondence to the manipulation amount of the
brake pedal 21. The difference calculated by subtracting the base
hydraulic brake force FB from the driver target brake force FT is
distributed to the regenerative brake force (executed regenerative
brake force FG) by the regenerative brake device A and the
controlled hydraulic brake force FC by the pump driving, so that
the driver target brake force FT is controlled to be generated as
calculated. The operation property in FIG. 3 is stored in the brake
ECU 60 in advance as a map in the form of a table or as relational
expressions and is used as occasion arises.
[0046] It is to be noted that each of the brake forces is expressed
by two-uppercase symbols and will hereafter be referred to as that
to which a numeral is suffixed appropriately. The numeral suffixed
is for the purpose of easing the reference to each of particular
values of the brake forces exemplified in the drawings, and the
same uppercase symbols represent brake forces of the same kind even
if they have different numerals suffixed.
[0047] Next, description will be made regarding the control
operation of the brake ECU 60 in the first embodiment. FIG. 4 is a
flow chart showing the control processing of the brake ECU 60 in
the first embodiment, and the control processing will be referred
to as the case that the active cruise control function has been in
operation. As illustrated, the brake ECU 60 performs an input
processing at step S1. Specifically, the brake ECU 60 reads
detection signals of the pedal stroke sensor 21a, the pressure
sensor P and the following distance sensor 61 and exchanges
information with the hybrid ECU 50.
[0048] At step S2, the brake ECU 60 obtains a manipulation amount
Z1 of the brake pedal 21 based on the detection signals of the
pedal stroke sensor 21a and the pressure sensor P and calculates a
driver target brake amount FT1 corresponding to the manipulation
amount Z1 from the operation property in FIG. 3. Although the
detection signals of both of the pedal stroke sensor 21a and the
pressure sensor P are used in order to make the detected
manipulation amount Z1 enhanced in accuracy, the detection signal
of either one of the sensors may be used. The driver target brake
amount FT1 is usually the amount which is calculated taking the
whole vehicle into consideration. However, in the illustrated
control processing flow chart, the amount FT1 is considered as the
amount per wheel which is obtained by dividing that for the whole
vehicle by the number of the wheels. Step 2 corresponds to the
driver target brake force calculation means or section in the
claimed invention.
[0049] Step S3 is executed to calculate compensation brake forces
FD1 for the respective wheels 7FR, 7FL, 7RR, 7RL. In the active
cruise control (ACC) function, a setting is made for compensation
brake forces FD1 that become necessary in dependence on the
following distance detected by the following distance sensor 61.
Different compensation brake forces FD1 may be set for the
respective wheels. Step 3 corresponds to the compensation brake
force setting means or section in the claimed invention.
[0050] Sep 4 is executed to calculate compensated target brake
forces FU1 for the respective wheels 7FR, 7FL, 7RR, 7RL. In the
active cruise control function, a larger one is selected from the
driver target brake force FT1 and each compensation brake force
FD1, and the base hydraulic brake force FB1 obtained from FIG. 3 is
subtracted from the selected one force to obtain the compensated
target brake force FU1 for each wheel. The compensated target brake
force FU1 is the brake force which should be undertaken by the
executed regenerative brake force FG and the controlled hydraulic
brake force FC. Step 4 corresponds to the selection compensation
means or section in the claimed invention.
[0051] At step S5, the right side sum SR obtained by adding the
compensated target brake forces FU1 for the front and rear right
wheels is compared with the left side sum SL obtained by adding the
compensated target brake forces FU1 for the front and rear left
wheels. Step S5 corresponds to the left right comparison means or
section in the claimed invention.
[0052] Step 6 is reached when the both of the sums SR, SL are
equal, and the double of the right side sum SR is set as a demand
regenerative brake force FR. Thus, the demand regenerative brake
force FR coincides with the sum of the compensated target brake
forces FU1 for the four wheels. If there is a difference between
the both of the sums SR, SL at step S5, step S7 is reached, wherein
a smaller one of the right side sum SR and the light side sum SL is
doubled to be set as the demand regenerative brake force FR. Steps
S6 and S7 merge at step S8 to deliver the demand regenerative brake
force FR to the hybrid ECU 50, that is, to command the generator
motor 20 to generate the demand regenerative brake force FR. The
generator motor 20 generates as much regenerative brake force as
possible within the demand regenerative brake force FR, and the
hybrid ECU 50 transmits the executed regenerative brake force FG
back to the brake ECU 60.
[0053] At step S9, the brake ECU 60 acquires the executed
regenerative brake force FG which was exerted by the generator
motor 20, from the hybrid ECU 50. At next step S10, the value made
by dividing the executed regenerative brake force FG by four (4) is
subtracted from the respective compensated target brake forces FU1
for the four wheels to set respective controlled hydraulic brake
forces FC1 for the four wheels. Steps S5-S10 correspond to the
distribution control means or section in the claimed invention.
Further, step S6 and steps S8-S10 correspond to the left right
equal-time distribution control means or section in the claimed
invention, and steps S7-S10 correspond to the left right
unequal-time distribution control means or section in the claimed
invention.
[0054] At final step S11, in order to realize the respective
controlled hydraulic brake forces FC1 on the four wheels, the brake
ECU 60 controls solenoids of the respective valves in the hydraulic
control nit 25 and also controls the motor M to drive the pumps 37,
47. Thus, one cycle of the control processing is completed, and
return is made to step S1 to repetitively execute the control
processing thereafter.
[0055] In the case that the brake assist (BA) function operates,
the processing at step S3 and S4 are changed from those
aforementioned. That is, at step S3, an emergency braking
manipulation is recognized from the manipulation amount P1 of the
brake pedal and the manipulation speed being the time-dependant
change rate, and a compensation brake force FE1 to be added, to the
driver target brake force FT1 is set. At step S4, the compensation
brake force FE1 is added to the driver target brake force FT1, and
the base hydraulic brake force FB1 is subtracted from the sum of
the addition to set the compensated target brake force FU1 for each
wheel. In this case, step S4 corresponds to the addition
compensation means or section in the claimed invention.
[0056] Next, description will be made regarding the operation and
effects of the vehicle brake system 1 in the first embodiment
constructed hereinabove. FIG. 5 is a combination of graphs
schematically exemplifying the result that the brake ECU executed
the control processing shown in FIG. 4 during the operation of the
active cruise control function. The upper graph in the figure
exemplifies the distribution of the brake forces to the front right
wheel 7FR, while the lower graph represents the compensation brake
force FD2 set in the active cruise control function. The axis of
abscissas in the graphs is a common time axis (t).
[0057] FIG. 5 exemplifies the case wherein the stepping of the
brake pedal 21 begins at time t1, the manipulation amount Z of the
pedal 21 is gradually increased until time t3, the manipulation
amount Z is kept almost fixed from time t3 to time t9, the
manipulation amount Z is returned to zero from time t9 to time t10,
and the compensation brake force FD2 is set during the period from
time t4 to time t8. The driver target brake force FT2 which varies
in correspondence to the manipulation amount Z of the brake pedal
21 is changed to represent a trapezoidal form, as indicated by the
solid line. Further, the base hydraulic brake force FB2 which
varies in correspondence to the manipulation amount Z of the brake
pedal 21 is changed to represent a trapezoidal form lower in height
than that of the driver target brake force FT2, as indicated by the
broken line.
[0058] In this case, during each period of the time t1-t4 and time
time t8-t10 with the compensation brake force FD2 being not set,
the compensated target brake force FU2 is calculated by subtracting
the base hydraulic brake force FB2 from the driver target brake
force FT2. Further, during the period of time t4-t8 with the
compensation brake force FD2 being set to be larger than the driver
target brake force FT2, the compensated target brake force FU2 is
calculated by subtracting the base hydraulic brake force FB2 from
the compensation brake force FD2. In the upper graph, the range
indicated by a declining hatching is undertaken by the executed
regenerative brake force FG2, and the range indicated by dots is
undertaken by the controlled hydraulic brake force FC2.
[0059] As illustrated, the base hydraulic brake force FB2 is
generated at the same time as the driver target brake force FT2 is
generated at time t1, and the compensated target brake force FU2 is
undertaken by the executed regenerative brake force FG2. When at
time t2, the increase of the executed regenerative brake force FG2
becomes gentle and unable to follow the compensated target brake
force FU2, the controlled hydraulic brake force FC2 is generated,
in which state time t4 is reached. The both of the executed
regenerative brake force FG2 and the controlled hydraulic brake
force FC2 are being generated at time t4, and when the active
cruise control function is brought into operation at this time to
cause the compensated target brake force FU2 to increase abruptly,
the increment is undertaken by the controlled hydraulic brake force
FC2. After the time t4, the controlled hydraulic brake force FC2 is
replaced by the executed regenerative brake force FG2 which is
increased gradually thereafter, and during the period of time
t5-t6, the whole of the compensated target brake force FU2 is
undertaken by the executed regenerative brake force FG2. As the
executed regenerative brake force FG2 decreases after time t6, a
part of the compensated target brake force FU2 is undertaken again
by the controlled hydraulic brake force FC2. Further, when the
executed regenerative brake force FG2 becomes zero at time t7, the
whole of the compensated target brake force FU2 is undertaken by
the controlled hydraulic brake force FC2, and this state continues
unit time t10.
[0060] In the present embodiment, when the compensation brake force
FD2 exceeding the driver target brake force FT2 is set by the
active cruise control function, the regenerative brake device A can
be used to cover or undertake the range which exceeds the driver
target brake force FT2. Heretofore, the hydraulic brake device B
has exclusively been used to cover the range exceeding the driver
target brake force FT2. In this sense, according to the present
embodiment, the efficiency in regeneration can be improved than
that in the prior art.
[0061] Also in the case of adding a compensation brake force to the
driver target brake force FT2 in the brake assist function, the
present embodiment operates likewise as described above. Further,
without being limited to the active cruise control function and the
brake assist function, the present embodiment operates likewise as
described above in the case where the brake ECU 60 automatically
sets a brake force for each wheel exceeding the driver target brake
force FT2.
[0062] Next, description will be made regarding a specific method
of controlling the distribution of brake forces to the respective
wheels 7FR, 7FL, 7RR, 7RL. FIGS. 6(A)-6(D) are schematic diagrams
for explaining specific examples of distribution controls in which
the left right equal-time distribution control means or section
(step S6 and steps S8-S10 in FIG. 4) executes the distribution of
brake forces to the respective wheels 7FR, 7FL, 7RR, 7RL. FIG. 6(A)
indicates the compensated target brake forces FU3 for the
respective wheels 7FR, 7FL, 7RR, 7RL, and each of FIGS. 6(B)-6(D)
indicates the executed regenerative brake forces FG3 (numerical
value at the upper row by each wheel) and the controlled hydraulic
brake forces FC3 (numerical value at the lower row by each wheel)
which were distributed to the respective wheels.
[0063] In the example shown in FIG. 6(A), the compensated target
brake forces FU3 of the respective wheels 7FR, 7FL, 7RR, 7RL are
all 2 units. Thus, each of the right side sum SR3 and the left side
sum SL3 is 4 units, and the left right equal-time distribution
control means or section is used. The demand regenerative brake
force FR3 becomes 8 units which is calculated by doubling the right
side sum SR3 of 4 units. At this time, where the operation
condition of the regeneration brake device A is in satisfaction,
the executed regenerative brake force FG3 of 8 units which meets
the demand regenerative brake force FR3 are exerted as the total on
the front right wheel 7FR and the front left wheel 7FL, as shown in
FIG. 6(B). Accordingly, the controlled hydraulic brake force FC3
becomes unnecessary.
[0064] Further, where the operation condition of the regeneration
brake device A is mean or moderate, as shown in FIG. 6(C), the
regenerative brake force of 2 units can be exerted at each of the
front right wheel 7FR and the front left wheel 7FL, so that the
executed regenerative brake force FG3 becomes 4 units. Accordingly,
1 unit which is obtained by dividing the 4 units of the executed
regenerative brake force FG3 by 4 is subtracted from the 2 units of
the compensated target brake force FU3 for each wheel, so that 1
unit is set as the controlled hydraulic brake force FC3 for each
wheel 7FR, 7FL, 7RR, 7RL. Further, where the operation condition of
the regeneration brake device A is insufficient, the executed
regenerative brake force FG3 becomes zero, as shown in FIG. 6(D).
Therefore, the controlled hydraulic brake force FC3 for each wheel
7FR, 7FL, 7RR, 7RL becomes 2 units as a result of the compensated
target brake force FU3 remaining as it is without being undertaken
by the executed regenerative brake force FG3.
[0065] FIGS. 7(A)-7(D) are schematic diagrams for explaining
specific examples of distribution controls in which the left right
unequal-time distribution control means or section (steps S7-S10 in
FIG. 4) executes the distribution of brake forces to the respective
wheels 7FR, 7FL, 7RR, 7RL. FIG. 7(A) indicates the compensated
target brake forces FU4 for the respective wheels 7FR, 7FL, 7RR,
7RL, and each of FIGS. 7(B)-7(C) indicates the executed
regenerative brake forces FG4 (numerical value at the upper row by
each wheel) and the controlled hydraulic brake forces FC4
(numerical value at the lower row by each wheel) which were
distributed to the respective wheels.
[0066] In the example shown in FIG. 7(A), the compensated target
brake forces FU4 for the front right wheel 7FR and the rear right
wheel 7RR are each 4 units, and the compensated target brake forces
FU4 for the front left wheel 7FL and the rear left wheel 7RL are
each 2 units. Thus, the right side sum SR4 becomes 8 units, and the
left side sum SL4 becomes 4 units, in which case the left right
unequal-time distribution control means or section is used. The
executed regenerative brake force FR4 becomes 8 units which is
calculated by doubling the 4 units of the left side sum SL4 being
the sum on the smaller side. At this time, where the operation
condition of the regenerative brake device A is in satisfaction, as
shown in FIG. 7(B), the executed regenerative brake force FG4 of 8
units which meets the demand regenerative brake force FR4 can be
exerted as the total on the front right wheel 7FR and the front
left wheel 7FL. Then, 2 units obtained by dividing the 8 unit of
the executed regenerative brake force by 4 is subtracted from each
of the compensated target brake forces FU4 for respective wheels to
obtain controlled hydraulic brake forces FC4 for the respective
wheels. Accordingly, as the controlled hydraulic brake forces FC4,
2 units is set for each of the front right wheel 7FR and the rear
right wheel 7RR, zero is set for each of the front left wheel 7FL
and the rear left wheel 7RL.
[0067] Further, where the operation condition of the regeneration
brake device A is mean or moderate, as shown in FIG. 7(C), the
regeneration brake force of 2 units can be exerted at each of the
front right wheel 7FR and the front left wheel 7FL, so that the
executed regenerative brake force FG4 becomes 4 units. Then, 1 unit
obtained by dividing the 4 units of the executed regenerative brake
force FG4 by 4 is subtracted from the compensated target brake
force FU4 for each wheel, so that the controlled hydraulic brake
force FC4 becomes 3 units for each of the front right wheel 7FR and
the rear right wheel 7RR and 1 unit for each of the front left
wheel 7FL and the rear left wheel 7RL. Further, where the operation
condition of the regeneration brake device A is insufficient, the
executed regenerative brake force FG4 becomes zero, as shown in
FIG. 7(D). Therefore, the controlled hydraulic brake force FC4 for
each wheel 7FR, 7FL, 7RR, 7RL becomes the compensated target brake
force FU4 for each wheel remaining as it is without being covered
by the executed regenerative brake force FG4.
[0068] As means for applying different controlled hydraulic
pressures to the wheel cylinders which are connected to the same
piping passage in the hydraulic control unit 25, the brake ECU 60
cyclically controls those selected from the valves in the hydraulic
control unit 25 to be opened and closed cyclically. For example,
with respect to the cylinders 7FR, 7RL connected to the first
piping passage L1, the following control is executed to lower the
controlled hydraulic pressure in the wheel cylinder WC2 for the
front right wheel 7FR than that in the wheel cylinder WC1 for the
rear left wheel 7RL. The pump 37 is driven, the hydraulic control
valve 31 is brought into the different pressure state, the pressure
increase valve 32 on the wheel cylinder WC1 side is opened, and the
pressure reducing control valve 35 is closed. Thus, the full
pressure of the controlled hydraulic pressure built by the pump 37
is applied to the wheel cylinder WC1. In this state, the pressure
increase valve 33 and the pressure reducing valve 36 on the wheel
cylinder WC2 side are controlled to be opened and closed
cyclically. Thus, the operating oil flowing from the pressure
increase valve 33 to the wheel cylinder WC2 is decreased in
comparison with the operating oil flowing to the wheel cylinder
side WC1, and at the same time, the operating oil outflows from the
wheel cylinder WC2 to the pressure reducing valve 36. As a result,
the controlled hydraulic pressure in the wheel cylinder WC2 is
controlled to be lower than that in the wheel cylinder WC1.
Further, by making the pressure increase valve 33 and the pressure
reducing valve 36 changed in the rate of the opening period to the
closing period, it is possible to variably adjust the controlled
hydraulic pressure in the wheel cylinder WC2 with the wheel
cylinder WC1 keeping the controlled hydraulic pressure fixed.
[0069] In the first embodiment, as exemplified in FIGS. 6(A)-6(D)
and 7(A)-7(D), it can be realized to supply the generator motor 20
with the maximum executed regenerative brake force FR3, FR4
satisfying the condition that, where the wheels are divided into
those on the right side and those on the left side, does not
provide an excess brake force on the wheels on either side.
Further, it can be realized to adjust the distribution of the brake
forces to the front wheels and the rear wheels, in other words, to
the driving wheels and the driven wheels in dependence on the
strength of the executed regenerative brake force FR3, FR4 by the
regenerative brake device A. Accordingly, it can be realized to
generate the executed regenerative brake force FR3, FR4 which is
the maximum as far as the right side sum SR3, SR4 and the left side
sum SL3, SL4 are not changed, so that the efficiency in
regeneration can remarkably be enhanced.
Second Embodiment
[0070] Next, description will be made regarding a vehicle brake
system in a second embodiment which differs from the first
embodiment in the calculation method for the demand regenerative
brake force FR. The vehicle brake system in the second embodiment
takes the same apparatus construction as that of the first
embodiment shown in FIGS. 1 and 2, but differs therefrom in a
control processing shown in FIG. 8. FIG. 8 is a flow chart showing
the control processing executed by the brake ECU 60 in the second
embodiment. In the second embodiment, step S5A in FIG. 8 replaces
steps S5-S7 in FIG. 4, and step S10A in FIG. 8 differs from step
S10 in details of calculation.
[0071] At step S5A in FIG. 8, the brake ECU 60 calculates a demand
regenerative brake force FR5 by multiplying the smallest value of
the compensated target brake forces FU1 for the driving wheels (the
front right wheel 7FR and the front left wheel 7FL) by the number
of the driving wheels. Further, at step S10A, the brake ECU 60
calculates respective controlled hydraulic brake forces FC5 by
subtracting the executed regenerative brake force FG5 from each of
the compensated target brake forces FU1 for the wheels 7RL, 7FR,
7FL, 7RR. This calculation is required for substantially the
driving wheels only. Step S5A and step 8 in FIG. 8 correspond to
the regeneration demand means or section in the claimed invention,
step 9 corresponds to the regeneration acquire means or section in
the claimed invention, and step 10A corresponds to the regeneration
reflecting means or section in the claimed invention.
[0072] FIGS. 9(A)-9(D) are explanatory views for showing specific
examples of distribution controls in which brake forces are
distributed to the respective wheels 7FR, 7FL, 7RR, 7RL in the
second embodiment. FIG. 9(A) indicates the compensated target brake
forces FU6 for the respective wheels 7FR, 7FL, 7RR, 7RL, and each
of FIGS. 9(B)-9(D) indicates the executed regenerative brake forces
FG6 (numerical value at the upper row by each wheel) and the
controlled hydraulic brake forces FC6 (numerical value at the lower
row by each wheel) which were distributed to the respective wheels.
In the example shown in FIG. 9(A), the compensated target brake
forces FU6 for the front right wheel 7FR and the rear right wheel
7RR are each 4 units, and the compensated target brake forces FU6
for the front left wheel 7FL and the rear left wheel 7RL are each 2
units. Thus, the smallest value of the compensated target brake
forces FU6 for the driving wheels is 2 units, and since the driving
wheels are two, the demand regenerative brake force FR5 becomes 4
units.
[0073] At this time, where the operation condition for the
regenerative brake device A is in satisfaction, as shown in FIG.
9(B), the executed regenerative brake force FG6 of 4 units which
meet the demand regenerative brake force FR5 can be exerted as the
total on the front right wheel 7FR and the front left wheel 7FL.
Then, with respect to the front right wheel 7FR and the front left
wheel 7FL, the respective executed regenerative brake forces FG6
are subtracted from the respective compensated target brake forces
FU6, so that the controlled hydraulic brake force FC6 becomes 2
units for the front right wheel 7FR and zero for the front left
wheel 7FL. The controlled hydraulic brake forces FC6 for the rear
right wheel 7RR and the rear left wheel 7RL are set to the
respective compensated target brake forces FU6 remaining as they
are without being undertaken by the executed regenerative brake
force FG6.
[0074] Further, where the operation condition for the regenerative
brake device A is mean or moderate, as shown in FIG. 9(C), the
regenerative brake force of 1 unit can be exerted at each of the
front right wheel 7FR and the front left wheel 7FL, so that the
executed regenerative brake force FG6 becomes 2 units in total.
Further, the controlled hydraulic brake force FC6 for the front
right wheel 7FR becomes 3 units, and the controlled hydraulic brake
force FC6 for the front left wheel 7FL becomes 1 unit. The
controlled hydraulic brake forces FC6 for the rear right wheel 7RR
and the rear left wheel 7RL are set to the respective compensated
target brake forces FU6 remaining as they are. Where the operation
condition for the regenerative brake device A is insufficient, the
executed regenerative brake force FG6 becomes zero, as shown in
FIG. 9(D). Accordingly, the controlled hydraulic brake forces FC6
for the respective wheels 7RL, 7FR, 7FL, 7RR are set to the
respective compensated target brake forces FU6 remaining as they
are.
[0075] In the second embodiment, as exemplified in FIGS. 9(A)-9(D),
it can be realized to supply the generator motor 20 with the
maximum demand regenerative brake force FR5 satisfying the
condition that does not provide an excess brake force on the
driving wheels. Further, it can be realized to adjust the
controlled hydraulic brake force FC6 for the driving wheels (the
front right wheel 7FR and the front left wheel 7FL) in dependence
on the regeneration brake fore FG6 exerted by the regenerative
brake device A. Accordingly, it can be realized to generate the
executed regenerative brake force which is the maximum as far as
the compensated target brake forces FU6 for the respective wheels
7FR, 7FL, 7RR,7RL are not changed, so that the efficiency in
regeneration can remarkably be enhanced.
[0076] Various features and many of the attendant advantages in the
foregoing embodiments will be summarized as follows:
[0077] In the vehicle brake system in the foregoing first
embodiment typically shown in FIGS. 1-5, the brake control device
60, 50 which cooperatively controls the hydraulic brake device B
and the regenerative brake device A selects a larger one of the
driver target brake force FT1 corresponding to the manipulation
amount of the braking manipulation member 21 and the compensation
brake force FD1 set by the brake control device 60, 50 itself for
each wheel, subtracts the base hydraulic brake force FB1 from the
selected one brake force to set the compensated target brake force
FU1 for each wheel, and distributes the compensated target brake
force FU1 to the controlled hydraulic brake force FC for each wheel
and the regenerative brake force FG for each driving wheel. Thus,
when the compensation brake force FD1 exceeds the driver target
brake force FT1, at least a part of the brake force which part
corresponds to the surplus is distributed to the regenerative brake
device A. This results in bringing the regenerative brake device A
into operation though the same has heretofore not been operated
when the compensation brake forces FD1 set by the brake control
device 60, 50 itself are generated during the active cruise control
function or the like, and therefore, the efficiency in regeneration
can be enhanced.
[0078] Also in the vehicle brake system in the foregoing first
embodiment typically shown in FIGS. 1-5, the brake control device
60, 50 which cooperatively controls the hydraulic brake device B
and the regenerative brake device A adds the driver target brake
force FT1 corresponding to the manipulation amount of the braking
manipulation member 21 and the compensation brake force FE1 set by
the brake control device 60, 50 itself for each wheel to obtain the
sum, subtracts the base hydraulic brake force FB1 from the sum to
set the compensated target brake force FU1 for each wheel, and
distributes the compensated target brake force FU1 to the
controlled hydraulic brake force FC for each wheel and the
regenerative brake force FR for each driving wheel. Thus, at least
a part of the compensation brake force FU1 is distributed to the
regenerative brake device A. This results in bringing the
regenerative brake device A into operation though the same has
heretofore not been operated when the compensation brake forces FE1
set by the brake control device 60, 50 itself are generated during
the brake assist function or the like, and therefore, the
efficiency in regeneration can be enhanced.
[0079] Also in the vehicle brake system in the foregoing first
embodiment typically shown in FIG. 1-4, the distribution control
means or section (steps S5-S10 in FIG. 4) compares the right side
sum SR of the compensated target brake forces FU1 and the left side
sum SL of the compensated target brake forces FU1 and applies the
demand regenerative brake force FR which is obtained by the
addition of the compensated target brake forces FU1 for the four
wheels, to the generator motor 20 if the sums SR, SL are equal, but
applies the demand regenerative brake force FR which is obtained by
doubling the smaller one of the sums SR, SL if the sums SR, SL
differ. Further, in either case, the distribution control means or
section subtracts the value which is obtained by dividing the
executed regenerative brake force FG by 4, from the respective
compensated target brake forces FU1 for the four wheels to set the
differences as the controlled hydraulic brake forces FC1 for the
four wheels. That is, the distribution control section operates to
supply the generator motor 20 with the executed regenerative brake
force FG which is the maximum as far as the condition is satisfied
that, where the wheels are divided into those on the right side and
those on the left side, does not provide an excess braking on the
wheels on either side, and to cover the deficiency in the executed
regenerative brake force FG which was actually exerted, by the
controlled hydraulic brake forces FC1 for the respective wheels.
Accordingly, in generating the compensation brake forces FD1/FE1
set by the brake control device 60, 59 itself, it can be realized
to make the executed regenerative brake force FG become the maximum
as far as the right side sum and the left side sum of the
compensated target brake forces are not changed, and therefore, the
efficiency in regeneration can remarkably be enhanced.
[0080] Further, in the vehicle brake system in the foregoing second
embodiment typically shown in FIGS. 1-2 and 8, the distribution
control means or section (steps S5A-S10A in FIG. 8) operates to
supply to the generator motor 20 the demand regenerative brake
force FR5 which is calculated by multiplying the smallest value of
the compensated target brake forces FU1 for the driving wheels 7FL,
7RL by the number of the driving wheels 7FL, 7RL, and to distribute
the controlled hydraulic brake forces FC5 to the respective wheels
based on the executed regenerative brake force FG which was
actually exerted by the generator motor 20. That is, the
distribution control section operates to supply to the generator
motor 20 the demand regenerative brake force FR5 which is the
maximum as far as the condition that does not apply an excess
braking to the driving wheels 7FL, 7RL is satisfied, and to cover
the deficiency in the executed regenerative brake force FG which
was actually exerted, by the controlled hydraulic brake forces FC5
for the respective wheels. Accordingly, in generating the
compensation brake forces FD1/FE1 set by the brake control device
60, 50 itself, it can be realized to make the executed regenerative
brake force FG become the maximum as far as the compensated target
brake forces FU1 for the respective wheels are not changed, and
therefore, the efficiency in regeneration can remarkably be
enhanced.
[0081] Obviously, numerous further modifications and variations of
the present invention are possible in light of the above teachings.
It is therefore to be understood that within the scope of the
appended claims, the present invention may be practiced otherwise
than as specifically described herein.
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