U.S. patent application number 16/690858 was filed with the patent office on 2020-11-26 for electric booster having force-feedback-control structure.
The applicant listed for this patent is Hyundai Motor Company, Kia Motors Corporation. Invention is credited to Se-Ra Hwang, Gab-Bae Jeon, Yong-Pil Kim, Joung-Hee Lee, Jae-Hun Shim.
Application Number | 20200369254 16/690858 |
Document ID | / |
Family ID | 1000005207285 |
Filed Date | 2020-11-26 |
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United States Patent
Application |
20200369254 |
Kind Code |
A1 |
Hwang; Se-Ra ; et
al. |
November 26, 2020 |
ELECTRIC BOOSTER HAVING FORCE-FEEDBACK-CONTROL STRUCTURE
Abstract
An electric booster is provided having a force-feedback-control
structure. The electric booster includes a master piston having a
nut unit rectilinearly moved in a booting cylinder space by
receiving driving power generated by a motor and a hydraulic
pressure generated by a pedal effort. A first screw has a first end
connected to the motor and a second end extending into the boosting
cylinder, and is rotated by the motor operating with the brake
pedal. A second screw is disposed to face the first screw to have a
separation space . A connecting member connects the first screw and
the second screw. A pressure balancing member has contact surfaces
in contact with the second end of the first screw and the
connecting member, respectively, and is deformed by a difference
between two pressures when applied to the contact surfaces in a
longitudinal direction of the first screw, respectively.
Inventors: |
Hwang; Se-Ra; (Suwon,
KR) ; Shim; Jae-Hun; (Hwaseong, KR) ; Lee;
Joung-Hee; (Hwaseong, KR) ; Jeon; Gab-Bae;
(Hwaseong, KR) ; Kim; Yong-Pil; (Incheon,
KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hyundai Motor Company
Kia Motors Corporation |
Seoul
Seoul |
|
KR
KR |
|
|
Family ID: |
1000005207285 |
Appl. No.: |
16/690858 |
Filed: |
November 21, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60T 8/171 20130101;
B60T 7/042 20130101; B60T 13/745 20130101 |
International
Class: |
B60T 13/74 20060101
B60T013/74; B60T 8/171 20060101 B60T008/171; B60T 7/04 20060101
B60T007/04 |
Foreign Application Data
Date |
Code |
Application Number |
May 20, 2019 |
KR |
10-2019-0058980 |
Claims
1. An electric booster having a force-feedback-control structure,
comprising: a master piston including a nut unit; a boosting
cylinder having a space in which the master piston is rectilinearly
moved by receiving driving power generated by a motor and a
hydraulic pressure generated by a pedal effort applied to a brake
pedal; a first screw having a first end connected to the motor and
a second end extending into the boosting cylinder, wherein the
first screw is rotated by the motor that operates in conjunction
with the brake pedal; a second screw disposed to face the first
screw to have a separation space and thread-coupled to the nut
unit; a connecting member which connects the first screw and the
second screw; and a pressure balancing member disposed to have
contact surfaces in contact with the second end of the first screw
and the connecting member, respectively, and deformed by a
difference between two pressures when the two pressures are applied
to the contact surfaces in a longitudinal direction of the first
screw, respectively.
2. The electric booster of claim 1, wherein the first screw has a
horizontal portion which is formed in the longitudinal direction,
and a vertical portion which extends from the second end of the
first screw in a direction perpendicular to the horizontal
portion.
3. The electric booster of claim 1, wherein a first side surface of
the pressure balancing member, as the contact surface, is in
contact with the second end of the first screw such that the
pressure balancing member operates together with the first screw,
and a second side surface of the pressure balancing member is
positioned to be stationary.
4. The electric booster of claim 2, wherein the pressure balancing
member has a greater size than the vertical portion and has a
smaller size than the connecting member.
5. The electric booster of claim 2, wherein the contact surface of
the pressure balancing member, which is in contact with the
vertical portion, is a first contact surface corresponding to a
part of a cross section of the vertical portion except for a cross
section of the horizontal portion, and the contact surface of the
pressure balancing member, which is in contact with the connecting
member, is a second contact surface corresponding to a part of a
cross section of the pressure balancing member except for the cross
section of the vertical portion.
6. The electric booster of claim 5, wherein a pressure applied to
the first contact surface in the longitudinal direction of the
first screw and a pressure applied to the second contact surface
are equal to each other.
7. The electric booster of claim 5, wherein a pressure applied to
the first contact surface is equal to a pressure of a hydraulic
fluid provided in the separation space which is applied to a cross
section of the horizontal portion.
8. The electric booster of claim 1, wherein a flow path is formed
in the connecting member to supply a hydraulic fluid to the
separation space.
9. The electric booster of claim 1, further comprising: a first
sensor configured to measure a displacement of the brake pedal; and
a second sensor configured to measure a rotation angle of the
motor, wherein the first sensor and the second sensor operate in
conjunction with each other.
10. The electric booster of claim 1, wherein when the two pressures
applied to the contact surfaces are different from each other, the
pedal effort applied to the brake pedal is changed to rotate the
motor.
11. The electric booster of claim 1, further comprising: a third
sensor configured to measure a displacement of the first screw,
wherein the motor is rotated based on a measured value of the third
sensor when the first screw is displaced as the two pressures
applied to the contact surfaces are different from each other.
12. The electric booster of claim 1, wherein a master cylinder
having a space in which a braking pressure is formed by a movement
of the master piston, is provided at one side of the boosting
cylinder.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority under 35 U.S.C. .sctn. 119
to Korean Patent Application No. 10-2019-0058980, filed on May 20,
2019, the disclosure of which is incorporated herein by reference
in its entirety.
BACKGROUND
1. Field of the Invention
[0002] The present invention relates to an electric booster having
a force-feedback-control structure, and more particularly, to an
electric booster having a force-feedback-control structure capable
of adjusting a pressure balance by receiving pressure feedback from
the outside of a cylinder and comparing a pedal effort applied to a
brake pedal and a force generated by a motor.
2. Description of the Related Art
[0003] 4Typically, in an electric booster-type braking system, when
a driver engages a brake pedal, a pedal effort sensor detects a
pedal effort of the driver (e.g., amount of force exerted onto the
pedal), an electronic control unit (ECU) that operates a motor of a
booster based on a measured value of the pedal effort sensor and
transmits a boosted force to a master cylinder. The master cylinder
transmits a braking pressure to a wheel brake based on the boosted
force transmitted from a reciprocating motion of a master
piston.
[0004] Then, an electronic stability control (ESC) device for a
vehicle adjusts hydraulic pressure to be applied to the wheel brake
based on braking modes to perform an appropriate braking operation.
However, when a pressure outside the master cylinder is changed due
to a change in rigidity of a brake system, since the braking
pressure transmitted by the master piston is unable to be
appropriately transmitted to the wheel brake, a pressure balance
between the pressure generated by the pedal effort applied to the
brake pedal and the braking pressure applied to the wheel brake is
adjusted. In particular, the driver is required to further engage
the brake pedal to generate a desired braking force, and as a
result, there occurs non-uniformity in braking.
[0005] In the related art, a system has been developed in which an
electronic control unit calculates a braking pressure using a
detection result of a pedal stroke sensor and adjusts a braking
force by moving a piston in a pump to meet the braking
pressure.
[0006] In other words, a motor is rotated to position the piston at
a first position calculated using a braking pressure, which is
calculated by detecting a manipulation degree of a brake pedal, and
information regarding piston positions which are listed in a lookup
table and match with the braking pressure, the braking pressure is
compared with a fluid pressure measured by a pressure sensor, and
the motor is rotated corresponding to a difference between the
braking pressure and the fluid pressure.
SUMMARY
[0007] The present invention provides a new type of invention that
adjusts a pressure balance in a way different from the related
art.
[0008] An exemplary embodiment of the present invention provides an
electric booster having a force-feedback-control structure and the
electric booster may include: a master piston having a nut unit; a
boosting cylinder which provides a space in which the master piston
may be moved rectilinearly by receiving driving power generated by
a motor and a hydraulic pressure generated by a pedal effort
applied to a brake pedal; a first screw which having a first end
connected to the motor and a second end extending into the boosting
cylinder, and may be rotated by the motor that operates in
conjunction with the brake pedal; a second screw which is disposed
to face the first screw so as to have a separation space and
thread-coupled to the nut unit; a connecting member which connects
the first screw and the second screw; and a pressure balancing
member disposed to have contact surfaces in contact with the second
end of the first screw and the connecting member, respectively, and
deformed by a difference between two pressures when the two
pressures are applied to the contact surfaces in a longitudinal
direction of the first screw, respectively.
[0009] According to the present invention, it may be possible to
actively adjust a pressure balance by receiving pressure feedback
from the outside of the master cylinder, comparing the pedal effort
applied to the brake pedal and the force generated by the motor,
and then moving the first screw. Additionally, the separation space
may be formed between the first screw and the second screw and
thus, the state of the pressure balancing member may be changed
when the pressure balance is changed, and the pressure balancing
member in the normal state may be designed more easily.
[0010] According to the present invention, a gradient of the boost
ratio, which is desired by the driver, may be maintained by
changing the pedal effort applied to the brake pedal based on the
deformed state of the pressure balancing member, and as a result,
non-uniformity in braking may be minimized. Additionally, the third
sensor may be configured to measure the deformed state of the
pressure balancing member, and the motor may be automatically
rotated, and thus, the boost ratio desired by the driver may be
maintained, and as a result, non-uniformity in braking may be
further minimized.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] A brief description of each drawing is provided to more
sufficiently understand drawings used in the detailed description
of the present invention.
[0012] FIG. 1 is a view illustrating a schematic configuration of
an electric booster having a force-feedback-control structure
according to an exemplary embodiment of the present invention;
[0013] FIG. 2 is an enlarged view of part A in FIG. 1 according to
an exemplary embodiment of the present invention;
[0014] FIG. 3 is a view illustrating a surface of a cross section
of a pressure balancing member to which a pressure is applied
according to an exemplary embodiment of the present invention;
[0015] FIG. 4A is a view illustrating a state of the pressure
balancing member when a pressure applied to a first contact surface
and a pressure applied to a second contact surface are equal to
each other according to an exemplary embodiment of the present
invention;
[0016] FIG. 4B is a view illustrating a state of the pressure
balancing member when a pressure applied to the first contact
surface is higher than a pressure applied to the second contact
surface according to an exemplary embodiment of the present
invention;
[0017] FIG. 4C is a view illustrating a state of the pressure
balancing member when a pressure applied to the first contact
surface is less than a pressure applied to the second contact
surface according to an exemplary embodiment of the present
invention;
[0018] FIG. 5 is a view illustrating a state in which a pedal
effort applied to a brake pedal is higher than a force generated by
a motor in FIG. 1 according to an exemplary embodiment of the
present invention;
[0019] FIG. 6 is a view illustrating a state in which a pedal
effort applied to the brake pedal is lower than a force generated
by the motor in FIG. 1 according to an exemplary embodiment of the
present invention;
[0020] FIG. 7 is a view illustrating a boost ratio which is a
relationship between the pedal effort applied to the brake pedal
and the force generated by the motor according to an exemplary
embodiment of the present invention; and
[0021] FIG. 8 is a view illustrating a boost ratio which is a
relationship between the pedal effort applied to the brake pedal
and the force generated by the motor when there is a third sensor
according to an exemplary embodiment of the present invention.
DETAILED DESCRIPTION
[0022] It is understood that the term "vehicle" or "vehicular" or
other similar term as used herein is inclusive of motor vehicles in
general such as passenger automobiles including sports utility
vehicles (SUV), buses, trucks, various commercial vehicles,
watercraft including a variety of boats and ships, aircraft, and
the like, and includes hybrid vehicles, electric vehicles,
combustion, plug-in hybrid electric vehicles, hydrogen-powered
vehicles and other alternative fuel vehicles (e.g. fuels derived
from resources other than petroleum).
[0023] Although exemplary embodiment is described as using a
plurality of units to perform the exemplary process, it is
understood that the exemplary processes may also be performed by
one or plurality of modules. Additionally, it is understood that
the term controller/control unit refers to a hardware device that
includes a memory and a processor. The memory is configured to
store the modules and the processor is specifically configured to
execute said modules to perform one or more processes which are
described further below.
[0024] Furthermore, control logic of the present invention may be
embodied as non-transitory computer readable media on a computer
readable medium containing executable program instructions executed
by a processor, controller/control unit or the like. Examples of
the computer readable mediums include, but are not limited to, ROM,
RAM, compact disc (CD)-ROMs, magnetic tapes, floppy disks, flash
drives, smart cards and optical data storage devices. The computer
readable recording medium can also be distributed in network
coupled computer systems so that the computer readable media is
stored and executed in a distributed fashion, e.g., by a telematics
server or a Controller Area Network (CAN).
[0025] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the invention. As used herein, the singular forms "a", "an" and
"the" are intended to include the plural forms as well, unless the
context clearly indicates otherwise. It will be further understood
that the terms "comprises" and/or "comprising," when used in this
specification, specify the presence of stated features, integers,
steps, operations, elements, and/or components, but do not preclude
the presence or addition of one or more other features, integers,
steps, operations, elements, components, and/or groups thereof. As
used herein, the term "and/or" includes any and all combinations of
one or more of the associated listed items.
[0026] Unless specifically stated or obvious from context, as used
herein, the term "about" is understood as within a range of normal
tolerance in the art, for example within 2 standard deviations of
the mean. "About" can be understood as within 10%, 9%, 8%, 7%, 6%,
5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated
value. Unless otherwise clear from the context, all numerical
values provided herein are modified by the term "about."
[0027] Hereinafter, exemplary embodiments of an electric booster
having a force-feedback-control structure according to the present
invention will be described in detail with reference to the
drawings. Terms or words used herein should not be interpreted as
being limited to a general or dictionary meaning and should be
interpreted as a meaning and a concept which conform to the
technical spirit of the present invention based on a principle that
an inventor can appropriately define a concept of a term to
describe his/her own invention by the best method.
[0028] Meanwhile, based on directions illustrated in the drawings
in the present specification, an X direction includes a +X
direction (right direction) and a -X direction (left direction),
and a Y direction includes a +Y direction (up direction) and a -Y
direction (down direction).As illustrated in FIG. 1, the electric
booster having the force-feedback-control structure according to
the exemplary embodiment of the present invention may include a
pedal chamber unit 100, a boosting chamber unit 200, and a master
chamber unit 300.
[0029] The pedal chamber unit 100 may include a pedal cylinder 110
which defines a space in which a hydraulic pressure is formed and
generated by a pedal effort applied to a brake pedal, a push rod
120 which receives the pedal effort applied to the brake pedal, and
a pedal piston 130 connected to the push rod 120, and a first
return spring 140 which provides an elastic force to the pedal
piston 130. A reservoir 400, which stores a hydraulic fluid, may
provide the hydraulic fluid to the pedal cylinder 110 through a
first connecting flow path 152 to thus provide the hydraulic fluid
in the pedal cylinder 110.
[0030] When the pedal effort is applied to the brake pedal, the
pedal piston 130 moves downward (in the -Y direction) to form a
hydraulic pressure in the pedal cylinder 110. On the contrary, when
the pedal effort applied to the brake pedal is removed, the pedal
piston 130 is moved upward (in the +Y direction) by the first
return spring 140, and thus, the hydraulic pressure formed in the
pedal cylinder 110 may be removed.
[0031] Meanwhile, the pedal chamber unit 100 may include a first
sensor 160. The first sensor 160 may be configured to measure a
manipulation degree of the brake pedal by the driver and may be
configured to convert an output voltage into a depth to which the
brake pedal is pushed, that is, a stroke value. The first sensor
160 may be configured to measure a movement displacement of the
brake pedal, the push rod 120, or the pedal piston 130.
[0032] The boosting chamber unit 200 may include a boosting
cylinder 210, a first screw 220, a pressure balancing member 240, a
second screw 250, and a connecting member 260. The boosting
cylinder 210 may be supplied with the hydraulic fluid from the
pedal cylinder 110 through a second connecting flow path 154, and
thus, the hydraulic fluid may be provided in the boosting cylinder
210. A motor 500 may be disposed at one side of the boosting
cylinder 210, and driving power generated by the motor 500 may be
transmitted into the boosting cylinder 210. The boosting cylinder
210 accommodates the first screw 220, the pressure balancing member
240, the second screw 250, and the connecting member 260.
[0033] Meanwhile, the motor 500 may include a second sensor 560.
The second sensor 560 may be configured to measure a rotation angle
of the motor 500 and convert an output voltage into a movement
distance of a nut unit 270 to be described below. The second sensor
560 may be configured to operate in conjunction with the first
sensor 160 and measure the rotation angle of the motor 500 which
corresponds to the manipulation degree of the brake pedal which is
measured by the first sensor 160.
[0034] A first end of the first screw 220 may be connected to the
motor 500, and a second end of the first screw 220 may be
positioned in the boosting cylinder 210. Therefore, the first screw
220 may be formed to penetrate one side surface of the boosting
cylinder 210. An aperture through which the first screw 220
penetrates one side surface of the boosting cylinder 210 may be
sealed to prevent the hydraulic fluid from leaking to the outside
of the boosting cylinder 210 when the first screw 220 is inserted
therein.
[0035] The first screw 220 may include a horizontal portion 222
formed in a longitudinal direction, and a vertical portion 224
which extends from the second end of the first screw 220 in a
direction perpendicular to the horizontal portion 222. Bearings 290
may be provided at both sides of the horizontal portion 222 to
support the first screw 220 and the rotation of the first screw
220. Therefore, the first screw 220 may move in the longitudinal
direction (X direction), but the movement of the first screw 220 in
a radial direction (Y direction) may be restricted by the bearings
290.
[0036] The pressure balancing member 240 may be made of a material
that is deformed by a pressure and assumes a posture to surround
the horizontal portion 222 of the first screw 220, and the pressure
balancing member 240 may have a cylindrical shape to be rotated
more easily. Therefore, when the first screw 220 rotates, the
pressure balancing member 240 also rotates.
[0037] A part of a side surface (e.g., a first side surface) of the
pressure balancing member 240 in the -X direction may be in contact
with a first contact surface 242 which is a side surface at the
second end of the first screw 220 in the +X direction, and the
pressure balancing member 240 may be deformed in the X direction by
a pressure. In particular, the first contact surface 242 refers to
a part of a cross section of the vertical portion 224 except for a
cross section of the horizontal portion 222. In addition, a second
side surface of the pressure balancing member 240 may be positioned
to be stationary and unable to move in the X direction.
[0038] The second screw 250 may be disposed in the longitudinal
direction of the first screw 220, and the second end of the first
screw 220 and a first end of the second screw 250 may be disposed
face each other in a state in which the second end of the first
screw 220 and first end of the second screw 250 are spaced apart
from each other at a predetermined distance. The nut unit 270 may
be thread-coupled to an outer circumferential surface of the second
screw 250, and the nut unit 270 may move in the X direction when
the second screw 250 rotates. The nut unit 270 may be in contact
with the master piston 230 to help the master piston 230 to move in
the X direction.
[0039] The connecting member 260 may connect and rotate the first
screw 220 and the second screw 250 and may have a cylindrical shape
to allow the connecting member 260 to accommodate the second end of
the first screw 220, first end of the second screw 250, and the
pressure balancing member 240, and the connecting member 260 may
rotate more easily. Therefore, when the first screw 220 rotates,
the second screw 250 also rotates.
[0040] As illustrated in FIG. 2, the second end of the first screw
220 and the first end of the second screw 250 maybe spaced apart
from each other at a predetermined distance and accommodated in the
connecting member 260, and thus, a separation space SP may be
formed between the first screw 220 and the second screw 250.
Particularly, the movement of the first screw 220 and the movement
of the second screw 250 in the Y direction may be restricted, but
the first screw 220 and the second screw 250 may freely move in the
X direction, and thus, a size of the separation space SP may vary
based on the movement of the first screw 220 and the movement of
the second screw 250.
[0041] Meanwhile, a supply flow path 280 may be formed in the
connecting member 260 to supply the hydraulic fluid to the
separation space SP. The hydraulic pressure generated by the
hydraulic fluid supplied to the separation space SP may vary based
on the size of the separation space SP. In other words, the
hydraulic pressure may be decreased as the size of the separation
space SP is increased, and the hydraulic pressure may be increased
as the size of the separation space SP is decreased.
[0042] A part of a side surface of the pressure balancing member
240 in the -X direction may be in contact with a second contact
surface 244 which is a side surface of the connecting member 260 in
the +X direction, and the pressure balancing member 240 may be
deformed in the X direction by a pressure. In particular, the
second contact surface 244 is a part of the side surface of the
pressure balancing member 240 in the -X direction except for the
first contact surface 242.
[0043] The master chamber unit 300 may be disposed at first side of
the boosting chamber unit 200 and may include a master cylinder
310, which is a space in which a hydraulic pressure may be formed
and generated by the movement of the master piston 230, and a
second return spring 340. The reservoir 400, which stores the
hydraulic fluid, may provide the hydraulic fluid to the master
cylinder 310 through a third connecting flow path 352, and thus,
the hydraulic fluid may be provided in the master cylinder 310. A
portion between the master cylinder 310 and the boosting cylinder
210 may be sealed to prevent the hydraulic fluid from flowing
between the master cylinder 310 and the boosting cylinder 210.
[0044] As described above, when the pedal effort is applied to the
brake pedal and the driving power is generated by the motor 500
such that the master piston 230 moves in the -X direction, a
braking pressure may be formed in the master cylinder 310. On the
contrary, when the pedal effort applied to the brake pedal and the
driving power generated by the motor 500 are removed, the master
piston 230 may be moved in the +X direction by the second return
spring 340, and thus, the braking pressure formed in the master
cylinder 310 may be removed.
[0045] The hydraulic pressure formed in the master cylinder 310 may
be transmitted through a fourth connecting flow path 354 to an
electronic stability control (ESC) module for operating a brake or
a caliper of the brake.
[0046] Meanwhile, as described above, the pedal effort applied to
the brake pedal and the driving power generated by the motor 500
have a first boost ratio {circumflex over (1)}, and the first boost
ratio {circumflex over (1)} may be measured by the first sensor 160
and the second sensor 560 and required to design the electric
booster according to the present invention. For example, when the
first boost ratio {circumflex over (1)} is 9 and the pedal effort
applied to the brake pedal is 1, the driving power generated by the
motor is 9.
[0047] However, the pedal effort applied to the brake pedal and the
driving power generated by the motor 500 are unable to have the
first boost ratio {circumflex over (1)} when the pressure outside
the master cylinder 310 connected through the fourth connecting
flow path 354 is increased or decreased and transmitted into the
master cylinder 310. In particular, the master piston 230 moves a
distance less than or greater than a distance calculated based on
the first boost ratio {circumflex over (1)}. Therefore, the pedal
effort applied to the brake pedal needs to be increased or
decreased to generate a braking force desired by the driver.
[0048] When the pedal effort applied to the brake pedal and the
driving power generated by the motor 500 is unable have the first
boost ratio {circumflex over (1)}, the electric booster having the
force-feedback-control structure according to the present invention
may maintain the first boost ratio {circumflex over (1)} by
changing the pedal effort applied to the brake pedal and thus, the
deformed pressure balancing member 240 may maintain an original
shape.
[0049] Hereinafter, a state in which the pressure balancing member
is deformed by the pressure applied to the first contact surface or
the second contact surface and a process of designing the pressure
balancing member will be described with reference to FIGS. 3 and 4A
to 4C.
[0050] Referring to FIG. 3, in the cross section of the pressure
balancing member 240, an area of the first contact surface 242 is a
difference between a cross-sectional area of the vertical portion
224 and a cross-sectional area of the horizontal portion 222. In
particular, a difference between the cross-sectional area
calculated based on a diameter D2 of the vertical portion 224 and
the cross-sectional area calculated based on a diameter D1 of the
horizontal portion 222 may be calculated using a formula for
calculating an area of a circle. In addition, in the cross section
of the pressure balancing member 240, an area of the second contact
surface 244 is a difference between a cross-sectional area of the
pressure balancing member 240 and a cross-sectional area of the
vertical portion 224. In other words, a difference between a
cross-sectional area calculated based on a diameter D3 of the
pressure balancing member 240 and the cross-sectional area
calculated based on the diameter D2 of the vertical portion 224 may
be calculated using a formula for calculating an area of a
circle.
[0051] A pressure P1 applied to the first contact surface 242 may
be expressed as a force applied to the area of the first contact
surface 242, and the pressure P1 is equal to a force applied to the
area of the horizontal portion 222 from the hydraulic pressure
which is formed in the separation space SP. In addition, the
hydraulic pressure formed in the separation space SP is equal to a
pressure transmitted through the second connecting flow path 152
and the supply flow path 280 from the pedal effort which may be
applied to the brake pedal. Therefore, the pressure P1 applied to
the first contact surface 242 may be generated from the pedal
effort applied to the brake pedal.
[0052] A pressure P2 applied to the second contact surface 244 may
be expressed as a force applied to the area of the second contact
surface 244, and the pressure P2 is equal to a reaction force
transmitted to the connecting member 260 as the nut unit 270 is
moved forward by the motor 500. Therefore, the pressure P2 applied
to the second contact surface 244 may be generated from the driving
power generated by the motor 500.
[0053] Referring to FIG. 4A, when the pressure P1 applied to the
first contact surface 242 and the pressure P2 applied to the second
contact surface 244 are equal to each other, the cross section of
the pressure balancing member 240 may be maintained in a flat
state. This state is referred to as a normal state. The pressure
balancing member 240 may be designed such that P1 and P2 are equal
to each other. In particular, since P1 and P2 have the same value,
P1 and P2 define a balancing pressure.
[0054] Specifically, assuming that the force applied to the first
contact surface 242 is F1 and the force applied to the second
contact surface 244 is F2, F1 and F2 may be obtained by the
following Calculation Formula 1.
F 1 = BALANCING PRESSURE .times. .pi. ( D 2 2 - D 1 2 ) 4 F 2 =
BALANCING PRESSURE .times. .pi. ( D 3 2 - D 2 2 ) 4 Calculation
Formula 1 ##EQU00001##
[0055] A ratio between F1 and F2 may be obtained by the following
Calculation Formula 2.
F 2 F 1 = D 3 2 - D 2 2 D 2 2 - D 1 2 Calculation Formula 2
##EQU00002##
[0056] In particular, assuming that the boost ratio is a ratio
between the force applied to the brake pedal and the force
generated by the motor, F2/F1 may be referred to as the boost
ratio. Therefore, D1 to D3 of the pressure balancing member 240 may
be designed based on the first boost ratio {circumflex over (1)}
required to design the electric booster according to the present
invention.
[0057] Referring to FIG. 4B, when the pressure P1 applied to the
first contact surface 242 is greater than the pressure P2 applied
to the second contact surface 244, the cross section of the
pressure balancing member 240 is in a state in which the first
contact surface 242 is further recessed inward in the +X direction
than the second contact surface 244. This state may be referred to
as an insufficient motor-rotation state.
[0058] Referring to FIG. 4C, when the pressure P1 applied to the
first contact surface 242 is less than the pressure P2 applied to
the second contact surface 244, the cross section of the pressure
balancing member 240 is in a state in which the second contact
surface 244 protrudes further outward in the -X direction than the
first contact surface 242. This state is referred to as an
excessive motor-rotation state.
[0059] Hereinafter, an operating process of the electric booster
having the force-feedback-control structure according to the
present invention in the state in which the pedal effort applied to
the brake pedal and the force generated by the motor are not equal
to each other will be described with reference to FIGS. 5 to 7.
[0060] Referring to FIG. 5, when rigidity of a brake caliper or the
like is increased, the force (e.g., driving power) generated by the
motor 500 is insufficiently applied in comparison with the pedal
effort applied to the brake pedal. Therefore, since the pressure P1
applied to the first contact surface 242 is greater than the
pressure P2 applied to the second contact surface 244, the pressure
balancing member 240 is in the insufficient motor-rotation state,
and the first screw 220 is moved in the +X direction by the
pressure difference. Then, since the pressure in the separation
space SP is decreased, the second screw 250 and the master piston
230 are moved in the +X direction by the elastic restoring force of
the second return spring 340. In other words, based on a second
boost ratio {circumflex over (2)} being less than the first boost
ratio {circumflex over (1)}, the master piston 230 moves a distance
that is less than the distance in the -X direction calculated in
the normal state.
[0061] When the pedal effort applied to the brake pedal is
increased in this state, the motor 500 rotates in a first direction
based on the measurement of the first sensor 160 and the
measurement of the second sensor 560, and thus, the first screw 220
and the second screw 250 rotate to move the master piston 230 in
the +X direction. Then, the pressure balancing member 240 may
return to the normal state from the insufficient motor-rotation
state, and the second boost ratio {circumflex over (2)} may be
changed to the first boost ratio {circumflex over (1)}.
[0062] Referring to FIG. 6, when rigidity of the brake caliper or
the like is decreased, the force (e.g., driving power) generated by
the motor 500 may be excessively applied in comparison with the
pedal effort applied to the brake pedal. Therefore, since the
pressure P1 applied to the first contact surface 242 is less than
the pressure P2 applied to the second contact surface 244, the
pressure balancing member 240 is in the excessive motor-rotation
state, and the first screw 220 is moved in the -X direction by the
pressure difference. Then, since the pressure in the separation
space SP is increased, the second screw 250 and the master piston
230 move in the -X direction while overcoming the elastic restoring
force of the second return spring 340. In other words, based on a
third boost ratio {circumflex over (3)} being greater than the
first boost ratio , the master piston 230 moves a distance that is
greater than the distance in the -X direction calculated in the
normal state.
[0063] When the pedal effort applied to the brake pedal is
decreased in this state, the motor 500 rotates in a second
direction based on the measurement of the first sensor 160 and the
measurement of the second sensor 560, and thus, the first screw 220
and the second screw 250 rotate to move the master piston 230 in
the -X direction. Then, the pressure balancing member 240 may
return to the normal state from the excessive motor-rotation state,
and the third boost ratio {circumflex over (3)} may be changed to
the first boost ratio {circumflex over (1)}.
[0064] FIG. 7 is a view illustrating a boost ratio, in which the X
axis indicates the pedal effort F1 applied to the brake pedal, and
the Y axis indicates the force F2 generated by the motor. The first
boost ratio {circumflex over (1)} may be implemented when the
pressure balancing member 240 is in the normal state, the second
boost ratio {circumflex over (2)} may be implemented when the
pressure balancing member 240 is in the insufficient motor-rotation
state, and the third boost ratio {circumflex over (3)} may be
implemented when the pressure balancing member 240 is in the
excessive motor-rotation state.
[0065] When the pressure balancing member 240 is in the
insufficient motor-rotation state, the second boost ratio
{circumflex over (2)} may be changed to a boost ratio {circumflex
over (2)}-1 having the same gradient as the first boost ratio at a
point in time C1 at which the pedal effort applied to the brake
pedal is increased. In addition, when the pressure balancing member
240 is in the excessive motor-rotation state, the third boost ratio
{circumflex over (3)} may be changed to a boost ratio {circumflex
over (3)}-1 having the same gradient as the first boost ratio at a
point in time C1' at which the pedal effort applied to the brake
pedal is decreased.
[0066] Meanwhile, the electric booster having the
force-feedback-control structure according to the present invention
may further include a third sensor 580. The third sensor 580 may be
configured to measure a movement displacement of the first screw
220 based on the state of the pressure balancing member 240 in the
normal state when the pressure balancing member 240 is deformed by
the movement of the first screw 220. An output voltage of the third
sensor 580 rotates the motor 500 to move the first screw 220 in the
direction opposite to the movement displacement of the first screw
220.
[0067] Specifically, when the first screw 220 is moved in the -X
direction in the insufficient motor-rotation state, the third
sensor 580 may be configured to measure the movement displacement
of the first screw 220, and the motor 500 may rotate in a first
direction to move the first screw 220 in the +X direction by the
changed distance. In addition, when the first screw 220 is moved in
the +X direction in the excessive motor-rotation state, the third
sensor 580 may be configured to measure the movement displacement
of the first screw 220, and the motor 500 may rotate in the second
direction to move the first screw 220 in the -X direction by the
changed distance. When the third sensor 580 is in the insufficient
motor-rotation state or the excessive motor-rotation state, the
pressure balancing member 240 may return to the normal state
without changing the pedal effort applied to the brake pedal.
[0068] Referring to FIG. 8, when the pressure balancing member 240
is in the insufficient motor-rotation state, the second boost ratio
{circumflex over (2)} has a large gradient {circumflex over (2)}-2
and increases at the point in time C2 at which the output voltage
of the third sensor 580 is generated, and the gradient of the
second boost ratio {circumflex over (2)} becomes equal to the
gradient of the first boost ratio {circumflex over (1)} when the
pressure balancing member reaches the normal state. In addition,
when the pressure balancing member 240 is in the excessive
motor-rotation state, the third boost ratio {circumflex over (3)}
has a small gradient and decreases at a point in time C2' at which
the output voltage of the third sensor 580 is generated, and the
gradient of the third boost ratio {circumflex over (3)} becomes
equal to the gradient of the first boost ratio {circumflex over
(1)} when the pressure balancing member 240 reaches the normal
state.
[0069] In other words, with the third sensor 580, the motor 500 may
rotate to compensate for a difference in boost ratio between the
insufficient motor-rotation state or the excessive motor-rotation
state and the normal state, and as a result, it may be possible to
more accurately operate the electric booster and minimize
non-uniformity in braking in comparison with a case in which there
is no third sensor 580.
[0070] Meanwhile, in the electric booster having the
force-feedback-control structure according to the exemplary
embodiment of the present invention, the first sensor 160, the
second sensor 560, and the third sensor 580 may be connected to a
separate controller (not illustrated) such as an electric control
unit (ECU), and the motor 500 may be rotated based on a signal from
the controller (not illustrated).
[0071] The present invention has been described with reference to
the limited exemplary embodiments and the drawings, but the present
invention is not limited thereto. The described exemplary
embodiments may be variously changed or modified by those skilled
in the art to which the present invention pertains within the
technical spirit of the present invention and within the scope
equivalent to the appended claims.
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