Description
Title of Invention
RAILWAY VEHICLE BRAKE DISC
~echnicalF ield
[00011
The present invention relates to a brake disc which is
a key component of a braking device in a railway vehicle, and
particularly to a railway vehicle brake disc in which a disc
section servingas a sliding surface is fastenedtoawheelwith
a bolt.
Background A r t
[00021
As thebrakingdevice ofthe railwayvehicle, adisc brake
excellent in braking performance is frequently used with
increase in speed and size of a vehicle. In the disc brake,
abrake disc ismountedonawheelbybeing fastenedwithabolt,
a braking force due to frictional resistance is generated by
a brake lining pushed against a sliding surface of the brake
disc, and thus the rotation of the wheel is braked to regulate
a speed of the vehicle.
[00031
FIGS. 1A and 1B are diagrams schematically i l l u s t r a t i n g
a mounting structure of a typical railway vehicle brake disc
onto a wheel; F I G . 1A i l l u s t r a t e s a plan view of a 1/4 circular
portion in a front surface view; and FIG. 1B illustrates a
cross-sectional view taken along the radial direction of a 1/2
circular portion. FIGS. 2A to 2C are schematic views
illustrating a configuration of a railway vehicle brake disc
of the related art; FIG. 2A illustrates a partial perspective
view when viewed from a rear surface side; FIG. 2B illustrates
a partial plan view in a rear surface view; and FIG. 2C
illustrates a partial cross-sectional view taken along the
radial direction.
[ 0 0 04 I
As illustrated in FIGS. 1A and 1B and 2A to 2C, a brake
disc 1 includes a donut-shaped disc section 2 having a sliding
surface on a front surface 2a side. In a rear surface 2b of
the disc section 2, a plurality of fin sections 3 is convexly
provided in a radial pattern. A bolt hole 4 passing through
the disc section 2 is formed almost at a central position in
the radial direction in some of the plurality of fin sections
3.
[0005]
A wheel 10 includes a boss section 11 pressed fit into
an axle, a rim section 12 containing a wheel tread which comes
into contact with a rail, and a plate section 13 which connects
these sections. One set of two brake discs 1 is disposed so
as to interpose the plate section 13 of a wheel 10 therebetween
in a state where each front surface 2a faces outward; a bolt
15 is inserted into each bolt hole 4; and a nut 16 is fastened
to each bolt 15. Thereby, the brake disc 1 is mounted on the
wheel 10 in a state where a front end surface 3a of the fin
sections 3 are in press contact with the plate section 13 of
the wheel 10 over the entire area in the radial direction.
[ 0 0 0 6 I
Here, in the case of a high speed railway vehicle such
as the Shinkansen running at a speed exceeding 300 km/h, the
brakedisc1rotatesintegrallywiththewheel10 atahighspeed
during the running. Accordingly, the ambient air of the brake
disc 1 is sucked from an inner peripheral side into a space
between the brake disc 1 and the wheel 10, that is, a space
surrounded by the disc section 2 and the fin section 3 of the
brake disc 1 and the plate section 13 of the wheel 10, and
discharged from an outer peripheral side (see solid arrows in
FIGS. 2A to 2C). In short, a gas stream of the air is caused
between the brake disc 1 and the wheel 10 during the running
of the railway vehicle. The gas stream remarkably appears in
a high speed running state of more than 300 km/h, and induces
noises called aerodynamic noise. Therefore, it is necessary
to reduce the aerodynamic noise in views of environmental
concerns.
[0007]
As a solution for such a request, for example, Patent
Literature 1 discloses a brake disc in which a rib is added
between neighboring fin sections along a circumferential
direction, and the gas stream is suppressed by the rib.
According to the brake disc disclosed in the above literature,
the aerodynamic noise can be reduced to a desired level.
However, a problem of lower cooling performance of the brake
disc at the time of braking with suppression of the gas stream
by the rib becomes apparent.
[00081
In addition, in a case where an emergency brake is used
in the high speed running state, for example, as described in
Patent Literatures 2 and 3, deformation of the brake disc
associated with thermal expansion, and a stress load on a
fastening bolt due to the deformation increase, and it becomes
difficult to secure the durability of the brake disc and the
bolt.
Citation List
Patent Literature
[0009]
Patent Literature 1: Japanese Patent Application
Publication (JP-A) No. 2007-205428
Patent Literature 2: JP-A No. 2006-009862
Patent Literature 3: WO 2010/071169
Summary of Invention
Technical Problem
[OOlOI
The present invention has been made in view of the above
problem, and an object of the present invention is to provide
a railway vehicle brake disc which can reduce aerodynamic noise
raised during the running at a high speed, improve cooling
performance at the time of braking, and furthermore improve
durability including that of a fastening bolt.
Solution to Problem
[OOll]
In order to achieve the above object, the present
inventors have extensivelystudiedthroughvarious experiments
and analysis on an assumption that a brake disc is the brake
disc illustrated in FIGS. 2A to 2C, that is, a brake disc
comprisingadonut-shapeddisc sectionhavingaslidingsurface
on a front surface side, a plurality of fin sections each
convexly provided in a rear surface of the disc section, and
aboltholepassingthroughthediscsectionandthefinsection,
in which the disc section is mounted on a wheel in a state where
the fin sections are in press contact with a plate section of
the wheel by being fastened with a bolt inserted into the bolt
hole. As a result, the present inventors have obtained the
following findings (a) to (d) .
[00121
(a) As describedinpatent Literature 3, there is astrong
correlation between an air flow rate of the air flowing into
the space surrounded by the disc section and the fin section
of the brake disc and the plate section of the wheel, and the
level of the aerodynamic noise. Here, the air flow rate is
obtained by thermal and flow analysis, and the level of the
aerodynamic noise is experimentally obtained. Since there is
a strong correlation between the air flow rate and the
aerodynamic noise level, the aerodynamic noise level can be
evaluated using the air flow rate as an index, and the
aerodynamic noise may be reduced by reducing the air flow rate.
Then, the air flow rate is effectively reduced by increasing
a pressure drop in the gas stream, and in order to increase the
pressure drop, it is necessary to install a corner portion
easilycausingthepressuredroporasurface facingadirection
of the gas stream in the space raising the gas stream.
[0013]
(b) It becomes necessary to secure a sufficient area in
a pressure drop section of the gas stream space described in
(a) in order to improve the cooling performance. This is
because heat transfer to the gas becomes high in the pressure
drop section.
[0014]
(c) FIG. 3 is a cross-sectional view schematically and
exaggeratingly illustrating deformation behavior due to
thermal expansion during a period of braking in a brake disc
of the related art. At the time of braking, since the brake
disc 1 generates heat by friction due to sliding on the brake
lining, thediscsection2andthefinsection3tendtothermally
expand in the radial direction. However, since the fin section
3 is in press contact with the plate section 13 of the wheel
10 over the entire area in the radial direction, the thermal
expansion in the radial direction of the fin section 3 is
constrained. Therefore, in the case of the brake disc 1 of the
related art, as illustrated in FIG. 3, the brake disc 1 deforms
in an arch shape about an end on the inner peripheral side and
an end on the outer peripheral side of the front end surface
3a of the fin section 3 as supporting points.
[00151
Then, a tensile stress is loaded on the fastening bolt
15, andabending stress is furtherloadedthereon. Inaddition,
as thebraking is repeated, thebrakedisclrepeatsthethermal
expansion at the time of braking and the contraction due to
cooling after the braking, and thus plastically deforms in a
warped state.
[00161
In order to reduce the deformation associated with the
thermal expansion of such a brake disc, it becomes necessary
to alleviate the constraint on the thermal expansion of the fin
section during a period of braking and to substantially allow
the thermal expansion/contraction in the radial direction of
the fin section.
[0017]
(d) Based on the above findings (a) to (c) , without newly
installing the rib as in the brake disc disclosed in Patent
Literature 1, in the fin section a groove may be formed along
a circumferential direction in at least one of the area on the
inner peripheral side and the area on the outer peripheral side
of the bolt hole when viewed in the radial direction of the disc
section. Further, the groove may be formed along the
circumferential direction in the area on the inner peripheral
sideandtheareaontheouterperipheral side. This isbecause,
by forming the groove in the fin section, the pressure drop
section as indicated above in (a) and (b) is naturally installed,
and the thermal expansion/contraction in the radial direction
of the fin section as indicated above in (c) is substantially
allowed.
[0018]
The present invention has been completed based on the
findings described above in (a) to (d) , and a gist thereof is
to provide the following railway vehicle brake disc.
[0019]
That is, the railway vehicle brake disc of the present
invention is a railway vehicle brake disc comprising a
donut-shaped disc section having a sliding surface on a front
surface side, apluralityof finsectionseachconvexlyprovided
in a rear surface of the disc section in a radial pattern, and
aboltholepassingthroughthedisc sectionandthe finsection,
in which the disc section is mounted on a wheel in a state where
the fin sections are in press contact with a plate section of
the wheel by being fastened with a bolt inserted into the bolt
hole, characterized in that the fin section has a groove formed
along a circumferential direction in at least one of an area
on an inner peripheral side and an area on an outer peripheral
side of the bolt hole when viewed in a radial direction of the
disc section.
[0020]
In the above invention, a surface on an outer peripheral
side of the groove is preferably a plane or a concave surface.
[0021]
In addition, in the present invention, the fin section
has the groove preferably formed along the circumferential
direction in the area on the inner peripheral side and the area
on the outer peripheral side.
[00221
In the brake disc, a ratio h /o~f a depth 'h" of the groove
to a height H of the fin section preferably falls within a range
of 0.2 to 0.8.
[0023]
In addition, in the brake disc, a width in the
circumferential direction of the area on the outer peripheral
side of the fin section is preferably larger than a width in
the circumferential direction of the area on the inner
peripheral side of the fin section.
[0024]
Inaddition, the railwayvehiclebrake disc ofthepresent
invention is a railway vehicle brake disc comprising a
donut-shaped disc section having a sliding surface on a front
surface side, apluralityof finsections eachconvexlyprovided
in a rear surf ace of the disc section in a radial pattern, and
aboltholepassingthroughthediscsectionandthefinsection,
in which the disc section is mounted on a wheel in a state where
the fin sections are in press contact with a plate section of
the wheel by being fastened with a bolt inserted into the bolt
hole, characterized in that the fin section has a groove formed
along a circumferential direction in an area on an inner
peripheral side and an area on an outer peripheral side in a
radial direction which interpose the bolt hole therebetween.
Advantageous Effects of Invention
[0025]
According tothe railwayvehiclebrakedisc ofthepresent
invention, since the groove is formedalongthe circumferential
direction in the finsectionhavingthebolthole formedtherein,
the aerodynamic noise raised during the running at a high speed
can be reduced, the cooling performance of the brake disc at
the time of braking can be improved, and furthermore the
durabilityof the brake disc includingthatof a fasteningbolt
can be improved.
Brief Description of Drawings
[0026]
FIGS. 1A and B are diagrams schematically illustrating
a mounting structure of a typical railway vehicle brake disc
onto a wheel; FIG. 1A illustrates a plan view of a 1/4 circular
portion in a front surface view; and FIG. 1B illustrates a
cross-sectional view taken along the radial direction of a 1/2
circular portion.
FIGS. 2A to 2C are schematic views illustrating a
configuration of a railway vehicle brake disc of the related
art; FIG. 2A illustrates apartialperspectiveviewwhenviewed
from a rear surface side; FIG. 2B illustrates a partial plan
view in a rear surface view; and FIG. 2C illustrates a partial
cross-sectional view taken along the radial direction.
FIG. 3 is a cross-sectional view schematically and
exaggeratingly illustrating deformation behavior due to
thermal expansion during a period of braking in a brake disc
of the related art.
FIGS. 4A to 4C are schematic diagrams illustrating an
example of a configuration of a railway vehicle brake disc
accordingtoa secondembodiment ofthepresent invention; F I G .
4A illustrates a partial perspective view when viewed from a
rear surface side; FIG. 4B illustrates a partial plan view in
a rear surface view; and F I G . 4C illustrates a partial
cross-sectional view taken along the radial direction.
F I G . 5 is adiagramillustratinganinfluenceofthedepth
of a groove in a fin section on an air flow rate and cooling
performance.
F I G . 6 is adiagramillustratinganinfluenceofthewidth
in the radial direction of the groove in the fin section on the
air flow rate and the cooling performance.
F I G S . 7Ato 7Care schematicviews illustratinganexample
of a configuration of a railway vehicle brake disc according
to a third embodiment of the present invention; FIG. 7A
illustrates a partial perspective view when viewed from a rear
surface side; F I G . 7B illustrates a partial plan view in a rear
surfaceview; andFIG. 7Cillustrates apartialcross-sectional
view taken along the radial direction.
F I G . 8 is adiagramillustratinganinfluenceofthewidth
in the circumferential direction of the fin section on the air
flow rate and the cooling performance.
FIGS. 9Ato 9Care schematicviewsillustratinganexample
of a configuration of a railway vehicle brake disc according
to a first embodiment of the present invention; FIG. 9A
illustrates a partial perspective view when viewed from a rear
surface side; FIG. 9B illustrates a partial plan view in a rear
surfaceview; andFIG. 9Cillustratesapartialcross-sectional
view taken along the radial direction.
Description of Embodiments
[00271
A railway vehicle brake disc according to the present
invention is a railway vehicle brake disc comprising a
donut-shaped disc section having a sliding surface on a front
surface side, apluralityof finsectionseachconvexlyprovided
in a rear surface of the disc section in a radial pattern, and
aboltholepassingthroughthe disc sectionandthe finsection,
in which the disc section is mounted on a wheel in a state where
the fin sections are in press contact with a plate section of
the wheel by being fastened with a bolt inserted into the bolt
hole, characterized in that the fin section has a groove formed
along a circumferential direction in at least one of an area
on an inner peripheral side and an area on an outer peripheral
side of the bolt hole when viewed in a radial direction of the
disc section.
[00281
Hereinafter, embodiments of the railway vehicle brake
disc according to the present invention will be described.
In the present invention, the groove may be formed along
the circumferential direction only in the area on the inner
peripheral side in the fin section, may be formed along the
circumferential direction only in the area on the outer
peripheral side in the fin section, and may be formed along the
circumferential direction in both of the area on the inner
peripheral side and the area on the outer peripheral side in
the fin section.
Hereinafter, anaspect inwhichthegroove is formedalong
the circumferential direction in one of the area on the inner
peripheral side or the area on the outer peripheral side in the
fin section will be described as a first embodiment, an aspect
in which the groove is formed along the circumferential
direction in both of the area on the inner peripheral side and
the area on the outer peripheral side in the fin section will
be described as a second embodiment, and an aspect in which the
width in the circumferential direction of the area on the outer
peripheral side in the fin section is larger than the width in
the circumferential direction of the area on the inner
peripheral side of the fin section will be described as a third
embodiment.
Incidentally, in the present specification, the railway
vehicle disc brake may be simply referred to as a disc brake.
[00291

FIGS. 9At0 9Care schematicviews illustratinganexample
of a configuration of a railway vehicle brake disc according
to a first embodiment of the present invention; FIG. 9A
illustrates a partial perspective view when viewed from a rear
surface side; FIG. 9B illustrates a partial plan view in a rear
surfaceview; andFIG. 9~illustratesapartialcross-sectional
view taken along the radial direction. Incidentally, in FIGS.
9A and 9B, a 1/12 circular portion of the brake disc is
representatively illustrated.
[003'0]
As illustrated in FIGS. 9A to 9C, a brake disc 1 of the
first embodiment comprises adonut-shapeddisc section2 having
a slidingsurface onafrontsurface 2a side. Inarearsurface
2b of the disc section 2, a plurality of fin sections 3 is
convexly provided in a radial pattern. A bolt hole 4 passing
throughthe disc section2 is formedalmostatacentralposition
in the radial direction in some of the pluralityof fin sections
3.
[0031]
In a fin section 3 having the bolt hole 4 formed therein,
a groove 5b is formed along the circumferential direction in
the area on the outer peripheral side of the bolt hole 4 when
viewed in the radial direction of the disc section 2. Further,
ina fin section3 havingnobolthole 4 formedtherein, asimilar
groove 5dis also formedon the same circumference as the groove
5b.
[0032]
As illustrated in FIGS. 1A and B, one set of two brake
discs 1 having such a configuration is disposed so as to
interpose a plate section 13 of a wheel 10 therebetween in a
state where each front surface 2a faces outward; a bolt 15 is
inserted into each bolt hole 4; and a nut 16 is fastened to each
bolt 15. Thereby, the brake disc 1 is mounted on the wheel 10
in a state where a front end surface 3a of the fin section 3
is in press contact with the plate section 13 of the wheel 10
except the areas where the grooves 5b and 5d are formed.
[00331
In the brake disc 1 of the first embodiment, since the
groove 5b is formed along the circumferential direction in the
fin section 3 having the bolt hole 4 formed therein, a corner
portionof the groove 5b anda surface 20 onanouter peripheral
side of the groove 5b serve as a pressure drop section of a gas
stream. Therefore, an air flow rate of the air flowing into
a space raising the gas stream is reduced, and as a result,
aerodynamic noise raised during the running at a high speed can
bereduced. Moreover, since thepressuredropsectioniswidely
formed by the groove 5b along the circumferential direction,
it becomes possible to sufficiently secure the area of the
pressuredropsectioninwhichheattransfertogasbecomeshigh,
and as a result, cooling performance of the brake disc 1 at the
time of braking can be improved. These effects are enhanced
still more by also forming the groove 5d in the fin section 3
having no bolt hole 4 formed therein.
[0034]
Furthermore, since the groove 5b is formed along the
circumferential direction in the fin section 3 having the bolt
hole 4 formed therein, the groove 5b can allow the thermal
expansion/contraction in the radial direction of the fin
section 3. Therefore, since constraints on the thermal
expansion of the fin section 3 is alleviated during a period
of braking and deformation associated with the thermal
expansion of the brake disc 1 is reduced, stress loads on a
fasteningbolt and thebrakedisc lare relieved, andasaresult,
the durability of the brake disc 1 including that of the
fastening bolt can be improved.
[0035]
Further, inthebrakedisc lofthe first embodiment, since
the groove 5b may be formed in the fin section 3 without newly
installing a rib as in the brake disc disclosed in Patent
Literature 1, there is also an advantage of a simple
configuration and excellent productivity. In addition, it
becomes possible to reduce the weight of the brake disc 1 by
forming the groove 5b in the fin section 3.
[0036]
Incidentally, in FIGS. 9A to 9C, the fin section has the
groove formed along the circumferential direction in the area
on the outer peripheral side of the bolt hole when viewed in
the radial direction of the disc section, but the present
invention is not limited thereto. In the fin section, the
groovemaybe formedalongthe circumferentialdirectioninthe
area on the inner peripheral side of the bolt hole when viewed
in the radial direction of the disc section. Even in a case
where the groove is formed along the circumferential direction
in the area on the inner peripheral side in the fin section,
the same effects as those described above are obtained.
[0037]
In a case where the groove is formed along the
circumferential direction in one of the area on the inner
peripheral side or the area on the outer peripheral side in the
fin section, an area where the groove is formed may be one of
the area on the inner peripheral side and the area on the outer
peripheral side in the fin section. Incidentally, the
aerodynamic noise is efficiently reduced by forming the groove
in the area on the inner peripheral side. This is because, in
general, a flow path on the inner peripheral side is narrower
and thus a large pressure drop can be given. In addition, when
the cooling performance is secured in priority, the cooling
performance is effectively securedbyformingthe groove in the
area on the outer peripheral side. This is because the surface
area can be easily expanded while the pressure drop is given.
[0038]
In addition, in a case where the brake disc comprises the
fin section having the bolt hole formed therein and the fin
section having no bolt hole therein, the groove may be formed
along the circumferentialdirectionat least in the finsection
having the bolt hole formed therein. In particular, it is
preferable that the groove be formed along the circumferential
direction inboth of the fin sectionhavingthe bolt hole formed
therein and the fin section having no bolt hole formed therein.
By also forming the groove in the fin section having no bolt
hole formed therein as described above, the aerodynamic noise
raised during the running a t a high speed can be reduced s t i l l
more, and the cooling performance of the brake disc a t the t i m e
of braking can be improved still more.
[0039]
The shape of the groove formed in the f i n section is not
particularly limited.
In particular, since the surface on the outer peripheral
side of the groove serves as the surface facing the direction
of the gas stream and serves as the pressure drop section, the
surfaceonthe outerperipheral side ofthegroove is preferably
a plane or a concave surface. In a case where the surface on
the outer peripheral side of the groove is a convex surface,
the surf ace facing the direction of the gas stream is d i f f i c u l t
tobe formed, andthecornerportionofthegrooveisalsorounded
orlostinthesurfaceontheouterperipheralsideofthegroove,
so that there is concern that the area of the pressure drop
section is not sufficiently secured. On the other hand, in a
casewhere the surfaceontheouterperipheral sideofthegroove
isaplaneoraconcave surface, the surface facingthedirection
of the gas stream is easily formed, the corner portion of the
groove is a l s o e a s i l y formed in the surface on the outer
peripheral side o f t h e groove, and the areaofthepressure drop
section can be sufficiently secured. In addition, in a case
where the surface on the outer peripheral side of the groove
is a concave surface, the surface facing the direction of the
gas stream can be made large, and the pressure drop section can
also be increased. Therefore, the aerodynamic noise raised
during the running at a high speed can be reduced still more,
and the cooling performance of the brake disc at the time of
braking can be improved still more.
Here, in the surface on the outer peripheral side of the
groove, the concave surface means a surface having a concave
shape denting toward the outer peripheral side of the disc
section, and the convex surface means a surface having a convex
shape protruding toward the inner peripheral side of the disc
section.
[0040]
On the other hand, a surface on an inner peripheral side
of the groove may be any of the plane, the concave surface, or
the convex surface. In a case where the surface on the inner
peripheralsideofthegrooveistheplaneortheconcavesurface,
the corner portion of the groove easily causing the pressure
drop is easily formed in a similar manner to the above case.
Here, in the surface on the inner peripheral side of the
groove, the concave surface means a surface having a concave
shape denting toward the inner peripheral side of the disc
section, and the convex surface means a surface having a convex
shape protruding toward the outer peripheral side of the disc
section.
[0041]
In addition, in a case where the groove 5b is formed along
the circumferential direction in the area on the outer
peripheral side in the fin section 3 as illustrated in FIG. 9B,
a width t2 in the circumferential direction of the area on the
outer peripheral side in the fin section 3 is preferably larger
than the diameter of the bolt hole 4. Since the length in the
circumferential direction of the groove 5b formed in the area
on the outer peripheral side in the fin section 3 becomes long,
the pressure drop section is expanded. Therefore, the
aerodynamic noise raised during the running at a high speed can
be reduced, and the cooling performance of the brake disc 1 at
the time of braking can be improved.
In addition, while not illustrated in the figures, in a
case where the groove is formed along the circumferential
direction in the area on the inner peripheral side in the fin
section, awidthtlinthe circumferentialdirectionof the area
on the innerperipheral side in the fin section 3 as illustrated
in FIG. 9B is preferably larger than the diameter of the bolt
hole 4. The same effects as those described above are also
obtained in this case.
[0042]
As illustrated in FIG. 9C, depths 'h" of the grooves 5b
and 5d in a direction from the front end surface 3a of the fin
section 3 toward the rear surface 2b of the disc section 2 may
be equal to or different from each other.
[0043]
In addition, as illustrated in FIG. 9C, assuming that the
depth of the groove 5b, 5d in the direction from the front end
surface 3a of the fin section 3 toward the rear surface 2b of
the disc section 2 is "h" , and the height of the fin section
3 from the rear surface 2b of the disc section 2 to the front
end surface 3a of the fin section 3 is H, a ratio h/H of the
depth "h" of the groove Sb, 5d to the height H of the fin section
3preferablyfallswithinarangeof0.2to0.8. Morepreferably,
the ratio falls within a range of 0.4 to 0.8. This is because
when the ratio h/H falls within the above range, the air flow
rate becomes small, a heat dissipation rate becomes large, the
aerodynamic noise level is lowered, and thus the cooling
performance becomes excellent. Incidentally, the reason will
be described in the following second embodiment, and the
explanation thereof is omitted here.
In addition, in FIG. 9C, in the fin section the groove
is formed along the circumferential direction in the area on
the outer peripheral side of the bolt hole when viewed in the
radial direction of the disc section. However, similarly, in
a case where the groove is formed along the circumferential
direction in the area on the inner peripheral side in the fin
section, the ratio h/H of the depth "h" of the groove to the
height H of the fin section preferably falls within the above
range.
[00441
As illustrated in FIG. 9C, widths w2 in the radial
direction of the grooves 5b and 5d formed in the fin section
3 may be equal to or different from each other.
LO0451
In addition, as illustrated in FIG. 9C, assuming that the
width in the radial direction of the groove 5b, 5d formed in
the fin section 3 is w2 and the entire length in the radial
direction of the front end surface 3a of the fin section 3 is
W, a ratio w2/W of the width w2 in the radial direction of the
groove 5b, 5d to the entire length W in the radial direction
of the front end surface 3a of the fin section 3 is preferably
equal to or more than 0.05. This is because when the ratio w 2 / ~
falls within the above range, the air flow rate becomes small,
the heat dissipation rate becomes large, the aerodynamic noise
level is lowered, and thus the cooling performance becomes
excellent. In addition, an upper limit of the ratio w2/~is
preferablysettobe equal toor less than 0.3 inorder to secure
a reinforcing effect of the fin section on the brake disc.
[0046]
As a material of the brake disc, cast iron, cast steel,
forged steel, aluminum, carbon, and the like can be employed.
100471

FIGS. 4A to 4C are schematic diagrams illustrating an
example of a configuration of a railway vehicle brake disc
according to a second embodiment of the present invention; FIG.
4A illustrates a partial perspective view when viewed from a
rear surface side; FIG. 4B illustrates a partial plan view in
a rear surface view; and FIG. 4C illustrates a partial
cross-sectional view taken along the radial direction.
Incidentally, in FIGS. 4A and 4B, a 1/12 circular portion of
the brake disc is representatively illustrated.
[00481
As illustrated in FIGS. 4A to 4C, a brake disc 1 of the
second embodiment includes adonut-shapeddisc section2 having
a sliding surface on a front surface 2a side. Ina rear surface
2b of the disc section 2, a plurality of fin sections 3 is
convexly provided in a radial pattern. A bolt hole 4 passing
throughthe disc section2 is formedalmostatacentralposition
in the radial direction in some of the plurality of fin sections
3.
[0049]
In a fin section 3 having the bolt hole 4 formed therein,
grooves 5aand5bare formedalongthe circumferentialdirection
in an area on an inner peripheral side and an area on an outer
peripheral side inthe radial directionwhich interpose thebolt
hole 4 therebetween, that is, in an area on an inner peripheral
side and an area on an outer peripheral side of the bolt hole
4 when viewed in the radial direction of the disc section 2.
Inthe finsection3, awidthtlinthe circumferentialdirection
of the area on the inner peripheral side and a width t2 in the
circumferential direction of the area on the outer peripheral
sideare equaltoeachother. Further, ina finsection3 having
no bolt hole 4 formed therein, grooves 5c and 5d similar to the
grooves 5a and 5b are also formed on the same circumference as
the grooves 5a and 5b.
[00501
As illustrated in FIGS. 1A and B, one set of two brake
discs 1 having such a configuration is disposed so as to
interpose a plate section 13 of a wheel 10 in a state where each
front surface 2a faces outward; a bolt 15 is inserted into each
bolt hole 4; and a nut 16 is fastened to each bolt 15. Thereby,
the brake disc 1 is mounted on the wheel 10 in a state where
a front endsurface 3aofthe finsections 3 are inpress contact
with the plate section13 of the wheel10 except the areas where
the grooves 5a to 5d are formed.
[0051]
The brake disc of the second embodiment obtains the same
effects as those of the brake disc of the first embodiment.
Particularly, since the grooves are formed along the
circumferential direction in both of the area on the inner
peripheral side and the area on the outer peripheral side in
the fin section, the above effects can be enhanced still more.
[0052]
That is, in the brake disc 1 of the second embodiment,
since thegrooves 5aand5bare formedalongthecircumferential
direction in the fin section 3 having the bolt hole 4 formed
therein, corner portions of the grooves 5a and 5b and surfaces
on outer peripheral sides of the grooves 5a and 5b serve as a
pressure drop section of a gas stream. Therefore, an air flow
rate of the air flowing into a space raising the gas stream is
reduced, and as a result, the aerodynamic noise raised during
the running at a high speed can be reduced. Moreover, since
the pressure drop section is widely formed by the grooves 5a
and5balongthe circumferentialdirection, it becomes possible
to sufficiently secure the area of the pressure drop section
in which heat transfer to gas becomes high, and as a result,
cooling performance of the brake disc 1 at the time of braking
can be improved. These effects are enhanced still more by also
forming the grooves 5c and 5d in the fin section 3 having no
bolt hole 4 formed therein.
[0053]
Furthermore, since in the fin section 3 having the bolt
hole 4 formed therein the grooves 5a and 5b are formed along
the circumferential direction while interposing the bolt hole
4 therebetween, the grooves 5a and 5b can allow the thermal
expansion/contraction in the radial direction of the fin
section 3. Therefore, since constraints on the thermal
expansion of the fin section 3 is alleviated during a period
of braking and deformation associated with the thermal
expansion of the brake disc 1 is reduced, stress loads on a
fasteningboltandthebrakedisc lare relieved, andasaresult,
the durability of the brake disc 1 including that of the
fastening bolt can be improved.
[0054]
Further, in the brake disc 1 of the second embodiment,
since the grooves 5a and 5b may be formed in the fin section
3 without newly installing the ribas inthebrakediscdisclosed
in Patent Literature 1, there is also an advantage of a simple
configuration and excellent productivity. In addition, it
becomes possible to reduce the weight of the brake disc 1 by
forming the grooves 5a and 5b in the fin section 3.
[0055]
Preferable aspects in the second embodiment are same as
those in the first embodiment.
That is, in a case where the brake disc includes the fin
section having the bolt hole formed therein and the fin section
having no bolt hole therein, the groove may be formed along the
circumferential direction at least in the fin section having
the bolt hole formed therein. In particular, it is preferable
that the groove be also formed along the circumferential
directioninthe finsectionhavingnobolthole formedtherein.
[0056]
In the brake disc 1 of the second embodiment, the shapes
of the grooves 5a to 5d formed in the fin section 3 are not
particularly limited.
Inparticular, inasimilarmannertothe first embodiment,
the surface on the outer peripheral side of the groove is
preferably a plane or a concave surface. On the other hand,
a surface on an inner peripheral side of the groove may be any
of a plane, a concave surface, or a convex surface.
[0057]
In addition, as illustrated in FIG. 4B, a width tl in the
circumferential direction of the area on the inner peripheral
side andawidtht2 in the circumferentialdirectionofthe area
on the outerperipheral side in the finsection3 are preferably
larger than the diameter of the bolt hole 4. Since the length
in the circumferential direction of the groove 5a, 5b formed
in the fin section 3 becomes long, the pressure drop section
is expanded. Therefore, the aerodynamic noise raised during
the running at a high speed can be reduced, and the cooling
performance of the brake disc 1 a t the time of braking can be
improved.
[0058]
As i l l u s t r a t e d in F I G . 4C, depths 'h" of the grooves 5a
to 5d in a direction from the front end surface 3a of the f i n
section 3 toward the rear surface 2b of the disc section 2 may
be equal to or different from each other.
[0059]
Inaddition, as illustratedinFIG. 4C, assumingthateach
of the depths of the grooves 5a to 5d in the direction from the
front endsurface 3aofthe finsection3 towardtherear surface
2bofthe disc section2 is 'h", and the height of the f i n section
3 from the rear surface 2b of the disc section 2 to the front
end surface 3a of the fin section 3 is H, a r a t i o h/H of each
of the depths 'h" of the grooves 5a to 5d to the height H of
the f i n section 3 preferably f a l l s within a range of 0.2 to 0 . 8 .
More preferably, the r a t i o f a l l s within a range of 0.4 to 0 . 8 .
The reason is as follows.
[0060]
FIG. 5 is adiagramillustratinganinfluenceofthedepth
of the groove in the f i n section on an a i r flow rate and cooling
performance . In the figure, the a i r flow rate indicated in the
horizontal axis is obtainedthroughthermaland flow analysis,
and has a strong correlation with the aerodynamic noise level,
and thus is usedas anevaluation indexof theaerodynamicnoise
level. This means that, as the a i r flow rate is smaller, the
aerodynamic noise level is lower. In addition, the heat
dissipationrate indicatedintheverticalaxis is anintegrated
valueof anaveragedheattransfercoefficientonthebrakedisk
surface obtained as a result of performing the thermal and flow
analysis on the assumption of a steady running at 360 km/h and
the surface area per brake disk, and is used as the evaluation
index of the cooling performance of the brake disc. This means
that, as the heat dissipation rate is larger, the cooling
performance is more excellent.
[0061]
Representative conditions for a model of the brake disc
used in the analysis are as follows.
- Material: Forged Steel
- Inner Diameter of Disc Section: 417 mm, Outer Diameter
of Disc Section: 715 mm
- Total Height from Sliding Surface of Disc Section to
Front End Surface of Fin Section: 45 mm
- Fastening with Bolt: 12 bolt holes centered on the same
circumference having a diameter of 560 mm are formed at equal
angular intervals, and a bolt is inserted into each bolt hole
to fasten the brake disc and the wheel.
roo621
Here, the ratio h / w~as changed to 0 (no groove), 0.1,
0.2, 0.4, 0.6, 0.8, and 1.0. In addition, as illustrated in
FIG. 4C, assuming that the width in the radial direction of the
groove 5a, 5c on the inner peripheral side formed in the fin
section3 was wl, thewidthinthe radial directionofthe groove
5b, 5dontheouterperipheralsidewas w2, andtheentire length
in the radial direction of the front end surface 3a of the fin
section 3 was W, a ratio l1 (wl + w2)/WI1 of the total width "wl
+ w2I1 of the grooves 5a to 5d to the entire length W of the front
end surface 3a of the fin section 3 was set to be a constant
of 0.3.
[0063]
As illustrated in FIG. 5, when the ratio h/H falls within
a range of 0.2 to 0.8, the air flow rate becomes small, the heat
dissipation rate becomes large,the aerodynamic noise level is
lowered, and thus it is obvious that the cooling performance
becomes excellent. However, in a case where the ratio h/H is
0.2, since the heat dissipation rate is smaller than that in
thecasewheretheratioh/His 0.4 whentheairflowratebecomes
almost the same degree, it is preferable that a lower limit of
the ratio h/H be equal to or more than 0.4. In addition, in
a case where the ratio h/H is 1.0, that is, a case where the
depth 'h" of the groove and the height H of the fin section are
equal to each other, since the fin section is completely absent
in the groove, the case becomes inappropriate in that the
reinforcing effect of the fin section on the brake disc is
degraded.
100641
As illustrated in FIG. 4C, the widths wl and w2 in the
radial direction of the grooves 5a to 5d formed in the fin section
3 may be equal to or different from each other.
[0065]
In addition, the ratio (wl + w2)/wI1 of the total width
"wl + w2" of the groove 5a, 5c on the inner peripheral side and
the groove 5b, 5d on the outer peripheral side formed in the
fin section 3 to the entire length W of the front end surface
3a of the fin section 3 is preferably equal to or more than 0.1.
More preferably, the ratio is equal to or more than 0.15. The
reason is as follows.
100661
FIG. 6 isadiagramillustratinganinfluenceofthewidth
of the groove in the fin section on the air flow rate and the
cooling performance . In the figure, the air flow rate and the
heat dissipation rate indicated respectively in the horizontal
axis and the vertical axis are the same as those in FIG. 5.
Representative conditions for a model of the brake disc used
in the analysis are also the same as those described above, but
here the ratio (wl + w2) /Wu was changed to 0 (no groove) , 0.1,
0.15, 0.3, and 0.45. In addition, the ratio h /w~as set to be
a constant of 0.6.
100671
As illustrated in FIG. 6, when the ratio "(wl + w2)/wU
is equal to or more than 0.1, the air flow rate becomes small,
the heat dissipation rate becomes large, and the aerodynamic
noise level is lowered, and thus it is obvious that the cooling
performance becomes excellent. However, in a case where the
ratio " (wl + w2) /Wu is 0.1, since the heat dissipation rate is
smaller than that in the case where the ratio (wl + w2) /Wl1 is
0.15 when the air flow rate becomes almost the same degree, the
ratio (wl + w2) /Wn is preferably equal to or more than 0.15.
In addition, an upper limit of the ratio "(wl + w2)/w1' is
preferably equal to or less than 0.6 in order to secure the
reinforcing effect of the fin section on the brake disc.
[0068]
A material of the brake disc 1 is the same as in the first
embodiment. The material as a representative condition of the
modelofthebrakediscusedintheaboveanalysiswasthe forged
steel, but the same effect can be obtained regardless of the
material.
[0069]

FIGS. 7At0 7Care schematicviews illustratinganexample
of a configuration of a railway vehicle brake disc according
to a third embodiment of the present invention; FIG. 7A
illustrates a partial perspective view when viewed from a rear
surface side; FIG. 7B illustrates a partial plan view in a rear
surfaceview; andFIG. 7Cillustrates apartialcross-sectional
view taken along the radial direction. Incidentally, FIGS. 7A
and 7B representatively illustrate a 1/12 circular portion of
the brake disc in a similar manner to FIGS. 4A and 4B.
[00701
ThebrakediscofthethirdembodimentillustratedinFIGS.
7A to 7C has the same basic configuration as the brake disc of
the second embodiment illustrated in FIGS. 4A to 4C, but is
different from the brake disc of the second embodiment in the
following points. That is, as illustrated in FIGS. 7A to 7C,
in a fin section 3 of the third embodiment, a width t2 in the
circumferentialdirectionofanareaonanouterperipheralside
is made larger than a width tl in the circumferential direction
of an area on an inner peripheral side.
[0071]
Inabrake disclof the thirdembodiment, since the length
in the circumferential direction of groove 5b, 5d on the outer
peripheral side formed in the fin section 3 is longer than that
of the brake disc 1 of the second embodiment, the pressure drop
section is expanded. Therefore, the aerodynamic noise raised
during the running at a high speed can be reduced still more,
and the cooling performance of the brake disc 1 at the time of
braking can be improved.
[0072]
In addition, in a similar manner to the brake disc
illustrated in FIGS. 7A to 7C, the brake disc illustrated in
FIGS. 9A to 9C has the fin section 3 in which the width t2 in
the circumferential direction of the area on the outer
peripheral side is made larger than the width tl in the
circumferential direction of the area on the inner peripheral
side.
In a similarly manner to the above, since the length in
the circumferential direction of the groove 5b formed in the
area on the outer peripheral side in the fin section 3 also
becomes long inthis case, thepressuredropsectionis expanded.
Therefore, the aerodynamic noise raised during the running at
a high speed can be reduced, and the cooling performance of the
brake disc 1 at the time of braking can be improved.
[0073]
FIG. 8 is adiagramillustrating an influence of the width
in the circumferential direction of the fin section on the air
flow rate and the cooling performance . In the figure, the air
flow rate and the heat dissipation rate indicated respectively
in the horizontal axis and the vertical axis are the same as
those illustrated in FIG. 5. Representative conditions for a
model of the brake disc used in analysis are also the same as
those described above. Here, a brake disc in which the width
in the circumferential direction of the fin section was set to
be a constant of 27 mm (corresponding to the second embodiment)
was usedas Example lofthe present invention, andabrake disc
in which the widths in the circumferential direction of the fin
section were set such that the width (54 mm) on the outer
peripheral side was larger than the width (27 mm) on the inner
peripheral side of the fin section (corresponding to the third
embodiment) was used as Example 2 of the present invention. In
the above both examples, a ratio h/H was set to be a constant
of 0.6 and a ratio "(wl + w2)/Wu was set to be a constant of
0.3. In addition, a brake disc in which no groove was formed
in the fin section and the width in the circumferential
direction of the fin section was set to be a constant of 27 mm
was used for comparison.
[00741
As in Example 2 of the present invention indicated by a
white rectangular mark in FIG. 8, when the width in the
circumferential direction of the fin section is made larger in
theouterperipheralsidethanthatontheinnerperipheralside,
it is obvious that both the reduction in the aerodynamic noise
level and the improvement in the cooling performance become
remarkable.
[00751
In addition, in the third embodiment, the stress loads
on a fastening bolt and the brake disc are also relieved, and
it becomes possible to improve the durability of the brake disc
including that of the fastening bolt. The analysis results
which prove the effects are shown in the following Table 1.
[00761
[Table 11
Table 1
Note) Anumericalvalueinparentheses ( ) meansarelativevalue
based on a numerical value of the comparative example
[00771
Here, deformation analysis was performed by FEM using
models having the same conditions as those in Example 2 of the
present invention and the comparative example illustrated in
FIG. 8, a bending stress variation and a tensile stress
variation of the fastening bolt were calculated, and a
Tensile Stress
Variation of Bolt [Mpa]
Bending Stress
Variation of Bolt [Mpa]
Deformation Amount of
Disc (Warp) [mm]
Comparative
Example
280 (1)
59 (1)
0.022 (1)
Example 2 of
Present Invention
216 (0.77)
7(0.12)
0.012 (0.55)
deformation amount of the brake disc was further calculated.
Among them, the stress variation of the fastening bolt was
obtained by assuming a case where an emergency brake was used
once during the running at 360 km/h, and determining a stress
variation generated in the bolt in that case (maximum stress
- minimum stress) . In addition, the deformation amount of the
brake disc was obtained by assuming a case where the emergency
brake was used three times during the running at 360 km/h and
thereafter the brake disc was cooled, and determining a warp
of the brake disc after the cooling (a maximum value of
displacement in the axial directionwith respect tothe initial
state) .
[0078]
It can be seen from the result shown in Table 1 that, in
Example 2 of the present invention corresponding to the third
embodiment, both the stress variationof the fastening bolt and
the deformation amount of the brake disc become small and the
durability of the brake disc including that of the fastening
bolt is improved compared to the comparative example in which
no groove is formed in the fin section.
Industrial Applicability
[00791
The railway vehicle brake disc of the present invention
can be effectively applied to any disc brake of the railway
vehicle, and is particularly useful in a high speed railway
vehicle.
Reference Signs List
[00801
1 Brake disc
2 Disc section
2a Front surface
2b Rear surface
3 Fin section
3a Front end surface
4 Bolt hole
5a, 5b, 5c, 5d Groove
10 Wheel
11 Boss section
12 Rim section
13 Plate section
15 Bolt
16 Nut
20 Surface on outer peripheral side of groove
We claim:
1. A railway vehicle brake disc comprising a donut-shaped
disc section having a sliding surface on a front surface side,
a plurality of fin sections each convexly provided in a rear
surface of the disc section in a radial pattern, and a bolt hole
passing through the disc section and the fin section, in which
the disc section is mounted on a wheel in a state where the fin
sections are in press contact with a plate section of the wheel
by being fastened with a bolt inserted into the bolt hole,
characterized in that
the fin section has a groove formed along a
circumferentialdirectioninat least one of anarea onan inner
peripheral side and an area on an outer peripheral side of the
bolt hole whenviewed ina radial direction of the disc section.
2. The railway vehicle brake disc according to claim 1,
characterized in that a surface on an outer peripheral side of
the groove is a plane or a concave surface.
3 . The railway vehicle brake disc according to claim 1 or
2, characterized in that the fin section has the groove formed
along the circumferential direction in the area on the inner
peripheral side and the area on the outer peripheral side.
4. The railway vehicle brake disc according to any one of
claims 1 to 3, characterized in that a ratio h /o~f a depth h
of the groove to a height H of the fin section falls within a
range of 0.2 to 0.8.
5. The railway vehicle brake disc according to any one of
claims 1 to 4, characterized in that a width in the
circumferential direction of the area on the outer peripheral
side of the fin section is larger than a width in the
circumferential direction of the area on the inner peripheral
side of the fin section.