DESCRIPTION
TITLE OF INVENTION: RAILWAY WHEEL WITH BRAKE DISC
TECHNICAL FIELD
[OOOl]
The present invention relates to a railway wheel with brake disc (hereafter,
also referred to as a "railway wheel with BD"), in which brake discs are fastened to a
wheel for a railway vehicle.
BACKGROUND ART
[0002]
As a braking system for railway vehicles, disc brakes which have excellent
braking performance become more frequently used as the speed of vehicle and the
size thereof increase. A disc brake is configured such that a brake lining is pressed
against a sliding surface of a brake disc attached to a wheel. As a result, braking
force is generated in a rotating wheel, thereby controlling the speed of vehicle.
[0003]
The type of disc brake includes a center-fastening type (sliding-surface
fastening type) brake disc in which brake discs are fastened to a wheel in a region
within a sliding surface, and an inner-circumference fastening type brake disc in
which brake discs are fastened to a wheel in a region located closer to the inner
circumference than the sliding surface is. The inner-circumference fastening type
brake disc requires a portion to be used for fastening, aside from a portion including
a sliding surface. On the other hand, the center-fastening type brake disc does not
need to be provided with such a portion to be used for fastening, and therefore is
advantageous in weight reduction.
[0004]
FIGS. 1A and 1B are diagrams to show an overall structure of a railway wheel
with brake disc constituting a disc brake for a railway vehicle, in which FIG. 1A
shows a plan view of a quarter circle portion, and FIG. 1B shows a sectional view
along the radial direction of a half circle portion, respectively. FIGS. 2A to 2C are
diagrams to topically show the structure of a conventional railway wheel with BD, in
which FIG. 2A shows a perspective view of a back face of a brake disc seen from the
inner peripheral surface side, FIG. 2B shows a plan view of a brake disc seen from a
back face side, and FIG. 2C shows a sectional view along the radial direction,
respectively. All of the brake discs shown in FIGS. lA, lB, and 2A to 2C are of
center-fastening type.
[0005]
As shown in FIGS. lA, IB, and 2A to 2C, a brake disc 1 includes an annular
circular plate portion 2 whose front face 2a provides the sliding surface. In the back
face 2b of the circular plate portion 2, a plurality of fin portions 3 are projected in a
radial manner. In some of the plurality of fin portions 3, a bolt hole 4 passing
through to the circular plate portion 2 is formed at an approximately central position
in the radial direction.
[0006]
A wheel 10 includes a boss portion 11 into which an axle shaft is to be press
fit, a rim portion 12 including a head which is to be in contact with a rail, and a plate
portion 13 for combining them together. The brake discs 1 are disposed in a set of
two so as to interpose the plate portion 13 of the wheel 10 therebetween with the
front face 2a of each brake disc facing outwardly. A bolt 5 is inserted into each bolt
hole 4, and a nut 6 is screwed onto each bolt 5 and fastened thereto. As a result, the
brake disc 1 is fastened to the wheel 10 in such a way that a front end surface of the
fin portion 3 is in pressure contact with a side face 13a of the plate portion 13 of the
wheel 10 over the entire range of the radial direction.
[0007]
The brake disc 1 is fastened to the plate portion 13 in a region within the
sliding surface. In the center-fastening type brake disc, regarding the radial
direction of the brake disc 1, it is preferable that the brake disc 1 is fastened to the
wheel 10 in the vicinity of a central portion between the inner circumference and the
outer circumference of the brake disc 1, for example, a portion between a position to
internally divide the inner circumference and the outer circumference into a ratio of
1 : 3, and a position to internally divide the inner circumference and the outer
circumference into a ratio of 3 : 1.
[OOOS]
Substantially the entire surface of the front face of the brake disc 1 serves as a
sliding surface,-and as shown in FIG. lB, a large gap (for example, a gap of 70 to
120 mm) is formed over the entire circumference between the boss portion 11 and
the circular plate portion 2. That is, the brake disc 1 does not extend to the vicinity
of the boss portion 1 1, thus realizing weight reduction of the brake disc 1. A
conventional railway wheel with BD having such a configuration is disclosed in, for
example, Patent Literature 1.
[0009]
While a railway vehicle is travelling, the brake disc 1 rotates integrally with
the wheel 10 at a high speed. Accordingly, air around the brake disc 1 flows from
the inner circumference side (a gap between the boss portion 11 and the circular plate
portion 2) into a space formed between the brake disc 1 and the wheel 10,
specifically, a space surrounded by the circular plate portion 2 and the fin portion 3
of the brake disc 1, and the plate portion 13 of the wheel 10, and flows out from the
outer circumference side (see solid arrows in FIGS. 2A to 2C). That is, while the
railway vehicle is travelling, a gas flow of air occurs in a space between the brake
disc 1 and the wheel 10. Such a gas flow becomes significant when the vehicle
travels at a high speed of inore than 300 lunlh, like a high-speed railway vehicle such
as the Shinkansen (R), thereby inducing noise referred to as aerodynamic sound.
For that reason, reduction of aerodynamic sound is required fiom consideration of
the environment.
[0010]
In an inner-circumference fastening type brake disc, the gap between the boss
portion 11 and the circular plate portion 2 is very small compared with a centerfastening
type brake disc. For that reason, while the vehicle is travelling, the
amount of air that flows into the space surrounded by the circular plate portion 2 and
the fin portion 3 of the brake disc 1, and the plate portion 13 of the wheel 10 is small,
and generally aerodynamic sound at a level that causes a problem will not be
generated. Therefore, it can be said that the generation of aerodynamic sound is a
problem peculiar to the center-fastening type brake disc.
[OOll]
Prior arts that address the need to reduce aerodynamic sound associated with a
center-fastening type brake disc include the followings.
[0012]
For example, Patent Literature 2 discloses a railway wheel with BD, in which
a brake disc is additionally provided with a rib between adjacent fin portions along
the circumferential direction so that the gas flow is suppressed by the rib.
According to the railway wheel with BD disclosed in the above described literature,
it is possible to reduce the aerodynamic sound to a desired level.
[0013]
However, in the technique disclosed in Patent Literature 2, cooling
performance for the brake disc during braking deteriorates as the gas flow is
suppressed by the rib. For this reason, increases in the deformation caused by
thermal expansion of the brake disc, and in the stress load inflicted upon the
fastening bolt thereby, coupled with increase in the stiffness of the brake disc itself
due to the addition of the ribs may cause a risk that durability of the brake disc and
the bolt deteriorates.
[0014]
A prior art to solve this problem is disclosed in Patent Literature 3.
FIGS. 3A and 3B are diagrams to topically show the structure of a
conventional railway wheel with BD disclosed in Patent Literature 3, in which FIG.
3A shows a perspective view of a back face of a brake disc seen from its inner
peripheral surface side, and FIG. 3B shows a sectional view along the radial direction.
As shown in these figures, in the railway wheel with BD disclosed in Patent
Literature 3, the brake disc 1 is added with ribs 7 in the circumferential direction
each between adjacent fin portions 3, and further a slit 7a is formed along the radial
direction in a central portion in the circumferential direction of each rib 7.
[0015]
According to this railway wheel with BD, a gas flow is ensured by the slit 7a.
Since this allows to maintain the cooling performance for the brake disc 1 during
braking, and to lighten the increase in stiffness due to addition of the rib, deformation
accompanying thermal expansion of the brake disc 1 and stress load inflicted on the
fastening bolt are mitigated, thereby suppressing the deterioration in the durability of
the brake disc 1 and the bolt.
CITATION LIST
PATENT LITERATURE
[0016]
Patent Literature 1 : Japanese Patent Application Publication No. 2006-9862
Patent Literature 2: Japanese Patent Application Publication No. 2007-205428
Patent Literature 3: International Application Publication No. W02010/071169
SUMMARY OF INVENTION
TECHNICAL PROBLEM
[0017]
As described so far, a conventional railway wheel with BD for reducing
aerodynamic sound is configured such that a rib is added in the circular plate portion
of the disc brake, and further a slit is formed on the rib with the aim of suppressing
the gas flow in a space surrounded by the circular plate portion and the fm portion of
the brake disc, and the plate portion of the wheel. As a result of that, the shape of
the brake disc becomes complicated, thus inevitably leading to deterioration in
productivity of the brake disc.
[0018]
Specifically, since additional work (machining, etc.) to adjust the heights of
not only the fin portion but also the rib becomes necessary, and further additional
work to form a slit in the rib becomes necessary, the production process of the brake
disc becomes complicated. Particularly, when the brake disc is produced by forging,
the load on the die increases, shortening of die life will be undeniable.
[0019]
The present invention has been made in view of the above described problems,
and has its objective to provide a railway wheel with brake disc having the following
characteristics.
- The brake disc has a simple shape and an excellent productivity.
- The aerodynamic sound during high speed travelling is effectively reduced.
SOLUTION TO PROBLEM
[0020]
A railway wheel with brake disc of an embodiment of the present invention
includes:
a wheel for a railway vehicle including a boss portion, a rim portion, and a
plate portion for combining them together; and
a brake disc including an annular circular plate portion whose front face
provides a sliding surface, and a plurality of fin portions which are radially projected
on a back face of the circular plate portion, wherein
two of the brake discs interpose the plate portion of the wheel with each of
sliding surfaces thereof facing outwardly, and are fastened in a region within the
sliding surface, and wherein
regarding an area of a section crossing a space formed between the brake disc
and the wheel along a circumferential direction, a minimum section portion in which
the sectional area is minimum is present in a region formed by an outer peripheral
surface of the circular plate portion and an inner peripheral surface of the rim portion,
and
the outer peripheral surface of the circular plate portion has a shape that
follows the inner peripheral surface of the rim portion in a region extending to an
outer side from the minimum section portion.
[0021]
In the above described railway wheel with BD, the configuration may be such
that the inner peripheral surface of the rim portion includes a comer surface
connecting to a side face of the rim portion, and a fillet surface connecting to the
corner surface and a side face of the plate portion, wherein the minimum section
portion is present at a boundary between the comer surface and the fillet surface
within the inner peripheral surface of the rim portion.
[0022]
In the above described railway wheel with BD, the configuration may be such
that the inner peripheral surface of the rim portion includes a comer surface
connecting to a side face of the rim portion, and a fillet surface connecting to the
comer surface and a side face of the plate portion, wherein the minimu'm section
portion is present in a region of the fillet surface within the inner peripheral surface
of the rim portion. In the case of this configuration, the minimum section portion is
preferably present closest to the back face within the outer peripheral surface of the
circular plate portion.
[0023]
Moreover, in the above described railway wheel with BD, a configuration
may be adopted in which the comer surface of the inner peripheral surface of the rim
portion has a contour of arc shape in a section along the axial direction.
ADVANTAGEOUS EFFECTS OF INVENTION
[0024]
The railway wheel with brake disc of the present invention has the following
remarkable effects:
- The brake disc has a simple shape and an excellent productivity; and
- The aerodynamic sound during high speed travelling can be effectively
reduced.
BRIEF DESCRIPTION OF DRAWINGS
[0025]
[FIG. 1 A] FIG. 1A is a diagram to show an overall structure of a railway wheel with
brake disc, showing a plan view of a 114 circular portion.
[FIG. lB] FIG. 1B is a diagram to show an overall structure of a railway wheel with
brake disc, showing a sectional view along the radial direction of a semi-circular
portion.
[FIG. 2A] FIG. 2A is a diagram to topically show a structure of a conventional
railway wheel with brake disc, showing a perspective view of the back face of the
brake disc seen from the inner peripheral surface side.
[FIG. 2B] FIG. 2B is a diagram to topically show a structure of a conventional
railway wheel with brake disc, showing a plan view of the brake disc seen from the
back face side.
[FIG. 2C] FIG. 2C is a diagram to topically show a structure of a conventional
railway wheel with brake disc, showing a sectional view along the radial direction.
[FIG. 3A] FIG. 3A is a diagram to topically show a shucture of a conventional
railway wheel with brake disc disclosed in Patent Literature 3, showing a perspective
view of the back face of the brake disc seen from the inner peripheral surface side.
[FIG. 3B] FIG. 3B is a diagram to topically show a structure of a conventional
railway wheel with brake disc disclosed in Patent Literature 3, showing a sectional
view along the radial direction
[FIG. 41 FIG. 4 is a diagram to show a correlation between the sum total of opening
areas, and the aerodynamic sound level and the air flow rate in a railway wheel with
brake disc.
[FIG. 5A] FIG. 5A is a diagram to show a distribution of gas pressure variation in a
solid surface (surfaces of the brake disc and the wheel) obtained by a transient gas
flow analysis.
[FIG. 5B] FIG. 5B is a diagram to show a distribution of gas pressure variation in a
solid surface (depicted as seen through the brake disc) obtained by a transient gas
flow analysis.
[FIG. 6A] FIG. 6A is a sectional view along the radial direction to show a structure
of a railway wheel with brake disc, which is a first embodiment of the present
invention.
[FIG. 6B] FIG. 6B is a sectional view to topically show the railway wheel with brake
disc of FIG. 6A, showing the rectangular region in FIG. 6A.
[FIG. 7A] FIG. 7A is a sectional view along the radial direction to show a structure
of a railway wheel with brake disc, which is a second embodiment of the present
invention.
[FIG. 7B] FIG. 7B is a sectional view to topically show the railway wheel with brake
disc of FIG. 7A, showing the rectangular region in FIG. 7A.
[FIG. 8A] FIG. 8A is a sectional view along the radial direction to show a structure
of a railway wheel with brake disc, which is a third embodiment of the present
invention.
[FIG. 8B] FIG. 8B is a sectional view to topically show the railway wheel with brake
disc of FIG. 8A, showing the rectangular region in FIG. 8A.
[FIG. 9A] FIG. 9A is a sectional view along the radial direction to show a structure
of a railway wheel with brake disc, which is used as Comparative Example in the
analysis of Examples.
[FIG. 9B] FIG. 9B is a sectional view to topically show the railway wheel with brake
disc of FIG. 9A, showing the rectangular region in FIG. 9A.
[FIG. 101 FIG. 10 is a diagram to show relationship between the heat dissipation rate,
which is an analysis result of Examples, and the aerodynamic sound level.
[FIG. 111 FIG. 11 is a diagram to show temporal changes of air flow rate which are
analysis results of Examples.
DESCRIPTION OF EMBODIMENTS
[0026]
As described in Patent Literature 3, there is a strong correlation between the
flow rate of the air, which flows through a space formed between the brake disc and
the wheel, particularly, a space surrounded by the circular plate portion and the fin
portion of the brake disc and the plate portion of the wheel, and the level of
aerodynamic sound.
[0027]
FIG. 4 is a diagram to show a correlation between the sum total of opening
areas, and the aerodynamic sound level and the air flow rate in the railway wheel
with brake disc. The sum total of opening areas mentioned herein refers to a sum
total of opening areas over the entire range of the circumferential direction when
seen from the inner circumferential side of the hrake disc regarding a space
surrounded by the circular plate portion and the fin portion of the brake disc, and the
plate portion of the wheel. In other words, the sum total of opening areas refers to
an area of a minimum section portion in which area of the spatial cross section is
minimum regarding a section (hereafter, referred to as a "spatial cross section") that
crosses along the circumferential direction the space formed between the hrake disc
and the wheel. For example, like a railway wheel with BD shown in FIGS. 3A and
3B, in a case in which a rib is added between fin portions of the brake disc, and a slit
is formed in the rib, since the minimum section portion is located at the position of
the rib, the area of the spatial cross section at the position of the rib corresponds to
the sum total of opening areas shown in FIG. 4. Note that the air flow rate has been
obtained by a heat transfer and flow analysis (per one brake disc), and the level of
aerodynamic sound has been obtained by experiment.
[0028]
It is seen as shown in FIG. 4 that the aerodynamic sound level increases as the
area (sum total of opening areas) of the minimum section portion increases, and the
air flow rate shows a similar tendency.
[0029]
However, in reality, the aerodynamic sound is caused by unsteady change of
the gas pressure (propagation phenomenon of compressional wave). For this reason,
when predicting generation of aerodynamic sound by a numerical analysis, it is
preferable to directly evaluate substantially unsteady changes of gas flow and
changes of sound pressure associated therewith.
[0030]
Accordingly, with the conventional railway wheel with BD shown in FIGS.
3A and 3B, that is, a railway wheel with BD in which a rib with a slit is added
between fin portions as a target, a direct prediction of aerodynamic sound level based
on transient gas flow analysis was performed. In this analysis, the travelling speed
was constant at 360 kmlhr.
[003 11
Typical conditions for a model of railway wheel with BD which was used for
the transient gas flow analysis are as follows.

- Forged steel disc for Shinkansen (R)
- Inner diameter of circular plate portion: 417 rnm, outer diameter of circular
plate portion: 715 mm
- Length from the sliding surface of the circular plate portion to the front end
surface (contact surface with wheel plate portion) of the fin portion: 45 mm
- 12 bolt holes whose centers are located on an identical circle of a diameter
of 560 min are formed at an equal interval, and a bolt is inserted through each bolt
hole to fasten the brake disc and the wheel.

- Rolled wheel for Shinkansen (R)
- Inner diameter: 196 mm, Outer diameter: 860 mm
[0032]
First, measurement of aerodynamic sound level was performed by the method
described in Patent Literatwe 2 to verify the appropriateness of the calculation
method of transient gas flow analysis. Specifically, after sound pressure was
measured by a precision noise meter through experiment, frequency analysis was
conducted to perform an A-weighting correction, and thereafter 113 octave band
processing was performed to calculate frequency characteristic data and an overall
value. Then, for the overall value, an experimental value (1 14.5 [dB(A)]) and a
calculated value (1 14.8 [dB(A)]) were compared to each other to confirm
consistency therebetween.
[0033]
FIGS. 5A and 5B show the distribution of gas pressure variation on solid
surfaces (surfaces of the brake disc and the wheel) obtained by a transient gas flow
analysis. FIG. 5A depicts it on both of the surfaces of the brake disc and the wheel,
and FIG. 5B depicts it as seen through the brake disc.
[0034]
The gas pressure variation on the solid surface shown in FIGS. 5A and 5B
indicates square mean quantities of time differential values of pressure, which
correspond to a sound source distribution on the solid surfaces (surfaces of the brake
disc and the wheel). As obvious from the distribution of dark part in the gray scale
depiction in FIGS. 5A and 5B, a major sound source during travelling appears in a
gas outflow region and the vicinity thereof, that is, an outer circumferential region of
the circular plate portion of the brake disc and the vicinity thereof, within a space
formed between the brake disc and the wheel.
[0035]
For this reason, to reduce the aerodynamic sound, the present invention has
paid attention, within the space formed between the brake disc and the wheel, not to
the space surrounded by the circular plate portion and the fin portion of the brake
disc, and the plate portion of the wheel, which was paid attention to by prior art, but
to the outer circumferential region of the circular plate portion of the brake disc,
which becomes a gas outflow region, that is, a region formed by the outer peripheral
surface of the circular plate portion of the brake disc and the inner peripheral surface
of the rim portion of the wheel.
[0036]
Then, effects of the form of the outer circumferential region of the circular
plate portion of the brake disc on the aerodynamic sound level and the cooling
performance have been investigated by using numerical calculation by the above
described transient gas flow analysis. As a result of that, the present inventors have
obtained a finding that appropriately specifying the shape of the outer peripheral
surface of the brake disc allows to further suppress the aerodynamic sound level
while maintaining the cooling performance at a level equivalent to or not lower than
that of prior art, thus completing the present invention.
[0037]
In general, the abrupter the directional change of gas flow becomes, the more
kinetic energy due to viscous stress is dissipated, thus becoming more likely to he
converted into a type of energy that generates sound. Regarding this, the present
invention has paid attention to the gas flow in the gas outflow region and adjusted the
direction of gas flow from between the brake disc and the wheel so as to follow the
surface (side face) of the rim portion of the wheel such that it merges, at a small
angle, with the gas flow generated in a radially outward direction along the sliding
surface as the brake disc rotates. As a result, the directional change of gas flow in
the vicinity of the merging point, which tends to become a sound source, is
minimized, thus realizing reduction of aerodynamic sound.
[0038]
Hereafter, embodiments of the railway wheel with brake disc of the present
invention will he described in detail.
[0039]

FIG. 7A is a sectional view along the radial direction to show a structure of a
railway wheel with brake disc, which is a second embodiment of the present
invention. FIG. 7B is a sectional view to topically show the railway wheel with
brake disc of FIG. 7A, showing the rectangular region in FIG. 7A. The railway
wheel with BD of the second embodiment is based on the configuration of the first
embodiment, and is subjected to change in the following points with respect to the
first embodiment.
[OOSO]
In the railway wheel with BD of the second embodiment, a minimum section
portion of the spatial cross section between the brake disc 1 and the wheel 10 is
present in a region of the fillet surface 12bb of the rim portion 12 (see point b4 in
FIG. 7B) within the region formed by the outer peripheral surface 2c of the circular
plate portion 2 of the brake disc 1 and the inner peripheral surface 12b of the rim
portion 12 of the wheel 10.
[005 11
Corresponding to this, the outer peripheral surface 2c (a range from point a1
to point a3 in FIG. 7B) of the circular plate portion 2 of the brake disc 1 is configured
such that the shape of a region (a range from point a1 to point a4 in FIG. 7B)
extending from a position a4, which faces the minimum section portion (point b4 in
FIG. 7B) in the fillet surface 12bb of the rim portion 12, to the outer side (the front
face 2a side) along the thickness direction corresponds to a shape that follows parts
of the corner surface 12ba and the fillet surface 12bb within the inner peripheral
surface 12b of the rim portion 12. That is, in the range of that region, the outer
peripheral surface 2c of the circular plate portion 2 of the hrake disc 1 and the inner
peripheral surface 12b of the rim portion 12 of the wheel 10 are opposed in proximity
to each other. On the other hand, in a region (a range from point a4 to point a3 in
FIG. 7B) extending to the inner side (the back face 2b side of the hrake disc 1) away
from the aforementioned region, the outer peripheral surface 2c of the circular plate
portion 2 extends apart from the inner peripheral surface 12b of the rim portion 12
without following it.
[0052]
The railway wheel with BD of the second embodiment having such
configuration achieves the same effects as those of the first embodiment as described
above.
[0053]

FIG. 8A is a sectional view along the radial direction to show a structure of a
railway wheel with brake disc, which is a third embodiment of the present invention.
FIG. 8B is a sectional view to topically show the railway wheel with brake disc of
FIG. 8A, showing the rectangular region in FIG. 8A. The railway wheel with BD
of the third embodiment is a modified aspect of the second embodiment.
[0054]
That is, in the railway wheel with BD of the third embodiment, a minimum
section portion of the spatial cross section between the brake disc 1 and the wheel 10
is present closest to the back face 2b (see point a3 in FIG. 8B) within the outer
peripheral surface 2c of the circular plate portion 2, in the region formed by the outer
peripheral surface 2c of the circular plate portion 2 of the brake disc 1 and the inner
peripheral surface 12b of the rim poltion 12 of the wheel 10.
[OOS5]
The outer peripheral surface 2c (a range from point a1 to point a3 in FIG. 8B)
of the circular plate portion 2 of the brake disc 1 is configured such that the shape of
a region extending from a position a3, which is closest to the back face 2b, to the
outer side (the front face 2a side) along the thickness direction corresponds to a
shape that follows substantially entire surface of the comer surface 12ba and part of
the fillet surface 12bb within the inner peripheral surface 12b of the rim portion 12.
That is, the outer peripheral surface 2c of the circular plate portion 2 of the brake disc
1 is opposed in proximity to the inner peripheral surface 12b of the rim portion 12 of
the wheel 10 over the entire range in the thickness direction.
[0056]
In this case, the minimum section portion of the spatial cross section between
the brake disc 1 and the wheel 10 is present in a region of the fillet surface 12bb of
the rim portion 12 of the wheel 10 corresponding to the position a3 closest to the
back face 2b (see point b5 in FIG. 8B) within the outer peripheral surface 2c of the
circular plate portion 2 of the brake disc 1.
[0057]
The railway wheel with BD of the third embodiment having such
configuration achieves the same effects as those of the first embodiment as described
above.
EXAMPLES
[0058]
To confirm the effects by the railway wheel with BD of the present invention,
a transient gas flow analysis and a heat transfer and flow analysis were performed to
evaluate the aerodynamic sound level, cooling performance, and air flow rate. As
the target of analysis, the railway wheel with BD of the first embodiment shown in
FIGS. 6A and 6B was adopted as Inventive Example 1 of the present invention, and
the railway wheel with BD of the third embodiment shown in FIGS. 8A and 8B was
adopted as Inventive Example 2 of the present invention.
[0059].
Further, as Comparative Example, a railway wheel with BD was adopted in
which a rib 7 with a slit 7a between fin portions 3 was added as shown in FIGS. 9A
and 9B. The railway wheel with BD shown in FIGS. 9A and 9B is the same as the
conventional railway wheel with BD shown in FIGS. 3A and 3B. In the railway
wheel with BD of Comparative Example, the outer peripheral surface 2c of the
circular plate portion 2 of the brake disc 1 extends apart from the inner peripheral
surface 12b of the rim portion 12 without following it.
[0060]
In all of the railway wheels with BD of Inventive Examples 1 and 2 of the
present invention and Comparative Example, the brake disc was center fastened.
[0061]
Typical conditions for a model of the railway wheel with BD which was used
for analysis were the same as those in the above described transient gas flow analysis.
Also, the technique for transient gas flow analysis was the same as described above.
The traveling speed was assumed to be constant at 360 kmh either in the transient
gas flow analysis and the heat transfer and flow analysis.
[0062]
As an evaluation index for cooling performance, a heat dissipation rate was
introduced, the heat dissipation rate being defined as a product of an average heat
transfer coefficient of surface and a surface area per one brake disc. The larger the
heat dissipation rate is, the better the cooling performance is.
[0063]
The evaluation of air flow rate was performed by a time average of air flow
rate and a variation range thereof in the minimum section portion of the spatial cross
section between the brake disc and the wheel.
The results are shown in the following Table 1, and FIGS. 10 and 11.
[0064]
[Table 11
TABLE 1
[0065]
FIG. 10 is a diagram to show relationship between the heat dissipation rate,
which is an analysis result of Examples, and the aerodynamic sound level. FIG. 11
is a diagram to show temporal changes of air flow rate which are analysis results of
Examples. As shown in Table 1 and FIG. 10, it can be confirmed that Inventive
Examples 1 and 2 of the present invention can reduce the aerodynamic sound level
further than Comparative Example while achieving a cooling performance equal to
or better than that of Comparative Example. Moreover, since Inventive Examples 1
and 2 each have a larger area of the minimum section portion than that of
Comparative Example, they exhibit increased average air flow rate, thus achieving
higher cooling performance. Furthermore, as shown in Table 1 and FIG. 1 1,
Inventive Examples 1 and 2 each exhibit a smaller variation range of air flow rate
than that of Comparative Example, and therefore improved quietness. From these,
it can be said that the quietness of a railway wheel with BD and the cooling
performance of brake disc during braking can be appropriately controlled by properly
changing the area of the minimum section portion, which is a design factor.
INDUSTRIAL APPLICABILITY
[0066]
The railway wheel with brake disc of the present invention can be effectively
utilized for every railway vehicle equipped with a disc brake, and is particularly
useful for high speed railway vehicles.
REFERENCE SIGNS LIST
1 : Brake disc, 2: Circular plate portion,
2a: Front face, 2b: Back face,
2c: Outer peripheral surface, 3: Fin portion,
4: Bolt hole, 5: Bolt, 6: Nut,
7: Rib, 7a: Slit, 10: Wheel,
11: Boss portion, 12: Rim portion,
12a: Side face, 12b: Inner peripheral surface,
12ba: Comer surface, 12bb: Filet surface,
13: Plate portion, 13a: Side face
We claim:
1. A railway wheel with brake disc comprising:
a wheel for a railway vehicle, comprising a boss portion, a rim portion, and a
plate portion for combining them together; and
a brake disc comprising an annular circular plate portion whose front face
provides a sliding surface, and a plurality of fin portions which are radially projected
on a back face of the circular plate portion, wherein
two of the brake discs interpose the plate portion of the wheel with each of
sliding surfaces thereof facing outwardly, and are fastened in a region within the
sliding surface, and wherein
regarding an area of a section crossing a space formed between-the brake disc
and the wheel along a circumferential direction, a minimum section portion in which
the sectional area is minimum is present in a region formed by an outer peripheral
surface of the circular plate portion and an inner peripheral surface of the rim portion,
and
the outer peripheral surface of the circular plate portion has a shape that
follows the inner peripheral surface of the rim portion in a region extending to an
outer side from the ininimum section portion.
2. The railway wheel with brake disc according to claim 1, wherein
the inner peripheral surface of the rim portion includes a comer surface
connecting to a side face of the rim portion, and a fillet surface connecting to the
corner surface and a side face of the plate portion, and
the ininimum section portion is present at a boundary between the comer
surface and the fillet surface within the inner peripheral surface of the rim portion.
3. The railway wheel with brake disc according to claim 1, wherein
the inner peripheral surface of the rim poition includes a comer surface
connecting to a side face of the rim portion, and a fillet surface connecting to the
comer surface and a side face of the plate portion, and
. ~
. .
the niinimum section portion is present in a region of the fillet surface within
the inner peripheral surfaceof the rimportion.
4. The railway wheel with brake disc according to claim 3, wherein
the minimum section portion is present closest to the back face within the
outer peripheral surface of the circular plate portiom
5. The I-ailway wheel with brake disc according to any one of claims 2 to 4,
wherein
the cornel surface in the inner periphel-a1 surface of the lim portion has a
contour of arc shape in a section along the axlal direction.