TECHNICAL FIELD
[0001] The present invention relates to a bogie for a railway vehicle. The object of the
invention is to reduce a decrease in a wheel load that occurs when traveling at low
speed, particularly in an exit easement curve section.
BACKGROUND ART
[0002] As shown in FIG. 4, two bogies 2 are typically disposed at the front and the back
of a railway vehicle 1 in the direction of travel. Four air springs 4 are installed
in a bogie frame 3 which constitutes each of the bogies 2, with two springs disposed
in a width direction on each of the two sides of the railway vehicle to support a
vehicle body 5.
[0003] In a railway vehicle having the above construction, a height of the vehicle body
5 is varied according to the number of passengers, by relaxing the spring rigidity
of the air springs 4, in order to enhance the riding comfort of the passengers. Therefore,
an automatic height adjusting device 6 (referred to below as an LV) is installed in
the vehicle body 5. The LV 6 detects the height of the air springs, supplies air,
and vents air, so as to maintain a constant height of the vehicle body 5 and to eliminate
a difference in level with a platform, to ensure safety when passengers alight from
the railway vehicle. In FIG. 4, Reference Numeral 7 is a wheel set on which are mounted
wheels 7b attached to both sides of a shaft 7a, and Reference Numeral 8 is a rail.
[0004] As shown in FIG. 5, the LV 6 is installed on both sides in a width direction of the
railway vehicle 5, and one end of a lever 11 is attached to an operating shaft 6a.
The other end of the lever 11 is rotatably coupled to one end of a coupling rod 12
so that the other end thereof rotates freely in the bogie frame 3 (see paragraph 0002
and FIG. 10 of Patent Reference 1). Reference Numeral 9 in FIG. 5 is an axle box which
supports the wheel set 7 so that it rotates freely. Reference Numeral 10 is an axle
spring mounted on the axle box 9.
[0005] Straight sections and curved sections of the rail are connected via an easement curve
section in which a rail surface twists with a gradually changing curvature and cant.
[0006] When traveling through a curved section, a high lateral force operates on the wheels
on an outer rail side of a wheel set on the front side in the traveling direction
of the bogie (referred to below as the front axle).
[0007] While the bogie travels through the easement curve section in which the rail surface
twists, the height of the axle springs and the air springs changes in order for the
wheels to follow the rail, and this change in the height of the springs causes the
resulting spring force to vary the wheel load. In particular, the wheel load decreases
when the air springs on the outer rail side of the front axle expand, resulting in
an easing of the wheel load. Accordingly, the derailment coefficient, obtained by
dividing the lateral force Q by the wheel load P, increases at the exit easement curve
section (see FIG. 6).
[0008] Moreover, when traveling at a low speed in the exit easement curve section, the twisting
of the rail surface causes the air springs on the outer rail side of the front axle
to expand, and the air springs on the inner rail side of the front axle to compress,
the LV operates, while the air springs on the outer rail side are vented, so the inner
pressure drops, and the air springs on the inner rail side are supplied with air,
so the inner pressure rises. The decrease in wheel load becomes significant on the
outer rail side of the front axle, because the spring force of the air springs decreases
due to the reduced inner pressure of the air springs on the outer rail side.
PRIOR ART REFERENCES
PATENT REFERENCES
SUMMARY OF THE INVENTION
PROBLEMS TO BE SOLVED BY THE INVENTION
[0010] The problem that the present invention aims to solve is that in the case of a prior
art bogie for a railway vehicle, when traveling at low speed through an exit easement
curve section, a decrease in wheel load occurs in a front wheel on an outer rail side,
and the LV promotes this decrease in wheel load.
MEANS FOR SOLVING THESE PROBLEMS
[0011] Because a wheel follows a twisting of a rail surface when traveling through an exit
easement curve section, a wheel load varies according to changes in a height of an
axle spring. An amount of change in wheel load ΔP
bogie from when the railroad vehicle is at rest (stationary wheel load) can be obtained
from the following formula, having a spring constant k of an axle spring mounted on
both sides in a width direction in a bogie frame, a distance b
1 between the axial centers of the axle springs on both sides, and a distance b
c between the contact points of a wheel and a rail (see FIG. 1).
![](https://data.epo.org/publication-server/image?imagePath=2016/17/DOC/EPNWA1/EP14814492NWA1/imgb0001)
(Where θ is the angle of twisting of the rail surface, and C is a coefficient determined
by the stationary wheel load.)
[0012] In order to inhibit a decreased wheel load when traveling at low speed in an exit
easement curve section, the inventors conceived of mounting axle springs disposed
on both sides in a width direction of the railway vehicle so as to position it as
much as possible on the center side in the width direction of the railway vehicle.
[0013] Moreover, in order to study a height detection position (the position of the distance
indicated by b
2 in FIG, 1) of an LV that promotes a decrease in a wheel load, the inventors simulated
a ratio of the decrease in the wheel load when a standard commuter train passes through
an easement curve section at a speed of 5 km/h, where the easement curve section has
a radius of curvature of 200 m, a cant of 105 mm, and a cant diminution rate of 300-fold.
[0014] As a result, it was found that the ratio of the decrease in wheel load, when the
height detection position of the LV was changed from an outer side of a width direction
of a railway vehicle to a center of the railway vehicle in the width direction, decreased
more when it was located on the center side of the railway in the width direction
from the axial center of the air springs, as shown in FIG. 3. It was also found that
the ratio of decrease in wheel load increases when the height detection position of
the LV is located on the center side in the width direction of the railway vehicle
than when disposed in the axial center of the axle springs. The ratio of decrease
in wheel load shown in FIG. 3 shows a case where the value is 1 at a current height
detection position of the LV when disposed in the width direction of the railway vehicle
on a side which is more on the outside than the air springs which are disposed on
both sides in the width direction of the railway vehicle in the bogie frame.
[0015] The present invention was designed on the basis of the above concepts and the research
carried out by the inventors. In particular, the present invention employs the following
construction in order to reduce the decrease in wheel load on the outer rail side
of the front axle when traveling at low speed in an exit easement curve section.
[0016] The present invention is a bogie for a railway vehicle comprising a bogie frame supported
by axle springs disposed on axle boxes which rotatably support a wheel set, air springs
disposed on both sides of the railway vehicle in a width direction of the bogie frame,
an LV provided for each of the air springs for maintaining a constant height of a
vehicle body which is supported by the air springs, wherein the axle boxes are disposed
at positions closer to the center side of the railway vehicle in the width direction
than the wheels attached to both sides of a shaft which constitutes a wheel set, and
a height of the LV is detected at a position of the LV which is located between an
axial center of the air springs and an axial center of the axle springs.
[0017] According to the present invention, the axle boxes provided with axle springs are
disposed at positions closer to the center side of the railway vehicle in the width
direction than the wheels attached to both sides of the shaft which constitutes the
wheel set. Therefore, the distance between the two axle springs disposed on both sides
in the width direction of the railway vehicle becomes narrower, and the amount of
change in the height of the air springs decreases, so there is less fluctuation in
wheel load when traveling through an exit easement curve section.
[0018] In addition, according to the present invention, the height of the LV is detected
at a location between the axial center of the air springs and the axial center of
the axle springs. Therefore, there is a greater reduction in the decrease in wheel
load than when the height detection position of the LV is located on the outer side
of the air springs in the width direction of the railway vehicle.
ADVANTAGEOUS EFFECTS OF THE INVENTION
[0019] According to the present invention, the bogie is constructed so that the distance
between the two axle springs disposed on both sides in the width direction of the
railway vehicle becomes smaller, and the height detection position of the LV is located
more on the center side in the width direction of the railway vehicle than in the
prior art. Therefore, when traveling at low speed in an exit easement curve section,
it is possible to greatly reduce the decrease in wheel load on the outer rail side
of the front axle, thus improving the ability to pass through exit easement curve
sections.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020]
FIG. 1 is a drawing illustrating the schematic structure of a bogie for a railway
vehicle according to the present invention. FIG. 1 (a) is a frontal view in the direction
of travel of the railway vehicle. FIG. 1 (b) is a view from above the railway vehicle.
FIG. 2 is a drawing illustrating wheel load when traveling through an exit easement
curve section. FIG. 2 (a) shows a bogie for a railway vehicle according to the present
invention. FIG. 2 (b) shows a prior art bogie for a railway vehicle.
FIG. 3 is a graph showing the relationship between the height detection position of
the LV and the decrease in wheel load.
FIG. 4 is a drawing illustrating a prior art bogie for a railway vehicle in a manner
similar to FIG. 1 (b).
FIG. 5 is a drawing illustrating a prior art bogie for a railway vehicle in a manner
similar to FIG. 1 (a).
FIG. 6 is a graph showing the lateral force Q and the wheel load P which operate on
a front axle wheel while traveling through an exit easement curve section.
EMBODIMENT OF THE INVENTION
[0021] The object of the present invention is to reduce a decrease in wheel load on the
outer rail side of the front axle that occurs when traveling at low speed, particularly
in an exit easement curve section. This object is achieved by constructing the bogie
in such a manner that the distance between the two axle springs disposed on both sides
of the railway vehicle in the width direction becomes smaller, and by locating the
height detection position of the LV more on the center side in the width direction
of the railway vehicle than in the prior art.
EXAMPLE
[0022] An example of an embodiment is described below, making reference to FIG. 1.
[0023] FIG. 1 is a drawing illustrating the schematic structure of a bogie for a railway
vehicle according to the present invention.
[0024] Reference Numeral 21 is a bogie, and in the present invention, it is an inboard type
bogie wherein the axle boxes 9, provided with axle springs 10 that support a bogie
frame 22, are disposed at positions closer to the center side of the railway vehicle
in the width direction than the wheels 7b attached to both sides of the shaft 7a which
constitutes the wheel set 7.
[0025] Therefore, since the axle boxes 9 are disposed on the outer side from the wheels
7b in the width direction of railway vehicle, the construction differs from that of
the outboard type bogie 2 depicted in FIG. 4 and FIG. 5. Side beams 22a which constitutes
the bogie frame 22 are positioned on an inner side of the wheels 7b.
[0026] In other words, in the case of the inboard type bogie 21, the height detection position
of the LV 6 can be located closer to an inward side of the air springs 4 which are
disposed on both sides of the railway vehicle in the width direction in the bogie
frame 22.
[0027] Additionally, according to the present invention, the height detection position of
the LV 6 provided to the air springs 4 to maintain a constant height of the vehicle
body 5, is located between the axial center of the air springs 4 and the axial center
of the axle springs 10.
[0028] According to the present invention having the above construction, the distance b
1 between the two axle springs 10 disposed on both sides of the railway vehicle in
the width direction becomes narrower and the amount of change in the height of the
air springs decreases, so that, as shown in FIG. 2 (a), the wheel load P, which operates
on the four wheels 7b while traveling at low speed through an exit easement curve
section, becomes smaller than that for the outboard type bogie 2 depicted in FIG.
2 (b).
[0029] The stationary wheel load of the four wheels 7b does not become unbalanced, because
the height detection position of the LV 6 is located between the axial center of the
air springs 4 and the axial center of the axle springs 10. Therefore, the ratio of
decrease in the wheel load is reduced in comparison with the case where the height
detection position of the LV 6 is located on the outer side of the air springs 4.
[0030] According to the present invention described above, the decrease in wheel load on
the outer rail side of the front axle can be greatly reduced when traveling at low
speed in an exit easement curve section, thus making it possible to improve the ability
to pass through exit easement curve sections.
[0031] The present invention is not limited to the above-described example, and the preferred
embodiment may, of course, be advantageously modified within the scope of the technical
ideas recited in the claims.
[0032] For example, FIG. 1 shows a bolsterless bogie, but the present invention is also
suitable for a bogie with a bolster. Moreover, the present invention can also be used
in a steering bogie.
EXPLANATION OF THE REFERENCE NUMERALS
[0033]
- 1
- Railway vehicle
- 4
- Air spring
- 5
- Vehicle body
- 6
- LV
- 7
- Wheel set
- 9
- Axle box
- 10
- Axle spring
- 21
- Bogie
- 22
- Bogie frame