TECHNICAL FIELD OF THE INVENTION
[0001] The present invention relates to a wheel axle guiding assembly and to a running gear
for a rail vehicle.
BACKGROUND ART
[0002] A two-axle bogie for a rail vehicle described in
DE 31 23 858 C2 is provided with a wheel axle guiding assembly comprising: a pair of front left hydraulic
cylinders for moving the left wheel of the front wheel set towards and away from a
median transverse vertical plane of the bogie, a pair of front right hydraulic cylinders
for moving the right wheel of the front wheel set towards and away from the median
transverse vertical plane, a pair of rear left hydraulic cylinders for moving the
left wheel of the rear wheel set towards and away from the median transverse vertical
plane, a pair of rear right hydraulic cylinders for moving the left wheel of the rear
wheel set towards and away from the median transverse vertical plane, and hydraulic
connection to ensure that movements of the left, respectively right wheels of the
front wheel set towards, respectively away from the median transverse vertical plane
result in movements of the left, respectively right wheels of the front wheel set
towards, respectively away from the median transverse vertical plane. In other words,
the steering of the front and rear wheel sets is coordinated to negotiate tight curves
of the track.
[0003] It has been suggested in
EP1228937 to provide a bogie with specific bushings each mounted between one of the axle boxes
and the bogie frame, said bushings comprising a cylindrical outer case, a bolt coaxially
received within the outer case, and an elastomer body connecting the outer case to
the bolt so as to form two chambers, which are located between the outer case and
the bolt on opposite sides of the bolt. The two opposite chambers are filled with
fluid. A fluid path is formed between the two chambers to allow a fore-and-aft movement
of the bashing axle within the outer case. Further fluid connections may be provided
to interconnect the chambers of the different bushings with a pressure source to constitute
an active steering system. Due to the shape of the bushing, the amount of elastomer
is limited, as well as the pumping area. As a result the effectiveness and lifespan
of these specific bushings is limited.
[0004] A similar bashing is disclosed in
EP1457706. In order to obtain a stiffness that varies with the frequency, an arcuate channel
is provided between the two chambers of the bashing. The frequency response of the
bashing depends on the pumping area, as well as on the length and cross-section of
the channel and, for a given set of parameters, the stiffness increases with the frequency.
However, due to its size, the capabilities of the bashing are limited.
[0005] A running gear unit for a rail vehicle, having a running gear frame, supported on
a pair of wheel sets via a primary suspension system is disclosed in
WO2014170234. The two wheel sets are coupled with one another via a coupling arrangement in such
a way that a first transverse displacement of the first wheel set with respect to
the running gear frame in the transverse direction results in a second, identically
directed transverse displacement of the second wheel set with respect to the running
gear frame in the transverse direction. Concurrently, the coupling arrangement is
such that a first rotation of the first wheel set with respect to the running gear
frame about a vertical axis results in a second rotation in the opposite direction
of the second wheel set with respect to the running gear frame. The coupling arrangement
comprises bushings each comprising a cylindrical outer case, a bolt coaxially received
within the outer case, and an elastomer body connecting the outer case to the bolt
so as to form four chambers. Due to their size, the capabilities of the bushings are
limited.
[0006] A primary suspension system disclosed in
US4932330 includes a pair of spaced vertical springs connected between a journal bearing retainer
and a side frame of a railway truck. Pairs of angularly disposed elastomeric springs
are also connected between a lower support housing and opposite angular ends of the
journal bearing retainer to provide lateral and longitudinal stiffness. However, these
elastomeric springs do not provide a frequency dependent stiffness.
SUMMARY OF THE INVENTION
[0007] The invention aims to provide wheel axle guiding assemblies with more robust hydro-mechanical
converters that provide long strokes and improved capabilities, within the space requirement
of conventional running gears.
[0008] According to a first aspect of the invention, there is provided a wheel axle guiding
assembly comprising:
- an axle box defining a horizontal revolution axis and a longitudinal horizontal direction
perpendicular to the revolution axis;
- an axle box carrier, the axle box being located longitudinally between a front part
and a rear part of the axle box carrier; and
- a front longitudinal hydro-mechanical converter fixed to the axle box and the front
part of the axle box carrier and a rear longitudinal hydro-mechanical converter fixed
to the axle box and the rear part of the axle box carrier to allow a fore-and-aft
movement of the axle box relative to the axle box carrier parallel to the longitudinal
direction; wherein each of the front and rear longitudinal hydro-mechanical converters
includes a housing, a plunger and an elastomeric body fixed to the housing and to
the plunger so as to allow a fore-and-aft relative movement parallel to the longitudinal
direction between the plunger and the housing, a single variable volume hydraulic
chamber being formed between the housing, the plunger and the elastomeric body, each
of the front and rear longitudinal hydro-mechanical converters further including a
hydraulic port for connecting the variable volume hydraulic chamber to an external
hydraulic circuit.
[0009] As one hydro-mechanical converter is provided on each side of the axle boxes and
each hydro-mechanical converter is provided with a single variable volume chamber
between the plunger and the housing, more room is available for each variable volume
chamber than the prior art. Both the effective pumping area and the stroke of the
hydro-mechanical converters can be increased. The larger effective pumping area and
a larger size of the elastomeric body are predominant factors for defining a stiffer
dynamic response, which takes advantage from a large pumping area, and a greater ratio
between the dynamic stiffness and the static stiffness of the wheel axle guiding assembly.
[0010] Preferably the axle box houses a bearing having an inner diameter defining a cross-sectional
area
AΦ of an end of a wheel axle to be received in the bearing and the plunger has an effective
area
Ae measured in a plane perpendicular to the longitudinal direction, which is greater
than half the cross-sectional area
AΦ, preferably greater than the cross-sectional area
AΦ.
[0011] The elastomeric body is annular, preferably with a circular, elliptic or rectangular
cross-section between the plunger and the housing. According to a preferred embodiment
and in order not to overstress the elastomeric body, the elastomeric body can be fixed
to an annular cylindrical or frustro-conical surface of the housing facing the plunger
and an annular cylindrical or frustro-conical surface of the plunger facing the housing.
[0012] Preferably, each of the front and rear longitudinal hydro-mechanical converters has
a longitudinal stiffness, which increases with a frequency of the fore-and-aft movement
of the axle box relative to the axle box carrier from a quasistatic stiffness value
to a dynamic stiffness value, wherein the plunger and the elastomeric body have dimensions
such that a ratio R of the dynamic stiffness value to the quasistatic stiffness value
is greater than 10, preferably greater than 20, preferably greater than 50. As a result,
the wheel axle guiding assembly has a soft response to quasistatic longitudinal loads,
in particular passive steering movement, and simultaneously efficiently counteracts
hunting oscillations at higher frequencies.
[0013] An abutment may be provided between the plunger and the housing for limiting a contraction
movement of the plunger. In order to increase comfort, the abutment is preferably
provided with an elastomeric buffer.
[0014] According to a preferred embodiment, the wheel axle guiding assembly further comprises
a vertical suspension unit provided between the axle box and an upper part of the
axle box carrier. The vertical suspension unit is preferably independent from the
longitudinal hydro-mechanical converters, in order to control the stiffness and deflection
in the vertical direction independently from the longitudinal direction. According
to one embodiment, the vertical suspension unit comprises a chevron spring having
a V-shaped cross-section in a vertical transversal plane parallel to the revolution
axis. The vertical suspension unit also provides stiffness in the transverse direction,
i.e. the direction parallel to the revolution axis of the axle box. Alternatively
the vertical suspension unit comprises a sandwich spring having a set of planar elastomeric
elements extending in a horizontal plane. In order to take advantage of the room available
below the axle box, the vertical suspension unit may be provided with an elastomeric
pad between the axle box and a lower part of the axle box carrier.
[0015] If the deflection of the axle box in the vertical and/or transverse direction is
significant, e.g. because the vertical suspension unit has a low stiffness, it may
be advisable to release the hydro-mechanical converters from the corresponding displacements.
To this end, each of the front and rear longitudinal hydro-mechanical converters further
comprises a decoupling spring with a longitudinal stiffness at least ten times, preferably
at least twenty times, preferably fifty times greater than a longitudinal stiffness
of the elastomeric body, a lateral stiffness less than a two times the lateral stiffness
of the elastomeric body, preferably less than the lateral stiffness of the elastomeric
body and a vertical stiffness less than two times the vertical stiffness of the elastomeric
body, preferably less than the vertical stiffness of the elastomeric body.
[0016] According to one embodiment the axle box carrier forms a ring around the axle box.
[0017] According to one embodiment a vertical suspension assembly connects the axle box
carrier to a running gear frame. The vertical suspension units between the axle box
carrier and the running gear frame will allow deflection of substantial magnitude
in the vertical direction, without negatively impacting the longitudinal hydro-mechanical
converters. If vertical suspension units are provided both between the axle box and
the axle box carrier and between the axle box carrier and the running gear frame,
the latter will preferably have a lower stiffness than the former, preferably more
than 1,5 times lower.
[0018] According to an alternative embodiment the axle box carrier is a constituent portion
of a running gear frame of a running gear. This will be possible in particular with
a flexible running gear frame.
[0019] According to one embodiment a hydraulic reservoir is hydraulically connected to the
hydraulic chamber, preferably with a check valve allowing a flow a fluid only from
the hydraulic reservoir to the hydraulic chamber, preferably with a volume at least
twice the volume of the hydraulic chamber. The hydraulic reservoir provides a temperature
compensation volume and delivers additional hydraulic fluid to offset losses in the
hydraulic circuit and maintain the function of the system for an extra period of time
in case of leakage. The reservoir may advantageously be provided with a leakage indicator.
The hydraulic reservoir may be connected to the hydraulic chamber via an appropriate
valve arrangement, in particular a check valve, to ensure a fail-safe operation.
[0020] According to another aspect of the invention, there is provided A running gear for
a rail vehicle, comprising at least a pair of wheel axle guiding assemblies as described
above, a first hydraulic circuit for establishing a hydraulic connection between a
first variable volume hydraulic chamber and a second variable volume hydraulic chamber,
and a second hydraulic circuit for establishing a hydraulic connection between a third
variable volume hydraulic chamber and a fourth variable volume hydraulic chamber,
the first, second, third and fourth variable volume hydraulic chambers being all different
chambers and each of the first, second, third and fourth variable volume hydraulic
chambers being the variable volume hydraulic chamber of one of the front and rear
longitudinal hydro-mechanical converters of one of the wheel axle guiding assemblies
of the pair of wheel axle guiding assemblies. Preferably, the first and/or the second
hydraulic circuit further comprise a hydraulic reservoir. The hydraulic connection
between variable volume hydraulic chambers is effective to allow a circulation of
fluid and a balance of pressures when the wheel sets are subjected to quasistatic
load.
[0021] One option is to connect the variable volume chamber of the front longitudinal hydro-mechanical
converter of each wheel axle guiding assembly with the variable volume chamber of
the rear longitudinal hydro-mechanical converter of the same wheel axle guiding assembly.
[0022] Preferred alternative embodiments, however, dispense with any hydraulic connection
between the chamber of the front longitudinal hydro-mechanical converter and the chamber
of the rear longitudinal hydro-mechanical converter of the same wheel axle guiding
assembly.
[0023] Another option is to connect the variable volume chamber of the front longitudinal
hydro-mechanical converter of one wheel axle guiding assembly on each lateral side
of the running gear with the variable volume chamber of the rear longitudinal hydro-mechanical
converter of the other wheel axle guiding assembly on the same lateral side of the
running gear and to connect the variable volume chamber of the rear longitudinal hydro-mechanical
converter of said one wheel axle guiding assembly on each lateral side of the running
gear with the variable volume chamber of the front longitudinal hydro-mechanical converter
of said other wheel axle guiding assembly on the same lateral side of the running
gear.
[0024] Preferably, the first hydraulic circuit establishes a hydraulic connection between
the variable volume hydraulic chamber of the front longitudinal hydro-mechanical converter
of one of the wheel axle guiding assemblies of the pair of the wheel axle guiding
assemblies and the variable volume hydraulic chamber of the front longitudinal hydro-mechanical
converter of the other of the wheel axle guiding assemblies of the pair of the wheel
axle guiding assemblies and second hydraulic circuit establishes a hydraulic connection
between the variable volume hydraulic chamber of the rear longitudinal hydro-mechanical
converter of one of the wheel axle guiding assemblies of the pair of the wheel axle
guiding assemblies and the variable volume hydraulic chamber of the rear longitudinal
hydro-mechanical converter of the other of the wheel axle guiding assemblies of the
pair of the wheel axle guiding assemblies.
[0025] According to one embodiment, the running gear further comprises at least a front
wheel set and a rear wheel set and the such that an end of the front wheel set is
supported by the axle box of a front wheel axle guiding assembly of the pair of wheel
axle guiding assemblies and that an end of the rear wheel set is supported by the
axle box of a rear wheel axle guiding assembly of the pair of wheel axle guiding assemblies.
In particular, one option is to connect the variable volume chamber of the front longitudinal
hydro-mechanical converter of one wheel axle guiding assembly on each lateral side
of the running gear with the variable volume chamber of the front longitudinal hydro-mechanical
converter of the other wheel axle guiding assembly on the same lateral side of the
running gear and similarly for the variable volume chambers of the rear longitudinal
hydro-mechanical converters. This will ensure that the two-wheel sets will rotate
in opposite direction about a vertical axis. Another option with similar effect is
to connect the variable volume chamber of the front longitudinal hydro-mechanical
converter of one wheel axle guiding assembly on each lateral side of the running gear
with the variable volume chamber of the rear longitudinal hydro-mechanical converter
of the other wheel axle guiding assembly on the other lateral side of the running
gear and similarly between the two other variable volume chambers, to form a cross
connection.
[0026] According to a most preferred option, however, the running gear comprises at least
one wheel set, a left end of the wheel set is supported by the axle box of a left
wheel axle guiding assembly of the pair of wheel axle guiding assemblies, and a right
end of the wheel set is supported by the axle box of a right wheel axle guiding assembly
of the pair of wheel axle guiding assemblies. With this embodiment, the longitudinal
translation movement of the wheel set are limited, e.g. when the vehicle accelerates
or decelerates, whilst the rotation of the wheel set about a vertical axis is still
possible. Moreover, this embodiment provides a fail-safe operating mode in case of
leakage.
[0027] Preferably, the running gear does not include any hydraulic connection between the
chamber of the front longitudinal hydro-mechanical converter and the chamber of the
rear longitudinal hydro-mechanical converter of the same wheel axle guiding assembly.
BRIEF DESCRIPTION OF THE FIGURES
[0028] Other advantages and features of the invention will then become more clearly apparent
from the following description of a specific embodiment of the invention given as
non-restrictive examples only and represented in the accompanying drawings in which:
- Figure 1 illustrates a longitudinal section of a wheel axle guiding assembly for a
running gear of a rail vehicle according to a first embodiment of the invention by
a longitudinal vertical plane along section line I-I of Figure 3;
- Figure 2 illustrates a section of the wheel axle guiding assembly of Figure 1 by a
horizontal plane along section line II-II of Figure 1;
- Figure 3 is a vertical section of the wheel axle guiding assembly of Figure 1, along
section line III-III of Figure 1;
- Figure 4 is a vertical section along section line IV-IV of Figure 1;
- Figure 5 is a longitudinal section of a wheel axle guiding assembly according to a
second embodiment of the invention;
- Figure 6 is a longitudinal section of a wheel axle guiding assembly according to a
third embodiment of the invention;
- Figure 7 illustrates a section of the wheel axle guiding assembly of Figure 6 by a
horizontal plane;
- Figure 8 is a longitudinal section of a wheel axle guiding assembly according to a
fourth embodiment of the invention;
- Figure 9 is a longitudinal section of a wheel axle guiding assembly according to a
fifth embodiment of the invention;
- Figure 10 is a longitudinal section of a wheel axle guiding assembly according to
a sixth embodiment of the invention;
- Figure 11 is a schematic view of a first embodiment of a running gear provided with
sets of the wheel axle guiding assemblies according to any one of the previous embodiments
of the invention;
- Figure 12 is a schematic view of a second embodiment of a running gear provided with
sets of the wheel axle guiding assemblies according to any one of the previous embodiments
of the invention;
- Figure 13 is a schematic view of a third embodiment of a running gear provided with
sets of the wheel axle guiding assemblies according to any one of the previous embodiments
of the invention;
- Figure 14 is a schematic view of a fourth embodiment of a running gear provided with
sets of the wheel axle guiding assemblies according to any one of the previous embodiments
of the invention;
- Figure 15 is a schematic view of a fifth embodiment of a running gear provided with
sets of the wheel axle guiding assemblies according to any one of the previous embodiments
of the invention;
- Figure 16 is a schematic view of running gear of Figure 15, operating in a fail-safe
mode of operation.
[0029] Corresponding reference numerals refer to the same or corresponding parts in each
of the figures.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0030] A wheel axle guiding assembly
10 for a running gear
12 of a rail vehicle is illustrated in Figures
1 to
4. This wheel axle guiding assembly
10 comprises an axle box
14 located longitudinally between a front part
16 and a rear part
18 of an axle box carrier
20 formed by a C-shaped end portion of a frame
22 of the running gear
12. The axle box carrier
20 is supported on the axle box
14 by way of a vertical primary suspension unit
24, which comprises a chevron spring
26 having a V-shaped cross-section in a vertical transversal plane parallel to a revolution
axis
100 defined by the axle box
14. As is well known in the art, the axle box
14 houses a bearing
28, usually a roller bearing, for guiding an end portion of a wheel axle
30.
[0031] A front longitudinal hydro-mechanical converter
32 is fixed to the axle box
14 and to the front part
16 of the axle box carrier
20 and a rear longitudinal hydro-mechanical converter
34 is fixed to the axle box
14 and to the rear part
18 of the axle box carrier
20 to allow a fore-and-aft movement of the axle box
14 relative to the axle box carrier
20 parallel to a longitudinal direction
200. The longitudinal direction
200 in this context and in the whole application is the horizontal direction perpendicular
to the horizontal revolution axis
100 defined by the axle box in a reference position. Each of the front and rear longitudinal
hydro-mechanical converters
32, 34 includes a housing
36 fixed to the axle box
14 or integral with the axle box
14, a plunger
38 fixed to or integral with the axle box carrier
20 and an annular elastomeric body
40 adhered by vulcanisation or otherwise fixed in a sealed manner to the housing
36 and to the plunger
38 so as to form a single variable volume hydraulic chamber
42 between the housing
36, the plunger
38 and the elastomeric body
40. A hydraulic inlet and outlet port
44 (see Figure
2) is provided for connecting the variable volume hydraulic chamber
42 to a hydraulic circuit, as will be discussed later on in connection with Figures
9 to
13.
[0032] In this preferred embodiment, the interface
46 between the annular elastomeric body
40 and the housing
36 and the interface
48 between the annular body
40 and the plunger
38 are cylindrical and coaxial. This ensures that the annular elastomeric body
40 is only subjected to shear stress when the plunger
38 and housing
36 move relative to one another in the longitudinal direction
200. The radial dimension of the annular body
40, i.e. the distance between the two interfaces
46, 48 is preferably greater than its longitudinal dimension.
[0033] This arrangement result in a low stiffness of each longitudinal hydro-mechanical
converter
32, 34 in the longitudinal direction
200 while the stiffness is much higher in the radial directions, notably in the vertical
and transverse directions. The chevron spring
26 has a stiffness which is higher than the hydro-mechanical converters
32, 34 in the vertical and transverse directions but lower in the longitudinal direction
200. As a result, the vertical primary suspension unit
24 is the main path for vertical loads and shares the transverse load with the hydro-mechanical
converters
32, 34, which form the main path for longitudinal loads.
[0034] Due to its geometry, and in particular to their large pumping area, the hydro-mechanical
converters
32, 34 have a stiffness, which significantly increases with the frequency of the applied
load, as become more apparent from the discussion below.
[0035] When the axial load varies at a very low frequency, the hydraulic fluid moves in
and out of the variable volume hydraulic chamber
42 through the hydraulic port
44 in phase with the motion of the plunger
38 relative to the housing
36. The static stiffness
Cstatic of the hydro-mechanical converter depends mainly on the geometry of the elastomeric
body
40 and decreases when the ratio of the radial dimension to the longitudinal dimension
of the elastomeric body
40 increases.
[0036] When the frequency of the longitudinal movement of the axle boxes
14 increases, the motion of the hydraulic fluid in and out of the hydraulic chambers
42 is increasingly out of phase with the relative motion between the plunger
38 and the housing
36. When the frequency is sufficiently high the hydraulic chambers
42 can be almost considered as closed chambers, since the movement of the fluid in and
out of the chambers becomes insignificant. The behaviour is dependent on the viscosity
of the fluid and the hydraulic circuit connecting the chambers, in particular the
length and diameter of the connecting pipes. Relative fore and aft movement between
the plunger and the housing is still possible despite the incompressible fluid in
the hydraulic chamber thanks to a dynamic swell deformation of the elastomeric body
40. The elastomeric body
40 is therefore characterised by a dynamic swell stiffness
Cswell which is added to the static stiffness
Cstatic at higher frequencies. This dynamic swell stiffness increases approximately linearly
with the effective pumping area
A of the hydro-mechanical converter, which is the ratio of the elementary variation
of volume Δ
V of the chamber to the corresponding elementary longitudinal relative movement Δ
x between the plunger and the housing:

[0037] In practice, the pumping area
A is greater than or equal to the effective area
Ae of the plunger, i.e. the area of the geometric projection of the surface of the plunger
within the housing on a plane
P perpendicular to the longitudinal direction. In other words, the greater the effective
area
Ae of the plunger, the greater the pumping area
A, the dynamic swell stiffness
Sswell and the ratio
R of the dynamic stiffness to the static stiffness of the longitudinal hydro-mechanical
converter
32, 34. As a rule of thumb, the effective area
Ae of the plunger should preferably be greater than half the area of the cross-section
AΦ of the wheel axle measured in a plane perpendicular to the rotation axis of the wheel
axle passing through a roller bearing of the axle box:

[0038] Thanks to the geometry of the arrangement of the hydro-mechanical converters on each
side of the wheel axle, the effective pumping area
A can be large, and the dynamic stiffness, will also be very large. Concurrently, the
static stiffness can be kept low, which leads to a high ratio of the dynamic stiffness
to the static stiffness, preferably of more than 10, preferably of more than 20, and
preferably more than 50.
[0039] Due to this high ratio of the dynamic stiffness to the static stiffness, the wheel
axle guiding assembly provides a smooth response to the various longitudinal loads
at low frequency and a stiffer response at higher frequency, which is particularly
advantageous. The wheel axle guiding assembly will respond with a very low stiffness
Cstatic to quasistatic longitudinal loads so that the wheel axle 30 will naturally rotate
about a vertical axis and find their position in a curve. The stroke of the longitudinal
hydro-mechanical converters
32, 34 is greater than with conventional elastomeric or hydro-elastic bushings, which ensures
a sufficient deflection of the wheel axle
30 in curves. In response to high frequency longitudinal vibrations, on the other hand,
the system will provide a high dynamic stiffness that includes the component
Cswell so as to efficiently counteract hunting oscillations and provide an excellent stability.
[0040] The cutoff frequency in the frequency response of the system depends not only on
the characteristic of the hydro-mechanical converters
32, 34 but also on the characteristics of the hydraulic circuit. Preferably, the cutoff
frequency should be less than 4Hz, ideally between 0,5Hz and 1,5Hz.
[0041] A wheel axle guiding assembly
10 for a running gear
12 of a rail vehicle according to a second embodiment of the invention is illustrated
in Figure
5. This wheel axle guiding assembly
10 comprises an axle box
14 located longitudinally between a front part
16 and a rear part
18 of a ring-shaped axle box carrier
20 formed by a C-shaped end portion of a frame
22 of the running gear and a C-shaped lower bracket
120. The axle box carrier
20 is supported on the axle box
14 by way of a vertical primary suspension unit
24, which comprises a sandwich spring
126 having a set of planar elastomeric elements extending in a horizontal plane.
[0042] A front longitudinal hydro-mechanical converter
32 is fixed to the axle box
14 and to the front part
16 of the axle box carrier
20 and a rear longitudinal hydro-mechanical converter
34 fixed to the axle box
14 and to the rear part
18 of the axle box carrier
20 to allow a fore-and-aft movement of the axle box
14 relative to the axle box carrier
20 parallel to the longitudinal direction
200 of the running gear
12. Each of the front and rear longitudinal hydro-mechanical converters
32, 34 includes a housing
36 fixed to or integral with the axle box
14, a plunger
38 fixed to or integral with the axle box carrier
20 and an annular elastomeric body
40 adhered by vulcanisation or otherwise fixed in a sealed manner to the housing
36 and to the plunger
38 so as to form a single variable volume hydraulic chamber
42 between the housing
36, the plunger
38 and the elastomeric body
40. In this embodiment, the interface between the annular elastomeric body and the plunger
is frustum-shaped and coaxial with the interface between the annular body and the
housing.
[0043] This arrangement results in a low stiffness of each longitudinal hydro-mechanical
converter
32, 34 in the longitudinal direction while the stiffness is much higher in the radial directions,
notably in the vertical and transverse directions. The sandwich spring
126 has a static stiffness, which is higher than the hydro-mechanical converters
32, 34 in the vertical directions but lower in the longitudinal and transverse directions.
As a result, the sandwich spring
126 is the main path for vertical loads while the hydro-mechanical converters
32, 34 form the main path for longitudinal and transverse loads. The response of the wheel
axle guiding assembly
10 of Figure
5 to static and dynamic longitudinal loads is essentially similar to that of the first
embodiment.
[0044] A wheel axle guiding assembly
10 for a running gear
12 of a rail vehicle according to a third embodiment of the invention is illustrated
in Figures
6 and
7. This wheel axle guiding assembly
10 comprises an axle box
14 located longitudinally between a front part
16 and a rear part
18 of an axle box carrier
20 formed by a ring-shaped frame element fixed to the frame
22 of the running gear
12. The axle box carrier
20 is supported on the axle box
14 by way of a vertical primary suspension unit
24, which comprises an upper elastomeric pad
226 and a lower elastomeric pad
227. A front longitudinal hydro-mechanical converter
32 is provided between the axle box
14 and the front part
16 of the axle box carrier
20 and a rear longitudinal hydro-mechanical converter
34 is provided between the axle box
14 and the rear part
18 of the axle box carrier
20 to allow a fore-and-aft movement of the axle box
14 relative to the axle box carrier
20 parallel to the longitudinal direction
200 of the running gear
12. Each of the front and rear longitudinal hydro-mechanical converters
32, 34 includes a housing
36 fixed to the axle box carrier
20 or integral with the axle box carrier
20, a plunger
38 integral with the axle box
14 and an annular elastomeric body
40 adhered by vulcanisation or otherwise fixed in a sealed manner to the housing
36 and to the plunger
38 so as to form a single variable volume hydraulic chamber
42 between the housing
36, the plunger
38 and the elastomeric body
40. In this embodiment, the interface
46, 48 between the annular elastomeric body
40 and the housing
36 and between the annular body
40 and the plunger
38 are tapered. An elastomeric buffer
338 forms an abutment between the plunger
38 and the housing
36 for limiting a contraction movement of the hydro-mechanical converter
32, 34. The response of the wheel axle guiding assembly of Figure
6 and
7 to static and dynamic longitudinal loads is essentially similar to that of the previous
embodiments.
[0045] The axle guiding assemblies of the various embodiments of Figures
1 to
7 are particularly adapted to a running gear with a flexible running gear frame that
will undergo deformation to respond to vertical load. The embodiment of Figure
8 is more adapted to a rigid running gear frame, which remains substantially without
deformation under the usual operative conditions. The axle guiding assembly
10 of Figure
8 differs from the axle guiding assembly of Figures
6 and
7 essentially in that the ring-shaped axle box carrier
20 is not rigidly fixed to the running gear frame
22. Instead, the running gear frame
22 bears on a pair of vertical primary suspension units
426, which consist in rubber springs that allow a substantial relative vertical movement
between the running gear frame
22 and the axle box carrier
20 and transmit the longitudinal and lateral loads without substantial deformations.
The upper and lower elastomeric pads
226, 227 between the axle box carrier
20 and the axle box
14 can be kept very stiff to substantially reduce the relative vertical and transverse
motion between the axle box carrier
20 and the axle box
14 and limit the deformation of the elastomeric body
40 of each of the front and read hydro-mechanical converters
32, 34 in directions perpendicular to the longitudinal direction
200. The response of the wheel axle guiding assembly
10 of Figure
8 to static and dynamic longitudinal loads is essentially similar to that of the previous
embodiments.
[0046] The axle box guiding assembly of Figure
9 derives from the embodiment of Figures
1 to
4 and differs from that embodiment in that an additional spring
526 is interposed between the axle box
14 and each of the longitudinal hydro-mechanical converter
32, 34. This additional decoupling spring
526 has vertical stiffness less than two times the vertical stiffness of the hydro-mechanical
converter
32, 34, a longitudinal stiffness at least ten times greater than the longitudinal stiffness
of the hydro-mechanical converter
32, 34 and a lateral stiffness less than two times than the lateral stiffness of the hydro-mechanical
converter
32, 34. The decoupling spring
526 can be an elastomer ring around a fixed volume hydraulic chamber
527 filled with hydraulic fluid.
[0047] The axle box guiding assembly of Figure
10 derives from the embodiment of Figures
9 and differs from that embodiment merely in that no fixed volume hydraulic chamber
is provided.
[0048] A running gear
12 including two pairs of wheel axle guiding assemblies according to the invention is
illustrated in Figure
10. In Figure
10, the vertical primary suspension units have been left out for simplicity. The running
gear
12 of Figure
11 is a bogie with a two-wheel sets
50, each comprising left and right wheels
51 at opposite ends
52 of a wheel axle
30. Each end
52 of each wheel axle
30 is guided for rotation in an axle box
14 of a wheel axle guiding assembly
10. The two wheel axle guiding assemblies
10 on the same left or right side of the running gear
12 are hydraulically connected with one another via four independent hydraulic circuits
54, 56. More specifically, the variable volume hydraulic chamber
42 of the front hydro-mechanic converters
32 of the front and rear wheel axle guiding assemblies
10 on the left side are connected with one another via a hydraulic circuit
54 and the variable volume hydraulic chamber
42 of the rear hydro-mechanic converters
34 of the front and rear wheel axle guiding assemblies
10 on the left side are connected with one another via a hydraulic circuit
56. Similar hydraulic connections are provided between the axle guiding assemblies
10 on the right side of the running gear
10. A hydraulic reservoir
58 is connected via a check valve
60 to each of the hydraulic circuits to provide a temperature and leakage compensation.
Preferably, each hydraulic reservoir
58, or more generally each hydraulic circuit
52, 54, is provided with a leakage detector
63. This type of hydraulic link between the front and rear axle will result in passive
steering of the front and rear axles
30 in opposite directions.
[0049] An alternative connection between the individual variable volume hydraulic chambers
42 is shown in Figure
12. The variable volume hydraulic chamber
42 of the front hydro-mechanic converters
32 of the front wheel axle guiding assembly
10 on each side is connected with the variable volume hydraulic chamber
42 of the rear hydro-mechanic converters
34 of the rear wheel axle guiding assembly
10 on the same side of the running gear
12 via a hydraulic circuit
64, while the variable volume hydraulic chamber
42 of the rear hydro-mechanic converters
34 of the front wheel axle guiding assembly
10 on each side is connected with the variable volume hydraulic chamber
42 of the front hydro-mechanic converters
32 of the rear wheel axle guiding assembly
10 on the same side of the running gear via a hydraulic circuit
66. This type of hydraulic link between the front and rear axle will result in passive
steering of the front and rear axles in the same direction.
[0050] An alternative connection between the individual variable volume hydraulic chambers
42 is shown in Figure
13. The variable volume hydraulic chamber
42 of the front hydro-mechanic converters
32 of the front wheel axle guiding assembly
10 on each side is connected with the variable volume hydraulic chamber
42 of the rear hydro-mechanic converters
34 of the rear wheel axle guiding assembly
10 on the other side of the running gear
12 via a hydraulic circuit
154, while the variable volume hydraulic chamber
42 of the rear hydro-mechanic converters
34 of the front wheel axle guiding assembly
10 on each side is connected with the variable volume hydraulic chamber
42 of the front hydro-mechanic converters
32 of the rear wheel axle guiding assembly
10 on the other side of the running gear via a hydraulic circuit
156. This type of hydraulic link between the front and rear axle will result in passive
steering of the front and rear axles in opposite directions.
[0051] It may be appropriate to provide the running gear with additional distribution valves
so as to switch configurations between two types of hydraulic circuits depending on
the revolution speed of one of the wheel axles, e.g. with the configuration of Figure
11 or Figure
13 at low speed and the configuration of Figure
12 at higher speed.
[0052] A wheel set
50 provided with two wheel axle guiding assemblies
10 according to the invention for guiding the two opposite ends
52 of a wheel axle
30 is illustrated in Figure
14. Two independent hydraulic circuits
68, 70 are formed, each to connect the variable volume hydraulic chamber
42 of the front hydro-mechanic converters
32 of one wheel axle guiding assembly
10 with the variable volume hydraulic chamber
42 of the rear hydro-mechanic converters
34 of the same wheel axle guiding assembly
10. A hydraulic reservoir
58 is provided in each of the hydraulic circuits
68, 70. This embodiment can be implemented in a one-axle running gear or in a two-axle bogie.
[0053] An alternative connection between the individual variable volume hydraulic chambers
42 is shown in Figure
15. Two independent hydraulic circuits
72, 74 are formed, one to connect the variable volume hydraulic chambers
42 of the front hydro-mechanic converters
32 of the left and right wheel axle guiding assemblies
10 with one another and another one to connect the variable volume hydraulic chamber
42 of the rear hydro-mechanic converters
32 of the left and right wheel axle guiding assemblies. A hydraulic reservoir
58 is provided in each of the hydraulic circuits
72, 74. This embodiment can be implemented in a one-axle running gear or in a two-axle bogie.
This embodiment is particularly advantageous as it combines a very low static stiffness
for rotation about the vertical axis with a limitation of translation movement of
the axle parallel to the longitudinal axis. This is particularly helpful to preserve
the steerability when the vehicle brakes or accelerates, the longitudinal forces being
transmitted with minimal longitudinal translation of the axle.
[0054] Moreover, this embodiment provides a fail-safe operating mode illustrated in Figure
16. If one of the hydraulic circuits leaks (in Figure
16, the hydraulic circuit
72) and there is not enough hydraulic fluid left in that circuit, the reservoir
58 of the other hydraulic circuit will provide additional fluid in that circuit to force
the wheel axle
30 towards the abutment position illustrated in Figure
16. In this position, the wheel set
50 will not be able to rotate about the vertical axis, but will remain in a stable position.
To this end, each reservoir
58 should preferably have a capacity superior to the volume of the respective hydraulic
circuit, i.e. in practice at least twice and preferably more than twice the volume
of the hydraulic chambers
42.
[0055] While the above examples illustrate preferred embodiments of the present invention
it is noted that various other arrangements can also be considered, in particular
combinations of features from different embodiments.
1. A wheel axle guiding assembly (10) comprising:
- an axle box (14) defining a horizontal revolution axis (100) and a longitudinal
horizontal direction (200) perpendicular to the revolution axis (100);
- an axle box carrier (20), the axle box (14) being located longitudinally between
a front part (16) and a rear part (18) of the axle box carrier (20); and
- a front longitudinal hydro-mechanical converter (32) fixed to the axle box (14)
and the front part (14) of the axle box carrier (20) and a rear longitudinal hydro-mechanical
converter (34) fixed to the axle box (14) and the rear part (18) of the axle box carrier
(20) to allow a fore-and-aft movement of the axle box (14) relative to the axle box
carrier (20) parallel to the longitudinal direction (200);
characterised in that each of the front and rear longitudinal hydro-mechanical converters (32, 34) includes
a housing (36), a plunger (38) and an elastomeric body (40) fixed to the housing (36)
and to the plunger (38) so as to allow a fore-and-aft relative movement parallel to
the longitudinal direction (200) between the plunger (38) and the housing (36), a
single variable volume hydraulic chamber (42) being formed between the housing (36),
the plunger (38) and the elastomeric body (40), each of the front and rear longitudinal
hydro-mechanical converters (32, 34) further including a hydraulic port (44) for connecting
the variable volume hydraulic chamber (42) to an external hydraulic circuit (54, 56,
64, 66, 68, 70, 72, 74).
2. The wheel axle guiding assembly of claim 1, wherein the axle box (14) houses a bearing
(28) having an inner diameter defining a cross-sectional area AΦ of an end (52) of a wheel axle (30) to be received in the bearing (28) and the plunger
has an effective area Ae measured in a plane perpendicular to the longitudinal direction (200), which is greater
than half the cross-sectional area AΦ, preferably greater than the cross-sectional area AΦ.
3. The wheel axle guiding assembly of any one of the preceding claims, wherein each of
the front and rear longitudinal hydro-mechanical converters (32, 34) has a longitudinal
stiffness, which increases with a frequency of the fore-and-aft movement of the axle
box (14) relative to the axle box carrier (20) from a quasistatic stiffness value
to a dynamic stiffness value, wherein the plunger (38) and the elastomeric body (40)
have dimensions such that a ratio R of the dynamic stiffness value to the quasistatic
stiffness value is greater than 10, preferably greater than 20, preferably greater
than 50.
4. The wheel axle guiding assembly of any one of the preceding claims, further comprising
a vertical suspension unit (24) provided between the axle box (14) and an upper part
of the axle box carrier (20).
5. The wheel axle guiding assembly of any one of the preceding claims, wherein each of
the front and rear longitudinal hydro-mechanical converters (32, 34) further comprises
a decoupling spring (526) with a longitudinal stiffness at least ten times, preferably
at least twenty times, preferably fifty times greater than a longitudinal stiffness
of the elastomeric body (40), a lateral stiffness less than a two times the lateral
stiffness of the elastomeric body (40), preferably less that the lateral stiffness
of the elastomeric body (40) and a vertical stiffness less than two times the vertical
stiffness of the elastomeric body (40), preferably less than the vertical stiffness
of the elastomeric body (40).
6. The wheel axle guiding assembly of any one of the preceding claims, wherein the axle
box carrier (20) forms a ring around the axle box.
7. The wheel axle guiding assembly of any one of claims 1 to 6, further comprising a
vertical suspension assembly (426) for connecting the axle box carrier (20) to a running
gear frame (22).
8. The wheel axle guiding assembly of any one of claims 1 to 6, wherein the axle box
carrier (20) is a constituent portion of a running gear frame (22) of a running gear
(12).
9. The wheel axle guiding assembly of claim 8, wherein the running gear frame (22) is
flexible.
10. The wheel axle guiding assembly of any one of the preceding claims, further comprising
a hydraulic reservoir (58) hydraulically connected to the hydraulic chamber (42),
preferably with a check valve allowing a flow a fluid only from the hydraulic reservoir
(58) to the hydraulic chamber (42), preferably with a volume at least twice the volume
of the hydraulic chamber (42).
11. A running gear (12) for a rail vehicle, comprising at least a pair of wheel axle guiding
assemblies (10) according to any one of the preceding claims, a first hydraulic circuit
(54, 64, 68, 72) for establishing a hydraulic connection between a first variable
volume hydraulic chamber (42) and a second variable volume hydraulic chamber (42),
and a second hydraulic circuit (56, 66, 70, 74) for establishing a hydraulic connection
between a third variable volume hydraulic chamber (42) and a fourth variable volume
hydraulic chamber (42), the first, second, third and fourth variable volume hydraulic
chambers (42) being all different chambers and each of the first, second, third and
fourth variable volume hydraulic chambers being the variable volume hydraulic chamber
(42) of one of the front and rear longitudinal hydro-mechanical converters (32, 34)
of one of the wheel axle guiding assemblies (10) of the pair of wheel axle guiding
assemblies (10).
12. The running gear of claim 11, wherein the first hydraulic circuit (54, 64, 68, 72)
establishes a hydraulic connection between the variable volume hydraulic chamber (42)
of the front longitudinal hydro-mechanical converter (32) of one of the wheel axle
guiding assemblies (10) of the pair of the wheel axle guiding assemblies (10) and
the variable volume hydraulic chamber (42) of the front longitudinal hydro-mechanical
converter (32) of the other of the wheel axle guiding assemblies (10) of the pair
of the wheel axle guiding assemblies (10) and second hydraulic circuit (56, 66, 70,
74) establishes a hydraulic connection between the variable volume hydraulic chamber
(42) of the rear longitudinal hydro-mechanical converter (34) of one of the wheel
axle guiding assemblies (10) of the pair of the wheel axle guiding assemblies (10)
and the variable volume hydraulic chamber (42) of the rear longitudinal hydro-mechanical
converter (34) of the other of the wheel axle guiding assemblies (34) of the pair
of the wheel axle guiding assemblies (34).
13. The running gear of any one of claims 11 to 12, further comprising at least a front
wheel set (50) and a rear wheel set (50), wherein an end (52) of the front wheel set
(50) is supported by the axle box (14) of a front wheel axle guiding assembly (10)
of the pair of wheel axle guiding assemblies (10), and an end (52) of the rear wheel
set (50) is supported by the axle box (14) of a rear wheel axle guiding assembly (10)
of the pair of wheel axle guiding assemblies (10).
14. The running gear of any one of claims 11 to 12, further comprising at least one wheel
set (50), wherein a left end (52) of the wheel set (50) is supported by the axle box
(14) of a left wheel axle guiding assembly (10) of the pair of wheel axle guiding
assemblies (10), and a right end (52) of the wheel set (50) is supported by the axle
box (14) of a right wheel axle guiding assembly (10) of the pair of wheel axle guiding
assemblies (10).
15. The running gear of any one of claims 11 to 14, wherein the running gear does not
include any hydraulic connection between the chamber (42) of the front longitudinal
hydro-mechanical converter (32) and the chamber (42) of the rear longitudinal hydro-mechanical
converter (32) of the same wheel axle guiding assembly (10).