Patent Application
20200216101
The present invention relates to a running gear with independent wheels for a rail vehicle.
Running gears for rail vehicle include running gears with wheelsets, i.e. pairs of wheels attached to a common axle, which rotate together with the axle, and running gears with independent wheels, i.e. wheels that rotate independently from one another.
Both types of running gears have different advantages and drawbacks. Running gears with wheelsets are subject to hunting oscillations, i.e. swaying motion of the running gear caused by the coning action on which the directional stability of an adhesion railway depends. Various strategies can be developed to counteract such undesired oscillation, including steering, as disclosed e.g. in EP 1 193 154 A1.
The hunting oscillations depend on both wheels of a wheelset rotating at the same angular speed. Therefore, running gears with independent wheels are not subject to hunting oscillations. Despite this absence of hunting oscillations, it has been proposed in EP 1 063 143 A1 to counteract the yaw oscillations of a powered running gear provided with two independent left and right wheels supported by a common frame by means of a passive centring mechanism combined with an adapted control of the independent motors that power the left and right wheels. Running gears with independent wheels, however, are subject to another type of uncontrolled positioning relative to the track, which is not counterbalanced by a passive centring system: more specifically, in certain situations on a straight track, the flange of the wheel on one side of the running gear may contact the head of the rail and stay in contact for a substantial period of time while the running gear is running, which results in undesired differential wear of the wheels on the left and right side of the running gear.
The invention aims to provide means for minimising the differential wear of wheel flanges on a running gear provided with independent wheels.
According to a first aspect of the invention, there is provided a running gear for a rail vehicle, comprising first and second independent wheel assemblies on opposite first and second sides of a longitudinal vertical median plane of the running gear, each of the first and second independent wheel assemblies comprising an independent wheel and a bearing assembly for guiding the independent wheel about a revolution axis fixed relative to the bearing assembly, wherein in a reference position of the running gear, the revolution axis of the first independent wheel assembly and the revolution axis of the second independent wheel assembly are coaxial and are perpendicular to the longitudinal vertical median plane, characterised in that the running gear further comprises one or more steering actuators for moving the bearing assembly of at least one of the two independent first and second wheel assemblies away from the reference position in a longitudinal direction parallel to the longitudinal vertical median plane, a wheel flange contact detection unit for detecting a contact between a flange of the independent wheel of any of the two independent first and second wheel assemblies with a rail, and a controller for controlling the one or more steering actuators based on signals from the wheel flange contact detection unit.
Thanks to the wheel flange contact detection unit and controller, appropriate actions can be taken to minimise the contact between the wheel flange and the rail, irrespective of whether the wheels are powered or not.
According to a preferred embodiment, the controller is such that whenever a contact between a flange of the independent wheel of a given one of the two independent first and second wheel assemblies is detected while the running gear is running in a running direction, the controller controls the one or more steering actuators to the effect that:
Preferably, the controller comprises means for determining the running direction of the running gear. This simple strategy proves efficient to move the flange of the affected wheel away from the rail head. The controller may include a running direction detector for detecting in which direction the running gear is running.
According to a preferred embodiment, the wheel flange contact detection unit comprises one or more of the following sensors:
In practice, the processing of the output signals from the one or more sensors may include one or more of the following:
According to a preferred embodiment, the wheel flange contact detection unit comprises at least a first sensor for detecting a physical parameter of the first independent wheel assembly, a second sensor for detecting a physical parameter of the second independent wheel assembly and a comparator for delivering a flange contact detection signal based on a comparison between signals from the first sensor and second sensor. Comparing measurements on the first independent wheel assembly and second independent wheel assembly helps discriminate the wheel flange contact from artefacts. The comparison may advantageously take place after the output signals from the sensors have been pre-processed. As an example, if the sensors are transverse accelerometers on the first and second bearing assemblies, the output signals of the accelerometers are processed through a low pass filter and an RMS value is computed for each side before the RMS values are compared. A wheel flange contact is detected if the absolute value of the difference between the two RMS values is above a predetermined threshold. The sign of the algebraic difference between the two RMS values defines which of the two sides is subject to wheel flange contact.
According to one embodiment, the bearing assembly of the first independent wheel assembly and the bearing assembly of the first independent wheel assembly are linked by a flexible frame of the running gear. Preferably, the one or more steering actuators are connected to the flexible frame.
According to one embodiment, the flexible frame comprises one or more transverse beams linking to one another the first and second independent wheel assemblies and located below the revolution axes of the first and second independent wheel assemblies in the reference position. Preferably, the wheel flange contact detection unit comprises a first transverse accelerometer for detecting a transverse acceleration of the bearing assembly of the first independent wheel assembly in a first transverse direction parallel to the revolution axis of the first independent wheel assembly, and a second transverse accelerometer for detecting a transverse acceleration of the bearing assembly of the second independent wheel assembly in a second transverse direction parallel to the revolution axis of the second independent wheel assembly.
According to a preferred embodiment, the first transverse accelerometer is located above the revolution axis of the first independent wheel assembly and the second transverse accelerometer is located above the revolution axis of the second independent wheel assembly. This configuration takes advantage from the fact that the flexibility of the flexible frame results in different transverse accelerations on the first and second hand side of the longitudinal vertical median plane of the running gear.
According to another aspect of the invention, there is provided a running gear for a rail vehicle, comprising first and second independent wheel assemblies on opposite first and second sides of a longitudinal vertical median plane of the running gear, each of the first and second independent wheel assemblies comprising an independent wheel and a bearing assembly for guiding the independent wheel about a revolution axis fixed relative to the bearing assembly, wherein in a reference position of the running gear, the revolution axis of the first independent wheel assembly and the revolution axis of the second independent wheel assembly are coaxial and are perpendicular to the longitudinal vertical median plane, characterised in that the running gear further comprises a flexible frame that links the bearing assembly of the first independent wheel assembly and the bearing assembly of the first independent wheel assembly.
By “flexible frame”, what is meant is a frame that will actually elastically deform in standard operational conditions. The flexible frame may comprise one or more transverse beams linking to one another the first and second independent wheel assemblies and located below the revolution axes of the first and second independent wheel assemblies in the reference position.
A main normal mode of deformation of the structure is characterised by a bending deformation of the transverse beams, in particular in a vertical plane.
The wheel flange contact detection unit preferably comprises a first transverse accelerometer for detecting a transverse acceleration of the bearing assembly of the first independent wheel assembly in a first transverse direction parallel to the revolution axis of the first independent wheel assembly, and a second transverse accelerometer for detecting a transverse acceleration of the bearing assembly of the second independent wheel assembly in a second transverse direction parallel to the revolution axis of the second independent wheel assembly.
The first transverse accelerometer is preferably located above the revolution axis of the first independent wheel assembly and the second transverse accelerometer is located above the revolution axis of the second independent wheel assembly.
According to a preferred embodiment, the running gear further comprises a wheel flange contact detection unit for detecting a contact between a flange of the independent wheel of any of the two independent first and second wheel assemblies with a rail, wherein the wheel flange contact detection unit comprises at least a first sensor for detecting a physical parameter of the first independent wheel assembly, a second sensor for detecting a physical parameter of the second independent wheel assembly and a comparator for delivering a flange contact detection signal based on a comparison between signals from the first sensor and second sensor.
According to a preferred embodiment, the running gear further comprises one or more steering actuators for moving the bearing assembly of at least one of the two independent first and second wheel assemblies away from the reference position in a longitudinal direction parallel to the longitudinal vertical median plane.
According to a preferred embodiment, the running gear further comprises a controller for controlling the one or more steering actuators based on signals from the wheel flange contact detection unit.
According to another aspect of the invention, there is provided a rail vehicle comprising a vehicle body and one or more running gears according to any one of the preceding claims, wherein the one or more steering actuator are linked to the vehicle body.
Preferably, the rail vehicle is a low floor light rail vehicle. Accordingly, part of the vehicle body is located below an upper end of the wheel of the first and second wheel assemblies.
According to another aspect of the invention, there is provided a control method for controlling a running gear of a rail vehicle, the running gear comprising first and second independent wheel assemblies on opposite first and second sides of a longitudinal vertical median plane of the running gear, each of the first and second independent wheel assemblies comprising an independent wheel and a bearing assembly for guiding the independent wheel about a revolution axis fixed relative to the bearing assembly, wherein in a reference position of the running gear, the revolution axis of the first independent wheel assembly and the revolution axis of the second independent wheel assembly are coaxial and are perpendicular to the longitudinal vertical median plane, the method comprising the following steps:
Advantageously, the running gear runs in a running direction, and the step of moving the bearing assembly of at least one of the two independent first and second wheel assemblies away from the reference position in a longitudinal direction parallel to the longitudinal vertical median plane based on a result of said detection step comprises, whenever a contact between a flange of the independent wheel of a given one of the two independent first and second wheel assemblies is detected while the running gear is running in a running direction, at least one of the following two steps:
The method may include a step of detecting the predetermined running direction.
According to a preferred embodiment, detecting a contact between a flange of the independent wheel of any of the two first and second independent wheel assemblies with a rail comprises detecting a physical parameter of the first independent wheel assembly, detecting a physical parameter of the second independent wheel assembly and issuing an output signal based on a comparison between the detected physical parameter of the first independent wheel assembly and the detected physical parameter of the second independent wheel assembly.
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:
Corresponding reference numerals refer to the same or corresponding parts in each of the figures.
A portion of a low floor light rail vehicle 10 illustrated in
The running gear 14 comprises a light rectangular cast frame 16 on which first and second independent wheel assemblies 18.1, 18.2 are mounted on opposite first and second (left and right) sides of the longitudinal vertical median plane 100 of the running gear 14. Each of the first and second independent wheel assemblies 18.1, 18.2 comprises a wheel 20.1, 20.2 and a bearing assembly 22.1, 22.2 for guiding the independent wheel 20.1, 20.2 about a revolution axis 200.1, 200.2 fixed relative to the bearing assembly 22.1, 22.2. The cast frame 16 consists of two parallel bendable transverse beams 24, 26 and two short first and second longitudinal beams 28.1, 28.2 which are integral with a fixed part of the respective bearing assembly 22.1, 22.2. The transverse beams 24, 26 have a stiffness which allows elastic deformations in the standard operational conditions of the running gear 14. The main normal mode of deformation of the structure is characterised by a bending deformation of the transverse beams 24, 26, in particular in a vertical plane. In a reference position of the running gear 14, the revolution axes 200.1, 200.2 of the two wheel assemblies 18.1, 18.2 are coaxial and perpendicular to the vertical median longitudinal reference plane 100 of the running gear 14. In the reference position, the two revolution axes 200.1, 200.2 are above the transverse beams 24, 26. More specifically, the two revolution axes 200.1, 200.2 are parallel to and at a distance above a horizontal plane containing the neutral axes of the two transverse beams 24, 26. This arrangement is somewhat similar to a dropped axle arrangement in an automotive vehicle and provides the advantage of lowering the floor of the vehicle body 12 without decreasing the diameter of the wheels 20.1, 20.2.
The vehicle body 12 is connected to the frame 16 by means of a vertical suspension including vertical springs 30, which have been depicted as coil springs but could alternatively be air springs or any suitable type of vertical suspension elements.
The frame 16 is further linked to the vehicle body 16 by means of a bidirectional steering actuator 32 on one side of the frame 16 and of a connecting rod 34 on the other side.
The expression “steering actuator” in this context designates any kind of actuator that is capable of effecting a displacement of the corresponding part of the frame 16 in the longitudinal direction of the running gear 14. The steering actuator 32 itself can be a hydraulic cylinder, which can be oriented in the longitudinal direction as illustrated in
As will be readily understood, a displacement of the side of the frame linked to the steering actuator 32 in the longitudinal direction of the running gear 14 results in a pivot movement of the whole frame 16 and of the running gear 14 about an imaginary instantaneous vertical pivot axis defined by the connecting rod connection on the opposite side of the frame 16.
The running gear 14 is instrumented with a pair of accelerometers 36.1, 36.2 connected to a processing unit 38. Each accelerometer 36.1, 36.2 is fixed to one of the bearing assemblies 22.1, 22.2 or longitudinal beams 28.1, 28.2 and positioned as far as possible from the horizontal plane containing the neutral axes of the transverse beams 24, 26. Each accelerometer 36.1, 36.2 is oriented to measure the transverse acceleration, i.e. the acceleration in a direction parallel to the revolution axis 200.1, respectively 200.2 of the associated wheel. Due to the elasticity of the running gear frame 16, the accelerations measured by the two accelerometers 36.1, 36.2 differ and the information delivered by each accelerometer signal reflects primarily the acceleration of the associated wheel 20.1, 20.2 in the direction of its revolution axis 200.1, 200.2.
The processing unit 38 comprises a wheel flange contact detection unit 40 for detecting a contact between a flange of the wheel 20.1, 20.2 of any of the first and second independent wheel assemblies 18.1, 18.2 with the corresponding rail 15.1, 15.2, and a controller 42 for controlling the one or more steering actuators 32 based on signals from the wheel flange contact detection unit 40.
As illustrated in the flow chart of
The controller 42 is programmed to control the bidirectional steering actuator 32 based on the output of the wheel flange contact detection unit 40 and on the running direction of the rail vehicle, which can be detected locally e.g. with a rotation sensor 58 housed in one of the bearing assemblies, or obtained from another source on the vehicle. The input signal for the running direction can be either “+1” or “−1”, e.g. “+1” if the left side in the running direction coincides with the first side of the running gear 14 and “−1” if the left side in the running direction coincides with the second side of the running gear 14.
If the output of the wheel flange contact detection 40 unit is “0”, no action is taken, i.e. the steering actuator does not change the position of the running gear frame. If the output of the wheel flange contact detection unit 40 is “+1” (contact of the flange of the first wheel with the rail) or “−1” (contact of the flange of the second wheel with the rail), the controller 42 will control the steering actuator 32 to effect an incremental displacement of the running gear frame 16, so to either move forward in the running direction the wheel 20.1, 20.2 on which the contact has been detected or move the opposite wheel 20.1, 20.2 in the rearward direction, i.e. in the direction opposed to the running direction. In both cases, this results in a pivotal movement of the frame 16 about an imaginary instantaneous vertical axis defined by hinged connection of the connecting rod 34 in one and the same rotation direction.
Let us assume that the connecting rod 34 is located on the second side of the running gear frame 16 and that this first side of the running gear corresponds the right side in the running direction of the running gear. If the output of the wheel flange contact detection unit is “+1”, i.e. if a flange contact has been detected on the first wheel, (i.e. left wheel in the running direction), the steering actuator will be controlled to move the first wheel in the running direction by a given increment, which has been identified as “+1” in the third column of Table 1 below. This results in an incremental clockwise rotation of the running gear with respect to the vehicle body about an imaginary instantaneous vertical axis of the connecting rod 34 in
This process is iterated at the sampling rate of the wheel flange contact detection unit 40. As will be readily understood, moving the wheel flange that is in contact with the rail 15.1, 15.2 in the running direction relative to the opposite wheel and to the vehicle body taken as a reference reduces the contact force between the wheel flange and the rail and in the end moves the flange away from the rail.
Depending on the type of steering actuator, the controlled physical parameter can be a force, a pressure or a displacement. If the controlled parameter is a force or a pressure, the corresponding displacement increment will vary depending on the running conditions. According to one non-limitative example, the control physical parameter is a force and each increment is of 200 N for a sampling rate of 2 Hz.
As a variant, the connecting rod 34 can be replaced with a second steering actuator which operates with the same magnitude as the first steering actuator but in the opposite direction. As a result, the running gear frame 18 pivots about an imaginary pivot axis, which is located in the median vertical longitudinal plane 100.
The wheel flange contact detection unit 40 for detecting a contact between a flange of the wheel 20.1, 20.2 of any of the two independent first and second wheel assemblies 18.1, 18.2 with a rail 15.1, 15.2 may comprise a couple of axial load cells linked to the wheel axles or bearing assemblies of the first and second wheel assemblies, to measure an axial load on each wheel parallel to the revolution axis of the wheel. Such axial load cells may be integrated into a rolling bearing of the bearing assembly. Rolling bearings with axial force sensors are well known in the art, see e.g. DE 10 2011 085 711 A1, US 2014/0086517, DE 42 18 949.
In
| Number | Date | Country | Kind |
|---|---|---|---|
| 1715373.5 | Sep 2017 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2018/075645 | 9/21/2018 | WO | 00 |
