Patent Publication Number: US-8534200-B2

Title: Suspension apparatus and method

Description:
FIELD OF THE INVENTION 
     Embodiments of the invention relate to rail vehicles. Other embodiments relate to wheel trucks for rail vehicles and to motor suspensions for rail vehicle wheel trucks. 
     BACKGROUND OF THE INVENTION 
     A high-speed train car or locomotive may be supported on two trucks or bogies, each truck or bogie having two or more powered and/or non-powered axles carrying wheels. Each powered axle is driven by a motor through a gear train that includes a pinion gear driven by the traction motor shaft and driving a bull gear mounted on the axle. By way of example, a truck or bogie for use on a diesel-electric rail vehicle includes a frame, an axle mounted on the frame by journal bearings, wheels on the axle, a bull gear on the axle, and a motor and pinion gear attached to the frame. The pinion gear is operably coupled to the bull gear for the traction motor to move the pinion and thereby the bull gear, axle, and wheels. Such a system can result in disadvantageously high forces on the underlying track, due to inertia of “unsprung” mass. 
     To explain further, mass supported directly on an axle (i.e., not through a vehicle&#39;s primary suspension) is known as “unsprung” mass. In operation of high-speed rail systems, the presence of unsprung mass can induce low frequency dynamic forces at the interface of each wheel with the rail. These low-frequency dynamic forces at the wheel-rail interfaces can cause degradation of track geometry. 
     It is known that track maintenance is the largest expense for operation of a rail corridor. Thus, it is desirable to reduce the unsprung mass of each truck or bogie on a high-speed rail car or locomotive, so as to mitigate the expense of track maintenance. 
     Unsprung mass may be reduced by supporting the traction motor and/or the gear train of each axle from the truck frame, rather than directly from the axle. For example, leaf springs may be used to support the traction motor with swaying or surging motions relative to the truck frame. However, supporting a motor and/or gearbox from the truck frame (a “suspended motor” configuration) can have the undesirable effect, during operation of the high-speed rail system, of producing relatively large displacements between the traction motor shaft and the axle as compared to conventional trucks or bogies having axle-mounted motors and gearboxes. These large displacements detract from dynamic stability and track-following of the rail vehicle, thereby limiting the achievable speed. The large displacements also increase mechanical stress and wear on power train components, in turn reducing the mean-time-between-failures (MTBF) and maintenance life span for suspended motor configurations, relative to conventional truck frame configurations. 
     In view of the above, a need exists for relatively simple apparatus that will effectively reduce unsprung mass on a high-speed rail truck, while also mitigating displacements between a motor shaft and a power axle driven from the traction motor shaft. 
     BRIEF DESCRIPTION OF THE INVENTION 
     Embodiments of the invention relate to various configurations for suspending a traction motor from a high-speed or other rail vehicle truck frame. 
     In some embodiments of the invention, the traction motor is suspended by an apparatus that includes a suspension linkage connected between the traction motor and the truck frame at least at first and second locations. The suspension linkage includes at the first location a first pin pivotally connecting the traction motor with the truck frame, and includes at the second location at least one elastomeric element deformable to provide displacement and torsion within limited ranges, such that the traction motor is fully suspended from the truck frame. 
     In some embodiments of the invention, the traction motor is suspended from the truck frame by an apparatus that includes a pivotal connection of the traction motor to a cross member of the truck frame, and a spring connected between the traction motor and the truck frame. The spring provides displacement and torsion within limited ranges, such that the traction motor is fully suspended from the truck. 
     In one aspect of the invention, dynamic loading of high-speed or other rail systems is mitigated by fully suspending a traction motor from a rail vehicle truck frame. 
     In some embodiments of the invention, a suspension apparatus includes a rail vehicle truck frame, which has a cross member, a first side member connected to a first end of the cross member and perpendicular thereto, and a second side member connected to a second end of the cross member and perpendicular thereto. The suspension apparatus also includes a traction motor connected to the cross member of the truck frame by way of a pivot, such that a long axis of the traction motor can move relative to a long axis of the cross member while remaining parallel thereto. The suspension apparatus also includes a biasing assembly operably engaged between the traction motor and the truck frame, and deformable to fully suspend the traction motor about the pivot. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be better understood from reading the following description of non-limiting embodiments, with reference to the attached drawings, wherein below: 
         FIG. 1  shows a top perspective view of a rail truck. 
         FIG. 2  shows a bottom perspective view of a rail truck with a motor suspended according to a first embodiment of the claimed invention. 
         FIG. 3  shows a detail view of the motor suspension according to the first embodiment of the present invention. 
         FIG. 4  shows a detail view of a motor suspension, according to a second embodiment of the present invention. 
         FIG. 5  shows a detail view of a motor suspension, according to a third embodiment of the present invention. 
         FIG. 6  shows a detail view of a motor suspension, according to a fourth embodiment of the present invention. 
         FIG. 7  shows a detail view of a motor suspension, according to a fifth embodiment of the present invention. 
         FIG. 8  shows a side view of an S-spring usable in either embodiment shown in  FIG. 6  or  FIG. 7 . 
         FIG. 9  shows in perspective view the traction motor suspension shown in  FIG. 4 . 
         FIG. 10  shows in perspective view the traction motor suspension shown in  FIG. 5 . 
         FIG. 11  shows in perspective view the traction motor suspension shown in  FIG. 6 . 
         FIG. 12  shows in perspective view the traction motor suspension shown in  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the present invention relate to motor suspension assemblies for rail vehicle trucks/bogies, which may be suitable for high-speed rail applications. Reference will be made below in detail to exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numerals used throughout the drawings refer to the same or like parts. However, the use of the same reference numerals for the same or like parts does not mean a particular embodiment has to have those parts. 
     Referring to  FIGS. 1-3 , in a first embodiment of the invention, a rail truck frame  100  (e.g., suitable for use in a high-speed rail vehicle) has two side members  102  that are connected at their midpoints by a transverse beam or cross member  104  (e.g., cross member may be a central cross member) and at their ends by two end members  106  to form a “B” shaped truck configuration. In other embodiments the end members may be omitted to provide an “H” shaped truck. The truck frame is supported by wheels  108  that are carried on at least one power axle  110  that extends orthogonally to, and between, the two side members  102 . The power axle is suspended from the side members on axle suspensions  111 . Thus, the side members and the cross member are “sprung” mass within the dynamic system of the truck frame  100 . The power axle  110  is driven from a traction motor  112  via a gearbox  114 . The traction motor  112  is hung from the truck frame by a motor suspension  115 . Thus, relative to the wheels  108 , the traction motor  112  also is “sprung” mass. The gearbox  114  is supported at least on the power axle  110  and is connected with the traction motor  112  via a coupling  116  that is capable of carrying transverse loading and accommodating angular deflections between the gearbox and the traction motor. The coupling  116  may, for example, be a quill shaft coupling. 
     In operation, the wheels  108  rest on a track or rail (not shown) disposed beneath the truck, which supports a rail vehicle platform, e.g., frame of a rail car or other unpowered rail vehicle, or a frame of a locomotive or other powered rail vehicle. In the embodiment shown in  FIGS. 1-3 , the truck includes coil springs  118  for elastically supporting the rail vehicle platform, as well as a traction pin assembly  120  for receiving a traction pin protruding downward from the rail vehicle platform. One of ordinary skill will appreciate that the invention is not limited to any specific method of connecting the truck frame to the rail vehicle platform. 
     Referring specifically to  FIG. 2 , each axle suspension  111  includes a hub box or journal box  122  that supports an end of the associated power axle  110 . Each hub box  122  is operably connected with the cross member  104  via a wishbone  124 , and is operably connected with the side member  102  via a pair of coil springs  126 . The wishbone  124  resists deflection of the hub box  122  along or transverse to the side member  102 , as well as torsion of the hub box around the wishbone. The coil springs  126  resist deflection of the hub box toward or away from the side member  102 , as well as torsion of the hub box orthogonal to the wishbone  124 . Thus the truck frame  100  is “fully” sprung or suspended in six axes or degrees of freedom (DOF) relative to each hub box  122 . 
     Referring to  FIG. 3 , each motor suspension  115  includes an upper pivot  135  that is formed by one or more upper brackets  136  rigidly fastened to the transverse beam  104 , a pivot pin  138  that is inserted through the upper brackets, and one or more motor brackets  140  through which the pivot pin also is inserted. The upper pivot  135  can also include one or more elastomeric sleeves or bushings  144  that surround the pivot pin as restoring elements where the pin passes through one or more of the brackets. “Elastomeric” is meant to include any natural or synthetic polymer exhibiting toughness, elastic deformation, and hysteresis in compression and tension, such as, by way of example, EPDM, TPR, latex, silicone rubber, and similar extant or after-developed compounds. 
     Each motor suspension  115  also includes a lower link  146 , which is connected between a first elastomeric bushing  148  mounted on a pivot of the traction motor  112  and a second elastomeric bushing  150  mounted on a pivot of the cross member  104 . The lower link is horizontally disposed for absorbing sway, torsion, and lengthwise displacement of the traction motor  112  within limited ranges relative to the truck. In other words, in consideration of the loads exerted by the motor under design conditions of rail vehicle speed and track layout, the lower link  146  acts as a rigid member restricting, for example, pivotal movement of the traction motor  112 . The bushings are operably engaged between the lower link  146  and the cross member  104  so as to cushion displacement of the traction motor  112  relative to the pivot  135  and the truck frame  100 . 
     In certain embodiments, elastomeric elements (e.g., elastomeric bushings  148 ) are characterized as being deformable to provide displacement and torsion within limited ranges, or providing limited torsion and cocking, or the like. In such cases, “limited” means a range of motion as defined by the elastomeric properties of the elastomeric bushing or other element, such as the maximum amount the elastomeric element can deform under force. 
     The embodiment shown in  FIG. 3  provides for full suspension of the traction motor  112  relative to the wheels  108  and relative to the side member  102 . This embodiment also is usable on an “H” frame lacking end members  106 , as the traction motor  112  is hung only from the cross member  104 . Referring back to  FIGS. 1 and 2 , for each traction motor the upper brackets  136  and the lower bushings  148 ,  150  are offset from a longitudinal midline of the truck frame  100 , such that the cross member  104  can act as a torsion spring between the respective motors. 
     According to a second embodiment of the present invention, as shown in  FIG. 4 , the traction motor  112  can be hung from the cross member  104  via a suspension  415 . The suspension  415  includes an upper pivot  135  that connects the traction motor to the cross member  104 , and also includes one or more four bar linkages  451  that connect the traction motor to the cross member. Each of the four bar linkages  451  includes links  446  that are pivotally connected at first ends to elastomeric bushings  450  mounted on pins  453  protruding from the cross member, and at second ends by pins  455  to elastomeric bushings  454  mounted in a heavy link  452 , which in this embodiment is the long movable bar of the parallelogram linkage. The pins  453  and  455  collectively provide a set of second pins in addition to the pin within the upper pivot  135 . As shown, the heavy link  452  may include left and right legs  452   a ,  452   b  as well as a head bracket  452   c  for receiving the elastomeric bushing  448 . 
     The heavy link is pivotally connected, at an end distal from the cross member  104 , to another elastomeric bushing  448  that is mounted on a lower pivot of the traction motor. The links  446  are vertically disposed so that the various bushings act as restoring elements for absorbing sway, torsion, cocking, and vertical displacement of the traction motor within limited ranges relative to the truck. Again, this second embodiment is usable either on an “H” frame or on a “B” frame.  FIG. 9  shows that, in one embodiment, the links  446  in the four bar linkage  451  are arranged such that the bushings  448 ,  450 ,  454  together can act as a biasing assembly for restraining oscillation of the traction motor  112  about a vertical axis through the cross member  104 . 
     Referring to  FIG. 5 , in a suspension apparatus  515  according to a third embodiment of the present invention, the traction motor  112  is hung from the cross member  104  via an upper pivot  135 . The traction motor  112  also is connected to the cross member via a coil spring piston assembly  555  that is mounted under the cross member. The coil spring piston assembly houses a spring  556  that engages a piston disc  558  mounted on a hollow shaft  560 . The hollow shaft is rigidly connected with a lower bracket  548  mounted to the traction motor  112 . Thus, the spring  556  may act together with the hollow shaft and the lower bracket as a biasing assembly to absorb and resist displacement of the traction motor about the upper pivot  135 . Adjacent to the lower bracket, an air spring  561  provides additional resistance to swaying motions of the traction motor. Referring to  FIG. 10 , the piston assembly  555  for each of the traction motors  112  is horizontally offset from the other across a longitudinal midline of the truck frame  100 . 
     In a suspension apparatus  615  according to a fourth embodiment of the invention, as shown in  FIG. 6 , the traction motor  112  is hung from the cross member  104  by an upper pivot  135  and also is sprung from the cross member  104  via an S-spring  662  (further discussed below with reference to  FIG. 8 ). The S-spring is mounted to the traction motor via a bracket  648  and is mounted to the cross member via a bracket  650 . The S-spring strongly resists vertical displacement of the traction motor, and provides for limited displacement of the traction motor along the truck as well as torsion and sway of the traction motor around the upper pivot. As shown in  FIG. 11 , the S-spring  662  corresponding to each of two motors  112  is horizontally offset from the other S-spring. 
       FIG. 7  shows a suspension apparatus  715  according to a fifth embodiment of the invention, wherein the traction motor is hung from the cross member  104  via an upper pivot  135  and also is hung from one of the end members  106  via an S-spring  662 . In this embodiment, the S-spring is mounted directly to the end member and is mounted to the traction motor via a bracket  648  and a beam  748 .  FIG. 12  shows that the traction motors  112  may be horizontally offset from each other across the truck frame  100 . 
     Referring to  FIG. 8 , an S-spring  662  includes laminated and interbonded layers of elastomer  866 , metal  868 , and bondant resin  870 . In some embodiments the elastomer layers  866  include silicone rubber, for example, room temperature vulcanized (RTV) silicone. In other embodiments the elastomer layers include latex. In some embodiments the metal layers  868  include steel, for example, mild sheet steel. In some embodiments the bondant resin layers  870  include epoxy (polyepoxide). In some embodiments the layers  866 ,  868 ,  870  can be laminated together as a flat structure, then bent to form the S-spring  662 ; in other embodiments, the metal layers  868  are bent together, separated, and then laminated with the relatively flexible elastomer layers  866  and the bondant resin layers  870 . Arrows in  FIG. 8  indicate three degrees of freedom provided by the S-spring  662 : axial deflection in tension and compression, and bending in two orthogonal vertical planes. In some embodiments, mechanical interaction of the S-spring layers provides hysteresis damping or cushioning of cyclic displacements and shock loads. As discussed above, the S-spring may be used as part of a biasing assembly in embodiments of the inventive suspension apparatus. 
     In use, a suspension apparatus according to an embodiment of the present invention includes a suspension linkage connected between a traction motor and a rail vehicle truck frame at least at first and second locations. The suspension linkage includes at the first location a first pin pivotally connecting the traction motor with a cross member of the truck frame, and includes at the second location at least one elastomeric element deformable to provide displacement and torsion within limited ranges, such that the traction motor is fully suspended from the truck frame. The suspension apparatus may include at least one link connected between a first elastomeric bushing on the traction motor and a second elastomeric bushing on the truck frame. The at least one link may be pivoted within a plane extending transverse to the first pin. The suspension apparatus may include a four bar linkage connected between the traction motor and the truck frame. The four bar linkage may be pivotally connected to the truck frame for movement within a plane extending transverse to the first pin. The four bar linkage may be a parallelogram linkage. The traction motor may be pivotally connected to a heavy link of the parallelogram linkage. The four bar linkage may include at least one second pin mounted in an elastomeric bushing providing limited torsion and cocking of the four bar linkage transverse the first pin. Each second pin of the four bar linkage may be mounted in an elastomeric bushing. 
     In another embodiment of the invention, a suspension apparatus includes a pivotal connection of a traction motor to a cross member of a truck frame, and a spring connected between the traction motor and the truck frame. The spring may provide displacement and torsion within limited ranges, such that the traction motor may be fully suspended from the truck. The spring may be an S-spring connected between the traction motor and the truck. The truck further may include an end member extending between and orthogonal to the side members distal from the cross member, with one end of the S-spring connected to the traction motor, and the other end of the S-spring connected to the end member. Alternatively, the S-spring may be connected between the traction motor and a cross member of the truck. The S-spring may be connected along a direction transverse to the pivotal connection of the traction motor to the truck. 
     In another embodiment of the invention, the spring connected between the traction motor and the truck may be a coil spring operably connected between the traction motor and a cross member of the truck along a spring axis transverse to the pivotal connection. The coil spring may be supported on a piston rigidly connected to the traction motor and slidingly connected to the cross member. 
     In one aspect of the invention, dynamic loading of high-speed rail systems may be mitigated by fully suspending a traction motor of a high-speed rail vehicle truck from the high-speed rail vehicle truck. Fully suspending the traction motor may include pivotally connecting the traction motor to the high-speed rail vehicle truck via a pin, and pivotally connecting the traction motor to the high-speed rail vehicle truck via a pendulum linkage including an elastomeric element. 
     In another embodiment of the invention, a suspension apparatus includes a rail vehicle truck frame, which has a cross member, a first side member connected to a first end of the cross member and perpendicular thereto, and a second side member connected to a second end of the cross member and perpendicular thereto. The suspension apparatus also includes a traction motor connected to the cross member of the truck frame by way of a pivot, such that a long axis of the traction motor can move relative to a long axis of the cross member while remaining parallel thereto. The suspension apparatus also includes a biasing assembly operably engaged between the traction motor and the truck frame, and deformable to fully suspend the traction motor about the pivot. 
     As noted, embodiments of the invention are applicable for use in high-speed rail vehicles. In one aspect, high-speed means configured for traveling at sustained speeds of at least 177 km/hr (based on U.S. Federal Railroad Administration standards). In another aspect, high-speed means configured for traveling at sustained speeds of at least 200 km/hr (based on European Union standards; also generally comports with the U.S. Department of Transportation&#39;s guidelines). 
     One of ordinary skill in the art will understand that the above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments (and/or aspects thereof) may be used in combination with each other. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. While the dimensions and types of materials described herein are intended to define the parameters of the invention, they are by no means limiting and are exemplary embodiments. Many other embodiments will be apparent to those of ordinary skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Moreover, in the following claims, the terms “first,” “second,” “third,” “upper,” “lower,” “bottom,” “top,” etc. are used merely as labels, and are not intended to impose numerical or positional requirements on their objects. Further, the limitations of the following claims are not written in means-plus-function format and are not intended to be interpreted based on 35 U.S.C. §112, sixth paragraph, unless and until such claim limitations expressly use the phrase “means for” followed by a statement of function void of further structure. 
     This written description uses examples to disclose several embodiments of the invention, including the best mode, and also to enable any person of ordinary skill in the art to practice the embodiments of invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. 
     As used herein, an element or step recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural of said elements or steps, unless such exclusion is explicitly stated. Furthermore, references to “one embodiment” of the present invention are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Moreover, unless explicitly stated to the contrary, embodiments “comprising,” “including,” or “having” an element or a plurality of elements having a particular property may include additional such elements not having that property. 
     Since certain changes may be made to the above-described embodiments of the inventive motor suspension apparatus and method, without departing from the spirit and scope of the invention herein involved, it is intended that all of the subject matter of the above description or shown in the accompanying drawings shall be interpreted merely as examples illustrating the inventive concept herein and shall not be construed as limiting the invention.