Abstract:
A vehicle tow bar assembly having a latch assembly and a remotely operated actuator for unlatching the tow bar assembly from a tow line. The latch assembly may have a pivot lever that is retained by a latch pin until released. Alternatively, the latch assembly may have a pair of jaws that are opened by a linear motor and a set of cams. A method of towing a vehicle with a tow bar assembly that is unlatched and released when the vehicle is moving at a selected speed in a test procedure.

Description:
TECHNICAL FIELD 
       [0001]    This disclosure relates to vehicle towing apparatus latch mechanisms and a method of towing a vehicle in a test procedure. 
       BACKGROUND 
       [0002]    Vehicles are tested extensively for many different performance characteristics such as fuel economy, aerodynamic drag, noise, vibration and harshness, and for many other reasons. Tests developed over the years for internal combustion powered vehicles resulted in establishing standards that are now being applied to hybrid vehicles, partial hybrid vehicles and electric vehicles. Normal vehicle sign-off procedures require verification of drive times, speeds, and loads that may be outside the normal operating capabilities of most electric vehicles. Test engineers may also need to disengage from the tow vehicle to allow for “free maneuvers” or unique drive evaluations. There is also a need to allow drivers of towed and towing test vehicles to release and steer clear of each other in case of emergency. 
         [0003]    Land vehicles are tested for aerodynamic drag and mechanical drag in a test that is known as a “Certification Coast Down Test” that is specified in SAE J2263 DEC2008. The Certification Coast Down Test requires vehicles to be towed at unusually high speeds (over 115 km/h) for extended periods of time. In the Coast Down Test, a vehicle is normally driven to reach a speed of 115 km/h at which point internal combustion powered vehicles are shifted to neutral and allowed to coast until a speed of 15 km/h is reached. The time required to coast until reaching the lower speed is measured and analyzed. 
         [0004]    Drivetrains of hybrid vehicles and electric vehicles are difficult, or impossible, to disconnect while the vehicles are moving. Hybrid vehicles and electric vehicles cannot use their own drivetrain to accelerate the vehicle to the desired speed to start the test because the electrical portion of the drivetrain cannot be completely disconnected while the vehicle is moving. One way to accelerate hybrid and electric test vehicles is to push the vehicles from the rear but this approach may damage the test vehicle and it is difficult to control. Towing such vehicles to reach the desired speed is unacceptable because the towing vehicle may interfere with the test results by disturbing the air flow around the test vehicle. The towing cable, if not released from the towed vehicle, may interfere with the test results. 
         [0005]    Glider aircraft are normally towed to reach a desired altitude and are released by a cable release mechanism. This approach to releasing a towed glider is simple and effective but requires a cable guide system and can only be operated by the pilot of the towed or towing aircraft. 
         [0006]    This disclosure addresses one or more of the above problems and other problems as summarized below. 
       SUMMARY 
       [0007]    According to one aspect of this disclosure, a tow bar assembly is disclosed for a land vehicle that may be remotely released. The tow bar assembly includes a tow bar that is attached to the towed vehicle. The tow bar supports a latch assembly that has a latched position and an unlatched position. An actuator is operatively connected to the latch assembly for shifting the latch assembly from the latched position to the unlatched position. A switch is disposed in a remote location relative to the latch assembly for controlling the actuator. 
         [0008]    According to another optional aspect of this disclosure, the latch assembly may further comprise a pivot link attached to the tow bar that is selectively pivoted from the latched position to the unlatched position. A latch pin engages the pivot link to hold the pivot link in the latched position. The latch pin is moved out of engagement with the pivot link by the actuator in the unlatched position. 
         [0009]    Alternatively, the tow bar assembly may further comprise a pair of jaws operatively connected to the tow bar that pivot between a latched position and an unlatched position. At least one of the jaws may have a reaction cam surface that is engaged by a linear motor having at least one cam surface that is driven into the reaction cam surface to shift the latch assembly from the latched position to the unlatched position. 
         [0010]    In another alternative embodiment, the tow bar assembly may further comprise a first jaw and a second jaw that are operatively connected to the tow bar to pivot between a latched position and an unlatched position. The first jaw has a first reaction cam surface and the second jaw has a second reaction cam surface. A linear motor having a first cam surface is driven into engagement with first reaction cam surface and a second cam surface that is driven into the second reaction surface to shift the latch assembly from the latched position to the unlatched position. 
         [0011]    The tow bar assembly may further comprise a communication link operatively connecting the switch to the actuator to provide an unlatch signal to the actuator when the switch is operated. The communication link may be either a radio frequency signal or an electrical wire. 
         [0012]    The tow bar assembly may include an actuator that may be a magnetic plunger, a solenoid, or a linear motor. 
         [0013]    The tow bar assembly may further comprise a transmitter operatively connected to and operated by the switch, and a receiver that is operatively connected to the actuator. The transmitter sends a radio frequency signal to the transmitter to shift the actuator from the latched position to the unlatched position. 
         [0014]    The tow bar assembly may also further comprise a first portion of the tow bar that is attached to the vehicle and a second portion of the tow bar that supports the latch assembly. The first portion of the tow bar and the second portion of the tow bar may be connected by a pivot connector. 
         [0015]    Another aspect of this disclosure relates to a method of towing a vehicle in a test with a towing vehicle using a remotely controlled tow hitch latch on the towed vehicle. The method comprises attaching a flexible strand between the towing vehicle and the tow hitch. Towing the towed vehicle until a selected speed is reached and actuating a switch that is remote from the tow hitch. The flexible strand is released from the tow hitch in response to actuating the switch while the towed vehicle is moving at the selected speed. 
         [0016]    According to other aspects of this method, the method may further comprise measuring the road load force as a function of speed during operation of a vehicle during coast down. The road load force may include aerodynamic drag and mechanical drag as a function of vehicle speed. 
         [0017]    According to the method, the switch may be actuated from the towed vehicle, from a stationary location on a test track, or from the towing vehicle. 
         [0018]    The above aspects of this disclosure will be described below in greater detail with reference to the attached drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  is a side elevation view of a towed vehicle with a tow assembly attached to the front end of the vehicle. 
           [0020]      FIG. 2  is a side elevation view of the tow assembly shown in  FIG. 1  in a latched position. 
           [0021]      FIG. 3  is a side elevation view of the tow assembly shown in  FIG. 1  in an unlatched position. 
           [0022]      FIG. 4  is a side elevation view of an alternative embodiment of a tow assembly in a latched position. 
           [0023]      FIG. 5  is a side elevation view of the tow assembly of  FIG. 4  in an unlatched position. 
           [0024]      FIG. 6  is side elevation view of another embodiment of a tow assembly that includes a pivot connection on the tow bar in a latched position. 
           [0025]      FIG. 7  is side elevation view of another embodiment of a tow assembly in a latched position. 
           [0026]      FIG. 8  is a partial cut-away side elevation view of the tow assembly of  FIG. 7  in an unlatched position. 
           [0027]      FIG. 9  is a partial cut-away side elevation view of the tow assembly of  FIG. 7  in a latched position. 
           [0028]      FIG. 10  is a fragmentary side elevation view of one wall of the tow assembly of  FIG. 7 . 
           [0029]      FIG. 11  is a schematic diagram of a set of transmitters and receivers for remotely operating the tow assembly. 
       
    
    
     DETAILED DESCRIPTION 
       [0030]    A detailed description of the illustrated embodiments of the present invention is provided below. The disclosed embodiments are examples of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale. Some features may be exaggerated or minimized to show details of particular components. The specific structural and functional details disclosed in this application are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art how to practice the invention. 
         [0031]    Referring now to  FIG. 1 , a vehicle  10  is illustrated that has a tow assembly  20  attached to the frame of a towed vehicle  10 . The illustrated vehicle  10  is a hybrid-electric sedan, but the tow assembly  20  may be configured for use in any type of motor vehicle including, e.g., sedans, pick-up trucks, vans, SUVs, electric or hybrid-electric vehicles. The tow assembly  20  is mounted at a front end of the vehicle  10  to a part of the frame  30  of the vehicle near a front fascia  40 . Tow assembly  20  includes a tow bar  50  that is attached to the vehicle main frame  30 . 
         [0032]    Referring to  FIG. 2 , the tow assembly  20  is shown to include a latch assembly  60 . The latch assembly  60  is connected to a remotely controllable actuator  70 . Actuator  70  includes a solenoid, magnetically actuated plunger, or linear motor that is electrically linked to a vehicle battery (not shown) or other electrical source. A receiver-transmitter  80  is provided at the top of the actuator  70  for receiving a release command for releasing the latch assembly  60 . Actuator  70  includes a rod  90  that is attached to a rotatable link  100  by a fastener  110 . Link  100  rotates with respect to the lateral axis of the vehicle about a fastener  120 . Link  100  includes a pin  130  that extends through the link  100 . A pivot arm  140  is shown in a latched position in  FIG. 2 . Pivot arm  140  (or “swing away bar”) is pivotally attached to a base  150  of the tow assembly  20  to pivot about point  160 . A ring  170  is attached to a pivot arm  140  and linked to a strap  180  that is attached to a towing vehicle  185 . 
         [0033]    Referring to  FIG. 3 , latch assembly  60  is shown in an open position with the pivot arm  140  rotated approximately 180° counterclockwise with respect to the closed position shown in  FIG. 2 . Ring  170 , as shown in  FIG. 2 , is pulled off of the pivot arm  140  when latch assembly  60  is in the open position. Referring to  FIG. 3 , pivot arm  140  includes a notch  190  at one end that forms a seat on the pivot arm  140  for a pin  130 . The pin  130  holds the pivot arm  140  in the closed position. 
         [0034]    Referring to  FIG. 4 , another example of a tow assembly  200  is illustrated that includes a latch assembly  210 . Latch assembly  210  is mounted to a lower side of a mounting bracket  220 . Latch assembly  210  is linked to a remotely controlled actuator  230 . Actuator  230  in this embodiment is a magnetic plunger, or solenoid. Actuator  230  is electrically linked to a battery. A receiver-transmitter  240  is operatively connected to the actuator  230  for receiving a command to release the latch assembly  210 . Actuator  230  includes a piston  250  that is pivotally connected to a pivotable link  260  by a pivot pin  270 , or fastener. Link  260  pivots with respect to the lateral axis of the vehicle about a pivot pin  280 , or fastener. Clevis link  260  includes a pin  290  that extends in the lateral direction across the clevis link  260 . A pivot arm  300  is shown in a latched or locked position. Pivot arm  300  is attached to a base  310  of the tow assembly  200  to pivot about pivot pin  320 . A ring similar to the ring  170  shown in  FIG. 2  is received on pivot arm  300  and is linked to a strap that is attached to a towing vehicle. 
         [0035]    Referring to  FIG. 5 , latch assembly  210  is shown in an open position. Pivot arm  300  is rotated 180 degrees clockwise with respect to the latched position. Ring  170 , as shown in  FIG. 2 , is pulled open or drops down away from pivot arm  300  when latch assembly  210  is in the open position. Pivot arm  300  includes a notch  330  formed at one end. Notch  330  assists in securing the end of pivot arm  300  receives the pin  290  in a notch  330  when in the latched position, as shown in  FIG. 4 . 
         [0036]    Another example of a tow assembly  400  is illustrated in  FIG. 6 . A latch assembly  405  that is similar to the latch assemblies shown in  FIG. 1-5  is attached to a magnetic plunger  415 , or solenoid, that actuates the tow assembly. Mounting bracket  410  is attached to the towed vehicle frame  30  and is linked to a pivot joint  420 . The pivot joint  420  adds a degree of freedom that allows the towed vehicle to maneuver laterally with respect to the towing vehicle. 
         [0037]    Referring to  FIGS. 7-10 , another embodiment of a vehicle tow assembly  500  is illustrated that includes an actuator  510 . The actuator  510  may be a magnetic actuator, a solenoid, a linear motor or a rotary actuator. Actuator  510  may include a receiver-transmitter  520  that communicates with a remotely located transmitter. A rod  530  is linked to a push rod  550  of a latch assembly  540 . Push rod  550  includes a head  560  with a tapered distal end  570 . Push rod  550  and head  560  are received in the latch assembly  540  that includes a jaw assembly  590  attached to one end. Tow assembly  590  includes a set of pivoting jaws  600  that are attached to latch assembly  580  by pivot pins  610  and  620 . Each jaw  600  includes a semi-circular recess  630  at a distal end of the jaws  600 . When the push rod  550  is fully inserted in the latch assembly  580 , the jaws  600  are aligned with the push rod in a locked position. When in the locked position, as shown in  FIG. 9 , the recesses  630  may be latched to a ring  170 , similar to the ring shown in  FIG. 2 , or other connector. 
         [0038]    As shown in  FIG. 8 , when the push rod  550  is retracted from the latch assembly  580 , the jaws  600  are opened to a release position. Jaws  600  include a cam surface  605  that converts the linear movement of push rod  550  into pivotal movement of the jaws  600 . 
         [0039]    Referring to  FIG. 10 , one wall of the latch assembly  580  includes a recessed guide track  640  for the head  560  (as shown in  FIGS. 7-9 ). Guide track  640  is an oblong recess formed in an inner surface of the housing. The head  560  of the push rod  550 , as shown in  FIGS. 8-9 , slides within guide track  640 . A slot  650  is provided in each side plate of the latch assembly to assure that the ring  170  does not hang-up on the jaws  600 . Latch assembly  580  includes a series of orifices  660  that receive fasteners or pins for attaching the jaws  600  to the housing and hold the latch assembly  580  together. 
         [0040]    The illustrated tow assemblies may be remotely actuated by the driver of the towed vehicle or the towing vehicle. Alternatively, the tow assembly may be remotely actuated by a sensor associated with a location on a test track. A schematic illustration of a receiver-transmitter for actuating the tow assemblies is shown in  FIG. 11 . A tow assembly  700  includes an actuator that is linked to a receiver-transmitter  720 . Actuator  710  is configured to control a latch assembly, e.g.,  60 ,  210 ,  405 , or  540  as previously described with reference to  FIGS. 2-10 . Receiver-transmitter  720  is configured to receive a release command from a key fob  730 . Key fob  730  includes a release switch  740  labeled with a circle and a crossed out “TOW” in this embodiment. Key fob  730  also includes a receiver-transmitter  750 . When the actuator  710  is actuated to release the latch of tow assembly  700 , a configuration signal may be sent to the receiver-transmitter  750  in the key fob  730 . Upon receipt of the confirmation signal, an indicator light  760  is illuminated. 
         [0041]    In other embodiments, the release button and/or indicator can be located in other devices, e.g., on the instrument panel for the towed or towing vehicle, in a control tower or on a laptop computer. 
         [0042]    While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.