Patent Publication Number: US-2023138277-A1

Title: Dolly

Description:
TECHNICAL FIELD 
     The present invention relates to a dolly to be used in a vehicle combination comprising a truck or a tractor and at least one semitrailer. The dolly is provided with a steerable axle, a drive unit propelling a second axle and a cover. 
     BACKGROUND ART 
     There are several initiatives to allow for longer vehicle combinations. In one example, a truck pulls a semitrailer using a dolly for the semitrailer, which gives a vehicle length of 25.25 metres. In another example, a tractor pulls two semitrailers using a dolly for the second semitrailer, which gives a vehicle length of 32.00 metres. Longer vehicle combinations, known as road trains, may pull three or more semitrailers. 
     One reason for using longer vehicle combinations is to reduce fuel usage. At the same time, road usage is reduced, and the cost for drivers are reduced as well, since a single driver may drive two or three full 40 ft. containers. 
     In such a vehicle combination, the semitrailer is coupled to a dolly, which is a small vehicle comprising one, two or three wheel axles, a drawbar and a fifth wheel coupling for the semitrailer. The drawbar is normally a rigid drawbar. The dolly may also comprise brakes. 
     In order to increase the manoeuvrability of such a long vehicle combination, it is known to provide the dolly with an active steering functionality, such that e.g. the turning radius of the vehicle combination is reduced. This will allow the vehicle combination to better negotiate curves and roundabouts. It has also been proposed to provide an autonomous dolly with an electric motor for propulsion and a power source (battery) for the electric motor, steering capability, and braking capability.  
     WO 2018162030 A1 discloses an autonomous dolly comprising an electric motor for propulsion, a power source (battery) for the electric motor, a trailer coupling device (e.g. including a fifth wheel for coupling to the semi-trailer), steering capability, and braking capability. The autonomous dolly does not have any cab. EP 3290305 A1 discloses a dolly comprising a steerable front axle. 
     These known dollies work well in some applications, but there is still room for improvements. 
     DISCLOSURE OF INVENTION 
     An object of the invention is therefore to provide an improved dolly for a vehicle combination. A further object of the invention is to provide a vehicle combination comprising such a dolly. 
     The solution to the problem according to the invention is described in the characterizing part of claim  1  with regards to dolly and in claim  14  with regards to the vehicle combination. The other claims contain advantageous embodiments and further developments of the dolly. 
     In a dolly adapted to be coupled to a semitrailer, where the dolly comprises a first steerable axle and a second axle provided with a drive unit, and where the dolly comprises a fifth wheel and a drawbar, the object of the invention is achieved in that the dolly further comprises a cover having a front compartment in front of the first axle, where the front compartment comprises a first radiator, and where the cover comprises a first air opening adjacent the drawbar. 
     By this first embodiment of the dolly according to the invention, the dolly is provided with a cover that will reduce wind drag and that will further help to protect installed components of the dolly from environmental influences and from dirt etc. expelled from the wheels of various vehicles. The cover may further provide a pleasant view and the design of the dolly can be  used to distinguish the dolly from other producers. The inventive dolly allows for the incorporation of a component that requires cooling, such as a drive unit or a battery. The dolly is in one example provided with a drive unit and a battery, each having a radiator arranged at the front of the dolly, where the air intake to the radiator is arranged adjacent the drawbar. 
     The position of the air intake adjacent the drawbar, arranged at the centre of the dolly, provides several advantages. One advantage is that the air intake is arranged as far as possible from the outer sides of the dolly and thus of the vehicle combination, which reduces the exposure for road spray and thus dirt etc. from other vehicles. Another advantage is that the central position of the air intake takes advantage of the air flow from the vehicle in front of the dolly in a vehicle combination. The distance between the vehicle in front of the dolly and the semitrailer that is coupled to the dolly will cause an underpressure between the vehicle and the semitrailer, which will lead cold air from above the vehicle down towards the centrally positioned drawbar. This cold air will at the same time push away warmer air originating from the engine of the truck or tractor. A further advantage is that the air intake is not very visible from the sides of the dolly, which may give a design advantage and a cleaner appearance of the dolly. 
     A radiator is provided in a front compartment of the dolly, in front of the first axle. The radiator is in one example arranged more or less vertically, but depending on the installation and internal air deflectors, the radiator may also be arranged in any position between vertically to horizontally. In one example, the radiator is arranged in a closed section in the front compartment, where the closed section is provided with an air intake corresponding to the air opening of the cover, and with an air outlet ending in front of a wheelhouse of the dolly. The radiator will divide the closed section in a cold, front part and a warmer, rear part with the radiator in between. This will prevent any recirculation of warm air to the front of the radiator, which may otherwise decrease the cooling capacity of the  radiator. This is especially important when the radiator is adapted to cool heat sensitive equipment, such as batteries. 
     The radiators are in the shown example liquid radiators, connected to liquid cooling circuits. The first radiator is connected to a first cooling circuit and the second radiator is connected to a second cooling circuit. The first cooling circuit is adapted to cool the drive unit of the dolly, and the second cooling circuit is adapted to cool the battery. In the shown example, the first cooling circuit is adapted for a coolant temperature of maximum 50 degrees Celsius, and the second cooling circuit is adapted for a coolant temperature of maximum 35 degrees Celsius. 
     The advantage of having two separate cooling circuits is that different coolant temperatures can be used, one lower temperature for a more heat sensitive component such as a battery, and one higher temperature for a component that is not very heat sensitive, such as an electric motor or a power converter. This will reduce energy loss of the drive system. In normal drive conditions, the regular airflow to the radiators may e.g. be sufficient to hold the temperature of the first cooling circuit at a required level without having to use the radiator fan. In some conditions, the battery may require less cooling than the drive unit, and in this case, the second cooling circuit may not require the use of a radiator fan. 
     In one example, each cooling circuit comprises two radiators, where the radiators for the second cooling circuit are positioned in front of the radiators for the first cooling circuit. In this way, the radiator area can be increased, and the temperature of the second cooling circuit can be held at a low value. The air that arrives at the first cooling circuit will then be warmer, which will increase the efficiency of the first cooling circuit, which is held at a higher temperature. The temperature of the first cooling circuit may e.g. be held at a temperature between 50 to 70 degrees.  
     The second cooling circuit may also comprise a compressor and a condenser in order to increase the cooling capacity, e.g. when the air temperature is too high. This will ensure that the temperature of the second cooling circuit can be held at a temperature that is optimal for e.g. batteries. 
     The dolly may also comprise a wind deflector adapted to further direct the air flow to the air openings of the cover and thus to the air intake for the radiators. The wind deflector extends from the upper surface of the drawbar to the upper surface of the cover, and the width of the wind deflector preferably corresponds to the width of the drawbar. The wind deflector may be made of metal and may be an integral part of the drawbar, or may be made of plastic and attached to the drawbar. The wind deflector comprises in one example a central opening that will further help to direct the airflow to the air openings of the cover. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The invention will be described in greater detail in the following, with reference to the embodiments that are shown in the attached drawings, in which 
         FIG.  1    shows a vehicle combination comprising a dolly according to the invention, 
         FIG.  2    shows a dolly according to the invention, and 
         FIG.  3    shows a cut view of a dolly according to the invention. 
     
    
    
     MODES FOR CARRYING OUT THE INVENTION  
     The embodiments of the invention with further developments described in the following are to be regarded only as examples and are in no way to limit the scope of the protection provided by the patent claims. 
       FIG.  1    shows a vehicle combination and  FIGS.  2  and  3    shows a dolly. 
     The vehicle combination  40  shown in  FIG.  1    comprises a tractor  41 , a semitrailer  42  coupled to the tractor, a dolly  1  and a semitrailer  42  coupled to the dolly. Such a vehicle combination is often referred to as an A-double. The dolly can of course be used in other types of vehicle combinations, such as e.g. a rigid truck/semitrailer combination or an A-triple combination. 
     The dolly is adapted to be coupled to a semitrailer  42  through a fifth wheel  5  arranged on top of the dolly  1 . The position of the fifth wheel is preferably between the first axle and the second axle of the dolly, such that the weight of the semitrailer is evenly distributed to the two axles, but may be positioned somewhat rearwards depending on the used axles. In the shown example, the rear axle is provided with twin wheels, which may have a higher load capacity. 
     The dolly  1  is provided with two axles, a steerable front axle  2  and a driven rear axle  3 . The steerable front axle may be a conventional steering axle comprising a steering servo. The rear axle  3  is driven by a drive unit  4 . In the shown example, the drive unit is an electrical drive unit comprising an electric motor and an electronic power converter that will convert the DC power of a battery unit to a suitable AC power to drive the electric motor. Each rear wheel of the dolly may comprise an electric motor directly driving the rear wheel, or an electric motor may drive the wheels through a differential gear. The drive unit may also comprise a combustion engine, either alone or arranged as a hybrid drive unit. 
     The dolly is further provided with a drawbar  6  arranged centrally at the front of the dolly. The drawbar is a rigid drawbar fixedly integrated with the  chassis of the dolly. The drawbar is provided with a trailer coupling  26  adapted to couple the dolly to a truck or a tractor. 
     The dolly comprises a cover  7  that covers the complete chassis of the dolly, except for the wheels. The cover preferably comprises several parts that are mounted to each other, which will simplify service and repair of components of the dolly. The dolly further comprises at least one radiator arranged in front of the first axle. In the shown example, the dolly comprises two radiators arranged on each side of the dolly, a first radiator  9  arranged at the right side of the dolly and a second radiator  10  arranged at the left side of the dolly. The chassis of the dolly may e.g. comprise two longitudinal side beams interconnected by cross beams. In this case, each radiator is arranged on the outside of a side beam. 
     The radiators are arranged at the front of the dolly, in a front compartment  8  in front of the front axle  2 . The front compartment may be open to the interior of the dolly and towards the ground. The cover is provided with a first air opening  11  arranged close to the drawbar, at the right side of the drawbar, and adapted to lead air to the first radiator at the right side of the compartment. The cover is also provided with a second air opening  12  arranged close to the drawbar, at the left side of the drawbar, and adapted to lead air to the second radiator at the left side of the compartment. The first air opening and the second air opening may further be provided with an air deflector to direct the air flow directly to the radiator. 
     In one example, each radiator is arranged in a closed section, where the first radiator  9  is arranged in a first closed section  15 , and where the second radiator  10  is arranged in a second closed section  16 . The first closed section is provided with a first air intake  17  corresponding to the first air opening  11  of the cover, and a first air outlet  19  ending in front of the right wheelhouse. The second closed section is provided with a second air intake  18  corresponding to the second air opening  12  of the cover, and a second air outlet  20  ending in front of the left wheelhouse.  
     The air outlets  19 ,  20  may be directed downwards, towards the road, or upwards. In a closed section, the air flow is better controlled. Air will enter the closed section in a front part and will be forced through the radiator to a rear part and is let out into a wheelhouse or towards the ground. This will prevent any recirculation of warm air to the front of the radiator, which may otherwise decrease the cooling capacity of the radiator. This is especially important when the radiator is adapted to cool heat sensitive equipment, such as batteries. Each radiator may be provided with a fan, which can increase the air flow through the radiator. 
     The radiators are in the shown example liquid radiators, connected to liquid cooling circuits. The first radiator  9  is connected to a first cooling circuit and the second radiator  10  is connected to a second cooling circuit. The first cooling circuit is adapted to cool the drive motor and the power electronics of the drive unit, and the second cooling circuit is adapted to cool the battery unit. In the shown example, the first cooling circuit is adapted for a coolant temperature of maximum 50 degrees Celsius or more, and the second cooling circuit is adapted for a coolant temperature of maximum 35 degrees Celsius. 
     The advantage of having two separate cooling circuits is that different coolant temperatures can be used, one lower temperature for a more heat sensitive component such as a battery, and one higher temperature for a component that is not very heat sensitive. This will reduce energy loss of the drive system. In normal drive conditions, the regular airflow to the radiators may be sufficient to hold the temperature of e.g. the first cooling circuit at a required level without having to use the radiator fan. In some conditions, the battery may require less cooling than the drive unit, and in this case, the second cooling circuit may not require the use of the radiator fan. 
     In one example, each cooling circuit comprises two radiator elements, where the radiator elements for the second cooling circuit are positioned in  front of the radiator elements for the first cooling circuit. In this way, the radiator area can be increased, and the temperature of the second cooling circuit can be held at a low value. The air will in this case first cool down the liquid in the second cooling circuit to a relatively low value. The temperature of the air is increased by the front radiator elements for the second cooling circuit, and arrives at the radiator elements for the first cooling circuit with a higher temperature. This will increase the efficiency of the first cooling circuit, which is held at a higher temperature. The temperature of the first cooling circuit may e.g. be held at a temperature between 50 to 70 degrees. 
     The second cooling circuit may also comprise a compressor and a condenser in order to increase the cooling capacity further, e.g. when the surrounding air temperature is too high. This will ensure that the temperature of the second cooling circuit can be held at a temperature that is optimal for e.g. batteries. 
     In the shown example, the dolly comprises a wind deflector  22  adapted to further direct the air flow to the air openings  11 ,  12  of the cover and thus to the air intake  17 ,  18  for the radiators. The wind deflector extends from the upper surface  23  of the drawbar to the upper surface  24  of the cover, and the width of the wind deflector preferably corresponds to the width of the drawbar. The wind deflector may be made of metal and may be an integral part of the drawbar, or may be made of plastic and attached to the drawbar. The shown wind deflector comprises a central opening  25  that will further help to direct the airflow to the air openings of the cover. 
     The invention is not to be regarded as being limited to the embodiments described above, a number of additional variants and modifications being possible within the scope of the subsequent patent claims. The dolly may have any size and shape, and may comprise various components that require cooling.  
     REFERENCE SIGNS 
       1 . Dolly 
       2 : First axle 
       3 : Second axle 
       4 : Drive unit 
       5 : Fifth wheel 
       6 : Drawbar 
       7 : Cover 
       8 : Front compartment 
       9 : First radiator 
       10 : Second radiator 
       11 : First air opening 
       12 : Second air opening 
       15 : First closed section 
       16 : Second closed section 
       17 : First air intake 
       18 : Second air intake 
       19 : First air outlet 
       20 : Second air outlet 
       21 : Wheel house 
       22 : Wind deflector 
       23 : Upper surface of drawbar 
       24 : Upper surface of cover 
       25 : Central opening 
       26 : Trailer coupling 
       40 : Vehicle combination 
       41 : Tractor 
       42 : Semitrailer