Abstract:
A small-sized vehicle is capable of cooling an electric motor of a power steering apparatus that supplies a steering shaft with an assisting steering force. The electric motor is arranged so as to receive cooling air from a cooling fan disposed on the rear side of a radiator that cools the engine cooling water with outside air.

Description:
[0001]     Applicant(s) claim(s) benefit under 35 U.S.C. § 119(e) of U.S. provisional application No. 60/573,414 filed May 24, 2004. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to, for example, a small-sized vehicle such as a saddle type three-wheel or four-wheel vehicle used for farming, an ATV (All Terrain Vehicle) for sportive traveling off-road, a golf cart, and other small-sized vehicles. More specifically, the present invention relates to a small-sized vehicle having an electric motor-driven power steering apparatus.  
         [0004]     2. Description of the Related Art  
         [0005]     Generally, a small-sized vehicle used for traveling off-road has the following structure. Front and rear wheels each having a balloon tire with low pressure and wide diameter are disposed at the front and rear of a vehicle body frame, and an engine unit is mounted between the front and rear wheels. Further, a steering shaft is arranged between the left and right front wheels, and a wheel-type steering handle or a bar-type steering handle is attached to the upper end of the steering shaft. A small-sized vehicle of this type can travel off-road at will by turning the steering handle from side to side.  
         [0006]     In recent years, some users expect further operational improvements when maneuvering the small-sized vehicle so as to reduce a load on operating the steering handle.  
         [0007]     Accordingly, an electric motor-driven power steering apparatus which is connected to a steering shaft to thereby supply the steering shaft with an assisting steering force from the electric motor has been suggested.  
         [0008]     In the power steering apparatus, under steering operations, the electric motor always operates and generates heat. When traveling at high speeds, a steering angle or a steering speed is rarely increased, such that the amount of heat generated by the electric motor is relatively small. In addition, when traveling at high speeds, the electric motor is cooled by moving air, and thus, requires less cooling. In contrast, when traveling at low speeds, the steering speed and angle are often increased. In that case, the amount of heat generated is increased, and the amount of cooling provided by the moving air is decreased. Accordingly, the electric motor requires increased cooling when traveling at low speeds.  
       SUMMARY OF THE INVENTION  
       [0009]     To overcome the problems described above, preferred embodiments of the present invention provide a small-sized vehicle having an electric motor-driven power steering apparatus, which is capable of sufficiently cooling the electric motor even when traveling at low speeds.  
         [0010]     According to preferred embodiments of the present invention, when a small-sized vehicle includes an electric motor-driven power steering apparatus for supplying a steering shaft with an assisting steering force and a radiator for cooling engine cooling water with outside air, an electric motor is arranged so as to receive cooling air from a cooling fan disposed on the rear side of the radiator.  
         [0011]     According to preferred embodiments of the present invention, the electric motor of the power steering apparatus is arranged at a location to receive the cooling air from the cooling fan disposed on the rear side of the radiator. Accordingly, even when traveling at low speeds, the electric motor is sufficiently cooled.  
         [0012]     Note that the temperature of the cooling air that passes through the radiator is increased to a temperature that is higher than the outside temperature due to heat from the engine cooling water. Nevertheless, the temperature of the cooling air that passes through the radiator is much lower than the temperature of the electric motor in operation. Therefore, with the cooling air that passes through the radiator, the electric motor is sufficiently cooled.  
         [0013]     According to one preferred embodiment of the present invention, the electric motor is disposed toward one side in the vehicle width direction from the center line of the vehicle in the vehicle width direction, and the cooling fan is disposed toward one side in the vehicle width direction corresponding to the location of the electric motor. The electric motor is disposed between the left oblique rear position and the right oblique rear position of the steering shaft so as to be spaced from the steering shaft, and the cooling fan is disposed in front of the electric motor.  
         [0014]     In this preferred embodiment, the electric motor and the cooling fan are arranged at substantially the same location in the vehicle width direction. Accordingly, the electric motor receives the cooling air from the cooling fan so as to be sufficiently cooled.  
         [0015]     According to another preferred embodiment of the present invention, an air shroud for guiding the air that passes through the radiator rearward is arranged on the rear side of the radiator, the cooling fan is arranged in the air shroud, and the electric motor is arranged at a location that is in an airflow path from a rear-end opening of the air shroud. The electric motor is disposed toward one side in the vehicle width direction from the center of the vehicle in the vehicle width direction, and the center of the rear-end opening of the air shroud is disposed toward one side in the vehicle width direction from the center of a front-end opening in the vehicle width direction so as to be substantially aligned with the electric motor.  
         [0016]     In this preferred embodiment, the cooling air that passes through the radiator is guided to the electric motor by the air shroud, to ensure cooling of the electric motor.  
         [0017]     According to still another preferred embodiment of the present invention, a flow direction of the airflow from the air shroud substantially coincides with the center line of the vehicle in the vehicle width direction or crosses the center line of the vehicle.  
         [0018]     In this preferred embodiment, by arranging the electric motor along a line of the flow direction of the airflow, the airflow from the air shroud is guided to the electric motor, such that the electric motor is sufficiently cooled.  
         [0019]     According to still another preferred embodiment of the present invention, the area of the rear-end opening of the air shroud is preferably designed to be smaller than the area of the front-end opening of the air shroud.  
         [0020]     In this preferred embodiment, the velocity of the airflow from the air shroud increases, such that the cooling of the electric motor is further ensured.  
         [0021]     According to preferred embodiments of the present invention, when a small-sized vehicle includes a power steering apparatus for supplying a steering shaft with an assisting steering force, an electric motor of the power steering apparatus is arranged between the left oblique rear position and the right oblique rear position of the steering shaft so as to be spaced from the steering shaft, and not directly behind the steering shaft.  
         [0022]     According to preferred embodiments of the present invention, the electric motor of the power steering apparatus is arranged between the left oblique rear position to the right oblique rear position of the steering shaft so as to be spaced from the steering shaft, that is, at locations other than directly behind the steering shaft. Accordingly, the steering shaft location does not disturb the airflow from the radiator, such that the cooling performance for the electric motor is not inhibited by the steering shaft.  
         [0023]     Other features, elements, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments with reference to the attached drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]      FIG. 1  is a left side view of a small-sized vehicle for traveling off-road according to a first preferred embodiment of the present invention, in which some components are shown by solid lines, and some components are shown by chain-double dashed lines and dotted lines;  
         [0025]      FIG. 2  is a left side view of the front portion of the small-sized vehicle according to the first preferred embodiment, in which the structural arrangement between vehicle components such as a radiator, an electric motor, a battery, and other components is shown;  
         [0026]      FIG. 3  is a plan view of the front portion of the small-sized vehicle according to the first preferred embodiment, in which the structural arrangement between the vehicle components such as the radiator, the electric motor, the battery, and other components are shown;  
         [0027]      FIG. 4  is a plan view showing the structural arrangement between the radiator and the electric motor of the small-sized vehicle according to the first preferred embodiment of the present invention;  
         [0028]      FIG. 5  is a plan view showing the structural arrangement between a radiator and an electric motor of a small-sized vehicle according to a second preferred embodiment of the present invention;  
         [0029]      FIG. 6  is a plan view showing the structural arrangement between a radiator and an electric motor of a small-sized vehicle according to a third preferred embodiment of the present invention; and  
         [0030]      FIG. 7  is a schematic plan view illustrating an applicable arrangement area for the electric motor according to preferred embodiments of the present invention. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0031]     Hereinafter, preferred embodiments according to the present invention will be described with reference to the attached drawings. Note that the indications of front, rear, left, and right in the description of these embodiments represent the front, rear, left, and right from an operator in a seated on a seat of the small-sized vehicle.  
         [0032]     In  FIG. 1  to  FIG. 4 , “ 1 ” denotes a small-sized vehicle for traveling off-road. This small-sized vehicle  1  includes a vehicle body frame  2 , left and right front wheels  3 ,  3  disposed at left and right front portions of the vehicle body frame  2 , left and right rear wheels  4 ,  4  disposed at left and right rear portions of the vehicle body frame  2 , an engine unit  5  mounted between the front wheels  3 ,  3  and the rear wheels  4 ,  4  of the vehicle body frame  2 , and a steering system  11  disposed between the left and right front wheels  3 ,  3 .  
         [0033]     The vehicle body frame  2  is a double cradle type frame in which left and right side frames  6 ,  6  are connected by a plurality of cross pipes. Each of the side frames  6  has a lower pipe  6   a  arranged approximately at a height of the axes of the front and rear wheels  3 ,  4  and extending in a front to rear direction, and an upper pipe  6   b  arranged approximately at a height of the lower portion of a saddle type seat  8  and extending in the front to rear direction. At the front end portion of the upper pipe  6   b,  a front-end vertical pipe  6   c  is formed by bending the upper pipe  6   b  so as to extend downward. The lower end portion of the front-end vertical pipe  6   c  is connected to the front end portion of the lower pipe  6   a.  Further, the lower pipe  6   a  and the upper pipe  6   b  are connected with each other by a rear-end vertical pipe  6   d,  and intermediate vertical pipes  6   e,    6   f  on the front and rear sides, respectively. Furthermore, the front-end vertical pipe  6   c  and the intermediate vertical pipe  6   e  on the front side, and the rear-end vertical pipe  6   d  and the intermediate vertical pipe  6   f  on the rear side are coupled to each other by intermediate horizontal pipes  6   g,    6   h  arranged in parallel with the lower pipe  6   a,  respectively.  
         [0034]     The engine unit  5  is mounted in the space surrounded by the lower and upper pipes  6   a,    6   b,  and the front and rear intermediate vertical pipes  6   e,    6   f.  In front of an engine case  5   a  having a built-in crankshaft of the engine unit  5  and a built-in variable speed gear, a cylinder block  5   b,  a cylinder head  5   c,  and a head cover  5   d  are stacked and fastened. Further, an exhaust unit  5   e  is connected to the front wall of the cylinder head  5   c.  The exhaust unit  5   e  extends rearward at a height of the cylinder block  5   b.  Further, a carburetor  5   f  is connected to the rear wall of the cylinder head  5   c.    
         [0035]     The left and right front wheels  3 ,  3  are supported by a double wishbone type front-wheel suspension system  9  in a vertically swingable and horizontally steerable manner. The front-wheel suspension system  9  includes a lower arm  9   a  supported by the front portion of the lower pipe  6   a  in a vertically swingable manner, an upper arm  9   b  supported by the intermediate horizontal pipe  6   g  on the front side in a vertically swingable manner, and a cushion unit  9   c  disposed between the front-end vertical pipe  6   c  and the lower arm  9   a.    
         [0036]     Also, the left and right rear wheels  4 ,  4  are supported by a double wishbone type rear-wheel suspension system  10  in a vertically swingable manner. The rear-wheel suspension system  10  includes a lower arm  10   a  supported by the rear portion of the lower pipe  6   a  in a vertically swingable manner, an upper arm  10   b  supported by the intermediate horizontal pipe  6   h  on the rear side in a vertically swingable manner, and a cushion unit  10   c  disposed between the rear-end vertical pipe  6   d  and the lower arm  10   a.    
         [0037]     Between tip portions of the lower arm  9   a  and the upper arm  9   b,  a knuckle  9   d  for the front wheel  3  is coupled to the lower arm  9   a  and the upper arm  9   b  via a ball joint so as to support the front wheel  3  in a rotatable. manner. Similarly, between the lower arm  10   a  and the upper arm  10   b,  a knuckle  10   d  for the rear wheel is coupled to the lower arm  10   a  and the upper arm  10   b  in an axially rotatable manner so as to support the rear wheel  4  in a rotatable manner.  
         [0038]     In front of the steering system  11 , a winch  36  is provided, and above the winch  36 , a radiator  29  is provided for cooling the cooling water of the engine unit  5 . Further, between the radiator  29  and the steering system  11 , various vehicle components are provided, such as a battery  30 , a control unit  31  for the engine unit  5 , a control unit  32  for a power steering apparatus which will be described later, a relay  33 , and other suitable components. Incidentally, the winch  36  includes a wire cable that is wound around a drum that is driven to rotate by a motor, and the winch  36  is used, for example, to extricate the small-sized vehicle if the small-sized vehicle gets stuck in a swamp.  
         [0039]     The radiator  29  has a substantially tabular shape and includes a pair of left and right side tanks  29   a,    29   a  that extend vertically, and an element  29   b  arranged between the side tanks  29   a,    29   a  and which functions as a heat exchanger. On the rear surface side of the element  29   b,  a fan case  29   d  is provided having an opening at its rear end and arranged toward the left side in the vehicle width direction. The fan case  29   d  is configured to cover substantially the left half of the element  29   b  and includes a cooling fan  29   e  disposed therein. A fan motor  29   g  which drives the cooling fan  29   e  projects rearward from the fan case  29   d.  Incidentally, a bracket for fixedly supporting the fan motor  29   g  to the rear surface side of the-element  29   b  is denoted by “ 29   f”,  and “ 29   c ” is a cap for an opening from which the cooling water is supplied into the side tank  29   a.    
         [0040]     Here, the radiator  29  is mounted in the vehicle body frame  2  such that a center line in the vehicle width direction of the radiator  29  and a center line L of the vehicle in the vehicle width direction coincide with each other. Accordingly, the cooling fan  29   e  is disposed toward the left side from the center line L of the vehicle.  
         [0041]     The steering system  11  includes a steering shaft  12  arranged substantially at the center of the front wheels  3 ,  3 , a steering handle  13  attached to the upper end of the steering shaft  12 , and an electric motor-driven power steering apparatus  14  connected to the lower end of the steering shaft  12 . The lower end portion of the steering shaft  12  and an input shaft of the power steering apparatus  14  are connected by a connecting pipe  26  to form a substantially straight line. Further, the steering shaft  12  is arranged so as to be tilted rearward.  
         [0042]     The steering shaft  12  has a cylindrical column portion  12   a,  a bracket  12   b  for mounting a handle which is fixed to the upper end portion of the cylindrical column portion  12   a  and to which the steering handle  13  is mounted in a detachable manner, and a coupling shaft portion  12   c  coaxially fixed at the lower end portion thereof.  
         [0043]     The coupling shaft portion  12   c  is axially supported by the vehicle body frame  2  via a lower bearing  20 , and the column portion  12   a  is axially supported by the vehicle body frame  2  via an upper bearing  19  at a substantially the center of the column portion  12   a  in the axial direction thereof.  
         [0044]     The power steering apparatus  14  includes a reduction gear  15 , and an electric motor  16  integrally fixed to a gear case of the reduction gear  15 . A worm  16   a  attached to an output shaft of the electric motor  16  is engaged with a worm wheel  15   a  in the reduction gear  15 . A lower projection of the output shaft of the reduction gear  15  is coupled to the knuckle  9   d  for the left and right front wheels via a pitman arm  27  and a tie rod (not shown). Incidentally, the reduction gear  15  is disposed above the left and right intermediate horizontal pipes  6   g,    6   g  of the vehicle body frame  2 .  
         [0045]     Here, the worm  16   a  attached to the output shaft of the electric motor  16  is engaged with the worm wheel  15   a  in the reduction gear  15  at the rear side portion on the steering shaft  12 . Specifically, the engaged portion is substantially aligned with the center line L of the vehicle. While the electric motor  16  extends leftward from the center line L of the vehicle in the vehicle width direction. As a result, as shown in  FIG. 4 , the electric motor  16  is arranged directly behind the cooling fan  29   e,  that is, at a location that is exposed to the cooling air “f” from the cooling fan  29   e.    
         [0046]     In this first preferred embodiment, the electric motor  16  of the power steering apparatus  14  is disposed leftward in the vehicle width direction from the center line L of the vehicle in the vehicle width direction, and the cooling fan  29   e  is disposed toward the same side as of the electric motor  16 . Specifically, the electric motor  16  is arranged directly behind the cooling fan  29   e  disposed on the rear side of the radiator  29 . Accordingly, even when traveling at low speeds, the electric motor  16  receives the cooling air from the cooling fan  29   e,  such that the electric motor  16  is sufficiently cooled.  
         [0047]     Here, in a preferred embodiment of the present invention, as shown in  FIG. 7 , it is possible to arrange the electric motor  16  within the range from the left oblique rear position to the right oblique rear position of the steering shaft  12  so as to be spaced from the steering shaft  12  as shown by an arrow A, that is, other than a portion directly behind the steering shaft  12 .  
         [0048]     Thus, when the electric motor  16  of the power steering apparatus  14  is arranged within the range shown by the arrow A, that is, other than the portion directly behind the steering shaft  12 , the electric motor  16  receives the cooling air from the cooling fan without disturbances by the steering shaft  12 , in other words, the cooling performance for the electric motor  16  is not inhibited by the steering shaft  12 .  
         [0049]     Such a structure in which the electric motor  16  is arranged within the range other than directly behind the steering shaft  12  is also applicable to a case in which no radiator is provided. When configured in such a manner, the electric motor  16  receives the moving air without disturbances by the steering shaft  12 , that is, the cooling performance for the electric motor  16  is not inhibited by the steering shaft  12 .  
         [0050]      FIG. 5  is a plan view illustrating a structural arrangement of an electric motor and a radiator according to a second preferred embodiment of the present invention. In this second preferred embodiment, an air shroud  37  is provided on the rear side of a radiator  29  for guiding the air that passes through the radiator  29  rearward.  
         [0051]     The air shroud  37  is configured such that a front-end opening  37   a  has a larger area than a rear-end opening  37   b.  Specifically, the front-end opening  37   a  is designed to cover substantially all of the element  29   b,  while the rear-end opening  37   b  is designed to cover substantially the left half of the element  29   b.  The center of the rear-end opening  37   b  of the air shroud  37  is arranged so as to be displaced leftward in the vehicle width direction from the center of the front-end opening  37   a  in the vehicle width direction.  
         [0052]     The cooling fan  29   e  is disposed toward the side of the rear-end opening  37   b  in the air shroud  37 . Further, the electric motor  16  is arranged in the airflow from the rear-end opening  37   b  of the air shroud  37 .  
         [0053]     Also, in this second preferred embodiment, the cooling air that passes through the radiator  29  flows from the rear-end opening  37   b  of the air shroud  37  substantially in parallel with the center line L of the vehicle. Therefore, the cooling air from the air shroud  37  is guided to the electric motor  16 , such that the electric motor  16  is sufficiently cooled.  
         [0054]     Further, in this second preferred embodiment, the rear-end opening  37   b  of the air shroud  37  is narrowed, such that the velocity of the airflow from the air shroud  37  increases to thereby cool the electric motor  16  more efficiently.  
         [0055]      FIG. 6  is a plan view illustrating a structural arrangement of an electric motor and a radiator according to a third preferred embodiment of the present invention. In this third preferred embodiment, an air shroud  38  is provided on the rear side of a radiator  29  for guiding air that passes through the radiator  29  rearward.  
         [0056]     In this third preferred embodiment, the cooling fan  29   e  is arranged so as to be displaced leftward of the center line in the width direction of the vehicle, while the electric motor  16  is arranged so as to be displaced rightward of the center line in the width direction of the vehicle. The air shroud  38  preferably has a substantially cylindrical shape (duct shape), the front portion  38   a  thereof surrounds the cooling fan  29   e,  and the rear portion  38   b  thereof is configured to bend rightward toward the electric motor  16 . Accordingly, the cooling air that passes through the radiator  29  is guided by the air shroud  38  to be applied to the electric motor  16 . As a result, the electric motor  16  is sufficiently cooled even though it is located on the opposite side of the cooling fan  29   e.    
         [0057]     The present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof.  
         [0058]     The present preferred embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the present invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.  
         [0059]     While the present invention has been described with respect to preferred embodiments, it will be apparent to those skilled in the art that the disclosed invention may be modified in numerous ways and may assume many embodiments other than those specifically set out and described above. Accordingly, it is intended by the appended claims to cover all modifications of the invention which fall within the true spirit and scope of the invention.