Abstract:
A torque distribution control system comprises a torsion unit for detecting traction on wheels of a primary driving axle that is continuously engaged with a drive source or a source of torque power. The amount of traction detected is converted to a signal with variable signal strength, the signal strength correlating to the amount of traction detected by the torsion unit. The signal strength capable of being adjusted automatically based on select parameters and/or manually based on a driver&#39;s input. And, in response to the signal, actuators engage and control operations of the vehicle such as the drive source, a braking system, and/or an axle clutch, with the level of engagement dependent upon the signal strength.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Related Applications 
         [0002]    This application is a continuation-in-part application of U.S. patent application Ser. No. 12/280,556, filed Dec. 22, 2008, which is the National Stage of International Application No. PCT/BG2007/000003, filed Feb. 22, 2007. This application claims benefit of Bulgarian Patent Application No. 109454, filed Feb. 24, 2006. The above applications are incorporated by reference herein. 
         [0003]    2. Field of Invention 
         [0004]    The invention relates to a system for controlling torque distribution applicable in mechanical engineering. This torque distribution control system can be used in motor vehicles or in applications requiring the automatic control of torque in functionally connected objects. 
       RELATED ART 
       [0005]    An increasing number of motor vehicles incorporate torque distribution control systems to provide greater vehicle stability and increased fuel efficiency. The effectiveness of these torque distribution control systems depends primarily on how quickly the system reacts. 
         [0006]    A prevailing number of torque distributors for use in four-wheel drive vehicles operate with one primary driving axle, which is continuously engaged to a drive source or a source of torque power when a primary clutch is engaged. When the wheels on the primary driving axle lose traction with the road, the torque distributors automatically engage a secondary driving axle that is not continuously engaged. The selective engagement of the secondary driving axle can be carried out by a multi-disc clutch, which is typically activated by hydraulic or electromagnetic actuators via control signals. These control signals are generated by electronic control equipment. 
         [0007]    Under prior art electronic control systems, torque distribution occurs through the following stages: collection and generation of speed and acceleration data; calculation and determination of traction loss; generation of the appropriate control signals to correct the traction loss; transmission of control signals to actuators; and operation of the actuators to activate the clutch, which transfers torque to the secondary driving axle. With this system, loss of traction is calculated indirectly by evaluating data received from speed and acceleration sensors, located on the anti-lock braking system (ABS), in light of other relevant parameters such as engine mode and turning angle. The speed and acceleration sensors do not directly detect loss of traction. Therefore, calculation and determination of traction loss is done after loss of traction has already occurred, thereby adversely affecting cruising stability of the vehicle. 
         [0008]    A disadvantage of these prior art torque distributors is the delay caused by the reliance on the indirect determination of traction loss. These systems use discrepancies between the rotational speeds of the wheels to calculate loss of traction. However, the detection of such discrepancies by the ABS sensors represents a delayed detection of traction loss. Another disadvantage of electronically controlled torque distribution systems is the complete absence of quantitative data regarding the magnitude of the lost traction. An accurate reading on the loss of traction is required to effectively determine what corrective measures should taken to correct the traction loss. 
       SUMMARY OF THE INVENTION 
       [0009]    Accordingly, it is an object of the invention to directly detect changes in the traction between the wheels of the continuously engaged primary driving axle and the road, thereby ensuring an accurate quantitative assessment of traction. 
         [0010]    It is another object of the invention to minimize the delay between detection of traction loss and the execution of corrective measures to correct the traction loss. 
         [0011]    It is a further object of the invention to provide a system for controlling torque distribution that utilizes a quantitative assessment of traction to determine appropriate corrective measures to correct the traction loss. 
         [0012]    It is a further object of the invention to provide a system for controlling torque distribution that improves cruising stability of a vehicle. 
         [0013]    According to one aspect of the present invention, these and other objects are attained by a torque distribution control system, comprising: 
         [0014]    means for detecting traction on wheels of a primary driving axle that is continuously engaged with a drive source or a source of torque power; 
         [0015]    means for converting the amount of traction detected to a signal with a variable signal strength, the signal strength correlating to the amount of traction detected by the detection means; 
         [0016]    means for adjusting the signal strength, said adjustment means making signal strength adjustments automatically based on select parameters and/or manually based on a driver&#39;s input; and 
         [0017]    in response to the signal, means for engaging mechanisms and other systems, with the level of engagement dependent upon the signal strength. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is a schematic system diagram illustrating a first preferred embodiment of the present invention. 
           [0019]      FIG. 2  is a schematic system diagram illustrating a second preferred embodiment of the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0020]    Referring to the drawings, a description will be made with regards to preferred embodiments of a torque distribution control system according to the present invention. 
         [0021]      FIG. 1  shows a first preferred embodiment of the present invention. A drive source  24 , which can include a transmission and an engine (not shown), generates torque and transfers the torque to a first shaft portion  1 A when a primary clutch (not shown) is engaged. The torque causes the first shaft portion  1 A to rotate about its longitudinal axis. In a torsion unit  3 , deformable elastic elements  4  connect the first shaft portion  1 A to a housing  31  located at one end of a second shaft portion  1 B. The other end of second shaft portion  1 B is mechanically connected to a primary driving axle  2  that is continuously engaged to the drive source, the primary driving axle  2  equipped with rotatably mounted primary driving wheels  32 . As the first shaft portion  1 A rotates, torque is transferred to the second shaft portion  1 B through elastic elements  4 . The torque powers the primary driving axle  2 , causing the primary driving wheels  32  to spin. 
         [0022]    When the primary driving wheels  32  have no traction with the road, it provides little resistance to the torque generated by the drive source, so the difference between the rotational speed of first shaft portion  1 A and the rotational speed of the second shaft portion  1 B is relatively small, causing minimal deformation of elastic elements  4  due to torsion. However, when the primary driving wheels  32  have traction with the road, the traction builds resistance to the torque. This resistance decreases the rotational speed of the second shaft portion  1 B relative to the rotational speed of first shaft portion  1 A, causing elastic elements  4  to twist and deform. Sensors (not shown) can be applied to the elastic elements  4 , the torsion unit  3 , or the shaft portions to obtain a quantitative reading of the torsion data. 
         [0023]    Attached to the housing  31  is a converter unit  5 , comprising a hollow rotary component  6 , a disk  9 , and a control lever  12 , which is suspended on a stationary pivot  13 . Dimples  7  cut into the rotary component  6  are capable of interacting with round ends of stems  8  protruding from the disk  9 , which is connected to the first shaft portion  1 A by a spline joint  10 . The disk  9  is also connected by a hinge  11  to the one end of the control lever  12 . When the primary wheels  32  lose traction, it causes the second shaft portion  1 B and the rotary component  6  to rotate at a higher speed than the first shaft portion  1 A and the disk  9 . This discrepancy in rotational speeds forces the round ends of stems  8  out of the dimples  7 , causing disk  9  to slide along first shaft portion  1 A, which causes the control lever  12  to rotate about pivot  13 . On the other side of the pivot  13 , the control lever  12  is connected to actuators used for controlling the operation of the mechanisms and systems of the vehicle, including a clutch line  14  and a brake line  19 . As represented by the dotted lines, the control lever  12  can control other systems of the vehicle, for example the engine and the transmission. 
         [0024]    The control lever  12 , via a clutch control signal of variable strength, is capable of controlling at least one axle clutch  16  servicing a secondary driving axle  17 . Unlike the primary driving axle  2 , the secondary driving axle  17  is not continuously engaged to the drive source  24 . The control lever  12  transmits the clutch control signal through the clutch line  14  to the engagement device  15 , which then activates the axle clutch  16 . The signal strength depends on the input provided by converter unit  5  and can be adjusted by a clutch adjuster  18 , which can make adjustments to the signal strength manually based on a driver&#39;s input or automatically based on relevant parameters such as engine mode and turning angle. 
         [0025]    The control lever  12 , via a brake control signal of variable strength, is also capable of controlling a braking system  20 . The control lever  12  transmits the brake control signal through the brake line  19 , which then activates the braking system  20 . The signal strength depends on the input provided by converter unit  5  and can be adjusted by a brake adjuster  21 , which can make adjustments to the signal strength manually based on a driver&#39;s input or automatically based on relevant parameters such as engine mode and turning angle. 
         [0026]      FIG. 2  shows a second preferred embodiment of the present invention. Reference numbers in  FIG. 2  relating to elements in the second preferred embodiment correspond to the reference numbers in  FIG. 1  for like elements in the first preferred embodiment. 
         [0027]    In this second preferred embodiment, a first shaft portion  1 A is bookended by spline joints  10  and screw couplings at both ends. Along with elastic elements  4 , one of the spline joints  10  and one of the screw couplings are enclosed in a housing  31  at one end of second shaft portion  1 B, thereby forming torsion unit  3 . As shown in  FIG. 2 , helical springs can be used for elastic elements  4  to detect rotational resistance. The second shaft portion  1 B is mechanically connected to a continuously engaged primary driving axle (not shown) equipped with rotatably mounted primary driving wheels (not shown). 
         [0028]    As in the first preferred embodiment, the primary driving wheels are powered by the transfer of torque from a drive source (not shown) via the first shaft portion  1 A, the elastic elements  4 , and the second shaft portion  1 B. When primary driving wheels have no traction with the road, it provides little resistance to the torque generated by the drive source, so the difference between the rotational speed of first shaft portion  1 A and the rotational speed of the second shaft portion  1 B is relatively small, causing minimal deformation of elastic elements  4  due to torsion. However, when the primary driving wheels have traction with the road, the traction builds resistance to the torque, causing elastic elements  4  to twist and deform. This forces the first shaft portion  1 A to slide along the spline joints  10 . A disk  9  attached to the first shaft portion  1 A also slides in the same direction as the first shaft portion  1 A, causing a control lever  12  to trigger the signal process described above in the first preferred embodiment. 
         [0029]    A third preferred embodiment of the present invention is a variant of the second preferred embodiment of the present invention. The third preferred embodiment instead uses a disk  9  made with a cammed profile, which extends along the length of the shaft  1  in such a way that the control lever  12  follows the cammed profile by means of slide couplings. 
         [0030]    A fourth preferred embodiment of the present invention is a variant of the first preferred embodiment of the present invention. In this preferred embodiment, the torque is exerted with inclined cogs onto shaft  1  through disk  9 . In this variant, the elastic elements  4  should be placed on both sides of disk  9 . 
         [0031]    While the above preferred embodiments utilize exemplary mechanical structures to illustrate the mechanisms of the present invention, one skilled in the art will be able to appreciate that prior art devices can be used as alternatives to the mechanical structures. For example, hydraulic, electric, or other mechanical signal mechanisms and actuators can be used to generate, transmit, and adjust the signals that control the axle clutch. Similarly, the components in the torsion unit can be replaced by other means of gathering and evaluating the torsion data, such as magnetic and photoelectric sensors. Another variant of the present invention blends hydraulics with the mechanical features of the preferred embodiments. This would require that the housing of the torsion unit to be watertight, thereby encasing and submerging the elastic elements in a fluid-filled enclosure. 
         [0032]    In addition, one skilled in the art will be able to appreciate that the torsion unit and the converter unit can be positioned on other parts of the torque distribution system as well. For example, the torsion unit can be positioned to retrieve torsion information on any portion of the shafts or axles of the vehicle. This setup provides control over additional clutches such as those used in systems that distribute torque to each wheel independently. 
         [0033]    While the foregoing is a description of the preferred embodiments carried out the invention, it will be understood that the invention is not limited to the particular embodiments shown and described herein, but that various changes and modifications may be made without departing from the scope or spirit of this invention as defined by the following claims.