Abstract:
An apparatus for reducing torque fluctuations of a combustion engine includes a crankshaft mounted in the engine, flywheel coupled to the crankshaft, and a first actuator and a second actuator coupled to the flywheel. The flywheel generates a counter torque to the torque generated by the engine during combustion, and the first and the second actuators are operated to adjust the magnitude and the phase of the counter torque generated by the flywheel to suppress fluctuations associated the engine torque.

Description:
FIELD 
       [0001]    The present invention relates to an apparatus for reducing engine torque fluctuations. More specifically, the present invention relates to an apparatus for reducing the rotational irregularities of a crankshaft in an internal combustion engine. 
       BACKGROUND 
       [0002]    The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art. 
         [0003]    Generally, the rotation of the crankshaft of internal combustion engines is not uniform because of the work cycles associated with the pistons of the engines. This non-uniformity increases with decreasing number of cylinders, low speeds, and high loads. Attempts to counteract these rotation irregularities include torsionally connecting a large mass to the crankshaft. For example, a linkage system has been employed between a flywheel and a crankshaft so that the flywheel oscillates relatively to the crankshaft the same number of times per crankshaft revolution as the combustion event. The linkage is arranged such that the counter torque generated by the oscillations of the flywheel is in the opposite direction of the engine torque. In these arrangements, however, only the magnitude (and not the phase) of the counter torque generated by the flywheel oscillation is adjustable, even though both the phase and the magnitude of the engine torque fluctuation changes with the engine speed and load. 
       SUMMARY 
       [0004]    In view of the foregoing, there is a need to be able to adjust both the phase and magnitude of the flywheel oscillation relative to the crankshaft angular position. Accordingly, in an aspect of the invention, an apparatus for reducing torque fluctuations of a combustion engine includes a crankshaft mounted in the engine, flywheel coupled to the crankshaft, and a first actuator and a second actuator coupled to the flywheel. The flywheel generates a counter torque to the torque generated by the engine during combustion, and the first and the second actuators are operated to adjust the magnitude and the phase of the counter torque generated by the flywheel to suppress fluctuations associated the engine torque. 
         [0005]    Further features, advantages, and areas of applicability will become apparent from the following description and appended drawings and from the claims. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0006]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like reference numerals designate corresponding parts throughout the views. In the drawings: 
           [0007]      FIG. 1  is a front view of an apparatus for reducing engine torque fluctuations in accordance with the principles of the invention; 
           [0008]      FIG. 2  is a front view of the apparatus in another state; 
           [0009]      FIG. 3  is a front view of the apparatus in yet another state; and 
           [0010]      FIG. 4  is graph of torque versus time illustrating the reduction of engine torque fluctuations by flywheel counter torque in accordance with the principles of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
         [0012]    Referring now to the drawings, an apparatus embodying the principles of the present invention is illustrated in  FIGS. 1 through 3  and designated as  10 . As its primary components, the apparatus  10  includes crankshaft  12  with a radially protruding arm  14 . The crankshaft  12  is connected to a piston of a reciprocating internal combustion engine with a connecting rod and rotates about an axis A. The arm  14  can be connected to the crankshaft  12  or can be formed integrally with the crankshaft  12 . A flywheel  16  is mounted adjacent the arm  14 , and a control ring  18  is axially adjacent to the flywheel  16 . 
         [0013]    A circular coupling  22  is mounted about control ring  18  and includes a protruding radial arm  24 . The radial arm  24  is connected to coupling members  26  and  28  at a hinge or pivot pin  32 . The coupling element  26  is also connected to the arm  14  at a hinge or pivot pin  34 , and the coupling element  28  is connected to the flywheel  16  at a hinge or pivot pin  30 . The coupling members  26  and  28  are hinged coaxially to the arm  24  of the circular coupling  22  at the pivot pin  32 . The pivot axes of the joints  30 ,  32  and  34  are parallel to each other and to the rotational axis A of the crankshaft  12 . 
         [0014]    The control ring  18  pivots and the circular coupling  22  rotates about a rotational axis B. The control ring  18  includes two protruding arm  40  and  48  extending in opposite directions. The arm  40  is connected at a hinge or pivot joint  42  to an arm  38  associated with a linear actuator  36 , and the arm  48  is connected at a hinge or pivot joint  50  to an arm  46  associated with a second linear actuator  44 . The actuators  36  and  44  may be mounted in a motor housing. The arms  38  and  46  of the actuators  36  and  44  may be moved in any suitable manner. For example, the actuators  36  and  44  may be hydraulic cylinders or electric motors that move the arms  38  and  46 , respectively. The vertical mobility of the arm  38  may be limited by a set of stops  52  and  54  while a set of guides  56  and  58  ensures that the arm  46  moves horizontally. The apparatus  10  can be arranged in a nested manner to form a compact configuration, such that the flywheel  16  and the crankshaft  12  are concentrically arranged with rotational axis A; circular coupling  22  through its arm  24  and coupling members  26  and  28  and also through crankshaft arm  14  provide the coupling between the flywheel  16  and crankshaft  12 . The circular coupling  22  rotates about the axis B, which can be offset from the rotational axis A of the crankshaft  12  in a desired direction by controlling the linear displacement of the linear actuator  36  and  44 . Due to the offset of the axis B from the axis A, the distance between the center point of pivot pin  32  and axis A varies as the crankshaft  12  rotates. As a result, pivot pin  32  moves close to and away from axis A as the crankshaft rotates, and therefore creates a relative oscillatory angular motion between the flywheel  16  and crankshaft  12 . The phase and magnitude of the oscillatory angular motion of the flywheel  16  relative to the crankshaft  12  are determined by the position of the axis B. The position of axis B can be moved freely by actuators  36  and  44 . If axis B moves to the position coincide with the axis A, the magnitude of the oscillatory of the flywheel  16  relative to the crankshaft  12  becomes zero. 
         [0015]    In a particular arrangement, the actuators  36  and  44  are hydraulic cylinders, in which the hydraulic fluid is pressurized engine lubrication oil, so that no separate source of hydraulic pressure is required. The hydraulic cylinders are operated with controlled valves that are actuated by an electronic control device as a function of the load at each point of the internal combustion engine as required to suppress torque surge. The apparatus is suitable for use in reciprocating internal combustion engines or as well as rotary piston internal combustion engines. Instead of or in addition to the adjustability of the control ring  18 , the flywheel  16  may formed so that its moment of inertia is changeable. 
         [0016]    The apparatus  10  can be configured in different arrangements. For example, the flywheel  16  and its coupling with the crankshaft  12  can be arranged differently, such as, at one end of the crankshaft, or for multi-cylinder engines, among the pistons. On a crankshaft, several flywheels  16  and associated components may be provided. 
         [0017]    As seen in  FIG. 1 , axis B is offset from the axis A maximally in −90 degree direction with the appropriate movement of the arms  46  and  38  by the actuators  44  and  36 . 
         [0018]    In  FIG. 2 , the axis A lines up with the axis B with the appropriate movement of the arms  46  and  38  by the actuators  44  and  36 . Hence, the center of the control ring  18  is centered with the center of the crankshaft  12 . Accordingly, the apparatus  10  moves from a state of maximum eccentricity ( FIG. 1 ) to a state of minimum eccentricity as shown in  FIG. 2 . As such, the circular coupling  22  rotates coaxially with the crankshaft  12 , where the relative position between the arm  14 , the coupling members  26  and  28 , and the radial arm  24  is constant, so that there is no relative angular motion between the flywheel and the crankshaft. 
         [0019]    Turning to  FIG. 3 , the actuator  44  moves the arm  46  towards the crankshaft  12  and the actuator  36  moves the arm  38  to a position where the A axis and the B axis are aligned vertically but offset horizontally as shown in the figure. Accordingly, the center of the control ring  18  (which is the axis B) is off centered from that of the crankshaft  12  (which is the axis A) in the 0° direction.  FIGS. 1 and 3  show the axis B off centered from axis A in −90° and −0° directions respectively; however, by operating actuator  36  and  44 , axis B can be off centered in any direction. 
         [0020]    The oscillatory angular motion of the flywheel  16  relative to the crankshaft  12  generates counter torque on the crankshaft. The phase and magnitude of the counter torque is determined by the position of the axis B (the center of the control ring  18 ). The actuator  36  and  44  control the position of axis B in the way such that the counter torque of the flywheel is always in the opposite direction of the engine combustion torque with an appreciable magnitude. 
         [0021]      FIG. 3  shows a graph of engine torque and flywheel torque fluctuations over time. Specifically, the abscissa is the time and the ordinate indicates the engine combustion torque  60 , the flywheel counter torque  62 , and the net engine torque  64  resulting from the flywheel counter torque mitigating the engine combustion torque. With the appropriate use of the actuators  36  and  44 , both the magnitude and the phase of the flywheel counter torque can be controlled. As can been seen in  FIG. 3 , the maximum engine combustion torque  60  is countered by the minimum flywheel counter torque and the minimum engine combustion torque is countered by the maximum flywheel counter torque, resulting in the net engine torque  64  with difference between the high and low torque values being significantly less than those of the engine combustion torque, which provides a much smoother operating engine. 
         [0022]    The description of the invention is merely exemplary in nature and variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.