Abstract:
An automotive internal combustion engine control system drives auxiliary machinery by a starting motor while an internal combustion engine is at a standstill and efficiently regenerates energy by operating the starting motor as a power generator while the internal combustion engine is in operation. The output of the starting motor  5  capable of operating as a power generator is transmitted to an input/output pulley  10  mounted on the output shaft of the internal combustion engine  1  by an endless transmission belt  11  to start the internal combustion engine  1 . The output of the engine is transmitted to auxiliary machinery  6, 7  and  8  by the endless transmission belt  11  while the internal combustion engine  1  is in operation. The output of the starting motor  5  is transmitted to the auxiliary machinery  6, 7  and  8  by the endless transmission belt  11  while the engine is in an intentional standstill. A speed-change mechanism  41  combined with the engine  1  transmits the rotation of the starting motor  5  at a high first gear ratio to the engine  1  to start the same, and transmits the rotation of the output shaft  2  of the engine  1  at a low second gear ratio to the starting motor  5  to make the starting motor  5  generate power while the engine  1  is in operation. The speed-change mechanism  41  is disposed so as to overlap the input/output pulley  10  at least partially with respect to an axial direction in which the output shaft  2  of the engine  1  extends. The input/output pulley  10  defines an oil chamber  39  for containing lubricating oil.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Technical Field  
           [0002]    The present invention relates to a control system for controlling power transmission from an automotive internal combustion engine and a starting motor to auxiliary machinery.  
           [0003]    2. Description of the Related Art  
           [0004]    Techniques for reducing the fuel consumption of an internal combustion engine have been developed and applied to practical uses. Such techniques stop an internal combustion engine mounted on a vehicle temporarily, for example, when the vehicle stops for a while to wait for the traffic light to change. Usually, auxiliary machinery, such as an air conditioner stops when the internal combustion engine stops.  
           [0005]    If both the internal combustion engine and the air conditioner stop when the vehicle stops temporarily while the vehicle is running in traffic congestion in hot summer, the passenger compartment becomes hot and uncomfortable.  
           [0006]    A technique disclosed in, for example, JP 11-23012 A drives the auxiliary machinery by a motor when the internal combustion engine stops.  
           [0007]    The technique disclosed in JP 11-23012 A drives the motor for rotation in the normal direction to start the internal combustion engine and disconnects the motor from the auxiliary machinery to intercept torque transmission from the motor to the auxiliary machinery when the internal combustion engine is at a standstill, and drives the motor for rotation in the reverse direction to drive the auxiliary machinery and disconnects the motor from the internal combustion engine to intercept torque transmission from the motor to the internal combustion engine when the internal combustion engine is at a standstill.  
           [0008]    This prior art technique does not use the motor as a power generator and does not use the motor for energy regeneration.  
           [0009]    If it is desired to operate the air conditioner while the internal combustion engine is at a standstill, it is wiser to regenerate energy as much as possible because the air conditioner consumes much power.  
           [0010]    The present invention has been made in view of such a problem and it is therefore an object of the present invention to provide a compact automotive internal combustion engine control system capable of driving auxiliary machinery by a starting motor while an internal combustion engine is at a standstill, of efficiently regenerating energy while the internal combustion engine is in operation, and of satisfactorily lubricating a speed-change gear.  
         SUMMARY OF THE INVENTION  
         [0011]    The present invention provides, to achieve the object, an automotive internal combustion engine control system that transmits an output of a starting motor through an endless transmission belt to an input/output pulley mounted on an output shaft of an internal combustion engine in starting the internal combustion engine, transmits an output of the internal combustion engine through the endless transmission belt to auxiliary machinery while the internal combustion engine is in operation, and transmits an output of the starting motor through the endless transmission belt to the auxiliary machinery while the internal combustion engine is at an intentional stand still: wherein the starting motor has a power generating function; the automotive internal combustion engine control system includes a speed-change mechanism which transmits rotation of the starting motor to the internal combustion engine at a high first gear ratio in starting the internal combustion engine and which transmits rotation of the internal combustion engine to the starting motor at a low second gear ratio to operate the starting motor as a power generator while the internal combustion engine is in operation, the speed-change mechanism being built within the input/output pulley of the internal combustion engine.  
           [0012]    Since the rotation of the output shaft of the starting motor is transmitted to the internal combustion engine at the high first gear ratio in starting the internal combustion engine to transmit the output of the starting motor to the auxiliary machinery wile the internal combustion engine is at an intentional standstill, the internal combustion engine can be started by the amplified drive force of the starting motor and hence the starting motor may be a small one. Since the power of the internal combustion engine is transmitted at the low second gear ratio to the starting motor to use the starting motor as a power generator, energy can be efficiently regenerated.  
           [0013]    Since the speed-change mechanism is built within the input/output pulley, the control system can be formed in a short axial length, which is effective in forming the control system in compact construction.  
           [0014]    According to the present invention, the speed-change mechanism is disposed so as to overlap the input/output pulley at least partially with respect to an axial direction in which the output shaft of the internal combustion engine extends. The input/output pulley defines an internal space opening in a direction opposite a direction toward the internal combustion engine, and the speed-change mechanism is received in the space.  
           [0015]    Preferably, the speed-change mechanism includes a planetary gear including mutually meshed gears serving as a sun gear, planet pinions and a ring gear, and a carrier supporting the planet pinions for rotation, the mutually meshed gears being helical gears, a one-way clutch is interposed between a stationary part and the sun gear, and a centrifugal clutch is provided which is capable of engaging the carrier and the ring gear by the agency of centrifugal force of a predetermined level or above, and of capable of being disengaged by thrust produced by the helical gears.  
           [0016]    Preferably, a sleeve is put on the output shaft of the internal combustion engine, a cylindrical sun gear member with the sun gear is put on the sleeve, the input/output pulley has an inner cylindrical part mounted on the output shaft of the internal combustion engine and an outer cylindrical part formed integrally with the inner cylindrical part so as to surround the latter, and the inner cylindrical part surrounds the sun gear member.  
           [0017]    The outer cylindrical part extends in a direction opposite a direction toward the internal combustion engine such that the outer cylindrical part and the sun gear member define an annular space therein. The inside surface of the sleeve is interlocked with the carrier for torque transmission.  
           [0018]    The annular space can receive the planet pinions, the ring gear and the centrifugal clutch.  
           [0019]    Preferably, the speed-change mechanism comprises a planetary gear including mutually meshed gears serving as a sun gear, planet pinions and a ring gear, and a carrier supporting the planet pinions, the mutually meshed gears being helical gears, the carrier being fastened to an output shaft of the internal combustion engine, the ring gear being connected to the input/output pulley, the sun gear being interlocked with a stationary member by a one-way clutch; and a centrifugal clutch capable of engaging the carrier and the ring gear by the agency of centrifugal force that acts on weights, and of being disengaged by thrust produced by the helical gears.  
           [0020]    Since the speed-change mechanism includes the planetary gear and the centrifugal force, which are mechanical modules, the control system is simple.  
           [0021]    An oil chamber for containing lubricating oil can be formed inside the input/output pulley.  
           [0022]    The control system can be formed in compact construction by forming the oil chamber for containing lubricating oil inside the input/output pulley, and the speed-change mechanism can be satisfactorily lubricated to a necessary and sufficient extent.  
           [0023]    The input/output pulley may have an inner cylindrical part mounted on the output shaft of the internal combustion engine, an outer cylindrical part surrounding the inner cylindrical part and a flat, annular part connecting the inner and the outer cylindrical part, and the oil chamber may be defined by a cover covering an annular space defined by the input/output pulley, the inner cylindrical part, the outer cylindrical part and the flat, annular part. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]    [0024]FIG. 1 is a diagrammatic view of an automotive internal combustion engine control system in a preferred embodiment of the present invention;  
         [0025]    [0025]FIG. 2 is a longitudinal sectional view of mechanical modules forming the automotive internal combustion engine control system shown in FIG. 1;  
         [0026]    [0026]FIG. 3 is a sectional view for explaining the first step of an assembling process for assembling the mechanical module;  
         [0027]    [0027]FIG. 4 is a sectional view for explaining the second step of the assembling process;  
         [0028]    [0028]FIG. 5 is a sectional view for explaining the third step of the assembling process;  
         [0029]    [0029]FIG. 6 is a sectional view for explaining the fourth step of the assembling process;  
         [0030]    [0030]FIG. 7 is a sectional view for explaining the fifth step of the assembling process;  
         [0031]    [0031]FIG. 8 is a sectional view for explaining the last step of the assembling process;  
         [0032]    [0032]FIG. 9 is a longitudinal sectional view of an input/output pulley;  
         [0033]    [0033]FIG. 10 is a sectional view taken on the line X-X in FIG.  9 ; and  
         [0034]    [0034]FIG. 11 is a view for explaining a carrier assembling process. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0035]    A preferred embodiment of the present invention will be described with reference to FIGS.  1  to  11 . FIG. 1 is a diagrammatic view of an automotive internal combustion engine control system in the preferred embodiment. A vehicle is provided with an internal combustion engine  1 . The internal combustion engine  1  drives drive wheels  4  through a transmission  3 .  
         [0036]    A mechanical module  20 , i.e., a speed-change mechanism, is interposed between the crankshaft  2  of the internal combustion engine  1 , and an input/output pulley  10 . An auxiliary machinery drive belt  11  is extended around the input/output pulley  10 , a pulley  5   a  mounted on the drive shaft of a starting motor  5  capable of serving as a power generator, and the respective driven pulleys  6   a ,  7   a  and  8   a  of an air conditioner  6 , a water pump  7  and an oil pump  8  included in an automatic transmission for power transmission.  
         [0037]    Electrical energy stored in a battery  9  is supplied to the starting motor  5  when an ignition switch, not shown, is operated to drive the starting motor  5 . The rotation of the drive shaft of the starting motor  5  is transmitted through the auxiliary machinery drive belt  11  and the mechanical module  20  to the crankshaft  2  to start the internal combustion engine  1 .  
         [0038]    When the internal combustion engine  1  starts, the rotation of the crankshaft  2  is transmitted through the mechanical module  20  and the accessory drive belt  11  to the starting motor  5  to drive the starting motor  5  for power generation. Electric energy thus regenerated by the starting motor  5  is stored in the battery  9 . At the same time, the internal combustion engine  1  drives the air conditioner  6 , the water pump  7  for pumping cooling water, and the oil pump  8  of the automatic transmission through the auxiliary machinery drive belt  11 .  
         [0039]    The mechanical module  20  includes, in combination, a planetary gear  41 , a centrifugal clutch  50 , one-way clutch  25 , and a band brake  21  coupled with the centrifugal cutch  50  by the one-way clutch  25 . FIG. 2 shows the construction of the mechanical module  20 . The construction of the mechanical module  20  will be described with reference to FIGS.  3  to  7  in order of assembling steps.  
         [0040]    Referring to FIGS. 2 and 3, a chain case  12  is attached to a side surface of a crankcase to define a chain chamber  13 . A seal ring  14  is fitted in a cylindrical part  12   a  of the chain case  12 . A brake drum  22  having a cylindrical body  22   a  and included in the band brake  21  is received in a space defined by the cylindrical part  12   a . The brake drum  22  can be connected to the chain case  12  by a band  23  wound around the cylindrical body  22   a.    
         [0041]    The brake drum  22  has a cylindrical projection  22   b  projecting from the inner circumference of the cylindrical body  22   a . A thrust bearing  24  is put on the cylindrical projection  22   b . A one-way clutch  25  is fitted in the cylindrical body  22   a.    
         [0042]    Referring to FIG. 4, the chain case assembly thus constructed is attached to the internal combustion engine  1  so as to surround the crankshaft  2 . A threaded hole  2   b  is formed in and coaxially with a reduced end part  2   a  of the crankshaft  2 . The threaded hole  2   b  is connected to an oil passage  2   c  formed in the crankshaft  2 .  
         [0043]    A sprocket  15  and a spur gear  16  are mounted on and splined to the reduced end part  2   a  of the crankshaft  2 . The chain case assembly is disposed such that the cylindrical projection  12   a  of the chain case  12  is coaxial with the spur gear  16 , and the brake drum  22  is positioned near the spur gear  16 .  
         [0044]    Then, as shown in FIG. 5, an assembly formed by rotatably supporting a cylindrical sun gear member  28  on a sleeve  26  by a radial bearing  27  is inserted in the brake drum  22  so that the inner end, i.e., a left end as viewed in FIG. 5, of the sleeve  26  is pressed against the spur gear  16 , and a radial bearing  29  is fitted in an annular space between the sleeve  26  and the brake drum  22 .  
         [0045]    Splines  26   a  are formed in the inside surface of a right end part, as viewed in FIG. 5, of the sleeve  26 . A helical sun gear  28   a  is formed in a right end part of the sun gear member  28  projecting from the cylindrical projection  22   b  of the brake drum  22 .  
         [0046]    Then, as shown in FIG. 6, the input/output pulley  10  is supported on the cylindrical projection  22   b  of the brake drum  22  by a radial bearing  30  with its boss pressed against the thrust bearing  24  resting on the body part  22   b  of the brake drum  22 .  
         [0047]    Referring to FIG. 9, the input/output pulley  10  has a substantially cylindrical hub  10   a , a cylindrical rim  10   c , and a flat, annular part  10   b  extending between the hub  10   a  and the rim  10   c . As shown in FIG. 6, the radial bearing  30  is fitted in the space between the hub  10   a  and the cylindrical projection  22   b  of the brake drum  22 . The thrust bearing  24  is held between the inner end of the hub  10   a  and the cylindrical body  22   a  of the brake drum  22 . The space between the hub  10   a  and the cylindrical part  12   a  of the chain case  12  is sealed by the seal ring  14 .  
         [0048]    The rim  10   c  has a belting part  10   d  provided with a plurality of V-grooves in its outer circumference. The belting part  10   d  coincides substantially with the flat, annular part  10   b  with respect to the axial direction. The rim  10   c  has a cylindrical part  10   e  extending axially outward from the belting part  10   d.    
         [0049]    Referring to FIGS. 9 and 10, a plurality of threaded holes  10   f  are formed in the outer end surface of the cylindrical part  10   e  in a circumferential arrangement. Grooves  10   g  are formed at equal angular intervals so as to correspond to the three threaded holes  10   f , respectively, in the inner circumference of the cylindrical part  10   e . The grooves log have a sectional shape resembling a segment of a circle.  
         [0050]    An outer end part of the hub  10   a  is reduced to form a flange  10   h  having an L-shaped section. As shown in FIG. 6, the flange  10   h  covers the cylindrical projection  22  of the brake drum  22 , and the radial bearings  29  and  30 .  
         [0051]    Referring to FIG. 6, the flat, annular part  10   b  and the three radial bearings  27 ,  29  and  30  are disposed on a plane L passing the middle of the belting part  10   d  of the input/output pulley  10 . Oil holes are formed in the sleeve  26 , the sun gear member  28  and the cylindrical projection  22   b  of the brake drum  22  to lubricate the radial bearings  27 ,  29  and  30 .  
         [0052]    A splined ring  31  of a big diameter provided with splines  31   a  in its outer circumference is mounted on and welded to an outer end part of the hub  10   a  of the input/output pulley  10 .  
         [0053]    When the input/output pulley  10  is thus mounted on the brake drum  22 , the bore of the sleeve  26  opens to the right as viewed in FIG. 6, and the sun gear member  28 , the cylindrical part  10   e  and the flat, annular part  10   b  define an annular concave space  10   i  around the sleeve  26 .  
         [0054]    Then, as shown in FIG. 7, a carrier assembly  40  is placed in the annular space  10   i . As shown in FIG. 11, the carrier assembly  40  is assembled by mounting the centrifugal clutch  50  on the carrier  42  of the planetary gear  41 .  
         [0055]    As shown in FIG. 11, the carrier  42  has a central boss  42   b  projecting inward from a central part of a radial, flat, annular part  42   a . An engaging part provided with ridges and furrows is formed on the outer circumference of the carrier  42 . A plurality of shafts  44  are projected inward, i.e., leftward, from a radially middle part of the flat, annular part  42   a . The planet pinions  43  are supported for rotation on the shafts  44 . A ring  42   c  protrudes from a radially middle part of the outer end surface, i.e., the right end surface as viewed in FIG. 11, of the flat, annular part  42   a.    
         [0056]    The planet pinions  43  are meshed with a ring gear  45   a  formed on a ring gear member  45 . A clutch drum  51  is engaged with the engaging part of the carrier  42  so as to be axially slidable and to rotate together with the carrier  42 . The centrifugal clutch  50  is interlocked with the carrier  42  and the ring gear member  45  through the cutch drum  51 .  
         [0057]    The centrifugal clutch  50  includes a multiple-disk clutch unit  52  interposed between the cutch drum  51  and the ring gear member  45 , and flyweights  53  disposed on the outer circumference of the cutch drum  51  for turning together with the cutch drum  51  (and the carrier  42 ). The flyweights  53  are turned by centrifugal force. When the rotating speed of the clutch drum  51  exceeds a threshold rotating speed, the fly-weights  53  shifts the clutch drum  51  axially to engage the multiple-disk clutch  52 .  
         [0058]    The planet pinions  43  the ring gear  45   a  and the sun gear  28   a  of the planetary gear  41  are helical gears. The thrust produced by the helical gearing acts on the ring gear member  45  so as to push the multiple-disk clutch unit  52  axially for disengagement.  
         [0059]    The carrier assembly  40  is assembled by arranging the components of the planet gear  41  excluding the sun gear member  28 , and the centrifugal clutch  50  on the inner side, i.e., on the left side as viewed in FIG. 11, of the flat, annular part  42   a  of the carrier  42 . As shown in FIGS. 7 and 11, the splines  42   d  formed in the outer circumference of the central boss  42   b  of the carrier  42  are to be engaged with the splines  26   a  of the sleeve  26 , the splines  45   b  formed in the inner circumference of the ring gear member  45  are to be engaged with the splines  31   a  of the splined ring  31 , and the planet pinions  43  are to be engaged with the sun gear  28   a  of the sun gear member  28 .  
         [0060]    The carrier assembly  40  is installed in the annular space  10   i  formed around the sleeve  26  by mounting the input/output pulley  10  on the brake drum  22  such that the splines  42   d  and the splines  26   a  are engaged, the splines  45   b  and the splines  31   a  are engaged, and the planet pinions  43  and the sun gear  28   a  are engaged as shown in FIG. 8.  
         [0061]    The splined ring  31  of a big diameter provided with the splines  31   a  is welded to the outer end part, on the side of the ring gear member  45 , of the hub  10   a  of the input/output pulley  10 . Since the splines  31   a  and  45   b  are formed on a circle of a large diameter, pressure acting on the side surfaces of the splines  31   a  and  45   b  is low, a low frictional resistance acts on the sliding movement of the splines  31   a  and  45   b , and hence the thrust produced by the helical gearing can be transmitted to the clutch drum  51  without loss. Those component parts can be easily assembled and the construction facilitates assembling work.  
         [0062]    After the component parts have been thus assembled, the sleeve  26  and the carrier  42  are splined for simultaneous rotation, the input/output pulley  10  and the ring gear member  45  are splined for simultaneous rotation.  
         [0063]    The speed-change mechanism of the carrier assembly  40  is disposed inside the input/output pulley  10 , the carrier assembly  40  partly overlaps the belting part  10   d  of the input/output pulley  10  with respect to the axial direction, and most part of the carrier assembly  40  is contained in the annular space  10   i . Consequently, the internal combustion engine control system can be formed in compact construction and in a short axial length.  
         [0064]    A thrust bearing  32  is interposed between the flange  10   h  of the input/output pulley  10  and the shafts  44  supported on the carrier  42 . A seal ring  33  is put on the ring  42   c  slightly protruding from the outer end surface, i.e., the right end surface as viewed in FIG. 11, of the flat, annular part  42   a.    
         [0065]    As shown in FIG. 8, a crankshaft bolt  35  with collar, i.e., a collar bolt, is passed through the central boss  42   b  of the carrier  42  and is screwed in the threaded hole  2   b  of the crankshaft  2 . An O-ring  36  is fitted in a groove formed in the inside surface of the central boss  42   b  to seal the space between the crankshaft bolt  35  screwed in the threaded hole  2   b  and the central boss  42   b.    
         [0066]    The collar of the crankshaft bolt  35  is pressed against the carrier  42  to hold the sprocket  15 , the spur gear  16  and the sleeve  26  between the carrier  42  and the shoulder at the inner end of the reduced part  2   c  of the crankshaft  2 . Thus, the carrier  42  of the planetary gear  41  rotates together with the crankshaft  2 .  
         [0067]    As shown in FIG. 2, the crankshaft bolt  35  is provided with an axial oil passage  35   a  of a length from its tip, and a radial oil passage  35   b  connected to the axial oil passage  35   a . The opposite ends of the radial oil passage  35   b  open into a space between the sleeve  26  and the crankshaft bolt  35 .  
         [0068]    A substantially annular cover  37  is attached to the right end surface of the input/output pulley  10  to cover the annular space  10   i  receiving the carrier assembly  40 . The cover  37  has an outside diameter equal to that of the input/output pulley  10 . A peripheral part  37   a  of the cover  37  is fastened to the end surface of the cylindrical part  10   e  of the input/output pulley  10  by screwing bolts  38  in threaded holes  10   f . An inner peripheral part of the cover  37  is bent inward to form an inner cylindrical part  37   b . The seal ring  33  is fitted in the inner cylindrical part  37   b . Thus, the cover  37  covers the annular space  10   i  receiving the carrier assembly  40  hermetically to define an oil chamber  39 .  
         [0069]    The radial bearings  27 ,  29  and  30  are arranged in the plane L passing the middle of the belting part  10   d  of the input/output pulley  10  in the oil chamber  39 . The flat, annular part  10   b , the rim  10   c , and the combination of the cover  37 , the seal ring  33  and the carrier  42  serve as the inner end wall, i.e., left end wall as viewed in FIG. 2, the circumferential wall and the outer end wall, respectively, of the oil chamber  39 .  
         [0070]    Since the planetary gear  41  and the centrifugal clutch  50  forming the speed-change mechanism are received in the oil chamber  39  inside the input/output pulley  10 , the control system is compact, and the speed-change mechanism can be lubricated to a necessary and sufficient extent.  
         [0071]    Oil is poured through the threaded hole  10   f  opening into the groove  10   g  into the oil chamber  39 , and the bolt  38  is screwed in the same threaded hole  10   f  to complete the assembling work.  
         [0072]    The mechanical module  20  is assembled by the foregoing assembling process and can be readily disassembled by reversing the assembling process. Thus, the mechanical module  20  can be easily assembled and disassembled.  
         [0073]    The three grooves  10   g  formed at equal angular intervals in the inner circumference of the input/output pulley  10  can be used as drain grooves for adjusting the oil level in the oil chamber  39 . The grooves  10   g  stir the oil to lubricate the gears and the bearings when the input/output pulley  10  rotates in a neutral state.  
         [0074]    The seal ring  33  is disposed at a radial position near the axis of the crankshaft  2  where centrifugal oil pressure is low, prevents missealing and oil leakage. When the input/output pulley  10  is at a standstill, the oil surface S is at a level indicated by a broken line in FIG. 2 below the level of the seal ring  33 , so that the oil leaks hardly even while the input/output pulley  10  is at a standstill.  
         [0075]    Since the oil passage  2   c  and the threaded hole  2   b  of the crankshaft  2  communicate with the oil passage  35   a  of the crankshaft bolt  35 , and the oil passage  35   a  communicates with the space inside the sleeve  26  by means of the radial oil passage  35   b , the oil can be supplied into the oil chamber  39  through the crankshaft  2  when necessary.  
         [0076]    The auxiliary machinery drive belt  11  is wound around the input/output pulley  10  of the mechanical module  20  mounted on the crankshaft  2 , the respective pulleys  5   a ,  6   a ,  7   a  and  8   a  of the starting motor  5 , the air conditioner  6 , the water pump  7  and the oil pump  8 .  
         [0077]    In starting the internal combustion engine  1 , the band brake  21  is applied to use the starting motor  5  for its principal purpose.  
         [0078]    When the band brake  21  is applied, the one-way clutch  25  is locked to keep the sun gear  28   a  stationary. The driving force of the starting motor  5  is transmitted to the input/output pulley  10  and the ring gear  45   a  by the auxiliary machinery drive belt  11  to drive the input/output pulley  10  and the ring gear  45   a  for rotation. Consequently, thrust produced by the planetary gear  41  disengages the centrifugal clutch  50 , the planetary gear  41  serves as a reduction gear having a gear ratio in the range of 1.4 to 1.6 to drive the crankshaft  2  through the carrier  42  at a reduced rotating speed by an amplified torque to start the internal combustion engine  1 .  
         [0079]    When the band brake  21  is released, the sun gear  28   a  becomes free to rotate, the planetary gear  41  is neutralized, the power of the starting motor  5  is not transmitted to the crankshaft  2  and, consequently, the starting motor  5  drives only the auxiliary machinery including the air conditioner  6 , the water pump  7  and the oil pump  8  efficiently.  
         [0080]    After the internal combustion engine  1  has been started, the starting motor  5  stops functioning as a drive motor. As the engine speed increases beyond a threshold engine speed, the centrifugal clutch  50  is engaged. Then, the carrier  42  fastened to the crankshaft  2  is directly connected to the ring gear  45   a  rotating together with the input/output pulley  10  to set the planetary gear for a gear ratio of 1. Consequently, the starting motor  5  is driven through the auxiliary machinery drive belt  11  to use the starting motor  5  as a power generator. Consequently, energy can be efficiently regenerated.  
         [0081]    Although the one-way clutch  25  permits the sun gear  28   a  to rotate and hence the input/output pulley  10  is free to rotate even in a state where the band brake  21  is applied, it is desirable to release the band brake  21  to avoid power consumption.  
         [0082]    Since the band brake  21  is connected to and held on the chain case  12  by the band  23  wound around the cylindrical body  22   a  of the brake drum  22 , the chain case  12  can be effectively used as a load-bearing member for fixing the sun gear  28   a , i.e., a reaction member, through the one-way clutch  25 .  
         [0083]    The carrier  42  is fastened to the crankshaft  2 , and the ring gear  45   a  is connected to the input/output pulley  10  in the speed-change mechanism including the planetary gear  41 , and the speed-change mechanism is designed such that its gear ratio is in the range of 1.4 to 1.6, taking into consideration braking performance and starting time.  
         [0084]    If the speed-change mechanism includes a planetary gear having a carrier fastened to the crankshaft  2 , a sun gear connected to the input/output pulley  10 , the speed-change mechanism has a high gear ratio in the range of about 2.4 to about 4.3.  
         [0085]    However, when the planetary gear  41  is installed in the space defined by the input/output pulley  10 , the speed-change mechanism mentioned above, in which the ring gear  45   a  is connected to the input/output pulley  10 , and the sun gear  28   a  is disposed near the axis of the crankshaft  2  so as to be connectable to the chain case, is desirable for effective space utilization.  
         [0086]    If a planetary gear having a high gear ratio is used, reaction torque increases, adversely affecting the performance of the brake and the one-way clutch and the rigidity of the chain case and, as a consequence, a high-performance brake, a high-performance one-way clutch and a chain case having a high rigidity are needed and the cost increases.  
         [0087]    Simulation of restarting an internal combustion engine showed that time necessary to start the internal combustion engine did not decrease drastically, the starting motor needed to be driven at a high operating speed, energy loss increased and differential rotation that must be absorbed during speed change increased excessively, when a planetary gear having a gear ratio of 2 or above was used.  
         [0088]    Thus, in the speed-change mechanism employed in the embodiment of the present invention, the carrier  42  is fastened to the crankshaft  2 , the ring gear  45   a  is connected to the input/output pulley  10 , and the planetary gear has a gear ratio in the range of about 1.4 to about 1.6.  
         [0089]    In the speed-change mechanism employed in the embodiment of the present invention, the carrier  42  and the ring gear  45   a , namely, input and output members, are connected directly when the multiple-disk centrifugal clutch  50 , namely, a lock-up clutch, is engaged. Although the sun gear  28   a , namely, a reaction member, may be connected directly to an input member or an output member by a lock-up clutch, it is most suitable to connect an input and an output member directly in view of torque transmission in a directly connected state.  
         [0090]    Even if necessary clutch capacity can be reduced by directly connecting a reaction member, and an input or an output member, power is transmitted to the output member by a gear train. Such a mode of power transmission is not preferable because the rotation of the crankshaft varies, the NV characteristic (noise vibration characteristic) becomes worse due to the vibration of the crankshaft, and a speed-change mechanism of a very complicated configuration is needed.  
         [0091]    Thus, the speed-change mechanism included in the embodiment of the present invention employs a simple mechanism that connects the carrier  42 , namely, an input member, and the ring gear  45   a , namely, an output member, directly by the centrifugal clutch  50 , and has excellent NV characteristic.