Abstract:
The invention relates to a coupling device between a shaft ( 14 ) and a pulley ( 11 ) as well as to an engine block suitable for being installed in a motor vehicle. The shaft ( 14 ) and a pulley ( 11 ) can rotate relative to one another about an axis ( 15 ). According to the invention, the device includes a separate declutchable means ( 36, 37, 40, 42, 45, 50 ) for driving the shaft ( 14 ) by the pulley ( 11 ) only allowing the shaft ( 14 ) to be driven by the pulley ( 11 ) when the latter is rotating at a rotation speed that is higher than a predetermined rotation speed. The engine block includes a heat engine, a reversible alternator for starting the heat engine and generating electric power, an accessory, the heat engine and the reversible alternator being suitable for rotating the accessory by means of a belt. The engine block includes a coupling device according to the invention between an output shaft ( 14 ) of the heat engine and a pulley ( 11 ) driven by the belt ( 10 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is the US National Stage under 36 U.S.C.§371 of International App. No. PCT/FR2011/050210 filed Feb. 2, 2011, and which claims priority to French App. No. 1050888 filed Feb. 9, 2010, which are hereby incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    The invention relates to a coupling device between a shaft and a pulley and an engine block suitable for installation in an automotive vehicle and comprising a coupling device. 
         [0003]    Automotive vehicles generally include several accessories that require an energy supply for their operation. The energy can be supplied by an electrical network of the vehicle or directly through the engine of the vehicle upstream of the transmission. For example, the combustion engine of the vehicle can drive the climate control assembly through the intermediary of a belt, often called a drive belt. The climate control assembly generally comprises a piston compressor driven by a rotating shaft. By supplying mechanical energy from the combustion engine to the shaft of the climate control assembly, there is no need for a dedicated electric motor to power the climate control assembly. 
         [0004]    The drive belt associated with the combustion engine generally drives an electrical machine used as an alternator for supplying electrical energy to the electrical network of the vehicle. This electrical machine is reversible and used to start the combustion engine and is referred to as a reversible alternator. 
         [0005]    The general trend is to limit the consumption of fossil fuels in automotive vehicles. For this purpose, hybrid vehicles have been developed with twin engines, such as a combustion engine and an electric motor supplied by batteries installed in the vehicle. The electric motor is used as long as the battery charge permits. However, the twin engine poses a problem for the supply of electrical energy to accessories such as the climate control assembly, when these accessories are driven by the drive belt. Indeed, the belt drive is only possible when the combustion engine is running. Therefore, the climate control assembly stops when the hybrid vehicle is powered by its electric motor. 
         [0006]    The invention remedies this problem by disengaging the combustion engine from the drive belt and using a reversible alternator to drive the accessories, such as the climate control assembly, when the combustion engine is not running. 
         [0007]    To this end, the invention is a coupling device between a shaft and a pulley, which rotate relative to each other around an axis, whereby the pulley surrounds the shaft. According to the invention, the coupling device comprises an independent disengagement device for driving the shaft through the pulley so that the driving of the shaft by the pulley is prohibited when the pulley runs at a rotational speed lower than a given rotational speed, while the driving of the shaft by the pulley is allowed when the pulley runs at a rotational speed greater than the given rotational speed. 
         [0008]    Advantageously, the independent disengagement device comprises a clutch for connecting the shaft to the pulley through a coupling effect and at least one inertial mass that displaces radially relative to the axis during the rotation of the pulley. The displacement of the inertial mass generates a coupling force. 
         [0009]    The coupling force is axially transmitted from the inertial mass to the clutch by a conical plate against which the inertial mass locates during its radial displacement. The terms axial and radial are relative to the axis of rotation of the pulley. 
         [0010]    The device comprises a return spring opposing the coupling force and maintaining the clutch disengaged when the rotational speed of the pulley is lower than the given rotational speed. 
         [0011]    According to another embodiment, the clutch is conical. This arrangement allows for high torque to be transmitted in a small volume. 
         [0012]    To further increase the torque transmitted by the clutch, the clutch comprises several friction cones divided into two alternate assemblies. The first assembly rotationally connects with the pulley, and the second assembly rotationally connects with the shaft. 
         [0013]    The invention also relates to an engine block suitable for installation in an automotive vehicle, which comprises a combustion engine, whereby a reversible alternator starts the combustion engine and generates electrical energy for an accessory, such as for instance a climate control assembly, and the combustion engine and the reversible alternator rotationally drive the accessory with a belt. The engine block comprises a coupling device according to the invention between the output shaft of the combustion engine and a pulley driven by the belt. 
         [0014]    The foregoing and other features, and advantages of the disclosure as well as embodiments thereof will become more apparent from the reading of the following description in connection with the accompanying drawings. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0015]    In the accompanying drawings which form part of the specification: 
           [0016]      FIG. 1  is perspective view of a drive belt of an automotive vehicle and linked to several elements; 
           [0017]      FIG. 2  is a section view of a disengageable coupling device between the pulley driven by the drive belt and a shaft; and 
           [0018]      FIG. 3  is a perspective exploded view of the disengageable coupling device of  FIG. 2 . 
       
    
    
       [0019]    Corresponding reference numerals indicate corresponding parts throughout the several figures of the drawings. 
       DETAILED DESCRIPTION 
       [0020]    The following detailed description illustrates the claimed invention by way of example and not by way of limitation. The description clearly enables one skilled in the art to make and use the disclosure, describes several embodiments, adaptations, variations, alternatives, and uses of the disclosure, including what is presently believed to be the best mode of carrying out the claimed invention. Additionally, it is to be understood that the disclosure is not limited in its application to the details of construction and the arrangements of components set forth in the following description or illustrated in the drawings. The disclosure is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. 
         [0021]      FIG. 1  shows a drive belt  10  of an automotive vehicle connected to several elements. The automotive vehicle comprises a combustion engine and a pulley  11  disposed at the end of the crankshaft of the combustion engine. Among the elements driven by belt  10 , a reversible alternator  12  and a climate control assembly  13  are shown in  FIG. 1 , however, other accessories can also be driven by the belt  10 . 
         [0022]    The reversible alternator  12  can be used either as a starter to start the combustion engine, or as an alternator to supply the electrical network of the vehicle. For these two uses, the reversible alternator  12  and the combustion engine are permanently coupled. To this end, the pulley  11  connects to the crankshaft. 
         [0023]    The invention allows the reversible alternator  12  to be used in another way for the transmission of mechanical power through the belt  10 , even when the combustion engine is not running. To this end, pulley  11  is disengageable.  FIG. 2  shows a cross-section of the coupling device of pulley  11  and visually displays an independent disengagement device of the crankshaft through belt  10 . One free end of the crankshaft constitutes a shaft  14  which rotates freely around an axis  15 . The pulley  11  either spins freely relative to shaft  14  or rigidly connects with it. The invention provides an independent disengagement device for the driving shaft  14  through the pulley  11 . The rotational connection between pulley  11  and shaft  14  is obtained for a rotational speed of the pulley  11  around axis  15  greater than a given speed. Below this speed, the pulley  11  freely rotates relative to the shaft  14 . The reversible alternator  12  can be electrically supplied to the drive pulley  11  through the intermediary of the belt  10  at a speed greater than the given speed and start the combustion engine. The reversible alternator  12  can be electrically supplied so that the rotational speed of pulley  11  is lower than the given speed, to keep the pulley  11  freely rotating relative to shaft  14  and not starting the combustion engine. No exterior action is required to obtain the engagement or disengagement of shaft  14  and pulley  11 . The rotation of pulley  11  alone causes the engagement or disengagement. The given rotational speed is, for instance, 1500 revolutions per minute (or 157 radians per second in the international system). Below this speed, the combustion engine is not connected to pulley  11 . On the other hand, above this speed, the crankshaft and the pulley are connected. 
         [0024]    Pulley  11  comprises a revolution surface  16  intended to receive the belt  10 . To increase the mechanical energy transmitted between the belt  10  and the pulley  11 , the belt  10  includes grooves and the revolution surface  16  defines several grooves  17  which correspond to the grooves of belt  10 . The pulley  11  comprises a rim  18  of which one exterior peripheral part  19  connects with the surface  16 . An elastic liner  20  inserts between the exterior peripheral part  19  and the surface  16  to filter any asynchronous occurrences in the rotation of pulley  11  or in the rotation of shaft  14 . A ball bearing  21  connects the central part  22  of rim  18  and shaft  14 . Rim  18  forms a first lateral face of pulley  11 . A second lateral face of pulley  11  forms by a closing plate  23  which connects with the exterior peripheral part  19 . A second ball bearing  24  connects the closing plate  23  and shaft  14 . The two ball bearings  21  and  24  form the bearings around which pulley  11  rotates relative to shaft  14  around axis  15 . 
         [0025]    The independent disengagement device for driving shaft  14  through pulley  11  is housed in a space situated between rim  18  and closing plate  23 . This space is limited radially by the exterior peripheral part  19  of rim  18 . The independent disengagement device comprises a clutch for connecting shaft  14  with pulley  11 . For instance, the clutch is conical and comprises several friction cones  30  to  35  divided in two alternate assemblies. A first assembly  36  comprising cones  30 ,  32  and  34  rotationally connects with rim  18 . A second assembly  37  comprising cones  31 ,  33  and  35  rotationally connects with shaft  14  through the intermediary of a hub  38  and a cross-piece  39 , both connect with shaft  14 . Cross-piece  39  allows for rotational connection of assembly  37  relative to shaft  14  around axis  13 , while leaving a degree of freedom in translation according to axis  13 . Due to this degree of freedom in translation, the two assemblies  36  and  37  frictionally contact each other to ensure power transmission between shaft  14  and pulley  11 . To ensure a high friction coefficient between the two assemblies  36  and  37 , cones  30  to  35  can be made of carbon or be coated with carbon. 
         [0026]    The independent disengagement device comprises at least one inertial mass moves radially relative to the axis  15  during the rotation of pulley  11 . In the example shown, four inertial masses  40  to  43  are present and two are visible on  FIG. 2 . The masses  40  to  43  are distributed radially around axis  13 . The inertial masses  40  to  43  are rotationally driven by pulley  11 , through the intermediary of then closing plate  23  around axis  15 . When the pulley  11  rotates, masses  40  to  43  move in translation radially relative to axis  15  until they come in contact with plate  45 , which is a body of revolution around axis  15 . Masses  40  to  43  are all identical in order to move simultaneously under the effect of the rotation of pulley  11 . Plate  45  is free to translate according to axis  15 . The movement of the plate is guided by the exterior peripheral part  19  of rim  18 . The plate  45  comprises a conical surface  46  which seats against another conical surface  48  belonging to each of the inertial masses  40  to  43 . This contact between the two conical surfaces  47  and  48  transforms the radial force exercised by the masses during their movement in an axial effort resulting in the coupling of shaft  14  and pulley  11 . 
         [0027]    The conical plate  45  seats against a pressure plate  50 , which is a body of revolution, free in translation relative to the rim  18 . The device comprises a return spring  51  opposing the axial coupling force. The spring  51  rests against the rim  18  on one side and pushes against the pressure plate  50  on the other side. The calibration of spring  51  allows for regulation of the given rotational speed of pulley  11  beyond which coupling takes place. In other words, the return spring  51  keeps the clutch disengaged when the rotational speed of pulley  11  is lower than the given rotational speed. 
         [0028]    The pressure plate comprises a conical surface  52  intended to seat against the friction cone  35 . When the force exercised against the conical plate  45  by the inertial masses  40  to  43  is sufficient to compress spring  51 , the friction cones  30  to  35  press against each other and connect the pulley  11  with the shaft  14 . 
         [0029]      FIG. 3  shows an exploded view in perspective of the disengageable coupling device, where the axial guiding of pressure plate  50  defines grooves  55  arranged on an exterior cylindrical surface  56  of the pressure plate and corresponding grooves  57  on an interior cylindrical surface of rim  18 . Alternatively, other guiding means are possible, such as a system using a key mounted on the pressure plate  50  which can slide in a slot made in rim  18 . We distinguish also the rotational driving of cones  30 ,  32  and  34  by rim  18 . Each of the cones  30 ,  32  and  34  disposes of several fingers  30   a,    30   b  and  30   c  for cone  30 ,  32   a    32   b  and  32   c  for cone  32  and  34   a  for  34   b  and  34   c  for cone  34 . These fingers cooperate with corresponding slots  18   a,    18   b  and  18   c  made in rim  18 . Similarly, fingers are made in cones  31 ,  33  and  35 . These fingers cooperate with grooves  39   a,    39   b  and  39   c  of cross-piece  39  to ensure the rotational driving of cones  31 ,  33  and  35 . In  FIG. 3 , all fingers are not visible. For the same cone, they are regularly distributed around axis  13 . The same applies to the slots. The masses  40  to  43  are rotationally driven by closing plate  23  through radial abutments  23   a,    23   b,    23   c  and  23   d  made in projecting manner in closing plate  23 . Each of the inertial masses  40  to  43  is guided in its radial displacement between two of these radial abutments. For instance, mass  41  moves radially along closing plate  23  while remaining confined between radial abutments  23   a  and  23   d.    
         [0030]    Changes can be made in the above constructions without departing from the scope of the disclosure, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.