Abstract:
A vehicular AC generator comprising a pair of cores included in a rotor and supported by a rotating shaft, a plurality of trapezoidal-shaped claws as magnetic poles protruding on the outer periphery edges of the pair of cores, and a pair of fans attached to the front side and the rear side of the cores, at least one of the fans having an outer diameter in the range between 85% and 96% of the outer diameter of each of the cores, each of the claws having a tapered portion for gradually decreasing the outer diameter of a shoulder portion of the claw in the direction toward the end surface of the core so that the outer diameter of at least one of the cores faced to the at least one of the fans becomes substantially the same as the outer diameter of the at least one of the fans, whereby the sound caused by cutting wind by the rotation of the centrifugal fans can be reduced without deteriorating the cooling efficiency of the coil ends of the stator.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    (1) Field of the Invention  
           [0002]    The present invention relates to a vehicular AC generator having a salient-pole-rotating stator supported by brackets.  
           [0003]    (2) Description of the Related Art  
           [0004]    A conventional general vehicular AC generator will be described with reference to FIG. 1 to FIG. 4. In the figures, a reference numeral  1  represents rear brackets of the generator each having an inlet opening  1   a  and an outlet opening  1   b.  A reference numeral  2  represents a rectifier,  3  is a brush holder having a regulator  3   a,  and  4  is a rotor consisting of a pair of cores  4   a   1  and  4   a   2  and is supported and fixed to a rotating shaft  5 . A reference symbol  4   b  designates a plurality of trapezoidal-shaped claws functioning as magnetic poles periodically protruding from the edges of the outer peripheries of the cores  4   a   1  and  4   a   2 . The claws  4   b  of the core  4   a   1  and the claws  4   b  of the core  4   a   2  are alternately arranged in such a way that each of the claws belonging to one of the pair of cores is arranged in a concave portion between adjacent two of the claws belonging to the other one of the pair of cores. A reference numeral  6  is a coil field accommodated within both of the cores  4   a   1  and  4   a   2 . Reference symbols  7   a  and  7   b  designate centrifugal fans respectively attached to the side surfaces of the cores  4   a   1  and  4   a   2 . Reference numeral  8  represents a stator arranged on the outer periphery of the rotor  4 , and consisting of a core  8   a  and coil ends  8   b  and  8   c . Reference numeral  9  is a front bracket having an inlet opening  9   a  for sucking outside air and an outlet opening  9   b  for exhausting air. Reference numerals  10   a  and  10   b  represent bearings for supporting the rotating shaft  5 .  
           [0005]    Next, in the vehicular AC generator constructed as above, a cooling channel will be described. First, outside air is sucked from the rear bracket  1  through the inlet opening la to cool the rectifier  2  and the regulator  3   a.  Then, the cooling air is strongly sucked by the centrifugal fans  7   a  to be bent so as to cool the coil end  8   b  of the rear side of the stator  8 , and is exhausted from the outlet opening  1   b.  On the other hand, outside air from the front bracket  9  is flown through the inlet opening  9   a  and is separated to be flown into two channels, i.e., on one hand, is sucked by the centrifugal fans  7   b  to be bent so as to cool the coil end  8   b  of the front side of the stator  8  and is exhausted from the outlet opening  1   b,  and on the other hand, to cool the coil field  6  and then is flown to the rear side and is exhausted from the outlet opening  1   b.    
           [0006]    In such a general type of the conventional vehicular AC generator, since the gap between the outer periphery surface of the shoulder portion of each of the claws  4   b  and the coil end  8   b  or  8   c  is small, and since the inner surfaces of the coil ends  8   b  and  8   c  are irregular, there is a problem in that ragged sound caused by cutting wind (interfering sound between the coils  4   a   1  and  4   a   2  and the coil ends  8   b  and  8   c ) is generated.  
           [0007]    A prior art AC generator to solve such a problem is disclosed in, for example, Japanese Laid Open Patent Application (Kokai) No. 1-74163/89. This prior art AC generator will be described with reference to FIG. 5.  
           [0008]    In FIG. 5, the same parts as those in the above-described conventional general AC generator are denoted by the same reference symbols, and the explanation thereof are omitted here. Reference numeral  11  designate tapered portions of the outer periphery surfaces of the shoulders of the claws  4   b  each having a sloping surface against the end surface in the shaft direction.  
           [0009]    By forming the tapered portions  11  in the claws  4   b  as above, the gap between each tapered portion  11  of the outer periphery surface of the claw  4   b  and each of the coil ends  8   b  and  8   c  is gradually increased in the direction toward the end surface, resulting in that the interference sound generated, during the rotation of the cores  4   a   1  and  4   a   2 , between each of the cores  4   a   1  and  4   a   2  and each of the coil ends  8   b  and  8   c  is reduced.  
           [0010]    In the prior art vehicular AC generator shown in FIG. 5, although the interference noise between each of the cores  4   a   1  and  4   a   2  and each of the coil ends  8   b  and  8   c  can be reduced by the tapered portions  11  in the outer periphery surfaces of the claws  4   b , however, the gap between each of the centrifugal fans  7   a  and  7   b  and each of the coil ends  8   b  and  8   c  is still kept to be narrow in order to ensure a cooling efficiency of the coil ends  8   b  and  8   c . Because the gap between each of the centrifugal fans  7   a  and  7   b  and each of the coil ends  8   b  and  8   c  is so narrow, there is a problem in that noise sound caused by cutting wind is generated between each of the coil ends  8   b  and  8   c  and each of the centrifugal fans  7   a  and  7   b  during the rotation of the centrifugal fans  7   a  and  7   b.    
         SUMMARY OF THE INVENTION  
         [0011]    An object of the present invention is to resolve the above-mentioned problems, and to provide a vehicular AC generator in which noise sound caused by cutting wind by the rotation of centrifugal fans can be reduced.  
           [0012]    Another object of the present invention is to provide a vehicular AC generator in which the cooling efficiency of coil ends of a stator by means of the centrifugal fans is not lowered even when the outer diameters of the centrifugal fans are made small.  
           [0013]    Still another object of the present invention is to provide a vehicular AC generator in which noise sound caused by cutting wind by cores can be reduced by making the lowering of the output current due to the decrease of the outer diameters of centrifugal fans to be smaller.  
           [0014]    According to the first aspect of the present invention, there is provided, for achieving the above object, a vehicular AC generator in which at least one of a pair of front and rear fans attached to the both ends of a core of a rotor has a outer diameter in the range between 85% and 96% of an outer diameter of the core.  
           [0015]    According to the second aspect of the present invention, there is provided a vehicular AC generator having a side plate fixed to the end portion of one of the fans and having an outer diameter smaller than the outer diameter of the fan.  
           [0016]    According to the third aspect of the present invention, there is provided a vehicular AC generator in which each of the tapered portions formed in the claws is provided in at least the front side of the direction of rotation in the width of the circumferential direction of each claw.  
           [0017]    As stated above, according to the first aspect of the present invention, since the diameter of the fan is made to be in the range between 85% and 96% of the outer diameter of the core, noise caused by the fans themselves can be reduced, and the sound caused by cutting wind generated between the fans and the coil ends during the rotation of the fans can be reduced.  
           [0018]    Further, according to the second aspect of the present invention, since the side plate is attached to the fan, the reduction of the amount of the cooling wind due to the decrease of the outer diameter of the fan can be prevented.  
           [0019]    Still further, according to the third aspect of the present invention, since each of the tapered portions is provided in at least the front side of the direction of rotation in the width of the circumferential direction of each claw, the lowering of the output current due to the decrease of the outer diameter of the rotor core can be prevented.  
           [0020]    The above and further objects and novel features of the invention will more fully appear from the following detailed description when the same is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for the purpose of illustration only and are not intended as a definition of the limits of the invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]    [0021]FIG. 1 is a cross-sectional view showing a general vehicular AC generator in its shaft direction;  
         [0022]    [0022]FIG. 2 is a perspective view showing a rotor in FIG. 1;  
         [0023]    [0023]FIG. 3 is a plan view showing a core in FIG. 2;  
         [0024]    [0024]FIG. 4 is a perspective view showing a claw of the core shown in FIG. 3;  
         [0025]    [0025]FIG. 5 is a cross-sectional view showing a prior art vehicular AC generator in its shaft direction;  
         [0026]    [0026]FIG. 6 is a cross-sectional view showing a vehicular AC generator in its shaft direction, according to a first embodiment of the present invention;  
         [0027]    [0027]FIG. 7 is a perspective view showing a rotor in FIG. 7;  
         [0028]    [0028]FIG. 8 is a plan view showing a core in FIG. 8;  
         [0029]    [0029]FIG. 9 is a perspective view showing a claw of the core shown in FIG. 8;  
         [0030]    [0030]FIG. 10 is a graph showing a result of measurement of wind noise in the embodiment 1 of the present invention;  
         [0031]    [0031]FIG. 11 is a graph showing a result of measurement of the output in the embodiment 1 of the present invention;  
         [0032]    [0032]FIG. 12 is a diagram showing the relation between a stator coil and a rotor core and a detail size of each portion in the vehicular AC generator according to the embodiment 1 of the present invention;  
         [0033]    [0033]FIG. 13 is a graph showing a comparison of wind noises in the embodiment 1 of the present invention and in the prior art example;  
         [0034]    [0034]FIG. 14 is a cross-sectional view showing a relation between a stator coil and a rotor core in an embodiment 3 of the present invention;  
         [0035]    [0035]FIG. 15 is a perspective view showing a claw of the rotor core in FIG. 14;  
         [0036]    [0036]FIG. 16 is a cross-sectional view showing a relation between a stator coil and a rotor core in the embodiment 4 of the present invention;  
         [0037]    [0037]FIG. 17 is a perspective view showing a claw of the rotor core in FIG. 15;  
         [0038]    [0038]FIG. 18 is a cross-sectional view showing a relation between a stator coil and a rotor core in the embodiment 5 of the present invention;  
         [0039]    [0039]FIG. 19 is a perspective view showing a claw of the rotor core at the front side in FIG. 18; and  
         [0040]    [0040]FIG. 20 is a perspective view showing a claw of the rotor core at a different front side in the embodiment 5 of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     Embodiment 1  
       [0041]    An embodiment of the present invention will be described with reference to FIG. 6 to FIG. 9. FIG. 6 is a cross-sectional view in the shaft direction; FIG. 7 is a perspective view of a rotor in FIG. 6; FIG. 8 is a plan view of a rotor core in FIG. 7; and FIG. 9 is a perspective view of a claw of the core in FIG. 8. The same as or the corresponding parts to those in the above-described prior art are denoted by the same reference symbols and the explanations thereof are omitted here.  
         [0042]    In the figures, reference symbols  12   a  and  12   b  are centrifugal fans respectively attached to the cores  4   a   1  and  4   a   2  of the rotor  4 . The outer diameter of each fan has a size of 92% of the outer diameter of each of the cores  4   a   1  and  4   a   2 . Reference symbols  13   a  and  13   b  are side plates fixed to the respective ends of the centrifugal fans  12   a  and  12   b . Each of the side plates  13   a  and  13   b  has a outer diameter equal to or smaller than the outer diameter of each of the centrifugal fans  12   a  and  12   b . Reference numeral  14  is a tapered portion formed at a shoulder portion of the claw  4   b  of each of the cores  4   a   1  and  4   a   2 . The tapered portion  14  is constructed in such a way that the shoulder portion of the claw  4   b  is made to have a sloping surface toward the end surface of the core  4   a   1  or  4   a   2  in its shaft direction so that the outer diameter of the core  4   a   1  or  4   a   2  at its end surface becomes to be almost the same as the outer diameter of each of the centrifugal fans  12   a  and  12   b.    
         [0043]    In such a vehicular AC generator constructed as above, outside air is flown through a cooling channel from the rear bracket  1  through the inlet opening  1   a  to cool the rectifier  2  and the regulator  3   a , and then the cooling wind is strongly sunk by the centrifugal fan  12   a  to be bent at the inner side of the side plate  13   a , and then it cools the coil end  8   b  and is exhausted from the outlet opening  b.  Since there is the side plate  13   a , the cooling wind sunk by the centrifugal fan  12   a  is smoothly bent so that the amount of the cooling wind is not decreased even though the outer diameter of the centrifugal fan  12   a  is 92% of the outer diameter of the core  4   a   1 .  
         [0044]    On the other hand, outside air from the front bracket  9  is flown through the inlet opening  9   a  and is separated to be flown into two channels, i.e., a one channel through which the air is sucked by the centrifugal fan  12   b  to be bent through the inner side of the side plate  13   b  so as to cool the coil end  8   c  of the front side of the stator  8  and is exhausted from the outlet opening  1   b,  and an another channel through which the air cools the coil field  6  and then is flown to the rear side and is exhausted from the outlet opening  1   b.  In this case also, since there is the side plate  13   b , the cooling wind sunk by the centrifugal fan  12   b  is smoothly bent so that the amount of the cooling wind is not decreased even though the outer diameter of the centrifugal fan  12   a  is 92% of the outer diameter of the core  4   a   2 .  
         [0045]    As described above, the cooling wind can be efficiently flown, and, in addition, since the outer diameter of each of the centrifugal fans  12   a  and  12   b  and each of the side plates  13   a  and  13   b  is made to be the size of 92% of the outer diameter of each of the cores  4   a   1  and  4   a   2 , the noise sound caused by the centrifugal fans  12   a  and  12   b  themselves can be reduced. Further, since the gap between each of the centrifugal fans  12   a  and  12   b  and each of the stator coil ends  8   b  and  8   c  is expanded, the sound caused therein by cutting wind can be reduced.  
         [0046]    Still further, since the surfaces of the outer peripheries of the claws  4   b  of the rotor  4  opposite to the stator coil ends  8   b  and  8   c  are made to have sloping surfaces so as to form the tapered portions  14  which are tapered toward the respective end surfaces of the rotor  4  in the shaft direction, the outer diameter of each of the cores  4   a   1  and  4   a   2  at their end surfaces in the shaft direction becomes almost the same size as the outer diameter of each of the centrifugal fans  12   a  and  12   b  and the side plates  13   a  and  13   b , so that the gap between each of the stator coil ends  8   b  and  8   c  and each of the tapered portions  14  of the claws  4   b  of the rotor  4  is expanded, resulting in the reduced sound caused by cutting wind.  
         [0047]    Here, the result of measurement of the wind noise and the output in the vehicular AC generator according to the present invention are illustrated in FIG. 10 and FIG. 11. In the measurement, the size of each portion is set as shown in FIG. 12. The outer diameter (φ 91 .  5 ) of each of the side plates  13   a  and  13   b  and each of the centrifugal fans  12   a  and  12   b  with respect to the outer diameter (φ 100 . 2 ) of each of the cores  4   a   1  and  4   a   2  is set to be in the range of 100% to 80% (corresponding to φ 100 . 2  to φ 80 . 16  in FIG. 12), and each measured value is compared with a reference value which is obtained when the outer diameter of each of the side plates  13   a  and  13   b  and each of the centrifugal fans  12   a  and  12   b  with respect to the outer diameter of each of the cores  4   a   1  and  4   a   2  is set to be 100% (corresponding to φ 100 . 2  in FIG. 12). According to this result, the overall values of the wind noise is gradually decreased when the outer diameter of each of the side plates  13   a  and  13   b  and each of the centrifugal fans  12   a  and  12   b  with respect to the outer diameter of each of the cores  4   a   1  and  4   a   2  becomes smaller than 96% (corresponding to φ 96 . 192  in FIG. 12). The output is not largely changed as long as the outer diameter of each of the side plates  13   a  and  13   b  and each of the centrifugal fans  12   a  and  12   b  with respect to the outer diameter of each of the cores  4   a   1  and  4   a   2  is in the range between 100% and 85%, however, the output is gradually lowered when it is smaller than 85% (corresponding to φ 85 . 17  in FIG. 12). From these results, it is preferable to set the outer diameter of each of the side plates  13   a  and  13   b  and each of the centrifugal fans  12   a  and  12   b  with respect to the outer diameter of each of the cores  4   a   1  and  4   a   2  to be in the range between 96% and 85% (corresponding to φ 96 . 192  to φ 85 . 17  in FIG. 12).  
         [0048]    It should be noted that, in FIG. 12, the size of each portion is expressed by the unit of millimeter. Also, it should be noted that a rectangular step (having a height of φ0. 75 mm) is formed between the outer diameter (φ 100 . 2  mm) of each of the cores  4   a   1  and  4   a   2  of the rotor  4  and the starting point of the sloping surface of each tapered portion  14 .  
         [0049]    By the provision of the step, the life time of the cool forging metal mold of the claws  4   b  can be elongated.  
         [0050]    The comparison of the overall values of wind noise between the vehicular AC generator of this embodiment and the prior art AC generator is shown in FIG. 13, in which a solid curve represents the embodiment and a broken curve represents the prior art example.  
       Embodiment 2  
       [0051]    In the above-described embodiment 1, the side plates  13   a  and  13   b  are fixed to the centrifugal fans  12   a  and  12   b , however, the side plates  13   a  and  13   b  may be omitted. When the side plates  13   a  and  13   b  are omitted, the increase in the amount of wind by means of the side plates  13   a  and  13   b  can not be expected, however, in addition to the effect to further reduce the noise due to the fans themselves, the effect to reduce the noise generated between the fans and the coil ends when the fans are rotated can be obtained as in the above-described first embodiment 1.  
         [0052]    It should be noted that the centrifugal fan  12   a  or  12   b  and the side plate  13   a  or  13   b  may be provided at one side of the cores  4   a   1  and  4   a   2 , and the prior art centrifugal fan may be provided at the other side. In this case, the effect will be reduced to some extent when compared with the above-described embodiment 1, however, the effect derived from the one centrifugal fan and the side plate is the same as the effect derived from the one centrifugal fan and the side plate in the above-described embodiment 1.  
       Embodiment 3  
       [0053]    In the above-described embodiment 1, the tapered portion  14  formed by the claw  4   b  is illustrated as a sloping surface, however, it may be a tapered portion  14 A formed by a curved surface as illustrated in FIG. 14 and FIG. 15.  
       Embodiment 4  
       [0054]    Alternatively, as illustrated in FIG. 16 and FIG. 17, it may be a tapered portion  14 B formed by two sloping surfaces between which a step is provided. In this case, since the step in the tapered portion  14 B suppresses the influence of the magnetic flux, the output current is not largely lowered so that the noise caused by cutting the wind between the fans and the coil ends can be reduced.  
       Embodiment 5  
       [0055]    In the above-described embodiments 1 to 4, each of the tapered portions  14 ,  14 A, and  14 B is formed in the full width of the circumferential width of the claw  4   b , however, a tapered portion  14 C may be formed in at least front side in the direction of rotation in the circumferential width of the claw  4   b . For example, as illustrated in FIG. 18 and FIG. 19, the tapered portion  14 C is formed in the front-half portion in the circumferential width, or as illustrated in FIG. 20, the tapered portions  14 C are formed in both the front and the real portions in the width in the circumferential direction.  
         [0056]    By making the tapered portions  14 C as parts of the claw  4   b  in the circumferential width, the decrease in the outer diameters of the rotor  4  can be limited, and accordingly, the lowering of the output current can be prevented. It is a matter of course that the noise caused by cutting wind between the fans and the coil ends  8   b  and  8   c  can be reduced due to the presence of the tapered portions  14 C. It is also a matter of course that each of the shapes of the surfaces of the tapered portions  14 C may be any one of the sloping surface, curved surface, and two slope surfaces having a step.  
         [0057]    As described above, according to the present invention, since the outer diameter of the centrifugal fan is made to be smaller than the outer diameter of the core, there is an effect in that the noise caused by cutting wind during rotating the centrifugal fan can be reduced.  
         [0058]    Further, according to the present invention, nevertheless of the decrease of the outer diameter of the centrifugal fan, there is an effect in that the cooling efficiency of the coil end of the stator by means of the centrifugal fan is not lowered.  
         [0059]    Still further, according to the present invention, since the lowering of the output current due to the decrease of the outer diameter of the stator core is made to be smaller, there is an effect in that the noise caused by cutting wind by means of the core can be made small.