Abstract:
The bearing cooling device causes cooling media to flow into the interior of a journal bearing  8  for supporting a shaft part  7  by lubrication of high viscous fluid and the interior of the shaft part  7  to cool the shaft part  7  and the bearing  8.  At this time, cooling medium temperature of the bearing  8  is set to be higher than cooling medium temperature of the shaft part  7.  It is constituted so that the cooling medium passes the cooling medium passage and thereafter passes the cooling medium passage internally of the bearing. A heated medium supply device for supplying a heated medium to each cooling medium passage may be provided. The bearing cooling device is used suitably for a gear pump.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a bearing cooling device used for a gear pump for carrying high viscous fluid such as molten resins, and the like.  
           [0003]    2. Description of the Related Art  
           [0004]    A conventional gear pump for carrying molten resins has a pair of gear rotors. The gear rotor is supported rotatably on a pump body through a bearing. This bearing is a journal bearing, which is a self-lubricating type in which a part of molten resins carried serves as bearing lubricant. In the gear pump of this kind, it is important to increase production amount (carrying amount). Methods for increasing the production amount (carrying amount) include a method for increasing the number of revolutions, and a method for widening face width. However, any of methods increase the burden on the bearing. Therefore, there is high possibility of resulting in backing, and it has not been easy to increase the production amount.  
           [0005]    When the number of revolutions is increased, the shearing speed becomes high to increase heat generation of resins. Then, the viscosity of resins lowers, and the bearing support ability lowers. Further, when the face width is widened, the load increases, and the bearing support ability lowers.  
           [0006]    In the gear pump of this kind, it is most effective for enhancing the bearing ability to lower the temperature of molten resin as lubricant to raise the viscosity of resins.  
           [0007]    Cooling methods for the lubricant (molten resins) include cooling a rotor shaft, cooling a bearing, or a combing the formers.  
           [0008]    Incidentally, the cooling of a bearing as described above is important, but there gives rise to a problem that the excessive cooling of a baring brings forth shrinkage of a bearing itself, as a result of which bearing clearance reduces resulting in baking.  
         SUMMAY OF THE INVENTON  
         [0009]    It is an object of the present invention to provide a cooling device for a bearing for achieving higher speed (higher production amount) of the device and preventing baking of a bearing.  
           [0010]    In the present invention, cooling medium is caused to flow intothe interior of a journal bearing for supporting a shaft part by lubrication of high viscous fluid and the interior of the shaft part to cool the shaft part and the bearing. The temperature of the cooling medium of the bearing is set to be higher than a temperature of cooling medium of the shaft part.  
           [0011]    In this case, preferably, the cooling medium after having been flown into the shaft part is caused to flow into the bearing.  
           [0012]    Further, an annular space formed internally of the bearing and a partitioning wall provided spirally within the annular space constitute a cooling medium passage. Preferably, the cooling medium passage is a two-spiral groove.  
           [0013]    The bearing cooling device of the present invention is suitably used for a gear pump. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    [0014]FIG. 1 is a sectional view of a gear pump showing an embodiment of the present invention;  
         [0015]    [0015]FIG. 2 is a sectional view taken on line A-A of FIG. 1;  
         [0016]    [0016]FIG. 3 is a sectional view taken on line B-B of FIG. 1; and  
         [0017]    [0017]FIG. 4 is a peripheral developed view of an annular space (cooling jacket). 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0018]    The embodiments of the present invention will be described hereinafter with reference to the drawings.  
         [0019]    [0019]FIG. 1 to FIG. 3 show a gear pump for carrying quantitative molten resins in a mixing granulating system. The gear pump has a block-like body  1 . A glasses-like rotor housing hole  2  extends through and is formed in the body  1 . Further, a resin inlet  3  and outlet  4  are formed, through the rotor housing hole  2 , on the both sides of the latter.  
         [0020]    As shown in FIG. 1, a pair of rotors  5 ,  5  are housed in the rotor housing hole  2 . The rotor  5  comprises gear parts  6  and shaft parts formed on both sides thereof. The both gear parts  6  are always meshed with each other. The shaft part  7  is supported rotatably by a journal bearing  8  fitted in the rotor housing hole  2 . The bearing ( 8 ) is prevented from slipping out of the rotor housing hole  2  by a bearing retainer  10  secured to the body  1  by means of a bolt  9 .  
         [0021]    A seal member  11  is secured to the bearing retainer  10 . In the seal member  11  and the shaft part  7 , the molten resins are prevented from flowing outside by means of a labyrinth seal.  
         [0022]    One end of the shaft part  7  of the rotor  5  is connected to a drive device  12 . The rotor  5  is rotated and driven in a direction indicated by arrow of FIG. 3, and the molten resins are carried from the resin inlet  3  to the outlet  4 .  
         [0023]    The gear pump is of a self-lubricating type, in which a par of the molten resins carried is supplied as lubricant for the bearing  8  and the shaft part  7 . For the self-lubricating construction, a well known construction (for example, U.S. Pat. No. 5,292,237) can be employed. The seal member  11  is provided to prevent leakage of the molten resins outside used for lubrication of a bearing.  
         [0024]    As shown in FIG. 2, the journal bearing  8  is formed internally with a cooling medium passage  13 , and is constituted as a cooling bearing device.  
         [0025]    The cooling medium passage  13  is constituted by an annular space  14  formed internally of the bearing  8 , and a partitioning wall  15  provided in the annular space  14 .  
         [0026]    The partitioning wall  15  is provided spirally as shown in the peripheral developed view of FIG. 4. By the partitioning wall  15 , the cooling medium passage  13  comprising two spiral grooves is formed in the annular space  14 . A cooling medium inlet  16  is formed at the end of one groove, and a cooling medium outlet  17  is formed at the end of the other groove. An inlet pipe  18  and an outlet pipe  19  extending through the bearing retainer  10  and the seal member  11  are connected to the cooling medium inlet  16  and outlet  17 .  
         [0027]    As shown in FIG. 2, the bearing  8  is constituted by integrally connecting an inner circumferential member  20  and an outer circumferential member  21 . The cooling medium passage  13  is formed in a boundary between the inner circumferential member  20  and the outer circumferential member  21 .  
         [0028]    In this embodiment, the inner circumferential member  20  is formed in the outer circumferential surface  21  with an annular recess forming the annular space  14 , and a spiral partitioning wall  15  shown in FIG. 14 is formed within the annular recess. Methods for integrating of the inner circumferential member  20  is formed in the outer circumferential surface  21  include welding, welding after shrinkage fitting and the like.  
         [0029]    In the integrated state as described above, the outer circumferential surface of the partitioning wall  15  is in contact with the inner circumferential surface of the outer circumferential member  21 . That is, the annular space  14  is surrounded by the inner circumferential surface of the outer circumferential member  21  and the outer circumferential surface of the annular recess of the inner circumferential member  20 , and the partitioning wall  15  is formed over the inner and outer circumferential surfaces.  
         [0030]    The partitioning wall formed over the inner and outer circumferential surfaces of the annular space  14  functions as a strengthening member. Accordingly, even if the annular space is made large, the lowering of the bearing strength can be compensated for.  
         [0031]    As shown in FIG. 1, the shaft center part of the rotor  5  is bored with a hole  22  in an axial direction from one end thereof. A pipe  23  is inserted into the hole  22  through an annular clearance, which clearance serves as a cooling medium passage  24 . The cooling medium passage is provided, at least, so as to correspond to the shaft part  7  of the rotor  5 .  
         [0032]    A rotational joint  25  is provided on the end of the rotor  5 , and the joint  25  is provided with a cooling medium inlet  26  and outlet  27 . The inlet  26  is communicated with the cooling medium passage  24 , and the outlet  27  is communicated with the interior of the pipe  23 . The cooling medium supplied from the inlet  26  passes through the cooling medium passage  24 , enters pipe  23  from the end opening of the pipe  23 , and flows out of the outlet  27 . A temperature adjusting medium supply device  28  as a cooling medium supply device is connected to the cooling medium inlet  16  and outlet  17  for cooling a bearing, and the inlet  26  and outlet  27  for cooling a rotor.  
         [0033]    In the temperature adjusting medium supply device  28 , a cooling medium supply source  29  and a heated medium supply source  30  are free to be switched by a three-way valve  31 . At start of the gear pump, the heated medium is supplied from the heated medium supply source  30  to the bearing  8  and the rotor  5  to thereby preheat and melt the cooled and solidified medium. When preheating is completed, the three-way valve  31  is switched to supply cooling medium from the cooling medium source  29  to cool the bearing  8  and at least the shaft part  7  of the rotor  5 .  
         [0034]    Piping of the temperature adjusting medium supply device  28  is first connected from the three-way valve  31  to the inlet  26  for cooling a rotor, piping from the outlet  27  is connected to the inlet pipe  18  for cooling a bearing, and piping from the outlet pipe  19  for cooling a bearing is returned to the temperature adjusting medium supply device  28 .  
         [0035]    That is, the medium from the temperature adjusting medium supply device  28  first passes the rotor  5  and thereafter passes the bearing  8 .  
         [0036]    By the provision of the piping construction as described above, the cooling medium temperature within the bearing  8  can be set to be higher than the cooling medium temperature within the rotor  5 .  
         [0037]    According to cooling of the above constitution, the cooling temperature of the bearing  8  can be set to be higher than the rotor  5 , shrinkage of the inside diameter of the bearing caused by excessive cooling is prevented. Accordingly, the reduction in the bearing clearance is prevented and the baking is prevented.  
         [0038]    It is noted that the present invention is not limited to the above-described embodiment, but the cooling medium supply device of the bearing may be provided separately from that of the rotor, and the temperature control of the bearing  8  may be carried out independently of the rotor  5 .  
         [0039]    Further, the medium from the temperature adjusting medium supply device  28  is not limited to an arrangement that the cooling medium supply device  29  and the heated medium supply device  30  are free to be switched by the three-way valve  31 , but there may be employed an arrangement that there is temperature adjusting range from cooling to heating, and the medium is supplied from a single supply source. In this case, preferably, the temperature adjusting medium is heated (preheated) by hot oil at 100˜200°, and cooling is carried out by temperature control of a hot oil unit.  
         [0040]    Further, the gear pump is not limited to one for carrying molten resin. Further, the type of the cooling medium passage of the bearing  8  or the rotor  5  may be of the conventional type. Furthermore, the temperature adjusting medium supply device  28  may be of a type in which only the cooling medium is supplied.