Patent Publication Number: US-2017370477-A1

Title: External control type fluid coupling

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority under 35 U.S.C. §119 to Japanese Patent Application 2016-125695, filed on Jun. 24, 2016, the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     This disclosure relates to an external control type fluid coupling. 
     BACKGROUND DISCUSSION 
     In the related art, as an external control type fluid coupling, for example, a structure described in JP2011-231896A (Reference 1) is known. The external control type fluid coupling includes a rotary shaft that is fixed to a drive disk, a housing (closed vessel) that is supported by the rotary shaft, and a partition plate that partitions an inside of the housing into an oil reservoir and a torque transmission chamber in which the drive disk is installed. Moreover, an oil supply adjusting hole is formed in the partition plate to communicate with the oil reservoir and the torque transmission chamber. In addition, the external control type fluid coupling includes a leaf spring-like valve member capable of opening and closing the oil supply adjusting hole by generating a biasing force for closing the oil supply adjusting hole, and an electromagnet that generates an attraction force for opening the oil supply adjusting hole against the biasing force of the valve member. Oil is supplied into the torque transmission chamber through the oil supply adjusting hole so that the drive disk transmits a rotation torque to the housing or an object to be driven integrally with the housing. 
     However, in such an external control type fluid coupling, since the electromagnet is turned on (excited) to generate the attraction force which is described above, if an abnormality occurs in the electromagnet or a power supply system, the oil supply adjusting hole cannot be opened. That is, the oil cannot be supplied through the oil supply adjusting hole and thereby the rotation torque cannot be transmitted to the housing or the object to be driven integrally with the housing. 
     Thus, a need exists for an external control type fluid coupling which is not susceptible to the drawback mentioned above. 
     SUMMARY 
     An external control type fluid coupling according to an aspect of this disclosure includes a drive disk that is fixed to a rotary shaft; a housing that is rotatably supported by the rotary shaft and defines an internal space; a partition plate that is provided in the housing and partitions the internal space into an operation chamber accommodating the drive disk and a storage chamber storing a fluid; a supply hole that is formed in the partition plate and supplies the fluid from the storage chamber to the operation chamber; a valve body that is provided in the housing and is made of a magnetic material capable of opening and closing the supply hole; and an electromagnet that generates an attraction force between the electromagnet and the valve body so that the valve body is displaced to a closed state for closing the supply hole. The valve body is rotatably connected to the housing. The center of gravity of the valve body is set such that the valve body is rotated to a side on which the supply hole is opened by a centrifugal force acting with rotation of the housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and additional features and characteristics of this disclosure will become more apparent from the following detailed description considered with the reference to the accompanying drawings, wherein: 
         FIG. 1  is a sectional view illustrating a structure of an external control type fluid coupling of an embodiment; 
         FIG. 2  is a perspective view illustrating a valve portion of the external control type fluid coupling of the same embodiment; and 
         FIGS. 3A and 3B  are enlarged views illustrating an opening and closing operation of the external control type fluid coupling of the same embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, an embodiment of an external control type fluid coupling will be described. 
     As illustrated in  FIG. 1 , an external control type fluid coupling  1  includes a rotary shaft  10  as a drive-side rotation body, a driving portion  20 , a housing  30  as a driven-side rotation body, and a drive disk  40 . 
     The rotary shaft  10  has a flange portion  11  protruding outward from a tip of one side thereof (right side in the drawing). A drive torque is input from an engine (not illustrated) to the flange portion  11  and thereby the rotary shaft  10  rotates around a rotation axis O 1 . In addition, the rotary shaft  10  has a substantially columnar large-diameter portion  12 , a medium-diameter portion  13 , and a small-diameter portion  14  which gradually decrease in diameter as separating from a flange portion  11  side along the rotation axis O 1 . Moreover, the large-diameter portion  12 , the medium-diameter portion  13 , and the small-diameter portion  14  are concentric with the rotation axis O 1 . 
     The driving portion  20  has a substantially ring-shaped electromagnet  21  around the rotation axis O 1  and a case  22  that defines a ring groove  22   a  accommodating the electromagnet  21  and is made of a magnetic material. The electromagnet  21  becomes a magnetic generation source, for example, by being energized by a control signal from an external controller (not illustrated). The case  22  is rotatably supported on the large-diameter portion  12  via a first annular bearing portion  23  (bearing) fitted to an inner peripheral surface  22   b , and is fixed to an engine block (not illustrated). In other words, the case  22  allows the rotation of the large-diameter portion  12  (rotary shaft  10 ) in a state of being fixed to the engine block. 
     The housing  30  has a first housing  31  and a second housing  32  which are divided into two in a direction of the rotation axis O 1 . The first housing  31  positioned on the flange portion  11  side (right side in the drawing) has a substantially cylindrical bottomed shape around the rotation axis O 1  and has a substantially cylindrical boss portion  31   b  protruding around the rotation axis O 1  in an inner peripheral portion of a bottom portion  31   a  positioned on the flange portion  11  side. The first housing  31  is rotatably supported on the medium-diameter portion  13  via a second annular bearing portion  33  (bearing) fitted to an inner peripheral surface  31   c  of the boss portion  31   b.    
     On the other hand, the second housing  32  positioned on a side separating from the flange portion  11  (left side in the drawing) has a substantially cylindrical bottomed shape around the rotation axis O 1  and a fan (not illustrated) for cooling the engine as an object to be driven in an outer periphery  32   a.    
     Moreover, inner diameters of the first housing  31  and the second housing  32  are set to be equal to each other in size, and a substantially annular outward flange portion  31   d  formed on an outer peripheral portion of the first housing  31  and an opening end  32   b  of the second housing  32  are in close contact with each other, and liquid-tightly coupled to each other, thereby forming an internal space  34 . A viscose fluid (not illustrated) such as silicone oil is stored in the internal space  34 . The first housing  31  and the second housing  32  (fan) integrally rotate around the medium-diameter portion  13 . 
     Here, a substantially annular peripheral groove  31   e  around the rotation axis O 1  is formed in the bottom portion  31   a  of the first housing  31  to be recessed toward a side (left side in the drawing) separating from the flange portion  11 . The peripheral groove  31   e  faces the case  22  (driving portion  20 ) in the direction of the rotation axis O 1 . In addition, a through hole  31   f  is formed in the bottom portion  31   a  of the first housing  31  to penetrate substantially parallel to the rotation axis O 1  in conformity with a predetermined angular position (angular position on a lower side of the drawing) of the peripheral groove  31   e.    
     Therefore, a yoke  50  made of a magnetic material formed in conformity with the peripheral groove  31   e  is attached to the peripheral groove  31   e  of the first housing  31  (bottom portion  31   a ). That is, the yoke  50  has a substantially annular outer yoke  51  having an outer diameter equal to an inner diameter of the peripheral groove  31   e  in size on an outer peripheral side and fixed to the peripheral groove  31   e , and a substantially annular inner yoke  52  having an inner diameter equal to the inner diameter of the peripheral groove  31   e  in size on an inner peripheral side and fixed to the peripheral groove  31   e . Moreover, the inner diameter of the outer yoke  51  is set greater than the outer diameter of an inner yoke  52  in size, and a gap  53  is set between the outer yoke  51  and the inner yoke  52  in the radial direction. A sealing unit made of an appropriate non-magnetic material is provided in the gap  53  and the outer yoke  51  and the inner yoke  52  are cooperated with each other to close the through hole  31   f  of the first housing  31  (bottom portion  31   a ). 
     The outer yoke  51  and the inner yoke  52  face the case  22  (driving portion  20 ) in the direction of the rotation axis O 1 , and respectively have substantially cylindrical outer side wall  51   a  and inner side wall  52   a  standing upright along the outer peripheral surface and the inner peripheral surface of the case  22 . Therefore, the outer yoke  51  and the inner yoke  52  (yoke  50 ) close an opening  22   c  in a state where the case  22  is interposed between the outer side wall  51   a  and the inner side wall  52   a.    
     A substantially donut-plate-shaped partition plate  60  is provided at an opening end portion of the first housing  31  so as to divide the internal space  34  formed between the first housing  31  and the second housing  32  into two in the direction of the rotation axis O 1 . Therefore, the internal space  34  defines a storage chamber  34   a  and an operation chamber  34   b  respectively on the yoke  50  side and the second housing  32  side with the partition plate  60  interposed therebetween. Moreover, a recovery path (not illustrated) is formed in the first housing  31  to communicate with the storage chamber  34   a  and the operation chamber  34   b.    
     A first labyrinth portion  61  having a substantially comb-shaped cross section is formed at the outer peripheral portion of the partition plate  60  on the operation chamber  34   b  side, and a supply hole  62  penetrating the partition plate  60  substantially parallel to the direction of the rotation axis O 1  is formed at the predetermined angular position (angular position on the lower side of the drawing). The supply hole  62  communicates with the storage chamber  34   a  and the operation chamber  34   b.    
     The substantially donut-plate-shaped drive disk  40  disposed on the operation chamber  34   b  side is connected to the small-diameter portion  14  of the rotary shaft  10  so as to be integrally rotated. That is, an inner peripheral portion  41  of the drive disk  40  is engaged with the small-diameter portion  14  of the rotary shaft  10  so that the drive disk  40  is integrally rotated with the rotary shaft  10 . 
     A second labyrinth portion  42  is formed at an outer peripheral portion of the drive disk  40  facing the first labyrinth portion  61  in the direction of the rotation axis O 1 . The second labyrinth portion  42  has a substantially comb-shaped cross section so as to protrude alternately with the first labyrinth portion  61 . The first labyrinth portion  61  and the second labyrinth portion  42  cooperate to constitute a torque transmission portion. 
     A valve portion  70  is provided at the predetermined angular position (angular position on the lower side of the drawing) within the operation chamber  34   b  in the first housing  31 . 
     That is, as also illustrated in  FIG. 2 , the valve portion  70  has a pair of block-shaped support portions  71  standing upright parallel to each other from the bottom portion  31   a  of the first housing  31  substantially parallel to the rotation axis O 1  with a space in a tangential direction in the peripheral direction around the rotation axis O 1 . In addition, the valve portion  70  has a substantially columnar shaft portion  72  which is an axis (hereinafter, referred to as “rotation axis O 2 ”) extending in the tangential direction, and a substantially S-shaped valve body  73  made of a magnetic material. The both support portions  71  unrotatably support both ends of the shaft portion  72 . The shaft portion  72  passes through a center portion of the valve body  73  and rotatably supports the valve body  73 . Therefore, the valve body  73  rotates around the rotation axis O 2 . 
     The valve body  73  has an electromagnet-side valve body portion  74  and a supply hole-side valve body portion  75  on an inner side and an outer side of the shaft portion  72  in the radial direction around the rotation axis O 1 . The supply hole-side valve body portion  75  is set to have a plate thickness greater than that of the electromagnet-side valve body portion  74  and has a mass greater than that of the electromagnet-side valve body portion  74 . That is, the center of gravity G of the valve body  73  is positioned on the supply hole-side valve body portion  75  side, that is, outside the rotation axis O 2  of the shaft portion  72  in the radial direction around the rotation axis O 1 . In addition, facing planar portions  74   a  and  75   a  where the yoke  50  (gap  53 ) and the partition plate  60  (supply hole  62 ) face on a rotation locus around the rotation axis O 2  are respectively formed in the electromagnet-side valve body portion  74  and the supply hole-side valve body portion  75 . 
     Here, as illustrated in  FIG. 3A , the valve body  73  is configured such that when the rotation axis O 2  and the center of gravity G are in a state of being aligned in a straight line (on a straight line LN) in the radial direction (vertical direction in the drawing) around the rotation axis O 1 , the facing planar portions  74   a  and  75   a  are respectively separated from the yoke  50  and the partition plate  60 . On the other hand, the valve body  73  is configured such that when the facing planar portion  75   a  is in a state of abutting against the partition plate  60  (peripheral portion of the supply hole  62 ), the facing planar portion  74   a  abuts against or approaches the yoke  50 . 
     Next, an operation of the external control type fluid coupling of the embodiment will be described. 
     As illustrated in  FIGS. 3A and 3B , in the external control type fluid coupling  1 , for example, the drive torque is input from the engine (not illustrated) so that the drive disk  40  rotates around the rotation axis O 1  together with the rotary shaft  10 . In this case, when the supply hole  62  is opened, a fluid within the storage chamber  34   a  flows into the operation chamber  34   b  (torque transmission portion) via the supply hole  62  so that the drive disk  40  transmits the rotation torque to the partition plate  60  utilizing the viscosity of the fluid. Therefore, the first housing  31  (and the second housing  32 ) rotates integrally with the partition plate  60  and the fan rotates. The external control type fluid coupling  1  controls the rotation of the fan by switching opening and closing states of the supply hole  62  by the valve portion  70 . Moreover, even in a state where the fluid is not present in the operation chamber  34   b  of the internal space  34 , the rotation torque of the drive disk  40  is slightly transmitted to the housing  30 . Therefore, when the drive disk  40  rotates, the housing  30  also rotates accordingly. 
     The valve body  73  switches between an open state in which the supply hole  62  of the partition plate  60  is opened and a closed state in which the supply hole  62  is closed. Therefore, the valve portion  70  supplies the fluid within the storage chamber  34   a  to the operation chamber  34   b  or cuts off the supply thereof. 
     Since the valve body  73  is provided in the housing  30  (second housing  32 ), a centrifugal force F generated around the rotation axis O 1  acts and the valve body  73  separates from the partition plate  60  so that the valve body  73  is in the open state. Specifically, the center of gravity G thereof is displaced so as to be positioned on the straight line LN. Therefore, the supply hole-side valve body portion  75  of the valve body  73  is separated from the partition plate  60 . 
     In addition, an attraction force (magnetic force) generated by energization of the electromagnet  21  by a control signal from an external controller acts to cover a peripheral edge portion of the supply hole  62  so that the valve body  73  is in the closed state. Specifically, the electromagnet-side valve body portion  74  of the valve body  73  of the magnetic material is attracted to the electromagnet  21  side so that the supply hole-side valve body portion  75  approaches the partition plate  60  (peripheral edge portion of the supply hole  62 ). Therefore, the facing planar portion  75   a  abuts against the partition plate  60  (peripheral edge portion of the supply hole  62 ) and the valve body  73  is in the closed state in which the facing planar portion  74   a  abuts against or approaches the yoke  50 . That is, the electromagnet  21  generates a sufficient attraction force to close the valve body  73  against the centrifugal force F. 
     As described above, according to the embodiment, the following effects can be obtained. 
     (1) In the embodiment, the valve body  73  is rotated toward a side where the supply hole  62  is opened by the centrifugal force F acting with the rotation of the housing  30  when the electromagnet  21  is in a non-energized state. Accordingly, the fluid is supplied from the storage chamber  34   a  to the operation chamber  34   b  so that the rotation torque of the drive disk  40  is transmitted to the housing  30  or the fan integrated with the housing  30 . Therefore, for example, even in a case where an abnormality occurs in the electromagnet  21  or the power supply system thereof, the rotation torque of the drive disk  40  can be transmitted to the housing  30  or the fan integrated with the housing  30 . 
     (2) As illustrated in  FIGS. 3A and 3B , when the valve body  73  is in the closed state, the valve body  73  is separated from the straight line LN extending in the radial direction passing through the shaft portion  72  of the valve body  73  by a predetermined distance ΔL and is set so as to reduce the distance separating from the straight line LN in accordance with the rotation on the side where the supply hole  62  is opened. Therefore, in the embodiment, when the valve body  73  is in the closed state, the distance of the center of gravity G separating from the straight line LN is maximum (predetermined distance ΔL). That is, since an accommodation space required for the valve body  73  may be secured based on a rotation range that permits the movement of the center of gravity G up to the predetermined distance ΔL, it is possible to suppress an increase of the accommodation space in size. 
     (3) In the embodiment, the electromagnet-side valve body portion  74 , the rotation axis O 2  of the valve body  73 , and the supply hole-side valve body portion  75  are formed so as to be disposed in this order in a radial outward direction around the rotation axis O 1  of the rotary shaft  10 . Therefore, the electromagnet-side valve body portion  74  is disposed closer to the radial inward than the rotation axis O 2  of the valve body  73 . That is, the electromagnet  21  attracts the electromagnet-side valve body portion  74  positioned on the relatively inner peripheral side of the valve body  73 . Therefore, the dimension in the radial direction of the electromagnet  21  can be reduced and it is possible to suppress an increase thereof in size. 
     (4) In the embodiment, in the valve body  73 , the center of gravity G is disposed outside the shaft portion  72  in the radial direction around the rotation axis O 1  by changing the plate thicknesses of the supply hole-side valve body portion  75  and the electromagnet-side valve body portion  74 . Therefore, it is possible to reduce the dimension of the electromagnet-side valve body portion  74  in the longitudinal direction, for example, compared to a case where the plate thicknesses of the supply hole-side valve body portion  75  and the electromagnet-side valve body portion  74  are equal to each other. Thus, it is possible to suppress expansion of an occupied space required for the rotation of the valve body  73 . 
     Moreover, the embodiment described above may be modified as follows.
         In the embodiment, two or more sets of the valve portion  70  and the supply hole  62  may be provided.   In the embodiment, the first labyrinth portion  61  is provided in the second housing  32  and the second labyrinth portion  42  may be provided on a side facing the second housing  32 . That is, the drive disk  40  and the second housing  32  may cooperate to constitute the torque transmission portion.   In the embodiment, the yoke  50  may be fixed to the case  22 . In this case, it is preferable to form a non-penetrating hole shape instead of the through hole  31   f  of the first housing  31 .   In the embodiment, the supply hole  62  may be opened by energizing the electromagnet  21 . That is, for example, in the valve portion, the electromagnet-side valve body portion of the valve body is formed by a permanent magnet. Therefore, when the electromagnet  21  is deenergized, the electromagnet-side valve body portion and the yoke  50  abuts against or approaches each other so that the closed state may be established, and when the electromagnet  21  is energized, the electromagnet-side valve body portion and the electromagnet  21  repel each other so that the open state may be established. Even if the rotational speed of the housing  30  is low and the centrifugal force F is small, the valve body  73  can be brought into the open state in cooperation with the centrifugal force F and the rotational speed of the housing  30  can be increased more rapidly.   In the embodiment, the plate thickness of the supply hole-side valve body portion  75  may be set equal to or less than the plate thickness of the electromagnet-side valve body portion  74 . That is, the mass may be changed by changing the width dimension or the longitudinal dimension of the supply hole-side valve body portion  75  and the electromagnet-side valve body portion  74 .   In the embodiment, a sealing member having a sealing property may be provided on the facing planar portion  75   a  of the supply hole-side valve body portion  75 .   In the embodiment, a biasing member having a biasing force for holding the valve body  73  in the closed state may be provided. In this case, the attraction force of the electromagnet  21  required to bring the valve body  73  into the closed state can be reduced and it is possible to decrease the electromagnet  21  in size.       

     An external control type fluid coupling according to an aspect of this disclosure includes a drive disk that is fixed to a rotary shaft; a housing that is rotatably supported by the rotary shaft and defines an internal space; a partition plate that is provided in the housing and partitions the internal space into an operation chamber accommodating the drive disk and a storage chamber storing a fluid; a supply hole that is formed in the partition plate and supplies the fluid from the storage chamber to the operation chamber; a valve body that is provided in the housing and is made of a magnetic material capable of opening and closing the supply hole; and an electromagnet that generates an attraction force between the electromagnet and the valve body so that the valve body is displaced to a closed state for closing the supply hole. The valve body is rotatably connected to the housing. The center of gravity of the valve body is set such that the valve body is rotated to a side on which the supply hole is opened by a centrifugal force acting with rotation of the housing. 
     According to this configuration, the valve body is rotated to a side on which the supply hole is opened by the centrifugal force acting with the rotation of the housing when the electromagnet is in a non-energized state. Accordingly, the fluid is supplied from the storage chamber to the operation chamber and thereby the rotation torque of the drive disk is transmitted to the housing or an object to be driven integrally with the housing. Therefore, for example, even in a case where an abnormality occurs in the electromagnet or a power supply system thereof, the rotation torque of the drive disk can be transmitted to the housing or the object to be driven integrally with the housing. 
     In the external control type fluid coupling, it is preferable that the center of gravity is positioned closer to an outside than a shaft of the valve body in a radial direction around an axis of the rotary shaft, is separated from a straight line extending in the radial direction through the shaft of the valve body by a predetermined distance when the valve body is in the closed state, and is set so as to reduce a distance separating from the straight line in accordance with the rotation of the valve body to a side on which the supply hole is opened. 
     According to this configuration, the distance of the center of gravity separating from the straight line is the maximum (predetermined distance described above) when the valve body is in the closed state. That is, since an accommodation space required for the valve body may be secured based on a rotation range allowing movement of the center of gravity up to the predetermined distance, it is possible to suppress an increase in size of the accommodation space. 
     In the external control type fluid coupling, it is preferable that the electromagnet is provided so as to pass through the rotary shaft, the valve body has a supply hole-side valve body portion that closes the supply hole and an electromagnet-side valve body portion that is attracted to the electromagnet when in the closed state, and the valve body is formed so that the electromagnet-side valve body portion, an axis of the valve body, and the supply hole-side valve body portion are disposed in this order in a radial outward direction around the axis of the rotary shaft. 
     According to this configuration, the electromagnet-side valve body portion is disposed closer to the radial inward than the axis of the valve body. That is, the electromagnet attracts the electromagnet-side valve body portion positioned on a relatively inner peripheral side of the valve body. Therefore, it is possible to reduce a dimension of the electromagnet in the radial direction and to suppress an increase in size thereof. 
     According to the aspect of this disclosure, even in a case where an abnormality occurs in the electromagnet or a power supply system, the rotation torque can be transmitted to the housing or the object to be driven integrally with the housing. 
     The principles, preferred embodiment and mode of operation of the present invention have been described in the foregoing specification. However, the invention which is intended to be protected is not to be construed as limited to the particular embodiments disclosed. Further, the embodiments described herein are to be regarded as illustrative rather than restrictive. Variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present invention. Accordingly, it is expressly intended that all such variations, changes and equivalents which fall within the spirit and scope of the present invention as defined in the claims, be embraced thereby.