Abstract:
A pulley is configured to receive a torque from a drive source for rotation. The pulley includes a resinous pulley body having a belt engagement portion on the outer periphery of the pulley body. The pulley includes a base plate integrally provided to a pin protruding from the pulley body at a predetermined position to engage another member other than the pulley and being insert molded within the pulley body.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2004-111281 filed on Apr. 5, 2004; the entire contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a pulley and a power transmission device using the same, and more specifically to a pulley and a power transmission device, which are suitable for use in driving a compressor built in a refrigeration cycle of a car air conditioner.  
         [0004]     2. Descriptions of the Related Arts  
         [0005]     For example, a power transmission device having a torque limiter function is disclosed in Japanese Patent Laid-Open No. Hei 8 (1996)-135752. This power transmission device includes a pulley as a driving-side rotation member driven upon receipt of power from an engine. The power transmission device includes a hub as a driven-side rotation member, which is disposed coaxially in parallel with the pulley and rotatably driven by the pulley. The pulley and the hub have an engaging mechanism having a torque limiter function therebetween. The engaging mechanism links the pulley and the hub and transmits rotation torque to the hub during normal driving. The engaging mechanism releases the link between the pulley and the hub during an abnormal time, for example, at the time of locking due to seizing failure of a compressor. Thus, breakages of other portions in the power transmission device are prevented during the abnormal time.  
         [0006]     To be concrete, the engaging mechanism includes a metallic pin pressed into a press hole of the pulley made of metal. The engaging mechanism includes a metallic holding member fixed to the hub. The engaging mechanism includes an elastic body that is linked to the pin and held in a clearance of the holding member. During normal driving, the elastic body links the hub and the pulley while being held in the clearance of the holding member. During abnormal driving, the elastic body is deformed elastically, and slips through the clearance of the holding member to release the link between the hub and the pulley.  
         [0007]     In this device, if the pulley made of a metal is changed to a pulley made of a resin, the device is preferably lightened. However, extremely large rotation torque is applied to the pin provided in the pulley. Accordingly, there is no other choice but to adopt a pulley made of metal in terms of the structure of the device, in order to use the device over a prolonged period so that the pin does not fall down even if the large rotation torque is applied to the pin. For this reason, a change from the metallic pulley to the resin pulley has not been considered.  
         [0008]     On the condition that the device has a structure that the press hole for pressing the pin thereinto is provided in the resin pulley and the pin is pressed thereinto, even if a design precision of the pin and press hole is made extremely high, sufficient fastening power can not be obtained due to difference of a thermal shrinkage factor between the pin and the resin pulley. If a resin pulley is adopted, which is made in such a manner that pins are located in predetermined positions in a metal mold and then resin is injected into the metal mold to be insert molded, the fastening power between the resin pulley and the pins decreases by shrinkage of the melted resin at the time the resin solidified.  
       SUMMARY OF THE INVENTION  
       [0009]     An object of the invention is to provide a pulley made of a resin in which a pin does not fall down even when a large rotation torque is applied thereto.  
         [0010]     The first aspect of the invention provides a pulley configured to receive a torque from a drive source for rotation. The pulley includes a resinous pulley body having a belt engagement portion on the outer periphery of the pulley body. The pulley includes a base plate integrally provided to a pin protruding from the pulley body at a predetermined position to engage another member other than the pulley and being insert molded within the pulley body.  
         [0011]     The second aspect of the invention provides a power transmission device. The device includes a pulley as a driving-side rotation member to receive a torque from a drive source for rotation. The device includes a driven-side rotation member arranged coaxially parallel to the pulley to be rotatably driven by the pulley. The device includes a link mechanism. The link mechanism includes a pin protruding from the pulley toward the driven-side rotation member. The link mechanism includes a link member provided to the driven-side rotation member and engaging the pin of the pulley. The link mechanism transmits a driving force form the pulley to the driven-side rotation member. The link mechanism cuts off the driving force to be transmitted when the driven-side rotation member has a drive load over a predetermined value. The pulley includes a resinous pulley body having a belt engagement portion on the outer periphery of the pulley body. The pulley includes a base plate integrally provided to a pin protruding from a pulley body at a predetermined position to engage another member other than a pulley and being insert molded within the pulley body.  
         [0012]     Two or more pins may protrude from the base plate.  
         [0013]     The base plate may include a protrusion piece protruding in a direction crossing a direction of rotating the pulley.  
         [0014]     The pulley may include a bearing as an insert component located on the inner periphery of the pulley and insert molded within the pulley body. The base plate has a fitting-into opening having the outer periphery of the bearing fitted thereinto. The base plate and the bearing as insert components are insert molded within the pulley body, with the base plate and the bearing fitted with each other.  
         [0015]     The base plate may have windows.  
         [0016]     The base plate and the bearing may include engagement portions engaging with each other for preventing relative rotation between the base plate and the bearing. The base plate and the bearing as insert components are insert molded within the pulley body, with the base plate and the bearing joined each other.  
         [0017]     According to the first and second aspects, unlike in the case of a structure where pins are merely insert molded in a pulley main body, the structure is adopted, where the base plate having the pins provided integrally therewith is insert molded in the pulley main body. In this structure, the base plate functions as a base of the pins within the pulley main body, thus enhancing connection strength between the pins and the pulley main body. Therefore, even when a large load is applied to the pins from another member, this structure prevents the pins  24  from falling down out of the pulley main body made of resin, and from coming off out of the pulley main body. The structure achieves lighter resin pulley, with abolishing a metallic pulley, and a lighter power transmission device.  
         [0018]     The pins protruding from the base plate does not require insert molding of separately retained pins in the pulley main body, thus facilitating manufacture of the pulley.  
         [0019]     The base plate includes the protrusion piece protruding in the direction crossing the rotation direction of the pulley, and the structure enhances rotation-preventing force of the base plate within the pulley body, thus providing a structure where the pin hardly falls down.  
         [0020]     The fitting-into opening of the base plate serves as a positioning guide of the base plate, thus facilitating the positioning of the pins.  
         [0021]     The windows formed to the base plate allow melted resin to flow through the windows of the base plate if the base plate exists within the metal mold during the insert molding, thus suppressing deterioration in flowability of the melted resin as low as possible. The structure enhances connection strength between the pulley main body and the base plate  
         [0022]     The base plate and the bearing include engagement portions engaging each other to prevent relative rotation between the base plate and the bearing, and the base plate and the bearing are insert-molded as insert components, with the base plate and the bearing connected. Therefore, the bearing and the base plate are mechanically connected before they are molded with a resin. In other words, in the pulley made of a resin, the base plate functions as a flange portion protruding from the external circumference of the bearing. This structure enlarges a contact area of the pulley main body and the bearing, thus enhancing the connection strength between the bearing and the pulley body.  
     
    
     BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS  
       [0023]      FIG. 1  is a side view of a substantial part of a power transmission structure according to a first embodiment of the present invention;  
         [0024]      FIG. 2  is a longitudinal section view of a power transmission device of  FIG. 1 ;  
         [0025]      FIG. 3  is a schematic perspective view of a resin pulley used for the power transmission device of  FIG. 1 ;  
         [0026]      FIGS. 4A and 4B  are perspective views illustrating an assemble state of a bearing and a board as an insert component;  
         [0027]      FIG. 5  is an illustrative view of an assemble method of the power transmission device of  FIG. 1 ;  
         [0028]      FIG. 6  is a side view illustrating a substantial part of the power transmission device of  FIG. 1  after power shutoff;  
         [0029]      FIG. 7  is a perspective view illustrating a first modification of a pulley board of  FIG. 3 ;  
         [0030]      FIG. 8  is a perspective view illustrating a second modification of the pulley board of  FIG. 3 ;  
         [0031]      FIGS. 9A, 9B  and  9 C are section views illustrating a structural example of a pin of the board of  FIG. 3 ;  
         [0032]      FIG. 10  is a section view illustrating a pulley of another embodiment;  
         [0033]      FIGS. 11A and 11B  are illustrative views for schematically explaining an assemble state of a board and a bearing insert molded into the pulley of  FIG. 10 ;  
         [0034]      FIG. 12  is a view for illustrating an appearance as a comparison example, which shows that a pin is insert molded with a resin; and  
         [0035]      FIG. 13  is a block diagram illustrating a compressor system using the power transmission structure of  FIG. 1 .  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0036]     Embodiments of the invention will be described with reference to drawings.  
       First Embodiment  
       [0037]     An entire structure of a power transmission device  1  will be described. In  FIG. 2 , a housing  2  of a clutchless compressor (driven-side rotation member) is provided, and a pulley  20  (driving-side rotation member) is rotatably supported by a boss portion  2   a  of the housing  2 . The housing  2  houses a rotation shaft  7  that is coaxially located with respect to the boss portion  2   a  and protrudes to the outside from the boss portion  2   a . The rotation shaft  7  has an end portion, and a hub  10  (driven-side rotation member) is fixed to the end portion thereof.  
         [0038]     The hub  10  has a plurality of pin insertion holes  11  at predetermined intervals (120° in this embodiment) on the identical circumference locating the rotation shaft  7  at the center. The pin insertion holes  11  have cylindrical pins  13 , a respective one of which is fixed to a corresponding one of the pin insertion holes  11 , while passing through the hole  11 .  
         [0039]     As illustrated in  FIG. 1 , the pulley  20  has a plurality of cylindrical pins  24  (three pieces in this embodiment) that stand on one end face thereof (on a hub side). The pins  24  are located at predetermined angular intervals (120° in this embodiment) on the identical circumference locating the center point of the pulley  20  at the center. A respective one of the pins  24  of the pulley  20  is linked to a corresponding one of the pins  13  of the hub  10  by use of a link member  12 .  
         [0040]     The link member  12  has a leaf spring-like shape fabricated from a spring material such as high carbon steel. The link member  12  is formed by stacking one or more plate members M, which are punched off into a predetermined shape so as to have the identical shape and size, in the thickness direction (see  FIG. 1 ). Although the number of the plates M is two in this embodiment, the number of the plate members M may be one. This link member  12  has a forked shape, and includes a pair of opposed side pieces  12   a  with a slit-like clearance  16  interposed therebetween. The link member  12  has a through-hole  14  on the lining end side. The through-hole  14  is formed so as to communicate with the clearance  16  and contacts the external periphery of the pin  13  for rotatably engaging with the pin  24 . The link member  12  has, on the open-end side, pinching portions  15  that are formed in the tip portions of the side pieces  12   a  and retain the pin  24  therebetween. Each of the pinching portions  15  is structured as a concave curve plane  15  formed along the external periphery of the pin  24 . This concave curve plane  15  has, at both ends, convex portions  17 A and  17 B that contact the external periphery of the pin  24 . The convex portions  17 A and  17 B are formed so as to have a convex circular shape, and only the convex portions  17 A and  17 B in each of the concave curve portions  15  contact the external periphery of the pin  24 . Portions of the concave curve plane  15  other than the convex portions  17 A and  17 B have a clearance from the external periphery of the pin  24 . The distance L 1  between the convex portions  17 A and  17 A on the link end side (base end side) is larger than the distance L 2  between the convex portions  17 B and  17 B on the opening end side (tip end side). The clearance  16  between the pair of side pieces  12   a  has the width W 1  that is slightly larger than the diameter of the external periphery of the pin  24 , allowing the pin  24  to be movably housed therein.  
         [0041]     When the pulley  20  and the hub  10  are linked in an assembly step of the power transmission device  1 , the link member  12  links the pin  24  of the pulley  20  and the pin  13  of the hub  10  to each other. To be concrete, the pin  13  is first fitted into the through-hole  14  of the link member  12  as shown in  FIG. 5 , and the pin  24  is inserted in the clearance  16  of the link member  12 . Subsequently, in a state where the hub  10  is fixed so as not to be rotated, the pulley  20  is rotated (in the arrow direction R 1 ). The rotation allows the pin  24  in the clearance  16  to move to the open-end side, and the pin  24  is pressed into the pinching portions  15  on the open-end side. Thus, the pin  24  elastically deforms the side-pieces  12   a  of the link member  12  to be separate from each other, and the pin  24  is pressed between the pinching portions  15 . Finally, the side-pieces  12   a  of the link member  12  are elastically restored to an original shape thereof, with the pin  24  retained between the pinching portions  15  of the link member  12  as shown in  FIG. 1 .  
         [0042]     Next, the operation of the power transmission device structured as above will be described. A power of an engine  101  shown in  FIG. 13  is transmitted to the pulley  20  using a belt (not shown), and the pulley  20  is rotated. The rotation of the pulley  20  is transmitted to the hub  10  through the pin  24 , the link member  12  and the pin  13 , permitting the rotation shaft  7  to be rotated. The rotation provides the power of the engine as a driving machine to a compressor  102  as a driven machine for operation.  
         [0043]     When seizure and the like are produced within the compressor, causing a load torque to exceed a predetermined value, the pin  24  retained by the pinching portions  15  of each link member  12  spreads out the side pieces  12   a  of the link member  12  from each other to separate from the link member  12 . This separation cuts off transmission of the power from the pulley  20  to the rotation shaft  7  for idling the pulley  20  (see  FIG. 6 ), without any damage to other portions of the power transmission device  1  in addition to the compressor and the engine.  
         [0044]     Herein, operation and benefits achieved by using the link member  12  will be described.  
         [0045]     The link member  12  has a structure in which only the convex portions  17 A and  17 B formed in the tips of the pinching portions  15  retaining the pin  24  therebetween contact the external periphery of the pin  24 . This structure permits the pin  24  to be securely retained without wobbling. This structure prevents occurrence of noisy sound and wear of the link member  12 . This structure advantageously stabilizes a force to separate the pin  24  retained between the pinching portions  15  toward the open-end side.  
         [0046]     The convex portions  17 A and  17 B have a structure that they are formed in the convex circular shape and have a point contact with the external periphery of the pin  24 . This structure advantageously reduces wear of the convex portions  17 A and  17 B, thus hardly varying force in magnitude to separate the pin  24  from the convex portions  17 A and  17 B.  
         [0047]     This structure is that the distance L 1  between the convex portions  17 A on the link end side is larger than the distance L 2  between the convex portions  17 B and  17 B on the open end side. Therefore, the force for opening the side pieces  12   a  from each other to press the pin  24  inserted in the clearance  16  between the curve planes  15  and  15 , is smaller than the force for opening the side pieces  12   a  from each other to separate the pin  24  retained between the curve planes  15  and  15  toward the open end side.  
         [0048]     The link member  12  has a structure where the clearance  16  extending from the open-end side to the link the end side of the member  12  communicates with the through-hole  14  on the link end side. Therefore, when in a linking step, the pin  24  inserted in the clearance  16  is pressed between the pinching portions  15  provided on the open end side of the clearance  16 , the link member  12  deforms over the entire length. This reduces size of the link member  12 .  
         [0049]     The link member  12  has a structure constructed by stacking the plurality of plate members M (two in this embodiment) in the thickness direction. The structure facilitates a punching step for the plate member M constituting the link member  12 , thus improving workability, and is hard to produce burr, deformation and the like, for improvement in the dimensional precision of the link member  12 .  
         [0050]     The pulley  20  of this embodiment is a resin pulley, and descriptions for the pulley  20  will be described in detail.  
         [0051]     The pulley  20  of this embodiment includes a pulley main body  21  made of a resin, which has a belt engagement portion  21   a  in the external periphery, as shown in  FIGS. 2 and 3 . The pulley  20  includes a bearing  22  as an insert component that is located on the internal periphery side and is insert molded integrally therewith in the pulley main body  21 . Similarly, the pulley  20  includes a metallic base plate  23  as an insert component that is insert molded integrally therewith in the pulley main body  21 .  
         [0052]     The base plate  23  is a metallic plate in which the plurality of pins  24  (three in this embodiment) engaging with the link member  12  are formed integrally therewith as shown in  FIG. 2  and  FIG. 4A  As shown in  FIG. 4A , the base plate  23  has an annular circular plate having at the central portion a fitting-into opening  23   a , into which the external periphery of the bearing  22  is to be fitted.  
         [0053]     The insert-molded member composed of the metallic bearing  22 , the base plate  23  and the resin pulley main body  21  is made in the following manner. As shown in  FIG. 4B , an assembled product produced by fitting of the bearing  22  into the base plate  23  is previously located within a metal mold for injection molding (not shown) as an insert component, and a resin is injected into the metal mold. Subsequently, the resinous pulley main body  21 , the metallic bearing  22  and the base plate  23  are united with each other.  
         [0054]     Benefits of this embodiment will be described below.  
         [0055]     First, according to this embodiment, unlike in the case of a structure where pins are merely insert molded in a pulley main body, the structure is adopted, where the base plate  23  having the pins  24  provided integrally therewith is insert molded in the pulley main body  21 . In this structure, the base plate  23  functions as a base of the pins  24  within the pulley main body  21 , thus enhancing connection strength between the pins  24  and the pulley main body  21 . Therefore, even when a large load is applied to the pins  24  from other members (the link member  12  in this embodiment), this structure prevents the pins  24  from falling down out of the pulley main body  21  made of resin, and from coming off out of the pulley main body  21 . The structure achieves the resin pulley  20  lighter than a metallic pulley, thus reducing weight of the power transmission device  1 .  
         [0056]     As an additional benefit, provision of the pins  24  integrally with the base plate  23  facilitates positioning of the pins  24  by use of the base plate  23  as a guide. The base plate  23  functions as a skeleton member of the pulley main body  21 . Accordingly, increase in the strength of the pulley main body  21  is also expected.  
         [0057]     Secondly, this embodiment has a structure in which the plurality of pins  24  are provided so as to protrude from the base plate  23 . This structure eliminates necessity to insert mold the plurality of pins  24  to the pulley main body while retaining the pins  24  separately, thus facilitating manufacture of the pulley. As a comparison example,  FIG. 12  is an example in which pins  124  are insert molded to the pulley main body  21 , with the pins  124  separately retained. In such a case, it is necessary to use positioning pins  125  and  126  for retaining both ends of the respective pins  124  for each pin  124 , thus rendering a metal insert mold complicated. In  FIG. 12 , only one pin  124  is illustrated as a representative of the pins  124 , and illustrations of other pins  124  are omitted.  
         [0058]     Thirdly, this embodiment has a structure where the base plate  23  includes the fitting-into opening  23   a  for fitting the external periphery of the bearing  22  thereinto. In this structure, the fitting-into opening  23   a  of the base plate  23  serves as a positioning guide of the base plate  23 , thus further facilitating the positioning of the pins  24 . Particularly, the embodiment enhances coaxility of the pulley main body  21 , the bearing  22  and the pins  24 .  
         [0059]     Next, modifications of the base plate will be described.  
         [0060]      FIG. 7  is a first modification of the base plate. The base plate  23 B of the first modification includes protrusion pieces  31  protruding in the direction crossing the rotation direction of the pulley  20  (normal to the rotation direction in this modification, i.e., the axial direction). These protrusion pieces  31  are formed by punching out parts of the base plate  23 B, which is a metallic plate as a material, into approximately like a letter “U”, and by bending the parts thereof to the outside erectly. The punched-out parts by the bending serve as windows  32 . When this base plate  23 B of the first modification is used, the base plate  23 B is structured with the protrusion pieces  31  that protrude in the direction crossing the rotation direction of the pulley  20 . This structure increases a force to prevent a rotation of the base plate  23 B in the pulley main body  21 , thus hardly falling down the pins  24 .  
         [0061]      FIG. 8  is a second modification of the base plate. The base plate  23 C of the second modification has a structure where a plurality of windows  41  (three in this modification) are formed. The windows  41  are formed as a fan along the circumferential direction of the base plate  23 C, and thus the base plate  23 C includes an internal periphery portion  42  and an external periphery portion  42 , which are opposite to each other with the windows  41  interposed therebetween.  
         [0062]     The use of the base plate  23 C of this second modification decreases the volume of the base plate  23 C made of metal that mounts weight, thus further lightening the pulley  4  and the power transmission device  1 . When the base plate  23 C of the second modification is used, melted resin flows through the windows  41  of the base plates  23 C even if the base plate  23 C exists in a metal mold during the insert molding. Therefore, deterioration in flowability of the melted resin due to the existence of the base plate in the metal mold is suppressed as low as possible. The second modification has also a benefit that the connection strength between the pulley main body  21  and the base plate  23 C is enhanced.  
       Second Embodiment  
       [0063]      FIGS. 10, 11A  and  11 B show a pulley  20  of a power transmission device according to a second embodiment of the invention. The pulley  20  of the second embodiment includes engaging portions  51  and  52  in the base plate  23 D and the bearing  22 D. The engaging portions  51  and  52  engage with each other to prevent a relative rotation therebetween. More specifically, engaging convex portions  51  protrude radially inwardly from the periphery of the fitting-into opening  23   a  of the base plate  23 D, and the convex portions  51  are arranged at equal intervals in the circumferential direction of the base plate  23 D. On the other hand, engaging concave portions  52  are concaved radially inwardly on the external circumference of an external wheel of the bearing  22 D, and the engaging concave portions  52  are arranged at equal intervals in the circumferential direction of the bearing  22 D.  
         [0064]     According to the second embodiment, in addition to the benefits of the first embodiment, the structure is that both members  23 D and  22 D are insert molded as insert components, with the base plate  23 D and the bearing  22 D connected. Therefore, as shown in FIG,  11 B, the bearing  22 D and the base plate  23 D are mechanically connected before they are molded with a resin. In other words, in the pulley  21  made of a resin, the base plate  23 D functions as a flange portion protruding from the external circumference of the bearing  22 D. This structure enlarges a contact area of the pulley main body  21  and the bearing  22 D, thus enhancing the connection strength between the bearing  22 D and the pulley main body  21 . Thus, the pins  24  are made to fall down more hardly by virtue of this structure.  
         [0065]     In the first and second embodiments, the pins  24 A and the base plate  23  were integrally molded as shown in  FIG. 9A . While, the invention is not limited to this, and the pin  24 B may be jointed to the base plate  23  by welding, as shown in  FIG. 9B . As shown in  FIG. 9C , the pin  24 C may protrude from the base plate  23  by press working while taking a hollow cylindrical shape. The example shown in  FIG. 9A  has a merit that strength of the pin  24 A is maintained at a high level. The example shown in  FIG. 9B  has a benefit that the conventional pin  24 B can be diverted without any adjustment. The example of  FIG. 9C  is advantageous that it is desired to allow the external circumference shape of the pin  24 C to have slight flexure.  
         [0066]     In the embodiments, the fork-shaped link member  12  is used as the link member. On the other hand, in the present invention, other link members may be used. Alternatively, other linking means may be used.  
         [0067]     In the embodiments, the descriptions were made by exemplifying the power transmission device in which the hub (driven-side rotation member) fixed to the rotation shaft of the compressor of the car air conditioner and the pulley (driving-side rotation member) rotating by the engine are linked. While, the invention may be applied to a power transmission device that links another driven-side rotation members and the driving-side rotation member to each other.  
         [0068]     In the embodiment, the pulley used for the power transmission device was described. While, the present invention can be applied to a pulley used for another devices.  
         [0069]     Although the invention has been described above by reference to certain embodiments of the invention, the invention is not limited to the embodiments described above. Modifications and variations of the embodiments described above will occur to those skilled in the art, in light of the above teachings. The scope of the invention is defined with reference to the following claims.