Patent Publication Number: US-2005143208-A1

Title: Pulley

Description:
BACKGROUND OF THE INVENTION  
      (i) Field of the Invention  
      The present invention relates to a pulley that is used, for example, in a compressor of an air conditioning system for vehicles.  
      (ii) Description of the Related Art  
      In general, as a compressor that is used in an air-conditioning system for vehicles, there has been known a compressor that comprises a compressor main body formed in a hollow condition, a compression section that compresses a fluid sucked into the compressor main body, a drive shaft connected to the compression section, and a pulley that rotates the drive shaft, and transmits the power of an engine to the pulley by use of a belt wound around the pulley thereby to rotate the drive shaft, drive the compression section and perform the suction and discharge of a cooling medium (for example, in the Japanese Patent Publication 2003-269489).  
      As a pulley that is used in the above-described compressor, there has been known a pulley that comprises an annular pulley main body formed of synthetic resin and an annular insertion member made of metal into which a bearing is inserted, in which the pulley main body and the insertion member are integrally formed by what is called insert molding that involves injecting synthetic resin by disposing the insertion member in a mold and molding the pulley main body on the side of an outer circumferential surface of the insertion member (for example, refer to the Japanese Patent Publication 2001-227620).  
      Incidentally, in the above-described pulley, to prevent the insertion member from becoming rusty, the pulley main body is injection molded on the side of an outer circumferential surface of the insertion member after subjecting the surface of the insertion member to plating as rust preventive treatment. When injection molding is performed by use of phenol resin, for example, the temperature in the mold during molding becomes a high temperature of about 180° C. and further becomes also a high temperature of about 200° C. in size stabilizing treatment (baking) after molding. For this reason, highly heat resistant plating, such as hard chromium plating and nickel plating, has hitherto been adopted for the plating of the insertion member. However, such heat resistant plating is expensive compared to general plating, posing the problem that the plating increases the manufacturing cost of products.  
      Furthermore, because the adhesion between the insertion member the surface of which is plated and the pulley made of resin is not high, this has posed the problem that the interface between the insertion member and the pulley main body is apt to cause slippage.  
     SUMMARY OF THE INVENTION  
      In view of the above-described problems, the object of the present invention is to provide a pulley that can prevent the rusting of an insertion member without using expensive heat resistant plating and can effectively prevent the slippage of an interface surface between a pulley main body and the insertion member.  
      To achieve the above-described object, in the invention there is provided a pulley that comprises an annular pulley main body made of synthetic resin and an annular insertion member made of metal into which a bearing is inserted, and in this pulley, the pulley main body and the insertion member are integrally formed by injection molding the pulley main body on the side of an outer circumferential surface of the insertion member. In this pulley, painting having rust preventive properties and heat resistant properties is applied to at least part of a surface including an outer circumferential surface of the insertion member and the pulley main body is formed on the side of the outer circumferential surface of the insertion member.  
      As a result of this, the rusting of the insertion member is prevented by the painting applied to the surface of the insertion member and, at the same time, even when the interior of a mold during the injection molding of the pulley main body and the like comes to a high temperature state, the painting applied to the surface of the insertion member will not deteriorate due to the high temperature. Therefore, the insertion member can be subjected to rust preventive treatment by relatively inexpensive painting without using expensive heat resistant plating and hence a decrease in manufacturing cost can be achieved. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a side sectional view of an embodiment of a power transmission device that uses a pulley of the invention;  
       FIG. 2  is a sectional view taken along the line A-A of  FIG. 1 ;  
       FIG. 3  is a partial side sectional view of a power transmission device;  
       FIG. 4  is a side sectional view that shows operation during a power shutoff;  
       FIG. 5  is a perspective view of an insertion member;  
       FIG. 6  is a partial side sectional view of an insertion member;  
       FIG. 7  is a partial side sectional view that shows a manufacturing process of a pulley;  
       FIG. 8  is a partial side sectional view that shows a manufacturing process of a pulley;  
       FIG. 9  is a partial side sectional view of a pulley main body and an insertion member; and  
       FIG. 10  is a partial side sectional view that shows a modification of this embodiment. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      The power transmission device shown in  FIG. 1  to  FIG. 9  is used in an air-conditioning system for vehicles and transmits power to a drive shaft  2  that protrudes from one end of a compressor main body  1 .  
      That is, the power transmission device of the invention comprises a pulley  10  to which powder from outside is transmitted, a transmission ring  11  that is rotated by the power transmitted to the pulley  10 , multiple cushion rubbers  12  that transmit a torque of the pulley  10  to the transmission ring  11 , a hub  13  connected to the drive shaft  2 , multiple balls  14  that transmit the torque of the transmission ring  11  to the hub  13 , and ball depressing ring  15  that axially depresses each of the balls  14 .  
      The pulley comprises an annular pulley main body  10   a  formed of synthetic resin and an annular insertion member  10   b  that is provided on the side of an inner circumferential surface of the pulley main body  10   a  and into which a bearing  16  is inserted, and the pulley main body  10   a  is constructed so that a V-belt not shown in the drawing can be wound around an outer circumferential surface thereof. An end face of the pulley main body  10   a  is provided with an annular groove part  10   c  that extends circumferentially, and within the groove part  10   c  there are provided multiple protrusions  10   d  that are circumferentially space from each other and protrude axially. The insertion member  10   b  is formed from a cylindrical metal member, and a flange  10   e  that bends to the radial inside is provided on an axial end of the insertion member  10   c.    
      The transmission ring  11  is disposed so that an end thereof is opposed to an end face of the pulley  10  and the surface opposed to the pulley  10  is provided with multiple protrusions  11   a  that are circumferentially spaced from each other and protrude axially. Each of the protrusions  11   a  is inserted into the groove part  10   c  of the pulley  10 , and the protrusions  11   a  and the protrusions  10   d  of the pulley  10  are alternately disposed in the circumferential direction. The protrusions  11   a  are circumferentially spaced from the protrusions  10   d  of the pulley  10  and opposite thereto. A locking ring  11   b  that engages and locks with each of the balls  14  from the radial outside is attached to the inner circumferential surface of the transmission ring  11 . Multiple tapered surfaces  11   c  that form a prescribed angle with each other are formed on an inner circumferential surface of the locking ring  11   b , and each of the balls  14  abuts against one of the tapered surfaces  11   c  that are adjacent to each other so as to be positioned radially outside.  
      Each of the cushion rubbers  12  is formed in block shape and disposed between the protrusion  10   d  of the pulley  10  and the protrusion  11   a  of the transmission ring  11 . Each of the cushion rubbers  12  is constituted by a pair of cushion parts  12   a , which are disposed each on both sides of the protrusion  10   d  of the pulley  10  in the circumferential direction, and each of the cushion parts  12   a  are formed with a width substantially equal to the groove part  10   c  of the pulley  10  so as to bend along the groove part  10   c.    
      The hub  13  is formed in disk shape and disposed on the inner circumferential surface side of the transmission ring  11 . On one end face side of the hub  13 , a connecting part  13   a  that connects the drive shaft  2  is provided, and the drive shaft  2  is fixed to the hub  13  by a nut  13   b  that screws the drive shaft  2  from the other end face of the hub  13 . Multiple ball grooves  13   c  that engage with each of the balls  14  to move them respectively radially are circumferentially spaced from each other on the other end face of the hub  13 , and each of the balls  14  is circumferentially locked on the inner surface side of the ball grooves  13   c . In this case, a convexity  13   d  that protrudes axially is provided on the radial outside of each of the ball grooves  13   c , and the convexity  13   d  abuts axially against the ball  14  positioned on the radial outside of the ball groove  13   c . In the radial middle of the other end face of the hub  13 , an extending part  13   e  that extends axially in cylindrical form is provided so as to cover the nut  13   b.    
      The balls  14  are spaced from each other in the circumferential direction of the hub  13 , and each of the balls  14  is disposed within each of the ball groves  13   c  of the hub  13 .  
      The ball depressing ring  15  is axially movably engages with the extending part  13   e  of the hub  13  and one end side of the ball depressing ring  15  abuts against each of the balls  14 . An inclined surface  15   a  that protrudes axially gradually from the axial outside toward the inside is provided on one end face of the ball depressing ring  15 , and the ball  14  positioned on the radial outside of each of the ball grooves  13   c  abuts against the radial outside of the inclined surface  15   a . A coned disc spring  15   b  that engages with the extending part  13   e  of the hub  13  is provided on the other end face side of the ball depressing ring  15 , and the ball depressing ring  15  is urged to the ball  14  side by the coned disc spring  15   b . The coned disc spring  15   b  is disposed in a compressed condition between an annular nut  15   c  that is screwed to the extending part  13   e  and it is possible to arbitrarily set a depressing force of the ball depressing ring  15  by the coned disc spring  15   b  by adjusting the fastening force of the nut  15   c.    
      In the power transmission device constructed as described above, the transmission ring  11  rotates integrally with the pulley  10  when the power from an engine is input to the pulley  10 . On that occasion, the torque of the pulley  10  is transmitted to the transmission ring  11  via each of the cushion rubbers  12 , and each of the cushion rubbers  12  is elastically deformed between the concavity  10   d  of the pulley  10  and the concavity  11   a  of the transmission ring  11 , with the result that impacts by abrupt torque changes etc. are absorbed. The torque of the transmission ring  11  is transmitted to the hub  13  via the locking ring  11   b  and each of the balls  14  and the drive shaft  2  rotates along with the hub  13 . On that occasion, each of the balls  14  is depressed to the radial outside of each of the ball grooves  13   c  by the inclined surface  15   a  of the ball depressing ring  15 , and the torque of the transmission ring  11   b  is transmitted to the hub  13  by the circumferential engagement and locking of each of the balls  14  with the tapered surface  11   c  of the locking ring  11   b.    
      If an excessive rotation load is applied to the pulley  10  side, for example, by the burn-out and sticking of a compressor, due to the depressing of the tapered surface  11   c  of the locking ring  11   b , as shown in  FIG. 3 , each of the balls  14  moves to the radial inside of the ball groove  13   c  against the depressing force of the ball depressing ring  15 . As a result of this, each of the balls  14  is held on the radial inside of the ball groove  13   c  by the convexity  13   d  of the ball groove  13   c  and the ball depressing ring  15  and each of the balls  14  is under constraint in a position incapable of engagement and locking with the locking ring  11   b . Therefore, the transmission ring  11  becomes idle with respect to the hub  13  and hence the transmission of power from the pulley  10  side to the drive shaft  2  is shut off.  
      In making the above-described pulley  10 , after the application of painting having rust preventive properties and heat resistant properties to the whole surface of the insertion member  10   b , the insertion member  10   b  is disposed within a mold for injection molding (not shown) and synthetic resin such as phenol resin is injected into the mold, whereby as shown in  FIG. 7 , the pulley main body  10   a  is integrally formed on the outer circumferential surface side of the insertion member  10   b . In this case, a paint film  10   f  applied to the insertion member  10   b  is formed in such a manner that the break strength of the paint film  10   f  itself is smaller than the adhesive strength between the pulley main body  10   a  and the insertion member  10   b . When the above-described paint film  10   f  is formed, for example, epoxy resin painting, acrylic resin painting or cationic electrodeposition painting is preferable.  
      The bearing  16  is inserted into the pulley  10  formed as described above from the other end side of the insertion member  10   b  in the axial direction and, as shown in  Fig. 8 , the other end portion of the insertion member  10   b  in the axial direction is caused to protrude to the axial inside by caulking, whereby the bearing  16  is held between this caulked part  10   g  and the flange  10   e.    
      Thus, according to the pulley of this embodiment, the pulley main body  10   a  is integrally formed by the injection molding of synthetic resin on the outer circumferential surface side of the insertion member  10   b  in which painting having rust preventive properties and heat resistant properties is applied to at least part of surfaces including the outer circumferential surface. Therefore, the rusting of the insertion member  10   b  can be effectively prevented and besides even when the interior of a mold during injection molding comes to a high temperature state, the painting applied to the surface of the insertion member  10   b  will not deteriorate due to the high temperature and the corrosion resistance of the insertion member  11   b  will not be decreased. Accordingly, the insertion member  10   b  can be subjected to rust preventive treatment by relatively inexpensive painting without using expensive heat resistant plating and hence a decrease in manufacturing cost can be achieved.  
      The paint film  10   f  applied to the insertion member  10   b  is formed in such a manner that the break strength of the paint film  10   f  itself is smaller than the adhesive strength between the pulley main body  10   a  and the insertion member  10   b . Therefore, as shown in  FIG. 9 , before the exfoliation of an interface S 1  between the pulley main body  10   a  and the paint film  10   f  or an interface S 2  between the insertion member  10   b  and the paint film  10   f , owing to the elasticity of the paint film  10   f  it is possible to absorb shearing forces in the slip directions of the pulley main body  10   a  and the insertion member  10   b  as shown in the solid-line arrows in the figure, and the slippage between the paint film  10   f  and the pulley main body  10   a  or between the paint film  10   f  and the insertion member  10   b  can be effectively prevented.  
      In the above-described embodiment, the slippage between the pulley main body  10   a  and the insertion member  10   b  is prevented by the elasticity of the paint film  10   f . As shown in  FIG. 10 , however, the outer circumferential surface of the insertion member  10   b  may be provided with a concavity  10   h  as an engaging part that engages with the inner circumferential surface of the pulley main body  10   a  to ensure that the slippage between the pulley main body  10   a  and the insertion member  10   b  is prevented by the engagement of the concavity  10   h  with the pulley main body  10   a . Incidentally, the engaging is not limited to the concavity  10   h . For example, the insertion member  10   b  may be provided with a convexity or an engaging part of another shape may be provided.  
      Incidentally, although in the above-described embodiments, a pulley used in the power transmission device of a compressor was described, the invention can be applied to a pulley used in other rotary devices.