Abstract:
A chain guide member used in a chain transmission apparatus, and manufacturing method and apparatus thereof. The chain guide member has a sliding contact section extending along a traveling surface of a chain and coming into sliding contact with the chain, and a reinforcement main body reinforcing and supporting the sliding contact section along the traveling surface of the chain. A part or all of a joint portion between the sliding contact section and the reinforcement main body is joined by melting.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a chain guide member such as a chain tensioner and a chain guide used in a chain transmission device, a manufacturing method thereof and a manufacturing apparatus thereof. 
     In a chain transmission device applied to a valve moving system of a four stroke cycle internal combustion engine, a chain tensioner for eliminating looseness of the chain or a chain guide for preventing disengagement of the chain from a sprocket has a sliding contact section coming into sliding contact with the chain. The sliding contact section is required to be made of a material having a good abrasion resistance and a low frictional resistance. 
     However, such a material is generally expensive and has low workability and low mechanical strength. Accordingly, in a chain guide member described in Japanese Patent No. 2818795, a reinforcement main body section of high mechanical strength and a sliding section of high abrasion resistance are piled up and extend in a chain traveling direction, and the reinforcement main body section and the sliding section are integrally connected through a dovetail joint. 
     According to the above-mentioned chain guide member of dovetail joint structure, the joint portion becomes necessarily thick from viewpoint of joint strength, the whole chain guide member is large-sized and cost-lowering and weight-reducing is difficult. 
     The chain guide member is manufactured in a manner that a supporting body with a dovetail key forming a greater part of the chain guide member is formed by injection, then a slide lining body is injected onto the support body. Therefore, when the slide lining body is formed by injection, temperature of the supporting member has been lowered, and resin for the slide lining body injected later comes into contact with the supporting body of low temperature to be cooled. As the result, the supporting body and the slide lining body are not joined integrally in a sufficiently melted state and the joint portion is weak. 
     SUMMARY OF THE INVENTION 
     In order to overcome the above-mentioned difficulties, the present invention provides a chain guide member having a sliding contact section extending along a traveling surface of a chain and coming into sliding contact with the chain and a reinforcement main body reinforcing and supporting the sliding contact section along the traveling surface of the chain, wherein a part or all of a joint portion between the sliding contact section and the reinforcement main body is joined by melting. 
     The sliding contact section and the reinforcement main body are connected to each other strongly, and miniaturization and cost-lowering of the chain guide member is possible. 
     The chain guide member may be made of thermoplastic resin. A cheap chain guide member having relatively high strength and good self-lubricating nature can be obtained. 
     The present invention provides a chain guide member manufacturing method, comprising steps of: partitioning a cavity of a mold by a partitioning member to form a space for forming a slide contact section of a chain guide member; injecting molten resin for the sliding contact section into the space; removing the partitioning member; and injecting molten resin for a reinforcement main body of the chain guide member into a remaining space of the cavity. According to the method, it is unnecessary to use respective molds for forming the sliding contact section and the reinforcement main body, and a chain guide member can be produced in a short time easily. 
     In the above chain guide member manufacturing method, a gas may be injected into the molten resin for the reinforcement main body injected into the cavity, a cave may be formed within the reinforcement main body in the cavity, and the reinforcement main body may be pressed against the sliding contact section by pressure of the gas within the cave. According to this method, the reinforcement main body and the sliding contact section can be connected more strongly and the chain guide member can be miniaturized. 
     The present invention provides a chin guide member manufacturing apparatus, comprising: a mold for forming a chain guide member; a partitioning member capable of going into a cavity of the mold to partition the cavity and form a space for a sliding contact section of the chain guide member; means for driving the partitioning member into the cavity; means for injecting molten resin for the sliding contact section into the space for the sliding contact section; and means for injecting molten resin for a reinforcement main body of the chain guide member into a space for the reinforcement main body in the cavity other than the space for the sliding contact section. According to this apparatus, the above-mentioned chain guide member manufacturing method can be carried out easily and surely. 
     The above manufacturing apparatus may include an opening for injecting molten resin for the slide contact section positioned on one end of the chain guide member, and an opening for injecting molten resin for the reinforcement main body positioned on another end of the chain guide member. According to this manufacturing apparatus, a portion of the resin for sliding contact section positioned near the opening for injecting molten resin for the reinforcement main body that has been injected most early and cooled is re-heated by molten resin for reinforcement main body injected from the opening for the reinforcement main body to prevent lowering of the temperature. On the other hand, a portion of the resin for the sliding contact section positioned near the opening for injecting resin for the sliding contact section that has been injected most lately is kept in relatively high temperature. As the result, temperature of the sliding contact section is kept substantially equal over the total length. Therefore, the sliding contact section resin and the reinforcement main body resin are melt-joined substantially equally and strongly along the total length of the chain guide member, and strength and durability of the chain guide member are improved remarkably. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic view of a chain power transmission mechanism having a chain guide member of the present invention; 
     FIG. 2 is a side view of the chin guide member; 
     FIG. 3 is a sectional view of a chain guide member manufacturing apparatus showing its initial manufacturing stage; 
     FIG. 4 is a sectional view of the chain guide member manufacturing apparatus showing its middle manufacturing stage; and 
     FIG. 5 is a sectional view of the chin guide member manufacturing apparatus showing its final manufacturing stage. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 to  5 . 
     FIG. 1 shows a chain power transmission mechanism in a valve moving system of a four stroke cycle internal combustion engine (not shown). An endless chain  5  is wound round a drive sprocket  2  fixed to a crankshaft  1  rotating clockwise and driven sprockets  4  fixed to camshafts  3 . A chain tensioner  6  for eliminating looseness of the chain  5  is disposed on a loose side (left side in FIG. 1) of the chain  5 , and a chain guide  7  is disposed on a strained side of the chain  5 . 
     A chain guide member  10  constituting above-mentioned chain tensioner  6  has an upper end  10   a  pivoted on a pivot  8  supported by a main body of the internal combustion engine so that the chain guide member  10  can be rocked about the pivot  8  supported by a main body of the internal combustion engine so that the chain guide member  10  can be rocked about the pivot  8  right and left. A lifter  9  is provided at a lower portion  10   b  of the chain guide member  10  when the chain  5  is loosened, the lifter rocks the chain guide member  10  about the pivot  8  counterclockwise. After looseness of the chain  5  is eliminated and the chain  5  is strained, the chain guide member  10  is fixed to the position by a pressing holding force of the lifter  9  so that the chain  5  is not loosened. 
     The chain guide member  10  comprises a sliding contact section (a section coming into sliding contact with the chain)  11  made of nylon-46 curved along a traveling surface of the chain, and a reinforcement main body  12  joined with the sliding contact section  11  by melting as will be described later. The reinforcement main body  12  is strengthened by glass fiber mixed at a ratio of about 40% (30%-50%). 
     A chain guide member manufacturing apparatus  13  for manufacturing the above-mentioned chain guide member is shown in FIGS. 3 to  5 . The apparatus  13  comprises three separate molds  14 ,  15 ,  16 , a partitioning member  18  capable of going into a cavity  17  formed by the molds  14 ,  15 ,  16  to partition the cavity, a partitioning member driving air cylinder  16  for driving the partitioning member  18  into the cavity  17 , a sliding contact section injecting apparatus (not shown) for injecting nylon-46  23  through a sliding contact section injecting passage  20  provided in the mold  14  at a position shown in FIG. 2, and a reinforcement main body injecting apparatus (not shown) for injecting nylon-46GF  24  with glass fiber of 40% mixed through a reinforcement main body injecting passage  21  provided in the mold  15  at a position shown in FIG.  2 . The mold  16  is formed with a pressurized gas charging passage  22  for charging a pressurized gas at a position shown in FIG.  2 . 
     In addition, an injection control apparatus for controlling action of the partitioning member driving air cylinder  19 , injecting action of the sliding contact section injecting apparatus and injecting action of the reinforcement main body injecting apparatus, and mold temperature control apparatus for controlling temperature of the molds  14 ,  15 ,  16  are provided. 
     In a state that temperature of the molds  14 ,  15 ,  16  are kept at about 130° C., the partitioning member  18  is projected into the cavity  17  by the partitioning member driving air cylinder  19 , and then into a space of the cavity  17  partitioned by the partitioning member  18  is injected molten nylon-46  23  of about 300° C. during 3 seconds through the sliding contact section injecting passage  20  from the sliding contact injecting apparatus. When a time of 1 second elapses after the completion of the injection, the partitioning member  18  is pulled out from the cavity  17  by the partitioning member driving air cylinder  19 , and immediately nylon-46GF  24  of about 300° C. mixed with glass fiber of 40% is injected into the cavity during about 4 seconds through the reinforcement main body injecting passage  21  from the reinforcement main body injecting apparatus. Simultaneously, a high pressure gas is charged into the nylon-46GF  24  within the cavity  17  through the pressurized gas charging passage  22  (during about 15 seconds). After cooling time of about 30 seconds, the chain guide member  10  is taken out from the molds  14 ,  15 ,  16 . After 10 seconds, next chain guide member manufacturing can be started. 
     Thus, during the nylon-46  23  for the sliding contact section  11  has not been sufficiently solidified yet, the nylon-46GF  24  having a volume larger that that of the sliding contact section  11  is injected to join the sliding contact section  11  and the reinforcement main body  12  to each other by melting. Therefore, the sliding contact section  11  and the reinforcement main body  12  can be joined integrally and strongly, the joined portion can be made thin and the chain guide member  10  can be formed compact. 
     A cave  25  is formed in the reinforcement main body by charging the high pressure gas into the injected nylon-46GF  24  and a joining portion of the reinforcement main body  12  adjacent to the sliding contact section  11  is strongly pressed against the sliding contact section  11  by the high pressure gas in the cave  25 . Therefore, melt-joining of the sliding contact section  11  and the reinforcement main body  12  can be carried out more precisely and surely. 
     As shown in FIG. 2, the sliding contact section injecting passage  20  and the reinforcement main body injecting passage  21  are positioned at both ends of the chain guide member  11  respectively. Therefore, a part of the nylon-46  23  of relatively low temperature injected from the sliding contact section injecting passage  20  early and having reached a neighborhood of the pressurized gas charging passage  22  is heated by nylon-46GF  24  injected from the reinforcement main body injecting passage  21 , and a part of the nylon-46GF  24  injected from the reinforcement main body injecting passage  21  early and having reached a neighborhood of the sliding contact section injecting passage  20  comes into contact with a part of the nylon-46  23  that is not so cooled. Accordingly, the nylon-46  23  and the nylon-46GF  24  are contacted with each other at a substantially uniform temperature condition all over the length of the chain guide member  10 , so that the sliding contact section  11  and the reinforcement main body  12  are integrally joined uniformly over all the length of the chain guide member  10 . 
     Since the sliding contact section  11  of smaller volume is injected early and then the reinforcement main body  12  of larger volume is injected, the joining portions of the sliding contact section  11  and the reinforcement main body  12  are kept at a sufficiently high temperature by the reinforcement main body  12  of larger volume so that sufficient melt-joining is possible. 
     The present invention can be applied to the chain guide  7  as well as the chain guide member  10  comprising the sliding contact section  11  and the reinforcement main body  12 . 
     In the above embodiment, both the sliding contact section  11  and the reinforcement main body  12  are made of the same kind of nylon-46 and the reinforcement main body  12  is strengthened by glass fiber. However, the sliding contact section  11  may be made of a thermoplastic resin that has high self-lubricating nature and low friction though mechanical strength and rigidity are low, and the reinforcement main body  12  may be made of other thermoplastic resin having high mechanical strength and rigidity.