Patent Publication Number: US-2016238121-A1

Title: Rack belt

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority under 35 U.S.C. §119 to Japanese Patent Application 2015-025474, filed on Feb. 12, 2015, the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     This disclosure relates to a rack belt. 
     BACKGROUND DISCUSSION 
     In related art, for example, in a rack belt that is used to drive a sunroof and the like, strength is ensured by embedding a pair of metal core wires which extend in extending directions thereof and are parallel to each other. However, two core wires are disposed at a certain distance within the rack belt thereby impairing bending flexibility of the rack belt. 
     Therefore, for example, a technique, in which only one core wire is disposed in a center portion on the inside of the rack belt, is disclosed in JP 2007-21036 2 A (Reference 1). 
     However, in Reference 1, bonding strength between a belt body made of resin forming an outer shape of the rack belt and the core wire is reduced and then mechanical strength of the rack belt can be reduced due to a decrease in the number of the core wires and a decrease in surface area accordingly. 
     SUMMARY 
     Thus, a need exists for a rack belt which is not suspectable to the drawback mentioned above. 
     A rack belt according to an aspect of this disclosure includes a toothed belt body that is made of resin or rubber and is adapted to move in an extending direction; a first core wire made of metal which is embedded in the belt body in a state of extending in the extending direction of the belt body; and a second core wire made of metal which is embedded in the belt body in a state of being wound around the first core wire. 
    
    
     
       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 plan view illustrating a sunroof apparatus to which an embodiment applied; 
         FIG. 2  is a perspective view illustrating the embodiment; and 
         FIG. 3A  is a sectional view that is taken along line  3 A- 3 A of  FIG. 3B  and  FIG. 3B  is a sectional view that is taken along line  3 B- 3 B of  FIG. 3A . 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, an embodiment of a rack belt will be described. Moreover, hereinafter, forward and backward directions of a vehicle are referred to as “forward and backward directions”. 
     As illustrated in  FIG. 1 , a sunroof apparatus  11  is mounted on a roof  10  of the vehicle such as an automobile. That is, a substantially rectangular opening  10   a  is formed in the roof  10  and a substantially rectangular movable panel  12 , which is formed of, for example, a glass plate, is disposed in the roof  10 . The movable panel  12  opens and closes the opening  10   a  by moving in the forward and backward directions. 
     A pair of guide rails  13  are disposed in both edge portions of the opening  10   a  of the vehicle in a width direction. Each guide rail  13  is made of, for example, an extruded material of aluminum alloy, has a constant cross-section in a longitudinal direction, and extends in the forward and backward directions. Then, a function component  20  is guided and supported on each guide rail  13  to be movable in the forward and backward directions. The movable panel  12  is linked and supported on both function components  20  in a state of being bridged between both the function components  20 . Both the function components  20  open and close the movable panel  12  with movement thereof in the forward and backward directions along the guide rails  13 . 
     In addition, front ends of both guide rails  13  are connected together via a front housing  14  extending in the width direction of the vehicle. An electric driving source  15  having an output gear composed of, for example, a spur gear and a motor is disposed in an intermediate portion of the front housing  14  in the longitudinal direction. The electric driving source  15  is connected to each function component  20  via each of a pair of substantially strip-shaped rack belts  16  and moves both the function components  20  simultaneously in the forward and backward directions. Moreover, each rack belt  16  extends in the width direction of the vehicle along the front housing  14 , is turned around in the vicinity of a front end of the guide rail  13 , and extends on a rear side of the vehicle along the guide rail  13 . 
     Next, a structure of the rack belt  16  described above will be described. 
     As illustrated in  FIGS. 2, 3A, and 3B , the rack belt  16  has a belt body  21  made of resin or rubber (for example, made of elastomer) which forms an outer shape. The belt body  21  has a toothed portion having a rack portion  21   a  capable of engaging with the output gear described above. Thus, if the output gear rotates, the belt body  21  moves in an extending direction accordingly. Of course, the movement of the function component  20  in the forward and backward directions is achieved by the movement of the belt body  21  extending along the guide rail  13  in the forward and backward directions. 
     A first core wire  22  made of metal is embedded in the belt body  21  in a state of extending along the extending direction and a second core wire  23  made of metal is embedded in the belt body  21  in a state of being wound helically around the first core wire  22  at a predetermined pitch. The first and second core wires  22  and  23  are disposed in a center portion of the belt body  21  in a tooth width direction. 
     The first core wire  22  is formed by twisting (so-called twisted wire) a plurality of element wires  22   a  made of, for example, hard steel wires such as piano wires and the second core wire  23  is made of one hard steel wire. A diameter of the element wire  22   a  is set to be smaller than a diameter of the second core wire  23 . In addition, a twisted pitch of each element wire  22   a  and a winding pitch of the second core wire  23  are different from each other. That is, the twisted pitch of each element wire  22   a  and the winding pitch of the second core wire  23  are opposite to each other. 
     As described above, according to the embodiment, the following advantages can be achieved. 
     (1) In the embodiment, both the first core wire  22  and the second core wire  23  are embedded in the belt body  21 . Thus, it is possible to increase bonding strength with the belt body  21  and to suppress a reduction of mechanical strength of the rack belt  16  by increasing a surface area combining the first core wire  22  and the second core wire  23 . On the other hand, the first core wire  22  and the second core wire  23  are collectively disposed in a state where the second core wire  23  is wound around the first core wire  22 . Thus, it is possible to ensure bending flexibility of the rack belt  16 . 
     (2) In the embodiment, the pitch of the element wire  22   a  and the pitch of the second core wire  23  are different from each other. Thus, it is possible to further increase bonding strength with the belt body  21  by an inclination of the element wires  22   a  and the second core wire  23 . 
     (3) In the embodiment, the pitch of the element wire  22   a  and the pitch of the second core wire  23  are opposite to each other. Thus, it is possible to increase the inclination of the element wires  22   a  and the second core wire  23  and to further increase bonding strength with the belt body  21  compared to, for example, a case where the pitch of the element wire  22   a  and the pitch of the second core wire  23  are in the same direction as each other. 
     (4) In the embodiment, mechanical strength of the rack belt  16  is appropriately ensured. Thus, it is possible to stabilize and hold a posture of the rack belt  16 , for example, even when pressing the function component  20  to open the movable panel  12 . 
     (5) In the embodiment, since the second core wire  23  is only wound around the first core wire  22  having a twisted wire structure, it is unlikely to influence the tensile strength and bending elasticity of the first core wire  22  itself, and it is possible to suppress an increase in sliding resistance, for example, when the rack belt  16  moves. 
     Moreover, the embodiment described above may be changed as follows. 
     In the embodiment described above, in the belt body  21 , the tooth of the rack portion  21   a  may be one that is along the tooth width direction or may be one (so-called helical rack) that is inclined with respect to the tooth width direction. 
     In the embodiment described above, the belt body  21  of the rack belt  16  may be made of, for example, natural rubber. 
     In the embodiment described above, the first core wire  22  may be configured of one hard steel wire. 
     This disclosure may be applied to a timing belt for transmitting rotation of a crankshaft of an engine to a cam shaft or a water pump. In addition, if a rack belt is included in a power wind apparatus (regulator) that is driven to open and close a side glass, a power slide door apparatus that is driven to open and close a slide door, a power back door apparatus that is driven to open and close a back door, and the like, this disclosure may be applied to them. Furthermore, this disclosure may also be applied to a rack belt mounted on an arbitrary apparatus other than the vehicle. In short, it may be a rack belt driving an object to be driven in accordance with the movement in the extending direction. 
     A rack belt according to an aspect of this disclosure includes a toothed belt body that is made of resin or rubber and is adapted to move in an extending direction; a first core wire made of metal which is embedded in the belt body in a state of extending in the extending direction of the belt body; and a second core wire made of metal which is embedded in the belt body in a state of being wound around the first core wire. 
     According to the configuration, it is possible to increase bonding strength with the belt body and to suppress a decrease in mechanical strength of the rack belt by increasing a surface area combining the first core wire and the second core wire by embedding both the first core wire and the second core wire in the belt body. On the other hand, it is possible to ensure bending flexibility of the rack belt by collectively disposing the first core wire and the second core wire in a state where the second core wire is wound around the first core wire. 
     With respect to the rack belt, it is preferable that the first core wire is formed by twisting a plurality of element wires, and a pitch of the element wires and a pitch of the second core wire are different from each other. 
     According to this configuration, the pitch of the element wires and the pitch of the second core wire are different from each other. Thus, it is possible to further increase bonding strength with the belt body by an inclination of the element wires and the second core wire. 
     With respect to the rack belt, it is preferable that the pitch of the element wires and the pitch of the second core wire are opposite to each other. 
     According to this configuration, the pitch of the element wires and the pitch of the second core wire are opposite to each other. Thus, it is possible to increase inclination of the element wires and the second core wire and to further increase bonding strength with the belt body compared to, for example, a case where the pitch of the element wires and the pitch of the second core wire are in the same direction as each other. 
     With respect to the rack belt, it is preferable that the second core wire is embedded in the belt body in a state of being wound helically around the first core wire. 
     The aspects of this disclosure have an effect of further increasing the mechanical strength. 
     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.