Abstract:
There is provided an automotive wheel with a cavity between the bolt holes in a hub mounting section, and more particularly, to an automotive wheel with a cavity between the bolt holes in a hub mounting section, wherein a cavity between the bolt holes in a hub mounting section structured to secure an automotive wheel to a wheel hub is uniformly formed to reduce the weight and noise of the automotive wheel, and wherein a damper rubber is inserted into the cavity to reduce the vibration and noise generated during driving an automobile.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Korean Patent Application No. 10-2015-0059075, filed on May 27, 2015 the disclosure of which is hereby incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an automotive wheel with a cavity between the bolt holes in a hub mounting section, and more particularly, to an automotive wheel with a cavity between the bolt holes in a hub mounting section, wherein a cavity between the bolt holes in a hub mounting section structured to secure an automotive wheel to a wheel hub is uniformly formed to reduce the weight and noise of the automotive wheel, and wherein a damper rubber is inserted into the cavity to reduce the vibration and noise generated during driving an automobile. 
     2. Description of the Related Art 
     Automotive wheels are manufactured using metal materials, usually steel or aluminium. Generally, this automotive wheel is secured to an automotive wheel hub comprising a brake drum or brake disk by a spherical head screw or conical head screw. 
     To improve the fuel-efficiency of an automobile through decreasing the weight of the automobile, aluminium which is a light material has been used for an automotive wheel. Further, a technology to structurally lighten the weight has been also developed. 
     Usually, when a wheel is designed, it is considered to primarily satisfy the strength requirements. The structures, such as the thicknesses and designs of a hub mounting section  21  and a spoke section  22  of a disk member  2 , have been designed to satisfy the minimum required strength of the wheel. Then, a process for secondary weight lightening (decrease of weight) has been performed inside the hub mounting section  21  and the spoke section  22  of the wheel to improve the fuel-efficiency. 
     However, as the wheel weight has been lightened through the aforementioned ways, the stiffness becomes insufficient, causing vibration and noise of the wheel during the driving of the automobile. To prevent these problems, casting thickness is again provided inside the hub mounting section  21  and the spoke section  22  of the wheel. Even the entire shape of the disk member  2  is thickened to increase the unnecessary stiffness rather than the minimum required strength. This again increases the weight and therefore, it is restricted in the improvement of fuel-efficiency. 
     Korean Patent Published Application No. 10-2006-0044653 (hereinafter, referred to as ‘Prior Art 1’) discloses a technology to decrease weight and block noise by forming a hollow chamber in a rim. The technology of forming a hollow chamber in the rim and spoke is disclosed in not only Prior Art 1 but also Korean Patent Published Application Nos. 1999-0062973 and 10-2013-0044465. The method of forming the hollow chamber has the effect of reducing weight and absorbing noise but it has a problem in that durability is weakened. 
     Korean Patent Published Application No. 10-2007-0053386 (hereinafter, referred to as ‘Prior Art 2’) discloses technology to absorb noise and vibration by forming a hollow chamber in a rim and filling it with an aluminum foam core. The technology of forming a hollow chamber in the rim and spoke and filling it with the foam core has a better effect of absorbing noise in comparison with Prior Art 1 but less effect of reducing weight. 
     PRIOR ART DOCUMENT 
     Patent Document 
     (Patent Document 1) Prior Art 1: Korean Patent Published Application No. 10-2006-0044653 
     (Patent Document 2) Prior Art 2: Korean Patent Published Application No. 10-2007-0053386 
     (Patent Document 3) Prior Art 3: Korean Patent Published Application No. 1999-0062973 
     (Patent Document 4) Prior Art 4: Korean Patent Published Application No. 10-2013-0044465 
     SUMMARY OF THE INVENTION 
     Therefore, it is an object of the present invention to solve the above problems and to provide an automotive wheel with a cavity between the bolt holes in a hub mounting section which is designed to decrease weight by maintaining the high tilting strength and high torsional strength and the tightening torque of a wheel bolt. 
     Especially, the present invention is to provide a structure to decrease the weight in a hub mounting section rather than a rim section and a spoke section, thereby having the effects of easy manufacturing, high cost-effectiveness and decreased vibration and noise in comparison with the conventional art. 
     In accordance with an embodiment of the present invention, there is provided an automotive wheel with a cavity between the bolt holes in a hub mounting section, comprising a disk member through which an axle is connected and a rim member on which a tire is to be mounted, the disk member includes: a hub mounting section in a circular shape through which the axle is connected and a plurality of spokes positioned in a radial shape from an outer circumferential edge of the hub mounting section, the hub mounting section further includes: a hub hole in its center; a plurality of bolt holes positioned, at equally spaced intervals, in a radial shape outside the hub hole; and a plurality of cavities positioned, at equally spaced intervals proximate the bolt holes, and the cavity includes an entrance formed in the back. 
     Each of the cavities may be circular, oval or polygonal in cross section. 
     The automotive wheel of the present invention may further comprise a damper rubber inserted into each cavity. 
     The damper rubber may be any one of chloroprene rubber (CR), nitrile rubber (NBR: nitrile-butadiene rubber), ethylene propylene rubber (EPDM: ethylene propylene diene monomer), fluororubber (FPM; fluorocarbon rubber), polybutadiene rubber (BR), styrene-butadiene rubber (SBR), isobutylene isoprene rubber (IIR) and chlorosulphonated polyethylene (CSM) rubber. 
     Each cavity may include an extension portion inside. 
     The damper rubber may comprise: a contact portion to be in contact with the cavity; an incline portion to be tapered such that an inner diameter is widened from the contact portion; a shaft diameter portion to narrow the inner diameter from the incline portion; and a vertical portion to be formed vertically from the shaft diameter portion. 
     The hub mounting section in the back may further comprise: a drain hole formed around each cavity so as to be recessed from the flat surface of the hub mounting section in the back; and drain slits formed in the drain hole in a radial shape towards the center of the axle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features and advantages of the present invention will become more apparent to those of ordinary skill in the art by describing in detail the preferred embodiments thereof with reference to the attached drawings in which: 
         FIG. 1  is a cross-section view of an automotive wheel of the conventional art; 
         FIG. 2  is an entire perspective view of an automotive wheel according to an embodiment of the present invention; 
         FIG. 3  is a cross-sectional perspective view of the automotive wheel according to the present invention; 
         FIG. 4  is an enlarged perspective view of main parts of the automotive wheel according to the present invention; 
         FIG. 5  is a cross-sectional view of the automotive wheel according to the present invention; 
         FIG. 6  is a cross-sectional enlarged perspective view of the main parts of the automotive wheel according to the present invention; and 
         FIG. 7  is an enlarged perspective view of main parts according to another embodiment of the present invention. 
     
    
    
     DESCRIPTION OF NUMBERS FOR CONSTITUENTS IN DRAWINGS 
     
       
         
               
               
               
             
               
               
               
             
               
               
               
             
               
               
             
               
             
               
               
               
             
               
               
             
           
               
                   
               
             
             
               
                 1: tire 
                 2: disk member 
                 3: rim member 
               
             
          
           
               
                 21: hub mounting section 
                 210: hub hole 
                 220: bolt hole 
               
             
          
           
               
                 230: drain hole 
                 240: drain slit 
                 300: cavity 
               
             
          
           
               
                 310: cavity entrance 
                 320: extension portion 
               
             
          
           
               
                 330: contact portion 
               
             
          
           
               
                 40: damper rubber 
                 41: contact portion 
                 42: incline portion 
               
             
          
           
               
                 43: shaft diameter portion 
                 44: vertical portion 
               
               
                   
               
             
          
         
       
     
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     All terms used herein have the same meaning as commonly used and understand by one of ordinary skill in the art to which this invention belongs. In some specific cases, some terms are discretionally selected by an applicant of the invention. In these cases, the terms should be interpreted as having their meaning in the context of the detailed description to work the invention rather than the simple names of the terms. 
     In the description of an embodiment(s) of the present invention, when an automotive wheel is mounted onto an automobile, a side of the wheel being visible to the eyes is called the “design face”. The design face is also called the “front” and the opposite side of the design face is called the “back”. 
     A direction towards the central axis line, “L”, of the automotive wheel is called as an “inside” and its reverse direction is called as an “outside”. A vertical direction is based on the position that the back faces the ground, that is, the front faces up the sky. 
     The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which the preferred embodiment(s) of the invention is shown so that those of ordinary skill in the art can easily carry out the present invention. 
       FIG. 1  shows an ordinary automotive wheel. A hub mounting section  21  is formed in a solid type, except for bolt holes  220 . 
     In this automotive wheel, a section connected with an axle (not shown) is a support end to receive the load of a cantilever. Therefore, the reason to make the solid hub mounting section  21  is for the support end to have the strength to bear the weight of the automobile itself and the impulsive load. 
     An ordinary automotive wheel is integrally formed by casting an aluminium alloy and it includes a disk member  2  and a rim member  3  on which a tire  1  is mounted. 
     When the tire  1  is mounted on the automotive wheel, a tire air chamber in a ring shape is formed to be closed by the rim member  3  and the tire  1 . 
     The disk member  2  includes the hub mounting section  21  in a nearly circular shape, and a plurality of spokes  22  positioned in a radial shape from an outer circumferential edge of the hub mounting section  21 . The hub mounting section  21  includes a hub hole  210  and a plurality of bolt holes  220 . The hub hole  210  is formed in the center of the hub mounting section  21 . The bolt holes  220  are positioned, at equally spaced intervals, in a radial shape around the outside of the hub hole  210  (in a peripheral direction of the wheel). A decorative opening  23  may be formed between the adjacent spokes  22 . 
     A spoke extension section extending from the spokes  22  and the decorative openings  23  is formed in a circular shape to be connected with the rim member  3 . 
     The rim member  3  includes a front flange  31   a  and a back flange  31   b  at both front and back ends of the rim member  3 . The front flange  31   a  and the back flange  31   b  are to keep beads  11   a ,  11   b  of the tire  1 . A front bead seat  32   a  and a back bead seat  32   b  are positioned to be coupled to the front flange  31   a  and the back flange  31   b , respectively, to support and secure the beads  11   a ,  11   b  to sit on the wheel. 
     A well  33  is positioned between the front bead seat  32   a  and the back bead seat  32   b . The well  33  has a smaller diameter than the diameter of the front bead seat  32   a , so that the tire beads release when the tire  1  is mounted. A well wall  34  is formed to connect the front bead seat  32   a  and the well  33  which are different from each other in diameter. 
     An automotive wheel with a cavity between the bolt holes in a hub mounting section according to the present invention provides improvements to the hub mounting section  21  and therefore it will be described focused on the improvements. 
     In  FIG. 2  and  FIG. 3 , the hub mounting section  21  includes a hub hole  210 , a plurality of bolt holes  220  and a plurality of cavities  300 . The hub hole  210  is positioned in the center of the hub mounting section  21 . The bolt holes  220  are positioned, at equally spaced intervals, in a radial shape outside the hub hole  210 . The cavities  300  are positioned at equal intervals among the bolt holes  220 . 
     An axle (not shown) is connected through the hub hole  210 . A wheel hub (not shown) and bolts (not shown) are secured through the bolt holes  220 . To this end, the bolt holes  220  are threaded even, not shown. 
     If the cavity  300  has a structure to offset, in a wide cavity, noise passing through a narrow entrance being circular, oval or polygonal in cross section, the present invention does not limit the shape thereof. 
     Therefore, when noise generated during driving enters into the cavity  300 , it is offset in the cavity through mutual interference, to provide comfort during driving. 
     Further, since the cavities  300  are formed, the weight is decreased by about 10˜15% while maintaining the same strength. 
     The cavity  300  includes an extension portion  320  inside. The inner diameter d 1  of the extension portion  320  is greater than the diameter of an entrance  310  and that of the bolt hole  220 . 
     Referring to  FIG. 2  through  FIG. 5 , the inner diameter d 1  of the extension portion  320  of each cavity  300  is formed to be greater according to a preferred embodiment of the present invention. Therefore, the five cavities  300  function as five (5) Helmholtz resonance absorbers (see  FIG. 2 ). 
     A sound frequency enabling a decrease is defined according to the capacity of the cavity  300 , the opening diameter and length, etc. of the entrance  310 , such that each cavity  300  has the effect of decreasing the road noise generated during driving. Therefore, the capacity of the cavity  300 , the opening diameter and length of the entrance  310  are defined to decrease the sound wave of a specific frequency band (for example, 180 Hz˜270 Hz) causing a resonance in the road noise. 
     In the embodiment of the present invention, the five (5) cavities  300  are designed to have the same capacity. However, the capacity of each cavity and the size of the entrance may vary to decrease a number of sound waves within the range of the specific frequency band. 
     Further, the inner diameter d 1  inside the cavity  300  may be formed to be greater than the bolt hole  220 , to maximize the effect of decreasing the weight. 
     The axle is connected through the hub hole  210  of the hub mounting section  21  and the wheel hub is secured through the bolt holes  220  of the hub mounting section  21  using bolts. Therefore, in consideration of the strength of the wheel, the factors to maintain the strength of the axle and the hub mounting section  21  are the distance D 1  from the outer diameter of the hub hole  210  to the outer diameter of the extension portion  320  of the cavity  300 , and the capacity of the hub mounting portion  20  where the cavities  300  are not formed, that is, the distance D 2  from the contact side of the cavity  300  to the front. 
     In  FIG. 3 , the bolt hole  220  includes a bolt head receiving portion  221  and a screw inserting portion  222 . The bolt head receiving portion  221  has a wide diameter to safely receive the head of the bolt which is inserted from the front. The screw inserting portion  222  has a narrow diameter to receive the screw of the bolt inserted. Here, the factor to influence on the strength of the wheel is the distance D 3  from the outer diameter of the bolt head receiving portion  221  to the outer diameter of the hub hole  210 . 
     Therefore, it is preferable to make the distance D 1  from the outer diameter of the hub hole  210  to the outer diameter of the extension portion  320  of the cavity  300  to be the same as the distance D 3  to the outer, diameter of the bolt head receiving portion  221  to the hub hole  210 , to form the length l 1  of the cavity  300  to be about ½ of the thickness of the hub mounting section  21  and to form the entrance  310  of the cavity  300  in the back. 
     The stiffness of the front where the distance D 3  to the outer diameter of the bolt head receiving portion  221  to the hub hole  210  is narrow can be secured by the hub mounting section  21  which is solid where no cavities are formed. The stiffness of the back where the distance D 1  from the outer diameter of the hub hole  210  to the outer diameter of the extension portion  320  of the cavity  300  is narrow can be secured by the hub mounting section  21  where the distance D 4  is wide through the screw inserting portion  222  having a narrow diameter. 
     Accordingly, it is preferable to form the entrance  310  of the cavity  300  in the back. 
     Considering the aforementioned factors of the strength of the automotive wheel in design, it is also important to select the optimum capacity of the cavity  300  to decrease the weight of the wheel while maintaining the strength of the wheel. 
     Referring to  FIG. 4 , the hub mounting section  21  in the back includes a drain hole  230  and a drain slit  240 . The drain hole  230  around the cavity  300  is formed to be recessed from the flat surface of the hub mounting section  21  in the back. The drain slits  240  are formed in the drain hole  230  in a radial shape towards the center of the axle. 
     The flat surface of the hub mounting section  21  in the back is in contact with the wheel hub when the automotive wheel is assembled to the wheel hub. The drain slits  240  formed in the drain hole  230  are formed to be recessed from the flat surface of the hub mounting section  21  in the back, to form a drainage channel. Therefore, when the automotive wheel is assembled to the wheel hub, rain water, etc, is discharged, through the drain slits  240  to the outside of the rotating wheel. 
     Here, it is preferable to form the entrance  310  of the cavity  300  to be level with the drain slit  240 , to enhance the drainage efficiency. 
     Referring to  FIG. 5  and  FIG. 6 , a damper rubber  40  may be further inserted into the cavity  300 , not only to decrease the noise but also to provide impact absorption and buffer function. 
     To this end, the damper rubber  40  may be any one of chloroprene rubber (CR), nitrile rubber (NBR: nitrile-butadiene rubber), ethylene propylene rubber (EPDM: ethylene propylene diene monomer), fluororubber (FPM; fluorocarbon rubber), polybutadiene rubber (BR), styrene-butadiene rubber (SBR), isobutylene isoprene rubber (IIR) and chlorosulphonated polyethylene (CSM) rubber. 
     Since the properties of the rubber are well-known, no detailed description is presented. 
     The damper rubber  40  includes a contact portion  41  being in contact with the cavity  300 , an incline portion  42  being tapered from the contact portion  41  such that an inner diameter widens, a shaft diameter portion  43  narrowing the inner diameter from the incline portion  42 , and a vertical portion  44  being vertical from the axial portion  43 . 
     The contact portion  41  of the damper rubber  40  is in contact with a contact portion  330  of the cavity  300 , so that these portions may be in contact with each other by side to side, line to line or point to point. 
     Since the incline portion  42  is formed to be tapered such that the inner diameter widens from the contact portion  41 , a certain closed space S is formed within the cavity  300 . Therefore, the noise generated during driving is decreased in the closed space S and the vibration is decreased by the damper rubber  40  inserted into the cavity  300 . 
     The shaft diameter portion  43  is designed to sharply narrow the inner diameter from the incline portion  42 , to be in contact with a support portion  321  of the extension portion  320  of the cavity  300 . 
     The incline portion  42  and the support portion  321  may be in contact with each other by side to side, line to line, or point to point. However, it is preferable that the incline portion  42  and the support portion  321  are in contact with each other by correspondingly side to side, to improve the support force. The damper rubber  40  is formed horizontally but may be formed to be tilted to prevent its loss as shown in  FIG. 7 . Further, the incline portion  42  and the support portion  321  may be formed in a wave shape or a concavo-convex shape K, to increase the griping force. Thereby, the damper rubber  40  inserted into the cavity  300  does not dislodge by itself during driving. 
     The vertical portion  44  vertically extends from the shaft diameter portion  43  and circumscribes with the entrance  310  of the cavity  300 . 
     The outer diameter d 2  of the damper rubber is formed to be the same as or slightly greater than the inner diameter d 1  of the extension portion  320  and the outer diameter d 4  of the vertical portion  44  is formed to be the same as or slightly greater than the inner diameter d 3  of the entrance  310  of the cavity  300 , thereby keeping the closing/sealing force to maximize the effect of decreasing the vibration and to prevent foreign materials from entering the cavities  300 . 
     The length l 2  of the damper rubber  40  is formed to be the same as the length l 1  of the cavity  300 , to be level with the flat surface of the drain slit  230 , thereby maximizing the drainage efficiency. The length l 4  of the incline portion  42  is formed to be the same as or slightly greater than the length l 3  of the extension portion  320 , to improve the closing/sealing force. 
     In the automotive wheel with the cavity between the bolt holes in the hub mounting section according to the present invention, the cavity is formed between the bolt holes in the hub mounting section and the damper rubber is inserted into the cavity, thereby having the effect of decreasing the weight by about 10˜15% while maintaining the same strength. 
     Further, the present invention has the effect of significantly decreasing the vibration generated during driving the automobile by the damper rubber. 
     Further, since the incline portion is formed in the damper rubber, the closed space is formed in the state that the damper rubber is inserted into the cavity. Therefore, the present invention has the effect of significantly decreasing the noise generated during driving the automobile through the space. 
     Further, since the support portion is formed in the cavity and the shaft diameter portion is formed in the damper rubber, the present invention has the effect that the damper rubber inserted into the cavity does not dislodge even during high-speed driving. 
     The invention has been described using preferred exemplary embodiments. However, it is to be understood that the scope of the invention is not limited to the disclosed embodiments. On the contrary, the scope of the invention is intended to include various modifications and alternative arrangements within the capabilities of persons skilled in the art using presently known or future technologies and equivalents. The scope of the claims, therefore, should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.