Abstract:
A windshield of a laminated glass curved to protrude toward the vehicle outside. An interlayer of the laminated glass is tensioned so that the windshield has a force acting to cause the entire laminated glass to flex toward a passenger compartment. The windshield is configured in its entirety to be flexible toward the inside of the passenger compartment, so that the impact of an object colliding with the windshield from the vehicle outside can be absorbed and impact received by the colliding object can be mitigated.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to a vehicle windshield for mitigating an impact on a colliding object colliding with the windshield from the front of the vehicle.  
         BACKGROUND OF THE INVENTION  
         [0002]    This kind of windshield is known as disclosed, for example, in Japanese Patent Laid-Open Publication No. HEI-4-19136 as a laminated safety glass which consists of an annealing glass, a resin interlayer bonded to the interior side of the annealing glass, and an impermeable film bonded to the surface on the interior side of the resin interlayer.  
           [0003]    Another known example of such a windshield is shown in FIGS. 8A and 8B. These figures illustrate a state in which a colliding object is colliding with a windshield from the interior of the vehicle. In the figures, OUT indicates the outside of a passenger compartment and IN the inside of the passenger compartment.  
           [0004]    [0004]FIG. 8A illustrates a colliding object  111  heading toward a windshield  112 . The windshield  112  is made from a glass having two glasses  113  and  114  curved from the passenger compartment toward the vehicle outside bonded together with a plastic interlayer  115  (hereinafter referred to as a “laminated glass”).  
           [0005]    The laminated safety glass in HEI-4-19136 or the windshield  112  shown in FIG. 8A takes into account the safety of vehicle passengers, and mitigates the impact on the head of a passenger hitting against the laminated safety glass or the windshield  112  upon a vehicle collision. However, no consideration is given to the safety of pedestrians, that is, a colliding object from the outside of the vehicle compartment toward the laminated safety glass or the windshield  112 .  
           [0006]    In FIG. 8B, when the colliding object  111  hits on the windshield  112 , the windshield  112  is partially broken, mitigating the impact of collision. However, as described above, the windshield  112  does not allow for impact from the outside of the passenger compartment. Further, the windshield  112  has a shape curved outward of the passenger compartment, that is, a so-called “arch” shape in cross section, and is thus more unbreakable against a load from the outside of the passenger compartment than from the inside of the passenger compartment.  
           [0007]    Further, recent years&#39; trends toward short-nose vehicles with passenger compartments expanded in space and slant-nose vehicles with front end portions inclined downward to reduce air resistance in high-speed travel result in increased collisions from the vehicle front toward windshields. On the other hand, with an increased rate of seatbelt wearing and the widespread adoption of airbags, importance is being attached to consideration to the safety of pedestrians in addition to the safety of vehicle passengers. In other words, it is desired to effectively mitigate the impact on a colliding object colliding with a windshield from the outside of a vehicle compartment.  
         SUMMARY OF THE INVENTION  
         [0008]    According to one aspect of the present invention, there is provided a vehicle windshield which comprises: a laminated glass curved outward of a passenger compartment, the curved laminated glass being previously provided with a flexing force acting inward of the passenger compartment.  
           [0009]    Since the force directed inward of the passenger compartment is previously provided to the windshield carved to protrude toward the vehicle outside, the windshield in its entirety is flexible toward the inside of the passenger compartment. When an object collides with the windshield from the vehicle outside, for example, the windshield can flex toward the vehicle inside, thereby absorbing the impact of the collision and mitigating impact received by the colliding object. Further, the windshield can flex toward the vehicle inside in a concave shape, thereby preventing the colliding object from being thrown out toward the side of the vehicle body after colliding with the windshield.  
           [0010]    In a preferred form, the force is produced by applying tension to the interlayer to be disposed in the middle of the laminated glass so that the interlayer has a length larger than a free length. That is, the force is produced in the entire laminated glass by the interlayer constituting a part of the laminated glass, which eliminates the need for the addition of other extra components and can prevent increase in the number of components.  
           [0011]    According to another aspect of the present invention, there is further provided a vehicle windshield which comprises: a plurality of sheet glasses curved outward of a vehicle; and an interlayer made from a resin material interposed between the sheet glasses for bonding the sheet glasses together, the interlayer being tensioned in every direction to have a return force.  
           [0012]    According to a further aspect of the present invention, there is provided a method of producing a vehicle windshield, which method comprises the steps of: curving a plurality of sheet glasses into a concave shape; applying tension to an interlayer made from a resin material so that the interlayer is stretched in every direction; interposing the tensioned interlayer between the curved sheet glasses; and bonding the curved sheet glasses and the tensioned interlayer together.  
           [0013]    In accordance with this method, the curved windshield can be easily provided with a return force. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    Certain preferred embodiments of the present invention will be described in detail below, by way of example only, with reference to the accompanying drawings, in which:  
         [0015]    [0015]FIG. 1 is a perspective view illustrating a part of a vehicle with a windshield according to the present invention;  
         [0016]    [0016]FIG. 2 is an exploded perspective view of the windshield shown in FIG. 1;  
         [0017]    [0017]FIG. 3 is a cross-sectional view of the windshield taken along line  3 - 3  in FIG. 1;  
         [0018]    [0018]FIGS. 4A and 4B are diagrams illustrating force acting on an interlayer of the windshield according to the present invention;  
         [0019]    [0019]FIGS. 5A to  5 D are diagrams illustrating states of the windshield when an object collides with the windshield from the front of the vehicle;  
         [0020]    [0020]FIG. 6 is a perspective view of a production line illustrating a process of producing the windshield according to the present invention;  
         [0021]    [0021]FIG. 7 is a diagram illustrating the application of tension to the interlayer shown in FIG. 6; and  
         [0022]    [0022]FIGS. 8A and 8B are cross-sectional views of the conventional windshield. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0023]    The following description is merely exemplary in nature and is in no way intended to limit the invention, its application or uses.  
         [0024]    Reference is made initially to FIG. 1 showing in perspective the front of a vehicle according to the present invention. A vehicle  10  has a windshield  12  at the front of a passenger compartment. Reference numeral  15  denotes a hood covering an upper portion of an engine compartment,  16  and  17  left and right front fenders,  18  a front bumper,  21  a front wheel (another front wheel is not shown),  23  and  24  left and right A-pillars,  25  a front door, and  26  a door mirror.  
         [0025]    As shown in FIG. 2, the windshield  12  is made from a laminated glass, including an outer glass  32  arranged outside of the passenger compartment, an inner glass  33  arranged inside of the passenger compartment, and an interlayer  34  made of soft resin interposed between the outer glass  32  and the inner glass  33 , bonding the outer glass  32  and the inner glass  33  together.  
         [0026]    Laminated glasses for automobiles are included in automobile safety glasses specified in JIS, defined-as ones having at least two sheet glasses bonded together with plastic as an interlayer so as to prevent, when broken by an external force, most broken pieces from scattering with the interlayer. The laminated glasses have improved safety as compared with tempered glasses which are also included in the automobile safety glasses, and are mainly used for windshields and sunshine roofs.  
         [0027]    The interlayer  34  is a film of polyvinyl butyral (PVB), and is flexible and tough. When the glass is broken, the interlayer  34  prevents the scattering of broken pieces and the entire collapse of the glass, and is also resistant to the penetration of a colliding object.  
         [0028]    The interlayer  34  is bonded to the outer glass  32  and the inner glass  33  while being tensioned to a predetermined degree in the production process.  
         [0029]    [0029]FIG. 3 illustrates the windshield  12  mounted between the left and right A-pillars  23  and  24 .  
         [0030]    The windshield  12  is curved outward of the vehicle from the interior of a passenger compartment  36 . As will be described below, when an external force of a given magnitude acts on the windshield  12  from the vehicle outside, the tension in the interlayer  34  causes the entire windshield  12  to be more flexible, and further mitigates the impact of collision of a colliding object from the vehicle outside if any than in a conventional manner.  
         [0031]    Now the function of the interlayer  34  of the windshield  12  will be described with reference to FIGS. 4A and 4B.  
         [0032]    In FIG. 4A, with the curved windshield  12  mounted between the A-pillars  23  and  24 , contracting forces R, R in the directions of arrows occur in the interlayer  34  because tension is applied to the interlayer  34  during the production process. When an elastic cord is stretched and fixed at its opposite ends, for example, the elastic cord attempts to contract to the original length.  
         [0033]    In FIG. 4B, with the outer glass  32  and the inner glass  33  entirely broken ( 32 A and  33 A denote broken pieces.) by an object colliding with the windshield  12 , there is no restraint on the interlayer  34  which then changes from a curved state into an upright state as shown by an arrow between the A-pillars  23  and  24 . A rubber string stretched in a curved shape, for example, becomes straight when no external force acts thereon.  
         [0034]    As described with FIGS. 4A and 4B, the interlayer  34  previously tensioned acts to change from a curved state into an upright state. The windshield  12  thus also acts to change from a curved state into an upright state. Specifically, a force C directed toward the passenger compartment as shown by an arrow is produced by a return force of the interlayer  34  in the windshield  12 .  
         [0035]    The function of the above-described windshield  12  will be described with reference to FIGS. 5A to  5 D.  
         [0036]    When a colliding object  38  heads toward the windshield  12  from the front of the vehicle  10  as shown by an arrow in FIG. 5A, for example, and collides with the windshield  12  as in FIG.  5 B, a central portion of the windshield  12  is broken as shown in FIG. 5C. If the impact is great, the broken part spreads over the entire windshield  12  as shown in FIG. 5D.  
         [0037]    In FIGS. 5C and 5D, the windshield  12 , when broken, becomes flexible by the above-described force C in the direction of the passenger compartment (see FIG. 4A), and the broken part becomes upright. After being upright, the windshield  12  is curved inward of the passenger compartment  36  as shown in FIG. 5D by an inertia force of the colliding object  38 .  
         [0038]    The windshield  12  thus configured to be broken by an external force of a given magnitude and to be flexible, can further absorb the impact of the colliding object  38 .  
         [0039]    [0039]FIG. 6 is a perspective view of a production line illustrating a process of producing the windshield  12  according to the present invention, in which process steps are affixed the letters (a) to (k) and will be described in that order.  
         [0040]    Step (a): Material plates  51  are prepared.  
         [0041]    Step (b): The material plates  51  are cut into a predetermined shape to produce flat plates  52  which are stamped with a mark and chamfered.  
         [0042]    Step (c): The flat plates  52  are washed by a cleaning device  53  and then dried.  
         [0043]    Step (d): The flat plates  52  are provided with prints as necessary.  
         [0044]    Step (e): The flat plate  52  to be the outer glass  32  of the windshield  12  (hereinafter referred to as an “outer plate”) is superimposed on the flat plate  52  to be the inner glass  33  (hereinafter referred to as an “inner plate”). The flat plates  52  are put on a die  54  for bending by sagging.  
         [0045]    Step (f): The die  54  with the two flat plates  52  placed thereon is passed through a furnace  56  for heating, and then slowly cooled.  
         [0046]    Step (g): Resultant bent outer plate  57  and inner plate  58  are washed by a cleaning device  59 .  
         [0047]    Step (h): An interlayer  61  cut into a predetermined dimension after washing and inspection is inserted between the outer plate  57  and the inner plate  58  while being tensioned. A portion of the interlayer  61  extending off the edges of the outer plate  57  and inner plate  58  is trimmed.  
         [0048]    Step (j): An assemblage  62  resulting in the step (h) is inserted into a rubber bag and is passed through a preparative press-bonding device  63  for heating. This heating may be skipped.  
         [0049]    Step (k): The pre-bonded assemblage  62  is pressurized and heated by an autoclave device  64  for the final press-bonding of the assemblage  62 .  
         [0050]    The windshield  12  is produced in this manner. The windshield  12  is then inspected and packaged for shipment.  
         [0051]    Now the application of tension to the interlayer  61  will be described with reference to FIG. 7.  
         [0052]    First, the interlayer  61  are pulled at its sides  71  to  74  in arrow directions to apply tension to the interlayer  61 . As a result, the interlayer  61  is expanded from a free length of longitudinal length F1 and transverse length F2 (length before the application of tension) into a set length (longitudinal length S1 and transverse length S2). That is, the interlayer  61  is tensioned to stretch in every direction.  
         [0053]    On the interlayer  61  in this state, the outer plate  57  and the inner plate  58  are superimposed from the opposite sides as shown by hollow arrows for bonding.  
         [0054]    The present disclosure relates to the subject matter of Japanese Patent Application No. 2002-169159, filed Jun. 10, 2002, the disclosure of which is expressly incorporated herein by reference in its entirety.