Patent Publication Number: US-2010107867-A1

Title: Lifter for lid of motor vehicle

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to Korean Patent Application Number 10-2008-0107200, filed on Oct. 30, 2008, the entire contents of which is incorporated herein for all purposes by this reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates, in general, to a lifter for the lid of a motor vehicle, which is installed between a tail gate or a trunk lid and a body of the motor vehicle so as to enable a user to easily open or close the tail gate or the trunk lid. 
     2. Description of Related Art 
     Recently, a lifter has been installed between a trunk lid, a tailgate or a hood (bonnet) and a body so as to help a user open or close the trunk lid, tailgate or hood. Generally, such a lifter is filled up with gas, and thus is called a gas lifter. The trunk lid and tailgate are means of opening or closing a trunk, while the hood is means for opening or closing an engine compartment. The trunk lid, tailgate and hood are all configured with the same panel type as is the body, and thus the user has a great difficulty in opening or closing each and all of the trunk lid, the tailgate and the hood. The lifter is installed between each of these open-close means and the body so as to provide an opening force, and thus helps the user manipulate these open-close means without applying an excessive force. 
     The lifter is generally filled with a fluid consisting of either gas or liquid, thus expanding a cylinder rod using the force of the filled fluid so as to help manipulate the open-close means. The opening force is determined by pressure of the fluid filled in the cylinder, and is a function of the reaction force when the open-close means is closed. For this reason, it is necessary to very carefully determine the amount of the filled fluid. 
     However, the conventional lifter includes a cylinder and a rod sliding on one side of the cylinder. If the amount of filled fluid is increased in order to increase the opening force, an excessive closing force is required, which causes the user inconvenience. In detail, when the pressure of the fluid is increased, the force of the user required for closing increases. As such, when the pressure of the fluid is reduced for the convenience of the user, the pressure required to open the open-close means is insufficient. Thus, the opening force of the open-close means or a quality of operation when the open-close means is closed is a problem requiring selection of one of the alternatives from the viewpoint of the structure of the lifter. 
     The information disclosed in this Background of the Invention section is only for enhancement of understanding of the background of the invention, and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known to a person skilled in the art. 
     BRIEF SUMMARY OF THE INVENTION 
     Various aspects of the present invention are directed to provide a lifter for the lid of a motor vehicle, which secures pressure required for opening, and does not require excessive pressure when in a closed state, thereby simultaneously satisfying an opening force and quality of the operation thereof when in the closed state. 
     In an aspect of the present invention, the lifter for the lid of a motor vehicle may include a cylinder in which a fluid is filled, a first rod passing through one end of the cylinder so as to permit reciprocation therethrough, connected with a first piston slidably disposed in the cylinder and having at least an opening for a fluid communication through in the cylinder, and a second rod passing through a second, opposite end of the cylinder so as to permit reciprocation therethrough, connected with a second piston disposed in the cylinder and having at least an opening for a fluid communication in the cylinder so as to be opposite to the first piston, wherein the second rod has a cross section which is less than that of the first rod such that a magnitude of reaction force applied toward an outside of the cylinder is less than that of the first rod., wherein the openings of the first and second pistons are orifice. 
     The first and second pistons may be identically shaped, and the cylinder includes first and second through-holes in opposite ends thereof which have cross sections identical to those of the first and second rods, and first and second sealing members on opposite sides thereof which enclose the respective rods inside the first and second through-holes so as to prevent leakage of the fluid. 
     The first and second sealing members may include a shock absorbing member on an inner surface of the first and second sealing members respectively so as to face the first and second pistons. 
     In another aspect of the present invention, the cylinder may have a length greater than a sum of lengths of the first and second rods. 
     In further another aspect of the present invention, the first and second rods may include first and second connectors on outer ends thereof which are connected to a body or a tail gate of the vehicle outside the cylinder in a ball-joint connecting fashion, respectively, wherein the second rod is contracted toward an inside of the cylinder when the tail gate is closed, and the first rod is contracted after the second rod is completely contracted, and wherein the first rod is first expanded toward the outside of the cylinder when the tail gate is open, and the second rod is expanded after the first rod has been completely expanded. 
     According to embodiments of the present invention, the lifter can maintain sufficient opening force and improve the quality of operation when closing using two simple rods sharing the fluid in the cylinder, wherein the two rods have different cross sections. 
     Further, although the fluid minutely leaks out toward an outside of the cylinder, the two rods share the fluid in one cylinder, and maintain a pressure difference thereof, so that the pressure difference between the rods can be maintained in the event of closing and opening. 
     In addition, a stroke of each rod is reduced by half as compared to a conventional lifter, so that durability of each rod sealing member is increased. 
     The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description of the Invention, which together serve to explain certain principles of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view illustrating an exemplary lifter for the lid of a motor vehicle according to the present invention. 
         FIG. 2  is a cross-sectional view illustrating a first rod in the exemplary lifter for the lid of a motor vehicle illustrated in  FIG. 1 . 
         FIG. 3  is a cross-sectional view illustrating a second rod in the exemplary lifter for the lid of a motor vehicle illustrated in  FIG. 1 . 
         FIG. 4  illustrates the first operation of the exemplary lifter for the lid of a motor vehicle illustrated in  FIG. 1 . 
         FIG. 5  illustrates the second operation of the exemplary lifter for the lid of a motor vehicle illustrated in  FIG. 1 . 
         FIG. 6  illustrates the third operation of the exemplary lifter for the lid of a motor vehicle illustrated in  FIG. 1 . 
         FIG. 7  illustrates the fourth operation of the exemplary lifter for the lid of a motor vehicle illustrated in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is/are intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims. 
       FIG. 1  is a cross-sectional view illustrating a lifter for the lid of a motor vehicle according to various embodiments of the present invention. According to various embodiments of the present invention, the lifter for the lid of a motor vehicle includes a cylinder  100  in which a fluid G is filled, a first rod  340  passing through one end of the cylinder  100  so as to permit reciprocation, connected with a first piston  360  having an orifice  362  for a flow of the fluid G in the cylinder  100 , and having the shape of a bar, and a second rod  540  passing through the other end of the cylinder  100  so as to permit reciprocation, connected with a second piston  560  which has an orifice  562  for a flow of the fluid G in the cylinder  100  so that the flow is opposite to that of the first piston  360 , and having the shape of a bar having a cross section less than that of the first rod  340  such that magnitude of reaction force applied toward the outside of the cylinder  100  is less than that of the first rod  340 . 
     The cylinder  100  is a hollow cylinder having a predetermined length, and is provided with two rods  340  and  540  on opposite sides thereof which slide for contraction and expansion. As the fluid G in the cylinder  100 , either of gas or liquid can be used for filling. The rods are coupled with connectors and pistons, thereby forming rod assemblies  300  and  500 . Connection of each component will be described in detail. The first and second rod assemblies  300  and  500  are installed on the opposite sides of the cylinder  100 , respectively. The rod assemblies include the first and second pistons  360  and  560  on inner ends thereof inside the cylinder  100 , and the first and second connectors  320  and  520  on outer ends thereof outside the cylinder  100 . The first and second connectors  320  and  520  are connected to an open-close means (e.g., a tail gate or a trunk lid) and a body of the motor vehicle in a ball-joint connecting fashion, respectively. 
     In various embodiments of the present invention, the first and second pistons  360  and  560  have a circular cross section so as to be in close contact with an inner circumference of the cylinder I  00 , and are of a predetermined diameter. If the first and second pistons  360  and  560  are formed in the same shape, the costs of production are reduced. Thus, the first and second pistons  360  and  560  preferably have the same cross section and thickness. The first and second pistons  360  and  560  have outer diameters identical to an inner diameter of the cylinder  100 . Oil is filled between the first and second pistons  360  and  560 , thereby preventing the fluid G from leaking to the outside of the first and second pistons  360  and  560  and allowing the first and second pistons  360  and  560  to be smoothly slid. 
     The first and second pistons  360  and  560  have the respective orifices  362  and  562 , through which the fluid G in the cylinder  100  flows to left and right sides of the pistons. Since the orifices  362  and  562  are formed in the first and second pistons  360  and  560 , the fluid G has the same pressure on the left and right sides of each piston, so that the pressure of the fluid G itself is equally maintained regardless of position in the cylinder  100 . Of course, when the pistons abruptly slide, the left-sided and right-sided pressures of the fluid may instantaneously differ from each other. This instantaneous pressure difference can be regulated by adjustment in the number and size of the orifices. 
     The first and second rods  340  and  540  are connected to the respective pistons in the cylinder  100  at first ends thereof and are exposed to the outside of the cylinder  100  at the second ends thereof, and are configured in such a manner that the cross sections thereof differ from each other. In various embodiments, the cross section of the second rod  540  is smaller than that of the first rod  340 . The first and second rods  340  and  540  retract or protrude through first and second through-holes  140  and  160  formed in the opposite ends of the cylinder  100 . The first and second through-holes  140  and  160  have different diameters depending on the cross sections of the rods. The cylinder  100  is provided therein with first and second sealing members  120  and  130  on the sides of the first and second through-holes  140  and  160  so as to block outward leakage of the fluid G. Further, through-holes of the first and second through-holes  140  and  160  through which the rods pass also have different diameters depending on the cross sections of the rods. The reason why a difference is made between the cross sections of the rods is for differentiating magnitudes of reaction forces applied to the rods, and a detailed principle thereof will be described below with reference to  FIGS. 2 and 3 . 
     In various embodiments of the present invention, shock absorbing members  145  and  147  may be installed in inner surface of the first and second sealing members  120  and  130  so as to absorb the impact that the first and second pistons  360  and  560  may act thereon. 
       FIG. 2  is a cross-sectional view illustrating a first rod, and  FIG. 3  is a cross-sectional view illustrating a second rod. The first and second pistons  360  and  560  connected with the first and second rods  340  and  540  include the respective orifices  362  and  562 , so that the pressures of the fluid G on the left and right sides of each piston in the cylinder  100  are identical to each other. The reaction force applied to the pistons and rods is always applied toward the outside of the cylinder  100 , because the pressures applied to each piston on the opposite sides of each piston are different from each other. This pressure difference is generated by the cross section difference between the rods. In detail, a description will be made taking the first rod  340  of  FIG. 2  by way of an example. The fluid is fully filled on the right side of the first piston  360 , while the fluid is fully filled on the left side of the first piston  360  but is short of a volume of the first rod  340 . Thus, since force caused by the applied pressure is derived from the product of a cross section and pressure per unit area, the force applied to the first piston  360  on the right side of the first piston  360  is greater than that applied to the first piston  360  on the left side of the first piston  360  because of the cross section of the first rod  340 . This difference results in the reaction force by which the first rod  340  is pushed toward the outside of the cylinder. Of course, although pressure corresponding to external atmospheric pressure or weight of the open-close means will be applied to the cross section of the first rod  340 , the pressure of the fluid G in the cylinder  100  is greater than this pressure, and thus the predetermined reaction force is applied to the first rod  340 . 
     As described above, the reaction force applied to each rod is dependent on the cross section of each rod. In detail, as the cross section of each rod increases, the reaction force pushing the corresponding piston and rod in an outward direction increases. Comparing the first rod  340  of  FIG. 2  with the second rod  540  of  FIG. 3 , the cross section of the first rod  340  is greater than that of the second rod  540 , and thus the reaction force applied to the first rod  340  is greater than that applied to the second rod  540 . The difference between these reaction forces makes it smooth to open and close the open-close means. 
       FIGS. 4 through 7  illustrate the process in which an open-close means is closed in an open state, and then is opened again.  FIG. 4  illustrates the state in which an open-close means is open. When the open-close means is open, the first piston  360  reaches the first sealing member  120 , so that the maximum expansion of the first rod  340  is achieved. The second piston  560  also reaches the second sealing member  130 , so that the maximum expansion of the second rod  540  is achieved. In this state, the open-close means maintains the maximum opening angle. However, this configuration is merely one embodiment. In the practical realization, the maximum opening angle may be maintained in the state in which the second piston  560  does not reach the second sealing member  130 . 
     Meanwhile, when the user presses the open-close means in a downward direction in this state so as to transmit predetermined force, this force causes the second rod  540  having a weak reaction force to react first to be slidably contracted toward the inside of the cylinder  100  (see  FIG. 5 ). The second rod  540  continues to be contracted until the second connector  520  reaches the end of the cylinder  100 . After the contraction of the second rod  540  is completed, the first rod  340  begins to be contracted. In the state in which the first rod  340  is contracted to some extent, the open-close means maintains a completely closed state (see  FIG. 6 ). In this state, when the user releases locking of the open-close means, the first rod  340  having a strong reaction force is expanded first (see  FIG. 7 ). After the expansion of the first rod  340  is completed, the second rod  540  is expanded to enter the initial state of  FIG. 4 . 
     As described above, the difference between the reaction forces applied to the first and second rods  340  and  540  is always maintained in that state. The reaction force applied to the first rod  340  toward the outside of the cylinder  100  is adapted to be greater than that applied to the second rod  540  by making the cross section of the first rod  340  greater than that of the second rod  540 . Thereby, the first rod  340  has an expanding force greater than that of the second rod  540 . Further, the second rod  540  is contracted first when the open-close means is closed, and the first rod  340  is expanded first when the open-close means is open. 
     Thus, the open-close means begins to be closed by the contraction of the second rod  540  having a relative weak reaction force, while the open-close means begins to be opened by the expansion of the first rod  340  having a relative strong reaction force. As a result, when the open-close means is closed, the user can close the open-close means without applying strong force thereto. Further, the open-close means is opened by a relatively strong force. Unlike the conventional lifter, the opening force required when opening is increased, and simultaneously the reaction force generated when closing is decreased. Thus, quality of the operation which the user feels is improved. Further, the fluid G having the same pressure is shared in the cylinder  100 , so that the difference between the reaction forces of the first and second rods  340  and  540  can be uniformly maintained although the fluid leaks out. 
     Since the two rods  340  and  540  are contracted or expanded on the opposite sides of the cylinder  100 , a stroke of each rod is reduced by half as compared to the conventional lifter. Thus, the length of each rod exposed outside or entering inside is reduced, and thus a probability of damaging the sealing members  120  and  130  is remarkably reduced. 
     Meanwhile, in order to prevent the first and second pistons  360  and  560  from colliding with each other in the cylinder, the length of the cylinder  100  is designed to be greater than the sum of the lengths of the first and second rods  340  and  540 . 
     In various embodiments of the present invention, the number and size of respective orifices  362  and  562  may be changed according to a variety of embodiments so that the damping coefficient of the first and second pistons  360  and  560  can be adjusted. 
     For convenience in explanation and accurate definition in the appended claims, the terms “outside”, “inner”, “upwards”, and “downwards” are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures. 
     The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.