Abstract:
A variable damping valve of a shock absorber is capable of properly adjusting a damping force according to read conditions, travel conditions and the like while a vehicle is traveling, thereby improving ride comfort and control stability. A flow of oil is controlled to generate a damping force and the damping force is simultaneously adjusted according to pressure in a pilot chamber. The damping valve comprises an upper retainer communicating with a high-pressure side and a main valve installed below the upper retainer. The main valve comprises a valve body defining a pilot chamber, a disk ring installed on a top surface of the valve body, and a housing for containing the valve body and the disk ring and integrally confining the valve body and the disk ring by being curled at upper and lower ends of the housing.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a variable damping valve of a shock absorber, and more particularly, to a shock absorber mounted with a variable damping valve capable of properly adjusting a damping force according to road conditions, travel conditions and the like while a vehicle is traveling, thereby improving ride comfort and control stability.  
         [0003]     2. Description of the Related Art  
         [0004]     A shock absorber of a suspension system mounted in a vehicle is a vibration-proof and shock-absorbing apparatus installed between an axle and a vehicle body to improve ride comfort by absorbing a vibration or shock transmitted from a road to the axle when the vehicle travels. The interior of the shock absorber is filled with oil and/or gas.  
         [0005]     Shock absorbers include a variable damping shock absorber adapted to properly adjust a damping characteristic according to road and travel conditions so as to improve ride comfort or control stability. The variable damping shock absorber has a configuration in which a variable damping valve for adjusting a damping force is provided at a side surface of an outer tube of a conventional shock absorber.  
         [0006]     Conventional variable damping valves are classified into a normal type variable valve and a reverse type variable valve according to methods of controlling a damping force in response to the movement of a vehicle. The reverse type variable valve is characterized in that compression and extension strokes are controlled by an additional valve in response to the movement of a vehicle. Thus, in the reverse type variable valve, a weak damping force is generated during the extension stroke and a strong damping force is generated during the compression stroke, or a strong damping force is generated during the extension stroke and a weak damping force is generated during the compression stroke. However, since the reverse type variable valve employs such an additional valve, there are disadvantages in that production costs thereof increase and the use of the additional valve results in a relatively larger size and deteriorated mountability.  
         [0007]     In the normal type variable valve, a single valve is used to control damping forces during both the compression and extension strokes. Thus, in the normal type variable valve, strong damping forces or weak damping forces are generated during both the compression and extension strokes.  
         [0008]     A conventional reverse type variable valve is disclosed in Korean Patent Application No. 1997-58101 entitled “Damping force-adjustable hydraulic shock absorber,” wherein a damping force generating valve  11  is connected to a side of a variable damping shock absorber  1 . The damping force generating valve will be described with reference to  FIG. 1 .  
         [0009]     Since compression-side and extension-side valve mechanisms of the damping force generating valve  11  have the substantially same structure, an enlarged view common to them is shown in  FIG. 2 .  
         [0010]     As shown in the figures, the damping force generating valve  11  is constructed in such a manner that two bottomed cylindrical valve bodies  13  and  14  are fitted into a bottomed cylindrical case  12 , a proportional solenoid actuator  15  (hereinafter, referred to as “actuator  15 ”) is mounted in an opening of the case  12 , and the interior of the case  12  is partitioned into three fluid chambers  12   a,    12   b  and  12   c  by the valve bodies  13  and  14 .  
         [0011]     Annular sealing members  16  and  17  are fitted into openings of the valve bodies  13  and  14 , respectively, and a cylindrical guide member  18  threadly coupled to the actuator  15  penetrates through the valve bodies  13  and  14  and the sealing members  16  and  17  and is then secured by a nut  19 . A sidewall of the case  12  is provided with connection holes  20 ,  21  and  22  communicating respectively with the fluid chamber  12   a,    12   b  and  12   c.  The connection holes  20 ,  21  and  22  are connected to a cylinder through flow passages of the shock absorber, respectively.  
         [0012]     A plurality of circumferentially arranged flow passages  26  and  27  (inlet passages) (only two flow passages are shown in  FIG. 1 ) are formed at lower portions of the valve bodies  13  and  14  to axially penetrate through the valve bodies, respectively. Further, on an inner wall at the lower portion of each of the valve bodies  13  and  14 , an annular inner sealing part  28  or  29  (see  FIG. 2 ) is provided to protrude at an inner peripheral side of the passage  26  or  27 , an annular valve seat  30  or  31  (see  FIG. 2 ) is provided to protrude at an outer peripheral side of the passage  26  or  27 , and an annular outer sealing part  32  or  33  (see  FIG. 2 ) is provided outside the annular valve seat  30  or  31  and in the vicinity of a sidewall of the valve body  13  or  14 . Annular grooves  34  and  35  are formed between the valve seats  30  and  31  and the outer sealing parts  32  and  33 , respectively. The grooves  34  and  35  communicate with the fluid chambers (as at  12   b  and  12   c  in  FIG. 1 ) through flow passages  36  and  37  (outlet passages), respectively.  
         [0013]     As shown in  FIG. 2 , a disk-shaped orifice plate  38  or  39 , which will be described later, and a spacer  40  or  41  are stacked on the inner sealing part  36  or  37  of each of the valve bodies  13  and  14 . A disk valve  42  or  43  is stacked thereon; a retainer disk  44  or  45  with a diameter slightly smaller than that of the disk valve  42  or  43  is additionally stacked thereon; a plurality of disk-shaped leaf springs  46  or  47  (spring means) (only three leaf springs are shown in the figure) with a diameter smaller than that of the retainer disk  44  or  45 , and a spacer  48  or  49  are further stacked thereon; and an outer periphery of the disk valve  42  or  43  is placed on the valve seat  30  or  31 .  
         [0014]     A flexible sealing ring  50  or  51  is fitted into the valve body  13  or  14 . An inner periphery of the flexible sealing ring comes into contact with an outer periphery of the retainer disk  44  or  45  while slightly overlapping with each other, and an outer periphery of the flexible sealing ring comes into contact with the outer sealing part  32  or  33 . A retainer ring  52  or  53  comes into contact with the top of the outer periphery of the flexible sealing ring  50  or  51 , and an outer periphery of an annular sealing spring  54  or  55  comes into contact with the top of the retainer ring. The sealing member  16  or  17  fitted into the valve body  13  or  14  is in contact with the inner peripheries of the spacer  48  or  49  and the sealing spring  54  or  55 , and secures the inner peripheries of the disk valve  42  or  43 , the retainer disks  44  or  45  and the leaf springs  46  or  47  to the inner sealing part  28  or  29  and simultaneously secures the outer periphery of the sealing ring  50  or  51  to the outer sealing part  32  or  33 .  
         [0015]     The sealing member  16  or  17 , the retainer disk  44  or  45 , and the sealing ring  50  or  51  define a pilot chamber  56  or  57  at the rear of the disk valve  42  or  43  within the valve body  13  or  14 . At this time, the sealing spring  54  or  55  seals a gap between the valve body  13  or  14  and the sealing member  16  or  17 . Further, to securely seal a contact portion of the retainer disk  44  or  45  and the sealing ring  50  or  51 , the sealing ring  50  or  51  is assembled in such a manner that the outer periphery thereof is at a level slightly lower than that of the inner periphery thereof with respect to the bottom of the valve body  13  or  14 , thereby pressing down the retainer disk  44  or  45 . In the figures, reference numerals  58 ,  59 ,  60 ,  61  and  62  designate O-rings.  
         [0016]     A sidewall of the guide member  18  is provided with ports  63  and  64  communicating respectively with the pilot chambers  56  and  57 , and ports  65  and  66  communicating respectively with the fluid chambers  12   b  and  12   c.  The orifice plate  38  or  39  mounted on the inner sealing part  28  or  29  is provided with fixed orifices  67  or  68 . An upstream passage is constructed by the fixed orifices  67  or  68 , a cut-away portion  69  or  70  of the inner sealing part and a groove  71  or  72  of an outer periphery of the guide member  18 . With the upstream passage, the flow passage  26  or  27 , and the port  63  or  64 , i.e., pilot chamber  56  or  57 , communicate with each other. A spool  73  is slidably fitted into the guide member  18  to adjust the area of the flow passage (downstream passage) between the port  63  or  65  and the port  64  or  66 . The spool  73  is urged (forced) toward the actuator  15  by a compression spring  74  and is moved against the pressing force of the spring  74  by an actuating rod  75  of the actuator  15 , so that the areas of flow passages of the port  63  and the port  66  (variable orifice) can be adjusted.  
         [0017]     However, in such a conventional structure, the respective pilot chambers  56  and  57  formed at the rears of the disk valves  42  and  43  within the valve bodies  13  and  14  by being partitioned by the sealing members  16  and  17 , the retainer disks  44  and  45 , and the sealing rings  50  and  51  have a very complicated structure in which the sealing rings  50  and  51  are fixed by the retainers  52  and  53  placed thereon. If the retainers  52  and  53  have uneven top and bottom surfaces, unbalance occurs in the pressing forces of the retainers  50  and  51 . This causes a problem in that pressure in the pilot chambers  56  and  57  becomes unstable, resulting in dispersion of a damping force. That is, the occurrence of the dispersion in the pilot chambers  56  and  57  greatly deteriorates the performance of the shock absorber.  
       SUMMARY OF THE INVENTION  
       [0018]     The present invention is conceived to solve the aforementioned problems in the prior art. Accordingly, an object of the present invention is to provide a variable damping valve of a shock absorber, wherein a main valve of a damping force generating valve is more simplified in structure and the occurrence of dispersion of a damping force in a pilot chamber is suppressed.  
         [0019]     According to the present invention for achieving the object, there is provided a variable damping valve of a shock absorber, comprising an upper retainer communicating with a high-pressure side, and a main valve installed below the upper retainer, wherein the main valve comprises a valve body defining a pilot chamber therein, a disk ring installed on a top surface of the valve body, and a housing for containing the valve body and the disk ring therein and integrally confining the valve body and the disk ring by being curled at upper and lower ends of the housing, whereby a flow of oil is controlled to generate a damping force and the damping force is simultaneously adjusted according to pressure in the pilot chamber in a state where dispersion of the damping force is reduced in the pilot chamber. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]     The above and other objects, features and advantages of the present invention will become apparent from the following description of a preferred embodiment given in conjunction with the accompanying drawings, in which:  
         [0021]      FIG. 1  is a sectional view showing a conventional reverse type variable damping valve;  
         [0022]      FIG. 2  is an enlarged view of a portion of the variable damping valve of  FIG. 1 ;  
         [0023]      FIG. 3  shows a damping force generating valve in a variable damping shock absorber according to the present invention; and  
         [0024]      FIG. 4  is an enlarged view of a main valve of the damping force generating valve according to the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0025]     Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.  
         [0026]      FIG. 3  shows a damping force generating valve in a variable damping shock absorber according to the present invention, and  FIG. 4  is an enlarged view of a main valve of the damping force generating valve according to the present invention.  
         [0027]     As shown in  FIG. 3 , the damping force generating valve  200  installed at a side of a base shell  101  of the shock absorber comprises a case  201  installed to communicate with the base shell  101 ; and a spool  210  and a spool rod  220 , an upper retainer  240  and a main valve  250  fitted around an outer peripheral surface of the spool rod  220 , and an upper retainer guide  260 , which are included in the case  201 .  
         [0028]     Further, an actuator  202  is fixed to one end of the case  201  by means of a nut  204 .  
         [0029]     The spool  210 , which is inserted into and slidably moved in a hollow of the spool rod  220  to be described later, is moved by an actuating rod  203  of the actuator  202 , which is inserted into the spool rod  220 , while the spool compresses a spring  216  disposed in front of the spool. The spool  210  has a plurality of stepped portions with different outer diameters in a vertical direction. Among the stepped portions, a stepped portion with a larger outer diameter is formed with first and second variable orifices  212  and  213 .  
         [0030]     The first variable orifice  212  is constructed to have a higher rate of change in area than that of the second variable orifice  213  when the spool  210  reciprocates.  
         [0031]     The initial position of the spool  210  is adjusted by means of a plug  218  by which the spring  216  is supported.  
         [0032]     The spool rod  220  for guiding the movement of the spool  210  has a cylindrical hollow and includes a plurality of connection ports  221 ,  222  and  223  in a radial direction.  
         [0033]     The ring-shaped upper retainer  240  and the main valve  250  sequentially fitted and stacked around the outer peripheral surface of the spool rod  220  are fixed in a tight contact state using a nut  230 , and a sealing member  232  is installed at the tightly contacted portion to achieve sealing.  
         [0034]     The upper retainer  240  includes primary passages  242  for connection with a high-pressure side, which are vertical through-holes formed equidistantly on a concentric circle, and secondary passages  244  formed in a radial direction perpendicular to the primary passages  242 .  
         [0035]     An outer portion of the upper retainer  240  is partially contained in the upper retainer guide  260  that communicates with a separator tube  102 .  
         [0036]     Further, the upper retainer guide  260  is circumferentially formed with a plurality of flow passage grooves  262  in an outer peripheral surface thereof, so that oil can be introduced into a space between the base shell  101  and the separator tube  102 , i.e., a reservoir  103  constituting a low-pressure side.  
         [0037]     Meanwhile, the main valve  250  shown in  FIG. 4  is fitted around the spool  210  such that it is disposed below the upper retainer  240 . The main valve  250  controls the flow of oil introduced into the primary passages  242  to generate a damping force and simultaneously adjusts the damping force according to pressure in a pilot chamber  259 .  
         [0038]     As shown in the figure, the main valve  250  is preferably constructed as a single unit comprising a valve body  252 , multi-disks  254 , a disk ring  256  and a housing  258 .  
         [0039]     The valve body  252  is formed with a plurality of vertical flow passages  252   a  on a concentric circle, and has seat surfaces  252   b  formed to protrude from upper and lower surfaces of the valve body.  
         [0040]     The disk ring  256  is seated on the upper seat surface  252   b,  and the multi-disks  254  are installed on the disk ring  256  and the lower seat surface  252   b.  A plurality of slits  254   a  for guiding the flow of oil are circumferentially formed on the multi-disks  254 .  
         [0041]     Here, the slits  254   a  of the disks  254  serve as fixed orifices.  
         [0042]     To integrally confine the disk ring  256  to the vale body  252 , the housing  258  is installed around an outer peripheral surface of the valve body  252  with the disk ring  256  stacked thereon.  
         [0043]     The housing  258  is in the form of a hollow cylinder with open top and bottom. The stacked disk ring  256  and valve body  252  are inserted into the housing  258  and then integrated together by curling or caulking upper and lower ends of the housing.  
         [0044]     In designing the housing  258 , it is preferred that upon curling or caulking, the housing  258  be adapted to press down the disk ring  256  with a certain force at a fixed position.  
         [0045]     The operation of the variable damping valve of the shock absorber according to the present invention constructed as above is as follows.  
         [0046]     The flow of oil will be discussed by referring back to  FIG. 3 . With the movement of a piston, the oil is introduced toward an inlet side of the upper retainer guide  260  communicating with the high-pressure side of the shock absorber, and the introduced oil moves to the primary passages  242  of the upper retainer  240 .  
         [0047]     At this time, in case of a damping force in a soft mode which is established at a low speed and in which the flow rate of the oil is not high, as designated by a dotted line, some of the oil is introduced into the connection port  222  through the slits  254   a  of the disks  254  of the main valve  250 . Then, the oil is moved by means of the actuating rod  203  of the actuator  202 , so that the oil is moved into the spool rod  220  through the first variable orifice  212  of the spool  210  in a state where the first variable orifice is opened, and then moved to the secondary passages  244  of the upper retainer  240  through the hollow of the spool rod  220  and the connection port  221 .  
         [0048]     The oil that has passed through the secondary passages  244  is drained into the reservoir  103 , i.e., low-pressure side, through the flow passage grooves  262  of the upper retainer guide  260 .  
         [0049]     The term “high-pressure side” used herein means a portion connected to an extension chamber of the cylinder, and the term “low-pressure side” means a portion connected to the reservoir  103 .  
         [0050]     Meanwhile, the oil, which has been introduced into the primary passages  242  while the flow rate thereof increases during the extension or compression stroke, sequentially passes through the slits  254   a  of the disks  254 , the connection port  222  of the spool rod  220 , the second variable orifice  213  of the spool  210 , and the connection port  223  of the spool rod  220  to the pilot chamber  259 . Some of the moved oil (designated by a one-dot chain line) moves to the flow passage grooves  262  of the upper retainer guide  260  through the slits  254   a  of the disks  254 .  
         [0051]     The oil, which has not passed through the fixed orifices, i.e., the slits  254   a  of the disks  254 , remains in the pilot chamber  259  on the side of the flow passage grooves  262 .  
         [0052]     If a difference in pressure between the high-pressure side and the pilot chamber  259  increases due to increase of the flow rate during the extension or compression stroke, a force generated due to the pressure difference causes the disks  254  and the disk ring  256  to be bent toward the pilot chamber  259 . Thus, according to the pressure at the high-pressure side, the pressure in the pilot chamber  259  and initial preload on the disk ring  256 , a gap is produced between the seat surface  252   b  of the upper retainer  240  and the disks  254  so that the oil (designated by a solid line) can flows directly from the high-pressure side to the low-pressure side.  
         [0053]     If the flow rate decreases during the extension or compression stroke, the difference in pressure between the high-pressure side and the pilot chamber  259  decreases and the disks  254  returns to the original state, so that the gap between the seat surface  252   b  and the disks  254  disappears.  
         [0054]     Therefore, a main flow passage opened by the disks  254  is opened at different pressure according to the pressure in the pilot chamber  259 . The pressure in the pilot chamber  259  is generated by means of the operation of the second variable orifice  213  installed above the pilot chamber and the operation of the slits  254   a  of the disks  254  installed below the pilot chamber. The area of the second variable orifice  213  is controlled to increase the pressure in the pilot chamber  259 , thereby achieving switching to a hard mode. Further, the provision of the first variable orifice  212  having a higher rate of change in area than that of the second variable orifice  213  allows a flow from the high-pressure side to the low-pressure side. As the area of the second variable orifice  213  increases, the area of the first variable orifice  212  deceases. As the area of the second variable orifice  213  decreases, the area of the first variable orifice  212  increases.  
         [0055]     With such a characteristic, in the hard mode, it is possible to secure a characteristic by which the entire flow rate at a low speed region before blow-off timing is low than that in the soft mode under the same pressure condition. Even though the operating area of the high-pressure side is smaller than that of the pilot chamber  259 , such a structure enables the occurrence of blow-off timing in the hard mode at a low flow rate and high pressure. Since a proper damping force characteristic can be obtained irrespective of the area, there is an advantage in that the structure of the main valve  250  can be more simplified.  
         [0056]     Moreover, there is an advantage in that it is possible to greatly reduce the occurrence of dispersion of a damping force in the pilot chamber  259  due to force unbalance by the disk ring  256  which is formed integrally with and acts on the valve body  252  with a uniform force in the main valve  250 .  
         [0057]     In the variable damping valve  200  improved as above, the structure is simplified as well as the occurrence of the dispersion in the pilot chamber  259  is reduced.  
         [0058]     In the variable damping valve of a shock absorber according to the present invention described above, the structure of the main valve of the variable damping valve is more simplified, and the occurrence of dispersion of a damping force in the pilot chamber is reduced, thereby obtaining a stable damping force and improving the performance of the shock absorber.  
         [0059]     The foregoing is merely an embodiment for implementing the variable damping valve of a shock absorber according to the present invention. The present invention is not limited to the embodiment. It will be apparent that those skilled in the art can make modifications and changes thereto without departing from the scope and technical spirit of the present invention defined by the appended claims.