Patent Publication Number: US-2023135744-A1

Title: Shock absorber

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Korean Patent Application No. 10-2021-0149852, filed on Nov. 3, 2021 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND 
     1. Field 
     Embodiments of the present disclosure relate to a shock absorber, and more particularly, to a shock absorber capable of realizing a step-by-step damping force according to the amount of shock transmitted from a road surface during a compression stroke, and buffering the shock during the compression stroke at an extremely low speed so as to improve ride comfort and adjustment stability. 
     2. Description of the Related Art 
     In general, buffers that improve riding comfort by buffering shocks or vibrations that axles receive from road surfaces during driving are installed in vehicles, and shock absorbers are used as one of the buffers. 
     The shock absorbers are operated according to the vibrations of the vehicles according to conditions of the road surfaces, and in this case, damping forces generated by the shock absorbers vary according to the operating speed of the shock absorber, that is, whether the operating speed is fast or slow. 
     Since the ride comfort and driving stability of the vehicles can be controlled depending on how characteristics of the damping forces generated by the shock absorbers are adjusted, it is important to adjust the characteristics of the damping forces of the shock absorbers when vehicles are designed. 
     Such a shock absorber is typically provided with a cylinder filled with a working fluid (oil), a piston rod that is connected to a vehicle body side and reciprocates, and a piston valve that is coupled to a lower end of the piston rod, slides in the cylinder, and controls the flow of the working fluid. 
     The piston valve is designed to have a constant damping characteristic at a high speed, a medium speed, and a low speed using a single flow path. However, such a piston valve has a structure in which it is difficult for a damping force to act when the compression stroke is performed at an extremely low speed. 
     Further, there is a need to secure a length of the cylinder over a predetermined length so that the piston rod performs the compression stroke over a predetermined stroke, and this causes excessive increases in the length and volume of the shock absorber. 
     RELATED ART DOCUMENT 
     Patent Document 
     Korean Patent Application Publication No. 10-2018-0083725 (Jul. 23, 2018) 
     SUMMARY 
     Therefore, it is an aspect of the present disclosure to provide a shock absorber configured to prevent an excessive increase in the length and volume of a device by providing an additional damping force over a certain stroke during a compression stroke. 
     It is another aspect of the present disclosure to provide a shock absorber capable of improving ride comfort and adjustment stability of a vehicle by providing a step-by-step damping force over a certain stroke during the compression stroke. 
     Additional aspects of the disclosure will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the disclosure. 
     In accordance with one aspect of the present disclosure, a shock absorber including a cylinder filled with a fluid and a piston valve coupled to a piston rod and configured to partition an inside of the cylinder into a tension chamber and a compression chamber, includes a support member coupled to an end of the cylinder and provided with a connection flow path, a first guide member forming a first pressing chamber and provided with a first flow path formed to vertically pass therethrough, a second guide member forming a second pressing chamber and having a second flow path configured to allow the second pressing chamber to communicate with the compression chamber, an opening/closing member coupled to an end of the piston rod and provided to press the second guide member upon lowering the piston rod, a first elastic member provided between the first guide member and the support member, and a second elastic member provided between the first guide member and the second guide member. 
     The first pressing chamber may be formed between the support member and the first guide member which are disposed to be spaced apart from each other. 
     The second pressing chamber may be formed between the first guide member and the second guide member which are disposed to be spaced apart from each other. 
     An outer circumferential surface of the first guide member may be in close contact with an inner circumferential surface of the cylinder, and the first flow path may be provided at a central portion of the first guide member. 
     The first flow path may include a first main flow path formed to pass through the central portion of the first guide member in an axial direction and a first slit flow path formed to be recessed in a bottom surface of the first guide member in a direction perpendicular to the axial direction. 
     An outer circumferential surface of the second guide member may be in close contact with an inner circumferential surface of the cylinder, and the second flow path may be provided at a central portion of the second guide member. 
     The second flow path may include a second main flow path formed to pass through the central portion of the second guide member in an axial direction and a second slit flow path formed to be recessed in a top surface of the second guide member in a direction perpendicular to the axial direction. 
     The opening/closing member may include a body, a flange formed to extend radially outward from a bottom surface of the body, and a hole which is provided in the body and into which the end of the piston rod is inserted. 
     An outer diameter of the flange may be provided greater than an inner diameter of the second main flow path and smaller than an inner diameter of the second slit flow path. 
     One side of the first elastic member may be inserted into a first groove provided in a bottom surface of the first guide member, and the other side thereof may be inserted into a second groove provided in a top surface of the support member. 
     One side of the second elastic member may be coupled to a first protrusion provided on a top surface of the first guide member, and the other side thereof may be coupled to a second protrusion provided on a bottom surface of the second guide member. 
     The shock absorber may further include an outer tube disposed to be spaced apart from an outside of the cylinder and having a reservoir chamber formed between the cylinder and the outer tube. 
     The shock absorber may further include a body valve coupled to a lower end of the support member, configured to allow the connection flow path to communicate with the reservoir chamber, and configured to generate a damping force. 
     An elastic modulus of the first elastic member may be provided greater than an elastic modulus of the second elastic member. 
     An elastic modulus of the first elastic member may be provided smaller than an elastic modulus of the second elastic member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects of the disclosure will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
         FIG.  1    is a cross-sectional view illustrating a shock absorber according to an embodiment of the present disclosure; 
         FIG.  2    is an enlarged cross-sectional view illustrating the shock absorber according to the embodiment of the present disclosure; 
         FIG.  3    is an exploded perspective view illustrating a part of the shock absorber according to the embodiment of the present disclosure; 
         FIG.  4    is a perspective view illustrating an opening/closing member and a second guide member of the shock absorber according to the embodiment of the present disclosure; 
         FIG.  5    is a perspective view illustrating a bottom surface of a first guide member of the shock absorber according to the embodiment of the present disclosure; 
         FIG.  6    is an operation diagram illustrating an operation of a valve assembly according to a stroke length of a piston rod during a compression stroke in a first section in the shock absorber according to the embodiment of the present disclosure; 
         FIG.  7    is an operation diagram illustrating an operation of the valve assembly according to the stroke length of the piston rod during the compression stroke in a second section in the shock absorber according to the embodiment of the present disclosure; 
         FIG.  8    is an operation diagram illustrating an operation of the valve assembly according to the stroke length of the piston rod during the compression stroke in a third section in the shock absorber according to the embodiment of the present disclosure; 
         FIG.  9    is an enlarged cross-sectional view illustrating a shock absorber according to a modified embodiment of the present disclosure; 
         FIG.  10    is an operation diagram illustrating an operation of a valve assembly according to a stroke length of a piston rod during a compression stroke in a first section in the shock absorber according to the modified embodiment of the present disclosure; 
         FIG.  11    is an operation diagram illustrating an operation of the valve assembly according to the stroke length of the piston rod during the compression stroke in a second section in the shock absorber according to the modified embodiment of the present disclosure; and 
         FIG.  12    is an operation diagram illustrating an operation of the valve assembly according to the stroke length of the piston rod during the compression stroke in a third section in the shock absorber according to the modified embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The following embodiments are presented to sufficiently convey the spirit of the present disclosure to those skilled in the art to which the present disclosure pertains. The present disclosure is not limited to the embodiments presented herein and may be embodied in other forms. In the drawings, illustration of components irrelevant to the description will be omitted to clarify the present disclosure, and the sizes of the components may be slightly exaggerated to help understanding. 
       FIG.  1    is a cross-sectional view illustrating a shock absorber according to an embodiment of the present disclosure,  FIG.  2    is an enlarged cross-sectional view illustrating the shock absorber according to the embodiment of the present disclosure,  FIG.  3    is an exploded perspective view illustrating a part of the shock absorber according to the embodiment of the present disclosure,  FIG.  4    is a perspective view illustrating an opening/closing member and a second guide member of the shock absorber according to the embodiment of the present disclosure, and  FIG.  5    is a perspective view illustrating a bottom surface of a first guide member of the shock absorber according to the embodiment of the present disclosure. 
     Referring to  FIGS.  1  to  5   , a shock absorber  1  according to the embodiment of the present disclosure may include a piston rod  30  that reciprocates inside a cylinder  10  filled with a fluid, a piston valve  31  mounted on the piston rod  30  and configured to partition an inside of the cylinder  10  into a tension chamber  11  and a compression chamber  12 , and a valve assembly  100  coupled to an end of the cylinder  10  and configured to change a damping force according to displacement of the piston rod  30 . Further, the shock absorber  1  according to the embodiment of the present disclosure may further include an outer tube  20  which is provided outside the cylinder  10  and in which a reservoir chamber  21  is formed and a body valve  40  coupled to a lower end of the valve assembly  100 , allowing the reservoir chamber  21  to communicate with the valve assembly  100 , and configured to generate the damping force. 
     The cylinder  10  may be provided in a cylindrical shape having a space formed therein, and a working fluid (oil) fills the cylinder  10 . Further, the inside of the cylinder  10  may be partitioned into the lower compression chamber  12  and the upper tension chamber  11  by the piston valve  31 . 
     One end of the piston rod  30  is located inside the cylinder  10 , and the other end thereof extends outward from the cylinder  10  and is connected to a vehicle body (not illustrated) or wheel side of a vehicle. In this case, the piston valve  31  and an opening/closing member  32  are mounted on the one end of the piston rod  30 . 
     The piston valve  31  together with the piston rod  30  is provided to reciprocate inside the cylinder  10  filled with the fluid in a state of being coupled through the piston rod  30 . In this case, at least one compression flow path and at least one tension flow path are formed to vertically pass through the piston valve  31  so that the fluid may move during a compression stroke or a tension stroke. The piston valve  31  generates a damping force due to the resistance of the fluid while flowing the fluid into the compression chamber  12  or the tension chamber  11  during the compression stroke or the tension stroke within the cylinder  10 . 
     The valve assembly  100  may be coupled to an end of the cylinder  10  and provided to change the damping force according to displacement of the piston rod  30 . In detail, the valve assembly  100  may generate an additional damping force according to a stroke length of the piston rod  30  during the compression stroke of the piston valve  31 . A detailed description of the valve assembly  100  will be made below. 
     The body valve  40  may be coupled to a lower end of the valve assembly  100  and generate an additional damping force. In detail, the body valve  40  may include a body interposed between the valve assembly  100  and a valve case  50  and having at least one flow path that is vertically passes therethrough, a plurality of disks provided at upper and lower ends of the body and configured to adjust the flow of the fluid passing through the flow path so as to generate a damping force, and a fastening member configured to fasten the plurality of disks to the body. 
     The outer tube  20  may be provided in a cylindrical shape having a space formed therein, the inner diameter of the outer tube  20  is provided greater than the cylinder  10 , and the cylinder  10  is accommodated inside the outer tube  20 . In this case, the reservoir chamber  21  filled with the working fluid (the oil) is formed between the inside of the outer tube  20  and the outside of the cylinder  10 . The reservoir chamber  21  is provided to communicate with the cylinder  10  through the body valve  40  and the valve assembly  100 . 
     Hereinafter, the valve assembly  100  of the shock absorber  1  according to the embodiment of the present disclosure will be described in detail. 
     The valve assembly  100  according to the embodiment of the present disclosure may include a support member  110  coupled to the end of the cylinder  10  and provided with a connection flow path  111 , a first guide member  120  which forms a first pressing chamber  14  between the support member  110  and the first guide member  120  and through which a first flow path  121  is formed to pass, a second guide member  130  which forms a second pressing chamber  13  between the first guide member  120  and the second guide member  130  and has a second flow path  131  formed to allow the second pressing chamber  13  to communicate with the compression chamber  12 , the opening/closing member  32  coupled to the end of the piston rod  30  and provided to press the second guide member  130  when the piston rod  30  is lowered, a first elastic member  150  provided between the first guide member  120  and the support member  110 , and a second elastic member  140  provided between the first guide member  120  and the second guide member  130 . 
     The valve assembly  100  may additionally add a damping force according to the stroke length of the piston rod  30  during the compression stroke. A detailed description of an operation of the valve assembly  100  will be given below in the following description of the operation. 
     The support member  110  may be provided such that one side thereof is coupled to the end of the cylinder  10  to support a lower end of the first elastic member  150  and the body valve  40  is coupled to the other side thereof. 
     In detail, the support member  110  may include a small-diameter portion  110   a  press-fitted to the end of the cylinder  10  and a large-diameter portion  110   b  which has a larger radius than the small-diameter portion  110   a  and has a hollow connection chamber  15  formed at a lower end thereof and to which the body valve  40  is coupled. 
     The support member  110  may be provided with the connection flow path  111  that is vertically formed through a central portion thereof and is provided to allow the fluid to flow therethrough. Accordingly, the connection flow path  111  allows the first pressing chamber  14  to communicate with the connection chamber  15 . 
     The support member  110  may be provided with a groove  112  formed in an upper surface thereof and configured to accommodate and support the lower end of the first elastic member  150 . For example, the groove  112  may be provided to be recessed in a circumferential direction in the upper surface of the support member  110 . 
     The first guide member  120  is disposed between and spaced apart from the support member  110  and the second guide member  130 , forms the first pressing chamber  14  between the support member  110  and the first guide member  120 , and forms the second pressing chamber  13  between the first guide member  120  and the second guide member  130 . 
     The first guide member  120  is provided with the first flow path  121  allowing the first pressing chamber  14  to communicate with the second pressing chamber  13 . 
     In detail, the first flow path  121  may include a first main flow path  121   a  provided in the form of a plurality of cylindrical holes radially arranged and formed to vertically pass through the first guide member  120 , and a first slit flow path  121   b  recessed in a bottom surface of the first guide member  120  to communicate with the first main flow path  121   a  and extending in the form of a slit toward a central portion of the first guide member  120 . In this case, the first slit flow path  121   b  may be provided in the form in which at least portions of the first main flow path  121   a  is connected to each other. 
     Accordingly, the first guide member  120  allows the first pressing chamber  14  to communicate with the second pressing chamber  13  and enables the fluid to flow through the first slit flow path  121   b  even when in close contact with the support member, and thus it is possible to prevent a negative pressure from being generated in the first pressing chamber  14 . 
     A lower end of the first guide member  120  is elastically supported by the first elastic member  150 , and an upper end thereof is elastically supported by the second elastic member  140 . 
     The elastic modulus of the first elastic member  150  may be provided smaller than the elastic modulus of the second elastic member  140 . Accordingly, when the opening/closing member  32  coupled to the end of the piston rod  30  presses the second guide member  130  during the compression stroke, the second guide member  130  may press the first guide member  120  through the second elastic member  140  while lowering, and the first elastic member  150  may be compressively and elastically deformed. 
     The first guide member  120  may have a groove provided in a bottom surface thereof and configured to accommodate an upper end of the first elastic member  150 , and the first guide member  120  may have a protrusion  123  provided on an upper surface thereof and inserted into a lower end of the second elastic member  140 . 
     The second guide member  130  is disposed above the first guide member  120  and forms the second pressing chamber  13  between the first guide member  120  and the second guide member  130 . 
     The second guide member  130  is provided with a second flow path  131  configured to allow the compression chamber  12  to communicate with the second pressing chamber  13 . 
     In detail, the second flow path  131  may include a second main flow path  131   a  formed to vertically pass through a central portion of the second guide member  130  in a cylindrical shape, and a second slit flow path  131   b  formed to be recessed in a direction perpendicular to an axial direction in an upper surface of the second guide member  130  to communicate with the second main flow path  131   a  and formed to extend radially. 
     In this case, an inner diameter r 1  of the second main flow path  131   a  is provided smaller than an outer diameter r 3  of a bottom surface of the opening/closing member  32 , and an inner diameter r 2  of the second slit flow path  131   b  is provided greater than an outer diameter r 3  of the bottom surface of the opening/closing member  32 . Accordingly, the second guide member  130  may allow the compression chamber  12  to communicate with the second pressing chamber  13  through the second slit flow path  131   b  even when the opening/closing member  32  is lowered to come into close contact with the second guide member  130 , and can prevent a negative pressure from being generated in the second pressing chamber  13  when the opening/closing member  32  returns. 
     The second guide member  130  may have a protrusion  132  provided on a bottom surface thereof and configured to accommodate an upper end of the second elastic member  140 . For example, the protrusion  132  may be formed to protrude in a ring shape in a circumferential direction from the bottom surface of the second guide member  130  and may be inserted into the upper end of the second elastic member  140 . 
     The second guide member  130  is spaced apart from the first guide member  120 , and a lower end of the second guide member  130  is elastically supported by the second elastic member  140 . During the compression stroke, the second guide member  130  may be lowered by pressing the opening/closing member  32  and may return to an original position thereof by an elastic force of the second elastic member  140 . A detailed operation of the second guide member  130  will be described below. 
     The opening/closing member  32  may be provided in the compression chamber  12 , spaced apart from the second guide member  130 , and pressed by the piston rod  30 . 
     The opening/closing member  32  is coupled to an end of the piston rod  30 , is vertically movably provided together with the piston rod  30 , and is provided to press the second guide member  130 . 
     The opening/closing member  32  may include a body  32   a,  a flange  32   b  extending radially outward from the body  32   a,  and a hole  32   c  which is provided in the body  32   a  and into which the end of the piston rod  30  may be inserted. 
     The outer diameter r 3  of the flange  32   b  of the opening/closing member  32  may be greater than the inner diameter r 1  of the second main flow path  131   a  and smaller than the inner diameter r 2  of the second slit flow path  131   b.  Accordingly, even when the opening/closing member  32  comes into close contact with the second guide member  130  when the opening/closing member  32  is lowered, the compression chamber  12  and the second pressing chamber  13  may communicate with each other through the second slit flow path  131   b.    
     Hereinafter, an operation of the shock absorber  1  according to the embodiment of the present disclosure during the compression stroke will be described. 
       FIGS.  6  to  8    are operation diagrams illustrating the operation of the valve assembly  100  according to the stroke length of the piston rod  30  during the compression stroke of the shock absorber  1  according to the embodiment of the present disclosure. 
     Referring to  FIGS.  6  to  8   , the shock absorber  1  according to the embodiment of the present disclosure generates different damping forces according to the stroke length or displacement of the piston rod  30  during the compression stroke. 
     The shock absorber  1  may be operated to increase a damping force according to the stroke length (the displacement) by which the piston rod  30  is lowered. In detail, as the piston rod  30  is lowered, the damping force is gradually increased in a first section that is a stroke section before the opening/closing member  32  reaches the second guide member  130 , a second section that is a stroke section before the first guide member  120  reaches the support member  110  by lowering of the second guide member  130 , and a third section that is a stroke section before the second guide member  130  reaches the first guide member  120 . 
     Referring to  FIG.  6   , an operation of the shock absorber  1  in the first section that is a displacement section before the opening/closing member  32  reaches the second guide member  130  while the piston rod  30  is lowered inside the cylinder  10  during the compression stroke will be described. 
     In the first section, during the compression stroke, the shock absorber  1  generates a damping force due to resistance of the fluid accommodated in the compression chamber  12  as the fluid passes through the piston valve  31  and moves to the tension chamber  11 . At the same time, the shock absorber  1  generates a damping force due to the resistance of the fluid accommodated in the compression chamber  12  as a portion of the fluid passes through the body valve  40  through the valve assembly  100 , moves to the reservoir chamber  21 , and is compressed. 
     In this case, since the connection flow path  111 , the first flow path  121 , and the second flow path  131  of the valve assembly  100  are in a fully opened state, almost no additional damping force is added. 
     That is, in the shock absorber  1 , only a damping force caused by the piston valve  31  and the body valve  40  is applied, and almost no damping force caused by the valve assembly  100  is applied. 
     Referring to  FIG.  7   , the operation of the shock absorber  1  in the second section that is a stroke section before, during the compression stroke, the piston rod  30  is lowered inside the cylinder  10 , the opening/closing member  32  presses the second guide member  130 , and the first guide member  120  reaches the support member  110  by the lowering of the second guide member  130  will be described. 
     In the second section, during the compression stroke, since the elastic modulus of the second elastic member  140  is provided greater than the elastic modulus of the first elastic member  150 , the shock absorber  1  is operated before, when the opening/closing member  32  presses the second guide member  130 , the second elastic member  140  presses the first guide member  120 , the first elastic member  150  is compressively elastically deformed, and the first guide member  120  is in close contact with the support member  110 . 
     In this case, as the opening/closing member  32  presses the second guide member  130 , the first and second pressing chambers  13  and  14  are in a high pressure state, and thus an additional damping force can be applied. 
     Referring to  FIG.  8   , an operation of the shock absorber  3  in the third section that is a stroke section before the second guide member  130  reaches the first guide member  120  while the piston rod  30  is lowered inside the cylinder  10  during the compression stroke will be described. 
     In the third section, the shock absorber  1  is operated so that the second guide member  130  is lowered while pressing the second elastic member  140  as the opening/closing member  32  presses the second guide member  130 . 
     In this case, in the third section, since the first guide member  120  is in close contact with the support member  110 , the area of a flow path of the fluid passing through the first guide member  120  is reduced, and thus an additional pressure is applied between the first guide member  120  and the support member  110 . 
     In detail, as the first guide member  120  is in close contact with the support member  110 , the first pressing chamber  14  is reduced, and thus the fluid passing through the first guide member  120  flows to the connection flow path  111  only through the first slit flow path  121   b  through the first main flow path  121   a.    
     Accordingly, in the shock absorber  1 , a damping force caused by a hydraulic pressure generated while the first guide member  120  and the support member  110  come into close contact with each other in the third section is additionally applied. 
     Thus, in the shock absorber  1  according to the embodiment of the present disclosure, during the compression stroke, an additional damping force is applied according to the stroke length of the piston rod  30 , and thus a variable damping force can be applied. 
     Hereinafter, a shock absorber  2  according to a modified embodiment of the shock absorber  1  according to the embodiment of the present disclosure will be described. 
     In the description of the shock absorber  2  according to the modified embodiment of the present disclosure, the same content as the shock absorber  1  according to the embodiment of the present disclosure will be omitted to prevent duplication. 
       FIG.  9    is an enlarged cross-sectional view illustrating a shock absorber according to a modified embodiment of the present disclosure. 
     Referring to  FIG.  9   , a valve assembly  200  according to the modified embodiment of the present disclosure may include the support member  110  coupled to the end of the cylinder  10  and provided with the connection flow path  111 , the first guide member  120  which forms the first pressing chamber  14  between the support member  110  and the first guide member  120  and through which the first flow path  121  is formed to pass, the second guide member  130  which forms the second pressing chamber  13  between the first guide member  120  and the second guide member  130  and has the second flow path  131  formed to allow the second pressing chamber  13  to communicate with the compression chamber  12 , the opening/closing member  32  coupled to the end of the piston rod  30  and provided to press the second guide member  130  when the piston rod  30  is lowered, a first elastic member  250  provided between the first guide member  120  and the support member  110 , and a second elastic member  240  provided between the first guide member  120  and the second guide member  130 . 
     In the shock absorber  2  according to the modified embodiment of the present disclosure, the elastic modulus of the first elastic member  250  may be provided greater than the elastic modulus of the second elastic member  240 . 
     Accordingly, when the opening/closing member  32  coupled to the end of the piston rod  30  presses the second guide member  130  during the compression stroke, as the second guide member  130  is pressed, the second elastic member  240  may be compressively and elastically deformed. 
     Accordingly, in the shock absorber  2  according to the modified embodiment of the present disclosure, compressive elastic deformation of the second elastic member  240  may be preemptively completed before the first guide member  120  is in close contact with the support member  110 . 
       FIGS.  10  to  12    are operation diagrams illustrating the operation of the valve assembly  200  according to the stroke length of the piston rod  30  during the compression stroke of the shock absorber  2  according to the modified embodiment of the present disclosure. 
     Referring to  FIGS.  10  and  12   , the shock absorber  2  according to the modified embodiment of the present disclosure generates different damping forces according to the stroke length or displacement of the piston rod  30  during the compression stroke. 
     The shock absorber  2  may be operated to increase a damping force according to the stroke length (the displacement) by which the piston rod  30  is lowered. In detail, as the piston rod  30  is lowered, the damping force is gradually increased in a first section that is a stroke section before the opening/closing member  32  reaches the second guide member  130 , a second section that is a stroke section before the second guide member  130  is lowered to reach the first guide member  120 , and a third section that is a stroke section before the first guide member  120  reaches the support member  110 . 
     Referring to  FIG.  10   , an operation of the shock absorber  2  in the first section that is a displacement section before the opening/closing member  32  reaches the second guide member  130  while the piston rod  30  is lowered inside the cylinder  10  during the compression stroke will be described. 
     In the first section, during the compression stroke, the shock absorber  2  generates a damping force due to resistance of the fluid accommodated in the compression chamber  12  as the fluid passes through the piston valve  31  and moves to the tension chamber  11 . At the same time, the shock absorber  2  generates a damping force due to the resistance of the fluid accommodated in the compression chamber  12  as a portion of the fluid passes through the body valve  40  through the valve assembly  200 , moves to the reservoir chamber  21 , and is compressed. 
     In this case, since the connection flow path  111 , the first flow path  121 , and the second flow path  131  of the valve assembly  200  are in a fully opened state, almost no additional damping force is added. 
     That is, in the shock absorber  2 , only a damping force caused by the piston valve  31  and the body valve  40  is applied, and almost no damping force caused by the valve assembly  200  is applied. 
     Referring to  FIG.  11   , the operation of the shock absorber  2  in the second section that is a stroke section before, during the compression stroke, the piston rod  30  is lowered inside the cylinder  10 , the opening/closing member  32  presses the second guide member  130 , and the second guide member  130  is lowered to reach the first guide member  120  will be described. 
     In the second section, during the compression stroke, since the elastic modulus of the second elastic member  240  is provided smaller than the elastic modulus of the first elastic member  250 , the shock absorber  2  is operated before, when the opening/closing member  32  presses the second guide member  130 , the second elastic member  240  is compressed and elastically deformed, and the second guide member  130  is in close contact with the first guide member  120 . 
     In this case, as the opening/closing member  32  presses the second guide member  130 , the first and second pressing chambers  13  and  14  are in a high pressure state, and thus an additional damping force can be applied. 
     Referring to  FIG.  12   , an operation of the shock absorber  3  in the third section that is a stroke section before the first guide member  120  reaches the support member  110  while the piston rod  30  is lowered inside the cylinder  10  during the compression stroke will be described. 
     In the third section, the shock absorber  2  is operated so that the opening/closing member  32  presses the second guide member  130 , the elastic deformation of the second elastic member  240  is completed, and thus the second elastic member  240  presses the first guide member  120  to move downward while compressing the first elastic member  250 . 
     In this case, in the third section, the first and second pressing chambers  13  and  14  are in a high pressure state, and thus an additional damping force is added. 
     Thus, in the shock absorber  2  according to the modified embodiment of the present disclosure, during the compression stroke, an additional damping force is applied according to the stroke length of the piston rod  30 , and thus a variable damping force can be applied. 
     As is apparent from the above description, a shock absorber according to an embodiment of the present disclosure prevents an excessive increase in the length and volume of a device by providing an additional damping force over a certain stroke during a compression stroke. 
     The shock absorber can improve ride comfort and adjustment stability of a vehicle by providing a step-by-step damping force over a certain stroke during the compression stroke. 
     As described below, although the present disclosure has been described with reference to limited embodiments and drawings, the present disclosure is not limited thereto. It is apparent that those skilled in the art to which the present disclosure belongs could derive various modifications and changes without departing from the technical spirit of the present disclosure and the equivalents of the appended claims.