Variable damping-characteristics shock absorber with adjustable orifice construction variable of fluid flow restriction depending upon fluid pressure difference

A variable damping force shock absorber, comprising:

• a hollow cylinder having cylindrical wall means defining a cylindrical bore containing a hydraulic damping fluid;
• a hollow piston rod;
• a piston fixedly mounted to said hollow piston rod and slidably disposed in said cylindrical bore to divide said cylindrical bore into a first chamber and a second chamber;
• said piston having a first axial end surface adjacent said first chamber and a second axial end surface adjacent said second chamber;
• said second axial end surface being formed with a first annular land, a radially outer groove surrounded by said first annular land, and a second annular land disposed radially inwardly of said first annular land and surrounded by said radially outer groove, and a radially inner groove surrounded by said second annular land;
• a damping valve having a valve disk seated on said first annular land and said second annular land to close fluid communication between said radially inner groove and said radially outer groove;
• said hollow piston rod being formed with a center axially extending opening, a first radially extending opening establishing fluid communication between said center axially extending opening and said first chamber, an annular peripheral groove axially spaced from said first radially extending opening, and a second radially extending opening disposed between said center axially extending opening and said annular peripheral groove to establish fluid communication therebetween;
• said piston being formed with an axial passage having one end opening to said radially inner groove and an opposite end communicating with said first chamber,
• said piston being formed with an obliquely extending opening having one end opening to said annular peripheral groove and an opposite end opening to said radially outer groove;
• and
• a rotary valve member rotatably disposed within said center axially extending opening and moveable to cover said first and second radially extending openings of said hollow piston rod, said rotary valve member being formed with a first group of valve openings mating with said first radially extending opening of said hollow piston rod and with a second group of valve openings mating with said second radially extending opening of said hollow piston rod, said rotary valve member having an axial chamber providing fluid communication between said first and second group of valve openings, said rotary valve member having a position wherein at least one of said first group of valve openings aligns with said first radially extending opening of said hollow piston rod and at least one of said second group of valve openings aligns with said second radially extending opening of said hollow piston rod to establish fluid communication between said first and second radially extending openings of said hollow piston rod.