Hydraulic shock absorber

1. A hydraulic shock absorber comprising:

a damper tube;

a rod guide disposed in one open end portion of the damper tube;

a support piece disposed in the other end portion of the damper tube;

a cylinder inserted inside the damper tube and sandwiched and secured between the rod guide and the support piece in the axial direction, the cylinder being multiple-walled with N units of tubes fitted together; and

a piston rod penetrating the rod guide and slidably inserted inside the innermost tube of the cylinder,

wherein contact surfaces, where at least one end surface of (N−1) units of tubes of the cylinder is in contact with a seating surface of at least one of the rod guide and the support piece in the axial direction, are formed at a plurality of discrete circumferential positions on the end surface of the tubes in the state where the tubes of the cylinder are sandwiched and secured.

2. The hydraulic shock absorber according to claim 1 , wherein the lengths of the tubes are set relative to each other such that the end surface of the tubes in which the contact surfaces are formed thereon comes into contact with the corresponding seating surface of the rod guide or the support piece earlier than the end surface of the tube in which the contact surfaces are not formed thereon, in the process of sandwiching the tubes of the cylinder therebetween and; wherein a buckling load to work between the end surface of the tubes in which the contact surfaces are formed thereon and the corresponding seating surface of at least one of the rod guide and the support piece is set smaller than a sandwiching and securing load to be applied to the cylinder by the rod guide and support piece disposed in the damper tube.

3. The hydraulic shock absorber according to claim 1 , wherein oil passages communicating the inside and the outside of the tubes are formed in non-contacting portions of the end surface, where the end surface of the tubes does not come in contact with the corresponding seating surface of the rod guide or the support piece, of the tubes in which the contact surfaces are formed thereon.

4. The hydraulic shock absorber according to claim 2 , wherein oil passages communicating between the inside and the outside of the tubes are formed in non-contacting portions of the end surface, where the end surface of the tubes does not come in contact with the corresponding seating surface of the rod guide or the support piece, of the tubes in which the contact surfaces are formed thereon.

5. The hydraulic shock absorber according to claim 1 , wherein the cylinder, which is a double-walled tube of an outer tube and an inner tube, is set inside the damper tube, wherein an oil chamber, including a piston-side oil chamber and a rod-side oil chamber, is formed by the piston rod inserted inside the inner tube, and wherein an outside passage connecting the piston-side oil chamber and the rod-side oil chamber is formed by an annular interspace between the outer tube and the inner tube, and an annular interspace between the damper tube and the outer tube is used as an oil reservoir chamber.

6. The hydraulic shock absorber according to claim 2 , wherein the cylinder, which is a double-walled tube of an outer tube and an inner tube, is set inside the damper tube, wherein an oil chamber, including a piston-side oil chamber and a rod-side oil chamber, is formed by the piston rod inserted inside the inner tube, and wherein an outside passage connecting the piston-side oil chamber and the rod-side oil chamber is formed by an annular interspace between the outer tube and the inner tube, and an annular interspace between the damper tube and the outer tube is used as an oil reservoir chamber.

7. The hydraulic shock absorber according to claim 3 , wherein the cylinder, which is a double-walled tube of an outer tube and an inner tube, is set inside the damper tube, wherein an oil chamber, including a piston-side oil chamber and a rod-side oil chamber, is formed by the piston rod inserted inside the inner tube, and wherein an outside passage connecting the piston-side oil chamber and the rod-side oil chamber is formed by an annular interspace between the outer tube and the inner tube, and an annular interspace between the damper tube and the outer tube is used as an oil reservoir chamber.

8. The hydraulic shock absorber according to claim 4 , wherein the cylinder, which is a double-walled tube of an outer tube and an inner tube, is set inside the damper tube, wherein an oil chamber, including a piston-side oil chamber and a rod-side oil chamber, is formed by the piston rod inserted inside the inner tube, and wherein an outside passage connecting the piston-side oil chamber and the rod-side oil chamber is formed by an annular interspace between the outer tube and the inner tube, and an annular interspace between the damper tube and the outer tube is used as an oil reservoir chamber.

9. The hydraulic shock absorber according to claim 5 , wherein the damper tube is fitted on a head portion of the rod guide and clinched, upper end inner peripheries of the outer tube and the inner tube of the cylinder are fitted respectively to a middle outside-diameter portion and a smaller outside-diameter portion provided below the head portion of the rod guide, and the upper end surfaces of the outer tube and the inner tube are brought into contact with seating surfaces provided on the outer peripheries of the middle outside-diameter portion and the smaller outside-diameter portion, wherein the seating surface provided on the outer periphery of the smaller outside-diameter portion of the rod guide has projections rising from a plurality of circumferential positions thereof, and the top surfaces of the projections form contact surfaces in contact with the end surface of the inner tube in the axial direction, and wherein vertical grooves are each formed between the smaller outside-diameter portion of the rod guide and adjacent projections on the outer periphery thereof, and the non-contacting portions which are not in contact with the top surfaces of the projections, of the end surface of the inner tube, jointly with the vertical grooves, form oil passages communicating the rod-side oil chamber with the outside passage.

10. The hydraulic shock absorber according to claim 6 , wherein the damper tube is fitted on a head portion of the rod guide and clinched, upper end inner peripheries of the outer tube and the inner tube of the cylinder are fitted respectively to a middle outside-diameter portion and a smaller outside-diameter portion provided below the head portion of the rod guide, and the upper end surfaces of the outer tube and the inner tube are brought into contact with seating surfaces provided on the outer peripheries of the middle outside-diameter portion and the smaller outside-diameter portion, wherein the seating surface provided on the outer periphery of the smaller outside-diameter portion of the rod guide has projections rising from a plurality of circumferential positions thereof, and the top surfaces of the projections form contact surfaces in contact with the end surface of the inner tube in the axial direction, and wherein vertical grooves are each formed between the smaller outside-diameter portion of the rod guide and adjacent projections on the outer periphery thereof, and the non-contacting portions which are not in contact with the top surfaces of the projections, of the end surface of the inner tube, jointly with the vertical grooves, form oil passages communicating the rod-side oil chamber with the outside passage.

11. The hydraulic shock absorber according to claim 7 , wherein the damper tube is fitted on a head portion of the rod guide and clinched, upper end inner peripheries of the outer tube and the inner tube of the cylinder are fitted respectively to a middle outside-diameter portion and a smaller outside-diameter portion provided below the head portion of the rod guide, and the upper end surfaces of the outer tube and the inner tube are brought into contact with seating surfaces provided on the outer peripheries of the middle outside-diameter portion and the smaller outside-diameter portion, wherein the seating surface provided on the outer periphery of the smaller outside-diameter portion of the rod guide has projections rising from a plurality of circumferential positions thereof, and the top surfaces of the projections form contact surfaces in contact with the end surface of the inner tube in the axial direction, and wherein vertical grooves are each formed between the smaller outside-diameter portion of the rod guide and adjacent projections on the outer periphery thereof, and the non-contacting portions which are not in contact with the top surfaces of the projections, of the end surface of the inner tube, jointly with the vertical grooves, form oil passages communicating the rod-side oil chamber with the outside passage.

12. The hydraulic shock absorber according to claim 8 , wherein the damper tube is fitted on a head portion of the rod guide and clinched, upper end inner peripheries of the outer tube and the inner tube of the cylinder are fitted respectively to a middle outside-diameter portion and a smaller outside-diameter portion provided below the head portion of the rod guide, and the upper end surfaces of the outer tube and the inner tube are brought into contact with seating surfaces provided on the outer peripheries of the middle outside-diameter portion and the smaller outside-diameter portion, wherein the seating surface provided on the outer periphery of the smaller outside-diameter portion of the rod guide has projections rising from a plurality of circumferential positions thereof, and the top surfaces of the projections form contact surfaces in contact with the end surface of the inner tube in the axial direction, and wherein vertical grooves are each formed between the smaller outside-diameter portion of the rod guide and adjacent projections on the outer periphery thereof, and the non-contacting portions which are not in contact with the top surfaces of the projections, of the end surface of the inner tube, jointly with the vertical grooves, form oil passages communicating the rod-side oil chamber with the outside passage.