SHOCK ABSORBER

This shock absorber includes a first valve assembly connected to one end of a tube in an axial direction, a piston assembly dividing an inner chamber of the tube into a first chamber and a second chamber, a piston rod extending from the tube through the first chamber with the piston assembly connected to an intermediate position in the axial direction, a cup provided in the second chamber, and a second valve assembly disposed in the second chamber to be connected to the piston rod and configured to enter and exit from the cup. The cup includes a sleeve disposed in the second chamber with a gap between itself and the tube in a radial direction, and a base adapter fixed to the sleeve by press fitting and provided between the sleeve and the first valve assembly.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a shock absorber.

Description of Related Art

There are shock absorbers in which a damping force increases when a rod reaches a predetermined range on a limit side during a compression stroke in which the rod is pushed into a cylinder (see, for example, the specification of U.S. Pat. No. 9,605,726).

Incidentally, there has been a demand to suppress an increase in cost in shock absorbers.

Accordingly, an objective of the present invention is to provide a shock absorber in which an increase in cost can be suppressed.

SUMMARY OF THE INVENTION

In order to achieve the above-described objective, one aspect of a shock absorber of the present invention includes a tube having an inner chamber inside, a first valve assembly connected to one end of the tube in an axial direction, a piston assembly dividing the inner chamber into a first chamber and a second chamber, a piston rod extending from the tube through the first chamber with the piston assembly connected to an intermediate position thereof in the axial direction, a cup provided in the second chamber, and a second valve assembly disposed in the second chamber to be connected to the piston rod and configured to enter and exit from the cup. The cup includes a sleeve disposed in the second chamber with a gap between itself and the tube in a radial direction, and a base adapter fixed to the sleeve by press fitting and provided between the sleeve and the first valve assembly.

According to the above-described aspect of the present invention, it is possible to suppress an increase in cost.

DETAILED DESCRIPTION OF THE INVENTION

First Embodiment

A shock absorber of a first embodiment according to the present invention will be described with reference toFIGS.1to3. Further, in the following description, for convenience of explanation, an upper side in the drawings will be referred to as “upper” and a lower side in the drawings will be referred to as “lower.”

As shown inFIG.1, a shock absorber1of the first embodiment is a dual-tube type hydraulic shock absorber. The shock absorber1is used in suspension devices of vehicles, specifically, automobiles. The shock absorber1includes a cylinder2. The cylinder2includes a tube3and a shell5. The tube3has a cylindrical shape. The shell5has a bottomed cylindrical shape. The shell5has an inner diameter larger than an outer diameter of the tube3. The tube3is disposed on a radial inner side of the shell5. A central axis of the tube3and a central axis of the shell5coincide with each other. The tube3has an inner chamber6inside. A reservoir chamber7is provided between the tube3and the shell5.

The shell5includes a barrel part11and a bottom part12. The barrel part11and the bottom part12are formed seamlessly and integrally. The barrel part11has a cylindrical shape. The bottom part12closes a lower portion of the barrel part11.

The shock absorber1includes a piston assembly17. The piston assembly17is disposed in the tube3of the cylinder2. The piston assembly17includes a piston18. In the piston assembly17, the piston18is fitted in the tube3to be slidable. The piston18divides the inner chamber6in the tube3into two chambers, a first chamber19on one side and a second chamber20on the other side. The first chamber19is on a side opposite to the bottom part12with respect to the piston18in an axial direction of the tube3. The second chamber20is on the bottom part12side with respect to the piston18in the axial direction of the tube3. In the cylinder2, an oil fluid L as a working fluid is sealed in the inner chamber6inside the tube3. In the cylinder2, the oil fluid L and a gas G are sealed as working fluids in the reservoir chamber7between the tube3and the shell5.

The shock absorber1includes a piston rod21. One side of the piston rod21in the axial direction is disposed in the tube3of the cylinder2. This one side of the piston rod21is connected to the piston assembly17. The other side of the piston rod21in the axial direction extends from the cylinder2to the outside of the cylinder2. The piston rod21extends from the tube3and the shell5, that is, the cylinder2, through the first chamber19with the piston assembly17attached thereto.

In the shock absorber1, a portion of the piston rod21extending from the cylinder2is disposed at an upper portion to be connected to a vehicle body of a vehicle. At the same time, in the shock absorber1, a mounting bracket22fixed to the barrel part11of the shell5is disposed at a lower portion to be connected to a wheel side of the vehicle.

The piston18is fixed to the piston rod21. Therefore, the piston18and the piston rod21move together. In the shock absorber1, a stroke in which the piston rod21moves in a direction to increase a protrusion amount from the cylinder2is an extension stroke in which the entire length increases. In the shock absorber1, a stroke in which the piston rod21moves in a direction to decrease the protrusion amount from the cylinder2is a compression stroke in which the entire length decreases. In the shock absorber1, the piston18moves to the first chamber19side during the extension stroke. In the shock absorber1, the piston18moves to the second chamber20side during the compression stroke.

A rod guide23is fitted to an upper end opening side of the tube3and an upper end opening side of the shell5. A seal member24is fitted to the shell5on an upper side of the rod guide23. Both the rod guide23and the seal member24are annular. The piston rod21is inserted through a radial inner side of the rod guide23and the seal member24. The piston rod21slides with respect to the rod guide23and the seal member24in the axial direction. The piston rod21extends from the inside of the cylinder2to the outside of the cylinder2from the seal member24.

The rod guide23restricts movement of the piston rod21in the radial direction with respect to the tube3and the shell5of the cylinder2. The piston rod21is fitted in the rod guide23and the piston18is fitted in the tube3. Thereby, a central axis of the piston rod21and a central axis of the tube3coincide with each other. The rod guide23supports the piston rod21to be movable in the axial direction of the piston rod21. The seal member24has an outer circumferential portion in close contact with the shell5. The seal member24has an inner circumferential portion in close contact with an outer circumferential portion of the piston rod21. The piston rod21moves in the axial direction of the seal member24with respect to the seal member24. The seal member24suppresses the oil fluid L in the tube3and the high-pressure gas G and the oil fluid L in the reservoir chamber7leaking out to the outside.

The rod guide23includes a large diameter part28and a small diameter part29. The large diameter part28has an outer diameter larger than an outer diameter of the small diameter part29. In the rod guide23, the small diameter part29is provided on a lower side of the large diameter part28. The rod guide23is fitted to an inner circumferential portion of an upper end of the tube3at the small diameter part29on the lower side. At that time, an upper end portion of the tube3is in contact with the large diameter part28in the axial direction of the tube3. The rod guide23is fitted to an upper inner circumferential portion of the shell5at the large diameter part28on the upper side.

A first valve assembly31is placed on the bottom part12of the shell5. The first valve assembly31includes a seat member32. The seat member32is placed in contact with an upper surface of the bottom part12of the shell5. The seat member32is positioned in the radial direction with respect to the shell5. The seat member32includes a large diameter part33and a small diameter part34. The large diameter part33has an outer diameter larger than an outer diameter of the small diameter part34. In the seat member32, the large diameter part33is provided on a lower side of the small diameter part34. The seat member32is fitted to an inner circumferential portion of a lower end of the tube3at the small diameter part34on an upper side. At that time, the lower end portion of the tube3comes in contact with the large diameter part33in the axial direction of the tube3. Thereby, the first valve assembly31is connected to one end of the tube3in the axial direction.

A swaged part35is provided at an upper end portion of the shell5. The swaged part35is formed by swaging the upper end portion of the shell5inward in the radial direction of the shell5. The seal member24is fixed to the cylinder2by being sandwiched between the swaged part35and the rod guide23. When the swaged part35is formed, the seal member24is pressed against the rod guide23in the axial direction of the shell5while the bottom part12of the shell5is placed on a table. Then, the seal member24, the rod guide23, the tube3, and the seat member32are in contact with each other without a gap in the axial direction. Thereby, an axial force is generated in the seal member24, the rod guide23, the tube3, and the seat member32. In this state, the swaged part35is formed. Therefore, after the swaged part35is formed, an axial force is generated in the seal member24, the rod guide23, the tube3, and the seat member32.

The piston rod21includes a rod main body41and an extender42.

The rod main body41includes a main shaft part51and a mounting shaft part52. Both the main shaft part51and the mounting shaft part52have a rod shape. The mounting shaft part52has an outer diameter smaller than has an outer diameter of the main shaft part51. The mounting shaft part52extends from one end of the main shaft part51in the axial direction. A central axis of the mounting shaft part52coincides with a central axis of the main shaft part51. The mounting shaft part52is disposed in the tube3in its entirety. The main shaft part51of the rod main body41of the piston rod21slides with respect to the rod guide23and the seal member24in the axial direction of them.

As shown inFIG.2, an end portion of the mounting shaft part52on a side opposite to the main shaft part51in the axial direction of the mounting shaft part52is a screw shaft part54. The screw shaft part54has a male screw formed on an outer circumferential portion. A portion of the mounting shaft part52between the main shaft part51and the screw shaft part54in the axial direction of the mounting shaft part52is a fitting shaft part55. An outer circumferential surface of the fitting shaft part55is a cylindrical surface.

The extender42includes a main shaft part61and a mounting shaft part62. Both the main shaft part61and the mounting shaft part62have a rod shape. The mounting shaft part62has an outer diameter smaller than an outer diameter of the main shaft part61. The mounting shaft part62extends from one end of the main shaft part61in the axial direction. A central axis of the mounting shaft part62coincides with a central axis of the main shaft part61.

A screw hole64is formed in the main shaft part61at an end portion of the main shaft part61on a side opposite to the mounting shaft part62in the axial direction. The screw hole64is formed at a center position of the main shaft part61in the radial direction. The screw hole64extends in the axial direction of the main shaft part61. The screw hole64opens upward.

An end portion of the mounting shaft part62on a side opposite to the main shaft part61in the axial direction of the mounting shaft part62is a screw shaft part65. The screw shaft part65has a male screw formed on an outer circumferential portion. A portion of the mounting shaft part62between the main shaft part61and the screw shaft part65in the axial direction of the mounting shaft part62is a fitting shaft part66. An outer circumferential surface of the fitting shaft part66is a cylindrical surface.

In the rod main body41, the screw shaft part54thereof is screwed into the screw hole64of the extender42. Thereby, the rod main body41and the extender42are connected with their central axes coincided with each other. Thereby, the piston rod21is formed. The extender42is disposed in the tube3in its entirety.

The piston18is attached to the piston rod21at the mounting shaft part52of the rod main body41. Then, the piston18is disposed between the main shaft part51of the rod main body41and the extender42. The piston18is fitted in the fitting shaft part55of the mounting shaft part52.

A through hole70is formed at a center of the piston18in the radial direction. The through hole70penetrates the piston18in the axial direction of the piston18. The fitting shaft part55of the rod main body41is fitted into the through hole70of the piston18. A first passage71and a second passage72are formed in the piston18on a side outward from the through hole70in the radial direction of the piston18. The first passage71and the second passage72penetrate the piston18in the axial direction of the piston18. A plurality of first passages71and a plurality of second passages72are formed in the piston18. The first passages71and the second passages72are alternately disposed in the circumferential direction of the piston18. Both the first passages71and the second passages72allow communication between the first chamber19and the second chamber20.

The piston assembly17includes a first damping valve75and a second damping valve76.

The first damping valve75is a disc valve constituted by laminating a plurality of annular discs. The fitting shaft part55of the rod main body41is fitted to a radial inner side of the first damping valve75. The first damping valve75is disposed between the piston18and the extender42. The first damping valve75opens the first passage71when a portion on the outer circumferential side is separated from the piston18. Thereby, the first damping valve75allows the oil fluid L to flow from the first chamber19to the second chamber20through the first passage71. At that time, the first damping valve75suppresses a flow of the oil fluid L to generate a damping force. The first damping valve75is provided in the first passage71to generate a damping force by suppressing the flow of the oil fluid L that occurs in the first passage71during the extension stroke. The first damping valve75closes the first passage71when the portion on the outer circumferential side comes in contact with the piston18. A fixed orifice (not shown) is provided at a portion between the first damping valve75and the piston18. The fixed orifice allows the oil fluid L to flow from the first chamber19to the second chamber20through the first passage71even if the portion on the outer circumferential side of the first damping valve75comes in contact with the piston18.

The second damping valve76is a disc valve constituted by laminating a plurality of annular discs. The fitting shaft part55is fitted to a radial inner side of the second damping valve76. The second damping valve76is disposed between the main shaft part51of the rod main body41and the piston18. The second damping valve76opens the second passage72when a portion on the outer circumferential side is separated from the piston18. Thereby, the second damping valve76allows the oil fluid L to flow from the second chamber20to the first chamber19via the second passage72. At that time, the second damping valve76generates a damping force by suppressing a flow of the oil fluid L. The second damping valve76is provided in the second passage72to generate a damping force by suppressing the flow of the oil fluid L that occurs in the second passage72during the compression stroke. The second damping valve76closes the second passage72when the portion on the outer circumferential side comes in contact with the piston18. A fixed orifice (not shown) is provided at a portion between the second damping valve76and the piston18. The fixed orifice allows the oil fluid L to flow from the second chamber20to the first chamber19through the second passage72even if the portion on the outer circumferential side of the second damping valve76comes in contact with the piston18.

The piston assembly17including the piston18, the first damping valve75, and the second damping valve76is attached to the mounting shaft part52of the rod main body41by the extender42. Therefore, the piston assembly17is disposed between the main shaft part51of the rod main body41and the extender42. The piston assembly17is connected to the piston rod21at an intermediate position in the axial direction.

The first valve assembly31includes a disc valve82, a disc valve83, a bolt84, and a nut85in addition to the seat member32described above. The disc valve82is provided on a lower side of the seat member32. The disc valve83is provided on an upper side of the seat member32. The bolt84is inserted into the disc valve83, the seat member32and the disc valve82from above. In this state, the nut85is screwed onto a lower portion of the bolt84. The bolt84and nut85thereby attach the disc valve82and the disc valve83to the seat member32.

The seat member32has an annular shape. The seat member32includes a base part88and a protruding part89. The base part88has a disc shape. As shown inFIG.3, the base part88has a through hole90formed at a center in the radial direction. The through hole90penetrates the base part88in the axial direction of the seat member32. The bolt84is inserted through the through hole90of the seat member32. A passage hole91and a passage hole92are formed in the seat member32on a side outward from the through hole90in the radial direction of the seat member32. The passage hole91and the passage hole92penetrate the base part88in the axial direction of the seat member32. The passage hole92is on a side outward from the passage hole91in the radial direction of the seat member32. A plurality of passage hole91and a plurality of passage holes92are formed in the seat member32.

The protruding part89protrudes downward from an outer circumferential portion of the base part88. The protruding part89is disposed on a side outward from the passage holes92in the radial direction of the base part88. The protruding part89of the seat member32is in contact with the bottom part12of the shell5. A passage groove93penetrating the protruding part89in the radial direction of the seat member32is formed in the protruding part89. A plurality of passage grooves93are provided in the seat member32at regular intervals in the circumferential direction of the seat member32. Thereby, a space between the seat member32and the bottom part12of the shell5communicates with a portion between the barrel part11of the shell5and the tube3shown inFIG.1. Therefore, the space between the seat member32and the bottom part12of the shell5also forms the reservoir chamber7.

As shown inFIG.2, the shock absorber1includes a cup101. The cup101is provided in the second chamber20. The cup101includes a sleeve102and a base adapter103.

The sleeve102has a cylindrical shape. The sleeve102has an outer diameter smaller than an inner diameter of the tube3. The sleeve102is disposed on a radial inner side of the tube3. A central axis of the sleeve102coincides with a central axis of the tube3. The sleeve102is disposed in the second chamber20with a gap between itself and the tube3in the radial direction.

The sleeve102includes a main body part111and an enlarged diameter part112. The main body part111has a cylindrical shape and is provided from an intermediate portion to a lower end portion in the axial direction of the sleeve102. The enlarged diameter part112is provided at an upper end portion of the sleeve102. An inner diameter of the enlarged diameter part112increases toward an upper end. An outer diameter of the enlarged diameter part112increases toward the upper end. The enlarged diameter part112increases in diameter in a direction away from the main body part111in the axial direction of the sleeve102.

The sleeve102includes a groove116extending in the axial direction of the sleeve102at an inner circumferential portion on one end side thereof in the axial direction. The groove116is provided on the inner circumferential portion of the upper end side of the sleeve102. The groove116is recessed outward in the radial direction of the sleeve102from an inner circumferential surface of the sleeve102. The groove116extends from the enlarged diameter part112to an upper portion of the main body part111. A plurality of grooves116are provided in the sleeve102at regular intervals in the circumferential direction of the sleeve102. The plurality of grooves116have different lengths from the upper end of the sleeve102. In other words, the plurality of grooves116have different lengths in the axial direction of the sleeve102.

The base adapter103has an annular shape. The base adapter103includes a main plate part121, a press-fitting part122, and a leg part123.

The main plate part121has a disc shape. As shown inFIG.3, a recessed part131recessed upward from a lower surface of the main plate part121is formed in the main plate part121at a central portion in the radial direction on one side in the axial direction.

The press-fitting part122is provided at one end of the base adapter103in the axial direction. The press-fitting part122protrudes upward from an upper surface of the main plate part121. The press-fitting part122has a cylindrical shape. The press-fitting part122has an outer diameter smaller than an outer diameter of the main plate part121. The press-fitting part122of the base adapter103is press-fitted into a lower end portion of the sleeve102. At that time, the upper surface of the main plate part121comes in contact with the lower end portion of the sleeve102. Thereby, the base adapter103is fixed to the sleeve102. In the way, the base adapter103is fixed to the sleeve102by press fitting.

The leg part123is provided at an end portion of the base adapter103on a side opposite to the press-fitting part122in the axial direction. The leg part123protrudes downward from an outer circumferential portion of the main plate part121. The leg part123has a cylindrical shape. The leg part123is disposed on a side outward from the recessed part131in the radial direction of the main plate part121. An inner circumferential portion135on an inner side of the leg part123in the radial direction becomes larger in diameter with distance away from the main plate part121in the axial direction of the base adapter103. In other words, the inner circumferential portion135of the leg part123becomes larger in diameter with distance away from the main plate part121in the axial direction.

A communication groove136penetrating the main plate part121and the leg part123in the axial direction of the base adapter103is formed in the outer circumferential portion of the main plate part121and the leg part123. The communication groove136opens outward in the radial direction of the base adapter103. The communication groove136is formed on a side of the main plate part121radially outward from the sleeve102. The communication groove136penetrates the leg part123in the radial direction of the base adapter103. Therefore, the communication groove136opens to the upper surface of the main plate part121, an outer circumferential surface of the main plate part121, an outer circumferential surface of the leg part123, a lower surface of the leg part123, and an inner circumferential surface of the leg part123. A plurality of communication grooves136are provided in the base adapter103at regular intervals in the circumferential direction of the base adapter103.

The cup101including the base adapter103and the sleeve102fixed to the base adapter103is fixed by press-fitting the main plate part121of the base adapter103into the tube3. At that time, the cup101is placed by bringing a lower end portion of the leg part123of the base adapter103into contact with an upper surface of the outer circumferential portion of the base part88of the seat member32. At that time, the base adapter103hitting the bolt84of the first valve assembly31is avoided by the recessed part131. At that time, the leg part123of the base adapter103surrounds the disc valve83of the first valve assembly31from an outer side in the radial direction. In other words, the leg part123is disposed to be spaced apart from the disc valve83on a side outward in the radial direction of the disc valve83. The base adapter103placed on the first valve assembly31is provided between the sleeve102and the first valve assembly31.

As described above, the press-fitting part122that is press-fitted into the sleeve102is provided at one end of the base adapter103in the axial direction. The leg part123placed on the first valve assembly31is provided at the other end of the base adapter103in the axial direction. The inner circumferential portion135of the leg part123increases in diameter toward the first valve assembly31in the axial direction of the base adapter103.

A third chamber141is provided between the first valve assembly31and the base adapter103. The third chamber141communicates with a portion of the second chamber20between the tube3and the sleeve102via a communication passage142in the communication groove136of the base adapter103. In other words, the communication passage142that allows communication between the second chamber20and the third chamber141is provided in the leg part123of the base adapter103.

In the first valve assembly31, the plurality of passage holes91allow the oil fluid L to flow between the third chamber141and the reservoir chamber7. The plurality of passage holes92allow the oil fluid L to flow between the reservoir chamber7and the third chamber141.

The disc valve82on the reservoir chamber7side allows the oil fluid L to flow from the third chamber141to the reservoir chamber7through the passage holes91. On the other hand, the disc valve82restricts a flow of the oil fluid L from the reservoir chamber7to the third chamber141through the passage holes91. The disc valve82opens during the compression stroke of the shock absorber1to allow the oil fluid L to flow from the second chamber20and the third chamber141to the reservoir chamber7and generate a damping force.

The disc valve83on the third chamber141side allows a flow of the oil fluid L from the reservoir chamber7to the third chamber141through the passage holes92. On the other hand, the disc valve83restricts a flow of the oil fluid L from the third chamber141to the reservoir chamber7through the passage holes92. The disc valve83allows constant communication between the third chamber141and the passage holes91. The disc valve83opens during the extension stroke of the shock absorber1to allow the oil fluid L to flow from the reservoir chamber7to the third chamber141and the second chamber and generate a damping force. Further, the disc valve83may be used as a suction valve that allows the oil fluid L to flow from the reservoir chamber7to the third chamber141and the second chamber substantially without generating a damping force.

As shown inFIG.2, the sleeve102of the cup101opens upward. The shock absorber1includes a second valve assembly151. The second valve assembly151is disposed in the second chamber20to be connected to the piston rod21. The second valve assembly151is attached to the mounting shaft part62of the extender42. The second valve assembly151enters from above and exits upward with respect to the sleeve102of the cup101via an opening at the upper end of the sleeve102.

The second valve assembly151includes a valve base152, a fitting member153, and a third damping valve154.

As shown inFIG.3, the valve base152includes a first base member161and a second base member162. The first base member161constitutes an upper portion of the valve base152. The second base member162constitutes a lower portion of the valve base152.

The first base member161has an annular shape. A notch part171is formed in the first base member161at an outer circumferential portion on a lower side. The notch part171is formed over the entire circumference of the first base member161. The notch part171has an annular shape.

The first base member161has a through hole172formed at a center thereof in the radial direction. The through hole172penetrates the first base member161in the axial direction of the first base member161. The fitting shaft part66of the extender42is fitted in the through hole172of the first base member161. A passage groove173is provided in the first base member161on a side outward from the through hole172in the radial direction of the first base member161. A passage groove174and a passage hole175are provided in the first base member161between the through hole172and the notch part171in the radial direction of the first base member161.

The passage groove173is formed at an upper end portion of the first base member161. The passage groove173is recessed downward from an upper end surface of the first base member161. The passage groove173has an annular shape that surrounds the through hole172from an outer side in the radial direction. The passage groove173opens upward.

The passage groove174is formed at a lower end portion of the first base member161. The passage groove173is recessed upward from a lower end surface of the first base member161. The passage groove174has an annular shape that surrounds the through hole172from an outer side in the radial direction. The passage groove174opens downward.

The passage hole175is formed at an intermediate portion of the first base member161in the axial direction. An upper end of the passage hole175opens at a bottom position of the passage groove173and a lower end thereof opens at a bottom position of the passage groove174. A plurality of passage holes175are formed in the first base member161at intervals in the circumferential direction of the first base member161.

The second base member162has an annular shape. The second base member162has a notch part181formed at an outer circumferential portion on an upper side. The notch part181is formed over the entire circumference of the second base member162. The notch part181has an annular shape.

The second base member162includes a groove part182formed at an outer circumferential portion on a lower side. The groove part182is recessed inward in the radial direction of the second base member162from an outer circumferential surface of the second base member162. The groove part182opens outward in the radial direction of the second base member162. The groove part182opens to the notch part181. The groove part182opens downward. A plurality of groove parts182are formed in the second base member162at intervals in the circumferential direction of the second base member162.

The second base member162has a through hole183formed at a center in the radial direction. The through hole183penetrates the second base member162in the axial direction of the second base member162. The fitting shaft part66of the extender42is fitted in the through hole183of the second base member162. A passage groove184is provided in the second base member162on a side outward from the through hole183in the radial direction of the second base member162. A passage hole185is provided in the second base member162between the through hole183and the notch part181in the radial direction of the second base member162.

The passage groove184is formed at an upper end portion of the second base member162. The passage groove184is recessed downward from an upper end surface of the second base member162. The passage groove184has an annular shape that surrounds the through hole183from an outer side in the radial direction. The passage groove184opens upward.

The passage hole185is formed from a middle to a lower end portion in the axial direction of the second base member162. An upper end of the passage hole185opens at a bottom position of the passage groove184. A plurality of passage holes185are formed in the second base member162at intervals in the circumferential direction of the second base member162.

In a state in which the valve base152is fitted to the fitting shaft part66of the extender42, a lower end surface of the first base member161is in contact with an upper end surface of the second base member162. Then, the passage groove173, the passage holes175, and the passage groove174of the first base member161communicate with the passage groove184and the passage holes185of the second base member162. These passage grooves173,174, and184and passage holes175and185form a third passage191. The third passage191is provided in the valve base152and penetrates the valve base152in the axial direction.

In the valve base152, the notch part171of the first base member161and the notch part181of the second base member162form a disposition groove195. The disposition groove195is recessed inward in the radial direction of the valve base152from an outer circumferential surface of the valve base152. The disposition groove195has an annular shape. The disposition groove195opens outward in the radial direction. The plurality of groove parts182open to the disposition groove195.

The fitting member153has an annular shape. The fitting member153has an outer diameter larger than an outer diameter of the valve base152. The fitting member153is disposed between the notch part171and the notch part181when the first base member161and the second base member162are assembled to the extender42. Thereby, the fitting member153is disposed in the disposition groove195of the valve base152. The fitting member153is movable in the axial direction with respect to the valve base152in the disposition groove195.

An interposing member197is provided between an inner circumferential portion of the fitting member153and a bottom portion of the disposition groove195. The interposing member197coaxially holds the fitting member153with respect to the valve base152. The interposing member197has an axial passage196penetrating therethrough in the axial direction. The interposing member197is, for example, cylindrical and has a shape in which a plurality of grooves penetrating an outer circumferential portion in the axial direction are formed. The interposing member197is press-Fitted in the inner circumferential portion of the fitting member153. Thereby, the interposing member197is fixed to the fitting member153. The plurality of grooves formed in the outer circumferential portion of the interposing member197form the axial passage196.

The third damping valve154is a disc valve constituted by laminating a plurality of annular discs. The fitting shaft part66of the extender42is fitted to a radial inner side of the third damping valve154. The third damping valve154is disposed between the main shaft part61of the extender42and the valve base152. The third damping valve154opens the third passage191when a portion on the outer circumferential side is separated from the valve base152. The third damping valve154closes the third passage191when the portion on the outer circumferential side comes in contact with the valve base152.

A nut201is screwed onto the screw shaft part65of the extender42. The second valve assembly151including the valve base152and the third damping valve154is attached to the mounting shaft part62of the extender42with the nut201. Therefore, as shown inFIG.2, the second valve assembly151is provided on the first valve assembly31side with respect to the piston assembly17of the piston rod21. The valve base152is fixed to the piston rod21. Therefore, the valve base152and the piston rod21move together.

Here, when the piston rod21is in a first predetermined range in which the second valve assembly151is disposed above the sleeve102and is not fitted to the sleeve102, the inside of the cup101becomes the second chamber20as a whole.

From this state, in the compression stroke, the piston rod21moves to a second predetermined range on the base adapter103side from the first predetermined range. Then, the second valve assembly151causes the fitting member153to be fitted into the sleeve102. At the beginning of this fitting, the fitting member153moves upward relative to the disposition groove195of the valve base152due to a frictional force with the sleeve102in contact therewith. As a result, an upper surface of the fitting member153is brought into contact with the valve base152. Then, the axial passage196is closed. In the compression stroke thereafter, the fitting member153is pushed by the valve base152while the axial passage196remains closed, and slides in the sleeve102to the base adapter103side.

When the fitting member153of the second valve assembly151is fitted into the sleeve102, the second chamber20is divided into a fourth chamber211and a fifth chamber212. The fourth chamber211is a portion between the second valve assembly151and the base adapter103in the cup101. The fifth chamber212is a portion of the second chamber20excluding the fourth chamber211. The fifth chamber212includes a portion between the tube3and the cup101and a portion between the piston assembly17and the second valve assembly151.

In the compression stroke in the second predetermined range, the second valve assembly151, together with the piston rod21, moves to the base adapter103side while the axial passage196is closed as described above. At an upper portion of the second predetermined range, the fitting member153is at a position of the plurality of grooves116provided in the sleeve102and allows the oil fluid L to flow from the fourth chamber211to the fifth chamber212through the plurality of grooves116. At that time, as the second valve assembly151approaches the base adapter103, among the plurality of grooves116, the number of grooves116through which the oil fluid L flows from the fourth chamber211to the fifth chamber212decreases, and finally becomes zero.

Also, in the compression stroke in the second predetermined range, the second valve assembly151moves to the base adapter103side while the axial passage196is closed as described above. At that time, the third damping valve154opens depending on a piston speed which is a moving speed of the piston rod21, the piston18, and the valve base152with respect to the tube3. Then, the oil fluid L flows from the fourth chamber211to the fifth chamber212through the third passage191. Thereby, the third damping valve154suppresses an excessive increase in pressure in the fourth chamber211. The third damping valve154is provided in the third passage191and allows the oil fluid L to flow from the fourth chamber211to the fifth chamber212while generating a damping force by suppressing the flow of the oil fluid L that occurs during the compression stroke. Here, the third damping valve154has higher rigidity than the second damping valve76and is difficult to open. Therefore, the third damping valve154opens later than the second damping valve76and generates a higher damping force than the second damping valve76.

With the fitting member153fitted in the sleeve102of the cup101, the second valve assembly151, together with the piston rod21, moves to a side opposite to the base adapter103. Then, the fitting member153moves downward relative to the disposition groove195of the valve base152due to the frictional force with the sleeve102. As a result, the upper surface of the fitting member153is separated from the valve base152. Thereby, the axial passage196opens. In the extension stroke thereafter, the fitting member153is pushed by the valve base152while the axial passage196remains open, and slides in the sleeve102to a side opposite to the base adapter103. When the second valve assembly151moves to a side opposite to the base adapter103, the oil fluid L is allowed to flow from the fifth chamber212to the fourth chamber211, from the axial passage196through the passages in the groove parts182of the valve base152. Thereby, a resistance force to movement of the piston rod21in an extension direction is reduced.

The second valve assembly151is separated from the base adapter103by a predetermined distance during the extension stroke from a state in which the fitting member153is on the base adapter103side with respect to all the grooves116in the sleeve102. Then, the grooves116provided in the sleeve102open to the fourth chamber211. Then, the oil fluid L flows from the fifth chamber212to the fourth chamber211through the grooves116. At that time, as the second valve assembly151becomes further away from the base adapter103, among the plurality of grooves116, the number of grooves116through which the oil fluid L flows from the fifth chamber212to the fourth chamber211increases. Thereby, the resistance force to the movement of the piston rod21in the extension direction is reduced in stages.

Next, main operations of the shock absorber1will be described.

“Extension Stroke in which Piston Rod21is in First Predetermined Range”
{First Region in which Piston Speed is Lower than First Predetermined Value}

In this first region of the extension stroke, the oil fluid L from the first chamber19flows to the second chamber20from the first passage71through the fixed orifice (not shown) between the first damping valve75and the piston18in the piston assembly17. Therefore, in the first region of the extension stroke, a damping force having orifice characteristics (in which the damping force is substantially proportional to the square of the piston speed) is generated.

{Second Region in which Piston Speed is Equal to or Higher than First Predetermined Value}

In this second region of the extension stroke, the oil fluid L from the first chamber19flows to the second chamber20by opening the first damping valve75from the first passage71in the piston assembly17. Therefore, in the second region of the extension stroke, a damping force having valve characteristics (in which the damping force is substantially proportional to the piston speed) due to the first damping valve75is generated.

“Compression Stroke in which Piston Rod21is in First Predetermined Range”
{Third Region in which Piston Speed is Lower than Second Predetermined Value}

In this third region of the compression stroke, the oil fluid L from the second chamber20flows to the first chamber19from the second passage72through the fixed orifice (not shown) between the second damping valve76and the piston18in the piston assembly17. Therefore, in the third region of the compression stroke, a damping force having orifice characteristics is generated.

{Fourth Region in which Piston Speed is Equal to or Higher than Second Predetermined Value}

In this fourth region of the compression stroke, the oil fluid L from the second chamber20flows to the first chamber19by opening the second damping valve76from the second passage72in the piston assembly17. Therefore, in the fourth region of the compression stroke, a damping force having valve characteristics due to the second damping valve76is generated.

“Compression Stroke in which Piston Rod21is in Second Predetermined Range”

In this compression stroke, the piston assembly17operates in the same manner as in the first predetermined range. In addition, the second valve assembly151moves to the base adapter103side in the axial direction of the tube3to cause the fitting member153to be fitted into the sleeve102. Then, the fitting member153closes the axial passage196at the beginning thereof.

With the axial passage196closed in this way, the second valve assembly151moves to the base adapter103side. Then, the oil fluid L flows from the fourth chamber211to the fifth chamber212through the plurality of grooves116provided in the sleeve102. At that time, as the second valve assembly151approaches the base adapter103, among the plurality of grooves116, the number of grooves116through which the oil fluid L flows from the fourth chamber211to the fifth chamber212decreases, and finally becomes zero. Thereby, a damping force of the second valve assembly151increases in stages, and a resistance force to movement of the piston rod21in a compression direction increases in stages. Here, a length of a press-fitting axis between the press-fitting part122of the base adapter103and the sleeve102is set so that the sleeve102does not come off from the press-fitting part122even when the fourth chamber211reaches a maximum pressure.

Here, when the second valve assembly151moves to the base adapter103side, the third damping valve154opens depending on the piston speed. Then, the oil fluid L flows from the fourth chamber211to the fifth chamber212through the third passage191. Thereby, an excessive increase in pressure in the fourth chamber211is suppressed.

“Extension Stroke in which Piston Rod21is in Second Predetermined Range”

In this extension stroke, the piston assembly17operates in the same manner as in the first predetermined range. In addition, the second valve assembly151moves to a side opposite to the base adapter103. Then, the fitting member153opens the axial passage196at the beginning thereof.

With the axial passage196opened in this way, the second valve assembly151moves to a side opposite to the base adapter103. Then, the oil fluid L flows from the fifth chamber212to the fourth chamber211through the axial passage196and the passages in the groove parts182of the valve base152. When the fitting member153of the second valve assembly151passes a position of the grooves116provided in the sleeve102from a state in which it is on the base adapter103side with respect to all the grooves116provided in the sleeve102, the oil fluid L flows from the fifth chamber212to the fourth chamber211through the passages116. At that time, as the second valve assembly151becomes further away from the base adapter103, among the plurality of grooves116, the number of grooves116through which the oil fluid L flows from the fifth chamber212to the fourth chamber211increases. In other words, as the second valve assembly151becomes further away from the base adapter103, the damping force becomes lower, and the resistance force to the movement of the piston rod21in the extension direction becomes lower.

The specification of U.S. Pat. No. 9,605,726 described above discloses a shock absorber in which a damping force is increased when a rod reaches a predetermined range on a limit side during a compression stroke in which the rod is pushed into a cylinder. Incidentally, there has been a demand to suppress an increase in cost in shock absorbers. For example, FIG. 13 of the specification of U.S. Pat. No. 9,605,726 discloses a structure in which a tube is connected to a cup and the cup is connected to a valve assembly. When the shock absorber is assembled, an axial force is input to the tube from the shell. With the structure disclosed in FIG. 13 of the specification of U.S. Pat. No. 9,605,726, the axial force of the tube should be received by the cup. Therefore, it is necessary to increase a strength of the cup. As a result, the costs increase.

The shock absorber1of the first embodiment includes the tube3, the first valve assembly31, the piston assembly17, the piston rod21, the cup101, and the second valve assembly151. The tube3has the inner chamber6inside. The first valve assembly31is connected to one end of the tube3in the axial direction. The piston assembly17divides the inner chamber6into the first chamber19and the second chamber20. The piston rod21extends from the tube3through the first chamber19with the piston assembly17connected to an intermediate position thereof in the axial direction. The cup101is provided in the second chamber20. The second valve assembly151is disposed in the second chamber20to be connected to the piston rod21and enters and exits from the cup101. The cup101includes the sleeve102and the base adapter103. The sleeve102is disposed in the second chamber20with a gap between itself and the tube3in the radial direction. The base adapter103is fixed to the sleeve102by press fitting and provided between the sleeve102and the first valve assembly31.

When the shock absorber1is assembled, an axial force is input to the tube3from the swaged part35and the bottom part12of the shell5via the seal member24, the rod guide23, and the first valve assembly31. In the shock absorber1, the first valve assembly31is connected to one end of the tube3in the axial direction. Therefore, the axial force to the tube3can be received by the first valve assembly31. Thereby, there is no need for the base adapter103to receive the axial force of the tube3. Therefore, a strength of the base adapter103can be made low compared to when receiving the axial force of the tube3. As a result, since a degree of freedom in material of the base adapter103is increased, a low-cost material can be selected. Therefore, an increase in costs of the shock absorber1can be suppressed. Also, a lightweight material can be selected for the base adapter103. Therefore, an increase in weight of the shock absorber1can be suppressed.

In the shock absorber1, the base adapter103is fixed to the sleeve102by press fitting. Therefore, the base adapter103and the sleeve102can be integrated before being assembled to the shock absorber1. Therefore, since the base adapter103and the sleeve102can be handled as a single part, handling is facilitated, and assembly to the shock absorber1is also facilitated.

The shock absorber1includes the press-fitting part122press-fitted into the sleeve102provided at one end of the base adapter103in the axial direction, and the leg part123placed on the first valve assembly31provided at the other end of the base adapter103in the axial direction. The communication passage142that allows the third chamber141between the first valve assembly31and the base adapter103to communicate with the second chamber20is provided in the leg part123. Since the communication passage142is provided in the leg part123in this way, a gap in the radial direction between the tube3and the sleeve102can be reduced compared to a case in which the communication passage is provided on a side inward from the leg part123in the radial direction of the main plate part121.

In the shock absorber1, the inner circumferential portion135of the leg part123increases in diameter toward the first valve assembly31. As a result, an outer diameter of the disc valve83of the first valve assembly31can be increased compared to a case in which the inner circumferential portion135has a constant diameter. Therefore, a variable width of the damping force of the disc valve83can be increased. Particularly, when the disc valve83is used as a suction valve that substantially does not generate a damping force, the damping force can be brought close to zero by increasing the diameter of the disc valve83.

Second Embodiment

Next, a shock absorber of a second embodiment will be described mainly on the basis ofFIG.4, focusing on differences from the first embodiment. Further, parts common to those in the first embodiment will be denoted by the same terms and the same reference signs.

A shock absorber1A of the second embodiment includes a cup101A that is partially different from the cup101instead of the cup101. The cup101A includes a sleeve102A that is partially different from the sleeve102instead of the sleeve102. The sleeve102A includes a main body part111A that is partially different from the main body part111instead of the main body part111.

As in the sleeve102, a plurality of grooves116extending in an axial direction of the sleeve102A are provided at an inner circumferential portion on one end side of the sleeve102A in the axial direction. A groove116A extending in the axial direction of the sleeve102A is also provided at an inner circumferential portion on the other end side of the sleeve102A in the axial direction. The groove116A is provided on an inner circumferential portion of a lower end of the sleeve102A. The groove116A is recessed outward in a radial direction of the sleeve102A from an inner circumferential surface of the sleeve102A. A plurality of grooves116A are provided in the sleeve102A at regular intervals in the circumferential direction of the sleeve102A. The plurality of grooves116A have the same length from the lower end of the sleeve102A. In other words, the plurality of grooves116A have the same length in the axial direction of the sleeve102A.

A press-fitting part122of a base adapter103is press-fitted into the lower end portion of the sleeve102A. At that time, an upper surface of a main plate part121comes in contact with the lower end portion of the sleeve102A. Thereby, lower ends of the plurality of grooves116A are closed and the base adapter103is fixed to the sleeve102A. The plurality of grooves116A extend above the press-fitting part122.

A piston rod21moves from a first predetermined range in which a second valve assembly151is not fitted in the sleeve102A to a second predetermined range in a compression stroke. Then, the second valve assembly151causes a fitting member153to be fitted into the sleeve102A. At the beginning of this fitting, the fitting member153closes an axial passage196.

In the compression stroke in the second predetermined range, the second valve assembly151, together with the piston rod21, moves to the base adapter103side while the axial passage196is closed as described above. At an upper portion of the second predetermined range, the fitting member153is at a position of the plurality of grooves116provided in the sleeve102A and allows an oil fluid L to flow from a fourth chamber211to a fifth chamber212through the plurality of grooves116. At that time, as the second valve assembly151approaches the base adapter103side, among the plurality of grooves116, the number of grooves116through which the oil fluid L flows from the fourth chamber211to the fifth chamber212decreases, and finally becomes zero.

Also, in the compression stroke in the second predetermined range, the second valve assembly151moves to the base adapter103side while the axial passage196is closed as described above. At that time, a third damping valve154opens depending on a piston speed. Then, the oil fluid L flows from the fourth chamber211to the fifth chamber212through a third passage191. Thereby, the third damping valve154suppresses an excessive increase in pressure in the fourth chamber211.

Here, in the compression stroke, when the second valve assembly151approaches a lower limit position of the second predetermined range, the fitting member153is positioned at a position of the plurality of grooves116A provided in the sleeve102A. Then, the oil fluid L flows from the fourth chamber211to the fifth chamber212through the plurality of grooves116A provided in the sleeve102A. Thereby, the plurality of grooves116A suppress an excessive increase in pressure in the fourth chamber211.

From this state, the second valve assembly151, together with the piston rod21, moves to a side opposite to the base adapter103. Then, the fitting member153opens the axial passage196. In this state, when the second valve assembly151moves to a side opposite to the base adapter103, the oil fluid L is allowed to flow from the fifth chamber212to the fourth chamber211, from the axial passage196through a passage in a groove part182of a valve base152. At the same time, the oil fluid L is allowed to flow from the fifth chamber212to the fourth chamber211through the plurality of grooves116A. Thereby, a resistance force to movement of the piston rod21in an extension direction is reduced.

When the fitting member153is positioned on a side opposite to the base adapter103with respect to all the grooves116A in the sleeve102A, the second valve assembly151allows the oil fluid L to flow from the fifth chamber212to the fourth chamber211only through a flow path from the axial passage196through the passage in the groove part182of the valve base152.

In the shock absorber1A of the second embodiment, the grooves116extending in the axial direction of the sleeve102A are provided at an inner circumferential portion on one end side of the sleeve102A in the axial direction, and the grooves116A extending in the axial direction of the sleeve102A are provided at an inner circumferential portion on the other end side of the sleeve102A in the axial direction. Thereby, at the beginning of the compression stroke in the second predetermined range, a rate of change in damping force becomes gentle due to the grooves116on the upper end side. Since there is no groove in the middle of the sleeve102A in the axial direction, the damping force increases at the middle position in the second predetermined range of the compression stroke. On the lower end side of the second predetermined range, an increase in damping force is suppressed by the grooves116A. The grooves116A can serve the role of a relief.

Further, in the embodiments, a hydraulic shock absorber has been shown as an example of the shock absorbers1and1A, but the above-described structure can also be employed for a shock absorber using water or air as a working fluid.

EXPLANATION OF REFERENCES