Shock absorber

Patent metadata

Field	Value
Publication number	US-2016281815-A1
Application number	US-201414778213-A
Country	US
Kind code	A1
Filing date	Mar 20, 2014
Priority date	Mar 22, 2013
Publication date	Sep 29, 2016
Grant date	—

Abstract

Shock absorber including a suction passage allowing flow only from a reservoir towards a pressure side chamber, a rectifying passage allowing flow only from the pressure side chamber towards an expansion side chamber, and a damping force variable valve allowing flow only from the expansion side chamber towards the reservoir. A large pressure-side pressure chamber communicating with the pressure side chamber, and an outer peripheral expansion-side pressure chamber communicating with the expansion side chamber sandwich a free piston slidably moving within a bottom housing forming a pressure chamber. Because a pressure-side pressure-receiving area of the free piston is larger than an expansion-side pressure-receiving area in a contraction operation in which a piston moves downward, the free piston can move downward even in a uniflow-type shock absorber in which pressure in the expansion side and pressure side chambers become equal whereby damping force can be reduced during an input of high-frequency vibration.

First claim

1 . A shock absorber, comprising:
a cylinder; a piston slidably inserted into the cylinder, the piston defining an expansion side chamber and an pressure side chamber inside the cylinder; a reservoir; a suction passage that allows only a flow of liquid from the reservoir toward the pressure side chamber; a rectifying passage that allows only a flow of liquid from the pressure side chamber toward the expansion side chamber; a damping force adjusting unit that allows only a flow of liquid from the expansion side chamber toward the reservoir, the damping force adjusting unit being configured to change resistance provided to the flow of liquid; a housing that forms a pressure chamber; and a free piston slidably inserted into the pressure chamber to form an expansion-side pressure chamber and a pressure-side pressure chamber inside the pressure chamber, the expansion-side pressure chamber communicating with the expansion side chamber, the pressure-side pressure chamber communicating with the pressure side chamber, wherein a pressure derived from the pressure side chamber acts on the free piston to press the free piston to one side in a sliding direction, and a pressure derived from the expansion side chamber acts on the free piston to press the free piston to another side in the sliding direction, and a pressure-side pressure-receiving area on which the pressure-side-chamber-derived pressure of the free piston acts is larger than an expansion-side pressure-receiving area on which the expansion-side-chamber-derived pressure of the free piston acts.

2 . The shock absorber according to claim 1 , wherein
the pressure chamber includes a small-cross-sectional-area portion and a large-cross-sectional-area portion, the small-cross-sectional-area portion having a small area defined by a cross-sectional surface of an inner wall, the large-cross-sectional-area portion having a larger area defined by a cross-sectional surface of an inner wall than the area of the small-cross-sectional-area portion, the free piston includes: a small-piston portion slidably inserted into the small-cross-sectional-area portion of the pressure chamber; and a large-piston portion slidably inserted into the large-cross-sectional-area portion of the pressure chamber, the free piston defines a small chamber inside the small-cross-sectional-area portion using the small-piston portion, defines an outer peripheral chamber in an outer periphery of the small-piston portion inside the large-cross-sectional-area portion, and defines a large chamber inside the large-cross-sectional-area portion using the large-piston portion, one of the small chamber and the outer peripheral chamber is the expansion-side pressure chamber, and another communicates with the reservoir, and the large chamber is the pressure-side pressure chamber.

3 . The shock absorber according to claim 1 , further comprising:
a pressure-side first passage and a pressure-side second passage that communicate between the pressure-side pressure chamber and the pressure side chamber; a first valve disposed in the pressure-side first passage, the first valve being configured to allow only a flow of liquid from the pressure-side pressure chamber toward the pressure side chamber while providing resistance to the flow; and a second valve disposed in the pressure-side second passage, the second valve being configured to allow only a flow of liquid from the pressure side chamber toward the pressure-side pressure chamber while providing resistance of the flow.

4 . The shock absorber according to claim 3 , further comprising:
a valve disc coupled to the housing via a coupling rod, the valve disc being disposed inside the pressure side chamber; and a cap mounted on an outer periphery of the coupling rod, the cap fitting the valve disc to define a room inside the pressure side chamber, wherein the pressure-side pressure chamber communicates with the room via a rod internal passage formed inside the coupling rod, the valve disc includes a first port and a second port that communicate between the room and the pressure side chamber, the pressure-side first passage is formed by the first port and the rod internal passage, the pressure-side second passage is formed by the second port and the rod internal passage, on a side of the pressure side chamber in the valve disc, the first valve is formed by laminating a leaf valve configured to open and close the first port, and on a side of the room in the valve disc, the second valve is formed by laminating a leaf valve configured to open and close the second port.

5 . The shock absorber according to claim 3 , further comprising:
a valve disc housed in a hollow portion disposed inside the housing, the valve disc partitioning the hollow portion into the pressure chamber and an empty portion, the empty portion communicating with the pressure side chamber, wherein the valve disc includes a first port and a second port that communicate between the empty portion and the pressure-side pressure chamber, the pressure-side first passage is formed by the first port, the pressure-side second passage is formed by the second port, on a side of the empty portion in the valve disc, the first valve is formed by laminating a leaf valve configured to open and close the first port, and on a side of the pressure-side pressure chamber in the valve disc, the second valve is formed by laminating a leaf valve configured to open and close the second port.

6 . The shock absorber according to claim 1 , further comprising
a cushioning member configured to prevent a collision between the free piston and the housing.

7 . The shock absorber according to claim 1 , further comprising
a fluid-pressure cushioning mechanism configured to reduce a collision between the free piston and the housing.

8 . The shock absorber according to claim 1 , further comprising:
an outer pipe disposed outside the cylinder; and an intermediate pipe disposed between the cylinder and the outer pipe, wherein the housing fits end portions of the cylinder and the intermediate pipe, the reservoir is formed between the intermediate pipe and the outer pipe, a gap between the cylinder and the intermediate pipe forms a discharge passage, the discharge passage causing the expansion side chamber to communicate with the reservoir, the damping force adjusting unit is disposed between the discharge passage and the reservoir, and the expansion-side pressure chamber communicates with the expansion side chamber via the discharge passage.

9 . The shock absorber according to claim 2 , wherein
the housing includes:
a case member that includes a hollow portion into which the free piston is inserted movably in an above-below direction; and
a lid member that obstructs the hollow portion of the case member so as to form the pressure chamber.

Assignees

• Kayaba Industry Co Ltd

Inventors

• Teraoka Takashi
• Masamura Tatsuya

Classifications

• F16F9/5165 Primary

  by use of spherical valve elements or like free-moving bodies · CPC title

• F16F9/5126

  Piston, or piston-like valve elements (F16F9/504 takes precedence) · CPC title

• F16F9/34

  Special valve constructions ({F16F9/44, F16F9/50 take precedence; filtering details F16F9/3285} ; valves in general F16K); Shape or construction of throttling passages · CPC title

• F16F9/061

  Mono-tubular units · CPC title

• F16F9/187

  with uni-directional flow of damping fluid through the valves · CPC title