JP2001295877A - Shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shock absorber having a rod capable of smoothly moving regardless of the moving speed and the stroke of the rod. SOLUTION: This shock absorber 10A is equipped with a main cylinder 11 and a sub-cylinder 40. A free piston 41 is stored in the sub-cylinder 40. A liquid chamber 60 is formed on the one side of the free piston 41, and a gas chamber 62 is formed on the other side of the free piston 41. A metal bellows 42 is provided in the free piston 41. The metal bellows 42 expands and contracts in the axial direction of the sub-cylinder 40 in response to the pressure of hydraulic oil in the liquid chamber 60.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shock absorber mounted on a suspension mechanism of a vehicle.

[0002]

2. Description of the Related Art A single-cylinder type shock absorber mounted on a suspension mechanism of a vehicle is provided with an oil chamber and a gas chamber inside a cylinder called a so-called monotube, and a rod moves axially with respect to the cylinder. The volume of the gas chamber changes according to the insertion amount of the rod at that time. In this type of shock absorber, high-pressure gas is sealed in a gas chamber to prevent cavitation and aeration from occurring in hydraulic oil due to rod stroke.
The hydraulic oil is pressurized by the pressure of the high-pressure gas. The pressure of this gas acts in the direction of pushing the rod out of the cylinder.

The oil chamber and the gas chamber are generally separated by a free piston, and when the volume of the gas chamber changes,
The free piston slides in the axial direction of the cylinder. An O-ring is provided on the outer periphery of the free piston for sealing between the oil chamber and the gas chamber. Therefore, when the free piston slides, friction occurs between the O-ring and the inner surface of the cylinder. Therefore, for example, in a region where the free piston moves at an extremely low speed, such as when the free piston starts to move, the friction becomes a force that hinders the movement of the free piston, and gives resistance to the movement of the rod. In that case, a desired damping force set in advance may not be obtained.

In order to solve the above problem, it has been proposed to separate the oil chamber and the gas chamber by bellows instead of the free piston. When the bellows expands and contracts, it does not generate friction like a free piston, so the rod can move smoothly even at extremely low speeds such as when the rod starts moving, and the pressure of the enclosed high-pressure gas To the oil chamber.

[0005]

However, when a bellows is housed in a vehicle shock absorber, a considerably long bellows is required to absorb a change in the volume of the gas chamber due to the stroke of the rod. For this reason, accommodating the bellows of a desired length in a cylinder has difficulty. Also, depending on the rod stroke, the bellows may not be able to absorb the change in volume of the gas chamber and may extend beyond the allowable limit in the axial direction. The movement of the vehicle is restricted, which causes the ride comfort of the vehicle to deteriorate.

Accordingly, it is an object of the present invention to provide a shock absorber in which the rod can move smoothly regardless of the moving speed and stroke of the rod, and the riding comfort is improved.

[0007]

According to a first aspect of the present invention, there is provided a shock absorber including a free piston housed in a cylinder, and a hydraulic fluid formed on one side of the free piston in the cylinder. A liquid chamber to be filled, a gas chamber formed inside the cylinder on the other side of the free piston and filled with a pressurized gas, and a gas chamber provided in the free piston and according to the pressure of the hydraulic fluid in the liquid chamber. And a metal bellows that expands and contracts in the axial direction of the cylinder. The free piston may be provided with a stroke restricting means for restricting the expansion and contraction stroke of the metal bellows on the extension side and the contraction side.

In the shock absorber of the present invention, when the moving speed is small and the stroke is small, such as when the rod starts to move, the volume of the gas chamber is changed by bending the metal bellows according to the pressure of the hydraulic fluid. When the moving speed or stroke of the rod increases, the free piston slides inside the cylinder in addition to the bending of the metal bellows, thereby absorbing the change in the volume of the gas chamber.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a shock absorber 10A according to a first embodiment of the present invention will be described with reference to FIGS. Shock absorber 10A shown in FIG.
Has a main cylinder 11, a rod 12 inserted into the main cylinder 11, a reservoir tank 13, and the like. The rod 12 can move in the axial direction of the main cylinder 11. A piston portion 15 is provided at one end of a rod 12 located inside the main cylinder 11. The piston portion 15 is provided with a damping force generating mechanism 16 including an orifice, a disc valve, and the like for generating a damping force when the rod 12 relatively moves in the axial direction of the cylinder 11.

In this embodiment, a variable orifice member 20 is provided at the end of the rod 12. The control member 21 for driving the variable orifice member 20 is the rod 1
2 is inserted. By operating the operation element 22 provided on the other end side of the control member 21, the flow path cross-sectional area of the variable orifice member 20 can be changed.

The interior of the main cylinder 11 includes a first liquid chamber 31 located above the piston section 15 and a piston section 1.
5 and a second liquid chamber 32 located below. These liquid chambers 31, 32 are filled with oil as an example of a working liquid. The upper end 35 of the rod 12 is connected to, for example, a member 36 on the vehicle body side, and the lower end 37 of the main cylinder 11 is connected to, for example, a wheel support member (not shown).

The reservoir tank 13 includes a cylindrical sub-cylinder 40, a free piston 41 housed inside the sub-cylinder 40, a metal bellows 42 provided on the free piston 41, a throttle valve 43 and the like. The free piston 41 can reciprocate in the axial direction of the sub cylinder 40. An O-ring 44 is provided on the outer periphery of the free piston 41. The O-ring 44 is in contact with the inner surface of the sub-cylinder 40 and has a function of sealing a liquid chamber 60 and a gas chamber 62 described below.

A rod-shaped stopper member 51 is inserted into a hole 50 formed in the center of the free piston 41.
This stopper member 51 is movable in the axial direction of the free piston 41.

As shown in an enlarged manner in FIG. 2, the metal bellows 42 is provided on one side of the free piston 41,
It is provided on the 0 side. The metal bellows 42 is a bellows body 5 in which peaks and valleys are alternately formed by a thin metal plate.
5 and a bellows cap 56 that seals the distal end side of the bellows main body 55. The base of the bellows body 55 is hermetically welded to the free piston 41 over the entire circumference.

One end 51a of the stopper member 51 is fixed to the back side of the bellows cap 56. The other end of the stopper member 51 is provided with a tapered prevention valve 58 whose diameter is enlarged. The extension prevention valve 58 is
When the extension-side deflection of the bellows body 55 reaches a predetermined stroke, the bellows body 55 is prevented from further extending by contacting the tapered portion 57 of the free piston 41. That is, the stopper member 51 functions as a stroke restricting means for restricting the maximum stroke on the extension side of the metal bellows 42.

The free piston 41 is provided with a cylindrical stopper wall 59 on the side facing the back surface of the bellows cap 56. The stopper wall 59 is provided on the bellows main body 5.
When the bellows cap 5 is bent by a predetermined amount toward the contraction side, the bellows cap 56
This prevents the bellows body 55 from shrinking further. That is, the stopper wall 59 functions as a stroke restricting means for restricting the stroke of the metal bellows 42 on the contraction side.

Inside the sub cylinder 40, a liquid chamber 60 is formed on one side of the free piston 41. The liquid chamber 60 contains the same oil as the hydraulic oil in the main cylinder 11. The liquid chamber 60 of the sub cylinder 40
It communicates with the liquid chamber 32 of the main cylinder 11 via the flow path 61. Inside the sub cylinder 40, a gas chamber 62 is formed on the other side of the free piston 41. The gas chamber 62 is filled with a chemically inert gas such as pressurized nitrogen. The gas chamber 62 communicates with the space inside the bellows 42 via the hole 50.

Next, the shock absorber 10A having the above-described structure is used.
The operation of will be described. When the rod 12 moves in the direction of being pushed into the main cylinder 11, the oil in the second liquid chamber 32 flows into the first liquid chamber 31 through the damping force generating mechanism 16, thereby causing the damping force. Is generated, and oil corresponding to the movement amount of the rod 12 flows into the liquid chamber 60 of the reservoir tank 13 through the flow path 61 and the throttle valve 43,
The metal bellows 42 will be pressurized. Since the O-ring 44 is provided between the sub cylinder 40 and the free piston 41, the friction of the O-ring 44
The movement of 1 receives resistance. However, since the metal bellows 42 does not substantially generate friction, when the moving speed and the stroke are small, such as when the rod 12 starts moving, the gas is compressed by the metal bellows 42 flexing to the contraction side.

When the rod 12 is further pushed into the main cylinder 11, the metal bellows 42 bends to the full contraction side, and the bellows cap 56 comes into contact with the stopper wall 59, whereby the bending of the metal bellows 42 is restricted. At the same time, when the free piston 41 moves in the direction indicated by the arrow F1, the gas chamber 62 is compressed and its volume decreases.

Conversely, when the rod 12 moves in the direction protruding from the main cylinder 11, the reservoir tank 13
A part of the oil in the liquid chamber 60 flows into the liquid chamber 32 of the main cylinder 11 through the flow path 61, and the pressure of the liquid chamber 60 decreases. In this case, while the moving speed and the stroke are small, such as when the rod 12 starts to move, the metal bellows 42 bends toward the extension side.

When the stroke of the rod 12 becomes large, the valve 58 for preventing the extension of the stopper member 51 comes into contact with the tapered portion 57 of the free piston 41, whereby the extension of the metal bellows 42 is restricted and the free piston 41 is moved. By moving in the direction indicated by the arrow F2, the volume of the gas chamber 62 increases.

As described above, according to the shock absorber 10A of this embodiment, while the moving speed and the stroke of the rod 12 are small, the rod 12 can be moved smoothly by mainly bending the metal bellows 42. The free piston 41 moves when the moving speed and the stroke of the rod 12 increase, so that the volume of the gas chamber 62 changes. For this reason, even if the frictional resistance when the free piston 41 moves is large,
By the cooperation of the free piston 41 and the metal bellows 42, good damping force characteristics are obtained, and the riding comfort is further improved.

Next, a shock absorber 10B according to a second embodiment of the present invention will be described with reference to FIG. The shock absorber 10B shown in FIG. 3 includes a cylinder 70 and a rod 71 (only a part is shown). The rod 71 can move in the axial direction of the cylinder 70. A piston 72 is provided at one end of a rod 71 located inside the cylinder 70. The piston portion 72 is provided with a damping force generating mechanism 73 including an orifice, a disc valve, and the like for generating a damping force when the rod 71 relatively moves in the axial direction of the cylinder 70.

Inside the cylinder 70, a first liquid chamber 75 located above the piston 72, a second liquid chamber 76 located below the piston 72, and a gas chamber 77 are formed. . The liquid chambers 75 and 76 are filled with oil as an example of a working fluid. The gas chamber 77 is filled with a pressurized inert gas such as nitrogen.

Further, a free piston 80 and a metal bellows 81 attached to the free piston 80 are accommodated in the cylinder 70. The free piston 80 can reciprocate in the axial direction of the cylinder 70. An O-ring 82 is provided on the outer periphery of the free piston 80. The O-ring 82 contacts the inner surface of the cylinder 70 and
6 has a function of sealing the gas chamber 77.

A rod-shaped stopper member 86 is inserted into a hole 85 formed at the center of the free piston 80.
This stopper member 86 is movable in the axial direction of the free piston 80.

The metal bellows 81 includes a free piston 80
, Ie, on the liquid chamber 76 side. The metal bellows 81 has a bellows body 90 in which peaks and valleys are alternately formed by a thin metal plate, and a bellows cap 91 that seals a tip end of the bellows body 90.
The base of the bellows body 90 is hermetically welded to the free piston 80 over the entire circumference. The space inside the bellows 81 communicates with the gas chamber 77 via the hole 85.

One end 86a of a stopper member 86 is fixed to the back side of the bellows cap 91. The other end of the stopper member 86 is provided with an extension prevention valve 93 whose diameter increases in a tapered shape. The extension prevention valve 93 is
When the extension-side deflection of the bellows main body 90 reaches a predetermined stroke, the bellows main body 90 is prevented from further extending by contacting the tapered portion 92 of the free piston 80. That is, the stopper member 86 functions as a stroke restricting means for restricting the maximum stroke of the metal bellows 81 on the extension side.

The free piston 80 is provided with a cylindrical stopper wall 94 on the side facing the back surface of the bellows cap 91. The stopper wall 94 is provided on the bellows body 9.
When the bellows cap 91 is bent by a predetermined amount toward the contraction side,
This prevents the bellows body 90 from shrinking further. That is, the stopper wall 94 functions as a stroke restricting means for restricting the stroke of the metal bellows 81 on the contraction side.

Next, the shock absorber 10B having the above-described structure is used.
The operation of will be described. When the rod 71 moves in the direction of being pushed into the cylinder 70, the second liquid chamber 76
When the oil inside flows into the first liquid chamber 75 through the damping force generating mechanism 73, a damping force is generated, and the oil in the liquid chamber 76 presses the metal bellows 81.
Since the O-ring 82 is provided between the cylinder 70 and the free piston 80, the friction causes the movement of the free piston 80 to be resisted. However, since the metal bellows 81 does not substantially generate friction, when the moving speed and the stroke are small, such as when the rod 71 starts to move, the gas is compressed by the metal bellows 81 flexing to the contraction side.

When the rod 71 is further pushed into the cylinder 70, the metal bellows 81 bends to the full contraction side, and the bellows cap 91 comes into contact with the stopper wall 94, so that the metal bellows 81 can no longer bend. As the free piston 80 moves in the direction indicated by the arrow F3, the gas chamber 77 is compressed and its volume decreases.

Conversely, when the rod 71 moves in a direction to protrude from the cylinder 70, the pressure in the liquid chamber 76 decreases. In this case, while the moving speed and the stroke of the rod 71 are small, such as when the rod 71 starts to move, the metal bellows 81 bends toward the extension side. When the stroke of the rod 71 is increased, the valve 93 for preventing the extension of the stopper member 86 from coming into contact with the tapered portion 92 of the free piston 80 restricts the extension of the metal bellows 81, and the free piston 80 is moved by the arrow F4. By moving in the direction shown, the volume of the gas chamber 77 increases.

As described above, according to the shock absorber 10B of this embodiment, while the moving speed and the stroke of the rod 71 are small, the rod 71 can be moved smoothly by mainly bending the metal bellows 81. The free piston 80 moves when the moving speed and the stroke of the rod 71 increase, so that the volume of the gas chamber 77 changes. For this reason, even if the frictional resistance when the free piston 80 moves is large,
Good damping force characteristics can be obtained by the cooperation of the free piston 80 and the metal bellows 81.

In practicing the present invention, each element constituting the present invention, including the specific shape and structure of a cylinder, a rod, a free piston, a metal bellows, and the like, is appropriately changed without departing from the gist of the present invention. It is needless to say that the present invention can be carried out in a modified form.

[0035]

According to the first and second aspects of the present invention, since the metal bellows and the free piston cooperate in accordance with the moving speed and stroke of the rod, the rod can move smoothly. Riding comfort is improved. Moreover, according to the present invention, the shock absorber can be made smaller in comparison with the case where only the metal bellows is used. According to the third aspect of the present invention, the maximum bending amount of the metal bellows on the extension side or the contraction side can be regulated by the stroke regulating means such as the stopper member provided on the free piston, and the flexure of the bellows is increased. Sometimes the free piston can slide.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a shock absorber according to a first embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing a part of the shock absorber shown in FIG. 1;

FIG. 3 is a longitudinal sectional view of a shock absorber according to a second embodiment of the present invention.

[Explanation of symbols]

 10A, 10B Shock absorber 11 Main cylinder 12 Rod 40 Sub cylinder 41 Free piston 42 Metal bellows 60 Liquid chamber 62 Gas chamber 70 Cylinder 71 Rod 75, 76 Liquid chamber 77 Gas chamber 80 … Free piston 81… Metal bellows

Claims (3)

[Claims] A cylinder; a rod inserted into the cylinder so as to be movable in the axial direction; a free piston housed inside the cylinder and slidable in the axial direction of the cylinder; A liquid chamber formed on one side of the free piston and filled with hydraulic fluid; a gas chamber formed on the other side of the free piston inside the cylinder and filled with pressurized gas; A metal bellows that is provided and that expands and contracts in the axial direction of the cylinder in accordance with the pressure of the hydraulic fluid in the liquid chamber. 2. A main cylinder, a rod movably inserted in the main cylinder in an axial direction, a sub-cylinder provided outside the main cylinder and communicating with the main cylinder through a flow path, A free piston housed inside the cylinder and slidable in the axial direction of the sub-cylinder; a liquid chamber formed on one side of the free piston inside the sub-cylinder and filled with hydraulic fluid; A gas chamber formed inside the other side of the free piston and filled with pressurized gas, and provided in the free piston and in the axial direction of the sub-cylinder in accordance with the pressure of the hydraulic fluid in the liquid chamber. A shock absorber, comprising: a metal bellows that expands and contracts. 3. The shock absorber according to claim 1, further comprising a stroke restricting means for restricting an expansion stroke of the metal bellows with respect to the free piston.