JP2019056420A - Piston-type damper and isolator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To construct a damper capable of attenuating even a minute vibration. SOLUTION: A piston type damper 1 includes a piston 2 in which rods 4 are provided on both sides in the axial direction and a plurality of grooves 23 extending from one surface 21 in the axial direction to the other surface 22 are formed. Further, the piston type damper 1 is a cylinder 3 in which through holes 5 through which rods 4 provided on both sides in the axial direction penetrate are formed and contains the piston 2, and fluid flows in the gap between the inner wall and the piston 2. It includes a filled cylinder 3. [Selection diagram] Fig. 1

Description

  The present invention relates to a piston type damper that attenuates vibration and an isolator using the piston type damper.

  In a structure that performs highly accurate positioning or directivity control, in order to increase control resolution, reduction of minute vibrations generated by a drive device is required. Patent Documents 1 to 3 describe a vibration isolation device that attenuates broadband vibration.

Patent Document 1 describes a welded bellows damper that uses oil as a working fluid and expands and contracts according to the flow of oil.
The bellows described in Patent Document 1 is made of metal and has environmental resistance. The bellows has a structure in which a thin plate is formed or a structure in which a thin plate is welded because it is necessary to ensure free stretchability within a specified dimension in the axial direction. From the viewpoint of extending the service life, it is recommended that the bellows has a structure in which a thin plate is welded so that stress is not easily concentrated.

  Patent Document 2 describes a device having a piston type damper using oil as a working fluid. Piston dampers are effective for large-amplitude vibration, but there is a problem that the effect of reducing minute vibrations is difficult to obtain due to large friction. For this reason, in Patent Document 2, the reduction of minute vibration is reduced by using a viscoelastic body in addition to the piston type damper.

  Patent Document 3 describes a coupling method in which a minute gap is not generated in a fastening member of a damper in order to insulate minute vibrations.

JP 2017-0667272 A Japanese Patent Laid-Open No. 11-141174 JP 2005-126947 A

As described in Patent Document 1, the bellows has a volume elasticity due to deformation of the bellows plate in addition to the stretchability in the axial direction. Volume elasticity is stretchability in a direction orthogonal to an axis to which a load is input. When the bellows receives a compressive force due to vibration, the oil flow rate that flows from the bellows to the orifice and develops attenuation is the amount obtained by excluding the volume expanded by volume elasticity from the volume changed by the expansion and contraction of the bellows in the axial direction. Become.
In the bellows type damper described in Patent Document 1, there is a problem that the volume expanded by volume elasticity at the time of minute vibration becomes significant, and the damping performance is deteriorated.

  On the other hand, since the piston type damper described in Patent Document 2 has almost no volume elasticity, this deterioration does not occur even if the vibration is minute. However, there is a problem that the friction described above is large.

  An object of the present invention is to constitute a damper capable of attenuating minute vibrations.

The piston type damper according to the present invention is
A piston provided with rods on both sides in the axial direction, and formed with a plurality of grooves extending in the axial direction from one surface in the axial direction to the other surface;
A through-hole through which each of the rods provided on both sides penetrates is formed, and the cylinder includes the piston, and a cylinder in which a fluid is filled in a gap between the inner wall and the piston.

  In the present invention, since the plurality of grooves extending in the axial direction are formed in the piston, the piston is prevented from coming into contact with the tilt cylinder. Thereby, frictional resistance can be suppressed, and even minute vibrations can be attenuated.

FIG. 3 is a cross-sectional view of the piston type damper 1 according to the first embodiment. The figure which shows the state which cut | disconnected and expanded the inner cylinder 31 which concerns on Embodiment 1. FIG. Explanatory drawing of the groove | channel 23 which concerns on Embodiment 1. FIG.

Embodiment 1 FIG.
*** Explanation of configuration ***
With reference to FIGS. 1 to 3, the configuration of the piston damper 1 according to the first embodiment will be described.

As shown in FIG. 1, the piston damper 1 includes a piston 2 and a cylinder 3. The piston 2 is provided with rods 4 on both sides in the axial direction. The cylinder 3 is formed with through holes 5 through which the rods 4 provided on both sides penetrate, and contains the piston 2. In the cylinder 3, the fluid between the inner wall and the piston 2 is filled with a highly viscous fluid such as oil. Here, this fluid is hereinafter referred to as oil.
The cylinder 3 has an inner cylinder 31 that encloses the piston 2 and an outer cylinder 32 that encloses the inner cylinder 31 with a gap. A hole 51 that is the through hole 5 is formed in the inner cylinder 31, and a hole 52 that is the through hole 5 is formed in the outer cylinder 32. When the rod 4 passes through the hole 51, a gap is formed between the opening end of the hole 51 in the inner cylinder 31 and the rod 4. Further, when the rod 4 is passed through the hole 52, a gap is formed between the opening end of the hole 52 in the outer cylinder 32 and the rod 4.
Oil filled in the cylinder 3 can flow through a gap between the inner cylinder 31 and the piston 2 and a gap between the outer cylinder 32 and the inner cylinder 31 through a hole 51 formed in the inner cylinder 31. That is, the oil can flow through the gap between the opening end of the hole 51 in the inner cylinder 31 and the rod 4.

  As shown in FIGS. 2 and 3, the piston 2 is formed with a plurality of grooves 23 extending in the axial direction from one surface 21 in the axial direction to the other surface 22. As shown in FIG. 3, each of the plurality of grooves 23 is deeper at the end in the axial direction and becomes shallower as it approaches the central portion in the axial direction. Each of the plurality of grooves 23 has, for example, a wedge-shaped, semi-circular, semi-elliptical, or U-shaped cross section in a direction perpendicular to the axial direction.

As shown in FIG. 1, the piston damper 1 includes a lid 6 and a bellows 7 corresponding to the rods 4 provided on both sides. The lid 6 is provided outside the cylinder 3 and is connected to the end of the corresponding rod 4. The bellows 7 surrounds the corresponding rod 4, and connects the lid 6 connected to the end of the corresponding rod 4 and the outer cylinder 32. One end of the bellows 7 is coupled to the surface of the lid 6 on the outer cylinder 32 side, and the other end is coupled to the surface of the outer cylinder 32 on the lid 6 side. In addition, the bellows 7 corresponding to each rod 4 provided on both sides has the same size and rigidity.
Oil is filled in the gap between the bellows 7 and the rod 4. Oil can flow through the gap between the bellows 7 and the rod 4 and the gap between the outer cylinder 32 and the inner cylinder 31 through a hole 52 formed in the outer cylinder 32. That is, the oil can flow through the gap between the opening end of the hole 52 in the outer cylinder 32 and the rod 4.

  As shown in FIG. 1, the piston damper 1 includes a fixing flange 8 for fixing the cylinder 3.

The piston damper 1 can constitute an isolator that insulates vibration. When the isolator is configured using the piston damper 1, the piston damper 1 and the primary spring are installed in parallel. The isolator insulates vibrations having a frequency higher than the resonance frequency of the primary spring.
The bellows 7 included in the piston damper 1 can be made to function as a primary spring of an isolator by imparting appropriate rigidity in the expansion / contraction direction. That is, by providing the bellows 7 with appropriate rigidity in the expansion and contraction direction, an isolator can be configured without using a separate primary spring.

*** Explanation of operation ***
The operation of the piston damper 1 according to the first embodiment will be described with reference to FIG.
When vibration is transmitted to the rods 4 on both axial sides, the piston 2 moves, so that the space on one side of the piston 2 inside the inner cylinder 31 is pressurized and the space on the other side is decompressed. Then, the oil in the pressurized space flows through a gap between the opening end of the hole 51 in the inner cylinder 31 and the rod 4. Thereby, the vibration is attenuated.
Note that the gap between the opening end of the hole 51 and the rod 4 is set to a gap size and shape that causes vibration attenuation due to kinematic viscosity resistance of oil.

If the axis of the piston 2 has a slight angle with respect to the central axis of the cylinder 3, that is, if the axis of the piston 2 is inclined, the piston 2 comes into contact with the inner cylinder 31 when it moves. That is, the piston 2 comes into contact with the inner cylinder 31. Thereby, frictional resistance is generated.
However, in the piston damper 1, a plurality of grooves 23 are formed in the piston 2. The plurality of grooves 23 cause oil to exert a force for restoring the tilt of the piston 2 when the shaft of the piston 2 is tilted. As a result, the axis of the piston 2 is prevented from tilting, and the piston 2 is prevented from hitting the inner cylinder 31. As a result, the frictional resistance is reduced.
Specifically, when the piston 2 moves, if the piston 2 is likely to hit one side, the gap between the groove 23 formed in the part that is likely to hit one side and the inner wall of the inner cylinder 31 becomes narrower. Therefore, the pressure is locally increased. On the other hand, the gap between the groove 23 formed in the axial target portion and the inner wall of the inner cylinder 31 is widened with respect to the portion likely to hit. Therefore, the pressure is locally reduced. Due to this pressure difference, a moment force is generated with respect to the piston 2 in a direction that avoids one-side contact. In particular, each of the plurality of grooves 23 is deeper at the end portion in the axial direction and becomes shallower as it approaches the central portion in the axial direction. For this reason, a moment force that avoids the one-sided contact is likely to be generated.
Here, each of the plurality of grooves 23 is formed from the surface 21 to the surface 22 in the axial direction, and there is no portion where the depth becomes zero. Therefore, even when the piston 2 starts moving from a state in which the piston 2 does not move and the piston 2 hits the inner wall of the inner cylinder 31, the flow rate of oil in each of the plurality of grooves 23 is zero. It will not be. Therefore, immediately after the piston 2 starts moving, a moment force is generated in a direction that avoids the one-side contact. As a result, the piston 2 does not hit one side.

When vibration is transmitted to the rods 4 on both sides in the axial direction and the piston 2 moves, the oil in the pressurized space passes through a gap between the opening end of the hole 51 in the inner cylinder 31 and the rod 4. Flowing. The inner cylinder 31 is included in the outer cylinder 32. Therefore, the oil that flows through the gap between the opening end of the hole 51 in the inner cylinder 31 and the rod 4 flows into the space between the outer cylinder 32 and the inner cylinder 31.
The space on the side where the piston 2 has moved and the pressure has been reduced is negative. Therefore, the oil in the space between the outer cylinder 32 and the inner cylinder 31 flows into the space on the decompressed side.
Here, the outer cylinder 32 encloses the inner cylinder 31 with a gap. The gap has a cross-sectional area that allows oil to flow easily. Therefore, the flow rate of oil accompanying the movement of the piston 2 is almost zero. Therefore, the internal pressure of the space between the outer cylinder 32 and the inner cylinder 31 becomes substantially constant regardless of the pressure inside the inner cylinder 31 due to vibration.

It is conceivable to use the piston type damper 1 for a product used in space such as an artificial satellite. In this case, the external pressure is 1 atmosphere on the ground, but the external pressure is almost zero on the orbit. For this reason, the relative pressure of the oil inside the piston damper 1 is zero on the ground, but becomes a positive pressure of +1 atm on the orbit. In addition, the volume is increased or decreased due to a change in the temperature of the oil due to a severe change in the temperature environment.
In the piston damper 1, fluctuations in the pressure inside the inner cylinder 31 can be absorbed by the space between the outer cylinder 32 and the inner cylinder 31. Therefore, even when the piston type damper 1 is used for a product used in space, it is possible to reduce the change in the damping performance due to the fluctuation of the pressure inside the inner cylinder 31.

Bellows 7 are arranged opposite to each other on both outer sides in the axial direction of the cylinder 3. The bellows 7 relieves pressure by volume elasticity. The total length of the two bellows 7 arranged on both outer sides is fixed by the rod 4. Since the total length of the two bellows 7 is fixed, when one bellows 7 is compressed, the other bellows 7 expands by the amount compressed. The oil can flow in the space between the bellows 7 and the outer cylinder 32 and the space between the outer cylinder 32 and the inner cylinder 31.
Therefore, the two bellows 7 do not affect the flow rate of the oil excited by the piston 2. On the other hand, the two bellows 7 can absorb a change in static pressure and prevent a decrease in damping performance.

*** Effects of Embodiment 1 ***
As described above, in the piston damper 1 according to the first embodiment, the gap between the inner cylinder 31 and the piston 2 is filled with oil, and the piston 2 is formed with a plurality of grooves 23 that become shallower at the center. Yes. Thereby, the moment force of the direction which avoids a piece hitting generate | occur | produces, and a piece hit is prevented. As a result, the frictional resistance is reduced.

  In the piston damper 1, the outer cylinder 32 includes the inner cylinder 31 with a gap. Accordingly, it is possible to prevent a decrease in the damping performance based on factors such as a change in internal pressure of the inner cylinder 31 and a temperature change.

In the piston damper 1, bellows 7 are arranged on both outer sides in the axial direction of the cylinder 3. Thereby, the change of pressure can be absorbed and the fall of attenuation performance can be prevented.
In addition, when the bellows 7 is used, the volume expanded by volume elasticity becomes significant, and there is a problem that the damping performance is deteriorated. This problem is solved by allowing oil to flow through the space between the bellows 7 and the outer cylinder 32 and the space between the outer cylinder 32 and the inner cylinder 31.

That is, the conventional piston type damper does not cause a decrease in flow rate due to bulk elasticity, but has a problem 1 that the frictional resistance is large. The conventional bellows type damper does not cause frictional resistance, but the flow rate decreases due to volumetric elasticity. There was a problem 2 that occurred. In addition, the conventional oil damper for space use has a problem 3 in which it is necessary to stabilize the damping performance by having a function of relaxing pressure fluctuation due to the environment.
On the other hand, the piston type damper 1 according to the first embodiment solves the problems 1 and 2 by having the thin groove 23 around the side surface of the piston 2.
Further, the piston type damper 1 according to the first embodiment solves the above-described problem 3 by including two bellows mechanisms that operate in opposition to each other without changing the overall length. That is, the bellows mechanism included in the piston damper 1 according to the first embodiment relieves pressure by the volume elasticity of the bellows 7 and, as a means for solving the problem 3 that occurs when the bellows mechanism is used, two pairs of bellows arrangements The oil in the part can flow freely, so that the internal pressure does not fluctuate.

That is, in order to solve the problems 1 and 2, the piston damper 1 according to the first embodiment is
A piston provided with rods on both sides in the axial direction and formed with a plurality of grooves extending from one surface in the axial direction to the other surface;
A through-hole through which each of the rods provided on both sides penetrates is formed, and the cylinder includes the piston, and a cylinder in which a fluid is filled in a gap between the inner wall and the piston.

In order to solve the problem 3, the piston damper 1 according to the first embodiment includes
A piston with rods on both sides in the axial direction;
A through hole through which each of the rods provided on both sides is formed, and a cylinder containing the piston;
A lid provided on the outside of the cylinder corresponding to each of the rods provided on both sides, and connected to an end of the corresponding rod;
A bellows provided corresponding to each of the rods provided on both sides, surrounding the periphery of the corresponding rod, and connecting the lid to which the end of the corresponding rod is connected and the cylinder.

In order to solve the problem 3, the piston damper 1 according to the first embodiment includes
For each of the rods provided on both sides, the total volume of the space formed by the rod, the bellows, the lid, and the outer cylinder is constant.

In order to solve the problem 3, the piston damper 1 according to the first embodiment includes
Fluid is filled so as to be able to flow through a gap between the outer cylinder and the inner cylinder, and a space formed by the rod, the bellows, the lid, and the outer cylinder.

  1 piston type damper, 2 pistons, 21 and 22 surfaces, 23 grooves, 3 cylinders, 31 inner cylinders, 32 outer cylinders, 4 rods, 5 through holes, 51, 52 holes, 6 lids, 7 bellows, 8 fixed flanges.

Claims (8)

A piston provided with rods on both sides in the axial direction and formed with a plurality of grooves extending from one surface in the axial direction to the other surface;
A piston-type damper comprising: a cylinder in which a through-hole through which each of the rods provided on both sides is formed is formed, the cylinder containing the piston, and a fluid filled in a gap between the inner wall and the piston. 2. The piston-type damper according to claim 1, wherein the plurality of grooves become shallower as they approach a central portion in the axial direction. The cylinder is
An inner cylinder containing the piston;
The piston type damper according to claim 1, further comprising an outer cylinder that encloses the inner cylinder with a gap. The piston-type damper according to claim 3, wherein the fluid can flow through a gap between the inner cylinder and the piston and a gap between the outer cylinder and the inner cylinder. The piston type damper further includes:
A lid provided on the outside of the cylinder corresponding to each of the rods provided on both sides, and connected to an end of the corresponding rod;
A bellows provided corresponding to each of the rods provided on both sides, surrounding the periphery of the corresponding rod, and connecting the lid to which the end of the corresponding rod is connected and the cylinder. The piston type damper according to any one of 1 to 4. The piston type damper according to claim 5, wherein the total volume of the space formed by being surrounded by the rod, the bellows, the lid, and the outer cylinder for each of the rods provided on both sides is constant. The piston according to claim 6, wherein the fluid can flow through a gap between the outer cylinder and the inner cylinder, and a space formed by the rod, the bellows, the lid, and the outer cylinder. Expression damper.   The isolator which has a piston type damper of any one of Claim 1-7.

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