JP2006342868A - Accumulator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an accumulator provided with structure capable of securing high responsiveness to a small change of volume and improved in durability of a bladder itself. <P>SOLUTION: This accumulator 1 is provided with a free piston 3 slidably housed inside a cylinder 2 to divide the inside of the cylinder 2 into a gas chamber A and a liquid chamber O and the bladder 4 provided on the liquid chamber O side of the free piston 3. A bladder chamber B surrounded by the bladder 4 and the free piston 3 is communicated with the gas chamber A through a communication hole provided in the free piston 3, and the communication hole is provided with an orifice 5 for regulating deformation quantity of the bladder when volume of the liquid chamber is changed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an improvement of a free piston type accumulator used in hydraulic equipment such as a hydraulic shock absorber.

  2. Description of the Related Art Conventionally, accumulators used in hydraulic equipment such as hydraulic shock absorbers are separated into a liquid chamber and an air chamber by a free piston that is slidably housed in a cylinder as a housing.

  This accumulator increases the air chamber volume by reducing the liquid chamber volume by moving the free piston in the axial direction while sliding in the cylinder, or decreases the air chamber volume by increasing the liquid chamber volume. In addition to the above, in addition to the above, the piston rod that enters or exits the cylinder that becomes excessive or insufficient during expansion or contraction is compensated for volume changes due to temperature changes in the liquid chamber. To compensate for the volume.

  By the way, the above-mentioned free piston is provided with a seal such as an O-ring on the outer peripheral side for the purpose of separating the liquid chamber and the air chamber, and this seal is subjected to a predetermined contact surface pressure action on the cylinder inner peripheral surface. It is in contact.

  Therefore, when the free piston moves in the axial direction with respect to the cylinder, friction is generated between the seal and the cylinder, and the free piston is required if the pressure in the liquid chamber does not become higher than the pressure in the air chamber by the influence of the frictional force. Because it cannot move, this conventional accumulator can have a negative impact on the response and reliability of the connected hydraulic equipment, and it can have a negative impact on vibration absorption when used in a hydraulic shock absorber. At the same time, a problem that the attenuation characteristic is not stable occurs.

  Therefore, there is a proposal (see Patent Document 1) in which the free piston is formed in an annular shape and a rubber bladder is provided on the inner peripheral side.

In this proposal, even if the movement of the free piston is hindered by friction with the cylinder, the bladder is deflected to compensate for the volume change in the liquid chamber, and the above-described problems can be solved.
JP 2004-11864 A (FIG. 1)

  Although the above-mentioned proposal exhibits an excellent effect in that the problems of the conventional accumulator are solved, there is a possibility that it is pointed out that this proposal has the following problems.

  That is, in the above proposal, since the bladder must be bent with respect to a slight volume change that does not satisfy the frictional force between the free piston and the cylinder, it is necessary to set the film thickness of the bladder to be relatively thin. .

  For this reason, when it is used in such a way that it repeatedly deforms with a large amount of deflection, there may be a problem in the durability of the bladder.

  Therefore, the present invention was devised in order to improve the above-mentioned problems, and an accumulator having a structure capable of improving the durability of the bladder itself as well as ensuring high responsiveness to a slight volume change. Is to provide.

  In order to achieve the above object, the present invention provides a free piston that is slidably housed in a housing to define an air chamber and a liquid chamber, and a bladder provided on the liquid chamber side of the free piston. The bladder chamber surrounded by the bladder and the free piston via the communication hole provided in the free piston and the air chamber are communicated with each other, and the volume of the liquid chamber is changed to the communication hole. A deformation amount restricting portion for restricting the deformation amount of the bladder is provided.

  According to the present invention, since the bladder deformation amount restricting portion is provided in the communication hole that connects the bladder chamber surrounded by the bladder and the free piston, and the air chamber, the deformation amount of the bladder when the volume of the liquid chamber changes. It can be arbitrarily regulated.

  Therefore, for example, when a hydraulic shock absorber is used as a hydraulic device and the volume of the piston of the hydraulic shock absorber is slightly changed in a very low speed range, the bladder is actively deformed and the piston speed is changed to a medium speed range or a high speed range. If the deformation amount restricting portion is set so that the free piston itself moves with almost no bending of the bladder with respect to a large volume change in the region, it is possible to reliably prevent the bladder from repeatedly deforming with a large bending amount.

  Therefore, it is possible to improve the durability of the bladder itself as well as to ensure high responsiveness to a slight volume change.

  Hereinafter, embodiments of the present invention embodied in an accumulator used in a hydraulic shock absorber used in a suspension device for an automobile will be described with reference to the drawings.

  The accumulator 1 includes a cylinder 2 as a housing, and a free piston 3 that is slidably accommodated in the cylinder 2 and defines an oil chamber O and an air chamber A as liquid chambers. And a bladder 4 provided on the oil chamber O side of the free piston 3, and a bladder chamber B surrounded by the bladder 4 and the free piston 3 and the air chamber A communicate with the free piston 3. An orifice 5 is provided as a deformation amount restricting portion of the present invention.

  More specifically, the cylinder 2 is formed in a bottomed cylindrical shape, and the hydraulic oil of the hydraulic shock absorber is guided to the upper side of the free piston 3 to form the oil chamber O. On the lower side, nitrogen gas is sealed at a predetermined pressure to form the air chamber A.

  The free piston 3 is mounted with an annular main body 7 having an outer peripheral surface in sliding contact with the inner peripheral surface of the cylinder 2 and inserted into the main body 7, and between the bladder chamber B and the air chamber A at the center of the bottom. A bottomed cylindrical mounting portion 8 having a communicating orifice 5 and a cap-shaped rubber bladder 4 having a lower opening end fitted to the mounting portion 8 are configured.

  The main body 7 has two upper and lower annular grooves 9a and 9b formed on the outer peripheral surface thereof, and the upper annular groove 9a is provided for improving the linear sliding property of the free piston 3 with respect to the inner peripheral surface of the cylinder 2. A wear ring 10 for firmly fixing the mounting portion 8 and the bladder 4 to the main body 7 is mounted.

  The lower annular groove 9b abuts against the inner peripheral surface of the cylinder 2 under the action of a predetermined contact surface pressure, and seals the space between the free piston 3 and the cylinder 2 to provide the oil chamber and the air chamber. A seal ring 11 to be separated is attached.

  The attachment portion 8 has a fitting groove 8a formed on the outer peripheral surface of the opening side, and a fitting protrusion directed inwardly protruding from the inner peripheral surface of the lower opening end of the bladder 4 into the fitting groove 8a. By fitting the portion 4a, the bladder 4 is fixed to the mounting portion 8, and when the bladder 4 is inserted into the main body 7, the lower outer peripheral surface of the bladder 4 contacts the inner peripheral surface of the main body 7. By restricting deformation to the outer peripheral side, the bladder 4 is prevented from being detached from the mounting portion 8.

  The mounting portion 8 is formed with a protruding portion 8b projecting downward at the center of the bottom portion, and the orifice 5 is formed at the center of the protruding portion 8b.

  Then, by setting the hole diameter of the orifice 5, resistance is given to the gas flow between the bladder chamber B and the air chamber A, and the free piston 3 does not move due to the frictional force caused by the seal ring 11. For slight volume changes in the low speed region of the piston speed of the hydraulic shock absorber, the bladder 4 acts to positively deform, and for large volume changes in the medium speed range and high speed range of the piston speed. The free piston 3 itself moves so that the bladder 4 hardly bends, so that the bladder 4 does not repeat large deformation.

  A nut 13 is screwed onto the outer periphery of the protrusion 8b. The outer peripheral end of the upper surface of the nut 13 is brought into contact with the lower end of the main body 7, and the lower outer peripheral surface of the mounting portion 8 and the lower inner periphery of the main body 7. The mounting portion 8 and the main body 7 are positioned and fixed by a downward C-pin 14 interposed between them and the surface.

  The accumulator 1 of the hydraulic shock absorber configured as described above has this volume by introducing or discharging hydraulic oil that becomes excessive or insufficient in the hydraulic shock absorber when the hydraulic shock absorber is expanded or contracted. Compensate for changes.

  At this time, in a slight volume change in the very low speed region of the piston speed of the hydraulic shock absorber so that the free piston 3 does not move due to the frictional force caused by the seal ring 11, there is a difference between the bladder chamber B and the air chamber A. When gas flows through the orifice 5 without resistance, the bladder 4 is positively bent and compensates for this volume change.

  Also, in the case of a large volume change in the high speed region among the piston speed of the hydraulic shock absorber, gas flows in a state where a large flow resistance is applied to the orifice 5 between the bladder chamber B and the air chamber A. The internal pressure of the bladder chamber B rises due to the resistance, the deformation of the bladder 4 is regulated, and the free piston 3 itself moves to compensate for this volume change.

  In this way, by setting the hole diameter of the orifice 5 provided on the protrusion 8a of the mounting portion 8, the amount of deformation of the bladder 4 according to the piston speed is regulated. Can be prevented from repeating large deformations.

  Therefore, it is possible to reliably prevent a decrease in durability caused by the bladder 4 repeatedly deforming with a large deflection amount as shown in the conventional example.

  In addition, since the mounting portion 8 provided with the orifice 5 is provided as a separate member from the main body 7, if a plurality of types of mounting portions 8 in which the setting of the orifice 5 is changed are prepared, specifications with different operating ranges of the bladder 4 are provided. Can be set easily.

  Further, since the wear ring 10 is provided on the outer peripheral surface of the main body of the free piston 3, the mounting portion 8 and the bladder 4 can be securely fixed to the main body 7, and the straight movement of the free piston 3 itself relative to the cylinder 2 can be achieved. Can be improved.

  Further, since the fixing portion 8 is fixed to the main body 7 with the nut 13 screwed into the protrusion 8b of the mounting portion 8 and the C pin 14 mounted between the mounting portion 8 and the main body 7, it is simple and strong. Can be fixed.

  In addition, this invention is not limited to the said embodiment, For example, it can also be changed and embodied as follows.

  1) In the present embodiment, an annular main body 7 having an outer peripheral surface slidably in contact with the inner peripheral surface of the cylinder 1 is inserted into and attached to the main body 7, and the bladder chamber B and the air chamber A are installed at the bottom center. Although it is embodied in the free piston 3 formed from the bottomed cylindrical mounting portion 8 provided with the orifice 5 communicating with each other, the present invention is not limited to this, and the main body 7 and the mounting portion 8 are integrated. The present invention may be embodied in a free piston 3 that is realized.

  2) In the present embodiment, the nut 13 screwed into the protrusion 8a of the mounting portion 8 and the C pin 14 provided between the main body 7 and the mounting portion 8 are used to fix the mounting portion 8 to the main body 7. However, the present invention is not limited to this, and a threaded portion may be provided on the outer peripheral surface of the mounting portion 8 so as to be directly screwed to the main body 7 to fix them.

  3) In this embodiment, when the bladder 4 is attached to the attachment portion 8, both are fixed by fitting the fitting protrusion 4a of the bladder 4 into the fitting groove 8a of the attachment portion 8. The method is not limited, and the bladder 4 may be fixed to the attachment portion 8 by using another fixing means such as adhesion or welding.

It is principal part sectional drawing of the accumulator which shows the best form of this invention.

Explanation of symbols

1 Accumulator 2 Cylinder (Housing)
3 Free piston 4 Bladder 5 Orifice (deformation restriction part)
7 Body 8 Mounting part A Air chamber B Bladder chamber O Oil chamber as liquid chamber

Claims (3)

An accumulator comprising a free piston, which is slidably housed in a housing and defines an air chamber and a liquid chamber, and a bladder provided on the liquid chamber side of the free piston, provided in the free piston A deformation amount restricting portion that allows the bladder chamber surrounded by the bladder and the free piston and the air chamber to communicate with each other through the communication hole and restricts the deformation amount of the bladder when the volume of the liquid chamber changes in the communication hole. An accumulator characterized by comprising: The accumulator according to claim 1, wherein the deformation amount restricting portion is formed by restricting the communication hole into an orifice shape. The free piston includes an annular main body and a bottomed cylindrical mounting portion that is inserted into and attached to the main body, and the bladder is attached to the opening end of the attachment portion, and the bottom portion of the attachment portion is The accumulator according to claim 1, wherein the communication hole is provided.

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