JP4028952B2 - Hydraulic shock absorber - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a structure of an accumulator provided in a hydraulic shock absorber.
[0002]
[Prior art]
Conventionally, there are the following structures of accumulators provided in hydraulic shock absorbers.
(1) A structure in which a predetermined amount of gas is sealed together with hydraulic oil in the cylinder and no free piston is provided to partition the gas chamber.
(2) A structure including a free piston that encloses a predetermined amount of gas together with hydraulic oil in a cylinder and partitions the gas chamber.
(3) A structure in which an elastic body made of closed cell sponge or the like is interposed in the cylinder.
[0003]
In either structure, when the piston rod enters the cylinder and the pressure in the cylinder rises, the gas or elastic body contracts to absorb the hydraulic oil for the intruding volume of the piston rod.
[0004]
[Problems to be solved by the invention]
Since the structure of (1) does not include a free piston, the structure can be simplified and a troublesome degassing operation is not required in the manufacturing process. However, when this structure is applied to a single cylinder type cylinder, the hydraulic oil is ejected into the gas as the piston moves, and the gas is mixed into the hydraulic oil, so that the desired damping characteristics cannot be obtained. There was a point. For this reason, it is necessary to apply the oil chamber partitioned by the piston and the gas chamber in which the gas is enclosed to the inside and outside of the cylinder, respectively, which leads to an increase in the size of the shock absorber.
[0005]
The structure (2) prevents the gas from being mixed with the hydraulic oil via the free piston, and can also be applied to a single cylinder cylinder. However, the provision of a free piston not only increases the cost of the product by complicating the structure, but also has the problem that the friction increases as the free piston moves and the operability deteriorates. Furthermore, since it is necessary to fill only the hydraulic oil so that gas (air) does not enter the cylinder, there is a problem in that productivity is poor because a process for extracting the gas from the cylinder is required.
[0006]
In the structure (3) , since no gas is sealed in the cylinder, the gas is not mixed with the hydraulic oil, and it is not necessary to provide a free piston, so that the structure can be simplified. However, also in this case, since it is necessary to fill only the hydraulic oil so that the gas does not enter the cylinder, there is a problem in that productivity is poor because a process of extracting the gas from the cylinder is required.
[0007]
The present invention has been made in view of the above problems, and has a structure that is relatively simple and does not require troublesome work such as degassing, and can be applied to a wide range of hydraulic shock absorbers from small to large. The purpose is to provide.
[0008]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a hydraulic shock absorber in which a piston rod is inserted into a cylinder, and an accumulator that allows a volume of hydraulic oil to enter and exit the cylinder is communicated with an oil chamber formed in the cylinder. was an elastic member chamber closed cell sponge is housed, and a gas chamber partitioned by a closed cell sponge, and which is characterized in that communicating with the oil chamber via an elastic member chamber gas chamber.
[0009]
According to a second invention, in the first invention, a bearing member that slidably supports the piston rod is interposed in the cylinder, an elastic body chamber and a gas chamber are defined between the bearing member and the cylinder, and are cylindrical. The elastic body was interposed between the bearing member and the cylinder.
[0010]
According to a third invention, in the first or second invention, a bush made of an elastic material is attached to the tip of a piston rod extending from the cylinder.
[0011]
Operation and effect of the invention
According to the first invention, the accumulator is constituted by the elastic body chamber in which the elastic body is accommodated and the gas chamber partitioned by the elastic body, and the free piston partitioning the gas chamber is abolished. The friction can be reduced to improve the operability of the shock absorber, and the structure can be simplified.
[0012]
Even if gas (air) enters the cylinder in the manufacturing process, the gas mixed in the cylinder by the expansion / contraction operation of the hydraulic shock absorber collects in the gas chamber via the elastic body. The gas once collected in the gas chamber is stopped from returning to the oil chamber side due to differences in the moving speed of hydraulic oil, pressure change, contraction speed of the elastic body, and the like.
[0013]
In this way, the gas that has entered the cylinder is confined in the gas chamber, so that the desired attenuation characteristic can be obtained, and the process of extracting the gas from the cylinder is not required, so that the productivity can be increased and the cost of the product can be reduced.
[0014]
According to the second invention, since the elastic body chamber and the gas chamber are defined between the bearing member and the cylinder, it is possible to lengthen the bearing member by using the space for providing the accumulator, and to support the piston rod. Sufficient rigidity can be secured.
[0015]
According to the third aspect of the invention, when the piston rod comes into contact with the other side through the bush, the bush is elastically deformed in the axial direction, so that the impact is relieved and the generation of loud noise and vibration is prevented.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0017]
A hydraulic shock absorber 10 shown in FIG. 1 includes a cylindrical cylinder 1, a piston 3 that partitions the inside of the cylinder 1 into an extension side oil chamber R 1 and a pressure side oil chamber R 2, and a piston rod that extends from the cylinder 1 in conjunction with the piston 3. 2 and an accumulator 11 that allows the hydraulic oil in and out of the cylinder 1 to enter and exit the piston rod 2.
[0018]
The cylinder 1 has a cylindrical cylinder portion 1a for slidably housing the piston 3, and a bottom portion 1b, which are integrally formed by molding a resin. The outer peripheral surface of the cylinder part 1a is formed in a taper shape so as to become gradually thinner from the opening end to the bottom part 1b, and the cylinder 1 can be easily inserted into a mounting hole (not shown).
[0019]
A resin stopper 15 is fitted to the open end of the cylinder 1, and an annular oil seal 4 is interposed between the stopper 15 and the piston rod 2, and the oil seal 4 prevents hydraulic oil from leaking. The
[0020]
The cylinder 1 may be integrally formed of metal, and the opening end portion thereof may be bent inward to fix the annular oil seal or the like by caulking.
[0021]
The piston rod 2 is supported by the cylinder 1 through a resin bearing member 5 so as to be slidable in the axial direction. The bobbin-shaped bearing member 5 has flange portions 5a and 5b at both ends thereof. The flange portion 5 a is fitted to the plug body 15, and the flange portion 5 b is fitted to the cylinder 1.
[0022]
A ring 6 is fitted to the end of the piston rod 2. When the ring 6 contacts the end surface of the bearing member 5, the piston rod 2 is prevented from coming off.
[0023]
The piston rod 2 and the piston 3 are provided separately without being coupled to each other. A spring 8 that presses the piston 3 against the piston rod 2 is provided, and the piston 3 follows the piston rod 2 by the biasing force of the spring 8. The coiled spring 8 is interposed between the piston rod 2 and the bottom 1b of the cylinder 1 in a compressed state.
[0024]
The piston 3 has an orifice 3c that allows the expansion side oil chamber R1 and the pressure side oil chamber R2 to communicate with each other, and a pressure side check valve 14 that opens with respect to the flow of hydraulic oil from the expansion side oil chamber R1 toward the pressure side oil chamber R2. Be dressed. Thereby, the damping force at the time of the pressure side operation in which the piston rod 2 enters the cylinder 1 is higher than the damping force at the time of the extension side operation in which the piston rod 2 extends from the cylinder 1.
[0025]
The accumulator 11 includes an elastic body chamber 12 in which the elastic body 9 is accommodated and a gas chamber 13 partitioned by the elastic body 9, and the gas chamber 13 is communicated with the oil chamber R <b> 1 through the elastic body chamber 12.
[0026]
The elastic body chamber 12 is defined between the cylinder 1 and the bearing member 5, and communicates with the extension side oil chamber R <b> 1 through a communication path 5 c formed by notching the flange portion 5 b of the bearing member 5.
[0027]
The elastic body 9 is formed, for example, by molding a nitrile rubber foam into a cylindrical shape. The foam (closed cell sponge) has a large number of independent voids (bubbles) as a whole, and expands and contracts by the pressure guided to the elastic body chamber 12.
[0028]
An annular step portion 5d is formed in the middle of the bearing member 5, and the elastic body 9 is interposed between the annular step portion 5d and the flange portion 5b.
[0029]
The gas chamber 13 is defined as a cylindrical space between the cylinder 1, the bearing member 5, and the plug body 15, and communicates with the extension-side oil chamber R1 via the elastic body chamber 12 and the communication passage 5c.
[0030]
When the hydraulic shock absorber 10 is assembled, the cylinder 1 is filled with a predetermined amount of hydraulic oil (for example, silicon oil), and then the cylinder rod 1 is assembled with the piston rod 2 and the plug body 15 in the cylinder 1. A predetermined amount of gas (air) is sealed.
[0031]
The hydraulic shock absorber 10 is attached so that the position of the gas chamber 13 does not become lower than that of the elastic body chamber 12, and the gas in the cylinder 1 is guided to the gas chamber 13 by its buoyancy. In the present embodiment, the hydraulic shock absorber 10 is attached so as to extend substantially horizontally.
[0032]
A bush 22 made of a soft resin as an elastic material is attached to the tip of the piston rod 2. The bush 22 having a bottomed cylindrical shape is fitted into a hard resin cap 21, and the cap 21 is press-fitted into the tip of the piston rod 2. The bush 22 has a bellows shape having three annular recesses 22a on its outer periphery. When the piston rod 2 abuts against the other side via the bush 22, the bush 22 is elastically deformed in the axial direction, so that the impact is reduced and the generation of loud noise and vibration is prevented.
[0033]
Next, the operation will be described.
[0034]
During the pressure side operation in which the piston rod 2 is pushed into the cylinder 1, the check valve 14 is closed, and the hydraulic oil in the pressure side oil chamber R2 flows into the expansion side oil chamber R1 through the orifice 3c. Thus, a damping force is generated by the resistance applied by the orifice 3c to the flow of hydraulic oil, and the hydraulic shock absorber 10 contracts slowly. At this time, hydraulic oil corresponding to the intruding volume of the piston rod 2 flows from the extension side oil chamber R1 into the elastic body chamber 12 and the gas chamber 13 through the communication passage 5c.
[0035]
During the extension side operation in which the piston rod 2 extends from the cylinder 1, the check valve 14 opens, and the hydraulic oil in the extension side oil chamber R1 flows into the pressure side oil chamber R2 through the check valve 14 and the orifice 3c, respectively. In this way, almost no damping force is generated by increasing the flow path area, and the hydraulic shock absorber 10 is quickly extended. At this time, hydraulic oil corresponding to the intruding volume of the piston rod 2 is returned from the gas chamber 13 and the elastic body chamber 12 to the pressure side oil chamber R2 through the communication passage 5c.
[0036]
Even if gas (air) is mixed into the hydraulic oil in each of the oil chambers R1 and R2 of the hydraulic shock absorber 10 in the manufacturing process, if the hydraulic shock absorber 10 is attached and expanded and contracted several times, the pressure side operation and the expansion side operation are performed. Since the pressure change speed in the cylinder 1 and the expansion / contraction speed of the elastic body 9 are different from time to time, the gas in the cylinder 1 enters the gas chamber 13 through the elastic body chamber 12, and the gas that has entered the gas chamber 13 flows into the pressure side oil chamber R2. Returning to is stopped by the elastic body 9.
[0037]
More specifically, since the piston rod 2 slowly enters the cylinder 1 due to the damping force during the pressure side operation, the hydraulic oil for the intrusion volume of the piston rod 2 together with the gas passes through the communication passage 5c from the pressure side oil chamber R2 and passes through the elastic body 9. The gas flows into the elastic body chamber 12 while being contracted, and the gas flowing into the elastic body chamber 12 flows into the gas chamber 13. On the other hand, since the piston rod 2 quickly extends from the cylinder 1 during the extension side operation, only the hydraulic oil passes from the elastic body chamber 12 through the communication passage 5c and the pressure side oil chamber R2 while the gas remains in the gas chamber 13. The gas in the gas chamber 13 is confined through the elastic body 9.
[0038]
In this way, the gas in the cylinder 1 gathers in the gas chamber 13 and escapes from the expansion side oil chamber R1 and the pressure side oil chamber R2, so that the flow of hydraulic oil passing through the orifice 3c is not affected by the gas, and the desired damping characteristic is obtained. Is obtained.
[0039]
Since the accumulator 11 is constituted by an elastic body chamber 12 in which the elastic body 9 is accommodated and a gas chamber 13 partitioned by the elastic body 9, a conventional gas chamber is defined via a free piston that is in sliding contact with the cylinder. The structure can be simplified compared to the structure and the like.
[0040]
When the hydraulic shock absorber 10 is assembled, the cylinder 1 is filled with a predetermined amount of hydraulic oil, and the cylinder 15 is assembled with a plug 15 and the like so that a predetermined amount of gas is sealed in the cylinder 1. A process of removing gas from the cylinder 1 during assembly of the shock absorber 10 is not necessary, and a process of wiping off the working oil overflowing from the cylinder 1 is not necessary, thereby improving productivity.
[0041]
Since the elastic body chamber 12 and the gas chamber 13 are defined between the bearing member 5 and the cylinder 1, the bearing member 5 can be lengthened using the space where the accumulator 11 is provided, and the piston rod 2 is supported. Sufficient rigidity can be secured.
[0042]
As a result, it is possible to provide a structure that does not couple the piston rod 2 to the piston 3, avoiding malfunction due to the assembly error of both, and not requiring high machining accuracy for the piston rod 2 or the piston 3, The piston rod 2 can be formed in a simple columnar shape, and productivity can be improved.
[0043]
The present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a hydraulic shock absorber according to an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Cylinder 2 Piston rod 3 Piston 3c Orifice 5 Bearing member 8 Spring 9 Elastic body 10 Hydraulic buffer 11 Accumulator 12 Elastic body chamber 13 Gas chamber 14 Check valve R1 Extension side oil chamber R2 Pressure side oil chamber

Claims (3)

In a hydraulic shock absorber in which a piston rod is inserted into a cylinder, and an accumulator that allows the flow of hydraulic oil in a volume that allows the piston rod to enter and exit from the cylinder communicates with an oil chamber formed in the cylinder, the accumulator is independent hydraulic shock bubbles sponge comprises an elastic member chamber to be accommodated, and a gas chamber partitioned by the closed cell sponge, characterized in that the gas chamber was communicated with the oil chamber via the elastic member chamber vessel.   A bearing member that slidably supports the piston rod is interposed in the cylinder, the elastic body chamber and the gas chamber are defined between the bearing member and the cylinder, and the cylindrical elastic body is The hydraulic shock absorber according to claim 1, wherein the hydraulic shock absorber is interposed between a bearing member and the cylinder.   The hydraulic shock absorber according to claim 1 or 2, wherein a bush made of an elastic material is attached to a tip of the piston rod extending from the cylinder.

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