JP6748073B2 - Piston type accumulator piston seal structure - Google Patents

Description

The present invention relates to a piston seal structure provided in a piston type accumulator.

Conventionally, as shown in FIG. 6, a piston type accumulator 51 in which a piston 53 is displaced inside a cylinder 52 is known, and a gas G sealed in a gas chamber 54 leaks to an oil O side at an outer peripheral portion of the piston 53. The gas side seal part 55 is provided so as to prevent the oil O flowing through the pressure piping system from entering the gas chamber 54 side, and the oil side seal part 56 is provided. The piston 53 is displaced in the axial direction (center axis direction, left-right direction in the drawing) inside the cylinder 52 so that the gas pressure and the oil pressure are balanced.

Each of the gas-side seal portion 55 and the oil-side seal portion 56 is constituted by an O-ring 58 made of a rubber-like elastic body and fitted in a fitting groove 57 provided on the outer peripheral surface of the piston 53.

JP-A-8-296601

However, since the O-ring 58 made of a rubber-like elastic material has a circular or substantially circular cross-sectional shape, it is possible to set a large permeation distance for the gas G to pass through the O-ring 58, particularly in the inner peripheral portion of the ring. Can not. Therefore, the gas G may permeate the O-ring 58, and the permeation of the gas G may lead to leakage.

Further, the rubber-like O-ring 58 is likely to be twisted in the mounting groove 57. Therefore, when the O-ring 58 is twisted, there is an inconvenience that leads to leakage.

Furthermore, the O-ring 58 made of a rubber-like elastic material may deteriorate in material due to contact with the oil O. Therefore, the deterioration of the material of the O-ring 58 in this way causes a problem of leakage.

In view of the above points, the present invention provides a piston seal structure provided in a piston type accumulator, which is capable of suppressing deterioration of sealing performance due to gas permeation, twisting of the seal, or deterioration of material. The purpose is to provide.

To achieve the above object, a piston seal structure according to claim 1 of the present invention is a piston seal structure provided in a piston type accumulator in which a piston is displaced inside a cylinder, wherein a gas side seal portion and a gas side seal portion are provided on an outer peripheral portion of the piston. In a piston seal structure in which oil-side seal parts are arranged in parallel, the gas-side seal part is a rubber-like elastic D-ring having an outer peripheral surface with an arcuate cross section that slidably contacts the inner surface of the cylinder. The oil-side seal portion includes a resin slider seal having an outer peripheral surface that slidably contacts the inner surface of the cylinder, and a rubber-like elastic back ring disposed on the inner peripheral side of the slider seal. And a taper surface large-diameter cylindrical portion whose outer diameter gradually increases from the gas side to the oil side on the outer peripheral surface of the slider seal, and the large-diameter cylindrical portion has an oil side on the oil side. A stepped portion is provided, and a small-diameter tubular portion whose outer diameter dimension is set smaller than that of the large-diameter tubular portion is provided on the oil side of the stepped portion .

A piston seal structure according to a second aspect of the present invention is the piston seal structure according to the first aspect, wherein the gas side seal portion includes a backup ring arranged on the oil side of the D ring. And

Further, the piston seal structure according to claim 3 of the present invention, in the piston seal structure according to claim 1 or 2, wherein the above, pre-Symbol slider seal, said by the piston displacement direction comprises an outer circumferential surface of asymmetrical shape cylinder The pressure gradient is set to the contact surface pressure with respect to the inner surface of the.

The piston seal structure of the present invention having the above configuration is provided with a rubber-like elastic D ring as the gas side seal portion, and a resin slider seal and a rubber elastic body back ring as the oil side seal portion. It is characterized by having a combination seal.

As the name implies, the rubber-like elastic D-ring has a D-shaped or substantially D-shaped cross-section, and the outer peripheral surface that slidably contacts the inner surface of the cylinder has an arc-shaped or substantially arc-shaped cross-section. However, the inner peripheral portion has a rectangular or substantially rectangular cross section. Therefore, since the thickness (axial width) of the inner peripheral portion of the ring is larger than that of an O-ring having a circular or substantially circular cross section, the permeation distance through which the gas permeates can be set to a large extent, and the gas permeation hardly occurs. Become. Further, according to this D ring, it is possible to exert an effect also in preventing seal collapse due to low temperature embrittlement, that is, while the O ring easily twists in the mounting groove, the D ring does not easily collapse in the mounting groove and twists. Hateful. Therefore, it is possible to suppress the deterioration of the gas sealing property at low temperatures.

In addition, the slider slider made of resin is less likely to deteriorate in quality when contacted with oil as compared with the D ring made of a rubber-like elastic body. Therefore, since the slider seal seals the oil, the oil does not come into contact with the D ring, so that it is possible to prevent the D ring made of the rubber-like elastic body from coming into contact with the oil and deteriorating in quality. R.

Further, in the gas side seal portion, the D ring may be damaged by protruding into the gap between the piston and the cylinder, however, for this, a backup ring is arranged on the oil side of the D ring and this backup ring is used. By supporting the D ring, it is possible to suppress the protrusion. As for the backup ring, a backup ring may be arranged on the gas side of the slider seal and the backup ring may support the slider seal.

A resin slider seal may be provided with an asymmetric outer peripheral surface in the piston displacement direction so that a pressure gradient can be set for the contact surface pressure with respect to the inner surface of the cylinder. Since the local peak value is set for the surface pressure, it is possible to improve the sealing performance against oil. The pressure gradient (surface pressure gradient) is set by forming a taper or a step on the outer peripheral surface of the slider seal.

According to the present invention, as described above, in the piston seal structure provided in the piston type accumulator, there is provided a piston seal structure that suppresses deterioration of sealing performance due to gas permeation, twist of the seal, or deterioration of material. be able to.

Sectional drawing of the principal part of the piston type accumulator provided with the piston seal structure which concerns on the Example of this invention. (A) is an enlarged cross-sectional view of a main part of a gas-side seal part included in the piston seal structure, and (B) is an enlarged cross-sectional view of a main part of an oil-side seal part included in the piston seal structure. X direction arrow view in FIG. Sectional drawing of the principal part of the piston type accumulator which concerns on the other Example of this invention. View in the Y direction in FIG. Sectional drawing of the principal part of the piston type accumulator provided with the piston seal structure which concerns on a prior art example.

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a piston type accumulator 1 including a piston seal structure 11 according to an embodiment of the present invention. This piston type accumulator 1 is a cylinder (shell) 2 having a bottomed cylinder, in which a piston 3 is assembled so as to be displaceable in the axial direction (center axis direction, vertical direction in the figure). The space between the bottom surface portions (end wall portions) 2a of 2 is a gas chamber 4 for enclosing a gas (nitrogen gas, etc.) G, and the opposite side of the piston 3 is the oil O side of the pressure piping system. The piston 3 is displaced in the axial direction so that the pressure and the oil pressure are balanced. A gas injection port 5 is provided in the end wall portion 2a of the cylinder 2, and is closed by a gas plug 6 after the gas is injected. A retaining ring 7 for retaining the piston 3 is attached to the inner surface of the opening of the cylinder 2, and a screw-like connecting portion 8 for connecting the cylinder 2 to the pressure piping system is provided on the outer surface of the opening.

A piston seal structure 11 is provided on the outer peripheral portion of the piston 3 for sealing the gas G and the oil O, that is, the gas G sealed in the gas chamber 4 does not leak to the oil O side. The seal portion 21 is provided, and the oil side seal portion 31 is provided so that the oil O of the pressure piping system does not enter the gas chamber 4 side.

As shown in an enlarged view in FIG. 2(A), the gas-side seal portion 21 is made of a rubber-like elastic body such as HNBR rubber which is mounted in an annular mounting groove 9 (FIG. 1) provided on the outer peripheral surface of the piston 3. The D ring 22 is provided with a backup ring 23 made of a resin material such as PTFE on the oil O side of the D ring 22.

As the name implies, the D ring 22 is formed into a D-shaped or a substantially D-shaped cross section, and has an outer peripheral surface 22a having an arcuate cross section that slidably contacts the inner surface of the cylinder 2 and a linear (cylindrical) cross section. Since the peripheral surface 22b and the axially opposite end surfaces 22c and 22d, which are also linear in cross section (plane perpendicular to the axis), are provided, the D ring 22 has an outer peripheral portion 22e having a semicircular or substantially semicircular cross section and a rectangular or rectangular cross section. The inner peripheral portion 22f having a substantially rectangular shape has a shape combined in the radial direction. The backup ring 23 is formed into a rectangular or substantially rectangular cross section that is long in the radial direction.

On the other hand, as shown in an enlarged view in FIG. 2B, the oil-side seal portion 31 is made of a resin material such as PTFE that is mounted in the annular mounting groove 10 (FIG. 1) provided on the outer peripheral surface of the piston 3. A slider seal 32 is provided, and a back ring 33 made of a rubber-like elastic material such as HNBR rubber is arranged in parallel on the inner peripheral side of the slider seal 32.

The slider seal 32 includes an outer peripheral surface 32a slidably contacting the inner surface of the cylinder 2, an inner peripheral surface 32b having a linear cross section (cylindrical surface shape), and both axial ends having the same linear cross section (plane perpendicular to the axis). And surfaces 32c and 32d. Further, of these, the outer peripheral surface 32a has an asymmetrical shape in the piston displacement direction (axial direction, vertical direction in the drawing), whereby the slider seal 32 has a pressure gradient (contact pressure gradient) in the contact surface pressure with respect to the inner surface of the cylinder 2. Is set.

The asymmetrical shape described above is specifically configured as follows.

That is, the outer peripheral surface 32a of the slider seal 32 is provided with a large-diameter cylindrical portion 32e having a tapered surface shape whose outer diameter gradually increases from the gas G side to the oil O side. A small-diameter cylindrical portion 32g is provided on the oil O side through a step portion 32f. The large-diameter tubular portion 32e has a larger outer diameter dimension compared to the small-diameter tubular portion 32g, and conversely, the smaller-diameter tubular portion 32g has a smaller outer diameter dimension compared to the large-diameter tubular portion 32e. There is something. Therefore, with such a shape, the end portion of the large-diameter cylindrical portion 32e on the oil O side has a maximum outer diameter dimension, and the peak value of the pressure gradient described above is set here.

The back ring 33 made of a rubber-like elastic body is arranged on the inner peripheral side of the slider seal 32 and between the inner peripheral surface 32b of the slider seal 32 and the bottom surface of the mounting groove 10 in a compressed state. It is supported from the inner peripheral side and pressed against the inner surface of the cylinder 2. The cross-sectional shape of the back ring 33 is circular or substantially circular in view of the relationship of the filling rate with respect to the mounting groove 10 or the like, but may be other shapes, such as a rectangular or substantially rectangular cross-section, depending on the conditions.

In the piston seal structure 11 having the above configuration, the D ring 22 is mounted in the mounting groove 9 as the gas side seal portion 21, and the D ring 22 has a thickness of the inner peripheral portion 22f as compared with the O ring 58 having a substantially circular cross section ( Since the width in the axial direction) is large, it is possible to set a large permeation distance for the gas G to permeate and make it difficult for the gas G to permeate. Therefore, the gas impermeability can be improved, and the sealing property against the gas G can be maintained and improved.

Further, since the D ring 22 has a large contact area with the inner surface of the mounting groove 9 in the mounting groove 9, it is hard to fall down and twist. Therefore, the sealing property against the gas G can be maintained/improved even in a situation where brittleness due to low temperature is a concern.

Further, the slider seal 32 made of resin is less likely to deteriorate due to its material when it comes into contact with the oil O as compared with the D ring 22 made of a rubber-like elastic body. Therefore, since the slider seal 32 seals the oil O, the oil O does not come into contact with the D ring 22, so that the rubber-like elastic D ring 22 is prevented from coming into contact with the oil O and being deteriorated in quality. be able to.

Further, in the gas side seal portion 21, since the backup ring 23 is arranged in parallel on the oil O side of the D ring 22, it is possible to prevent the D ring 22 from protruding and being damaged in the gap between the piston 3 and the cylinder 2. You can

Further, since the slider seal 32 in the oil side seal portion 31 is provided with the outer peripheral surface 32a having an asymmetrical shape in the piston displacement direction, and thereby the pressure gradient is set in the contact surface pressure with respect to the inner surface of the cylinder 2, the inner surface of the cylinder 2 is formed. It is possible to set a local peak value for the contact surface pressure with respect to. Therefore, compared with the case where such a peak value does not exist, the sealability with respect to the oil O can be improved.

Further, as a specific shape of the asymmetric shape, a large-diameter cylindrical portion 32e having a tapered surface whose outer diameter size gradually increases from the gas G side to the oil O side is formed on the outer peripheral surface 32a of the slider seal 32. Since the small-diameter cylindrical portion 32g is provided on the oil O side of the large-diameter cylindrical portion 32e via the step portion 32f, the scraper action as described below is caused by such a shape and the pressure gradient based on the shape. Is demonstrated.

That is, when the piston 3 is displaced from the oil O side to the gas G side, an oil film is formed on the inner surface of the cylinder 2, while the slider seal 32 is disposed when the piston 3 is displaced from the gas G side to the oil O side. Scrapes and collects the oil film at the maximum outer diameter portion of the large-diameter cylindrical portion 32e. Therefore, the scraper action of the slider seal 32 is exerted there, and thus the sealability against the oil O can be improved.

In the accumulator 1 according to the above-described embodiment, as shown in FIG. 1, the outer end surface of the bottom surface portion 2a of the cylinder 2 is attached by a mounting jig (not shown) when the accumulator 1 is mounted at a mounting location. Since the mounting recess 41 for holding 1 is provided, the mounting jig is engaged with the mounting recess 41 and the accumulator 1 is held by the mounting jig, so that the mounting work can be performed smoothly and quickly. It is possible to do this.

As shown in FIG. 3, a plurality of mounting recesses 41 (four positions in the drawing) are equidistantly provided on the outer peripheral surface of the outer end surface of the bottom surface 2 a of the cylinder 2. Since each recess 41 is provided at the outer peripheral edge of the outer end surface of the bottom surface 2a of the cylinder 2, the recess 41 is open not only in one axial direction of the cylinder 2 but also outward in the radial direction of the cylinder 2.

Further, the mounting concave portion 41 may have a structure in which the mounting convex portion is provided by enlarging the formation angle and forming a relative convex portion.

4 and 5 show an example in which the mounting projection 42 is provided in this way, that is, a mounting jig (FIG. 4) is mounted on the outer end surface of the bottom surface 2a of the cylinder 2 when mounting the accumulator 1 at a mounting location. A mounting projection 42 for holding the accumulator 1 is provided by (not shown).

As shown in FIG. 5, a plurality of mounting projections 42 (four locations in the figure) are provided on the outer peripheral surface of the bottom surface 2 a of the cylinder 2 in an equal distribution. Since each convex portion 42 is provided on the outer peripheral edge portion of the outer end surface of the bottom surface portion 2a of the cylinder 2, it has a surface not only on one side in the axial direction of the cylinder 2 but also on the outside in the radial direction of the cylinder 2. There is.

In addition, according to the structure in which the mounting projection 42 is provided in this manner, the weight of the cylinder 2 is reduced because the cutting volume at the time of formation is larger than that in the structure in which the mounting recess 41 is provided. Can be changed). The mounting projection 42 may be formed by forging instead of cutting.

1 Accumulator 2 Cylinder 2a Bottom part 3 Piston 4 Gas chamber 5 Gas injection port 6 Gas plug 7 Retaining ring 8 Connection part 9,10 Mounting groove 11 Piston seal structure 21 Gas side seal part 22 D ring 22a, 32a Outer peripheral surface 22b, 32b Inner peripheral surface 22c, 22d, 32c, 32d End surface 22e Outer peripheral portion 22f Inner peripheral portion 23 Backup ring 31 Oil side seal portion 32 Slider seal 32e Large diameter tubular portion 32f Step portion 32g Small diameter tubular portion 33 Back ring 41 For mounting Recess 42 Convex for mounting G gas O oil

Claims (3)

A piston seal structure provided in a piston type accumulator in which a piston is displaced inside a cylinder, in a piston seal structure in which a gas side seal portion and an oil side seal portion are arranged side by side on an outer peripheral portion of the piston,
The gas side seal portion includes a rubber-like elastic D ring having an outer peripheral surface having an arcuate cross-section that slidably contacts the inner surface of the cylinder.
The oil-side seal portion includes a resin slider seal having an outer peripheral surface that slidably contacts the inner surface of the cylinder, and a rubber-like elastic back ring arranged on the inner peripheral side of the slider seal. Prepare ,
On the outer peripheral surface of the slider seal, a large-diameter cylindrical portion having a tapered surface whose outer diameter gradually increases from the gas side to the oil side is provided,
A step portion is provided on the oil side of the large-diameter tubular portion,
A piston seal structure for a piston type accumulator, characterized in that a small-diameter cylindrical portion having an outer diameter dimension smaller than that of the large-diameter cylindrical portion is provided on the oil side of the stepped portion . The piston seal structure according to claim 1,
The piston seal structure of the piston type accumulator, wherein the gas side seal portion includes a backup ring arranged on the oil side of the D ring. The piston seal structure according to claim 1 or 2,
Before Symbol slider seal, piston seal structure of a piston-type accumulator and setting a pressure gradient in the contact surface pressure against the inner surface of the cylinder by the piston displacement direction comprises an outer circumferential surface of asymmetrical shape.

Images