JP2011144934A - Sealing structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sealing device superior in both of sealability and wear resistance in regard to the sealing device sealing a gap between two members functioning such that a shaft member and a passage member surrounding its outer periphery relatively reciprocate. <P>SOLUTION: A cut surface of an annular body 71b comprising one part of a rod packing (the sealing device) has a form of projecting one part of a face (a sliding face) S abutting on an outer peripheral surface of a piston (a rod part) toward the outer peripheral surface of the rod part of rectangular shapes with thickness direction lengths of a size H and radial lengths of a size T. A projection formed on the sliding face S has a slope S2 and a slope S3 of different tilt angles on both of its skirts. Of both side walls of an annular groove attached with the annular body 71b, a chamfering part (a slope) S4 is formed on a boundary of the sliding face S and a side face (an atmosphere side face) W of the annular body 71b facing the side wall hitting an opening end side of a hydraulic cylinder. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a shaft member and a passage member that surrounds the outer periphery of the shaft member, and in particular, to a sealing device that seals a gap between both members that functions so that either one member reciprocates with respect to the other member. .

  Conventionally applied to hydraulic cylinders of construction machines such as bulldozers and transport vehicles such as forklifts, etc., and sealing the gap between the piston and cylinder type outer shell (hereinafter simply referred to as cylinder) prevents hydraulic oil leakage Sealing devices for doing this are known.

  Usually, in a sealing device used for such an application, sufficient sealing performance (sealing performance) is ensured between the members to be sealed, and the piston (cylinder) reciprocates with respect to the cylinder (piston). At this time, it is required that the sliding resistance generated between the two members is sufficiently low, and that it has sufficient durability against friction and the like.

  FIG. 10 is a cross-sectional view showing an example of a sealing structure of a hydraulic cylinder to which this type of sealing device is attached.

  As shown in FIG. 10, the sealing device 301 has an annular appearance as a whole, and includes an outer peripheral surface of a piston 302 that reciprocates along the axial direction, and an inner peripheral surface of a cylinder 303 that surrounds the outer periphery of the piston 302. Is attached to an annular groove formed on the inner peripheral surface of the cylinder 303 in order to seal the gap formed between the two. When applied to a sealing structure as shown in the figure, the outer peripheral surface of the sealing device 301 is in close contact with the groove bottom of the annular groove, and the inner peripheral surface is slidable with respect to the inner peripheral surface (opposing surface) of the piston 302. It will contact | abut.

  FIG. 11 is a schematic diagram schematically illustrating the structure and function of an example of a conventional sealing device applied to such a sealing structure.

  The sealing device shown in FIG. 11 is known as a so-called U-packing. The U packing 311 is an annular body that is usually formed of an elastic material such as rubber and has a U-shaped cross section. The U-packing 311 is easy to ensure a suitable contact pressure distribution with the mating member (piston 312) and has excellent sealing properties due to the characteristics of the shape and material.

  However, in this type of sealing device (U-packing), when the relative operation between the cylinder and the piston is increased in speed, poor lubrication tends to occur, and the friction between both members tends to increase. Such poor lubrication has led to an increase in the wet sliding resistance, particularly under high pressure conditions, and deteriorates the operability of the hydraulic cylinder.

Therefore, as shown in FIGS. 12A and 12B, a sealing device 311 ′ and a sealing device 311 ″ having a two-layered annular structure (double structure) are also considered. In other words, by forming a member (sliding contact member) on the side in sliding contact with the facing surface from a resin material such as, for example, ethylene tetrafluoride (PTFE), the wear resistance of the sealing device is increased and sliding on the facing surface is performed. Reduce resistance. On the other hand, by forming the member that contacts the groove bottom with a material having sufficient elastic force such as rubber, a certain contact pressure is secured between the sliding contact member and the opposing surface. .

  However, according to the sealing device having the double structure (FIGS. 12A and 12B), the wear resistance of the device itself is improved under high pressure conditions and at high speed operation, and the sliding resistance with respect to the facing surface is reduced. However, it was difficult to avoid a decrease in sealing performance.

  The present invention has been made in view of such circumstances, and the object of the present invention is between the two members functioning so that the shaft member and the passage member surrounding the outer periphery thereof relatively reciprocate. An object of the present invention is to provide a sealing device that seals a gap and is excellent in both sealing performance and wear resistance.

  In order to achieve the above object, the invention described in claim 1 is any one of an outer peripheral surface of a shaft member reciprocating in an axial direction and an inner peripheral surface of a passage member surrounding the outer periphery of the reciprocating shaft member. In a sealing device that is attached to an annular groove formed on one of the peripheral surfaces and seals a gap between the outer peripheral surface of the shaft member and the inner peripheral surface of the passage member, it slides on the opposing peripheral surface of the annular groove. The gist of the invention is that it includes an annular resin member having a sliding surface that comes into contact, and the sliding surface of the annular resin member has a convex portion biased along the axial direction.

  The reciprocating operation in the axial direction by the shaft member means a relative operation with respect to the passage member. That is, the reciprocating motion includes an operation by the passage along the axial direction of the shaft member.

  According to the said structure, the abrasion resistance improvement of a sealing device itself obtained by applying the structure which slides the cyclic | annular resin member which has moderate hardness and elasticity together with the other member in a sealing part, and sliding resistance The effect of reducing the pressure and the sealing performance are compatible at a high level.

  In particular, at this time, the partition between the space filled with the relatively high pressure fluid and the space filled with the low pressure fluid is partitioned by the sealing device, and the configuration in which the convex portion is biased toward the high pressure space is applied. Thus, the fluid filled in the high pressure space is suitably held (sealed) in the high pressure space.

  The gist of the invention according to claim 2 is that, in the sealing device according to claim 1, the convex portion forms inclined surfaces having different inclination angles at both hems thereof.

  According to this configuration, the sealing performance required for the sealing device can be easily obtained from the relationship between the inclination angles of both slopes formed at both hems of the convex portion. Moreover, adjustment and member processing for obtaining desired sealing performance can be easily performed.

  In particular, at this time, the boundary between the space filled with the relatively high pressure fluid and the space filled with the low pressure fluid is partitioned by the sealing device, and the convex portion is formed on the skirt facing the high pressure space side. By applying the configuration in which the inclined surface is relatively enlarged, the fluid filled in the high pressure space is suitably held (sealed) in the high pressure space.

  According to a third aspect of the present invention, in the sealing device according to the second aspect, the annular resin member is a side surface facing a side wall of the annular groove, and is smaller than both hems of the convex portion. The gist is that the boundary between the side surface on the hem side where the inclined surface having the inclined angle is formed and the sliding surface is chamfered.

  According to this configuration, even if the reciprocating motion of the shaft member is in a high speed state under high pressure conditions, the protrusion of the annular resin member from the annular groove is suitably suppressed.

  According to a fourth aspect of the present invention, in the sealing device according to the second or third aspect, the annular resin member is a side surface opposed to a side wall of the annular groove, and among both hems of the convex portion, The gist is to have a flat surface that is substantially parallel to the axial direction from the side surface on the skirt side where a slope with a larger inclination angle is formed to the base end of the skirt side.

  According to the same configuration, when a predetermined pressure is applied to the space sandwiched between the slope with the larger inclination angle and the flat surface, the pressure appropriately presses the slope, The shape of the convex portion is suitably held. And since the shape of a convex part is stabilized, the surface pressure distribution received from the opposing surface is kept constant for the convex part, and the sealing performance between both (the convex part and the opposing surface) is improved.

  According to a fifth aspect of the present invention, in the sealing device according to any one of the first to fourth aspects, the resin member is provided around the groove bottom of the annular groove, and the resin member is slid from the groove bottom. The gist of the present invention is to further include an annular elastic member that is biased in a direction toward the surface.

  According to this configuration, a sufficient and stable sealing performance in the annular groove (side) is ensured, while a sufficient urging force toward the opposed peripheral surface of the annular groove is easily obtained for the annular resin member. Be able to.

  According to the first aspect of the present invention, the wear resistance of the sealing device itself obtained by applying a configuration in which an annular resin member having both appropriate hardness and elasticity is slid with the mating member at the sealing portion is improved. The effect of reducing sliding resistance and the sealing performance are compatible at a high level.

  According to the second aspect of the present invention, the sealing performance required for the sealing device can be easily obtained from the relationship between the inclination angles of the two slopes formed at both hems of the convex portion. In addition, adjustment and member processing for obtaining desired sealing performance can be easily performed.

  According to the invention described in claim 3, even if the reciprocating motion of the shaft member is in a high speed state or under a high pressure condition, the protrusion of the annular resin member from the annular groove is suitably suppressed. .

  According to the invention described in claim 4, when the shape of the convex portion is stabilized, the surface pressure distribution received from the opposing surface is kept constant for the convex portion, and between the two (the convex portion and the opposing surface). The sealing performance in the case is improved.

  According to the fifth aspect of the present invention, sufficient sealing performance in the annular groove is ensured, while a sufficient biasing force toward the opposed peripheral surface of the annular groove can be easily obtained for the annular resin member. become.

The perspective view etc. which show schematically the external appearance and internal structure about one Embodiment which applied the sealing device of this invention to the rod packing of the cylinder for hydraulic drive. Sectional drawing which shows the shape of the cut surface obtained by cut | disconnecting the rod packing of the embodiment along the radial direction. The figure which shows typically the sealing structure formed with the rod packing of the embodiment. Sectional drawing etc. which expand and show the shape of the cut surface about the annular body which makes a part of rod packing of the embodiment. Explanatory drawing which shows schematically the apparatus and experimental content which were used for the 1st verification experiment for verifying the sealing function obtained by the embodiment. The graph which shows transition of the amount of oil leaks according to the continuous reciprocation operation | movement by a hydraulic cylinder about each of the rod packing of the same embodiment, and the conventional apparatus. The graph which shows the change of the sliding resistance according to the oil_pressure | hydraulic provided to the oil_pressure | hydraulic space sealed about each of the rod packing of the same embodiment, and the conventional apparatus. The graph shown about each of the rod packing of this Embodiment, and the conventional apparatus. 1 is a cross-sectional view schematically showing an embodiment in which a sealing device of the present invention is applied to a piston packing such as a hydraulic piston. Sectional drawing which shows schematically the modification of one Embodiment which applied the sealing device of this invention to the rod packing of the hydraulic cylinder. Sectional drawing which shows schematically the sealing structure formed by the conventional sealing device and the sealing device. The schematic diagram explaining the structure and function roughly about an example of the conventional sealing device. Sectional drawing which shows schematically an example of the conventional sealing device which has a two-layered cyclic structure.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be exemplarily described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified. .

  Hereinafter, an embodiment in which a sealing device of the present invention is applied to a rod packing attached to a hydraulic drive cylinder of a construction machine will be described with reference to the drawings.

  FIG. 1 (a) is a perspective view schematically showing a part of the external appearance and internal structure of the hydraulic drive cylinder according to the present embodiment, and FIG. 1 (b) is a view of the hydraulic drive piston. 1 is a schematic diagram showing a side cross section along with a propagation path of hydraulic oil.

  As shown in FIGS. 1 (a) and 1 (b), a hydraulic drive cylinder (hereinafter referred to as a hydraulic cylinder) 100 is roughly a cylinder type outer shell (hereinafter referred to as a cylinder) that forms a bottomed cylindrical passage 11. ) 10 and a piston 20 that reciprocates along the passage 11. The part accommodated in the passage 11 in the cylinder 10 as a part of the piston 20 has a cylindrical rod portion 20a and an outer diameter slightly larger than the rod portion 20a, which is screwed to the outer periphery of the rod portion 20a. And this also forms the plunger part 20b which makes a cylindrical shape.

  Further, as shown in detail in FIG. 1B, the passage 11 includes a plunger sliding portion 11b having an inner peripheral surface adjacent to the bottom portion 11a and having substantially the same diameter (a slightly larger diameter) as the outer periphery of the plunger portion 20b, and an opening. It consists of the rod sliding part 11c which adjoins the end 11d, and has an inner peripheral surface of the same diameter (slightly larger diameter) as the outer periphery of the rod part 20a.

  The cylinder 10 is provided with oil holes 12 and 13 that allow the inner peripheral surface thereof to communicate with the outside, and high-pressure hydraulic oil is sent into and out of the cylinder 10 from the outside through the oil holes 12 and 13. . Also, the internal space α of the cylinder 10 communicating with the oil hole 12 and the internal space β of the cylinder 10 communicating with the oil hole 13 (the gap between the inner peripheral surface of the cylinder 10 and the outer peripheral surface of the rod portion 20a) are the plunger. It is partitioned off by the part 20b.

That is, by appropriately adjusting the hydraulic pressure of the hydraulic oil sent and received through the oil hole 12 and the oil hole 13, the piston 20 main body reciprocates in the direction of the arrow X, and its behavior is freely controlled.

  Annular grooves 30, 40, 50 having a rectangular cross-sectional shape are formed around the outer peripheral surface of the plunger portion 20b. The annular grooves 30, 40, 50 are respectively provided with a wear ring 31, a piston packing 41, and a contamination. A seal 51 is attached. The wear ring 31 has a function as a bearing exclusively, such as suppressing eccentricity of the piston 20. The piston packing 41 has a function of restricting the propagation of hydraulic oil between the internal space α and the internal space β and maintaining a sealed state between the spaces α and β. The contamination seal 51 prevents, for example, metal powder mixed in the working oil from entering the gap between the outer peripheral surface of the plunger portion 20 b and the inner peripheral surface of the cylinder 10.

  In addition, annular grooves 60, 70, 80 having a rectangular cross-sectional shape are formed around the inner peripheral surface of the rod sliding portion 11c, and each of the annular grooves 60, 70, 80 has a dust seal 61, A rod packing 71 and a buffer ring 81 are attached. The dust seal 60 prevents foreign matter from entering the cylinder 10 from the outside. The rod packing 71 has a function of maintaining a sealed state between the internal space β and the outside and preventing leakage of hydraulic oil to the outside. The buffer ring 81 protects the rod packing 71 by buffering the impact pressure or the fluctuating pressure of the hydraulic oil filled in the internal space β or the propagation of heat of the hydraulic oil at a high temperature.

  Here, the function of the rod packing 71 mounted in the annular groove 70 of the rod sliding portion 11c will be described in detail.

  In FIG. 2, the shape of the cut surface obtained by cut | disconnecting the rod packing 71 single-piece | unit which has a ring shape along the radial direction is shown.

  As shown in FIG. 2, the rod packing 71 includes a rubber O-ring 71a and an annular body 71b made of ethylene tetrafluoride (PTFE) resin having an outer diameter substantially equal to the inner diameter of the O-ring 71a. It is formed in close contact with. The cross-sectional shape of the O-ring 71a is almost a perfect circle, and the outer diameter of the true circle is substantially equivalent to the groove width H of the annular groove 71 (shown by a broken line) in which the rod packing 71 is mounted (from the groove width H). Slightly small). On the other hand, the cross-sectional shape of the annular body 71b formed in close contact with the inner side (inner circumference) of the O-ring has a thickness in the axial direction (reciprocating direction of the piston 10) substantially equal to the groove width H (slightly larger than the groove width H). (Small) Basically, it has a rectangular shape and has a convex shape whose inner peripheral surface is biased along the axial direction.

  In the rod packing 71 having such a double structure, the rod packing 71 incorporated in the annular groove 70 is shown in FIG. 3A and FIG. That is, a part of the inner peripheral surface of the annular body 71b having a convex shape biased along the axial direction protrudes from the inner peripheral surface of the rod sliding portion 11c (FIG. 3A). . When the piston 20 is attached to the passage 11 in the cylinder 10, the outer peripheral surface of the rod portion 20a comes into contact with the inner peripheral surface of the annular body 71b and presses this, thereby being relatively elastic compared to the annular body 71b. Large O-ring 71a bends. Thus, the entire rod packing 71 is pushed into the annular groove 70, and the mounting of the rod packing 71 to the hydraulic cylinder 100 is completed. That is, a sealing structure that seals the hydraulic oil filled in the internal space β from the outside between the rod portion 20a and the rod sliding portion 11c is constructed (FIG. 3B).

  Next, the PTFE resin-made annular body 71b forming a part of the rod packing 71 will be described in detail.

FIG. 4A shows an enlarged view of the shape of the cut surface obtained by cutting the annular body 71b along the radial direction. In addition, the arrow P shown for convenience in the drawing corresponds to the radial direction of the annular body 71b, and the arrow Q corresponds to a direction orthogonal to the arrow P. Incidentally, in the state where the rod packing 71 (annular body 71b) is mounted on the hydraulic cylinder 100, the arrow Q is the reciprocating direction (axial direction) of the piston 10 in the same manner as the arrow X shown in FIG. Will be shown. Hereinafter, the arrow Q (X) direction is referred to as the thickness direction, and the arrow P direction is referred to as the radial direction.

  As shown in FIG. 4 (a), the cut surface of the annular body 71b has an outer periphery of the piston 20 (rod portion 20a) in a rectangular shape having a length H in the thickness direction and a dimension T in the radial direction. A part of a surface (hereinafter referred to as a sliding surface) S that is in contact with the surface protrudes toward the outer peripheral surface of the rod portion 20a.

  That is, of the sliding surface S, the surface S1 closest to the internal space β (see FIG. 1) of the passage 11 along the thickness direction X is formed so as to be substantially parallel to the outer peripheral surface (axial direction) of the rod portion 20a. The bumps (convex portions) adjacent to the same surface S1 are formed by the slope S2 and the slope S3. In other words, the inclined surface S2 and the inclined surface S3 form both hems of the convex portion, while the surface S1 is the side surface of the annular body 71b that faces the side wall of the annular groove 70 on the side of the internal space β in the hydraulic cylinder 100. A flat surface that is substantially parallel to the axial direction of the rod portion 29a is formed from the (hydraulic side surface) I to the base end of the slope (the skirt of the convex portion) S2.

  Incidentally, FIG. 4B shows the contact pressure that the sliding surface S receives from the opposing surface (the outer peripheral surface of the rod portion 20a) when the annular body 71b is mounted on the hydraulic cylinder 100 as a part of the rod packing 71. It is a distribution map which shows distribution on the same scale along the same axial direction (thickness direction) X as Fig.4 (a).

  As shown in FIG. 4B, the highest contact pressure P on the sliding surface S is at the top of the convex portion corresponding to the boundary between the slope S2 and the slope S3, and as the distance from the top increases. The contact pressure P will decrease. At this time, if the annular body is formed of a material having appropriate elasticity and hardness (for example, PTFE resin), the maximum value (dP / dX) max, p of the contact pressure gradient received by the slope S2 and the slope S3 It has been confirmed by the inventor that the maximum value (dP / dX) max, m of the contact pressure gradient to be received is approximately determined by the inclination angle of the slope S2 and the slope S3 with respect to the opposing surface (rod portion 20a).

  For example, when a space (hydraulic side space) filled with oil of a predetermined hydraulic pressure is sealed from the outside (atmosphere side space) by a so-called reciprocating seal at the periphery of the shaft member, the oil sealing performance by the reciprocating seal is , Determined by the difference between the contact pressure gradient (absolute value) that the seal body receives from the outer peripheral surface of the shaft member in the hydraulic side space and the contact pressure gradient (absolute value) that the seal body receives from the peripheral surface of the shaft member in the atmosphere side space It is generally known that

  That is, by applying a cross-sectional shape such as that of the annular body 71b, it is possible to easily obtain a desired sealing performance by adjusting the inclination angle of the inclined surface S2 and the opposed surface of the inclined surface S2. Incidentally, the optimum inclination angle of the slopes S2 and S3 depends on the hydraulic pressure applied to the hydraulic oil in the internal space β, the characteristics of the hydraulic oil, and the like, but the rod packing 71 attached to the hydraulic cylinder 100 in the present embodiment. As described above, by setting the inclination angle C of the slope S2 to about 8 ± 2 ° and the inclination angle d of the slope S3 to about 45 ± 2 °, an oil film formed between the sliding surface S and the rod portion 20a. Was kept in a sufficiently thin state, and it was confirmed that the optimum sealing state of the hydraulic oil was secured.

  Similarly, it is confirmed that the dimension b corresponding to the protrusion of the sliding surface S (height of the convex portion) is preferably set to about 25 to 35% of the radial length (dimension) T of the annular body 71b. It was done.

  Similarly, it was confirmed that the thickness direction length (dimension) a of the slope S2 is preferably set to about 15 to 20% of the thickness direction length (dimension) H of the annular body 71b main body.

  Further, of both side walls of the annular groove 70 to which the annular body 71b is mounted, at the boundary between the side surface (atmosphere side surface) W of the annular body 71b facing the side wall corresponding to the opening end side of the hydraulic cylinder 100 and the sliding surface S. A chamfered portion (slope) S4 is formed. By forming such a chamfered portion on the atmosphere side (reverse pressure side) side surface of the annular body 71b, even if a high pressure hydraulic pressure is applied to the internal space β, the annular body 71b from the annular groove 70 is provided. Protrusion of the ink is suitably suppressed.

  Further, when the rod portion 20a reciprocates in the hydraulic cylinder 100, the hydraulic pressure of the hydraulic oil filled in the space sandwiched between the flat surface S1 and the inclined surface S2 presses the inclined surface S2 appropriately. And the shape of the convex part formed by slope S3 will be held suitably. And since the shape of a convex part is stabilized, distribution of the surface pressure which the convex part receives from the outer peripheral surface of the rod part 20a is also kept constant, and the sealing performance between both improves.

  The radial length (dimension) T of the annular body 71b is determined by the distance A from the annular groove 70 schematically shown in FIG. 4C to the outer peripheral surface of the rod portion 20a and the characteristic (elasticity) of the O-ring 71a. Setting based on the relationship secures an optimum crushing amount when the rod packing 71 is mounted on the hydraulic cylinder 100, and maintains a stable surface pressure between the sliding surface S and the rod portion 20a. preferable. Incidentally, in this embodiment, it was confirmed that it is optimal to set the dimension T to about 40 to 50% of the distance A.

The length (dimension) H in the thickness direction of the annular body 71b is set to about 90 to 95% (a value slightly smaller than the groove width B) of the groove width B of the annular groove 70 shown in FIG. Is preferred. That is, by ensuring such a relationship between the thickness direction length H of the annular body 71b and the groove width of the annular groove 70, the annular body 71b is sufficiently affected even when hydraulic pressure is applied to the internal space β. Stable stability can be maintained. If the behavior of the annular body 71b is sufficiently stable in a state where hydraulic pressure is applied to the internal space β, a constant surface pressure distribution is secured on the sliding surface S, and the sliding surface S and the rod portion are secured. This is because the sealing performance between 20a is also stabilized.
(Verification test)
A verification experiment was performed to compare the sealing performance obtained when the rod packing 71 according to the present embodiment was applied as a sealing device for a hydraulic drive cylinder with that of a conventional sealing device.

  FIG. 5 is an explanatory diagram schematically showing the apparatus used in the first verification experiment and the contents of the experiment. As shown in the figure, the test apparatus 200 used in the first verification experiment is a reciprocating motion housed in an annular groove at the periphery of a shaft member (rod portion) 220, similar to the hydraulic cylinder 100 shown in FIG. A space (hydraulic side space) γ filled with oil of a predetermined hydraulic pressure is sealed from the outside (atmosphere side space) using a seal (sealing device).

  In the first verification test, when the rod part 220 is continuously reciprocated at an operation speed (sliding speed) of 0.15 m / sec, the amount of oil leakage (accumulation amount) corresponding to the integrated distance for the operation. ) Was measured.

  FIG. 6 shows, as a result of the first verification test, the transition of oil leakage amount (●) observed when the rod packing 71 according to the present embodiment is applied, and the previous FIG. 12B. It is a graph which shows together the transition ((circle)) of the amount of oil leaks seen when applying the conventional sealing device which was applied on the same axis | shaft (integrated distance).

As shown in FIG. 6, when the conventional sealing device is applied, the leakage amount increases as the sliding distance increases. However, when the rod packing 71 according to the present embodiment is applied, the integrated distance is set. Even when the rod part 220 is operated for 50 km or more, it was revealed that almost no oil leakage occurred.

  Next, the second verification test will be described.

  In the first verification test described above, the rod portion was continuously reciprocated at a predetermined operation speed (sliding speed), and the amount of oil leakage (integrated amount) corresponding to the integrated distance required for the operation was measured. On the other hand, in the second verification test, the rod portion is similarly reciprocated at a predetermined operating speed (sliding speed), and the hydraulic pressure applied to the hydraulic side space γ is changed, so that the outer periphery of the sealing device and the rod portion is changed. How the sliding resistance with respect to the surface changes varies when the rod packing (sealing device) 71 in the present embodiment is applied and the conventional sealing device (U packing) shown in FIG. And the results were compared with each other. In addition, the test apparatus 200 (FIG. 5) similar to the 1st verification test was used also for the 2nd verification test.

  FIG. 7 shows the change in sliding resistance observed when the rod packing 71 according to the present embodiment is applied as a result of the second verification test, and the conventional sealing device shown in FIG. It is a graph which shows the change of the sliding resistance seen in the case of applying together on the same axis | shaft (magnitude | size of hydraulic pressure).

  As shown in FIG. 7, when the conventional sealing device is applied, the sliding resistance increases as the hydraulic pressure applied to the hydraulic side space γ increases. However, the rod packing 71 according to the present embodiment is applied. In this case, it became clear that even when a hydraulic pressure of 20 MPa or more was applied to the hydraulic side space γ, the sliding resistance hardly increased.

  That is, in a sealing structure using a conventional sealing device (see FIGS. 12 (a) and 12 (b)) in which an elastic body and a resin member are combined, the wear resistance of the sealing device itself is improved, and the sliding at the sealing portion is performed. While the function of reducing dynamic resistance is achieved, it has been difficult to obtain sufficient sealing performance.

  Similarly, a sealing structure using a so-called U-packing (see FIG. 11) can obtain a sufficient sealing property under normal use conditions. However, poor lubrication occurs particularly when used under high pressure and high speed conditions. It was easy to wear the sealing device itself. Furthermore, as described above in the prior art, such poor lubrication promotes an increase in sliding resistance and deteriorates the operability of the hydraulic cylinder under high pressure conditions.

  In this regard, the rod packing 71 according to the present embodiment is employed to seal a space (hydraulic side space) filled with oil of a predetermined hydraulic pressure from the outside (atmosphere side space), for example, at the periphery of the shaft member rod portion. If the structure for this is constructed | assembled, various functions, such as improvement of the abrasion resistance of sealing device itself, reduction of the sliding resistance in a seal | sticker site | part, and the improvement of sealing performance, can be made compatible at a high level now.

In the present embodiment, an annular ring is provided around the inner peripheral surface of the rod sliding portion 11c to seal the hydraulic oil filled in the internal space β from the outside in the gap between the rod portion 20a and the rod sliding portion 11c. The sealing device of the present invention was applied to the sealing device (rod packing 71) mounted in the groove (see FIG. 1 and the like). Not limited to this, as shown in FIGS. 1 and 8, for example, the hydraulic oil filled in the internal space α and the hydraulic oil filled in the internal space β are sealed from each other in the gap between the plunger portion 20 b and the cylinder 10. The present invention may be applied to the piston packing 41 as a sealing device. That is, one of the outer peripheral surfaces of the outer peripheral surface of a shaft member (for example, a piston or a rod) that reciprocates in the axial direction and the inner peripheral surface of a passage member (for example, a cylinder) that surrounds the outer periphery of the reciprocating shaft member. If it is a sealing device that is attached to an annular groove formed on the circumference and seals the gap between the outer peripheral surface of the coaxial member and the inner peripheral surface of the passage member, the boundary between the two spaces filled with oil is sealed. The sealing device of the present invention can be applied regardless of whether it is to seal the boundary between two spaces filled with oil on one side and gas on the other side. In addition, even when an annular groove is formed around the outer peripheral surface of the shaft member and a sealing device is attached to the annular groove, an annular groove is formed around the inner peripheral surface of the passage member and the sealing device is attached to the annular groove. Even in this case, by applying the sealing device of the present invention, an effect equivalent to or equivalent to the present embodiment can be obtained.

  For example, as shown in FIG. 9A as a cross-sectional shape, the slopes S2 and S3 of the convex portions formed on the sliding surface S of the annular body 71b may be curved surfaces. Further, as shown in FIG. 9B, the sliding surface S of the annular body 71b is not provided with a surface S1 (see FIG. 4) substantially parallel to the outer peripheral surface of the rod portion or a chamfered portion S4. An effect similar to that of the embodiment can be achieved.

  Further, if a plurality of sealing devices having the same structure as the rod packing 71 employed in the present embodiment are attached in parallel to the outer peripheral surface (annular groove) of the shaft member or the inner peripheral surface of the passage member, one layer can be obtained. High sealing performance can also be obtained.

  In this embodiment, the PTFE resin is used as the material of the annular body 71b. However, other resin materials having appropriate elasticity and hardness, such as PFA, ETFE, POM, PBT, etc. are used. Also good.

  Moreover, it is preferable that a filler is mixed in these resin materials including the PTFE resin so as to enhance the pressure resistance and wear resistance of the annular body.

  Further, the cross-sectional shape of the O-ring 71a is not limited to a perfect circle shape, and may be another shape such as an ellipse, a polygon, an X shape, or the like. In addition, for example, nitrile rubber, hydrogenated nitrile rubber, fluororubber, etc. (various rubber-like elasticity with sufficient elasticity, heat resistance, and chemical resistance (oil resistance), such as nitrile rubber) By adopting a material, an effect equivalent to or equivalent to the present embodiment can be obtained.

10 Cylinder type outer shell (cylinder)
11 passage 11a bottom part 11b plunger sliding part 11c rod sliding part 11d open end 12, 13 oil hole 20 piston 20a rod part 20b plunger part 30, 40, 50, 60, 70, 80 annular groove 31 wear ring 41 piston packing 51 Contamination seal 61 Dust seal 71 Rod packing 71a O-ring 71b (made of resin) annular body 81 Buffer ring 100 Hydraulic drive cylinder (hydraulic cylinder)
200 Test apparatus α, β Internal space S Sliding surface S (S2, S3) Slope S (S4) Chamfered portion W Side surface (atmosphere side surface)

Claims (5)

Of the outer peripheral surface of the shaft member that reciprocates in the axial direction and the inner peripheral surface of the passage member that surrounds the outer periphery of the reciprocating shaft member, it is attached to an annular groove formed on one of the peripheral surfaces, In a sealing device for sealing a gap between the outer peripheral surface of the shaft member and the inner peripheral surface of the passage member,
An annular resin member having a sliding surface in sliding contact with the opposing circumferential surface of the annular groove;
And the sliding surface of the said cyclic | annular resin member has a convex part biased along the said axial direction, The sealing device characterized by the above-mentioned. The sealing device according to claim 1.
The said convex part forms the slope of a different inclination angle in the both skirts, The sealing device characterized by the above-mentioned.   The annular resin member includes a side surface facing a side wall of the annular groove, a side surface on a hem side where a slope having a smaller inclination angle is formed, and the sliding surface. The sealing device according to claim 2, wherein the boundary between and is chamfered.   The annular resin member is a side surface facing the side wall of the annular groove, and a base end of the skirt from a side surface on the skirt side where a slope with a larger inclination angle is formed among both hems of the convex portion. The sealing device according to claim 2, further comprising a flat surface substantially parallel to the axial direction. In the sealing device according to any one of claims 1 to 4,
A sealing device further comprising an annular elastic member that is provided around the groove bottom of the annular groove and biases the resin member in a direction from the groove bottom toward the sliding surface.

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