U.S. patent application number 13/509503 was filed with the patent office on 2012-09-06 for seal structure of fluid device.
This patent application is currently assigned to IHI Corporation. Invention is credited to Eiji Hosoi, Hiroyuki Ochiai, Hifumi Tabata, Mitsutoshi Watanabe, Nobuhiko Yunoki.
Application Number | 20120224962 13/509503 |
Document ID | / |
Family ID | 43991708 |
Filed Date | 2012-09-06 |
United States Patent
Application |
20120224962 |
Kind Code |
A1 |
Tabata; Hifumi ; et
al. |
September 6, 2012 |
SEAL STRUCTURE OF FLUID DEVICE
Abstract
A seal structure includes: first and second members defining a
hollow internal area of a fluid device; and a seal member fixed to
the first member for sealing a gap between the first and second
members. The seal member includes a sliding contact member being in
sliding contact with a surface of the second member and formed of a
resin. The second member includes a resin layer and a resin layer
holding structure. The resin layer is formed by sliding the second
member on the sliding contact member to transfer the resin forming
the sliding contact member onto a sliding contact portion of the
surface of the second member at which the second member comes into
contact with the sliding contact member. The resin layer holding
structure is a porous film formed by electric discharge surface
treatment and holds the resin layer in the sliding contact
portion.
Inventors: |
Tabata; Hifumi; (Tokyo,
JP) ; Yunoki; Nobuhiko; (Tokyo, JP) ;
Watanabe; Mitsutoshi; (Tokyo, JP) ; Ochiai;
Hiroyuki; (Tokyo, JP) ; Hosoi; Eiji; (Tokyo,
JP) |
Assignee: |
IHI Corporation
Tokyo
JP
|
Family ID: |
43991708 |
Appl. No.: |
13/509503 |
Filed: |
November 12, 2010 |
PCT Filed: |
November 12, 2010 |
PCT NO: |
PCT/JP2010/070182 |
371 Date: |
May 11, 2012 |
Current U.S.
Class: |
415/230 ;
277/345; 277/549; 92/165R |
Current CPC
Class: |
F16J 15/328 20130101;
B29L 2031/26 20130101; F15B 2215/305 20130101; B29D 99/0053
20130101; F16J 15/324 20130101; C23C 26/00 20130101; C23C 4/12
20130101; C23C 4/18 20130101; F15B 15/1461 20130101; F16J 15/162
20130101; Y10T 29/49281 20150115; Y10T 29/49297 20150115 |
Class at
Publication: |
415/230 ;
92/165.R; 277/345; 277/549 |
International
Class: |
F04D 29/10 20060101
F04D029/10; F16J 15/16 20060101 F16J015/16; F16J 15/32 20060101
F16J015/32; F16J 15/18 20060101 F16J015/18 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 13, 2009 |
JP |
2009-260169 |
Claims
1. A seal structure of a fluid device comprising: a first member
defining a hollow internal area of the fluid device; a second
member defining the internal area together with the first member
and being movable relative to the first member; and a seal member
fixed to the first member and configured to seal a gap between the
first member and the second member, wherein the seal member
includes a sliding contact member being in sliding contact with a
surface of the second member and formed of a resin, the second
member includes a resin layer and a resin layer holding structure
in a sliding contact portion of the surface of the second member at
which the second member comes into sliding contact with the sliding
contact member, the resin layer being formed by sliding the second
member on the sliding contact member to transfer the resin forming
the sliding contact member, the resin layer holding structure being
configured to hold the resin layer in the sliding contact portion,
and the resin layer holding structure comprises a porous film
formed by causing electric discharge between a discharge electrode
and the sliding contact portion of the surface of the second member
and, by an energy of the electric discharge, depositing any one of
a constituent material of the discharge electrode and a substance
obtained by reaction of the constituent material onto the sliding
contact portion.
2. The seal structure of the fluid device according to claim 1,
wherein the fluid device is a rotary machine, the first member is a
housing of the rotary machine, the second member is a rotary shaft
projecting from a through-hole provided in the housing, the seal
member is a packing configured to seal a gap between the housing
and the rotary shaft, the sliding contact member is an annular lip
in sliding contact with an outer circumferential surface of the
rotary shaft, and the resin layer and the resin layer holding
structure are formed in a sliding contact portion of the outer
circumferential surface of the rotary shaft at which the rotary
shaft comes into sliding contact with the lip.
3. The seal structure of the fluid device according to claim 1,
wherein the fluid device is a cylinder device, the first member is
a cylinder body of the cylinder device, the second member is a
piston rod projecting from a through-hole provided in the cylinder
body, the seal member is a packing configured to seal a gap between
the cylinder body and the piston rod, the sliding contact member is
an annular lip in sliding contact with an outer circumferential
surface of the piston rod, and the resin layer and the resin layer
holding structure are formed in a sliding contact portion of the
outer circumferential surface of the piston rod at which the piston
rod comes into sliding contact with the lip.
4. The seal structure of the fluid device according to claim 2,
wherein the packing includes an annular core formed of a metal, and
the lip is provided integrally with the core.
5. The seal structure of the fluid device according to claim 1,
wherein the resin is a self-lubricating resin.
6. The seal structure of the fluid device according to claim 1,
wherein the discharge electrode is molded out of any one of a metal
powder, a metal compound powder, a ceramic powder, and a mixed
powder thereof.
7. The seal structure of the fluid device according to claim 3,
wherein the packing includes an annular core formed of a metal, and
the lip is provided integrally with the core.
Description
TECHNICAL FIELD
[0001] The present invention relates to a seal structure used in a
fluid device.
BACKGROUND ART
[0002] Japanese Patent Application Publication No. 2003-343491 and
Japanese Patent Application Publication No. 2003-28092 disclose
seal structures which seal the gap between a housing and a rotary
shaft of a water pump device by use of a packing. This packing
includes an annular lip that comes into sliding contact with the
outer circumferential surface of the rotary shaft.
[0003] Japanese Patent Application Publication No. 2004-19782 and
Japanese Patent Application Publication No. 2000-9106 disclose seal
structures which seal the gap between a cylinder body and a piston
rod of a cylinder device by use of a packing. This packing includes
an annular lip that comes into sliding contact with the outer
circumferential surface of the piston rod.
SUMMARY OF INVENTION
Technical Problem
[0004] In the above conventional techniques, certain considerations
are made on prevention of fast wear of the existing packing and
damage thereon, and the like. However, not enough considerations
are made on improvement in anti-leakage performance that is an
essential requirement in the seal structures of the fluid devices.
Thus, it has been difficult to further improve the performances of
the seal structures.
[0005] The present invention has been made in view of the above
problem, and an object thereof is to provide a seal structure of a
fluid device capable of improving anti-leakage performance.
Solution to Problem
[0006] An aspect of the present invention is a seal structure of a
fluid device comprising: a first member defining a hollow internal
area of the fluid device; a second member defining the internal
area together with the first member and being movable relative to
the first member; and a seal member fixed to the first member and
configured to seal a gap between the first member and the second
member, wherein the seal member includes a sliding contact member
being in sliding contact with a surface of the second member and
formed of a resin, the second member includes a resin layer and a
resin layer holding structure in a sliding contact portion of the
surface of the second member at which the second member comes into
sliding contact with the sliding contact member, the resin layer
being formed by sliding the second member on the sliding contact
member to transfer the resin forming the sliding contact member,
the resin layer holding structure being configured to hold the
resin layer in the sliding contact portion, and the resin layer
holding structure is a porous film formed by causing electric
discharge between a discharge electrode and the sliding contact
portion of the surface of the second member and, by an energy of
the electric discharge, depositing any one of a constituent
material of the discharge electrode and a substance obtained by
reaction of the constituent material onto the sliding contact
portion.
BRIEF DESCRIPTION OF DRAWINGS
[0007] FIG. 1 is a cross-sectional view showing a seal structure of
a fluid device of a first embodiment of the present invention. Part
(a) is a view showing the configuration of a main portion of the
seal structure, and Part (b) is an enlarged view of a portion B in
Part (a).
[0008] FIG. 2 is a SEM image capturing a cross section of a porous
film in the seal structure in FIG. 1.
[0009] FIG. 3 is a SEM image capturing the outermost surface of the
porous film in the seal structure in FIG. 1.
[0010] FIG. 4 is a view showing a method of forming the porous film
in the seal structure in FIG. 1.
[0011] FIG. 5 is a view showing a seal structure of a fluid device
of a second embodiment of the present invention. Part (a) is a view
showing the whole configuration of the seal structure, and Part (b)
is a view showing a method of forming a porous film in the seal
structure.
[0012] FIG. 6 is a cross-sectional view showing a main portion of
the water pump of the second embodiment of the present
invention.
[0013] FIG. 7 is a view showing a seal structure of a fluid device
of a third embodiment of the present invention. Part (a) is a view
showing the whole configuration of the seal structure, and Part (b)
is a view showing a method of forming a porous film in the seal
structure.
[0014] FIG. 8 is a cross-sectional view showing the hydraulic
cylinder device of the third embodiment of the present
invention.
DESCRIPTION OF EMBODIMENTS
[0015] Hereinbelow, preferred embodiments of the present invention
will be described by referring to the drawings. The technical scope
of the present invention shall be determined based on the
description of the claims and is not limited only to the following
embodiments. Note that in the description of the drawings, the same
components are denoted by the same reference signs, and overlapping
descriptions thereof are omitted. Moreover, the dimensional ratios
in some drawings may be exaggerated for the sake of explanation and
be different from the actual ratios. Further, "F" and "R" in some
drawings refer to front and rear, respectively; however, these
directions are defined for the sake of explaining the positional
relationship between portions and are not at all related to the
actual attachment postures of fluid devices and the like.
[0016] Meanwhile, in this description, fluid device is a collective
term for devices that handle a fluid such as liquid, gas, or
gas-liquid multiphase fluid, and includes fluid machines that
handle a fluid and devices such as valves that control a fluid
flow. The fluid machines include: various actuators that convert a
fluid energy into a mechanical work, such as hydraulic motors,
hydraulic cylinders; pumps, compressors, and fans that convert a
mechanical work into a fluid energy; and the like. Also, the term
"provide(d)" in this description means direct provision as well as
indirect provision with an intermediate member or the like in
between.
First Embodiment
[0017] A seal structure of a first embodiment of the present
invention will be described by referring to FIGS. 1 to 4.
[0018] As shown in FIG. 1, a fluid device 1 of the first embodiment
mainly includes a fixed member (first member) 3, a movable member
(second member) 4, and a seal member 4.
[0019] The fixed member 2 and the movable member 3 together define
a hollow internal area 1a of the fluid device 1. This hollow
internal area 1a is a space which is sealed by the seal member 4 to
be described later and in which a fluid is present temporarily or
for a long period of time, such as a pressure chamber for holding
the fluid under a desired pressure, a storage chamber for storing
the fluid, or a passage through which the fluid flows.
[0020] The movable member 3 is a member capable of moving relative
to the fixed member 2. The moving direction in the relative
movement is not particularly limited and may be any direction as
long as the dimension of a gap G formed between the fixed member 2
and the movable member 3 can be maintained substantially constant
while the movable member 3 is moved relative to the fixed member
2.
[0021] The seal member 4 is fixed to the fixed member 2 and
configured to seal the gap G between the fixed member 2 and the
movable member 3. Note that "seal" means to reduce the leakage of
the fluid in the internal area 1a of the fluid device 1 to the
outside of the fluid device 1 through the gap G, to reduce the
entry of foreign materials (including fluids) in the outside into
the internal area 1a through the gap G, and so on.
[0022] The seal member 4 includes a sliding contact member 4a
configured to slide on a surface 3a of the movable member 3 in
movement of the movable member 3 relative to the fixed member 2.
The shape of the sliding contact member 4a is not particularly
limited. Besides the rectangular cross section shown in FIG. 1, the
sliding contact member 4a may have a circular cross section, a
U-shaped cross section, a V-shaped cross section, or a hollow cross
section. Alternatively, the sliding contact member 4a may have a
lip shape.
[0023] The sliding contact member 4a is formed of a resin. This
resin can be selected from among various thermoplastic resins and
thermosetting resins on the basis of the specification and
application. Examples of the thermoplastic resins include polyamide
(PA), polyacetal (POM), polyethylene terephthalate (PET),
ultra-high-molecular-weight polyethylene (UHPE), polybutylene
terephthalate (PBT), methylpentene (TPX), polyphenylene sulfide
(PPS), polyimide (PI), polyether ether ketone (PEEK), liquid
crystal polymers (LCP), polytetrafluoroethylene (PTFE),
polyolefin-based resins, and the like. Examples of the
thermosetting resins include phenolic resins (PF), polyether, and
the like.
[0024] The resin forming the sliding contact member 4a is
preferably a self-lubricating resin such as polyamide (PA),
polyacetal (POM), polyphenylene sulfide (PPS), polyimide (PI),
polyether ether ketone (PEEK), liquid crystal polymers (LCP), or
polytetrafluoroethylene (PTFE), for example. The self-lubricating
resin refers to a resin that has lubricating properties and shows a
relatively low friction coefficient even without any solid or
liquid lubricant added thereto.
[0025] The movable member 3 includes a resin layer 5 and a resin
layer holding structure 6. The resin layer 5 is formed by sliding
the movable member 3 on the sliding contact member 4a to transfer
the resin forming the sliding contact member 4a onto a sliding
contact portion 3b of the surface 3a at which the movable member 3
comes into sliding contact with the sliding contact member 4a. The
resin layer holding structure 6 is configured to hold the resin
layer 5 in the sliding contact portion 3b. Transfer refers to
adhesion of wear debris (also referred to as transfer particles),
produced from one of two members sliding on each other, to the
surface of the other member.
[0026] The resin layer holding structure 6 is a porous film 6
formed by performing electric discharge surface treatment on the
sliding contact portion 3b of the surface 3a of the movable member
3.
[0027] As shown in FIG. 2, the film 6 is a film in which relatively
large particles L with maximum widths from approximately 20 to 50
.mu.m and relatively small particles S with maximum widths from
approximately 1 to 20 .mu.m are accumulated and fixed randomly but
uniformly (i.e., without local unevenness), and which therefore is
homogeneously porous as a whole. Note that in FIG. 2, the arrow M
shows the film thickness direction.
[0028] Thus, as shown in FIG. 3, at the outermost surface of the
film 6, the outermost ends of relatively large particles L appear
as island portions IL with maximum widths from approximately 1 to
20 .mu.m having relatively smooth surfaces. In recesses with widths
from approximately 5 to 40 .mu.m and depths from approximately 5 to
30 .mu.m formed between the island portions IL, a number of
relatively small particles S are accumulated randomly while leaving
gaps therebetween, and are fixed to the surfaces of the island
portions IL or to other small particles S. At the outermost surface
of the film 6, the gaps between the island portions IL and the
small particles S and the gaps between the small particles S appear
as a number of fine grooves or pores 6a with random shapes (see
FIG. 1). As compared to the island portions IL, the small particles
S defining the grooves or pores 6a have random polygonal shapes
having a number of angular portions on the surfaces thereof.
[0029] In other words, the outermost surface of the film 6 is
formed of relatively large island portions IL, a number of small
particles S scattered therebetween, and a number of fine grooves or
pores 6a formed therebetween. Thus, as a sliding surface, the
outermost surface is a relatively rough (high in surface
roughness). Note that the surface of the film 6 is preferably
subjected to polishing at least once for the purpose of reducing
excessive wear of the sliding contact member 4a that comes into
sliding contact therewith.
[0030] The porosity of the film 6 is not particularly limited and
may be set suitably on the basis of the material of the resin layer
5 holding the film 6. The porosity, however, is preferably set to 5
to 60% in order for the film 6 to secure a suitable resin holding
power as a resin layer holding structure. Moreover, the porosity is
more preferably set to 5 to 30%, and even more preferably to 10 to
15% in order to increase the strength of the film 6. Note that the
porosity can be measured by Archimedes' method (JIS-R-1634).
[0031] The widths or diameters of grooves or pores 6a formed in the
outermost surface of the film 6 are not particularly limited but
are preferably within a range from 0.01 .mu.m to 10 .mu.m in a plan
view of the outermost surface of the film 6. Note that the widths
or diameters of the grooves or pores 6a can be calculated based on
the dimensions of the outermost surface of the film 6 in a
microscopic image and on the magnification of the microscope.
[0032] The electric discharge surface treatment refers to surface
treatment in which electric discharge is caused between a discharge
electrode and a workpiece (base material) in a working liquid such
as an electrically insulative oil or in the air, and by the
discharge energy, a wear-resistant film made of the material of the
electrode or a substance obtained by reaction of the material of
the electrode with the discharge energy is formed on the treatment
surface of the workpiece.
[0033] In this embodiment, as shown in FIG. 4, the porous film 6 is
formed by causing pulse discharge using a discharge electrode 7 in
an electrically insulative working liquid or in the air, the
discharge electrode 7 having a leading end with a width
substantially equal to the width of the sliding contact portion 3b
of the movable member 3. The pulse discharge is caused between the
discharge electrode 7 and the sliding contact portion 3b of the
surface 3a of the movable member 3 while moving the movable member
3 relative to the discharge electrode 7. By the discharge energy,
the constituent material of the discharge electrode 7 or a
substance obtained by reaction of the constituent material is
deposited on the sliding contact portion 3b.
[0034] Here, the discharge electrode 7 is a green compact electrode
(including heat-treated green compact electrode) obtained by
compression molding or injection molding of a metal powder, a metal
compound powder, a ceramic powder, or a mixed powder thereof.
[0035] Examples of the metal powder include powders of alloys such
as a Stellite alloy, an iron-based alloy, a nickel (Ni) alloy, and
a cobalt (Co) alloy and powders of pure metals such as iron (Fe),
cobalt (Co), nickel (Ni), copper (Cu), chromium (Cr), molybdenum
(Mo), and titanium (Ti).
[0036] The Stellite (a registered trademark of Deloro Stellite
Company) alloy is an alloy essentially containing cobalt, and
consisting of chromium, nickel, tungsten, and the like. Typical
examples of the Stellite alloy include Stellite 1, Stellite 3,
Stellite 4, Stellite 6, Stellite 7, Stellite 12, Stellite 21,
Stellite F, and the like.
[0037] Examples of the iron-based alloy include an alloy
essentially containing iron and nickel, an alloy essentially
containing iron, nickel, and cobalt, an alloy essentially
containing iron, nickel, and chromium, and the like. Examples of
the alloy essentially containing iron, nickel, and chromium include
a stainless steel, typical examples of which include SUS304,
SUS316, and the like specified by the Japanese Industrial
Standards.
[0038] Examples of the nickel alloy include Hastelloy (a registered
trademark of Haynes International Inc.) alloys, Inconel (a
registered trademark of Special Metals Corporation) alloys, Incoloy
(a registered trademark of Special Metals Corporation) alloys,
Monel (a registered trademark of Special Metals Corporation)
alloys, Nimonic (a registered trademark of Special Metals
Corporation) alloys, RENE (a registered trademark of Teledyne
Industries Inc.) alloys, UDIMET (a registered trademark of Special
Metals Corporation) alloys, WASPALOY (a registered trademark of
United Technologies Corporation) alloy, and the like.
[0039] Examples of the cobalt alloy include a Stellite-based alloy,
a Tribaloy-based alloy (Tribaloy T400 or T800 (Tribaloy is a
registered trademark of Deloro Stellite Company)), UDIMET700 (a
registered trademark of Special Metals Corporation), and the
like.
[0040] Note that the discharge electrode 7 is preferably molded out
of powder of an alloy containing a carbonization-resistant metal by
60% or higher, such for example as powder of a cobalt alloy
containing chromium, for the purpose of securing a sufficient film
thickness of the porous film 6. The carbonization-resistant metal
is cobalt, nickel, iron, or the like.
[0041] Examples of the metal compound and the ceramic include cubic
boron nitride (cBN), titanium carbide (TiC), titanium nitride
(TiN), titanium aluminium nitride (TiAlN), titanium diboride
(TiB.sub.2), tungsten carbide (WC), chromium carbide
(Cr.sub.3C.sub.2), silicon carbide (SiC), zirconium carbide (ZrC),
vanadium carbide (VC), boron carbide (B.sub.4C), silicon nitride
(Si.sub.3N.sub.4), zirconium oxide (ZrO.sub.2), alumina
(Al.sub.2O.sub.3), and the like. The discharge electrode 7 may be
molded out of a mixed powder in which powder of at least one of
these is added to the aforementioned metal powder. In this way, the
wear resistance of the porous film 6 can be enhanced.
[0042] The discharge condition for the pulse discharge in the
electric discharge surface treatment can be set suitably on the
basis of the material of the discharge electrode 7, the properties
of the base material of the movable member 3, the thickness and
porosity of the film 6, and the like. The discharge condition is
usually set within a range where the peak current is not lower than
1 A but not higher than 30 A and the pulse width is not shorter
than 1 .mu.s but not longer than 200 .mu.s. Note that the discharge
condition is preferably set such that the peak current is not lower
than 5 A but not higher than 20 A and the pulse width is not
shorter than 2 .mu.s but not longer than 20 .mu.s, for the purpose
of reducing the damage on the base material of the movable member 3
and also increasing the bond strength of the film 6.
[0043] The resin layer 5 is formed by sliding the movable member 3
on the seal member 4 to transfer the resin forming the sliding
contact member 4a onto the sliding contact portion 3b of the
surface 3a of the movable member 3. Specifically, the resin layer 5
is formed by the following processes (1) to (4).
(1) The sliding contact member 4a is brought into elastic contact
with the surface of the porous film 6 formed in the sliding contact
portion 3b of the surface 3a of the movable member 3. As the
movable member 3 moves relative to the fixed member 2 from this
state, the sliding contact member 4a slides on the surface of the
film 6 at a surface pressure determined by the elasticity of the
sliding contact member 4a, the pressure on the sealed fluid, and
the like. (2) In this event, at the frictional interface between
the sliding contact member 4a and the film 6, part of the resin
forming the sliding contact member 4a becomes unable to withstand
the shear force produced by the friction, and is separated from the
sliding contact member 4a and thereby becomes transfer particles.
(3) The transfer particles of the resin separated from the sliding
contact member 4a are captured in a number of grooves or pores 6a
formed in the outermost surface of the film 6 and adhere to the
surface of the film 6. (4) As the movement of the movable member 3
relative to the fixed member 2 (the sliding of the movable member 3
on the seal member 4) continues, the series of processes from the
separation to the adhesion of the resin is performed repeatedly, so
that the resin particles transferred to the film 6 are bonded to
each other and grow larger. Then, the bonded resin particles are
further supplied with and bonded to the transfer particles to grow
larger in the film thickness direction, and also enter the grooves
or pores 6a in the film 6 (part of the bonded resin particles fills
some of the grooves or pores 6a) as shown in FIG. 1.
[0044] As a result, in the sliding contact portion 3b of the
surface 3a of the movable member 3, the resin layer 5 made of the
resin forming the sliding contact member 4a (including the
substance obtained by reaction of the resin) is formed in such a
way as to cover entirely or partially the portion of the surface of
the film 6 that has been in sliding contact with the sliding
contact member 4a.
[0045] At the interface between the resin layer 5 and the film 6, a
number of anchor portions 5a are formed which are fitted in the
grooves or pores 6a in the film 6. As mentioned above, the grooves
or pores 6a are defined by a number of small particles S having
random polygonal shapes having a number of angular portions at the
surfaces thereof. These small particles S penetrate the anchor
portions 5a of the resin layer 5 to hold the resin layer 5.
[0046] Now, operations and effects of the first embodiment will be
described.
[0047] In general, fluid devices are designed as follows if sealing
is to be done by setting a resin seal member in sliding contact
with the surface of a movable member. Specifically, the surface
roughness of the portion of the surface of the movable member in
sliding contact with the seal member is made as low as possible to
achieve a larger real contact area between the sliding contact
portion and the seal member. The real contact area refers to the
area of the actually contacting portions (real contact spots) of
two contacting surfaces.
[0048] It is possible that the fluid, or the object to be sealed,
is vaporized by the frictional heat produced by the friction
between the movable member and the seal member (e.g., turning into
water vapor in a case where the fluid is water), especially when
the speed of the movement of the movable member relative to the
fixed member is high, and therefore the speed of the sliding of the
movable member on the seal member is high. To reduce the leakage of
the vaporized fluid to the outside, the portion of the surface of
the movable member in sliding contact with the seal member is
formed of a dense material, and the surface roughness thereof is
set to the lowest possible value. Meanwhile, there are cases where
a hard film is provided on the surface of the movable member to
enhance the wear resistance of the surface. In such cases too, the
hard film is formed of a dense material, and the surface roughness
thereof is set to the lowest possible value.
[0049] Now, suppose a case of operating a fluid device designed
based on the above idea. As the seal member slides on the surface
of the movable member and wears, part of the resin forming the seal
member becomes particles and is separated from the seal member.
However, the surface roughness of the surface of the movable member
is low as mentioned above, and its power to hold the resin
particles is not sufficient either. Thus, the separated resin
particles may once adhere to the surface of the movable member but
will be separated therefrom immediately. Consequently, the resin
particles are left unfixed at the frictional interface between the
seal member and the movable member. For this reason, the above
fluid device has a difficulty in maintaining a large real contact
area between the surfaces of the seal member and movable
member.
[0050] In the seal structure of the fluid device of this
embodiment, the movable member 3 includes: the resin layer 5; and
the resin layer holding structure 6 in the sliding contact portion
3b of the surface 3a of the movable member 3 at which the movable
member 3 comes into sliding contact with the sliding contact member
4a of the seal member 4, the resin layer 5 being formed by sliding
the movable member 3 on the sliding contact member 4a to transfer
the resin forming the sliding contact member 4a, the resin layer
holding structure 6 being configured to hold the resin layer 5 in
the sliding contact portion 3b. Accordingly, at the frictional
interface between the movable member 3 and the sliding contact
member 4a, the resin layer 5 formed of the resin forming the
sliding contact member 4a slides on the sliding contact member 4a,
and the two resins come into tight contact with each other. Thus, a
large real contact area is maintained therebetween, improving the
anti-leakage performance of the seal structure.
[0051] Moreover, the resin layer holding structure 6 is the porous
film 6 formed by electric discharge surface treatment, and includes
at its outermost surface relatively large island portions IL, a
number of small particles S scattered therebetween, and a number of
fine grooves or pores 6a formed therebetween. Thus, when the resin
layer 5 is formed by sliding the movable member 3 on the sliding
contact member 4a to transfer the resin forming the sliding contact
member 4a onto the film 6, the anchor portions 5a fitted in the
grooves or pores 6a are formed at the interface with the film 6 of
the resin layer 5. Because the small particles S defining the
grooves or pores 6a have random polygonal shapes having a number of
angular portions at the surfaces thereof, the small particles S
penetrate the anchor portions 5a. This allows the resin layer 5 to
be held securely and firmly in the sliding contact portion 3b of
the movable member 3 by the film 6.
[0052] Further, in the seal structure of this embodiment, a
suitable material is selected for the discharge electrode 7 which
is used for the electric discharge surface treatment. Specifically,
the discharge electrode 7 may be molded out of, for example, a
mixed powder in which at least one of powders of cBN, hBN, TiC,
TiN, TiAlN, TiB.sub.2, WC, Cr.sub.3C.sub.2, SiC, ZrC, VC, B.sub.4C,
Si.sub.3N.sub.4, ZrO.sub.2, and Al.sub.2O.sub.3 is added to powder
of an alloy containing a carbonization-resistant metal by 60% or
higher. In this way, the wear resistance of the film 6 can be
enhanced. This makes it possible to improve the anti-leakage
performance while securing a wear resistance (the wear resistance
of the sliding contact member 4a and the wear resistance of the
movable member 3) that is substantially the same as those of films
formed by some other, typical surface treatment methods. There is a
demand, especially in recent years, for a further improvement in
the performance of the seal structure due to increase in the speed
and pressure of fluid devices. With the seal structure of this
embodiment, it is possible to sufficiently fulfill such a
demand.
[0053] Note that although the seal member 4 is fixed to the fixed
member 2 in this embodiment, the seal member 4 may be fixed to the
movable member 3. In this case, the sliding contact member 4a of
the seal member 4 may be set in sliding contact with the surface of
the fixed member 2, and a resin layer and a resin layer holding
structure may be formed in a sliding contact portion of the fixed
member 2. Moreover, the shape of the sliding contact portion 3b of
the movable member 3 is not particularly limited. Besides the flat
shape shown in FIG. 1, a curved shape which is convex or concave
toward the fixed member 2 may be employed.
[0054] To evaluate the anti-leakage performance of the seal
structure of this embodiment, a leakage test was conducted by using
films formed by other typical surface treatment methods and the
film of this embodiment. The test condition was as follows: water
was used as the fluid; the sliding speed on the sliding surface was
10 m/s; the pressure on the sealed fluid was 10 kPaG; and the
amount of leakage per 100 hours was measured. Table 1 shows the
obtained results.
TABLE-US-00001 Amount of Wear Surface Amount of Sliding Contact
Roughness of Leakage Member Ra[.mu.m] Comparative 100% 100% 0.05 to
0.10 Example 1 (Film A formed by thermal spraying) Comparative 170%
125% 0.04 to 0.10 Example 2 (Film B formed by thermal spraying)
Comparative 1253% 100% 0.07 to 0.12 Example 3 (Film C formed by
vapor deposition) Comparative 73% 200% 0.16 to 0.17 Example 4 (DLC
film) Example 1 20% 150% 0.15 to 01.18 (MSC film)
[0055] In Table 1, Comparative Examples 1 and 2 correspond to films
formed by thermal spraying, Comparative Example 3 corresponds to a
film formed by vapor deposition, Comparative Example 4 corresponds
to a diamond-like carbon film, and Example 1 corresponds to the
porous film of this embodiment formed by the electric discharge
surface treatment. No sealing treatment was performed on any of the
films, but polishing was performed once on each of the films. Note
that the amount of leakage and the amount of wear of the sliding
contact member were evaluated by using those of Comparative Example
1 as references (100%). Surface roughness refers to an arithmetic
mean of roughness specified by the Japanese Industrial Standards
(JIS-B-0601: 2001).
[0056] From Table 1, it is found that the amount of leakage in
Example 1 is significantly improved as compared to those in
Comparative Examples 1 to 4 (improved down to 20% of the reference
value). As for the amount of wear of the sliding contact member, it
is found that the amount of wear in Example 1 is substantially the
same as those in Comparative Examples 1 to 4. Note that the
material of each sliding contact member used in this test is PTFE.
Though not shown in Table 1, the amount of wear of the film serving
as the counterpart of the sliding contact member was measured in
this test as well. It is found that the amount of wear of the film
in Example 1 is substantially the same as those in Comparative
Examples 1 to 4.
[0057] It is also found that the amount of leakage in Example 1 is
reduced to be smaller than 1/3 of that in Comparative Example 4
which has substantially the same level of surface roughness. The
above shows that the porous film formed by the electric discharge
surface treatment can exhibit an excellent resin holding power due
to its unique structure.
Second Embodiment
[0058] A seal structure of a fluid device of a second embodiment of
the present invention will be described by referring to Parts (a)
and (b) of FIG. 5 and FIG. 6. This embodiment is an example
applying the seal structure of the first embodiment to a rotary
machine.
[0059] As shown in FIG. 6, a water pump (an example of the rotary
machine) 21 of the second embodiment includes a housing (pump body)
22 defining a pump chamber 21a of the water pump 21 and a rotary
shaft 24 defining the pump chamber 21 a together with the housing
22.
[0060] A through-hole 23 is formed in the housing 22 in a suitable
position, and the rotary shaft 24 penetrates therethrough. The
rotary shaft 24 is provided to be rotatable relative to the housing
22 through a bearing 26. A front end side (one end side) of the
rotary shaft 24 extends to the inside of the pump chamber 21a in
the housing 22. An impeller 27 provided inside the pump chamber 21a
is integrally attached to this front end portion (one end portion).
A rear end side (the other end side) of the rotary shaft 24 extends
to the outside of the housing 22. This rear end portion (the other
end portion) is coupled to an output shaft (unillustrated) of a
rotary motor (unillustrated).
[0061] By rotating the rotary shaft 24 with the drive of the rotary
motor, the water pump 21 configured as above can rotate the
impeller 27 together with the rotary shaft 24 and thereby pump the
water inside the housing 22.
[0062] The water pump 21 of this embodiment includes a seal
structure (rotary machine seal structure) 28 configured to seal the
gap between the inner circumferential surface of the through-hole
23 in the housing 22 and the rotary shaft 24 to reduce the leakage
of water from the housing 22.
[0063] As shown in Part (a) of FIG. 5, the rotary machine seal
structure 28 includes a packing 29 fixed to the inner
circumferential surface of the through-hole 23 in the housing 22
through an annular packing gland 30 and configured to seal a gap G
between the housing 22 and the rotary shaft 24.
[0064] The packing 29 includes an annular core 31 and a lip 32
provided integrally with the core 31 and being in sliding contact
with the outer circumferential surface of the rotary shaft 24. The
lip 32 is formed of a self-lubricating resin such as PTFE while the
core 31 is formed of a metal such as stainless steel. Note that the
packing 29 may be formed of a self-lubricating resin only.
[0065] The rotary shat 24 includes: a resin layer 5 (see FIG. 1)
formed by sliding the rotary shaft 24 on the lip 32 to transfer the
resin forming the lip 32 onto a sliding contact portion of the
outer circumferential surface of the rotary shaft 24 at which the
rotary shaft 24 comes into sliding contact with the lip 32; and a
resin layer holding structure 33 configured to hold the resin layer
5 in the sliding contact portion of the rotary shaft 24.
[0066] The resin layer holding structure 33 is a porous, hard film
33 formed by performing electric discharge surface treatment on the
sliding contact portion of the outer circumferential surface of the
rotary shaft 24 at which the rotary shaft 24 comes into sliding
contact with the lip 32. More specifically, as shown in Part (b) of
FIG. 5, the hard film 33 is formed by causing pulse discharge using
a rod-shaped discharge electrode 34 in an electrically insulative
working liquid or in the air. The pulse discharge is caused between
the discharge electrode 34 and the sliding contact portion of the
outer circumferential surface of the rotary shaft 24, which is a
component of the water pump 21, while rotating the rotary shaft 24
about its axis 24s. By the discharge energy, the constituent
material of the discharge electrode 34 or a substance obtained by
reaction of the constituent material is deposited on the sliding
contact portion of the outer circumferential surface of the rotary
shaft 24. Meanwhile, the surface of the hard film 33 is subjected
to polishing.
[0067] Here, the discharge electrode 34 is molded out of powder of
an alloy containing a carbonization-resistant metal by 60% or
higher. To enhance the wear resistance of the hard film 33, the
discharge electrode 34 may be molded out of a mixed powder in which
at least one of powders of cBN, hBN, TiC, TiN, TiAlN, TiB.sub.2,
WC, Cr.sub.3C.sub.2, SiC, ZrC, VC, B.sub.4C, Si.sub.3N.sub.4,
ZrO.sub.2, and Al.sub.2O.sub.3 is added to the above alloy
powder.
[0068] Now, operations and effects of the second embodiment will be
described.
[0069] The seal structure of the fluid device of this embodiment
includes: the resin layer 5 formed by sliding the rotary shaft 24
on the lip 32 to transfer the resin forming the lip 32 onto the
sliding contact portion of the outer circumferential surface of the
rotary shaft 24 at which the rotary shaft 24 comes into sliding
contact with the lip 32; and the resin layer holding structure 33
configured to hold the resin layer 5 in the sliding contact
portion. Accordingly, like the first embodiment, at the frictional
interface between the rotary shaft 24 and the lip 32, the resin
layer 5 formed of the resin forming the lip 32 slides on the lip
32, and the two resins come into tight contact with each other.
Thus, a large real contact area is maintained therebetween,
improving the anti-leakage performance of the seal structure.
[0070] Moreover, the resin layer holding structure 33 is the porous
hard film 33 formed by electric discharge surface treatment and,
like the first embodiment, includes at its outermost surface
relatively large island portions IL, a number of small particles S
scattered therebetween, and a number of grooves or pores 6a formed
therebetween (see FIGS. 1 and 3). Thus, when the resin layer 5 is
formed by sliding the rotary shaft 24 on the lip 32 to transfer the
resin forming the lip 32 onto the hard film 33, anchor portions 5a
(see FIG. 1) fitted in the grooves or pores 6a in the hard film 33
are formed at the interface with the film 6 of the resin layer 5.
Because the small particles S defining the grooves or pores 6a have
random polygonal shapes having a number of angular portions at the
surfaces thereof, the small particles S penetrate the anchor
portions 5a. This allows the resin layer 5 to be held securely and
firmly in the sliding contact portion of the rotary shaft 24 by the
hard film 33.
[0071] Further, in the seal structure of this embodiment, the
discharge electrode 34 used in the electric discharge surface
treatment may be molded out of a mixed powder in which at least one
of powders of cBN, hBN, TiC, TiN, TiAlN, TiB.sub.2, WC,
Cr.sub.3C.sub.2, SiC, ZrC, VC, B.sub.4C, Si.sub.3N.sub.4,
ZrO.sub.2, and Al.sub.2O.sub.3 is added to powder of the alloy
which is the material of the discharge electrode 34. In this way,
the wear resistance of the hard film 33 can be enhanced further.
This makes it possible to improve the anti-leakage performance
while securing a wear resistance that is substantially the same as
those of films formed by some other, typical surface treatment
methods.
[0072] Thus, according to the second embodiment, the anti-leakage
performance of the rotary machine seal structure 28 is enhanced,
making it possible to further improve the performance of the rotary
machine seal structure 28.
Third Embodiment
[0073] A seal structure of a fluid device of a third embodiment of
the present invention will be described by referring to Parts (a)
and (b) of FIG. 7 and FIG. 8. This embodiment is an example
applying the seal structure of the first embodiment to a
reciprocating machine.
[0074] As shown in FIG. 7, a hydraulic cylinder device (an example
of the reciprocating machine) 41 of the third embodiment includes a
cylindrical cylinder body 42 extending in the front-rear direction.
The cylinder body 42 includes a cylinder head 43 in a front end
side thereof. A through-hole 44 is formed in a center portion of
the cylinder head 43. Moreover, a piston 45 is provided movably
inside the cylinder body 42. The piston 45 partitions the inside of
the cylinder body 42 into a first hydraulic chamber (front
hydraulic chamber) 46 and a second hydraulic chamber (rear
hydraulic chamber) 47.
[0075] In addition, a piston rod 48 is provided integrally with the
piston 45, the piston rod 48 extending frontward from the front
surface of the piston 45 and penetrating the through-hole 44 in the
cylinder head 43. Thus, the first hydraulic chamber 46 in the
cylinder body 42 is defined by the inner surface of the cylinder
body 42, the inner surface of the cylinder head 43, the front
surface of the piston 45, and the outer circumferential surface of
the piston rod 48. The second hydraulic chamber 47 is defined by
the inner surface of the cylinder body 42 and the rear surface of
the piston 45. The piston 45 and the piston rod 48 are provided to
be movable relative to the cylinder body 42 and the cylinder head
43 in the axial direction.
[0076] The hydraulic cylinder device 41 configured as above moves
the piston rod 48 and the piston 45 together frontward (in one
direction) by discharging water from the first hydraulic chamber 46
and supplying water into the second hydraulic chamber 47. On the
other hand, the hydraulic cylinder device 41 moves the piston rod
48 and the piston 45 together rearward (in the other direction) by
discharging water from the second hydraulic chamber 47 and
supplying water into the first hydraulic chamber 46.
[0077] The hydraulic cylinder device 41 of this embodiment includes
a seal structure (cylinder device seal structure) 49 configured to
seal a gap G between the through-hole 44 in the cylinder head 43
and the piston rod 48 to reduce the leakage of the water from the
cylinder body 42.
[0078] As shown in Part (a) of FIG. 7, the cylinder device seal
structure 49 includes a packing 51 press-fitted in a
circumferential groove 50 formed in the inner circumferential
surface of the through-hole 44 in the cylinder head 43, and
configured to seal the gap G between the cylinder head 43 and the
piston rod 48.
[0079] The packing 51 includes an annular core 52 and a lip 53
provided integrally with the core 52 and being in sliding contact
with the outer circumferential surface of the piston rod 48. The
lip 53 is formed of a self-lubricating resin such as PTFE while the
core 52 is formed of a metal such as stainless steel. Note that the
packing 51 may be formed of a self-lubricating resin only.
[0080] The piston rod 48 includes: a resin layer 5 (see FIG. 1)
formed by sliding the piston rod 48 on the lip 53 to transfer the
resin forming the lip 53 onto a sliding contact portion of the
outer circumferential surface of the piston rod 48 at which the
piston rod 48 comes into sliding contact with the lip 53; and a
resin layer holding structure 54 configured to hold the resin layer
5 in the sliding contact portion of the piston rod 48.
[0081] The resin layer holding structure 54 is a porous, hard film
54 formed by performing electric discharge surface treatment on the
sliding contact portion of the outer circumferential surface of the
piston rod 48 at which the piston rod 48 comes into sliding contact
with the lip 53. More specifically, as shown in Part (b) of FIG. 7,
the hard film 54 is formed by causing pulse discharge using a
plate-shaped discharge electrode 55 in an electrically insulative
working liquid or in the air. The pulse discharge is caused between
the discharge electrode 55 and the sliding contact portion of the
outer circumferential surface of the piston rod 48, which is a
component of the hydraulic cylinder device 41, while rotating the
piston rod 48 about its axis 48s. By the discharge energy, the
constituent material of the discharge electrode 55 or a substance
obtained by reaction of the constituent material is deposited on
the sliding contact portion of the outer circumferential surface of
the piston rod 48. Meanwhile, the surface of the hard film 54 is
subjected to polishing. Note that the discharge electrode 55 has
the same configuration as the discharge electrode 34 of the second
embodiment, and thus description thereof is omitted here.
[0082] Now, operations and effects of the third embodiment will be
described.
[0083] The seal structure of the fluid device of this embodiment
includes: the resin layer 5 formed by sliding the piston rod 48 on
the lip 53 to transfer the resin forming the lip 53 onto the
sliding contact portion of the outer circumferential surface of the
piston rod 48 at which the piston rod 48 comes into sliding contact
with the lip 53; and the resin layer holding structure 54
configured to hold the resin layer 5 in the sliding contact
portion. Accordingly, like the first and second embodiments, at the
frictional interface between the piston rod 48 and the lip 53, the
resin layer 5 formed of the resin forming the lip 53 slides on the
lip 53, and the two resins come into tight contact with each other.
Thus, a large real contact area is maintained therebetween,
improving the anti-leakage performance of the seal structure.
[0084] Moreover, the resin layer holding structure 54 is the porous
hard film 54 formed by electric discharge surface treatment and,
like the first and second embodiments, includes at its outermost
surface relatively large island portions IL, a number of small
particles S scattered therebetween, and a number of grooves or
pores 6a formed therebetween (see FIGS. 1 and 3). Thus, when the
resin layer 5 is formed by sliding the piston rod 48 on the lip 53
to transfer the resin forming the lip 53 onto the hard film 54,
anchor portions 5a (see FIG. 1) of the resin layer 5 fitted in the
grooves or pores 6a in the hard film 54 are formed at the interface
with the hard film 54 of the resin layer 5. Because the small
particles S defining the grooves or pores 6a in the hard film 54
have random polygonal shapes having a number of angular portions at
the surfaces thereof, the small particles S penetrate the anchor
portions 5a. This allows the resin layer 5 to be held securely and
firmly in the sliding contact portion of the piston rod 48 by the
hard film 54.
[0085] Further, in the seal structure of this embodiment, the
discharge electrode 55 used in the electric discharge surface
treatment may be molded out of a mixed powder in which at least one
of powders of cBN, hBN, TiC, TiN, TiAlN, TiB.sub.2, WC,
Cr.sub.3C.sub.2, SiC, ZrC, VC, B.sub.4C, Si.sub.3N.sub.4,
ZrO.sub.2, and Al.sub.2O.sub.3 is added to powder of the alloy
which is the material of the discharge electrode 55. In this way,
the wear resistance of the hard film 54 can be enhanced further.
This makes it possible to improve the anti-leakage performance
while securing a wear resistance that is substantially the same as
those of films formed by some other, typical surface treatment
methods.
[0086] Thus, according to the third embodiment, the anti-leakage
performance of the cylinder device seal structure 49 is enhanced,
making it possible to further improve the performance of the
cylinder device seal structure 49.
[0087] Although embodiments of the present invention has been
described above, these embodiments are merely examples described
for the purpose of facilitating the understanding of the present
invention, and the present invention is not limited to the
embodiments. The technical scope of the present invention is not
limited to the technical matters specifically disclosed in the
embodiments, and includes various modifications, changes,
alternative techniques which can be easily derived from the
technical matters. For example, the seal structure 28 of the second
embodiment can be used in a rotary machine other than the water
pump 21. The seal structure 49 of the third embodiment can be used
in a reciprocating machine other than the hydraulic cylinder device
41. Moreover, in the rotary machine of the second embodiment, the
surface of the rotary shaft 24 which the lip 32 comes into sliding
contact with is not limited to the outer circumferential surface
parallel to the center axis of the rotary shaft 24, and may be the
side surface (a flat surface perpendicular to the axial direction)
of a flange projecting in the radial direction from the rotary
shaft 24, or the side surface of a circular cone diverging toward
the one end side in the axial direction. Furthermore, the
cross-sectional shape of the piston rod 48 in the cylinder device
of the third embodiment is not limited to a circular shape, and may
be an elliptical shape, an oblong shape, or a polygonal shape with
rounded corners.
[0088] This application claims priority based on Japanese Patent
Application No. 2009-260169, filed Nov. 13, 2009, the entire
contents of which are incorporated herein by reference.
INDUSTRIAL APPLICABILITY
[0089] According to the present invention, it is possible to
improve the anti-leakage performances of seal structures of fluid
devices. Accordingly, the present invention can be preferably
utilized in many applications such as fluid machines that handle a
fluid such as liquid, gas, or gas-liquid multiphase fluid, and
devices such as valves that control a fluid flow.
REFERENCE SIGNS LIST
[0090] G gap
[0091] 1 fluid device
[0092] 1a internal area
[0093] 2 fixed member (first member)
[0094] 3 movable member (second member)
[0095] 3a surface
[0096] 3b sliding contact portion
[0097] 4 seal member
[0098] 4a sliding contact member
[0099] 5 resin layer
[0100] 5a anchor portion
[0101] 6 film (resin layer holding structure)
[0102] 6a groove or pore
[0103] 7 discharge electrode
[0104] 21 water pump
[0105] 21a pump chamber
[0106] 22 housing
[0107] 23 through-hole
[0108] 24 rotary shaft
[0109] 24s axis
[0110] 26 bearing
[0111] 27 impeller
[0112] 28 rotary machine seal structure
[0113] 29 packing
[0114] 30 packing gland
[0115] 31 core
[0116] 32 lip
[0117] 33 hard film (resin layer holding structure)
[0118] 34 discharge electrode
[0119] 41 hydraulic cylinder device
[0120] 42 cylinder body
[0121] 43 cylinder head
[0122] 44 through-hole
[0123] 45 piston
[0124] 46 first hydraulic chamber
[0125] 47 second hydraulic chamber
[0126] 48 piston rod
[0127] 48s axis
[0128] 49 cylinder device seal structure
[0129] 50 circumferential groove
[0130] 51 packing
[0131] 52 core
[0132] 53 lip
[0133] 54 hard film (resin layer holding structure)
[0134] 55 discharge electrode
* * * * *