U.S. patent application number 10/696169 was filed with the patent office on 2004-07-08 for shaft seal, compressor having the same and method for sealing shaft.
Invention is credited to Koide, Tatsuya, Yamada, Takeshi, Yokomachi, Naoya.
Application Number | 20040131475 10/696169 |
Document ID | / |
Family ID | 29542265 |
Filed Date | 2004-07-08 |
United States Patent
Application |
20040131475 |
Kind Code |
A1 |
Yokomachi, Naoya ; et
al. |
July 8, 2004 |
Shaft seal, compressor having the same and method for sealing
shaft
Abstract
A shaft seal for sealing an outer circumferential surface of a
rotary shaft to a housing includes a lip seal. The lip seal
includes a lip body, a lip portion, a support portion and a
receiving portion. The lip body is fixed at a housing side. The lip
portion extends from the lip body and has inner and outer
circumferential surfaces. The inner circumferential surface of the
lip portion is in contact with the outer circumferential surface of
the rotary shaft. The lip portion is deformable. The support
portion is formed at the outer circumferential surface side of the
lip portion for applying tensile force to the lip portion when the
lip portion is deformed toward the inner circumferential surface
side of the lip portion. The receiving portion is formed at the
outer circumferential surface side of the lip portion for receiving
the pressure in the housing.
Inventors: |
Yokomachi, Naoya;
(Kariya-shi, JP) ; Yamada, Takeshi; (Kariya-shi,
JP) ; Koide, Tatsuya; (Kariya-shi, JP) |
Correspondence
Address: |
MORGAN & FINNEGAN, L.L.P.
345 Park Avenue
New York
NY
10154
US
|
Family ID: |
29542265 |
Appl. No.: |
10/696169 |
Filed: |
October 28, 2003 |
Current U.S.
Class: |
417/269 |
Current CPC
Class: |
F16J 15/3232 20130101;
F04B 27/1036 20130101; F16J 15/3276 20130101; F16J 15/3268
20130101; F16J 15/3208 20130101; F16J 15/3228 20130101 |
Class at
Publication: |
417/269 |
International
Class: |
F04B 001/12 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 30, 2002 |
JP |
2002-128546 |
Claims
What is claimed is:
1. A shaft seal for sealing an outer circumferential surface of a
rotary shaft to a housing, comprising: a lip seal including: a lip
body fixed at a housing side; a lip portion extending from the lip
body, the lip portion having inner and outer circumferential
surfaces, the inner circumferential surface of the lip portion
being in contact with the outer circumferential surface of the
rotary shaft, the lip portion being deformable; a support portion
formed at the outer circumferential surface side of the lip portion
for applying tensile force to the lip portion when the lip portion
is deformed toward the inner circumferential surface side of the
lip portion; and a receiving portion formed at the outer
circumferential surface side of the lip portion for receiving the
pressure in the housing.
2. The shaft seal according to claim 1, wherein the support portion
is arranged at the top end of the lip portion.
3. The shaft seal according to claim 1, wherein a plurality of the
support portions is arranged in the circumferential direction of
the lip portion at a predetermined interval.
4. The shaft seal according to claim 1, wherein the support portion
connects the outer circumferential surface of the lip portion with
the lip body.
5. The shaft seal according to claim 4, wherein the support portion
is formed integrally with the lip body and the lip portion.
6. The shaft seal according to claim 4, wherein the support portion
is formed separately from the lip body and lip portion.
7. The shaft seal according to claim 1, wherein the support portion
is constituted of elastic member.
8. The shaft seal according to claim 7, wherein the elastic member
is made of one of rubber, resin and metal.
9. The shaft seal according to claim 7, wherein the elastic member
is one of a coil spring and a leaf spring.
10. The shaft seal according to claim 1, wherein the support
portion forms a rod having one of rectangular and circular
transverse cross sections in shape.
11. The shaft seal according to claim 1, wherein the support
portion forms a thin plate in shape.
12. The shaft seal according to claim 1, further comprising a
holding member arranged at the inner circumferential surface side
of the lip portion for holding the lip portion.
13. A compressor comprising: a housing; a compression mechanism
placed in the housing for compressing refrigerant; a drive shaft
rotatably supported by the housing for driving the compression
mechanism; a shaft seal interposed between the housing and the
drive shaft for sealing an outer circumferential surface of the
drive shaft to the housing, the shaft seal including: a lip seal
including: a lip body fixed at a housing side; a lip portion
extending from the lip body, the lip portion having inner and outer
circumferential surfaces, the inner circumferential surface of the
lip portion being in contact with the outer circumferential surface
of the drive shaft, the lip portion being deformable; a support
portion formed at the outer circumferential surface side of the lip
portion for applying tensile force to the lip seal when the lip
portion is deformed toward the inner circumferential surface side
of the lip portion; and a receiving portion formed at the outer
circumferential surface side of the lip portion for receiving the
pressure in the housing.
14. The compressor according to claim 13, wherein the support
portion is arranged at the top end of the lip portion.
15. The compressor according to claim 13, wherein a plurality of
the support portions is arranged in the circumferential direction
of the lip portion at a predetermined interval.
16. The compressor according to claim 13, wherein the support
portion connects the outer circumferential surface of the lip
portion with the lip body.
17. The compressor according to claim 16, wherein the support
portion is formed integrally with the lip body and the lip
portion.
18. The shaft seal according to claim 16, wherein the support
portion is formed separately from the lip body and lip portion.
19. The compressor according to claim 13, wherein the support
portion is constituted of elastic member.
20. The compressor according to claim 19, wherein the elastic
member is made of one of rubber, resin and metal.
21. The compressor according to claim 19, wherein the elastic
member is one of a coil spring and a leaf spring.
22. The compressor according to claim 13, wherein the support
portion forms a rod having one of rectangular and circular
transverse cross sections in shape.
23. The compressor according to claim 13, wherein the support
portion forms a thin plate in shape.
24. The compressor according to claim 13, the shaft seal includes a
holding member arranged at the inner circumferential surface side
of the lip portion for holding the lip portion.
25. A method for sealing an outer circumferential surface of a
rotary shaft to a housing, the method comprising the steps of:
interposing a lip seal having a lip portion between the housing and
the rotary shaft; contacting the lip portion with an outer
circumferential surface of the rotary shaft; forming a support
portion at an outer circumferential surface side of the lip portion
so as to apply tensile force to the lip portion when the lip
portion is deformed toward an inner circumferential surface side of
the lip portion; and forming a receiving portion at the outer
circumferential surface side of the lip portion so as to receive
the pressure in the housing.
Description
BACKGROUND OF THE INVENTION
[0001] The invention relates to a shaft seal that seals the outer
circumferential surface of a rotary shaft to a housing, for
example, to a shaft seal that is suitable for sealing the outer
circumferential surface of the drive shaft of a compressor to a
housing.
[0002] Conventionally, for example, in a compressor, a shaft seal
is interposed between a drive shaft that drives a compression
mechanism and a housing so as to seal the outer circumferential
surface of the drive shaft to the housing. In the shaft seal, a lip
portion of a lip seal made of rubber or resin is in contact with
the outer circumferential surface with predetermined elastic force.
Therefore, the shaft seal prevents refrigerant in the housing from
leaking to the outside of the housing along the outer
circumferential surface of the drive shaft. Since such a lip seal
is utilized in severe environments, such as high pressure, high
speed and high temperature, excellent thermal resistance and
excellent abrasion resistance are required. Particularly, when the
pressure in the housing is relatively high, the force resulting
from the pressure in the housing is applied to the lip portion,
which is in contact with the outer circumferential surface of the
drive shaft, from the outer circumferential surface side of the lip
portion. The lip portion is deformed toward the inner
circumferential surface side of the lip portion. The contact area
of the lip portion with the outer circumferential surface of the
drive shaft becomes large, and abnormal abrasion is caused.
[0003] In order to solve such a problem, for example, a shaft seal
as disclosed in Japanese Unexamined Patent No. 2001-193842 is
proposed. In the shaft seal, a reinforcing member that is made of
resin and the flexural strength of which is larger than that of the
lip portion is insert-molded into the lip portion of the lip seal,
or the outer circumferential surface of the lip portion is covered
with a reinforcing member. Therefore, the deformation of the lip
portion caused by the high pressure is suppressed.
[0004] In the above shaft seal, the deformation of the lip portion
caused by the high pressure in the housing is suppressed by
increasing the flexural strength of the lip portion by the
reinforcing member. Therefore, the above shaft seal is
significantly effective for decreasing or stopping the abnormal
abrasion. On the contrary, it is possible to deteriorate the
flexibility of the lip portion.
SUMMARY OF THE INVENTION
[0005] The present invention provides a shaft seal, in which the
flexibility of a lip portion of a lip seal can be maintained and
the deformation of the lip portion can be suppressed, for sealing
the outer circumferential surface of a rotary shaft to a housing by
contacting the lip portion with the outer circumferential surface
of a drive shaft.
[0006] In accordance with the present invention, a shaft seal for
sealing an outer circumferential surface of a rotary shaft to a
housing includes a lip seal. The lip seal includes a lip body, a
lip portion, a support portion and a receiving portion. The lip
body is fixed at a housing side. The lip portion extends from the
lip body and has inner and outer circumferential surfaces. The
inner circumferential surface of the lip portion is in contact with
the outer circumferential surface of the rotary shaft. The lip
portion is deformable. The support portion is formed at the outer
circumferential surface side of the lip portion for applying
tensile force to the lip portion when the lip portion is deformed
toward the inner circumferential surface side of the lip portion.
The receiving portion is formed at the outer circumferential
surface side of the lip portion for receiving the pressure in the
housing.
[0007] The present invention also provides a method for sealing an
outer circumferential surface of a rotary shaft to a housing. The
method comprising the steps of interposing a lip seal having a lip
portion between the housing and the rotary shaft, contacting the
lip portion with an outer circumferential surface of the rotary
shaft, forming a support portion at an outer circumferential
surface side of the lip portion so as to apply tensile force to the
lip portion when the lip portion is deformed toward an inner
circumferential surface side of the lip portion, and forming a
receiving portion at the outer circumferential surface side of the
lip portion so as to receive the pressure in the housing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The features of the present invention that are believed to
be novel are set forth with particularity in the appended claims.
The invention together with objects and advantages thereof, may
best be understood by reference to the following description of the
presently preferred embodiments together with the accompanying
drawings in which:
[0009] FIG. 1 is a longitudinal cross-sectional view of a variable
displacement compressor of a preferred embodiment according to the
present invention;
[0010] FIG. 2 is a partially enlarged view of FIG. 1 showing a
shaft seal of the preferred embodiment according to the present
invention;
[0011] FIG. 3 is a partially enlarged cross-sectional view of the
compressor showing the whole of the shaft seal in the direction of
the arrow I in FIG. 2.
[0012] FIG. 4 is a cross-sectional view showing a first lip seal of
a first alternative preferred embodiment according to the present
invention;
[0013] FIG. 5 is a cross-sectional view showing a first lip seal of
a second alternative preferred embodiment according to the present
invention;
[0014] FIG. 6 is a cross-sectional view showing a first lip seal of
a third alternative preferred embodiment according to the present
invention;
[0015] FIG. 7 is a cross-sectional view showing a first lip seal of
a fourth alternative preferred embodiment according to the present
invention;
[0016] FIG. 8 is a cross-sectional view showing a first lip seal of
a fifth alternative preferred embodiment according to the present
invention;
[0017] FIG. 9 is a cross-sectional view showing a first lip seal of
a sixth alternative preferred embodiment according to the present
invention; and
[0018] FIG. 10 is a perspective view of a support portion utilized
in the first lip seal of the sixth alternative preferred embodiment
according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0019] A preferred embodiment according to the present invention
will now be described by referring to FIGS. 1 through 3. A
clutchless type variable displacement compressor is described in
the preferred embodiment. FIG. 1 is a longitudinal cross-sectional
view of a variable displacement compressor 100 of the preferred
embodiment. FIG. 2 is a partially enlarged view of FIG. 1. FIG. 3
is a view in the direction of the arrow I in FIG. 2. In FIG. 1, the
left side and the right side respectively correspond to the front
side and the rear side.
[0020] As shown in FIG. 1, a clutchless variable displacement
compressor 100 includes a cylinder block 1, a front housing 2 and a
rear housing 5. The front housing 2 is fixed to the front side of
the cylinder block 1. The rear housing 5 is fixed to the rear side
of the cylinder block 1. A valve plate assembly 6 is interposed
between the cylinder block 1 and the rear housing 5. The rear
housing 5 and the valve plate assembly 6 define a suction chamber 3
and a discharge chamber 4. Refrigerant is introduced into the
suction chamber 3 and is compressed. The compressed refrigerant is
discharged into the discharge chamber 4. A suction port 3a is
formed in the valve plate assembly 6 and interconnects the suction
chamber 3 with a cylinder bore 1a, which is formed in the cylinder
block 1, through a suction valve 3b. A discharge port 4a is formed
in the valve plate assembly 6 and interconnects the discharge
chamber 4 with the cylinder bore 1a through a discharge valve 4b. A
bleed passage 16 is formed in the valve plate assembly 6 and
interconnects the suction chamber 3 with a crank chamber 9 that is
defined by the cylinder block 1 and the front housing 2.
[0021] A drive shaft 8 is inserted through the cylinder block 1 and
the front housing 2. The drive shaft 8 corresponds to a rotary
shaft of the present invention. The drive shaft 8 is supported by
the cylinder block 1 and the front housing 2 through two bearings 7
that are respectively arranged in the cylinder block 1 and the
front housing 2. The drive shaft 8 is directly coupled to a vehicle
engine as an external drive source, which is not shown in the
drawings, without a clutch mechanism. The drive shaft 8 is driven
by the rotation of the vehicle engine. The rotation of the drive
shaft 8 drives a compression mechanism that is placed in the
housing for compressing the refrigerant and that includes a piston
15 as will be described later.
[0022] A disc-shaped rotary swash plate 11 is accommodated in the
crank chamber 9. A through hole 12 is formed substantially at the
center of the swash plate 11. The drive shaft 8 is interposed
through the shaft hole 12. A pair of pins 13 is fixed to the front
side of the swash plate 11. Each of the pins 13 has a substantially
spherical portion 13a at its top end. A rotor 30 is secured to the
drive shaft 8 and is integrally rotated with the drive shaft 8. The
rotor 30 has a disc-shaped lug plate 31, a pair of support arms 32
and a balance weight 33. A through hole 30a is formed in the lug
plate 31, and the drive shaft 8 is inserted through the through
hole 30a.
[0023] The rotor 30 is connected with the swash plate 11 through a
hinge mechanism 20. The support arms 32 of the rotor 30
respectively engage with the pins 13 on the side of the swash plate
11, thereby, constituting the hinge mechanism 20. Each of the
support arms 32 has a support hole 32a whose shape corresponds to
the spherical portion 13a of the pin 13. The spherical portion 13a
is inserted into the support hole 32a. In this state, the support
arm 32 supports the pin 13 while the pin 13 is slidable with
respect to the support hole 32a. Therefore, while the support arm
32 engages with the pin 13, the hinge mechanism 20 transmits the
rotating torque of the drive shaft 8 to the swash plate 11 and
allows the swash plate 11 to incline with respect to a rotary axis
L of the drive shaft 8. Namely, the swash plate 11 is slidable and
inclinable with respect to the drive shaft 8.
[0024] A plurality of the cylinder bores 1a is circumferentially
disposed in the cylinder block 1 at a regular interval. The piston
15 is slidably inserted into each of the cylinder bores 1a. Each of
the pistons 15 is connected to the swash plate 11 through a pair of
shoes 14 at the front side of the piston 15. Thereby, the
rotational movement of the swash plate 11 is converted into the
reciprocating movement of the piston 15 in the corresponding
cylinder bore 1a while the swash plate 11 is rotated in accordance
with the rotation of the drive shaft 8. In accordance with the
reciprocating movement of the piston 15, the refrigerant is
introduced into the cylinder bores 1a from the suction chamber 3
and is compressed. The compressed refrigerant is discharged from
the cylinder bores 1a to the discharge chamber 4.
[0025] A thrust bearing 40 is interposed between the rotor 30 and
the front housing 2 and is in contact with the front side of the
lug plate 31. The front housing 2 receives compression reactive
force, which is generated in compressing the refrigerant by the
piston 15. The compression reactive force travels through the
piston 15, the shoes 14, the swash plate 11, the hinge mechanism 20
and the thrust bearing 40.
[0026] Displacement of the compressor 100 is determined by stroke
of the piston 15 or a distance between the top dead center and the
bottom dead center of the piston 15. The stroke of the piston 15 is
determined by an inclination angle .theta. of the swash plate 11
with respect to the rotary axis L of the drive shaft 8. Namely, as
the inclination angle .theta. of the swash plate 11 becomes large,
the stroke of the piston 15 and the discharge amount of the
refrigerant also become large. On the other hand, as the
inclination angle .theta. of the swash plate 11 becomes small, the
stroke of the piston 15 and the discharge amount of the refrigerant
become small. The inclination angle .theta. of the swash plate 11
is determined by pressure differential between the cylinder bores
1a and the crank chamber 9. The above pressure differential is
regulated by a displacement control valve 18. In FIG. 1, the
inclination angle .theta. of the swash plate 11 is at the largest
angle. Namely, in the above state, the displacement of the
compressor 100 is the largest, and load on the compressor 100 is
relatively high. In contrast, when the load on the compressor 100
is relatively low, the swash plate 11 is located at a position
indicated by the two-dot chain line as shown in FIG. 1.
[0027] A supply passage 17 is formed in the cylinder block 1 and
the rear housing 5 and interconnects the discharge chamber 4 with
the crank chamber 9. The displacement control valve 18 is located
on the supply passage 17. The displacement control valve 18 is an
electromagnetic valve and adjusts the opening degree of the supply
passage 17. The pressure in the crank chamber 9 is varied by
adjusting the opening degree of the supply passage 17. Thereby, the
pressure differential between the cylinder bores 1a and the crank
chamber 9 is regulated. As a result, the inclination angle of the
swash plate 11 is varied, and the stroke of the piston 15 is
varied. Ultimately, the displacement of the compressor 100 is
regulated.
[0028] Next, a shaft seal 50 that is a characteristic part of the
present preferred embodiment will be described by referring to
FIGS. 2 and 3. As shown in FIG. 2, the shaft seal 50 is interposed
between the front housing 2 and the drive shaft 8 for sealing the
outer circumferential surface of the drive shaft 8 to the front
housing 2. The shaft seal 50 includes first and second lip seals 51
and 56 as well as first and second metal retainers 57 and 58. The
first and second lip seals 51 and 56 are in contact with the outer
circumferential surface 8a of the drive shaft 8. The first lip seal
51, for example, is made of rubber and is arranged at the side of
the crank chamber 9. The first lip seal corresponds to a lip seal
of the present invention. The second lip seal 56, for example, is
made of resin and is interposed between the first lip seal 51 and
the metal retainer 58. The first and second metal retainers 57 and
58 are made of metal. The first metal retainer 57 holds the first
lip seal 51. The second metal retainer 58 holds the second lip seal
56. An annular seal chamber 60 is formed between the front housing
2 and the drive shaft 8 at the outer circumferential surface side
of the first lip seal 51 and communicates with the crank chamber 9.
Therefore, the first lip seal 51 experiences the pressure in the
crank chamber 9 through the seal chamber 60. The pressure in the
seal chamber 60 corresponds to the pressure in a housing in the
present invention.
[0029] The seal chamber 60 is formed by the front housing 2. When
the shaft seal 50 is assembled between the front housing 2 and the
drive shaft 8, more particularly when the shaft seal 50 is mounted
around the drive shaft 8, the first and second lip seals 51 and 56
are radially pressed by the circumferential surface 8a of the drive
shaft 8. In this state, the first and second lip seals 51 and 56
apply predetermined elastic force (clamping force) to the outer
circumferential surface 8a of the drive shaft 8. The above elastic
force seals the outer circumferential surface 8a of the drive shaft
8 to the front housing 2 and prevents the refrigerant from leaking
from the seal chamber 60 to the outside of the compressor 100 along
the circumferential surface 8a of the drive shaft 8.
[0030] The first lip seal 51 includes a cylindrical fixed portion
52, a disc portion 53 and a lip portion 54. The fixed portion 52 is
fittingly fixed to the inner circumferential surface of the housing
2 in the seal chamber 60 formed by the front housing 2. The disc
portion 53 extends from the fixed portion 52 inwardly. The fixed
portion 52 and the disc portion 53 correspond to a lip body of the
present invention. The lip portion 54 extends from the disc portion
53 inwardly. The inner circumferential surface of the lip portion
54 is in contact with the outer circumferential surface of the
drive shaft 8. The lip portion 54 is deformable and forms
substantially funnel in shape, the inner diameter of which
gradually is reduced toward the top end of the lip portion 54. As
shown in FIG. 3, a plurality of support portions 55 is arranged in
the circumferential direction of the lip portion 54 at a regular
interval between an outer circumferential surface 54a of the lip
portion 54 and the inner circumferential surface of the fixed
portion 52 at a top portion 54b of the lip portion 54. In the
present preferred embodiment, the number of the support portions 55
is eight. Each of the support portions 55 forms a rod having a
rectangular or circular transverse cross section in shape and
extends in the radial direction of the first lip seal 51. Namely,
the support portion 55 connects the outer circumferential surface
54a of the lip portion 54 with the inner circumferential surface of
the fixed portion 52.
[0031] In the present preferred embodiment, the support portion 55
is formed integrally with the fixed portion 52 and the lip portion
54 upon forming the first lip seal 51. The force resulting from the
pressure in the seal chamber 60 is applied to the outer
circumferential surface 54a of the lip portion 54 through spaces
55a that are formed between the support portions 55. Namely, the
force resulting from the pressure in the seal chamber 60 is applied
to the whole outer circumferential surface 54a of the lip portion
54 other than the part of outer circumferential surface 54a of the
lip portion 54 corresponding to where the support portions 55 are
arranged. The whole outer circumferential surface 54a of the lip
portion 54 other than the above part of outer circumferential
surface 54a of the lip portion 54, to which the force resulting
from the pressure in the seal chamber 60 is applied, corresponds to
a receiving portion of the present invention.
[0032] In the present preferred embodiment, the support portion 55
is formed at the lip portion 54 of the first lip seal 51. When the
lip portion 54 is deformed toward the inner circumferential surface
side of the lip portion 54, or toward the outer circumferential
surface side of the drive shaft 8, by the force resulting from the
pressure in the seal chamber 60 that is applied to the outer
circumferential surface 54a of the lip portion 54, the deformation
is suppressed by elastically pulling the lip portion 54 from the
outer circumferential surface side of the lip portion 54 by the
support portion 55. Namely, when the lip portion 54 is deformed
toward the inner circumferential surface side of the lip portion
54, the support portion 55 applies tensile force to the lip
portion. At this time, the support portion 55 functions as an
elastic member. In this case, suppressing the deformation of the
lip portion 54 by the support portion 55 does not mean suppressing
completely the deformation of the lip portion 54 toward the inner
circumferential surface side of the lip portion 54, and means
reducing the degree of the deformation of the lip portion 54.
[0033] In the above-constructed shaft seal 50, when the pressure in
the seal chamber 60, or in the crank chamber 9, is relatively high,
the lip portion 54 is deformed toward the inner circumferential
surface side of the lip portion 54, or toward the outer
circumferential surface side of the drive shaft 8, for example, as
shown by the two-dot chain line in FIG. 2. Therefore, the contact
area of the lip portion 54 with the outer circumferential surface
8a of the drive shaft 8 does not increase relatively. Namely, the
deformation of the lip portion 54 toward the inner circumferential
surface of the lip portion 54 by applying the force resulting from
the pressure in the seal chamber 60 means the deformation that the
inner diameter of the lip portion 54 is reduced from the top
portion 54b to the base of the lip portion 54 that is connected
with the disc portion 53. The support portion 55 suppresses such
deformation by the tensile force from the outer circumferential
surface side of the lip portion 54. Furthermore, since the
plurality of support portions 55 is arranged in the circumferential
direction of the lip portion 54 at the regular interval, the
well-balanced suppression against the deformation of the lip
portion 54 can be performed.
[0034] Meanwhile, when the pressure in the seal chamber 60
increases, it is preferable that the top portion 54b of the lip
portion 54 is in contact with the outer circumferential surface 8a
of the drive shaft 8 with the strength corresponding to the
pressure in the seal chamber 60, that is, the shaft seal 50
performs self-sealing function. For that purpose, the lip portion
54 needs to have flexibility so as to follow the pressure in the
seal chamber 60. In the present preferred embodiment, the force
resulting from the pressure in the seal chamber 60 is applied to
the whole outer circumferential surface 54a of the lip portion 54
other than the part of the outer circumferential surface 54a of the
lip portion 54 corresponding to where the support portions 55 are
arranged. Also, when the lip portion 54 is mounted around the drive
shaft 8, the top portion 54b of the rubber support portion 55 is
stretched outwardly by the width corresponding to interference,
thereby, bending the support portions 55 slightly. As a result, the
lip portion 54 has flexibility. For the reason, the lip portion 54
can be in contact with the outer circumferential surface 8a of the
drive shaft 8 in accordance with the pressure in the seal chamber
60, that is, self-sealing function in accordance with the pressure
in the seal chamber 60 can be obtained.
[0035] As mentioned above, in the shaft seal 50 of the present
preferred embodiment, the deformation of the lip portion 54 of the
first lip seal 51 is suppressed, and also the lip portion 54 has
flexibility. Therefore, abnormal abrasion can be avoided, and
appropriate sealing performance can be maintained. The degree of
the tensile force against the deformation of the lip portion 54 can
be adjusted freely by changing the number and thickness of the
support portion 55. Thereby, the flexibility of the lip portion 54
can be adjusted. Furthermore, even when the position of the lip
portion 54 is different from a desired position upon mounting the
lip portion 54 around the drive shaft 8, for example, even when the
rotary axis L of the drive shaft 8 is different from the axis of
the lip portion 54, the flexibility of the lip portion 54 absorbs
the positional difference.
[0036] Furthermore, the top portion 54b of the lip portion 54 is
conspicuously easy to abrade. In the present preferred embodiment,
the support portion 55 is arranged at the top portion 54b of the
lip portion 54 so as to support the top portion 54b of the lip
portion 54. Therefore, abrasion of the top portion 54b of the lip
portion 54 can be effectively suppressed. Meanwhile, according to
the present preferred embodiment, the support portion 55 also can
be formed with the fixed portion 52, the disc portion 53 and the
lip portion 54 at the same time when the first lip seal 51 is
manufactured. Therefore, the first lip seal 51 is advantageous in
manufacture.
[0037] The present invention is not limited to the above-mentioned
preferred embodiment, and various applications and modifications
are considered. Following alternative embodiments may be practiced
by modifying from the above-mentioned preferred embodiment.
[0038] Although the support portion 55 is formed integrally with
the fixed portion 52 and the lip portion 54 in the above-mentioned
preferred embodiment, the structure of the support portion 55 can
be modified according to need. Now, first lips according to the
following alternative preferred embodiments will be described by
referring to FIGS. 4 through 10. The same elements other than the
first lip seal are numbered by the identical reference numerals as
those in the above-mentioned preferred embodiment.
[0039] In a first alternative preferred embodiment, as shown in
FIG. 4, a first lip seal 151 includes a fixed portion 152 and a lip
portion 154. In the first lip seal 151, a support portion 155 is
arranged between an outer circumferential surface 154a of the lip
portion 154 and the fixed portion 152 at a top portion 154b of the
lip portion 154. The support portion 155 is made of resin or metal
and is formed separately from the fixed portion 152 and the lip
portion 154. The support portion 155 forms a rod in shape that
extends in the radial direction of the first lip seal 151, and the
ends of the support portion 155 are respectively bonded to the lip
portion 154 and the fixed portion 152. Namely, the support portion
155 connects the outer circumferential surface 154a of the lip
portion 154 with the inner circumferential surface of the fixed
portion 152. Also, a plurality of the support portions 155 is
arranged in the circumferential direction of the lip portion 154 at
an appropriate interval. According to such structure, the
substantially same advantageous effects can be obtained as
mentioned in the above-mentioned preferred embodiment as shown in
FIGS. 2 and 3.
[0040] In a second alternative preferred embodiment, as shown in
FIG. 5, a first lip seal 251 includes a fixed portion 252 and a lip
portion 254. In the first lip seal 251, a support portion 255 is
arranged between an outer circumferential surface 254a of the lip
portion 254 and the fixed portion 252 at a top portion 254b of the
lip portion 254. The support portion 255 is constituted of a coil
spring made of metal or resin. The ends of the support portion 255
are respectively bonded to the lip portion 254 and the fixed
portion 252. Namely, the support portion 255 connects the outer
circumferential surface 254a of the lip portion 254 with the inner
circumferential surface of the fixed portion 252. Also, a plurality
of the support portions 255 is arranged in the circumferential
direction of the lip portion 254 at an appropriate interval.
According to such structure, the substantially same advantageous
effects can be obtained as mentioned in the above-mentioned
preferred embodiment as shown in FIGS. 2 and 3.
[0041] In a third alternative preferred embodiment, as shown in
FIG. 6, a first lip seal 351 includes a fixed portion 352 and a lip
portion 354. A support portion 355 that is the same support portion
as in the above-mentioned preferred embodiment as shown in FIGS. 2
and 3 is formed in the first lip seal 351. In addition, a holding
member 359 is arranged at the inner circumferential surface side of
the lip portion 354 for holding the lip portion 354. The holding
member 359 is made of metal or resin and has a relatively large
flexural strength. The holding member 359 includes a holding
portion 359a and a disc portion 359b. The holding portion 359a has
substantially a cylindrical shape corresponding to the inner
circumferential surface of the lip portion 354. The disc portion
359b extends from the holding portion 359a outwardly. The disc
portion 359b is axially interposed between the first lip seal 351
and a second lip seal 356. According to such structure, the
deformation of the lip portion 354 toward the inner circumferential
surface side of the lip portion 354 can be effectively suppressed
by cooperation of the support portion 355 and the holding member
359.
[0042] In a fourth alternative preferred embodiment, as shown in
FIG. 7, a first lip seal 451 includes a fixed portion 452, a disc
portion 453 and a lip portion 454. In the first lip seal 451, a
support portion 455 is arranged at the outer circumferential
surface side of a top portion 454b of the lip portion 454 and
extends in the axial direction of the lip portion 454. The support
portion 455 is constituted of a leaf spring that is made of resin
or metal. The support portion 455 includes a step portion 455a
between the ends of the support portion 455. The ends of the
support portion 455 are respectively bonded to the top portion of
an outer circumferential surface 454a of the lip portion 454 and
the side surface of the disc portion 453. Namely, the support
portion 455 connects the outer circumferential surface 454a of the
lip portion 454 with the side surface of the disc portion 453. A
plurality of the support portions 455 is arranged in the
circumferential direction of the lip portion 454. Also according to
such structure, the substantially same advantageous effects can be
obtained as mentioned in the above-mentioned preferred embodiment
as shown in FIGS. 2 and 3.
[0043] In a fifth alternative preferred embodiment, as shown in
FIG. 8, a first lip seal 551 includes a fixed portion 552, a disc
portion 553 and a lip portion 554. In the first lip seal 551, a
support portion 555 is arranged in a space surrounded by an outer
circumferential surface 554a of the lip portion 554, the inner
circumferential surface of the fixed portion 552 and the side of
the disc portion 453. The support portion 555 connects the outer
circumferential surface 554a of the lip portion 554, the inner
circumferential surface of the fixed portion 552 and the side of
the disc portion 553. In the fifth alternative preferred
embodiment, the support portion 555 extends in the radial direction
of the first lip seal 551 and forms a thin plate in shape. A
plurality of the support portions 555 is arranged in the
circumferential direction of the lip portion 554 at a regular
interval. The support portion 555 that is constituted of the thin
plate is formed integrally with the fixed portion 552, the disc
portion 553 and the lip portion 554 at the same time when the first
lip seal 551 is manufactured. The outer circumferential surfaces
554a of the lip portion 554 are formed between the thin plates.
Also according to such structure, the substantially same
advantageous effects can be obtained as mentioned in the
above-mentioned preferred embodiment as shown in FIGS. 2 and 3.
[0044] In a sixth alternative preferred embodiment, as shown in
FIGS. 9 and 10, a first lip seal 651 includes a disc portion 653
and a lip portion 654. In the first lip seal 651, a support portion
655 includes a cylindrical body 655a made of the resin or metal.
The cylindrical body 655a includes a relatively large number of
flexible portions 655b that are arranged in the circumferential
direction of the cylindrical body 655a at a regular interval and
that form substantially teeth of a comb in shape. In the sixth
alternative preferred embodiment, the cylindrical body 655a
includes fourteen flexible portions 655b. The support portion 655
is fitted such that the cylindrical body 655a covers an outer
circumferential surface 654a of the lip portion 654. The flexible
portions 655b are bonded to the outer circumferential surface 654a
of the lip portion 654. The cylindrical body 655a also includes a
flange portion 655c. The flange portion 655c is bonded to the side
of the disc portion 653. Namely, the support portion 655 connects
the outer circumferential surface 654a of the lip portion 654 with
the side surface of the disc portion 653. Also according to such
structure, the substantially same advantageous effects can be
obtained as mentioned in the above-mentioned preferred embodiment
as shown in FIGS. 2 and 3.
[0045] Although the shaft seal 50 of the clutchless variable
displacement compressor is described in the above-mentioned
preferred embodiment, the present invention also can be applied to
a shaft seal of a compressor including a clutch mechanism.
Furthermore, the present invention can be applied to shaft seals
other than shaft seals of compressors.
[0046] The present examples and embodiments are to be considered as
illustrative and not restrictive, and the invention is not to be
limited to the details given herein but may be modified within the
scope of the appended claims.
* * * * *