Technical Field
[0001] The present invention relates to a scroll compressor.
Background Art
[0002] A scroll compressor is equipped with a fixed scroll and an orbiting scroll. Each
of the fixed scroll and the orbiting scroll is a disk-shaped end plate provided with
a spiral wrap on one surface side. Such a fixed scroll and an orbiting scroll are
arranged to face each other with their wraps intermeshed, and the orbiting scroll
is caused to revolve with respect to the fixed scroll. Then, a compression chamber
between both of the scrolls is filled with a gas drawn through the outermost circumferential
portions of the wraps. The gas is compressed as the volume of the compression chamber
decreases with the revolution of the orbiting scroll. The gas is discharged through
a port positioned at the central portion of the end plate in a maximally compressed
state.
[0003] In general, the fixed scroll and the orbiting scroll are each provided with a tip
seal at its tip of the wrap. The compressed gas is introduced into seal grooves accommodating
the tip seals. Each tip seal is pressed against the end plate by a back pressure caused
by the compressed gas to seal a clearance between the wraps and the end plates.
[0004] In a scroll compressor described in Patent Literature 1, a tip seal is divided into
two parts in a circumferential direction, and the divided two seals are connected
together. The tip seal positioned at an inner circumferential side of each wrap is
formed from a material more excellent in heat-resistance and abrasion-resistance than
that of the tip seal positioned at an outer circumferential side.
[0005] In the meantime, there is a scroll compressor formed such that a wrap is shorter
at an inner circumferential side than at an outer circumferential side and a counterpart
end plate correspondingly projects toward the inside more at the inner circumferential
side than at the outer circumferential side in order to decrease the volume of a compression
chamber not only in a circumferential direction but also in a height direction, thereby
achieving a high compression ratio (Patent Literature 2). In this type of a scroll
compressor called 3D Scroll®, a step is formed at both wraps and end plates.
[0006] In such a three-dimensional type (3D type) scroll compressor, each tip seal is placed
as divided into portions at the inner and outer circumferential sides of the step
of the wrap as described in Patent Literature 2.
Citation List
Patent Literature
Summary of Invention
Technical Problem
[0008] In a scroll compressor, temperature and pressure rise with proximity to the central
portion of a scroll. Each tip seal is required to have high abrasion resistance and
heat resistance to endure the pressing load and high temperature due to the high pressure
at the central portion.
[0009] In general, however, a material having high abrasion resistance and heat resistance
is expensive, so the material for the tip seals is selected in consideration of the
cost.
[0010] Here, the division of the tip seals as in Paten Literature 1 increases the number
of parts, and thus this requires the cost of joining the tip seals together. Generally,
in the case of an ordinary scroll compressor of not 3D type as in Patent Literature
1, an integral tip seal formed from the same material is provided along the entire
length of each wrap from the outermost circumferential portion to the innermost circumferential
portion.
[0011] In contrast, in the case of a 3D-type scroll compressor, it is hard to form a tip
seal integrally on both sides (inward and outward) of the step of each wrap. As a
result, in the 3D-type scroll compressor, each tip seal is inevitably divided into
portions at inner and outer circumferential sides of the step of the wrap as in Patent
Literature 2.
[0012] The present invention has been made in view of that in the 3D-type scroll compressor,
each tip seal is divided into portions on both sides of the step of the wrap, and
aims to improve the reliability of the 3D-type scroll compressor by improving the
durability of the tip seals.
Solution to Problem
[0013] The present invention is a scroll compressor including a fixed scroll and an orbiting
scroll, the fixed scroll and the orbiting scroll each having a spiral wrap configured
to decrease in height from an outer circumferential side to an inner circumferential
side via a stepped portion and an end plate having a stepped wall being erected following
the stepped portion of the counterpart wrap.
[0014] In the present invention, an inner circumferential tip seal provided in an inner
circumferential side of the stepped portion and lying between the wrap and the counterpart
end plate and an outer circumferential tip seal provided in an outer circumferential
side of the stepped portion and lying between the wrap and the counterpart end plate
are different in material at least at portions facing the end plate.
[0015] According to the present invention, among the tip seals formed as inevitably divided
into portions on both sides of the stepped portion of each wrap of a 3D scroll, only
the inner circumferential tip seal can be formed from a material satisfying a desired
condition based on the temperature and the pressure of the central portion of each
scroll, and the outer circumferential tip seal can be formed from other, inexpensive
material.
[0016] Also, in the 3D-type scroll compressor, it is assumed that the inner circumferential
tip seal and the outer circumferential tip seal are placed as set apart and separated
by the stepped portion, and thus such a scroll compressor does not require the cost
of joining both the inner and outer circumferential tip seals together.
[0017] Therefore, according to the present invention, the durability of the tip seals can
be improved while holding down the cost, compared with the case in which both the
inner and outer circumferential tip seals are formed from the same material.
[0018] An object of the present invention can be achieved if the inner circumferential tip
seal and the outer circumferential tip seal are formed from different materials at
least at the portions facing the end plate.
[0019] In the scroll compressor of the present invention, it is preferable that the stepped
portion be positioned in an outer circumferential side of a rotation angle corresponding
to a central value of a temperature range within which a temperature of the wrap rises
from a rotation angle at an outermost circumferential portion of the wrap to a rotation
angle at an innermost circumferential portion of the wrap, and that the inner circumferential
tip seal be formed from a material satisfying at least one requirement of a higher
heat resistant temperature, a smaller comparative abrasion quantity, and a smaller
linear expansion coefficient than those of a material of the outer circumferential
tip seal.
[0020] The term "heat resistant temperature" means an upper-limit temperature causing no
change in appearance or no decrease in mechanical properties to a tip seal when it
is used continuously.
[0021] The term "comparative abrasion quantity" is obtained by dividing the abrasion quantity
expressed in volume by the distance a tip seal has slid and the vertical load.
[0022] A material that is hardly abraded has a small comparative abrasion quantity. Also,
a tip seal formed of a material having a small linear expansion coefficient can avoid
being strongly pressed against the end plate due to the heat expansion, and is therefore
hardly abraded. In the present invention, the comparative abrasion quantity and the
linear expansion coefficient are measures associated with the abrasion resistance
showing how small a volume is that is reduced under friction.
[0023] The term "durability" of a tip seal as used herein includes heat resistance expressed
by the heat resistant temperature, and the above abrasion resistance.
[0024] The present invention also encompasses a configuration in which the materials of
each of the inner circumferential tip seal and the outer circumferential tip seal
are different only at the portions facing the end plate.
[0025] Examples of such a configuration include one in which a heat resistant temperature
of a material of the portion of the inner circumferential tip seal facing the end
plate is higher than that of a material of the portion of the outer circumferential
tip seal facing the end plate, one in which a comparative abrasion quantity of a material
of the portion of the inner circumferential tip seal facing the end plate is smaller
than that of a material of the portion of the outer circumferential tip seal facing
the end plate, and one in which a linear expansion coefficient of a material of the
portion of the inner circumferential tip seal facing the end plate is smaller than
that of a material of the portion of the outer circumferential tip seal facing the
end plate. The present invention can contribute to improving the durability of the
inner circumferential tip seal by any of these configurations.
[0026] The durability of each tip seal can be improved if the material of the inner circumferential
tip seal satisfies one of the requirements above.
[0027] Further, because the heat resistant temperature of the outer circumferential tip
seal can be kept to be a temperature equal to or lower than the central value of the
temperature rise range, a less inexpensive material whose heat resistant temperature
is not so high can be selected as the material for the outer circumferential tip seal.
[0028] In the scroll compressor of the present invention, it is preferable that the stepped
portion be positioned in an outer circumferential side of the rotation angle corresponding
to the central value of the temperature range within which the temperature of the
wrap rises from the rotation angle at the outermost circumferential portion of the
wrap to the rotation angle at the innermost circumferential portion of the wrap, and
that the inner circumferential tip seal be formed from a coating of an abrasion-resistant
material at least at a portion facing the end plate.
[0029] The term "coating" means a film provided on a surface of the base material of a tip
seal by any method such as painting, plating, sputtering, chemical vapor deposition,
and physical vapor deposition. The coating can be constituted by one or more layers
provided on the surface of the base material.
[0030] Abrasion resistance higher than that of the outer circumferential tip seal can be
imparted to the inner circumferential tip seal by forming the inner circumferential
tip seal from the coating at least at the portion facing the end plate. Therefore,
necessary abrasion resistance can be achieved while holding down the material cost
by forming the base material of the inner circumferential tip seal from the same material
for the base material of the outer circumferential tip seal.
[0031] Also, even if it is difficult to use a material more excellent in abrasion-resistance
than the material that can be used for the base material, for the material of the
base material of the tip seal, the abrasion resistance can be further improved by
selecting such a material as the material for the coating.
[0032] Further, if the application of the coating can give a surface that is smoother than
that of the base material, the coefficient of friction of the surface of the inner
circumferential tip seal reduces. The abrasion resistance can also be enhanced in
that the abrasion loss is reduced.
[0033] In the scroll compressor of the present invention, it is preferable that the stepped
portion be positioned in an outer circumferential side of the rotation angle corresponding
to the central value of the temperature range within which the temperature of the
wrap rises from the rotation angle at the outermost circumferential portion of the
wrap to the rotation angle at the innermost circumferential portion of the wrap, and
that a thickness dimension of the inner circumferential tip seal be greater than a
thickness dimension of the outer circumferential tip seal.
[0034] Because the tip seals slide against the end plate while being pressed against it
to be gradually abraded, they are replaced periodically. The inner circumferential
tip seal, which is subjected to a large pressing load due to back pressure, is abraded
more easily than the outer circumferential tip seal.
[0035] Then, the inner circumferential tip seal, if made thick, can leave a thickness sufficient
for the seal even when greatly abraded. This can ensure the reliability of the tip
seal as well as decreasing the frequency of the replacement.
[0036] In addition, the thickness of the outer circumferential tip seal can be kept sufficient
for the seal, thereby holding down the cost.
[0037] The scroll compressor of the present invention includes a fixed scroll and an orbiting
scroll, the fixed scroll and the orbiting scroll each having a spiral wrap configured
to decrease in height from an outer circumferential side to an inner circumferential
side via a stepped portion, and an end plate having a stepped wall being erected following
the stepped portion of the counterpart wrap, in which a thickness dimension of an
inner circumferential tip seal provided in an inner circumferential side of the stepped
portion and lying between the wrap and the counterpart end plate is greater than a
thickness dimension of an outer circumferential tip seal provided in an outer circumferential
side of the stepped portion and lying between the wrap and the counterpart end plate.
[0038] The present invention also utilizes the fact that in a 3D-type scroll compressor,
each tip seal is divided into portions on both sides of a step of a wrap.
[0039] In the case of an ordinary scroll compressor without any step formed on the wraps,
if the inner circumferential tip seal and the outer circumferential tip seal are different
in thickness, a bottom of each seal groove accommodating the tip seal is stepped as
well as joining the inner circumferential tip seal and the outer circumferential tip
seal together. In this case, the position of the step in the seal groove and the position
of the joint of the tip seals are easily misaligned to cause leakage.
[0040] In the present invention, among the tip seals formed as inevitably divided into portions
on both sides of the stepped portion of the wrap of the 3D scroll, the thickness of
the inner circumferential tip seal is made greater than that of the outer circumferential
tip seal.
[0041] Then, even if the inner circumferential tip seal, which is subjected to a large pressing
load due to back pressure, is greatly abraded, the inner circumferential tip seal
can leave a thickness sufficient for the seal. This improves the durability and the
reliability of the tip seals.
[0042] In addition, the thickness of the outer circumferential tip seal can be kept sufficient
for the seal, thereby holding down the cost.
[0043] In each of the above scroll compressors, it is preferable that the stepped portion
be positioned within a rotation angle range exceeding 2π in an inner circumferential
side from the rotation angle at the outermost circumferential portion of the wrap.
[0044] The value 2π corresponds to a rotation angle obtained by one revolution of the orbiting
scroll. While the orbiting scroll makes one revolution, suction inlets open at the
outermost circumferential portions of the wraps and then close again.
[0045] If the stepped portion is positioned exceeding 2π from the outermost circumferential
portion, the length of the outer circumferential tip seal of 2π or more can be assured.
This can ensure the cost reduction effect by using an inexpensive material for the
outer circumferential tip seal.
[0046] Also, it is preferable that the stepped portion be positioned within a rotation angle
range exceeding 3π in an inner circumferential side from the rotation angle at the
outermost circumferential portion of the wrap.
[0047] If the stepped portion is positioned exceeding 3π from the outermost circumferential
portion, the stepped portion does not exist in compression chambers when the suction
inlets are closed to close up the compression chambers, and the compression chambers
would not decrease in volume in the height direction of the wrap. This can maximize
the volume of the compression chambers positioned at the outermost circumferential
portion, thereby ensuring a large compression ratio.
[0048] The scroll compressor of the present invention can compress any working fluid such
as a refrigerant and air, but is especially preferably used in an air-compressing
scroll compressor. If used for compressing air, the temperature rises significantly
at the central portion of each scroll, and thus the present invention, which can impart
durability to the inner circumferential tip seal, has a great effect.
[0049] Also, the present invention can be applied to both a scroll compressor using an oil
for seal, cooling, and lubrication of the scroll and a scroll compressor of an oil-free
type not using oil, but is especially useful when applied to the oil-free type scroll
compressor. This is because in the oil-free type scroll compressor, the tip seals
slide directly against the end plate without an oil (lubricant), and thus the temperature
rises significantly at the inner circumferential side.
[0050] Therefore, the effect of the present invention is pronounced when the present invention
is applied to an air-compressing, oil-free scroll compressor.
Advantageous Effect of Invention
[0051] According to the present invention, a 3D-type scroll compressor with improved reliability
can be provided by improving the durability of a tip seal.
Brief Description of Drawings
[0052]
[FIG. 1] FIG. 1 is a view showing a scroll compressor according to a first embodiment,
which is partially cut away to show a main part.
[FIG. 2] FIG. 2 is a plan view showing respective wraps of a fixed scroll and an orbiting
scroll with the wrap of the orbiting scroll being partially cut away.
[FIG. 3] FIG. 3 is a perspective view of the fixed scroll and the orbiting scroll.
[FIG. 4] FIG. 4 is a cross-sectional view showing the wrap and an end plate at a stepped
portion.
[FIG. 5] FIG. 5 is a graph showing a relation between a rotation angle of the wrap
and a temperature of the wrap.
[FIG. 6] FIG. 6 is a cross-sectional view showing a wrap and an end plate at a stepped
portion in a scroll compressor of a second embodiment.
[FIG. 7] FIG. 7 is a cross-sectional view showing a wrap and an end plate at a stepped
portion in a scroll compressor of a third embodiment.
[FIG. 8] FIG. 8 is a schematic view showing a modified example of the present invention.
Description of Embodiments
[0053] Hereinafter, embodiments of the present invention will be described with reference
to the attached drawings.
[First Embodiment]
[0054] A scroll compressor 10 shown in FIG. 1 is suitably used for, for example, a brake
or an air spring of a railroad car as a compressed air source.
[0055] The scroll compressor 10 includes a fixed scroll 20 fixed to a case (not shown),
an orbiting scroll 30 which is caused to revolve with respect to the fixed scroll
20, and a motor 11 providing torque to the orbiting scroll 30.
[0056] The scroll compressor 10 draws air in between the fixed scroll 20 and the orbiting
scroll 30 with the motor 11 as a power source and discharges air compressed at compression
chambers S formed between the fixed scroll 20 and the orbiting scroll 30.
[0057] The scroll compressor 10 is an oil-free type compressor not using oil for seal, cooling,
and lubrication of a scroll, unlike a conventional scroll compressor which compresses,
together with air, oil for seal, cooling, and lubrication of a scroll.
[0058] The scroll compressor 10 is accommodated in a case (not shown) together with a fan
for cooling the motor 11 or a bearing, a device for cooling and dehumidifying compressed
air to be discharged, and an electric box.
[0059] It is to be noted that grease is used for the lubrication of the motor 11 or the
bearing.
[0060] The motor 11 is configured to include a stator and a rotor accommodated in a motor
case 12.
[0061] The motor 11 outputs a torque by energizing the stator and rotating the rotor. The
torque is transmitted to a shaft 15 that is coupled by a coupling 14 to an output
shaft 13 provided to the rotor.
[0062] The shaft 15 is provided at its end portion with an eccentric pin 151 that is eccentric
with respect to the shaft center.
[0063] The fixed scroll 20 includes a fixed end plate 200 and a spiral wrap 21 erected on
one surface side of the fixed end plate 200.
[0064] The orbiting scroll 30 also includes an orbiting end plate 300 and a spiral wrap
31 erected on one surface side of the orbiting end plate 300.
[0065] The fixed scroll 20 and the orbiting scroll 30 are formed from a metal such as aluminum,
an aluminum alloy, and iron (e.g., cast iron or steel). Surfaces of the fixed scroll
20 and the orbiting scroll 30 may be subjected to a surface treatment such as alumite
treatment if the scrolls are of an aluminium based material, or quenching and tempering,
nitriding, and carburization if the scrolls are of an iron/steel material.
[0066] The orbiting scroll 30 is coupled to the above eccentric pin 151 by a boss 34 provided
on a back surface of the orbiting end plate 300. When the shaft 15 rotates, the orbiting
scroll 30 is caused to revolve with respect to the shaft center of the shaft 15 while
being prevented from rotating by an Oldham ring (not shown).
[0067] As shown in FIG. 2, the wrap 21 of the fixed scroll 20 and the wrap 31 of the orbiting
scroll 30 are off-centered from each other by a predetermined amount, and intermeshed
out of phase with each other by 180 degrees.
[0068] The compression chambers S are formed point-symmetrically to the central portions
(the innermost circumferential portions) of the spirals of the wraps 21 and 31 between
the fixed scroll 20 and the orbiting scroll 30.
[0069] When the orbiting scroll 30 revolves from the state shown in FIG. 2, a suction inlet
IN of air is formed between an end portion at an outermost circumferential portion
of the wrap 21 and the wrap 31 and also between an end portion at an outermost circumferential
portion of the wrap 31 and the wrap 21.
[0070] When the suction inlets IN are closed to the state shown in FIG. 2 with the revolution
of the orbiting scroll 30, the compression chambers S are formed that are filled with
the air drawn through the suction inlets IN. The compression chambers S are gradually
forced to an inner circumferential side while decreasing the volume, with the revolution
of the orbiting scroll 30. The air inside the compression chambers S is discharged
through a discharge port 201 (FIG. 1) formed at the central portion of the spiral
on the fixed end plate 200.
[0071] The scroll compressor 10 is a 3D-type scroll compressor, and the volumes of the compression
chambers S formed between the both scrolls 20 and 30 decrease also in the height direction
of the wraps 21 and 31 in the middle of the spiral. Thus, in both of the fixed scroll
20 and the orbiting scroll 30, the height of the wraps 21 and 31 is lower at the inner
circumferential side than at the outer circumferential side and the counterpart end
plates 300 and 200 that respectively face the wraps 21 and 31 are projected toward
the inside more at the inner circumferential side than at the outer circumferential
side as shown in FIG. 3.
[0072] Accordingly, the wraps 21 and 31 respectively have stepped portions 21C and 31C that
become lower from the outer circumferential side to the inner circumferential side,
and the end plates 300 and 200 respectively have stepped walls 20C and 30C that become
taller from the outer circumferential side to the inner circumferential side. The
stepped walls 20C and 30C are respectively formed in an arc shape in a plan view of
the end plates 200 and 300.
[0073] The wrap 21 of the fixed scroll 20 is divided into an inner circumferential wrap
21A positioned in an inner circumferential side of the stepped portion 21C and an
outer circumferential wrap 21B positioned in an outer circumferential side of the
stepped portion 21C.
[0074] A bottom of the orbiting end plate 300 facing the wrap 21 is segmented into an inner
circumferential bottom 30A and an outer circumferential bottom 30B at the stepped
wall 30C.
[0075] Also, the wrap 31 of the orbiting scroll 30 is divided into an inner circumferential
wrap 31A positioned in an inner circumferential side of the stepped portion 31C and
an outer circumferential wrap 31B positioned in an outer circumferential of the stepped
portion 31C.
[0076] A bottom of the fixed end plate 200 facing the wrap 31 is segmented into an inner
circumferential bottom 20A and an outer circumferential bottom 20B at the stepped
wall 20C.
[0077] Hereinafter, a tip seal provided to each of the wraps 21 and 31 will be described.
[0078] As shown in FIG. 3, the inner circumferential wrap 21A of the fixed scroll 20 has
an inner circumferential tip seal 41 at its tip. The inner circumferential tip seal
41 lies between the inner circumferential wrap 21A and the inner circumferential bottom
30A of the orbiting end plate 300. The inner circumferential tip seal 41 is provided
along almost the entire length of the inner circumferential wrap 21A from a starting
end of the inner circumferential wrap 21A positioned close to the stepped portion
21C to a terminal end of the inner circumferential wrap 21A positioned at the central
portion of the spiral.
[0079] Also, the outer circumferential wrap 21B of the fixed scroll 20 has an outer circumferential
tip seal 42 at its tip. The outer circumferential tip seal 42 lies between the outer
circumferential wrap 21B and the outer circumferential bottom 30B of the orbiting
end plate 300. The outer circumferential tip seal 42 is provided along almost the
entire length of the outer circumferential wrap 21B from a starting end of the outer
circumferential wrap 21B positioned at an outermost circumferential portion of the
spiral to a terminal end of the outer circumferential wrap 21B positioned close to
the stepped portion 21C.
[0080] In the embodiment, the inner circumferential tip seal 41 and the outer circumferential
tip seal 42 are formed to have the same thickness.
[0081] As for the orbiting scroll 30, the inner circumferential wrap 31A also has an inner
circumferential tip seal 51 at its tip. The inner circumferential tip seal 51 lies
between the inner circumferential wrap 31A and the inner circumferential bottom 20A
of the fixed end plate 200. The inner circumferential tip seal 51 is formed similarly
to the inner circumferential tip seal 41.
[0082] Also, the outer circumferential wrap 31B has an outer circumferential tip seal 52
at its tip. The outer circumferential tip seal 52 lies between the outer circumferential
wrap 31B and the outer circumferential bottom 20B of the fixed end plate 200. The
outer circumferential tip seal 52 is formed similarly to the outer circumferential
tip seal 42.
[0083] These tip seals 41, 42, 51, and 52 are accommodated in their respective seal grooves
D formed in the wraps into which the tip seals are provided as shown in FIG. 4. In
each of the seal grooves D, compressed air is introduced through a gap G between an
inner wall of the seal groove D positioned at the inner circumferential side and the
tip seal, along the seal groove D to a back surface side of the tip seal. This causes
a negative pressure at the surface side of the tip seal relative to the back surface
side to lift the tip seal from the seal groove D, thereby pressing the tip seal against
the end plate. Then, a clearance between the tip seal and the end plate is sealed,
thereby keeping the compression chambers S airtight.
[0084] In the present embodiment, a material of the inner circumferential tip seals 41 and
51 and a material of the outer circumferential tip seals 42 and 52 are different from
each other.
[0085] The material of the inner circumferential tip seals 41 and 51 and the material of
the outer circumferential tip seals 42 and 52 are determined based on the temperature
and the pressure which rise with the compression of air.
[0086] FIG. 5 shows how the temperature of the wraps 21 and 31 rises with proximity to the
central portion (the innermost circumferential portion) from the outermost circumferential
portion (0 rad) of the spiral.
[0087] The rotation angle from 0 rad to 2π rad corresponds to a rotation angle from the
opening to the close of the suction inlets IN. Within the angular range of rotation,
the inside of the compression chambers S is under the atmosphere outside the scrolls
20 and 30, and thus the temperature hardly rises. In the example shown in FIG. 5,
the temperature of the wraps 21 and 31 from the outermost circumferential portion
to 2π rad does not increase beyond about 50°C.
[0088] When the rotation angle exceeds 2π rad to start the compression within the compression
chambers S, the temperature of the wraps 21 and 31 rises with the temperature rise
of the air by the compression, and thus the temperature rises to 225°C at the central
portion of the spiral (about 7π rad).
[0089] The temperature shown in FIG. 5 is just an example. The temperature and the slope
of the temperature rise change in accordance with the volume and the compression ratio
of the compression chambers S, and the rotation angle from the outermost circumferential
portion to the innermost circumferential portion of the wraps 21 and 31. In any case,
the temperature similarly rises slowly from the outermost circumferential portion
to 2π and rises gradually after exceeding 2π toward the central portion.
[0090] The inner circumferential tip seals 41 and 51 disposed at the inner circumferential
sides of the wraps 21 and 31 including the central portions of the spirals are required
to have heat resistance to withstand high temperatures as above.
[0091] Also, the inner circumferential tip seals 41 and 51 are subjected to high back pressure
due to the compressed air compared with the outer circumferential tip seals 42 and
52. As a result, the inner circumferential tip seals 41 and 51 slide while being strongly
pressed against the end plates, resulting in a large frictional force between the
inner circumferential tip seals 41 and 51 and the end plates. Accordingly, in order
to avoid early wear of the inner circumferential tip seals 41 and 51 due to the friction,
the inner circumferential tip seals 41 and 51 are also required to have abrasion resistance.
[0092] Further, because the inner circumferential tip seals 41 and 51 are disposed at the
inner circumferential sides which reach high temperatures and frictional heat acts
between the inner circumferential tip seals 41 and 51 and the end plates, the inner
circumferential tip seals 41 and 51 undergo a large amount of thermal expansion. Thus,
the inner circumferential tip seals 41 and 51 are abraded significantly when pressed
against the end plates more strongly. In order to reduce the abrasion loss, it is
desirable that the inner circumferential tip seals 41 and 51 have a small linear expansion
coefficient.
[0093] Here, back pressure and thermal expansion are different between the inner circumferential
tip seals 41 and 51 and the outer circumferential tip seals 42 and 52. Accordingly,
even when the inner circumferential tip seals 41 and 51 are being pressed against
the end plates 300 and 200, a clearance could exist between the outer circumferential
tip seals 42 and 52 and the end plates 300 and 200. In order to avoid this, the linear
expansion coefficient of the inner circumferential tip seals 41 and 51 and that of
the outer circumferential tip seals 42 and 52 are preferably balanced.
[0094] The material for the inner circumferential tip seals 41 and 51 is selected from resins
and metals satisfying the heat resistance and the abrasion resistance under the conditions
of high temperatures and high pressures as described above.
[0095] Resins which may be used for the inner circumferential tip seals 41 and 51 include
PI (polyimide), PEEK (polyether ether ketone), and PTFE (polytetrafluoroethylene).
Other resins such as PAI (polyamide imide) and PPS (polyphenylene sulfide) may also
be adopted. Fillers such as a metal or carbon may be mixed in these resins.
[0096] The inner circumferential tip seals 41 and 51 may be formed by, for example, injection
molding from the resins as described above.
[0097] The inner circumferential tip seals 41 and 51 may also be formed by, for example,
press blanking from a metal like iron.
[0098] Here, respective materials of the inner circumferential tip seals 41 and 51 may be
different from each other. The same applies to the outer circumferential tip seals
42 and 52.
[0099] A heat resistant temperature and a linear expansion coefficient of each material
under continuous use will be exemplified below.
PI (example): 240°C, 1.7 to 4.5 × 10-5/°C
PEEK (example): 260°C, 3.0 to 5.7 × 10-5/°C
PTFE (example): 260°C, 8.3 to 15.2 × 10-5/°C
PAI (example): 250°C, 4.0 × 10-5/°C
PPS (example): 230°C, 1.8 to 8.7 × 10-5/°C
[0100] The heat resistance and the abrasion resistance required for the inner circumferential
tip seals 41 and 51 vary in accordance with the temperature and the pressure at the
central portion of the spiral.
[0101] In the example shown in FIG. 5, the inner circumferential tip seals 41 and 51 preferably
have a heat resistant temperature of 240°C or more.
[0102] On the other hand, the outer circumferential tip seals 42 and 52, which are disposed
at the outer circumferential sides of the wraps 21 and 31 including the outermost
circumferential portions at which air is drawn, rise in temperature by a small amount
and are subjected to a smaller back pressure than at the inner circumferential sides,
resulting in a small pressing load. Accordingly, the outer circumferential tip seals
42 and 52 may have a smaller heat resistance and abrasion resistance and a higher
linear expansion coefficient than those of the inner circumferential tip seals 41
and 51.
[0103] Resins which may be used for the outer circumferential tip seals 42 and 52 include
PAI (polyamide imide), PPS (polyphenylene sulfide), and PA (polyamide). Other resins
such as PTFE (polytetrafluoroethylene) may also be adopted.
[0104] The outer circumferential tip seals 42 and 52 may also be formed from a metal like
iron.
[0105] In the present embodiment, the inner circumferential tip seals 41 and 51 are formed
from a material satisfying at least one requirement of a higher heat resistant temperature,
a smaller comparative abrasion quantity, and a smaller linear expansion coefficient
than those of the material of the outer circumferential tip seals 42 and 52, as long
as the materials satisfy the heat resistances, the abrasion resistances required for
the inner circumferential tip seals 41 and 51 and the outer circumferential tip seals
42 and 52 and their balance of thermal expansion.
[0106] Accordingly, the inner circumferential tip seals 41 and 51 and the outer circumferential
tip seals 42 and 52 may be formed from materials having comparable heat resistant
temperatures and different comparative abrasion quantities or linear expansion coefficients.
[0107] Alternatively, they may be formed from materials having comparable comparative abrasion
quantities and different heat resistant temperatures or linear expansion coefficients,
or may be formed from materials having comparable linear expansion coefficients and
different heat resistant temperatures or comparative abrasion quantities.
[0108] Here, only two combination examples of the material which may be used for the inner
circumferential tip seals 41 and 51 and the material which may be used for the outer
circumferential tip seals 42 and 52 are shown.
- (1) material of inner circumferential tip seal: PI, material of outer circumferential
tip seal: PPS
- (2) material of inner circumferential tip seal: ferrous metal, material of outer circumferential
tip seal: PA
[0109] In the embodiment, the outer circumferential tip seals 42 and 52 are formed from
a material less expensive than that of the inner circumferential tip seals 41 and
51 as long as the inner circumferential tip seals 41 and 51 have durability necessary
for the high temperature and the high pressure at the central portion of the spiral
and the outer circumferential tip seals 42 and 52 satisfy a necessary heat resistance
and abrasion resistance.
[0110] Here, positions of the stepped portions 21C and 31C separating the inner circumferential
tip seals 41 and 51 from the outer circumferential tip seals 42 and 52 are set for
achieving improved durability and reduced cost of the tip seal in a well-balanced
manner.
[0111] The positions of the stepped portions 21C and 31C mean sites at which the outer circumferential
wrap 21B erects from the inner circumferential wrap 21A.
[0112] In determining the positions of the stepped portions 21C and 31C, two indexes are
used in the present embodiment. A first index is an angle corresponding to the central
value of a temperature range within which the temperatures of wraps 21 and 31 rise.
A second index is a rotation angle of 2π rad, which is obtained by one revolution
of the orbiting scroll 30.
[0113] In the example of FIG. 5, the temperature range of the wraps 21 and 31 ranges from
25°C at 0 rad to 225°C at about 7π rad with the central value at 125°C. The rotation
angle corresponding to the central value at 125°C is 4π rad (the first index).
[0114] Also, the rotation angle of 2π rad (the second index) corresponding to one revolution
corresponds to the rotation angle from the opening to the close of the suction inlets
IN at the outermost circumferential portions of the wraps 21 and 31. The value 2π
rad is used to ensure the cost reduction effect obtained by selecting an inexpensive
material for the outer circumferential tip seals 42 and 52.
[0115] Using the above first and second indexes, the positions of the stepped portions 21C
and 31C are each preferably set within a range of 2π rad or more and 4π rad or less
in the inner circumferential sides from the outermost circumferential portions of
the wraps 21 and 31.
[0116] Here, if the positions of the stepped portions 21C and 31C are at 4π rad or less,
the heat resistant temperature of the outer circumferential tip seals 42 and 52 can
be kept to temperatures equal to or lower than the central value of the temperature
rise range.
[0117] Also, if the stepped portions 21C and 31C are positioned exceeding 2π from the outermost
circumferential portions, the length of the outer circumferential tip seals 42 and
52 of 2π rad or more can be assured. This can ensure the cost reduction effect by
selecting an inexpensive material for the outer circumferential tip seals 42 and 52.
[0118] In consideration of the above, the positions of the stepped portions 21C and 31C
are set at 2π in the present embodiment, but the stepped portions 21C and 31C may
be provided at any position in a range of 2π rad or more and 4π rad or less from the
outermost circumferential portions of the wraps 21 and 31.
[0119] Here, if the stepped portions 21C and 31C are positioned 3π rad or more in the inner
circumferential sides from the outermost circumferential portions, the stepped portions
21C and 31C do not exist in the compression chambers S when the suction inlets IN
are closed to close up the compression chambers S. The compression chambers S each
form a space having a uniform dimension between the end plates 200 and 300 with no
volume reduction in the height direction of the wraps 21 and 31. This can maximize
the volume of the compression chambers S positioned in the outermost circumferential
portions, thereby ensuring a large compression ratio.
[0120] It is to be noted that the positions of the stepped portions 21C and 31C tolerate
some errors due to dimensional errors or assembly errors of the scrolls 20 and 30.
[0121] In accordance with the present embodiment described above, in the 3D-type scroll
compressor 10, among the inner circumferential tip seals 41 and 51 and the outer circumferential
tip seals 42 and 52 set apart and separated by the stepped portions 21C and 31C of
the wraps 21 and 31, the inner circumferential tip seals 41 and 51 are formed from
a material determined by the high temperature and high pressure at the central portions
of the spirals, while the outer circumferential tip seals 42 and 52 are formed from
an inexpensive material.
[0122] Therefore, the wraps 21 and 31 and the end plates 300 and 200 can be kept sealed
therebetween without causing erosion, an abnormal abrasion, or a seizure to the tip
seals, thereby ensuring the reliability of the scroll compressor 10 as well as contributing
to cost reduction.
[Second Embodiment]
[0123] Next, referring to FIG. 6, a second embodiment of the present invention will be described.
[0124] The second embodiment will be described mainly focusing on points different from
those in the first embodiment. Configurations similar to those in the first embodiment
will be given the same characters.
[0125] In the second embodiment, the inner circumferential tip seals 41 and 51 are coated
with an abrasion-resistant material instead of differentiating the materials between
the inner circumferential tip seals 41 and 51 and the outer circumferential tip seals
42 and 52.
[0126] As shown in FIG. 6, the inner circumferential tip seal 41 has an abrasion resistant
coating 45 on a surface. Examples of a material of the coating 45 to be used include
PTFE (polytetrafluoroethylene), PEEK (polyether ether ketone), DLC (diamond-like carbon),
TiN (titanium nitride), and CrN (chromium nitride).
[0127] The abrasion resistance of the coating 45 is determined as appropriate according
to the pressure at the central portion of the spiral.
[0128] A film thickness of the coating 45 may be set according to the comparative abrasion
quantity required for the coating 45.
[0129] In the inner circumferential tip seal 41, the coating 45 at least forms a surface
45S (surface) facing the inner circumferential bottom 30A of the end plate 300, and
faces the counterpart end plate 300. The material of the portion of the inner circumferential
tip seal 41 facing the end plate 300 (coating 45) is different from that of the portion
of the outer circumferential tip seal 42 without a coating facing the end plate 300.
[0130] The inner circumferential tip seal 51 may be provided with a coating 45 similar to
that of the inner circumferential tip seal 41.
[0131] A coating 45 of PTFE or PEEK may be formed by spraying and applying a liquid material
prepared by mixing resin powder into a solution onto the inner circumferential tip
seals 41 and 51 (base material) with an air spray gun and then heating the applied
liquid material at a melting point of the resin or higher to fuse it with the inner
circumferential tip seals 41 and 51. The liquid material is repeatedly applied and
heated until a predetermined film thickness is obtained. In addition to such an air
spray method, an electrostatic powder coating method of applying resin powder to a
base material using static electricity, a dip method, and the like may be used. In
any case, resin is fused with a base material by applying heat.
[0132] A coating 45 of DLC may be formed by plasma-enhanced chemical vapor deposition (PECVD)
or physical vapor deposition (PVD).
[0133] A coating 45 of TiN or CrN may be formed by PVD.
[0134] As the material for the base materials for the inner circumferential tip seals 41
and 51 on which the coating 45 is formed, one that does not melt by heat applied during
the process of forming the coating 45 is selected.
[0135] The base materials of the inner circumferential tip seals 41 and 51 may be made of
the same material as that of the outer circumferential tip seals 42 and 52.
[0136] In the present embodiment, abrasion resistance higher than that of the outer circumferential
tip seals 42 and 52 can be imparted to the inner circumferential tip seals 41 and
51 by applying the coating 45 to the inner circumferential tip seals 41 and 51. Therefore,
necessary abrasion resistance can be achieved while holding down the material cost
by forming the base material of the inner circumferential tip seals 41 and 51 from
the same material as that of the outer circumferential tip seals 42 and 52.
[0137] Also, even if it is difficult in terms of thickness or cost to use a material more
excellent in the abrasion resistance than a material that can be used for the base
material, for the base material of the tip seals, abrasion resistance can be further
improved by selecting such a material as the material for the coating 45.
[0138] Further, if the application of the coating 45 can give a surface that is smoother
than that of the base material, the coefficient of friction of the surfaces of the
inner circumferential tip seals 41 and 51 reduces. Among the materials of the coating
45 described above as examples, DLC has a coefficient of friction of about 0.1 (dry
condition), for example. The abrasion resistance can be increased also in that the
abrasion loss reduces due to the small coefficient of friction.
[0139] In the second embodiment, the base materials of the inner circumferential tip seals
41 and 51 may be formed from a material different from that of the outer circumferential
tip seals 42 and 52.
[0140] Also, it is allowed to apply, to the outer circumferential tip seals 42 and 52, a
coating of a material different from that of the coating 45 applied to the inner circumferential
tip seals 41 and 51.
[Third Embodiment]
[0141] Next, referring to FIG. 7, a third embodiment of the present invention will be described.
The third embodiment will be described also mainly focusing on points different from
those in the first embodiment, and configurations similar to those already described
will be given the same characters.
[0142] In the third embodiment, the inner circumferential tip seals and the outer circumferential
tip seals are different in thickness. The inner circumferential tip seals and the
outer circumferential tip seals are the same in material.
[0143] As shown in FIG. 7, the inner circumferential tip seal 61 provided to the inner circumferential
wrap 21A and the outer circumferential tip seal 42 provided to the outer circumferential
wrap 21B are different in thickness. It is to be noted that the inner circumferential
tip seal provided to the inner circumferential wrap 31A is formed similarly to the
inner circumferential tip seal 61, and the outer circumferential tip seal provided
to the outer circumferential wrap 31B is formed similarly to the outer circumferential
tip seal 42.
[0144] A thickness of the outer circumferential tip seal 42 is set to T1 in the depth direction
of the seal groove D. This thickness is the same as that of the outer circumferential
tip seal 42 in the first and second embodiments.
[0145] A thickness T2 of the inner circumferential tip seal 61 is larger than the thickness
T1 of the outer circumferential tip seal 42.
[0146] The inner circumferential tip seal 61, if made thick, can leave a thickness sufficient
for the seal even when greatly abraded. This ensures the reliability of the tip seal.
[0147] In addition, the thickness T1 of the outer circumferential tip seal 42 can be kept
sufficient for the seal, thereby holding down the cost.
[0148] The third embodiment may be combined with the first or second embodiment. That is,
in the third embodiment, the inner circumferential tip seals 41 and 51 may be formed
from a material different from that of the outer circumferential tip seals 42 and
52, or the inner circumferential tip seals 41 and 51 may be provided with the coating
45.
[0149] In accordance with any configuration of the above described first to third embodiments,
durability to withstand the high temperature and high pressure at the inner circumferential
side of the wraps can be imparted to the inner circumferential tip seals, thereby
improving the reliability of the scroll compressor.
[0150] Here, because in the scroll compressor 10 that compresses air, a compression ratio
is generally high, and the temperature rises significantly at the central portions
of the spirals, imparting durability to the inner circumferential tip seals by each
configuration of the first to third embodiments has a great effect on the air-compressing
scroll compressor.
[0151] Furthermore, in a compressor of oil-free type like the scroll compressor 10, a cooling
effect by the oil cannot be obtained, and the temperature rises all the more significantly
at the inner circumferential side. Besides, a lubricating effect by the oil is not
obtained and tip seals slide directly against the end plates without a lubricant,
thereby easily being abraded. Accordingly, the effect of the present invention will
be pronounced when the invention is applied to an air-compressing, oil-free scroll
compressor.
[0152] Even among scroll compressors that compress a refrigerant, in some scroll compressors
like ones used in a large refrigerator or air-conditioning apparatus, the temperature
and the compression ratio may become as high as those in air-compressing scroll compressors
at the central portions of the spirals. The present invention has a great effect even
in such a case. The effect of the present invention is also pronounced in oil-free
scroll compressors that compress a refrigerant like that.
[0153] Although the stepped portion is provided only at one site in a circumferential direction
of each wrap in the scroll compressors of the first to third embodiments, the stepped
portions may be provided at a plurality of sites in the circumferential direction
of the wrap.
[0154] For example, if stepped portions 211 and 212 are provided at two sites in the circumferential
direction of the wrap 21 as shown in FIG. 8, there exist an innermost circumferential
tip seal 71 provided at a position including the innermost circumferential portion
(the central portion of the spiral), an outermost circumferential tip seal 73 provided
at a position including the outermost circumferential portion, and an intermediate
tip seal 72 provided at an intermediate position.
[0155] In this case, when one of the two stepped portions 211 and 212 that is positioned
at the outer circumferential side is called a first stepped portion 211 and one positioned
at the inner circumferential side is called a second stepped portion 212, the intermediate
tip seal 72 and the innermost circumferential tip seal 71 positioned in the inner
circumferential side of the first stepped portion 211 and the outermost circumferential
tip seal 73 positioned in the outer circumferential side of the first stepped portion
211 may be different in material or thickness, based on the first stepped portion
211.
[0156] Alternatively, the innermost circumferential tip seal 71 positioned in the inner
circumferential side of the second stepped portion 212 and the intermediate tip seal
72 and the outermost circumferential tip seal 73 positioned in the outer circumferential
side of the second stepped portion 212 may be different in material or thickness,
based on the second stepped portion 212.
[0157] Further, the outermost circumferential tip seal 73, the intermediate tip seal 72,
and the innermost circumferential tip seal 71 may be different stepwise in material
or thickness.
[0158] That is, the intermediate tip seal 72 positioned in the inner circumferential side
of the first stepped portion 211 and the outermost circumferential tip seal 73 positioned
in the outer circumferential side of the first stepped portion 211 may be different
in material or thickness and at the same time the innermost circumferential tip seal
71 positioned in the inner circumferential side of the second stepped portion 212
and the intermediate tip seal 72 positioned in the outer circumferential side of the
second stepped portion 212 may be different in material or thickness.
[0159] In any case, since the temperature and the pressure of the gas rise from the outermost
circumferential portion toward the innermost circumferential portion of each wrap,
the temperature and the pressure become higher at more inward portions. Therefore,
it may be configured such that the material of the inner circumferential tip seals
positioned relatively more inwardly is more excellent in heat resistance and abrasion
resistance than the material of the outer circumferential tip seals positioned relatively
outwardly and that the inner circumferential tip seal is thicker than the outer circumferential
tip seal.
[0160] In addition to the above embodiments, some configurations may be chosen from those
mentioned in the embodiments or modified as appropriate to other configurations without
departing from the spirit of the present invention.
[0161] The scroll compressor of the present invention is not limited to one powered by motor
torque, and may be powered by a driving force transmitted from an engine through a
belt to the shaft.
Reference Signs List
[0162]
- 10
- Scroll compressor
- 11
- Motor
- 12
- Motor case
- 13
- Output shaft
- 14
- Coupling
- 15
- Shaft
- 20
- Fixed scroll
- 20A
- Inner circumferential bottom
- 20B
- Outer circumferential bottom
- 20C
- Stepped wall
- 21
- Wrap
- 21A
- Inner circumferential wrap
- 21B
- Outer circumferential wrap
- 21C
- Stepped portion
- 30
- Orbiting scroll
- 30A
- Inner circumferential bottom
- 30B
- Outer circumferential bottom
- 30C
- Stepped wall
- 31
- Wrap
- 31A
- Inner circumferential wrap
- 31B
- Outer circumferential wrap
- 31C
- Stepped portion
- 34
- Boss
- 41
- Inner circumferential tip seal
- 42
- Outer circumferential tip seal
- 45
- Coating
- 45S
- Facing surface
- 51
- Inner circumferential tip seal
- 52
- Outer circumferential tip seal
- 61
- Inner circumferential tip seal
- 151
- Eccentric pin
- 200
- Fixed end plate
- 201
- Discharge port
- 300
- Orbiting end plate
- D
- Seal groove
- G
- Gap
- IN
- Suction inlet
- S
- Compression chamber
- T1, T2
- Thickness dimension