FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
SCROLL COMPRESSOR
MITSUBISHI ELECTRIC CORPORATION, A CORPORATION ORGANISED AND
EXISTING UNDER THE LAWS OF JAPAN, WHOSE ADDRESS IS 7-3,
MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 1008310, JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION
AND THE MANNER IN WHICH IT IS TO BE PERFORMED
2
DESCRIPTION
Technical Field
[0001]
5 The present disclosure relates to a scroll compressor used in air-conditioners,
refrigerators, and other apparatuses.
Background Art
[0002]
Scroll compressors used in air-conditioners, refrigerators, and other
10 apparatuses include a compression mechanism unit to compress refrigerant in
compression chambers defined by a combination of a fixed scroll and an orbiting
scroll, and a shell accommodating the compression mechanism unit. The fixed scroll
and the orbiting scroll each include a wrap projected from a base plate. The
respective wraps of these scrolls mesh with each other to define the compression
15 chambers. As the orbiting scroll is caused to orbit, the compression chambers move
while decreasing in volume, and thus refrigerant is sucked in and compressed in the
compression chambers. To reduce the size and cost of this type of scroll
compressors, an increasingly important aim of technological developments for such
scroll compressors is to maximize available suction volume of the compression
20 chambers for the same shell diameter to thereby increase compressor capacity.
Increasing the suction volume of the compression chambers for the same shell
diameter requires careful designing of the spiral shape of the wraps.
[0003]
In some related-art techniques, the spiral shape of the scroll compressor is
25 defined by the involute curve of a base circle that is a perfect circle with a
predetermined radius, and the wraps are formed with a circular overall profile. By
contrast, in some recent techniques, the overall profile of the wraps is flattened rather
than circular, and the spiral shape of the wraps is also flattened (see, for example,
Patent Literature 1).
30 [0004]
3
An Oldham ring is disposed near the compression mechanism unit of the scroll
compressor to prevent rotation of the orbiting scroll. From the viewpoint of avoiding
interference with a key part of the Oldham ring, it is desirable to form the base plate of
the orbiting scroll with a flattened, rather than circular, outer shape in improving the
5 mounting density of compressor components. If the base plate is formed with a
flattened outer shape as described above, by likewise forming the wraps with a
flattened spiral shape, it is possible to effectively use the limited available space on
top of the base plate to thereby provide increased suction volume of the compression
chambers. Therefore, forming the wraps with a flattened spiral shape as described
10 in Patent Literature 1 is effective in increasing the suction volume of the compression
chambers.
Citation List
Patent Literature
[0005]
15 Patent Literature 1: Japanese Unexamined Patent Application Publication No.
10-54380
Summary of Invention
Technical Problem
[0006]
20 Although Patent Literature 1 describes flattening the profile and spiral shape of
each wrap, Patent Literature 1 does not describe a specific definition of the spiral
shape. As for the spiral shape of the wrap, as described above, techniques exist in
which the spiral shape is defined by the involute curve of a base circle that is a
perfect circle with a predetermined radius. In this regard, it is necessary, for cases
25 where the wrap has a flattened spiral shape as well, to specifically define the spiral
shape in fabricating the wrap.
[0007]
If the orbiting scroll and the fixed scroll are made of dissimilar materials, due to
the difference in physical property between the materials of their respective wraps,
30 these wraps are designed to differ in tooth thickness from the viewpoint of ensuring
4
sufficient strength. Specifically, one of the two wraps that is made of a material with
the lesser strength is designed to have a greater tooth thickness than the other wrap
made of a material with the greater strength.
[0008]
5 To date, no techniques are known to exist that individually design the
respective spiral shapes of the orbiting scroll and the fixed scroll. Therefore, in
forming the orbiting scroll and the fixed scroll with different strengths, the two scrolls
need to be designed with the same tooth thickness that is equal to the tooth thickness
required for the scroll with the lesser strength. As a result, the wrap made of the
10 weaker material is designed with excessive tooth thickness. This constrains the
available space on top of the base plate, leading to reduced suction volume.
[0009]
The present disclosure has been made in view of the above-mentioned
problem. Accordingly, it is an object of the present disclosure to provide a scroll
15 compressor in which the spiral shape of each wrap having a flattened profile can be
defined by equations, and the tooth thicknesses of the respective wraps of the
orbiting scroll and the fixed scroll can be individually designed to thereby prevent or
minimize a decrease in suction volume.
Solution to Problem
20 [0010]
According to an embodiment of the present disclosure, there is provided a
scroll compressor including a fixed scroll and an orbiting scroll, the fixed scroll having
a fixed wrap projected from a fixed base plate, the orbiting scroll having an orbiting
wrap projected from an orbiting base plate, the fixed wrap and the orbiting wrap
25 meshing with each other to define a compression chamber in which refrigerant is
compressed. A base curve is used to determine an outer curve of one wrap and an
inner curve of an other wrap, the one wrap being one of the fixed wrap and the
orbiting wrap, the other wrap being an other one of the fixed wrap and the orbiting
wrap, the base curve being defined in an x-y coordinate system by equation (1) and
30 equation (2) by using an involute angle  and a radius "a" of a base circle. An
5
inverse curve is used to determine an inner curve of the one wrap and an outer curve
of the other wrap, the inverse curve being a curve obtained by rotating the base curve
by  [rad] with respect to a center of the base circle. In equation (1) and equation (2),
w() is a function varying in a sinusoidal or cosine manner with a period of  [rad]
5 relative to the involute angle . A dissimilar tooth-thickness ratio is defined as  = tf /
(tf + tO), where tf
is a tooth thickness of the fixed wrap and tO is a tooth thickness of
the orbiting scroll, and an orbit radius of the orbiting scroll is defined as "e". The
outer curve of the one wrap is an inner envelope to a group of circles of radius e
each having a center lying on the base curve, and the inner curve of the one wrap is
10 an outer envelope to a group of circles of radius e each having a center lying on the
inverse curve. The inner curve of the other wrap is an outer envelope to a group of
circles of radius e(1 - ) each having a center lying on the base curve, and the outer
curve of the other wrap is an inner envelope to a group of circles of radius e(1 - )
each having a center lying on the inverse curve. The dissimilar wrap-thickness ratio
15  is in the range of 0 <  < 1.
x = a(cos + w()sin) (1)
y = a(sin - w()cos) (2)
Advantageous Effects of Invention
[0011]
20 According to an embodiment of the present disclosure, by using a base curve
defined by equation (1) and equation (2), an inverse curve obtained by rotating the
base curve by  [rad] relative to the center of the base circle, a group of circles of
radius e, and a group of circles of radius e(1-), the spiral shape of each wrap
having a flattened profile can be defined by equations, and the wall thicknesses of the
25 respective wraps of the orbiting scroll and the fixed scroll can be designed individually.
This makes it possible to prevent or minimize a decrease in suction volume.
x = a(cos + w()sin) (1)
y = a(sin - w()cos) (2)
Brief Description of Drawings
30 [0012]
6
[Fig. 1] Fig. 1 is a schematic longitudinal sectional view of a scroll compressor
according to Embodiment 1, illustrating the general configuration of the scroll
compressor.
[Fig. 2] Fig. 2 is a transverse sectional view of a compression mechanism unit
5 of the scroll compressor according to Embodiment 1.
[Fig. 3] Fig. 3 is a plan view of a fixed wrap and an orbiting wrap of the
compression mechanism unit of the scroll compressor according to Embodiment 1.
[Fig. 4] Fig. 4 illustrates a compression process, depicting operation during one
revolution of an orbiting scroll in the scroll compressor according to Embodiment 1.
10 [Fig. 5] Fig. 5 illustrates how to draw each spiral shape constituting the
compression mechanism unit of the scroll compressor according to Embodiment 1.
[Fig. 6] Fig. 6 illustrates the characteristics of w() that determine the spiral
shape of each wrap in a scroll compressor according to Embodiment 2.
[Fig. 7] Fig. 7 illustrates the spiral shape of each wrap in the scroll compressor
15 according to Embodiment 2.
[Fig. 8] Fig. 8 illustrates the characteristics of w() that determine the spiral
shape of each wrap in a scroll compressor according to Embodiment 3.
[Fig. 9] Fig. 9 illustrates the spiral shape of each wrap in the scroll compressor
according to Embodiment 3.
20 [Fig. 10] Fig. 10 illustrates the characteristics of w() that determine the spiral
shape of each wrap in a scroll compressor according to Embodiment 4.
[Fig. 11] Fig. 11 illustrates the spiral shape of each wrap in the scroll
compressor according to Embodiment 4.
[Fig. 12] Fig. 12 illustrates the characteristics of w() that determine the spiral
25 shape of each wrap in a scroll compressor according to Embodiment 5.
[Fig. 13] Fig. 13 illustrates the spiral shape of each wrap in the scroll
compressor according to Embodiment 5.
Description of Embodiments
[0013]
30 A scroll compressor according to embodiments is described below with
7
reference to the drawings or other illustrations. In the drawings below including Fig.
1, components designated by the same reference signs represent the same or
corresponding components throughout the following description of embodiments.
The specific arrangements of elements described throughout the specification are
5 intended to be illustrative only and not restrictive.
[0014]
Embodiment 1
Fig. 1 is a schematic longitudinal sectional view of a scroll compressor
according to Embodiment 1, illustrating the general configuration of the scroll
10 compressor.
The scroll compressor according to Embodiment 1 includes a compression
mechanism unit 8, a motor mechanism unit 110, which drives the compression
mechanism unit 8 via a rotary shaft 6, and other components. These components
are accommodated in a hermetic shell 100 that defines the exterior of the scroll
15 compressor. The compression mechanism unit 8 is disposed in an upper portion of
the interior of the hermetic shell 100, and the motor mechanism unit 110 is disposed
below the compression mechanism unit 8.
[0015]
A frame 7 and a sub-frame 9 are further disposed within the hermetic shell 100
20 such that the frame 7 and the sub-frame 9 face each other with the motor mechanism
unit 110 therebetween. The frame 7 is disposed over the motor mechanism unit 110
and located between the motor mechanism unit 110 and the compression mechanism
unit 8. The sub-frame 9 is disposed under the motor mechanism unit 110. The
frame 7 is secured to the inner periphery surface of the hermetic shell 100 by shrink25 fitting, welding, or other methods. The sub-frame 9 is secured via a sub-frame
holder 9a to the inner periphery surface of the hermetic shell 100 by shrink-fitting,
welding, or other methods.
[0016]
A pump element 112 including a positive displacement pump is mounted below
30 the sub-frame 9. The pump element 112 supplies refrigerating machine oil stored in
8
an oil reservoir 100a in the bottom portion of the hermetic shell 100 to sliding parts of
the compression mechanism unit 8, such as a main bearing 7a described later. The
pump element 112 supports, on its top end face, the rotary shaft 6 in the axial
direction.
5 [0017]
The hermetic shell 100 is provided with a suction pipe 101 for sucking
refrigerant, and a discharge pipe 102 for discharging refrigerant.
[0018]
The compression mechanism unit 8 has the function of compressing refrigerant
10 sucked in through the suction pipe 101, and discharging the compressed refrigerant
to a high-pressure part provided in an upper portion of the interior of the hermetic
shell 100. The compression mechanism unit 8 includes a fixed scroll 1, and an
orbiting scroll 2.
[0019]
15 The fixed scroll 1 is secured via the frame 7 to the hermetic shell 100. The
orbiting scroll 2 is disposed under the fixed scroll 1, and supported by an eccentric
shaft part 6a of the rotary shaft 6, which will be described later, in a manner that
allows orbital motion of the orbiting scroll 2.
[0020]
20 The fixed scroll 1 includes a fixed base plate 1a, and a fixed wrap 1b in the
form of a spiral projection projected from one surface of the fixed base plate 1a. The
orbiting scroll 2 includes an orbiting base plate 2a, and an orbiting wrap 2b in the form
of a spiral projection projected from one surface of the orbiting base plate 2a. The
fixed scroll 1 and the orbiting scroll 2 are disposed within the hermetic shell 100 in a
25 symmetrical spiral arrangement such that the fixed wrap 1b and the orbiting wrap 2b
are intermeshed in an opposite phase relationship to each other. The fixed wrap 1b
and the orbiting wrap 2b define compression chambers 71 therebetween, which have
a volume that progressively decreases from a radially outer portion toward a radially
inner portion as the rotary shaft 6 rotates. Although the present example assumes
30 that the fixed wrap 1b and the orbiting wrap 2b are disposed within the hermetic shell
9
100 in a symmetrical spiral arrangement, the fixed wrap 1b and the orbiting wrap 2b
may be disposed within the hermetic shell 100 in an asymmetrical spiral arrangement
with these wraps intermeshed in phase with each other.
[0021]
5 A baffle 4 is secured to a surface of the fixed base plate 1a of the fixed scroll 1
opposite to the surface near the orbiting scroll 2. The baffle 4 has a through-hole 4a
in communication with a discharge port 1c of the fixed scroll 1. A discharge valve 11
is provided over the through-hole 4a. A discharge muffler 12 is attached to the baffle
4 so as to cover the discharge port 1c.
10 [0022]
The frame 7 has a thrust surface to which the fixed scroll 1 is secured and
which axially supports a thrust force acting on the orbiting scroll 2. The frame 7 has
two introduction channels 7c penetrating the frame 7 and through which refrigerant
sucked in through the suction pipe 101 is introduced into the compression mechanism
15 unit 8.
[0023]
An Oldham ring 14 is disposed on the frame 7 to prevent the orbiting scroll 2
from rotating on its own axis during its orbital motion. The Oldham ring 14 has a key
part 14a disposed near the outer periphery of the orbiting base plate 2a of the orbiting
20 scroll 2.
[0024]
The motor mechanism unit 110 provides a rotational drive force to the rotary
shaft 6. The motor mechanism unit 110 includes a motor stator 110a, and a motor
rotor 110b. To obtain electric power from outside, the motor stator 110a is connected
25 by a lead wire (not illustrated) to a glass terminal (not illustrated) located between the
frame 7 and the motor stator 110a. The motor stator 110a is secured to the rotary
shaft 6 by shrink fitting or other methods. To provide overall balancing of the
rotational system of the scroll compressor, a first balancing weight 60 is secured to
the rotary shaft 6, and a second balancing weight 61 is secured to the motor stator
30 110a.
10
[0025]
The rotary shaft 6 includes the eccentric shaft part 6a defining an upper portion,
a main shaft part 6b defining an intermediate portion, and a sub-shaft part 6c defining
a lower portion. The eccentric shaft part 6a is eccentric relative to the center of the
5 axis of the rotary shaft 6. The eccentric shaft part 6a is engaged with the orbiting
scroll 2 via a balancing-weight-equipped slider 5 and an orbiting bearing 2c. This
allows the orbiting scroll 2 to make orbital motion as the rotary shaft 6 rotates. The
main shaft part 6b is engaged with the main bearing 7a via a sleeve 13, the main
bearing 7a being disposed on the inner periphery of a cylindrical boss part 7b
10 provided to the frame 7. The main shaft part 6b slides against the main bearing 7a
with an oil film therebetween that is created by refrigerating machine oil. The main
bearing 7a is secured within the boss part 7b such as by press-fitting of a bearing
material used for a slide bearing such as a copper-lead alloy.
[0026]
15 A sub-bearing 10 in the form of a ball bearing is provided over the sub-frame 9.
The sub-bearing 10 radially supports the rotary shaft 6 in a rotatable manner under
the motor mechanism unit 110. As the sub-bearing 10, a bearing other than a ball
bearing may be used to support the rotary shaft 6 in a rotatable manner. The subshaft part 6c is engaged with the sub-bearing 10, and slides against the sub-bearing
20 10 with an oil film therebetween that is created by refrigerating machine oil. The
main shaft part 6b and the sub-shaft part 6c are coaxial with the rotary shaft 6.
[0027]
The internal space of the hermetic shell 100 is defined as follows. The
internal space of the hermetic shell 100 includes a first space 72 defined as a space
25 located closer to the motor rotor 110b than the frame 7 is. The internal space also
includes a second space 73 defined as a space bounded by the inner wall of the
frame 7 and by the fixed base plate 1a. The internal space also includes a third
space 74 defined as a space located closer to the discharge pipe 102 than the fixed
base plate 1a is. The second space 73 includes a suction space 73a defined as a
30 space located outside a structure formed by a combination of the fixed wrap 1b and
11
the orbiting wrap 2b.
[0028]
Reference is now made to how various components of the compression
mechanism unit 8 are arranged within the hermetic shell 100.
5 Fig. 2 is a transverse sectional view of the compression mechanism unit of the
scroll compressor according to Embodiment 1. Fig. 3 is a plan view of the fixed wrap
and the orbiting wrap in the compression mechanism unit of the scroll compressor
according to Embodiment 1. In Fig. 2 and Fig. 3, the orbiting wrap 2b of the orbiting
scroll 2 is shown dotted to facilitate the differentiation between the fixed wrap 1b of
10 the fixed scroll 1 and the orbiting wrap 2b of the orbiting scroll 2. The same applies
to figures that will be described later.
[0029]
The hermetic shell 100 has the shape of a perfect circle in plan view. Within
the hermetic shell 100, the outer periphery surface of the frame 7 is secured in
15 contact with the inner periphery surface of the hermetic shell 100. Thus, the outer
periphery surface of the frame 7 also has the shape of a perfect circle. The key part
14a of the Oldham ring 14 is disposed in the second space 73. Reference signs 21
and 22 in Fig. 2 will be described later.
[0030]
20 If the key part 14a of the Oldham ring 14 is disposed in the second space 73 as
described above, such an arrangement requires the orbiting base plate 2a to be
positioned clear of the area within which the key part 14a can move. For this reason,
the orbiting base plate 2a is formed with a flattened outer shape. As used herein,
the term flattened shape refers to an oval shape, which also includes oblong and
25 elliptical shapes. That is, a flattened shape generically refers to any shape that
appears flattened relative to a perfect circle.
[0031]
As described above, the orbiting base plate 2a has a flattened outer shape.
Thus, by forming the orbiting wrap 2b such that its spiral shape is also flattened, the
30 space on top of the orbiting base plate 2a can be effectively utilized. This allows for
12
more efficient space usage. The same applies to the fixed base plate 1a. That is,
the fixed base plate 1a is formed with a flattened outer shape, and the fixed wrap 1b
is formed with a flatted spiral shape. Increasing space efficiency in this way helps to
ensure that the compression chambers 71 can be increased in volume for the same
5 size of the hermetic shell 100, and thus compressor capacity can be improved.
Conversely speaking, the size of the hermetic shell 100 required to provide the same
compressor capacity can be reduced. In the following description, the term "wrap" or
"wraps" is used to generically refer to both the fixed wrap 1b and the orbiting wrap 2b
when no distinction is to be made between these wraps. The same applies to the
10 base plates. That is, the term "base plate" or "base plates" is used to generically
refer to both the fixed base plate 1a and the orbiting base plate 2a when no distinction
is to be made between these base plates.
[0032]
The fixed scroll 1 is made of, for example, a casting. To reduce centrifugal
15 force, the orbiting scroll 2 is made of, for example, an aluminum alloy with a lower
specific gravity than a material such as a casting. Using the above-mentioned
materials results in the orbiting wrap 2b having a low yield strength relative to the
fixed wrap 1b. Accordingly, to ensure sufficient strength of the orbiting wrap 2b, the
tooth thickness of the orbiting wrap 2b is set greater than the tooth thickness of the
20 fixed wrap 1b as illustrated in Figs. 2 and 3. One characteristic feature of
Embodiment 1 resides in the ability to individually set the respective tooth thicknesses
of the orbiting wrap 2b and the fixed wrap 1b. This will be described later again.
[0033]
Reference is now made to operation of the scroll compressor.
25 [0034]
Fig. 4 illustrates a compression process, depicting operation during one
revolution of the orbiting scroll in the scroll compressor according to Embodiment 1.
Fig. 4(a) illustrates the position of each wrap at a rotation phase of 0 [rad] (2 [rad]).
Fig. 4(b) illustrates the position of each wrap at a rotation phase of /2 [rad]. Fig.
30 4(c) illustrates the position of each wrap at a rotation phase of  [rad]. Fig. 4(d)
13
illustrates the position of each wrap at a rotation phase of 3/2 [rad].
[0035]
When the motor stator 110a of the motor mechanism unit 110 is energized, the
motor rotor 110b receives a rotational force and rotates. Accordingly, the rotary shaft
5 6 secured to the motor rotor 110b is rotationally driven. The rotational motion of the
rotary shaft 6 is transmitted to the orbiting scroll 2 via the eccentric shaft part 6a.
The orbiting wrap 2b of the orbiting scroll 2 makes orbital motion with an orbit radius
while having its rotation restricted by the Oldham ring 14. The term orbit radius
means the amount of eccentricity of the eccentric shaft part 6a relative to the main
10 shaft part 6b.
[0036]
Driving of the motor mechanism unit 110 causes refrigerant to flow from an
external refrigeration cycle into the first space 72 within the hermetic shell 100
through the suction pipe 101. Low-pressure refrigerant entering the first space 72
15 passes through each of the two introduction channels 7c defined in the frame 7, and
flows into the suction space 73a. Upon entering the suction space 73a, the lowpressure refrigerant is sucked into the compression chambers 71 due to the relative
orbital movement between the orbiting wrap 2b and the fixed wrap 1b in the
compression mechanism unit 8. As illustrated in Fig. 4, the refrigerant sucked into
20 the compression chambers 71 is raised from a low pressure to a high pressure due to
geometrical changes in the volume of the compression chambers 71 associated with
the relative movement between the orbiting wrap 2b and the fixed wrap 1b. The
refrigerant raised to a high pressure then passes through the discharge port 1c of the
fixed scroll 1 and the through-hole 4a of the baffle 4, and pushes open the discharge
25 valve 11 before being discharged to the interior of the discharge muffler 12. The
refrigerant discharged to the interior of the discharge muffler 12 is discharged into the
third space 74, and then discharged through the discharge pipe 102 to the outside of
the compressor as high-pressure refrigerant. The arrows in Fig. 1 represent the flow
of refrigerant mentioned above.
30 [0037]
14
According to Embodiment 1, as described above, the respective profiles of the
orbiting wrap 2b and the fixed wrap 1b are flattened, and their respective spiral
shapes are also flattened. Further, the orbiting wrap 2b and the fixed wrap 1b differ
in tooth thickness. In the compression mechanism unit 8 with the above-mentioned
5 wraps, if the orbiting wrap 2b is caused to move in an orbit with a predetermined
radius as illustrated in Fig. 4, the orbiting wrap 2b moves with its outward-facing and
inward-facing surfaces respectively making contact with the corresponding opposed
inward-facing and outward-facing surfaces of the fixed wrap 1b.
[0038]
10 Embodiment 1 is characterized in that the spiral shape of each of the orbiting
wrap 2b and the fixed wrap 1b, which each have a flattened profile, is defined by
using equations. The defining of the spiral shape also includes the ability to
individually set the tooth thickness of each of the orbiting wrap 2b and the fixed wrap
1b. The following description is first directed to equations for determining a spiral
15 shape, and then to a method for drawing wraps with different tooth thicknesses by
using such equations.
[0039]
The spiral shape of the wrap is determined by an outer curve and an inner
curve, the outer curve being a curve that determines the outward-facing surface of the
20 wrap, the inner curve being a curve that determines the inward-facing surface of the
wrap. In defining the spiral shape of the wrap by using equations, first, a base curve
for determining one of the outer and inner curves of the wrap, and an inverse curve
for determining the other one of the outer and inner curves are defined. The base
curve, which is the involute of a base circle, is a curve defined in the x-y coordinate
25 system by equation (1) and equation (2) below by using an involute angle . The
inverse curve is a curve obtained by inverting the base curve by  [rad] relative to the
center of the base circle.
[0040]
In equation (1) and equation (2), w() is given by a function that varies in a
30 sinusoidal or cosine manner with a period of  [rad] relative to the involute angle .
15
The spiral shape of the wrap with a flattened profile can be thus defined by equations.
Although w() varies in a sinusoidal or cosine manner as described above,
Embodiment 1 is directed to an exemplary case where w() is varied in a sinusoidal
manner as represented by equation (3) below. In equation (3), "a" denotes base5 circle radius. Symbol  denotes a coefficient representing the degree of flattening.
Symbol N denotes a natural number greater than or equal to 1. Symbol  denotes a
constant [rad] representing an angle in the direction of flattening.
[0041]
[Math. 1]
10 x = a(cos + w()sin) (1)
[0042]
[Math. 2]
y = a(sin - w()cos) (2)
[0043]
15 [Math. 3]
w() = ( + (sin - ))2N) (3)
[0044]
Fig. 5 illustrates how to draw each spiral shape forming the compression
mechanism unit of the scroll compressor according to Embodiment 1. Referring to
20 Fig. 5, the spiral shapes are drawn by steps (a) to (f).
[0045]
First, as illustrated in Fig. 5(a), a base curve 30 is drawn, which is the involute
of a base circle. In this regard, as described above, w() varies in a sinusoidal
manner with a period of  [rad] in accordance with the involute angle .
25 [0046]
Subsequently, as illustrated in Fig. 5(b), an inverse curve 31 is drawn, which is
a curve obtained by rotating the base curve 30 drawn in step (a) by  [rad] relative to
the base-circle center O.
[0047]
30 Subsequently, as illustrated in Fig. 5(c), plural circles 32 of radius e are drawn,
16
the circles 32 each having a center lying on the base curve 30 drawn in step (a) or on
the inverse curve 31 drawn in step (b). Symbol "e" denotes the orbit radius of the
orbiting wrap 2b. Symbol  denotes a dissimilar tooth-thickness ratio between the
tooth thickness tf of the fixed wrap 1b and the tooth thickness tO of the orbiting wrap
5 2b. The dissimilar tooth-thickness ratio  is defined as  = tf / (tf + tO). The value of
 is in the range of 0 <  < 1. If  is 0.5, the tooth thickness tf of the fixed wrap 1b
and the orbiting wrap 2b are equal.
[0048]
Subsequently, as illustrated in Fig. 5(d), an envelope to each group of circles
10 drawn in step (c) is drawn. At this time, an inner envelope 33 to the group of circles
lying on the base curve 30 defines the outer curve of the orbiting wrap 2b. An outer
envelope 34 to the group of circles lying on the inverse curve 31 defines the inner
curve of the orbiting wrap 2b. The dotted region as illustrated in step (d) represents
a cross-section of the orbiting wrap 2b.
15 [0049]
Subsequently, as illustrated in Fig. 5(e), plural circles 35 of radius e(1 - ) are
drawn, the circles 35 each having a center lying on the base curve 30 or on the
inverse curve 31.
[0050]
20 Then, as illustrated in Fig. 5(f), an envelope to each group of circles drawn in
step (e) is drawn. At this time, an outer envelope 36 to the group of circles lying on
the base curve 30 defines the inner curve of the fixed wrap 1b. An inner envelope
37 to the group of circles lying on the inverse curve 31 defines the outer curve of the
fixed wrap 1b. The hatched region as illustrated in step (f) represents a cross25 section of the fixed wrap 1b.
[0051]
As described above,  is in the range of 0 <  < 1. In this regard, the
difference in tooth thickness between the fixed wrap 1b and the orbiting wrap 2b can
be set as desired by changing the value of . If  = 0.5, the fixed wrap 1b and the
30 orbiting wrap 2b are equal in tooth thickness as described above. As  is decreased
17
from 0.5, the orbiting wrap 2b and the fixed wrap 1b respectively increase and
decrease in tooth thickness relative to each other. As  is increased from 0.5, the
relationship between the two tooth thicknesses is reversed, such that the orbiting
wrap 2b and the fixed wrap 1b respectively decrease and increase in tooth thickness
5 relative to each other.
[0052]
One way to increase air-conditioning capacity without increasing the size of the
scroll compressor is to increase the speed of the scroll compressor. Increasing the
speed of the scroll compressor, however, leads to increased centrifugal force on the
10 orbiting scroll that makes orbital motion as the motor mechanism unit 110 rotates.
This results in damage to the internal components of the compressor. One measure
to address this is to change the material of the orbiting scroll from a high specific
gravity material such as a casing to a low specific gravity material such as an
aluminum alloy to thereby reduce the centrifugal force. If such a measure is to be
15 employed, to improve the resistance to seizure between the fixed and orbiting scrolls,
the fixed scroll facing and sliding against the orbiting scroll is in some cases made of
a material different from the material of the orbiting scroll.
[0053]
If the orbiting scroll 2 and the fixed scroll 1 are made of dissimilar materials,
20 due to the difference in physical property between the materials of their respective
wraps, these wraps are designed to differ in tooth thickness from the viewpoint of
ensuring sufficient strength. Specifically, one of the two wraps that is made of a
material with the lesser strength is designed to have a greater tooth thickness than
the other wrap made of a material with the greater strength. Therefore, if the fixed
25 scroll 1 is made of a casting, and the orbiting scroll 2 is made of an aluminum alloy,
which has a lesser strength than a casting, then from the viewpoint of deformation
and strength of the wrap of each scroll, the tooth thickness tf of the fixed wrap 1b and
the tooth thickness to of the orbiting wrap 2b have the following relationship: tf < to.
In this case,  is set in the range of 0 <  < 0.5.
30 [0054]
18
In this way, the respective spiral shapes of the fixed wrap 1b and the orbiting
wrap 2b with different tooth thicknesses can be created. Fig. 3 depicts the
respective shapes of the fixed wrap 1b and the orbiting wrap 2b for a case where, in
equation (3),  has a value of 0.3,  has a value of 0.4, N has a value of 1, and  has
5 a value of 0.
[0055]
In this regard, as described above,  is a coefficient representing the degree of
flattening. By changing the value of , the flattening ratio of the profile of each wrap
can be set as desired. Specifically, as the value of  increases, the flattening ratio of
10 the wrap profile increases, resulting in a more flattened shape. A flattening ratio is
defined as the ratio between the major and minor axes of the wrap profile.
[0056]
As described above,  is a constant representing an angle in the direction of
flattening. By changing the value of , an angle in the direction of flattening can be
15 set as desired. As described above, Fig. 3 depicts a case where  is 0. In this case,
each wrap has a shape such that the direction of its flattening, in other words, the
direction of its major axis is oriented in the direction of an angle of 0 [rad] centered at
the base-circle center O. If  is set to, for example, /2, then the wrap has a tilted
shape with the direction of its major axis oriented in the direction of an angle of /2
20 centered at the base-circle center O.
[0057]
As described above, according to Embodiment 1, the spiral shape of each wrap
is defined by using the base curve 30 and the inverse curve 31. The base curve 30
is defined by equation (1) and equation (2) mentioned above by using the involute
25 angle  and the base-circle radius "a". The inverse curve 31 is a curve obtained by
inverting the base curve 30 by  [rad] relative to the base-circle center O. In
equation (1) and equation (2), w() is a function that varies in a sinusoidal or cosine
manner with a period of  [rad] relative to the involute angle .
[0058]
A dissimilar tooth-thickness ratio is defined as  = tf / (tf + tO), where tf 30 is the
19
tooth thickness of the fixed wrap 1b, and tO is the tooth thickness of the orbiting wrap
2b. The orbit radius is defined as "e". By using the above definitions, and also
using the respective equations of the base curve 30 and the inverse curve 31, the
outer and inner curves of the orbiting wrap 2b and the outer and inner curves of the
5 fixed wrap 1b are determined. That is, the outer curve of the orbiting wrap 2b is
defined by as inner envelope to a group of circles of radius e each having a center
lying on the base curve 30. The inner curve of the orbiting wrap 2b is defined by an
outer envelope to a group of circles of radius e each having a center lying on the
inverse curve 31. The inner curve of the fixed wrap 1b is defined by an outer
10 envelope to a group of circles of radius e(1 - ) each having a center lying on the
base curve 30. The outer curve of the fixed wrap 1b is defined by an inner envelope
to a group of circles of radius e(1 - ) each having a center lying on the inverse curve
31. The value of  is in the range of 0 <  < 1. Although the foregoing description
is directed to creating the orbiting wrap 2b by using a group of circles of radius e and
15 to creating the fixed wrap 1b by using a group of circles of radius e(-1), the groups of
circles to be used may be reversed.
[0059]
In this way, the respective spiral shapes of the orbiting wrap 2b and the fixed
wrap 1b each having a flattened profile can be defined by using equations. Such
20 definitions include the ability to individually set the respective tooth thicknesses of the
orbiting wrap 2b and the fixed wrap 1b. As a result, the respective tooth thicknesses
of the fixed wrap 1b and the orbiting wrap 2b can be designed independently in
ensuring sufficient strength. This helps to avoid a design with excessive strength,
resulting in increased suction volume. Therefore, the compressor can be improved
25 in capacity without increasing in size. Alternatively speaking, the compressor can be
reduced in size for equivalent compressor capacity.
[0060]
According to Embodiment 1, setting the value of  in the range of 0 <  < 0.5
allows the orbiting wrap 2b to have a tooth thickness greater than the tooth thickness
30 of the fixed wrap 1b.
20
[0061]
According to Embodiment 1, w() is given by equation (3) mentioned above.
By changing the values of  and  in the function expression of w(), the flattening
ratios of the respective profiles of the wraps, and the dissimilar tooth-thickness ratio
5 between the wraps can be set in accordance with the shapes of the corresponding
base plates. This helps to improve the mounting density of the wraps through
optimization of the wrap profile, and also increase suction volume. As a result, the
compressor can be improved in capacity without increasing in size. Alternatively
speaking, the compressor can be reduced in size for equivalent compressor capacity.
10 Further, by changing the value of  in the function expression of w(), the direction of
flattening of each wrap can be set.
[0062]
In Fig. 2, the dotted circles represent an over-compression relief port 21 and an
over-compression relief port 22 that are provided in the fixed base plate 1a. The
15 over-compression relief port 21 and the over-compression relief port 22 are provided
to ensure that, in operation under partial load with a small compression ratio, gas
refrigerant within the compression chambers is discharged in the axial direction at
some point during the compression process. By allowing gas refrigerant to be
discharged at some point during the compression process in this way, loss due to
20 over-compression within the compression chambers 71 can be reduced.
[0063]
To reduce leaks from between the compression chambers 71, each of the overcompression relief port 21 and the over-compression relief port 22 needs to be
disposed not to simultaneously communicate with adjacent compression chambers
25 71. Accordingly, the over-compression relief port 21 and the over-compression relief
port 22 each need to be designed with a port diameter smaller than the tooth
thickness of the corresponding wrap. In this regard, increasing the port diameter is
effective for efficient discharge of gas refrigerant in the compression process.
Accordingly, a design constraint on the port diameter of each of the over-compression
30 relief port 21 and the over-compression relief port 22 presents a problem in improving
21
the performance of partial-load operation.
[0064]
The spiral shape of the wrap according to Embodiment 1 is such that the wrap
has a greater tooth thickness at involute angles of 0 [rad] and  [rad] than at involute
5 angles of /2 [rad] and 3/2 [rad]. Thus, the wrap according to Embodiment 1 has a
spiral shape whose tooth thickness increases or decreases. Accordingly, the
following effect can be provided by disposing each of the over-compression relief port
21 and the over-compression relief port 22 within the area of the path traced by the
movement of a portion of increased tooth thickness of the orbiting wrap 2b associated
10 with the orbital motion of the orbiting scroll 2. That is, the above-mentioned
configuration makes it possible to set the port diameter as large as possible within a
range not exceeding the tooth thickness of the orbiting wrap 2b, and also prevent
adjacent compression chambers 71 from communicating with each other by way of
the over-compression relief port 21 and the over-compression relief port 22. This
15 allows for efficient discharge of gas refrigerant during partial-load operation, and
consequently reduce over-compression of refrigerant. As a result, wasted power
consumption due to over-compression of refrigerant can be reduced.
[0065]
Embodiment 2
20 The following description of Embodiment 2 is directed to changes in spiral
shape according to the characteristics of w(). Embodiment 2 is described below
with focus on features different from those according to Embodiment 1, and features
not described with reference to Embodiment 2 below are similar or identical to those
according to Embodiment 1.
25 [0066]
Fig. 6 illustrates the characteristics of w() that determine the spiral shape of
each wrap in the scroll compressor according to Embodiment 2. Fig. 6(a), and Fig.
6(b), Fig. 6(c), and Fig. 6(d) respectively correspond to equation (3) described above
with reference to the Embodiment 1, and equations (4) to (6) below. The horizontal
30 axis in Fig. 6 represents involute angle  [rad]. The vertical axis in Fig. 6 represents
22
w(). Fig. 7 illustrates the spiral shape of each wrap in the scroll compressor
according to Embodiment 2. Fig. 7(a) to Fig. 7(d) respectively depict spiral shapes
with w() varied as illustrated in Fig. 6(a) to Fig. 6(d). Fig. 7(a) and Fig. 7(b) each
depict a spiral shape when  has a value of 0.3,  has a value of 0.4, N has a value of
5 1, and  has a value of 0. Fig. 7(c) and Fig. 7(d) each depict a spiral shape when 
has a value of 0.15,  has a value of 0.4, N has a value of 1, and  has a value of 0.
[0067]
[Math. 4]
w( = ( + (cos( - ))2N) (4)
10 [0068]
[Math. 5]
w( = ( + sin2( - )) (5)
[0069]
[Math. 6]
15 w( = ( + cos2( - )) (6)
[0070]
According to Embodiment 2, by changing w() as in equations (4) to (6), the
respective profiles of the fixed wrap 1b and the orbiting wrap 2b can be set as desired.
Therefore, even if the orbiting base plate 2a has a shape different from that according
20 to Embodiment 1, an effect similar or identical to Embodiment 1 can be provided.
[0071]
Embodiment 3
The foregoing description of Embodiment 1 and Embodiment 2 is directed to a
spiral shape such that the wrap increases or decreases in tooth thickness from the
25 wrap start portion toward the wrap terminal portion. Embodiment 3 is directed to a
spiral shape with relatively small changes in the tooth thickness of the wrap from the
wrap start portion toward the wrap terminal portion. Embodiment 3 is described
below with focus on features different from those according to Embodiment 1, and
features not described with reference to Embodiment 3 below are similar or identical
30 to those according to Embodiment 1.
23
[0072]
Fig. 8 illustrates the characteristics of w() that determine the spiral shape of
each wrap in the scroll compressor according to Embodiment 3. Fig. 8(a), Fig. 8(b),
Fig. 8(c), and Fig. 8(d) respectively correspond to equations (7) to (10) below. The
5 horizontal axis in Fig. 8 represents involute angle  [rad]. The vertical axis in Fig. 8
represents w(). Fig. 9 illustrates the spiral shape of each wrap in the scroll
compressor according to Embodiment 3. Fig. 9(a) to Fig. 9(d) respectively depict
spiral shapes with w() varied as illustrated in Fig. 8(a) to Fig. 8(d). Fig. 9(a) and Fig.
9(b) each depict a spiral shape when  has a value of 1.4,  has a value of 0.4, N has
10 a value of 1, and  has a value of 0. Fig. 9(c) and Fig. 9(d) each depict a spiral
shape when  has a value of 0.7,  has a value of 0.4, N has a value of 1, and  has
a value of 0.
[0073]
[Math. 7]
w( = ( + (sin( - ))2N 15 ) (7)
[0074]
[Math. 8]
w( = ( + (cos( - ))2N) (8)
[0075]
20 [Math. 9]
w( = ( + sin2( - )) (9)
[0076]
[Math. 10]
w( = ( + cos2( - )) (10)
25 [0077]
Equations (7) to (10) above differ from equation (3) and equations (4) to (6)
mentioned above in that  is not multiplied by . According to Embodiment 3, as
with Embodiment 1, by changing the function expression of w(), the respective
profiles of the fixed wrap 1b and the orbiting wrap 2b can be set as desired. Further,
30 according to Embodiment 3, setting w() as in one of equations (7) to (10) makes it
24
possible to obtain an oval-shaped wrap with relatively small changes in tooth
thickness from the wrap start portion toward the wrap terminal portion. According to
Embodiment 3, even if large changes in tooth thickness are not permitted in designing
the shape of the wrap, the wrap can be formed in an oval shape to thereby provide
5 increased suction volume as in Embodiment 1.
[0078]
Embodiment 4
According to Embodiment 4, the function of w() in each of equations (3) to (6)
mentioned above is provided with a term of , which represents a degree of decrease
10 in the tooth thickness of the wrap. Embodiment 4 is described below with focus on
features different from those according to Embodiment 1, and features not described
with reference to Embodiment 4 below are similar or identical to those according to
Embodiment 1.
[0079]
15 Fig. 10 illustrates the characteristics of w() that determine the spiral shape of
each wrap in the scroll compressor according to Embodiment 4. The horizontal axis
in Fig. 10 represents involute angle  [rad]. The vertical axis in Fig. 10 represents
w(). In Fig. 10, the dotted line represents w() in equation (11) described below.
The solid line represents w() in equation (3) according to Embodiment 1, which is
20 illustrated for the purpose of comparison. Fig. 11 illustrates the spiral shape of each
wrap in the scroll compressor according to Embodiment 4. Fig. 11 depicts a spiral
shape when  has a value of 0.3,  has a value of 0.007,  has a value of 0.4, N has
a value of 1, and  has a value of 0, and when the function expression of w() is
represented by equation (11) below. In equations (11) to (14) below,  has a positive
25 value greater than or equal to 0.
[0080]
According to Embodiment 4, w() is represented by a function in which the
function of w() in each of equations (3) to (6) is multiplied by (1 - ).
[0081]
30 [Math. 11]
25
w() = ( + (sin - ))2N) (1 - ) (11)
[0082]
[Math. 12]
w() = ( + (cos - ))2N) (1 - ) (12)
5 [0083]
[Math. 13]
w() = ( + sin2( - )) (1 - ) (13)
[0084]
[Math. 14]
10 w() = ( + cos2( - )) (1 - ) (14)
[0085]
The wrap according to Embodiment 4 with w() determined by using one of
equations (11) to (14) has a shape described below. That is, the wrap has a shape
such that its mean tooth thickness progressively decreases from the wrap start
15 portion toward the wrap terminal portion with a period of 2 relative to the involute
angle. In equations (11) to (14),  has a positive value. As the value of  increases,
the degree of decrease in tooth thickness increases. Reference is now made to the
effect of the above-mentioned arrangement, that is, shaping the wrap such that its
mean tooth thickness progressively decreases from the wrap start portion toward the
20 wrap terminal portion with a period of 2 relative to the involute angle.
[0086]
The pressure difference between the compression chambers 71 defined within
the compression mechanism unit 8 is greater toward the central area where
refrigerant is compressed to an elevated pressure, that is, toward the central portion
25 of the wrap. In other words, the pressure difference between the compression
chambers 71 is greater in the wrap start portion than in the wrap terminal portion.
Accordingly, in designing the tooth thickness of the wrap, the tooth thickness needs to
be designed to be large enough to withstand the pressure difference occurring in the
central portion of the wrap. Now, a case is considered in which the wrap is designed
30 with a uniform thickness from the wrap start portion toward the wrap terminal portion
26
that is large enough to withstand the pressure difference occurring in the central
portion of the wrap. In this case, the wrap is designed with excessive strength in the
vicinity of the wrap terminal portion where the pressure difference between the
compression chambers 71 is small. In other words, the wrap is formed with an
5 unnecessarily large tooth thickness. As a result, the volume of the compression
chambers 71 at the completion of suction, that is, the suction volume is unnecessarily
reduced.
[0087]
By contrast, according to Embodiment 4, for an arrangement in which the wrap
10 progressively decreases in mean tooth thickness from the wrap start portion toward
the wrap terminal portion with a period of 2 relative to the involute angle, the degree
of decrease in tooth thickness can be set as desired by suitably setting the value of .
Consequently, by suitably setting the value of  in accordance with, for example, the
compressor specifications and operating conditions, a wrap can be obtained that,
15 while having a tooth thickness large enough to provide a strength required for the
wrap start portion, has a decreased tooth thickness in the wrap terminal portion to
thereby provide increased suction volume within a limited space. Specifically, as  is
increased from a value greater than or equal to 0, the degree of decrease in tooth
thickness increases from the wrap start portion toward the wrap terminal portion.
20 Accordingly, if there is a large pressure difference between the compression
chambers 71 in the central portion of the wrap, then the value of  may be increased,
whereas if there is only a small pressure difference between the compression
chambers 71 in the central portion of the wrap, then the value of  may be decreased.
[0088]
25 According to Embodiment 4, as with Embodiment 1, by changing the function
expression of w(), the respective profiles of the fixed wrap 1b and the orbiting wrap
2b can be set as desired. Further, according to Embodiment 4, by setting w() as in
one of equations (11) to (14), a wrap can be obtained whose mean tooth thickness
progressively decreases from the wrap start portion toward the wrap terminal portion
30 with a period of 2 relative to the involute angle. In this case, by suitably setting the
27
value of , the degree of decrease in tooth thickness can be changed. This makes it
possible to decrease the tooth thickness of the wrap near the wrap terminal portion
where the pressure difference exerted on the wrap is small. This makes it possible
to avoid a design in which the wrap has an excessive tooth thickness near the wrap
5 terminal portion, thus allowing for increased suction volume.
[0089]
Embodiment 5
According to Embodiment 5, the function of w() in each of equations (7) to
(10) mentioned above with reference to Embodiment 3 is provided with a term of ,
10 which represents a degree of decrease in the tooth thickness of the wrap.
Embodiment 5 is described below with focus on features different from those
according to Embodiment 3, and features not described with reference to
Embodiment 5 below are similar or identical to those according to Embodiment 3.
[0090]
15 Fig. 12 illustrates the characteristics of w() that determine the spiral shape of
each wrap in a scroll compressor according to Embodiment 5. The horizontal axis in
Fig. 12 represents involute angle  [rad]. The vertical axis in Fig. 12 represents w().
In Fig. 12, the dotted line represents w() in equation (15) mentioned below. The
solid line represents w() in equation (7) according to Embodiment 3, which is
20 illustrated for the purpose of comparison. Fig. 13 illustrates the spiral shape of each
wrap in the scroll compressor according to Embodiment 5. Fig. 13 depicts a spiral
shape when  has a value of 1.4,  has a value of 0.007,  has a value of 0.4, N has
a value of 1, and  has a value of 0, and when the function expression of w() is
represented by equation (15). In equations (15) to (18) below,  has a positive value.
25 [0091]
According to Embodiment 5, w() is represented by a function in which the
function of w() in each of equations (7) to (10) is multiplied by (1 - ).
[0092]
[Math. 15]
w() = ( + (sin( - ))2N 30 ) (1 - ) (15)
28
[0093]
[Math. 16]
w() = ( + (cos( - ))2N) (1 - ) (16)
[0094]
5 [Math. 17]
w() = ( + sin2( - )) (1 - ) (17)
[0095]
[Math. 18]
w() = ( + cos2( - )) (1 - ) (18)
10 [0096]
The wrap according to Embodiment 5 with w() determined by using one of
equations (15) to (18) has a shape described below. That is, the wrap has a shape
such that its mean tooth thickness progressively decreases from the wrap start
portion toward the wrap terminal portion with a period of 2 relative to the involute
15 angle. In equations (15) to (18),  has a positive value. As the value of  increases,
the degree of decrease in tooth thickness increases. The effect of the abovementioned arrangement, that is, shaping the wrap such that its mean tooth thickness
progressively decreases from the wrap start portion toward the wrap terminal portion
with a period of 2 relative to the involute angle, is as described above.
20 [0097]
According to Embodiment 5, for an arrangement in which the wrap
progressively decreases in mean tooth thickness from the wrap start portion toward
the wrap terminal portion with a period of 2 relative to the involute angle, the degree
of decrease in tooth thickness can be set as desired by suitably setting the value of .
25 Consequently, by suitably setting the value of  in accordance with, for example, the
compressor specifications and operating conditions, a wrap can be obtained that,
while having a tooth thickness large enough to provide a strength required for the
wrap start portion, has a decreased tooth thickness in the wrap terminal portion to
thereby provide increased suction volume within a limited space. Specifically, as  is
30 increased from a value greater than or equal to 0, the degree of decrease in tooth
29
thickness increases as described above. Accordingly, if there is a large pressure
difference between the compression chambers 71 in the central portion of the wrap,
then the value of  may be increased, whereas if there is only a small pressure
difference between the compression chambers 71 in the central portion of the wrap,
5 then the value of  may be decreased.
[0098]
According to Embodiment 5, as with Embodiment 3, by changing the function
expression of w(), the respective profiles of the fixed wrap 1b and the orbiting wrap
2b can be set as desired. Further, according to Embodiment 5, by setting w() as in
10 one of equations (15) to (18), a wrap can be obtained whose mean tooth thickness
progressively decreases from the wrap start portion toward the wrap terminal portion
with a period of 2 relative to the involute angle. In this case, by suitably setting the
value of , the degree of decrease in tooth thickness can be changed. This makes it
possible to decrease the tooth thickness of the wrap near the wrap terminal portion
15 where the pressure difference exerted on the wrap is small. This makes it possible
to avoid a design in which the wrap has an excessive tooth thickness near the wrap
terminal portion, thus allowing for increased suction volume.
[0099]
Although the foregoing description of Embodiments 1 to 5 is directed to a case
20 where the scroll compressor is of a low-pressure shell type in which refrigerant is at
low pressure within the hermetic shell 100, the same effects as mentioned above can
be likewise obtained for a case where the scroll compressor is of a high-pressure
shell type in which refrigerant is at high pressure within the hermetic shell 100.
Reference Signs List
25 [0100]
1: fixed scroll, 1a: fixed base plate, 1b: fixed wrap, 1c: discharge port, 2:
orbiting scroll, 2a: orbiting base plate, 2b: orbiting wrap, 2c: orbiting bearing, 4: baffle,
4a: through-hole, 5: balancing-weight-equipped slider, 6: rotary shaft, 6a: eccentric
shaft part, 6b: main shaft part, 6c: sub-shaft part, 7: frame, 7a: main bearing, 7b: boss
30 part, 7c: introduction channel, 8: compression mechanism unit, 9: sub-frame, 9a: sub-
30
frame holder, 10: sub-bearing, 11: discharge valve, 12: discharge muffler, 13: sleeve,
14: Oldham ring, 14a: key part, 21: over-compression relief port, 22: overcompression relief port, 30: base curve, 31: inverse curve, 32: circle, 33: inner
envelope, 34: outer envelope, 35: circle, 36: outer envelope, 37: inner envelope, 60:
5 first balancing weight, 61: second balancing weight, 71: compression chamber, 72:
first space, 73: second space, 73a: suction space, 74: third space, 100: hermetic shell,
100a: oil reservoir, 101: suction pipe, 102: discharge pipe, 110: motor mechanism unit,
110a: motor stator, 110b: motor rotor, 112: pump element.
31
We Claim:
[Claim 1]
A scroll compressor comprising a fixed scroll and an orbiting scroll, the fixed
scroll having a fixed wrap projected from a fixed base plate, the orbiting scroll having
5 an orbiting wrap projected from an orbiting base plate, the fixed wrap and the orbiting
wrap meshing with each other to define a compression chamber in which refrigerant
is compressed,
wherein a base curve is used to determine an outer curve of one wrap and an
inner curve of an other wrap, the one wrap being one of the fixed wrap and the
10 orbiting wrap, the other wrap being an other one of the fixed wrap and the orbiting
wrap, the base curve being defined in an x-y coordinate system by equation (1) and
equation (2) by using an involute angle  and a radius "a" of a base circle:
[Math. 1]
x = a(cos + w()sin) (1)
15 [Math. 2]
y = a(sin - w()cos) (2),
wherein an inverse curve is used to determine an inner curve of the one wrap
and an outer curve of the other wrap, the inverse curve being a curve obtained by
rotating the base curve by  [rad] relative to a center of the base circle,
20 wherein w() in the equation (1) and the equation (2) is a function varying in a
sinusoidal or cosine manner with a period of  [rad] relative to the involute angle ,
wherein a dissimilar tooth-thickness ratio is defined as  = tf / (tf + tO), where tf
is a tooth thickness of the fixed wrap and tO is a tooth thickness of the orbiting scroll,
and an orbit radius of the orbiting scroll is defined as "e",
25 wherein the outer curve of the one wrap is an inner envelope to a group of
circles of radius e each having a center lying on the base curve, and the inner curve
of the one wrap is an outer envelope to a group of circles of radius e each having a
center lying on the inverse curve,
wherein the inner curve of the other wrap is an outer envelope to a group of
30 circles of radius e(1 - ) each having a center lying on the base curve, and the outer
32
curve of the other wrap is an inner envelope to a group of circles of radius e(1 - )
each having a center lying on the inverse curve, and
wherein the dissimilar wrap-thickness ratio  is in a range of 0 <  < 1.
[Claim 2]
5 The scroll compressor of claim 1, wherein the dissimilar wrap-thickness ratio 
is in a range of 0 <  < 0.5.
[Claim 3]
The scroll compressor of claim 1, wherein the function w() is given by
equation (3):
10 [Math. 3]
w() = ( + (sin - ))2N) (1 - ) (3),
where  and  are coefficients, N is a natural number greater than or equal to 1, and
 is a constant [rad].
[Claim 4]
15 The scroll compressor of claim 1, wherein the function w() is given by
equation (4):
[Math. 4]
w() = ( + (cos - ))2N) (1 - ) (4),
where  and  are coefficients, N is a natural number greater than or equal to 1,  is a
20 constant [rad].
[Claim 5]
The scroll compressor of claim 1, wherein the function w() is given by
equation (5):
[Math. 5]
25 w() = ( + sin2( - )) (1 - ) (5),
where  and  are coefficients, N is a natural number greater than or equal to 1,  is a
constant [rad].
[Claim 6]
The scroll compressor of claim 1, wherein the function w() is given by
30 equation (6):
33
[Math. 6]
w() = ( + cos2( - )) (1 - ) (6),
where  and  are coefficients, N is a natural number greater than or equal to 1,  is a
constant [rad].
5 [Claim 7]
The scroll compressor of claim 1, wherein the function w() is given by
equation (7):
[Math. 7]
w() = ( + (sin( - ))2N) (1 - ) (7),
10 where  and  are coefficients, N is a natural number greater than or equal to 1,  is a
constant [rad].
[Claim 8]
The scroll compressor of claim 1, wherein the function w() is given by
equation (8):
15 [Math. 8]
w() = ( + (cos( - ))2N) (1 - ) (8),
where  and  are coefficients, N is a natural number greater than or equal to 1,  is a
constant [rad].
[Claim 9]
20 The scroll compressor of claim 1, wherein the function w() is given by
equation (9):
[Math. 9]
w() = ( + sin2( - )) (1 - ) (9),
where  and  are coefficients, N is a natural number greater than or equal to 1,  is a
25 constant [rad].
[Claim 10]
The scroll compressor of claim 1, wherein the function w() is given by
equation (10):
[Math. 10]
30 w() = ( + cos2( - )) (1 - ) (10),
34
where  and  are coefficients, N is a natural number greater than or equal to 1,  is a
constant [rad].
[Claim 11]
The scroll compressor of any one of claims 3 to 10, wherein the coefficient  is
5 set greater than or equal to 0.
[Claim 12]
The scroll compressor of any one of claims 1 to 11, wherein the orbiting base
plate has a flattened outer shape.