Sealed-type scroll compressor with relatively shifted scrolls based on thermal coefficient of expansion

In a sealed-type scroll compressor having a stationary scroll member and an orbiting scroll member, the stationary scroll member is fixed after rotating it in an orbiting direction of the orbiting scroll member by a predetermined angle from a phase angle position where a possible orbiting radius between both scroll members is made maximum at the temperature before driving the scroll compressor.

FIELD OF THE INVENTION AND RELATED ART STATEMENT 
1. Field of the Invention 
The present invention relates to a sealed-type scroll compressor and its 
assembling method. 
2. Description of the Related Art 
The specification of U.S. Pat. No. 3,884,599 discloses a conventional 
scroll-type fluid machinery. This fluid machinery has a stationary scroll 
member and an orbiting scroll member which are formed to have 
involute-curved shapes. These scroll members are inwardly engaged with 
each other with their wraps facing together. The orbiting scroll member is 
driven by a crank shaft to make orbiting motion. Volume of a compressed 
gas space defined by two scroll members decreases in response to movement 
of the space toward the center of the scroll members caused by the 
orbiting motion in one direction which is hereinafter referred to as the 
orbiting direction. 
In the above-mentioned scroll-type fluid machinery, generally, a pair of 
compressed gas spaces are defined by side walls of two wraps of the 
stationary scroll member and the orbiting scroll member. These compressed 
gas spaces are sealed by adjacent two wraps located closer to each other 
and gradually made smaller to increase a pressure in the gas space. 
Accordingly, positioning of both scroll members should be carried out with 
high accuracy. 
To be concrete, the stationary scroll member should be located and fixed in 
a position where a proper minute gap is formed between adjacent two wraps 
of the stationary scroll member and the orbiting scroll member without 
making contact with each other at any rotational position around a crank 
axis. 
The conventional method for assembling the sealed-type scroll compressor is 
disclosed in e.g., Japanese published patent application TOKKAI Hei 
2-221693. According to the method disclosed in this publication, the 
orbiting scroll member sequentially makes orbiting motion to go to 
predetermined angular positions. In each of the predetermined angular 
positions, the stationary scroll member is moved until it makes contact 
with the orbiting scroll member. When the stationary scroll member has 
come into contact with the orbiting scroll member, X-position or 
Y-position is measured. Based on these X-positions and Y-positions, the 
position to which the stationary scroll member is to be located is 
determined. Further, by providing a .theta.-table on the XY-tables, it is 
possible to relatively position the stationary scroll member with respect 
to the orbiting scroll member in the orbiting direction of the orbiting 
scroll member. 
FIG. 1 is a cross-sectional view showing a compressor chamber 1 of the 
scroll compressor. In FIG. 1, the stationary scroll member 4 is fixed with 
the frame 2 by a bolt 7. The orbiting scroll member 5 is driven by the 
crank shaft 3. A clearance "E" is formed between an inner face of a wrap 
5b of the orbiting scroll member 5 and an outer face of a wrap 4b of the 
stationary scroll member 4. A clearance "F" is formed between an outer 
face of the wrap 5b of the orbiting scroll member 5 and an inner face of 
the wrap 4b of the stationary scroll member 4. What is important in 
assembling the compressor chamber is to locate the stationary scroll 
member 4 with respect to the orbiting scroll member 5 so that the 
clearances of "E" and "F" can be always constant at any rotational 
position of the crank shaft 3. 
Hereupon, in the above-mentioned sealed-type scroll compressor, what 
influence occurs on the positional relation between both scroll members by 
the thermal expansion will be described. 
Under the condition that materials of the stationary scroll member 4 and 
the orbiting scroll member 5 are equal to each other in regard to their 
coefficients of thermal expansion, a clearance between both wraps 4b and 
5b at the time of assembly is compared with a clearance after the thermal 
expansion has occurred. Further, a relative phase angle for obtaining the 
maximum clearance at the time of assembly is compared with that after the 
thermal expansion has occurred. 
In that case, each configuration of both wraps 4b and 5b has expand in its 
radius of a base circle of the involute curve in response to an extent of 
temperature rise. Therefore, the clearance between both wraps 4b and 5b 
during the driving becomes larger than the initial set clearance. However, 
the relative phase angle for obtaining the maximum clearance is kept 
constant even when the thermal expansion has occurred. In the scroll 
compressors, the relative phase angle for obtaining the maximum clearance 
is constant even when radii of the base circles of the involute curves for 
the stationary scroll member 4 and the orbiting scroll member 5 are 
different from each other. 
In recent years, employment of an inverter-controlled scroll compressor 
goes on increasing, and further high-speed driving of the compressor in 
comparison with the conventional one is being expected for higher 
efficiency and smaller size of the scroll compressor. Accordingly, to 
reduce the centrifugal force of the orbiting scroll member 5, reduction of 
weight of the orbiting scroll member 5 is making continuous progress. 
In the above-mentioned circumstances, there often exists the case that a 
material of the stationary scroll member 4 is different from a material of 
the orbiting scroll member 5 in regard to a coefficient of the thermal 
expansion. The clearance between the two wraps 4b, 5b and the relative 
phase angle for obtaining the maximum clearance are both varied whenever 
radii of the base circles of the involute curves are equal to or different 
from each other. Therefore, even when the stationary scroll member 4 is 
fixed to the optimum position, a proper clearance cannot be held between 
both wraps 4b and 5b during the actual operation of the scroll compressor. 
As a result, freezing ability lowers, and an input power increases, thus 
lowering an efficiency of the scroll compressor. 
Next, description will be made in detail about how the clearance is 
influenced by the thermal expansion of the scroll members 4 and 5. 
FIGS. 7-10 are graphs each showing a relation between a possible orbiting 
radius (graduated on ordinate) and a relative phase angle (graduated on 
abscissa) between the stationary scroll member 4 (FIG. 1) and the orbiting 
scroll member 5 (FIG. 1). When a shift of phase is 180.degree., it is 
defined 0.degree.. As shown in FIG. 3, a direction of positive is defined 
by a counter-orbiting direction of the orbiting scroll member 5 with 
respect to the stationary scroll member 4, and a direction of negative is 
defined by an orbiting direction of the orbiting scroll member 5. The term 
of "possible orbiting radius" is defined as an orbiting radius required to 
obtain a predetermined clearance between the stationary scroll member 4 
and the orbiting scroll member 5, and the "orbiting radius" is defined as 
an eccentric distance between the center axis of the orbiting scroll 
member 4 and the center axis of the crank shaft 3 (FIG. 1). 
As an example, description will be made hereinafter about the position of 
0.degree.. The description about the states of other phase angles is 
omitted because it is similar to the following description. 
In FIG. 7, a characteristic (a) is obtained under the condition: a material 
of the stationary scroll member 4 (FIG. 1) has the same coefficient of 
thermal expansion as a material of the orbiting scroll member 5 (FIG. 1); 
and radii of the base circles are equal to each other. In this 
characteristic, a relative phase angle .theta..sub.c presenting the 
maximum possible orbiting radius is 0.degree., and both scroll members 4 
and 5 are coupled with each other with a predetermined clearance between 
the wraps 4b and 5b (FIG. 1). 
When the stationary scroll member 4 is fixed with respect to the orbiting 
scroll member 5 within the positive domain, a predetermined clearance is 
formed between an inner side wall of the wrap 5b of the orbiting scroll 
member 5 and an outer side wall of the wrap 4b of the stationary scroll 
member 4, whereas a clearance larger than a predetermined value is formed 
between an outer side wall of the wrap 5b of the orbiting scroll member 5 
and an inner side wall of the wrap 4b of the stationary scroll member 4. 
When the stationary scroll member 4 is fixed with respect to the orbiting 
scroll member 5 within the negative domain, there arises a reverse state 
to the above-mentioned state occurred in the positive domain. 
When the scroll compressor is driven after the stationary scroll member 4 
has been assembled in the state of the relative phase angle 0.degree., 
radii of the base circles of both scroll members 4 and 5 expands due to 
the thermal expansion. However, since the coefficients of thermal 
expansion are equal to each other, a relative phase angle .theta..sub.H 
presenting the maximum possible orbiting radius is still 0.degree. 
(=.theta..sub.c) as shown in a characteristic (b) in FIG. 7. Thus, 
although the clearance between the wraps 4b and 5b slightly expands due to 
the thermal expansion, an optimum positional relationship between both 
scroll members 4 and 5 is maintained. 
Next, in FIG. 8, a characteristic (a) is obtained under the condition: a 
material of the stationary scroll member 4 has the same coefficient of 
thermal expansion as a material of the orbiting scroll member 5; and radii 
of the base circles are different from each other. In this state, the 
maximum possible orbiting radius appears in a relative phase angle away 
from 0.degree.. The angle .theta..sub.c is not zero degree. 
When a radius of the base circle of the scroll member 5 is smaller than a 
radius of the base circle of the stationary scroll member 4, the relative 
phase angle presenting the maximum possible orbiting radius moves toward 
the negative domain (.theta..sub.c &lt;0.degree.). When a radius of the base 
circle of the orbiting scroll member 5 is larger than the radius of the 
base circle of the stationary scroll member 4, the relative phase angle 
presenting the maximum possible orbiting radius moves toward the positive 
domain (.theta..sub.c &gt;0.degree.). 
When the scroll compressor is driven after the stationary scroll member 4 
has been assembled in the state of the relative phase angle .theta..sub.c, 
radii of the base circles of both scroll members 4 and 5 expand due to the 
thermal expansion. However, since the coefficients of thermal expansion 
are equal to each other, a relative phase angle .theta..sub.H presenting 
the maximum possible orbiting radius is equal to the angle .theta..sub.c, 
which is the angle at the time of the assembly, as shown in a 
characteristic (b) in FIG. 8. Thus, although the clearance between the 
wraps 4b and 5b slightly expands due to the thermal expansion, an optimum 
positional relationship between both scroll members 4 and 5 is maintained. 
Thus, even after the thermal expansion has occurred, the relative phase 
angle presenting the maximum possible orbiting radius is kept equal to 
that at the time of assembly only on condition that coefficients of 
thermal expansion of materials for both scroll members 4 and 5 are 
equivalent to each other. In other words, the relative phase angle does 
not vary whenever radii of the base circles are equal to or different from 
each other. Therefore, a state of clearance between both wraps 4b and 5b 
is maintained substantially as it is in the assembly. 
However, when the coefficients of thermal compression of the materials for 
both scroll members 4 and 5 are different from each other, a state of 
clearance between the wraps 4b and 5b varies after the thermal expansion 
as compared with the state in the assembly. FIG. 9 is a graph showing 
relations between the relative phase angle and the possible orbiting 
radius. A characteristic (a) is obtained on condition that: materials of 
the scroll members 4 and 5 are different from each other in regard to 
coefficients of thermal expansion; and radii of the base circles of both 
scroll members 4 and 5 are equal to each other. The maximum possible 
orbiting radius is obtained in a position where the relative phase angle 
.theta..sub.C is zero degree. This characteristic (a) is similar to the 
characteristic (a) shown in FIG. 7. 
When the scroll compressor is driven under the condition that both scroll 
members 4 and 5 are assembled with a relative phase angle of 0.degree., 
radii of the base circles of both scroll members 4 and 5 expand due to the 
thermal expansion. At that time, since the coefficient of thermal 
expansion are different from each other, a radius of the base circle of 
the stationary scroll member 4 is different from that of the orbiting 
scroll member 5 after the thermal expansion has occurred. As a result, the 
relative phase angle .theta..sub.H presenting the maximum possible 
orbiting radius is shifted from the angle .theta..sub.C (=0.degree.) at 
the time of the assembly as shown in a characteristic (b) in FIG. 9. When 
the coefficient of the thermal expansion in the orbiting scroll member 5 
is larger than that in the stationary scroll member 4, the relative phase 
angle .theta..sub.H sifts to the positive domain (i.e., .theta..sub.C 
.theta..sub.H) as shown in the characteristic (b) in FIG. 9. When the 
coefficient of the thermal expansion in the orbiting scroll member 5 is 
smaller than that in the stationary scroll member 4, the relative phase 
angle .theta..sub.H shifts to the negative domain (i.e., .theta..sub.C 
.theta..sub.H). 
In the characteristic (b) in FIG. 9, the relative phase angle 
(.theta..sub.C =0.degree.) in the assembly is positioned in the negative 
side (i.e., .theta..sub.C &lt;.theta..sub.H) from the relative phase angle 
.theta..sub.H which presents the maximum possible orbiting radius after 
the thermal expansion has occurred. Therefore, a clearance between the 
inner side wall of the wrap 5b of the orbiting scroll member 5 and the 
outer side wall of the wrap 4b of the stationary scroll member 4 is larger 
than a predetermined value, and a clearance between the outer side wall of 
the wrap 5b of the orbiting scroll member 5 and the inner side wall of the 
wrap 4b of the stationary scroll member 4 is smaller than a predetermined 
value. 
As a result, the condition at the time of assembly can not be maintained, 
thus lowering performance of the scroll compressor. Further, depending on 
the present clearance, the side walls of the wraps 4b and 5b may come into 
contact with each other after the thermal expansion has occurred, thereby 
undesirably applying the wraps 4b and 5b with an excessive force. As a 
result, the input power increases, or the scroll compressor stops. 
Further, the wraps 4b and 5b may be destroyed. Thus, the reliability of 
the scroll compressor lowers. 
FIG. 10 is also a graph showing relations between the relative phase angle 
(on abscissa) and the possible orbiting radius (on ordinate). These 
characteristics (a) and (b) are obtained under the condition that: 
materials of the scroll members are different from each other in regard to 
the coefficients of thermal expansion; and radii of the base circles of 
both scroll members 4 and 5 are different from each other. As has been 
made the similar description for the characteristic (a) in FIG. 8, the 
maximum possible orbiting radius is obtained at a relative phase angle 
.theta..sub.C (.noteq.0.degree.) which is shifted from 0.degree.. When the 
radius of the base circle of the orbiting scroll member 5 is smaller than 
that of the stationary scroll member 4, the relative phase angle 
.theta..sub.C presenting the maximum possible orbiting radius shifts to 
the negative domain (i.e., .theta..sub.C &lt;0.degree.). When the radius of 
the base circle of the orbiting scroll member 5 is larger than that of the 
stationary scroll member 4, the relative phase angle .theta..sub.C 
presenting the maximum possible orbiting radius shifts to the positive 
domain (i.e., .theta..sub.C &gt;0.degree.). 
In this state, when the scroll compressor is driven, the radii of the base 
circles of both scroll members 4 and 5 expand due to the thermal 
expansion. Since the coefficients of thermal expansion of both scroll 
members 4 and 5 are different from each other, the radii of the base 
circles of the stationary scroll member 4 and the orbiting scroll member 5 
become respective other values or may accidentally be equal to each other 
in a specific condition. However, as shown in a characteristic (b) in FIG. 
10, the relative phase angle .theta..sub.H (.noteq..theta..sub.C) 
presenting the maximum possible orbiting radius is shifted from the 
position of the angle .theta..sub.C in the assembly. 
Thus, in the condition such that coefficients of thermal expansion of the 
materials for both scroll members 4 and 5 are different from each other, 
the relative phase angle presenting the maximum possible orbiting radius 
varies after the thermal expansion as compared with that in the assembly 
whenever the radii of the base circles are equal to or different from each 
other. Therefore, the clearance between both wraps 4b and 5b varies as 
compared with the value of initial setting. The desirable condition at the 
time of assembly is thus not maintained, resulting in lowering performance 
of the scroll compressor. Further, depending on the present clearance, the 
side walls of the wraps 4b and 5b may come into contact with each other 
after the thermal expansion has occurred. Such contact will damage the 
wraps 4b and 5b, and the reliability of the scroll compressor lowers 
accordingly. 
OBJECT AND SUMMARY OF THE INVENTION 
An object of the present invention is to offer a sealed-type scroll 
compressor and its assembling method by which both scroll members are 
precisely positioned to make a condition of the positional relation 
optimum even when the temperature rises in the scroll members having 
coefficients of thermal expansion different from each other. 
In order to achieve the above-mentioned object, the sealed-type scroll 
compressor of the present invention comprises a compression chamber 
consisting of a stationary scroll member and an orbiting scroll member, 
both of which are engaged with each other with inner faces of respective 
wraps facing to each other, the stationary scroll member and the orbiting 
scroll member being made of materials whose coefficients of thermal 
expansion are different from each other, wherein an improvement is that: 
the stationary scroll member and the orbiting scroll member are located in 
position by relatively shifting one of scroll members having a coefficient 
of thermal expansion larger than the other scroll member by a 
predetermined phase angle in a counter-orbiting direction of the orbiting 
scroll member from a position defined by a predetermined positional 
relationship between the stationary scroll member and the orbiting scroll 
member where a possible orbiting radius between the stationary scroll 
member and the orbiting scroll member is made maximum. 
In another aspect, the present invention is a method for assembling a 
sealed-type scroll compressor having a stationary scroll member to be 
fixed to a frame and an orbiting scroll member to be engaged with said 
stationary scroll member, the method comprising the steps of: 
temporarily positioning the stationary scroll member on the frame to come 
into engagement with the orbiting scroll member; 
relatively positioning one of the scroll members with respect to the other 
scroll member in a phase angle direction of wraps of the scroll members; 
positioning the stationary scroll member with respect to the orbiting 
scroll member in X-direction and Y-direction of the scroll members; 
shifting one of the scroll members, which has a coefficient of thermal 
expansion smaller than the other scroll member, in an orbiting direction 
of the orbiting scroll member by a predetermined phase angle; and 
fixing the stationary scroll member to the frame. 
According to the present invention, the clearance between both scroll 
members is kept optimum in condition in any orbiting direction during the 
driving of the scroll compressor. Accordingly, power loss in the 
compression chamber is reduced without any improvement in accuracy of 
parts, and performance of the scroll compressor is therefore improved. 
While the novel features of the invention are set forth particularly in the 
appended claims, the invention, both as to organization and content, will 
be better understood and appreciated, along with other objects and 
features thereof, from the following detailed description taken in 
conjunction with the drawings.

It will be recognized that some or all of the Figures are schematic 
representations for purposes of illustration and do not necessarily depict 
the actual relative sizes or locations of the elements shown. 
DESCRIPTION OF THE PREFERRED EMBODIMENT 
Hereafter, a preferred embodiment of the present invention will be 
described with reference to the accompanying drawings. 
FIG. 1 is a cross-sectional view showing a compressor chamber 1 of the 
scroll compressor. In FIG. 1, a stationary scroll member 4 is to be fixed 
with a frame 2 by a bolt 7. An orbiting scroll member 5 is driven by a 
crank shaft 3. A clearance "E" is formed between an inner face of a wrap 
5b of the orbiting scroll 5 and an outer face of a wrap 4b of the 
stationary scroll 4. A clearance of width "F" is formed between an outer 
face of the wrap 5b of the orbiting scroll member 5 and an inner face of 
the wrap 4b of the stationary scroll member 4. What is important in 
assembling the compressor chamber is to fix the stationary scroll member 4 
to the orbiting scroll member 5 so that the clearances of "E" and "F" can 
be always constant at any rotational position of the crank shaft 3. The 
stationary scroll member 4 and the orbiting scroll member 5 are engaged 
with each other, thereby defining a compression space 6 therebetween. The 
stationary scroll member 4 consists of a disc-shaped end plate 4a and an 
upright wrap 4b which is formed to have an involute curve. A radius of a 
base circle of the involute curve is defined "a.sub.T ", and a coefficient 
of thermal expansion of a material of the stationary scroll member 4 is 
defined "K.sub.T ". The orbiting scroll member 5 consists of a disc-shaped 
end plate 5a, an upright wrap 5b and a boss member 5c formed on a face 
reverse to the wrap 5b of the end plate 5a. The wrap 5b is formed to have 
an involute curve in which a radius of a base circle is defined "a.sub.D 
". A coefficient of thermal expansion of a material of the orbiting scroll 
member 5 is defined "K.sub.D ", and this is larger than the 
above-mentioned coefficient K.sub.T of the stationary scroll member 4. 
When a temperature of the stationary scroll member 4 and the orbiting 
scroll member 5 rises uniformly by T.degree. C during the driving, the 
radius a.sub.T of the wrap 4b and the radius a.sub.D of the wrap 5b hold 
the following equations: 
EQU a.sub.T .times.(1+K.sub.T .times.T)=a.sub.D .times.(1+K.sub.D 
.times.T)=a.sub.H. 
Under the relation of K.sub.T &lt;K.sub.D, the above equation necessarily 
introduces a relation of a.sub.T &gt;a.sub.D. As shown in the above-noted 
notations, the stationary scroll member 4 rising by T.degree.C and the 
orbiting scroll member 5 rising by T.degree.C are set to have the same 
radius, designated a.sub.H. 
Hereafter, a method for assembling the scroll compressor will be described 
with reference to FIGS. 11 and 12. 
FIG. 11 is a front view showing an assembling machine of the scroll 
compressor, and FIG. 12 is a side view showing the same assembling 
machine. In FIG. 11 or FIG. 12, an X-table 9 is provided on a Y-table 8, 
and a .theta.-table 10 is provided on the X-table 9. A first chuck member 
11 and a second chuck member 12 are provided above the .theta.-table 10 on 
opposite sides to each other so as to chuck therebetween the stationary 
scroll member 4 which is put on the .theta.-table 10. A third chuck member 
13 and a fourth chuck member 14 are provided similarly to the above so as 
to chuck therebetween a frame 2. A crank axis revolving unit 16 is 
provided to go downward, grip and revolve a crank axis 3. A first pushing 
member 17 is provided to push the X-table 9 and the Y-table 8 from a 
negative side of the X-direction, and a second pushing member 18 is 
provided to push the X-table 9 and the Y-table 8 from a positive side of 
the X-direction. A third pushing member 19 (FIG. 12) is provided to push 
the X-table 9 and the Y-table 8 from a negative side of the Y-direction, 
and a fourth pushing member 20 (FIG. 12) is provided to push the X-table 9 
and the Y-table 8 from a positive side of the Y-direction. A driving unit 
21 (FIG. 11) for the X-direction is provided to move the X-table 9 and the 
Y-table 8 in the X-direction, and a position detector 22 for the 
X-direction measures a moved amount of the X-table 9 and detects a 
position in the X-direction. A driving unit 23 (FIG. 12) for the 
Y-direction is provided to move the X-table 9 and the Y-table 8 in the 
Y-direction, and a position detector 24 for the Y-direction measures a 
moved amount of the Y-table 8 and detects a position in the Y-direction. A 
pushing rod 25 (FIG. 11) for the X-direction is provided to fixedly hold 
the X-table 9 and the Y-table 8 against a force given by the driving unit 
21 for the X-direction. A pushing rod 26 (FIG. 12) for the Y-direction is 
provided to fixedly hold the X-table 9 and the Y-table 8 against a force 
given by the driving unit 23 for the Y-direction. Based on the positions 
detected, a control unit 27 (FIG. 12) calculates a clearance and a 
position to be located and operates respective actuators (not shown). 
Next, a method for assembling the scroll compressor will be described with 
reference to FIGS. 1, 4, 5 and 6. 
FIG. 4 is illustrations showing a positional relationship between the 
stationary scroll member 4 and the orbiting scroll member 5 in four 
angular positions of 0.degree., 90.degree., 180.degree. and 270.degree. 
when the crank shaft 3 (FIG. 1) is revolved. 
To carry out the assembly of the compression chamber of the scroll 
compressor in FIGS. 11 and 12, the first step is to put on the 
.theta.-table 10 the compression chamber 1 with the bolt 7 being released. 
The stationary scroll member 4 is fixedly held by the first chuck member 
11 and the second chuck member 12 therebetween, and the frame 2 is fixedly 
held by the third chuck member 13 and the fourth chuck member 14 
therebetween. Further, the crank axis revolving unit 16 is lowered to grip 
the crank shaft 3. Next, the crank axis 3 is revolved to make a positional 
relationship of the orbiting scroll member 5 and the stationary scroll 
member 4 into a state of 0.degree. shown in FIG. 4. 
FIGS. 5 and 6 are graphs showing a relation between the relative phase 
angle of the stationary scroll member 4 with respect to the orbiting 
scroll 5 and positions in the X-direction. First, an angle .theta..sub.1 
is assumed as the maximum-clearance relative phase angle .theta..sub.0. 
Next, around the phase angle .theta..sub.1 which is as the center 
position, the stationary scroll member 4 is sequentially rotated to two 
angular positions of a phase angle .theta..sub.2 in a negative direction 
and a phase angle .theta..sub.3 in a positive direction, wherein an angle 
of .vertline..theta..sub.2 -.theta..sub.1 .vertline. is equal to an angle 
of .vertline..theta..sub.3 -.theta..sub.1 .vertline.. In each of the 
angular positions, the stationary scroll member 4 is pushed toward the 
orbiting scroll member 5 by the first pushing member 17 (FIG. 11), and 
thereafter the fixed pushing member 17 returns to the home position. In a 
state that the stationary scroll member 4 is in contact with the orbiting 
scroll member 5, a position in the X-direction is detected by the detector 
22 for the X-direction. Thus, three positions X.sub.5, X.sub.6 and X.sub.7 
which correspond to the phase angles .theta..sub.2, .theta..sub.1 and 
.theta..sub.3 are detected by the detector 22. Since the relation has been 
known to have an isosceles-triangular mountain-shaped lines symmetrical 
with respect to a chain line L (FIG. 5) on the phase angle .theta..sub.0, 
the phase angle .theta..sub.0 presenting the maximum clearance can be 
derived from the mountain-shaped lines assumed. 
In FIG. 5, the relative phase angle .theta..sub.0 is within a range from 
the phase angle .theta..sub.1 to the phase angle .theta..sub.3, and a 
value of the position X.sub.5 is smaller than a value of the position 
X.sub.7. 
First, a phase angle .theta..sub.4 at which a value in the X-direction is 
equal to X.sub.7 is detected by means of the following equation: 
##EQU1## 
The relative phase angle .theta..sub.0 which is located in the middle of 
the phase angles .theta..sub.4 and .theta..sub.3 is represented by an 
equation: 
EQU .theta..sub.0 =(.theta..sub.4 +.theta..sub.3)/2. 
FIG. 6 is a graph showing another relationship in a state that the relative 
phase angle .theta..sub.0 presenting the maximum clearance falls within a 
range from the phase angle .theta..sub.1 to the phase angle .theta..sub.2. 
In FIG. 6, a value of the position X.sub.5 is larger than the value 
X.sub.7. 
First, a phase angle .theta..sub.4 at which a value in the X-direction is 
equal to X.sub.5 is detected by means of the following equation: 
##EQU2## 
The relative phase angle .theta..sub.0 which is located in the middle of 
the phase angle .theta..sub.4 and .theta..sub.2 is represented by an 
equation: 
EQU .theta..sub.0 =(.theta..sub.4 +.theta..sub.2)/2. 
First, an angle .theta..sub.1 is assumed as the relative phase angle 
.theta..sub.0 presenting the maximum clearance. Next, around the phase 
angle .theta..sub.1 which is as the center position, the stationary scroll 
member 4 is sequentially rotated to two angular positions of a phase angle 
.theta..sub.2 in a negative direction and a phase angle .theta..sub.3 in a 
positive direction, wherein an angle of .vertline..theta..sub.2 
-.theta..sub.1 .vertline. is equal to an angle of .vertline..theta..sub.3 
-.theta..sub.1 .vertline.. Further, in the positional relation of 
0.degree. shown in FIG. 4, the stationary scroll member 4 is pushed toward 
the orbiting scroll member 5 by the first pushing member 17 (FIG. 11), and 
thereafter the fixed pushing member 17 returns to the home position. After 
that, position in the X-direction is detected. Based on a fact that 
position in the X-direction varies in a linear shape, the relative phase 
angle .theta..sub.0 presenting the maximum clearance can be detected by 
obtaining at least three positions in the X-direction. 
Relative phase angle to be held between the stationary scroll member 4 and 
the orbiting scroll member 5 is thus determined. 
Next, positioning in the X- and Y-directions will be described. First, the 
crank shaft 3 (FIG. 1) is revolved to get the positional relation between 
the orbiting scroll member 5 and the stationary scroll member 4 into the 
state of 0.degree. shown in FIG. 4. The X-table 9 (FIG. 11) is pushed 
toward the positive side by the first pushing member 17 (FIG. 11), thereby 
getting the stationary scroll member 4 into contact with the orbiting 
scroll member 5. When the first pushing member 17 is restored to the home 
position thereby making the pushing force zero, the stationary scroll 
member 4 is naturally in contact with the orbiting scroll 5. A position in 
the X-direction in this contacting state is detected by the detector 22 
for the X-direction, and the detected position in the X-direction is 
stored in the control unit 27 (FIG. 12) as X.sub.1. 
Next, the crank shaft 3 is revolved by 90.degree., thereby getting the 
positional relation between the stationary scroll member 4 and the 
orbiting scroll member 5 into the state of 90.degree. shown in FIG. 4. 
Further, the Y-table 8 (FIG. 12) is pushed toward the positive side by the 
third pushing member 19 (FIG. 12), thereby getting the stationary scroll 
member 4 into contact with the orbiting scroll member 5. When the 
stationary scroll member 4 comes into contact with the orbiting scroll 5, 
the third pushing member 19 is restored to the home position. In the state 
wherein the stationary scroll member 4 is naturally in contact with the 
orbiting scroll member 5, a position in the Y-direction of the Y-table 8 
is detected by the detector 24 (FIG. 12) for the Y-direction. The detected 
position in the Y-direction is stored in the control unit 27 (FIG. 12) as 
Y.sub.1. 
Next, the crank shaft 3 is revolved again by 90.degree. to get the 
positional relation between the orbiting scroll member 5 and the 
stationary scroll member 4 into the state of 180.degree. shown in FIG. 4. 
The X-table 9 (FIG. 11) is pushed toward the negative side by the second 
pushing member 18 (FIG. 11), thereby getting the stationary scroll member 
4 into contact with the orbiting scroll member 5. Thereafter the second 
pushing member 18 is restored to the home position. A position in the 
X-direction in this contacting state is detected by the detector 22 (FIG. 
11) for the X-direction, and the detected position in the X-direction is 
stored in the control unit 27 (FIG. 12) as X.sub.2. 
Next, the crank shaft 3 is revolved again by 90.degree., thereby getting 
the positional relation between the stationary scroll member 4 and the 
orbiting scroll member 5 into the state of 270.degree. shown in FIG. 4. 
Further, the Y-table 8 (FIG. 12) is pushed toward the negative side by the 
fourth pushing member 20 (FIG. 12), thereby getting the stationary scroll 
member 4 into contact with the orbiting scroll member 5. When the 
stationary scroll member 4 comes into contact with the orbiting scroll 5, 
the fourth pushing member 20 is restored to the home position. In the 
state wherein the stationary scroll member 4 is naturally in contact with 
the orbiting scroll member 5, a position in the Y-direction of the Y-table 
8 is detected by the detector 24 (FIG. 12) for the Y-direction. The 
detected position in the Y-direction is stored in the control unit 27 
(FIG. 12) as Y.sub.2. 
Next, based on the data X.sub.1, X.sub.2, Y.sub.1 and Y.sub.2, clearances 
C.sub.X (X-direction) and C.sub.Y (y-direction) between the two wraps 4b 
and 5b (FIG. 1) and a position (X, Y) to be located are determined by the 
following equations: 
EQU C.sub.X =(X.sub.1 -X.sub.2)/2, 
EQU C.sub.Y =(Y.sub.1 -Y.sub.2)/2, 
EQU X=X.sub.2 +(X.sub.1 -X.sub.2)/2, 
and 
EQU Y=Y.sub.2 +(Y.sub.1 -Y.sub.2)/2. 
Next, the X-table 9 (FIGS. 11 and 12) and the Y-table 10 (FIGS. 11 and 12) 
are moved by means of the driving unit 21 (FIG. 11) for the X-direction 
and the driving unit 23 (FIG. 12) for the Y-direction, thereby locating 
the stationary scroll member 4 into the above-mentioned position. 
Thereafter, the X-table 9 and the Y-table 10 are fixedly held by the 
pushing rod 25 (FIG. 11) for the X-direction and the pushing rod 26 (FIG. 
12) for the Y-direction. 
The state after completion of the above-mentioned procedures corresponds to 
a position P on a dotted line in FIG. 2. Since the radius a.sub.T is 
larger than the radius a.sub.D, a relative phase angle .theta..sub.c 
(=.theta..sub.0, in FIGS. 5 and 6) presenting the maximum possible 
orbiting radius is shifted to the negative domain as shown in the 
characteristic (a) of FIG. 10. In FIG. 2, an orbiting radius is R.sub.c. 
Clearances between both scroll members 4 and 5 are uniformly of the 
predetermined clearance C.sub.c. 
When the temperature rises by T.degree. C, the present state is represented 
by a position P' on a solid line of FIG. 2. Radii of the base circles of 
both scroll members 4 and 5 become to a.sub.H due to the thermal 
expansion, and their configurations of the base circles are equal to each 
other. However, since the relative phase angle .theta..sub.c is located in 
the negative side from a relative phase angle .theta..sub.H (=0.degree.) 
presenting the maximum possible orbiting radius after the temperature has 
risen, a clearance between the outer side wall of the wrap 5b of the 
orbiting scroll member 5 and the inner side wall of the wrap 4b of the 
stationary scroll member 4 is smaller than the predetermined clearance 
C.sub.c, whereas a clearance between the inner side wall of the wrap 5b of 
the orbiting scroll member 5 and the outer side wall of the wrap 4b of the 
stationary scroll member 4 is larger than the predetermined clearance 
C.sub.c. Its difference is r.sub.1 shown in FIG. 2. 
In view of above, to make the clearance between both wraps 4 and 5 
substantially equal to each other after the thermal expansion, the 
stationary scroll member 4 is rotated with the .theta.-table 10 to the 
negative direction (i.e., orbiting direction) by an angle of 
.theta..sub.c. This means to relatively rotate the orbiting scroll member 
5 to the positive direction (i.e., counter-orbiting direction) by the same 
angle. Then, the present state is represented by a position Q' on the 
dotted line in FIG. 2. In this state, a clearance between the outer side 
wall of the wrap 5b of the orbiting scroll member 5 and the inner side 
wall of the wrap 4b of the stationary scroll member 4 is larger than the 
predetermined clearance C.sub.c, whereas a clearance between the inner 
side wall of the wrap 5b of the orbiting scroll member 5 and the outer 
side wall of the wrap 4b of the stationary scroll member 4 is smaller than 
the predetermined clearance C.sub.c. Its difference is r.sub.2 shown in 
FIG. 2. 
In the above-mentioned state, when the temperature rises by T.degree. C, 
the present state is represented by a position Q on the solid line of FIG. 
2. Radii of the base circles of both scroll members 4 and 5 become to 
a.sub.H due to the thermal expansion, and their configurations of the base 
circles are equal to each other. Further, since the relative phase angle 
.theta..sub.C shifts to the relative phase angle .theta..sub.H (=0) 
currently presenting the maximum possible orbiting radius, clearances 
between both wraps 4b and 5b are secured even with each other, thereby 
presenting the ideal positional relationship. Of course, the clearance 
becomes slightly larger than the predetermined clearance C.sub.c because 
of the thermal expansion. This expansion results in increase of orbiting 
radius r.sub.3 shown in FIG. 2. However, this increase of radius r.sub.3 
brings no problem only by taking it into consideration in setting the 
clearance C.sub.c beforehand. 
Finally, the X-table 9 (FIG. 11) and the Y-table 8 (FIG. 11) are fixedly 
held by the pushing rod 25 (FIG. 11) for the X-direction and the pushing 
rod 26 (FIG. 12) for the Y-direction. Thereafter, the bolt 7 is fixed, 
thereby completing the assembly. 
In the scroll compressor assembled by the above-mentioned procedure, the 
radius of the base circle of the orbiting scroll member 5 is smaller than 
that of the stationary scroll member 4 before driving the scroll 
compressor. However, since the radii of the base circles of both scroll 
members 4 and 5 become equal to each other at the temperature under the 
driving, it is possible to keep the clearance in very good state during 
the important actual driving state. Performance of the scroll compressor 
is thereby improved. 
Although the present invention has been described in terms of the presently 
preferred embodiments, it is to be understood that such disclosure is not 
to be interpreted as limiting. Various alterations and modifications will 
no doubt become apparent to those skilled in the art to which the present 
invention pertains, after having read the above disclosure. Accordingly, 
it is intended that the appended claims be interpreted as covering all 
alterations and modifications as fall within the true spirit and scope of 
the invention.