Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
. i
CA 02374372 2002-03-04
SCROLL TYPE COMPRESSOR
BACKGROUND OF THE INVENTION
The present invention relates to a scroll type
compressor and more particularly to structure of a
fixed scroll member and a movable scroll member
which constitute a compression mechanism in a
volute shape.
In general, the scroll type compressor has a
housing in which the fixed scroll member and the
movable scroll member are provided. The fixed
scroll member has a fixed scroll base plate and a
fixed scroll wall that extends from the fixed scroll
base plate. The movable scroll member has a
movable scroll base plate and a movable scroll wall
that extends from the movable scroll base plate.
Each scroll wall is engaged with each other. The
fixed scroll member and the movable scroll member
cooperatively form a plurality of compression
chambers as a compression region. As the movable
scroll member orbits about an axis of the fixed
scroll member, the compression chambers move
radially inward while their volume decreases.
Since bending moment is applied to each scroll
wall by high pressure generated in the compression
chambers due to the compression performance, the
bending moment deforms each scroll wall. Therefore,
clearance between the scroll walls is increased and
compressed fluid leaks through the clearance.
Accordingly, high compression performance is not
obtained.
1 - -
i ~ s~~i. ....I ~. i
CA 02374372 2002-03-04
To obtain the high compression performance by
preventing the compressed fluid from leaking, as
shown in FIG. 4A, a scroll wall 1 was
conventionally created in a taper shape from a
joining portion to a base plate 2 toward a distal end
of the scroll wall 1.
Still referring to FIG. 4A, in the above
constitution, the scroll wall 1 is strengthened
against bending moment. Therefore, clearance
between the scroll walls l was effectively
restrained from increasing. There, such a
constitution was employed that a tip seal 3 slides
the surface of the opposing base plate 2 to ensure
sealing performance in the clearance between the
distal end of the scroll wall 1 and the opposing base
plate 2.
However, as it is taken into consideration that
the compressor used in high speed vehicles is
nowadays required to be compact and lightweight
for its fuel efficiency, the following problem has
occurred in the above prior art. The thickness of the
scroll wall 1 is increased when the tip seal 3 is used.
As a result, configuration of the compressor is
increased in size.
As shown in FIG. 4A, when the distal end of the
scroll wall 1 is provided with the tip seal 3,
thickness c of the distal end of the scroll wall 1 is
determined as follows. c=a+2*b where width of the
tip seal 3 is expressed by a, and thickness of an
outer wall of a groove formed in the distal end is
- 2 - -
,~ ,i i
CA 02374372 2002-03-04
expressed by b. Thickness of the portion joining to
the scroll wall l, which is expressed by d, is-also
determined to be relatively thick due to increase of
the thickness c.
On the contrary, as shown in FIG. 4B, when the
distal end of the scroll wall 1 has similar thickness
to the width a of the tip seal 3 in size, thickness a of
the portion joining to the base plate 2 becomes
relatively small. Accordingly, the compressor
including the scroll wall 1 shown in FIG. 4A, has
less capacity in the compression chambers than that
of FIG. 4B, because of an increase in thickness of
the scroll wall 1 provided with the tip seal 3. To
maintain the capacity in the compression chambers,
the configuration of the compressor is inevitably
increased in size.
SUMMARY OF THE INVENTION
The present invention addresses a scroll type
compressor which is hard, compact and lightweight
with high quality sealing performance.
According to the present invention, A scroll
type compressor has a fixed scroll member and a
movable scroll member. The fixed scroll member has
a fixed scroll base plate and a fixed scroll wall
extending from the fixed scroll base plate. The
movable scroll member has a movable scroll base
plate and a movable scroll wall extending from the
movable scroll base plate. The fixed scroll member
and the movable scroll member cooperatively form a
compression region. The movable scroll member
- 3 - -
I i
CA 02374372 2002-03-04
orbits relative to the fixed scroll member to
compress refrigerant in the compression region.
Each scroll wall is formed in a taper shape from each
base plate toward each distal end of the scroll wall.
The distal end is non-contact with the opposing
scroll base plate. Clearance between the distal end
and the opposing scroll base plate is less than or
equal to the limit clearance value which maintains
airtight performance between the distal end and the
opposing scroll base plate.
BRIEF DESCRIPTION OF THE DRAWINGS
The features of the present invention that are
believed to be novel are set forth with particularity
in the appended claims. The invention together with
objects and advantages thereof, may best be
understood by reference to the following
description of the presently preferred embodiments
together with the accompanying drawings in which:
FIG. 1 is a diagram in a cross-sectional view
illustrating a first preferred embodiment of the
scroll type compressor according to the present
invention;
FIG. 2 is a diagram in a partial enlarged view
illustrating first and second preferred embodiments
of the scroll type compressor according to the
present invention;
FIG. 3 is a graph illustrating a relation
between clearance in the direction of an axis and a
ratio of COP according to the present invention;
4 - -
i
CA 02374372 2002-03-04
FIG. 4A is a diagram in a partial
cross-sectional view illustrating a scroll wall with a
tip seal according to the prior art; and
FIG. 4B is a diagram in a partial
cross-sectional view illustrating a scroll wall
without a tip seal according to the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED
EMBODIMENTS
A scroll type compressor according to a first
preferred embodiment of the present invention will
be described with reference to Figs. 1 through 3.
As shown in FIG. l, a front housing 30, a
center housing 31 and a rear housing 32 are
connected to form a configuration of the compressor.
A fixed scroll member 35 is integrally formed with
the center housing 31. The fixed scroll member 35
has a fixed scroll base plate 33 and a fixed scroll
wall 34 that extends from the fixed scroll base plate
33. An inlet 36 for introducing refrigerant is also
formed in the center housing 31 and is connected to
an external refrigerant circuit. A movable scroll
member 39 is accommodated in a space defined by
the center housing 31 and the front housing 30. The
movable scroll member 39 has a movable scroll base
plate 37 and a movable scroll wall 38 that extends
from the movable scroll base plate 37. The fixed
scroll wall 34 and the movable scroll wall 38 engage
with each other. Thereby, a plurality of compression
- 5 - __
CA 02374372 2002-03-04
chambers 40 is defined as a compression region
between the fixed scroll member 35 and the movable
scroll member 39. A discharge hole 42 is formed
substantially at the center of the fixed scroll base
plate 33. Compressed refrigerant in the compression
chambers 40 is discharged into a discharge chamber
41 defined between the center housing 31 and the
rear housing 32 through the discharge hole 42. An
outlet 43 is formed in the rear housing 32 to flow
refrigerant in the discharge chamber 41 into the
external refrigerant circuit.
Still referring to FIG. 1, one end of a drive
shaft 45 is rotatably supported in the front housing
30 by bearing 44 and the other end of the drive shaft
45 extends outside of the configuration of the
compressor. A crankshaft 46 is mounted on one end
of the drive shaft 45. The crankshaft 46 is received
by a bushing 47, which is inserted in a boss 48 of
the movable scroll member 39. A self rotation
preventing mechanism 49 prevents the movable
scroll member 39 from rotating about its axis, while
allowing the movable scroll member 39 to orbit
about an axis of the fixed scroll member 35.
As shown in FIG. 2, the fixed scroll wall 34
and the movable scroll wall 38 are respectively
formed in a taper shape from portions joining to the
scroll base plates 33 and 37 toward the respective
distal ends. The fixed scroll wall 34 has a pair of
side surfaces 34a and 34b which incline by angles of
and 8 Z with respect to the direction of an axis
of the drive shaft 45 (which is perpendicular to the
scroll base plates 33 and 37), respectively. In a
6 - -
i
CA 02374372 2002-03-04
similar manner, the movable scroll wall 38 has a
pair of side surfaces 38a and 38b which incline by
angles of B 3 and 8 4 with respect to the direction
of the axis of the drive shaft 45 (which is
perpendicular to the scroll base plates 33 and 37),
respectively. At this time, the side surfaces 34b and
38a which face each other are equal in inclination
angle. That is, 8 Z equals 8 3. In a similar manner,
the side surfaces 34a and 38b which face each other
are also equal in inclination angle. That is,
equals 8 q. In addition, when the side surfaces 34a
and 34b of the fixed scroll wall 34 are equal in
inclination angle, 8 ~ equals 8 Z. In a similar
manner, when the side surfaces 38a and 38b of the
movable scroll wall 38 are equal in inclination
angle, 8 3 also equals 8 4. In this case, the fixed
scroll wall 34 and the movable scroll wall 38 are
equal in inclination angle. The above inclination
angle is formed not only by cutting but also by
utilizing a draft upon casting.
Still referring to FIG. 2, when the compressor
is assembled by engaging the movable scroll member
39 with the fixed scroll member 35, the distal end of
the fixed scroll wall 34 and the opposing surface of
the movable scroll base plate 37 are maintained to
have clearance G1 therebetween so as not to contact
with each other. In a similar manner, the distal end
of the movable scroll wall 38 and the opposing
surface of the fixed scroll base plate 33 are
maintained to have clearance G2 therebetween so as
not to contact with each other. The clearance GI
generally equals the clearance G2.
- 7 -
CA 02374372 2002-03-04
Now, a method for searching the optimal value
of the clearance G1 and GZ will be explained with
reference to FIG. 3. In this graph the value of x-axis
represents length of clearance G~ and GZ in the
direction of the axis expressed by unit of
micrometer or ,c.c m and the value of y-axis
represents a ratio of Coefficient of Performance or
COP of a compressor according to the present
invention, which is not provided with the tip seal, to
that of a compressor which is provided with the tip
seal. In both cases that oil circulating inside exists
and doesn't exist, relation between the length of
clearance and the ratio of COP is respectively drawn
by line graph. Even in the case that the distal end is
provided with the tip seal, the length of the
clearance represents distance between the distal end
of the scroll wall and the opposing surface of the
scroll base plate.
Still referring to FIG. 3, note that efficiency of
load L which is required due to a heat absorption in
an evaporator is generally expressed by COP as
follows. COP=Qer~L, where Qer denotes efficiency of
refrigeration.
In view of total performance of the compressor,
the ratio of COP is allowable if it is more than or
equal to 0.9. At this time, in the case that the oil
circulating inside exists, FIG. 3 reads that the
length of the clearance is less than or equal to 60
,u m. In the case that no oil circulating inside exists,
FIG. 3 reads that the length of the clearance is less
than or equal to 47 ,c.Z m. Accordingly, it is required
that the clearance GI and G2 are each less than or
- 8 - _
,.; , i . . i
CA 02374372 2002-03-04
equal to the above upper limit value.
Then, function of the first preferred
embodiment will be explained. As shown in FIG. 1,
when the drive shaft 45 that extends outside of the
configuration of the compressor is rotated by
driving force of an external drive source such as a
vehicle engine, which is connected to the drive shaft
45 through a pulley which is not shown, the movable
scroll member 39 orbits about the axis of the fixed
scroll member 35. Refrigerant gas introduced from
the external refrigerant circuit through the inlet 36
is compressed to be predetermined pressure in the
compression chambers 40 and discharged into the
discharge chamber 41 through the discharge hole 42
by the orbital movement. The pressurized
refrigerant gas discharged into the discharge
chamber 41 is sent to the external refrigerant circuit
through the outlet 43.
As shown in FIG. 2 in combination with FIG. 1,
during the above compression process, bending
moment is applied to the scroll walls 34 and 38 due
to compression movement in the compression
chambers 40. In this constitution, however, the
fixed scroll wall 34 and the movable scroll wall 38
are respectively formed in a taper shape from the
portions joining to the scroll base plates 33 and 37
toward the respective distal ends, while having
relatively sufficient thickness of the portions.
Accordingly, the fixed scroll wall 34 and the
movable scroll wall 38 are restrained from being
deformed, thus effectively maintaining a sealing
performance therebetween.
- 9 - -
n I , I
CA 02374372 2002-03-04
Still referring to FIG. 2, while the distal ends
of the fixed scroll wall 34 and the movable scroll
wall 38 are not in contact with the respective
opposing surfaces of the movable scroll base plate
37 and the fixed scroll base plate 33, sealing
performance is respectively ensured since the
distance therebetween is less than or equal to the
upper limit clearance value which maintains airtight
performance. Thus, total sealing performance in the
compression region is relatively and sufficiently
maintained. Therefore, high compressing
performance is obtained. Besides, since the distal
ends of the scroll wall 34 and 38 and the respective
. opposing surfaces of the scroll base plates 37 and 33
are prevented from directly contacting, power loss
is also restrained to be extremely small while the
compressor is driven.
Especially, as shown in FIG. 3 in combination
with FIG. 1, in the case that the oil circulating
inside exists when the clearance in the direction of
the axis of the drive shaft 45 is less than or equal to
36 ,cc m, the ratio of COP is more than or equal to 1.
In a similar manner, in the case that no oil
circulating inside exists when the clearance in the
direction of the axis of the drive shaft 45 is less
than or equal to 30 ,ct m, the ratio of COP is also
more than or equal to 1. These mean that the
compressor according to the present invention has
superior efficiency of refrigeration to the
compressor provided with the tip seal when the
clearance G1 and G2 are less than or equal to the
foregoing upper limit value. This is regarded
- 10 - -
CA 02374372 2002-03-04
because the compressor provided with the tip seal
losses power due to sliding friction generated
between the tip seal and the opposing surface of the
scroll base plate. Accordingly, in the above
S description while the clearance G, and GZ are less
than or equal to 60 ,u m, more preferably, in the case
that the oil circulating inside exists, the clearance
G~ and G2 are less than or equal to 36 ,ct m. In a
similar manner, while the clearance G, and G2 are
less than or equal to 47 ~t m, more preferably, in the
case that no oil circulating inside exists, the
clearance G1 and G2 are less than or equal to 30 ,u
m.
Referring back to FIG. 2, in this embodiment,
since the distal ends of the scroll walls 34 and 38
are not provided with the tip seal, while provided in
the prior art, the thickness of the distal ends of the
scroll walls 34 and 38 is prevented from inevitably
increasing by providing the tip seal. Accordingly,
the thickness of the scroll wall is determined to be
minimized. In spite of the relatively sufficient
thickness of the joint portion, the configuration of
the compressor is not increased in size.
In this embodiment the following effects are
obtained. Firstly, still referring to FIG. 2, since the
scroll walls 34 and 38 are restrained from being
deformed to resist to bending moment by relatively
and sufficiently ensuring the thickness of the joint
portions of the scroll walls 34 and 38, sealing
performance is ensured. In addition, sealing
performance is also ensured in clearance between
the distal ends of the scroll walls 34 and 38, and the
- 11 - -
:..~:i : I : ' i
CA 02374372 2002-03-04
respective opposing surfaces of the scroll base
plates 37 and 33. As a result, total sealing
performance in the compression region is relatively
and sufficiently maintained. Thus, high compressing
performance is obtained.
Secondly, since sealing performance is
sufficiently ensured therebetween while the distal
ends of the scroll walls 34 and 38 are not in contact
with the respective opposing surfaces of the scroll
base plates 37 and 33, relatively sufficient
efficiency of compression is ensured by the distal
ends of the scroll walls 34 and 38 with necessary
minimal thickness, and the scroll walls 34 and 38,
as a whole, have necessary minimal thickness.
Accordingly, capacity in the compression region is
increased, and in its turn, the compressor is, as a
whole, reduced in size and weight.
Thirdly, the side surface 34a of the scroll wall
34 and the side surface 38b of the scroll wall 38
facing each other are equal in inclination angle.
Also, the side surface 34b of the scroll wall 34 and
the side surface 38a of the scroll wall 38 facing
each other are equal in inclination angle. Therefore,
airtight constitution in the compression region is
easily obtained by a draft upon casting. In addition,
the side surfaces 34a and 34b of the scroll wall 34
are each equal in inclination angle. Also, the side
surfaces 38a and 38b of the scroll wall 38 are equal
in inclination angle. Moreover, since these side
surfaces 34a, 34b, 38a and 38b are each set to be
equal in inclination angle even between the scroll
members 35 and 39, molding for casting is easily
- 12 - -
"~.: i I i
CA 02374372 2002-03-04
manufactured.
Fourthly, since the inclination angles of the
side surfaces 34a, 34b, 38a and 38b of the scroll
walls 34 and 38 are formed by utilizing a draft upon
casting, cutting process is not required. Therefore,
person-hour for manufacturing is reduced. In
addition, since casting surface or surface as forged
is used in this case, the compressor which is high in
surface hardness and durability is obtained.
A scroll type compressor according to a second
preferred embodiment of the present invention will
be described with reference to FIG. 2. In this
embodiment, the side surfaces 34a, 34b of the scroll
wall 34 are different in inclination angle. Also, the
side surfaces 38a, 38b of the scroll wall 38 are
different in inclination angle. That is, inclination
angles 8 ~, 8 2 of the side surfaces 34a, 34b of the
scroll wall 34 are different from each other. Also,
inclination angles 8 3, 8 4 of the side surfaces 38a,
38b of the scroll wall 38 are different from each
other. However, the side surfaces 34a, 38b and 34b,
38a of the scroll walls 34 and 38 which are facing
each other are equal in inclination angle. That is,
the relation between 8 1, 8 Z, 8 3 and 8 4 is
expressed as follows. 8 Z= 8 3. 8
As described above, side surfaces of a scroll
wall are different in inclination angle. When the
scroll member is formed, for example, by casting, it
may be required that the side surfaces of the scroll
wall are different in draft in a casting plan.
Accordingly, inclination angles of the side surfaces
- 13 - -
..,~ ~,.~ . >-I -: i
CA 02374372 2002-03-04
are predetermined differently. The other
constitution of the second embodiment is similar to
the constitution of the first embodiment, and the
overlapped explanation is omitted.
As constituted above, since each pair of side
surfaces 34a, 38b and 34b, 38a of the scroll walls 34
and 38 facing each other is equal in inclination
angle even if the side surfaces 34a, 34b and 38a, 38b
of the scroll walls 34 and 38 are each different in
inclination angle, sealing performance in the
compression chambers 40 is ensured. Thus,
compression cycle in the compression chambers 40
is performed without obstruction.
In this embodiment, the above described
effects of the first embodiment are obtained. In
addition, the following effect is also obtained.
Since it is possible that each side surface of the
scroll wall of the scroll member is different in
inclination angle, a design in a casting plan is
relatively freely performed. As a result, the scroll
member is easily manufactured.
In the present invention, the following
embodiment is also practiced. The scroll type
compressor according to the above embodiments has
the drive shaft which protrudes outside of the
configuration of the compressor and is operatively
connected to the external drive source such as an
engine. However, the above external drive source
may be built in type or canned motor type. That is,
electric motor for driving the drive shaft may be
installed in the compressor.
14 - -
~.i:,.~..lli ~ I
CA 02374372 2002-03-04
As described above, in the present invention,
since thickness of the joint portion of the scroll
wall is larger than that of the distal end of the scroll
wall, the scroll wall is prevented from being
deformed. In addition, sealing performance is
ensured in clearance between the distal end of the
scroll wall and the opposing surface of the scroll
base plate. Therefore, airtight performance in the
compression region is, as a whole, maintained. As a
result, high compressing performance is obtained.
Moreover, since the distal end is not provided with
the tip seal, the scroll wall has, as a whole,
relatively small thickness. As a result, the scroll
1 S wall becomes compact and lightweight. Thus,
various prominent effects are obtained.
The present examples and preferred
embodiments are to be considered as illustrative and
~ not restrictive and the invention is not to be limited
to the details given herein but may be modified
within the scope of the appended claims.
15 - -
