Rotary expansible chamber devices – Working member has planetary or planetating movement – Helical working member – e.g. – scroll
Reexamination Certificate
2002-01-09
2004-02-24
Denion, Thomas (Department: 3748)
Rotary expansible chamber devices
Working member has planetary or planetating movement
Helical working member, e.g., scroll
Reexamination Certificate
active
06695598
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to scroll compressors installed in air conditioners, refrigerators and the like.
2. Description of the Related Art
Scroll compressors are composed of fixed scroll members and revolving scroll members (i.e., pairs of scroll members) whose centrifugal walls (or spiral walls) are arranged in engagement with each other and which are subjected to revolving motions. That is, the scroll compressor operates in such a way that the revolving scroll member revolves with respect to the fixed scroll member. Thus, it performs fluid compression of its compression space, which is formed between the walls of the scroll members, and is gradually reduced in volume during compression.
FIGS. 7A and 7B
show a pair of scroll members that are installed in the conventional scroll compressor described above.
FIG. 8
is a plan view diagrammatically showing a center portion of a centrifugal wall of a scroll member, which is installed in the scroll compressor disclosed in Japanese Unexamined Patent Publication No. Sho 59-58187.
FIGS. 9A and 9B
diagrammatically show a center portion of a centrifugal wall of a scroll member, which is installed in the scroll compressor disclosed in Japanese Unexamined Patent Publication No. Hei 9-68177.
FIG. 10
is a plan view diagrammatically showing a center portion of a centrifugal wall of a scroll member, which is installed in the scroll compressor disclosed in Japanese Unexamined Patent Publication No. Hei 10-68392.
Operations of the aforementioned scroll compressors having paired scroll members will be discussed below.
A first example of the scroll compressor has a combination of a fixed scroll member
1
shown in
FIG. 7A
in which a centrifugal wall
1
b
is arranged on an end board
1
a
, and a revolving scroll member
2
shown in
FIG. 7B
in which a centrifugal wall
2
b
is arranged on an end board
2
a
. These scroll members
1
and
2
are combined together in such a way that the centrifugal walls
1
b
and
2
b
engage with each other and are shifted from each other with a certain angle of dislocation, which is about 180 degrees (180°). In the engaged state of the scroll members, the revolving scroll member
2
is revolved so that a closed space being formed between the centrifugal walls
1
b
and
2
b
moves inwardly from its outer position to its inner position while being gradually reduced in volume. Thus, it is possible to perform fluid compression in the compression space.
The closed space located in its innermost position bears a high pressure, whereas the closed space located in its outer position becomes low in pressure. This causes reaction of compressed gas in the center portion of the centrifugal walls
1
b
and
2
b
combined together. Repeatedly revolving the scroll member
2
causes repetition of the reaction of the compressed gas being effected in the center portions of the centrifugal walls
1
b
and
2
b
. The center portions also correspond to spiral-starting portions of the centrifugal walls
1
b
and
2
b
, which bear shortage of rigidity. Therefore, fatigue failure may occur at root portions at which the centrifugal walls
1
b
and
2
b
are respectively affixed to the end boards
1
a
and
2
a.
A second example of the scroll compressor disclosed in Japanese Unexamined Patent Publication No. Sho 59-58187 is provided to solve the aforementioned problem, which will be described with reference to FIG.
8
.
FIG. 8
shows a center portion (or a spiral-starting portion) of a centrifugal wall
3
of the scroll member installed in the scroll compressor, wherein involute curves are drawn with respect to an exterior and an interior of the centrifugal wall
3
respectively. A first position is fixed at a certain involute angle &agr; on the first involute curve corresponding to the exterior of the centrifugal wall
3
, while a second position is fixed at an involute angle (&agr;+180°) on the second involute curve corresponding to the interior of the centrifugal wall
3
. In addition, a small circular arc is drawn with respect to the first position on the first involute curve, while a large circular arc is drawn with respect to the second position on the second involute curve. Hence, the center portion of the centrifugal wall
3
is formed by connecting the involute curves with the circular arcs. Thus, it is possible to increase the thickness of the centrifugal wall
3
at its center portion, which yields an improvement in strength. However, the aforementioned technique does not provide sufficient improvement in rigidity because a high concentration of stress still remains in proximity to the small circular arc of the center portion of the centrifugal wall
3
.
A third example of the scroll compressor disclosed in Japanese Unexamined Patent Publication No. Hei 9-68177 provides a further improvement in rigidity, which will be described with reference to
FIGS. 9A and 9B
.
That is, it is characterized by providing stepped wall surface portions for both of the fixed and revolving scroll members.
FIGS. 9A and 9B
show a centrifugal wall
4
installed in the scroll compressor, wherein a stepped wall surface portion is formed between a first position, which is fixed at a certain involute angle &agr; on an involute curve corresponding to an exterior of the centrifugal wall
4
, and a second position which is fixed at an involute angle (&agr;+180°) on an involute curve corresponding to an interior of the centrifugal wall
4
. A closed space is defined as a combination of a spiral-inside closed space and a spiral-back-side closed space being formed between the centrifugal walls of the scroll members combined together, and its volume changes in response to engaged states of the scroll members. The center portions of the centrifugal walls of the scroll members combined together are shaped to establish a profile of complete engagement in which the volume of the closed space at its innermost position becomes substantially zero. In addition, the thickness of the stepped wall surface portion of the centrifugal wall
4
is changed in such a step-by-step manner that the thickness is gradually reduced upwards from the end board. Due to the provision of the stepped wall surface portion for the center portion of the centrifugal wall, it is possible to selectively increase the thickness of the center portion of the centrifugal wall at its root portion only. This allows a further improvement in the strength of the scroll member installed in the scroll compressor.
A fourth example of the scroll compressor disclosed in Japanese Unexamined Patent Publication No. Hei 10-68392 will be described with reference to FIG.
10
.
FIG. 10
shows a centrifugal wall
5
of the scroll member whose center portion has a stepped wall surface portion. In addition, the center portion of the centrifugal wall
5
is partially shaped to allow provision of a root fillet
5
a
in a certain area defined between connection points of spiral curves and circular arcs drawn for the exterior and interior of the centrifugal wall
5
. Similarly, a root fillet (not shown) is also provided for another centrifugal wall
6
that engages with the centrifugal wall
5
. In order to avoid interference between the root fillets of the centrifugal walls
5
and
6
, a gap is provided therebetween in a wall thickness direction. This reduces concentration of stress at the root portion of the centrifugal wall. Therefore, it is possible to further improve the strength of the scroll member.
The third example of the scroll compressor shown in
FIGS. 9A and 9B
bears the following problems. The closed space formed between the centrifugal wall of the fixed scroll member and the centrifugal wall of the revolving scroll member has a dead volume at a last step of compression. The dead volume corresponds to the volume of the ‘innermost’ closed space that is established at a seal-off point, at which the innermost closed space communicates with a second closed space having a crescent shape that is located one lap outside from the innermos
Fujita Katsuhiro
Itoh Takahide
Maruiwa Yasuharu
Miura Shigeki
Ogawa Hiroshi
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