Rotary expansible chamber devices – Working member has planetary or planetating movement – Helical working member – e.g. – scroll
Reexamination Certificate
1998-09-15
2001-04-10
Vrablik, John J. (Department: 3748)
Rotary expansible chamber devices
Working member has planetary or planetating movement
Helical working member, e.g., scroll
Reexamination Certificate
active
06213742
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to scroll-type fluid mover such as scroll-type vacuum pumps and compressors.
Scroll-type fluid mover, for example, scroll-type compressors have a movable scroll and a fixed scroll. Each scroll includes a base plate and a volute portion formed on the base plate. The volute portions cooperate to form a compression chamber. An eccentric shaft is formed on a drive shaft. The movable scroll is rotatably supported by the eccentric shaft. When the drive shaft rotates, the movable scroll orbits the axis of the drive shaft. Then, the compression chamber contracts from the periphery to the center of the volute portions, which compresses gas.
FIG. 6
shows a prior art structure for supporting a movable scroll with respect to the drive shaft. The structure of
FIG. 6
is described as being prior art in Japanese Examined Publication No. 63-59032. In the apparatus of
FIG. 6
, an eccentric shaft
41
is formed on the drive shaft
42
. The axis of the eccentric shaft
42
is displaced with respect to the axis of the drive shaft
42
in the radial direction by a distance equal to the revolution radius of a movable scroll
44
. The drive shaft
42
is supported by a housing
48
of the compressor and a bearing
46
. The movable scroll
44
includes a base plate
44
a,
a volute portion
44
b
projecting from the base plate
44
a
, a boss
43
formed on the opposite side of the base plate
44
a
from the volute portion
44
b.
The volute portion
44
b
cooperates with a volute portion
45
b
of a fixed scroll
45
, which forms a compression chamber
47
between the scrolls
44
,
45
. The eccentric shaft
41
is inserted in the boss
43
and supports the movable scroll
44
through the boss
43
. Accordingly, the eccentric shaft
41
supports the movable scroll
44
at a position outside of a working region R, which includes the volute portion
44
b.
In other words, the movable scroll
44
is supported at a position that is axially spaced from the compression chamber
47
.
Centrifugal force is applied to the movable scroll
44
when it revolves. Also, compression reaction force generated by compressing gas in the compression chamber
47
is applied to the movable scroll
44
. A resultant radial working force K, which combines the centrifugal force and the compression reaction force, is especially high in the working region R. However, the eccentric shaft
41
supports the movable scroll
44
at a position axially spaced from the region R. For this reason, the working force K applies an inclination moment to the movable scroll
44
with the supporting position of the eccentric shaft
41
at the center. For example, when there is a measurement error between the eccentric shaft
41
and the boss or between the volute portions
44
b,
45
b,
the inclination moment inclines the movable scroll
44
with respect to the fixed scroll
45
. Thus parts of the movable scroll
44
apply concentrated, localized forces to the fixed scroll
45
. As a result, the smooth orbital movement of the movable scroll
44
is interrupted and the sealing of the compression chamber
47
between the scrolls
44
,
45
deteriorates, thus causing rattling and gas leakage from the compression chamber
47
.
To solve this problem, Japanese Examined Publication No. 63-59032 reveals the construction shown in
FIG. 7. A
movable scroll
44
has a boss
43
projecting on both sides of a base plate
44
a
. An eccentric shaft
41
, which passes through the boss
43
, is provided in the middle of a drive shaft
42
. Accordingly, the eccentric shaft
41
supports the movable shaft
44
in a working region R, which includes the volute portion
44
b.
The drive shaft
42
has a first portion
42
a
and a second portion
42
b,
which are at opposite ends of the eccentric shaft
41
. The first portion
42
a
is supported by bearings
46
and a compressor housing
48
. The second portion
42
b
is supported by bearings
46
and a fixed scroll
45
. Accordingly, the drive shaft
42
supports the movable scroll
44
at both sides of the working region R, or both sides of the compression chamber.
When a radial working force K based on centrifugal force and compression reaction force is applied to the movable scroll
44
, the force K is received by the portions
42
a,
42
b
of the drive shaft
42
, which are located at both ends of the eccentric shaft
41
. As a result, there is no inclination moment applied to the movable scroll
44
, and the movable scroll
44
does not incline with respect to the fixed scroll
45
.
To achieve smooth rotation of the drive shaft
42
, the axes of the portions
42
a,
42
b
of the drive shaft
42
must be precisely aligned and the axes of the bearings
46
must be precisely aligned. However, this increases the cost of production.
To insert the eccentric shaft
41
, which is in the middle of the drive shaft
42
, in the boss
43
, at least one of the portions
42
a,
42
b
of the drive shaft
42
must be separate from the eccentric shaft
41
. After the eccentric shaft
41
is inserted in the boss
43
, the separate part is fixed to the eccentric shaft
41
. However, in this procedure, the number of parts and steps increase and the assembly work is difficult, thus increasing the manufacturing costs.
SUMMARY OF THE INVENTION
The present invention is designed to solve the above problems. The objective of the present invention is to provide scroll-type fluid mover that prevents the movable scroll from inclining with respect to the fixed scroll and that is easily machined due to a simple construction.
To achieve the above objective, the scroll-type fluid mover according to the present invention includes a fixed scroll, which includes a base plate and a volute portion extending from the base plate, and a movable scroll, which includes a base plate and a volute portion extending from the base plate. The two volute portions cooperate to form a variable displacement fluid pocket between the two scrolls. A drive shaft is driven to rotate about its axis. An eccentric shaft is connected to the drive shaft. The axis of the eccentric shaft is offset from the axis of the drive shaft. The eccentric shaft has a proximal end and a distal end. The proximal end is fixed to the drive shaft and the distal end is radially unsupported. The eccentric shaft rotatably supports the movable scroll so that the movable scroll orbits the axis of the drive shaft without rotating about its own axis when the drive shaft rotates. Gas is introduced into and compressed in the fluid pocket in accordance with the orbital movement of the movable scroll. The eccentric shaft extends axially such that at least a part of the eccentric shaft is located in a location that is radially aligned with the volute portion of the movable scroll, whereby the eccentric shaft supports the movable scroll to prevent inclination of the movable scroll with respect to the fixed scroll.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.
REFERENCES:
patent: 4466784 (1984-08-01), Hiraga
patent: 5098265 (1992-03-01), Machida et al.
patent: 5336068 (1994-08-01), Sekiya et al.
patent: 63-59032 (1988-11-01), None
patent: 1-106988 (1989-04-01), None
patent: 2-277988 (1990-11-01), None
patent: 2-277985 (1990-11-01), None
patent: WO 96/20345 (1996-07-01), None
Goto Kunifumi
Hoshino Nobuaki
Uetsuji Kiyoshi
Kabushiki Kaisha Toyoda Jidoshokki Seisakusho
Morgan & Finnegan L.L.P.
Vrablik John J.
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