Rotary expansible chamber devices – Working member has planetary or planetating movement – Helical working member – e.g. – scroll
Reexamination Certificate
1999-11-04
2001-03-06
Denion, Thomas (Department: 3748)
Rotary expansible chamber devices
Working member has planetary or planetating movement
Helical working member, e.g., scroll
C418S270000, C137S856000
Reexamination Certificate
active
06196815
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a reciprocating-type fluid apparatus and, in particular, to a scroll-type fluid apparatus, such as a scroll compressor, for use in an air conditioner for a railroad car, an automobile, a house, and the like.
Referring to
FIG. 1
, an existing scroll compressor will be described. In the manner which will presently be described, the scroll compressor comprises a drive shaft or a crank shaft
1
, a counterweight
2
, an eccentric bush
3
, a movable scroll member
4
, and a fixed scroll member
5
. The crank shaft
1
has an enlarged spindle portion
10
with a crank pin
110
eccentrically coupled thereto. The rotation of the crank shaft
1
on its own axis
99
(depicted by a dash-and-dot line in
FIG. 1
) causes the revolution of the crank pin
110
around the axis
99
of the crank shaft
1
. The crank pin
110
is fitted into a crank pin receptacle
30
formed in the eccentric bush
3
. The revolution of the crank pin
110
provides the revolution of the eccentric bush
3
.
The movable scroll member
4
has a side plate
41
, a spiral or involute lap
40
formed on one side of the side plate
41
, and an annular boss
42
formed on the other side. The spiral or involute lap
40
will be called hereinafter a spiral element. The eccentric bush
3
is coupled to the boss
42
via a needle bearing
230
to be smoothly rotatable in the boss
42
.
With the above-mentioned structure, the eccentric bush
3
and the movable scroll member
4
coupled thereto perform the revolution with respect to the crank shaft
1
.
In order to suppress the rotation of the movable scroll member
4
, a rotation inhibiting mechanism
210
is provided. The rotation inhibiting mechanism
210
comprises a pair of annular races
211
and a ball
212
. By the rotation inhibiting mechanism
210
, the movable scroll member
4
is allowed to perform the revolution alone.
Referring to
FIG. 2
together with
FIG. 1
, the movable scroll member
4
has the spiral element
40
as described above. Likewise, the fixed scroll member
5
is provided a spiral element
50
having a shape similar to that of the spiral element
40
. The movable scroll member
4
and the fixed scroll member
5
are arranged to be eccentric with each other by a predetermined distance with the spiral elements
40
and
50
shifted from each other by an angle of 180°. With this structure, a plurality of closed spaces G are defined between the spiral elements
40
and
50
as illustrated in FIG.
2
. An inner one and an outer one of the closed spaces G are smaller and greater in volume, respectively.
Therefore, a fluid sucked into the closed spaces G through a suction port (not shown) is transferred radially inward to be gradually compressed into a compressed fluid. Finally, the compressed fluid is led to a discharge port
6
. The discharge port
6
is connected to a discharge chamber
8
through a discharge valve
7
. The discharge chamber
8
is kept at a high pressure and the discharge valve
7
is normally closed under the high pressure in the discharge chamber
8
. When the compressed fluid reaches the discharge port
6
, the discharge valve
7
is opened under an increased pressure in the discharge port
6
so that the compressed fluid is discharged into the discharge chamber
8
.
Thus, a series of operations mentioned above are carried out when the fluid is compressed by the scroll compressor. The components mentioned above are sealed in a casing
9
and a front housing
100
to be protected. A combination of the movable and the fixed scroll members
4
and
5
is referred to as a scroll-type transferring mechanism.
As illustrated in
FIG. 1
, the discharge valve
7
is attached to a base end wall
501
of the fixed scroll member
5
together with a retainer
80
by the use of a bolt
801
screwed into the base end wall
501
through the fixing hole
70
.
Referring to
FIGS. 3A through 3D
, the structure of the discharge valve
7
will be described.
In
FIG. 3A
, the discharge valve
7
has a fixed portion
7
a
supported on the fixed scroll
5
and having a fixing hole
70
, a closing portion
7
b
closing the discharge port
6
, and a bridging portion
7
c
connecting the fixed portion
7
a
and the closing portion
7
b
. An outer contour of the discharge valve
7
is defined by a first arc
700
a
of the fixed portion
7
a
, a second arc
700
b
of the closing portion
7
b
, and a pair of straight lines
700
c
of the bridging portion
7
c
. The discharge valve
7
is a flap valve comprising an elastic plate. More particularly, the discharge valve
7
has a cantilevered structure having the fixed portion
7
a
fixedly supported on the fixed scroll member
5
and the closing portion
7
b
brought into contact with a peripheral edge of the discharge port
6
to close the discharge port
6
.
The first arc
700
a
of the fixed portion
74
extends along a circle of a first diameter while the second arc
700
b
of the closing portion
7
b
extends along a circle of a second diameter. In the discharge valve
7
of
FIG. 3A
, the second diameter is determined greater than the first diameter. It will be understood that a diameter of the discharge port
6
is smaller than the second diameter. With this structure, the bridging portion
7
c
is widened from the fixed portion
7
a
towards the closing portion
7
b
. Contrary to the above-mentioned uniform strength beam, the bending stress is increased from the closing portion
7
b
towards the fixed portion
7
a
so that the discharge valve
7
is difficult to deflect. In addition, the stress is smaller towards the closing portion
7
b
, resulting in inefficiency.
The fixed portion
7
a
connected to a narrowest part of the bridging portion
7
c
may be subjected to stress concentration when the load is applied from the compressed fluid in the discharge port
6
. Therefore, the life of the discharge valve
7
is inevitably shortened.
In
FIG. 3B
, the second diameter is determined smaller than the first diameter. With this structure, the bridging portion
7
c
connecting the fixed portion
7
a
and the closing portion
7
b
is gradually narrowed towards the closing portion
7
b
. However, the first arc
700
a
of the fixed portion
7
a
and the second arc
700
b
of the closing portion
7
b
are simply connected by the straight lines
700
c
of the bridging portion
7
c
. The diameter of the discharge port
6
must be smaller than the second diameter that is smaller than the first diameter.
In
FIG. 3C
, the second diameter is determined equal to the first diameter. In this case also, the valve-opening force is greater than that of the uniform strength beam mentioned above.
In
FIG. 3D
, the second diameter is determined greater than the first diameter, like in FIG.
3
A. The first arc
700
a
of the fixed portion
7
a
and the second arc
700
b
of the closing portion
7
b
are connected by the parallel straight lines
700
c
of the bridging portion
7
c
. Even in this case, the valve-opening force is greater than that of the uniform strength beam mentioned above, like the structure illustrated in FIG.
3
C. In addition, stress concentration may possibly occur at a portion depicted by a broken line in
FIG. 3D
between the first arc
700
a
and the straight lines
700
c.
In each of the discharge valves of
FIGS. 3A through 3D
, the first arc
700
a
of the fixed portion
7
a
and the second arc
700
b
of the closing portion
7
b
are simply connected to each other by the straight lines
700
c
of the bridging portion
7
c.
Referring to
FIGS. 4A and 4B
, description will be made about the technical background to discuss the rigidity problem.
At first, consideration will be made about a cantilevered beam comprising a rectangular plate illustrated in FIG.
4
A. The rectangular plate will hereinafter be called a parallel beam.
The parallel beam has a rectangular section. The parallel beam has one end as a fixed end supported on a wall and the other end as a free end. The free end is subjected to a concentrated load.
The deflection y and the
Baker & Botts L.L.P.
Denion Thomas
Sanden Corporation
Trieu Theresa
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