Scroll compressor

Details Scroll compressor Scroll compressor

2002-02-20

2004-06-08

Denion, Thomas (Department: 3748)

Rotary expansible chamber devices

Working member has planetary or planetating movement

Helical working member, e.g., scroll

C418S055500, C418S057000

Reexamination Certificate

active

06746224

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a scroll compressor furnished in an air conditioner, a refrigerator, or the like.
BACKGROUND ART
A scroll compressor is one where a fixed scroll and an orbiting scroll are arranged as a pair of spiral walls assembled together, and the orbiting scroll is orbitally rotated with respect to the fixed scroll in order to gradually reduce the volume of a compression chamber formed between the walls and thereby compress the fluid inside the compression chamber.
The compression ratio in the design of the scroll compressor is a ratio of the maximum capacity of the compression chamber (the capacity at a point in time where the wall pairs are combined to form the compression chamber) to the minimum capacity of the compression chamber (the capacity immediately before the wall pairs become disengaged and the compression chamber disappears), and is expressed by the following equation (I):
Vi={A
(&thgr;
suc
)·
L}/{A
(&thgr;top)·
L}=A
(&thgr;
suc
)/
A
(&thgr;top)   (
I)
In equation (I), A(&thgr;) is a function representing the cross-sectional area parallel to the orbit plane of the compression chamber for which the volume is changed corresponding to the orbiting angle &thgr; of the orbiting scroll, &thgr;suc is the orbit angle of the orbiting scroll for when the compression chamber becomes a maximum volume, &thgr;top is the orbit angle of the orbiting scroll for when the compression chamber becomes a minimum volume, and L is the length of the lap (overlap) of the wall pairs.
Conventionally, in order to improve the compression ratio Vi of a scroll compressor, a method was adopted of increasing the winding number for the walls of the two scrolls so that the cross-section area A(&thgr;) of the compression chamber at the time of maximum volume was increased. However, with this conventional method of increasing the winding number of the walls, the external shape of the scroll is increased so that the compressor itself is increased in size. Hence there is a problem in that it is difficult to employ this in an air conditioner such as for an automobile where restrictions on size are severe.
In order to solve the above problems, in Japanese Examined Patent Application, Second Publication, No. 60-17956, there is proposed a scroll compressor where spiral shape upper rims of the walls of both the fixed scroll and the orbiting scroll are made of a stepped shape with the central side low and the outer peripheral end side high, and corresponding to the stepped shape of these upper rims, the side faces of end plates of the two scrolls are both are formed stepped with the central side high and the outer peripheral end side low.
The device shown in
FIG. 41A
is a fixed scroll
150
, and comprises an end plate
150
a
and a wall
150
b
of a spiral shape upstanding on one side face of the end plate
150
a
. Furthermore, the device shown in
FIG. 41B
is an orbiting scroll
151
. The orbiting scroll
151
also comprises an end plate
151
a
and a spiral wall
151
b
upstanding on one side face of the end plate
151
a,
similar to that of the fixed scroll
150
.
On the side faces of the end plates
150
a
and
151
a
of the fixed scroll
150
and the orbiting scroll
151
, there is formed steps
152
at a position &pgr; radians (rad) from the outer peripheral end of the spirals of the walls
150
b
and
151
b,
and these steps have their central sides high and their outer peripheral end sides low. Furthermore, corresponding to the steps
152
of the end plates
150
a
and
151
a,
there are formed steps
153
on the spiral shape upper rims of the walls
150
b
and
151
b
furnished on the two scrolls
150
and
151
, with their central sides low and the outer peripheral end sides high.
In the scroll compressor as described above, the condition where the respective walls
150
b
and
151
b
of the fixed scroll
150
and the orbiting scroll
151
are engaged, and a compression chamber P of maximum capacity is formed, is shown in
FIG. 42A
, and a cross-section along the spiral direction of the compression chamber P, is shown in FIG.
42
B. The leftward direction of
FIG. 42B
is the spiral central side.
As will be understood from
FIG. 42B
, a lap length L
1
on the outer peripheral end side from the step
152
is formed longer than a lap length Ls for the inside. Therefore, compared to the case where the lap lengths are the same, it can be seen that the maximum volume of the compression chamber P becomes larger by the amount that the lap length outside from the step
52
is longer. Consequently, it is possible to improve the design compression ratio even if the winding number of the walls is not increased.
As described above, since the lap length of the compression chamber at the time of maximum capacity is L
1
and the lap length of the compression chamber at the time of minimum capacity is Ls, then a design compression ratio Vi′ can be expressed by the following equation (II).
Vi′={A
(&thgr;
suc
)·
L
1
}/{
A
(&thgr;top)·
Ls}
  (II)
In equation (II), the lap length L
1
of the compression chamber at the time of maximum capacity is larger than the lap length of the compression chamber at the time of minimum capacity so that L
1
/Ls>1 results. Therefore, it is possible to increase the design compression ratio even if the winding number for the walls is not increased.
Furthermore, Japanese Unexamined Patent Application, First Publication, No. 4-311693 discloses a structure which adopts a stepped shape for the scroll, and there is provided a tip seal on an outer peripheral lap tip, with the, purpose of reducing leakage at the outer peripheral side.
Incidentally, in general in a scroll compressor, since the compression chamber P becomes a higher pressure at the central portion of the scroll, the temperature is higher compared to at the outer peripheral portion. Therefore, the thermal expansion amount for the wall becomes larger at the central portion, so that geometric distortion occurs in the engagement between the fixed scroll
150
and the orbiting scroll
151
, with the problem of likelihood in an increase in leakage and a reduction in reliability.
Furthermore, in the conventional scroll compressor, the steps
152
formed on the side faces of the end plates
150
a
and
151
a
of the scrolls
150
and
151
are positioned at &pgr; (rad) from the outer peripheral end of the spiral. Therefore, as will be understood from
FIG. 42B
, the lap length Ls from the step
152
towards the central portion is shorter than the lap length L
1
for the outer peripheral end side, so that even at the time of maximum volume, a sufficiently large volume cannot be obtained.
Moreover, as shown in the cross-sectional view of
FIG. 43
, the construction is such that a discharge port
154
passing through the end plate
150
a
is formed in the central portion of the fixed scroll
150
for discharging high pressure fluid inside the compression chamber P. However, since the volume inside this discharge port
154
is comparatively large, there is a problem in that the fluid cannot be discharged smoothly, making it difficult to improve the operating efficiency.
As described above, in relation to where the step
152
is formed on the side face of the end plate
150
a
of the fixed scroll
150
, then for the central portion of the end plate
150
a
, the thickness becomes comparatively thicker than for the outer peripheral portion bounded by the step
152
. Therefore, the length of the discharge port
154
becomes longer, and consequently the volume inside the discharge port
154
becomes comparatively large.
The fluid flowing from the compression chamber P to inside the discharge port
154
causes elastic deformation at a rectangular flat plate discharge valve
155
, so that the discharge port
154
is opened, and due to the opening, the fluid flows out towards a discharge cavity (not shown in the figure). However, since the volume of the discharge cavity is large, up until the discharge valv

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