Rotary expansible chamber devices – Working member has planetary or planetating movement – Helical working member – e.g. – scroll
Reexamination Certificate
2001-07-20
2003-03-18
Denion, Thomas (Department: 3748)
Rotary expansible chamber devices
Working member has planetary or planetating movement
Helical working member, e.g., scroll
C418S057000, C418S056000, C418S055400
Reexamination Certificate
active
06533561
ABSTRACT:
TECHNICAL FIELD
This invention relates to a scroll type compressor, and particularly relates to measures against reduction of its operating efficiency.
BACKGROUND ART
As compressors for compressing refrigerant in a refrigeration cycle, there have been conventionally used scroll type compressors disclosed for example in Japanese Unexamined Patent Publication No. 5-312156. The scroll type compressor is provided in its casing with a fixed scroll and a movable scroll which have respective volute laps meshed with each other. The fixed scroll is fixed to the casing, and the movable scroll is coupled to an offset shaft portion of a drive shaft. Further, the scroll type compressor is arranged so that the movable scroll does not rotates on the axis of the fixed scroll but travels bodily around the fixed scroll to contract a compression space defined between both the laps thereby compressing refrigerant.
Meanwhile, as shown in
FIG. 14
, compressing the refrigerant causes the movable scroll (OS) to experience a thrust load PS as an axial force and a radial load PT as a lateral force. Therefore, in an arrangement wherein a high-pressure section (P) is provided for making a high refrigerant pressure PA act on the back face (bottom face) of the movable scroll (OS) to press the movable scroll (OS) against the fixed scroll (FS) with a force counteracting the axial force PS, if the pressing force is small and a vector as the resultant of forces acting on the movable scroll (OS) passes outside of the outer periphery of a thrust bearing, the movable scroll (OS) will be inclined (upset) as being shown in
FIG. 15
by the action of so-called upsetting moment M. This induces leakage of the refrigerant, resulting in decreased efficiency. On the other hand, in the arrangement wherein the movable scroll (OS) is pressed against the fixed scroll (FS) with the force counteracting the axial force PS as shown in
FIG. 14
, if the pressing force is contrariwise large (and a vector as the resultant of forces acting on the movable scroll (OS) passes inside of the outer periphery of the thrust bearing), it will be possible to prevent the movable scroll (OS) from upsetting.
In the meantime, the scroll type compressor has a constant volume ratio. Therefore, as shown in
FIG. 16
, even if the operating conditions change so that a high pressure or a low pressure varies to change the compression ratio, the axial force PS and the lateral force PT do not largely change. In contrast, the pressing force from the above-mentioned refrigerant pressure (referred to as a back pressure in the figure) on the back face of the movable scroll (OS) changes to a large extent with the change in the compression ratio.
Here, if the area of the high-pressure section (P) which makes a high pressure act on the movable scroll (OS) is set so as not to upset the movable scroll (OS) under conditions of high compression ratios as shown in
FIG. 17A
, the movable scroll (OS) will be easily upset under conditions of low compression ratios because of lack of the pressing force, for example, due to a reduced high pressure.
On the other hand, if the area of the high-pressure section (P) is set in conformity with the conditions of low compression ratios, a high compression ratio induced for example by an increase in the high pressure will cause the pressing force of the movable scroll (OS) against the fixed scroll (FS) to be excessive relative to a minimum pressing force determined by the axial force PS and the lateral force PT as shown in FIG.
17
B. As a result, a significant thrust force upward when viewed in
FIG. 14
acts on the movable scroll (OS) so that mechanical loss will be increased to reduce the efficiency.
The above is substantially the case for the variation in the low pressure (which usually varies together with the high pressure). Accordingly, generally speaking, in scroll compressors of the type which uses a refrigerant pressure or the like to press the movable scroll (OS) against the fixed scroll (FS), upset of the movable scroll tends to easily occur at lower compression ratios with reference to a compression ratio substantially specific for each compressor while the pressing force tends to easily become excessive at higher compression ratios.
The present invention has been devised in view of such problems, and an object thereof is to prevent decrease in efficiency by controlling the pressing force of the movable scroll against the fixed scroll.
DISCLOSURE OF INVENTION
The present invention provides for controlling a pressing force of a movable scroll (
22
) against a fixed scroll (
21
) depending upon operating conditions in a manner to change the pressing force in accordance with the variation in the compression ratio.
Specifically, a solution taken in the present invention is predicated upon a scroll type compressor including: a fixed scroll (
21
) fixed inside of a casing (
10
); a movable scroll (
22
) meshed with the fixed scroll (
21
); and pressing means (
40
) for pressing the movable scroll (
22
) against the fixed scroll (
21
). Further, the pressing means (
40
) is arranged to control a pressing force of the movable scroll (
22
) against the fixed scroll (
21
) in accordance with variation in compression ratio. Thus, the pressing force can be suppressed at high compression ratios while the suppression can be relieved at low compression ratios, thereby providing control of the pressing force depending upon operating conditions. It is to be noted that the manner to control the pressing force in accordance with the variation in the compression ratio can include using, for example, a pressure differential between high and low pressures or the high pressure (a discharge pressure).
In the above construction, for example, the pressing means (
40
) can be arranged to have a high-pressure space (S
2
) that serves a back face side of the movable scroll (
22
) and to suppress the pressing force of the movable scroll (
22
) against the fixed scroll (
21
) when the compression ratio exceeds a predetermined value (i.e., when the movable scroll (
22
) comes into a condition to be pressed with a sufficient force against the fixed scroll (
21
)). It is to be noted that, in this case, as the working condition that “the compression ratio exceeds a predetermined value”, use can be made of approximate conditions such as whether the pressure differential between high and low pressures has reached a preset given value (this is also the case for the following respective arrangements).
Further, in the above arrangement, the pressing means (
40
) can have a structure that includes an oil groove (
43
) formed between contact surfaces of the fixed scroll (
21
) and the movable scroll (
22
) in contact with each other and high-pressure oil introducing means (
46
) for introducing a high-pressure oil into the oil groove (
43
) when the compression ratio exceeds the predetermined value.
Furthermore, in the above arrangement, the highpressure space (S
2
) is preferably a high-pressure oil working space into which the high-pressure oil is supplied, and the high-pressure oil introducing means (
46
) is preferably arranged to guide the high-pressure oil in the high-pressure oil working space (S
2
) into the oil groove (
43
) when the compression ratio exceeds the predetermined value.
Moreover, in the above arrangement, the high-pressure oil introducing means (
46
) preferably has a structure that includes a high-pressure oil introduction passage (
44
) communicating from the high-pressure oil working space (S
2
) to the oil groove (
43
) and a high-pressure oil introduction valve (
45
) for opening/closing the high-pressure oil introduction passage (
44
).
Further, in the above arrangement, the high-pressure oil introduction valve (
45
) is preferably arranged to open the high-pressure oil introduction passage (
44
) upon excess of the compression ratio over the predetermined value while closing the high-pressure oil introduction passage (
44
) at the compression ratio equal to or less than the predetermined value.
Furthermore, in the above arrange
Furusho Kazuhiro
Higuchi Masahide
Kato Katsumi
Kitaura Hiroshi
Komori Keiji
Daikin Industries Ltd.
Denion Thomas
Studebaker Donald R.
Trieu Theresa
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