Pumps – With condition responsive pumped fluid control – Pressure responsive relief or bypass valve
Reexamination Certificate
1999-06-29
2001-05-15
Thorpe, Timothy S. (Department: 3746)
Pumps
With condition responsive pumped fluid control
Pressure responsive relief or bypass valve
Reexamination Certificate
active
06231316
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a scroll-type variable-capacity compressor suitably used as a refrigerant compressor for an automotive air-conditioning system, for example.
2. Description of the Related Art
A conventional scroll-type compressor is known in which a fixed scroll engages a movable scroll and the refrigerant is compressed in a pair of compression chambers formed between the fixed scroll and the movable scroll. Another compressor of this type is known which further comprises a bypass port operated for changing the capacity. In a scroll-type compressor disclosed in Japanese Unexamined Patent Publication (Kokai) No. 9-296787, for example, a bypass port is opened or closed when a pair of compression chambers are located at an equivalent position under a state of a changing capacity.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a scroll-type compressor with the capacity thereof changed by opening or closing bypass ports communicating with a pair of compression chambers, wherein the bypass ports are selectively located at an optimum open position. Specifically, the Japanese Unexamined Patent Publication (Kokai) No. 9-296787 quoted above describes only that a pair of bypass ports are located at an equivalent position but fails to disclose the position where the bypass ports are closed at the same time that the pair of the compression chambers reach a predetermined capacity. The bypass ports illustrated in the same patent publication appear to open to the neighborhood of the spiral wall of a fixed scroll. In actual operation, therefore, a pair of the bypass ports communicating with a pair of the compression chambers are not in such relative positions as to open or close at the same time.
The present invention has been developed by the present inventors based on a unique study, as described later, and provides a scroll-type variable-capacity compressor in which a pair of bypass ports open to a pair of compression chambers respectively are opened or closed by moving a single valve spool thereby to change the capacity, or especially the bypass ports are open to a specific position.
More specifically, a first bypass port is arranged in the inner surface of the spiral wall of a fixed scroll in the neighborhood of a contact point (X) between the inner surface of the spiral wall of the fixed scroll and the outer surface of the spiral wall of the movable scroll constituting compression chambers in the state where the capacity is to be controlled, i.e. in the state where the volume of the compression chambers is reduced to a predetermined level.
A second bypass port is opened to the side of the discharge port far from the first bypass port in such a position that the discharge port is not located on the line connecting the second bypass port and the first bypass port. The opening of the second bypass port is of course located at a position adapted to be closed by the spiral wall of the movable scroll defining the compression chambers reaching the predetermined capacity described above.
According to a second aspect of the invention, the second bypass port is formed at an angular position leading the contact point (Y) between the outer surface of the spiral wall of the fixed scroll and the inner surface of the spiral wall of the movable scroll.
According to a third aspect of the invention, in contrast, the second bypass port is formed at an angular position retarded from the contact point (Y).
According to a fourth aspect of the invention, the first bypass port and the second bypass port are closed substantially at the same time by the spiral wall of the movable scroll so that the two compression chambers have substantially the same compression ratio.
According to a fifth aspect of the invention, the first bypass port and the second bypass port has a timing, slightly displaced from each other, when the conduction of the first bypass port and the second bypass port with the compression chamber is blocked by the movable scroll, with the result that the compression ratios of the two compression chambers are slightly different from each other.
According to a sixth aspect of the invention, a third bypass port is formed which conducts only in the initial stage of starting compression of the compression chambers. This configuration is useful when the second bypass port is arranged at an angular position leading the contact point (Y) as in the second aspect of the invention.
According to a seventh aspect of the invention, the third bypass port has a smaller opening area than the first and second bypass ports.
According to an eighth aspect of the invention, the bypass ports are formed as round holes to facilitate the machining.
According to a ninth aspect of the invention, a plurality of bypass ports are formed, thereby increasing the opening area of the bypass ports as a whole and thus facilitating the outflow of the refrigerant from the compression chamber to the bypass ports.
According to a tenth aspect of the invention, the bypass ports are arcuate in shape extending along the involute curve of the spiral wall of the movable scroll, thereby increasing the opening area of the bypass ports and facilitating the outflow of the refrigerant.
According to an 11th aspect of the invention, the diameter of the bypass ports is not larger than the thickness of the spiral wall of the movable scroll, thereby permitting the bypass ports to be blocked positively by the spiral wall of the movable scroll.
According to 12th and subsequent aspects of the invention, the position and shape of the bypasses and the spool for opening and closing the bypass ports are specifically defined. Especially in a 13th aspect of the invention, the bypass has a larger sectional area than the bypass ports, thereby having a buffer effect on the refrigerant flow and preventing pressure pulsations.
REFERENCES:
patent: 5451146 (1995-09-01), Inagaki et al.
patent: 5885063 (1999-03-01), Makino et al.
patent: 9-296787 (1997-11-01), None
Iwanami Shigeki
Uno Keiichi
Wakisaka Takeshi
Denso Corporation
Pillsbury & Winthrop LLP
Rodriguez W.
Thorpe Timothy S.
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