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Suction structure in piston type compressor

Suction structure in piston type compressor description/claims

The present invention relates to a suction structure for allowing refrigerant from a suction pressure region in a piston type compressor. More specifically, the compressor has a rotary valve that is integrally rotated with a rotary shaft and that has a supply passage for introducing refrigerant from the suction pressure region into a compression chamber defined in a cylinder bore by a piston.

In piston type compressors, there are two types of suction valves. One is a rotary valve as disclosed in Unexamined Japanese Patent Publications No. 7-119631 and No. 2006-083835. The other is a reed type suction valve as disclosed in Unexamined Japanese Patent Publications No. 64-088064 and No. 2000-145629. The piston type compressors including the rotary valves has lower suction resistance in introducing refrigerant into cylinder bores, and has superior energy efficiency, compared to the piston type compressors including the reed type suction valves.

At the start of a conventional compressor disclosed in the above reference No. 7-119631, torque is rapidly increased in accordance with the compression of refrigerant gas, and is applied as a load to a vehicle engine (internal combustion). Thereby the vehicle speed is temporarily decreased at the start of the compressor, and the passengers of the vehicle feel start-up shock.

In the piston type compressor disclosed in the above reference No. 7-119631, the rotary valve is provided so as to be axially movable in the direction of the axis of the rotary shaft. The position of the rotary valve is displaced in accordance with the pressure supplied to a control pressure chamber. A bypass groove is formed in the rotary valve so as to communicate almost all the cylinder bores to a suction port formed at the center of a cylinder block. The rotary valve is located at a position in the axial direction of the rotary shaft in such a manner that almost all the cylinder bores are communicable with the suction port through the bypass groove at the stop and at the start of the compressor. Therefore, even when the piston performs compression of the refrigerant gas in the cylinder bore at the start of the compressor, the refrigerant gas in the cylinder bore is returned to the suction port through the bypass groove. The shock at the start of the compressor does not occur, accordingly.

In order to prevent leakage of the refrigerant gas along the periphery of the rotary valve, and also to allow the rotary valve to rotate, it is required that clearance around the periphery of the rotary valve is set as small as possible. However, with the structure in which the rotary valve is movable in the axial direction of the rotary shaft, the rotary valve needs clearance to allow the rotary valve to be movable in the axial direction of the rotary shaft. It is hard to set such clearance appropriately.

A compressor disclosed in Unexamined Japanese Patent Publication No. 2000-145629 includes a pressure differential detecting valve which is opened and closed in accordance with the pressure differential between discharge pressure and suction pressure. The pressure differential detecting valve is located between a low-pressure refrigerant passage for introducing refrigerant from the outside of the compressor and a suction chamber in the compressor. When the compressor is started in a state where the pressure in the compressor is balanced, the pressure differential detecting valve is closed, and the flow of the refrigerant from the outside of the compressor into the suction chamber is stopped. Thereby the shock at the start of the compressor is suppressed.

However, in the compressor disclosed in the reference No. 2000-145629, the refrigerant is remained in the suction chamber even when the pressure differential detecting valve is closed. The residual refrigerant is introduced into the cylinder bore and compressed therein. The volume of the suction chamber is set large so as to suppress the suction pulsation. Thereby large amount of refrigerant is introduced into the cylinder bore in a state where the pressure differential detecting valve is closed, and the effect in suppressing the shock at the start of the compressor is not sufficiently obtained.

The present invention is directed to increase the effect in suppressing the shock at the start of the compressor.

In accordance with the present invention, a suction structure is provided for allowing refrigerant from a suction pressure region in a piston type compressor. The compressor has cylinder bores arranged around a rotary shaft for accommodating a respective piston. A cam body is formed with the rotary shaft. The piston is engaged with the cam body so that rotation of the rotary shaft is transmitted to the piston. A compression chamber is defined by the piston in the respective cylinder bore. A rotary valve has a supply passage for introducing the refrigerant from the suction pressure region to the compression chamber. The rotary valve is rotated integrally with the rotary shaft. The suction structure includes a shifting device. The shifting device shifts between a connecting state and a disconnecting state. In the connecting state the outlet of the supply passage is connected to the suction pressure region and in the disconnecting state the outlet of the supply passage is disconnected from the suction pressure region. The shifting device includes a valve body, a return spring, and a permanent magnet. The valve body is movable between a connecting position and a disconnecting position. The connecting position corresponds to the connecting state and the disconnecting position corresponds to the disconnecting state. The return spring urges the valve body from the connecting position toward the disconnecting position. The permanent magnet attracts the valve body by magnetic force from the connecting position toward the disconnecting position.

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.

The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. The invention together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:

FIG. 1 is a longitudinal cross-sectional view of a compressor according to a first preferred embodiment of the present invention;

FIG. 2A is a cross-sectional view which is taken along the line I-I in FIG. 1;

FIG. 2B is a cross-sectional view which is taken along the line II-II in FIG. 1;

FIG. 3 is a partially enlarged cross-sectional view illustrating the suction structure of the compressor in a disconnecting state according to the first preferred embodiment of the present invention;

FIG. 4 is a partially enlarged cross-sectional view illustrating the suction structure of the compressor in a connecting state according to the first preferred embodiment of the present invention;

FIG. 5A is a graph showing torque fluctuation of the compressor having a permanent magnet according to the first preferred embodiment of the present invention;

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