The present invention relates to a swash plate type compressor that has single headed pistons and is used in an air conditioner of a vehicle, and more particularly, to improvement of a radial bearing that supports a drive shaft for reciprocating the pistons and to improvement of a lubricating structure of a shaft sealing assembly.
As shown in FIG. 6, the housing of a typical swash plate type compressor includes a front housing member 71, a cylinder block 72 and a rear housing member 73, which are secured to one another. A drive shaft 74 has a first end and a second end. The drive shaft 74 is supported by the housing through a first and second radial bearings 75, 76 such that the first end protrudes from the front housing member 71. A shaft sealing assembly 78 is located about the drive shaft 74 at a position between the first end and the first radial bearing 75. The sealing assembly 78 prevents refrigerant gas from leaking from a crank chamber 77 to the atmosphere.
Moving parts of a compressor such as bearings are lubricated by misted lubricant contained in refrigerant gas. Therefore, parts where refrigerant gas is stagnant are not effectively lubricated. A compressor that uses carbon dioxide (CO2) for a cooling circuit instead of chlorofluorocarbon has been introduced. When using CO2 as refrigerant, the refrigerant pressure is more than ten times that of a case where chlorofluorocarbon is used as refrigerant, which increases the load acting on bearings and shaft sealing assemblies. Accordingly, lubrication must be improved.
In the compressor of Japanese Unexamined Patent Publication No. 11-241681, the shaft sealing assembly 78 is located in an isolated chamber 80, which is forward of the first radial bearing 75. A decompression passage 79 is formed in the drive shaft 74. An outlet 79b of the decompression passage 79 opens to the end face of the second end of the drive shaft 74. A fan 81 is attached to the second end of the drive shaft 74. When the fan 81 rotates integrally with the drive shaft 74, refrigerant in the decompression passage 79 is drawn to the outlet 79b. The refrigerant then flows to the crank chamber 77 through the radial bearing 76.
The isolated chamber 80 is connected to the crank chamber 77 through the space in the radial bearing 75 and the space in a thrust bearing 82. The spaces in the radial bearing 75 and the thrust bearing 82 function as oil supplying passages.
Japanese Unexamined Patent Publication No. 8-165987 discloses a compressor shown in FIG. 7. In this compressor, a second end of the drive shaft 74 faces a chamber 84 that communicates with a suction chamber 83. An axial passage 85 is formed in the drive shaft 74. The inlet 85a of the passage 85 opens to an isolated chamber 80. The outlet 85b of the passage 85 opens to the chamber 84.
In the compressor of FIG. 6, the fan 81 attached to the drive shaft 74 draws some of refrigerant gas into the decompression passage 79 through the first radial bearing 75 or through the thrust bearing 82. The drawn refrigerant gas then returns to the crank chamber 77 through the second radial bearing 76. Accordingly, the radial bearings 75, 76 and the shaft sealing assembly 78 are reliably lubricated. However, to flow lubricant through the decompression passage 79, the fan 81 is required, which complicates the structure.
Instead of a fan, the chamber 84 is located adjacent to the second end of the drive shaft 74 of the compressor shown in FIG. 7, and the passage 85 is formed in the drive shaft 74 to connect the isolated chamber 80 with the chamber 84. Thus, refrigerant flows through the radial bearings 75, 76 or through the thrust bearing 82 in accordance with the pressure difference between the crank chamber 77 and the chamber 84. However, since the inlet 85a is located between the shaft sealing assembly 78 and the thrust bearing, flow of refrigerant is weakened either in the shaft sealing assembly 78 or in the thrust bearing, which results in insufficient lubrication.
Accordingly, it is an objective of the present invention to provide a swash plate type compressor that includes a simple structure for effectively lubricating radial bearings, which support a drive shaft, and a shaft sealing assembly.
To achieve the foregoing and other objectives and in accordance with the purpose of the present invention, a swash plate type compressor is provided. The compressor includes a housing, a drive shaft, first and second radial bearings, a piston, a cam plate, a shaft sealing assembly. A suction chamber, a discharge chamber and a crank chamber are defined in the housing. The housing has at least one cylinder bore. The drive shaft is rotatably supported by the housing and has a first end portion and a second end portion. The first end portion protrudes from the housing. The first and second radial bearings support the first and second end portions of the drive shaft, respectively. The piston is reciprocally accommodated in the cylinder bore. The cam plate is accommodated in the crank chamber and is operably coupled to the piston to convert rotation of the drive shaft into reciprocation of the piston. The shaft sealing assembly seals the space between the drive shaft and the housing and is accommodated in the suction chamber. The suction chamber is closer to the first end portion of the drive shaft than the first radial bearing is. A passage is formed in the drive shaft to connect the suction chamber to the crank chamber. The passage has an inlet and an outlet. The inlet is closer to the second end portion than the second radial bearing is. The outlet is closer to the second end portion than the first radial bearing is.
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.