Pumps – Condition responsive control of drive transmission or pump... – Adjustable cam or linkage
Reexamination Certificate
1998-03-12
2001-05-08
Thorpe, Timothy S. (Department: 3746)
Pumps
Condition responsive control of drive transmission or pump...
Adjustable cam or linkage
C417S307000, C417S440000, C062S498000
Reexamination Certificate
active
06227812
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a refrigerant circuit and compressor that are incorporated in vehicle air conditioners
A refrigerant circuit includes a compressor and an expansion valve. The outlet of the compressor is connected with the expansion valve by a high pressure conduit. The high pressure conduit includes a condenser. The inlet of the compressor is connected with the expansion valve by a low pressure conduit. The low pressure conduit includes an evaporator. The compressor compresses refrigerant gas and sends it to the condenser. The condenser receives high pressure, high temperature refrigerant gas from the compressor. The condenser then cools and liquefies the gas. The liquefied refrigerant is expanded by the expansion valve and is turned into mist. The refrigerant mist is drawn to the evaporator. In the evaporator, heat exchange takes place between the refrigerant mist and the air in a passenger compartment, and vaporizes the mist. At this time, the heat of vaporization cools the air. The cooled air is then used to cool the passenger compartment.
In prior art refrigerant circuits, heat exchangers such as condensers and evaporators have a small heat capacity and thus are easily heated. Contrarily, the compressor has relatively great heat capacity and is not easily heated. Therefore, when the compressor is stopped for an extended period, a change in the ambient temperature produces a temperature difference between the compressor and the heat exchangers. The temperature difference results in a pressure difference between the compressor and the heat exchangers. The pressure difference causes liquefied refrigerant in the heat exchangers to enter the compressor and to get mixed with lubricant oil stored in the compressor. When operation of the compressor is resumed, the liquefied refrigerant in the compressor foams up and quickly flows back to the refrigerant circuit. This also removes the oil mixed with the liquefied refrigerant from the compressor. Thus, lubrication of the compressor may become insufficient. In order to solve this problem, some prior art refrigerant circuits have a check valve in the vicinity of the compressor outlet for preventing liquefied refrigerant from entering the compressor.
However, a typical refrigerant circuit includes a relief valve to discharge abnormally high pressure from the refrigerant circuit. The relief valve is located in the high pressure conduit in the vicinity of the condenser. If such a circuit is provided with a check valve in the vicinity of the outlet of the compressor, a malfunction of the check valve can cause the pressure in the compressor to be abnormally high.
SUMMARY OF THE INVENTION
Accordingly, the objective of the present invention to provide a refrigerant circuit and compressor that prevent liquefied refrigerant from entering a compressor and prevents the pressure in the compressor from being abnormally high.
To achieve the above objective, the present invention provides a refrigerant circuit that includes a compressor and an expansion valve. A high pressure passage connects a discharge chamber in the compressor to the expansion valve to send high pressure refrigerant from the compressor to the expansion valve. A low pressure passage connects the expansion valve to a suction chamber in the compressor to send low pressure refrigerant from the expansion valve to the compressor. A valve device is located in the high pressure passage to selectively connect and disconnect the high pressure passage with the discharge chamber. A relief valve is located in the high pressure passage. The relief valve is located upstream of the valve device.
Also, the present invention provides a compressor that compresses refrigerant gas supplied from an external low pressure passage and discharges the compressed refrigerant gas from a discharge chamber to an external high pressure passage. The compressor includes an internal passage for connecting the discharge chamber to the high pressure passage. A valve device is located in the internal passage to selectively connect and disconnect the external high pressure passage with the discharge chamber. A relief valve is located between the discharge chamber and the valve device.
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.
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Moran et al., Fundementals of Engineering Thrmodynamics, Wiley & Sons, New York, p. 439.
Kawaguchi Masahiro
Kawamura Koji
Makino Yoshihiro
Sonobe Masanori
Kabushiki Kaisha Toyoda Jidoshokki Seisakusho
Morgan & Finnegan , LLP
Thorpe Timothy S.
Torrente David J.
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