Refrigeration – Processes – Compressing – condensing and evaporating
Reexamination Certificate
1999-10-04
2001-04-10
Wayner, William (Department: 3744)
Refrigeration
Processes
Compressing, condensing and evaporating
C062S228300, C236S07800D, C417S213000
Reexamination Certificate
active
06212893
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to air conditioning systems that utilize refrigerants and a compressor, and particularly to air conditioning systems capable of alleviating excessive increases in refrigerant discharge pressure within a heating circuit.
2. Description of the Related Art
A known air conditioning system is disclosed in Japanese Patent Application No. 7-19630 and includes a compressor
1
, a cooling circuit
51
, a heating circuit
52
and a controller
83
, as shown in FIG.
5
. The cooling circuit
51
includes a condenser
55
, a first expansion valve
57
and a heat exchanger
59
provided on a passage connecting a discharge port D to a suction port S of the compressor
1
. High pressure refrigerant discharged from the discharge port D of the compressor
1
is drawn through the above respective devices and back to the compressor
1
.
The heating circuit
52
includes a bypass passage
52
a
extending from the discharge port D of the compressor
1
to the heat exchanger
59
. A second expansion valve
63
provided within the bypass passage
52
a
between the discharge port D and the heat exchanger
59
. The high pressure refrigerant discharged from the compressor
1
is not directed to the condenser
55
, but rather is drawn by the compressor
1
through the second expansion valve
63
and the heat exchanger
59
. Such a heating circuit
52
is generally known as a hot gas bypass heater.
The operation of the cooling circuit
51
and the heating circuit
52
is changeably selected by opening and closing selector valves
53
a
and
53
b
, which opening and closing operations are performed by the controller
83
.
Because the refrigerant discharge pressure is higher when the heating circuit
52
is used than when the cooling circuit
51
is used, the air conditioning system must operate in a high pressure state when the heating circuit
52
is utilized. An abnormally high-pressure state may be created if the output discharge capacity of the compressor
1
temporarily increases during the operation of the heating circuit
52
. A refrigerant releasing passage
91
having a pressure relief valve
93
is provided in order to release excess pressure from the heating circuit
52
, if an abnormally high pressure state is reached. The refrigerant releasing passage
91
is connected to the heating circuit
52
and the cooling circuit
51
and the pressure relief valve
93
can be opened to release the refrigerant from the heating circuit
52
into the cooling circuit
51
when the refrigerant discharge pressure abnormally increases during the operation of the heating circuit
52
.
Because the cooling circuit
51
and the heating circuit
52
are alternatively selected by the selector valves
53
a
and
53
b
, the refrigerant is released into the cooling circuit
51
which is not used in operation of the heating circuit
52
, thereby preventing the discharge pressure at the heating circuit
52
from increasing abnormally.
However, because the refrigerant in the heating circuit
52
is released into the cooling circuit
51
whenever the discharge pressure abnormally increases, the amount of the refrigerant in the heating circuit
52
is reduced and heating performance may be reduced. Moreover, because the high pressure refrigerant is wastefully released from the heating circuit, energy efficiency is reduced.
Another known variable displacement compressor is disclosed in Japanese Patent Application No. 10-47242. Although this compressor is not explicitly shown in the drawings, a connecting passage having a capacity control valve is provided between a discharge port and a driving chamber (also known as the crank case) in a housing such that refrigerant is released from the discharge port into the driving chamber when the capacity control valve is opened. The capacity control valve is opened to increase pressure in the driving chamber when the discharge pressure is high. On the other hand, the capacity control valve is closed to decrease the pressure in the driving chamber when the discharge pressure is low.
The output discharge capacity is decreased when the pressure in the driving chamber is increased, and the output discharge capacity is increased when the pressure in the driving chamber is decreased. The output discharge capacity is decreased to decrease the discharge pressure when the discharge pressure increases, and the output discharge capacity is increased to increase the discharge pressure when the discharge pressure decreases.
If the variable displacement compressor disclosed in Japanese Patent Application No. 10-47242 is employed in the air conditioning system having the hot gas bypass heater circuit disclosed in Japanese Patent Application No. 7-19630, abnormally high pressure can be solved without the insufficiency in the heating performance due to release of the refrigerant in the hot gas bypass heater circuit into the cooling circuit and without low energy efficiency due to wasteful release of the refrigerant at highly increased pressure by causing the compressor to work.
However, a problem can occur due to a combination of a characteristics of the variable displacement compressor and a characteristics of the hot gas bypass heater by only employing the variable displacement compressor disclosed in Japanese Patent Application No. 10-47242 in the air conditioning system having the hot gas bypass heater circuit disclosed in Japanese Patent Application No. 7-19630. As described above, because a step of opening the capacity control valve of the compressor to increase the pressure in the driving chamber, a step of decreasing the output discharge capacity and a step of decreasing the discharge pressure are necessary to alleviate the abnormal high pressure state of the discharge pressure in utilizing the technique disclosed in Japanese Patent Application No. 10-47242.
Therefore, if the discharge pressure increases drastically during these steps, the discharge pressure may abnormally be increased and the hot gas bypass heater circuit may be damaged by such abnormal increase in pressure because above-explained steps require considerable time to be completed.
The technique disclosed in Japanese Patent Application No. 10-47242 does not have a hot gas bypass heater circuit and has only the cooling circuit. In such a case, the pressure of the refrigerant flowing through the cooling circuit is inherently lower than the pressure of the refrigerant flowing through the hot gas bypass heater circuit, and the cooling circuit may not be damaged by abnormal increase in pressure.
In other words, the technique disclosed in Japanese Patent Application No. 10-47242 is sufficient when the hot gas bypass heater circuit is not employed. However, if the air conditioning system has the hot gas bypass heater circuit, because the pressure of the refrigerant during operation of the hot gas bypass heater circuit is inherently high, the output discharge capacity control technique of the known variable displacement compressor is insufficient to quickly alleviate the abnormal increase in pressure.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide an air conditioning system that can alleviate abnormal high discharge pressure more sufficiently.
Preferably, an air conditioning system may include a compressor having a driving chamber, a heating circuit and a controller. This system may release high pressure refrigerant from the compressor discharge port into the compressor driving chamber by opening a capacity control valve when the discharge pressure of the refrigerant discharged from the compressor exceeds a predetermined reference value. By increasing the pressure within the driving chamber, the compressor discharge capacity can be reduced. As a result, the discharge pressure of the compressor will be reduced by the reduction in the compressor discharge capacity. Further, the controller may decrease the reference value in accordance with a value related to change in the discharge pressure. For example, increasin
Ban Takashi
Fujii Toshiro
Nakane Yoshiyuki
Okabe Takanori
Kabushiki Kaisha Toyoda Jidoshokki Seisakusho
Morgan & Finnegan,LLP
Wayner William
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