Refrigeration – Muffler or sound dampener
Reexamination Certificate
2001-11-13
2003-03-11
Tapolcai, William E. (Department: 3744)
Refrigeration
Muffler or sound dampener
C181S403000, C417S312000
Reexamination Certificate
active
06530239
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an improvement for reducing the moisture permeation into a refrigeration system, which is suitably used for a refrigeration system of an automotive air-conditioning system.
2. Description of the Related Art
In a conventional refrigeration system for an automotive air-conditioning system, a compressor is driven by the automobile engine and therefore is arranged in the same vibrating system as the engine. The other devices of the refrigeration system such as the condenser and the evaporator are fixedly mounted on the automotive body in a vibration system different from the compressor.
The vibrations between the two different vibration systems are absorbed by elastic rubber hoses used as a discharge pipe and an intake pipe of the compressor.
Rubber hose, however, has a much higher moisture permeation than metal pipe, and therefore moisture in the air unavoidably permeates into the system through the rubber hoses. During the operation of the refrigeration system, the refrigerant temperature sharply drops when the refrigerant on high-pressure side is reduced in pressure and expands in a reduction portion, of the decompression units, such as an expansion valve, and moisture in the system is frozen into ice. With the increase in the amount of moisture permeating into the system, the freezing thereof is liable to block the reduction portion of the decompression unit.
In order to prevent this inconvenience, the conventional system comprises a drier with a drying agent such as silica gel used in the system, whereby the moisture permeating into the system is absorbed. The problem, however, is that the dryer increases both the cost and the mounting space.
Japanese Unexamined Patent Publication No. 5-306843 describes a configuration in which the moisture permeation of the rubber hose on the discharge side of the compressor is increased beyond the moisture permeation of the rubber hose on the intake side of the compressor to release the moisture in the system outside from the rubber hose on the discharge side of the compressor. According to this prior art, the moisture permeation of the rubber hose on the discharge side of the compressor is so large that moisture permeating into the system through the rubber hose on discharge side during the service life (10 to 15 years, for example) cannot be suppressed.
SUMMARY OF THE INVENTION
In view of the aforementioned facts, the object of the present invention is to provide a refrigeration system in which the amount of moisture permeating into the system can be reduced at low cost and by using simple means.
According to the invention, means for achieving the above-mentioned object has been devised based on the technical knowledge described below. First, this technical knowledge will be explained. In the graphs of
FIGS. 3 and 4
, the ordinate represents the moisture content (in g) of the system and the abscissa the period (in years) during which the climate control system has been in operation.
FIG. 3
shows the change of moisture content of the system with the change in the moisture permeability (hence the amount of moisture permeation) of the rubber hose on the discharge side of the compressor. On the other hand,
FIG. 4
shows the change of the amount of moisture in the system with the change in the water permeability (hence the amount of moisture permeation) of the rubber hose on the intake side of the compressor. The amount of moisture in the system is the sum of the moisture dissolved in the refrigerant and the lubricating oil and the water separated from the refrigerant and the lubricating oil.
FIGS. 3 and 4
show the result of a computer simulation prepared by the inventor. The main numerical conditions include 650 g as the amount of refrigerant sealed in the system, 120 g as the amount of lubricating oil sealed in the system, 380 mm as the length of the rubber hose on the discharge side of the compressor, and 416 mm as the length of the rubber hose on the intake side of the compressor. The refrigerant is specifically HFC
134
a
, and the lubricating oil is specifically a synthetic oil of polyalkylene glycol.
In
FIG. 3
, the characteristics (
1
) to (
6
) are associated with different moisture permeability of the rubber hose on the discharge side, of which the uppermost characteristic (
1
) is associated with the conventional normal rubber hose.
The moisture permeability of this characteristic (
1
) is specifically 0.5 g/(m·168 hr). This water permeability is measured in the following way:
1. Drying the hose to be measured
The hose to be measured is dried for 24 hours at 100° C. in a constant temperature bath.
2. Sealing a drying agent in the hose to be measured
A predetermined amount of a drying agent corresponding to the inner diameter of the hose to be measured is inserted into the particular hose and the hose ends are hermetically sealed.
3. Measuring the moisture permeability of the hose to be measured
The hose to be measured is left to stand for a specified time (168 hrs) in a thermo-hygrostat regulated at 60° C. and the relative humidity of 95%.
Upon the lapse of the specified time (168 hrs), the hose to be measured is recovered, the drying agent is retrieved from within the hose, and the weight (in g) of the drying agent is measured.
The moisture permeation amount of the hose to be measured can be determined from the difference (W
2
−W
1
) between the weight W
2
(g) of the drying agent after the hose to be measured is left to stand for a specified time in the thermo-hygrostat and the weight W
1
(g) of the drying agent before insertion into the thermo-hygrostat.
Thus, the moisture permeability can be determined as (W
2
−W
1
)/L, i.e. the ratio between (W
2
−W
1
) and the hose length L.
On the other hand, the characteristics (
2
) to (
6
) have a progressively smaller moisture permeability of the rubber hose downward, i.e. 1/2, 1/3, 1/5, 1/10 and 1/20, of the conventional normal rubber hose corresponding to the characteristic (
1
).
The lowest characteristic (
6
), therefore, is the one for the rubber hose on the discharge side having a moisture permeability of 0.025 g/m·168 hrs. In
FIG. 4
, as in
FIG. 3
, the characteristics (
1
) to (
6
) are the ones associated with different moisture permeabilities of the rubber hose on the intake side, respectively, and specific moisture permeabilities thereof are identical to the corresponding ones shown in FIG.
3
.
For the rubber hose on the intake side, as shown in
FIG. 4
, the difference of moisture amount in the system with the change of elapsed years is small with the change of moisture permeability. The change in the moisture permeability of the rubber hose on the discharge side, on the other hand, is seen to increase the difference of the moisture amount in the system with the change of the elapsed years. Specifically, the moisture amount in the system is reduced only slightly with the reduction of moisture permeability of the hose on the intake side, while the moisture amount in the system is reduced much more with the reduction of the moisture permeability of the rubber hose on the discharge side.
Now, an explanation will be given of the reason why the effect of reducing the moisture amount in the system are greatly different between the intake side and the discharge side of the compressor.
The moisture permeation of the rubber hose is caused by the difference of the partial pressure of water vapor between outside and inside of the hose.
With the refrigeration system for the automotive climate control system, normally after being mounted on the vehicle in the vehicle assembly line of the automobile manufacturer, the flow path in the system is evacuated to discharge the moisture, air etc. out of the system. After that, a predetermined amount of each of the refrigerant and the lubricating oil are sealed in the system. Thus, immediately after the refrigeration system is mounted on the automobile, the system is free of moisture and air.
Immediately after the refrigeration system
Kitamura Keiichi
Nobuta Tetsuji
Denso Corporation
Harness Dickey & Pierce PLC
Tapolcai William E.
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