Refrigeration – Automatic control – Refrigeration producer
Reexamination Certificate
2000-05-04
2001-10-23
Tapolcal, William E. (Department: 3744)
Refrigeration
Automatic control
Refrigeration producer
C236S09200D
Reexamination Certificate
active
06305179
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an expansion valve of a refrigerating cycle including a compressor with variable capacity.
As the compressor in a refrigerating cycle of an air-conditioning system of an automobile directly is driven by the engine, the speed of the compressor cannot be controlled individually. In order to obtain proper refrigerating ability, speed compressors with variable capacity are used (e.g., compressors of the inclined plate type, the rotary type or the scroll type). The capacity of the compressor is changed in correspondence to the pressure of the inhaled refrigerant or the inhalation pressure.
The expansion valve in a refrigerating cycle is controlled based on variation of the temperature and the pressure of low-pressure refrigerant supplied from the evaporator. Since the outlet of the evaporator directly communicates with the inlet of the compresor, the pressure of the refrigerant exiting the evaporator is equal to the inhalation pressure of the compressor. Any variations of the pressure at the outlet of the evaporator directly affect the inhalation pressure of the compressor. If the capacity of compressor is changed due to a variation of the inhalation pressure, and if then the expansion valve opens and closes suddenly, corresponding to the variation of the capacity of the compressor, the outlet pressure of the evaporator quickly varies. The degree of the variation of the capacity of the compressor is also amplified by variations of the inhalation pressure, since the compressor has to follow the inhalation pressure variations. This amplification leads to an undesirable hunting effect over a certain period of time, e.g. seconds up to several minutes in the flow of the refrigerant.
OBJECTIONS AND SUMMARY OF THE INVENTION
It is an object of the present invention to provide an expansion valve in a refrigerating cycle suppressing the hunting of the flow of refrigerant as soon as the expansion valve opens, corresponding with a condition according to which the capacity of the compressor is changed. The hunting either is suppressed entirely or at least significantly attenuated.
Within the expansion valve, the cross-section for the refrigerant passing to the evaporator is controlled differently within a first stroke section adjacent to the fully closed state position and within further stroke sections where the valve body already has been lifted farther from the valve seat bore. In particular, the variation of the cross-section within the first stroke section is smaller at any stroke increment of the valve body than at stroke increments of the same magnitude but in the further stroke section. In other words, during an opening stroke of the expansion valve, the gradient of the curve representing the increase of the cross-section through the valve, i.e. a specific variation per stroke increment, is flatter within the first stroke section and is steeper within any further stroke section. The same is true for the movement of the valve body in closing direction. This behavior of the expansion valve effectively controls hunting of the flow of the refrigerant when the capacity of the compressor is changed. Hunting is further controlled by setting the value of the pressure at the outlet of the evaporator for the moment where the expansion valve starts to open into a certain relation to the maximum inhalation pressure within the range where the capacity of the compressor is changed, particularly so that the pressure at the outlet of the evaporator then is equal or lower than the maximum inhalation pressure. This measure effectively suppresses the hunting effect and guarantees a sufficient cooling effect within the refrigerating cycle.
According to another object of the invention, the expansion valve includes a body with a prolongation diving into the valve seat bore within a first opening stroke section close to the fully closed state position such that a progressively increasing variation of the cross-section for the refrigerant only takes place in the second part of the stroke where the expansion valve opens more progressively. In other words, during the first opening stroke section, the valve body is co-acting with the valve seat bore like a flow regulator with a controlled throttling effect, control of the amount of refrigerant corresponding to a predetermined ramp function. This regulating measure is applied exclusively within the first stroke section and where the influence of the expansion valve for hunting is the strongest.
REFERENCES:
patent: 4979372 (1990-12-01), Tanaka
patent: 5060485 (1991-10-01), Watanabe et al.
patent: 5255530 (1993-10-01), Janke
patent: 5277364 (1994-01-01), Heffner et al.
patent: 5916250 (1999-06-01), Osthues et al.
Nilles & Nilles SC
Tapolcal William E.
TGK Co. Ltd.
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