Refrigeration – Automatic control – Refrigeration producer
Reexamination Certificate
1999-04-07
2001-02-06
Tanner, Harry B. (Department: 3744)
Refrigeration
Automatic control
Refrigeration producer
C062S204000, C062S210000
Reexamination Certificate
active
06182456
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
The present application is related to, and claims priority from, pending Japanese Patent Application No. 10109426, filed Apr. 20, 1998, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a refrigerating cycle system wherein the pressure of a refrigerant on a high-pressure heat exchanger side exceeds the critical pressure of the refrigerant, and particularly to such a refrigerating cycle system having carbon dioxide (CO
2
) as its refrigerant (hereinafter a CO
2
cycle system).
2. Description of the Related Art
In a CO
2
cycle system, such as the one disclosed in Japanese Published Application No. Hei. 3-503206, refrigerating capacity is controlled via control of pressure on the heat exchanger outlet side.
In this connection, the present applicant has already proposed in Japanese Patent Application No. Hei. 8-11248 a CO
2
cycle system, or supercritical refrigerating cycle system, wherein the aperture of a valve disposed on the heat exchanger outlet side is adjusted in correspondence with the refrigerant temperature thereat.
Specifically, when the refrigerant temperature on the outlet side of the heat exchanger rises, the valve aperture is reduced to raise the refrigerant pressure on the heat exchanger outlet side. When the refrigerant temperature on the heat exchanger outlet side falls, the valve is adjusted to reduce the refrigerant pressure thereat.
However, a so-called variable capacity compressor has certain limitations when applied to a CO
2
cycle system in a vehicle air-conditioning system.
With not only CO
2
cycle systems but also with any refrigerating cycle system using a variable capacity compressor, when the engine speed is relatively high and the mass flow of refrigerant circulating in the refrigerating cycle is large, or when the temperature inside the passenger compartment is stable and the refrigerating capacity required of the air-conditioning system is relatively small, the refrigerant delivery capacity of the compressor is reduced to prevent the refrigerating capacity from becoming excessive.
When a variable capacity compressor and valve having its aperture controlled in correspondence with the refrigerant temperature on the heat exchanger outlet side as in the application mentioned above (Japanese Patent Application No. Hei. 8-11248) are combined, such as when the refrigerant delivery capacity on the compressor side is reduced to prevent the refrigerating capacity from becoming excessively large, the refrigerant pressure on the corresponding heat exchanger outlet side falls.
However, on the valve side, to maintain the refrigerant pressure on the outlet side of the heat exchanger at a pressure (refrigerating capacity) corresponding to the refrigerant temperature on the outlet side of the heat exchanger at that time, the aperture of the valve is reduced to raise the refrigerant pressure on the outlet side of the heat exchanger.
In other words, whereas the refrigerant delivery capacity of the compressor is controlled on the compressor side in correspondence with the required refrigerating capacity, control on the valve side attempts to maintain the refrigerating capacity corresponding to the refrigerant temperature on the heat exchanger outlet side. Thus when these two forms of control are combined, the CO
2
cycle cannot be adequately controlled.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a supercritical refrigerating cycle system having a variable capacity compressor, the system being adequately controlled even when the refrigerant delivery capacity of the variable capacity compressor changes.
To achieve the above-mentioned object and other objects, a preferred embodiment of the present invention includes a supercritical refrigerating cycle system having a variable capacity compressor. When it is determined that the refrigerant delivery capacity of the compressor has not changed, the aperture of a valve disposed on an outlet side of a heat exchanger for cooling refrigerant delivered from the compressor is controlled. The valve is controlled based on a first preset program corresponding to the temperature of refrigerant on the outlet side of the heat exchanger as detected by a refrigerant temperature detector. When it is determined that the refrigerant delivery capacity has changed, the aperture of the valve is controlled based on a second program different from the first program.
Alternatively, when it is determined that the refrigerant delivery capacity has changed, the controller may fix the valve aperture via the second program. Preferably, the aperture is fixed at a setting corresponding to the setting when the first program was initially suspended.
Another preferred embodiment of the present invention is similar to the above-discussed embodiment, except that when it is determined that the refrigerant delivery capacity has changed, the second program controls the valve aperture so that the aperture percentage change is smaller than when the aperture is controlled based on the first program.
In yet another preferred embodiment, when it is determined that the refrigerant delivery capacity has changed, the second program controls the valve aperture so that the pressure on the outlet side of the heat exchanger approaches a second target pressure lower than the first target pressure.
According to another preferred embodiment, when it is determined that the refrigerant delivery capacity has changed, the second program controls the valve aperture based on the aperture setting when the first program was suspended as long as the value detected by the intake pressure change detector remains above a predetermined value, or by suspending the first program for a predetermined time.
In all of the above-mentioned embodiments, it is possible to suppress the degree to which the variable capacity compressor is influenced by the valve side, and thus it is possible to accurately control the supercritical refrigerating cycle.
REFERENCES:
patent: 5245836 (1993-09-01), Lorentzen et al.
patent: 5685160 (1997-11-01), Abersfelder et al.
patent: 5694784 (1997-12-01), Frey et al.
patent: 5890370 (1999-09-01), Sakakibara et al.
patent: 0 604 417 B1 (1996-04-01), None
patent: 9-264622 (1997-10-01), None
International Journal Of Refrigeration—International Institute Of Refrigeration, vol. 16, No. 1, 1993.
Fujii Toshiro
Nishida Shin
Yamaguchi Motohiro
Yokomachi Naoya
Denso Corporation
Harness Dickey & Pierce PLC
Tanner Harry B.
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