Scroll compressor and air conditioner

Details Scroll compressor and air conditioner Scroll compressor and air conditioner

2001-08-06

2003-09-16

Tanner, Harry B. (Department: 3744)

Refrigeration

Automatic control

Refrigeration producer

C062S196100, C062S228400, C062S228500

Reexamination Certificate

active

06619062

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a scroll compressor and an air conditioner, and more specifically, it relates to a scroll compressor and an air conditioner capable of controlling switching between unloaded operation and full-loaded operation, controlling the capacity of refrigerant injection and controlling the rotational frequency of a motor on the basis of a result of detection of the operating state.
BACKGROUND ART
FIG. 17
shows an exemplary conventional refrigerant compressor. This compressor is disclosed in Japanese Patent Laying-Open No. 11-182479 (1999).
As shown in
FIG. 17
, the refrigerant compressor comprises a closed container
63
having a fixed scroll
56
and a rocking scroll (not shown) built therein. A cylinder
53
is formed on an end of the closed container
63
. A piston control valve
51
and a compression spring
52
are set in the cylinder
53
.
The cylinder
53
is further provided with a first passage
60
communicating with an intermediate pressure space
59
, a second passage
61
communicating with a suction pressure space
57
and a third passage
62
communicating with a discharge pressure space
58
through a discharge port
55
. A back pressure space
54
of the piston control valve
51
communicates with the third passage
62
.
In the compressor having the aforementioned structure, the piston control valve
51
moves in response to the difference between a suction pressure (Ps) and a discharge pressure (Pd) for a refrigerant to open/close the first passage
60
. Thus, the operating state of the compressor is switched between operation (full-loaded operation) closing the first passage
60
for attaining discharge capacity of 100% and operation (unloaded operation) opening the first passage
60
for reducing the discharge capacity.
The aforementioned compressor, automatically controlling switching between unloaded operation and full-loaded operation in response to the pressure condition in the compressor, has the following problem. This problem is now described with reference to FIG.
18
.
FIG. 18
illustrates the relation between a condensing temperature (Tc), an evaporating temperature (Te) and an operating pressure ratio (Pr).
When the evaporating temperature (Te) is low and the condensing temperature (Tc) is high (the region shown by slanting lines in
FIG. 18
) while required refrigerating ability is small in a refrigerating cycle, for example, the aforementioned compressor is not subjected to unloaded operation. This is because the suction pressure (Ps) for the refrigerant is reduced and the discharge pressure (Pd) is increased when the evaporating temperature (Te) is low and the condensing temperature (Tc) is high, to close the aforementioned first passage
60
.
When not subjected to unloaded operation but operated with small ability as described above, the compressor must unavoidably be operated at a low pressure with difficulty in lubrication. In such low-speed operation, further, motor efficiency is lower than that in intermediate- or high-speed operation, and efficiency may be reduced due to leakage of compression gas in the compressor or the like.
As hereinabove described, the conventional compressor automatically controls switching between unloaded operation and full-loaded operation without detecting the operating state. Therefore, the compressor cannot sometimes be properly and efficiently operated in response to the operating state. This problem can also arise in an air conditioner comprising the aforementioned compressor.
DISCLOSURE OF INVENTION
The present invention has been proposed in order to solve the aforementioned problem. An object of the present invention is to provide a scroll compressor and an air conditioner capable of selecting proper and efficient operation in response to every operating state.
A scroll compressor according to the present invention has a movable scroll (
2
) and a fixed scroll (
1
) forming a compression chamber (
40
) compressing a refrigerant, and comprises a variable-speed motor (
28
), capacity control means (
12
,
35
), an operating state detection part (
27
) and a control part (
26
). The variable-speed motor (
28
) drives the movable scroll (
2
). The capacity control means (
12
,
35
) controls the capacity of the scroll compressor by supplying the refrigerant into the compression chamber (
40
) or bypassing the refrigerant from the compression chamber (
40
) to a low-pressure side. The operating state detection part (
27
) detects the operating state of the scroll compressor. The control part (
26
) controls operation of the capacity control means (
12
,
35
) and the rotational frequency of the motor (
28
) in response to the operating state detected by the operating state detection part (
27
).
The scroll compressor comprises the aforementioned operating state detection part (
27
), so that the operating state of the scroll compressor can be detected. Further, the scroll compressor comprises the aforementioned control part (
26
), so that the operation of the capacity control means (
12
,
35
) and the rotational frequency of the motor (
28
) can be controlled in response to the operating state of the scroll compressor. Thus, proper and efficient operation can be selected under every operating condition. The aforementioned operating state detection part (
27
) and control part (
26
) may be set not only in the compressor but also in a refrigerating/air conditioner system.
In the scroll compressor according to the present invention, the operating state detection part (
27
) preferably includes an operating pressure ratio detection part detecting an operating pressure ratio indicating the value of the ratio of a suction pressure for the refrigerant to a discharge pressure for the refrigerant and a required ability detection part detecting required ability in operation of the scroll compressor, and the control part (
26
) preferably controls the operation of the capacity control means (
12
,
35
) and the rotational frequency of the motor (
28
) in response to the aforementioned operating pressure ratio and required ability.
The operating state detection part (
27
) has the operating pressure detection part and the required ability detection part as hereinabove described, whereby the operating state of the scroll compressor such as the operating pressure ratio or the required ability can be detected. The control part (
26
) controls the operation of the capacity control means (
12
,
35
) and the rotational frequency of the motor (
28
) in response to the operating pressure ratio and the required ability detected in the aforementioned manner, so that the scroll compressor can be operated in high efficiency under every operating condition.
In the scroll compressor according to the present invention, the capacity control means (
12
,
35
) preferably includes unloading means (
12
) for substantially delaying a compression starting point in the compression chamber (
40
) and performing unloaded operation.
The capacity control means (
12
,
35
) can be exemplified by the unloading means (
12
). When the scroll compressor comprises the unloading means (
12
), the unloading means (
12
) can be intentionally operated in response to the operating state of the scroll compressor for performing unloaded operation. More specifically, the unloading means (
12
) can be intentionally operated for performing unloaded operation under conditions of a low evaporating temperature, a high condensing temperature and small required refrigerating ability, for example. Thus, it is possible to avoid the general problem of low-speed operation with difficulty in lubrication.
In the scroll compressor according to the present invention, the capacity control means (
12
,
35
) includes refrigerant injection means (
35
) for injecting the refrigerant into the compression chamber (
40
).
The capacity control means (
12
,
35
) can alternatively be exemplified by the refrigerant injection means (
35
). When the scroll compressor comprises the refrigerant injection means (
35
), the injection means (
35

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