Pumps – Motor driven – Including means utilizing pump fluid for augmenting cooling,...
Reexamination Certificate
1999-05-07
2001-02-06
Walberg, Teresa (Department: 3742)
Pumps
Motor driven
Including means utilizing pump fluid for augmenting cooling,...
Reexamination Certificate
active
06183215
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electric motor driven compressor adapted to be used as a refrigerant compressor in an automotive air conditioning system or, in particular, to an electric motor driven compressor suitable for CO
2
as a refrigerant.
2. Description of the Related Art
In an air conditioning system for an electric motor driven vehicle such as an electric car or a home-use air conditioning system, it has been general practice to use freon gas, such as R134a or the like, as a refrigerant for the refrigeration cycle. Also, a refrigerant compressor used for compressing the refrigerant in the refrigeration cycle of these air conditioning systems is disclosed in JP-A-65580, for example, as what is called the “electric motor driven compressor” in which a motor portion and a compressor portion including a scroll-type compressor are integrally built in a common hermetic casing.
In the electric motor driven compressor, an intake chamber and a discharge chamber or other chambers are formed in the internal space of a casing in which the motor portion is arranged. If it is assumed that an intake chamber is formed in the internal spacing of the motor casing of an electric motor driven compressor of a conventional air conditioning system using the refrigeration cycle with the freon gas or the like as a refrigerant, generally, in the refrigeration cycle in which a flexible pipe such as a rubber hose is not used, the body or the like parts of the automotive vehicle are liable to develop noises and vibrations due to the effect of the discharge pulsation of the compressor unless the discharge chamber of the electric motor driven compressor has a sufficiently large capacity. The result would be an increased bulk of the pump portion, and a larger capacity of the discharge chamber would result in an increased bulk of the electric motor driven compressor as a whole.
In the case where the internal spacing of the motor casing is used as a discharge chamber, on the other hand, the motor casing is regarded as a pressure vessel, and therefore, a high pressure resistance value is required according to the law and regulations. Therefore, the thickness of the motor casing is required to be increased. The problem in this case is that the electric motor driven compressor would become not only bulky but also heavy. Further, in the case where carbon dioxide (CO
2
) is used as a refrigerant, the operating pressure, i.e. the discharge pressure of the refrigerant compressor is about ten times as high as that for a freon refrigerant. This problem is therefore not negligible.
SUMMARY OF THE INVENTION
The object of the present invention is to cope with the problem of the prior art described above and to provide a compact, lightweight electric motor driven compressor whose body does not become bulky even when an intake chamber is formed in a motor casing, wherein even in the case where the thickness of the motor casing is required to be increased with the increase in the discharge pressure of the electric motor driven compressor when CO
2
is used as a refrigerant of the refrigeration cycle, the thickness increase is minimized thereby to prevent the weight and volume of the electric motor driven compressor from increasing.
The present inventors have taken note of the fact that the operating pressure in the refrigeration cycle using the CO
2
refrigerant, i.e. the discharge pressure of the refrigerant compressor, is very high as compared with the corresponding pressure in the refrigeration cycle using freon as a refrigerant, so that the intake volume of the refrigerant compressor for the CO
2
refrigerant is as small as about one eighth of the volume of the compressor for the freon refrigerant, and the resulting smaller volume of the compressor portion creates a dead space around the compressor portion due to the difference in body size between the small compressor portion and the motor casing of a normal size.
The dead space is utilized by forming a discharge chamber having a comparatively large volume around the compressor portion, and an intake chamber is formed using the large space in the motor casing. In this way, the space can be reduced to a comparatively low pressure, and the thickness of the motor casing can be decreased. Thus, while minimizing the effect of the discharge pulsation, the body size of the electric motor driven compressor as a whole is reduced. Specifically, as a means for solving the problem mentioned above, there is provided an electric motor driven compressor having a configuration as described in each claim.
In the electric motor driven compressor according to claim
1
, at least a part of the intake chamber is formed by the gaps between the component parts of the motor portion in the motor casing, and therefore a sufficiently large volume can be secured as an intake chamber. At the same time, since the intake chamber is a component where the pressure is lowest in the system (refrigeration cycle) including the electric motor driven compressor, the thickness of the motor casing can be reduced resulting in a lighter weight of the electric motor driven compressor. Also, the discharge chamber is formed by the gap between the inner surface of the pump casing and the compressor portion mounted in the pump casing. Therefore, the volume of the discharge chamber can be increased by utilizing the dead space which is increased with the difference in size between the motor casing and the compressor portion when the latter is miniaturized, thereby the discharge pulsation is effectively suppressed.
If it is assumed that the interior of the motor casing is used as a discharge chamber, an expensive shaft seal portion such as a mechanical seal would be required on the part passing through the boundary surface around the shaft extending from within the motor casing constituting a high-pressure space through the boundary surface to the low-pressure space such as the intake chamber in the pump casing. According to the present invention, however, the interior of the motor casing constitutes an intake space, and therefore the shaft extends from the low-pressure intake space in the motor casing to the low-pressure space such as the intake chamber in the pump casing. Since there is no substantial pressure difference between the intake space in the motor casing and the intake chamber in the pump casing, a shaft seal portion is not required at the boundary surface through which the shaft is laid. This remarkably reduces the cost. Also, since the motor portion in the motor casing is sufficiently cooled by the returning refrigerant, the efficiency of the whole system is improved. Also, since the interior of the motor casing constitutes an intake space at a comparatively low pressure, the required degree of super-heat of the return refrigerant can be secured and the return of a liquid refrigerant is prevented in the case where this electric motor driven compressor is used as a refrigerant compressor in the refrigeration cycle, or especially, in the accumulator cycle of the air conditioning system. Thus, the system reliability is improved.
In the electric motor driven compressor according to claim
2
, an intermediate member can be utilized not only as a bearing support of the shaft but also as a partitioning plate between the intake chamber and the discharge chamber.
In the electric motor driven compressor according to claim
3
or
4
, the discharge chamber assumes a cylindrical shape, while in the electric motor driven compressor according to claim
5
or
6
, the discharge chamber assumes the shape of a bottomed cylinder.
The electric motor driven compressor according to one of claim
7
to
12
is used as a refrigerant compressor for compressing the CO
2
refrigerant in the air conditioning system. In the case where the cooling effect equivalent to the freon refrigerant can be secured, therefore, the discharge pressure is increased while the discharge rate is reduced to about one eighth. Therefore, the compressor portion can be considerably reduc
Kato Hiroyasu
Nakashima Masafumi
Sakai Takeshi
Uchida Kazuhide
Denso Corporation
Patel Vinod D.
Pillsbury Madison & Sutro LLP
Walberg Teresa
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