Pumps – Condition responsive control of drive transmission or pump... – Adjustable cam or linkage
Reexamination Certificate
1999-03-18
2001-08-21
Tyler, Cheryl J. (Department: 3746)
Pumps
Condition responsive control of drive transmission or pump...
Adjustable cam or linkage
C417S269000, C091S505000
Reexamination Certificate
active
06276904
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to variable displacement compressors which are employed in motor vehicle air-conditioning systems, for instance.
2. Description of the Related Art
FIG. 10
shows a conventionally known structure employed in a variable displacement compressor of this kind, in which cylinder bores
101
a
are formed in a housing
101
, a drive shaft
102
is rotatably supported in the housing
101
, a rotary support
103
is fixed to the drive shaft
102
, a cam plate
104
is supported by the drive shaft
102
which is passed through a through hole
104
a
formed in the cam plate
104
, and pistons
105
fitted in the individual cylinder bores
101
a
are joined to the cam plate
104
. A maximum inclination setting projection
106
protrudes from about a point Db of the cam plate
104
corresponding to a bottom dead center toward the rotary support
103
.
A hinge mechanism
107
comprises guide pins
108
provided close to a point Da of the cam plate
104
corresponding to a top dead center and supporting arms
109
provided on the rotary support
103
corresponding to the guide pins
108
. The guide pins
108
are firmly press-fitted into holes formed in the cam plate
104
and have bulbous parts
108
a
at extreme ends. On the other hand, guide holes
109
a
are formed in the individual supporting arms
109
. The guide pins
108
and the supporting arms
109
are joined together as the bulbous parts
108
a
of the former are fitted into the respective guide holes
109
a
of the latter.
With the bulbous parts
108
a
of the guide pins
108
fitted into the guide holes
109
a
in the individual supporting arms
109
, the cam plate
104
can rotate together with the drive shaft
102
. Thus, rotary motion of the drive shaft
102
is converted into reciprocating motion of the pistons
105
in the cylinder bores
101
a
by way of the rotary supports
103
, the hinge mechanism
107
and the cam plate
104
. As a consequence, a refrigerant gas is introduced into the cylinder bores
101
a
, compressed, and discharged in repeated cycles.
The drive shaft
102
supports the cam plate
104
in such a way that the cam plate
104
can vary its angle of inclination while sliding along the drive shaft
102
. This is because the bulbous parts
108
a
of the individual guide pins
108
and the guide holes
109
a
of the hinge mechanism
107
work as slide guides and the through hole
104
a
allows the cam plate
104
to slide along the drive shaft
102
. The stroke of the pistons
105
and, thus, the displacement capacity of the compressor are varied by adjusting the angle of inclination of the cam plate
104
. When the maximum inclination setting projection
106
of the cam plate
104
comes into contact with the rotary support
103
, the cam plate
104
is restrained from sliding and inclining further, where the cam plate
104
reaches its maximum angle of inclination.
When the cam plate
104
is set to its maximum angle of inclination, the stroke of the pistons
105
increases so that the refrigerant gas compression ratio also increases. As a result, a large compressive load acts on the supporting arms
109
by way of the pistons
105
, the cam plate
104
and the guide pins
108
so that the guide pins
108
receive a high level of reaction force from the supporting arms
109
which sustain the compressive load. The guide pins
108
employed in the conventional structure have a large diameter, for instance, so that they should be able to withstand the large reaction force. Furthermore, portions of the cam plate
104
where the guide pins
108
are fitted are made thicker to provide a sufficient mechanical strength for supporting the guide pins
108
.
The use of the large-diameter guide pins
108
, which have naturally a heavy weight, combined with the thickening of the portions around the holes in which the guide pins
108
are fitted results in a considerable increase in the weight of the cam plate
104
. In addition, there is the need to fit a large counterweight to make up for an unbalanced weight distribution around an axis L of the drive shaft
102
caused by the provision of the guide pins
108
and the thickened portions of the cam plate
104
. This also causes an increase in the weight of the cam plate
104
. A major problem resulting from such increase in the weight of the cam plate
104
in the conventional structure has been the delay in altering the angle of inclination of the cam plate
104
, or deterioration of the controllability of the displacement capacity of the compressor.
According to a proposal made in recent years, the weight of the compressor can be reduced by forming the cam plate
104
with an aluminum-based metallic material. The cam plate
104
formed of the aluminum-based metallic material has a lower stiffness than conventionally used iron-based metallic materials, however. It has therefore been difficult to produce the guide pins
108
with a desired length of fit which would be required for securely press-fitting the guide pins
108
into the cam plate
104
and, as a consequence, the guide pins
108
have tended to be mounted with low strength. Accordingly, what is important for producing the cam plate
104
with the aluminum-based metallic material is to lower the ratio of a load supported by the hinge mechanism
107
to a maximum compressive load acting on the cam plate
104
when the compressor is operated at its maximum displacement capacity.
SUMMARY OF THE INVENTION
The present invention has been made in the light of the aforementioned problems of prior art technology. Accordingly, it is an object of the invention to provide variable displacement compressors which makes it possible to lower the proportion of load supported by a hinge mechanism to a maximum compressive load exerted on a cam plate when the compressor is operated at its maximum displacement capacity and to reduce the weight of the cam plate.
According to a principal aspect of the invention, a variable displacement compressor comprises a hinge mechanism including a guiding projection provided on a cam plate or a rotary support at about a point corresponding to a top dead center of the cam plate and a guide provided on the cam plate or the rotary support on which the guiding projection is not provided, the guiding projection being slidably fitted in the guide, wherein a maximum inclination setting part formed on the cam plate comes into contact with the rotary support at least in a region closer to the point corresponding to the top dead center than an imaginary two-part dividing plane which intersects an imaginary plane including the point corresponding to the top dead center and an axis of a drive shaft and imaginarily divides the cam plate into two parts, and there is made a clearance between the guiding projection and the guide so that transmission of a compressive load between them is interrupted when the cam plate is in its maximum angle of inclination and supported by its maximum inclination setting part which has come into contact with the rotary support.
In this construction, the cam plate is supported at least in the region closer to the point corresponding to the top dead center than the imaginary two-part dividing plane as the maximum inclination setting part comes into contact with the rotary support when the cam plate is in its maximum angle of inclination. Thus, the hinge mechanism is not required to support any proportion of the compressive load in the region closer to the point corresponding to the top dead center than the imaginary two-part dividing plane. It has therefore been possible to construct the hinge mechanism in such a way that a clearance is created between the guiding projection and the guide so that transmission of the compressive load between them is interrupted.
According to another aspect of the invention, there are provided one pair each of guiding projections and guides, one each guiding projection and guide being located on both sides of the point corresponding to the top dead center of th
Kurakake Hirotaka
Kurita Hajime
Nishimura Kenta
Ota Masaki
Toyoda Automatic Loom Works, Ltd.
Tyler Cheryl J.
Woodcock Washburn Kurtz Mackiewicz & Norris LLP
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