Refrigeration – Automatic control – Refrigeration producer
Reexamination Certificate
2002-05-09
2004-02-03
Wayner, William (Department: 3744)
Refrigeration
Automatic control
Refrigeration producer
C251S129150, C310S015000, C417S222200
Reexamination Certificate
active
06684654
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a control valve for controlling the displacement of a variable displacement compressor in a refrigerant circuit of an air conditioner.
One type of such control valve includes a pressure sensing mechanism and an electromagnetic actuator. The pressure sensing mechanism detects the pressure at a pressure monitoring point located in the refrigerant circuit. A pressure sensing member is actuated based on changes of the pressure at the pressure monitoring point. Accordingly, a valve body is moved such that the displacement of the variable displacement compressor is changed to counteract the pressure changes. As a result, the pressure at the pressure monitoring point is maintained at a target level. The electromagnetic actuator changes the target level by changing electromagnetic force applied to the valve body in accordance with the level of electric current supplied from the outside.
FIG. 8
illustrates the structure of such an electromagnetic actuator
101
. The electromagnetic actuator
101
includes an accommodation cylinder
102
. A stator
103
and a plunger
104
are accommodated in the cylinder
102
. A coil
105
is located about the cylinder
102
. As electric current is supplied to the coil
105
, electromagnetic force is generated between the stator
103
and the plunger
104
. This moves the plunger
104
. The movement of the plunger
104
is transmitted to a valve body (not shown) by a rod
106
.
A flat inner surface
107
and a peripheral wall
108
are formed in the lower end of the stator
103
, which faces the plunger
104
. The inner circumferential surface of the peripheral wall
108
is referred to as an inclined surface
108
a.
The inner surface
107
is surrounded by the inclined surface
108
a.
The cross-section of the peripheral wall
108
defines an acute angle. The inner surface
107
and the peripheral wall
108
define a recess
109
. A flat distal surface
110
and an annular inclined surface
111
are formed in an upper end of the plunger
104
, which faces the plunger
104
. The inclined surface
111
is formed at the periphery of the distal surface
110
. The distal surface
110
and the inclined surface
111
define a frustum portion
112
.
When the coil
105
receives a low electric current, the position of the valve body, which is coupled to the plunger
104
, is unstable (this state will be described in the preferred embodiment section). This fluctuates the electromagnetic force as the distance between the plunger
104
and the stator
103
changes. The structure shown in
FIG. 8
suppresses thus fluctuation. The structure also increases the maximum level of the electromagnetic force applied to the valve body by the electromagnetic actuator
101
.
For example, suppose the stator
103
has a triangular cross-section and the plunger
104
is formed as a cone the shape of which corresponds to the stator
103
as schematically shown in FIG.
9
(
a
). This structure suppresses changes of the shortest distance between the stator
103
and the plunger
104
when the plunger
104
is moved.
Therefore, as shown in the graph of FIG.
9
(
b
), the electromagnetic force applied to the valve body by the actuator
101
is relatively gradually changed by changes of the position of the plunger
104
. This stabilizes the position of the valve body when the coil
105
receives a low current. The shapes of the plunger
104
and the stator
103
in
FIG. 8
are determined to obtain the effect of the structure shown in FIG.
9
(
a
). Specifically, the frustum portion
112
(having the inclined surface
111
) and the recess
109
(having the inclined surface
108
a
) face each other.
Also, suppose the entire lower surface of the stator
103
and the entire upper surface of the plunger
104
are flat as schematically shown in FIG.
10
(
a
). In this structure, the magnetic flux is increased when the plunger
104
approaches the stator
103
.
Therefore, as shown in the graph of FIG.
10
(
b
), the maximum value of the electromagnetic force applied to the valve body by the actuator
101
is increased. This permits a target pressure level, which is used as a reference in the operation of the pressure sensing mechanism, to be set to a higher level. In other words, a certain level of the target pressure can be set by a smaller actuator
101
. This reduces the size of the control valve. The shapes of the plunger
104
and the stator
103
in
FIG. 8
are determined to obtain the effect of the structure shown in FIG.
10
(
a
). Specifically, the frustum portion
112
having the flat distal surface
110
and the recess
109
having the flat inner surface
107
face each other.
However, in the prior art, the sizes and the shapes of the recess
109
of the stator
103
and the frustum portion
112
of the plunger
104
are not optimized. Thus, a sufficient effect cannot be obtained.
SUMMARY OF THE INVENTION
Accordingly, it is an objective of the present invention to provide a control valve for a variable displacement compressor that optimizes the shapes of parts of a plunger and a stator that face each other.
To achieve the foregoing and other objectives and in accordance with the purpose of the present invention, a control valve for changing the displacement of a compressor is provided. The control valve includes an accommodation cylinder, a coil located about the accommodation cylinder, a stator located in the accommodation cylinder, a plunger located in the accommodation cylinder, and a valve body coupled to the plunger. When electric current is supplied to the coil, electromagnetic force is generated between the stator and the plunger and the plunger moves relative to the stator in the accommodation cylinder, accordingly. When the plunger moves, the valve body moves accordingly and adjusts the opening degree of a valve hole. A flat surface and a peripheral wall surrounding the flat surface are formed in an end of one of the plunger and the stator that faces the other one of the plunger and the stator. The peripheral wall has a tapered cross-section with an inclined inner surface. The inclined inner surface and the flat surface define a recess. A frustum portion is formed in an end of the other one of the plunger and the stator that faces the recess. The frustum portion includes a flat distal surface and an annular inclined surface. The taper angle of the peripheral wall is equal to or less than twenty degrees. The diameter of the flat distal surface of the frustum portion is equal to or greater than eighty percent of the largest diameter of the annular inclined surface.
The present invention may also be applied to a compressor used in a refrigerant circuit of an air conditioner. The compressor includes a control chamber, a bleed passage, a supply passage, and a control valve. The compressor displacement is changed by adjusting the pressure in the control chamber. The bleed passage connects the control chamber to a suction pressure zone of the refrigerant circuit. The supply passage connects a discharge pressure zone of the refrigerant circuit to the control chamber. The control valve changes the displacement of a compressor. The control valve includes an accommodation cylinder, a coil located about the accommodation cylinder, a stator located in the accommodation cylinder, a plunger located in the accommodation cylinder, and a valve body coupled to the plunger. When electric current is supplied to the coil, electromagnetic force is generated between the stator and the plunger and the plunger moves relative to the stator in the accommodation cylinder, accordingly. When the plunger moves, the valve body moves accordingly and adjusts the opening degree of a valve hole. A flat surface and a peripheral wall surrounding the flat surface are formed in an end of one of the plunger and the stator that faces the other one of the plunger and the stator. The peripheral wall has a tapered cross-section with an inclined inner surface. The inclined inner surface and the flat surface define a recess. A frustum portion is formed
Adaniya Taku
Fukasaku Hiroshi
Hayashi Hirohito
Iwata Kitaru
Matsubara Ryo
Kabushiki Kaisha Toyota Jidoshokki
Morgan & Finnegan , LLP
Wayner William
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