Valves and valve actuation – Limit stop
Reexamination Certificate
2000-01-21
2001-04-24
Lee, Kevin (Department: 3754)
Valves and valve actuation
Limit stop
C251S903000, C251S129110
Reexamination Certificate
active
06220571
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an electronic expansion valve for a cooling cycle and, more particularly, to an electronic expansion valve for a cooling cycle which can precisely control an amount of coolant to be exhausted by controlling an opening of an orifice.
BACKGROUND OF THE INVENTION
Generally, a cooling cycle used in refrigerators or air conditioners is designed to reduce the temperature of the ambient air by compressing a coolant gas using a compressor, liquefying the compressed coolant gas using a condenser, reducing the pressure of the liquified coolant through an expansion valve, and evaporating the coolant in an evaporator. Particularly, in recent years, the cooling temperature has been automatically controlled by automatically controlling the RPMs of a compressor according to a target temperature using a frequency converting process such as an inverter control method.
Japanese unexamined patent No. S60-196477 discloses an electronic expansion valve which can actively adjust an amount of coolant according to a variation of the RPMs of a compressor through an inverter controller. The expansion valve will be described hereinbelow with reference to FIG.
1
.
As shown in the drawing, the electronic expansion valve comprises a valve part V and a stepping motor part M.
The valve part V comprises a valve housing
1
provided at its side with a coolant intake hole
1
a
on which a coolant tube A connected to a condenser (not shown) is coupled and at its bottom or distal end with a coolant exhaust hole
1
b
on which a coolant tube B connected to an evaporator(not shown) is coupled. A valve seat
2
a
is disposed on a partition wall
2
between the intake and exhaust holes
1
a
and
1
b
. A needle valve
3
is disposed to contact or move away from the valve seat
2
a
. That is, the needle valve
3
is slidable in an axial direction and supported within a male screw tube
4
screw-coupled on the valve housing
1
.
A sealed case
6
defining the stepping motor part M is disposed on a top or proximal end of the valve housing
1
. A stator
8
with a coil
7
is disposed around the case
6
and a rotor
9
is disposed inside the case
6
while being rotatably supported by the mail screw tube
4
.
The rotor
9
comprises a permanent magnet
11
embedded around a supporting case
10
. A female screw tube
12
is fixed on a lower-inner wall of the supporting case
10
and screw-coupled to the male screw tube
4
so that the rotor
9
is rotatable while being slidable in an axial direction.
A connecting wall
10
b
is defined at a middle-inner portion of the supporting case
10
and is provided with a penetrating hole
10
c
in which a smaller diameter portion
3
a
of the needle valve
3
is fixedly inserted. A coil spring
14
is disposed around the smaller diameter portion
3
a
of the needle valve
3
, while being abutted to the connecting wall
10
b.
A center rod
15
is fixed between the rotor
9
and the case
6
, and a spiral guide ring
16
is disposed around the center rod
15
. A slider
17
is coupled to the spiral guide ring
16
such that it can rotate while moving in a vertical direction along the spiral guide ring
16
. An outer end of the slider
17
is hooked on a support rod
18
located on the rotor
9
.
In operation, when electric power is applied to the coil
7
of the stator
8
, the rotor
9
rotates to ascend and descend the needle valve
3
and the slider
17
along the guide ring
16
. At this point, the rotation of the rotor
9
and the movement of the needle valve
3
are stopped at positions where the slider
17
contacts upper and lower ends
16
a
and
16
b
of the guide ring
16
. That is, by moving the needle valve
3
in the vertical direction, an amount of coolant passing through the valve housing
1
can be properly adjusted, thereby adjusting the pressure.
However, in the above described electronic expansion valve, since the rotor
9
is disposed inside the case
6
and the stator
8
is disposed outside the case
6
, an air gap between the coil
7
of the stator
8
and the permanent magnet
11
of the rotor
9
is increased. Accordingly, to precisely generate the torque required for the expansion valve, a relatively large or expensive magnet, e.g. a rare-earth magnet, should be used, increasing the size and manufacturing costs of the expansion valve.
Furthermore, to restrict the rotation range of the rotor
9
and a vertical movement range of the needle valve
3
, since the center rod
15
, the guide ring
16
, the slider
17
and the support rod
18
should be disposed on the top of the rotor
9
disposed inside the case
6
, the longitudinal length of the expansion valve is increased.
An initial position of the needle valve
3
is set by screw-coupling the male screw tube
4
to the valve housing
1
, then the female screw tube
12
of the rotor
9
to the male screw tube
4
. Generally, the initial position of the needle valve
3
is set at a position where the needle valve
3
closely contacts the valve seat
2
a
to completely close the fluid path. In this initial position, the slider
17
is located at the lower end
16
b
of the guide ring
16
, the slider
17
should then be secured on the support rod
18
located on the rotor
9
. However, since there is a limitation in precisely moving the screw, it is very difficult to accurately set the initial position of the needle valve
3
by screw-coupling the valve housing
1
to the male screw tube
4
and the female screw tube
12
to the male screw tube
4
. Furthermore, when assembling the expansion valve, there is the possibility that the slider
17
is not exactly secured on the support rod
18
even after the initial position of the needle valve
3
is set.
If the expansion valve is operated in a state where the slider
17
is not exactly secured on the support rod
18
, although the needle valve
3
starts its vertical movement from its initial position by the rotation of the rotor
9
, the slider
17
stays at the lower end
16
b
of the guide ring
16
until it contacts the support rod
18
. That is, the distance of the vertical movement of the needle valve
3
is defined by the slider
17
which moves between the upper and lower ends
16
a
and
16
b
of the guide ring
16
. At this point, since the slider
17
starts its vertical movement after the support rod
18
contacts the slider
17
, a target distance of the vertical movement of the needle valve
3
may not be obtained, making it difficult to precisely adjust an amount of coolant to be exhausted.
BRIEF SUMMARY OF THE INVENTION
Therefore, the present invention has been made in an effort to solve the above described problems.
It is an objective of the present invention to provide an electronic expansion valve for a cooling cycle which can be reduced in size by employing a stepping motor which is designed to have a smaller gap between a coil of a stator and a permanent magnet of a rotor.
It is another objective of the present invention to provide an electronic expansion valve for a cooling cycle which can be easily assembled by simplifying a coupling structure of a stepping motor and a needle valve.
It is still another objective of the present invention to provide an electronic expansion valve which can precisely adjust an amount of coolant to be exhausted by precisely adjusting an opening/closing timing of an orifice by exactly setting an initial position of a needle valve.
To achieve the above objectives, a first embodiment of the present invention provides an electronic expansion valve for a cooling cycle comprising: a valve housing having intake and exhaust holes and an orifice formed on the exhaust hole; a case disposed on the valve housing; a motor disposed within the case, the motor having a rotating drive shaft extending inside the valve housing; a guide tube disposed inside the valve housing, the guide tube being vertically or axially movable by rotation of the drive shaft; a needle valve for adjusting an opening of the orifice, the needle valve being mounted on the guide tube; and means
Kim Kwang-Il
Kim Wan-Yong
Park Lae-soo
Woo Gi-myung
Larson & Taylor PLC
Lee Kevin
Samsung Electronics Co,. Ltd.
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