Fluid handling – Processes – Cleaning – repairing – or assembling
Reexamination Certificate
2002-08-19
2004-08-03
Look, Edward K. (Department: 3754)
Fluid handling
Processes
Cleaning, repairing, or assembling
C137S315090, C137S315170
Reexamination Certificate
active
06769445
ABSTRACT:
The present application is based on Japanese Patent Application No. 2001-248919, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a motor-operated expansion valve, and more particularly to a mechanism for avoiding welding heat applied to a valve element.
Generally, a motor-operated expansion valve consists of a main body making up a valve mechanism and a housing for hermetically sealing the valve mechanism. For example, in a three-way valve in a motor-operated expansion valve
100
shown in
FIG. 13
(disclosed in Japanese Patent Publication No. JP-A-2000-310348), the opening and closing of two outflow pipes
106
a
and
106
b
are controlled by a single valve element
102
provided at a distal end of a rotor
101
. Therefore, to ensure that the heat from a tungsten inert gas (TIG) welding position
104
a
for gastightly sealing a housing
104
and a main body
105
will not adversely affect a sliding contact surface
102
a
of the valve element
102
, the valve element
102
is disposed in a central portion of the main body
105
which is the farthest from the welding position
104
a
at an outer periphery of the housing. Furthermore, to make it difficult for the welding heat from welds
105
b
at the outflow pipes
106
a
and
106
b
to be transmitted to the resin-made valve element
102
, a thick machined part having a large thermal capacity is used for a metallic valve seat plate portion.
In addition, communicating holes
107
a
and
107
b
communicating with the two outflow pipes
106
a
and
106
b
are formed in a valve seat
105
a
in such a manner as to be open to a valve chamber
109
, and are selectively caused to communicate with an inlet port
110
through the valve element
102
inside the valve chamber
109
. As shown in
FIGS. 14A
to
14
D, a rib
103
has a shape which surrounds a crescent recess
111
, and the single valve element
102
changes over the partition of the communicating holes
107
a
and
107
b
in four modes in correspondence with the angle of rotation of the rotating shaft
101
which is displaced in response to an electrical signal sent from a stator coil
112
. Namely,
FIG. 14A
shows a state in which the communicating hole
107
a
is closed and the communicating hole
107
b
is open;
FIG. 14B
shows a state in which both the communicating hole
107
a
and the communicating hole
107
b
are closed;
FIG. 14C
shows a state in which the communicating hole
107
a
is open and the communicating hole
107
b
is closed; and
FIG. 14D
shows a state in which both the communicating hole
107
a
and the communicating hole
107
b
are open.
In the mechanism shown in
FIG. 13
, in which the opening and closing of the two outflow pipes
106
a
and
106
b
are thus controlled by the single valve element
102
, firstly, the distance between the two outflow pipes
106
a
and
106
b
is short, and the working of parts and the blazing and welding operation are difficult. Secondly, since the changeover of the four modes (open/close, close/open, open/open, and close/close) shown in
FIGS. 14A through 14D
is effected while the single valve element
102
is turned by one revolution, there is no leeway in the space, which makes it impossible to construct a multi-way valve of four or more ways.
Thirdly, it is impossible to independently change the flowrate control pattern of the two outflow pipes
106
a
and
106
b
, and the pattern becomes a simple one comprising only the changeover between open and close. Fourthly, since the resin-made valve element
102
is brought into pressure contact with the valve seat
105
a
by a spring
108
, if the temperature of the metal becomes high, irregularities occur on the resin surface, and the surface roughness of the resin becomes destroyed due to heat, resulting in the occurrence of leakage in the fully closed state. Accordingly, to avoid the welding heat, it is necessary to finish TIG welding in a short time and effect rapid cooling after welding so as to minimize the effect on the resin-made valve element. For this reason, the operation requires expert skill, and uncertainty remains in the stability of quality and in reliability.
SUMMARY OF THE INVENTION
The object of the invention is to provide a valve drive device in which the above problem is overcome in a suitable manner.
To overcome the problem, there has been conceived and embodied a three-way valve
200
a
of a motor-operated expansion valve
200
having the construction shown in FIG.
15
. Valve elements
202
a
and
202
b
are separately provided for openings
207
a
and
207
b
of outflow pipes
206
a
and
206
b
which are selectively made to communicate with an inflow pipe
210
in a valve chamber
209
, and the valve elements
202
a
and
202
b
are rotated in response to inputs of electrical signals from a stator coil
212
so as to control the opening and closing of the openings
207
a
and
207
b.
However, since the positions of the valve elements
202
a
and
202
b
geared with and disposed radially from a pinion
203
formed integrally with a rotor
201
with respect to the two outflow pipes
206
a
and
206
b
are close to an outer peripheral portion
204
a
which is subject to heating by TIG welding for gastightly sealing a housing
204
and a main-body base plate
205
, the resin-made valve elements
202
a
and
202
b
which are held in pressure contact with a valve seat
205
a
by leaf springs
208
are directly exposed to welding heat and become deteriorated or deformed, possibly resulting in faulty functioning.
In addition, consideration must also be given to the fact that the valve elements
202
a
and
202
b
are similarly affected by welding heat from welds
205
b
for gastightly connecting the outflow pipes
206
a
and
206
b
to the main-body base plate
205
. To avoid the effect of such welding heat on the valve elements
202
a
and
202
b
, it is necessary to increase the thermal capacity by enlarging the circumference of the metallic main-body base plate
205
including the valve seat or by increasing the thickness thereof. Hence, there are problems in terms of cost and miniaturization.
In the present invention, to solve these problems, an air heat-insulation layer is formed by holding the valve element in an initial period of assembly and thereby providing a gap between the valve element and the valve seat.
In accordance with the invention, there is provided a valve drive device having a plurality of openings for communicating with an inflow pipe and an outflow pipe, said valve drive device comprising:
a valve element for opening and closing said openings;
a driving member for driving said valve element;
a rotation transmitting member for transmitting rotation from said driving member to said valve element;
a valve seat plate in which said openings are formed and on which said valve element is slid in pressure contact therewith so as to open and close said openings; and
a housing for gastightly sealing said valve seat plate and said valve element together with said driving member and said rotation transmitting member so as to form a hermetically sealed space; and
a holding device provided for tentatively retaining said valve element at a spaced-apart position spaced apart from said valve seat plate;
wherein said valve element is retained at the space-apart position when said valve seat plate and said housing are welded together.
By the above construction, an air layer extremely excelling in heat insulation is formed between the valve element and the valve seat plate, so that the valve element can be protected from welding heat, and the deformation of a sliding contact surface is prevented. Therefore, it is possible to satisfactorily maintain the sealing characteristic of the valve element.
In the invention, the holding device causes the valve element to be spaced apart from the valve seat plate in opposition to an urging device for bringing the valve element into pressure contact with the valve seat plate, the retention by the holding device is canceled aft
Hashimoto Katsuo
Ozawa Shigeru
Fristoe Jr. John K.
Kabushiki Kaisha Sankyo Seiki Seisakusho
Look Edward K.
Sughrue & Mion, PLLC
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