Pumps – Condition responsive control of pump drive motor – By control of electric or magnetic drive motor
Reexamination Certificate
2001-08-29
2003-04-01
Freay, Charles G. (Department: 3746)
Pumps
Condition responsive control of pump drive motor
By control of electric or magnetic drive motor
C417S415000, C417S417000, C310S012060, C318S135000
Reexamination Certificate
active
06540485
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a linear compressor available for a pulse tube type of cooling machine, and more particularly to a linear compressor equipped with a linear motor to drive a single piston unit forming part of the linear compressor to have the single piston unit perform a reciprocally linear motion. The present invention is concerned with an improved linear compressor so constructed as to ensure that the linear compressor effectively prevents vibrations thereof from being caused by a reciprocally linear motion of the single piston unit.
2. Description of the Related Art
Up until now, there have been proposed a wide variety of conventional linear compressors each equipped with a pair of linear motors to drive a pair of piston units forming part of the linear compressor to have each of the piston units perform a reciprocally linear motion.
The conventional linear compressors of this type have so far been available for such a pulse tube type of cooling machine for cooling a superconducting material used for an electronic component. The conventional linear compressor is operatively connected to the pulse tube type of cooling machine to have the pulse tube type of cooling machine supplied with a working fluid periodically compressed and decompressed by the conventional linear compressor.
One typical example of the conventional linear compressors is exemplified and shown in FIG.
8
. The conventional linear compressor
200
thus proposed comprises a casing member
201
formed with a casing chamber
202
, and a fixed member
203
accommodated in the casing chamber
202
of the casing member
201
and fixedly supported by the casing member
201
. The fixed member
203
is formed with a hermetically sealed compression chamber
204
to receive a working fluid therein and an inlet-outlet port
205
having the working fluid introduced therein and discharged therefrom.
The conventional linear compressor
200
further comprises a connecting pipe
206
formed with a passageway therein and connected at one end to the fixed member
203
with the passageway held in communication with the inlet-outlet port
205
of the fixed member
203
. The connecting pipe
206
is connected at the other end to the pulse tube type of cooling machine to have the working fluid fed to the pulse tube type of cooling machine through the passageway.
The conventional linear compressor
200
further comprises a pair of piston units
207
and
208
each including a piston head
207
a
and
208
a
axially movably received in the compression chamber
204
of the fixed member
203
and a piston rod
207
b
and
208
b
axially movably supported by the fixed member
203
. The piston rods
207
b
and
208
b
are respectively connected to the piston heads
207
a
and
208
a
to have each of the piston heads
207
a
and
208
a
axially move in the compression chamber
204
of the fixed member
203
. Each of the piston units
207
and
208
is axially movable with respect to the fixed member
203
under a reciprocally linear motion. The piston units
207
and
208
are located in symmetrical relationship with each other with respect to the compression chamber
204
. The conventional linear compressor thus constructed is generally called “opposed piston type of linear compressor”.
The conventional linear compressor
200
further comprises a plurality of resilient members
209
to
212
each intervening between the fixed member
203
and each of the piston units
207
and
208
to have the fixed member
203
and each of the piston units
207
and
208
resiliently connected with each other, and a pair of linear motors
213
and
214
designed to drive the piston units
207
and
208
, respectively. Each of the linear motors
213
and
214
has an electromagnet unit
213
a
and
214
a
respectively mounted on the piston rods
207
b
and
208
b
, and a permanent magnet unit
213
b
and
214
b
supported by the fixed member
203
to have each of the piston units
207
and
208
perform the reciprocally linear motion. The linear motor thus constructed is generally called “moving coil type of linear motor”.
The conventional linear compressor thus constructed, i.e., the opposed piston type of linear compressor, however, encounters the problem that the conventional linear compressor cannot be reduced in size, resulting from the fact that the large space of the conventional linear compressor is occupied by the pair of piston units located in symmetrical relationship with each other. This type of linear compressor further encounters the a problem that the conventional linear compressor is complicated in construction and thus expensive in production cost, resulting from the fact that the conventional linear compressor comprises the pair of piston units.
While it has been described in the above that the conventional linear compressor comprises a pair of piston units, the pair of piston units may be replaced by a single piston unit in order to have the conventional linear compressor reduced in size. The conventional linear compressor thus constructed is generally called “single piston type of linear compressor”. This type of linear compressor, however, encounters the problem that the reciprocally linear motion of the single piston unit causes detrimental vibrations bringing mechanical failure brought to the conventional linear compressor.
Though the conventional linear compressor has been described in the above as being equipped with at least one of the moving coil type of linear motors, each of the moving coil type of linear motors may be replaced by a linear motor having a permanent magnet unit mounted on the piston rod and an electromagnet unit supported by the fixed member. The linear motor thus constructed is generally called “moving magnet type of linear motor”. This type of linear motor is disclosed in the Japanese Patent Laid-Open Publication No. 6-189518. The conventional linear compressor equipped with at least one of the moving magnet type of linear motors, however, encounters the same problems as the conventional linear compressor equipped with the moving coil type of linear motor described in the above.
SUMMARY OF THE INVENTION
It is therefore a primary object of the present invention to provide a linear compressor that can effectively prevent the vibrations of the fixed member from being caused by the reciprocally linear motion of the single piston unit forming part of the linear compressor.
It is another object of the present invention to provide a linear compressor that can be reduced in size.
It is further object of the present invention to provide a linear compressor that can be simple in construction and thus inexpensive in production cost.
In accordance with one aspect of the present invention, there is provided a linear compressor, comprising: a fixed member formed with a hermetically sealed compression chamber to receive a working fluid therein; a movable member axially movably received in the compression chamber of the fixed member, the movable member axially movably supported by the fixed member to have the movable member axially move in the compression chamber of the fixed member; a plurality of resilient members each intervening between the fixed member and the movable member to have the fixed member and the movable member resiliently connected with each other, the movable member being axially movable with respect to the fixed member under a reciprocally linear motion to assume three different positions consisting of a compression position in which the working fluid is compressed by the movable member, a decompression position in which the working fluid is decompressed by the movable member, and a neutral position in which the movable member is resiliently retained by the resilient member s with respect to the fixed member under no influence of the working fluid in the compression chamber of the fixed member, driving means for driving the movable member at a predetermined driving frequency to have the movable member perform the reciprocally linear
Hagiwara Yasumasa
Murase Takashi
Nara Kenichi
Aitken Richard L.
Belena John F
Cryodevice Inc.
Freay Charles G.
Venable
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