Pumps – Motor driven – Electric or magnetic motor
Reexamination Certificate
2001-05-22
2002-12-31
Freay, Charles G. (Department: 3746)
Pumps
Motor driven
Electric or magnetic motor
C417S419000, C417S416000, C417S488000
Reexamination Certificate
active
06499972
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a linear compressor and more particularly to a moving magnet type of linear compressor that is of a high efficiency and used for a cooling machine. The present invention is concerned with an improved linear compressor so constructed as to ensure that the linear compressor effectively increases a density of magnetic flux passing through an electromagnet unit to impart an increased thrust force to a piston forming part of the linear compressor.
2. Description of the Related Art
There have so far been proposed a wide variety of prior-art linear compressors one of which is exemplified and shown in FIG.
8
. The prior-art linear compressor
10
thus proposed comprises a fixed member
11
formed with a hermetically sealed compression chamber to receive a working fluid therein, a piston rod
12
slidably movably supported by the fixed member
11
and connected to the piston serving to compress the working fluid in the compression chamber, a magnet unit
13
including a plurality of yoke portions
14
and
15
accommodated in the piston rod
12
and a permanent magnet
16
in the form of a rectangular shape in cross-section and supported by the yoke portions
14
and
15
to be positioned in the center portion of the piston rod
12
and an electromagnetic unit
17
including a peripheral portion
18
, a plurality of yoke portions
19
and
20
radially inwardly extending from the peripheral portion
18
and a plurality of magnetic coils
21
and
22
each wound around each of the yoke portions
19
and
20
. The permanent magnet
16
of the magnet unit
13
is arranged in face-to-face relationship with the yoke portions
19
and
20
of the electromagnet units
17
in the longitudinal direction of the piston rod
12
.
The prior-art linear compressor thus constructed encounters such a problem as failing to effectively increase the density of magnetic flux passing through the yoke portions
19
and
20
of the electromagnet units
17
by the reason that the permanent magnet
16
of the magnet unit
13
is embedded in the center portion of the piston rod
12
as shown in FIG.
8
. The failure in effective increase of the density of magnetic flux makes it almost impossible to impart an increased thrust force to the piston forming part of the linear compressor.
SUMMARY OF THE INVENTION
It is therefore a primary object of the present invention to provide a linear compressor that can effectively increase the density of magnetic flux passing through the electromagnet unit to impart an increased thrust force to the piston forming part of the linear compressor.
It is another object of the present invention to provide a linear compressor that can increase the operating efficiency.
It is a further object of the present invention to provide a linear compressor that can be reduced in size.
It is a still further object of the present invention to provide a linear compressor that can reduce the electric consumption.
It is a yet still further object of the present invention to provide a linear compressor that can reduce the electric heat value.
In accordance with a first aspect of the present invention, there is provided a linear compressor, comprising: a retaining member; a fixed member supported by the retaining member and formed with a hermetically sealed compression chamber to receive a working fluid therein, the fixed member having a longitudinally central portion formed with a inlet-outlet port having the working fluid introduced therein and discharged therefrom; a pair of pistons axially movably received in the compression chamber to assume respective compression positions where the working fluid is compressed in and discharged out of the compression chamber through the inlet-outlet port and respective retraction positions where the working fluid is expanded and introduced in the compression chamber through the inlet-outlet port; a pair of piston rods each having an outer peripheral portion and slidably movably supported by the fixed member, the piston rods respectively connected to the pistons to have the pistons axially move in the compression chamber, each of the piston rods made of a ferromagnetic material; a plurality of magnet units mounted on each of the outer peripheral portions of the piston rods, each of the magnet units having a plurality of magnet segments each made of a permanent magnet and circumferentially arranged with neighboring two magnet segments different in magnetic pole; a plurality of electromagnet units supported by the retaining member to be axially spaced apart from each other in predetermined relationship with the magnet units, respectively; and resilient means for resiliently urging the piston rods to cause the piston rods to assume respective neutral positions between the compression positions and the retraction positions.
Each of the electromagnet units may include a peripheral portion, a plurality of yoke portions radially inwardly extending from the peripheral portion and integrally formed with the peripheral portion, the yoke portions being circumferentially equally spaced apart from each other, and a plurality of magnetic coils each wound around each of the yoke portions.
Each of the yoke portions of electromagnet units may have an axial length substantially equal to that of each of the magnet units.
The magnet units may include neighboring two magnet units having respective center planes each perpendicular to the center axis of each of the piston rods, and the yoke portions of the electromagnet units have respective center planes each perpendicular to the center axis of each of the piston rods, each of the center planes of the yoke portions of the electromagnet units being positioned between the center planes of the neighboring two magnet units when the piston rods assume their respective neutral positions.
Each of the yoke portions of the electromagnet units may be constituted by a plurality of piled plates each made of a ferromagnetic material and having a plane extending along the center axis of each of the piston rods.
The linear compressor may further comprise a pair of positioning members each mounted on the fixed member with respect to the magnet units, each of the positioning members formed with a plurality of annular grooves axially spaced apart from each other, each of the annular grooves functioning to facilitate positioning of each of the yoke portions of the electromagnet units with the magnet units.
Each of the yoke portions of the electromagnet units may have a radially outer end portion made of a ferromagnetic material and a radially inner end portion made of a ferromagnetic material having a saturated density of magnetic flux higher than that of the ferromagnetic material of each of the radially outer end portions of the yoke portions to ensure that the density of magnetic flux of each of the yoke portions of the electromagnet units is more increased than that of each of the yoke portions of the electromagnet units which are made of the same ferromagnetic materials.
The ferromagnetic material of each of the radially inner end portions may be made of Permendur.
Each of the magnet segments of the magnet units may be constituted by a plurality of piled plates each made of a permanent magnet and having a plane extending perpendicular to the center axis of each of the piston rods.
The resilient means may include a plurality of resilient members disposed along each of the piston rods, each of the resilient members constituted by a plurality of leaf springs each having a plane extending perpendicular to the center axis of each of the piston rods, each of the resilient members having a inner end portion fixedly connected to each of the piston rods and a outer end portion fixedly connected to the fixed member to ensure that each of the piston rods is resiliently urged and restored to the respective neutral positions when each of the piston rods is axially moved to the compression positions and the retraction positions.
The fixed member may have an inner peripheral
Hagiwara Yasumasa
Takizawa Keiji
Yatsuzuka Shinichi
Aitken Richard L.
Cryodevice Inc.
Freay Charles G.
Gray Michael K.
Venable
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