Description

LINEAR COMPRESSOR AND THE METHOD FOR MANUFACTURING THE SAME

Technical Field

[1] The present invention relates to a linear compressor, and more particularly, to a linear motor reduing an eddy current loss by preventing a magnetic flux from being transferred from an inner stator to a cylinder, and a linear compressor using the same. Background Art

[2] FTG. 1 is a view illustrating a portion of a conventional linear compressor.

[3] The conventional linear compressor includes a cylinder 2, a frame 3, a piston 4, a linear motor 10 and a motor cover 18. The linear motor 10 includes an inner stator 12, an outer stator 14 and a permanent magnet 16. The linear motor 10 reciprocates the piston 4 by a mutual electromagnetic force. The piston 4 is reciprocated inside the cylinder 2 to compress a fluid.

[4] One end of the cylinder 2 is installed on the frame 3. The inner stator 12 is positioned on the outer circumference of the cylinder 2. The outer stator 14 is positioned between the frame 3 and the motor cover 18 with a predetermined interval from an outer circumferential surface of the inner stator 12 in a radius direction. The frame 3 and the motor cover 18 are fixed to each other by means of bolts.

[5] Here, the inner stator 12 is formed by stacking a plurality of inner cores in a circumference direction. In addition, the permanent magnet 16 is installed between the inner stator 12 and the outer stator 14 with a predetermined interval in a radius direction. One end of the permanent magnet 16 is connected to one end of the piston 4 to move the piston 4.

[6] FTG. 2 is a schematic view illustrating paths of a magnetic flux in the conventional linear compressor. In the conventional linear compressor, as the inner stator 12, the outer stator 14, the cylinder 2, the frame 3 and the piston 4 are made of a magnetic material, a magnetic flux flowing in the inner stator 12 spreads to the cylinder 2, the frame 3 and the piston 4. Here, an eddy current loss occurs in the linear motor 10.

[7] For example, an eddy current is generated when a magnetic field is applied to a conductor plate at a right angle and increased thereon. When the magnetic field increases, an eddy current turning to the left from a magnetic field direction is generated on the conductor plate to interrupt the increase of the magnetic field. For another example, an eddy current is generated when a magnet moves on a conductor

plate. A magnetic field of the eddy current interrupts the movement of the magnet. An eddy current loss means a power loss occurring when an eddy current generates a Joule heat due to a resistance of a conductor.

[8] Referring to FIG. 2, in the conventional linear compressor, as the cylinder 2, the frame 3 and the piston 4 are all made of a magnetic material, the magnetic flux not only flows in the linear motor 10, namely, the inner stator 12, the permanent magnet 16 and the outer stator 14 along path A, but also flows into the cylinder 2 and the piston 4 along path B. Therefore, an eddy current loss occurs.

[9] In order to prevent the eddy current loss, Korean Laid-Open Publication

2004-0110057 suggests a structure wherein a fixing member of a resin material is formed inside an inner stator, although it has a different resonance system. Referring to FIG. 3, a fixing member 233 for fixing steel sheets 231 to each other is formed in an inner stator 23 so that the steel sheets 231 coupled temporarily in a cylindrical shape through embossings 232 can maintain the cylindrical shape. The fixing member 233 surrounds and fixes the insides and the top and bottom ends of the plurality of steel sheets 231 stacked in a circumference direction. The plurality of steel sheets 231 stacked in the circumference direction are insert-molded to maintain the cylindrical arrangement. The fixing member 233 is made of resin such as plastic that is a nonconductor of electricity and that is easily molten. Accordingly, the steel sheets 231 can be continuously insulated from each other and stacked in the circumference direction by the fixing member 233. It is thus possible to prevent an eddy current and a resulting eddy current loss in the inner stator 23.

[10] In this configuration, as the resin material prevents a magnetic flux from being transferred to the cylinder 2 and the piston 4, the eddy current loss can be suppressed. However, since the inner stator 12 and the cylinder 2 are in a relatively high temperature environment of about 100 to 150 ⁰ C, the fixing member of the resin material may be deformed. Such deformation of the fixing member causes variations of an inner diameter and an outer diameter of the inner stator 12. Therefore, an interval between the inner stator 12 and the outer stator 14 is changed, so that noise and vibration may occur. In addition, the interval change between the inner stator 12 and the outer stator 14 results in a variation of an electromagnetic force applied to the permanent magnet 16. As a result, the operation reliability of the linear compressor is degraded. Disclosure of Invention

Technical Problem

[11] An object of the present invention is to provide a linear compressor.

[12] Another object of the present invention is to provide a linear compressor reducing an eddy current loss.

[13] A further object of the present invention is to provide a linear compressor reducing an eddy current loss by preventing a magnetic flux flowing in an inner stator from flowing to a cylinder.

[14] A still further object of the present invention is to provide a linear compressor and a linear motor reducing an eddy current loss by reducing a volume of an inner stator.

[15] A still further object of the present invention is to provide a linear compressor reducing an eddy current loss by forming a cylinder with a non-magnetic material.

[16] A still further object of the present invention is to provide a linear compressor reducing an eddy current loss by manufacturing an inner stator, a frame and a cylinder in a single body, and defining a non-magnetic region between the inner stator and the cylinder.

[17] A still further object of the present invention is to provide a linear compressor preventing a magnetic flux from flowing from an inner stator to a cylinder by means of an interval member made of a non-magnetic metal of a metal material, so that an interval between an inner stator and an outer stator can be maintained and that the operation reliability of the linear compressor can be improved. Technical Solution

[18] According to an aspect of the present invention, there is provided a linear compressor, including: a cylinder; a piston reciprocated inside the cylinder to compress refrigerant; a linear motor positioned along an outer circumferential surface of the cylinder, and provided with an inner stator at least partially made of a magnetic material to drive the piston; and an interval member made of a non-magnetic metal of a metal material and positioned inside the inner stator to prevent a magnetic flux from being transferred from the inner stator to the cylinder. In this configuration, as the interval member made of the non-magnetic metal of the metal material prevents the magnetic flux from being transferred from the inner stator to the cylinder, an interval between the inner stator and an outer stator is not changed due to the deformation of the interval member.

[19] According to another aspect of the present invention, the interval member made of the non-magnetic metal is formed integrally with the inner stator.

[20] According to a further aspect of the present invention, the interval member made of the non-magnetic metal is insert-molede by using an aluminum material and formed integrally with the inner stator.

[21] According to a still further aspect of the present invention, the interval member made of the non-magnetic metal is powder-injection-molded by using any one of austenite group stainless steel and non-magnetic cast iron, and sintered.

[22] According to a still further aspect of the present invention, the linear compressor further includes a fixing member for fixing the interval member made of the nonmagnetic metal to the cylinder.

[23] According to a still further aspect of the present invention, the fixing member pushes one end of the interval member to support the interval member, and the cylinder includes a groove so that the fixing member can be inserted thereinto.

[24] According to a still further aspect of the present invention, the linear compressor further includes a frame positioned at one side of the cylinder to fix the linear motor, wherein at least one of the cylinder and the frame is made of a non-magnetic metal material.

[25] According to a still further aspect of the present invention, the interval member made of the non-magnetic metal is formed integrally with the at least one made of the non-magnetic metal material of the cylinder and the frame, made of non-magnetic metal material of the cylinder and the frame.

[26] According to a still further aspect of the present invention, the linear compressor further includes a frame positioned at one side of the cylinder to fix the linear motor, wherein the interval member made of the non-magnetic metal is formed integrally with any one of the cylinder, the inner stator and the frame.

[27] According to a still further aspect of the present invention, two or more of the interval member made of the non-magnetic metal, the cylinder, the inner stator and the frame are formed integrally.

[28] In addition, according to an aspect of the present invention, there is provided a linear compressor, including: a cylinder; a piston reciprocated inside the cylinder to compress refrigerant; and a linear motor positioned along an outer circumferential surface of the cylinder, and provided with an inner stator at least partially made of a magnetic material to drive the piston, wherein the inner stator includes a cylindrical inner ring made of a non-magnetic metal material, and an inner core made of a magnetic metal material and stacked on an outer circumferential surface of the inner ring in a circumference direction.

[29] According to another aspect of the present invention, the linear compressor further includes a restriction means positioned between the inner ring and the inner core to restrict relative motions of the inner ring and the inner core.

[30] According to a further aspect of the present invention, the inner ring is formed integrally with the cylinder.

[31] According to a still further aspect of the present invention, the linear compressor further includes a frame positioned at one side of the cylinder to fix the linear motor, wherein the inner ring is formed integrally with the frame.

[32] According to a still further aspect of the present invention, the cylinder is formed integrally with the inner ring and the frame.

[33] Moreover, according to an aspect of the present invention, there is provided a method for manufacturing a linear compressor, including the steps of: positioning an inner core in an inner stator mold; injecting a metal with a lower melting point than that of the inner core into the inner stator mold; and coupling an inner stator to a cylinder.

[34] Further, according to an aspect of the present invention, there is provided a method for manufacturing a linear compressor, including: a first step of molding an interval member made of a non-magnetic metal by pressing non-magnetic metal powder in a mold; a second step of heating the interval member made of the non-magnetic metal that has been molded in the first step; and a third step of coupling the interval member made of the non-magnetic metal to an inner stator, a cylinder and a frame.

[35] Still further, according to an aspect of the present invention, there is provided a method for manufacturing a linear compressor, including: a first step of integrally molding an interval member made of a non-magnetic metal and a cylinder by pressing non-magnetic metal powder in a mold; a second step of heating the interval member made of the non-magnetic metal and the cylinder that have been molded in the first step; and a third step of coupling the interval member made of the non-magnetic metal to an inner stator and a frame.

[36] Still further, according to an aspect of the present invention, there is provided a method for manufacturing a linear compressor, including: a first step of integrally molding an interval member made of a non-magnetic metal, a cylinder and a frame by pressing non-magnetic metal powder in a mold; a second step of heating the interval member made of the non-magnetic metal, the cylinder and the frame that have been molded in the first step; and a third step of coupling the interval member made of the non-magnetic metal to an inner stator.

Advantageous Effects

[37] In a linear compressor according to the present invention, the power efficiency can be improved by reducing an eddy current loss. [38] In addition, in a linear compressor according to the present invention, an injection molding can be introduced to prevent a magnetic flux from flowing between a cylinder and an inner stator and to form the cylinder, the inner stator and a frame integrally. [39] Moreover, in a linear compressor according to the present invention, as a frame and a cylinder are made of a non-magnetic material, a magnetic flux can be prevented from flowing from an inner stator to the cylinder, and thus an eddy current can be reduced. [40] Further, in a linear compressor according to the present invention, an interval member reducing an eddy current loss by preventing a magnetic flux from flowing from an inner stator to a cylinder is made of a non-magnetic metal of a metal material.

Therefore, when exposed to a relatively high temperature environment, the interval member made of the non-magnetic material is less deformed. [41] Still further, in a linear compressor according to the present invention, as an interval member made of a non-magnetic metal inside an inner stator is less deformed, an interval between the inner stator and an outer stator can be maintained. As a result, noise and vibration of the compressor can be suppressed and the operation reliability thereof can be improved.

Brief Description of the Drawings

[42] FTG. 1 is a view illustrating a portion of a conventional linear compressor;

[43] FIG. 2 is a schematic view illustrating paths of a magnetic flux in the conventional linear compressor; [44] FIG. 3 is a view illustrating one example of the conventional linear compressor including a fixing member of a non-magnetic resin material; [45] FIGS. 4 and 5 are views illustrating portions of a linear compressor including an interval member made of a non-magnetic metal according to a first embodiment of the present invention; [46] FIG. 6 is a view illustrating a portion of a linear compressor including an interval member made of a non-magnetic metal according to a second embodiment of the present invention; [47] FIG. 7 is a view illustrating a portion of a linear compressor wherein an interval member made of a non-magnetic metal and a frame are formed integrally according to another embodiment of the present invention; and

[48] FIG. 8 is a view illustrating a portion of a linear compressor wherein an interval member made of a non-magnetic metal, a frame and a cylinder are formed integrally according to a further embodiment of the present invention.

Mode for the Invention [49] An eddy current loss in an inner stator of a linear motor is expressed by the following relational expression: [50]

W _loss = V _core CDOτ H dB

[51] Here, Vcore represents a volume of a core which is a magnetic material, H represents an intensity of a magnetic field [A/m], and B represents a density of a magnetic flux [Web]. Therefore, the volume of the core which is the magnetic material must be reduced to prevent the eddy current loss. For example, a method of reducing the volume of the core which is the magnetic material includes a method of reducing a size of the core and a method of forming the core with a non-magnetic material.

[52] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the aooompanying drawings.

[53] FIGS. 4 and 5 are views illustrating portions of a linear compressor including an interval member made of a non-magnetic metal according to a first embodiment of the present invention. The linear compressor according to the first embodiment of the present invention includes an inner ring 122 as the interval member made of the nonmagnetic metal. An inner stator 120 includes an inner core 121 that is a magnetic material, and the inner ring 122 that is one example of the interval member made of the non-magnetic metal. As the inner stator 120 includes the inner ring 122, a volume of the inner core 121 that is the magnetic material can be reduced in the inner stator 120. The inner ring 122 is installed on an outer circumference of a cylinder 20, and manufactured in a cylindrical shape. The inner core 121 is stacked in a plural number on the outer circumference of the inner ring 122 in a circumference direction. As the inner ring 122 made of the non-magnetic metal is installed on the outer circumference of the cylinder 20, a magnetic flux is prevented from flowing from the inner core 121 to the cylinder 20, thereby reducing an eddy current loss. Here, if a frame 30 is made of a non-magnetic material, a magnetic flux can be prevented from flowing into the cylinder 20 through the frame 30 and one end of the cylinder 20. Moreover, as the inner ring 122 is made of a metal, it is rarely deformed at 100 to 150 ⁰ C that is an

operating environment of the linear compressor. Therefore, an interval between the inner stator 120 and an outer stator (not shown) can be maintained to be constant, and a level of an electromagnetic force operated between the inner stator 120 and the outer stator (not shown) can be prevented from being changed unintendedly. Further, the inner core 121 and the inner ring 122 include, for example, a groove 121a and a protrusion 122a interlocked with each other so as to prevent relative motions therebetween.

[54] FIG. 5 shows the cylinder 20, the inner core 121 and the inner ring 122 according to the first embodiment of the present invention. The cylinder 20 includes a groove 2Oh so that the inner ring 122 can be fixed thereto. A fixing ring 25 is inserted into the groove 2Oh. The fixing ring 25 pushes one end of the inner ring 122 to fix the inner ring 122. The other end of the inner ring 122 is fixed by the frame 30. According to an assembly method of the linear compressor, the cylinder 20 is inserted into the frame 30, and the inner core 121 and the inner ring 122 coupled to each other are fitted around the cylinder 20 inserted into the frame 30. Thereafter, the fixing ring 25 is fitted into the groove 2Oh of the cylinder 20, so that the cylinder 20, the frame 30 and the inner stator 120 are fixed to each other.

[55] FIG. 6 is a view illustrating a portion of a linear compressor including an interval member made of a non-magnetic metal according to a second embodiment of the present invention. According to the second embodiment of the present invention, an inner core 121 may include a protrusion 121b and an inner ring 122 may include a groove 122b interlocked with the protrusion 121b so as to prevent relative motions therebetween.

[56] The inner core 121 and the inner ring 122 may be formed integrally by means of an injection molding. The inner ring 122 may be made of aluminum, austenite group stainless steel, non-magnetic cast iron, etc.. First, the inner ring 122 may be manufactured by the injection molding. The prepared inner core 121 that is the magnetic material is positioned in a mold for molding the inner ring 122, and a molten nonmagnetic material is poured into and injection-molded in the mold. As described above, when the interval member 130 made of the non-magnetic metal is formed by the injection molding, a melting point of the material of the interval member 130 made of the non-magnetic metal must be lower than a melting point of the material of the inner stator 120. Otherwise, the inner stator 120 is molten during the injection molding, so that the configuration of the inner stator 120 and the interval member 130 made of the non-magnetic metal may not be maintained. In addition, if the melting

point of the non-magnetic material of the interval member 130 made of the nonmagnetic metal is excessively high, the inner stator 120 made of the magnetic material may lose magnetism. Accordingly, when the injection molding is introduced, the material of the interval member 130 made of the non-magnetic metal is restricted to a non-magnetic metal with a low melting point, sich as aluminum.

[57] FIG. 7 is a view illustrating a portion of a linear compressor wherein an interval member made of a non-magnetic metal and a frame are formed integrally according to another embodiment of the present invention. According to this embodiment, the linear compressor includes an interval member 130 made of a non-magnetic metal between an inner stator 120 and a cylinder 20. Here, the inner stator 120 is made of a magnetic material, and a frame 30 is made of a non-magnetic material. Therefore, a magnetic flux flowing in the inner stator 120 of the magnetic material can be prevented from flowing into the cylinder 20 through the outer circumference of the cylinder 20. In addition, the magnetic flux can be prevented from flowing into the cylinder 20 through the frame 30 and one end of the cylinder 20.

[58] According to a further embodiment of the present invention, an interval member

130 made of a non-magnetic metal may be formed integrally with a frame 30 of a nonmagnetic material. Moreover, according to a still further embodiment of the present invention, an interval member 130 made of a non-magnetic metal may be formed integrally with an inner stator 120 and a frame 30. To this end, the inner stator 120 previously manufactured with a magnetic material is positioned in a mold for molding the frame 30 and the interval member 130 made of the non-magnetic metal, and a molten non-magnetic material with a relatively low melting point, such as aluminum, is poured into and injection-molded in the mold.

[59] In addition, an interval member 130 made of a non-magnetic metal and a frame 30 may be formed integrally by means of a sintering. This method is introduced when the interval member 130 made of the non-magnetic metal and the frame 30 are formed by using a material with a relatively high melting point between austenite group stainless steel and non-magnetic cast iron. As the austenite group stainless steel and the nonmagnetic cast iron have a higher melting point than the material of the inner stator 120, the interval member 130 and the frame 30 can not be formed by the injection molding. Accordingly, metal powder and resin are mixed, pressed and heated in a mold for molding the interval member 130 made of the non-magnetic metal and the frame 30. When the interval member 130 made of the non-magnetic metal and the frame 30 are formed integrally and heated, the inner stator 120 may lose magnetism. Therefore,

preferably, the interval member 130 made of the non-magnetic metal and the frame 30 are sintered, and then ooupled to the inner stator 120. Aocording to the sintering, the interval member 130 made of the non-magnetic metal and the frame 30 can be formed precisely, and the after-treatment process can be simplified. As a result, the entire manufacturing process can be simplified and shortened.

[60] According to a still further embodiment of the present invention, a cylinder 20 and a frame 30 may be made of a non-magnetic material, such as aluminum, austenite group stainless steel, non-magnetic cast iron, etc.. In this situation, although an interval member 130 made of a non-magnetic metal is not provided in a linear compressor and an inner stator 120 is installed directly on the cylinder 20, a magnetic flux can be prevented from flowing in the cylinder 20. In case of a metal with a low melting point, such as aluminum, the inner stator 120 previously manufactured with a magnetic material is positioned in a mold, and a molten non-magnetic material is poured into and injection-molded in the mold, so that the inner stator 120 and the cylinder 20 can be formed integrally. Meanwhile, in case of a metal with a relatively high melting point, such as austenite group stainless steel and non-magnetic cast iron, the cylinder 20 and the frame 30 are sintered and then coupled to the inner stator 120.

[61] FIG. 8 is a view illustrating a portion of a linear compressor wherein an interval member made of a non-magnetic metal, a frame and a cylinder are formed integrally according to a still further embodiment of the present invention. According to this embodiment, an interval member 130 made of a non-magnetic metal, a cylinder 20 and a frame 30 may be formed integrally by means of an injection molding. The frame 30 is made of a non-magnetic material. Here, the interval member 130 made of the nonmagnetic metal is formed between an inner stator 120 and the cylinder 20 so as to prevent a magnetic flux from flowing from the inner stator 120 to the cylinder 20. The interval member 130 made of the non-magnetic metal may be formed of aluminum, austenite group stainless steel, non-magnetic cast iron, etc.. In case of a metal with a low melting point, such as aluminum, the inner stator 120 previously manufactured with a magnetic material is positioned in a mold for integrally molding the cylinder 20, the frame 30 and the interval member 130 made of the non-magnetic metal, and a molten non-magnetic material is poured into and injection-molded in the mold. Meanwhile, in case of a metal with a relatively high melting point, such as austenite group stainless steel and non-magnetic cast iron, the cylinder 20, the frame 30 and the interval member 130 made of the non-magnetic metal are sintered and then coupled to the inner stator 120.

[62] As set forth above, when the interval member 130 made of the non-magnetic metal is formed between the inner stator 120 and the cylinder 20, a magnetic flux does not flow from the inner stator 120 to the cylinder 20, so that an eddy current is not generated during the driving of the linear compressor. In addition, the interval member 130 made of the non-magnetic metal is formed of a non-magnetic material of a metal material more resistant to heat than a nonmetal material such as resin. As compared with an interval member made of a non-magnetic material of a resin material, the interval member 130 secures the excellent reliability in the linear compressor operated at a relatively high temperature. On the other hand, when the resin material is insert- molded, it is seriously dispersed according to a manufacturing condition. Such dispersion affects the inner and outer diameters of the inner stator 120. On the contrary, according to the present invention, as the interval member 130 made of the non-magnetic metal is made of a metal material, it is less dispersed. Accordingly, the inner and outer diameters of the inner stator 120 can be maintained to be constant, and an interval between the inner stator 120 and an outer stator (not shown) can be maintained to be constant. As the interval between the inner stator 120 and the outer stator (not shown) is maintained to be constant, the performance of the linear compressor can be guaranteed, and noise and vibration can be suppressed.

[63] While the present invention has been illustrated and described in connection with the accompanying drawings and the preferred embodiments, the present invention is not limited thereto and is defined by the appended claims. Therefore, it will be understood by those skilled in the art that various modifications and changes can be made thereto without departing from the spirit and scope of the invention defined by the appended claims.