JP4550489B2 - Linear compressor - Google Patents

Description

  The present invention relates to a linear compressor, and more particularly to a linear compressor capable of reducing noise and vibration generated in a process of compressing a fluid and at the same time improving compression efficiency.

  Generally, in a linear compressor, a linear driving force of a linear motor is transmitted to a piston, and the piston sucks and compresses fluid while reciprocating linearly inside the cylinder.

FIG. 1 is a longitudinal sectional view illustrating a conventional linear compressor.
As shown in FIG. 1, the conventional linear compressor is provided with a cylindrical inner case 10 having a predetermined length inside the sealed container 1, and a fluid suction path 18 is provided on one side of the inner case 10. The formed back cover 20 is coupled, and a driving motor 30 for generating a driving force is mounted inside the inner case 10.

  A piston 40 having a fluid through passage 38 is connected to the drive motor 30, and a suction valve 50 that opens and closes the fluid through passage 38 is attached to the piston 40. The piston 40 is attached to the other side of the inner case 10. A cylinder block 60 having a cylinder portion 58 inserted so as to be able to advance and retreat is coupled, and a discharge valve 70 for opening and closing the cylinder portion 58 is attached to the cylinder block 60.

  A suction pipe 2 for sucking fluid from the outside is connected to the sealed container 1 so as to be positioned behind the fluid suction path 18 of the back cover 20.

  The drive motor 30 includes an outer core 31 made of a cylindrical laminate, an inner core 32 of a cylindrical laminate inserted with a certain gap from the outer core 31, and a coil wound around the outer core 31. A stator (S) composed of 33, a magnet 34 disposed between the outer core 31 and the inner core 32 so as to be able to advance and retract, and the piston 34 when the magnet 34 is fixed and the magnet 34 is advanced and retracted. And a magnet frame 36 connected to the piston 40 so that the valve 40 can move forward and backward.

  The outer core 31 is inserted into the inner case 10 and fixedly coupled to the back cover 20, the inner core 32 is fixedly coupled to a cylindrical coupling portion 21 formed on the back cover 20, and the magnet 34 is It is fixed to the outer periphery of the magnet frame 36 so as to be disposed between the outer core 31 and the inner core 32.

  The magnet frame 36 and the piston 40 are elastically supported by a first spring 37 a arranged between the cylinder block 60 and a second spring 37 b arranged between the inner core 32.

  The suction valve 50 has a plate valve structure in which one side is fixed to the piston 40 by a fastening bolt, and an opening / closing part that opens and closes the fluid through hole 38 of the piston 40 is elastically bent.

  The suction valve 50 opens the fluid through passage 38 while the opening and closing portion is pushed by the fluid in the fluid passage 38 when the piston 40 moves backward in the direction of the back cover 20. When moving forward in the direction of 70, the opening / closing portion closes the fluid through-passage 38 by the fluid between itself and the discharge valve 70 and its own elastic force.

  The discharge valve 70 is attached to the cylinder block 60 and connected to a discharge pipe 72 on one side thereof. The discharge valve 70 is elastically supported by the discharge cover 72 by a spring 74 and is in close contact with the end of the cylinder portion 58. And a valve body 76 that opens and closes the cylinder portion 58.

  On the other hand, in the linear compressor, when the suction valve 50 is opened and closed, the suction valve 50 hits the piston 40 to generate noise, and when the discharge valve 70 is opened and closed, the valve body 76 hits the cylinder portion 58. Noise. The noise generated in this manner is transferred to the outside of the sealed container 1 through the fluid through passage 38 of the piston 40, the fluid through hole of the inner core 32, and the fluid suction passage 18 of the back cover 20, as indicated by a dotted line in FIG. Reportedly.

Therefore, in order to prevent the noise, a separate noise leveler 80 is attached to the noise transmission path.
The noise device 80 is fixedly mounted on the rear side of the piston 40 so as to be separated from the fluid suction path 18 of the back cover 20, and the fluid sucked into the fluid suction path 18 of the back cover 20 is attached to the piston 40. A fluid through hole 82 is formed so as to be sucked into the fluid through path 38, and the inside is expanded.

The operation of the linear compressor as described above is as follows.
First, when a voltage is applied to the coil 33, the drive motor 30 is operated to cause the magnet 34 to reciprocate linearly. The linear reciprocation of the magnet 34 is transmitted to the piston 40 through the magnet frame 36, and the piston 40 is moved. A linear reciprocation is made in the cylinder part 58.

  Simultaneously with the reciprocating motion of the piston 40 in the cylinder portion 58, the discharge valve 70 and the suction valve 50 are opened and closed. At this time, the gas fluid flowing into the sealed container 1 passes through the fluid suction path 18 of the back cover 20, the inner through hole of the inner core 32, the noise unit 80, and the fluid through path 38 of the piston 40, and the cylinder part 58. Inhaled. Next, the gas fluid is compressed and then discharged. The discharged high temperature and high pressure fluid gas is discharged to the outside of the hermetic container 1 through a discharge pipe (not shown).

  However, the linear compressor according to the related art as described above is configured to reciprocate with the piston 40 in a state where the noise unit 80 is separated from the fluid suction path 18 of the back cover 20. Since the fluid sucked through the fluid suction passage 18 of the back cover 20 is not rapidly sucked into the fluid through passage 38 of the cylinder 40 through the noiser 80 as shown by a solid line in FIG. There is a problem that the performance is lowered.

  The present invention has been devised in order to solve the above-described problems of the prior art, and by making the volume of the noise level variable by the reciprocating motion of the piston, it is possible to generate high-efficiency and various noises in various bands. It aims at providing the linear compressor which can be reduced.

In order to achieve the above object, a linear compressor according to the present invention includes a cylinder having a discharge portion on one side, and a linear motor that compresses fluid while reciprocating the inside of the cylinder, and sucks it into the cylinder. A piston formed so as to pass through the flow path; and a first noiser that is fixed to a rear portion of the piston and linearly moves together with the piston, and has a flow path that leads to a suction flow path of the piston and a noise reduction space. A second noise device which is fixedly provided in the compressor and has an internal volume which changes when the first noise device moves linearly and has a flow path leading to a suction flow path of the first noise device and a noise reduction space. in the linear compressor having a preparative, the first noise device is formed in a cylindrical shape protruding to the rear of the piston, expansion chamber of formation of the high-frequency reduction ahead of the cylinder , Low frequency reduction for the Helmholtz resonator having a formed within the inner wall and the inner wall which is provided so as to have a space in the circumferential direction the communicating hole of the cylinder to the rear is formed.

The rear part of the first noiser is configured to reciprocate while being inserted into the second noiser.
A gap of 0.1 to 1.0 mm exists between the outer peripheral surface of the first noise leveler and the inner peripheral surface of the second noise leveler.

The second noiser is formed in a cylindrical shape, and the front surface of the cylinder has an open structure so that the first noiser is inserted, and a hole into which a fluid flows is formed on the rear surface.
A cylinder having a discharge part on one side, a piston compressed by a linear motor while reciprocating the inside of the cylinder and penetrating a suction passage leading to the inside of the cylinder; and A first noise leveler fixed to the rear portion and linearly moving with the piston and having a flow path leading to the suction flow path of the piston and a noise reduction space; and the first noise leveler fixedly provided in the compressor. A linear compressor comprising: a second noiser having a noise reduction space and a flow path leading to an intake flow path of the first noiser; Each of the second noise levelers has a collection space formed inside each rear side, and the collection space has a hole portion through which the fluid is sucked in the first noise level or the second level noise level direction of the noise level. Is extended to Formed by gradually extended suction pipe toward the rear.

A back cover having an opening hole in the center is coupled to the rear portion of the linear motor, and the second noiser is mounted and fixed in the opening hole of the back cover.
At least one of the first noise device and the second noise device is made of a nonmagnetic material.

  The linear compressor according to the present invention configured as described above is configured such that the volume inside the noise device changes as the piston reciprocates, and noise in various bands is generated in the variable space of the noise device. There is an effect that high frequency noise can be effectively reduced by blocking.

  In the linear compressor according to the present invention, since the suction flow path including the first noiser and the second noiser is formed between the back cover and the piston, the first and second noisers, the piston, Fluid leakage in the suction channel that follows the cylinder is minimized, and the pumping action is performed while the volume of the second noise unit is changed, so that the amount of suction fluid sucked into the cylinder is increased and suction efficiency is improved. There is an effect that can.

Hereinafter, embodiments of a linear compressor according to the present invention will be described with reference to the accompanying drawings.
Although there may be many possible embodiments of the linear compressor according to the present invention, the most preferred embodiment will be described below.
FIG. 2 is a longitudinal sectional view showing an embodiment of a linear compressor according to the present invention.

  As shown in FIG. 2, the linear compressor according to an embodiment of the present invention includes a sealed container 104 including a lower container 101 and an upper lid 102, and a first damper 106 mounted on one side of the sealed container 104. Mounted on a cylinder block 110 having a cylinder 109 mounted and supported in a bufferable manner, and a second damper 108 mounted on the other side of the sealed container 104 and supported in a bufferable manner to support the cylinder 109 and A back cover 120 spaced apart from the cylinder block 110; a linear motor 130 that is fixed between the cylinder block 110 and the back cover 120 and generates a driving force for compressing fluid; and an interior of the cylinder 109 The linear motor compresses the fluid inside the cylinder 109 while reciprocating the cylinder. 30, and a piston 144 having a suction valve 142 for opening and closing the through passage 140 is formed in the cylinder 109. The piston 144 includes a suction valve 142 that opens and closes the through passage 140. 109 and the piston 144 together with a discharge valve 150 that forms a compression chamber (C) to open and close the discharge portion of the cylinder 109, a communication hole 160a that is attached to the piston 144 and communicates with the through passage 140 of the piston 144, and a fluid A first noise device 160 having a noise reduction space formed therein, and an inner volume of the first noise device 160 is attached to the back cover 120 so that the internal volume changes when the first noise device 160 advances and retreats. Inhalation that communicates with the outside of the back cover 120 so that fluid outside the back cover 120 can be sucked And a second noiser 170 in which a hole 170a is formed.

  The airtight container 104 is connected so that a suction connection pipe 104a for sucking a fluid passes therethrough, and a discharge connection pipe 104b for discharging a compressed fluid is connected below the seal connection pipe 104a.

  The back cover 120 is formed with an opening hole 120a in which the second noiser 170 is mounted so that the fluid in the sealed container 104 is directly sucked into the suction hole 170a of the second noiser 170.

  Here, the opening hole 120a is located on the same line as the piston 144 and the center of the first noiser 160, and is slightly larger than the size of the first noiser 160 so that the first noiser 160 is inserted. It is desirable to form the same.

  The linear motor 130 is composed of a laminated outer core 131, a laminated inner core 132 disposed so as to have a certain gap from the outer core 131, and a coil 133 attached to the outer core 131. A child (S), a magnet 134 formed around the coil 133 to be advanced and retracted by electromagnetic force, and disposed between the outer core 131 and the inner core 132 so as to be movable back and forth. 144 and a movable element (M) comprising a magnet frame 136 fixed thereto.

  The outer core 131 is disposed between the cylinder block 110 and the opposite surface of the back cover 120 and fixedly coupled to the cylinder block 110 and the back cover 120 by a fastening means such as a fastening member. The cylinder block 110 is fixedly coupled to the cylinder block 110 by a clamping means such as a clamping member, and the magnet frame 136 is fixedly coupled to the piston 144 by a clamping means such as a clamping member.

  A part of the piston 144 is inserted into the cylinder 109 so as to be able to advance and retreat inside the cylinder 109, and the suction valve 142 is attached to the inserted part, and the part of the inserted part is inserted. On the opposite side, a fixing portion 146 fixed to the magnet frame 136 by a fastening means such as a fastening member protrudes in the radial direction.

  The piston 144 includes a first spring 144 a disposed between one surface of the fixed portion 146 and the cylinder block 110, and a second spring disposed between the other surface of the fixed portion 146 and the back cover 120. It is elastically supported by a spring 144b and moves forward and backward together with the mover (M) of the linear motor 130 and the first noiser 160.

  On the other hand, the suction valve 142 has a plate valve structure in which one side is fixed to the piston 144 and a portion corresponding to the fluid passage 140 of the piston 144 is elastically bent.

  The discharge valve 150 is fixed to the cylinder block 110 so as to communicate with the cylinder 109, and is arranged to be spaced apart from the inner discharge cover 152 having a fluid discharge hole 151 formed on one side thereof and the outer side of the inner discharge cover 152. And an outer discharge cover 154 connected to a discharge pipe 153 for discharging a fluid on one side, and the cylinder 109 while being elastically supported by the inner discharge cover 152 by a spring 156 and closely contacting and separating from the end of the cylinder 109. And a valve body 158 that opens and closes.

  It is preferable that at least one of the first noiser 160 and the second noiser 170 is made of a nonmagnetic material so that the compression efficiency of the linear compressor does not decrease.

  That is, since the linear motor 130 includes the coil 133 and the magnet 134, a strong magnetic force is formed. Normally, most of the components constituting the linear compressor are made of a steel material. If both the 160 and the second noise leveler 170 are made of a magnetic material, the magnetic force formed by the linear motor 130 is transmitted to the second noise level 170 and the back cover 120 through the first noise leveler 160 and electromagnetically lost. And the forward / backward movement of the first noiser 160 is less likely to be performed smoothly due to the magnetic force between the first noiser 160 and the second noiser 170.

  The first noiser 160 is formed in a cylindrical shape so as to have a resonance space for noise reduction, and the communication hole 160a is formed in the center of the surface in contact with the piston 144. The suction hole 160b is formed at the center of the surface to be advanced and retracted.

  The second noise unit 170 is formed in a cylindrical structure so as to have a resonance space therein, and is formed in a structure in which an entire surface is opened so that a rear portion of the first noise unit 160 is inserted, and the second noise unit 170 is formed at the center of the rear surface. The suction hole 170a is formed, and the first noise unit 160 reduces the noise in various bands while changing the resonance space.

  Reference numeral 200 is a loop pipe having one end connected to the discharge pipe 153 and the other end connected to the discharge connection pipe 104b.

  FIG. 3 is a cross-sectional view of a piston in a forward operation state in an embodiment of the linear compressor according to the present invention, and FIG. 4 is a cross-sectional view of a piston in a reverse operation state in an embodiment of the linear compressor according to the present invention.

  The first noiser 160 includes at least one expansion chamber 162 for reducing high frequencies or a Helmholtz Resonator 164 for reducing low frequencies.

The expansion chamber 162 is formed long in the length direction on the front side of the first noise leveler 160.
The Helmholtz resonator 164 is formed to have a space in the circumferential direction on the rear side of the first noiser 160 and communicates with the communication hole 163.

  The second noise unit 170 is disposed in an opening hole 120a formed in the back cover 120, a rear surface portion 172 in which the suction hole 170a is formed, and the first noise device forward from an edge of the rear surface portion 172. The cylindrical portion 180 is extended so as to surround a part of the outer periphery of 160 to prevent fluid leakage.

  It is preferable that the cylindrical portion 180 has a clearance (t) of 0.1 to 1.0 mm with respect to the outer periphery of the first noiser 160 at a portion surrounding a part of the outer periphery of the first noiser 160.

  That is, the cylindrical portion 180 maintains a clearance (t) of 0.1 mm or more with respect to the first noise leveler 160 in consideration of an assembly tolerance with the first noise leveler 160 or an advance / retreat operation of the first noise leveler 160. Desirably, if the gap (t) is too large, fluid leakage increases, so it is desirable to limit the gap (t) to 1 mm or less.

The operation of the linear compressor according to an embodiment of the present invention configured as described above is as follows.
First, when a voltage is applied to the coil 133 of the linear compressor 130, a magnetic field is formed around the coil 133, and the magnet 134 moves forward and backward due to interaction with the magnetic field around the coil 133. The advance / retreat operation 134 is transmitted to the piston 144 and the first noiser 160 through the magnet frame 136.

  The piston 144 advances and retreats inside the cylinder 109 to compress the inside of the compression chamber (C), and the first noiser 160 advances and retreats inside the second noiser 170 to move the second noiser 170. Change the internal volume. Accordingly, the second noise leveler 170 can block noise in various bands while changing the internal volume.

  On the other hand, the suction valve 142 and the discharge valve 150 are opened / closed according to pressure changes caused by the forward / backward movement of the piston 144 and the first noiser 160, and fluid (shown by a solid line in FIGS. 3 and 4) is used for the suction connection. The air is sucked into the sealed container 104 through the pipe 104a.

  The fluid sucked into the sealed container 104 is sucked into the second noise device 170 through the suction hole 170a of the second noise device 170, and is closed by the cylindrical portion 180 of the second noise device 170. The first noiser 160 is sucked into the first noiser 160 through the suction hole 160b of the first noiser 160 in a state where leakage around the noiser 160 is prevented to the maximum.

  The fluid sucked into the first noiser 160 passes through the communication hole 160 a, the passage 140 of the piston 144 and the suction valve 142 in order, and is sucked into the compression chamber (C) and compressed by the piston 144. After that, the discharge valve 150, the discharge pipe 153, the loop pipe 200, and the discharge connection pipe 104b are sequentially discharged.

  On the other hand, the linear compressor generates noise due to an impact when the intake valve and the discharge valve are opened and closed, and the noise passes through the through passage 140 and the communication hole 160a of the piston 144 as shown by dotted lines in FIGS. It is transmitted to the inside of the first noise leveler 160.

  The noise transmitted to the inside of the first noiser 160 passes through the Helmholtz resonator 164 and is cut off in the low frequency band, and the noise in the high frequency band that cannot be blocked by the first noiser 160 is the first noise. 2 The noise is transmitted to the inside of the noise leveler 170 to block the noise in the high frequency band.

  Meanwhile, the noise transmitted to the second noise leveler 170 is blocked by the internal space of the second noise leveler 170. At this time, the noise of various bands is blocked while the internal volume of the second noise leveler 170 changes. Therefore, the noise that is finally transmitted to the outside of the sealed container 104 through the second noise unit 170 is minimized.

FIG. 5 is a sectional view of the main part showing another embodiment of the linear compressor according to the present invention.
As shown in FIG. 5, the linear compressor according to another embodiment of the present invention is configured so that a collecting space for noise reduction is formed on the rear surface portion 172 side of the second noise unit 170. A suction pipe portion 174 is formed which protrudes in the direction of the first noise leveler 160 and forms a suction hole 170a whose inner diameter decreases toward the first noise leveler 160.

  The first noiser 160 has a suction hole 160b having the same or similar shape as the suction pipe part 174 in order to prevent collision or interference with the suction pipe part 174 or to collect noise. A suction pipe portion 166 is formed.

Since the other configurations and operations except the first noiser and the second noiser are the same as those of the above-described embodiment of the present invention, detailed description will be omitted by using the same reference numerals.
The suction pipe portion 174 is formed at the inner center of the cylindrical portion 180 so as to be separated from the inner wall surface of the cylindrical portion 180 of the second noise device 170, and performs the same function as the suction pipe portion 166 of the first noise device 160. Therefore, it is formed in a tubular shape.

The suction pipe portions 166 and 174 are preferably formed in a funnel shape that gradually expands toward the rear so that fluid can be sucked easily.
Reference numeral 165 is a protruding tube formed so as to protrude into the through passage 140 of the piston 144.

FIG. 6 is a cross-sectional view of the main part showing still another embodiment of the linear compressor according to the present invention.
In another embodiment of the linear compressor according to the present invention, as shown in FIG. 6, the second noise unit 170 is mounted inside the back cover 120, and the second noise unit is attached to the back cover 120. A communication hole 120b communicating with the suction hole 170a of 170 is formed, and the other configuration is the same as the configuration of the above-described embodiment of the present invention. Therefore, the same reference numerals are used and the detailed description is omitted.

  The communication hole 120b of the back cover 120 is preferably formed to be the same size as or slightly larger than the suction hole 170a of the second noise unit 170, and the fluid inside the sealed container 104 is connected to the communication hole 120b of the back cover and the second size. The noise is sucked through the suction hole 170a of the noise device in sequence.

  On the other hand, the present invention is not limited to the above-described embodiment, and is also applicable to providing a plurality of sets of a first noiser that moves forward and backward and a second noiser whose internal volume changes due to the first noiser. Is possible.

  As described in detail above, the linear compressor according to the present invention is configured such that the internal volume of the noise level is changed by the reciprocating motion of the piston. The high frequency noise can be effectively reduced by blocking the noise.

  In the linear compressor according to the present invention, since the suction flow path including the first noiser and the second noiser is formed between the back cover and the piston, the first and second noiser, piston, cylinder Since the fluid leakage of the suction flow path continued in the interior is minimized and the pumping action is performed while the volume of the second noise unit is changed, the amount of suction fluid sucked into the cylinder can be increased and the suction efficiency can be improved. There is.

1 is a longitudinal end view illustrating a conventional linear compressor. 1 is a longitudinal sectional view illustrating an embodiment of a linear compressor according to the present invention. FIG. 3 is a sectional view showing an operating state of the linear compressor according to the present invention when the piston moves forward in the embodiment of FIG. 2. FIG. 3 is a sectional view showing an operating state of the linear compressor according to the present invention when the piston is retracted in the embodiment of FIG. FIG. 3 is a cross-sectional view of a main part illustrating another embodiment of a linear compressor according to the present invention. FIG. 6 is a cross-sectional view of a main part illustrating still another embodiment of the linear compressor according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 ... Lower container 102 ... Upper cover 104 ... Sealed container 104a ... Suction connection pipe 104b ... Discharge connection pipe 106 ... 1st damper 108 ... 2nd damper 109 ... Cylinder 110 ... Cylinder block 120 ... Back cover 120a ... Opening hole 120b ... Communication Hole 130 ... Linear motor 131 ... Outer core 132 ... Inner core 133 ... Coil 134 ... Magnet 136 ... Magnet frame 140 ... Through passage 142 ... Suction valve 144 ... Piston 144a ... First spring 144b ... Second spring 150 ... Discharge valve 151 ... Discharge hole 152 ... inner discharge cover 153 ... discharge pipe 154 ... outer discharge cover 156 ... spring 158 ... valve body 160 ... first noise device 160a ... communication hole 160b ... suction hole 162 ... expansion chamber 163 ... communication hole 164 ... Helmholtz resonance 170 ... second noise unit 170a ... intake port 172 ... rear portion 174 ... intake pipe 180 ... cylindrical portion C ... compression chamber t ... clearance

Claims (7)

A cylinder having a discharge part on one side;
A piston which is formed so that a fluid is compressed while reciprocating the inside of the cylinder by a linear motor, and a suction flow path leading to the inside of the cylinder penetrates;
A first noiser fixed to a rear portion of the piston and linearly moving together with the piston, and having a flow path leading to a suction flow path of the piston and a noise reduction space;
A second noiser that is fixedly provided in the compressor and has an internal volume that changes when the first noiser moves linearly and has a flow path leading to a suction flow path of the first noiser and a noise reduction space; In a linear compressor comprising :
The first noiser is formed in a cylindrical shape protruding rearward of the piston, an expansion chamber for reducing high frequency is formed in front of the cylinder, and a space is provided in the circumference of the cylinder behind the cylinder. A linear compressor characterized in that a low frequency reducing Helmholtz resonator having an inner wall provided in this manner and a communication hole formed in the inner wall is formed .   The linear compressor according to claim 1, wherein the linear compressor has a structure that reciprocates with a rear portion of the first noiser inserted into the second noiser.   The linear compressor according to claim 2, wherein a gap of 0.1 to 1.0 mm exists between the outer peripheral surface of the first noise leveler and the inner peripheral surface of the second noise leveler.   The second noise unit is formed in a cylindrical shape, the front surface of the cylinder has an open structure so that the first noise unit is inserted, and the rear surface is formed with a hole into which a fluid flows. The linear compressor according to claim 1, wherein: A cylinder having a discharge part on one side;
A piston which is formed so that a fluid is compressed while reciprocating the inside of the cylinder by a linear motor, and a suction flow path leading to the inside of the cylinder penetrates;
A first noiser fixed to a rear portion of the piston and linearly moving together with the piston, and having a flow path leading to a suction flow path of the piston and a noise reduction space;
A second noiser that is fixedly provided in the compressor and has an internal volume that changes when the first noiser moves linearly and has a flow path leading to a suction flow path of the first noiser and a noise reduction space; In a linear compressor comprising:
Each of the first noiser and the second noiser is formed with a collection space inside the rear side, and the collection space is a hole portion through which fluid is sucked in the first noiser or the second noiser. A linear compressor characterized in that is formed by a suction pipe that is extended inwardly of the noise level and gradually expanded toward the rear .   The backside part of the linear motor is coupled with a back cover having an opening hole formed in a central part thereof, and the second noiser is mounted and fixed in the opening hole of the back cover. The linear compressor according to 1.   The linear compressor according to claim 1, wherein at least one of the first noiser and the second noiser is made of a nonmagnetic material.

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