JP2003148339A - Linear compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable linear compressor preventing a collision of a piston with a cylinder end surface, and preventing an impulsive sound of the piston and the cylinder end surface against impact force from an external part upon large transportation and a piston stroke upon operation. SOLUTION: This linear compressor is composed of a cylinder 10, the piston 20, the cylinder end surface 11, a movable part 40 and a fixed part 50 for constituting a linear motor part, coil springs 15 and 30, a head cover part 80, a support mechanism part 90, and a sealed vessel 100. A compression space 13 for compressing gas is formed in the cylinder 10. A spring member 61 of a spring mechanism member 60 is composed of the coil springs 15 and 30 having prescribed spring rigidity. When the coil spring 15 is most compressed, amplitude of the piston 20 of the linear compressor can be regulated by securing clearance in a piston 20 end surface and the cylinder end surface 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear compressor that reciprocates a piston fitted in a cylinder by a linear motor to compress gas.

[0002]

2. Description of the Related Art In a refrigerating cycle, an HCFC refrigerant represented by R22 is said to destroy the ozone layer due to its stable physical properties. In recent years, HCFC
An HFC-based refrigerant is used as an alternative refrigerant to the system-based refrigerant, and this HFC-based refrigerant has a property of promoting a warming phenomenon. Therefore, recently, HC-based refrigerants that do not significantly affect the ozone layer destruction and the warming phenomenon have begun to be adopted. However, since this HC-based refrigerant is flammable, it is necessary to prevent explosion and ignition from the viewpoint of ensuring safety, and for this reason, it is required to minimize the amount of the refrigerant used. On the other hand, the HC-based refrigerant has no lubricity as a refrigerant itself and has a property of easily dissolving in a lubricant. From the above, when using the HC-based refrigerant, an oilless or oil-poor compressor is required. The linear compressor, which has a small load in the direction perpendicular to the axis of the piston and has a small sliding surface pressure, is oilless compared to the reciprocating compressors, rotary compressors, and scroll compressors that have been widely used in the past. It is known as a compressor in which the piston movable part has a free piston stroke in which the piston position is freely determined by the motor thrust applied to the motor and the operating pressure condition.

[0003]

However, since this linear compressor has a free piston stroke and is not mechanically constrained by other members, the piston changes due to pressure changes during operation and disturbance forces during transportation. When the amplitude suddenly changes and the end face of the piston collides with the end face of the cylinder, a collision noise is generated, which may damage the piston or the like. Further, the linear compressor has a sliding surface between the cylinder and the piston, and the quality of the slidability of the sliding surface affects the efficiency and durability of the linear compressor. Furthermore, in order to make the linear compressor oilless, it is important that only a simple axial force acts in one direction between the cylinder and the piston, and for example, the twisting force generated by the coil spring supporting the piston be minimized. Is.

Therefore, an object of the present invention is to provide a highly reliable compressor which prevents a piston and a cylinder end surface from colliding with each other even during operation or transportation. Another object of the present invention is to provide a linear compressor suitable for downsizing by making the coil spring compact.

[0005]

A linear compressor of the present invention according to claim 1 is provided with a compression mechanism for compressing gas and a linear motor for operating the compression mechanism in a hermetically sealed container, and the compression mechanism is a cylinder. And a piston, having a compression chamber for compressing gas in the cylinder, the linear motor has a fixed portion connected to the cylinder and a movable portion connected to the piston, one end of which is A compression chamber side coil spring that presses against the piston or the movable part and the other end presses against the cylinder or the fixed part on the compression chamber side, and one end presses against the piston or the movable part and the other end on the side opposite the compression chamber. When the compression chamber side coil spring is most compressed in a linear compressor in which the piston is movably supported in the axial direction by a cylinder spring or an anti-compression chamber side coil spring that is pressed against the fixed portion. Characterized in that securing the gap between the piston end face and the cylinder end face. Claim 2
The described invention is the linear compressor according to claim 1, characterized in that the coil spring on the compression chamber side is a non-linear coil spring. The present invention according to claim 3 relates to claim 2
In the linear compressor described in the paragraph 1, the non-linear coil spring is an unequal pitch coil spring. According to a fourth aspect of the present invention, in the linear compressor according to the second aspect, the non-linear coil spring is a conical coil spring. The linear compressor of the present invention according to claim 5 is provided with a compression mechanism for compressing gas and a linear motor for operating the compression mechanism in a closed container, the compression mechanism having a cylinder and a piston, and the cylinder. A compression chamber for performing gas compression is provided therein, the linear motor has a fixed portion connected to the cylinder and a movable portion connected to the piston, and one end is pressed against the piston or the movable portion. A compression chamber side coil spring whose end is pressed against the compression chamber side cylinder or the fixed part and an end which is pressed against the piston or the movable part and the other end is pressed against the compression chamber side cylinder or the fixed part. With the compression chamber side coil spring,
In the linear compressor in which the piston is movably supported in the axial direction, the compression chamber side coil spring constant is smaller than the anti-compression chamber side coil spring constant. According to a sixth aspect of the present invention, in the linear compressor according to the fifth aspect, the amplitude of the piston is a, and the amount by which the piston is offset to the side opposite to the compression chamber by the gas force applied from the compression chamber during operation. Is α, the compression chamber side coil spring constant is k1, and the anti-compression chamber side coil spring constant is k2.
Then, the coil spring constants k1 and k2 are determined so that the relational expression of approximately k1 × (a + α) = k2 × (a−α) is satisfied. The present invention according to claim 7 is
In the linear compressor according to any one of claims 1 to 6, the compression chamber side coil spring or the anti-compression chamber side coil spring has an oval or elliptical cross-sectional shape.
The present invention according to claim 8 is characterized in that the linear compressor according to any one of claims 1 to 7 is operated by using a refrigerant containing carbon dioxide as a main component.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the first embodiment according to the present invention, a clearance is secured between the piston end surface and the cylinder end surface when the compression chamber side coil spring is most compressed. According to the present embodiment, the piston behavior suddenly changes due to a change in pressure during operation or a disturbance force during transportation, and when the piston amplitude increases, the piston amplitude is regulated by the compression chamber side coil spring. It is possible to avoid a collision between the cylinder and the cylinder end surface.

The second embodiment of the present invention is a linear compressor in the first embodiment, wherein the compression chamber side coil spring is a non-linear coil spring. According to the present embodiment, the non-linear coil spring increases the spring load as the spring deflection increases. Accordingly, since the piston speed approaching the top dead center is absorbed, the impact force relaxing effect can be expected.

The third embodiment of the present invention is the linear compressor of the second embodiment, in which the non-linear coil spring is an unequal pitch coil spring. According to the present embodiment, as the deflection of the unequal pitch coil spring increases, more wire-to-wire bonding occurs, the effective number of turns decreases, and the spring load increases as compared to the equidistant pitch coil spring. Absorbs the piston speed approaching the dead point, absorbs the impact force, and obtains good durability.

The fourth embodiment of the present invention is a linear compressor according to the second embodiment, wherein the non-linear coil spring is a conical coil spring. According to the present embodiment, when the spring deflection becomes large, the similar action of the unequal pitch coil spring becomes more remarkable and the spring load greatly increases. Therefore, it is effective as a brake that absorbs the piston speed approaching the top dead center. Can reduce the impact force of the piston, reduce impact noise, and improve reliability.

In the fifth embodiment of the present invention, the compression chamber side coil spring constant is made smaller than the anti-compression chamber side coil spring constant. During operation, the piston is offset to the side opposite to the compression chamber by the gas force in the compression chamber. It is necessary to increase the amount of deflection on the anti-compression side by the amount of this offset amount. Therefore, when the coil spring constants on the compression chamber side and the anti-compression side are the same, it is necessary to increase the maximum amount of deflection from the free length height of the spring to the contact height. In the present embodiment, the coil spring constant on the compression chamber side is made small and the coil spring constant on the anti-compression chamber side is made large, so that the maximum piston amount determined by the design can be determined more than when the coil spring constants on the compression chamber side and the anti-compression side are the same. The maximum deflection amount of the spring can be suppressed with respect to the stroke amount. Therefore, the coil spring can be made compact and the linear compressor can be made compact.

The sixth embodiment of the present invention is the linear compressor according to the fifth embodiment, wherein the piston amplitude is a and the piston is pushed to the side opposite to the compression chamber by the gas force applied from the compression chamber during operation. When the offset amount is α, the compression chamber side coil spring constant is k1, and the anti-compression chamber side coil spring constant is k2, k1 × (a + α) = k2 × (a−
The coil spring constant is determined so that the relational expression of α) is established. According to the present embodiment, the piston amplitude center position offset during operation is approximately the middle of the maximum deflection amounts of the compression chamber side coil spring and the anti-compression chamber side coil spring,
The maximum deflection of the spring can be suppressed. Therefore, the coil spring can be made compact, and the linear compressor can be made compact.

The seventh embodiment of the present invention is the linear compressor according to the first to sixth embodiments, in which the coil spring has an oval or elliptical cross-section. In the present embodiment, by making the coil spring wire rod an oval or elliptical cross-sectional shape, compared to a round wire cross-section,
It is possible to reduce the maximum stress generated in the wire when the spring is flexed. Therefore, since the height of the coil spring can be reduced,
The coil spring can be made compact, and the linear compressor can be made compact.

The eighth embodiment according to the present invention uses a refrigerant containing carbon dioxide as a main component in the linear compressor according to the first to seventh embodiments. Under a CO2 refrigerant that is highly lubricated with a high differential pressure refrigerant, it is much more efficient and more reliable than other compressors.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the linear compressor of the present invention will be described below with reference to the drawings. First, the overall structure of the linear compressor of the present invention will be described with reference to FIG. This linear compressor is roughly classified into a cylinder 10, a piston 20, a movable portion 40 and a fixed portion 50 which form a linear motor portion,
A spring mechanism section including a coil spring and a head cover section 80.
And a support mechanism 90 and a closed container 100. The cylinder 10 includes a cylinder end surface 11 on which a valve element (not shown) is assembled, a flange portion 14, and a boss portion 12 protruding from the flange portion 14 toward one side (leftward in the drawing). The piston 20 is provided with a frame body 22 that forms a recess for accommodating the column 21 and the coil spring 30. Piston 20
Is provided with a protrusion 23 on the inner bottom surface of the recess of the frame body 22.
A compression chamber 13 is formed between one end of the piston 20 and the cylinder end surface 11. The linear motor part is the movable part 40.
And a fixed part 50. The movable part 40 includes a permanent magnet 41.
And a cylindrical holding member 42 and the like. The fixed portion 50 is composed of an inner yoke 51, an outer yoke 52, a coil 53 and the like. The permanent magnet 41 is held by the cylindrical holding member 42. The cylindrical holding member 42 is arranged concentrically with the piston 20 and is fixedly held by the frame body 22. The inner yoke 51 is composed of a cylindrical body, and the cylinder 1
It is externally fixed to the boss portion 12 of 0. A minute gap is formed between the outer circumference of the inner yoke 51 and the cylindrical holding member 42. The coil 53 is provided on the outer yoke 52. On the other hand, the outer yoke 52 is also made of a cylindrical body, is concentrically arranged so as to form a minute gap on the outer periphery of the cylindrical holding member 42, and is fixed to the flange portion 14 of the cylinder 10. As described above, the movable portion 40 and the fixed portion 50 are concentrically held with high precision, and the reciprocating motion can be smoothly performed.

The spring mechanism portion is composed of a compression chamber side coil spring 15 and a non-compression chamber side coil spring 30 having a predetermined spring rigidity. The coil springs 15 and 30 are used as compression springs that are always used in a state compressed more than their natural length. One end 16 of the compression chamber side coil spring 15 is coupled to a step portion 19 formed on the other end surface of the piston 20.
The other end 17 of the compression chamber side coil spring 15 is coupled to the outer peripheral end surface portion 18 of the boss portion 12 of the cylinder 10. One end 31 of the anti-compression chamber side coil spring 30 is coupled to the protrusion 23 formed on the other end surface of the piston 20. The other end 32 of the coil spring 30 on the side opposite to the compression chamber is coupled to the protrusion 63. The anti-compression-chamber-side coil spring 30 uses the spring fixing member 62 to generate the preload due to the compression deflection.
Press 0 to the piston 20 side. The spring fixing member 62 is
Outer yoke 52 that serves as the fixed portion 50 of the linear motor portion
The outer yoke 5 and the outer yoke 5.
It is fixedly connected to the end of 2. The closed container 100 is made of a cylindrical container and has a space 101 formed therein. The space 101 accommodates the components of the linear compressor. Further, the closed container 100 includes a suction pipe (not shown),
A discharge pipe (not shown) is provided. The support mechanism section 90 is
A plurality of coil springs 91, 92 are arranged between the components of the linear compressor and the closed container 100, and prevent the vibration transmitted from the cylinder 10 to the closed container 100.

Next, the operation of the linear compressor of this embodiment will be described. First, when the coil 53 of the fixed portion 50 is energized,
A thrust force proportional to the current is generated between the movable portion 40 and the permanent magnet 41 in accordance with Fleming's left-hand rule. Due to the generation of this thrust, a driving force that retracts along the axial direction acts on the movable portion 40. Since the cylindrical holding member 42 of the movable portion 40 is connected to the piston 20, the piston 20 smoothly retreats along the axial direction. The alternating current when the coil 53 is energized is given by a sine wave, and forward and reverse thrusts are alternately generated in the linear motor section. Then, the pistons 20 reciprocate due to the forward and reverse thrusts generated alternately. The refrigerant is introduced into the closed container 100 of FIG. 1 through a suction pipe (not shown). The refrigerant introduced into the closed container 100 enters the compression chamber 13 from the suction side space of the head cover part 80 through a suction valve (not shown) assembled to the cylinder end surface 11. The refrigerant is compressed by the piston 20 and the cylinder end surface 11
From a discharge valve (not shown) assembled to the discharge pipe (not shown) through the discharge side space of the head cover portion 80.
Is discharged from the outside. The vibration of the cylinder 10 caused by the reciprocating motion of the piston 20 is damped by the coil springs 91 and 92.

In a free piston stroke linear compressor in which the position of the piston 20 is determined by the balance between the operating pressure condition and the output applied to the linear motor, the amplitude of the piston 20 may change abruptly. As a result, the piston 20 is driven beyond the allowable stroke of the linear motor, and the piston 20 moves to the cylinder end surface 1
There is a possibility of colliding with 1. Compression chamber side coil spring 15
Is assembled so that the position of the piston 20 when it is most compressed is the top dead center 29 of the piston 20. As a result, the piston 20 is mechanically constrained by the compression chamber side coil spring 15, the piston amplitude of the free piston stroke can be regulated, and the piston end 20 does not collide with the piston end surface. It is possible to prevent the piston tip from colliding with the cylinder end surface against disturbance force during transportation or transportation, thereby improving reliability. In addition, the compression chamber side coil spring 15 and the anti-compression chamber side coil spring 3
By making the cross-sectional shape of 0 an egg-shaped or elliptical spring, the maximum stress generated in the wire rod at the time of spring deflection can be lowered as compared with the round wire cross-section, so the coil spring height can be suppressed and the spring It becomes compact and the linear compressor can be downsized.

FIG. 2 is an enlarged view of a main part when the compression chamber side coil spring is a non-linear coil spring. Note that the other configurations are the same as those in FIG. In this embodiment, the non-linear coil spring 15 is composed of unequal pitch springs. Since the pitches of the unequal pitch spring are non-uniform, as the deflection of the spring increases, more wire-bonding occurs and the number of effective windings decreases as compared with the equal pitch spring. Therefore, as shown in FIG. 3, in a state where the deflection is large, the spring load is increased with a nonlinear load characteristic, the piston speed is absorbed, the impact force of the piston on the cylinder end surface 11 can be relaxed, and the impact sound is generated. It can be reduced and good durability can be obtained.

FIG. 4 is an enlarged view of the essential parts showing another embodiment in which the compression chamber side coil spring is a non-linear coil spring. Note that, also in this embodiment, the other configuration is the same as that of FIG. In this embodiment,
The non-linear coil spring 15 is a conical coil spring. In this embodiment, the compression chamber side coil spring 15 is thus
As a result of the conical coil spring, when the spring deflection becomes large, the same action as the above-mentioned unequal pitch coil spring becomes more prominent, and as shown in FIG. 5, the spring load greatly increases when the deflection is large. Therefore, as the piston speed gets closer to the top dead center, it works effectively as a brake that absorbs the piston speed, the impact force of the piston on the cylinder end face can be relaxed, the impact noise can be reduced, and the reliability can be enhanced.

Here, the compression chamber side coil spring 1 shown in FIG.
5 is a spring constant weaker than the coil spring 30 on the side opposite to the compression chamber. In particular, the constant k1 of the coil spring 15 which is the compression chamber side coil spring, and the coil spring 30 which is the anti-compression chamber side coil spring
When the spring constant k2 of the piston is the amplitude a of the piston and the offset amount α pushed to the side opposite to the compression chamber by the gas force applied from the compression chamber during operation of the piston, k1 × (a +
The relational expression of α) = k2 × (a−α) is established. FIG. 6 shows the correlation of the coil springs. Since both coil springs 15 and 30 are used as compression springs at the time of assembly, a preload is applied to compress the coil springs.
Add F0. During operation, the piston amplitude center position from the piston assembly position is offset α to the anti-compression chamber side by the gas force Fg of the compression chamber. Each coil spring 15,
Regarding the deflection amounts x1 and x2 of 30, the deflection amount x1 of the compression chamber side coil spring 15 having a small spring constant becomes large. From the drive frequency of the linear compressor, the predetermined coil spring constant is k1 +
Determined from the sum of k2 and the required piston stroke 2a
The offset amount α can be set by the operating pressure condition and the bore diameter of the piston 20. Based on these dimensions, by selecting each spring constant so that the above relational expression is satisfied, the piston amplitude center position O during operation causes the maximum deflection amount of the compression chamber side coil spring 15 and the anti-compression chamber side coil spring 30. Therefore, the maximum deflection amount of the spring can be suppressed as compared with the case where the coil spring constants on the compression chamber side and the anti-compression side are the same with respect to the piston maximum stroke amount determined by the design. Therefore, the coil spring can be made compact and the linear compressor can be made compact.

As described above, the piston 20 is mechanically restrained by the compression chamber side coil spring 15 even when it is most compressed by an external impact force during operation with a large piston stroke or during transportation. Since the piston amplitude can be regulated, the piston tip can be prevented from colliding with the cylinder end face, and a highly reliable compressor can be realized.
Further, by using the compression chamber side coil spring 15 as an unequal pitch spring or a conical coil spring,
When the piston approaches the top dead center, the spring load increases,
It works as a brake that absorbs the piston speed, can relax the piston impact force on the cylinder end face, reduce the impact noise,
Good durability can be obtained. In addition, each coil spring constant,
Excessive spring deflection is also required by making the compression chamber side coil spring constant smaller than the anti-compression chamber side coil spring constant so that the relational expression of k1 × (a + α) = k2 × (a−α) is almost satisfied. Since the coil spring is not provided, the coil spring can be made compact, and the linear compressor can be made compact. Also, by making the coil spring an egg-shaped or elliptical cross-sectional shape,
Compared to the round wire cross section, the maximum stress generated in the wire rod when the spring is flexed can be reduced and the coil spring height can be reduced, so that the coil spring can be made compact and the linear compressor can be made compact. In addition, although the linear compressor having a compression mechanism using gas has been described in the above-described embodiment, a pumping mechanism for a liquid other than gas may be used. Also,
Although the refrigerant to be used is not particularly described in the above embodiment, it is preferable to use a refrigerant containing carbon dioxide as a main component. Under a CO2 refrigerant that is highly lubricated with a high differential pressure refrigerant, it is much more efficient and more reliable than other compressors.

[0022]

According to the present invention, a clearance is secured between the piston end surface and the cylinder end surface when the compression chamber side coil spring is most compressed, so that a pressure change during operation or a disturbance during transportation or the like occurs. Even if the piston behavior suddenly changes due to the force, the piston amplitude is regulated by the compression chamber side coil spring when the piston amplitude increases, so it is possible to avoid collision between the piston tip and the cylinder end surface, and improve reliability. it can. Further, according to the present invention, the compression chamber side coil spring is a non-linear coil spring, so that the spring load increases as the spring deflection increases. Accordingly, since the piston speed approaching the top dead center is absorbed, the impact force relaxing effect can be expected. Further, according to the present invention, by using the non-uniform pitch coil spring as the non-uniform coil spring, as the deflection increases, more wire-to-wire bonding occurs and the effective number of turns decreases as compared with the equidistant pitch coil spring. Because it increases the load,
Absorbs the piston speed approaching the top dead center, absorbs the impact force, and obtains good durability. Further, according to the present invention, by making the compression chamber side coil spring a conical coil spring, when the spring deflection increases, the similar effect of the unequal pitch coil spring becomes more remarkable, and the spring load greatly increases. As a brake that absorbs the piston speed approaching the dead center, it works effectively, the impact force of the piston can be relaxed, the impact noise can be reduced, and the reliability can be improved. Further, according to the present invention, by designing the coil spring constant on the compression chamber side to be small and the coil spring constant on the anti-compression chamber side to be large, it is possible to design the compressor more than when the coil spring constants on the compression chamber side and the anti-compression side are the same. It is possible to suppress the maximum deflection amount of the spring with respect to the maximum piston amplitude determined by Therefore, the coil spring can be made compact and the linear compressor can be made compact. Further, according to the present invention, k1 × (a
By determining the coil spring constant so that the relational expression of + α) = k2 × (a−α) is satisfied, the piston amplitude center position offset during operation is approximately in the middle of the maximum deflection amount of the coil spring. Can be adjusted accurately,
Furthermore, since the maximum amount of deflection of the spring can be suppressed, the coil spring can be made compact and the linear compressor can be made compact. Further, according to the present invention, by making the coil spring into an egg-shaped or elliptical spring cross-sectional shape, the maximum stress generated in the wire rod at the time of spring deflection is reduced and the coil spring height is reduced as compared with the round wire cross-section. As a result, the coil spring can be made compact, and the linear compressor can be made compact. According to the invention,
It uses a refrigerant containing carbon dioxide as a main component, and is highly efficient and highly reliable under a CO2 refrigerant, which is a high differential pressure refrigerant and has severe lubrication, compared to other type compressors.

[Brief description of drawings]

FIG. 1 is a sectional view showing an overall configuration of a linear compressor according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of an essential part showing a coil spring means of the present invention.

FIG. 3 is a load characteristic diagram of the unequal pitch spring of the present invention.

FIG. 4 is an enlarged sectional view of an essential part showing another coil spring means of the present invention.

FIG. 5 is a load characteristic diagram of the conical coil spring of the present invention.

FIG. 6 is a schematic diagram of a deflection amount of a coil spring during operation according to an embodiment of the present invention.

[Explanation of symbols]

10 cylinders 13 compression chamber 15 Compression chamber side coil spring 20 pistons 21 Gap 30 Anti-compression chamber side coil spring 40 Moving part 41 permanent magnet 42 Cylindrical holding member 50 Fixed part 51 Inner yoke 52 Outer yoke 53 coils 80 Head cover part 90 Support mechanism 100 airtight container

Continued front page    (72) Inventor Nobuaki Ogawa             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Hiroshi Hasegawa             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F-term (reference) 3H076 AA02 BB01 CC03 CC28 CC31                       CC39

Claims (8)

[Claims] 1. A compression chamber having a compression mechanism for compressing gas and a linear motor for operating the compression mechanism, the compression mechanism having a cylinder and a piston, the compression chamber performing gas compression in the cylinder. The linear motor has a fixed portion connected to the cylinder and a movable portion connected to the piston, one end of which is pressed against the piston or the movable portion and the other end of which is on the compression chamber side of the cylinder. Or, by the compression chamber side coil spring that presses against the fixed portion and one end that presses against the piston or the movable portion and the other end presses against the cylinder on the side opposite to the compression chamber or the fixed portion, the compression chamber side coil spring, In a linear compressor in which the piston is movably supported in the axial direction, a gap is secured between the piston end surface and the cylinder end surface when the compression chamber side coil spring is most compressed. A linear compressor that is characterized by 2. The linear compressor according to claim 1, wherein the compression chamber side coil spring is a non-linear coil spring. 3. The linear compressor according to claim 2, wherein the non-linear coil spring is an unequal pitch coil spring. 4. The linear compressor according to claim 2, wherein the non-linear coil spring is a conical coil spring. 5. A compression chamber for compressing gas and a linear motor for operating the compression mechanism are provided in a closed container, the compression mechanism has a cylinder and a piston, and a compression chamber for compressing gas in the cylinder. The linear motor has a fixed portion connected to the cylinder and a movable portion connected to the piston, one end of which is pressed against the piston or the movable portion and the other end of which is on the compression chamber side of the cylinder. Or, by the compression chamber side coil spring that presses against the fixed portion and one end that presses against the piston or the movable portion and the other end presses against the cylinder on the side opposite to the compression chamber or the fixed portion, the compression chamber side coil spring, In the linear compressor in which the piston is movably supported in the axial direction, the compression chamber side coil spring constant is smaller than the anti-compression chamber side coil spring constant. A reduction machine. 6. The amplitude of the piston is a, the amount by which the piston is offset to the side opposite to the compression chamber by the gas force applied from the compression chamber during operation is α, the compression chamber side coil spring constant is k1, and the opposite side is The coil spring constants k1 and k2 are determined so that a relational expression of approximately k1 × (a + α) = k2 × (a−α) is established, where the compression chamber side coil spring constant is k2. 5. The linear compressor according to item 5. 7. The linear compressor according to claim 1, wherein the compression chamber side coil spring or the anti-compression chamber side coil spring has an oval or elliptical cross-sectional shape. 8. The linear compressor according to claim 1, which is operated by using a refrigerant containing carbon dioxide as a main component.