KR20060020014A - Linear compressor - Google Patents

Abstract

The present invention relates to a linear compressor in which a movable member is driven by a linear motor and sucks, compresses, and discharges refrigerant while reciprocating linear motion inside the fixed member. In particular, an elastic force supporting the movable member as the operating frequency of the linear motor increases. It is related with the linear compressor which makes it become large and makes resonance operation effective.

The linear compressor according to the present invention includes a fixed member having a compression space formed therein, a movable member compressing sucked refrigerant while reciprocating linear motion inside the fixed member, and connected to the movable member to reciprocally linearly move the movable member. A linear motor for driving, a gas spring in which the refrigerant contained in the compression space elastically supports the movable member in one direction, and installed on both sides of the movable member so as to elastically support in the movement direction of the movable member; It consists of at least one mechanical spring whose elastic force increases with increasing frequency.

Linear compressors, cylinders, pistons, linear motors, springs, coil springs

Description

Linear Compressor {LINEAR COMPRESSOR}             

1a and 1b is a graph showing the stroke and efficiency according to the load in the linear compressor according to the prior art,

Figure 2 is a side sectional view showing a spring support structure of the linear compressor according to the prior art,

3 is a graph showing the mechanical spring constant applied to FIG.

4 is a side sectional view showing a linear compressor according to the present invention;

5a and 5b is a graph showing the stroke and efficiency according to the load in the linear compressor according to the present invention,

6 to 8 are side cross-sectional views showing first, second and third embodiments of the spring support structure of the linear compressor according to the present invention, respectively;

9 is a graph showing the mechanical spring constant applied to FIGS. 6 to 8;

10 is a side sectional view showing a fourth embodiment of a spring supporting structure of the linear compressor according to the present invention;

FIG. 11 is a graph showing the mechanical spring constant applied to FIG. 10.

<Explanation of symbols on main parts of the drawings>

2: airtight container 4: cylinder

6: piston 7: muffler

8a, 8b: 1st, 2nd mechanical spring 10: linear motor

12: inner stator 14: outer stator

16: permanent magnet 22: suction valve

24: discharge valve assembly

The present invention relates to a linear compressor in which a movable member is driven by a linear motor and sucks, compresses, and discharges refrigerant while reciprocating linear motion inside the fixed member. In particular, an elastic force supporting the movable member as the operating frequency of the linear motor increases. It is related with the linear compressor which makes it become large and makes resonance operation effective.

In general, a compressor is a mechanical device that increases pressure by receiving power from a power generator such as an electric motor or a turbine to compress air, refrigerant, or various other working gases. It is widely used throughout.

Recently, a reciprocating linear movement of a reciprocating linear movement, in which a piston compresses a refrigerant while the piston reciprocates linearly in a cylinder, allows a compression space for operating gas to be absorbed and discharged between the piston and the cylinder. In order to improve the compression efficiency because there is no mechanical loss due to the motion conversion by connecting directly to the drive motor, a linear compressor having a simple structure has been developed.

Specifically, the linear compressor is installed so that the cylinder is fixed inside the sealed container, the piston is installed in the cylinder to reciprocate linear movement, the compression space in the cylinder as the piston reciprocating linear movement in the cylinder It is configured to compress and then discharge the refrigerant into the inlet, the inlet and outlet valve assembly is installed in the compression space to adjust the inflow and discharge of the refrigerant in accordance with the pressure in the compression space.

In addition, the linear motor for generating a linear movement force to the piston is installed to be connected to each other, the linear motor is installed in the inner stator and the outer stator configured to have a plurality of laminations circumferentially stacked around the cylinder with a predetermined gap. The coil is wound around the inner stator or the outer stator, and a permanent magnet is installed in the gap between the inner stator and the outer stator so as to be connected to the piston.

At this time, the permanent magnet is installed to be movable in the direction of movement of the piston, and the reciprocating linear motion in the direction of movement of the piston by the electromagnetic force generated as the current flows in the coil, the linear motor is a constant operation Not only is it operated at a frequency f _c but also causes the piston to reciprocate linearly with a predetermined stroke S.

On the other hand, the piston is provided with a variety of springs to be elastically supported in the direction of movement even if the linear motor reciprocating linear movement, specifically, a coil spring which is a kind of mechanical spring to the closed container and the cylinder in the direction of movement of the piston It is installed to be elastically supported, and the refrigerant sucked into the compression space also acts as a gas spring.

At this time, the coil spring has a constant mechanical spring constant (K _m ), the gas spring has a gas spring constant (K _g ) that is variable according to the load, the mechanical spring constant (K _m ) and gas spring constant (K _In consideration of _g ), the natural frequency f _n of the piston (linear compressor) is calculated according to Equation 1 below.

[Equation 1]

The calculated natural frequency f _n of the piston determines the operating frequency f _{c of} the linear motor, and the linear motor matches the operating frequency f _c with the natural frequency f _n of the piston. The efficiency can be increased by operating in the resonance state.

The linear compressor configured as described above has a natural frequency f _n of the piston which is calculated by the mechanical spring constant K _m of the coil spring and the gas spring constant K _g of the gas spring under the load considered by the linear motor in design. Since the linear motor is operated in a resonance state only in the intermediate load region considered in the design, as shown in FIGS. 1A and 1B, since the piston is configured to operate at an operating frequency f _c corresponding to At the same time, the compression efficiency can be increased.

However, the linear compressor as described above has a low load not considered in the design because the gas spring constant (K _g ) of the gas spring and the natural frequency (f _n ) of the piston calculated by considering the same change as the actual load varies. In the region and the high load region, since the linear motor is not operated in a resonance state, the piston reaches more than the top dead center (TDC) to generate friction and wear, or the piston does not reach the top dead center, thereby reducing the compressive force and the compression efficiency. Falls.

As a result, in the conventional linear compressor, the natural frequency f _n of the piston is variable as the load is varied, whereas the linear motor is not operated in a resonance state because the operating frequency f _{c of} the linear motor is constant. There is a problem in that the efficiency is lowered and the load cannot be released quickly due to the failure to actively respond to the load.

In order to solve the above problems, the input current is adjusted in proportion to the load so as to change the operating frequency f _c of the linear motor.

Specifically, the conventional linear compressor is installed so that the piston 56 is supported by a pair of coil springs 58a and 58b having the same mechanical spring constant K _{m in the} direction of motion as shown in FIG. The refrigerant included in the compression space P inside the cylinder 54 also acts as a gas spring having a gas spring constant K _g .

At this time, the coil spring (58a, 58b) is formed to have the same pitch and wire diameter in a constant one direction to have a constant mechanical spring constant (K _m ), as shown in Figure 3, the operating frequency of the linear motor It imparts a certain elastic force, even if (f _c), a predetermined load is applied to the piston 56 as a variable.

Therefore, although the operating frequency f _c of the linear motor is operated in a resonant state in synchronization with the natural frequency f _n of the piston in a predetermined load state, even if the gas spring constant K _g increases due to the load increase. As the increase is small, the natural frequency of the piston (f _n ) is also slightly increased. On the contrary, the operating frequency (f _c ) of the linear motor is greatly increased, making it difficult to operate in a resonance state and in an unstable state. There is a problem that the compression capacity and compression efficiency is reduced because it is operated.

The present invention has been made to solve the above-mentioned problems of the prior art, the elastic force of the mechanical spring is increased as the operating frequency of the linear motor increases so that the operating frequency of the linear motor matches the natural frequency of the piston, the resonance operation is It is an object to provide a linear compressor to be achieved.

The linear compressor according to the present invention for solving the above problems is a fixed member having a compression space therein, a movable member for compressing the sucked refrigerant while reciprocating linear movement inside the fixing member, and is connected to the movable member A linear motor for driving the movable member to reciprocate linearly, a gas spring for elastically supporting the movable member in one direction, and a refrigerant contained in the compression space, and elastically supporting both sides of the movable member in the movement direction of the movable member; It is installed is composed of at least one or more mechanical spring that the elastic force increases as the operating frequency of the linear motor increases.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

4 is a side cross-sectional view showing a linear compressor according to the present invention, Figures 5a and 5b is a graph showing the stroke and efficiency according to the load in the linear compressor according to the present invention.

As shown in FIG. 4, the linear compressor according to the present invention is provided with an inlet pipe 2a and an outlet pipe 2b through which refrigerant flows in and out of one side of the sealed container 2, and inside the sealed container 2. The cylinder 4 is installed to be fixed, and the piston 6 is installed in the cylinder 4 so as to reciprocate linear movement so as to compress the refrigerant sucked into the compression space P inside the cylinder 4. And a linear motor 10 generating a driving force to linearly reciprocate the piston 6 is installed to be connected to the piston 6, and the refrigerant in the compression space P also varies according to the load. It acts as a gas spring having a constant K _g and is installed such that the first and second mechanical springs 8a and 8b are elastically supported in the direction of movement of the piston 6, wherein the first and second mechanical springs 8a, 8b) is the operating frequency (f _c ) of the linear motor is changed to The greater the load acting on the piston 6, the greater the elastic force.

At this time, the linear motor 10 estimates the natural frequency f _n of the piston according to a predetermined frequency estimation algorithm even if the natural frequency f _n of the piston varies according to the load, and accordingly the operating frequency f _c. ), The piston 6 reaches the top dead center (TDC) as shown in Figs. 4A and 4B, so that not only the compression but also the compression efficiency can be improved in all load regions.

In addition, a suction valve 22 is installed at one end of the piston 6 in contact with the compression space P, and a discharge valve assembly 24 is provided at one end of the cylinder 4 in contact with the compression space P. ) Is installed, and the suction valve 22 and the discharge valve assembly 24 are automatically adjusted to open and close according to the pressure inside the compression space P, respectively.

Here, the airtight container (2) is installed so that the upper and lower shells are coupled to each other so that the inside is sealed, the inlet pipe (2a) and the outlet pipe (2b) for the coolant flow in one side is installed, the The piston 6 is installed inside the cylinder 4 so as to be elastically supported in the movement direction for reciprocating linear motion, and the linear motor 10 is assembled to each other by the frame 18 outside the cylinder 4. The assembly is installed to be elastically supported by a support spring 29 on the inner bottom surface of the sealed container (2).

In addition, a predetermined oil is contained in the bottom surface of the airtight container (2), and an oil supply device (30) for pumping oil is installed at the bottom of the assembly, and oil is provided in the lower frame (18) of the assembly. An oil supply pipe 18a is formed to be supplied between the 6 and the cylinder 4, so that the oil supply device 30 is operated by vibration generated by the reciprocating linear motion of the piston 6. The oil is pumped, and this oil is supplied along the oil supply pipe 18a to the gap between the piston 6 and the cylinder 4 for cooling and lubrication.

Next, the cylinder 4 is formed in a hollow shape so that the piston 6 can reciprocate linearly, and a compression space P is formed at one side thereof, and one end is located close to the inside of the inflow pipe 2a. It is preferable to be installed on the same straight line as the inflow pipe (2a) in the state.

Of course, the cylinder (4) is installed in one end close to the inlet pipe (2a) so as to reciprocate linear movement, the discharge valve assembly ( 24) is installed.

At this time, the discharge valve assembly 24 is provided to open and close the discharge cover 24a which is installed to form a predetermined discharge space on one end side of the cylinder 4, and one end of the compression space P side of the cylinder. And a discharge valve 24b and a valve spring 24c, which is a kind of coil spring that imparts an elastic force in the axial direction between the discharge cover 24a and the discharge valve 24b, and at one end of the cylinder 4 The O-ring (R) is installed in the fitting so that the discharge valve 24a is in close contact with one end of the cylinder (4).

In addition, a bent loop pipe 28 is installed between one side of the discharge cover 24a and the outlet pipe 2b. The loop pipe 28 guides the compressed refrigerant to be discharged to the outside. In addition, the vibration caused by the interaction of the cylinder 4, the piston 6, and the linear motor 10 buffers the transmission of the entire sealed container 2.

Therefore, when the pressure of the compression space P becomes equal to or greater than a predetermined discharge pressure as the piston 6 reciprocates linearly in the cylinder 4, the valve spring 24c is compressed and the discharge valve ( 24b) is opened, and the refrigerant is discharged from the compression space P, and then completely discharged along the loop pipe 28 and the outlet pipe 2b.

Next, the piston 6 has a refrigerant passage 6a formed at the center so that the refrigerant introduced from the inlet pipe 2a flows, and an intake valve 22 at one end inserted into the cylinder 4. And a piston flange 6b formed at one end of the opposite side thereof is connected to the linear motor 10 to reciprocate linearly.

At this time, the suction valve 22 is formed in a thin plate shape so that the center portion is partially cut to open and close the refrigerant passage 6a of the piston, and one side is fixed by a screw to one end of the piston 6a. It is installed as possible.

Therefore, as the piston 6 reciprocates linearly in the cylinder 4, when the pressure of the compression space P becomes lower than or equal to a predetermined suction pressure lower than the discharge pressure, the suction valve 22 is When the refrigerant is opened and sucked into the compression space P, and the pressure in the compression space P becomes equal to or greater than a predetermined suction pressure, the refrigerant in the compression space P is closed while the suction valve 22 is closed. Is compressed.

Next, the linear motor 10 is configured such that a plurality of laminations 12a are stacked in the circumferential direction, and the inner stator 12 and the coil are installed to be fixed to the outside of the cylinder 4 by the frame 18. A plurality of laminations 14b are laminated in the circumferential direction around the coil winding 14a configured to be wound so that a predetermined gap is formed between the inner stator 12 and the outside of the cylinder 4 by the frame 18. Permanent magnet 16 is installed in the gap between the outer stator 14 and the inner stator 12 and the outer stator 14 is installed so as to be connected by the piston 6 and the connecting member (17) The coil winding 14a may be installed to be fixed to the outer side of the inner stator 12.

As the current is applied to the coil winding 14a in the linear motor 10 as described above, an electromagnetic force is generated, and the permanent magnet 16 reciprocates by the interaction between the electromagnetic force and the permanent magnet 16. The piston 6 is linearly moved, and the piston 6 connected to the permanent magnet 16 is reciprocated linearly in the cylinder 4.

Of course, the linear motor 10 so that the resonance operation by regulated made to match the operating frequency (f _c) the natural frequency (f _n) of the piston estimated by a predetermined frequency estimation algorithm.

As described above, even when the piston 6 is reciprocated linearly while the operating frequency f _c of the linear motor is variable, the piston 6 is stably elastic in the movement direction without hitting peripheral components such as the cylinder 4. Specifically, the refrigerant in the compression space (P) acts as a gas spring to impart an elastic force to the piston (6) in one direction and at the same time the first and second machine spring (8a) on both sides of the piston flange (6b) 8b) is provided to impart elastic force in both directions to the piston (6).

In this case, the gas spring has a variable gas spring constant (K _g ) depending on the load, the gas contained in the compression space (P) increases its elastic force as the pressure of the refrigerant increases as the ambient temperature increases As the gas spring loads, the gas spring constant K _g increases.

On the other hand, the first and second mechanical springs (8a, 8b) has a mechanical spring constant (K _m ) which is changed in proportion to the operating frequency (f _c ) of the linear motor, based on the piston flange (6b) It is installed to be elastically supported on both sides. When the piston 6 is moved in the direction of compressing the refrigerant in the compression space P, the first machine spring 8a is restored and at the same time the second machine spring 8b. Is installed to be compressed, and the first and second machine springs 8a and 8b alternately repeat compression and restoration as the piston 6 reciprocates linearly.

For example, the first machine spring 8a is installed between one side of the piston flange 6a and a predetermined support frame 26 fixed to the linear motor 10, and the second machine spring 8b. Is installed between the other side of the piston flange (6b) and the cylinder (4), the first and second machine spring (8a, 8b) is elastically supported on the peripheral components in various directions in the movement direction of the piston (6) Can be installed as possible.

At this time, the first and second mechanical springs (8a, 8b) may be installed on each side of the piston flange (6b) only one, respectively, so that the piston 6 can be stably supported in both directions Four may be provided in the circumferential direction of the piston 6, respectively, and more preferably on the same straight line in the movement direction of the piston 6 so as to stably support the piston 6.

In general, the first and second mechanical springs 8a and 8b may be applied to various kinds of springs, but a lot of coil springs are applied, and the spring constant of such coil springs is calculated according to Equation 2 below.

[Equation 2]

 In this case, G is the elastic modulus of the material, d is the thickness (wire diameter) of the material, Na is the effective winding number of the material, D is the central diameter of the coil spring, a coil having various spring constants by varying the above variables Spring can be applied.

6 to 8 are side cross-sectional views showing first, second and third embodiments of the spring support structure of the linear compressor according to the present invention, and FIG. 9 is a graph showing the mechanical spring constant applied to FIGS. 6 to 8. .

For example, the first and second mechanical springs 8a and 8b applied to the first embodiment are applied to a variable pitch coil spring in which the pitch a is narrower in one direction as shown in FIG. 6. The coil spring may be applied to both the first and second mechanical springs 8a and 8b, or may be applied to only one of the first and second mechanical springs 8a and 8b.

In this case, as the operating frequency fc of the linear compressor increases, the variable pitch coil spring is configured so that the spring constant K _m of the variable pitch coil spring also increases as the load acting on the piston 6 increases. It is preferable that one end of the large silver pitch a is in contact with the piston 6.

In addition, the first and second machine springs 8a and 8b applied to the second embodiment are applied with a conical coil spring in which the wire diameter D is narrower in one direction as shown in FIG. 7. It may also be applied to only one of the first and second machine springs 8a and 8b, or may be applied to both the first and second machine springs 8a and 8b.

In this case, as the operating frequency f _c of the linear compressor increases, the conical coil spring increases so that the mechanical spring constant K _{m of} the conical coil spring also increases as the load acting on the piston 6 increases. It is preferable that the one end of which the silver wire diameter is large comes into contact with the piston 6.

In addition, the first and second mechanical springs 8a and 8b applied to the third embodiment are applied with symmetrical conical coil springs with narrower wire diameters D from the center to both ends, as shown in FIG. The conical coil spring may also be applied to only one of the first and second machine springs 8a and 8b, or may be applied to both the first and second machine springs 8a and 8b.

At this time, the symmetrical conical coil spring can support the piston 6 more stably than the conical coil spring applied in the second embodiment, thereby increasing the reliability of the operation.

As described above, a nonlinear spring whose spring constant changes with displacement as a load is applied such as a variable pitch coil spring, a conical coil spring, a symmetrical conical coil spring, and the like is operated by a linear compressor installed to elastically support the piston 6. As shown in FIG. 9, as the load increases, the driving frequency fc of the linear motor is changed, so that the load actually applied to the piston 6 is variable, and thus the load is applied to the piston 6. As it varies, the mechanical spring constant K _m also varies.

Accordingly, the operating frequency f _c of the linear motor is varied to actively respond to the load, and at the same time the gas spring constant K _g and the mechanical spring constant K _m vary according to the load. The natural frequency f _n is also relatively large, so that the operating frequency f _c of the linear motor is easily synchronized with the natural frequency f _n of the piston to achieve resonance operation.

FIG. 10 is a side sectional view showing a fourth embodiment of the spring support structure of the linear compressor according to the present invention, and FIG. 11 is a graph showing the mechanical spring constant applied to FIG.

On the other hand, the first and second machine springs 8a and 8b applied to the fourth embodiment have a constant displacement of the main coil spring and the piston 6 so as to be supported in the movement direction of the piston 6 as shown in FIG. The auxiliary coil spring is provided to be elastically supported only during the reciprocating motion, but the main coil spring and the auxiliary coil spring may also be applied to only one of the first and second machine springs 8a and 8b, and the first and second coil springs. It may be applied to both mechanical springs 8a and 8b.

At this time, the main coil spring is installed so that the wire diameter is larger than the auxiliary coil spring is installed so that the auxiliary coil spring is located inside the main coil spring, the main coil spring is installed to be directly supported by the piston (6) On the other hand, the auxiliary coil spring is preferably installed so as to be spaced apart from the piston 6 in one direction of the movement direction by a predetermined interval.

Of course, although the main coil spring has a larger wire diameter than the auxiliary coil spring, it is preferable that the spring constant of the main coil spring is larger than the auxiliary coil spring constant.

In addition, one main coil spring which is in direct contact with the piston 6 is installed, and a plurality of auxiliary coil springs may be installed at intervals with the piston 6 in steps therein. As the load is applied, the spring constant (K _m ) can be varied stepwise with displacement.

Referring to the operation of the linear compressor in which the main coil spring and the auxiliary coil spring are elastically supporting the piston 6 as described above, as shown in FIG. 11, the operating frequency f _c of the linear motor as the load increases. Is variable so that the load actually applied to the piston 6 is variable, and thus the mechanical spring constant K _m is also variable based on a constant displacement of the piston 6 as the load on the piston 6 is variable. do.

At this time, only the main coil spring elastically supports the piston 6 when the piston 6 reciprocates linearly below a certain displacement, while the piston 6 reciprocates linearly above a certain displacement. Since a coil spring and an auxiliary coil spring elastically support the piston 6 together, the mechanical spring constant K _m increases further from the first mechanical spring constant K _m1 based on the constant displacement of the piston 6. Variable by the second mechanical spring constant (K _m2 ).

Therefore, even if the operating frequency f _c of the linear motor is varied to actively respond to the load, the natural frequency f _n of the piston is varied as the gas spring constant K _g and the mechanical spring constant K _m are varied. ) Is also relatively large, so that the operating frequency f _c of the linear motor can be easily synchronized with the natural frequency f _n of the piston to achieve resonance operation.

In the above, the present invention is based on the embodiment of the present invention and the accompanying drawings in which a moving magnet type linear motor is operated, and a linear compressor that sucks, compresses, and discharges a refrigerant while the piston connected thereto reciprocates linearly inside the cylinder. It explained in detail. However, the scope of the present invention is not limited by the above embodiments and drawings, and the scope of the present invention will be limited only by the contents described in the claims below.

Since the linear compressor according to the present invention configured as described above is installed such that the piston is elastically supported by a nonlinear coil spring whose spring constant is variable with displacement as the load is applied, the operating frequency of the linear motor is increased to displace the piston. And the natural frequency of the piston is also increased, so that the operating frequency of the linear motor is synchronized with the natural frequency of the piston to achieve resonant operation. There is an advantage to increase.

Claims (6)

A fixed member having a compression space formed therein, A movable member which compresses the refrigerant sucked while reciprocating linearly inside the fixing member; A linear motor connected to the movable member to drive the movable member to reciprocate linearly; A gas spring in which the refrigerant contained in the compression space elastically supports the movable member in one direction; And at least one mechanical spring installed on both sides of the movable member to elastically support in the movement direction of the movable member, the elastic force of which increases as the driving frequency of the linear motor increases. The method of claim 1, The mechanical spring is a linear compressor, characterized in that the variable pitch coil spring formed narrower in one direction. The method of claim 1, The mechanical spring is a linear compressor, characterized in that the conical coil spring formed with a narrower wire diameter toward one direction. The method of claim 1, And the mechanical spring is a symmetrical conical coil spring formed with narrower wire diameters from the center to both ends thereof. The method of claim 1, And the mechanical spring comprises a main coil spring installed to support the piston in the direction of movement of the piston, and an auxiliary coil spring installed to elastically support the piston only when the piston reciprocates more than a certain displacement. The method of claim 5, wherein And the auxiliary coil spring is installed to be positioned inside the main coil spring.

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