US20050271526A1

Movatterモバイル変換

Info

Publication number: US20050271526A1
Application number: US11/109,743
Authority: US
Inventors: Keun Chang; Phil Chang
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 2004-06-04
Filing date: 2005-04-20
Publication date: 2005-12-08
Also published as: EP1607631A3; EP1607631A2; JP2005344708A

Abstract

A driving unit and control method for a reciprocating compressor for controlling a frequency of input power so that an operational frequency of the compressor follows a resonant frequency, which varies depending on a variation of the load applied to the compressor. The reciprocating compressor includes an inverter to adjust the frequency of the input power, so that the frequency of the input power is set at a value corresponding to the resonant frequency by the inverter. The resonant frequency is set in a range of 60% to 90% of the normal power frequency. The compressor further includes a controller to control the frequency of the input power so that the operational frequency of the compressor follows the resonant frequency, which varies depending on the operation of the compressor.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Patent Application No. 2004-40994, filed on Jun. 4, 2004 in the Korean Intellectual Property Office and Korean Patent Application No. 2004-73172, filed on Sep. 13, 2004 in the Korean Intellectual Property Office, the disclosures of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a reciprocating compressor, and more particularly, to a driving unit and control method for a reciprocating compressor for controlling a frequency of input power so that an operational frequency of the compressor is a resonant frequency which varies based on a variation of load applied to the compressor, and also for improving efficiency of the reciprocating compressor in a low load state.

2. Description of the Related Art

In general, compressors are used in air conditioning systems, refrigerators, etc. to compress a refrigerant. One type of compressor is a reciprocating compressor, which compresses the refrigerant by making use of variation in the volume of a compressing chamber caused by reciprocating movements of a piston. Certain reciprocating compressors employ a rotary motor as a driving unit, and others employ a conventional linear motor.

The reciprocating compressors employing the conventional linear motor are configured such that the piston, which reciprocates in the compressing chamber, is directly connected to a rectilinearly-reciprocating mover of the linear motor and is supported by an elastic resonant spring. In such a reciprocating compressor, the compression of the refrigerant is achieved as the mover rectilinearly reciprocates in correspondence with a frequency of input power when an alternating current is applied to the linear motor. The piston reciprocates in accordance with the rectilinear reciprocation of the mover. Here, the resonant spring achieves an exciting force which facilitates the movement of the piston and thus ensures smooth reciprocating motion of the piston.

The motion of the piston increases when operational efficiency of the piston coincides with the resonant frequency (i.e. natural frequency) of the compressors. Therefore, there have been attempts to make the resonant frequency of the compressors coincide with a typical power frequency for the purpose of improving the efficiency of the compressors. That is, in order to improve compression capability of the compressors, it is important to adjust the resonant frequency of the compressors to correspond to the typical power frequency. Such an adjustment of the resonant frequency of the compressors can be achieved through control of the mass of the moving units, including the piston and the mover of the linear motor, as well as controlling an elasticity of the resonant spring.

However, in conventional reciprocating compressors which are controlled to have the resonant frequency equal to the power frequency, the typical power having a high frequency (i.e., the conventional 60 Hz) must be used as an input power, resulting in an acceleration in an operational speed of the compressors. This makes it difficult to expand the available range of compression capabilities of the compressors and thus limits the operation of the compressors to a relatively low frequency range, and also results in reduced efficiency of the compressors due to motor core loss and mechanical friction loss.

Further, the conventional reciprocating compressors may experience a variation in resonant frequency due to a gas pressure variation acting on the piston when a load varies during operation of the compressors. Such a variation of the resonant frequency leads to an inconsistency between the resonant frequency and the operational frequency, resulting in a deterioration in the efficiency of the compressors.

SUMMARY OF THE INVENTION

Accordingly, it is an aspect of the present invention to provide a driving unit and control method for a reciprocating compressor for setting a resonant frequency of the compressor at a value less than a frequency of the typical power and making a frequency of input power to be applied to the compressor coincide with the resonant frequency, thereby being capable of expanding. Thus, the available range of compression capabilities of the compressor allows the compressor to resonate in a low frequency range which is less than the frequency of the typical power, resulting in an improvement in efficiency of the compressor.

It is another aspect of the present invention to provide a driving unit and control method for a reciprocating compressor for allowing an operational frequency of the compressor to coincide with a varying resonant frequency based on a variation of load applied to the compressor, thereby improving efficiency of the compressor.

Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the invention.

The forgoing and/or other aspects may be achieved by providing a reciprocating compressor including an inverter to receive a power and adjust a frequency of the received power and to input the adjusted power to the compressor, wherein: a resonant frequency of the compressor is less than a typical frequency of the received power, and a frequency of the input power corresponds to the resonant frequency.

The resonant frequency may be between 60% and 90% of the typical frequency of the power.

The compressor may further include a controller to control operation of the compressor, and the controller may control the frequency of the input power so that an operational frequency of the compressor follows the resonant frequency as the resonant frequency varies depending on the operation of the compressor.

The controller may determine a phase difference between the frequency of the input power and the operational frequency of the compressor, thereby controlling the inverter to increase or decrease the frequency of the input power according to a correction value corresponding to the phase difference.

The compressor may further include a current detector to detect the frequency of the input power applied from the inverter to the compressor; and a displacement detector to detect displacement of a piston mounted in the compressor so as to determine the operational frequency.

The compressor may further include a load detector to detect a load applied to the compressor; the controller may control the inverter so that the frequency of the input power is equal to the resonant frequency when the load detected by the load detector is a normal load, and the frequency of the input power is greater than the resonant frequency when the detected load is a higher than the normal load.

The forgoing and/or other aspects are achieved by providing a reciprocating compressor an inverter to adjust a frequency of power input to the compressor including: and a controller to control the inverter so that an operational frequency of the compressor coincides with the frequency of the input power according to a determined phase difference between the operational frequency and the frequency of the input power.

The forgoing and/or other aspects are achieved by providing a driving unit for driving a reciprocating compressor including: an inverter to adjust a frequency of input power to be applied to the compressor; a load detector to determine a load applied to the compressor; and a controller to control the inverter so that the frequency of the input power is equal to a resonant frequency of the compressor when the load determined by the load detector is a normal load, whereas the frequency of the input power is greater than the resonant frequency when the determined load is greater than the normal load.

The forgoing and/or other aspects are achieved by providing a driving unit for driving a reciprocating compressor including: a piston; an inverter to adjust a frequency of input power to be applied to the compressor; a current detector to detect the frequency of the input power; a displacement detector to detect a displacement of the piston to thereby determine an operational frequency of the compressor; and a controller to control the inverter to thereby determine a phase difference between the operational frequency and the frequency of the input power and then increase or decrease the frequency of the input power based on the determined phase difference, wherein the operational frequency follows a resonant frequency, which varies depending on an operation of the compressor.

The forgoing and/or other aspects are achieved by providing a control method for a reciprocating compressor including: determining whether a load applied to the compressor is a high load or normal load; applying a power, having a frequency equal to a resonant frequency of the compressor, to the compressor if the load applied to the compressor is the normal load; and applying a power, having a frequency greater than the resonant frequency of the compressor, to the compressor if the load applied to the compressor is the high load.

The forgoing and/or other aspects are achieved by providing a control method for a reciprocating compressor having an inverter, including: determining a phase difference between a frequency of input power and an operational frequency of the compressor; and controlling the inverter to increase or decrease the frequency of the input power with a correction value corresponding to the phase difference.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages of the invention will become apparent and more easily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 is a sectional view of a reciprocating compressor in accordance with an embodiment of the present invention;

FIG. 2 is a control block diagram of a driving unit provided in the reciprocating compressor ofFIG. 1; and

FIG. 3 is a flow chart illustrating a control method for the reciprocating compressor ofFIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Reference will now be made in detail to the embodiment of the present invention, an example of which is illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. The embodiment is described below to explain the present invention by referring to the figures.

FIG. 1 is a sectional view of a reciprocating compressor in accordance with an embodiment of the present invention. As shown inFIG. 1, the reciprocating compressor includes a hermetically sealedcontainer10 formed by coupling anupper container10aand alower container10b. The reciprocating compressor further includes: acompression unit20 having acylinder block21, apiston22 and acylinder head23; and alinear motor30. Thelinear motor30 drives thecompression unit20 and has amover31 and inner and

outer stators

32 and33. Thecompression unit20 and thelinear motor30 are mounted as a set in the hermetically sealedcontainer10.

Thecylinder block21 of thecompression unit20 includes: acylinder portion21ainternally defining acompressing chamber24 and a supportingportion21bradially extending from the outer circumference of a lower region of thecylinder portion21ato support theouter stator33 thereon. Thecylinder block21 is supported, at a lower end of the supportingportion21bthereof, by means of a plurality ofdamping members25, so that thecylinder block21 is spaced apart from an inner wall surface of thelower container10b.

Thepiston22 is mounted in thecompressing chamber24 of thecylinder block21 in a vertically reciprocable manner. Thecylinder head23 is located under thecylinder block21 and internally defines an introducingchamber23aand adischarge chamber23b. At the introducingchamber23aof thecylinder head23 is formed an introducingport23ccontaining an introducing valve plate, and at thedischarge chamber23bof thecylinder head23 is formed adischarge port23dcontaining a discharge valve plate. Reference numeral11 designates an outer introducing pipe,reference numeral12 designates an introducing pipe connected to the introducingchamber23a, andreference numeral13 designates a discharge pipe connected to thedischarge chamber23bso as to extend to the outside of the hermetically sealedcontainer10.

Thelinear motor30, adapted to actuate thepiston22, is mounted so that themover31 is located inside of thecylinder portion21aand the inner and

outer stators

32 and33 are located outside of thecylinder portion21a. Themover31 has a hollow cylindrical form so that anupper fixing portion31athereof is coupled to the outer circumference of an upper region of thepiston22, thereby allowing themover31 to vertically reciprocate along with thepiston22. Themover31 has amagnet35 attached to a lower end of theupper fixing portion31a. Themagnet35 allows themover31 to vertically reciprocate through an interaction between themagnet35 and theouter stator33.

Both theinner stator32 and theouter stator33 have a cylindrical form and are located, respectively, inside and outside of themover31. Theinner stator32 is fixed to the outer circumference of thecylinder portion21aand guides the vertical reciprocation of themover31 and ensures smooth flow of magnetic flux through themagnet35 of themover31. Theouter stator33 has anexciting coil34 to electromagnetically interact with themagnet35. A lower end of theouter stator33 is supported on the supportingportion21bof thecylinder block21 and an upper end of theouter stator33 is supported by a fixingframe36.

The reciprocating compressor further includes aresonant spring37 in the form of a multi-layered plate spring. Theresonant spring37 is mounted on the fixingframe36 to be spaced upward apart from themover31. Theresonant spring37 is centrally coupled to an upper end of thepiston22, and an outer circumferential edge of theresonant spring37 is coupled to aspring supporting member38 extending upward from the fixingframe36. Theresonant spring37 configured as described above produces an exciting force by making use of elasticity thereof, so as to improve the movability of thepiston22.

To theresonant spring37 are mounted asensor core41 and a coil-typedisplacement detecting sensor42. Thesensor core41 extends upward from an upper surface of themover31 and is reciprocatable following reciprocating movements of themover31 and thepiston22. Thedisplacement detecting sensor42 detects a distance of movement of thesensor core41.

In the reciprocating compressor configured as described above, theouter stator33 produces a magnetic field when an alternating current is applied to theexciting coil34 thereof. The polarity of the produced magnetic field alternates, causing vertical reciprocating movement of themover31 having themagnet35. As themover31 reciprocates, thepiston22 correspondingly reciprocates to achieve a compression operation, thereby enabling introduction and discharge of a refrigerant.

During the compression operation, if an operational frequency of thepiston22 coincides with a resonant frequency, i.e. the natural frequency of the compressor, resonance of the compressor is achieved. This increases the movability of thepiston22 and themover31 and improves efficiency of the compressor. As compared to conventional reciprocating compressors wherein the resonant frequency is controlled to coincide with typical power frequency, the reciprocating compressor of the embodiment of the present invention is controlled so that the resonant frequency of the compressor is set at a value less than the typical power frequency. Also, a frequency of input power to be supplied to the reciprocating compressor corresponds to the resonant frequency, which is less than the typical power frequency.

For example, if the typical frequency of the power is 60 Hz, the resonant frequency of the compressor is set at a value of approximately 50 Hz, and thus the frequency of the input power is approximately 50 Hz. In this case, if the resonant frequency and the frequency of the input power are excessively low, it may result in a deterioration in the efficiency of the compressor. Thus, when the typical frequency of the power is 60 Hz, the resonant frequency and the frequency of the input power are in a range of 35 to 55 Hz, corresponding to 60% to 90% of the power frequency.

Such a configuration of the reciprocating compressor as described above is employed in order to expand the available range of compression capabilities of the compressor as compared to the prior art, so that the compressor resonates even in a relatively low frequency range. This can increase the available range of compression capabilities depending on a load variation of a cooling system using the compressor, as well as the efficiency of the compressor. The fact that the compressor can resonate at the relatively low frequency range, which is less than the typical power frequency, means that the compressor can more effectively operate under a general, low-load, low-speed running condition (hereinafter, referred to as a normal load condition). The compressor operates with the operational frequency, which is less than the frequency of the normal power in the normal load condition to reduce any possible motor core loss or mechanical friction loss, which results in the conventionally apparatus.

FIG. 2 is a control block diagram of the driving unit provided in the reciprocating compressor ofFIG. 1. As shown inFIG. 2, the driving unit includes aninverter51 to adjust a voltage and frequency of input power to be supplied from an alternatingcurrent source50 to the reciprocating compressor, and acurrent detector53 to detect the frequency of the input power based on information transmitted from acurrent sensor52. The driving unit further includes: adisplacement detector54 to detect operational frequencies of thepiston22 and themover31 based on information transmitted from thedisplacement detecting sensor42 mounted in the compressor, aload detector55 to detect a temperature and discharge and introducing pressures of the compressor or a load applied to a cooling system containing the compressor, so as to detect a load applied to the compressor, and acontroller56 to control theinverter51 based on information detected via thecurrent detector53, thedisplacement detector54 and theload detector55 in order to control the frequency of the input power being applied to the reciprocating compressor.

Now, the compression operation of the reciprocating compressor according to the embodiment of the present invention and a method for effectively controlling the compression operation will be explained.

When power, having a frequency of 60 Hz, is supplied from the alternatingcurrent source50 to start the compressor, the normal power is converted into input power having a frequency corresponding to a resonant frequency of the compressor by theinverter51. That is, the frequency of the input power, being applied from theinverter51 to the compressor, is approximately 50 Hz, corresponding to the resonant frequency. Thereby, when the compressor is in a low load state, i.e. normal load state, thepiston22 reciprocates with an operation frequency of approximately 50 Hz, performing a compression operation. That is, the compressor resonates in a low frequency range less than the frequency of the normal power, showing improved operational efficiency in the normal load state, which occupies a high running percentage of the compressor.

In the course of achieving the compression operation as described above, thecontroller56 decides whether the load applied to the compressor is a normal load or a high load based on information transmitted from theload detector55. In the case of the normal load, thecontroller56 controls theinverter51 so that the frequency of the input power corresponds to the resonant frequency of the compressor.

When the compressor runs in the normal load state, thecontroller56 also controls theinverter51 so that the frequency of the input power always corresponds to the resonant frequency even if the resonant frequency varies depending on a variation of load applied to the compressor. This enables the compressor to continuously resonate, and achieves optimized efficiency of the compressor. During operation of the compressor, although the mass of moving elements such as thepiston22 and themover31 and the elasticity of theresonant spring37 are unchangeable, a gas pressure acting on thepiston22 varies depending on the load variation, inevitably resulting in a variation of the resonant frequency. Therefore, in order to continuously maintain the optimized efficiency of the compressor, the frequency of the input power varies according to the variation of the resonant frequency through a control operation of thecontroller56.

Such a control operation achieved by thecontroller56 will now be explained with reference toFIG. 3. That is, in order to allow the frequency of the input power to follow the resonant frequency, thedisplacement detector54 detects the displacement of thepiston22 to determine an operational frequency of the compressor (operation61), and thecurrent detector53 determines the frequency of the input power (operation62). On the basis of information determined by the

detectors

Meanwhile, if theload detector55 decides that the load applied to the compressor is higher than the normal load and thus the compressor is in the high load state, thecontroller56 controls theinverter51 to increase the frequency of the input power beyond the resonant frequency so that the high frequency of the input power is applied to the compressor in order to improve capability of the compressor. That is, as compared to the case of the normal load, wherein the frequency of the input power is controlled to coincide with the resonant frequency to maximize the efficiency of the compressor, in the case of the high load, the compressor is controlled to operate at the maximum compression rate possible without causing deterioration of the efficiency of the compressor. Since the compressor mainly runs in the normal load state rather than the high load state, the efficiency of the compressor can be maximized by optimizing the efficiency of the normal load state, which occupies a high running percentage of the compressor.

As is apparent from the above description, the embodiment of the present invention provides a reciprocating compressor in which a resonant frequency of the compressor is set at a value less than a typical power frequency, and a frequency of input power to be applied to the compressor is controlled to coincide with the resonant frequency. This expands the available range of compression capabilities of the compressor to allow the compressor to resonate even in a relatively low frequency range, which is less than the typical power frequency, resulting in an improvement in efficiency of the compressor. This improves the efficiency of the compressor under a normal load state, which occupies a high running percentage of the compressor, achieving optimized efficiency of the compressor.

Further, according to the embodiment of the present invention, even if the resonant frequency varies depending on a variation of a load applied to the compressor during operation of the compressor, an operational frequency of the compressor is controlled to follow the varied resonant frequency, so as to allow the continuous resonance of the compressor, resulting in maximized efficiency of the compressor.

Although an embodiment of the present invention has been shown and described, it would be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.

Claims

1. A reciprocating compressor comprising:

an inverter to receive a power and adjust a frequency of the received power and to input the adjusted power to the compressor, wherein:

a resonant frequency of the compressor is less than a typical frequency of the received power, and

a frequency of the input power corresponds to the resonant frequency.

2. The compressor according toclaim 1, wherein the resonant frequency is between 60% to 90% of the typical frequency of the received power.

3. The compressor according toclaim 2, further comprising:

a controller to control an operation of the compressor,

wherein the controller controls the frequency of the input power so that an operational frequency of the compressor follows the resonant frequency as the resonant frequency varies depending on the operation of the compressor.

4. The compressor according toclaim 3, wherein the controller determines a phase difference between the frequency of the input power and the operational frequency of the compressor, thereby controlling the inverter to increase or decrease the frequency of the input power according to a correction value corresponding to the phase difference.

5. The compressor according toclaim 4, further comprising:

a piston mounted in the compressor;

a current detector to detect the frequency of the input power; and

a displacement detector to detect a displacement of the piston to determine the operational frequency.

6. The compressor according toclaim 5, further comprising:

a load detector to detect a load applied to the compressor

wherein the controller controls the inverter so that the frequency of the input power is equal to the resonant frequency when the load detected by the load detector is a normal load, and the frequency of the input power is greater than the resonant frequency when the detected load is higher than the normal load.

7. A reciprocating compressor comprising:

an inverter to adjust a frequency of power input to the compressor; and

a controller to control the inverter so that an operational frequency of the compressor coincides with the frequency of the input power according to a determined phase difference between the operational frequency and the frequency of the input power.

8. The compressor according toclaim 7, wherein the controller controls the inverter to increase or decrease the frequency of the input power according to a correction value corresponding to the phase difference, thereby allowing the operational frequency to follow a resonant frequency of the compressor which varies depending on an operation of the compressor.

9. A driving unit for driving a reciprocating compressor, comprising:

an inverter to adjust a frequency of input power to be applied to the compressor;

a load detector to determine a load applied to the compressor; and

a controller to control the inverter so that the frequency of the input power is equal to a resonant frequency of the compressor when the load determined by the load detector is a normal load, whereas the frequency of the input power is greater than the resonant frequency when the determined load is greater than the normal load.

10. A driving unit for driving a reciprocating compressor, comprising:

a piston;

a current detector to detect the frequency of the input power;

a displacement detector to detect a displacement of the piston to thereby determine an operational frequency of the compressor; and

a controller to control the inverter to thereby determine a phase difference between the operational frequency and the frequency of the input power and then increase or decrease the frequency of the input power based on the determined phase difference, wherein the operational frequency follows a resonant frequency, which varies depending on an operation of the compressor.

11. A control method for a reciprocating compressor comprising:

determining whether a load applied to the compressor is a high load or normal load;

applying a power, having a frequency equal to a resonant frequency of the compressor, to the compressor if the load applied to the compressor is the normal load; and

applying a power, having a frequency greater than the resonant frequency of the compressor, to the compressor if the load applied to the compressor is the high load.

12. A control method for a reciprocating compressor having an inverter, comprising:

determining a phase difference between a frequency of input power and an operational frequency of the compressor; and

controlling the inverter to increase or decrease the frequency of the input power with a correction value corresponding to the phase difference.

13. The compressor according toclaim 4, wherein the controller maintains the frequency of the input power when the determined phase difference is zero.

14. The compressor according toclaim 5, wherein the resonant frequency varies according to a gas pressure acting on the piston.

15. A control method for a reciprocating compressor:

inputting a power having a frequency greater than a resonant frequency of the compressor;

adjusting the input power to the resonant frequency of the compressor; and

driving the compressor with the adjusted power.