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  System for adjusting resonance frequencies in a linear compressorUSPTO Application #: 20060110259Title: System for adjusting resonance frequencies in a linear compressor Abstract: A system for adjusting resonant frequencies in a linear compressor comprising, in the interior of a shell: a linear motor: a cylinder; a piston reciprocating inside the cylinder; and an actuating means operatively coupling the piston to the linear motor, said system comprising: a detecting means to detect a load imposed to the linear motor, in an operational condition of the latter related to the gas pressure in the discharge thereof; and a frequency adjusting means operatively associated with the detecting means and with the resonant assembly, in order to define, as a function of said operational condition, a frequency adjustment, by varying at least one of the values related to the mass of the resonant assembly and to the average stroke of the piston, to a value of the mechanical resonance frequency corresponding to the electrical supply frequency. (end of abstract)
Agent: Darby & Darby P.C. - New York, NY, US Inventors: Rinaldo Puff, Dietmar E Rich Bernhard Lilie, Egidio Berwanger USPTO Applicaton #: 20060110259 - Class: 417044200 (USPTO) Related Patent Categories: Pumps, Condition Responsive Control Of Pump Drive Motor, By Control Of Electric Or Magnetic Drive Motor, Responsive To Pump Fluid Pressure The Patent Description & Claims data below is from USPTO Patent Application 20060110259. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001] The present invention refers to a system for controlling and adjusting the resonance frequencies in a linear compressor of the type used in small refrigeration appliances, such as refrigerators, freezers, water fountains, etc. BACKGROUND OF THE INVENTION [0002] Linear compressors present a mechanical resonance frequency that is defined by the spring constant and by the masses of the movable components of said compressor when the latter is working with no gas load to be refrigerated (unloaded), i.e., with no gas being pumped. The mechanical resonance frequency of the mass-spring system of the compressor is a function of the mass-spring project thereof and defines the natural mechanical resonance frequency of the compressor. [0003] The mechanical resonance frequency during the operation of the compressor, with the latter pumping gas under a determined pressure ratio, said pressure ratio being defined as the discharge pressure divided by the suction pressure, is influenced by the gas-spring effect resulting from the compression of the refrigerant fluid in the compression chamber of the compressor, which effect is higher or lower, depending on the pressure/dead volume ratio. [0004] The mass-spring system of the compressor is designed to present a mechanical resonance frequency substantially close to the electrical supply frequency of the power system, i.e., about 50 Hz or 60 Hz, depending on the location. The attainment of this objective may be called operational tuning. [0005] In the tuning condition between the mechanical resonance frequency of the compressor and the electrical supply frequency of the power system, the energy that must be supplied to the compressor is basically the sum of the energy consumed for gas compression and the energy consumed with friction between the movable parts in operation. [0006] The known compressor designs usually present a mass-spring system with a natural mechanical resonance frequency, without considering the loads below the electrical supply frequency of the power system. [0007] In order to be efficient during operation in a refrigeration system, the linear compressor must have its mechanical resonance frequency equal or at least substantially equal to the electrical frequency supplied to the motor of the compressor, since in this condition there is a balance between the accumulation and liberation of energy, establishing a tuned operational condition. When the compressor is working out of tune, it needs to receive more energy to keep it running and also to generate compression work. [0008] The gas being pumped during the operation of the compressor in a refrigeration system acts as an additional spring in the mass-spring system of the compressor, modifying its mechanical resonance frequency, conducting the latter to values that can diverge upwardly or downwardly from the value of the electrical supply frequency of the power system. This additional spring, or gas-spring, presents an average constant which is a function of the pressure/dead volume ratio. When gas is compressed outwardly from the cylinder, part of the compression energy returns to the mechanical system, delivering work back to the mechanical system, resulting in a spring effect. In pressure ratio increase conditions, the gas-spring effect is intensified, increasing the mechanical resonance frequency. In dead volume increase conditions, upon reducing the capacity of the compressor, the gas-spring effect is also intensified, increasing the mechanical resonance frequency. [0009] In the refrigeration system, the pressures depend on the thermal load existing inside the refrigeration appliance, i.e., the source of thermal load existing in the interior thereof and which is generating heat, which the system has to remove; and on the temperature of the environment where the refrigerator is located, since, if the temperature of this environment is high, the temperature of the condenser must be higher than the temperature of the environment, since the condenser must work transferring heat to the environment that is external to that being refrigerated by the refrigeration appliance. [0010] In warmer days, as well as in conditions in which more load is to be refrigerated, the gas compression pressures rise and the compressor is forced to work more so that the refrigeration system can remove heat from the medium under refrigeration. The pressure variations in the refrigeration system vary the capacity of the compressor and modify the tuning condition between its mechanical resonance frequency and the electrical supply frequency of the power system. [0011] In determined situations, the loss of balance between the electrical and mechanical frequencies in the compressor results, for the latter, in a higher need of energy to maintain the pumping of gas. [0012] In a situation in which the refrigeration appliance is conducted from a turn-off condition to a turn-on condition, the refrigeration system of this appliance is submitted to high pressure peaks, with maximum pumping capacity, which increases the mechanical resonance frequency of the compressor, causing unbalance between said mechanical resonance frequency and the electrical supply frequency of the power system. In such conditions, the motor of the compressor has to increase its operational force to keep the mechanism in the same frequency as that of the power system. Since the motor yield is a function of its effort to operate, there is loss of motor efficiency whenever the mechanical resonance frequency is not equalized with the electrical supply frequency of the power system. [0013] There are known from the prior art solutions to adjust the electrical supply frequency with the mechanical resonance frequency of the compressor under operation. In one of said solutions, the frequency adjustment is obtained by electronic balance, rectifying the frequency of the power system and then altering the latter according to the changes that occur in the mechanical system. [0014] In a particular solution within this concept, the electronic balance is achieved by varying the velocity of the compressor motor (Brazilian patent document PI9601535-7). However, this solution is expensive and presents energy loss. [0015] There are not known prior art solutions for adjusting the mechanical resonance frequency, which allow, during operational conditions, correcting said frequency and making it substantially equal to the electrical supply frequency of the power system. OBJECTS OF THE INVENTION [0016] Thus, it is an object of the present invention to provide [0017] a system for adjusting the resonance frequencies in a linear compressor, which controls and conducts the mechanical resonance frequency of the compressor, at least in determined operational conditions, to values that are substantially close to the electrical supply frequency of the compressor, without presenting the high costs and high energy losses of the electronic control systems. [0018] It is a further object of the invention to provide a system such as mentioned above, which maintains the dead volume of the compressor at a minimum value during the operation thereof, maintaining an adequate volumetric yield, with minimum energy loss. DISCLOSURE OF THE INVENTION [0019] These and other objects are achieved through a system for adjusting the mechanical resonant frequencies in a linear compressor comprising, in the interior of a shell: a linear motor supplied by an AC electrical current presenting a predetermined electrical supply frequency; a cylinder, within which is defined a compression chamber closed by a valve plate; and a resonant assembly defined by a piston reciprocating inside the cylinder in consecutive suction and compression strokes, and an actuating means operatively coupling the piston to the linear motor. The system for adjusting the mechanical resonance frequency of the present invention comprises: a detecting means to detect a load imposed to the linear motor of the compressor, in an operational condition of the latter related to the gas pressure in the discharge thereof; and a frequency adjusting means operatively associated with the detecting means and with the resonant assembly, in order to define, as a function of the operational condition detected for the gas in the discharge of the compressor, a frequency adjustment by varying at least one of the values related to the mass of the resonant assembly and to the average stroke of the piston, to a value of the mechanical resonance frequency of the resonant assembly corresponding to the electrical supply frequency, maintaining unaltered the minimum distance between the piston and the valve plate at the end of each compression stroke. BRIEF DESCRIPTION OF THE DRAWINGS Continue reading... Full patent description for System for adjusting resonance frequencies in a linear compressor Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this System for adjusting resonance frequencies in a linear compressor patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like System for adjusting resonance frequencies in a linear compressor or other areas of interest. ### Previous Patent Application: Air compressor Next Patent Application: Device of micro vortex for ferrofluid power generator Industry Class: Pumps ### FreshPatents.com Support Thank you for viewing the System for adjusting resonance frequencies in a linear compressor patent info. 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