Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K7/00—Arrangements for handling mechanical energy structurally associated with dynamo-electric machines, e.g. structural association with mechanical driving motors or auxiliary dynamo-electric machines
  • H02K7/14—Structural association with mechanical loads, e.g. with hand-held machine tools or fans
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B17/00—Pumps characterised by combination with, or adaptation to, specific driving engines or motors
  • F04B17/03—Pumps characterised by combination with, or adaptation to, specific driving engines or motors driven by electric motors
  • F04B17/04—Pumps characterised by combination with, or adaptation to, specific driving engines or motors driven by electric motors using solenoids
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B35/00—Piston pumps specially adapted for elastic fluids and characterised by the driving means to their working members, or by combination with, or adaptation to, specific driving engines or motors, not otherwise provided for
  • F04B35/04—Piston pumps specially adapted for elastic fluids and characterised by the driving means to their working members, or by combination with, or adaptation to, specific driving engines or motors, not otherwise provided for the means being electric
  • F04B35/045—Piston pumps specially adapted for elastic fluids and characterised by the driving means to their working members, or by combination with, or adaptation to, specific driving engines or motors, not otherwise provided for the means being electric using solenoids
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
  • F04B49/06—Control using electricity
  • F04B49/065—Control using electricity and making use of computers
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K33/00—Motors with reciprocating, oscillating or vibrating magnet, armature or coil system
  • H02K33/02—Motors with reciprocating, oscillating or vibrating magnet, armature or coil system with armatures moved one way by energisation of a single coil system and returned by mechanical force, e.g. by springs
  • H02K33/10—Motors with reciprocating, oscillating or vibrating magnet, armature or coil system with armatures moved one way by energisation of a single coil system and returned by mechanical force, e.g. by springs wherein the alternate energisation and de-energisation of the single coil system is effected or controlled by movement of the armatures
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K33/00—Motors with reciprocating, oscillating or vibrating magnet, armature or coil system
  • H02K33/16—Motors with reciprocating, oscillating or vibrating magnet, armature or coil system with polarised armatures moving in alternate directions by reversal or energisation of a single coil system
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
  • H02P25/00—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details
  • H02P25/02—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details characterised by the kind of motor
  • H02P25/032—Reciprocating, oscillating or vibrating motors
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B2201/00—Pump parameters
  • F04B2201/02—Piston parameters
  • F04B2201/0201—Position of the piston
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B2201/00—Pump parameters
  • F04B2201/02—Piston parameters
  • F04B2201/0206—Length of piston stroke
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B2203/00—Motor parameters
  • F04B2203/04—Motor parameters of linear electric motors
  • F04B2203/0401—Current
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B2203/00—Motor parameters
  • F04B2203/04—Motor parameters of linear electric motors
  • F04B2203/0402—Voltage
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K11/00—Structural association of dynamo-electric machines with electric components or with devices for shielding, monitoring or protection

Definitions

• the present invention relates to fluid-pumping devices such as, for example, linear compressors and, particularly, to a system and a method for controlling this kind of device, being driven by a linear electric motor.
• a linear motor is an ancient idea, but it was carried out only re- cently with maturation in the field of control and actuation of electric machines.
• a linear motor replaces rotary electric motors with many advantages, among which the economy of electric energy, since it used a more direct conversion of electric energy with less loss.
• Especially the use of linear compressors in present-day cooling cycles has been scarce due to the techno- logic difficulties usually encountered.
• a linear motor and of a linear compressor may vary; the latter may be of simple or double effect, while the motor may comprise a work coil and a magnet; and this magnet may be either moveable or static.
• the linear compressor in question one has opted for the simple effect, a fixed coil and a moveable magnet.
• Linear-type compressors are known from the prior art and are constituted by a mechanism in which the piston makes an oscillatory movement, and in most cases there is an elastic means interconnecting the cylin- der and the piston, which imparts a resonant characteristic to this movement the energy being supplied by a linear-displacement motor.
• Equivalents such as piston-actuated water pumps or any fluid-pumping device can benefit from the object of the present invention.
• the mechanism is provided with a discharge valve constructed in such a way, that, if the piston exceeds the maximum displacement course expected in its oscillatory movement, for instance when the voltage imposed on the motor is excessive, there will be contact of the piston with this discharge valve, and this valve will allow the piston to ad- vance a little, thus preventing an impact against the plate of the valve head.
• a discharge valve constructed in such a way, that, if the piston exceeds the maximum displacement course expected in its oscillatory movement, for instance when the voltage imposed on the motor is excessive, there will be contact of the piston with this discharge valve, and this valve will allow the piston to ad- vance a little, thus preventing an impact against the plate of the valve head.
• Another known solution is described in document US 4,602,174, where the course of displacement of the piston is also primary proportional to the voltage imposed on the linear motor, which is of the moveable-magnet and fixed-coil type. In this solution the design of the mechanism does not allow the piston to advance past
• the ratio between the course of displacement of the piston and the diameter of the piston is not great, which makes the performance of the compressor more dependent upon the variations in the course of displacement of the piston.
• the gas-discharge process gives a very small option of the course, namely about 5% of the total.
• a monitoring system is foreseen for monitoring the times the piston passes by a determined reference point within the compressor. In this way, when the residence time of said piston beyond the reference point exceeds a pre-established value, the voltage level is momentarily reduced during the respective movement, thus avoiding a collision with the valve plate.
• the movement of the piston is controlled by counting discrete points thereof along the cylinder of the compressor. In case the piston moves excessively, the value of the average voltage applied to the respective motor is reduced so as to decrease the movement amplitude of said piston.
• the objective of the invention is to control stroke course of dis- placement of the piston of a linear compressor or of any fluid-pumping device, such as piston-actuated water pumps, allowing the piston to advance as far as the end of its mechanical course of displacement, even in extreme load conditions, without allowing the piston to collide with the valve system.
• Another objective of the present invention is to provide control over the course of displacement of the piston of a linear compressor or any other fluid-pumping device, without the need for information about the displacement of the middle point of oscillation of the piston.
• a control system foreseen for controlling the movement of a piston in a fluid- pumping device, the piston being displaceable in a block of the fluid-pumping device and being driven by a motor fed by a voltage.
• the system comprises a semiconductor electronic device that cyclically applies the voltage to the motor for driving the piston, a resistive element, a capacitive element, a piston-position sensor for indicating the passage of the piston by a point at the block of the fluid-pumping device, the capacitive element being charged by means of the resistive element at each cycle of application of voltage to the motor, the capacitive element being discharged at least partly when the piston passes by said point.
• the objectives are achieved by a method of controlling the movement of a piston in a fluid- pumping device, the piston being displaceable in a fluid-pumping device and being driven by a motor fed by a voltage.
• This method comprises the steps of: charging a capacitive element by means of a resistive element; monitoring the movement of the piston by means of a position sensor; maintaining the charge level of the capacitive element until the position sensor has detected the passage of the piston by a predetermined point at the compressor block; and discharging the capacitive element at least partly.
• a fluid-pumping device comprising a piston displaceable in a block, the piston being driven by a motor fed by a voltage.
• This device comprises a circuit having a semiconductor electronic device, a resistive element, a capacitive element, a piston-position sensor for indicating the passage of the piston by a point at the compressor block.
• the resistive element and the capacitive element are associated to the semiconductor electronic device, re-feeding an outlet and an inlet of the latter, the capacitive element being charged by means of the resistive element and being discharged at least partly when the piston passes by said point.
• FIG. 1 shows a linear compressor schematically
• a linear compressor 1 basically comprises a piston 10 that is displaced in oscillatory motion within the block 5, so as to compress a gas that is charged and discharged through a valve plate 11 , which comprises a charge valve 13 and a discharge valve 12.
• an elastic means such as a spring 4 is associated with the piston 10, so that the latter can have a resonant movement within the block 5 of the compressor 1.
• the movement of the piston 10 is induced by a linear-type motor 2, which in turn is driven by an electric voltage V, which should be controlled in order to prevent the piston 10 from colliding with the plate 11.
• V an electric voltage
• the object of the present invention is applicable to any fluid-pumping device 1 , as for example a water pump. For this purpose, one should only to take into consideration the constructive differences between such devices.
• the methods of controlling the movement of the piston 10 em- ployed in earlier techniques include monitoring motion times of the piston by means of microcontrolled circuits.
• the times to be monitored include: (i) residence time "t 0 " of the piston 10 beyond a point R that is physically defined in its course of displacement, and this point is close to the end of the maximum course of displacement M possible to the piston 10, (ii) the time "t c " of dura- tion of the complete cycle, (iii) the time "t om " corresponding to the maximum course of displacement M possible to the piston 10.
• the average voltage V m applied to the motor 2 is incremented, if the time "t 0 " is shorter than the desired time "tod", and vice-versa.
• the point M is very close to the valve plate 11 , being typically at a distance of some dozens of micrometers, while the point R is located close to the valve plate 11 , being typically at a distance of from 1 to 2 millimeters, a distance sufficient to avoid collision of the piston 10 with said plate 11.
• a re-feed (or self-fed) electronic circuit 30, 40 that alters the amplitude of the course of displacement of the piston 10, with the same approach employed in other systems that are controlled by microcontrollers, but without the need for monitoring the cited times.
• the detection of the passage of the piston by the defined physical point R may be effected by some type of physical sensor S installed inside the compressor 1 , be it of the contact, optical or inductive or any other type (see figure 3, in this case).
• this detection may also be effected by adding a magnetic disturbance to the voltage present in the terminals of the motor 2, this disturbance being created, for example, by a constructive detail of the magnetic circuit of the motor. This is the case of the construction of the circuit 40, figure 4.
• the position sensor S may comprise the circuits 30, 40 illustrated in figure 3 and 4, which include a position sensor S p by direct contact and a position sensor L s by inductive sensor, respectively, and which can effect the control automatically, without the need to employ a microcontrolled circuit.
• the control system and method are carried out by means of a tiristor semiconductor device or bidirectional power switch T, which cyclically applies an electric voltage V to the motor L.
• the trigger circuit G (gate or inlet G) of this switch T is actuated by means of the position sensor Sp, Ls, which sends a signal that generates the angle of triggering said switch T, this signal causing a retardation time proportional to the discharge level of the capacitor Cy.
• the gate circuit G connected to the capacitor Cy sends a voltage signal to the linear motor 2 for a longer or shorter time, for the purpose of adjusting the cooling capacity of said linear compressor 1.
• Figure 5 illustrates the wave shape of the voltage V applied to the motor 2 and the stretches where the semiconductor device T does not conduct, as well as the wave shape of the current I.
• the capacitor Cy is associated to the semiconductor device T, so that it will be associated between - and re-fed - the outlet SG and the inlet G of the latter, and also in association with the switch S, which indicates the passage of the piston by the point R.
• Figure 5 illustrates how this solution interferes with the voltage level V of the inlet of the motor L m .
• Raising the voltage in the branch of the capacitor Cy is a function of the capacitance values of the Cy and Cx and of the resistance RB. In this way, it is possible to adjust the circuit 30, 40 to varied constructions of the compressor 1 , so that the semiconductor electronic device T can be adequately triggered (see stretch A' in figure 5, where the semiconductor T conducts).
• the discharge velocity of the capacitor Cy is a function of the capacitance values of Cy, Cx and of the resistance values of R, RT (see stretch B of the curve in figure 5), which should be designed in an adequate way, so that the triggering of the electronic device T will occur in an adequate way.
• a first preferred embodiment of the movement-control system includes the circuit 30, which comprises a position sensor Sp constituted by an electromechanical switch that is directly driven by the piston 10 when the latter passes by the point R, resulting in alteration of operation of the semiconductor electronic device T.
• the capacitor Cy in the next semicycle, will cause the semiconductor elec- tronic device T to enter with some delay, as may be inferred from the deformation of the voltage curve V at the point 23, illustrated in figure 2 (see also figure 3).
• the residence time at zero level (or a sufficiently low level in the winding Lm of the motor 2, so that the latter will not operate) of voltage V will depend upon the time during which the contact of the position sensor Sp has remained closed and upon the value of Ri + Rt (for example, a thermostat).
• the values Ri + Rt should be such, that when Rt is at the condition of maximum resistance and the piston 10 reaches the point M, the capacitor Cy will be discharged at such a level, that the semiconductor electronic device T will not be triggered in the next semicycle.
• the senor S is carried out by means of a sensor or inductive element Lj.
• circuits 30, 40 are self-fed and, therefore, they dispense with the use of an external feed source, which reduces the costs of manufacture and maintenance.
• the transistor Ti closes the circuit in the two embodiments, so as to trigger the electronic device T, actuating as a bidirectional switch: now charging the capacitor Cy, now discharging it. Since this is a self-fed circuit 30, 40, the present invention brings about, as an advantage, the possibility of dispensing with the use of an external feed source, in addition to resulting in a low consumption of electricity (in the milliamperes range) and in addition to enabling the replacement thereof in the event of a failure.
• the present invention also foresees a method for controlling the movement of a piston 10 in a linear compressor 1 or any other fluid-pumping device 1. This method comprises the steps of:
• a fluid- pumping device 1 provided with the system for controlling the movement of the piston 10, to prevent the latter from bumping into the valve plate 11.
• the system and method of the present invention enable one to estimate, at each cycle, the oscillation amplitude of the piston 10 much more precisely, enabling the electronic control to react for compensating the variations in the cooling capacity (in the case of application in compressors), which are slow variations, maintaining the average amplitude of the course of oscillation of the piston 10 at the desired value and equal to P.
• This system and method also enables rapid reactions of the electronic control for compensating shape variations in the operation conditions caused by fluctuations in the feed voltage, and these corrections should be imposed at each oscillation cycle, so as to correct the amplitude of the stroke of the piston 10 in the final portion of its path, after passing by the physical reference point R.
• the system and method of the present invention result in the advantage of a rapid reaction, with corrections at each cycle, without the need for estimates based on the voltage and current imposed on the motor 2, and without mistakes due to secondary variables such as temperature, the construction of the motor 2 and the displacement of the middle point of oscillation of the piston due to the average difference in pressure between the faces 8, 9 of the piston 10.
• the present invention enables one to implement an effective control over the course of displacement of the piston 10, independently of the required cooling capacity, whereby one can prevent the piston 10 from bumping against the valve plate 11 , even in the presence of rapid disturbances caused by the natural fluctuation of the voltage in the commercial network of electric energy.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Computer Hardware Design (AREA)
• Control Of Positive-Displacement Pumps (AREA)
• Compressors, Vaccum Pumps And Other Relevant Systems (AREA)
• Reciprocating Pumps (AREA)

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• 2002
  • 2002-11-19 EP EP02780984A patent/EP1567769A1/de not_active Withdrawn
  • 2002-11-19 CN CNA02830165XA patent/CN1735749A/zh active Pending
  • 2002-11-19 WO PCT/BR2002/000158 patent/WO2004046550A1/en not_active Application Discontinuation
  • 2002-11-19 AU AU2002349191A patent/AU2002349191A1/en not_active Abandoned
  • 2002-11-19 JP JP2004552291A patent/JP2006506571A/ja active Pending
  • 2002-11-19 US US10/535,528 patent/US20060140777A1/en not_active Abandoned

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