JP2009536514A - Vibration control of a free piston machine via frequency adjustment - Google Patents

Abstract

  The present invention is a method and apparatus for minimizing the amplitude of mechanical vibrations of a mechanical device, which is coupled to the reciprocating mass of the driven machine and is free to drive reciprocating at a driving frequency. Including a prime mover that reciprocates linearly The combined prime mover and driven machine have a spring that applies a force to the reciprocating mass to form a main resonant system having a resonant frequency of the main system's reciprocating motion. The range of drive frequencies at which the driven machine operates at an acceptable operating efficiency is determined and stored. The machine operating parameters such as vibration amplitude or operating temperature are sensed and the prime mover is driven at the driving frequency according to the sensed parameter, which is the resonance of the reciprocating motion of the main system. This is a frequency that deviates from the frequency and whose operating efficiency is within the allowable drive frequency range and that reduces or minimizes the amplitude of the mechanical vibration of the mechanical device under existing operating conditions.

Description

  The present invention relates generally to minimizing mechanical vibrations of a mechanical device, the mechanical device including one or more masses driven in reciprocating motion by a freely reciprocating prime mover and controlling the prime mover. Use an electronic control unit.

  Freely linear reciprocating machines are frequently used because of their good durability, low wear, good controllability and efficiency. Free reciprocating machines include linear compressors, free piston Stirling engines, Stirling coolers, cryogenic coolers and heat pumps, linear motors, and linear alternators. Free linear reciprocating machines reciprocate with a controllable stroke, but are not limited to conventional crankshafts and connecting rods. However, freely linear reciprocating machines have significant vibrations because they have one or more masses that reciprocate linearly in a common housing and / or are attached to a common support frame. cause.

  In general, the main machine or system consists of a plurality of freely reciprocating machines connected to each other. One reciprocating machine is a prime mover that freely reciprocates linearly, such as a free piston Stirling engine or an electric linear motor, which can also be referred to as a Stirling linear motor. Other reciprocating machines have a free linear reciprocating load driven by a prime mover through a mechanical connection, such as a free piston compressor, a Stirling heat pump or cooler, or an electric alternator. The reciprocating composite mass of both the prime mover and the load it drives contributes to the vibration. This vibration is usually undesirable and various systems have been developed to minimize the amplitude of such vibration.

  In general, free pistons and other freely linear reciprocating machines are built with one or more springs that apply a spring force to the reciprocating mass. Both the prime mover and the machine it drives may include a spring. The spring may include one or a combination of a gas spring, a magnetic spring, and a mechanical spring. Gas springs and magnetic springs are devices designed to provide a spring force, that is, more generally, they are gases acting on machine parts and / or machines such as electric linear motors and alternators Is the result of the magnetic force from the electromagnet device or permanent magnet system used in the. The mass and springs of the prime mover that moves freely in linear reciprocation, and the driven free linear reciprocating machine together form the main machine that is a resonant system.

  In general, the main machine is designed to operate at or near the resonant frequency, since resonance maximizes the efficiency of the machine. The natural frequency of such a system is expressed by the following equation.

  Here, f is a resonance frequency expressed in cycles / second or hertz, K is a combined spring constant expressed in Newton / meter, and m is a combined mass expressed in Kg. The term “synthetic” is used to refer to the sum of the individual masses and springs of the main machine, and the terms “mass” and “spring” are used when the effects are summed with each other. Used to include

  The vibration problem includes the prime mover that drives the machine from which the mechanical device is the main machine or system, and is also coupled to other devices that include one or more secondary vibration systems. Can be more complicated. By attaching a secondary vibration system to be mechanically connected to the main system, such a secondary system may be coupled to the main machine, for example, This is because both systems are mounted on the same support frame. Secondary vibration systems may be devices that are designed to swing during operation with mass and springs, or are not intended to swing as part of their normal function, Nevertheless, it may be a device having a mass connected to a structure that acts as a spring. If not intended to vibrate during normal operation, the secondary vibration system coupled to the main system is a parasitic resonance system. If the resonance frequency of the parasitic resonance system is sufficiently close to the drive frequency of the main machine, the parasitic vibration system can vibrate with excessive amplitude. If the parasitic vibration system vibrates at the driving frequency and the phase shift with respect to the main system is less than 90 °, the overall vibration of the mechanical device may increase.

  In the prior art, various devices have been developed to reduce main machine vibration. These include "vibration absorbers" and are known by various names, but they are more accurately called vibration balancers because they do not "absorb" vibrations. A vibration balancer is a secondary vibration system that is mechanically coupled to the main system, usually by direct connection to the main system. The purpose of the vibration balancer is to reduce the vibrations caused by the reciprocating motion of the main machine, but since the vibration balancer is not part of the main machine or system, it is desirable to Considered as a form. A system that balances one general vibration is a counterbalance that reciprocates so that a force equal to the force generated by the oscillating mass of the main machine, but the opposite force is applied to the oscillating main machine. Drive the mass. The driven mass of the vibration balancer can be driven by its own prime mover, or alternatively it is driven by the vibration of the main machine that vibrates, and as a result resonates at the same drive frequency, It can be designed to reciprocate with a phase shift of 180 ° relative to the main machine vibration. An example of a system of the former nature is shown in US Pat. No. 5,620,068.

  Another system for reducing vibration is illustrated in US Pat. No. 6,040,672. The induced waveform in the electric motor drive signal is sensed and converted to a control waveform and added to the motor drive current to reduce vibration.

  These systems work satisfactorily at relatively stable operating conditions, but face difficulties when the operating conditions vary extremely. For example, Stirling cycle coolers may be exposed to extreme ambient temperature fluctuations. May operate in the range of -40 ° C to + 60 ° C. When a vibration balancer is attached to a Stirling cooler, such fluctuations in temperature change the stiffness of the cooler spring, thereby changing the spring constant and thus changing the natural frequency of the vibration balancer. The effective spring stiffness of the spring force in the cooler can also vary somewhat, but vibration balancers generally have a high Q (ie, sharp resonance peaks), while Stirling coolers generally have a relatively low Q, Variations in are usually not significantly affected. Therefore, if the driving frequency does not change, a relatively small variation in the natural frequency of the vibration balancer causes a large variation in the effective amplitude of the oscillation. As a result, the ability of the vibration balancer to counteract the vibration of the main machine that vibrates is significantly reduced. Similarly, changes in temperature can also result in changes in electrical parameters, which can change the effective spring constant of the magnetic spring effect. Temperature also changes the dynamic behavior of the Stirling engine and changes the operating frequency. Non-linear behavior of structural parts in response to mechanical springs or changing strokes can similarly change the natural frequency.

  As a result, a mechanical device with a vibration balancer balances well under certain operating conditions and exhibits an acceptable vibration amplitude, but if the operating condition deviates significantly from the predetermined operating condition, the change in the operating condition causes the resonance of the vibration balancer. Vibration balancers are less effective because they change the frequency or natural frequency, or the phase relationship to the main system, or both. As the effect of the vibration balancer decreases, the amplitude of vibration increases.

  Similarly, the resonant frequency of a secondary parasitic vibration system coupled to the main system can also change as a result of changes in operating conditions. As a result, when the operating condition changes greatly, a secondary system that does not deteriorate the vibration of the mechanical device under a certain operating condition may become a problem. When operating conditions change significantly, parts of mechanical devices that are free of vibration problems can become a problem. Parasitic vibration systems may also be discovered after the machine has been built.

  It would be possible to build a vibration balancer that could change the spring constant or otherwise the natural frequency of the swing, but such a vibration balancer would be more expensive than a conventional vibration balancer. I will. Vibrating balancers are not only costly, but also take up space and add weight to the product.

  A feature and object of the present invention is to supplement a vibration balancer by electrically compensating for the ability of the vibration balancer to cancel the vibrations as a result of variations in operating conditions.

  Another object and feature of the present invention is to provide a control system capable of compensating for secondary parasitic vibration systems for a main machine that is freely linearly reciprocating.

  Another object and feature of the present invention is to change the controlled operating characteristics of a prime mover that is freely linearly reciprocating, to account for various causes of resonant frequency changes associated with the main machine that is freely linearly reciprocated. Compensates for anything, and without this, compensates for any vibration balancer connected to the main machine, where uncompensated changes due to changes in operating conditions can lead to increased vibration This is to reduce vibrations electrically.

  Yet another object of the present invention is to compensate for changes in the resonance frequency of the main machine that freely and linearly reciprocates independently and in response to changes in the operating conditions of the machine.

  The present invention is a method and apparatus for minimizing the amplitude of mechanical vibrations of a mechanical device, which is coupled to a reciprocating mass of a driven machine and is driven in a reciprocating motion at a driving frequency. Includes motor. The coupled motor and driven machine have one or more springs that apply a force to the reciprocating composite mass to form a main resonant system having a resonant frequency of the main system's reciprocating motion. . The range of drive frequencies at which the driven machine operates at an acceptable operating efficiency is determined and stored. The operation parameter of the mechanical device is sensed, and the linear motor is driven at the drive frequency according to the sensed parameter, but this drive frequency is deviated from the resonance frequency of the reciprocating motion of the main system, A frequency whose operating efficiency is within an acceptable drive frequency range and which reduces or minimizes the amplitude of mechanical vibrations of the mechanical device under existing operating conditions.

  In describing the preferred embodiments of the invention illustrated in the drawings, specific techniques are utilized for the purpose of clarity. However, the present invention is not intended to be limited to the specific representations thus selected, and each specific representation is intended to be a technical all that operates in a similar manner to achieve a similar purpose. It should be understood to include equivalents.

  The present invention takes advantage of the observation that three frequencies are important in a mechanical device that includes a main machine that vibrates or reciprocates coupled to a secondary vibration system that may include a vibration balancer. These are the resonant (natural) frequency of the main machine that vibrates, the resonant (natural) frequency of the secondary vibration system, and the operating frequency of the main device. The operating frequency of the main machine is also the operating frequency of the vibration balancer and any other secondary vibration system coupled to the main machine.

  When the vibration frequency and vibration amplitude are displayed in a graph for an arbitrary resonance system, the plotted amplitude forms a resonance peak centered on the resonance frequency. These peaks broaden from a wide and gentle form to a steep and steep form, and rise and fall. As known to those skilled in the art, the sharper the peak, the higher the Q factor “Q” of the resonance system.

  The present invention has free linear reciprocating prime movers that drive driven machines that are freely linearly reciprocating, and these main machines that operate efficiently at or near their combined resonant frequencies are: Nevertheless, the observation that there is usually a drive frequency band that can be operated with acceptable efficiency is utilized. They are not limited to operating accurately at their resonant frequencies. This is partly because typical main machines, such as linear motors that drive Stirling coolers, typically exhibit low Q resonance peaks. While this is beneficial, the range of drive frequencies at which the driven machine operates with acceptable operating efficiency is not only determined by the mechanical resonance and reciprocating part quality of the main machine, It also depends on other design and operating characteristics of the machine. However, the designer of any particular machine can apply normal technical principles to the particular main machine and its application to determine the range of acceptable drive frequencies.

  FIG. 1 schematically illustrates a mechanical device 10 that includes an electromagnetic linear motor 14 that drives a Stirling cooler 16 in a reciprocating motion, a motor control circuit 18 having a data storage 20, and the operation of the linear motor 14. And a main machine 12 composed of a control unit. The main machine 10 may include a secondary vibration system 24 such as a vibration balancer 26 and a parasitic resonance system 28. All of the illustrated parts are mechanically coupled together to form the mechanical device 10. For example, they may be physically connected to each other in the same housing or on the same frame, or may be linked together by an intermediate physical structure capable of transmitting vibrations.

  The control system also senses the temperature of the vibration system 24, which can be detected by the exterior, but has a temperature sensor 22 that inputs temperature data to the motor controller 18. Since the spring of the vibration balancer is the main component whose temperature changes most and directly affects the resonance frequency of the vibration balancer, the temperature may be detected by a temperature sensor. Alternatively, the spring temperature can be approximated by sensing the ambient temperature or the temperature of a component that is thermally connected to the spring.

  The motor controller 18 may be conventional, typically a microprocessor-based computing system, or microcontroller, or digital signal processor, and may include additional sensors. The preferred control circuit is a microprocessor controller, but there are many alternative means of providing the function of the control circuit. As is known to those skilled in the art, there are a variety of commercially available non-microprocessor-based controllers that can provide the functions of the controller and are therefore equivalent and can replace the microprocessor controller. The sensing function can be executed by another circuit configuration, or can be provided on the control device. Suitable control devices can include commercially available equivalent digital and analog circuits. Examples of control devices that can be used in the control circuit of the present invention include microprocessors, microcontrollers, programmable gate arrays, digital signal processors, field programmable analog arrays, and logic gate arrays. Such a circuit may be a rudimentary digital logic circuit or may be constructed with discrete components such as diodes and transistors. Thus, the term “controller” is used generically to refer to any combination of available or known digital logic and analog signal processing circuitry and performs the logic functions of the control circuitry as described above. Therefore, it can be formed by construction, program, or otherwise.

  As is widely shown in the prior art, linear motors have a reciprocating set of magnets arranged to reciprocate within a stationary armature winding. The magnet is driven in a reciprocating motion by an alternating magnetic field generated by an alternating current applied to the armature winding. The support portion of the magnet is connected to the piston of the Stirling cooler 16 and drives it in a reciprocating motion. This reciprocating motion causes the Stirling cooler to pump heat energy from one location of the cooler to another where heat is removed. As is known in the art, because of these aforementioned heat pumping capabilities, such Stirling devices are more commonly known as heat pumps. A Stirling heat pump can be used to either heat an object with the rejected heat or cool the object by accepting the heat at the cooling location of the device and rejecting it into the surrounding environment. That is, the latter is often called a cooler, which includes a cooler that cools to an extremely low temperature. Details of linear motors and driven machines, such as Stirling heat pumps, compressors, or fluid pumps, are not illustrated, because they are not the present invention and numerous examples are shown in the prior art. The principle of this circuit can also be applied to driving loads such as other freely moving linearly reciprocating motors, linear compressors using a vibration balancer, and free piston Stirling engines.

  FIG. 2 shows an example of another embodiment of the present invention. The mechanical device 30 includes a main machine 32 that includes a linear motor 34 that drives the Stirling cooler 36 in a reciprocating motion, and a motor control unit 38 that controls the linear motor 34 including a control unit for its drive frequency. Have. The motor control unit includes a vibration amplitude sensor 40 such as an accelerometer, and detects a signal representing the vibration amplitude of the mechanical device 30 and inputs the signal to the motor control unit 38. All of these devices are physically coupled together as described in connection with FIG. The embodiment of FIG. 2 may be coupled to one or more secondary vibration systems such as vibration balancer 46 and parasitic vibration system 48.

FIG. 3 illustrates the principle by which the present invention operates. This represents typical and typical vibration values and curves, but the invention is not limited to these values and curves. For example, a reciprocating main machine is typically designed to resonate and operate at 60 Hz. However, many other operating frequencies are also practical, such as 50 Hz, 120 Hz or 400 Hz. Main machine of the described type are generally designed to resonate at the natural frequency i.e. the resonance frequency f ₀ of the vibration corresponding to f in the above equation in 1. The resonance peak M illustrates a typical resonance peak of the mechanical vibration of the main machine having a resonance frequency of 60 Hz. The resonance peak is relatively wide around its resonance frequency and thus exhibits a relatively low Q characteristic. The resonance peaks S1 and S2 exemplify typical resonance peaks of the secondary vibration system. These are relatively steep and steep and thus exhibit a relatively high Q characteristic.

The half-power point (70.7% amplitude) is one of the well-known methods for measuring the width of the resonance peak, but this measure is only applicable to the mechanical resonance surface of the system. is there. Other operating characteristics of the main machine, such as its cooling efficiency or performance factor, determine the operating efficiency of the driven machine. Thus, the range of drive frequencies at which a machine driven with acceptable efficiency operates may differ from the width of the resonance peak of a mechanically oscillating system, and is usually different. However, this acceptable range of drive frequencies can be determined by the designer and is usually determined. In FIG. 3, an example of an acceptable drive frequency range R is illustrated as being between 58 Hz and 62 Hz, but will be different for different main machines.

  The resonance peaks S1 and S2 are used when explaining the operation of the present invention, and may represent either a secondary vibration system that is a vibration balancer or a secondary vibration system that is a parasitic vibration system. Each will be described in turn.

  If the secondary vibration system is a vibration balancer and the main machine is operating under nominal or design conditions, it is operating at peak M representing the main machine and peak S1 representing the vibration balancer. Under this condition, this frequency matches the resonant frequency of the vibration balancer, so that the driven machine can be driven at the nominal resonant frequency of the main machine, in the example 60 Hz. However, if operating conditions such as temperature change significantly and the physical parameters of the main machine or secondary vibration system change one or both of the resonant frequencies, this change is displaced horizontally relative to each other. Will appear on the graph of FIG. 3 as one or both peaks. For example, peak S1 may move to the position of peak S2, or may move by a different interval in the other direction.

  When the main machine is continuously driven at the resonance frequency of the main machine, the efficiency of the vibration balancer is greatly reduced when the peak S1 is displaced to the position of S2. However, if the drive frequency of the main machine changes near the center of peak S2, the vibration balancer will be more effective at this frequency, in the example 62Hz, as long as the changed operating conditions are the same. If the peak of the vibration balancer is displaced to the center of 61 Hz or 62 Hz, the drive frequency will be moved to 61 Hz or 62 Hz, respectively. Therefore, in the present invention, the motor control system 18 or 38 drives the linear motor at a drive frequency that deviates from the resonance frequency of the main machine or system, and this frequency is in the vicinity of the displaced resonance frequency of the vibration balancer. Or this frequency, but the operating efficiency of the main machine is within the allowable drive frequency range.

  Accordingly, in one aspect of the present invention, the drive frequency of the linear motor changes the center vibration of the vibration balancer in response to changes in operating conditions that cause deviations in the center frequency of the resonance peak of the main machine and vibration balancer. Move close to a few. The drive frequency can be changed to be close to the resonant frequency of the displaced peak S2, but cannot move beyond the limit of the allowable drive frequency range R. This is because the operation of such a machine can cause unacceptable degradation.

If the secondary vibration system is a parasitic vibration system, its resonance peak is far away from the main machine center frequency f ₀ and is not expected to change from this, so this is never the case. It is not an element of the invention. However, other devices mounted on the mechanical device 10 or 30 introduce one or more parasitic vibration systems, any of which unexpectedly have a resonance peak close to the center frequency f ₀ , or a result of changes in operating conditions, there is a case where the resonance peak moves closer to the center frequency f _0. The peaks S1 and S2 can represent the resonance peak of such a parasitic secondary vibration system. When the peak S1 is the peak of the parasitic vibration system, the secondary parasitic vibration is increased by changing the drive frequency to either side of the center frequency of the peak S1 while remaining within the range R. FIG. 3 illustrates that it can be reduced. As a result, the drive frequency will be optimized to 58 Hz or 62 Hz. When peak S2 is the peak of the parasitic vibration system, in this example, the parasitic vibration is minimized by moving the drive frequency to 58 Hz, but this frequency is as far as possible from the center frequency of peak S2. However, the range R does not exceed the range.

  Although there are many ways to design and construct a control system that varies the drive frequency of a prime mover that is freely linearly reciprocating according to the above principles, six embodiments will be described. All of this involves sensing parameters of the operation of the machine, such as the amplitude of vibration of the machine or the temperature of a component of the machine. The sensed parameter may be sensed by a sensor provided to implement the present invention or may be a sensor that is part of another control system.

  FIG. 2 is the first of six embodiments. The vibration amplitude sensor 40 senses the vibration amplitude of the mechanical device. In general, the amplitude sensor can be placed on any component of the mechanical device that is mechanically coupled to each other, since the vibration of any one component is usually transmitted to the other component. The motor control unit 38 drives the linear motor 34 at each of several typical frequencies distributed within a range of allowable drive frequencies. Each frequency is stored in association with the amplitude of the sensed vibration. This is performed at the start, periodically after the start, depending on the amplitude of the sensed vibration above the selected level and / or depending on other conditions or algorithms. The software or logic circuitry of the motor controller 38 then selects the minimum vibration amplitude and drives the linear motor at the frequency associated with this minimum vibration amplitude. Thus, vibration is reduced or minimized in existing operating conditions when performing this process. By repeating this process, the control system can respond to the changed operating conditions.

  More specifically, a linear motor is driven at multiple frequencies within an acceptable range R by some arbitrary technique referred to herein as frequency sweep or dithering over a range of frequencies R. As a result, the motor control circuit 38 finds the frequency at which the vibration is minimized. The most common form of sweeping the frequency is to gradually change the frequency from one side of the range R to the other, either continuously or stepwise. However, alternatively, this sweep may be performed in a discontinuous or random manner and may be performed at selected spaced intervals.

  FIG. 1 shows a second embodiment of the present invention. The temperature sensor 22 senses the temperature of the vibration balancer 26 or the surrounding environment, and inputs temperature data to the motor control unit 18. As with all embodiments of the present invention, the range of drive frequencies at which operating efficiency is acceptable is determined and stored in response to tests on at least one mechanical device. This test is typically performed with laboratory equipment settings, but can also be based on technical design specifications. This experimentally determined range of operating frequencies at which operating efficiency is acceptable is then stored in a production replica of the machine.

  At least one heat pump machine is also typically tested in a laboratory environment by operating at a plurality of different operating temperatures, for each operating temperature the drive frequency is in the range of acceptable drive frequencies. Swept within. The drive frequency that results in the minimum vibration amplitude of the mechanical device is stored in association with each operating temperature. As a result, for each sensed operating temperature, the drive frequency that gives the minimum vibration is stored. These operating temperatures and the associated drive frequencies are stored as a look-up table in the storage device 20 connected in the frequency control system of the production replica of the tested mechanical device. Alternatively, the spring constant for the spring of the vibration balancer may be stored in a lookup table in association with each measured temperature, and the spring constant may be converted to a drive frequency using some algorithm. As an alternative, instead of using a collation table, a mathematical expression such as a polynomial series can be used to expand into an expression to approximate the collation table plot, thereby resulting in the result calculated by the motor control microprocessor. It is also possible to relate the vibration absorbing spring constant or the operating frequency to the sensed temperature.

  During operation of the production replica, the corresponding operating temperature of the replica is sensed and the associated drive frequency or spring constant is taken from the data store 20 or alternatively calculated by the previous equation. The linear motor is then driven at the drive frequency stored or calculated in relation to the sensed temperature. This process is repeated during operation of the manufacturing machine, and the machine is always driven at a drive frequency that gives the minimum vibration amplitude for the most recently sensed temperature.

  For mechanical devices that have both a parasitic secondary vibration system and a vibration balancer, additional resonance peaks will appear on a graph similar to FIG. However, the method and process of the present invention remain the same.

  FIG. 4 shows a third example of the embodiment of the present invention. This shows a prior art mechanical device and control system, but parts have been added to implement the present invention.

  The illustrated prior art system includes an electric linear motor 50 that is mechanically coupled to drive a drive load and its internal movable mass 52 and mechanically connected to a secondary vibration system 54. It has a main machine consisting of Sensor 56 senses main machine operating parameters, such as top dead center (TDC) or the position of one of the movable masses 52, and motor current and voltage are also sensed. These signals are applied to the signal conditioner 58 and as feedback signals to the summing junction 60 of the feedback control system, implemented in the software of the microcontroller or digital signal processor 62. A reference value is also added to summing junction 60 to provide an error signal, which is added to the transfer function and expanded into a control signal according to known feedback control system principles. In order to control the linear motor 50, a control signal is applied to the variable frequency inverter duty cycle generator circuit 64, which generates a square wave, and both the duty cycle and the frequency of the rectangular wave can be variably controlled. The duty cycle is controlled in a prior art manner by a control signal. The output of the generator circuit 64 is applied to an inverter output stage 66, which converts this square wave into opposing DC pulses having a pulse width corresponding to the duty cycle of the square wave to drive the linear motor 50. A variety of such circuits are known in the prior art, and the invention is not limited to any particular drive circuit having these general characteristics.

  In order to implement the present invention, a temperature sensor 68 is mounted near the vibration balancer 54A and this output signal is applied to the microcontroller 62 and the operating frequency as described in the lookup table 70 or as described with respect to FIG. Store the temperature data used in the corresponding equation used to determine. When the lookup table or equation provides a value corresponding to the vibration balancer spring constant for each sensed temperature, its output is converted by the frequency adjustment algorithm 72 to determine the operating frequency. If the lookup table or expression gives the frequency directly, the algorithm 72 can be omitted.

  FIG. 5 shows a fourth example of the embodiment of the present invention. This shows the same prior art machinery and control system illustrated in FIG. 4, but with the addition of parts to implement the present invention. To implement the present invention, a vibration sensor 80 is connected and the vibration amplitude is input to the microcontroller 82. Under control of the software module 84, the microcontroller 82 sweeps, dithers, or otherwise changes the operating drive frequency within the limits of the allowable range of the operating frequency as described above. Save the amplitude of the smallest vibration in the range. The microcontroller 82 then selects the stored operating frequency associated with the minimum vibration amplitude and operates the linear motor 86 at this operating frequency. In addition, as described above, this process is repeated at a selected interval or under a selected condition, and the electric linear motor 86 is always driven at a frequency with the minimum vibration amplitude even if the operating condition changes. The

  6 and 7 are diagrams showing fifth and sixth examples of the embodiment of the present invention. Both include the same prior art devices, but with the addition of circuitry to implement the present invention. Therefore, the common prior art part of both figures will be described first. 6 and 7 show the main machine, which is a free piston Stirling engine 100 that drives an electric linear alternator 102 for generating power from a heat source input. These may be designs known in the prior art and are generally mounted in the same housing. The reciprocating output piston of the Stirling engine is mechanically coupled to the reciprocating component of the alternator and is usually transported reciprocally in armature windings or coils mounted in a common housing. A series of permanent magnets supported on a vessel. The composite mass 104 of these reciprocating structures is mechanically coupled to the vibration balancer 106 and any parasitic vibration system 108 via reaction of the cylinder and exterior of the Stirling engine and alternator case. . These reaction forces are usually transmitted from the magnet to the armature coil to the cylinder and the exterior part through mechanical springs, working gas in the Stirling engine, and electromagnetic coupling. The output of the AC generator 102 is connected via a conventional tuning capacitor 109 used for power factor correction, and supplies power to the practical load 110.

  In order to connect an AC generator driven by Stirling engine 100 to the power grid, the frequency of Stirling engine 100 is controlled using principles known in the prior art to supply power to the power grid. When an alternator driven by a Stirling engine is designed to resonate near the frequency of the power grid, the swing of the Stirling engine is synchronized with the swing of the AC power of the power grid. The principle applied is that when connected to an external AC power source, the AC power source has a lower internal impedance than the AC generator and is driven by a Stirling engine if the frequency variation is negligible. The oscillation of the AC generator is synchronized with the voltage oscillation of the AC power supply. The above-described frequency variation applicable to the present invention is such a small variation.

  A variable frequency, variable amplitude power source 111 is used as an engine output frequency control device, and this AC output terminal is connected to the AC generator 102. Such power supplies are commercially available and will not be further described. The output of the variable frequency generator 118 of the microcontroller 114 is connected to the control input terminal 112 of the variable AC power supply 111 and becomes an input for controlling the frequency of the variable AC power supply 111. The output of the variable frequency generator 118 controls the AC power supply 111. Thus, within the small frequency variation used in the present invention, the operating frequency of the linear alternator 102 driven by the Stirling engine follows the frequency of the variable AC power source 111 and is therefore controlled by the microcontroller 114. The

  The implementation of the invention illustrated in FIG. 6 operates similarly to the embodiment illustrated in FIG. The controller 114 is programmed to perform logic and arithmetic functions to calculate the main machine operating frequency that minimizes the amplitude of vibration. A vibration sensor 116, such as an accelerometer, has an output that is connected to an input to the controller 114 to provide a signal representative of the sensed vibration amplitude of the prior art main machine illustrated in FIG. Is done. However, instead of inputting the nominal operating frequency as a command input to the engine frequency controller, a variable frequency generator 118 is inserted between the nominal operating frequency command input and the input to the variable AC power source 111. This allows the controller 114 to shift the commanded operating frequency from the nominal operating frequency in order to minimize vibration. The controller 114, under software control, varies the operating drive frequency within the limits of the allowable range of the operating frequency, sweeping, dithering, or otherwise, to minimize the minimum vibration within that range. Save the amplitude. The controller 114 then selects the stored operating frequency associated with the minimum vibration amplitude and operates the Stirling engine 100 at this operating frequency. In addition, as described above, this process is repeated under selected intervals or selected conditions, and the free piston Stirling engine 100 does not exceed the allowable range of operating frequencies even if the operating conditions change. , Always driven with frequency of minimum vibration amplitude.

The implementation of the present invention illustrated in FIG. 7 operates similarly to the embodiment illustrated in FIG. 2 and reduces the operating frequency of the free piston Stirling engine 100 as described in connection with the embodiment of FIG. The same working principle applies to control. The output of the temperature sensor 120 is the control device 1
22 is connected to provide a signal representative of the temperature of the vibration balancer 106. The controller 122 then operates the Stirling engine 100 over a range of acceptable operating frequencies and stores each temperature in association with the operating frequency, as described above in connection with FIGS. 2 and 4. The collation table 124 is given by the same process.

  While some of the preferred embodiments of the present invention have been disclosed in detail, it should be understood that various modifications can be employed without departing from the spirit of the invention or the scope of the appended claims. is there.

It is a block diagram which illustrates the example of the embodiment of the present invention. It is a block diagram which illustrates the 2nd example of an embodiment of the invention. It is a graph plot in the frequency domain of the resonance peak, illustrating the operation of the present invention. It is a block diagram which shows the example of the control circuit which implements this invention and uses a temperature sensor. It is a block diagram which shows the example of the control circuit which implements this invention and uses a vibration amplitude sensor. It is a block diagram which shows the example of the control circuit which implements this invention and uses a variable frequency generator. It is a block diagram which shows the example of the control circuit which implements this invention and has a temperature sensor.

Claims (12)

A method for minimizing the amplitude of mechanical vibrations of a mechanical device, wherein the mechanical device is coupled to a reciprocating mass of a driven machine and is free to drive the mass in a reciprocating motion at a driving frequency. A linear reciprocating prime mover, wherein the combined prime mover and the driven machine exert a force on the reciprocating mass to form a main resonant system having a resonant frequency of the main system reciprocating motion; Having a spring to apply,
(A) determining and storing a range of drive frequencies at which the driven machine operates at an acceptable operating efficiency;
(B) sensing operational parameters of the mechanical device;
(C) driving the prime mover at a drive frequency according to the sensed parameter, wherein the drive frequency is
(I) deviating from the resonance frequency of the reciprocating motion of the main system,
(Ii) the operating efficiency is within an acceptable driving frequency range;
(Iii) reducing or minimizing the amplitude of mechanical vibrations of the mechanical device under existing operating conditions
And a step that is a frequency to cause. The sensing step comprises sensing an amplitude of vibration of the mechanical device, the method comprising:
(A) sweeping the drive frequency over a range of frequencies including the resonant frequency of reciprocation of the main system;
(B) further comprising a step of storing the amplitude of the sensed vibration in association with a plurality of the sweep drive frequencies,
The method of claim 1, wherein the prime mover is driven at a drive frequency that is a stored drive frequency associated with a sensed stored minimum amplitude.   The method of claim 2, wherein the method is repeated periodically. A method for controlling a mechanical device, wherein the driven machine is a free piston Stirling heat pump device,
(A) a range of the driving frequency is determined and stored according to a test of at least one component of the mechanical device;
(B) at least one heat pump device of the mechanical device is operated during testing at a plurality of operating temperatures, and the driving frequency is within the allowable driving frequency range for each of the operating temperatures; The drive frequencies that are varied and result in the minimum vibration amplitude of the mechanical device are stored in association with the respective operating temperatures;
(C) the operating temperature and the associated drive frequency are stored as a collation table in a storage device connected in the multi-product frequency control system of the tested machine;
(D) the sensing step comprises sensing the operating temperature of the replica of the tested mechanical device;
The method of claim 1, wherein (e) the prime mover is driven at the stored drive frequency associated with the sensed temperature. A control system for a computer or logic circuit for minimizing the amplitude of mechanical vibrations of a mechanical device, said mechanical device comprising a prime mover with free linear reciprocating motion that drives the driven machine in reciprocating motion The main machine includes a mass and the mass so as to form a mechanical resonant oscillator having a resonant frequency in the vicinity of which the main machine is designed to be operatively driven. A control system having a spring for applying a force to
(A) a sensor for sensing machine operating parameters;
(B) a data storage unit for storing a range of drive frequencies at which the driven machine operates at an acceptable operating efficiency;
(C) Connected to receive inputs from the sensor and the data storage unit to control the prime mover, and from the resonance frequency of the reciprocating motion of the main machine according to the sensed parameter The drive frequency that is within the range of acceptable drive frequencies where the stored operating efficiency is acceptable and minimizes the mechanical vibration amplitude of the mechanical device under existing operating conditions, A control system having a microcontroller programmed to drive the prime mover.   The control system of claim 5, wherein the sensor senses an amplitude of vibration of the mechanical device.   The control system of claim 6, wherein the sensor is an accelerometer.   The control system according to claim 5, wherein the sensor is a temperature sensor.   The control system of claim 8, wherein the sensor is connected to sense the temperature of a vibration balancer spring.   The control system of claim 5, wherein the prime mover is a linear electric motor.   The control system of claim 5, wherein the prime mover is a free piston Stirling engine.   6. The control system of claim 5, wherein the driven machine is a free piston Stirling cooler.

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