Operation of linear compressor of household appliance

Abstract

The invention relates to an operating method (10-17) for operating a linear compressor (1, 1 ') of a domestic appliance (H), in which a desired current curve (i-ref) of a current (i) to be fed into a drive coil (9A) of the linear compressor (1, 1') is calculated as a function of a desired reversal position (x +, max, ref) of a front reversal point of a piston (3) of the linear compressor (1, 1 ') and a front actual reversal position (x +, max) of the piston, the current (i) to be fed into the drive coil (9A) is adjusted by means of the desired current profile (i-ref) and the actual current profile (i-), and the front-side actual reversal position (x +, max) is observed or measured. The invention also relates to a linear compressor (1, 1 ') of a household appliance (H), which is configured for carrying out said method (10-17). The invention further relates to a domestic appliance (H) having a linear compressor (1, 1 '), said domestic appliance being configured to carry out the method (10-17). The invention is particularly advantageously applicable to refrigeration equipment, such as refrigerators, freezers or combinations thereof.

Description

Technical Field

[0001] This invention relates to a method for operating a linear compressor for a household appliance. The invention also relates to a linear compressor with a corresponding configuration. Furthermore, the invention relates to a household appliance having such a linear compressor. The invention is particularly advantageously applicable to refrigeration equipment, such as refrigerators, freezers, or combinations thereof. Background Technology

[0002] Some refrigeration equipment uses a linear compressor as the drive unit for its refrigeration circuit. This linear compressor has a piston that can be linearly driven, the front face of which forms one end face of a working volume filled with a working medium. An inlet and an outlet for the working medium are located at opposite end faces of the working volume. When the piston moves towards the opposite end face (“forward”), the working volume is compressed, causing the working medium to exit through the outlet without flowing through the inlet. At this time, a gap remains between the front face of the piston and the opposite end face (also called a “valve plate”) to avoid mechanical contact between them. When the piston is at its maximum forward offset position (corresponding to the minimum gap with the opposite end face), a so-called “dead-point volume” still exists. When the piston moves away from the opposite end face (“backward”), the working volume expands, causing the working medium to be drawn in through the inlet without flowing through the outlet. Therefore, through the reciprocating motion of the piston, the working medium can move through a working medium circuit connected to the inlet and outlet. To achieve the piston movement, a corresponding AC voltage signal is input to the electromagnet driving the piston. Summary of the Invention

[0003] The objective of this invention is to at least partially overcome the deficiencies of the prior art, and in particular to provide a particularly efficient method for operating linear compressors of household appliances.

[0004] This task is solved according to the features of the independent claim. Preferred embodiments are particularly available from the dependent claims.

[0005] This task is solved by a method for operating a linear compressor for household appliances, in which: - At least based on the expected reversal position (also called "expected reversal position") of the front or upper reversal point of the piston or cylinder (2) which is the stroke body of the linear compressor and the actual reversal position of the front side of the stroke body, calculate the expected current (value) curve of the current to be input into the drive coil of the linear compressor. - Adjust the current or current curve to be input into the drive coil by comparing the desired current curve and the actual current curve, especially by comparing them; - Estimate or measure at least the actual reversal position of the front side using an observer.

[0006] This method offers the following advantages: the movement of the stroke body can be adjusted to the desired reversal position on its front side, thereby achieving, firstly, the desired reversal position can be reached with particular precision, resulting in high efficiency, more precisely, even when boundary conditions such as the temperature of the working medium, the temperature at the inlet, and / or the temperature at the outlet change; and secondly, the stroke body can be prevented from impacting the valve plate with particular reliability.

[0007] A linear compressor drives a working medium circulating in a loop. This loop can be a refrigeration loop or a heat pump loop. In addition to a linear compressor, the loop may also include at least one evaporator, at least one expansion device, and at least one condenser in a manner known in principle.

[0008] To achieve high efficiency in a linear compressor, efforts are made to minimize the dead-point volume, thus minimizing the maximum forward displacement of the piston (also known as the "front reversal point") while avoiding contact. In this case, selecting an appropriate initial or resting position of the piston relative to the valve plate is advantageous. The resting position significantly impacts the compressor's achievable cooling capacity. In particular, choosing this resting position ensures that a preset maximum cooling capacity, or "limited power," can be reached under symmetrical power supply or operation. However, in practice, the limited power is rarely invoked. For smaller cooling capacities more commonly required in practice, the AC voltage signal level can be reduced, thereby reducing the piston's proximity to the valve plate at the front reversal point and consequently decreasing efficiency due to the increased dead-point volume.

[0009] Under symmetrical energization, when the gas pressure is balanced, a nearly symmetrical vibration is generated around a mechanical zero-point position (rest position) determined by the mechanical spring. When the load conditions change (especially when the gas pressure is unbalanced), even under symmetrical energization, the vibration around the mechanical zero-point position (rest position) becomes asymmetrical; this asymmetry is referred to here as load asymmetry. This results in a shift of the mechanical zero-point position to a virtual zero-point position, which is determined by the mechanical spring and the gas pressure (as a gas spring).

[0010] By applying symmetrical current, the maximum cooling capacity under symmetrical current is achieved, and the maximum offset of the vibrating body corresponds to this maximum cooling capacity.

[0011] According to the invention, an additional asymmetrical current is superimposed on the symmetrical current supply, which enhances the load asymmetry. This is achieved through an additional suction stroke. x (by increasing the suction stroke at the lower reversal point through this additional suction stroke) increases the maximum cooling capacity. This additional suction stroke x is calculated by a pre-processing algorithm, taking into account the desired cooling capacity and boundary conditions such as frequency / temperature at the inlet and outlet of the stroke volume.

[0012] The following section will describe the additional inhalation strokes based on preset parameters. x generates additional asymmetric current.

[0013] Household appliances can be refrigeration equipment. Such refrigeration equipment can be, for example, a refrigerator, a freezer, or a combination thereof. Household appliances can also be clothing handling equipment equipped with a heat pump, such as a washing machine, a dryer, or a combination thereof, or a dishwasher.

[0014] The present invention relates to both a linear motor in which a piston is driven and moves relative to a cylinder as a stationary component, and a linear motor in which a cylinder is driven and moves relative to a piston as a stationary component.

[0015] The piston of a linear compressor is arranged in a cylinder within the compressor housing. The piston and cylinder are supported longitudinally, with one fixed within the housing and therefore fixed relative to the motor coil, while the other, as a stroke body, is movable. The stroke body is connected to a stationary component or housing via at least one elastic spring element. The stroke body, equipped with at least one permanent magnet, is typically driven by the magnetic field of at least one electromagnet and subjected to vibration, which is equipped with at least one coil operating at alternating voltage (“drive coil”). Depending on the direction of motion, the working volume defined by the cylinder and piston end faces increases or decreases. A linear compressor can also be considered a linear motor, with its stroke body corresponding to a rotor or “moving element.” The basic operating principle of a linear compressor in the refrigeration circuit of a refrigeration system or the circuit of a heat pump is known and will not be elaborated upon here.

[0016] Regarding the terms "AC voltage" and "sine voltage" in this specification: AC voltage refers to a periodic voltage in any signal form. Here, a symmetrical AC voltage is used to control the motor, which may otherwise have any signal form. Due to its simplicity, a sine wave is preferred, hence the references to sine voltage and sine wave generator in the examples.

[0017] To achieve the desired symmetrical current, a symmetrical AC voltage (e.g., a sinusoidal voltage) is generated by energizing the motor. Based on this AC voltage, PWM signals are generated for each winding, thereby creating a voltage pattern applied to the motor. This, in turn, generates the measured current in the motor.

[0018] Nonlinear loads behave like gas springs, depending on the current pressure conditions on the intake and pressure sides. Therefore, even with symmetrical current, asymmetrical motion of the stroke body will occur.

[0019] Here, the symmetrical desired current setting is typically aligned with current load conditions and varies over time, sometimes even in short periods. The symmetrical desired current setting is based on refrigeration technology requirements and aims to optimize current requirements and load conditions, such as maximum energy efficiency at a given cooling capacity. Regardless of refrigeration technology requirements, protective regulation mechanisms can be employed to prevent mechanical collisions between the stroke element and stationary components. This protective regulation mechanism does not alter the symmetry of the symmetrical desired current setting.

[0020] Currently, there exists a maximum cooling capacity achievable through symmetrical energization. This invention aims to superimpose an asymmetrical current component onto the symmetrical energization to achieve a cooling capacity greater than the maximum achievable through symmetrical energization.

[0021] The desired cooling capacity can be preset, and then symmetrical energization is applied until the maximum cooling capacity achievable through symmetrical energization is reached. This symmetrical energization corresponds to a specific stroke with a specific bottom dead center of the stroke body. For the remaining difference from the desired cooling capacity, the extension of the stroke body beyond the specific bottom dead center is calculated as an additional suction stroke.

[0022] Asymmetrical energization causes the stroke of the stroke body to extend beyond a specific bottom dead center, thus obtaining an additional suction stroke without actively changing the top dead center. The result is an increase in stroke volume, which in turn leads to an increase in delivery capacity, and ultimately an increase in cooling capacity.

[0023] The desired current curve is an alternating current curve, particularly a sinusoidal current (value) curve, which can be defined by its amplitude and its frequency (which corresponds to the "operating frequency" of the stroke body). The actual current curve, or the actual motor current, can be measured, for example, by a current measuring device. The voltage applied to the drive coil corresponds in particular to the control quantity used for current regulation. This current regulation is then nested or associated, in particular, with ("amplitude") regulation used to regulate the actual reverse position of the front side of the stroke body. Regulating the current or current curve to be input to the drive coil using the desired and actual current curves can include: directly applying regulation to the current curve. Alternatively or additionally, the current or current curve to be input to the drive coil can be indirectly regulated by the associated control quantity (i.e., the voltage applied to the drive coil). Regulation via this voltage is generally used below, even if not explicitly stated.

[0024] Estimating the actual reversal position of the front side using an observer may involve reconstructing or estimating the actual reversal position of the front side based on known input quantities (e.g., measurable disturbance quantities) and output quantities (e.g., control quantities and / or measurement parameters) of the observed reference system. For this purpose, the observed reference system may be modeled, for example, and measurable and therefore comparable state quantities may be tracked by a regulator. Possible input quantities in the observer may include, for example, at least the measured actual current and / or output voltage, or the excitation voltage and / or excitation frequency or operating frequency applied to the drive coil.

[0025] Measuring the actual reversal position of the front side may include: directly measuring the actual reversal position of the front side or deriving the actual reversal position of the front side from other measurement parameters.

[0026] The calculation of the desired current (value) curve based on the expected reversal position and the actual reversal position of the front side "at least" may include, for example, calculating the desired current curve based on other desired and / or actual positions. Similarly, the corresponding actual positions may then be estimated or measured by an observer.

[0027] One configuration involves additionally estimating or measuring the actual "rear" reversal position corresponding to the rear or lower reversal point of the stroke body using an observer. This actual rear reversal position can then be used, for example, to calculate the total stroke body stroke between the two reversal points and, for example, to estimate the internal pressure difference.

[0028] An extended approach is to additionally estimate or measure at least one reference position located between the two reversal points using an observer.

[0029] One configuration involves estimating or measuring the motion or position curve of the stroke body using an observer, thereby determining at least the actual forward reversal position of the stroke body, and if necessary, the actual rearward reversal position and / or at least one reference position. For example, the actual forward reversal position can be determined or extracted from the local maxima of the curve, the actual rearward reversal position from the local minima, and so on. In particular, the position of the stroke body can be estimated or measured at a constant measurement or sampling frequency. In an extended configuration, the curve can be a curve variation fitted to the estimated or measured position.

[0030] One configuration involves calculating the magnitude (“target current magnitude”) based at least on the desired reversal position and the actual reversal position of the front side, and then calculating the desired current curve based on the target current magnitude and the desired operating frequency of the stroke body. This is advantageously particularly easy to implement and produces robust regulation. The desired operating frequency can be arbitrarily specified in principle. For example, the desired operating frequency may correspond to the resonant frequency, i.e., the frequency at which the stroke body (with the same current magnitude) can deviate furthest from its non-driven rest position. However, the desired operating frequency may also correspond, for example, to a frequency higher or lower than the resonant frequency. For example, this configuration can be implemented by a sine wave generator or a similar sine wave generator that calculates or generates, for example, a sinusoidal desired current value or desired current curve based on preset parameters (target current magnitude and desired operating frequency).

[0031] One extension is that the target current value amplitude is also calculated based on the desired reversal position and the actual reversal position on the rear side. This has the advantage of being able to determine the internal pressure difference with particular accuracy, and thus the cooling capacity with particular accuracy.

[0032] One extended approach is to construct the current or current curve to be input into the drive coil using a pulsed voltage. To this end, in this extended approach, the (general) sinusoidal input current curve, with a sinusoidal generator as the control output, can be converted into a corresponding pulsed input voltage curve using a PWM element used as the control element. This may include: the first and second current half-waves (also between different periods) can have different durations, while the period duration is the same and, in particular, corresponds to the operating frequency. In other words, in pulse width modulation, the duty cycle or pulse duration for different periods can be different, while the period duration remains constant.

[0033] Alternatively or additionally, the current waveform can be generated from any harmonic of the fundamental frequency. This results in the following advantages: pressure pulsations caused by discontinuous movement of the inlet and outlet valves can be minimized, which can also lead to higher efficiency.

[0034] One configuration involves adding a specific additional amplitude value (“additional current value”) to the target current value amplitude and reducing the desired current curve by the same additional current value. This results in an asymmetrical desired current curve or asymmetrical energization relative to zero, generated from the originally symmetrical desired current curve or symmetrical energization. This asymmetrical desired current curve remains sinusoidal, etc., with the set operating frequency. However, compared to symmetrical energization, the absolute value of the positive / negative amplitude of the desired current curve relative to the equilibrium position increases the additional current value, while the average value or equilibrium value of the desired current curve decreases this additional current value. This advantageously achieves the following: the positive amplitude of the desired current curve used to move the stroke body forward remains unchanged. This is therefore achieved based on a pre-calculated controlled current curve, and additionally, the upper amplitude adjustment remains active. Therefore, the distance between the stroke body and the valve plate also remains unchanged at the forward reversal position. Conversely, the negative amplitude of the desired current curve used for backward offset increases significantly. Therefore, the stroke of the stroke body is significantly increased, thereby increasing the volumetric flow rate of the working medium, and thus increasing the cooling capacity. While this may result in lower energy efficiency than operation under symmetrical power-on conditions, it enables an increase in cooling capacity. This increase is particularly useful for relatively short cooling phases where increased cooling capacity is required, such as after the refrigeration unit is started or when the "super cooling" mode is activated. This, in turn, facilitates the design of the unit's dimensions to keep the effects of dead-point volume ("clearance volume") and related losses low for preset, typically sustained cooling capacity. Therefore, for refrigeration units, the following advantages are particularly evident: cooling capacity can be increased in the short term through asymmetrical operation of the linear compressor.

[0035] If, for example, under symmetrical energization, the desired positive amplitude A of the current curve is... + The value A > 0 and the amplitude A is negative. - If the value is -A, then the equilibrium position i of the current curve ~ For (A) + +A - (A + (-A)) / 2 = 0. If an additional current value ΔA > 0 is added under asymmetrical current supply, then the amplitude is A. + =A+ΔA and A - =-(A+ΔA). By lowering the equilibrium position by ΔA, the magnitude becomes A. + =A and A - =-(A+2 ΔA), the equilibrium position is (AA-2). ΔA) / 2 = -ΔA. Therefore, under asymmetrical current supply, the forward amplitude A + The amplitude A remains unchanged, while the amplitude A is negative. -With the additional current value doubled, the stroke body also shifts backward more strongly.

[0036] One configuration involves calculating the mechanical force required to act on the stroke body for the desired additional backward offset (i.e., away from the valve plate), and then calculating the additional current required to achieve this desired additional offset based on that mechanical force. This achieves the advantage of quickly and accurately setting additional cooling capacity at low cost. The additional backward offset can also be referred to as the additional suction stroke. Mechanical force F f For example, the spring constant k of the elastic spring hinged to the stroke body. f According to formula F f =k f Δx - (where Δx) - Calculated for the additional backward suction stroke. The mechanical force F f This is equivalent to the driving magnet causing an additional offset Δx in the stroke body. - The required force F m According to F m =k m Δi (where k) m (where Δi is the motor constant and Δi > 0 is the additional DC component), can be determined by Δi = (k f / k m ) Δx - The extra current value Δi is calculated. ΔA can then be calculated as ΔA = Δi / 2.

[0037] One configuration involves applying the additional current value in a slope-limited manner, meaning it is not suddenly applied at full value. This advantageously allows the stroke body vibration to adapt more uniformly to the additional current value. The slope limitation can, for example, include the additional current value increasing at a finite, particularly constant, slope. An extension is that the additional current value is applied in a slope-limited manner, increasing gradually, particularly through inclined steps with a specific slope. Another extension is that the additional current value returns in a slope-limited manner, meaning it does not suddenly return to full value. This can be achieved similarly to applying it in a slope-limited manner. An extension is that the additional current value is applied steadily, i.e., without noticeable jumps.

[0038] One configuration involves estimating the actual reversal position of the stroke body's leading edge using an observer, particularly a Luenberger-Beobachters. Alternatively, the actual reversal position can be estimated using a flux observer, a so-called "sliding mode" observer, or a Kalman filter. Another approach to increasing accuracy is through data-driven methods for improving the observer's precision, particularly through artificial intelligence. In extended schemes, these alternatives can be combined with nonlinear characteristic curves of machine parameters.

[0039] One configuration involves measuring the actual reverse position of the front side of the stroke body, at least via laser radiation. Alternatively, the actual reverse position of the front side can be measured using a position reference sensor. Other actual positions of the stroke body can also be measured accordingly.

[0040] One configuration allows the linear compressor to operate in one mode without an additional current value and in at least one other mode with an additional current value. This advantageously allows for simple, low-wear, and rapid switching between a particularly efficient operating mode that does not use an additional current value and an operating mode that uses an additional current value for high cooling capacity. An extension is that the linear compressor can operate in multiple operating modes with additional current values, distinguished by different additional current values ​​and therefore different additional cooling capacities. Generally, the additional cooling capacity can be arbitrarily adjusted within possible operating boundary conditions, such as continuously or quasi-continuously.

[0041] This task is also solved by a linear compressor in a household appliance, wherein the linear compressor is configured to perform the method described above. This linear compressor can be constructed similarly to (and vice versa) the method described, and has the same advantages.

[0042] A linear compressor may include a control or regulating device as a component, which is configured, for example, programmed to perform the methods described above. The linear compressor itself and the control device can be considered together as a single compressor module. This control or regulating device can be data-coupled with the control device of a household appliance, which can output signals, for example, for switching between different operating modes.

[0043] This task can also be solved by a household appliance having a linear compressor, particularly the aforementioned linear compressor, wherein the appliance is configured to perform the method described above. This appliance can be constructed similarly to the method and / or the linear compressor (or vice versa), and has the same advantages.

[0044] Therefore, in one configuration, the household appliance is a refrigeration device, such as a refrigerator, freezer, or a combination thereof. In this case, the working medium may also be referred to as a refrigeration medium or refrigerant. However, the household appliance is not limited to this; for example, a linear compressor can be used as the driving device for a heat pump. In this case, the description of the invention based on a refrigeration device or refrigeration circuit can be applied similarly, for example, in dishwashers or laundry handling equipment. Attached Figure Description

[0045] The above-described features, characteristics, and advantages of the present invention, as well as the manner in which these features, characteristics, and advantages are realized, will become clearer and more readily understood in conjunction with the following illustrative description of embodiments, which are set forth in more detail with reference to the accompanying drawings.

[0046] Figure 1 A simplified diagram of a possible linear compressor with a driven piston is shown as a sectional view or side view. Figure 2A A schematic diagram showing the variation of the desired current input to the drive coil of a linear compressor over time under sinusoidal symmetrical energization; Figure 2B Shown in accordance with Figure 2A A schematic diagram showing the change of the offset of the stroke body of a linear compressor under sinusoidal symmetrical energization as a function of time. Figure 3 A possible block diagram for symmetrical energization of a linear compressor is shown; Figure 4A A schematic diagram showing the variation of the desired current input to the drive coil of a linear compressor over time under sinusoidal asymmetric energization; Figure 4B Shown in accordance with Figure 4A A schematic diagram showing the change of the offset of the stroke body of a linear compressor under sinusoidal asymmetric energization over time. Figure 5 A possible block diagram of asymmetric energization of a linear compressor is shown; Figure 6 A simplified diagram of a possible linear compressor with a driven cylinder is shown as a sectional view or side view. Detailed Implementation

[0047] Figure 1 A linear motor is described in which a piston, as a stroke body, is driven and moves relative to a cylinder, which is a stationary component. Figure 6 A linear motor is described, in which a cylinder, as a stroke body, is driven and moves relative to a piston, which is a stationary component. Identical components are labeled with the same reference numerals, and corresponding components are labeled with apostrophes.

[0048] Figure 1A simplified diagram of a possible linear compressor 1 is shown as a sectional view or side view. The linear compressor 1 has a cylinder 2 rigidly connected to the housing 20 inside the housing 20, and a piston 3 (as indicated by double arrows) linearly displaceable within the cylinder 2. The rear end of the piston 3 is hinged to the housing 20 by a spring element 4, and its front end limits the working volume 5. The piston 3 is provided with a permanent magnet 3A. In operation, the piston 3 moves as a stroke body 23 relative to the cylinder 2, which is a stationary component. A one-way inlet 6 leads into the working volume 5 through which the working medium 7 flows, and a one-way outlet 8 leads into the working volume 5 through which the working medium 7 flows out. The linear compressor 1 also has an electromagnet or drive magnet 9 arranged outside the cylinder 2. The drive magnet 9 has a drive coil 9A (which is typically based on a possible pulsed AC voltage U). ~ The piston 3 is driven by a stator 9B made of magnetic material (e.g., steel plate segments). The driven magnet 9 applies magnetic force to the permanent magnet 3A of the piston 3, thereby exciting the stroke body 23 to perform linear oscillation motion within the cylinder 2. Under AC voltage U... ~ With the frequency remaining constant, the stroke body 23 vibrates at a specific frequency or operating frequency f. w The reciprocating motion occurs at a frequency or operating frequency that is at least approximately the same as the AC voltage U. ~ The voltage frequency corresponds to this. In particular, the operating frequency f w This can correspond to the resonant frequency f of a vibration system that includes at least the stroke body 23 and the spring element 4. res .

[0049] When the vibrating stroke body 23 moves forward or toward the spring element 4, it elastically stretches the spring element 4 and reduces the working volume 5, thereby pressurizing the working medium 7 and causing it to overcome the final pressure and flow out through the outlet 8. For example, a check valve prevents outflow through the inlet 6. When the stroke body 23 moves backward or in the opposite direction to the spring element 4, it elastically compresses the spring element 4 and increases the working volume 5, thereby generating a negative pressure there. This negative pressure, in turn, causes the working medium 7 to overcome the suction pressure and flow in through the inlet 6. For example, a check valve prevents inflow through the outlet 8. The inlet 6 and outlet 8 may, for example, be both located on the valve plate 2A at the end side of the cylinder 2.

[0050] based on Figure 2A - 5 pairs according to Figure 1 The control of the linear compressor and according to Figure 6 The control of a linear compressor is explained. The stroke positions x, x0, and the reversal point x are discussed. +,max x -,max According to Figure 1 For the linear compressor 1, it refers to the front end of the movable piston 3, for the... Figure 6 For a linear compressor 1', it refers to the cylinder bottom 21 of the movable cylinder 2'.

[0051] At the operating frequency f w Under certain or preset conditions, the upper (or front) reversal point x is obtained for the stroke body 23. +,max and the lower (or rear) reversal point x -,max They depend on the current i or current curve i input to the driving magnet 9 or the driving coil 9A. ~ The amplitude of the current. The larger the current amplitude, the farther the stroke body 23 usually deflects from its unapplied rest position x0. An effect occurs here: even with symmetrical excitation (such as...) Figure 2A As shown in the diagram, the stroke body 23 reverses forward at the front reversal point x. +,max The offset at that point is also smaller than the reverse point x on the rear side. -,max The offset at that point, that is, the absolute value that satisfies |x -,max -x0|>|x +,max -x0|. This asymmetric offset effect, which occurs even under symmetrical excitation, is caused by the working medium 7 located in the working volume 5, which applies a force to the stroke body 23 opposite to its motion. At the front reversal point x +,max At this point, a dead volume 5A will remain in the working volume 5. Dead volume 5A also includes the residual volume around inlet 6 and outlet 8. The following is not definitive: Front reversal point x +,max There is a gap between the stop and the valve plate 2A. Conversely, in the extended scheme, the valve plate 2A can even be contacted, since it has been shown that contacting the valve plate 2A will not cause damage to the entire system.

[0052] Figure 2B Based on Figure 2A The plot of the displacement x of the stroke body leaving its rest position x0 under symmetrical excitation as a function of time illustrates this effect. Figure 2A The diagram shows the sinusoidal current i or the current curve i of the input. ~ With positive current amplitude A + The positive current amplitude has the same characteristics as the negative current amplitude A. - With the same absolute value, the extreme values ​​are approximately 0.6A. However, Figure 2B The offset x of the stroke body 2 shown is asymmetrical, that is: the stroke body 23 moves forward from the rest position x0 to the front reversal point x. +,max It shifted by approximately 1.9mm, backwards until the rear reversal point x. -,max The offset is approximately 4.1 mm in absolute terms, which is about twice or even more than twice the forward offset. At this time, the dynamic average position or equilibrium position x of the stroke body 23... g,sIt is approximately [1.9mm + (-4.1mm)] / 2 = approximately -1.1mm.

[0053] Specifically, the AC voltage U can be designed accordingly. ~ Adjust the current i input to the drive magnet 9 or the drive coil 9A so that the front reversal point x is... +,max With a specific expected value x +,max,ref Correspondingly, a possible block diagram for such energization or regulation of the linear compressor 1 is shown in... Figure 3 The text shows: For example, the control device (not shown) of a household appliance H with a linear compressor 1 presets the desired reverse position x on the front side. +,max,ref For example, based on a specific operating frequency f w And the desired cooling capacity. Front side desired reverse position x +,max,ref Compared with the measured or observed actual reversal position x +,max The input is fed into the "amplitude regulator" 10, which can be configured as a PI regulator or a PID regulator, for example. The amplitude regulator 10 outputs the target current value amplitude A as the output quantity, which is required to achieve the desired reversal position x. +,max,ref .

[0054] Target current amplitude A and desired operating frequency f w The inputs are fed into a sine wave generator 11, which in turn generates, for example, a sinusoidal current expectation curve i. ~ref , where A + =A,A - =-A, frequency is f w And output it to the current regulator 12. The current regulator 12 will output the desired current value curve i. ~ref The measured (actual) curve i of the input current i ~ The voltage is compared and a corresponding voltage signal is output as a control quantity to be fed into the drive coil 9, if necessary via a PWM module (not shown). The current regulator 12 can be configured, for example, as a PI regulator or a PID regulator.

[0055] The actual reverse position x, reconstructed or measured, is transmitted via feedback device 13 (e.g., in the form of an observer or measuring device). +,max Feedback is sent to amplitude regulator 10.

[0056] Figure 4A This illustrates an asymmetric current or superposition with an amplitude value A that is asymmetric relative to zero. + and A - The curve of the current i. More precisely, in terms of absolute value, A is applicable. - >A + , where A+ Approximately 0.5A, A - It is approximately -0.9A. Therefore, the positive amplitude value A is... + Approximately the positive amplitude value A under symmetrical current conduction + Correspondingly and therefore only slightly lower, because the following effect is considered simultaneously: under asymmetrical current supply, the amplitude value A + It may decrease slightly because more energy is directed toward the rear reversal point x. -,max It enters spring 4 in the direction of [the current]. At this time, the equilibrium position x of the current curve [is...]. g,a It is no longer zero, but approximately -1.9 to -0.2A.

[0057] Figure 4B A plot showing the change in stroke body offset x from its rest position x0 over time is shown. Figure 4A The effect of asymmetrical excitation or energization. (Front-side reversal point x) +,max Maintain at approximately 1.9mm, with the rear reversal point x -,max The current value is approximately -6mm. At this point, the dynamic average position or equilibrium position x of the stroke body 23 is... g,a Approximately -2mm. Therefore, the dead volume 5A remains at least approximately constant, while the intake stroke is increased by an additional intake stroke Δx of approximately 1.9mm in absolute value. - Significant increase.

[0058] A possible block diagram for such energization or regulation of the linear compressor 1 is shown in Figure 5 As shown in the image. It is based on... Figure 3 The adjustments shown are marked with boxes or functional sections 10 to 14, but additionally with boxes 15 to 18.

[0059] When additional cooling capacity is required, the desired additional suction stroke Δx will be applied. - (for Figure 4B For example, in absolute terms, it is approximately 1.9 to 2 mm, which is input into box 15. Box 15 thus knows the spring constant k of spring 4. f In this case, calculate the (additional) force F required for this and forward it to box 16.

[0060] In box 16, based on the required additional force and the known motor constant k of the linear compressor 1. m Find the required additional DC component Δi and halve it in box 16 to obtain the additional current value ΔA = Δi / 2.

[0061] In box 17, the slope of the additional current value ΔA can optionally be limited.

[0062] Then, an additional current value ΔA is added to the target current value amplitude A output from box 10, thereby obtaining a still symmetrical current curve i. ~ref It has an increase of magnitude A in absolute value by ΔA. + and A - .

[0063] However, the expected current curve i output by block 11 is also shown. ~ref Subtracting this additional current value ΔA from the (DC component) results in a lower equilibrium position by ΔA compared to symmetrical current flow. Overall, this yields the same positive amplitude A as symmetrical current flow. + And increased by 2 in absolute value The negative amplitude A of ΔA - Therefore, the front reversal point x +,max It remains unchanged until the reversal point x on the back side. -,max The suction stroke is significantly increased, which in turn significantly increases the mass flow rate of the working medium 7.

[0064] These boxes should not be understood as hardware or software technology units, but can be implemented in any way that is functionally similar, such as as a computer program product. These boxes can also be understood as method steps or method parts.

[0065] Of course, the present invention is not limited to the embodiments shown.

[0066] Generally speaking, "a" or "an" can be understood as singular or plural, especially in the sense of "at least one" or "one or more", unless explicitly excluded, for example by expressions such as "exactly one".

[0067] Furthermore, numerical descriptions can be understood as exactly the numerical values ​​described and including the general tolerance range, unless explicitly excluded.

[0068] Figure 6An alternative possible linear compressor 1' is shown as a sectional view in side view. The linear compressor 1' has a cylinder 2' inside a housing 20', which is linearly displaceable relative to a piston 3' rigidly connected to the housing 20' (as indicated by the double arrows). The sidewalls and bottom 21 of the cylinder 2' (as movable walls) together with the front end of the piston 3' (as a fixed wall) limit the working volume 5. The cylinder 2' is provided with a permanent magnet 3A, which is arranged on a cylinder frame 22. The cylinder frame 22 extends the cylinder 2' beyond the bottom 21 relative to the working volume. The cylinder 2' is hinged to the housing 20' via a spring element 4 through the cylinder frame 22. During operation, the cylinder 2' moves as a stroke body 23 relative to the piston 3', which is a stationary component. A one-way inlet 6 leads into the working volume 5, through which the working medium 7 flows into the working volume 5, and a one-way outlet 8 leads into the working volume 5, through which the working medium 7 flows out of the working volume 5. The linear compressor 1 also has an electromagnet or drive magnet 9 disposed outside the housing 20'. The drive magnet 9 has a drive coil 9A (which is typically based on a possible pulsed AC voltage U). ~ The cylinder 2' operates with a stator 9B made of magnetic material (e.g., steel plate segments). The driven magnet 9 applies magnetic force to the permanent magnet 3A' of the cylinder 2', thereby exciting the stroke body 23 to perform linear oscillation relative to the fixed piston 3'. Under AC voltage U... ~ With the frequency remaining constant, the stroke body 23 vibrates at a specific frequency or operating frequency f. w The reciprocating motion occurs at a frequency or operating frequency that is at least approximately the same as the AC voltage U. ~ The voltage frequency corresponds to this. Specifically, the operating frequency f... w This can correspond to the resonant frequency f of a vibration system that includes at least the stroke body 23 and the spring element 4. res .

[0069] When the vibrating cylinder 2 moves forward or toward the spring element 4, it elastically stretches the spring element 4 and reduces the working volume 5, thereby pressurizing the working medium 7 and causing it to overcome the final pressure and flow out through the outlet 8. For example, a check valve prevents outflow through the inlet 6. In the opposite direction, either backward or toward the spring element 4, the cylinder 2 elastically compresses the spring element 4 and increases the working volume 5, thereby creating a negative pressure there. This negative pressure, in turn, causes the working medium 7 to overcome the suction pressure and flow in through the inlet 6. For example, a check valve prevents inflow through the outlet 8. The inlet 6 and outlet 8 may, for example, be both arranged on the valve plate 2A on the end side of the piston 3'.

[0070] List of reference numerals 1, 1' Linear Compressor 2, 2' cylinders 2a Valve plate 3, 3' Piston 3A permanent magnet 4. Spring element 5 Working volume 5A Dead Point Volume 6 entrances 7. Working medium 8 Exports 9. Driving magnet 9A drive coil 9B stator 10 Amplitude Adjusters 11 Sine Wave Generator 12 Current Regulator 13 Feedback device 14-17 Function blocks or flow blocks for asymmetrical power supply 20, 20' housing 21 Cylinder Bottom 22 Cylinder Frame 23-stroke body A. Target current value amplitude A + Positive current amplitude A - negative current amplitude ΔA Additional current value F force f w Operating frequency H Home Appliances i Current i g,s Equilibrium position of current curve under symmetrical current carrying i g,a Equilibrium position of current curve under asymmetrical current supply i ~ Current curve i ~ref Desired current curve Δi Additional DC component t time U ~ AC voltage x Offset of the stroke body x g,s Equilibrium position of offset under symmetrical energization x g,a Equilibrium position of offset under asymmetrical current supply x +,max Reversal point on the front side of the stroke body x +,max,ref Desired reversal point on the front side of the stroke body x -,max Reverse point of the stroke body x0 The rest position of the stroke body Δx - Additional inhalation stroke

Claims

1. A method for operating a linear compressor (1,1') of a household appliance (H), wherein in the method: - At least according to the desired reverse position (x) of the piston (3) or cylinder (2') of the stroke body (23) of the linear compressor (1,1'). +,max,ref ) and the actual reverse position (x) on the front side of the stroke body (23). +,max ), calculate the desired current curve (i) of the current (i) to be input into the drive coil (9A) of the linear compressor (1,1'). ~ref ); - Through the desired current curve (i ~ref ) and actual current curve (i ~ ), adjust the current (i) to be input into the drive coil (9A); - Estimate the actual reversal position (x) of at least the front side by means of an observer or by means of a sensor. +,max ).

2. The method according to claim 1, wherein the motion of the stroke body (23) is estimated or measured by an observer, and at least the actual reversal position (x) of the front side is determined based on the motion. +,max ).

3. The method according to any one of the preceding claims, wherein the actual rear reversal position (x) is additionally estimated by an observer or measured by a sensor. +,max ).

4. The method according to any one of the preceding claims, wherein, - At least according to the expected reversal position of the front side (x) +,max,ref ) and the actual reverse position of the front side (x) +,max ), calculate the target current value amplitude (A); - Based on the target current value amplitude (A) and the desired operating frequency (f) of the stroke body (23) w ), calculate the desired current curve (i ~ref ).

5. The method according to claim 3, wherein, - Add an additional current value (ΔA) to the target current value amplitude (A); and - The desired current curve (i ~ref Reduce the additional current value (ΔA).

6. The method according to claim 5, wherein, - The desired additional offset (Δx) of the stroke body (23) backward. - ), calculate the mechanical force (F) required to act on the stroke body (23) for this purpose; - Calculate the desired additional offset (Δx) to achieve the stroke body (23) based on the mechanical force (F). - The additional current value (ΔA) required.

7. The method of claim 6, wherein the additional current value (ΔA) is subject to a slope limit.

8. The method according to any one of the preceding claims, wherein the actual reversal position (x) of the front side of the stroke body (23) is estimated by a Lundberg observer. +,max ).

9. The method according to any one of claims 1 to 7, wherein the actual reverse position (x) of the front side of the stroke body (23) is measured by laser radiation. +,max ).

10. The method according to any one of claims 3 to 9, wherein the linear compressor (1,1') operates in one operating mode without an additional current value (ΔA) and in at least one other operating mode with an additional current value (ΔA).

11. A linear compressor (1,1') for a household appliance (H), wherein, The linear compressor (1,1') is configured to perform the method according to any one of the preceding claims.

12. The linear compressor (1) according to claim 11, wherein, The piston (3) as a stroke body (23) can move and be driven relative to the cylinder (2) as a stationary component.

13. The linear compressor (1') according to claim 11, wherein, The cylinder (2') as a stroke body can move and be driven relative to the piston (3') as a stationary component.

14. A household appliance (H) having a linear compressor (1,1'), wherein, The household appliance (H) is configured to perform the method according to any one of claims 1 to 8.

15. The household appliance (H) according to claim 14, wherein, The household appliance (H) is a refrigeration device, a dishwasher, or a laundry processing device.

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