WO2011120769A1

WO2011120769A1 - Linear motor for a linear compressor

Info

Publication number: WO2011120769A1
Application number: PCT/EP2011/053500
Authority: WO
Inventors: Hans-Wilhelm Klein; Eberhard Weidner
Original assignee: BSH Bosch und Siemens Hausgeräte GmbH
Priority date: 2010-04-01
Filing date: 2011-03-09
Publication date: 2011-10-06
Also published as: DE102010003625A1

Abstract

A linear motor for a linear compressor comprises a motor coil (120) for generating a magnetic field, an armature which can be deflected linearly in a deflection direction by the field generated by the motor coil (120), and a sensor arrangement for detecting the position of the armature in the deflection direction, wherein the sensor arrangement has a coupling transformer (330), the secondary side (334) of which is electrically connected to the motor winding (120), wherein the sensor arrangement, in order to detect the position of the armature, is designed to apply an excitation voltage to the primary side (332) of the coupling transformer (330) in order to excite the motor coil (120). Instead of the coupling transformer (330), the sensor arrangement may have at least one measurement coil which is provided in the region of a dead center of the armature in order to output a signal containing information regarding the position of the armature in the deflection direction.

Description

Linear motor for a linear compressor

The present invention relates to a linear motor for a linear compressor.

Typical linear compressors have a bushing in which a piston can be moved back and forth. The piston defines to one side a cylinder space in which an inlet valve in a valve plate gas can be admitted. During a compression stroke of the piston, the gas admitted into the cylinder space is compressed and discharged via an outlet valve in the valve plate. The piston is driven via a piston rod by a linear motor, which converts the electrical energy supplied to it into a linear, oscillating movement. Compared to piston compressors with a rotary drive, e.g. Via a connecting rod driven by a rotary motor, linear compressors have the advantage that the piston stroke can be changed and thus a higher efficiency can be achieved. Such linear compressors are used in the household sector for refrigerators and freezers and the like.

The control of the piston stroke in the liner can be done by detecting the current position of the piston. Here, the control of the piston stroke has to be done so that the piston is not driven on the high pressure side to the mechanical limit, since it can be damaged by such a striking. Furthermore, an improved efficiency can be achieved if the stroke length is adapted to the current operating state. For this purpose, however, a measurement of the piston position in both the top and bottom dead center is required.

WO 2004/025120 proposes as a sensor an inductive sensor, which is provided in a through hole in the valve plate and thus detects the approach of the piston to the valve plate. However, with this arrangement, only a detection of the piston position at top dead center is possible. Furthermore, the arrangement of the sensor in the valve plate involves problems with respect to the reliable sealing of the cylinder space.

From DE 297 95 315U1 and DE 197 48 647C2 a DC linear motor with integrated displacement measuring system is known in which the rotor displacements called inductance changes are evaluated for position detection. For this purpose, the voltage applied to two sub-coils of the motor drive voltages are evaluated, which on the one hand requires a complex coil winding and on the other hand a complex evaluation circuit. This method is also unsuitable for operation on an unregulated DC link. Furthermore, the temperature dependence of the winding resistance requires complex compensation.

It is therefore an object of the present invention to provide a linear motor for a linear compressor, in which the position of the piston can be detected with little effort, and in particular a simple sealing of the cylinder chamber allows light.

Preferably, the linear compressor is used in a refrigerator for compressing the refrigerant. A refrigeration appliance is understood in particular to be a household refrigeration appliance, that is to say a refrigeration appliance used for household purposes or possibly even in the gastronomy sector, and in particular for storing food and / or beverages in household quantities at specific temperatures, such as, for example, a refrigerator, a freezer , a fridge freezer, a freezer or a wine storage cabinet. According to one embodiment, a linear compressor for a linear compressor comprises a motor winding for generating a magnetic field, an armature which is linearly deflectable in a deflection direction by the field generated by the motor winding, and a sensor arrangement for detecting the position of the armature in the deflection direction, wherein the sensor arrangement a coupling transformer whose secondary side is electrically connected to the motor winding, wherein the sensor arrangement is designed to apply an excitation voltage for exciting the motor winding for detecting the position of the armature to the primary side of the coupling transformer.

Thus, the position of the piston of the linear compressor can be determined in a simple manner by detecting the armature position. In this case, no sensor arrangement in the cylinder chamber is necessary, so that the cylinder chamber can be sealed in a simple manner without having to provide supply lines to sensors or the like arranged therein. In this case, the excitation voltage for generating eddy current losses, which depend on the position of the armature, may be provided. One of these eddy current losses dependent variable can be fed to an evaluation circuit and evaluated by this.

The sensor arrangement can also be configured to detect the frequency of the excitation voltage or of a measurement voltage resulting in response to the excitation voltage on the primary side of the coupling transformer. In this measuring principle, for example, the inductance of the motor winding may depend on the position of the armature. If the excitation voltage is provided for example by an LC resonant circuit whose inductance is formed by the sensor arrangement, then a change in the armature position leads to a change in the frequency of the excitation voltage, which can be evaluated by a downstream evaluation voltage. The sensor arrangement may further comprise an oscillator circuit, by means of which an oscillating excitation voltage can be provided on the primary side of the coupling transformer. The frequency of this excitation voltage is advantageously a multiple of the frequency of the operating voltage of the linear motor. The primary side of the coupling transformer may be formed as part of a series resonant circuit. With a suitable adjustment of the resonance frequency of the series resonant circuit, this can serve as a blocking filter which does not transmit the voltage components of the linear motor supply transmitted to the primary side. Furthermore, the armature can be designed such that a dimension of the armature, in particular a width of the armature, varies along the deflection direction of the armature. This results in a position-dependent modulation of the eddy current losses, so that the position sensitivity of the sensor arrangement can be improved. For example, the armature can taper at least at one of its ends in the direction of deflection, in particular stepwise.

It is also possible that instead of the coupling transformer, the sensor arrangement has at least one measuring coil which is provided in the region of a dead center of the armature are to output a signal containing information about the position of the armature in the direction of deflection. Also in this case no sensor arrangement in the cylinder chamber is necessary, so that the advantages indicated above result. The measuring coil can be provided around the dead center of the armature, or near the dead center, eg less than one fifth or one tenth of the armature stroke in the direction of deflection away from the dead center.

In this case, the sensor arrangement may have at least two measuring coils, which are respectively provided at an upper and a lower dead center of the armature. Thus, a position detection is possible both at the top and at the bottom dead center of the anchor.

The two or more measuring coils may be electrically connected in series with each other. Thus, the evaluation of the output from the measuring coil sensor signal can be performed with a single evaluation circuit.

The linear motor may further include a Flußführungshülse, which surrounds the motor winding and the armature, wherein the measuring coil is embedded in the flux guide sleeve. This allows a space-saving arrangement of the measuring coil in the linear motor. The anchor may have at least one of its ends a material with greater conductivity than in a central region of the armature. For example, an aluminum ring may be provided at both ends of the armature. Thus, larger eddy current losses are produced when the aluminum rings are moved into the magnetic field formed by the sensor coils, so that a higher sensor sensitivity is achieved.

Further features and advantages of the invention will become apparent from the following description of embodiments with reference to the accompanying figures. Show

Fig. 1 is a schematic cross-sectional view of a linear motor for driving the piston of a linear compressor;

Fig. 2 is a cutaway perspective view of the linear motor; Fig. 3 is an equivalent circuit diagram of a circuit for driving the linear motor and a sensor arrangement for detecting the position of the armature;

4 shows a block diagram of a drive and evaluation circuit of the linear compressor; 5 shows a schematic cross-sectional view of a linear compressor with a linear motor according to a further embodiment;

6 shows an equivalent circuit diagram of a possible interconnection of the motor winding and the sensor coils; and

Fig. 7 shows a further embodiment of a drive circuit for the linear motor.

Unless otherwise indicated, like reference numerals in the figures denote like or functionally identical elements.

1 shows a schematic cross-sectional view of a linear motor 100 for driving the piston of a linear compressor. FIG. 2 shows a cutaway perspective view of the linear motor 100. The linear motor 100 comprises two E-shaped yokes 110, two motor windings 120 and one armature 130.

The E-shaped yokes 1 10 serve as a stator of the linear motor 100 and are made for example of packages of so-called dynamo sheet metal. The yokes 1 10 each have three arms 1 12, 1 14 and 1 16, which are in pairs opposite. The mutually facing ends of the arms 1 12, 1 14 and 1 16 each form pole pieces 1 18, which limit an air gap. One of the motor windings 120, which serve as excitation windings, is wound around the middle arms 14. The motor windings 120 can be acted upon by a current, wherein the current direction in the two motor windings 120 is set so that the two mutually opposite pole pieces 18 of the middle arms 14 form unequal magnetic poles. In this case, the motor windings 120 may be connected in parallel. The pole pieces 1 18 of the outer arms 1 12 and 1 16 form for each adjacent central arm 1 14 unlike magnetic poles.

In the air gap formed by the pole pieces 1 18 of the armature 130 is arranged. The armature 130 is movably mounted by means of two springs, not shown, that it in the arrow direction, which represents the deflection direction, ie in the longitudinal direction in the air gap formed by the pole pieces 1 18. The armature comprises a slide 132 and a four-pole permanent magnet 134. The four-pole permanent magnet can, for example, wise be glued into a provided in the carriage 132 bag. Alternatively, it is also possible to provide two two-pole permanent magnets, which are glued into corresponding pockets of the carriage 132. The permanent magnet 134 responds to the alternating magnetic field caused by the current flow through the motor windings 120, and the resulting force action is converted into an oscillating movement of the armature 130 in the stroke direction. The carriage 132 is made of a highly conductive material, such as aluminum.

Securely connected to the carriage 132 is one side of a piston rod 140. The other side of the piston rod 140 is fixedly connected to a piston which limits a not shown cylinder space of a linear compressor. By the oscillation of the armature 130 thus the volume of the cylinder space of the linear compressor is changed and in the cylinder space existing gas can be compressed.

3 shows an equivalent circuit diagram of a circuit 300 for driving the linear motor 100 and a sensor arrangement for detecting the position of the armature 100. The circuit 300 for driving the linear motor 100 comprises a DC voltage intermediate circuit 310 and an H-bridge circuit 320.

The DC intermediate circuit 310 comprises four rectifier diodes 31 1, 312, 313 and 314 as well as a smoothing capacitor 315. The four rectifier diodes 31 1, 312, 313 and 314 rectify an AC voltage U _A c, which may be given for example by a mains voltage. The smoothing capacitor 315 smoothes the voltage at the output of the diode circuit, so that at the two ends of the smoothing capacitor 315 a DC voltage U _D c is applied, which is supplied to the H-bridge circuit 320.

The H-bridge circuit 320 comprises four semiconductor switches 321, 322, 323 and 324. The semiconductor switches 321, 322, 323 and 324 each have a transistor, to each of which a freewheeling diode is connected in parallel. The transistors can be embodied, for example, as IGBTs or power MOSFETs, and can each be controlled by a controller (not shown). On the bridge of the H-bridge circuit 320, the motor windings 120 of the linear motor 100 are arranged, which can be connected in series, for example. The H bridge circuit 320 is used to adjust the intermediate Schenkreisspannung to the operating voltage of the linear motor 100 operated with pulse width modulation. In a first phase of the pulse width modulation, the semiconductor switches 321 and 324 are turned on, so that current flows through these semiconductor switches 321 and 324 and in a first direction through the linear motor 100 arranged therebetween. In a following freewheeling phase, the semiconductor switches 321 and 324 are disabled. The inductance of the motor windings maintains the flowing current which can flow across the diodes arranged in parallel with the transistors of the semiconductor switches 322 and 323. Next is a second phase in which the semiconductor switches 322 and 323 are turned on so that current flows through these semiconductor switches 322 and 322 and in a second direction opposite to the first direction through the linear motor 100 interposed therebetween. This is followed by another freewheeling phase in which the freewheeling current flows through the diodes arranged in parallel with the transistors of the semiconductor switches 321 and 324. Then the cycle starts from the beginning. By adjusting the length of the first and second phases, the stroke of the armature 130 can be adjusted.

A coupling transformer 330 is arranged in series with the motor winding 120 of the linear motor 100 and also on the bridge of the H bridge circuit 320. More specifically, the secondary side 334 of the coupling transformer 330 is arranged in series with at least one of the motor windings 120. The primary side 332 of the coupling transformer 330 is connected to a drive and evaluation circuit 400.

4 shows a block diagram of the drive and evaluation circuit 400. The drive and evaluation circuit 400 comprises an oscillator circuit 410, a voltage divider circuit 420, a filter circuit 430, an evaluation circuit 440 and a microcontroller 450.

The oscillator circuit 410 provides a high-frequency excitation voltage Us, which, after division with the voltage divider circuit 420, is fed via the coupling transformer 330 into the linear motor circuit. The excitation voltage Us is, for example, a sinusoidal voltage of constant amplitude having a frequency which is a multiple, eg, 10 times or 100 times or more, the maximum frequency of the PWM voltage with which the linear motor 100 is operated. Thus, the movement of the linear motor of the injected excitation voltage Us is not or only negligible affected. The voltage divider 420 comprises a resistive voltage divider resistor 422 and two terminals 424 and 426. The voltage divider resistor 422 is connected on one side to the output of the oscillator circuit 410 and on the other side to the input of the filter circuit 430. The terminal 424 is connected to the node connecting the voltage divider resistor 422 to the filter circuit 430. The terminal 426 is connected to ground or to a reference potential. The primary side 332 of the coupling transformer 330 is connected to the two terminals 424 and 426. The excitation voltage Us thus leads to an excitation of the motor winding 120, which is superimposed on the excitation by the PWM modulation of the linear motor 120.

Furthermore, the voltage applied to terminal 424 is tapped and supplied to the filter circuit 430. This voltage Um contains information about the position of the armature 130. This will be explained in more detail below: The motor winding 120 connected to the coupling transformer 330 has, as shown schematically in FIG. 3, an inductance Lm and a resistive coil resistance Rm Fig. 1 illustrated situation runs, due to the excitation of the motor winding 120, the magnetic flux from the pole piece 1 18 of the middle arm 1 14 through the air gap on both sides by the permanent magnet 134, from there again via the air gap to the side arms 1 12 and 1 16 and via the yoke base back into the middle arm 1 14. The permanent magnet 134 has only a low magnetic resistance, so that the magnetic flux flows substantially unhindered or prevented only by the air gap. If the armature 130 is now deflected to one side, for example to the left, then the permanent magnet 134 is no longer disposed relative to the arms 16, but now the carriage 132 is arranged. Since the carriage 132 is made of a material of high electrical conductance and low relative permeability such as aluminum, eddy currents are generated therein when it is brought into the magnetic field generated by the coil, thereby consuming power converted into heat. In other words, the starting voltage fed from the primary side excites an alternating magnetic field in the motor winding 120, which generates eddy currents in the electrical conductor of the carriage 132. In this state, the armature 130 thus acts like a switched-on consumer, the consumer power is greater, the more the slide 132 in the Magnetic field penetrates. This is modeled in the equivalent circuit diagram by the equivalent resistance Ra parallel to the inductance Lm, which increases due to the eddy current losses.

The filter circuit 430 may, for example, comprise a capacitive element which, together with the primary side 332 of the coupling transformer 330, forms a series resonant circuit. If now due to the eddy current losses of the equivalent resistance Ra increases, then this affects as a change in the quality of the oscillation amplitude and the resonant frequency of the resonant circuit. The electronic evaluation circuit 440 detects at least one of these two variables and generates as output a position-dependent DC voltage signal Ux, which contains information about the position of the armature 130 in the linear motor 100, and is for example proportional to the change of the equivalent resistance Ra. At the same time, the series resonant circuit acts as a blocking filter with respect to the lower PWM frequency of the motor supply. The evaluation circuit 440 can have, for example, an amplifier and a circuit part for peak value rectification with smoothing. The sensor signal Ux is supplied to an analog-to-digital converter 455 of the microcontroller 450, which converts the sensor signal Ux into a digital signal. In response to this sensor signal Ux, the microcontroller 450 regulates the power supply to the linear motor 100. By a suitable control can be ensured on the one hand that the piston does not abut against its stops, and on the other hand, that the operating conditions corresponding optimal efficiency is set.

In an advantageous embodiment, the carriage 132 may have different thicknesses along the deflection direction of the armature. Thus, the width of the air gap varies between the pole shoes and the armature along the deflection direction of the armature. With this configuration, the width of the air gap in the magnetic circuit formed by armature, yoke and motor winding changes depending on the position of the armature. For example, the carriage 132 may, for example, gradually taper at one or both of its ends. In this case, the width of the air gap between carriage 132 and yoke 1 10 depends on the position of the armature 130, and the width of the air gap increases with increasing approach of the armature 130 to its dead center. This affects the size of the eddy current losses, so that a position-dependent modulation of the eddy current losses arises. Thus, the position sensitivity of the Sensor arrangement can be improved. It is advantageous if the change in the width of the air gap over the Auslenkungsweg of the armature 130 is as large as possible.

In the arrangement described above, it is advantageous if the connection between the piston and armature 130 via the piston rod 140 is as rigid as possible, since the position of the armature 130 is to be closed to the position of the piston in the cylinder space. In a rigid connection occurs no positional distortion, for example, by a bending of the piston rod 140.

Furthermore, it is possible to compensate for temperature changes on the winding resistance of the motor winding 120. The influence of temperature changes on the winding resistance is greater by a factor of about 4 than the influence of temperature changes on the inductance of the motor winding 120. By a temperature measurement and subsequent computational correction with the microcontroller or the like, the influence of the temperature on the measurement result can be compensated ,

Furthermore, it is advantageous if the influence due to magnetic saturation on the measurement result is as low as possible. Magnetic saturation results in an increase in the magnetic scattering or coupling. This changes the inductance of the linear motor 100, which also affects the eddy current losses and thus the measurement result. It is therefore advantageous not to operate the linear motor in magnetic saturation. Furthermore, it is advantageous if the smallest possible eddy current losses occur on the stator side. This can be achieved, for example, by using dynamo sheets of small thickness. With the arrangement described above, position-dependent eddy-current losses in the magnetic circuit are detected and evaluated in their size. Alternatively, it is also possible to use an LC oscillator to provide the excitation voltage whose inductance is formed by the sensor arrangement with the coupling transformer. This inductance changes as a function of the inductance of the secondary-side motor winding 120, and thus depending on the position of the armature 130 in the linear motor 100, which leads to a change in the frequency of the excitation voltage. This frequency change can be done by the downstream evaluation circuit 440th be evaluated, which in this case outputs a signal which is proportional in amplitude to the inductance or inductance change.

During the measurement, the voltage drops at the semiconductor switches 321 to 324 cause a falsification of the measured value. This corruption can be corrected mathematically by the microcontroller 450.

5 shows a schematic cross-sectional view of a linear compressor 500 with a linear motor 540 according to a further embodiment. The linear compressor 500 has a compressor section 520 and a linear motor 540. The compressor section 520 includes a bushing 522 and a piston 524 oscillating in the bushing 522. The bushing 522 is closed to one side by a valve plate 526 in which an inlet and an outlet valve are provided, which are not shown in detail. The bushing 522, the piston 524, and the valve plate 526 define a cylinder space 528 into which coolant may be introduced through the inlet valve and compressed with the piston 524. In the rest position 530, the piston 524 is located in the middle of the compressor section 520. The cylinder chamber 528 corresponds to a compression region 532, in which the piston 524 moves during a compression stroke. In the expansion stroke, the piston 524 moves into an expansion region 534. The linear motor 540 includes an armature 542, which is rigidly connected to the piston 524 via a piston rod 544. The armature 542 may be formed, for example, as a cylindrical two-pole permanent magnet. Arranged around the armature 542 is a motor winding 546 designed as a ring winding. The motor winding 546 may extend substantially over the entire length of the linear motor 540 or be provided only in a central region of a bushing 548. Surrounding the motor winding 546 is a flux guide sleeve 550, which serves to guide the magnetic flux generated by the motor winding 546. The Flußführungshülse 550 and the liner 522 are accommodated in a cylindrical housing 560. In operation, the motor winding 546 is supplied with an alternating current. Depending on the direction of flow of the current flowing through the motor winding 546, a magnetic field is generated, to which the magnetic armature 542 responds and is thus deflected in the direction of deflection, that is to the left or to the right in FIG. 5. For detecting the position of the armature 542 in the linear motor 540, a sensor coil 570 is arranged in the region of the top dead center of the armature 542, and a sensor coil 572 is arranged in the region of the bottom dead center of the armature 542. The sensor coils 570 and 572 are formed as ring windings and surround the path of travel of the armature 542. In this case, the sensor coils 570 and 572 can be embedded, for example, in grooves provided in the flux guide sleeve 550. The sensor coils 570 and 572 are supplied with an AC voltage and generate a magnetic field. If now the armature 542 is moved into the magnetic field generated by one of the sensor coils 570 and 572, then eddy currents are generated in the armature 542, which lead to eddy current losses which can be detected in the manner described above, thus for example indirectly by the change of a is detected by the eddy current losses affected equivalent resistance.

The armature 542 may have at its two ends a material which has a greater electrical conductivity than the central portion formed by the permanent magnet. For example, 542 aluminum rings 543 may be provided at both ends of the armature. Thus, larger eddy current losses are produced as the aluminum rings 543 are moved into the magnetic field formed by the sensor coils 570 and 572, thus achieving higher sensor sensitivity. To achieve a high sensor sensitivity, it is also advantageous if the wall thickness of the Flußfüh- tion sleeve 550 is smaller than the diameter of the armature 542. As an alternative to a position detection by means of the detection of the eddy currents, it is also possible to deduce the position of the armature 542 from the change in the inductance of the sensor coils 570 and 572 when the armature 542 approaches the sensor coils 570 and 572. As with the embodiment described above, it is advantageous in the embodiment illustrated in FIG. 5 that sensors for position detection are not provided in the region of the cylinder space 528. Rather, the position of the armature 542 in the linear motor 540 is detected by means of the sensor coils 570 and 572. Because the piston 524 is rigidly connected to the armature 542 via the piston rod 544, the position of the armature 542 directly closes the position of the piston 524 in the sleeve 522. Since no sensors are provided in the cylinder space, the sealing of the cylinder space is simpler than, for example, the case when an inductive sensor is provided in the valve plate 526. Furthermore, it is advantageous in this embodiment, that the measuring circuit is galvanically decoupled from the control of the linear motor. Disturbances of the measuring signal can thus be avoided. By skillful arrangement of the measuring coils, a high sensitivity can be achieved.

6 shows an equivalent circuit diagram of a possible arrangement 600 of the motor winding 546 and the sensor coils 570 and 572. As shown in FIG. 6, the motor winding 546 may be connected via two terminals 580 and 582 to a drive circuit, for example the H-switch shown in FIG. Bridge circuit 320, be connected. Further, the sensor coils 570 and 572 may be electrically connected in series with each other, with one end of the sensor coil 572 connected to a port 584 and one end of the sensor coil 570 connected to a port 586. In this arrangement, only a single evaluation circuit for evaluating the signal output from the sensor coils 570 and 572 signal is necessary. Both sensor coils 570 and 572 cooperate with the armature 542 in the manner described above when it is moved into the magnetic field generated by one of the sensor coils 570 and 572. If the linear motor 540 is designed to be exactly symmetrical, it can not yet be determined from the signal which can be picked off at the terminals 584 and 586 whether the armature 542 is approaching its upper or lower dead center, but this can be done by comparison with the polarity of the motor winding 546 supplied stream. Alternatively, it is also possible, for example by appropriate design of the aluminum rings 543, to make the linear motor 540 asymmetric such that it can be detected from the signal applied to the terminals 584 and 586, whether the armature 542 approaches its top or bottom dead center ,

7 shows a further embodiment of a drive circuit for the linear motor 100, 520. In this embodiment, the linear motor 100, 520 is on one side with a bidirectional, non-turn-off semiconductor switch, eg a triac 700, and on the other side with a first supply terminal 710 connected. The other side of the triac 700 is connected to a second supply terminal 720. A supply voltage U c _A is applied to the power supply terminals 710 to 720. A control terminal of the triac 700 is connected to a motor controller, and the triac 700 can be switched through by applying a control signal to this control terminal. With this configuration, the linear motor 100 520 may be connected directly to a mains voltage U _A c, ie without an intermediate circuit. The linear motor 100, 520 is thus regulated in phase gating, wherein the motor voltage can be controlled by adjusting the phase angle. The position detection is carried out as described above. An advantage of this embodiment is that it is less expensive and can be realized with only one semiconductor switch. However, it is disadvantageous that the triac 700 can not be switched off after it has been turned on until the next zero crossing of the excitation voltage, ie the circuit is less flexible than the H-bridge formwork 320 in FIG. 3.

LIST OF REFERENCE NUMBERS

100 linear motor

1 10 yokes

1 12, 1 14, 1 16 arms

1 18 pole shoes

120 motor windings

130 anchors

140 piston rod

300 circuit for driving the linear motor 310 DC intermediate circuit

31 1, 312, 313, 314 rectifier diodes

315 smoothing capacitor

320 H bridge circuit

321, 322, 323, 324 semiconductor switch

330 coupling transformer

332 primary side

334 secondary side

400 control and evaluation circuit

410 oscillator circuit

420 voltage divider circuit

422 voltage divider resistor

424, 426 connections

430 filter circuit

440 evaluation circuit

450 microcontroller

455 analog-to-digital converter

500 linear compressors

520 compressor section

522 bushing

524 pistons

526 valve plate

528 cylinder chamber

530 rest position 532 compression range

534 expansion area

540 linear motor

542 anchors

544 piston rod

546 motor winding

548 bushing

550 flux guide sleeve

560 cylindrical housing

570, 572 sensor coils

600 arrangement of motor winding and sensor coils 700 triac

710, 720 supply connections

Claims

claims

Linear motor for a linear compressor, comprising:

a motor winding (120) for generating a magnetic field; and an armature (130) which is linearly deflectable by the field generated by the motor winding (120) in a deflection direction;

characterized by a sensor arrangement for detecting the position of the armature (130) in the deflection direction, wherein the sensor arrangement comprises a coupling transformer (330) whose secondary side (334) is electrically connected to the motor winding (120), wherein the sensor arrangement is designed to detect the Position of the armature (130) to the primary side (332) of the coupling transformer (330) to apply an excitation voltage for exciting the motor winding (120).

Linear motor according to claim 1, characterized in that the excitation voltage for generating eddy current losses, which depend on the position of the armature (130), is provided.

Linear motor according to claim 1 or 2, characterized in that the sensor arrangement is designed to detect the frequency of the excitation voltage or a test voltage resulting in response to the excitation voltage on the primary side (332) of the coupling transformer (330).

Linear motor according to one of the preceding claims, characterized in that the sensor arrangement further comprises an oscillator circuit (410) through which an oscillating excitation voltage on the primary side (332) of the coupling transformer (330) can be provided.

Linear motor according to one of the preceding claims, characterized in that a dimension of the armature (130), in particular a width of the armature (130), varies along the deflection direction of the armature (130).

6. Linear motor according to claim 5, characterized in that the armature (130) tapers at least at one of its ends in the deflection direction, in particular gradually tapers.

7. Linear motor according to claim 1, characterized in that the sensor arrangement has, instead of the coupling transformer (330) at least one measuring coil (570, 572) which is provided in the region of a dead center of the armature (542) to output a signal containing information about the position of the armature (542) in the deflection direction.

8. Linear motor according to claim 7, characterized in that the sensor arrangement has at least two measuring coils (570, 572), which are respectively provided at an upper and a lower dead center of the armature (542).

9. Linear motor according to claim 8, characterized in that the measuring coils (570, 572) are electrically connected to one another in a series connection.

10. Linear motor according to one of claims 7 to 9, characterized in that the armature (542) has at least one of its ends a material with greater conductivity than in a central region of the armature (542).

1 1. A linear compressor characterized by a linear motor according to one of claims 1 to 10.