EP2513479B1 - Coolant compressor with linear drive - Google Patents

Description

The invention relates to a refrigerant compressor with a hermetically sealed compressor housing, in the interior of a refrigerant-compressing piston-cylinder unit is arranged, the cylinder housing is closed at the end by means of a cylinder head, in which a suction port and a pressure port are provided, via which refrigerant sucked via a suction valve through the suction port and is compressed via a pressure valve through the pressure port, wherein the piston-cylinder unit has at least one piston guided in a piston bore of the cylinder housing, wherein between the cylinder head and a first end face of the piston, a working space for compression a refrigerant is formed, wherein a linear drive is provided, comprising at least one vibrating body surrounded by a field winding, which is connected to the piston in order to move it oscillating along a piston longitudinal axis, according to ß the preamble of claim 1.

The refrigeration process with azeotropic gases as such has long been known. The refrigerant is heated by energy intake from the space to be cooled in an evaporator and finally overheated, which leads to evaporation and compressed by a piston-cylinder unit of the refrigerant compressor to a higher pressure level, where it emits heat through a capacitor and a throttle , in which a pressure reduction and cooling of the refrigerant takes place, is transported back into the evaporator. Such refrigerant compressors are used in domestic and industrial applications, where they are usually arranged on the back of a refrigerator or refrigerator. The piston-cylinder unit comprises a cylinder housing provided with a piston bore, in which an oscillating piston is guided.

The piston bore of the cylinder housing is closed in a first axial end of a cylinder head or a valve plate, while the piston bore is open in a second axial end portion for receiving the piston or in the assembled state of the refrigerant compressor is penetrated by a connecting rod.

The cylinder head can generally be designed on the one hand as a solid, cap-shaped component, for example with a pressure chamber and a suction chamber, which carries a valve plate on its inside. It can be designed as an annular component which holds the valve plate on the cylinder housing, but it can also be designed only as a valve plate which is clamped by means of a clamping device on the cylindrical part of the cylinder housing. In the valve plate then the suction port for sucking the refrigerant from the refrigerant circuit is arranged, and the pressure port through which the compressed refrigerant is ejected after the compression process in the refrigerant circuit through the piston.

The valve plate is screwed to the most widespread refrigerant piston compressors with the front side of the cylinder housing. For this purpose, bores are arranged both on the cylinder housing and in the valve plate, wherein the bores in the cylinder housing are each provided with a thread, via which the screw connection is made. On the cylinder housing opposite side of the valve plate is provided in this most common type of refrigerant piston compressors, a cylinder cover having a pressure chamber in which the ejected from the cylinder, compressed Refrigerant is briefly cached, in order subsequently to flow into the refrigerant circuit. Embodiments are also known in which a suction chamber corresponding to the pressure chamber is provided, via which the refrigerant is sucked through the suction opening into the cylinder. Pressure chamber and suction chamber are separated from each other in such cases by appropriate structural measures in the cylinder cover.

A refrigerant compressor of conventional design comprises an electric motor which drives the piston oscillating in the piston bore via a crankshaft.

In order to make dispensable the provision of a crankshaft, there are various linear compressor solutions in which the piston is driven directly by an electric linear drive. In this case, the piston is connected to a vibrating body, which is surrounded by a field winding (also referred to as a stator) oscillating about a piston longitudinal axis is set in motion. The piston stroke (= piston travel) can be determined by a variably induced voltage at the linear drive.

Problematic in such solutions is the exact limitation of the piston travel during the oscillation of the piston. On the one hand, it is intended to prevent the piston from abutting the cylinder head or the valve plate arranged in the cylinder head in the region of top dead center. On the other hand, it should also be prevented that the top dead center of the piston moves too far down or that the piston approaching the cylinder head or the valve plate takes place too early reversing movement and thereby a power-reducing dead space is created.

In the pamphlets CN 101240793 A and DE 10 2006 009 270 A For this purpose, mechanical spring elements for buffering the piston and thus to limit the piston travel proposed. From the DE 10 2006 009 256 A It is known to change the piston stroke by means of adjustable spring elements.

The disadvantage of such systems is mechanical wear in the spring elements and the piston components. The spring elements take up valuable space and prove to be inflexible if the cooling capacity of the refrigerant compressor or the piston stroke to be changed.

The US 6379125 B1 also discloses a refrigerant compressor with linear drive, in which the piston is reset by means of a spring.

There are also linear compressors in which the piston is held in position during its oscillation exclusively by an electronic control of the linear drive. Such as from the WO 01/48379 A and the WO 2009/103138 A2 However, known solutions for limiting the piston travel can only be realized under the provision of expensive sensor and evaluation technology. In particular, sensors are provided which determine the duration of a piston movement, which are compared in a further sequence by a microprocessor with a stored on a storage medium reference period and from this the current position of the piston is calculated. Such systems are expensive and therefore find little use in the standard compressor manufacturing.

Linear drives, in which a piston occupies a central position due to the repulsion of Gleichpolpolter permanent magnets are in connection with vacuum pumps from US 2005/112001 A1 and the DE 10314007 A1 known. The DE 19504751 A1 discloses such a concept in the context of a magnetic pump for conveying liquid or gaseous media, none of which are disclosed in the last three documents mentioned However, devices meet the specific requirements of a refrigerant compressor.

The present invention is therefore based on the object to propose a simple and reliable way to limit the piston travel in refrigerant compressors with linear drive, which makes dispensable both a providence of mechanical spring elements and a provident consuming sensor and control electronics to limit the piston travel. In the cylinder housing occurring dead space should be reduced as possible.

According to the invention, these objects are achieved by a device having the characterizing features of claim 1.

It is provided that the piston-cylinder unit is equipped with at least one permanent magnet assembly comprising at least one arranged on the piston or on a component connected to the piston first permanent magnet and at least one arranged on the cylinder housing or on a component connected to the cylinder housing second Permanent magnet, wherein the first permanent magnet and the second permanent magnet, each having the same magnetic pole direction to each other to limit the piston travel in the region of top dead center and / or in the region of bottom dead center when approaching the first permanent magnet to the second permanent magnet a repulsive effect between the two To produce permanent magnets.

In this way, the piston travel of the piston can be limited easily and reliably. An abutment of the piston on elements of the cylinder housing, in particular on the valve plate is prevented even without electronic sensor and control elements.

In principle, any number of first and second permanent magnets can be arranged in any position and constellation.

In the component connected to the piston, on which the at least one first - movable - permanent magnet is arranged, it may be in a special embodiment of the invention to the oscillating body or a piston connecting the piston with the oscillating piston piston shaft.

When connected to the cylinder housing component, on or in which the at least one second - fixed - permanent magnet is arranged, it is in a preferred embodiment of the invention to the cylinder head.

In this case, a valve plate may be arranged in the cylinder head, wherein the at least one second permanent magnet on the

Valve plate, preferably at least partially sunk in the valve plate, is arranged. In this way, the piston travel is limited in the region of top dead center. The second permanent magnet can be arranged both outside and inside or even completely or partially in the valve plate. The limitation of the piston travel at bottom dead center can also be done with permanent magnets, but it can also be done conventionally, for example by means of spring elements.

According to a particularly preferred embodiment of the invention, the at least one second permanent magnet is disposed within the piston bore of the cylinder housing, in particular within the working space or the working space delimiting. For example, one of the permanent magnets could be recessed in the cylinder housing so that it limits the working space with its front side. The working space is formed by the cylinder housing and designates the space swept by the piston during its oscillation within the cylinder housing.

As already mentioned, according to a further embodiment variant of the invention, it would also be possible to arrange the second permanent magnet outside the piston bore or the working space.

Of course, the at least one first permanent magnet can also be arranged outside the piston bore or the working space, for example, as already proposed above, on the oscillating body or on the piston shaft.

A particularly simple embodiment provides that the at least one first permanent magnet is arranged in the region of the first end face of the piston facing the cylinder head.

In order to avoid dead space losses, it can be provided that - as in the case of the second permanent magnets - the at least one first permanent magnet is sunk in sections or entirely in the end face and / or in the piston skirt. In particular, it is possible for the recessed first and / or second permanent magnet to be encased by the material of the piston or of the cylinder head or of the valve plate, preferably encased on all sides.

According to a development of the invention it is provided that the permanent magnets are sunk in the end faces of the piston and / or the valve plate, that between the permanent magnet and the piston or permanent magnet and valve plate at least one free space is present, which communicates with the working space. This free space preferably extends along the entire circumference of the permanent magnet. The gap-shaped recess favors a free development of the magnetic effect of the permanent magnet or an expansion of the magnetic field lines emanating from the permanent magnet.

An expanding of the permanent magnet outgoing magnetic field lines is further favored by the free space is designed according to a preferred embodiment of the invention as a gap, the clear opening width widens in the direction of the working space.

The free space can be filled with a non-ferromagnetic material, such as plastic. By such a filling of the recess undesirable dead space (remaining space between the piston and cylinder head or valve plate at top dead center of the piston), which would reduce the performance of the refrigerant compressor can be avoided.

For optimal pairing of the piston side arranged first and the cylinder housing side arranged second permanent magnet measures according to the invention are proposed below. It should each have a focused effect of the permanent magnets each other and a stable position of the piston, in particular during its reversal movement at the dead centers, be ensured.

The permanent magnets can be made substantially cylindrical.

In particular, the permanent magnets may be made substantially annular, wherein the annular shape is preferably rotationally symmetrical to the piston longitudinal axis. The permanent magnets in this case preferably have a ring-cylindrical shape, so that sunk permanent magnets can be surrounded by a free space in the form of an annular gap.

The permanent magnets can also be arranged rotationally symmetrical to an axis which is parallel to the piston longitudinal axis.

Any modifications to the ring shape are also possible, e.g. oval or elliptical shapes. Alternative embodiments would be e.g. spiral or lattice-shaped permanent magnets. In a specific embodiment, a plurality of permanent magnets are arranged concentrically around the piston longitudinal axis.

If the end face of the at least one first permanent magnet arranged on the piston side runs substantially parallel to the end face of the at least one second permanent magnet arranged on the cylinder housing side, a uniform formation of the magnetic field is ensured.

According to a further preferred embodiment of the invention, the first permanent magnet arranged on the piston side essentially has a field strength of the same magnitude, that is, with the same material, preferably a substantially equal mass, on the second permanent magnet arranged on the cylinder housing side. This creates a symmetric magnetic field.

A uniform magnetic field is also achieved when a plurality of permanent magnets are arranged on a concentric to the piston longitudinal axis circle, wherein the angular distance of adjacent permanent magnets is substantially equal. In this case, the piston-side and the cylinder-housing-side permanent magnets are expediently arranged on a circle, whereby the piston-side and cylinder-housing-side permanent magnets lie opposite one another (ie cover in the piston longitudinal axis).

In a special construction, the piston can be designed as a double piston, comprising two at opposite End portions of the double piston arranged, one end face of the double piston forming piston sections. Between the first end face of the double piston and a first cylinder head comprising a first valve head, a first working space and between the second end face of the double piston and a second cylinder head comprising a second valve plate, a second working space is formed. The oscillating body is arranged between the two end faces of the double piston, preferably enclosed by the double piston, wherein an arrangement according to the invention of permanent magnets is provided for each cylinder head-piston portion pairing.

In a method according to the invention for determining the piston stroke of a linear compressor in a refrigerant compressor according to the preamble of claim 1, it is provided that the piston-cylinder unit is designed according to one of claims 1 to 20 and the drive strength of the linear drive is set in the case of predetermined permanent magnets in that the piston changes its direction of movement in a predetermined top dead center and / or bottom dead center without the use of a mechanical spring element.

It can e.g. be provided that the piston changes its direction of movement both at the top and bottom dead center due to only one permanent magnet arrangement. But it can also be provided that the piston changes its direction of movement due to a permanent magnet arrangement only at one dead center, while a known spring element is used for the change of the direction of movement in the other dead center.

With the permanent magnets of the piston forms together with the oscillating body and possibly the piston skirt a non-linear mass-spring system. As a result, different resonance frequencies are possible in this mass-spring system, if one does not take full advantage of the mass spring system, while in a linear mass spring system, such as the exclusive use of spring elements, only one resonant frequency occurs at which the piston is normally operated. According to the invention therefore different piston frequencies and thus different cooling capacities are possible.

Accordingly, it can therefore be provided that - to achieve different cooling capacities - in addition a certain frequency of the linear drive is specified.

As an additional safety measure, so that the piston does not hit the valve plate, it can be provided that the drive strength and / or frequency of the linear drive can be adjusted on the basis of measured position data of the piston or magnetic field strengths. Hall sensors such as those used in inductive encoders or current-voltage measurements of the exciter winding can be used for this purpose.

Fig. 1

eine schematische Darstellung eines erfindungsgemäßen Linearverdichters

Fig. 2

einen Längsschnitt durch eine erfindungsgemäßen Kolben-Zylinder-Einheit

Fig. 3

eine erfindungsgemäße Kolben-Zylinder-Einheit mit einem Federelement

Fig. 4

eine erfindungsgemäße Kolben-Zylinder-Einheit mit Dauermagneten am Schwingkörper des Linearantriebs

Fig. 5

die Ausführungsvariante gemäß Fig. 4, wobei sich der Kolben in seinem unteren Totpunkt befindet

Fig. 6

ein Detail "B" aus Fig. 4

Fig. 7

eine Modifizierung der Ausführungsvariante gemäß Fig. 4 mit Federelement

Fig. 8

eine schematische Darstellung der im Bereich der Dauermagnete entwickelten Magnetfelder in Form von Feldlinien (Kolben im unteren Totpunkt)

Fig. 9

Darstellung wie in Fig. 8 (Kolben am Weg Richtung oberer Totpunkt)

Fig. 10

Darstellung wie in Fig.8 (Kolben erreicht oberen Totpunkt)

Fig. 11

ein Kraft-Weg-Diagramm zur Darstellung des Anstiegs der Magnetkraft bei Annäherung des ersten an den zweiten Dauermagneten

Fig. 12

eine erfindungsgemäße Kolben-Zylinder-Einheit mit Doppelkolben

Fig. 13

eine schematische Darstellung eines in einem Verdichtergehäuse angeordneten erfindungsgemäßen Linearverdichters

The invention will now be explained in more detail with reference to an embodiment. Showing:

Fig. 1

a schematic representation of a linear compressor according to the invention

Fig. 2

a longitudinal section through a piston-cylinder unit according to the invention

Fig. 3

an inventive piston-cylinder unit with a spring element

Fig. 4

an inventive piston-cylinder unit with permanent magnets on the oscillating body of the linear drive

Fig. 5

the embodiment according to Fig. 4 with the piston in its bottom dead center

Fig. 6

a detail "B" off Fig. 4

Fig. 7

a modification of the embodiment according to Fig. 4 with spring element

Fig. 8

a schematic representation of the magnetic fields developed in the field of permanent magnets in the form of field lines (piston at bottom dead center)

Fig. 9

Representation as in Fig. 8 (Piston on the way to top dead center)

Fig. 10

Representation as in Figure 8 (Piston reaches top dead center)

Fig. 11

a force-displacement diagram illustrating the increase of the magnetic force upon approach of the first to the second permanent magnet

Fig. 12

a piston-cylinder unit according to the invention with double piston

Fig. 13

a schematic representation of a arranged in a compressor housing according to the invention linear compressor

Fig. 1 shows in a schematic way the structure of a linear compressor 23 according to the invention, which by means of a suspension device 28 within a in Figure 13 illustrated, hermetically sealed compressor housing 29 of a small refrigerant compressor is arranged. The linear compressor 23 comprises a piston-cylinder unit 21 with at least one piston 3 guided in a piston bore 2 of a cylinder housing 1. The cylinder housing 1 is closed at the end with a cylinder head 4, more precisely, with a valve plate 5 held in the cylinder head 4.

The piston 3 is oscillatingly movable by a linear drive 6 along a piston longitudinal axis 9. The linear drive 6 comprises in a known manner one of a field winding (a stator) 8 surrounded oscillating body 7, which is connected to the piston 3 rigid or articulated. In the present embodiment, the oscillating body 7 is connected to the piston 3 by means of a piston rod or a piston stem 22.

According to the invention, the piston-cylinder unit 21 is equipped with at least one permanent magnet arrangement (namely two: 11a and 12a, 11b and 12b), comprising in each case at least one component on the piston 3 or on a component connected to the piston 3 - in this case, in particular around the oscillating body 7 or around the piston skirt 22 acting-arranged first permanent magnet 11a, 11b and with at least one cylinder housing 1 or on a connected to the cylinder housing 1 component second permanent magnet 12a, 12b. In this case, the at least one first permanent magnet 11a, 11b and the at least one second permanent magnet 12a, 12b each have the same magnetic pole direction to each other, so that when approaching the at least one first permanent magnet 11 to the at least one second permanent magnet 12, a repulsive effect between the two permanent magnets 11th and 12 and thus the piston travel in the region of top dead center and / or in the region of the bottom dead center of the piston 3 limiting effect arises.

In the case of Fig. 1 are at the front side of the piston 3, a first permanent magnet 11a, on the opposite side, a further first permanent magnet 11b is mounted, namely an annular permanent magnet. On the cylinder head 4 and on the valve plate, a second permanent magnet 12a is attached, on the opposite side of the cylinder housing 1, where the piston shaft 22 passes through the cylinder housing 1, another second permanent magnet 12b. The latter is ring-shaped educated. In this case, the permanent magnets 11a and 12a cooperate and determine the force increase in the direction of the top dead center of the piston 3, while the permanent magnets 11b and 12b cooperate and determine the increase in force in the direction of the bottom dead center of the piston 3 due to their field strength. Depending on the load, the points at which the piston 3 actually reverses may vary.

In Fig. 2 is an embodiment similar to that in FIG Fig. 1 shown, only in Fig. 2 in the first end face 3 a of the piston 3, an annular permanent magnet 11 and corresponding thereto in the valve plate 5 of the cylinder head 4, an annular second permanent magnet 12 is sunk. The working space 14 facing surface of the first permanent magnet 11 is in a plane with the first end face 3 a of the piston 3. The working space 14 facing surface of the second permanent magnet 12 is in a plane with the flat inner surface of the valve plate. 5

The valve plate 5 has a suction opening 17, which is closable on the inside of the valve plate 5 with a suction valve 15. It also has a pressure opening 18 which can be closed on the outside of the valve plate 5 with a pressure valve 16.

In the intake stroke shown here (the piston 3 moves to the right), the refrigerant flows via the suction opening 17 past the opened suction valve 15 into a working space 14 formed between the valve plate 5 and a first end face 3a of the piston 3 facing it. During the compression stroke (the piston 3 then moves to the left), refrigerant is again conveyed out of the interior of the cylinder housing 1 via the pressure opening 18. The piston shaft 22 is in Fig. 2 not shown.

The two permanent magnets 11, 12 have identical dimensions and are made of the same ferromagnetic material, so that they have the same magnetic field strength. They are designed as annular cylinder, the inner and outer surfaces thus have the shape of a cylinder jacket, the support surface on the piston 3 has the shape of a circular ring, as well as the working space 14 facing surface of the permanent magnets 11, 12th

Both permanent magnets 11, 12 are recessed into annular recesses of the piston 3 and the valve plate 5, so that the working space 14 facing surface of the permanent magnets 11, 12 with the first end face 3a of the piston or with the inside of the valve plate 5 just finished. The permanent magnets 11, 12 are in each case at the bottom of the annular recess, between the cylinder surface designed as a cylindrical outer surface of the permanent magnets 11, 12 and the wall of the recess, however, a free space 13 is provided, so that the magnetic field lines - of the metallic material of the piston. 3 or the valve plate 5 undisturbed - can escape through the cylinder jacket-shaped outer surface of the permanent magnets 11, 12. The free space 13 may also, as shown in the piston 3, be filled with non-ferromagnetic material, such as plastic. As a result, the dead space is reduced, so that space between the piston at the dead center and valve plate, which may be filled with refrigerant.

With the execution according to Fig. 2 is the piston stroke at top dead center by the permanent magnets 11, 12 limited. To limit the piston travel at bottom dead center, either on the second end face 3b of the piston 3, a further first permanent magnet, such as permanent magnet 11b in Fig. 1 , are arranged with a corresponding permanent magnet 12b on the cylinder housing.

Or it can, as in Fig. 3 shown, a spring element 27 may be provided, which determines the bottom dead center of the piston 3. The design of the piston-cylinder unit is similar to that of Fig. 2 , Additionally is in Fig. 3 still the excitation winding 8 located.

In the embodiment according to the Fig. 4-6 the first permanent magnets 11a, 11b are not arranged on the piston 3, but on the cylindrical oscillating body 7 of the linear drive 6. The corresponding second permanent magnets 12a, 12b are arranged on the inside of the housing 24 of the linear drive 6, so that they are aligned in the direction of the piston longitudinal axis 9 with the permanent magnets 11a, 11b.

The permanent magnets 11a, 11b, 12a, 12b are formed here as a ring cylinder, but not recessed in the oscillating body 7 or housing 24, but attached to the circular surfaces of the oscillating body 7 and on opposite inner walls of the housing 24. The ring cylinders are arranged concentrically to the piston longitudinal axis 9.

When the piston 3 is at top dead center, see Fig. 4 , then have the permanent magnets 11a and 12a - seen in the direction of the piston longitudinal axis 9 - the least possible due to the forces acting on the oscillating body 7 force of the linear drive 6 distance from each other. However, the permanent magnets 11b and 12b have the greatest possible distance from one another, which essentially corresponds to the piston stroke of the piston 3.

If the piston 3 is at bottom dead center, see Fig. 5 , then have the permanent magnets 11 b and 12 b - seen in the direction of the piston longitudinal axis 9 - the lowest due to the force acting on the oscillating body 7 force of the linear drive 6 distance from each other. However, the permanent magnets 11a and 12a have the greatest possible distance from one another, which corresponds essentially to the piston stroke of the piston 3.

In Fig. 6 is detail B off Fig. 4 shown enlarged. Of the one permanent magnet arrangement (a), the permanent magnets 11a and 12a can be seen, of the second permanent magnet arrangement (b) only permanent magnet 11b. The radial outer diameter of the permanent magnets 11 a and 11 b corresponds almost to the radial diameter of the cylindrical oscillating body 7, the diameter of the permanent magnets 11 a, 11 b, 12 a, 12 b is only about 1-5% smaller than that of the oscillating body 7.

Fig. 7 shows a modification of the embodiment according to Fig. 4 in that the permanent magnet arrangement for determining the bottom dead center by Fig. 4 is replaced by a spring element 27. The permanent magnets 11a and 12a made Fig. 4 are retained, the permanent magnets 11 b and 12 b are replaced by the spring element 27.

Fig. 8 shows a schematic representation of the in the region of the permanent magnets 11, 12 of the Fig. 2 and 3 developed magnetic fields in the form of field lines 25 and 26, wherein the piston 3 is in the region of its bottom dead center. Magnetic field lines are closed, they emerge at the so-called "North Pole" from the permanent magnet and at the so-called "South Pole" in this one. When a permanent magnet with its south pole approaches the north pole of another permanent magnet, the permanent magnets attract and adhere to each other. If a permanent magnet is approximated with its north pole to the north pole of another permanent magnet (or with its south pole to the south pole of another permanent magnet), the two permanent magnets repel, it is not possible or only with a certain force, the permanent magnets so far to approach each other so that their south poles touch each other. This principle is exploited in this invention. Since the repulsive force between the magnetic poles of the same name is inversely proportional to the distance of the magnetic poles, and the force for approaching the piston 3 to the valve plate 5 is not linear to the distance between the piston 3 and Valve plate 5. This is an essential difference to a arranged between the valve plate 5 and piston 3 spring element, in which the force depends linearly on the distance between the valve plate 5 and piston 3.

Both valve plate 5 and piston 3 are made in this embodiment of steel, so are themselves ferromagnetic, the magnetic field lines 25, 26 can therefore penetrate into the valve plate 5 and the piston 3. The distance between the piston 3 and piston bore 2 is shown exaggerated here.

Fig. 9 shows the piston-cylinder assembly 21 with progressive compression stroke, the piston is on the way to top dead center. The first permanent magnet 11, which is arranged on the first end face 3a of the piston 3, approaches the stationary, second permanent magnet 12 which is sunk in the valve plate 5. The magnetic fields of the two permanent magnets 11, 12 affect each other significantly more than in Fig. 8 , In the working area 14, the distance between the own field lines 25, 26 of the permanent magnet decreases, the magnetic field strength is larger, the field lines are "stretched" like a spring.

According to Fig. 10 the piston 3 has reached its top dead center. An abutment of the first end face 3 a of the piston 3 to the valve plate 5 is prevented, since the two permanent magnets 11 and 12, each with the same Magnetpolrichtung (with the "north pole") face each other and therefore repel each other. If you were to turn off the excitation field of the excitation winding 8 now, the piston 3 would be moved by the repulsive force of the permanent magnets 11, 12 to the right.

In the same basic way as the piston travel according to Fig. 8-10 is limited in the range of top dead center, can also a limitation of the piston travel in the area of bottom dead center.

Fig. 11 shows a force-displacement diagram for illustrating the increase of the magnetic force when approaching the first 11 to the second permanent magnet 12. On the horizontal axis, the distance between the first 11 and second permanent magnet 12 in cm, plotted on the vertical axis, the magnetic force F in %, where 100% represents the repulsive magnetic force at top dead center. This force must apply the linear drive 6 and the inertia of the piston 3 with the vibrating body 7 to keep the piston 3 for a short time at top dead center. The top dead center is given in this example at a distance of 0.05-0.5 mm between the first 11 and second permanent magnet 12. Both the diamond-shaped measuring points and the measuring curve interpolated on the basis of the measuring points are shown.

Fig. 12 shows a piston-cylinder unit according to the invention with a double piston. The piston 3 is embodied as a double piston and comprises two piston sections 19, 20 arranged at opposite end regions, each forming an end face 3a, 3b of the double piston. Between the first end 3a of the double piston and a first cylinder head 4 comprising a first valve plate 5, a first working space is created 14 formed and between the second end face 3b of the double piston and a second valve plate 5 'comprehensive second cylinder head 4', a second working space 14 '. The oscillating body 7 is arranged between the two end faces 3a, 3b of the double piston, preferably enclosed by the double piston 3. For each cylinder head piston section pairing 4/19 or 4 '/ 20, a permanent magnet arrangement 11a, 12a or 11b, 12b according to the invention is provided.

LIST OF REFERENCE NUMBERS

1

cylinder housing

2

piston bore

3

piston

3a

first end of the piston

3b

second end face of the piston

4

cylinder head

4 '

second cylinder head

5

valve plate

5 '

second valve plate

6

linear actuator

7

oscillating body

8th

Excitation winding (stator)

9

piston longitudinal axis

11,11a, 11b

First permanent magnet

12,12a, 12b

Second permanent magnet

13

Blank

14

Working space of the piston 3

14 '

second working space of the piston 3

15

suction

15 '

second suction valve

16

pressure valve

16 '

second pressure valve

17

suction opening

17 '

second suction opening

18

pressure opening

18 '

second pressure opening

19

First piston section of the double piston

20

Second piston section of the double piston

21

Piston-cylinder unit

22

piston shaft

23

linear compressor

24

Housing of the linear drive

25

Field lines of the first permanent magnet

26

Field lines of the second permanent magnet

27

spring element

Claims (14)

1. A refrigerant compressor having a hermetically sealed compressor housing, in whose interior a piston-cylinder unit (21), which compresses a refrigerant, is arranged, whose cylinder housing (1) is frontally closed by means of a cylinder head (4), in which a suction opening (17) and a pressure opening (18) are provided, via which refrigerant is suctioned in via a suction valve (15) through the suction opening and compressed via a pressure valve (16) through the pressure opening, the piston-cylinder unit (21) having at least one piston (3) guided in a piston bore (2) of the cylinder housing (1), a working space (14) for compressing a refrigerant being formed between the cylinder head (4) and a first front side (3a) of the piston (3), a linear drive (6) being provided, comprising at least one oscillating body (7) enclosed by an exciter winding (8), which is connected to the piston (3), in order to move it along a piston longitudinal axis (9) in oscillating manner, the piston-cylinder unit (21) being equipped with at least one permanent magnet arrangement, comprising respectively at least one first permanent magnet (11) arranged on the piston (3) or on a component connected to the piston (3), characterized in that the at least one permanent magnet arrangement comprises at least one second permanent magnet (12) arranged on the cylinder housing (1) or on a component connected to the cylinder housing (1), the first permanent magnet (11) and the second permanent magnet (12) pointing toward one another with the same magnetic pole direction in each case, to generate a repelling effect between the two permanent magnets (11, 12) to delimit the piston travel in the region of the top dead center and/or in the region of the bottom dead center upon approach of the first permanent magnet (11) to the second permanent magnet (12), the component connected to the cylinder housing (1), on or in which the at least one second permanent magnet (12) is arranged, is the cylinder head (4), a valve plate (5) is arranged in the cylinder head (4) and the at least one second permanent magnet (12) is arranged on the valve plate (5), preferably at least sectionally countersunk in the valve plate (5), in order to delimit the piston travel in the region of the top dead center, the permanent magnets (11, 12) are countersunk into the front side (3a, 3b) of the piston (3) and/or the valve plate (5) so that at least one free space (13) is provided between permanent magnet and piston or valve plate, which communicates with the working space (14), and this free space (13) extends along the entire periphery of the permanent magnets (11, 12).
2. The refrigerant compressor according to Claim 1, characterized in that the component connected to the piston (3), on which the at least one first permanent magnet (11) is arranged, is the oscillating body (7) or a piston shaft (22) connecting the piston (3) to the oscillating body (7).
3. The refrigerant compressor according to one of Claims 1 to 2, characterized in that the at least one second permanent magnet (12) is arranged inside the piston bore (2) of the cylinder housing (1).
4. The refrigerant compressor according to one of Claims 1 to 3, characterized in that the at least one second permanent magnet (12) is arranged inside the working space (14) or to delimit the working space (14).
5. The refrigerant compressor according to one of Claims 1 to 4, characterized in that the at least one first permanent magnet (11) is arranged in the region of the first front side (3a) of the piston (3) facing toward the cylinder head (4).
6. The refrigerant compressor according to Claim 5, characterized in that the at least one first permanent magnet (11) is sectionally or entirely countersunk in the front side (3a) and/or in the piston shaft (22).
7. The refrigerant compressor according to one of Claims 1 or 6, characterized in that the free space (13) is implemented as a gap, whose clear opening width widens in the direction of the working space (14).
8. The refrigerant compressor according to one of Claims 6 or 7, characterized in that the free space (13) is filled using a non-ferromagnetic material.
9. The refrigerant compressor according to one of Claims 1 to 8, characterized in that the at least one first permanent magnet (11) is arranged opposite to the at least one second permanent magnet (12).
10. The refrigerant compressor according to one of Claims 1 to 9, characterized in that the permanent magnets (11, 12) are implemented as essentially ring-shaped, the ring shape preferably extending rotationally-symmetric to the piston longitudinal axis (9) and/or the free space preferably being implemented as a ring gap.
11. The refrigerant compressor according to one of Claims 1 to 10, characterized in that one front side (11a) of the at least one first permanent magnet (11) extends substantially parallel to one front side (12a) of the at least one second permanent magnet (12).
12. The refrigerant compressor according to one of Claims 6 to 11, characterized in that the at least one first permanent magnet (11) has an essentially equal field strength, preferably an essentially equal mass, as the at least one second permanent magnet (12).
13. The refrigerant compressor according to one of Claims 6 to 12, characterized in that multiple permanent magnets (11, 12) are arranged on a circle extending concentrically to the piston longitudinal axis (9), the angle spacing of adjacent permanent magnets (11, 12) being essentially equal.
14. The refrigerant compressor according to one of Claims 1 to 13, characterized in that the piston (3) is implemented as a double piston, comprising two piston sections (19, 20), arranged on opposing end regions of the double piston (3) and each forming one front side (3a, 3b) of the double piston, a first working space (14) being formed between the first front side (3a) of the double piston (3) and a first cylinder head (4) comprising a first valve plate (5) and a second working space (14') being formed between the second front side (3b) of the double piston (3) and a second cylinder head (4') comprising a second valve plate (5'), and the oscillating body (7) being arranged between the two front sides (3a, 3b) of the double piston (3), preferably enclosed by the double piston (3), and one permanent magnet arrangement according to one of the preceding claims being provided for each cylinder head-piston section pair (4/19, 4'/20).

Images