DE102013213380A1 - Linear compressor for a household appliance and household refrigeration appliance - Google Patents

Abstract

The invention relates to a linear compressor (16) for a domestic appliance (10), having a piston (24) which can be moved between an upper and lower dead center position in the longitudinal direction (20) of a cylinder (22), the piston outer surface (26) of which forms a radial gas pressure bearing Direction (28) of the cylinder (22) contactless with respect to a corresponding cylinder inner surface (30) is storable, wherein the piston outer surface (26) and the cylinder inner surface (30) at least in a respective predetermined region (40, 42) have a martensitic microstructure. Furthermore, the invention relates to a household refrigeration appliance (10) with a refrigeration circuit (14) and a compressor (16).

Description

The invention relates to a linear compressor and a household refrigerator specified in the preamble of the independent claims Art.

The WO 2008/055810 A1 and the WO 2006/089582 A1 each show a linear compressor for a household appliance, with a movable in the longitudinal direction of a cylinder between an upper and lower pressure point position piston, the piston outer surface to form a gas pressure bearing in the radial direction of the cylinder is contactless with respect to a corresponding cylinder inner surface storable. The linear compressor shown there are used in respective refrigeration cycles of household appliances.

Due to the refrigeration cycle, gas is sucked from a low-pressure side of the refrigeration circuit by the linear compressor and pumped into a high-pressure side of the refrigeration circuit. The gas pressure bearing used in the linear compressor is normally supplied from the high pressure side of the refrigeration cycle to prevent contact between the piston and the cylinder. When the linear compressor is switched on after a standstill phase, the pressure on the high pressure side and on the low pressure side is usually balanced. The gas pressure bearing can therefore not be designed accordingly and the piston outer surface has contact with the corresponding cylinder inner surface in the first seconds after the start of the linear compressor.

As a result, over the life of the linear compressor considerable wear can occur on the piston outer surface and on the corresponding cylinder inner surface. The resulting wear particles can clog corresponding gas pressure bearing nozzles, which support the piston with sufficient pressure on the high pressure side without contact with respect to the cylinder. As a result, the function of the gas pressure bearing can be lost and it can come in the worst case to a piston seizure.

The WO 2006/069881 A1 also shows a linear compressor for a household appliance, with a movable in the longitudinal direction of a cylinder between an upper and lower dead center piston, the piston outer surface is to form a gas pressure bearing in the radial direction of the cylinder without contact against a corresponding cylinder inner surface storable. According to the teaching of WO 2006/069881 A1 It is thereby provided to provide the mutually facing side surfaces of the piston and the cylinder with an abrasion-resistant sliding layer. However, this is associated with considerable additional effort and corresponding costs in the production of the linear compressor.

It is the object of the present invention to provide a linear compressor and a household refrigerator of the type mentioned, by means of which improved in an improved way the life of a linear compressor and its functioning can be ensured.

This object is achieved by a linear compressor and by a household refrigerator with the features of the independent claims. Advantageous embodiments with expedient and non-trivial developments of the invention are specified in the dependent claims.

The linear compressor according to the invention for a domestic appliance comprises a piston which can be moved between an upper and lower dead center position in the longitudinal direction of a cylinder, the piston outer surface of which can be mounted in contact with a corresponding cylinder inner surface in a contactless manner with the formation of a gas pressure bearing in the radial direction of the cylinder. For improved maintenance of the operability of the linear compressor and to increase the life of the linear compressor, it is inventively provided that the piston outer surface and the cylinder inner surface have a martensitic microstructure at least in a respective predetermined area. In other words, the piston outer surface and the cylinder inner surface are formed of a martensitic steel at least in the respective predetermined region.

As a result, corresponding cover layers of the piston outer surface and the cylinder inner surface in the at least one respective predetermined region no porous zone, instead, a particularly hard-wearing and tough layer is provided on the surface of each predetermined areas. By the solution according to the invention a sufficient wear resistance is achieved on the surfaces of the respective predetermined areas, so that the reliable design of the gas pressure bearing over the life of the linear compressor can be ensured. Furthermore, abrasion on the piston outer surface and the cylinder inner surface is largely avoided by the inventive solution, so that substantially no more wear particles. A possible blockage of corresponding gas pressure bearing nozzles, which serve to form the gas pressure bearing, is thereby reliably avoided.

Furthermore, it is also possible to use the linear compressor according to the invention in other applications than in household appliances, in particular wherever as well self-powered gas pressure bearing or dynamic bearings, such as turbines, are used. For example, the linear compressor according to the invention can be used in corresponding devices of the aerospace industry and in plants for power generation.

In an advantageous embodiment of the invention, it is provided that the piston outer surface and the cylinder inner surface each include a single of the predetermined areas where a contact of the piston outer surface with the cylinder inner surface is possible if no gas pressure bearing is formed or the gas pressure bearing has fallen below a predetermined pressure threshold. Thus, the respective predetermined areas are formed with the martensitic microstructure only where there is a risk that at an insufficient pressure supply of the linear compressor, a contact of the piston outer surface with the cylinder inner surface is even possible. A complex complete machining of the piston outer surface and the cylinder inner surface can be saved, which has a positive effect on the manufacturing costs of the respective components.

In a further advantageous embodiment of the invention, it is provided that the cylinder comprises a bush, which has the cylinder inner surface. Thus, the corresponding predetermined range with the martensitic microstructure on the cylinder must also be formed only on the socket, whereby the production of the cylinder can be considerably facilitated because a corresponding surface treatment must be made only on the socket and not on the entire cylinder.

In a further advantageous embodiment of the invention, it is provided that the respective predetermined areas are formed of a steel with the alloy X15T.N. As a result, a particularly abrasion-resistant and low-wear surface is provided at the respective predetermined areas.

In a further advantageous embodiment of the invention, it is provided that the microstructures of the respective predetermined regions comprise homogeneously distributed, spherical carbides. As a result, a particularly high wear resistance of the respective predetermined ranges is achieved. The term "spherical" is to be understood as meaning that the carbides have a substantially spherical shape, that is to say they have a maximum deviation from a theoretically optimum spherical shape in the range of approximately 10 to 15% within the usual manufacturing tolerances.

A further advantageous embodiment of the invention provides that the carbides have a diameter of 1 to 2 microns. As a result, a particularly fine microstructure in the form of very finely divided round carbides is made possible, whereby the wear resistance of the predetermined areas is further improved.

According to a further advantageous embodiment of the invention, it is provided that the respective predetermined areas are tempered, surface hardened and / or press-hardened. By a corresponding adjustment of respective process parameters and monitoring of these set process parameters, a corresponding cover layer can be formed in the respective predetermined areas, which essentially has no porous surface, whereby the desired wear-resistant and tough layer can be formed on the respective surfaces. Furthermore, the corresponding microstructure can be formed in a particularly simple manner by tempering, surface hardening and / or press hardening.

The domestic refrigerator according to the invention with a refrigeration cycle and a compressor is characterized in that the compressor is designed as the linear compressor according to the invention or as an advantageous embodiment of the linear compressor according to the invention.

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawings. The features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the description of the figures and / or in the figures alone can be used not only in the respectively specified combination but also in other combinations or in isolation, without the scope of To leave invention.

Embodiments of the invention are explained in more detail below with reference to schematic drawings. Show it:

1 a schematic longitudinal sectional view of an embodiment of a household refrigerator with a linear compressor; and

2 a side sectional view of the linear compressor, which comprises a piston movable in the longitudinal direction of a cylinder between an upper and lower dead center position.

In the figures, identical or functionally identical elements are provided with the same reference numerals.

A household refrigerator 10 is in 1 shown in a schematic longitudinal sectional view, which is a cooling device, a freezer or a cooling Freezer combination device can be. The household refrigerator 10 includes an interior 12 , which is designed to receive food. This interior 12 may be a refrigerated compartment, a freezer or a no-frost compartment, or at least two of these compartments.

The household refrigerator 10 includes a refrigeration cycle 14 , which is a linear compressor 16 includes. The linear compressor 16 is preferably in a machine room 18 Standing in the lower and rear of the household refrigerator 10 is located.

The linear compressor 16 So is in the refrigeration cycle 14 used, wherein of the linear compressor 16 Gas is sucked from an unspecified low-pressure side and pumped into an unspecified high-pressure side.

Based on 2 , in which the linear compressor 16 is shown in a side sectional view, this will be explained in more detail below. The linear compressor 16 includes a longitudinal direction 20 a cylinder 22 between a top and bottom dead center movable piston 24 whose piston outer surface 26 under formation of an unspecified gas pressure bearing in the radial direction 28 of the cylinder 22 contactless with respect to a corresponding cylinder inner surface 30 is storable.

In the case shown here, the cylinder comprises 22 a socket 32 through which the cylinder inner surface 30 is trained. Over a variety of yourself through the socket 32 extending holes 34 can compressed gas from a cavity 36 in a working chamber 38 arrive and there the gas pressure bearing in the form of a gas cushion between the piston outer surface 26 and the cylinder inner surface 30 train to these in the radial direction 28 store without contact.

The piston outer surface 26 and the cylinder inner surface 30 are in a given range 40 . 42 formed by a martensitic microstructure. The predetermined ranges 40 . 42 are formed there, where a touch of the piston outer surface 26 with the cylinder inner surface 30 is possible if no gas pressure bearing is formed or the gas pressure bearing has fallen below a predetermined pressure threshold. This is especially the case when the linear compressor 16 is switched on after a standstill phase, in which case the pressure on the high pressure side and on the low pressure side is normally balanced. In such a case, the gas pressure layer is not yet or not yet completely formed, that is to say with a correspondingly required pressure, so that the piston outer surface 26 and the cylinder inner surface 30 in the first few seconds after the start of the linear compressor 16 can get in touch with each other.

In the case shown here is the predetermined range 40 at those areas of the piston outer surface 26 formed, which parallel to the cylinder inner surface 30 are arranged. Furthermore, the default range 42 in the present case on the entire cylinder inner surface 30 the socket 32 educated. In alternative embodiments, the predetermined ranges 40 . 42 also only partially on the piston outer surface 26 and on the cylinder inner surface 30 be educated. For example, the shape of the piston outer surface 26 and / or the cylinder inner surface 30 be such that they can touch only in certain sections. In such cases, the given ranges 40 . 42 even only at these points of the cylinder inner surface 30 and on the piston outer surface 26 educated.

Through the respective predetermined areas 40 . 42 with its martensitic microstructure becomes undesirable wear on the piston outer surface 26 and on the cylinder inner surface 30 avoided.

The respective predetermined ranges 40 . 42 are made of a steel with the alloy X15T.N. The microstructure of the given areas 42 . 40 comprise homogeneously distributed, spherical carbides. The carbides have a diameter of 1 to 2 microns. The predetermined ranges 40 . 42 may be tempered, surface hardened and / or press-hardened to form the correspondingly described martensitic microstructure with the spherical carbides.

By providing the predetermined ranges 40 . 42 is over the life of the linear compressor 16 a wear on the piston outer surface 26 and on the cylinder inner surface 30 prevented or significantly reduced. As a result, it can be prevented that corresponding wear particles arise, which serve as the gas pressure bearing nozzles bores 34 could clog, so that a sufficient pressure supply to form the gas pressure bearing can be ensured throughout. In particular, the danger of a so-called piston eater can thereby be considerably reduced or even completely avoided.

LIST OF REFERENCE NUMBERS

10

 Household refrigerator

12

 inner space

14

 Refrigeration circuit

16

 linear compressor

18

 engine room

20

 longitudinal direction

22

 cylinder

24

 piston

26

 Outer piston surface

28

 Radial direction

30

 Cylinder inner surface

32

 Rifle

34

 drilling

36

 cavity

38

 working chamber

40

 Specified area

42

 Specified area

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2008/055810 A1 [0002]
• WO 2006/089582 A1 [0002]
• WO 2006/069881 A1 [0005, 0005]

Claims (8)

Linear compressor ( 16 ) for a household appliance ( 10 ), with a longitudinal ( 20 ) of a cylinder ( 22 ) between a top and bottom dead center movable piston ( 24 ) whose piston outer surface ( 26 ) under formation of a gas pressure bearing in the radial direction ( 28 ) of the cylinder ( 22 ) contactless with respect to a corresponding cylinder inner surface ( 30 ) is storable, characterized in that the piston outer surface ( 26 ) and the cylinder inner surface ( 30 ) at least in a respective predetermined area ( 40 . 42 ) have a martensitic microstructure. Linear compressor ( 16 ) according to claim 1, characterized in that the piston outer surface ( 26 ) and the cylinder inner surface ( 30 ) there each a single of the predetermined areas ( 40 . 42 ), where a contact of the piston outer surface ( 26 ) with the cylinder inner surface ( 30 ) is possible if no gas pressure bearing is formed or the gas pressure bearing has fallen below a predetermined pressure threshold. Linear compressor ( 16 ) according to claim 1 or 2, characterized in that the cylinder ( 22 ) a socket ( 32 ), which the cylinder inner surface ( 30 ) having. Linear compressor ( 16 ) according to one of the preceding claims, characterized in that the respective predetermined regions ( 40 . 42 ) are formed of a steel with the alloy X15T.N. Linear compressor ( 16 ) according to one of the preceding claims, characterized in that the microstructures of the respective predetermined regions ( 40 . 42 ) comprise homogeneously distributed spherical carbides. Linear compressor ( 16 ) according to claim 5, characterized in that the carbides have a diameter of 1 to 2 microns. Linear compressor ( 16 ) according to one of the preceding claims, characterized in that the respective predetermined regions ( 40 . 42 ) are tempered, surface hardened and / or press-hardened. Household refrigeration appliance ( 10 ) with a refrigeration cycle ( 14 ) and a compressor ( 16 ), characterized in that the compressor ( 16 ) is designed as a linear compressor according to one of the preceding claims.

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