Compressor, compression method and household appliance

Abstract

Disclosed is a compressor for a kitchen appliance such as a refrigerator, wherein two cylinder-piston arrangements are positioned in axial alignment and operated opposite to each other, wherein a common cylinder chamber is axially limited by opposite pistons of the cylinder-piston arrangements, a method to operate the compressor and a kitchen appliance.

Description

[0001] The present invention concerns a compressor for a household appliance, for instance a refrigerator, a method to compress air and a household appliance.

[0002] Electric household appliance such as refrigerators always have a compressor in order to compress a coolant such as a colling gas. Known compressors have a housing in which an axial cylinder-piston arrangement is positioned. The piston is driven in axial direction between two end positions by a linear electric motor. In an outer end position (expansion, suction phase), a cylinder chamber is maximised and gas to be compressed can enter the cylinder chamber. In an inner end position (compression, exhaust phase), the cylinder chamber is minimised and the compressed gas is feed to a connected piping system. Due to the axial movement of the piston and movable parts of the electric motor, vibrations are generated. In order to reduce a vibration transfer in the housing, the cylinder-position arrangement and the electric motor are supported by suspension springs inside the housing. In order to reduce the occurence of vibrations in general, a lot of effort is dedicated to a smooth running of the cylinder-piston arrangement and the electric motor.

[0003] It is an object of the present invention to provide an alternative vibration reduced compressor, a method in order to compress a gas quietly, and a noise reduced household appliance.

[0004] The object is achieved by a compressor with the features of claim 1, by a method with the features of claim 8 and by an electric household appliance with the features of claim 9. Advantageous embodiments are disclosed in the dependent claims, in the description, and in the drawings.

[0005] An inventive compressor for a household appliance such as a refrigerator comprises a housing, a cylinder-piston arrangement with a piston, an inlet and an outlet. The piston can be moved between two end positions inside the cylinder. In an outer end position, a cylinder chamber is maximised in order to receive a gas to be compressed, and in an inner end position the cylinder chamber is minimised in order to compress the gas. The inlet is provided to supply the gas to be compressed into the cylinder chamber from an input pipe system; and the outlet is provided in order to the discharge the compressed gas out of the cylinder chamber into an output pipe system. Further on, the compressor comprises an electric motor as power unit in order to drive the piston. According to the invention, a second cylinder-piston arrangement and a second electric motor are provided. The second cylinder-piston arrangement is positioned in axial alignment with the first cylinder-piston arrangement and works in opposite direction. Thereby the cylinder chamber is provided between the opposite pistons and limited by them in axial direction.

[0006] An inventive method for compressing a gas for a household appliance such as a refrigerator, provides two cylinder-piston arrangements in axial alignment opposite to each other such that a cylinder chamber adapted to receive and compress the gas is created between their pistons. The pistons are working in opposite axial directions such when the pistons are moved away from each other the cylinder chamber is maximized, and when the pistons are moved towards each other, the cylinder chamber is minimized.

[0007] An inventive household appliance (kitchen appliance) such as a refrigerator is equipped with an inventive compressor.

[0008] Thanks to the opposed working second cylinder-piston arrangements, the compressor is naturally balanced, thus resulting in reduced vibrations. Suspensions spring in order to support the cylinder-piston arrangements and their electric motors become no longer necessary. The omission of the suspension springs results in an extra space inside the housing which can be used for an optimisation of the cylinder-piston arrangements and / or the electric motors, or the housing can be fit perfectly to the cylinder-piston arrangements and their electric motors.

[0009] The manufacturing of the cylinders can be simplified, if they are built as single pipe, wherein in a middle portion of a pipe wall the outlet is provided.

[0010] Discharging of the compressed air out of the minimised cylinder chamber can be optimised if the outlet comprises a plurality of radial openings inside the middle portion of the pipe wall and, further on, a ring chamber which surrounds the middle portion and is in fluid connection with the output pipe system.

[0011] A sensitive and direct response of the pistons can be achieved if magnetic rings of the electric motors are positioned on piston sections outside the single pipe (cylinders).

[0012] In order to enable an expansion of the common cylinder chamber, as well as in order to enable a compression of the common cylinder chamber, the pistons can be cuplike bodies which are placed with their bottoms opposite to each other. In addition, in each bottom a valve is provided in order to create a fluid connection between the inlets and the cylinder chamber if the pistons are extended, this enabling a sensitive extension of the pistons during the expansion phase as any vacuum inside the cylinder chamber is prevented.

[0013] If valve bodies of the valves are spring biased in their closing position, any valve body vibration is prevented. Thereby, the spring forces are adapted to enable an opening of the valves if the pistons are extended.

[0014] In order to reduce noise caused by the flowing gas. in the inlets and the outlet are such designed that turbulences are reduced. Alternatively or in addition, mufflers in the inlets and / or the outlet can be provided.

[0015] In what follows, an exemplary embodiment of the present invention is explained with respect to the accompanying drawings. As is to be understood, the various elements and components are depicted as examples only, may be facultative and / or combined in a manner different than that depicted. Reference signs for related elements are used comprehensively and not defined again for each figure. Shown is schematically in the sole Fig. 1: an axial view of a compressor according to the invention in a very a schematical manner.

[0016] Terms such as "axial" and "radial" refer to a longitudinal axis of the cylinder-piston arrangements. Here, the axial direction extends in horizontal direction. Terms such as "left" and "right" refer to the horizontal orientation of the cylinder-piston arrangements in the Figure.

[0017] As schematically shown in the Figure, a compressor 1 for a household appliance such as refrigerator a housing 2, a first cylinder-piston arrangement 4a, a second cylinder-piston arrangement 4b, a first electric motor 6a and a second electric motor 6b. The housing 2 has an interior space 8 adapted to receive the cylinder-piston arrangements 4a, 4b and the electric motors 6a, 6b. Both, the cylinder-piston arrangements 4a, 4b and the electric motors 6a, 6b are joint to the housing 2 inside the interior without any suspension spring.

[0018] The cylinder-piston arrangements 4a, 4b are identical systems, which are aligned in axial direction X opposite to each other. Each cylinder-piston arrangement 4a, 4b has a piston 10a, 10b. A common single 12 pipe representing their cylinders. As well, the electric motors 6a, 6b are identical systems which are operated contrary to each other causing the pistons 10a, 10b of the cylinder-piston arrangements 4a, 4b to be moved simultaneously in opposite axial direction.

[0019] Each piston 10a, 10b can be moved in axial direction X between an outer end position 14a, 14b and an inner end position 16a, 16b. In their outer end positions 14a, 14b, the pistons are extended and a cylinder chamber 18 between them is maximised, ready to receive gas to be compressed. In their inner positions 16a, 16b, the pistons 10a, 10b are retracted and the cylinder chamber 18 between them is minimised such that the gas is compressed and, further on, the compressed gas can be feed to an output pipe system 20 of the compressor 1.

[0020] In addition, each cylinder-piston arrangement 4a, 4b has an inlet 22a, 22b in order to supply the gas to be compressed to a rear room 24a, 24b of the pistons 4a, 4b and a common outlet 26 in order to discharge the compressed gas out of the cylinder chamber 18 into the pipe system 20. The inlets 22a, 22b are in fluid connection with an inlet pipe system 28. Each inlet 22a, 22b is formed by an axial opening in a spring room 30a, 30b, which will be described later in more detail. The outlet 26 is formed by a plurality of radial openings 31, which are distributed evenly over a middle portion 32 of the single pipe 12. The middle portion 32 radially limits the common cylinder chamber 18. In axial direction, the cylinder chamber is limited by the pistons 4a, 4b. The middle portion 32, in particular the radial openings 31 are surrounded by a ring chamber 34 which is in fluid connection with the outer pipe system 28.

[0021] In order to feed the gas from the rear rooms 24a, 24b into the cylinder chamber 18 during the expansion phase, in each piston 4a, 4b a valve is provided. Each valve has a valve body 36a, 36b which is biased by a spring 38a, 38b in its closing direction. A spring force is adapted to enable an opening of the valves if the pistons are extended. In its closed state, an axial hole 40a, 40b in respective bottoms 42a, 42b is closed and a fluid connection between their rear rooms 24a, 24b and the cylinder chamber 18 is closed. In an opened state, the axial hole 40a, 40b is opened and a fluid connection between their rear rooms 24a, 24b and the cylinder chamber 18 is established.

[0022] Here, the pistons 4a, 4b have a cuplike shape, wherein their bottoms 42a, 42b forming the axial limitations of the cylinder chamber 18 (side walls) and are provided with the valves. Each rear room 24a, 24b is formed by a circumferential wall 44a, 44b of the pistons 4a, 4b. Their circumferential walls 44a, 44b have such an axial extension that they extend outside over the ends of the single pipe, even if the pistons 4a, 4b are in their inner end positions 16a 16b.

[0023] Each piston 4a, 4b is axially biased in the direction of its inner end position 16a, 16b via a spring 33a, 33b in the spring room 30a, 30b. The spring rooms 30a, 30b are positioned in direction of an inlet flow 49 before the rear rooms 24a, 24b and opened to them, such that the gas entering the spring rooms 30a, 30b via their inlets 22a, 22b, passes the spring rooms 30a, 30b, enters the respective rear room 24a, 24b and then enters the cylinder chamber 18 if the valves are opened.

[0024] In order to drive the pistons 4a, 4b axially, the electric motors 6a, 6b are provided. They are linear electric motors basically having a magnetic ring 46a, 46b and a stator 48a, 48b with an excitation coil 50a, 50b each. The magnetic rings 46a, 46b are positioned on piston sections 52a, 52b of the circumferential portions 44a, 44b outside the single pipe 12 and radially spaced apart from the excitation coils 50a, 50b of the stators 48a, 48b via an annular air gap 54a, 54b.

[0025] In order to reduce any noise caused by the inlet flow 49 or an outlet flow 56, in each rear room 24a, 24b and in the outlet 26 a muffler 58a, 58b, 60 is provided.

[0026] In the following, a preferred method to operate the compressor 2 is described.

[0027] The cylinder-pistons arrangements 4a, 4b are operated simultaneously contrary to each other. This means, if the piston 10a of the first piston arrangement 4a moves to the left until its outer end position14a is reached, at the same time the piston 10b of the second piston arrangement 4b moves to the right until its outer end position 14b is reached. If the piston 10a of the first piston arrangement 4a moves to the right until its inner end position 16a is reached, at the same time the piston 10b of the second piston arrangement 4b moves to the left until its inner end position 16b is reached.

[0028] Both distances between the inner end position and the outer end position are the same. As well, the moving speed of the pistons 10a, 10b is the same. As well, their effective surface facing to each other and delimiting the cylinder chamber 18 axially have the same size.

[0029] When the pistons 10a, 10b are in their outer end positions 14a, 14b, they are extended and the cylinder chamber 18 between them is maximised. If the pistons 10a, 10b are in their inner end position 16a, 16b, they are retracted and the cylinder chamber 18 between them is minimised.

[0030] The movements from their inner end positions 16a, 16b to their outer end positions 14a, 14b is the expansion phase or suction phase. During the expansion phase, the valves are opened and the gas to be compressed enters the widening cylinder chamber 18. The movements from their outer end positions 14a, 14b to their inner end positions 16a, 16b is the compression phase or exhaust phase. During the compression phase, the valves are closed and the cylinder chamber 18 is getting smaller such that the gas is compressed and finally discharged via the outlet 26 into the outer pipe system. 20

[0031] Disclosed is a compressor for a kitchen appliance such as a refrigerator, wherein two cylinder-piston arrangements are positioned in axial alignment and operated opposite to each other, wherein a common cylinder chamber is axially limited by opposite pistons of the cylinder-piston arrangements, a method to operate the compressor and a kitchen appliance.Reference signs

[0032] 1compressor 2housing 4a, 4bcylinder-piston arrangement 6a, 6belectric motor 8interior space of the housing 10a, 10bpiston 12single pipe (their cylinders) 14a, 14bouter end position 16a, 16binner end position 18cylinder chamber 20output pipe system 22a, 22binlet 24a, 24brear room 26outlet 28input pipe system 30a, bspring room 31radial openings 32middle portion 33a, 33bspring 34ring chamber 36a, 36bvalve body 38a, 38bspring 40a, 40baxial hole 42a, 42bbottom 44a, 44bcircumferential wall 46a, 46bmagnetic ring 48a, 48bstator 49inlet flow 50a, 50bexcitation coil 52a, 52bpiston section 54a, 54bannular air gap 56outlet flow 58a, 58bmuffler 60muffler Xaxial axis

Claims

1. A compressor (1) for a household appliance such as a refrigerator, comprising: • a housing (2); • a cylinder-piston arrangement (4a) having ∘ a piston (10a) which is movable in a cylinder (12), wherein the piston (10a) can be moved between two end positions (14a, 16a) , in which a cylinder chamber (18) is maximised in order to receive a gas to be compressed and in which the cylinder chamber (18) is minimised in order to compress the gas; ∘ an inlet (22a) in order to supply the gas to be compressed into the cylinder chamber (18) from an input pipe system (28); and ∘ an outlet (26) in order to the discharge the compressed gas out of the cylinder chamber (18) into an output pipe system (20); and • an electric motor as power (6a), characterised that • a second cylinder-piston arrangement (4b) and a second electric motor (6b) are provided, wherein • the second cylinder-piston arrangement (4b) is positioned in axial alignment with the first cylinder-piston arrangement (4a) and works in opposite direction, wherein the cylinder chamber (18) is provided between the opposite pistons (10a, 10b) and limited by them in axial direction.

2. The compressor according to claim 1, wherein the cylinder of the first cylinder-piston arrangement (4a) and the cylinder of the second piston-cylinder arrangement (4b) are one single pipe (12), wherein in a middle portion (32) of a pipe wall the outlet (26) is provided.

3. The compressor according to claim 2, wherein the outlet (26) comprises a plurality of radial openings (31) in the middle portion (32) of the single pipe (12) , a ring chamber (34) surrounding the middle portion (32) and which is in fluid connection with the output pipe system (20).

4. The compressor according to any of claims 1, 2 or 3, wherein magnetic rings (46a, 46b) of the electric motors (6a, 6b) are positioned on piston sections (52a, 52b) outside the single pipe (12).

5. The compressor according to any of the preceding claims, wherein the pistons (10a, 10b) have a cuplike bodies which are placed with their bottoms (42a, 42b) opposite to each other, wherein in each bottom (42a, 42b) a valve is provided in order to create a fluid connection between the inlets (22a, 22b) and the cylinder chamber (18) if the pistons (10a, 10b) are extended.

6. The compressor according to claim 5, wherein valve bodies (36a, 36b) of the valves are spring biased in their closing position, wherein the spring force is adapted to enable an opening of the valves if the pistons (10a, 10b) are extended.

7. The compressor according to any of the preceding claims, wherein in the inlets (22a, 22b) and the outlet (26) mufflers (58a, 58b, 60) are provided.

8. A method for compressing a gas for a household appliance such as a refrigerator, wherein two cylinder-piston arrangements are provided in axial alignment opposite to each other such that a cylinder chamber adapted to receive and compress the gas is created between their pistons, wherein the pistons are moved in opposite axial directions simultaneously such that when the pistons are extended the cylinder chamber is maximized; and when the pistons are retracted the cylinder chamber is minimized.

9. A household appliance such as a refrigerator equipped with a compressor according to any of the claims 1 to 7.

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