US 20080019852 A1
A linear compressor comprising a pump chamber wherein a moves reciprocatingly, a frame which is integral with the pump chamber and against which a floating body is reciprocatingly maintained by at least one spring, at least one electromagnet mounted on the frame for causing the reciprocating movement of the floating body. A translation rod is connected to the piston through a first articulation and to the floating body through a second articulation.
8. A linear compressor comprising:
a pumping chamber in which a piston moves reciprocatingly;
a frame fixedly connected to the pumping chamber;
an oscillating body being retained on the frame by means of at least one spring so that the oscillating body moves reciprocatingly;
at least one electromagnet mounted on the frame for driving the reciprocating movement of the oscillating body; and
a translation rod connected to the piston with a first joint and connected to the oscillating body by a second joint.
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This invention relates to a linear compressor, particularly a linear compressor which is suitable for compressing refrigerant in a refrigerating device.
U.S. Pat. No. 6,641,377 B2 discloses a linear compressor with a pumping chamber in which a piston moves reciprocatingly, a frame fixedly connected to the pumping chamber, on which an oscillating body can be moved reciprocatingly by means of at least one spring, an electromagnet mounted on the frame for driving the reciprocating movement of the oscillating body, and a piston rod which connects the oscillating body to the piston.
The spring is a diaphragm spring whose edge is fastened to the frame annularly surrounding the pumping chamber, and to whose centre the beaker-shaped oscillating body and one end of the piston rod are screwed. The other end of the piston rod is spherical and engages in a cup formed on the piston so that the piston rod and the piston are able to move pivotably relative to each other. The pivotable movement prevents the transmission of torques from the oscillating body via the piston rod to the piston, which could cause the piston to move in a tilting, difficult fashion in the pumping chamber. To provide sufficient protection against tilting the piston must of a considerable length. A great deal of space is therefore required in the pumping chamber for the piston so that the ratio of the pumping chamber volume to the throughput is rather unfavourable.
However, the piston rod may also transmit to the piston forces that are orientated transversely to the direction of movement of the piston in the pumping chamber, which forces press the piston against a lateral wall of the pumping chamber. A grinding contact between the piston and the lateral wall would result in considerable frictional wear, so that in the said publication it is proposed to provide an air bearing to prevent such contact between the lateral wall and the piston by causing compressed gas to be branched off from the high pressure side of the linear compressor and to be guided through openings in the lateral wall into the pumping chamber. The gas film formed here along the lateral wall prevents direct contact between the pumping chamber wall and the piston provided that the gas throughput is sufficiently high.
The greater are the transverse forces that the piston rod is able to exert on the piston the more gas must be returned to prevent contact between the piston and the wall. This reduces the efficiency of the compressor.
The object of the invention is to provide a linear compressor in which the transmission of transverse forces from the oscillating body to the piston is minimised.
The object is achieved in that the connection of a translation rod articulated to the piston to the oscillating body is formed by a second joint. The translation rod is therefore only able to transmit essentially tensile and shearing forces to the piston, but no appreciable lateral forces.
The two joints may be formed particularly easily and inexpensively by an elastically flexible rod.
This rod is preferably designed integrally with the translation rod and thinner than the latter in order to achieve the required degree of flexibility.
The first joint preferably connects the translation rod to a piston rod anchored rigidly on the piston and guided in the pumping chamber.
Further features and advantages of the invention are apparent from the following description of an exemplary embodiment with reference to the attached figures, where:
The linear compressor shown in
Two electromagnets with an E-shaped yoke and a coil wound round the central leg of the E are each arranged between oscillating body 8 and wall sections 1 with pole shoes facing the oscillating body, and serve to drive an oscillating movement of oscillating body 8.
Since piston rod 13, rigidly connected to piston 15, is guided in the end face bore of pumping chamber 14, piston 15 is protected against tilting, even when its extension in the direction of the reciprocating movement is small. Piston 15 therefore occupies little space in pumping chamber 14, so that a large effective volume is obtained with small external dimensions.
Pumping chamber 14 is surrounded annularly by a cavity 16, which communicates with pumping chamber 14 by a multiplicity of openings 17 in its lateral wall, and which is fed through a passage 18 with compressed gas branched from a pressure connection 19 of the pumping chamber. The compressed gas penetrating pumping chamber 14 through openings 17 forms on the lateral wall a cushion on which piston 15 slides essentially free of friction.
In the ideal case translation rod 9, as shown in
In principle tapered sections 11, 12 could also be replaced by ball and socket or cardan joints. However, the construction with tapered sections can be produced suitably and economically, particularly for miniaturisation.