Suction muffler for a hermetically enclosed refrigerant compressor

Applicant hereby claims foreign priority benefits under U.S.C. § 119 from German Patent Application No. 10 2008 014 328.6 filed on Mar. 14, 2008, the contents of which are incorporated by reference herein.

The invention concerns a suction muffler for a hermetically enclosed refrigerant compressor with a housing having, between an inlet and an outlet, a first muffling chamber in the flow direction and a second muffling chamber in the flow direction, an insert being arranged between the muffling chambers, the insert having a passage that connects the muffling chambers to each other.

Such a suction muffler is, for example, known from DE 199 23 734 C2. The housing has an upper part and a bottom part. The insert is fixed between the upper part and the bottom part. In the bottom part the inlet is arranged, which opens via an inlet channel into the first muffling chamber. With a space, the inlet channel extends into a tube channel, which forms the passage in the insert. The tube channel again extends into an outlet channel, a space being provided between the tube channel and the outlet channel, the space connecting the outlet to the second muffling chamber.

Such an embodiment is known from DE 101 28 225 C1. Also here a flow path is provided, which extends straightly from an inlet channel to an outlet channel and is connected to both muffling chambers.

Such suction mufflers for refrigerant compressors have proved to be efficient. They reduce noise that occurs because of pressure pulsations during suction of the refrigerant gas by the refrigerant compressor.

The suction muffler is usually arranged at the cylinder head of the refrigerant compressor. The refrigerant compressor is arranged in a hermetically enclosed case and is usually supported in relation to the case by means of springs. The case comprises an oil sump serving as reservoir, for lubrication of the moving parts of the compressor with oil. During compressor operation and for a certain time after standstill a part of the refrigerant is dissolved in the oil. Because of the high pressure in the case volume, this mixture remains after standstill of the system. The mixture will not be separated until the system is restarted. The vacuum arising in the case volume will separate the refrigerant from the oil, which shows in a short foaming of the refrigerant-oil mixture.

There is a tendency towards building smaller compressors. The smaller the compressor is, the more utilisation space is available in a refrigeration appliance, for example a refrigerator or a freezer. One method of reducing the dimensions is to reduce the height of the refrigerant compressor.

With the reduction of the height of the compressor, however, the suction muffler comes relatively close to the oil sump, meaning that there is a risk that to a higher degree oil from the oil sump will be drawn into the suction flow of refrigerant. However, a too heavy load of oil in the refrigerant gas should be avoided.

The invention is based on the task of ensuring a certain freedom for the positioning of the suction muffler in the compressor case.

With a suction muffler as mentioned in the introduction, this task is solved in that the insert has a tube that is led through the second muffling chamber, one end of the tube being led through the housing, the other end opening into the first muffling chamber.

With this embodiment, it is possible to shift the inlet from the bottom side of the housing and to arrange it in a different position. If, for example, the inlet can be positioned at the upper side of the housing or at least in the upper half of the housing, the suction muffler can be arranged substantially closer to the oil sump than it would be the case with an inlet in the lower half of the suction muffler. The inlet and the outlet can then be arranged in the same half of the suction muffler, for example both in the upper half, or even at the upper side of the housing. In this case, the housing can even be permitted to dip somewhat into the oil sump. The suction muffler is then made as a “schnorkel” suction muffler. By means of the tube, the refrigerant gas sucked in is led through the second muffling chamber. In this connection, the tube path for the refrigerant gas surrounded by the tube is sealed in relation to the second muffling chamber, so that no impermissible mixing between the gas sucked in and the gas in the second muffling chamber can take place. Also, sound waves from the second muffling chamber cannot right away trespass into the tube path, so that a sound propagation through the tube is avoided.

Preferably, the housing has an outwardly projecting first tube connection, the tube being led through said connection. As the suction muffler is a component of a refrigerant compressor, which is manufactured in large numbers, the accuracy of the parts, from which the suction muffler is manufactured, can only to a certain degree be increased. It is therefore assumed that a small clearance will remain, when the tube is led through the housing. This clearance causes that a small opening occurs between the tube and the housing, for example in the form of an annular gap. If a tube connection is used, the axial length of this annular gap will be increased, so that the annular gap can provide a substantial flow resistance, and thus also a resistance against the escape of sound waves from the second muffling chamber to the outside. As this opening, that is, the annular gap, opens outwards, that is, towards the inside of the compressor case, the efficiency of the suction muffler is practically not negatively influenced. Small openings or holes, opening towards the outside, change the acoustic properties of the suction muffler only to a small degree.

Preferably, the housing has an inwardly guided, second tube connection, through which the tube is led. Thus, the sealing “path” between the outside of the tube and the inside of the housing is extended. The resulting axial length of the annular gap provides a relatively good sealing, which prevents refrigerant gas from the second muffling chamber from escaping to the outside. Thus, also a sound propagation towards the outside is kept small.

Preferably, the second tube connection has a length, which corresponds to at least 75% of the smallest distance between the insert and the housing in the area of the second tube connection. Preferably, the second tube connection will even be so long that it practically reaches the insert. The larger the length of the second tube connection is, the better is the sealing achieved between the second tube connection and the tube.

Preferably, the insert has a jacket tube, which surrounds the second tube connection, at least on part of its length. Together, the jacket tube and the tube form an annular gap, into which the second tube connection of the housing projects. The inner diameter of the jacket tube is adapted to the outer diameter of the second tube connection. The inner diameter of the second tube connection is adapted to the outer diameter of the tube, small tolerances being acceptable. This embodiment provides some kind of labyrinth seal, which provides a relatively good protection against an escape of refrigerant gas from the second muffling chamber and thus a propagation of sound waves from the second muffling chamber to the outside. Further, after a certain operation time, a certain amount of oil will gather between the jacket tube and the second tube connection, which further improves the sealing between the jacket tube and the second tube connection.

It is preferred that the jacket tube has a length, which corresponds to at least 75% of the shortest distance between the insert and the housing in the area of the second tube connection. Thus, a relatively large part of the length of the second tube connection will be surrounded by the jacket tube. The larger the length, the better the sealing.

Preferably, the tube projects through the insert. This means that a certain length of the tube extends into the first muffling chamber. In a manner of speaking, this can be utilised to guide the suction refrigerant gas into the first muffling chamber. This guiding can be utilised to achieve improved muffling properties.

Preferably, the passage between the muffling chambers is formed by a tube channel, which is arranged in the insert and projects over the insert on both sides. A tube channel as such is known from DE 101 28 225 C1 mentioned in the introduction. With the tube channel it can be provided that the refrigerant gas is guided when passing from the first muffling chamber into the second muffling chamber.

It is particularly advantageous, if the tube channel and an outlet channel are arranged in series in the flow direction along the same axis. Between the tube channel and the outlet channel, a space exists, which ensures a connection to the second muffling chamber. Sound waves occurring because of pulsations can then propagate into the second muffling chamber without penetrating to the outside. However, the refrigerant gas from the first muffling chamber will be sucked into the refrigerant compressor with relatively little resistance.