Hermetric Refrigerant Compressor

Abstract

The invention relates to a hermetically enclosed refrigerant compressor having a hermetically tight compressor housing inside of which a piston/cylinder unit that compresses a refrigerant operates with a suction valve having a suction opening located in a valve plate of the unit. A suction sound damper having a filling volume is provided on the cylinder head of the piston/cylinder unit and refrigerant flows to the suction valve of the piston/cylinder unit via this suction sound damper. To this end, the suction sound damper has an entry cross-section via which refrigerant flows into the suction sound damper, and a compensation volume is provided, which is connected to the suction sound damper and to the interior of the compressor housing, and inside of which refrigerant oscillates. The compensation volume equals 0.5 to 3 times the displacement of the piston of the piston/cylinder unit.

Description

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a hermetically encapsulated refrigerant compressor, comprising a hermetically sealed compressor housing, in the interior of which a piston-cylinder unit works which compresses a refrigerant, on the cylinder head of which a muffler is arranged through which the refrigerant flows to the intake valve of the piston-cylinder unit, according to the preamble of claim 1.

STATE OF THE ART

Such refrigerant compressors have long been known and are predominantly used in refrigerators and cooling shelves. The annually produced number is accordingly very high.

Although the power consumption of an individual refrigerant compressor is only approximately between 50 and 150 watts, there is a very high power consumption when regarding all refrigerant compressors used worldwide, which consumption increases continuously as a result of the rapidly progressing development in poorer countries as well.

Any technical improvement made to a refrigerant compressor and increasing the efficiency thus offers an enormous potential for saving energy when extrapolating the refrigerant compressors used worldwide.

The refrigerant process as such has long been known. The refrigerant is heated in the compressor by taking up energy from the space to be cooled and finally overheats and is pumped by means of the refrigerant compressor to a higher pressure level where it emits heat via a condenser and is conveyed back to the evaporator via a throttle where there is a pressure reduction and a cooling of the refrigerant.

The largest and most important potential for a possible improvement of efficiency lies in the lowering of the temperature of the refrigerant at the beginning of its compression process. Every lowering of the intake temperature of the refrigerant into the cylinder of the piston-cylinder unit leads to a reduction of the required technical work for the compression process, as does the lowering of the temperature during the compression process and, in connection with the same, the push-out temperature.

In known hermetically encapsulated refrigerant compressors there is a strong heating of the refrigerant on its path from the compressor (cooling space) to the intake valve of the piston-cylinder unit as a result of the design.

The intake of the refrigerant occurs via a suction pipe coming directly from the compressor during an intake stroke of the piston-cylinder unit. In known hermetically encapsulated refrigerant compressors, the suction pipe usually opens into the hermetically encapsulated compressor housing, mostly close to the inlet cross section into the muffler, from where the refrigerant flows into the muffler and from the same directly into the intake valve of the piston-cylinder unit. The muffler is used primarily to keep the noise level of the refrigerant compressor as low as possible during the intake process. Known mufflers usually consist of several volumes which are in connection with each other and an intake cross section through which the refrigerant is sucked from the hermetically encapsulated compressor housing volume into the interior of the muffler and an opening which lies close to the intake valve of the piston-cylinder unit.

On the way between the entrance of the refrigerant into the compressor housing and the intake valve of the piston-cylinder unit there is (as already mentioned) an undesirable heating of the refrigerant. Measurements have shown that at a refrigerant temperature of 32° C. in the suction pipe (predetermined by standardized ASHRAE conditions) the refrigerant was heated already in the first muffler volume to a temperature of approx. 54° C. already shortly before entering the compressor housing. The cause for this undesirable heating of the refrigerant is the fact that the refrigerant freshly flowing from the suction pipe to the compressor housing is mixed with warmer refrigerant already situated in the compressor housing. The mixture is principally caused in such a way that the intake valve of the piston-cylinder unit is merely open over a crank angle range of approx. 180° per cycle and that refrigerant can be drawn into the cylinder of the refrigerant compressor merely within this time window. The intake valve is closed thereafter, during the compression cycle. The cold refrigerant has a virtually constant mass flow, even when the intake valve is closed, as a result of which it flows in from behind into the compressor housing and dwells there and cools the piston-cylinder unit in motion and its components, which again causes a heating of the refrigerant. As a result of the pressure oscillations during the compression phase, there are further flow processes from the compressor housing to the muffler and vice-versa, which thus causes an additional mixing.

In order to prevent this thorough mixture of warm refrigerant from the interior of the compressor housing with refrigerant freshly coming from the evaporator, the outlet of the suction pipe for the refrigerant is placed in known refrigerant compressors close to the inlet cross section of the muffler. This ensures that a relatively low amount of cold refrigerant can escape from the evaporator into the interior of the compressor housing. Subsequently, the suction pipe end was configured in such a way that an intermediate pipe could be inserted into the same. At the same time, the intermediate pipe was enclosed by a spiral spring which rests on the one hand on the entrance of the suction pipe into the housing and on the other hand on the intermediate pipe in order to achieve a linkage of the suction pipe to the muffler. All these known efforts to prevent a mixture of the cold refrigerant from the evaporator with the heated refrigerant in the interior of the compressor housing have merely caused a reduction in this mixing, but not a complete prevention.

It is known from WO 03/038280 to directly connect the inlet cross section of the muffler with the outlet of the suction pipe, so that refrigerant coming from the evaporator is guided directly into the muffler without reaching the interior of the compressor housing and without being heated there. As a result of the already mentioned fact that the cold refrigerant has a nearly constant mass flow even when the intake valve is closed and flows into the muffler (now via the direct connection), it is then necessary however to provide a compensating volume in the muffler in order to compensate a pressure rise in the muffler as a result of the refrigerant that is continuously flowing in and through which refrigerant contained in the muffler can flow out of the same again into the compressor housing. During the next intake stroke, the refrigerant situated in the muffler or flowing from the suction pipe into the muffler is drawn into the piston-cylinder unit via the intake valve on the one hand, and refrigerant situated in the interior of the compressor housing is drawn into the compensating volume for pressure compensation (as a result of leakage from the piston-cylinder unit and by the mentioned flow-out from the muffler) on the other hand.

The flow conditions occurring thereby, especially during the overflow into the compensating volume which would not occur without a direct connection of the suction pipe with the muffler, lead to the likelihood of increased flow losses.

SUMMARY 0F THE INVENTION

It is therefore the object of the present invention to avoid this disadvantage and to provide a refrigerant compressor of the kind mentioned above in which the refrigerant temperature is kept as low as possible at the beginning of the compression process and thus necessarily also during the intake into the cylinder of the piston-cylinder unit, with flow losses during the intake being avoided to the highest possible extent. It is a further object of the invention that the pressure fluctuations occurring in the interior of the compressor housing and in the muffler and the noise level during the overflow into compensating volume are kept as low as possible.

This is achieved in accordance with the invention by the characterizing features of claim 1.

By creating a compensating volume with a volume which amounts to 0.5 to 3 times the displacement of the piston of the piston-cylinder unit, it is guaranteed that the refrigerant coming from the suction pipe will not reach the compressor housing even when the intake valve is closed and will mix there with already heated refrigerant. It is guaranteed at the same time that during the intake process no refrigerant is drawn from the compressor housing via the compensating volume into the muffler or into the cylinder.

In addition, the noise development can be minimized which is caused with the creation of the compensating volume by the flow processes into the compensating volume and into the compressor housing, so that there will not be any disturbing noise for the operator, which is an especially important feature for household refrigerators. Furthermore, a slightly larger compensating volume can be produced more easily during manufacturing.

In accordance with the characterizing features of claim 2 it is provided that the smallest cross section in the compensating volume has a cross-sectional surface area which corresponds to ¼ to ¾ of the cross-sectional surface area of the intake opening. This ensures that the pressure difference will become small, the flow losses will decrease and the noise damping increases to the outside.

According to the characterizing feature of claim 3, the cross section of the compensating volume can correspond at most to 1.5 times the piston head surface area. This ensures that on the one hand the need for space for the compensating volume will not become too high and it is ensured on the other hand that cold and hot suction gas will not mix or form the boundary layer as described below.

The characterizing features of claim 4, according to which the compensating volume has a circular cross section and the ratio of the length of the compensating volume to its diameter is higher than 10, describe a preferred embodiment which leads to especially low flow losses.

In order to achieve the most compact configuration of the muffler despite the additional compensating volume, the characterizing features of claim 5 are provided, according to which the compensating volume is formed by a compensating pipe which has a substantially U-shaped cross section and wraps around the muffler at least partly.

The characterizing features of claims 6 to 9 describe a preferred embodiment of the connection of suction pipe and inlet cross section into the muffler.

The characterizing features of claims 10 and 11 describe two different embodiments of a hermetically encapsulated refrigerant compressor, in which the inlet cross section into the muffler and the transition from muffler to compensating volume is arranged once separately and. once coincidentally. Depending on the need for space in the interior of the compressor housing, the most advantageous embodiment must be chosen. In the case where the inlet cross section into the muffler and the transition from muffler to compensating volume coincide, a further preferred embodiment according to the characterizing features of claims 12 to 14 are provided. This embodiment comes with the advantage that a tight connection between suction pipe and muffler is not necessary.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention will now be explained in closer detail by reference to the drawings, wherein:

FIG. 1 shows a front view of a hermetically encapsulated refrigerant compressor in accordance with the invention with a compressor housing in a sectional view;

FIG. 2 shows a sectional side view of a refrigerant compressor hermetically encapsulated in accordance with the invention;

FIG. 3 shows a front view of a refrigerant compressor hermetically encapsulated in accordance with the invention;

FIG. 4 shows a sectional view of a muffler in accordance with the state of the art;

FIG. 5 shows a further sectional view of a known muffler;

FIG. 6 shows a sectional view of a muffler in accordance with the invention with a closed intake valve;

FIG. 7 shows a sectional view of a muffler in accordance with the invention with an opened intake valve;

FIG. 8 shows an oblique view of the muffler in accordance with the invention in the compressor housing;

FIG. 9 shows an alternative embodiment of a muffler in accordance with the invention;

FIG. 9a shows a further alternative embodiment of a muffler in accordance with the invention;

FIG. 10 shows an additional alternative embodiment of a muffler in accordance with the invention;

FIG. 11 shows a detailed view of a hermetically sealed connection between muffler and suction pipe;

FIG. 12 shows a detailed view of an alternative embodiment of a hermetically sealed connection between muffler and suction pipe;

FIG. 13 shows a detailed view of a further alternative embodiment of a hermetically sealed connection between muffler and suction pipe;

FIG. 14 shows a detailed view of a connection between a plastic hose with a suction pipe;

FIG. 15 shows a detailed view of a connection of a plastic hose with a suction pipe;

FIG. 16 shows a detailed view of a connection of a plastic hose with a suction pipe;

FIG. 17 shows a detailed view of a connection of a plastic hose with a suction pipe;

FIG. 18 shows a detailed view of a connection of a plastic hose with a suction pipe;

FIG. 19 shows an oblique view of an alternative muffler in accordance with the invention;

FIG. 20 shows a further oblique view of the muffler of FIG. 19 in accordance with the invention;

FIG. 21 shows a sectional view of the muffler of FIG. 19 in accordance with the invention;

FIG. 22 shows a further sectional view of the muffler of FIG. 19 in accordance with the invention.

FIGS. 1, 2 and 3 each show a sectional view through a hermetically encapsulated refrigerant compressor, with FIGS. 1 and 3 each showing a view in the direction of arrow A of FIG. 2. A piston-cylinder motor unit is elastically held by means of springs 2 in the interior of a hermetically sealing compressor housing 1.

The piston-cylinder-motor unit substantially consists of a cylinder housing 3 and the piston 4 performing a lifting movement therein, and a crankshaft bearing 5 which is arranged perpendicular to the cylinder axis 6. The crankshaft bearing 5 receives a crankshaft 7 and protrudes into a centric bore 8 of rotor 9 of an electromotor 10. A connecting rod bearing 12 is situated at the upper end of crankshaft 7, through which the connecting rod and consequently the piston 4 are driven. The crankshaft 7 comprises a lubricating oil bore 13 and is fixed to rotor 9 in the area 14. The muffler 16 is arranged on the cylinder head 15, which muffler is to reduce noise development to a minimum during the intake process of the refrigerant.

FIG. 4 shows a sectional view of a muffler 16 according to the state of the art. As is already shown in FIGS. 1, 2 and 3, the muffler 16 is arranged on the cylinder head 15 in the interior of the hermetically sealed compressor housing 1. The refrigerant coming from the evaporator, which refrigerant is cold in comparison with the warm refrigerant situated in the compressor housing 1, flows via a suction pipe 17 into the interior of the compressor housing 1 close to the inlet cross section 18 of the muffler 16 when such a known muffler 16 is used, where it mixes with the warm refrigerant already situated in the compressor housing 1 and is heated up and is drawn into the piston-cylinder unit via the muffler 16.

Mufflers 16 according to the state of the art usually consist of several successively connected and/or parallel connected volumes V1, V2, V_n which are connected via pipes with each other, and of an oil separator opening 31 at the lowest point. The cold refrigerant flows via suction pipe 17 into the interior of the compressor housing 1 where as a result of its configuration a first thorough mixing with the warm refrigerant occurs which is already situated in the compressor housing 1. The already mixed and heated refrigerant then flows through the inlet cross section 18 into the first volume V1 and then into the second volume V2 of the muffler 16 and mixes again with the warm refrigerant already situated both in V1 as well as V2, as a result of which there is a renewed heating of the refrigerant. In these known mufflers, the heating between the outlet from suction pipe 17 and shortly before the intake opening 24 in the muffler 16 is between 30K and 40K, depending on the output of the refrigerant compressor.

FIG. 5 shows a muffler 16 which is also known from the state of the art, namely from WO03/038280, whose inlet cross section 18 is tightly connected with the suction pipe 17. The cold refrigerant coming from the suction pipe 17 is unable to mix with the warm refrigerant situated in compressor housing 1 before it is drawn into the muffler 16. A compensating volume 21 is connected to the muffler 16, through which the pressure compensation can occur which is required as a result of the direct connection of the muffler 16 with the suction pipe 17, such that a connection exists both to the muffler 16 as well as into the interior of the compressor housing. The required pressure compensation leads to flow states of the refrigerant which can lead to the flow losses which offset the gain in energy which is achieved by the reduction of the refrigerant temperature at the beginning of the compression phase.

In order to avoid or minimize these flow losses, it is necessary to arrange the compensating volume 21 in such a way that the energy loss caused by the additionally occurring flow losses is lower than the energy gain achieved by the improved suction. An embodiment of a muffler in accordance with the invention is shown in FIG. 6. Muffler 16 is shown in FIG. 6 in a sectional view. FIGS. 1, 2 and 3 also show refrigerant compressors with such a muffler 16 in accordance with the invention. The inlet cross section 18 of muffler 16 is connected with the suction pipe 17 via a schematically shown, hermetically sealed connection 19. A tight connection 19 can principally be any preferably elastic connection as known to the person skilled in the art, such as a simple rubber tube which needs to be connected in a tight manner with the muffler 16 and the suction pipe 17. Examples for such connections are shown in FIG. 11 to FIG. 18. The muffler 16 in accordance with the invention delimits a filling volume 20 (with the arrangement of several filling volumes being possible and done). Adjacent to the muffler 16, a compensating volume 21 is arranged which is formed by a U-shaped compensating pipe 34. The illustrated U-shaped compensating pipe 34 offers the advantage of limiting a sufficient compensating volume 21 and of requiring only little additional space, and of producing the required flow conditions which minimize the mentioned losses. The compensating volume 21 and the compensating pipe 34 are in connection via a compensating opening 23 with the interior of the compressor housing 1 and with the filling volume 20 of the muffler 16 via the transition opening 26.

FIG. 6 shows the flow progress of the refrigerant with closed intake valve by means of arrows, which valve is situated behind the intake opening 24 of the muffler 16 on the side of the valve plate facing the piston.

The cold refrigerant flowing from the suction pipe 17 flows via the tight connection 19 to the muffler volume 20 and from there into the compensating volume 21, as a result of which the warmer refrigerant situated there is pressed from the compensating pipe 34 via the compensating opening 23 into the interior of the compressor housing 1. The line indicated with reference numeral 25 symbolizes the boundary layer which forms between the cold and warm refrigerant.

FIG. 7 shows the same muffler 16 in accordance with the invention, plus flow progress with opened intake valve. In this case, the refrigerant is drawn in both from the compensating volume 21 and from the filling volume 20 and the suction pipe 17. Since the refrigerant in the compensating volume 21 has a lower temperature than the warm refrigerant situated in the interior of the compressor housing 1, the mixing temperature of the refrigerants from the mentioned intake regions is lower than the mixing temperature of the refrigerants when using mufflers known from the state of the art, as a result of which the aforementioned undesirable temperature increase is prevented. As a result of the inventive feature that the compensating volume 21 has 0.5 to 3 times the lifting volume of the piston of the piston-cylinder unit, warm refrigerant is unable to flow from the interior of the compressor housing into the muffler, which in this embodiment is volume 20. Due to the fact that the smallest flow cross section 32 has a cross-sectional surface area in the compensating volume 21 which corresponds to ¼ to ¾ of the cross-sectional surface area of the intake opening 24, it is ensured that the pressure difference between muffler 16 and the interior of the compressor housing 1 is low and at the same time the noise damping in the interior of the compressor housing is high. An enlargement of the compensating volume also contributes to this, with the same being at least half, preferably 0.5 to 3 times the displacement of the piston of the piston-cylinder unit.

At the same time, the flow losses are minimized by the muffler in accordance with the invention and the refrigerant can easily flow into the compensating volume or from the same without negatively influencing the refrigerant process.

For the purpose of better clarity, FIG. 8 shows an oblique view of the muffler 16 in accordance with the invention in the compressor housing 1 without the piston-cylinder motor unit.

FIG. 9 shows an alternative embodiment of a muffler 16 in accordance with the invention, plus compensating volume 21. The compensating volume 21 and the muffler 16 are formed by an encasing pipe 34 which encases the intake opening 24 on the one hand and opens into the same, and encases an end section of the suction pipe 17 along a section on the other hand. The cold refrigerant flowing from the suction pipe 17 flows during the entire intake cycle into the section of the encasing pipe 34 forming the filling volume 20 of the muffler 16. In the subsequent compression cycle, the filling volume 20 of the muffler 16 can no longer receive any further refrigerant from the suction pipe 17 as a result of the closed intake valve, which is why the refrigerant flows back into the compensating volume 21 which is also formed by a section of the encasing pipe 34 and displaces the warm refrigerant contained therein via the compensating opening 23 into the interior of the compression housing 1.

As already described in FIGS. 5 and 6, this leads to the formation a boundary layer 25 between warm and cold refrigerant, which layer is movable depending on the intake cycle. During the next intake cycle, cold refrigerant can be drawn into the cylinder both from the suction pipe 17 as well as from the compensating volume 21 of the encasing pipe 34. The relevant aspect is that the boundary layer does not exceed the line designated with reference numeral 33, which in this embodiment simultaneously forms the inlet cross section 18 into the muffler 16 and the transitional opening 26, in the direction of intake opening 24 in order to prevent a thorough mixture of warm and cold refrigerant prior to the intake process.

At the same time, no cold refrigerant is allowed to be displaced from the suction pipe 17 from the compensating volume 21 into the compressor housing 1. The boundary layer 25 must thus not be displaced behind the line marked in FIG. 9 with reference numeral 23 (compensating opening). Irrespective of the embodiment, a precise adjustment of the volume of the compensating volume 21 to the refrigerating output and thus to the displacement of the piston-cylinder unit is necessary.

FIG. 9a shows a further alternative embodiment of a muffler 16 plus compensating volume 21, in which the muffler 16 is provided with an additional volume 20 in comparison with that of FIG. 9. In all other respects this variant is identical to the one shown in FIG. 9.

FIG. 10 shows an additional alternative embodiment of a muffler 16 in accordance with the invention. The reference numerals were maintained accordingly. As can be seen on the basis of the large number of different designs, the configuration of the compensating volume can principally be chosen freely as long as the features of compensating volume 21 in accordance with the invention which is situated upstream of the outlet opening of suction pipe 17 are maintained concerning its volume and the smallest flow cross section 32. Only then will optimal energy savings be achieved and the efficiency of the refrigerant compressor will be improved accordingly.

The question as to how the different compensating volumes 21 and the mufflers 16 are arranged is of lower importance as long as the features in accordance with the invention are realized and the gas column and the boundary layer 25 is allowed to oscillate in the compensating volume.

The muffler 16 in the embodiment according to FIG. 9 merely consists of a filling volume 20 which extends in a substantially conical manner, and in the embodiment according to FIG. 9a of a filling volume 20a extending in a substantially conical manner and of the filling volume 20, and in the embodiment according to FIG. 10 of the volumes V2 and V1. It is understood that the parallel or serial arrangement of additional volumes of the muffler 16 is possible at any time and leads to improved sound-damping properties of the muffler 16.

In the embodiment according to FIG. 9, the compensating volume 21 consists of a cylindrical volume. In the embodiment according to FIG. 9a, it also consists of a cylindrical volume and in the embodiment according to FIG. 10 of the volumes 21a and 21b . The further arrangement of the compensating volumes, whether parallel or serial, is obviously possible, with the same contributing to sound damping, like 21b for example. The smallest flow cross section 32 in accordance with the invention can be realized either by a baffle as in FIG. 9, 9a and 10, or by a spatial constriction as shown in FIG. 3. Alternatively, the entire compensating volume 21 can have a constant cross section with the features in accordance with the invention.

FIGS. 11 to 18 show different embodiments of the hermetically sealed connection from suction pipe 17 to muffler 16 in accordance with the invention. Only when this connection is actually tight, which means in other words that no warm refrigerant is drawn from the compressor housing 1 into the muffler 16, the compensating volume 21 will show its optimal effect, if it concerns an embodiment as described in FIG. 6 and FIG. 7.

The simplest connection is shown in FIG. 11. In this case, the elastic bellows 19 is merely pushed over the suction pipe 17 without any additional fixing, but preferably glued.

FIGS. 12 and 13 show a more complex but stable connection.

In FIG. 12, the wall of the compressor housing 1 comprises an inwardly facing nose 28 over which the elastic plastic hose 19 is pushed, which nose simultaneously protrudes into the inlet cross section 18 of the muffler 16. The plastic hose 19 which can also be arranged as an elastic pipe is enclosed by a spiral spring 27 which ensures required stability and fixing. An 0-ring 29 is each arranged both in the area of the nose 28 as well as in the area of the inlet cross section 18, which ring ensures the required tightness.

In FIG. 13, the muffler 16 also comprises a respective nose protruding into the interior of the compressor housing 1.

FIGS. 14 to 18 show different fastening possibilities 30 between elastic connecting means 19 and suction pipe 17 which can be arranged either as a toothing (FIG. 17, FIG. 18) or as barbs (FIG. 16) arranged on the elastic connecting means, or as simple shoulders (FIG. 14, FIG. 15).

In an embodiment of the compensating volume 21 including muffler 1 as described in FIGS. 9, 9a and 10, lacks the requirement of such a tight connection between muffler 16 and suction pipe 17 for the reasons as described above.

FIG. 19, FIG. 20, FIG. 21 and FIG. 22 show a further embodiment of a muffler 16 plus compensating volume 21 as already schematically described in FIGS. 9, 9a and 10. The suction pipe 17 is guided close to the inlet cross section 18 of the muffler 16. The inlet cross section 18 is connected by means of a plastic hose 19 tightly with the suction pipe 17.

The remaining parts of the refrigerant compressor were not drawn for reasons of clarity in FIG. 19, FIG. 20, FIG. 21 and FIG. 22.

Claims

1. A hermetically encapsulated refrigerant compressor, comprising a hermetically sealed compressor housing (1), in the interior of which a piston-cylinder unit works which compresses a refrigerant and comprises an intake valve with an intake opening (24) arranged in a valve plate of the same, with a muffler (16) being provided on the cylinder head (15) of the piston-cylinder unit, which muffler comprises a filling volume (20) and through which the refrigerant flows to the intake valve of the piston-cylinder unit, and with the muffler (16) having an inlet cross section (18) through which refrigerant flows into the muffler (16) and with a compensating volume (21) being provided which is in connection with the muffler (16) and the interior of the compressor housing (1) and in which the refrigerant oscillates, wherein the compensating volume (21)is 0.5 to 3 times the displacement of the piston of the piston-cylinder unit.

2. A hermetically encapsulated refrigerant compressor according to claim 1, wherein the smallest flow cross section (32) in the compensating volume (21) has a cross-sectional surface area which corresponds to ¼ to ¾ of the cross-sectional surface area of the intake opening (24).

3. A hermetically encapsulated refrigerant compressor according to claim 1, wherein the cross-sectional surface area of the compensating volume (21) is at most 1.5 times the piston head surface area of the piston of the piston-cylinder unit.

4. A hermetically encapsulated refrigerant compressor according to claim 1, wherein the compensating volume (21) has a circular cross section and the ratio of the length of the compensating volume (21) to its diameter is higher than 10.

5. A hermetically encapsulated refrigerant compressor according to claim 1, wherein the compensating volume (21) is formed by a compensating pipe (22) which has a substantially U-shaped cross section and wraps around the muffler (16) at least partly.

6. A hermetically encapsulated refrigerant compressor according to claim 1, wherein the connection of the inlet cross section (18) of the muffler (16) with the suction pipe (17) is an elastic plastic hose (19) made of PTFE, acrylonitrile, butadiene or fluorinated rubber.

7. A hermetically encapsulated refrigerant compressor according to claim 6, wherein the elastic plastic hose is a bellows.

8. A hermetically encapsulated refrigerant compressor according to claim 1, wherein the suction pipe (17) is provided with barbs.

9. A hermetically encapsulated refrigerant compressor according to claim 1, wherein the suction pipe (17) is provided with latching elements which cooperate with respective latching elements on the plastic hose (19).

10. A hermetically encapsulated refrigerant compressor according to claim 1, wherein the inlet cross section (18) and the connecting opening (26) between compensating volume (21) and filling volume (20) are arranged in different sections of the muffler housing.

11. A hermetically encapsulated refrigerant compressor according to claim 1, wherein the inlet cross section (18) is simultaneously the connecting opening (26) between compensating volume (21) and filling volume (20).

12. A hermetically encapsulated refrigerant compressor according to claim 11, wherein the compensating volume (21) is formed by an encasing pipe (34) which tightly encloses the intake opening (24) and the inlet cross section (18) respectively on the one hand and encloses the suction pipe (17) of the refrigerant at least along a section and faces into the compressor housing (1) on the other hand, which suction pipe is connected with the evaporator of the refrigerant compressor and protrudes into the interior of the compressor housing (1).

13 A hermetically encapsulated refrigerant compressor according to claim 12, wherein the suction pipe (17) is guided close to the intake opening (24)in the encasing pipe (34).

14. A hermetically encapsulated refrigerant compressor according to claim 12, wherein the encasing pipe (34) and the muffler (16) have an integral configuration.