Abstract:
A refrigerant compressor, comprising a hermetically sealed compressor housing ( 1 ), in whose interior ( 8 ) a piston-cylinder unit ( 4 ) compressing a refrigerant operates, which sucks in refrigerant from outside ( 9 ) the compressor housing ( 1 ) via a suction pipe ( 2 ) and expels the refrigerant under compression via a pressure section ( 3, 6 ), formed from a pressure pipe ( 3 ) manufactured from plastic and a connection pipe ( 6 ) manufactured from metal in the direction of a condenser situated outside ( 9 ) the compressor housing ( 1 ). In order to enable a reliable sealing connection between the pressure pipe ( 3 ) and the connection pipe ( 6 ), it is provided that the pressure pipe ( 3 ) is connected to form a seal to the connection pipe ( 6 ) using a sleeve-shaped connector ( 5 ), which is manufactured from plastic and is situated between the pressure pipe ( 3 ) and the connection pipe ( 6 ), the connection pipe ( 6 ) having an at least sectionally constricted end section ( 6   c ), facing toward the pressure pipe ( 3 ), which secures the connector ( 5 ) situated inside the connection pipe ( 6 ) in its axial location.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to a refrigerant compressor, comprising a hermetically sealed compressor housing, in whose interior a piston-cylinder unit which compresses a refrigerant operates, which sucks in refrigerant from outside the compressor housing via a suction pipe and expels the refrigerant under compression via a pressure section, which is formed by a pressure pipe manufactured from plastic and a connection pipe manufactured from metal, in the direction of a condenser situated outside the compressor housing, according to the preamble of Claim  1 . 
         [0002]    The refrigerating machine process using zeotropic gases has been known per se for some time. The refrigerant is heated by absorbing energy from the space to be cooled in the vaporizer and finally overheated, which results in vaporization, and is compressed to a higher pressure level using a piston-cylinder unit of the refrigerant compressor, where it dissipates heat via a condenser and is conveyed back into the vaporizer via a throttle, in which pressure reduction and cooling of the refrigerant occur. 
         [0003]    Such refrigerant compressors are predominantly used in refrigerators or refrigerated shelves. The yearly produced piece count is correspondingly high. Any technical improvement which is performed on a refrigerant compressor and reduces the production costs thus offers enormous savings potential when multiplied by the refrigerant compressors used worldwide. 
         [0004]    However, refrigerant compressors are also sources of noise, which can sometimes be annoying during the operation of the refrigerant compressor. The vibrations arising through the operation of the piston-cylinder unit and its drive motor also stress all parts of the refrigerant compressor which are subject to these vibrations, however. 
         [0005]    It has been shown that a substantial part of the oscillation transmission from the piston-cylinder unit to the compressor housing is to be attributed to the pressure pipe. On the other hand, the pressure pipe must have a certain mobility, in order to be able to absorb the vibrations exerted by the piston-cylinder unit. 
       PRIOR ART 
       [0006]    Conventional pressure pipes are manufactured from metal materials having high moduli of elasticity. In order to fulfill the requirements with respect to oscillation transmission and durability, the pressure pipes are therefore accordingly implemented as long and situated curved multiple times in the interior of the compressor housing. Pressure pipes of this type are therefore also referred to as serpentines. 
         [0007]    In order to reduce the oscillation transmission from the piston-cylinder unit to the compressor housing and the noise development, it has therefore been proposed in AT 007 698 U1 to manufacture the pressure pipe from plastic in its section leading through the interior of the compressor housing. Furthermore, heating of the interior of the compressor housing by the compressed refrigerant located in the pressure pipe can be reduced and the efficiency of the refrigerant compressor can be increased by an embodiment of the pressure pipe from plastic. 
         [0008]    In the case of plastic pressure pipes of this type, the question arises of a suitable attachment of the pressure pipe leading out of the interior of the compressor housing to a metal connection pipe leading to the condenser. A problem results in this case because of the differing coefficients of thermal expansion of the connection pipe, which is manufactured from metal, typically copper or steel, and the pressure pipe manufactured from plastic, in particular because operating temperatures of approximately 120° C. are reached in the interior of the compressor housing and the danger of leaks between the pressure pipe and the connection pipe arises during cool down of the system to room temperature after the refrigerant compressor has been shut down. 
         [0009]    While metal pressure and connection pipes are soldered, screwed, or glued to one another in a conventional manner, those according to AT 007 698 U1 were connected to one another using thermoplastic joints, for example. 
         [0010]    However, no cross-section reduction of the pressure section formed by the pressure pipe and connection pipe in the flow direction of the refrigerant is to occur upon the connection of a pressure pipe manufactured from plastic and a connection pipe manufactured from metal, so as not to obstruct the continuous flow of the refrigerant exiting from the piston-cylinder unit. For this reason, fastening variants in which the pressure pipe is plugged onto the connection pipe are to be avoided. 
         [0011]    Furthermore, plugging the (tubular or serpentine) pressure pipe onto the connection pipe would not allow satisfactory automated assembly. 
         [0012]    DE 31 02 576 A1 discloses a pipe connection, a first pipe being pluggable into a widened end area of a second pipe. Before these pipes, which are manufactured from aluminum, are plugged into one another, the outer jacket of the first pipe is provided with two film-type coatings situated adjacent to one another, namely with a silicone rubber layer and an adhesive layer. Both coatings have a layer thickness between 0.5 and 0.75 mm. Because of this relatively low layer thickness, a pipe connection of this type is not suitable for use in a pressure pipe attachment of refrigerant compressors according to the species, because the coatings could wear in case of relative movements between the pressure pipe and the connection pipe and the danger of a leak would result in the present connection area. 
         [0013]    WO 2007/011247 A discloses a refrigerant compressor having a pressure pipe manufactured from plastic, whose end section is crimped to a connection pipe leading in the direction of a condenser. The end section of the connection pipe is widened into a funnel shape for this purpose. 
       SUMMARY OF THE INVENTION 
       [0014]    It is therefore the object of the present invention to provide a reliably sealing attachment capability for a pressure pipe to a connection pipe, which is manufactured from metal, of a refrigerant compressor. In particular, the continuous flow of the refrigerant exiting from the piston-cylinder unit is not to be obstructed. 
         [0015]    In addition, reliable automatic assembly of the pressure pipe attachment is to be made possible. 
         [0016]    This object is achieved by a refrigerant compressor having the characterizing features of Claim  1 . A refrigerant compressor according to the species has a hermetically sealed compressor housing, in whose interior a piston-cylinder unit which compresses a refrigerant operates, which is connected to a suction pipe and a pressure pipe, a refrigerant flowing to the piston-cylinder unit via the suction pipe, and the refrigerant compressed therein being guided along a pressure section, which is formed by a pressure pipe, which is manufactured from plastic, and a connection pipe, which adjoins the pressure pipe and is manufactured from metal, through the interior of the compressor housing and then to the exterior of the compressor housing. It is provided according to the invention that the pressure pipe is connected to form a seal to the connection pipe, which is manufactured from metal, using a sleeve-shaped connector, which is manufactured from plastic and situated between the pressure pipe and the connection pipe, the connection pipe having an at least sectionally constricted end section facing toward the pressure pipe, which secures the connector situated inside the connection pipe in its axial location. 
         [0017]    By providing a sleeve-shaped elastic connector, which is adaptable according to the particular geometries of pressure pipe and connection pipe, between the pressure pipe and the connection pipe, the differing coefficient of thermal expansion of the pressure pipe manufactured from plastic from the connection pipe manufactured from metal can be ideally compensated for and leaks of the pressure section can thus be prevented. 
         [0018]    The design of the flow cross-section of the pressure section formed by pressure pipe and connection pipe can now be performed as desired, so that cross-section reductions in the flow direction of the refrigerant, as would occur if the pressure pipe was plugged onto the connection pipe, for example, are avoidable in future. The continuous flow of the refrigerant exiting from the piston-cylinder unit can thus be preserved. 
         [0019]    For this reason, it is preferably provided that an opening cross-section of the connector, which adjoins the end area of the pressure pipe and is delimited by a connector inner surface, is greater than or equal to a flow cross-section of the pressure pipe delimited by the pressure pipe inner surface. 
         [0020]    According to a preferred embodiment of the pressure pipe attachment according to the invention, it is provided that an outer side of the pressure pipe is jacketed to form a seal by the connector, the connector having a sealing connection to the connection pipe. In this way, a reliably sealing pressure section which is to be assembled in the automated method can be produced. 
         [0021]    In a further preferred embodiment of the invention, the sealing connection between the connector and the connection pipe is produced by a seal element situated between the connector and the connection pipe. This seal element is preferably an O-ring, which is held in a groove provided on an outer side of the connector. In this way, a simple and cost-effective seal is made possible between the connector and the connection pipe. 
         [0022]    Of course, additionally or alternatively to providing the seal element, other seal capabilities may be provided between the connector and the connection pipe, such as a seal using adhesive or by providing a press fit between the connector and the connection pipe. 
         [0023]    In a further preferred embodiment variant of the invention, it is provided that the inner surface of the connector is implemented as stepped, a first inner surface section, which jackets the pressure pipe, and a second inner surface section, which adjoins an end area of the pressure pipe, preferably at a front side of the pressure pipe, and is essentially aligned with an inner surface of the pressure pipe or lies outside of it, of the connector are provided. Through the stepped embodiment of the connector inner surface, a more secure hold and precise positioning of the pressure pipe end area in the connector are made possible. In that the second inner surface section, which follows the front side of the pressure pipe, of the connector aligns with the pressure pipe inner surface or (viewed in relation to the pipe axis) lies outside the pressure pipe inner surface, a continuous flow of the refrigerant exiting from the piston-cylinder unit is encouraged. 
         [0024]    In order to also allow a reliably sealing pressure section at the transition point from the pressure pipe to the connector, the connector can be connected to the pressure pipe by gluing, welding, or extrusion coating. 
         [0025]    In a particularly preferred embodiment, the connector is fastened on the pressure pipe using laser welding technology. For this purpose, at least the section of the connector adjoining the pressure pipe is transparent to at least infrared wavelengths in the range between 800 and 960 nm. In that the connector is thus implemented as at least regionally translucent, an infrared laser welding device provided for this purpose can radiate through the jacket of the connector and achieve a suitable welding temperature in the contact area between the pressure pipe outer side and the connector inner surface in this way. A connection of the pressure pipe to the connector of this type using infrared laser welding technology has an ultra-reliable sealing effect and allows economic manufacturing. 
         [0026]    In a preferred embodiment of the invention, the connection pipe is crimped to the connector. For this purpose, the outer side of the connector has a complementary geometry prepared for crimping with the connection pipe, preferably in the form of a concave recess. After completed insertion of the connector with pressure pipe into the connection pipe, the connection pipe is reshaped using a crimping tool, so that a jacket section of the connection pipe presses against the concave recess and thus causes axial fixing of the connector held in the connection pipe. 
         [0027]    The connector is produced from an elastomeric plastic in a preferred embodiment. Connectors manufactured from an elastomeric material may deform elastically under tension, pressure, or bending strain, so that greater robustness of the pressure section in relation to mechanically or thermally related force actions is achieved. 
         [0028]    To increase the stability of the pressure section exiting from the compressor housing, the connection pipe is fastened, preferably welded, on a wall of the compressor housing at the height of an end section of the pressure pipe which is held in the assembly location in the connection pipe or in the connector. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]    The invention is described in greater detail hereafter on the basis of exemplary embodiments. In the figures: 
           [0030]      FIG. 1  shows a perspective illustration of a refrigerant compressor having a compressor housing and an incoming suction pipe and an outgoing pressure section 
           [0031]      FIG. 2  shows a schematic illustration of the interior of the refrigerant compressor according to  FIG. 1 , only the parts relevant for the invention being shown for better clarity 
           [0032]      FIG. 3  shows an attachment according to the invention of a pressure pipe to a connection pipe using a plastic connector in a detail sectional view 
           [0033]      FIG. 4  shows an alternative embodiment of the pressure pipe attachment according to the invention in a detail sectional view 
           [0034]      FIG. 5  shows an alternative embodiment of the pressure pipe connection according to the invention in a detail sectional view 
           [0035]      FIG. 6  shows an alternative embodiment of the pressure pipe connection according to the invention having a crimped connection pipe in a detail sectional view 
           [0036]      FIG. 7  shows an alternative embodiment of the pressure pipe connection according to the invention having a crimped connection pipe in a detail sectional view 
           [0037]      FIG. 8  shows an alternative embodiment of the pressure pipe connection according to the invention having a crimped connection pipe in a detail sectional view 
       
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0038]      FIG. 1  shows a refrigerant compressor in a perspective view having a compressor housing  1  with a suction pipe  2  and a pressure section  3 ,  6 , which is formed by a pressure pipe  3  and a connection pipe  6 . 
         [0039]    The suction pipe  2  leads into the interior  8  of the compressor housing  1  and guides a refrigerant coming from a vaporizer (not shown) to a piston-cylinder unit  4  installed on the base plate  16  in the compressor housing  1 , in order to compress the refrigerant expanded in the vaporizer again. The compressed refrigerant is guided away from the piston-cylinder unit  4  again and/or guided out of the interior  8  of the compressor housing  1  via the pressure section  3 ,  6  (see also  FIG. 2 ). 
         [0040]    The section of the pressure section  3 ,  6  leading to the interior of the compressor housing  1 , namely the pressure pipe  3  connected to the piston-cylinder unit  4 , is shown in  FIG. 2 . This section is also designated as a “serpentine”. The end area  3   c  of the pressure pipe  3  is provided for connection to a connection pipe  6  situated outside the compressor housing  1 , which is also part of the pressure section  3 ,  6 , but is further away from the piston-cylinder unit  4  than the pressure pipe  3 . 
         [0041]    According to  FIG. 2 , the pressure section  3 ,  6  further also comprises a pressure sound damper  18 , which can also be situated outside the compressor housing  1 , however. 
         [0042]    In order to reduce heat being of the interior of the compressor housing  1  by the refrigerant guided in the pressure pipe  3  and damp vibrations, the pressure pipe  3 —as already known from the prior art—is manufactured from plastic, such as a thermoplastic, duroplastic, or elastomeric plastic. 
         [0043]    In contrast, the connection pipe  6  to be attached to the pressure pipe  3  is manufactured from metal. The connection pipe  6  preferably comprises copper, a copper alloy, or steel, but it can also be implemented from other metal materials and have optional jacket or internal coatings. 
         [0044]    Because the material copper has a coefficient of expansion approximately four times as high as plastic and operating temperatures of up to 120° C. result in the interior of the compressor housing  1 , special requirements are placed on a connection of the pressure pipe  3  and the connection pipe  6  to ensure the tightness of the pressure section  3 ,  6 . 
         [0045]    According to the invention, it is provided that the pressure pipe  3  is connected using a sleeve-shaped connector  5 , which is manufactured from plastic and is situated between the pressure pipe  3  and the connection pipe  6 , to the connection pipe  6 , which is manufactured from metal. 
         [0046]    It is to be noted that the pressure pipe  3  does not necessarily have to be located inside and the connection pipe  6  does not necessarily have to be located outside the compressor housing  1 . The connection area between pressure pipe  3  and connection pipe  6  and/or the attachment according to the invention shown in the figures using a connector  5  can be in an arbitrary area of the pressure section  3 ,  6 , i.e., thus also inside or outside the compressor housing  1 . 
         [0047]    The connector  5  according to the invention can be manufactured, for example, from polyamide (PA), polyethylene (PE), polypropylene (PP), syntactic polystyrene (SPS), or polytetrafluoroethylene (PTFE). The connector  5  is preferably produced from a thermoplastic, in order to allow good welding capability of the connector  5  to the pressure pipe  3 . A connector  5  which is pressed or glued into the connection pipe  6  and manufactured from thermoplastic can also move with the connection pipe  6  in case of heating thereof and thus allow a better seat of the connector  5  in the connection pipe  6 . 
         [0048]      FIG. 3  shows a first embodiment variant of the pressure pipe attachment according to the invention. In this case, the connection pipe  6  coming from the exterior  9  and/or leading to the vaporizer protrudes somewhat into the interior  8  of the compressor housing  1 , which is provided with a through opening  17 , and is connected, e.g., welded on an outer side  6   b  to the compressor housing  1 . 
         [0049]    Furthermore, according to the invention, the connector  5  is inserted, preferably pressed into the connection pipe  6  and is secured thereby in its axial location, in that the connection pipe  6  has a constricted end section  6   c  facing toward the pressure pipe  3 , which encompasses a front side  5   c  of the connector  5  situated inside the connection pipe  6  at least on one point of its circumference and/or secures it against axial shifting. According to  FIG. 3 , the end section  6   c  of the connection pipe  6  is bent over and/or compressed in the direction of an outer side  3   b  of the pressure pipe  3 . 
         [0050]    The outer side  3   b  of the pressure pipe  3  is jacketed to form a seal by an inner surface  5   a  of the connector  5 . In the present exemplary embodiment, the inner surface  5   a,    5   a ′ of the connector  5  is implemented as stepped, a first inner surface section  5   a,  which jackets the pressure pipe  3 , and a second inner surface section  5   a ′, which adjoins the end area  3   c  of the pressure pipe  3  and/or its front side, of the connector  5  being provided. 
         [0051]    In order not to obstruct the continuous flow of the refrigerant, which exits from the piston-cylinder unit and flows in the flow direction  15  from the pressure pipe  3  to the connection pipe  6 , a flow cross-section  11  of the connector  5 , which adjoins the end area  3   c  of the pressure pipe  3  and is defined by the second inner surface section  5   a ′, is greater than or equal to a flow cross-section  10  of the pressure pipe  3  defined by an inner surface  3   a  of the pressure pipe  3 . In the exemplary embodiment according to  FIG. 3 , the second inner surface section  5   a ′ of the connector  5  essentially aligns with the inner surface  3   a  of the pressure pipe  3  and/or lies just outside the inner surface  3   a  of the pressure pipe  3  (viewed in relation to the central axis). 
         [0052]    It is obvious in  FIG. 3  that the refrigerant flowing in the flow direction  15  from the pressure pipe  3  to the connection pipe  6  and/or into the exterior of the compressor housing  1  is exclusively guided in pipe sections  3 ,  5 ,  6  which have a flow cross-section  10 ,  11 ,  12  equal to or greater than the particular preceding pipe section. Because the refrigerant thus first flows through the flow cross-section  10  formed by the pressure pipe  3 , then the flow cross-section  11 , which is formed by the second inner surface section  5   a ′ of the connector  5  and is slightly enlarged in relation to the flow cross-section  10  of the pressure pipe  3 , and finally the flow cross-section  12 , which is formed by the connection pipe  6  and is in turn expanded in relation to the flow cross-section  11  of the connector  5 , the refrigerant does not have to pass a narrow point, but rather can expand unobstructed in the flow direction  15 . 
         [0053]    The connector  5  is attached on the pressure pipe  3  using sealing connection technologies, such as gluing, welding, pressing, or extrusion coating. 
         [0054]    In a particularly preferred type of connection, the connector  5  is fastened on the pressure pipe  3  using infrared laser welding technology. In this case, at least the section of the connector  5  adjoining the pressure pipe  3  is implemented as translucent and/or transparent at least to infrared wavelengths in the range between 800 and 960 nm, in order to radiate through the jacket of the pressure pipe  3  using a suitable infrared laser welding device and achieve a welding temperature in the contact area between the outer side  3   b  of the pressure pipe  3  and the inner surface  5   a  of the connector  5 . The pressure pipe  3 , in contrast, is manufactured from black or dark plastic, in order to allow optimum absorption of the energy emitted by the infrared laser welding device. 
         [0055]    The connector  5  which is connected to the pressure pipe  3  to form a seal also has a sealing connection to the connection pipe  6 . This sealing connection is produced in the exemplary embodiment shown by a seal element  7  situated between the connector  5  and the connection pipe  6 . 
         [0056]    In the exemplary embodiment according to  FIG. 3 , the seal element  7  is an O-ring, which is held in a groove  13  provided on the outer side  5   b  of the connector  5  and whose external diameter is at least greater than the internal diameter of the connection pipe  6  and/or the clearance of the flow cross-section  12 . 
         [0057]    The O-ring or the seal element  7  has a lenticular cross-section in  FIG. 3 . Alternatively thereto, the use of round, rectangular, or rhomboid O-rings  7  is also possible (see  FIGS. 4 and 5 ). According to  FIG. 4 , an O-ring  7  is laid in the groove  13  of the connector  5 , whose cross-section has an essentially square shape, the sides of the cross-sectional square each being implemented as concave, so that two sealing contact lines result both toward the inner surface  6   a  of the connection pipe  6  and also toward the outer side  5   a  of the connector  5 . Such a design of the seal element  7  allows an even better guarantee of the tightness between the connection pipe  6  and the connector  5 . 
         [0058]    In order to achieve a sealing connection of the connector  5  to the connection pipe  6 , however, a specially implemented connector  5 , which is manufactured from an elastomeric material, for example, could also be used. 
         [0059]    It is obvious that an alternative or additional possible seal between the connector  5  and the connection pipe  6  is possible, for example, by applying an adhesive to the connector outer side  5   b  and/or the connection pipe inner surface  6   b  or by providing a press fit between the connector outer side  5   b  and the connection pipe inner surface  6   b.  It is possible in particular for this purpose to achieve a form fit by hooking the connector  5  and the connection pipe  6  in one another. 
         [0060]      FIG. 6  shows an alternative embodiment of the invention, the connection pipe  6  being crimped to the connector  5 . For this purpose, the outer side  5   b  of the connector  5  has a complementary geometry, which is prepared for crimping with the connection pipe  6 , in the form of a concave recess  14 . After completed insertion and/or pressing of the connector  5  with pressure pipe  3  into the connection pipe  6 , the connection pipe  6  is crimped at least at one point of its circumference using a suitable device, so that a jacket section  6   d  of the connection pipe  6  presses against the concave recess  14  and thus causes axial fixing of the connector  5  held in the connection pipe  6 . 
         [0061]    As  FIG. 6  shows, the concave recess  14  of the connector  5  and/or the crimped jacket section  6   d  of the connection pipe  6  are situated in a position which encloses the end area  3   c  of the pressure pipe  3  held in the connector  5 . Through the described crimping procedure, the area of the connector  5  located below the jacket section  6   d  of the connection pipe  6  is pressed still more strongly against the pressure pipe  3  and the sealing effect between connector  5  and pressure pipe  3  is increased further. Such a configuration would prove advantageous in particular in the case of connectors  5  in an elastomeric embodiment, because providing a separate seal element  7  could be dispensed with. 
         [0062]    For reasons of stability, the connection pipe  6 , as already shown in  FIG. 1 , is fastened on the wall of the compressor housing  1  at the height of the end section  3   c  of the pressure pipe  3  held in the connection pipe  6  and/or in the connector  5 . 
         [0063]    In the case of a crimped embodiment of the pressure section  3 ,  6 , the seal elements  7  may also be used having arbitrary cross-sectional geometry and in arbitrary numbers (see also  FIGS. 7 and 8 ) or, as already noted, may also be dispensed with, because a sufficient sealing effect to the connection pipe  6  is already achieved by a connector  5  having a sealing geometry.