Abstract:
A casing for use with a refrigerant compressor of an air conditioning unit in a vehicle is disclosed, wherein the casing facilitates a maximization of pressure pulsation attenuation and an oil separation of a refrigerant/oil mixture flowing therethrough, and a space required thereby is minimized.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of German Patent Application No. 102006038726.0-15 COMBINED OIL SEPARATOR AND MUFFLER FOR REFRIGERANT COMPRESSOR filed on Aug. 11, 2006, hereby incorporated herein by reference in its entirety. 
       FIELD OF THE INVENTION 
       [0002]    The invention relates generally to a casing for use with a refrigerant compressor of an air conditioning unit in a vehicle, and more particularly to a casing that facilitates pressure pulsation attenuation and an oil separation of a refrigerant/oil mixture flowing therethrough. 
       BACKGROUND OF THE INVENTION 
       [0003]    In order to achieve high reliability and long life of refrigerant compressors, oil is used for lubrication to minimize the wear of the refrigerant compressors. In addition to the lubrication, the oil also performs a sealing function, particularly between a piston and a cylinder wall, and carries away heat as well. 
         [0004]    The oil is typically stored in an oil sump or a crankcase disposed in a foot region of the refrigerant compressor, and transported in the compressor unit through the compression of the refrigerant. 
         [0005]    However, it is desirable that the refrigerant/oil mixture be separated before leaving the refrigerant compressor casing, so that the oil may flow back into the oil sump of the crankcase. Prior art oil separators, such as cyclone separators, which include filtering means and quiescent spaces to reduce the velocity of flow, are known in the art. 
         [0006]    It is also desirable that during operation of the refrigerant compressor, a noise generated thereby which is perceptible by the vehicle occupants is minimized. Operating noise is primarily caused by pressure pulsations associated with compression. In practice, different structures are used for reducing the pressure pulsations, such as chambers where the pressure waves are attenuated by expansion. 
         [0007]    DE 36 43 567 A1, hereby incorporated herein by reference in its entirety, discloses a silencer for hermetically enclosed compressors. The silencer has two portions, the first portion causing attenuation of the pulsations and separation of oil from the refrigerant gas, the second portion damping the gas pulsations. For damping the gas pulsations, in the second portion a porous material is provided which forms voids and completely fills the second portion. For separating oil from the first or second portion of the silencer, a small tube is provided through which the oil can be drained off. 
         [0008]    DE 198 00 556 A1, hereby incorporated herein by reference in its entirety, discloses a compressor that also includes the functions of oil separation and pressure pulsation attenuation. Compressor operating means for suction are disclosed that in the multi-part crankcase compression and delivery of a refrigerant gas as well as oil separating means in form of a labyrinth are provided. The oil separating means are established integrally at the outer portions of the crankcase situated neighboring each other and mutually contacting in such a way that an inner space in at least one of the oil separating means is closed by another oil separating means so that a separation chamber is formed for the released refrigerant gas. The oil separating means as one piece is provided with elements which form passages, the elements partly dividing the separation chamber from its inlet to its outlet such that a serpentine-like separation flow path for the released refrigerant gas develops, while the separation chamber is connected to the crank chamber over an oil recirculation passage. 
         [0009]    Further, EP 0 926 341 A2, hereby incorporated herein by reference in its entirety, discloses a compressor with oil separation that is provided with two chambers which are connected to each other by channels and openings. Pressure pulsation attenuation of both chambers of the compressor is facilitated, but oil separation is only facilitated for the first, rectangular chamber. 
         [0010]    Other solutions of the generic kind are described in U.S. Pat. No. 6,523,455 B1, US 2005/0072307 A1 and DE 101 567 85 A1, all hereby incorporated herein by reference entirely. 
         [0011]    The essential disadvantages of the solutions known in prior art are that the oil separation devices and the silencer set significant space requirements within the compressor, which involves high manufacture costs. Furthermore, compressors requiring a large amount of space are submitted to certain installation limitations as to the packaging in small engine bays of vehicles. 
         [0012]    Accordingly, it would be desirable to produce a casing for use with a refrigerant compressor, wherein a pressure pulsation attenuation and an oil separation from a refrigerant/oil mixture flowing therethrough are maximized and a space requirement thereof is minimized. 
       SUMMARY OF THE INVENTION 
       [0013]    Harmonious with the present invention, a casing for use with a refrigerant compressor, wherein a pressure pulsation attenuation and an oil separation from a refrigerant/oil mixture flowing therethrough are maximized and a space requirement thereof is minimized. 
         [0014]    In one embodiment, a casing for use with a refrigerant compressor comprises a first chamber having an inlet in fluid communication with a source of a mixture of oil and refrigerant; a second chamber having a drain formed therein, the second chamber in fluid communication with the first chamber; a third chamber having an outlet, the third chamber in fluid communication with the second chamber; and a flow guiding device for directing a flow of the mixture of oil and refrigerant from the first chamber to the second chamber and from the second chamber to the third chamber. 
         [0015]    In another embodiment, a casing for use with a refrigerant compressor comprises a first chamber having an inlet in fluid communication with a source of a mixture of oil and refrigerant; a second chamber disposed adjacent the first chamber, the second chamber including an oil drain formed therein for facilitating drainage of an oil portion of the mixture of oil and refrigerant from the casing; a third chamber disposed adjacent the first chamber, the third chamber including an outlet for a refrigerant portion of the mixture of oil and refrigerant; and a flow guiding device disposed in the first chamber, the flow guiding device including a partition disposed between the first chamber and the third chamber and a funnel portion disposed between the first chamber and the second chamber, wherein the partition creates a substantially fluid tight seal between the first chamber and the third chamber and an annular gap is formed between the funnel portion of the flow guiding device and a casing inner wall. 
         [0016]    A method for oil separation and pressure pulsation attenuation within a casing for use with a refrigerant compressor is also disclosed. The method comprises the steps of causing a mixture of oil and refrigerant to enter a first chamber formed in the casing; attenuating a pressure pulsation in the first chamber by a reflection of pressure waves within the first chamber; causing the mixture of oil and refrigerant to flow into a second chamber; attenuating the pressure pulsation in the second chamber by a reflection of pressure waves within the second chamber; and separating an oil portion from a refrigerant portion of the mixture of oil and refrigerant. 
         [0017]    According to the concept of the invention the refrigerant compressor for air conditioning units, particularly a sound-attenuated refrigerant compressor with oil separation for use in vehicles at least comprises a casing coupled to the crankcase of the refrigerant compressor, the interior of the casing divided into several chambers which communicate with each other. According to the invention, the casing comprises, in direction of flow of the oil/refrigerant mixture, a first chamber with an inlet for the oil/refrigerant mixture. Downstream of the first chamber there is a second chamber with a drain placed at the deepest point with respect to gravity. The second chamber is followed by a third chamber with an outlet for the gaseous refrigerant. In addition, a flow guiding device is provided that, starting from the second chamber, extends channel-like through the first chamber up to the third chamber. The end region of the flow guiding device that is turned to the third chamber is formed as partition wall while the end region of the flow guiding device that is placed between the first chamber and the second chamber is formed as funnel with an annular gap developing between the funnel edge and the casing inner wall. 
         [0018]    The solution according to the invention provides a refrigerant compressor, in particular for gaseous refrigerants, which makes possible in cramped conditions both to efficiently separate oil from the oil/refrigerant mixture and attenuate pressure pulsations associated with compression. While the oil is separated utilizing centrifugal forces and nozzle principle, or the coalescence principle with nozzle injection in the second chamber, respectively, the attenuation of the pressure pulsation is carried out in each of the three chambers through pressure expansion. 
         [0019]    The design, i.e. the cross section, structural length and alignment of the flow guiding device are dimensioned based on the permissible total physical size of the refrigerant compressor as a design pretext and with the desired degree of oil separation in mind. In a preferred embodiment of the invention the flow guiding device, which is established channel-like, is placed coaxial to the longitudinal axis of the casing, which is coupled to the crankcase of the refrigerant compressor, the cross section of the flow guiding device being chosen to have a circular shape. 
         [0020]    The inlet provided for the inflow of the oil/refrigerant mixture into the first chamber is particularly preferred to be arranged orthogonal to the longitudinal axis of the channel-like flow guiding device in the casing wall. Preferably, the inlet can be established as one or several hole(s) arranged tangentially at the first chamber. Utilizing the centrifugal force the inflowing oil/refrigerant mixture can thus attach to the casing inner wall of the first chamber. After acceleration in the annular gap which develops in the transition region between the first chamber and the second chamber and the subsequent reversal of the direction of flow, the oil is separated from the oil/refrigerant mixture due to inertia according to the principle of gravity. 
         [0021]    In a particularly advantageous embodiment of the invention, an oil filter, which is connected to the oil outflow channel, is placed at the casing inner wall of the second chamber in the region of the annular gap, or immediately below. This oil filter can extend along the casing inner wall completely or only partially, e.g. punctually, in annular form. 
         [0022]    Additionally or alternatively to the oil filter, a fiber material or knitted fiber fabric, placed in the second chamber, preferably in the lower region of the second chamber, which is suitable for agglomerating the oil drops may be provided. 
         [0023]    According to the idea of the invention, the oil/refrigerant mixture is submitted to reversal of the direction of flow within the casing in the second chamber. Therefore both the funnel-like end region of the flow guiding device and the casing inner wall are accordingly established, or formed. A desired degree of oil separation can also be obtained by funnel flanks inclined at an angle as predefined at the factory. 
         [0024]    In practice the three chambers of the casing, which is coupled to the crankcase of the refrigerant compressor, each are preferably designed to be circular, whereby due to its position in the casing, namely an axial between the second and third chambers, the first chamber is designed as a cylinder. For hydrodynamic reasons and reasons of pressure strength, the distal ends of the second chamber and the third chamber are preferably established as spherical caps or cylindrical with rounded edges. 
         [0025]    According to the invention, the process of oil separation and pressure pulsation attenuation within a refrigerant compressor is performed by that pressure pulsation attenuation takes place due to reflection of the pressure waves in each of the three chambers, which communicate with each other, utilizing the flow guiding device, which changes the cross-section of flow. A specific constriction of the cross-section between the chambers and a subsequent enlargement of the cross-section in the chambers attenuates, or even completely eliminates the pressure wave associated with the compression in the refrigerant compressor. 
         [0026]    Oil separation, on the other hand, is achieved by tangential injection, expansion and cooling of the oil/refrigerant mixture over the inlet of the casing into the first chamber, utilizing the centrifugal force, gravity and the nozzle effect acting at the inlet and the annular gap in the second chamber. Alternatively or additionally, oil drops are agglomerated through a fiber material or knitted fiber fabric placed in the second chamber, and are separated using gravity and pressure difference. The fiber material or knitted fiber fabric is preferably established as knitted filtering fabric. 
         [0027]    The significant advantages and features of the invention over prior art essentially are: efficient separation of the oil from the refrigerant so that good lubrication and hence long life of the refrigerant compressor are achieved; efficient reduction of the pressure pulsation of the refrigerant resulting in lower operational noise perceptible in the vehicle; little space requirements of the refrigerant compressor due to functional integration so that the refrigerant compressor can also be used in smaller engine bays; low manufacture costs due to reduced material demand, lower manufacture costs and fewer bought-in components. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]    The above and other objects and advantages of the invention will become readily apparent to those skilled in the art from reading the following descriptions of several embodiments of the invention when considered in the light of the accompanying drawings in which: 
           [0029]      FIG. 1  is a schematic representation of a casing adapted to be coupled to a crankcase of a refrigerant compressor according to an embodiment of the invention; and 
           [0030]      FIG. 2  is a front cross sectional view of a casing adapted to be coupled to a crankcase of a refrigerant compressor according to another embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0031]    The following detailed description and appended drawings describe and illustrate various exemplary embodiments of the invention. The description and drawings serve to enable one skilled in the art to make and use the invention, and are not intended to limit the scope of the invention in any manner. In respect of the methods disclosed and illustrated, the steps presented are exemplary in nature, and thus, the order of the steps is not necessary or critical. 
         [0032]      FIG. 1  shows a casing  1 , which is adapted to be coupled to a crankcase (not shown) of a refrigerant compressor (not shown). The casing  1  shown is generally cylindrical in shape but may have any suitable shape as desired. The casing includes a first chamber  3  having a substantially tangential inlet  2  in fluid communication with a refrigerant/oil mixture. The inlet includes two cylindrical apertures that are formed in parallel with respect to each other. The first chamber  3  is bordered by a third chamber  6 , which is disposed above the first chamber  3 , and a second chamber  4 , which is disposed below the first chamber  3 . The third chamber  6  has an outlet  7  that extends substantially parallel to the inlet  2  in the embodiment shown. The three chambers  3 ,  4 ,  6  of the casing  1  are separated from each other by a hollow flow guiding device  9 . Starting from the second chamber  4 , the flow guiding device  9  extends substantially coaxially with a longitudinal axis  15  of the casing  1  through the first chamber  3  and up to the third chamber  6 . 
         [0033]    A first end region  10  of the flow guiding device  9 , which is disposed between the first chamber  3  and the third chamber  6 , is formed as partition  11  which, on the one hand, holds the flow guiding device  9  within the casing  1  and, on the other hand, separates the first chamber  3  from the third chamber  6  to create a substantially fluid tight seal therebetween. 
         [0034]    A second end region  12  of the flow guiding device  9 , which is disposed between the first chamber  3  and the second chamber  4 , is formed as a funnel portion  13 . An annular gap  14  is formed between a funnel edge and a casing inner wall  8 . A spacing of the annular gap  14  between the funnel edge and the casing inner wall  8  varies around a circumference of the funnel portion  13  in the embodiment shown. The annular gap  14  forms a flow path for the oil/refrigerant mixture from the first chamber  3  to the second chamber  4 . The funnel portion  13  facilitates a flow of a refrigerant portion of the oil/refrigerant mixture from the second chamber  4  into the hollow interior portion of flow guiding device  9  and into the third chamber  6 . 
         [0035]    In use, the oil/refrigerant mixture flows at a high flow velocity tangentially from the inlet  2  into the first chamber  3 . In the first chamber  3 , which is established as an expansion space, the oil/refrigerant mixture is cooled and the flow velocity thereof is reduced. A reflection of the pressure waves within the first chamber also attenuates the pulsation of the pressure of the oil/refrigerant mixture. Thus the first chamber  3  additionally acts as an expansion silencer. The inflowing oil/refrigerant mixture attaches to the casing inner wall  8  of the first chamber  3  as a result of a centrifugal force. The oil/refrigerant mixture, following gravity, now passes through the annular gap  14  between the funnel edge of the flow guiding device  9  and the casing inner wall  8  and is accelerated, which decreases the hydrostatic pressure thereof. 
         [0036]    In the second chamber  4 , which is established as a second expansion space, the oil/refrigerant mixture is cooled and the flow velocity thereof is reduced. A reflection of the pressure waves within the second chamber also attenuates the pulsation of the pressure of the oil/refrigerant mixture. The flow of the oil/refrigerant mixture is reversed at an acute angle at the casing inner wall  8  and/or the distal end of the second chamber  4 . Thereby the oil portion of the oil/refrigerant mixture is centrifuged towards the casing inner wall  8  due to its higher inertia and the gaseous refrigerant portion of the oil/refrigerant mixture flows over the funnel portion  13  of the flow guiding device  9  into the hollow interior of the flow guiding device  9 , which reduces the hydrostatic pressure thereof. The separated oil flows along the casing inner wall  8  in the direction of the distal end of the second chamber  4  down to an oil drain  5  formed in the second chamber  4 , which is coupled to an oil drain channel (not shown). 
         [0037]    The hollow interior of the flow guiding device  9  again causes attenuation of the pressure pulsations by a reflection of the pressure waves within the hollow interior of the flow guiding device  9 . The gaseous refrigerant portion of the oil/refrigerant mixture now flows from the flow guiding device  9  into the third chamber  6  and is relieved there, which further attenuates pressure pulsations by a reflection of the pressure waves within the third chamber  6 . The gaseous and oil-free refrigerant leaves the casing  1  through the outlet  7 . 
         [0038]    Function of the casing  1  facilitates a pressure pulsation attenuation in all three chambers  3 ,  4 ,  6  and in the flow guiding device  9 , and an oil separation in the second chamber  4 . Attenuation of the pressure pulsation is achieved by design in that utilizing constrictions immediately before the inflow of the oil/refrigerant mixture into the three chambers  3 ,  4 ,  6  the hydrostatic pressure of the oil/refrigerant mixture is decreased and the hydrodynamic pressure increased. Oil separation is achieved by tangential injection, expansion and cooling of the oil/refrigerant mixture over the inlet  2  of the casing  1  into the first chamber  3 , utilizing the centrifugal force, gravity and a nozzle effect acting at the inlet  2  and the annular gap  14  in the second chamber  4 . Further, a space requirement for the casing  1  is minimized. 
         [0039]      FIG. 2  shows a casing  101 , which is coupled to a crankcase (not shown) of a refrigerant compressor (not shown). Similar structure to that described above for  FIG. 1  includes the same reference number followed by a prime (′) symbol. The casing includes a first chamber  3 ′, a second chamber  104 , and a third chamber  106 . Distal ends of the second chamber  104  and the third chamber  106  are substantially cylindrical in shape and have rounded edges for hydrodynamic and pressure strength purposes. 
         [0040]    The casing  101  includes an oil filter  16  that is disposed in the second chamber  104  between an annular gap  14 ′ formed between a funnel portion  13 ′ of a flow guiding device  9 ′ and a casing inner wall  8 ′. The oil filter  16  is coupled to an oil drain channel (not shown). In the embodiment shown, the oil filter  16  is formed from a knitted fiber fabric, although oil filters formed from other materials can be used as desired. 
         [0041]    In use, the knitted fiber fabric of the oil filter  16  separates oil from the oil/refrigerant mixture. The separated oil forms into drops, which are caused to enlarge in the oil filter  16 . The drops of oil are drained from the casing  101  through the oil drain channel. A flow course  17  of the oil/refrigerant mixture, and the subsequent substantially oil-free refrigerant, is shown. Remaining function of the casing  101  is substantially the same as the function of the casing  1  described above for  FIG. 1 . 
         [0042]    From the foregoing description, one ordinarily skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications to the invention to adapt it to various usages and conditions.